Heterogeneous oxidation by gas-phase oxidants is an important chemical transformation pathway of secondary organic aerosol(SOA)and plays an important role in controlling the abundance,properties,as well as climate and...Heterogeneous oxidation by gas-phase oxidants is an important chemical transformation pathway of secondary organic aerosol(SOA)and plays an important role in controlling the abundance,properties,as well as climate and health impacts of aerosols.However,our knowledge on this heterogeneous chemistry remains inadequate.In this study,the heterogeneous oxidation ofα-pinene ozonolysis SOA by hydroxyl(OH)radicals was investigated under both low and high relative humidity(RH)conditions,with an emphasis on the evolution of molecular composition of SOA and its RH dependence.It is found that the heterogeneous oxidation of SOA at an OH exposure level equivalent to 12 hr of atmospheric aging leads to particle mass loss of 60%at 25%RH and 95%at 90%RH.The heterogeneous oxidation strongly changes the molecular composition of SOA.The dimer-to-monomer signal ratios increase dramatically with rising OH exposure,in particular under high RH conditions,suggesting that aerosol water stimulates the reaction of monomers with OH radicals more than that of dimers.In addition,the typical SOA tracer compounds such as pinic acid,pinonic acid,hydroxy pinonic acid and dimer esters(e.g.,C17H26O8 and C19H28O7)have lifetimes of several hours against heterogeneous OH oxidation under typical atmospheric conditions,which highlights the need for the consideration of their heterogeneous loss in the estimation of monoterpene SOA concentrations using tracer-based methods.Our study sheds lights on the heterogeneous oxidation chemistry ofmonoterpene SOA andwould help to understand their evolution and impacts in the atmosphere.展开更多
Heavy oil is an important resource in current petroleum exploitation, and the chemical composition information of heavy oil is crucial for revealing its viscosity-inducing mechanism and solving practical exploitation ...Heavy oil is an important resource in current petroleum exploitation, and the chemical composition information of heavy oil is crucial for revealing its viscosity-inducing mechanism and solving practical exploitation issues. In this study, the techniques of high-temperature gas chromatography and high-resolution mass spectrometry equipped with an electrospray ionization source were applied to reveal the chemical composition of typical heavy oils from western, central, and eastern China. The results indicate that these heavy oils display significant variations in their bulk properties, with initial boiling points all above 200℃. Utilizing pre-treatment and ESI high-resolution mass spectrometry, an analysis of the molecular composition of saturated hydrocarbons, aromatic hydrocarbons, acidic oxygen compounds, sulfur compounds, basic nitrogen compounds, and neutral nitrogen compounds within the heavy oil was conducted. Ultimately, a semi-quantitative analysis of the molecular composition of the heavy oil was achieved by integrating the elemental content. The semi-quantitative analysis results of Shengli-J8 heavy oil and a conventional Shengli crude oil show that Shengli-J8 heavy oil lacks alkanes and low molecular weight aromatic hydrocarbons, which contributes to its high viscosity. Additionally,characteristic molecular sets for different heavy oils were identified based on the semi-quantitative analysis of molecular composition. The semi-quantitative analysis of molecular composition in heavy oils may provide valuable reference data for establishing theoretical models on the viscosity-inducing mechanism in heavy oils and designing viscosity-reducing agents for heavy oil exploitation.展开更多
Dissolved organic matter(DOM)plays a major role in ecological systems and influences the fate and transportation of many pollutants.Despite the significance of DOM,understanding of how environmental and anthropogenic ...Dissolved organic matter(DOM)plays a major role in ecological systems and influences the fate and transportation of many pollutants.Despite the significance of DOM,understanding of how environmental and anthropogenic factors influence its composition and characteristics is limited,especially in urban stormwater runoff.In this article,the chemical properties(pollutant loads,molecular weight,aromaticity,sources,and molecular composition)of DOM in stormwater extracted from three typical end-members(traffic,residential,and campus regions)were characterized by UV–visible(UV–vis)spectroscopy,excitationemission matrix spectroscopy combined with parallel factor analysis(EEM-PARAFAC),and ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry(UPLC-Q-TOF-MS).There are three findings:(1)The basic properties of DOM in stormwater runoff varied obviously from three urban fields,and the effect of initial flush was also apparent.(2)The DOM in residential areas mainly came from autochthonous sources,while allochthonous sources primarily contributed to the DOM in traffic and campus areas.However,it was mainly composed of terrestrial humic-like components with CHO and CHON element composition and HULO and aliphatic formulas.(3)The parameters characterizing DOM were primarily related to terrestrial source and aromaticity,but their correlations varied.Through the combination of optical methods and UPLC-Q-TOF spectrometry,the optical and molecular characteristics of rainwater are effectively revealed,which may provide a solid foundation for the classification management of stormwater runoff in different urban regions.展开更多
Diesel molecular compositional model has important application for diesel quality prediction,blending,and molecular-level process model development.In this paper,different types of diesel molecular compositional and b...Diesel molecular compositional model has important application for diesel quality prediction,blending,and molecular-level process model development.In this paper,different types of diesel molecular compositional and blending models were constructed based on the SU-BEM framework.More than 1500 representative molecules were selected to form the molecular structure library.The probability density functions(PDFs)combination was determined by experimental data and experience.A quadratic optimization strategy combining genetic algorithm with local optimization algorithm was adopted to improve the accuracy of the compositional model.The model results show good agreement with the experimental data.The diesel blending model was constructed at the molecular-level based on the above diesel compositional models.The properties of the blending model accord with the experimental regulations.It is proved that the compositional models and blending model constructed have high accuracy and strong prediction capability,and are applicable to the industrial process.展开更多
Gold-tube pyrolysis experiments were performed on two Athabasca oil sand bitumens at 300℃to 525℃with 2℃/h rate and 25℃step under 50 MPa.Pyrolysis temperature of 425℃is critical for weight loss of bulk bitumen and...Gold-tube pyrolysis experiments were performed on two Athabasca oil sand bitumens at 300℃to 525℃with 2℃/h rate and 25℃step under 50 MPa.Pyrolysis temperature of 425℃is critical for weight loss of bulk bitumen and hydrocarbon generation and destruction.Polar compounds are the main source of saturated and aromatic hydrocarbon,gas and coke fractions.Molecular compositions in pyrolyzates vary systematically with increasing pyrolysis temperatures.High molecular weight n-alkanes(C26^+) are gradually destructed during pyrolysis due to thermal cracking.Moderate molecular weight n-alkanes(C21-C25)show the highest thermal stability in designed pyrolysis temperatures.The loss of low molecular weight n-alkanes(C20^-)might be caused by volatilization during pyrolysis,which may alter commonly used molecular parameters such as∑n-C20^-/∑n-C21^+,Pr/n-C17 and Ph/n-C18.Aromatic hydrocarbons were generated from 300 to 425℃,then condensation and dealkylation have been initiated at 425℃as evidenced by decreased summed alkylnaphthalenes to alkylphenanthrenes ratios and increased unsubstituted aromatics to substituted homologs ratios in higher temperatures.The occurrence of anthracene and benz[a]anthracene in pyrolysates indicates pyrogenic origin,while fluoranthene shows unexpected behaviors during pyrolysis.Ratios derived from them are not always reliable for pyrogenic source input diagnosis in environmental samples.展开更多
To improve the naphtha composition prediction model based on molecular type homologous series matrix （MTHS）, this paper puts forward a novel molecular matrix to characterize the naphtha composition and the norreal d...To improve the naphtha composition prediction model based on molecular type homologous series matrix （MTHS）, this paper puts forward a novel molecular matrix to characterize the naphtha composition and the norreal distribution hypothesis to better describe the molecular composition distribution within each homologous series of the molecular matrix. Through prediction calculation of eight groups of naphtha samples and eight groups of gasoline samples, it is verified that the normal distribution hypothesis is more applicable than gamma distribution hypothesis for the prediction model. According to the prediction results of the samples, the restrain range of normal distribution parameters during model computing process is summarized. With the bulk properties of naphtha samples and the value range of distribution parameters as input conditions, this study utilizes the improved novel molecular matrix to predict the composition of naphtha samples. As the results show, the novel molecular matrix can predict more detailed composition information of naphtha and improve prediction accuracy with less unknown parameters.展开更多
Low-temperature oxidation(LTO)is the main reaction that affects fuel formation in the in-situ combustion process,which has important significance for the subsequent combustion propulsion and the successful extraction ...Low-temperature oxidation(LTO)is the main reaction that affects fuel formation in the in-situ combustion process,which has important significance for the subsequent combustion propulsion and the successful extraction of crude oil.In this study,heavy oil was subjected to LTO reactions at different temperatures.Three types of reaction products with varying oxidation depths were characterized in terms of the number of oxygen atoms and the polarity of the molecule to reveal the low-temperature oxidation process of the heavy oil.Ketone compounds and acid polyoxides in the oil phase and deep oxidation products with a higher number of oxygen atoms in the coke were identified with increasing oxidation depth.The experimental results showed that the oxidation reaction of the heavy oil changed from kinetic-controlled to diffusion-controlled in the open oxidation system of the heavy oil as the oxidation depth increased.The oxidation reaction of the oil phase reached a maximum and stable value in oxygen content.The molecular compositions of the ketone compound and acid polyoxide did not change significantly with further increase in reaction temperature.The molecular compositions of the deep oxidation products with a higher number of oxygen atoms in the coke phase changed significantly.The coke precursor molecules with a lower oxygen content and condensation degree participated in the coke formation,and the oxidation reaction pathway and the complexity of the oxidation product component also increased.展开更多
Dissolved organic matter(DOM)occupies a huge and uncharted molecular space.Given its properties,DOM can be presented as a promising biotechnological resource.However,research into bioactivities of DOM is still in earl...Dissolved organic matter(DOM)occupies a huge and uncharted molecular space.Given its properties,DOM can be presented as a promising biotechnological resource.However,research into bioactivities of DOM is still in early stages.In this study,the biotechnological potential of terrestrial and marine DOM,its molecular composition and their relationships are investigated.Samples were screened for their in vitro antibacterial,antifungal,anticancer and antioxidant activities.Antibacterial activity was detected against Staphylococcus aureus in almost all DOM samples,with freshwater DOM showing the lowest IC50 values.Most samples also inhibited Staphylococcus epidermidis,and four DOM extracts showed up to fourfold higher potency than the reference drug.Antifungal activity was limited to only porewater DOM towards human dermatophyte Trichophyton rubrum.No significant in vitro anticancer activity was observed.Low antioxidant potential was exerted.The molecular characterization by FT-ICR MS allowed a broad compositional overview.Three main distinguished groups have been identified by PCoA analyses.Antibacterial activities are related to high aromaticity content and highly-unsaturated molecular formulae(O-poor).Antifungal effect is correlated with highly-unsaturated molecular formulae(O-rich).Antioxidant activity is positively related to the presence of double bonds and polyphenols.This study evidenced for the first time antibacterial and antifungal activity in DOM with potential applications in cosmeceutical,pharmaceutical and aquaculture industry.The lack of cytotoxicity and the almost unlimited presence of this organic material may open new avenues in future marine bioprospect-ing efforts.展开更多
The concentration of PM_(2.5)has considerably reduced in recent years,but remains relatively high in China.In particular,the increasing contribution of organic compounds to PM_(2.5)generates popular pressure for furth...The concentration of PM_(2.5)has considerably reduced in recent years,but remains relatively high in China.In particular,the increasing contribution of organic compounds to PM_(2.5)generates popular pressure for further reductions,resulting in an urgent need to study organic aerosol(OA).To investigate the molecular composition and source contribution of OA in the rural area of the Guanzhong Plain,Northwest China,PM_(2.5)samples were collected during 3–23 August 2016 and 5–20 January 2017 and studied for more than 100 organic tracer compounds.The mean concentration of total measured organic compounds is 662±296 ng/m^(3)in summer and 3258±1925 ng/m^(3)in winter.Levoglucosan is the most abundant single compound found throughout the sampling period,which is a crucial tracer for biomass burning emissions,preliminary suggesting that biomass burning is an essential source of OA.In summer,organic compounds such as lipid compounds,sugar compounds,and polycyclic aromatic hydrocarbons(PAHs),more come from higher plants,wood burning,vehicle exhausts,plastic waste,and other direct emission sources.Oxygenated PAHs(OPAHs),nitrophenols,and phthalic acids more come from the atmosphere through the oxidation reaction of aromatic precursors,especially photochemical oxidation.However,in winter,most of the increases in concentrations of organic compounds are attributed to biomass burning.The analysis of a haze event(14–19 January 2017)during the winter sampling period shows that the increases in the concentration of organic compounds are unaccompanied by strong secondary formation under lower relative humidity(49.1%±13.5%).The main reason for the growth of OA in this haze event is the accumulation of primary OA(POA).The source apportionment by the positive matrix factorization(PMF)model shows that biomass burning(37.1%)is the primary source of OA in the rural regions of the Guanzhong Plain,especially in winter(40.6%).The contribution of secondary formation decreases from 26.0%in summer to 16.9%in winter,and the contribution of fossil fuel emissions is comparable across both seasons.展开更多
The influences of reaction temperature,duration,pressure,and catalyst concentration on the molecular transformation of residual slurry phase hydrocracking process were investigated.The molecular composition of the het...The influences of reaction temperature,duration,pressure,and catalyst concentration on the molecular transformation of residual slurry phase hydrocracking process were investigated.The molecular composition of the heteroatom compounds in the residue feedstock and its upgrading products were characterized using high-resolution Orbitrap mass spectrometry coupled with multiple ionization methods.The simultaneous promotion of cracking and hydrogenation reactions was observed with increasing of the reaction temperature and time.Specifically,there was a significant increase in the cracking degree of alkyl side chain,while the removal of low-condensation sulfur compounds such as sulfides and benzothiophenes was enhanced.In particular,the cracking reactions were more significantly facilitated by high temperatures,while an appropriately extended reaction time can result in the complete elimination of the aforementioned sulfur compounds with a lower degree of condensation.Under conditions of low hydrogen pressure and catalyst concentration,the products still exhibit a high relative abundance of easily convertible compounds such as sulfoxides,indicating a significant deficiency in the effectiveness of hydrogenation.The hydrogen pressure exhibits an optimal value,beyond which further increments have no effect on the composition and performance of the liquid product but can increase the yield of the liquid product.At significantly high catalyst concentration,the effect of desulfurization and deoxidation slightly diminishes,while the aromatic saturation of highly condensed compounds was notably enhanced.This hydrogenation saturation effect cannot be attained through manipulation of other operational parameters,thereby potentially benefiting subsequent product processing and utilization.This present study demonstrates a profound comprehension of the molecular-level residue slurry phase hydrocracking process,offering not only specific guide for process design and optimization but also valuable fundamental data for constructing reaction models at the molecular level.展开更多
Water-soluble organic aerosol(WSOA)plays a significant role in air quality and human health.Here we characterized the chemical properties and molecular compositions of WSOA at a rural site in North China Plain during ...Water-soluble organic aerosol(WSOA)plays a significant role in air quality and human health.Here we characterized the chemical properties and molecular compositions of WSOA at a rural site in North China Plain during winter using a high-resolution aerosol mass spectrometer and electrospray ionization high-resolution orbitrap mass spectrometer(ESI-HRMS).Our results show that the mass concentration of WSOA was significantly higher than that observed in Beijing in winter 2020,contributing about 56%of OA on average.CHO compounds(56%-74%)and CHN compounds(66%-80%)dominated in negative mode and positive mode,respectively,while CHON accounted for 15%-41%across both modes.The chemical characteristics of WSOA varied with polluted levels and between day and night.As pollution intensified,the abundance of CHO-compounds with condensed aromatics increased by 9%and the number of highly oxygenated molecules(HOMs)molecular formula detected in server haze was more than double that of clean days.CHO-compounds with ten carbon atoms(C_(10))were more abundant at night while those with nine carbon atoms(C_(9))were higher during the day.High levels of CHN+compounds were linked to nighttime biomass burning,whereas CHON compounds were more abundant during the day.Increased pollution also led to the formation of more complex CHON-compounds,indicating that organonitrates continue to play a significant role in rural pollution.展开更多
A vacuum topped Canadian oilsands bitumen （VTB） was subjected to solvent precipitation and subsequently characterized by elemental analysis, gel permeation chromatograph （GPC）, IH-NMR spectroscopy and negative-ion...A vacuum topped Canadian oilsands bitumen （VTB） was subjected to solvent precipitation and subsequently characterized by elemental analysis, gel permeation chromatograph （GPC）, IH-NMR spectroscopy and negative-ion electrospray ionization （ESI） Fourier transform ion cyclotron resonance mass spectrometry （FT-ICR MS）. Effects of experimental conditions such as solvent types （n-Cs, n-C6, and n-C7）, solvent purity, and solvent washing time on asphaltenes yields, bulk composition, and molecular composition of detectable heteroatom compounds in ESI source were determined. Elemental nitrogen and sulfur were enriched in asphaltenes while elemental oxygen had comparable content in maltenes and asphaltenes. Molecular compo- sition of asphaltenes varies with separation conditions. The N1 and O1 species identified by ESI FT-ICR MS were enriched in maltenes. The 02 species exhibited two different double bond equivalents （DBE） distributions and solubility in normal paraffin solvents, indicating two types of molecular structures. Multi oxygen atom containing compounds mainly detected in asphal- tenes. Compound class distributions are similar for maltenes derived from n-Cs, n-C6, and n-C7 , as well as for asphaltenes. The cyclic paraffin impurities in normal paraffin solvents had a significant influence on asphaltenes yields and heteroatom molecu- lar composition. A portion of neutral N1 species and acidic 02 species adsorbed on asphaltenes could be dissolved by increas- ing washing time. Cautions should be exercised when interpreting the properties and composition of asphaltenes obtained with different experimental conditions.展开更多
Acquiring accurate molecular-level information about petroleum is crucial for refining and chemical enterprises to implement the“selection of the optimal processing route”strategy.With the development of data predic...Acquiring accurate molecular-level information about petroleum is crucial for refining and chemical enterprises to implement the“selection of the optimal processing route”strategy.With the development of data prediction systems represented by machine learning,it has become possible for real-time prediction systems of petroleum fraction molecular information to replace analyses such as gas chromatography and mass spectrometry.However,the biggest difficulty lies in acquiring the data required for training the neural network.To address these issues,this work proposes an innovative method that utilizes the Aspen HYSYS and full two-dimensional gas chromatography-time-of-flight mass spectrometry to establish a comprehensive training database.Subsequently,a deep neural network prediction model is developed for heavy distillate oil to predict its composition in terms of molecular structure.After training,the model accurately predicts the molecular composition of catalytically cracked raw oil in a refinery.The validation and test sets exhibit R2 values of 0.99769 and 0.99807,respectively,and the average relative error of molecular composition prediction for raw materials of the catalytic cracking unit is less than 7%.Finally,the SHAP(SHapley Additive ExPlanation)interpretation method is used to disclose the relationship among different variables by performing global and local weight comparisons and correlation analyses.展开更多
Lake Baiyangdian is one of China’s largest macrophyte-derived lakes,facing severe challenges related to water quality maintenance and eutrophication prevention.Dissolved organic matter(DOM)was a huge carbon pool and ...Lake Baiyangdian is one of China’s largest macrophyte-derived lakes,facing severe challenges related to water quality maintenance and eutrophication prevention.Dissolved organic matter(DOM)was a huge carbon pool and its abundance,property,and transformation played important roles in the biogeochemical cycle and energy flow in lake ecosystems.In this study,Lake Baiyangdian was divided into four distinct areas:Unartificial Area(UA),Village Area(VA),Tourism Area(TA),and Breeding Area(BA).We examined the diversity of DOM properties and sources across these functional areas.Our findings reveal that DOM in this lake is predominantly composed of protein-like substances,as determined by excitation-emission matrix and parallel factor analysis(EEM-PARAFAC).Notably,the exogenous tyrosine-like component C1 showed a stronger presence in VA and BA compared to UA and TA.Ultrahigh-resolution mass spectrometry(FT-ICR MS)unveiled a similar DOM molecular composition pattern across different functional areas due to the high relative abundances of lignan compounds,suggesting that macrophytes significantly influence the material structure of DOM.DOM properties exhibited specific associations with water quality indicators in various functional areas,as indicated by the Mantel test.The connections between DOM properties and NO_(3)-N andNH3-Nwere more pronounced in VA and BA than in UA and TA.Our results underscore the viability of using DOM as an indicator for more precise and scientific water quality management.展开更多
Steam flooding is a widely used technique to enhance oil recovery of heavy oil.Thermal viscosity reduction and distillation effect are considered as two main displacement mechanisms in steam flooding process.However,t...Steam flooding is a widely used technique to enhance oil recovery of heavy oil.Thermal viscosity reduction and distillation effect are considered as two main displacement mechanisms in steam flooding process.However,the molecular composition understanding and contribution for oil production are still unclear.In this study,the composition analysis of the heavy oil was investigated in the core scale steam flooding process with the temperature from 120 to 280℃.The crude oil,produced oils and residual oils were characterized comprehensively by gas chromatography and high-resolution mass spectrometry.It is found that steam flooding preferentially extracts aromatics and remains more resins in the residual oil.Viscosity reduction is the dominant mechanism when steam is injected at a low temperature.Large molecular heteroatoms with high carbon number and high double bond equivalent(DBE)are eluted into the produced oil,while compounds with low carbon number and low DBE are remained in the residual oil.As the steam temperature rises,the increased distillation effect results in the extraction of light hydrocarbons from the residual oil to the produced oil.More small heteroatoms with low carbon number and low DBE enter into the produced oil,especially in the none water cut stage.The compositional difference of produced oils is characterized in DBE versus carbon number distribution of the N and O containing compound classes.This work uses a variety of composition analysis methods to clarify the steam flooding mechanism and provides a novel understanding of steam flooding mechanisms with various temperatures and production stages from the molecular perspective.展开更多
A novel Ce-Y/SBA-15 catalyst was prepared by modifying HY/SBA-15 microporous-mesoporous composite molecular sieve with cerium using the impregnation method. The characterization results from scanning electron microsco...A novel Ce-Y/SBA-15 catalyst was prepared by modifying HY/SBA-15 microporous-mesoporous composite molecular sieve with cerium using the impregnation method. The characterization results from scanning electron microscopy/energy dispersive X-ray dispersive spectroscopy（SEM/EDS）, transmission electron microscopy（TEM）, and X-ray fluorescence（XRF） studies indicated that the Ce-modified catalyst maintained the microporous-mesoporous structure of Y/SBA-15. The Ce ions were found to be uniformly dispersed in the pores of the molecular sieve without aggregation. The results from pyrolysis coupled-Fourier transform infrared spectroscopy（Pyridine-FTIR） and temperature programmed desorption of ammonia（NH3-TPD） showed that the loading of cerium caused the hydroxyl group in the catalyst to display stronger Bronsted acidity. The efficiency of the modified Ce-Y/SBA-15 catalyst was evaluated by using it to catalyze the synthesis of n-butyl acetate. The optimal synthesis conditions were determined by orthogonal experiments. The highest esterification yield of 94.4% was obtained when the reaction time was 2.0 h, with acid/alcohol molar ratio of 1：1.2, and catalyst loading of 10 wt.%. The results in this study demonstrated that the loading of cerium and the structure of Y/SBA-15 microporous-mesoporous composite molecular sieve helped in improving the catalytic activity of this acidic catalyst.展开更多
ZSM-5/MCM-41 composite molecular sieve was prepared by the nano-assembling method.The ZSM-5 molecular sieve,the MCM-41 molecular sieve,the ZSM-5/MCM-41 mechanical mixture and the ZSM-5/MCM-41 composite molecular sieve...ZSM-5/MCM-41 composite molecular sieve was prepared by the nano-assembling method.The ZSM-5 molecular sieve,the MCM-41 molecular sieve,the ZSM-5/MCM-41 mechanical mixture and the ZSM-5/MCM-41 composite molecular sieve were characterized by X-ray powder diffractometry,N_2 adsorption isotherms,temperature programmed desorption of ammonia and scanning electron microscopy and their properties were analyzed.Using FCC gasoline as the feed,activities of different molecular sieves for reducing olefin content were investigated in a continuous high-pressure micro-reactor unit under the following conditions:a reaction temperature of 400℃,a reaction time of 2 h,a weight hourly space velocity of 3h^(-1),and a reaction pressure of 2.0 MPa.The results showed that the HMCM-41 molecular sieve had low reaction performance,and the HZSM-5 molecular sieve demonstrated high aromatization activity,while the ZSM-5/MCM- 41 composite molecular sieve exhibited a best olefin-reducing performance because of its high isomerization activity and moderate aromatization activity.With a largest olefin-reducmg capability and a reasonable distribution of products,the composite molecular sieve was more suitable for FCC gasoline upgrading compared to other three catalysts.展开更多
To improve oil quality,ZSM-22/SAPO-11 composite molecular sieves were synthesized by adding ZSM-22 into a synthetic gel of SAPO-11 for n-decane hydroisomerization.The mass ratios of ZSM-22/(ZSM-22+SAPO-11)in the compo...To improve oil quality,ZSM-22/SAPO-11 composite molecular sieves were synthesized by adding ZSM-22 into a synthetic gel of SAPO-11 for n-decane hydroisomerization.The mass ratios of ZSM-22/(ZSM-22+SAPO-11)in the composite molecular sieves were optimized and the optimal ZSM-22/SAPO-11 composite(ZS-9)was obtained.The electrostatic repulsions between the ZSM-22 precursors and the SAPO-11 crystalline nuclei produced small ZSM-22 and SAPO-11 crystallites in ZS-9,which increased the specific surface area and mesopore volume and thereby exposed more acid sites.In comparison with conventional SAPO-11,ZSM-22 and their mechanical mixture,ZS-9 with smaller crystallites and the optimal medium and strong Brønsted acid centers(MSBAC)content displayed a higher yield of branched C_(10) isomers(81.6%),lower cracking selectivity(11.9%)and excellent stability.The correlation between the i-C_(10) selectivity and the MSBAC density of molecular sieves indicated that the selectivity for branched C_(10) isomers first increased and then decreased with increasing MSBAC density on the molecular sieves,and the maximum selectivity(87.7%)occurred with a density of 9.6×10^(−2)μmol m^(−2).展开更多
Ethyl-cyanoethyl cellulose [(E-CE)C]/cross-linked polyacrylic acid [PAA] molecular composites with cholesteric order were prepared. It was found that the macromolecular cholesteric structure was changed with the swell...Ethyl-cyanoethyl cellulose [(E-CE)C]/cross-linked polyacrylic acid [PAA] molecular composites with cholesteric order were prepared. It was found that the macromolecular cholesteric structure was changed with the swelling of PAA in the composites. The selective reflection of the cholesteric phase shifted to the longer wavelength and the X-ray diffraction angle shifted to the high angle direction during swelling, which suggested that the cholesteric pitch and the number of the layers of ordered (E-CE)C chains in the cholesteric phase were increased.展开更多
Investigating the characteristics and transformation of water-soluble carbonaceous matter in the cryosphere regions is important for understanding biogeochemical process in the earth system.Water-soluble carbonaceous ...Investigating the characteristics and transformation of water-soluble carbonaceous matter in the cryosphere regions is important for understanding biogeochemical process in the earth system.Water-soluble carbonaceous matter is a heterogeneous mixture of organic compounds that is soluble in aquatic environments.Despite its importance,we still lack systematic understanding for dissolved organic carbon(DOC)in several aspects including exact chemical composition and physical interactions with microorganisms,glacier meltwater.This review presents the chemical composition and physical properties of glacier DOC deposited through anthropogenic emission,terrestrial,and biogenic sources.We present the molecular composition of DOC and its effect over snow albedo and associated radiative forcings.Results indicate that DOC in snow/ice is made up of aromatic protein-like species,fulvic acid-like materials,and humic acid-like materials.Light-absorbing impurities in surface snow and glacier ice cause considerable albedo reduction and the associated radiative forcing is definitely positive.Water-soluble carbonaceous matter dominated the carbon transport in the high-altitude glacial area.Owing to prevailing global warming and projected increase in carbon emission,the glacial DOC is expected to release,which will have strong underlying impacts on cryosphere ecosystem.The results of this work have profound implications for better understanding the carbon cycle in high altitude cryosphere regions.A new compilation of globally distributed work is required,including large-scale measurements of glacial DOC over high-altitude cryosphere regions,to overcome and address the scientific challenges to constrain climate impacts of light-absorbing impurities related processes in Earth system and climate models.展开更多
基金supported by the National Natural Science Foundation of China (Nos.22022607 and 42005090)the Shanghai Pujiang Program (No.20PJ1407600)。
文摘Heterogeneous oxidation by gas-phase oxidants is an important chemical transformation pathway of secondary organic aerosol(SOA)and plays an important role in controlling the abundance,properties,as well as climate and health impacts of aerosols.However,our knowledge on this heterogeneous chemistry remains inadequate.In this study,the heterogeneous oxidation ofα-pinene ozonolysis SOA by hydroxyl(OH)radicals was investigated under both low and high relative humidity(RH)conditions,with an emphasis on the evolution of molecular composition of SOA and its RH dependence.It is found that the heterogeneous oxidation of SOA at an OH exposure level equivalent to 12 hr of atmospheric aging leads to particle mass loss of 60%at 25%RH and 95%at 90%RH.The heterogeneous oxidation strongly changes the molecular composition of SOA.The dimer-to-monomer signal ratios increase dramatically with rising OH exposure,in particular under high RH conditions,suggesting that aerosol water stimulates the reaction of monomers with OH radicals more than that of dimers.In addition,the typical SOA tracer compounds such as pinic acid,pinonic acid,hydroxy pinonic acid and dimer esters(e.g.,C17H26O8 and C19H28O7)have lifetimes of several hours against heterogeneous OH oxidation under typical atmospheric conditions,which highlights the need for the consideration of their heterogeneous loss in the estimation of monoterpene SOA concentrations using tracer-based methods.Our study sheds lights on the heterogeneous oxidation chemistry ofmonoterpene SOA andwould help to understand their evolution and impacts in the atmosphere.
基金supported by the National Key R&D Program of China (2018YFA0702400)the Science Foundation of China University of Petroleum, Beijing (2462023QNXZ017)。
文摘Heavy oil is an important resource in current petroleum exploitation, and the chemical composition information of heavy oil is crucial for revealing its viscosity-inducing mechanism and solving practical exploitation issues. In this study, the techniques of high-temperature gas chromatography and high-resolution mass spectrometry equipped with an electrospray ionization source were applied to reveal the chemical composition of typical heavy oils from western, central, and eastern China. The results indicate that these heavy oils display significant variations in their bulk properties, with initial boiling points all above 200℃. Utilizing pre-treatment and ESI high-resolution mass spectrometry, an analysis of the molecular composition of saturated hydrocarbons, aromatic hydrocarbons, acidic oxygen compounds, sulfur compounds, basic nitrogen compounds, and neutral nitrogen compounds within the heavy oil was conducted. Ultimately, a semi-quantitative analysis of the molecular composition of the heavy oil was achieved by integrating the elemental content. The semi-quantitative analysis results of Shengli-J8 heavy oil and a conventional Shengli crude oil show that Shengli-J8 heavy oil lacks alkanes and low molecular weight aromatic hydrocarbons, which contributes to its high viscosity. Additionally,characteristic molecular sets for different heavy oils were identified based on the semi-quantitative analysis of molecular composition. The semi-quantitative analysis of molecular composition in heavy oils may provide valuable reference data for establishing theoretical models on the viscosity-inducing mechanism in heavy oils and designing viscosity-reducing agents for heavy oil exploitation.
基金supported by the National Natural Science Foundation of China(No.51778451)the 111 Project(No.B13017)the Academic Capability Improvement Project(No.0400219422)of Tongji University。
文摘Dissolved organic matter(DOM)plays a major role in ecological systems and influences the fate and transportation of many pollutants.Despite the significance of DOM,understanding of how environmental and anthropogenic factors influence its composition and characteristics is limited,especially in urban stormwater runoff.In this article,the chemical properties(pollutant loads,molecular weight,aromaticity,sources,and molecular composition)of DOM in stormwater extracted from three typical end-members(traffic,residential,and campus regions)were characterized by UV–visible(UV–vis)spectroscopy,excitationemission matrix spectroscopy combined with parallel factor analysis(EEM-PARAFAC),and ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry(UPLC-Q-TOF-MS).There are three findings:(1)The basic properties of DOM in stormwater runoff varied obviously from three urban fields,and the effect of initial flush was also apparent.(2)The DOM in residential areas mainly came from autochthonous sources,while allochthonous sources primarily contributed to the DOM in traffic and campus areas.However,it was mainly composed of terrestrial humic-like components with CHO and CHON element composition and HULO and aliphatic formulas.(3)The parameters characterizing DOM were primarily related to terrestrial source and aromaticity,but their correlations varied.Through the combination of optical methods and UPLC-Q-TOF spectrometry,the optical and molecular characteristics of rainwater are effectively revealed,which may provide a solid foundation for the classification management of stormwater runoff in different urban regions.
基金supported by the SINOPEC R&D Program(grant number 119014-1)
文摘Diesel molecular compositional model has important application for diesel quality prediction,blending,and molecular-level process model development.In this paper,different types of diesel molecular compositional and blending models were constructed based on the SU-BEM framework.More than 1500 representative molecules were selected to form the molecular structure library.The probability density functions(PDFs)combination was determined by experimental data and experience.A quadratic optimization strategy combining genetic algorithm with local optimization algorithm was adopted to improve the accuracy of the compositional model.The model results show good agreement with the experimental data.The diesel blending model was constructed at the molecular-level based on the above diesel compositional models.The properties of the blending model accord with the experimental regulations.It is proved that the compositional models and blending model constructed have high accuracy and strong prediction capability,and are applicable to the industrial process.
基金supported by National Natural Science Foundation of China(Grant Number 41573035,41873049)the Mitacs project at University of Calgary。
文摘Gold-tube pyrolysis experiments were performed on two Athabasca oil sand bitumens at 300℃to 525℃with 2℃/h rate and 25℃step under 50 MPa.Pyrolysis temperature of 425℃is critical for weight loss of bulk bitumen and hydrocarbon generation and destruction.Polar compounds are the main source of saturated and aromatic hydrocarbon,gas and coke fractions.Molecular compositions in pyrolyzates vary systematically with increasing pyrolysis temperatures.High molecular weight n-alkanes(C26^+) are gradually destructed during pyrolysis due to thermal cracking.Moderate molecular weight n-alkanes(C21-C25)show the highest thermal stability in designed pyrolysis temperatures.The loss of low molecular weight n-alkanes(C20^-)might be caused by volatilization during pyrolysis,which may alter commonly used molecular parameters such as∑n-C20^-/∑n-C21^+,Pr/n-C17 and Ph/n-C18.Aromatic hydrocarbons were generated from 300 to 425℃,then condensation and dealkylation have been initiated at 425℃as evidenced by decreased summed alkylnaphthalenes to alkylphenanthrenes ratios and increased unsubstituted aromatics to substituted homologs ratios in higher temperatures.The occurrence of anthracene and benz[a]anthracene in pyrolysates indicates pyrogenic origin,while fluoranthene shows unexpected behaviors during pyrolysis.Ratios derived from them are not always reliable for pyrogenic source input diagnosis in environmental samples.
基金Supported by the National Natural Science Foundation of China(U1462206)
文摘To improve the naphtha composition prediction model based on molecular type homologous series matrix （MTHS）, this paper puts forward a novel molecular matrix to characterize the naphtha composition and the norreal distribution hypothesis to better describe the molecular composition distribution within each homologous series of the molecular matrix. Through prediction calculation of eight groups of naphtha samples and eight groups of gasoline samples, it is verified that the normal distribution hypothesis is more applicable than gamma distribution hypothesis for the prediction model. According to the prediction results of the samples, the restrain range of normal distribution parameters during model computing process is summarized. With the bulk properties of naphtha samples and the value range of distribution parameters as input conditions, this study utilizes the improved novel molecular matrix to predict the composition of naphtha samples. As the results show, the novel molecular matrix can predict more detailed composition information of naphtha and improve prediction accuracy with less unknown parameters.
基金supported by the National Key R&D Program of China(2018YFA0702400)the PetroChina Exploration&Production Company(KS2020-01-05).
文摘Low-temperature oxidation(LTO)is the main reaction that affects fuel formation in the in-situ combustion process,which has important significance for the subsequent combustion propulsion and the successful extraction of crude oil.In this study,heavy oil was subjected to LTO reactions at different temperatures.Three types of reaction products with varying oxidation depths were characterized in terms of the number of oxygen atoms and the polarity of the molecule to reveal the low-temperature oxidation process of the heavy oil.Ketone compounds and acid polyoxides in the oil phase and deep oxidation products with a higher number of oxygen atoms in the coke were identified with increasing oxidation depth.The experimental results showed that the oxidation reaction of the heavy oil changed from kinetic-controlled to diffusion-controlled in the open oxidation system of the heavy oil as the oxidation depth increased.The oxidation reaction of the oil phase reached a maximum and stable value in oxygen content.The molecular compositions of the ketone compound and acid polyoxide did not change significantly with further increase in reaction temperature.The molecular compositions of the deep oxidation products with a higher number of oxygen atoms in the coke phase changed significantly.The coke precursor molecules with a lower oxygen content and condensation degree participated in the coke formation,and the oxidation reaction pathway and the complexity of the oxidation product component also increased.
基金Marie Skłodowska-Curie individual Fellowship,H2020-MSCA-IF-2016749586,Teresa S.Catalá,Carl von Ossietzky Universität Oldenburg.
文摘Dissolved organic matter(DOM)occupies a huge and uncharted molecular space.Given its properties,DOM can be presented as a promising biotechnological resource.However,research into bioactivities of DOM is still in early stages.In this study,the biotechnological potential of terrestrial and marine DOM,its molecular composition and their relationships are investigated.Samples were screened for their in vitro antibacterial,antifungal,anticancer and antioxidant activities.Antibacterial activity was detected against Staphylococcus aureus in almost all DOM samples,with freshwater DOM showing the lowest IC50 values.Most samples also inhibited Staphylococcus epidermidis,and four DOM extracts showed up to fourfold higher potency than the reference drug.Antifungal activity was limited to only porewater DOM towards human dermatophyte Trichophyton rubrum.No significant in vitro anticancer activity was observed.Low antioxidant potential was exerted.The molecular characterization by FT-ICR MS allowed a broad compositional overview.Three main distinguished groups have been identified by PCoA analyses.Antibacterial activities are related to high aromaticity content and highly-unsaturated molecular formulae(O-poor).Antifungal effect is correlated with highly-unsaturated molecular formulae(O-rich).Antioxidant activity is positively related to the presence of double bonds and polyphenols.This study evidenced for the first time antibacterial and antifungal activity in DOM with potential applications in cosmeceutical,pharmaceutical and aquaculture industry.The lack of cytotoxicity and the almost unlimited presence of this organic material may open new avenues in future marine bioprospect-ing efforts.
基金supported by National Natural Science Foundation of China(grant No.41977332)the Natural Science Basic Research Program of Shaanxi(grant No.2021JQ-971,2022JQ-242)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(grant No.XDB40000000)support of the Youth Innovation Promotion Association CAS(grant No.2020407).
文摘The concentration of PM_(2.5)has considerably reduced in recent years,but remains relatively high in China.In particular,the increasing contribution of organic compounds to PM_(2.5)generates popular pressure for further reductions,resulting in an urgent need to study organic aerosol(OA).To investigate the molecular composition and source contribution of OA in the rural area of the Guanzhong Plain,Northwest China,PM_(2.5)samples were collected during 3–23 August 2016 and 5–20 January 2017 and studied for more than 100 organic tracer compounds.The mean concentration of total measured organic compounds is 662±296 ng/m^(3)in summer and 3258±1925 ng/m^(3)in winter.Levoglucosan is the most abundant single compound found throughout the sampling period,which is a crucial tracer for biomass burning emissions,preliminary suggesting that biomass burning is an essential source of OA.In summer,organic compounds such as lipid compounds,sugar compounds,and polycyclic aromatic hydrocarbons(PAHs),more come from higher plants,wood burning,vehicle exhausts,plastic waste,and other direct emission sources.Oxygenated PAHs(OPAHs),nitrophenols,and phthalic acids more come from the atmosphere through the oxidation reaction of aromatic precursors,especially photochemical oxidation.However,in winter,most of the increases in concentrations of organic compounds are attributed to biomass burning.The analysis of a haze event(14–19 January 2017)during the winter sampling period shows that the increases in the concentration of organic compounds are unaccompanied by strong secondary formation under lower relative humidity(49.1%±13.5%).The main reason for the growth of OA in this haze event is the accumulation of primary OA(POA).The source apportionment by the positive matrix factorization(PMF)model shows that biomass burning(37.1%)is the primary source of OA in the rural regions of the Guanzhong Plain,especially in winter(40.6%).The contribution of secondary formation decreases from 26.0%in summer to 16.9%in winter,and the contribution of fossil fuel emissions is comparable across both seasons.
基金supported by the National Key R&D Program of China(2021YFA1501200)the National Natural Science Foundation of China(NSFC U23B20169 and 22021004)the Project of R&D Department of CNPC(2020B-2011)。
文摘The influences of reaction temperature,duration,pressure,and catalyst concentration on the molecular transformation of residual slurry phase hydrocracking process were investigated.The molecular composition of the heteroatom compounds in the residue feedstock and its upgrading products were characterized using high-resolution Orbitrap mass spectrometry coupled with multiple ionization methods.The simultaneous promotion of cracking and hydrogenation reactions was observed with increasing of the reaction temperature and time.Specifically,there was a significant increase in the cracking degree of alkyl side chain,while the removal of low-condensation sulfur compounds such as sulfides and benzothiophenes was enhanced.In particular,the cracking reactions were more significantly facilitated by high temperatures,while an appropriately extended reaction time can result in the complete elimination of the aforementioned sulfur compounds with a lower degree of condensation.Under conditions of low hydrogen pressure and catalyst concentration,the products still exhibit a high relative abundance of easily convertible compounds such as sulfoxides,indicating a significant deficiency in the effectiveness of hydrogenation.The hydrogen pressure exhibits an optimal value,beyond which further increments have no effect on the composition and performance of the liquid product but can increase the yield of the liquid product.At significantly high catalyst concentration,the effect of desulfurization and deoxidation slightly diminishes,while the aromatic saturation of highly condensed compounds was notably enhanced.This hydrogenation saturation effect cannot be attained through manipulation of other operational parameters,thereby potentially benefiting subsequent product processing and utilization.This present study demonstrates a profound comprehension of the molecular-level residue slurry phase hydrocracking process,offering not only specific guide for process design and optimization but also valuable fundamental data for constructing reaction models at the molecular level.
基金supported by the National Natural Science Foundation of China(No.42307139)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0760200)。
文摘Water-soluble organic aerosol(WSOA)plays a significant role in air quality and human health.Here we characterized the chemical properties and molecular compositions of WSOA at a rural site in North China Plain during winter using a high-resolution aerosol mass spectrometer and electrospray ionization high-resolution orbitrap mass spectrometer(ESI-HRMS).Our results show that the mass concentration of WSOA was significantly higher than that observed in Beijing in winter 2020,contributing about 56%of OA on average.CHO compounds(56%-74%)and CHN compounds(66%-80%)dominated in negative mode and positive mode,respectively,while CHON accounted for 15%-41%across both modes.The chemical characteristics of WSOA varied with polluted levels and between day and night.As pollution intensified,the abundance of CHO-compounds with condensed aromatics increased by 9%and the number of highly oxygenated molecules(HOMs)molecular formula detected in server haze was more than double that of clean days.CHO-compounds with ten carbon atoms(C_(10))were more abundant at night while those with nine carbon atoms(C_(9))were higher during the day.High levels of CHN+compounds were linked to nighttime biomass burning,whereas CHON compounds were more abundant during the day.Increased pollution also led to the formation of more complex CHON-compounds,indicating that organonitrates continue to play a significant role in rural pollution.
基金supported by the National Natural Science Foundation of China(U1162204 and 21236009)
文摘A vacuum topped Canadian oilsands bitumen （VTB） was subjected to solvent precipitation and subsequently characterized by elemental analysis, gel permeation chromatograph （GPC）, IH-NMR spectroscopy and negative-ion electrospray ionization （ESI） Fourier transform ion cyclotron resonance mass spectrometry （FT-ICR MS）. Effects of experimental conditions such as solvent types （n-Cs, n-C6, and n-C7）, solvent purity, and solvent washing time on asphaltenes yields, bulk composition, and molecular composition of detectable heteroatom compounds in ESI source were determined. Elemental nitrogen and sulfur were enriched in asphaltenes while elemental oxygen had comparable content in maltenes and asphaltenes. Molecular compo- sition of asphaltenes varies with separation conditions. The N1 and O1 species identified by ESI FT-ICR MS were enriched in maltenes. The 02 species exhibited two different double bond equivalents （DBE） distributions and solubility in normal paraffin solvents, indicating two types of molecular structures. Multi oxygen atom containing compounds mainly detected in asphal- tenes. Compound class distributions are similar for maltenes derived from n-Cs, n-C6, and n-C7 , as well as for asphaltenes. The cyclic paraffin impurities in normal paraffin solvents had a significant influence on asphaltenes yields and heteroatom molecu- lar composition. A portion of neutral N1 species and acidic 02 species adsorbed on asphaltenes could be dissolved by increas- ing washing time. Cautions should be exercised when interpreting the properties and composition of asphaltenes obtained with different experimental conditions.
基金the National Natural Science Foundation of China(22108307)the Natural Science Foundation of Shandong Province(ZR2020KB006)the Outstanding Youth Fund of Shandong Provincial Natural Science Foundation(ZR2020YQ17).
文摘Acquiring accurate molecular-level information about petroleum is crucial for refining and chemical enterprises to implement the“selection of the optimal processing route”strategy.With the development of data prediction systems represented by machine learning,it has become possible for real-time prediction systems of petroleum fraction molecular information to replace analyses such as gas chromatography and mass spectrometry.However,the biggest difficulty lies in acquiring the data required for training the neural network.To address these issues,this work proposes an innovative method that utilizes the Aspen HYSYS and full two-dimensional gas chromatography-time-of-flight mass spectrometry to establish a comprehensive training database.Subsequently,a deep neural network prediction model is developed for heavy distillate oil to predict its composition in terms of molecular structure.After training,the model accurately predicts the molecular composition of catalytically cracked raw oil in a refinery.The validation and test sets exhibit R2 values of 0.99769 and 0.99807,respectively,and the average relative error of molecular composition prediction for raw materials of the catalytic cracking unit is less than 7%.Finally,the SHAP(SHapley Additive ExPlanation)interpretation method is used to disclose the relationship among different variables by performing global and local weight comparisons and correlation analyses.
基金supported by the National Key Research and Development Program of China(No.2022YFC3204000).
文摘Lake Baiyangdian is one of China’s largest macrophyte-derived lakes,facing severe challenges related to water quality maintenance and eutrophication prevention.Dissolved organic matter(DOM)was a huge carbon pool and its abundance,property,and transformation played important roles in the biogeochemical cycle and energy flow in lake ecosystems.In this study,Lake Baiyangdian was divided into four distinct areas:Unartificial Area(UA),Village Area(VA),Tourism Area(TA),and Breeding Area(BA).We examined the diversity of DOM properties and sources across these functional areas.Our findings reveal that DOM in this lake is predominantly composed of protein-like substances,as determined by excitation-emission matrix and parallel factor analysis(EEM-PARAFAC).Notably,the exogenous tyrosine-like component C1 showed a stronger presence in VA and BA compared to UA and TA.Ultrahigh-resolution mass spectrometry(FT-ICR MS)unveiled a similar DOM molecular composition pattern across different functional areas due to the high relative abundances of lignan compounds,suggesting that macrophytes significantly influence the material structure of DOM.DOM properties exhibited specific associations with water quality indicators in various functional areas,as indicated by the Mantel test.The connections between DOM properties and NO_(3)-N andNH3-Nwere more pronounced in VA and BA than in UA and TA.Our results underscore the viability of using DOM as an indicator for more precise and scientific water quality management.
文摘Steam flooding is a widely used technique to enhance oil recovery of heavy oil.Thermal viscosity reduction and distillation effect are considered as two main displacement mechanisms in steam flooding process.However,the molecular composition understanding and contribution for oil production are still unclear.In this study,the composition analysis of the heavy oil was investigated in the core scale steam flooding process with the temperature from 120 to 280℃.The crude oil,produced oils and residual oils were characterized comprehensively by gas chromatography and high-resolution mass spectrometry.It is found that steam flooding preferentially extracts aromatics and remains more resins in the residual oil.Viscosity reduction is the dominant mechanism when steam is injected at a low temperature.Large molecular heteroatoms with high carbon number and high double bond equivalent(DBE)are eluted into the produced oil,while compounds with low carbon number and low DBE are remained in the residual oil.As the steam temperature rises,the increased distillation effect results in the extraction of light hydrocarbons from the residual oil to the produced oil.More small heteroatoms with low carbon number and low DBE enter into the produced oil,especially in the none water cut stage.The compositional difference of produced oils is characterized in DBE versus carbon number distribution of the N and O containing compound classes.This work uses a variety of composition analysis methods to clarify the steam flooding mechanism and provides a novel understanding of steam flooding mechanisms with various temperatures and production stages from the molecular perspective.
基金Project supported by the Research Fund for the Doctoral Program of Higher Education(20100042110008)the Talent Scientific Research Fund of Liaoning Shihua University
文摘A novel Ce-Y/SBA-15 catalyst was prepared by modifying HY/SBA-15 microporous-mesoporous composite molecular sieve with cerium using the impregnation method. The characterization results from scanning electron microscopy/energy dispersive X-ray dispersive spectroscopy（SEM/EDS）, transmission electron microscopy（TEM）, and X-ray fluorescence（XRF） studies indicated that the Ce-modified catalyst maintained the microporous-mesoporous structure of Y/SBA-15. The Ce ions were found to be uniformly dispersed in the pores of the molecular sieve without aggregation. The results from pyrolysis coupled-Fourier transform infrared spectroscopy（Pyridine-FTIR） and temperature programmed desorption of ammonia（NH3-TPD） showed that the loading of cerium caused the hydroxyl group in the catalyst to display stronger Bronsted acidity. The efficiency of the modified Ce-Y/SBA-15 catalyst was evaluated by using it to catalyze the synthesis of n-butyl acetate. The optimal synthesis conditions were determined by orthogonal experiments. The highest esterification yield of 94.4% was obtained when the reaction time was 2.0 h, with acid/alcohol molar ratio of 1：1.2, and catalyst loading of 10 wt.%. The results in this study demonstrated that the loading of cerium and the structure of Y/SBA-15 microporous-mesoporous composite molecular sieve helped in improving the catalytic activity of this acidic catalyst.
文摘ZSM-5/MCM-41 composite molecular sieve was prepared by the nano-assembling method.The ZSM-5 molecular sieve,the MCM-41 molecular sieve,the ZSM-5/MCM-41 mechanical mixture and the ZSM-5/MCM-41 composite molecular sieve were characterized by X-ray powder diffractometry,N_2 adsorption isotherms,temperature programmed desorption of ammonia and scanning electron microscopy and their properties were analyzed.Using FCC gasoline as the feed,activities of different molecular sieves for reducing olefin content were investigated in a continuous high-pressure micro-reactor unit under the following conditions:a reaction temperature of 400℃,a reaction time of 2 h,a weight hourly space velocity of 3h^(-1),and a reaction pressure of 2.0 MPa.The results showed that the HMCM-41 molecular sieve had low reaction performance,and the HZSM-5 molecular sieve demonstrated high aromatization activity,while the ZSM-5/MCM- 41 composite molecular sieve exhibited a best olefin-reducing performance because of its high isomerization activity and moderate aromatization activity.With a largest olefin-reducmg capability and a reasonable distribution of products,the composite molecular sieve was more suitable for FCC gasoline upgrading compared to other three catalysts.
基金The authors gratefully acknowledge the financial support of Science Foundation of China University of Petroleum,Beijing(Grant No.KYJJ2012-03-03).
文摘To improve oil quality,ZSM-22/SAPO-11 composite molecular sieves were synthesized by adding ZSM-22 into a synthetic gel of SAPO-11 for n-decane hydroisomerization.The mass ratios of ZSM-22/(ZSM-22+SAPO-11)in the composite molecular sieves were optimized and the optimal ZSM-22/SAPO-11 composite(ZS-9)was obtained.The electrostatic repulsions between the ZSM-22 precursors and the SAPO-11 crystalline nuclei produced small ZSM-22 and SAPO-11 crystallites in ZS-9,which increased the specific surface area and mesopore volume and thereby exposed more acid sites.In comparison with conventional SAPO-11,ZSM-22 and their mechanical mixture,ZS-9 with smaller crystallites and the optimal medium and strong Brønsted acid centers(MSBAC)content displayed a higher yield of branched C_(10) isomers(81.6%),lower cracking selectivity(11.9%)and excellent stability.The correlation between the i-C_(10) selectivity and the MSBAC density of molecular sieves indicated that the selectivity for branched C_(10) isomers first increased and then decreased with increasing MSBAC density on the molecular sieves,and the maximum selectivity(87.7%)occurred with a density of 9.6×10^(−2)μmol m^(−2).
基金This work was supported by the National Natural Science Foundation of China, the National Key Projects for Fundamental Research "Macromolecular Condensed State", the State Science & Technology Commission of China and Polymer Physics Laboratory. Changchun
文摘Ethyl-cyanoethyl cellulose [(E-CE)C]/cross-linked polyacrylic acid [PAA] molecular composites with cholesteric order were prepared. It was found that the macromolecular cholesteric structure was changed with the swelling of PAA in the composites. The selective reflection of the cholesteric phase shifted to the longer wavelength and the X-ray diffraction angle shifted to the high angle direction during swelling, which suggested that the cholesteric pitch and the number of the layers of ordered (E-CE)C chains in the cholesteric phase were increased.
基金supported by the second Tibetan Plateau Scientific Expedition and Research Program(STEP)(2019QZKK0605)the National Natural Science Foundation of China(41971080)the support of Youth Innovation Promotion Association CAS(2021429)。
文摘Investigating the characteristics and transformation of water-soluble carbonaceous matter in the cryosphere regions is important for understanding biogeochemical process in the earth system.Water-soluble carbonaceous matter is a heterogeneous mixture of organic compounds that is soluble in aquatic environments.Despite its importance,we still lack systematic understanding for dissolved organic carbon(DOC)in several aspects including exact chemical composition and physical interactions with microorganisms,glacier meltwater.This review presents the chemical composition and physical properties of glacier DOC deposited through anthropogenic emission,terrestrial,and biogenic sources.We present the molecular composition of DOC and its effect over snow albedo and associated radiative forcings.Results indicate that DOC in snow/ice is made up of aromatic protein-like species,fulvic acid-like materials,and humic acid-like materials.Light-absorbing impurities in surface snow and glacier ice cause considerable albedo reduction and the associated radiative forcing is definitely positive.Water-soluble carbonaceous matter dominated the carbon transport in the high-altitude glacial area.Owing to prevailing global warming and projected increase in carbon emission,the glacial DOC is expected to release,which will have strong underlying impacts on cryosphere ecosystem.The results of this work have profound implications for better understanding the carbon cycle in high altitude cryosphere regions.A new compilation of globally distributed work is required,including large-scale measurements of glacial DOC over high-altitude cryosphere regions,to overcome and address the scientific challenges to constrain climate impacts of light-absorbing impurities related processes in Earth system and climate models.
