In-situ DRIFTS was used to study the deep oxidation of propane, a side reaction during propane oxidative dehydrogenation to propene. Strong adsorption of propene was supposed to be the main reason for the deep oxidati...In-situ DRIFTS was used to study the deep oxidation of propane, a side reaction during propane oxidative dehydrogenation to propene. Strong adsorption of propene was supposed to be the main reason for the deep oxidation. It was found that gaseous oxygen in the feed and the reaction temperature had great influence on the reaction. To obtain a relative high selectivity to propene, the reaction temperature should be maintained at 150-250℃ with a proper content of gaseous oxygen in the feed for a certain catalyst and some modifiers which could weaken the adsorption of propene on the catalyst surface would be favorable.展开更多
Harmaline and harmine areβ-carboline alkaloids with effective pharmacological effects.Harmaline can be transformed into harmine after oral administration.However,enzymes involved in the metabolic pathway remain uncle...Harmaline and harmine areβ-carboline alkaloids with effective pharmacological effects.Harmaline can be transformed into harmine after oral administration.However,enzymes involved in the metabolic pathway remain unclear.In this study,harmaline was incubated with rat liver microsomes(RLM),rat brain microsomes(RBM),blood,plasma,broken blood cells,and heme peroxidases including horseradish peroxidase(HRP),lactoperoxidase(LPO),and myeloperoxidase(MPO).The production of harmine was determined by a validated UPLC-ESI-MS/MS method.Results showed that heme peroxidases catalyzed the oxidative dehydrogenation of harmaline.All the reactions were in accordance with the Hill equation.The reaction was inhibited by ascorbic acid and excess H_(2)0_(2).The transformation of harmaline to harmine was confirmed after incubation with blood,plasma,and broken blood cells,rather than RLM and RBM.Harmaline was incubated with blood,plasma,and broken cells liquid for 3 h,and the formation of harmine became stable.Results indicated an integrated metabolic pathway of harmaline,which will lay foundation for the oxidation reaction of dihydro-P-carboline.Moreover,the metabolic stability of harmaline in blood should not be ignored when the pharmacokinetics study of harmaline is carried out.展开更多
Chemical looping oxidative dehydrogenation (CL-ODH) is an economically promising method for convertingethane into higher value-added ethylene utilizing lattice oxygen in redox catalysts, also known as oxygen carriers....Chemical looping oxidative dehydrogenation (CL-ODH) is an economically promising method for convertingethane into higher value-added ethylene utilizing lattice oxygen in redox catalysts, also known as oxygen carriers. Inthis study, perovskite-type oxide SrCoO_(3-δ) and B-site Mn ion-doped oxygen carriers (SrCo_(1-x)MnxO_(3-δ), x=0.1, 0.2, 0.3)were prepared and tested for the CL-ODH of ethane. The oxygen-deficient perovskite SrCoO_(3-δ) exhibited high ethyleneselectivity of up to 96.7% due to its unique oxygen vacancies and lattice oxygen migration rates. However, its low ethyleneyield limits its application in the CL-ODH of ethane. Mn doping promoted the reducibility of SrCoO_(3-δ) oxygen carriers,thereby improving ethane conversion and ethylene yield, as demonstrated by characterization and evaluation experiments.X-ray diffraction results confirmed the doping of Mn into the lattice of SrCoO_(3-δ), while X-ray photoelectron spectroscopy(XPS) indicated an increase in lattice oxygen ratio upon incorporation of Mn into the SrCoO_(3-δ) lattice. Additionally, H2temperature-programmed reduction (H2-TPR) tests revealed more peaks at lower temperature reduction zones and a declinein peak positions at higher temperatures. Among the four tested oxygen carriers, SrCo0.8Mn0.2O_(3-δ) exhibited satisfactoryperformance with an ethylene yield of 50% at 710 °C and good stability over 20 redox cycles. The synergistic effect of Mnplays a key role in increasing ethylene yields of SrCoO_(3-δ) oxygen carriers. Accordingly, SrCo0.8Mn0.2O_(3-δ) shows promisingpotential for the efficient production of ethylene from ethane via CL-ODH.展开更多
Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for converting ethane to ethylene.In the current study MeO/LaCoO_(3)(MeO=Fe_(2)O_(3),NiO or Co_(2)O_(3))composite metal oxides w...Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for converting ethane to ethylene.In the current study MeO/LaCoO_(3)(MeO=Fe_(2)O_(3),NiO or Co_(2)O_(3))composite metal oxides were prepared via citrate gel and impregnation methods,and used as oxygen carriers for CL-ODH.X-ray diffraction results indicated that all oxygen carriers had a perovskite structure even after eight redox cycles.Under a reaction temperature of 650°C,a reaction pressure of 0.1 MPa,and a weight hourly space velocity(WHSV)of 7500 mL/(g·h),ethane conversion over Co_(2)O_(3)/LaCoO_(3) reached 100%and ethylene selectivity reached 60%,both of which were better than corresponding values attained over Fe_(2)O_(3)/LaCoO_(3) and NiO/LaCoO_(3).Ethylene selectivity remained stable for 80 cycles over Co_(2)O_(3)/LaCoO_(3),then decreased gradually after 80 cycles.X-ray photoelectron spectroscopy results and evaluation results indicated that lattice oxygen and O_(2)2-had a direct relationship with ethane conversion and ethylene selectivity.Co_(2)O_(3)/LaCoO_(3) exhibited a strong capacity to release and absorb oxygen,mainly due to interaction between Co_(2)O_(3) and LaCoO_(3).展开更多
Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for ethylene preparation.Fe_(2)O_(3)/MgO oxygen carrier was prepared using the co-precipitation method.The influence of added Ni...Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for ethylene preparation.Fe_(2)O_(3)/MgO oxygen carrier was prepared using the co-precipitation method.The influence of added NiO and its different loadings on Fe_(2)O_(3)/MgO were investigated.Then,a series of oxygen carriers were applied in the CL-ODH of the ethane cycle system.Brunauer-Emmett-Teller(BET),X-ray diffractometry(XRD),X-ray photoelection spectroscopy(XPS),and H2-temperature programmed reduction(TPR)were used to characterize the physicochemical properties of these oxygen carriers.It was confirmed that an interaction between NiO and Fe_(2)O_(3) occurred based on the XPS and H2-TPR results.Based on the CL-ODH activity performance tests conducted in a fixed-bed reactor,it was revealed that ethylene selectivity was significantly improved after NiO addition.Fe_(2)O_(3)-10%NiO/MgO showed the best activity performance with 93%ethane conversion and 50%ethylene selectivity at a reaction temperature of 650℃,atmospheric pressure,and space velocity of 7500 mL/(g·h).展开更多
Organoboron compounds have become important intermediates for the construction of new compounds in synthetic chemistry and pharmaceutical chemistry,and it has been found that pinacol biborate(B_(2)pin_(2))as the boron...Organoboron compounds have become important intermediates for the construction of new compounds in synthetic chemistry and pharmaceutical chemistry,and it has been found that pinacol biborate(B_(2)pin_(2))as the boron source and Cu^(Ⅱ) organophosphorus complex(L)as the catalyst can effectively realize the hydrogen-reduced borylation products and dehydrohydrated borylation products of aryl olefins.The reaction regioselectivity involvingβ-C positions of aryl olefins can be controlled by regulating the ligand and additive types.The formation mechanism of the product is conducted at LCu^(Ⅰ)Bpin formed from Cu^(Ⅱ),L and B_(2)pin_(2).Subsequently the substrate aryl olefins undergo addition reaction to form the active intermediate PhCH(LCu^(Ⅰ))CH_(2)Bpin.Followed by the metathesis of the active intermediate with water to form hydrogen reduction products,the same active intermediate can be oxidized with 2,2,6,6-tetramethylpiperidoxyl(TEMPO)to form trans dehydrogenation products.展开更多
Boron nitride containing hydroxyl groups efficiently catalysed oxidative dehydrogenation of ethane to ethylene,offering rather high selectivity（95%） but only small amount of CO2 formation（0.4%） at a given ethane c...Boron nitride containing hydroxyl groups efficiently catalysed oxidative dehydrogenation of ethane to ethylene,offering rather high selectivity（95%） but only small amount of CO2 formation（0.4%） at a given ethane conversion of 11%.Even at high conversion level of 63%,the selectivity of ethylene retained at 80%,which is competitive with the energy-demanding industrialized steam cracking route.A long-term test for 200 h resulted in stable conversion and product selectivity,showing the excellent catalytic stability.Both experimental and computational studies have identified that the hydrogen abstraction of B-OH groups by molecular oxygen dynamically generated the active sites and triggered ethane dehydrogenation.展开更多
A comprehensive single particle model which includes the mesoscale and microscale models was developed to study the influence of particle diameter on mass and heat transfer occurring within a ferrite catalyst during t...A comprehensive single particle model which includes the mesoscale and microscale models was developed to study the influence of particle diameter on mass and heat transfer occurring within a ferrite catalyst during the oxidative dehydrogenation of butene to butadiene process. The verified model can be used to investigate the influence of catalyst diameter on the flow distribution inside the particle. The simulation results demonstrate that the mass fraction gradients of all species, temperature gradient and pressure gradient increase with the increase of the particle diameter. It means that there is a high intraparticle transfer resistance and strong diffusion when applying the large catalysts. The external particle mass transfer resistance is nearly constant under different particle diameters so that the effect of particle diameter at external diffusion can be ignored. A large particle diameter can lead to a high surface temperature, which indicates the external heat transfer resistance. Moreover, the selectivity of reaction may be changed with a variety of particle diameters so that choosing appropriate particle size can enhance the production of butadiene and optimize the reaction process.展开更多
The oxidative dehydrogenation （ODH） reactions of ethane and propane were investigated in a catalytic membrane reactor, incorporating oxygen-permeable membranes based upon La2Ni0.9V0.1O4＋δor Ba0.5Sr0.5Co0.8Fe0.2O3-...The oxidative dehydrogenation （ODH） reactions of ethane and propane were investigated in a catalytic membrane reactor, incorporating oxygen-permeable membranes based upon La2Ni0.9V0.1O4＋δor Ba0.5Sr0.5Co0.8Fe0.2O3-δ. As a compromise between the occurrence of a measureable oxygen flux and excessive homogenous gas phase reactions, the measurements were conducted at an intermediate temperature, either at 550 or 650 oC. The results show the dominating role of the oxygen flux across the membrane and available sites at the membrane surface in primary activation of the alkane and, hence, in achieving high alkane conversions. The experimental data of ODH of propane and ethane on both membrane materials can be reconciled on the basis of Mars-van Krevelen mechanism, in which the alkane reacts with lattice oxygen on the membrane surface to produce the corresponding olefin. It is further demonstrated that the oxygen concentration in the gas phase and on the membrane surface is crucial for determining the olefin selectivity.展开更多
Propane dehydrogenation using CO_(2)as a mild oxidizer(CO_(2)-ODP)is a promising technology for high propylene production and CO_(2)reduction utilization.Among them,the reverse water gas shift reaction(RWGS)can change...Propane dehydrogenation using CO_(2)as a mild oxidizer(CO_(2)-ODP)is a promising technology for high propylene production and CO_(2)reduction utilization.Among them,the reverse water gas shift reaction(RWGS)can change the reaction equilibrium to increase the propylene yield,and the Boudouard reaction can assist in the carbon accumulation elimination.However,the efficiency of the catalysts developed so far is limited,we introduced the Cr active component during the synthesis of porous silica spheres to form a CO_(2)-ODP catalyst,with a uniform distribution of active sites via(NH_(4))_(3)[CrMo_(6)O_(24)H_(6)]·7H_(2)O produce a derivative.As anα-type Anderson series of polyoxometalates(POMs),this six octahedral structure formed by Mo participation surrounds the central atom Cr,which is more stable in structure by electrostatic effect,its derivatives generated after calcination are stably bound to the silica-based carrier,which reduces the formation of inertα-Cr_(2)O_(3)by CrO_(x)aggregation during the catalytic process.Meanwhile,the oxygen atoms rich in polyoxometalates are more likely to form Si-O bonds with the carrier,which makes the active sites evenly and stably branched in the inner wall of the pores of mesoporous silica spheres,reduces the influence of carbon accumulation,and facilitates the activation and regeneration.The CO_(2)conversion of the catalyst CrMoO_(x)@mesoporous silica spheres(MSS)is typically greater than 20%under selected ideal conditions.This synthesis method of assembling POMs with mesoporous materials opens a new pathway for developing propane dehydrogenation catalysts.Compared to traditional impregnation synthesis,this catalyst contains a lower Cr content while achieving higher CO_(2)consumption efficiency.展开更多
Ordered macroporous materials with rapid mass transport and enhanced active site accessibility are essential for achieving improved catalytic activity.In this study,boron phosphate crystals with a three-dimensionally ...Ordered macroporous materials with rapid mass transport and enhanced active site accessibility are essential for achieving improved catalytic activity.In this study,boron phosphate crystals with a three-dimensionally interconnected ordered macroporous structure and a robust framework were fabricated and used as stable and selective catalysts in the oxidative dehydrogenation(ODH)of propane.Due to the improved mass diffusion and higher number of exposed active sites in the ordered macroporous structure,the catalyst exhibited a remarkable olefin productivity of^16 golefin gcat^-1 h^-1,which is up to 2–100 times higher than that of ODH catalysts reported to date.The selectivity for olefins was 91.5%(propene:82.5%,ethene:9.0%)at 515℃,with a propane conversion of 14.3%.At the same time,the selectivity for the unwanted deep-oxidized CO2 product remained less than 1.0%.The tri-coordinated surface boron species were identified as the active catalytic sites for the ODH of propane.This study provides a route for preparing a new type of metal-free catalyst with stable structure against oxidation and remarkable catalytic activity,which may represent a potential candidate to promote the industrialization of the ODH process.展开更多
The effect of rare earth oxides （RE=Ce, La, Gd, and Dy） doping of alumina support in NiO/7-A1203 system was investi- gated on its catalytic performance in oxidative dehydrogenation （ODH） of cyclohexane. The physic...The effect of rare earth oxides （RE=Ce, La, Gd, and Dy） doping of alumina support in NiO/7-A1203 system was investi- gated on its catalytic performance in oxidative dehydrogenation （ODH） of cyclohexane. The physicochemical properties of various samples were followed up through N2 physisorption, temperature programmed reduction （H2-TPR）, X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and potentiometric acid-base titration techniques. In the parent NiO/y-A1203 catalyst, Ni species were found to be strongly interacted with alumina surface. Addition of rare earth dopants to ）＇-A1203 in the catalyst system affected the nickel-alumina interaction and resulted in significant modifications in the catalytic performances in the ODH reaction. The results re- vealed the beneficial role of both La203 and Gd2Os doping in enhancing the ODH catalytic activity and selectivity to cyclohexene. H2-TPR and XPS results indicated that majority of Ni species in NiO/La203 modified T-A1203 were more weakly interacted with La203 and alumina whereas both NiO like species and nickel aluminate were present on the surface. Doping with cerium or dyspro- sium increased the nickel-support interaction and led to a decrease in surface nickel concentration. In case of doping with Ce, surface concentration of cerium oxide was higher than those of the other RE oxides; the doped catalyst reached its steady state activity faster than the other catalysts. The acid-base results suggested that RE metals were interacted most likely with acidic surface hydroxyl groups. The degree of nickel-alumina interaction decreased in the following order： LaAI〉GdAI〉CeAI〉DyA1.展开更多
Boron-based metal-free catalysts for oxidative dehydrogenation of propane(ODHP)have drawn great attention in both academia and industry due to their impressive activity and olefin selectivity.Herein,the SiO2 and B2O3 ...Boron-based metal-free catalysts for oxidative dehydrogenation of propane(ODHP)have drawn great attention in both academia and industry due to their impressive activity and olefin selectivity.Herein,the SiO2 and B2O3 sequentially coated honeycomb cordierite catalyst is designed by a two-step wash-coat method with different B2O3 loadings(0.1%–10%)and calcination temperatures(600,700,800℃).SiO2 obtained by TEOS hydrolysis acts as a media layer to bridge the cordierite substrate and boron oxide via abundant Si\\OH groups.The welldeveloped straight channels of honeycomb cordierite make it possible to carry out the reactor under high gas hourly space velocity(GHSV)and the thin wash-coated B2O3 layer can effectively facilitate the pore diffusion on the catalyst.The prepared B2O3/SiO2@HC monolithic catalyst exhibits good catalytic performance at low boron oxide loading and achieves excellent propylene selectivity(86.0%),olefin selectivity(97.6%,propylene and ethylene)and negligible CO2(0.1%)at 16.9%propane conversion under high GHSV of 345,600 ml·(g B2O3)^-1·h^-1,leading to a high propylene space time yield of 15.7 g C3H6·(g B2O3)^-1·h^-1 by suppressing the overoxidation.The obtained results strongly indicate that the boron-based monolithic catalyst can be properly fabricated to warrant the high activity and high throughput with its high gas/surface ratio and straight channels.展开更多
Different mole ratio Al-B catalysts (Al-10B to Al-35B) were synthesized by using sol-gel (SG) method. Ethyl benzene (EB) dehydrogenation in the presence of oxygen and water steam was carried out on these catalysts at ...Different mole ratio Al-B catalysts (Al-10B to Al-35B) were synthesized by using sol-gel (SG) method. Ethyl benzene (EB) dehydrogenation in the presence of oxygen and water steam was carried out on these catalysts at 450–500℃ with EB contact time of 0.54 gcat.s.cm^–3. Acidity of Al-B catalysts was estimated by using NH3-TPD-mass spectral analysis studies. SEM-mapping images revealed fine distribution of boron up to 15% of its loading in alumina (Al-15B), whereas, boron aggregation was observed in higher boron content (Al-25B and Al-35B) catalysts. Essentially, acid sites of very weak strength (Tmax ≤ 125℃) were observed for Al and Al-10B catalysts and resulted in low EB conversion and styrene yield. On the other hand, acid sites of weak strength (Tmax ≤ 180℃) were observed for Al-25B and Al-35B catalysts and resulted in high EB conversion. However, greater styrene yield (43.2%) with reasonable EB conversion (46%) was obtained on acid sites of weak moderate strength in Al-15B catalyst. Further, Al-15B catalyst was synthesized by using co-precipitation (COP) and impregnation (IMP) methods. Acid sites related to NOx formation during the NH3-TPD-mass analysis on IMP and COP catalyst essentially improved the EB conversion to 66% and 63% respectively at 500℃. However, these acid sites were diminished in Al-B SG catalyst and resulted in 50% of EB conversion at 500 ℃. At 50% of EB conversion level, styrene selectivity of 73%, 82.5% and 84% were observed on Al-B IMP, Al-B COP and Al-SG catalysts, respectively. Hence, different method of preparation of Al-B catalyst generated acid sites of different strength and density and thereby influenced the styrene formation.展开更多
Oxidative dehydrogenation of light alkanes to alkenes is an attractive alternative route for industrial direct dehydrogenation because of favorable thermodynamic and kinetic characteristics,but encounters difficulties...Oxidative dehydrogenation of light alkanes to alkenes is an attractive alternative route for industrial direct dehydrogenation because of favorable thermodynamic and kinetic characteristics,but encounters difficulties in selectivity control for alkenes because of over-oxidation reactions that produce a substantial amount of undesired carbon oxides.Recent progress has revealed that boron nitride is a highly promising catalyst in the oxidative dehydrogenation of light alkanes because of its superior selectivity for and high productivity of light alkenes,negligible formation of CO2,and remarkable catalyst stability.From this viewpoint,recent works on boron nitride in the oxidative dehydrogenations of ethane,propane,butane,and ethylbenzene are reviewed,and the emphasis of this viewpoint is placed on discussing the catalytic origin of boron nitride in oxidative dehydrogenation reactions.After analyzing recent progress in the use of boron nitride for oxidative dehydrogenation reactions and finding much new evidence,we conclude that pure boron nitride is catalytically inert,and an activation period is required under the reaction conditions;this process is accompanied by an oxygen functionalization at the edge of boron nitride;the B-O species themselves have no catalytic activity in C-H cleavage,and the B-OH groups,with the assistance of molecular oxygen,play the key role in triggering the oxidative dehydrogenation of propane;the dissociative adsorption of molecular oxygen is involved in the reaction process;and a straightforward strategy for preparing an active boron nitride catalyst with hydroxyl groups at the edges can efficiently enhance the catalytic efficacy.A new redox reaction cycle based on the B-OH sites is also proposed.Furthermore,as this is a novel catalytic system,there is an urgent need to develop new methods to optimize the catalytic performances,clarify the catalytic function of boron species in the alkane ODH reactions,and disclose the reaction mechanism under realistic reaction conditions.展开更多
The discovery of the high activity and selectivity of boron-based catalysts for oxidative dehydrogenation(ODH)of alkanes to olefins has attracted significant attention in the exploration of a new method for the synthe...The discovery of the high activity and selectivity of boron-based catalysts for oxidative dehydrogenation(ODH)of alkanes to olefins has attracted significant attention in the exploration of a new method for the synthesis of highly active and selective catalysts.Herein,we describe the synthesis of porous boron-doped silica nanofibers(PBSNs)100-150 nm in diameter by electrospinning and the study of their catalytic performance.The electrospinning synthesis of the catalyst ensures the uniform dispersion and stability of the boron species on the open silica fiber framework.The one-dimensional nanofibers with open pore structures not only prevented diffusion limitation but also guaranteed high catalytic activity at high weight hourly space velocity(WHSV)in the ODH of alkanes.Compared to other supported boron oxide catalysts,PBSN catalysts showed higher olefin selectivity and stability.The presence of Si-OH groups in silica-supported boron catalysts may cause low propylene selectivity during the ODH of propane.When the ODH conversion of ethane reached 44.3%,the selectivity and productivity of ethylene were 84%and 44.2%g_(cat)^(-1)s^(-1),respectively.In the case of propane ODH,the conversion,selectivity of olefins,and productivity of propylene are 19.2%,90%,and 76.6 jimol g_(cat)^(-1)s^(-1),respectively.No significant variations in the conversion and product selectivity occurred during 20 h of operation at a high WHSV of 84.6 h^(-1).Transient analysis and kinetic experiments indicated that the activation of O2 was influenced by alkanes during the ODH reaction.展开更多
Highly ordered mesoporous NiMoO4 material was successfully synthesized using mesoporous silica KIT-6 as hard template via vacuum nanocasting method. The structure was characterized by means of XRD, TEM, N2 adsorption-...Highly ordered mesoporous NiMoO4 material was successfully synthesized using mesoporous silica KIT-6 as hard template via vacuum nanocasting method. The structure was characterized by means of XRD, TEM, N2 adsorption-desorption, Raman and FT-IR. The mesoporous NiMoO4 with the coexistence of a-NiMoO4 and fl-NiMoO4 showed well-ordered mesoporous structure, a bimodal pore size distribution and crystalline framework. The catalytic performance of NiMoOa was investigated for oxidative dehydrogenation of propane. It is demonstrated that the mesoporous NiMoO4 catalyst with more surface active oxygen species showed better catalytic performance in oxidative dehydrogena- tion of propane in comparison with bulk NiMoO4.展开更多
Hexagonal boron nitride(h-BN)is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes.Despite intense recent research effort,many aspects of the reaction mecha...Hexagonal boron nitride(h-BN)is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes.Despite intense recent research effort,many aspects of the reaction mechanism,such as the observed supra-linear reaction order of alkanes,remain unresolved.In this work,we show that the introduction of a low concentration of propane in the feed of ethane oxidative dehydrogenation is able to enhance the C_(2)H_(6) conversion by 47%,indicating a shared reaction intermediate in the activation of ethane and propane.The higher activity of propane makes it the dominant radical generator in the oxidative co-dehydrogenation of ethane and propane(ODEP).This unique feature of the ODEP renders propane an effective probe molecule to deconvolute the two roles of alkanes in the dehydrogenation chemistry,i.e.,radical generator and substrate.Kinetic studies indicate that both the radical generation and the dehydrogenation pathways exhibit a first order kinetics toward the alkane partial pressure,leading to the observed second order kinetics of the overall oxidative dehydrogenation rate.With the steady-state approximation,a radical chain reaction mechanism capable of rationalizing observed reaction behaviors is proposed based on these insights.This work demonstrates the potential of ODEP as a strategy of both activating light alkanes in oxidative dehydrogenation on BN and mechanistic investigations.展开更多
In this work, a series of Ni-Mo-Mg-O catalysts with mesoporous structure prepared by sol-gel method were investigated for the oxidative dehydrogenation of propane （ODHP）. The techniques of temperature-programmed red...In this work, a series of Ni-Mo-Mg-O catalysts with mesoporous structure prepared by sol-gel method were investigated for the oxidative dehydrogenation of propane （ODHP）. The techniques of temperature-programmed reduction with H2 （H2-TPR）, N2 adsorption-desolption, Fourier transform infrared spectroscopy （FT-IR）, X-ray diffraction （XRD） and X-ray photoelectron spectra （XPS） were employed for catalyst characterization. It is found that the activity of the catalysts for ODHP increases first and then decreases with the increase of Mo content. The catalyst with a Mo/Ni atomic ratio of 1/1 exhibits the best catalytic activity, which gives the propene selectivity of 81.4% at a propane conversion of 11.3% under 600 ~C and maintains the good catalytic performance for 22 h on stream. This is related not only to its high reducibility and dispersion as revealed by TPR and XRD, but also to the formation of more selective oxygen species on the MoOz-NiO interface as identified by XPS.展开更多
An industrial scale propylene production via oxidative dehydrogenation of propane （ODHP） in multi-tubular re- actors was modeled. Multi-tubular fixed-bed reactor used for ODHP process, employing 10000 of small diame...An industrial scale propylene production via oxidative dehydrogenation of propane （ODHP） in multi-tubular re- actors was modeled. Multi-tubular fixed-bed reactor used for ODHP process, employing 10000 of small diameter tubes immersed in a shell through a proper coolant flows. Herein, a theory-based pseudo-homogeneous model to describe the operation of a fixed bed reactor for the ODHP to correspondence olefln over V2O5/γ-Al203 catalyst was presented. Steady state one dimensional model has been developed to identify the operation parameters and to describe the propane and oxygen conversions, gas process and coolant temperatures, as well as other pa- rameters affecting the reactor performance such as pressure. Furthermore, the applied model showed that a double-bed multitubular reactor with intermediate air injection scheme was superior to a single-bed design due to the increasing of propylene selectivity while operating under lower oxygen partial pressures resulting in propane conversion of about 37.3%. The optimized length of the reactor needed to reach 100% conversion of the oxygen was theoretically determined. For the single-bed reactor the optimized length of 11.96 m including 0.5 m of inert section at the entrance region and for the double-bed reactor design the optimized lengths of 5.72 m for the first and 7.32 m for the second reactor were calculated. Ultimately, the use of a distributed oxygen feed with limited number of injection points indicated a significant improvement on the reactor performance in terms of propane conversion and propylene selectivity. Besides, this concept could overcome the reactor run- away temperature problem and enabled operations at the wider range of conditions to obtain enhanced propyl- ene production in an industrial scale reactor.展开更多
基金supported by the National Natural Science Foundation of China (20576045)the Program for New Century Excellent Talentsin University (NCET-06-740)
文摘In-situ DRIFTS was used to study the deep oxidation of propane, a side reaction during propane oxidative dehydrogenation to propene. Strong adsorption of propene was supposed to be the main reason for the deep oxidation. It was found that gaseous oxygen in the feed and the reaction temperature had great influence on the reaction. To obtain a relative high selectivity to propene, the reaction temperature should be maintained at 150-250℃ with a proper content of gaseous oxygen in the feed for a certain catalyst and some modifiers which could weaken the adsorption of propene on the catalyst surface would be favorable.
基金supported by the National Natural Science Foundation of China(Nos.82173885 and 81872933)the National Natural Science Foundation of Xinjiang Uyghur Autonomous Region of China(No.U1130303)+1 种基金the Technology Cooperation Projects of Science in Shanghai,China(No.20015800100)the Key Laboratory Open Project of Xinjiang Uyghur Autonomous Region(No.2019D04018).
文摘Harmaline and harmine areβ-carboline alkaloids with effective pharmacological effects.Harmaline can be transformed into harmine after oral administration.However,enzymes involved in the metabolic pathway remain unclear.In this study,harmaline was incubated with rat liver microsomes(RLM),rat brain microsomes(RBM),blood,plasma,broken blood cells,and heme peroxidases including horseradish peroxidase(HRP),lactoperoxidase(LPO),and myeloperoxidase(MPO).The production of harmine was determined by a validated UPLC-ESI-MS/MS method.Results showed that heme peroxidases catalyzed the oxidative dehydrogenation of harmaline.All the reactions were in accordance with the Hill equation.The reaction was inhibited by ascorbic acid and excess H_(2)0_(2).The transformation of harmaline to harmine was confirmed after incubation with blood,plasma,and broken blood cells,rather than RLM and RBM.Harmaline was incubated with blood,plasma,and broken cells liquid for 3 h,and the formation of harmine became stable.Results indicated an integrated metabolic pathway of harmaline,which will lay foundation for the oxidation reaction of dihydro-P-carboline.Moreover,the metabolic stability of harmaline in blood should not be ignored when the pharmacokinetics study of harmaline is carried out.
基金the SINOPEC Research and Development Project(No.JR22094).
文摘Chemical looping oxidative dehydrogenation (CL-ODH) is an economically promising method for convertingethane into higher value-added ethylene utilizing lattice oxygen in redox catalysts, also known as oxygen carriers. Inthis study, perovskite-type oxide SrCoO_(3-δ) and B-site Mn ion-doped oxygen carriers (SrCo_(1-x)MnxO_(3-δ), x=0.1, 0.2, 0.3)were prepared and tested for the CL-ODH of ethane. The oxygen-deficient perovskite SrCoO_(3-δ) exhibited high ethyleneselectivity of up to 96.7% due to its unique oxygen vacancies and lattice oxygen migration rates. However, its low ethyleneyield limits its application in the CL-ODH of ethane. Mn doping promoted the reducibility of SrCoO_(3-δ) oxygen carriers,thereby improving ethane conversion and ethylene yield, as demonstrated by characterization and evaluation experiments.X-ray diffraction results confirmed the doping of Mn into the lattice of SrCoO_(3-δ), while X-ray photoelectron spectroscopy(XPS) indicated an increase in lattice oxygen ratio upon incorporation of Mn into the SrCoO_(3-δ) lattice. Additionally, H2temperature-programmed reduction (H2-TPR) tests revealed more peaks at lower temperature reduction zones and a declinein peak positions at higher temperatures. Among the four tested oxygen carriers, SrCo0.8Mn0.2O_(3-δ) exhibited satisfactoryperformance with an ethylene yield of 50% at 710 °C and good stability over 20 redox cycles. The synergistic effect of Mnplays a key role in increasing ethylene yields of SrCoO_(3-δ) oxygen carriers. Accordingly, SrCo0.8Mn0.2O_(3-δ) shows promisingpotential for the efficient production of ethylene from ethane via CL-ODH.
文摘Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for converting ethane to ethylene.In the current study MeO/LaCoO_(3)(MeO=Fe_(2)O_(3),NiO or Co_(2)O_(3))composite metal oxides were prepared via citrate gel and impregnation methods,and used as oxygen carriers for CL-ODH.X-ray diffraction results indicated that all oxygen carriers had a perovskite structure even after eight redox cycles.Under a reaction temperature of 650°C,a reaction pressure of 0.1 MPa,and a weight hourly space velocity(WHSV)of 7500 mL/(g·h),ethane conversion over Co_(2)O_(3)/LaCoO_(3) reached 100%and ethylene selectivity reached 60%,both of which were better than corresponding values attained over Fe_(2)O_(3)/LaCoO_(3) and NiO/LaCoO_(3).Ethylene selectivity remained stable for 80 cycles over Co_(2)O_(3)/LaCoO_(3),then decreased gradually after 80 cycles.X-ray photoelectron spectroscopy results and evaluation results indicated that lattice oxygen and O_(2)2-had a direct relationship with ethane conversion and ethylene selectivity.Co_(2)O_(3)/LaCoO_(3) exhibited a strong capacity to release and absorb oxygen,mainly due to interaction between Co_(2)O_(3) and LaCoO_(3).
文摘Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for ethylene preparation.Fe_(2)O_(3)/MgO oxygen carrier was prepared using the co-precipitation method.The influence of added NiO and its different loadings on Fe_(2)O_(3)/MgO were investigated.Then,a series of oxygen carriers were applied in the CL-ODH of the ethane cycle system.Brunauer-Emmett-Teller(BET),X-ray diffractometry(XRD),X-ray photoelection spectroscopy(XPS),and H2-temperature programmed reduction(TPR)were used to characterize the physicochemical properties of these oxygen carriers.It was confirmed that an interaction between NiO and Fe_(2)O_(3) occurred based on the XPS and H2-TPR results.Based on the CL-ODH activity performance tests conducted in a fixed-bed reactor,it was revealed that ethylene selectivity was significantly improved after NiO addition.Fe_(2)O_(3)-10%NiO/MgO showed the best activity performance with 93%ethane conversion and 50%ethylene selectivity at a reaction temperature of 650℃,atmospheric pressure,and space velocity of 7500 mL/(g·h).
文摘Organoboron compounds have become important intermediates for the construction of new compounds in synthetic chemistry and pharmaceutical chemistry,and it has been found that pinacol biborate(B_(2)pin_(2))as the boron source and Cu^(Ⅱ) organophosphorus complex(L)as the catalyst can effectively realize the hydrogen-reduced borylation products and dehydrohydrated borylation products of aryl olefins.The reaction regioselectivity involvingβ-C positions of aryl olefins can be controlled by regulating the ligand and additive types.The formation mechanism of the product is conducted at LCu^(Ⅰ)Bpin formed from Cu^(Ⅱ),L and B_(2)pin_(2).Subsequently the substrate aryl olefins undergo addition reaction to form the active intermediate PhCH(LCu^(Ⅰ))CH_(2)Bpin.Followed by the metathesis of the active intermediate with water to form hydrogen reduction products,the same active intermediate can be oxidized with 2,2,6,6-tetramethylpiperidoxyl(TEMPO)to form trans dehydrogenation products.
基金supported by the National Natural Science Foundation of China (21225312, U1462120, 21473206)Cheung Kong Scholars Programme of China (T2015036)~~
文摘Boron nitride containing hydroxyl groups efficiently catalysed oxidative dehydrogenation of ethane to ethylene,offering rather high selectivity（95%） but only small amount of CO2 formation（0.4%） at a given ethane conversion of 11%.Even at high conversion level of 63%,the selectivity of ethylene retained at 80%,which is competitive with the energy-demanding industrialized steam cracking route.A long-term test for 200 h resulted in stable conversion and product selectivity,showing the excellent catalytic stability.Both experimental and computational studies have identified that the hydrogen abstraction of B-OH groups by molecular oxygen dynamically generated the active sites and triggered ethane dehydrogenation.
基金The National Science Foundation of China(No.2157604921576050)the Fundamental Research Funds for the Central Universities(No.2242014K10025)
文摘A comprehensive single particle model which includes the mesoscale and microscale models was developed to study the influence of particle diameter on mass and heat transfer occurring within a ferrite catalyst during the oxidative dehydrogenation of butene to butadiene process. The verified model can be used to investigate the influence of catalyst diameter on the flow distribution inside the particle. The simulation results demonstrate that the mass fraction gradients of all species, temperature gradient and pressure gradient increase with the increase of the particle diameter. It means that there is a high intraparticle transfer resistance and strong diffusion when applying the large catalysts. The external particle mass transfer resistance is nearly constant under different particle diameters so that the effect of particle diameter at external diffusion can be ignored. A large particle diameter can lead to a high surface temperature, which indicates the external heat transfer resistance. Moreover, the selectivity of reaction may be changed with a variety of particle diameters so that choosing appropriate particle size can enhance the production of butadiene and optimize the reaction process.
文摘The oxidative dehydrogenation （ODH） reactions of ethane and propane were investigated in a catalytic membrane reactor, incorporating oxygen-permeable membranes based upon La2Ni0.9V0.1O4＋δor Ba0.5Sr0.5Co0.8Fe0.2O3-δ. As a compromise between the occurrence of a measureable oxygen flux and excessive homogenous gas phase reactions, the measurements were conducted at an intermediate temperature, either at 550 or 650 oC. The results show the dominating role of the oxygen flux across the membrane and available sites at the membrane surface in primary activation of the alkane and, hence, in achieving high alkane conversions. The experimental data of ODH of propane and ethane on both membrane materials can be reconciled on the basis of Mars-van Krevelen mechanism, in which the alkane reacts with lattice oxygen on the membrane surface to produce the corresponding olefin. It is further demonstrated that the oxygen concentration in the gas phase and on the membrane surface is crucial for determining the olefin selectivity.
基金financial support by“Grassland Talents”of Inner Mongolia Autonomous Region,Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(No.NJYT23030)Technology Breakthrough Engineering Hydrogen Energy Field"Unveiling and Leading"Project(No.2024KJTW0018)+4 种基金“Steed plan High level Talents”of Inner Mongolia University,Carbon neutralization research project(No.STZX202218)the National Natural Science Foundation of China(No.U22A20107)Inner Mongolia Autonomous Region Natural Science Foundation(No.2023MS02002)Guangdong Provincial Key Laboratory of Materials and Technologies for Energy Conversion(No.MATEC2024KF011)National Key R&D Program of China(No.2022YFA1205201).
文摘Propane dehydrogenation using CO_(2)as a mild oxidizer(CO_(2)-ODP)is a promising technology for high propylene production and CO_(2)reduction utilization.Among them,the reverse water gas shift reaction(RWGS)can change the reaction equilibrium to increase the propylene yield,and the Boudouard reaction can assist in the carbon accumulation elimination.However,the efficiency of the catalysts developed so far is limited,we introduced the Cr active component during the synthesis of porous silica spheres to form a CO_(2)-ODP catalyst,with a uniform distribution of active sites via(NH_(4))_(3)[CrMo_(6)O_(24)H_(6)]·7H_(2)O produce a derivative.As anα-type Anderson series of polyoxometalates(POMs),this six octahedral structure formed by Mo participation surrounds the central atom Cr,which is more stable in structure by electrostatic effect,its derivatives generated after calcination are stably bound to the silica-based carrier,which reduces the formation of inertα-Cr_(2)O_(3)by CrO_(x)aggregation during the catalytic process.Meanwhile,the oxygen atoms rich in polyoxometalates are more likely to form Si-O bonds with the carrier,which makes the active sites evenly and stably branched in the inner wall of the pores of mesoporous silica spheres,reduces the influence of carbon accumulation,and facilitates the activation and regeneration.The CO_(2)conversion of the catalyst CrMoO_(x)@mesoporous silica spheres(MSS)is typically greater than 20%under selected ideal conditions.This synthesis method of assembling POMs with mesoporous materials opens a new pathway for developing propane dehydrogenation catalysts.Compared to traditional impregnation synthesis,this catalyst contains a lower Cr content while achieving higher CO_(2)consumption efficiency.
文摘Ordered macroporous materials with rapid mass transport and enhanced active site accessibility are essential for achieving improved catalytic activity.In this study,boron phosphate crystals with a three-dimensionally interconnected ordered macroporous structure and a robust framework were fabricated and used as stable and selective catalysts in the oxidative dehydrogenation(ODH)of propane.Due to the improved mass diffusion and higher number of exposed active sites in the ordered macroporous structure,the catalyst exhibited a remarkable olefin productivity of^16 golefin gcat^-1 h^-1,which is up to 2–100 times higher than that of ODH catalysts reported to date.The selectivity for olefins was 91.5%(propene:82.5%,ethene:9.0%)at 515℃,with a propane conversion of 14.3%.At the same time,the selectivity for the unwanted deep-oxidized CO2 product remained less than 1.0%.The tri-coordinated surface boron species were identified as the active catalytic sites for the ODH of propane.This study provides a route for preparing a new type of metal-free catalyst with stable structure against oxidation and remarkable catalytic activity,which may represent a potential candidate to promote the industrialization of the ODH process.
基金the Center of Research Excellence in Petroleum Refining & Petrochemicals (project: CoRE-PRP-06) established by the Ministry of Higher Education at the King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia for finical support of this work
文摘The effect of rare earth oxides （RE=Ce, La, Gd, and Dy） doping of alumina support in NiO/7-A1203 system was investi- gated on its catalytic performance in oxidative dehydrogenation （ODH） of cyclohexane. The physicochemical properties of various samples were followed up through N2 physisorption, temperature programmed reduction （H2-TPR）, X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and potentiometric acid-base titration techniques. In the parent NiO/y-A1203 catalyst, Ni species were found to be strongly interacted with alumina surface. Addition of rare earth dopants to ）＇-A1203 in the catalyst system affected the nickel-alumina interaction and resulted in significant modifications in the catalytic performances in the ODH reaction. The results re- vealed the beneficial role of both La203 and Gd2Os doping in enhancing the ODH catalytic activity and selectivity to cyclohexene. H2-TPR and XPS results indicated that majority of Ni species in NiO/La203 modified T-A1203 were more weakly interacted with La203 and alumina whereas both NiO like species and nickel aluminate were present on the surface. Doping with cerium or dyspro- sium increased the nickel-support interaction and led to a decrease in surface nickel concentration. In case of doping with Ce, surface concentration of cerium oxide was higher than those of the other RE oxides; the doped catalyst reached its steady state activity faster than the other catalysts. The acid-base results suggested that RE metals were interacted most likely with acidic surface hydroxyl groups. The degree of nickel-alumina interaction decreased in the following order： LaAI〉GdAI〉CeAI〉DyA1.
基金supported by State Key Program of National Natural Science Foundation of China(21733002)Joint Sino-German Research Project(21761132011)Cheung Kong Scholars Programme of China(T2015036)。
文摘Boron-based metal-free catalysts for oxidative dehydrogenation of propane(ODHP)have drawn great attention in both academia and industry due to their impressive activity and olefin selectivity.Herein,the SiO2 and B2O3 sequentially coated honeycomb cordierite catalyst is designed by a two-step wash-coat method with different B2O3 loadings(0.1%–10%)and calcination temperatures(600,700,800℃).SiO2 obtained by TEOS hydrolysis acts as a media layer to bridge the cordierite substrate and boron oxide via abundant Si\\OH groups.The welldeveloped straight channels of honeycomb cordierite make it possible to carry out the reactor under high gas hourly space velocity(GHSV)and the thin wash-coated B2O3 layer can effectively facilitate the pore diffusion on the catalyst.The prepared B2O3/SiO2@HC monolithic catalyst exhibits good catalytic performance at low boron oxide loading and achieves excellent propylene selectivity(86.0%),olefin selectivity(97.6%,propylene and ethylene)and negligible CO2(0.1%)at 16.9%propane conversion under high GHSV of 345,600 ml·(g B2O3)^-1·h^-1,leading to a high propylene space time yield of 15.7 g C3H6·(g B2O3)^-1·h^-1 by suppressing the overoxidation.The obtained results strongly indicate that the boron-based monolithic catalyst can be properly fabricated to warrant the high activity and high throughput with its high gas/surface ratio and straight channels.
基金funded by the Deanship of Scientific Research(DSR)at King Abdulaziz University,Jeddah,under grant no.(G-1281-135-1440)DSR for technical and financial support
文摘Different mole ratio Al-B catalysts (Al-10B to Al-35B) were synthesized by using sol-gel (SG) method. Ethyl benzene (EB) dehydrogenation in the presence of oxygen and water steam was carried out on these catalysts at 450–500℃ with EB contact time of 0.54 gcat.s.cm^–3. Acidity of Al-B catalysts was estimated by using NH3-TPD-mass spectral analysis studies. SEM-mapping images revealed fine distribution of boron up to 15% of its loading in alumina (Al-15B), whereas, boron aggregation was observed in higher boron content (Al-25B and Al-35B) catalysts. Essentially, acid sites of very weak strength (Tmax ≤ 125℃) were observed for Al and Al-10B catalysts and resulted in low EB conversion and styrene yield. On the other hand, acid sites of weak strength (Tmax ≤ 180℃) were observed for Al-25B and Al-35B catalysts and resulted in high EB conversion. However, greater styrene yield (43.2%) with reasonable EB conversion (46%) was obtained on acid sites of weak moderate strength in Al-15B catalyst. Further, Al-15B catalyst was synthesized by using co-precipitation (COP) and impregnation (IMP) methods. Acid sites related to NOx formation during the NH3-TPD-mass analysis on IMP and COP catalyst essentially improved the EB conversion to 66% and 63% respectively at 500℃. However, these acid sites were diminished in Al-B SG catalyst and resulted in 50% of EB conversion at 500 ℃. At 50% of EB conversion level, styrene selectivity of 73%, 82.5% and 84% were observed on Al-B IMP, Al-B COP and Al-SG catalysts, respectively. Hence, different method of preparation of Al-B catalyst generated acid sites of different strength and density and thereby influenced the styrene formation.
基金supported by State Key Program of the National Natural Science Foundation of China(21733002)the National Natural Science Foundation of China(U1462120,21403027)Cheung Kong Scholars Programme of China(T2015036)~~
文摘Oxidative dehydrogenation of light alkanes to alkenes is an attractive alternative route for industrial direct dehydrogenation because of favorable thermodynamic and kinetic characteristics,but encounters difficulties in selectivity control for alkenes because of over-oxidation reactions that produce a substantial amount of undesired carbon oxides.Recent progress has revealed that boron nitride is a highly promising catalyst in the oxidative dehydrogenation of light alkanes because of its superior selectivity for and high productivity of light alkenes,negligible formation of CO2,and remarkable catalyst stability.From this viewpoint,recent works on boron nitride in the oxidative dehydrogenations of ethane,propane,butane,and ethylbenzene are reviewed,and the emphasis of this viewpoint is placed on discussing the catalytic origin of boron nitride in oxidative dehydrogenation reactions.After analyzing recent progress in the use of boron nitride for oxidative dehydrogenation reactions and finding much new evidence,we conclude that pure boron nitride is catalytically inert,and an activation period is required under the reaction conditions;this process is accompanied by an oxygen functionalization at the edge of boron nitride;the B-O species themselves have no catalytic activity in C-H cleavage,and the B-OH groups,with the assistance of molecular oxygen,play the key role in triggering the oxidative dehydrogenation of propane;the dissociative adsorption of molecular oxygen is involved in the reaction process;and a straightforward strategy for preparing an active boron nitride catalyst with hydroxyl groups at the edges can efficiently enhance the catalytic efficacy.A new redox reaction cycle based on the B-OH sites is also proposed.Furthermore,as this is a novel catalytic system,there is an urgent need to develop new methods to optimize the catalytic performances,clarify the catalytic function of boron species in the alkane ODH reactions,and disclose the reaction mechanism under realistic reaction conditions.
文摘The discovery of the high activity and selectivity of boron-based catalysts for oxidative dehydrogenation(ODH)of alkanes to olefins has attracted significant attention in the exploration of a new method for the synthesis of highly active and selective catalysts.Herein,we describe the synthesis of porous boron-doped silica nanofibers(PBSNs)100-150 nm in diameter by electrospinning and the study of their catalytic performance.The electrospinning synthesis of the catalyst ensures the uniform dispersion and stability of the boron species on the open silica fiber framework.The one-dimensional nanofibers with open pore structures not only prevented diffusion limitation but also guaranteed high catalytic activity at high weight hourly space velocity(WHSV)in the ODH of alkanes.Compared to other supported boron oxide catalysts,PBSN catalysts showed higher olefin selectivity and stability.The presence of Si-OH groups in silica-supported boron catalysts may cause low propylene selectivity during the ODH of propane.When the ODH conversion of ethane reached 44.3%,the selectivity and productivity of ethylene were 84%and 44.2%g_(cat)^(-1)s^(-1),respectively.In the case of propane ODH,the conversion,selectivity of olefins,and productivity of propylene are 19.2%,90%,and 76.6 jimol g_(cat)^(-1)s^(-1),respectively.No significant variations in the conversion and product selectivity occurred during 20 h of operation at a high WHSV of 84.6 h^(-1).Transient analysis and kinetic experiments indicated that the activation of O2 was influenced by alkanes during the ODH reaction.
基金supported by NSFC(21073235,21173270,21177160,21376261)863 Program(2013AA065302)PetroChina Innovation Foundation(2011D-5006-0403)
文摘Highly ordered mesoporous NiMoO4 material was successfully synthesized using mesoporous silica KIT-6 as hard template via vacuum nanocasting method. The structure was characterized by means of XRD, TEM, N2 adsorption-desorption, Raman and FT-IR. The mesoporous NiMoO4 with the coexistence of a-NiMoO4 and fl-NiMoO4 showed well-ordered mesoporous structure, a bimodal pore size distribution and crystalline framework. The catalytic performance of NiMoOa was investigated for oxidative dehydrogenation of propane. It is demonstrated that the mesoporous NiMoO4 catalyst with more surface active oxygen species showed better catalytic performance in oxidative dehydrogena- tion of propane in comparison with bulk NiMoO4.
文摘Hexagonal boron nitride(h-BN)is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes.Despite intense recent research effort,many aspects of the reaction mechanism,such as the observed supra-linear reaction order of alkanes,remain unresolved.In this work,we show that the introduction of a low concentration of propane in the feed of ethane oxidative dehydrogenation is able to enhance the C_(2)H_(6) conversion by 47%,indicating a shared reaction intermediate in the activation of ethane and propane.The higher activity of propane makes it the dominant radical generator in the oxidative co-dehydrogenation of ethane and propane(ODEP).This unique feature of the ODEP renders propane an effective probe molecule to deconvolute the two roles of alkanes in the dehydrogenation chemistry,i.e.,radical generator and substrate.Kinetic studies indicate that both the radical generation and the dehydrogenation pathways exhibit a first order kinetics toward the alkane partial pressure,leading to the observed second order kinetics of the overall oxidative dehydrogenation rate.With the steady-state approximation,a radical chain reaction mechanism capable of rationalizing observed reaction behaviors is proposed based on these insights.This work demonstrates the potential of ODEP as a strategy of both activating light alkanes in oxidative dehydrogenation on BN and mechanistic investigations.
基金supported by the National Natural Science Foundation of China (20776089)the New Century Excellent Talent Project of China(NCET-05-0783)
文摘In this work, a series of Ni-Mo-Mg-O catalysts with mesoporous structure prepared by sol-gel method were investigated for the oxidative dehydrogenation of propane （ODHP）. The techniques of temperature-programmed reduction with H2 （H2-TPR）, N2 adsorption-desolption, Fourier transform infrared spectroscopy （FT-IR）, X-ray diffraction （XRD） and X-ray photoelectron spectra （XPS） were employed for catalyst characterization. It is found that the activity of the catalysts for ODHP increases first and then decreases with the increase of Mo content. The catalyst with a Mo/Ni atomic ratio of 1/1 exhibits the best catalytic activity, which gives the propene selectivity of 81.4% at a propane conversion of 11.3% under 600 ~C and maintains the good catalytic performance for 22 h on stream. This is related not only to its high reducibility and dispersion as revealed by TPR and XRD, but also to the formation of more selective oxygen species on the MoOz-NiO interface as identified by XPS.
文摘An industrial scale propylene production via oxidative dehydrogenation of propane （ODHP） in multi-tubular re- actors was modeled. Multi-tubular fixed-bed reactor used for ODHP process, employing 10000 of small diameter tubes immersed in a shell through a proper coolant flows. Herein, a theory-based pseudo-homogeneous model to describe the operation of a fixed bed reactor for the ODHP to correspondence olefln over V2O5/γ-Al203 catalyst was presented. Steady state one dimensional model has been developed to identify the operation parameters and to describe the propane and oxygen conversions, gas process and coolant temperatures, as well as other pa- rameters affecting the reactor performance such as pressure. Furthermore, the applied model showed that a double-bed multitubular reactor with intermediate air injection scheme was superior to a single-bed design due to the increasing of propylene selectivity while operating under lower oxygen partial pressures resulting in propane conversion of about 37.3%. The optimized length of the reactor needed to reach 100% conversion of the oxygen was theoretically determined. For the single-bed reactor the optimized length of 11.96 m including 0.5 m of inert section at the entrance region and for the double-bed reactor design the optimized lengths of 5.72 m for the first and 7.32 m for the second reactor were calculated. Ultimately, the use of a distributed oxygen feed with limited number of injection points indicated a significant improvement on the reactor performance in terms of propane conversion and propylene selectivity. Besides, this concept could overcome the reactor run- away temperature problem and enabled operations at the wider range of conditions to obtain enhanced propyl- ene production in an industrial scale reactor.
