Aromatization of alkanes represents an important process in the chemical industry,traditionally relying on noble metal catalysts.Developing a non-noble metal catalyst and a relevant new process offers significant pote...Aromatization of alkanes represents an important process in the chemical industry,traditionally relying on noble metal catalysts.Developing a non-noble metal catalyst and a relevant new process offers significant potential for promoting technologic progress in this field.Herein,we present Cu-ZSM-5 zeolite as a highly effective catalyst for alkane aromatization,achieving outstanding aromatics selectivity.In-situ Fourier transform infrared spectra of adsorbed nitric oxide,high-angle annular dark field scanning transmission electron microscopy,X-ray absorption spectroscopy,and electron paramagnetic resonance analyses reveal that the Cu^(2+)species act as the primary active centers for aromatics formation.During aromatization of alkanes,the reduction of Cu^(2+)to Cu^(+)species correlates with diminished aromatics selectivity.Notably,introducing CO_(2)into the reaction feed not only enhances aromatics selectivity by maintaining Cu^(2+)species in their active oxidation state under reducing conditions,but also improves catalytic stability by eliminating coke.Furthermore,CO_(2)is converted into CO and aromatic products during the reaction,offering a novel way for CO_(2)utilization through the coupling reaction of alkane and CO_(2).展开更多
Aromatization of light alkanes is a value-added process in both petrochemical and coal chemical industries.Here,single[Ga(OH)]^(2+)ion-exchanged mesoporous hollow-structured ZSM-5(Ga-MH-ZSM-5)material was prepared,and...Aromatization of light alkanes is a value-added process in both petrochemical and coal chemical industries.Here,single[Ga(OH)]^(2+)ion-exchanged mesoporous hollow-structured ZSM-5(Ga-MH-ZSM-5)material was prepared,and it shows unprecedented catalytic performance in light alkane aromatization,considering activity,product selectivity and catalytic stability.The average aromatics yields in ethane aromatization at 600℃and WHSV of 0.8 h^(-1) within 28 h and in propane aromatization at 580℃and WHSV of 1.1 h^(-1) within 20 h reach~18.4%and~70.8%with benzene,toluene and xylenes(BTX)accounting for~96%and~88%of aromatics,respectively.Ga-MH-ZSM-5-0.41 gave a TON for formation of aromatics(TON_(aromatics))from propane as high as 57479,whereas the reported catalysts maximally show a TON_(aromatics) of 5514.This also holds true for ethane aromatization;the TON_(aromatics) obtained on Ga-MH-ZSM-5-0.41 was³3845 in contrast to£392 on reported non-noble metal catalysts.The catalytic activity of Ga-MH-ZSM-5 highly depends on Ga species structures.[Ga(OH)]^(2+)ions are predominant species at Ga loading≤0.3 wt%,while more[Ga(OH)_(2)]^(+)and GaO_(x) oligomers are formed with increasing Ga content.Upon reduction with H_(2),[Ga(OH)]^(2+)and[Ga(OH)_(2)]^(+)are transformed into[GaH]^(2+)and[GaH_(2)]^(+)species,which show a propane dehydrogenation rate of 300 and 15 times of that of Brønsted acid sites respectively.The light alkanes are mainly dehydrogenated into light olefins on[GaH]^(2+)species,and then,oligomerized and cyclized into(alkyl)cycloalkanes on H^(+)sites,which is followed by possible ring expansion on H^(+)and sequential dehydrogenations into aromatics primarily on[GaH]^(2+).展开更多
Direct converting carbon dioxide(CO_(2))and propane(C_(3)H_(8))into aromatics with high carbon utilization offers a desirable opportunity to simultaneously mitigate CO_(2)emission and adequately utilize C_(3)H_(8) in ...Direct converting carbon dioxide(CO_(2))and propane(C_(3)H_(8))into aromatics with high carbon utilization offers a desirable opportunity to simultaneously mitigate CO_(2)emission and adequately utilize C_(3)H_(8) in shale gas.Owing to their thermodynamic resistance,converting CO_(2)and C_(3)H_(8) respectively remains difficult.Here,we achieve 60.2%aromatics selectivity and 48.8%propane conversion over H-ZSM-5-25 via a zeolite-catalyzing the coupling of CO_(2)and C_(3)H_(8).Operando dual-beam FTIR spectroscopy combined with ^(13)C-labeled CO_(2)tracing experiments revealed that CO_(2)is directly involved in the generation of aromatics,with its carbon atoms selectively embedded into the aromatic ring,bypassing the reverse water-gas shift pathway.Accordingly,a cooperative aromatization mechanism is proposed.Thereinto,lactones,produced from CO_(2)and olefins,are proven to be the key intermediate.This work not only provides an opportunity for simultaneous conversion of CO_(2)and C_(3)H_(8),but also expends coupling strategy designing of CO_(2)and alkanes over acidic zeolites.展开更多
1-hexene aromatization is a promising technology to convert excess olefin in fluid catalytic cracking(FCC)gasoline to high-value benzene(B),toluene(T),and xylene.Besides,the increasing market demand of xylene has put ...1-hexene aromatization is a promising technology to convert excess olefin in fluid catalytic cracking(FCC)gasoline to high-value benzene(B),toluene(T),and xylene.Besides,the increasing market demand of xylene has put forward higher requirements for new generation of catalyst.For increasing xylene yield in 1-hexene aromatization,the effect of mesopore structure and spatial distribution on product distribution and Zn loading was studied.Catalysts with different mesopore spatial distribution were prepared by post-treatment of parent HZSM-5 zeolite,including NaOH treatment,tetra-propylammonium hydroxide(TPAOH)treatment,and recrystallization.It was found the evenly distributed mesopore mainly prolongs the catalyst lifetime by enhancing diffusion properties but reduces the aromatics selectivity,as a result of damage of micropores close to the catalyst surface.While the selectivity of high-value xylene can be highly promoted when the mesopore is mainly distributed interior the catalyst.Besides,the state of loaded Zn was also affected by mesopores spatial distribution.On the optimized catalyst,the xylene selectivity was enhanced by 12.4%compared with conventional Zn-loaded parent HZSM-5 catalyst at conversion over 99%.It was attributed to the synergy effect of mesopores spatial distribution and optimized acid properties.This work reveals the role of mesopores in different spatial positions of 1-hexene aromatization catalysts in the reaction process and the influence on metal distribution,as well as their synergistic effect two on the improvement of xylene selectivity,which can improve our understanding of catalyst pore structure and be helpful for the rational design of high-efficient catalyst.展开更多
The number of independent reactions in the methanol aromatization system using a Zn/ZSM-5 molecular sieve as a catalyst is first determined by the atomic matrix method.Then,the thermodynamic network structure of the m...The number of independent reactions in the methanol aromatization system using a Zn/ZSM-5 molecular sieve as a catalyst is first determined by the atomic matrix method.Then,the thermodynamic network structure of the methanol aromatization system is proposed based on the double-cycle mechanism and independent reaction equations.Thermodynamic analysis is performed to determine the reaction enthalpy change,equilibrium constant,and Gibbs free energy at different temperatures for each reaction.The effects of temperature and pressure on the equilibrium composition are also investigated.The results indicated that the entire system is a process that generates a considerable amount of heat.Increasing the temperature is not conducive to forming olefins,alkanes,and aromatics,except for methanol decomposition.The equilibrium composition of aromatics tends to increase and then decrease with the temperature rise.The equilibrium molar fraction of aromatics at pressures below 1.5 MPa,except benzene,increases significantly with increasing pressure.Simulation analysis of equilibrium components at varying temperatures and pressures is conducted to narrow the range for selecting the appropriate reaction temperature and pressure.展开更多
The promoting effect of introducing Zn into nano-ZSM-5 zeolites by conventional impregnation method and isomorphous substitution on the performance of 1-hexene aromatization was investigated. The nano-ZSM-5 zeolite wa...The promoting effect of introducing Zn into nano-ZSM-5 zeolites by conventional impregnation method and isomorphous substitution on the performance of 1-hexene aromatization was investigated. The nano-ZSM-5 zeolite was synthesized by a seed-induced method without organic templates. The Zn-modified nano-ZSM-5 zeolite catalysts, xZ n/HNZ5 and y Zn/Al-HNZ5, were prepared by the conventional impregnation method and isomorphous substitution, respectively. The structure, chemical composition and acidity of the catalysts were characterized by XRD, XRF, N2 adsorption, SEM, NH3-TPD and Py-IR, while the catalytic properties were evaluated at 480 °C and a weight hourly space velocity（WHSV） of 2.0 h-1 in the aromatization procedure of 1-hexene. Compared with xZ n/HNZ5, y Zn/Al-HNZ5 exhibited smaller particles and higher dispersion of Zn species, which led to greater intergranular mesopore and homogeneous acidity distribution. Experimental results indicated that the synergy effect between the Brnsted and Lewis acid sites of the isomorphously substituted nano-ZSM-5 zeolites could significantly increase aromatics yield and improve catalytic stability in the 1-hexene aromatization.展开更多
We have developed an iron（III） phthalocyanine chloride‐catalyzed oxidation–aromatization ofα,β‐unsaturated ketones with hydrazine hydrate. Various 3,5‐disubstituted 1H‐pyrazoles were obtained in good to excel...We have developed an iron（III） phthalocyanine chloride‐catalyzed oxidation–aromatization ofα,β‐unsaturated ketones with hydrazine hydrate. Various 3,5‐disubstituted 1H‐pyrazoles were obtained in good to excellent yields. This method offers several advantages, including room‐tem‐perature conditions, short reaction time, high yields, simple work‐up procedure, and use of air as an oxidant. The catalyst can be recovered and reused five times without loss of activity.展开更多
The coking kinetics and reaction-regeneration on Zn/HZSM-5 （Zn/HZ） catalyst in the conversion of methanol to aromatics were investigated. The highest initial benzene, toluene and xylene （BTX） yield of ca. 67.7% wa...The coking kinetics and reaction-regeneration on Zn/HZSM-5 （Zn/HZ） catalyst in the conversion of methanol to aromatics were investigated. The highest initial benzene, toluene and xylene （BTX） yield of ca. 67.7% was obtained on fresh Zn/HZ catalyst, which showed the worst catalytic stability. The cycle of reaction-regeneration significantly modified the texture and acidity of Zn/HZ catalyst, which in turn affected its catalytic performance and coking behavior in methanol conversion to BTX. The residual carbon located on the surface of Zn/HZ catalyst led to the decrease of acid sites and the change on the acid sites distribution, which played an important roles on its activity and deactivation. It was found that the high B/L ratio and the low total acid sites concentration of the Zn/HZ catalyst favored to the high BTX yield and good catalytic stability in methanol conversion.展开更多
Aromatization of methanol over co-impregnated La/Zn/HZSM-5 zeolite catalyst was studied.The selectivity of aromatics and BTX(benzene,toluene,and xylene)reached 64.0%and 56.6%,respectively,using La/Zn/HZSM-5 at 437...Aromatization of methanol over co-impregnated La/Zn/HZSM-5 zeolite catalyst was studied.The selectivity of aromatics and BTX(benzene,toluene,and xylene)reached 64.0%and 56.6%,respectively,using La/Zn/HZSM-5 at 437°C,0.1 MPa and methanol WHSV(weight hourly space velocity)=0.8 h-1.Catalytic results showed that the La species was a very good promoter,increased selectivity of aromatics,and prolonged the catalyst lifetime on stream.The effects of the SiO2/Al2O3 ratio in zeolite,Zn and La loading,WHSV,reaction temperature, water content in the feed and H2 pretreatment of catalysts on the catalytic performance were studied in detail. Characterizations of the catalysts by thermogravimetric analysis(TGA),NH3-TPD(temperature programmed desorption),SEM(scanning electron micrograph),N2 adsorption-desorption,XRD(X-ray diffraction)and XRF (X-ray fluorescence),were carried out to understand the structure and discuss the aromatization performance of La/Zn/HZSM-5 zeolite catalyst.展开更多
Nanosized Ga-containing ZSM-5 zeolites were prepared via isomorphous substitution and impregnation followed by characterized using various techniques. The catalytic performance of the zeolites for the aromatization of...Nanosized Ga-containing ZSM-5 zeolites were prepared via isomorphous substitution and impregnation followed by characterized using various techniques. The catalytic performance of the zeolites for the aromatization of 1-hexene was investigated. The results indicate that isomorphous substitution promotes the incorporation of Ga heteroatoms into the framework along with the formation of extra-framework GaO;species（[GaO;]a） that have stronger interactions with the negative potential of the framework. In addition, based on the Py-IR results and catalytic performance, the [GaO;]aspecies with stronger Lewis acid sites produced a better synergism with moderate Br?nsted acid sites and thus improved the selectivity to aromatic compounds. However, the impregnation results in the formation of Ga;O;phase and small amounts of GaO;species that are mainly located on the external surface（[GaO;];）, which contribute to weaker Lewis acid sites due to weaker interactions with the zeolite framework. During 1-hexene aromatization, the nanosized Ga isomorphously substituted ZSM-5 zeolite samples（Gax-NZ5） exhibited better catalytic performance compared to the impregnated samples, and the highest aromatic yield（i.e.,65.4 wt%） was achieved over the Ga4.2-NZ5 sample, which contained with the highest Ga content.展开更多
The influences of binder and molding method on the catalytic performance of methane aromatization in the absence of O2 over MoO3/ZSM-5 catalysts were investigated.SEM,NH3-TPD,FT-IR of adsorbed pyridine,N2 adsorption-d...The influences of binder and molding method on the catalytic performance of methane aromatization in the absence of O2 over MoO3/ZSM-5 catalysts were investigated.SEM,NH3-TPD,FT-IR of adsorbed pyridine,N2 adsorption-desorption,cyclohexane adsorption and XPS were employed to characterize the physical and chemical properties of the catalysts.It was found that SiO2 was a suitable binder for the catalyst due to its appropriate weak acidity.The laminar catalyst comprising of an inert spherical core and a MoO3/ZSM-5 laminar shell with 0.1 0.2 mm in thickness showed a better catalytic performance than the extruded catalyst.The improved activity of the laminar catalyst could be attributed to the easy carbonization of Mo species and the quick removal of reaction products from the catalyst surface.展开更多
Zn/ZSM-5（NZ2） and Zn/Ni/ZSM-5（NZ3） as the catalysts for methanol to aromatics（MTA） were synthesized by a simple ultrasonic impregnation. The textural and acid properties of all catalysts were characterized using...Zn/ZSM-5（NZ2） and Zn/Ni/ZSM-5（NZ3） as the catalysts for methanol to aromatics（MTA） were synthesized by a simple ultrasonic impregnation. The textural and acid properties of all catalysts were characterized using XRD, HRTEM, NH;-TPD, Py-IR, XPS, XRF and TG techniques. The XRD and HRTEM results showed that the basic zeolite structures were not affected much with the incorporation of Zn and Ni species. However, great changes have taken place in acid properties. The Py-IR and XPS results indicated that the Zn-Lewis acid sites（ZnOH;species）, which have stronger interaction with the zeolite framework compared with ZnO species, were generated at the expense of B acid sites with the incorporation of zinc species. Moreover, the product analysis results showed that the incorporation of zinc species promoted the primary aromatization by enhancing the dehydroaromatization and suppressing the cracking and subsequent H-transfer reaction. Furthermore, the addition of Ni species well inhibited the loss of zinc species by converting partial ZnO species to ZnOH;species, and thus improved the aromatization activity and catalyst stability. The catalytic performance results showed that the NZ3 possess higher conversion of methanol in a longer time and lower average rate of coke formation compared with NZ2. In addition,the NZ3 also exhibited the highest yield of BTX as the reaction proceeds.展开更多
Platinum(Pt)supported on Zinc(Zn)modified silicalite-1(S-1)zeolite(denoted as Pt-Zn/S-1)was prepared by using a wetness-impregnation method and applied in the n-hexane aromatization reaction for the first time.Both Le...Platinum(Pt)supported on Zinc(Zn)modified silicalite-1(S-1)zeolite(denoted as Pt-Zn/S-1)was prepared by using a wetness-impregnation method and applied in the n-hexane aromatization reaction for the first time.Both Lewis and Bronsted acid sites were detected in Pt-Zn/S-1 catalyst by means of FT-IR adsorption of NH3 experiment,which were identified as mostly weak and medium ones.Besides,Pt and Zn species showed strong interaction,as revealed by the TPR(Temperature-programmed reduction)and XPS(X-ray photoelectron spectroscopy)experiments.Pt-Zn/S-1 catalyst exhibited excellent aromatization function rather than isomerization and cracking side reactions in the conversion of n-hexane.Pulse experimental study showed that 75.6%of n-hexane conversion and 76.8%of benzene selectivity were obtained over Pt0.1-Zn60/S-l catalyst at 550℃ and under atmospheric pressure.By spectroscopy tests and pulse experimental results,it was concluded that the n-hexane aromatization over Pt-Zn/S-1 catalyst follows a metal-acid bifunctional mechanism.Furthermore,with the assistance of Zn,the electron-deficient Pt species in Pt-Zn/S-1 showed good sulfur tolerance performance.展开更多
The non-oxidative aromatization of mixed CH4 with C3H8 over La-promoted Zn/HZSM-5 catalysts was studied in a fixed-bed reactor at 823 K with space velocity 600 h^-1 and CH4/C3H8 （mol ratio）=5：l. The propane convers...The non-oxidative aromatization of mixed CH4 with C3H8 over La-promoted Zn/HZSM-5 catalysts was studied in a fixed-bed reactor at 823 K with space velocity 600 h^-1 and CH4/C3H8 （mol ratio）=5：l. The propane conversion and the aromatic selectivities were up to 99% and 60% over the catalyst respectively, while methane conversion had an induction period with the highest conversion of 30%. The structure and surface acidity of the catalysts were characterized by XRD, NH3-TPD and TG-DTA. The influences of reaction and regenerative conditions on the activity and selectivity were also investigated.展开更多
The Pd-promoted Ga/HZSM-5 catalyst was prepared by impregnation method and its catalytic activity for non-oxidative aromatization of C1 to C3 hydrocarbons was assessed using a microreactor-GC system operated with temp...The Pd-promoted Ga/HZSM-5 catalyst was prepared by impregnation method and its catalytic activity for non-oxidative aromatization of C1 to C3 hydrocarbons was assessed using a microreactor-GC system operated with temperature at 823 K and space velocity at 410 h-1. The catalyst is more catalytically active for methane conversion than Ga/HZSM-5. The mass spectroscopy analyses confirmed that 13CH4 was converted to aromatic products.展开更多
1,3,5-Trisubstituted pyrazolines are rapidly and conveniently oxidized to their corresponding pyrazoles by 1,3-dichloro-5,5- dimethylhydantoin（DCH） in solution and solvent-free conditions under microwave irradiation...1,3,5-Trisubstituted pyrazolines are rapidly and conveniently oxidized to their corresponding pyrazoles by 1,3-dichloro-5,5- dimethylhydantoin（DCH） in solution and solvent-free conditions under microwave irradiation.The presence of silica gel as a supporting agent is shown to be effective in reducing the reaction times and increasing the yields.展开更多
In this work, nickel metal supported on different supports(SiO_2, Al_2O_3, ZSM-5) were prepared by spraying nickel nitrate on the supports and calcined at 873 K. Then, they were characterized by XRD, XRF, N_2 adsorpt...In this work, nickel metal supported on different supports(SiO_2, Al_2O_3, ZSM-5) were prepared by spraying nickel nitrate on the supports and calcined at 873 K. Then, they were characterized by XRD, XRF, N_2 adsorption–desorption, NH_3-TPD, MCH-TPD, H_2-TPR, and pyridine-FTIR,and tested as catalysts for the dehydrogenation aromatization and isomerization of methylcyclohexane(MCH) under the conditions of S-Zorb catalytic adsorption desulfurization(T ? 673 K, P ? 1.5 MPa, WHSV ? 5 h^(-1)). The H2-TPR results showed that the interaction of NiO with support decreased in the order of NiO/ZSM-5-Fe < NiO/ZSM-5 < NiO/Al_2O_3< NiO/SiO2. The decrease of the interaction appeared to facilitate the reduction of Ni and therefore to promote the dehydrogenation aromatization of MCH.It was found that a direct correlation existed between the gasoline components yields, cracking activity and the total number of different supports acid sites measured by NH_3-TPD tests. Higher total acidity of ZSM-5 resulted in gasoline loss because of higher cracking activity of MCH. The number of total acid sites of NiO/ZSM-5-Fe decreased and the medium strong Br€onsted acid sites necessary for MCH isomerization increased after the modification of ZSM-5 by iron metal. So, NiO/ZSM-5-Fe exhibited enhanced MCH conversion, aromatic and isomerization yields when compared to NiO/ZSM-5 and other Ni-based catalysts. This study shows that NiO/ZSM-5-Fe catalyst may be possible to be integrated into the S-Zorb system achieving the recovery of the octane number of gasoline.展开更多
In this article, transition metals of Cu, La and Zn were used as adjuvant to prepare modified HZSM-5 by impregnation method. The catalysts were characterized by XRD, BET, NH_3-TPD and Py-IR to reveal the microstructur...In this article, transition metals of Cu, La and Zn were used as adjuvant to prepare modified HZSM-5 by impregnation method. The catalysts were characterized by XRD, BET, NH_3-TPD and Py-IR to reveal the microstructure and acid property. The catalysis performances of methanol aromatization of catalysts were investigated in a fixed-bed reactor. The results show that the strength and distribution of acid center of these catalysts are significantly influenced by the species of transition metal. There are more mediate strong Lewis acid center in Zn modified HZSM-5 catalyst and therefore exhibits higher selectivity to aromatic, benzene, toluene and xylenes in the MTA reaction..展开更多
The aromatization of light alkenes in liquefied petroleum gas (LPG) with and without dimethyl ether (DME) addition in the feed was investigated on a modified ZSM-5 catalyst.The results showed that under the given reac...The aromatization of light alkenes in liquefied petroleum gas (LPG) with and without dimethyl ether (DME) addition in the feed was investigated on a modified ZSM-5 catalyst.The results showed that under the given reaction conditions the selectivity of alkenes to high-octane gasoline blending components was markedly enhanced and the formation of propane and butanes was greatly suppressed with the addition of DME.It was also found that the distribution of C5+ components was changed a lot with DME addition into the LPG feed.The formation of branched hydrocarbons (mainly C6 C8 i-paraffin) and multi-methyl substituted aromatics,which are high octane number gasoline blending components,was promoted significantly,while the content of n-paraffins and olefins in C5+ components was decreased obviously,indicating that in addition to the oligomerization,cracking,hydrogen-transfer and dehydrogenation-cyclization of alkenes,the methylation of the formed aromatics and olefins intermediates also plays an important role in determining the product distribution due to the high reactivity of surface methoxy groups formed by DME.And this process,in combination with the syngas-to-methanol/DME technology,provides an alternative way to the production of high-octane gasoline from coal,natural gas or renewable raw materials.展开更多
The influence of adding Fe, Cr, Co, and Ga into 3%Mo/HZSM-5 catalyst on methane aromatization, and the influence of additives ratio on methane conversion, selectivity to hydrocarbons and coke, as well as distribution ...The influence of adding Fe, Cr, Co, and Ga into 3%Mo/HZSM-5 catalyst on methane aromatization, and the influence of additives ratio on methane conversion, selectivity to hydrocarbons and coke, as well as distribution of aromatics were investigated. The experimental results showed that the addition of Fe, Cr, Co and Ga promoted the dehydrogenation and dissociation of methane. The results of NH3-TPD indicated that the acidity of HZSM-5 was changed by adding Fe and Co components, consequently the catalytic properties of Mo/HZSM-5 were changed. It was also revealed that strong acid sites were the center of methane aromatization. The results of XRD characterization showed that the crystallinity of Mo on ZSM-5 zeolite was increased after adding Fe, Co additives.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.22288101,22472016)the National Key Research and Development Program of the Ministry of Science and Technology(No.2022YFE0116000)+1 种基金the Chinese Academy of Sciences Strategy Leading Technology Project(No.XDA29000000)the Youth Innovation Promotion Association CAS(No.2021182)。
文摘Aromatization of alkanes represents an important process in the chemical industry,traditionally relying on noble metal catalysts.Developing a non-noble metal catalyst and a relevant new process offers significant potential for promoting technologic progress in this field.Herein,we present Cu-ZSM-5 zeolite as a highly effective catalyst for alkane aromatization,achieving outstanding aromatics selectivity.In-situ Fourier transform infrared spectra of adsorbed nitric oxide,high-angle annular dark field scanning transmission electron microscopy,X-ray absorption spectroscopy,and electron paramagnetic resonance analyses reveal that the Cu^(2+)species act as the primary active centers for aromatics formation.During aromatization of alkanes,the reduction of Cu^(2+)to Cu^(+)species correlates with diminished aromatics selectivity.Notably,introducing CO_(2)into the reaction feed not only enhances aromatics selectivity by maintaining Cu^(2+)species in their active oxidation state under reducing conditions,but also improves catalytic stability by eliminating coke.Furthermore,CO_(2)is converted into CO and aromatic products during the reaction,offering a novel way for CO_(2)utilization through the coupling reaction of alkane and CO_(2).
文摘Aromatization of light alkanes is a value-added process in both petrochemical and coal chemical industries.Here,single[Ga(OH)]^(2+)ion-exchanged mesoporous hollow-structured ZSM-5(Ga-MH-ZSM-5)material was prepared,and it shows unprecedented catalytic performance in light alkane aromatization,considering activity,product selectivity and catalytic stability.The average aromatics yields in ethane aromatization at 600℃and WHSV of 0.8 h^(-1) within 28 h and in propane aromatization at 580℃and WHSV of 1.1 h^(-1) within 20 h reach~18.4%and~70.8%with benzene,toluene and xylenes(BTX)accounting for~96%and~88%of aromatics,respectively.Ga-MH-ZSM-5-0.41 gave a TON for formation of aromatics(TON_(aromatics))from propane as high as 57479,whereas the reported catalysts maximally show a TON_(aromatics) of 5514.This also holds true for ethane aromatization;the TON_(aromatics) obtained on Ga-MH-ZSM-5-0.41 was³3845 in contrast to£392 on reported non-noble metal catalysts.The catalytic activity of Ga-MH-ZSM-5 highly depends on Ga species structures.[Ga(OH)]^(2+)ions are predominant species at Ga loading≤0.3 wt%,while more[Ga(OH)_(2)]^(+)and GaO_(x) oligomers are formed with increasing Ga content.Upon reduction with H_(2),[Ga(OH)]^(2+)and[Ga(OH)_(2)]^(+)are transformed into[GaH]^(2+)and[GaH_(2)]^(+)species,which show a propane dehydrogenation rate of 300 and 15 times of that of Brønsted acid sites respectively.The light alkanes are mainly dehydrogenated into light olefins on[GaH]^(2+)species,and then,oligomerized and cyclized into(alkyl)cycloalkanes on H^(+)sites,which is followed by possible ring expansion on H^(+)and sequential dehydrogenations into aromatics primarily on[GaH]^(2+).
文摘Direct converting carbon dioxide(CO_(2))and propane(C_(3)H_(8))into aromatics with high carbon utilization offers a desirable opportunity to simultaneously mitigate CO_(2)emission and adequately utilize C_(3)H_(8) in shale gas.Owing to their thermodynamic resistance,converting CO_(2)and C_(3)H_(8) respectively remains difficult.Here,we achieve 60.2%aromatics selectivity and 48.8%propane conversion over H-ZSM-5-25 via a zeolite-catalyzing the coupling of CO_(2)and C_(3)H_(8).Operando dual-beam FTIR spectroscopy combined with ^(13)C-labeled CO_(2)tracing experiments revealed that CO_(2)is directly involved in the generation of aromatics,with its carbon atoms selectively embedded into the aromatic ring,bypassing the reverse water-gas shift pathway.Accordingly,a cooperative aromatization mechanism is proposed.Thereinto,lactones,produced from CO_(2)and olefins,are proven to be the key intermediate.This work not only provides an opportunity for simultaneous conversion of CO_(2)and C_(3)H_(8),but also expends coupling strategy designing of CO_(2)and alkanes over acidic zeolites.
基金supported by National Natural Science Foundation of China(22021004).
文摘1-hexene aromatization is a promising technology to convert excess olefin in fluid catalytic cracking(FCC)gasoline to high-value benzene(B),toluene(T),and xylene.Besides,the increasing market demand of xylene has put forward higher requirements for new generation of catalyst.For increasing xylene yield in 1-hexene aromatization,the effect of mesopore structure and spatial distribution on product distribution and Zn loading was studied.Catalysts with different mesopore spatial distribution were prepared by post-treatment of parent HZSM-5 zeolite,including NaOH treatment,tetra-propylammonium hydroxide(TPAOH)treatment,and recrystallization.It was found the evenly distributed mesopore mainly prolongs the catalyst lifetime by enhancing diffusion properties but reduces the aromatics selectivity,as a result of damage of micropores close to the catalyst surface.While the selectivity of high-value xylene can be highly promoted when the mesopore is mainly distributed interior the catalyst.Besides,the state of loaded Zn was also affected by mesopores spatial distribution.On the optimized catalyst,the xylene selectivity was enhanced by 12.4%compared with conventional Zn-loaded parent HZSM-5 catalyst at conversion over 99%.It was attributed to the synergy effect of mesopores spatial distribution and optimized acid properties.This work reveals the role of mesopores in different spatial positions of 1-hexene aromatization catalysts in the reaction process and the influence on metal distribution,as well as their synergistic effect two on the improvement of xylene selectivity,which can improve our understanding of catalyst pore structure and be helpful for the rational design of high-efficient catalyst.
基金financially supported by the National Key R&D Program of China(2018YFB0604802).
文摘The number of independent reactions in the methanol aromatization system using a Zn/ZSM-5 molecular sieve as a catalyst is first determined by the atomic matrix method.Then,the thermodynamic network structure of the methanol aromatization system is proposed based on the double-cycle mechanism and independent reaction equations.Thermodynamic analysis is performed to determine the reaction enthalpy change,equilibrium constant,and Gibbs free energy at different temperatures for each reaction.The effects of temperature and pressure on the equilibrium composition are also investigated.The results indicated that the entire system is a process that generates a considerable amount of heat.Increasing the temperature is not conducive to forming olefins,alkanes,and aromatics,except for methanol decomposition.The equilibrium composition of aromatics tends to increase and then decrease with the temperature rise.The equilibrium molar fraction of aromatics at pressures below 1.5 MPa,except benzene,increases significantly with increasing pressure.Simulation analysis of equilibrium components at varying temperatures and pressures is conducted to narrow the range for selecting the appropriate reaction temperature and pressure.
基金Project(21276067)supported by the National Natural Science Foundation of China
文摘The promoting effect of introducing Zn into nano-ZSM-5 zeolites by conventional impregnation method and isomorphous substitution on the performance of 1-hexene aromatization was investigated. The nano-ZSM-5 zeolite was synthesized by a seed-induced method without organic templates. The Zn-modified nano-ZSM-5 zeolite catalysts, xZ n/HNZ5 and y Zn/Al-HNZ5, were prepared by the conventional impregnation method and isomorphous substitution, respectively. The structure, chemical composition and acidity of the catalysts were characterized by XRD, XRF, N2 adsorption, SEM, NH3-TPD and Py-IR, while the catalytic properties were evaluated at 480 °C and a weight hourly space velocity（WHSV） of 2.0 h-1 in the aromatization procedure of 1-hexene. Compared with xZ n/HNZ5, y Zn/Al-HNZ5 exhibited smaller particles and higher dispersion of Zn species, which led to greater intergranular mesopore and homogeneous acidity distribution. Experimental results indicated that the synergy effect between the Brnsted and Lewis acid sites of the isomorphously substituted nano-ZSM-5 zeolites could significantly increase aromatics yield and improve catalytic stability in the 1-hexene aromatization.
基金supported by the Industrial Research Project of Shaanxi Science and Technology Department(2014K08-29)Science and Technology Plan Project of Xi’an(CXY1511(7))Scientific Research Foundation of Northwest University~~
文摘We have developed an iron（III） phthalocyanine chloride‐catalyzed oxidation–aromatization ofα,β‐unsaturated ketones with hydrazine hydrate. Various 3,5‐disubstituted 1H‐pyrazoles were obtained in good to excellent yields. This method offers several advantages, including room‐tem‐perature conditions, short reaction time, high yields, simple work‐up procedure, and use of air as an oxidant. The catalyst can be recovered and reused five times without loss of activity.
基金supported by the National Ministry of Education(NCET-10-878)Shaanxi"13115"Innovation Project(2009ZDKJ-70)Shaanxi Key Innovation Project(2011ZKC4-08)
文摘The coking kinetics and reaction-regeneration on Zn/HZSM-5 （Zn/HZ） catalyst in the conversion of methanol to aromatics were investigated. The highest initial benzene, toluene and xylene （BTX） yield of ca. 67.7% was obtained on fresh Zn/HZ catalyst, which showed the worst catalytic stability. The cycle of reaction-regeneration significantly modified the texture and acidity of Zn/HZ catalyst, which in turn affected its catalytic performance and coking behavior in methanol conversion to BTX. The residual carbon located on the surface of Zn/HZ catalyst led to the decrease of acid sites and the change on the acid sites distribution, which played an important roles on its activity and deactivation. It was found that the high B/L ratio and the low total acid sites concentration of the Zn/HZ catalyst favored to the high BTX yield and good catalytic stability in methanol conversion.
基金Supported by the Fundamental Research Funds for the Central Universities,HUST(Z2009008)the National Natural Science Foundation of China(20973068)
文摘Aromatization of methanol over co-impregnated La/Zn/HZSM-5 zeolite catalyst was studied.The selectivity of aromatics and BTX(benzene,toluene,and xylene)reached 64.0%and 56.6%,respectively,using La/Zn/HZSM-5 at 437°C,0.1 MPa and methanol WHSV(weight hourly space velocity)=0.8 h-1.Catalytic results showed that the La species was a very good promoter,increased selectivity of aromatics,and prolonged the catalyst lifetime on stream.The effects of the SiO2/Al2O3 ratio in zeolite,Zn and La loading,WHSV,reaction temperature, water content in the feed and H2 pretreatment of catalysts on the catalytic performance were studied in detail. Characterizations of the catalysts by thermogravimetric analysis(TGA),NH3-TPD(temperature programmed desorption),SEM(scanning electron micrograph),N2 adsorption-desorption,XRD(X-ray diffraction)and XRF (X-ray fluorescence),were carried out to understand the structure and discuss the aromatization performance of La/Zn/HZSM-5 zeolite catalyst.
基金supported by the National Natural Science Foundation of China(Nos.21276067 and 21676074)Programs of International S&T cooperation(No.2014DFR41110)
文摘Nanosized Ga-containing ZSM-5 zeolites were prepared via isomorphous substitution and impregnation followed by characterized using various techniques. The catalytic performance of the zeolites for the aromatization of 1-hexene was investigated. The results indicate that isomorphous substitution promotes the incorporation of Ga heteroatoms into the framework along with the formation of extra-framework GaO;species（[GaO;]a） that have stronger interactions with the negative potential of the framework. In addition, based on the Py-IR results and catalytic performance, the [GaO;]aspecies with stronger Lewis acid sites produced a better synergism with moderate Br?nsted acid sites and thus improved the selectivity to aromatic compounds. However, the impregnation results in the formation of Ga;O;phase and small amounts of GaO;species that are mainly located on the external surface（[GaO;];）, which contribute to weaker Lewis acid sites due to weaker interactions with the zeolite framework. During 1-hexene aromatization, the nanosized Ga isomorphously substituted ZSM-5 zeolite samples（Gax-NZ5） exhibited better catalytic performance compared to the impregnated samples, and the highest aromatic yield（i.e.,65.4 wt%） was achieved over the Ga4.2-NZ5 sample, which contained with the highest Ga content.
基金supported by the National Basic Research Program of China(Grant 2005CB 221405)
文摘The influences of binder and molding method on the catalytic performance of methane aromatization in the absence of O2 over MoO3/ZSM-5 catalysts were investigated.SEM,NH3-TPD,FT-IR of adsorbed pyridine,N2 adsorption-desorption,cyclohexane adsorption and XPS were employed to characterize the physical and chemical properties of the catalysts.It was found that SiO2 was a suitable binder for the catalyst due to its appropriate weak acidity.The laminar catalyst comprising of an inert spherical core and a MoO3/ZSM-5 laminar shell with 0.1 0.2 mm in thickness showed a better catalytic performance than the extruded catalyst.The improved activity of the laminar catalyst could be attributed to the easy carbonization of Mo species and the quick removal of reaction products from the catalyst surface.
基金entrusted by the Project of "utilization of low rank coal" strategic leading special fundstrategic leading special fund of CAS (XDA-07070800 and XDA-07070400)the Opening Foundation of State Key Laboratory of Coal Conversion (J16-17-602)
文摘Zn/ZSM-5（NZ2） and Zn/Ni/ZSM-5（NZ3） as the catalysts for methanol to aromatics（MTA） were synthesized by a simple ultrasonic impregnation. The textural and acid properties of all catalysts were characterized using XRD, HRTEM, NH;-TPD, Py-IR, XPS, XRF and TG techniques. The XRD and HRTEM results showed that the basic zeolite structures were not affected much with the incorporation of Zn and Ni species. However, great changes have taken place in acid properties. The Py-IR and XPS results indicated that the Zn-Lewis acid sites（ZnOH;species）, which have stronger interaction with the zeolite framework compared with ZnO species, were generated at the expense of B acid sites with the incorporation of zinc species. Moreover, the product analysis results showed that the incorporation of zinc species promoted the primary aromatization by enhancing the dehydroaromatization and suppressing the cracking and subsequent H-transfer reaction. Furthermore, the addition of Ni species well inhibited the loss of zinc species by converting partial ZnO species to ZnOH;species, and thus improved the aromatization activity and catalyst stability. The catalytic performance results showed that the NZ3 possess higher conversion of methanol in a longer time and lower average rate of coke formation compared with NZ2. In addition,the NZ3 also exhibited the highest yield of BTX as the reaction proceeds.
基金financially supported by the National Natural Science Foundation of China (21603023)
文摘Platinum(Pt)supported on Zinc(Zn)modified silicalite-1(S-1)zeolite(denoted as Pt-Zn/S-1)was prepared by using a wetness-impregnation method and applied in the n-hexane aromatization reaction for the first time.Both Lewis and Bronsted acid sites were detected in Pt-Zn/S-1 catalyst by means of FT-IR adsorption of NH3 experiment,which were identified as mostly weak and medium ones.Besides,Pt and Zn species showed strong interaction,as revealed by the TPR(Temperature-programmed reduction)and XPS(X-ray photoelectron spectroscopy)experiments.Pt-Zn/S-1 catalyst exhibited excellent aromatization function rather than isomerization and cracking side reactions in the conversion of n-hexane.Pulse experimental study showed that 75.6%of n-hexane conversion and 76.8%of benzene selectivity were obtained over Pt0.1-Zn60/S-l catalyst at 550℃ and under atmospheric pressure.By spectroscopy tests and pulse experimental results,it was concluded that the n-hexane aromatization over Pt-Zn/S-1 catalyst follows a metal-acid bifunctional mechanism.Furthermore,with the assistance of Zn,the electron-deficient Pt species in Pt-Zn/S-1 showed good sulfur tolerance performance.
基金This work is supported by the National Science Foundation of China (Grant Nos 20343002 20433030) and PetroChina.
文摘The non-oxidative aromatization of mixed CH4 with C3H8 over La-promoted Zn/HZSM-5 catalysts was studied in a fixed-bed reactor at 823 K with space velocity 600 h^-1 and CH4/C3H8 （mol ratio）=5：l. The propane conversion and the aromatic selectivities were up to 99% and 60% over the catalyst respectively, while methane conversion had an induction period with the highest conversion of 30%. The structure and surface acidity of the catalysts were characterized by XRD, NH3-TPD and TG-DTA. The influences of reaction and regenerative conditions on the activity and selectivity were also investigated.
基金the National Natural Science Foundation of China （No. 20343002, 20433030） from PetroChina are gratefully acknowledged.
文摘The Pd-promoted Ga/HZSM-5 catalyst was prepared by impregnation method and its catalytic activity for non-oxidative aromatization of C1 to C3 hydrocarbons was assessed using a microreactor-GC system operated with temperature at 823 K and space velocity at 410 h-1. The catalyst is more catalytically active for methane conversion than Ga/HZSM-5. The mass spectroscopy analyses confirmed that 13CH4 was converted to aromatic products.
文摘1,3,5-Trisubstituted pyrazolines are rapidly and conveniently oxidized to their corresponding pyrazoles by 1,3-dichloro-5,5- dimethylhydantoin（DCH） in solution and solvent-free conditions under microwave irradiation.The presence of silica gel as a supporting agent is shown to be effective in reducing the reaction times and increasing the yields.
基金financial support from the National Natural Science Foundation of China(21433001,21406251 and 21403265)Science and Technology Development Projects of SINOPEC,China(No.113138,112008 and 110099)The Young Taishan Scholars Program of Shandong Province(tsqn20161052)
文摘In this work, nickel metal supported on different supports(SiO_2, Al_2O_3, ZSM-5) were prepared by spraying nickel nitrate on the supports and calcined at 873 K. Then, they were characterized by XRD, XRF, N_2 adsorption–desorption, NH_3-TPD, MCH-TPD, H_2-TPR, and pyridine-FTIR,and tested as catalysts for the dehydrogenation aromatization and isomerization of methylcyclohexane(MCH) under the conditions of S-Zorb catalytic adsorption desulfurization(T ? 673 K, P ? 1.5 MPa, WHSV ? 5 h^(-1)). The H2-TPR results showed that the interaction of NiO with support decreased in the order of NiO/ZSM-5-Fe < NiO/ZSM-5 < NiO/Al_2O_3< NiO/SiO2. The decrease of the interaction appeared to facilitate the reduction of Ni and therefore to promote the dehydrogenation aromatization of MCH.It was found that a direct correlation existed between the gasoline components yields, cracking activity and the total number of different supports acid sites measured by NH_3-TPD tests. Higher total acidity of ZSM-5 resulted in gasoline loss because of higher cracking activity of MCH. The number of total acid sites of NiO/ZSM-5-Fe decreased and the medium strong Br€onsted acid sites necessary for MCH isomerization increased after the modification of ZSM-5 by iron metal. So, NiO/ZSM-5-Fe exhibited enhanced MCH conversion, aromatic and isomerization yields when compared to NiO/ZSM-5 and other Ni-based catalysts. This study shows that NiO/ZSM-5-Fe catalyst may be possible to be integrated into the S-Zorb system achieving the recovery of the octane number of gasoline.
基金Supported by the Key Technology and Demonstration on Low Rank Coal Clean,Efficient and Cascade Application ProjectSynthesis Technology of Coal-based Bulk Chemical and FuelResearch on Key Technology of Methanol to Aromatics(MTA)(XDA07070800)
文摘In this article, transition metals of Cu, La and Zn were used as adjuvant to prepare modified HZSM-5 by impregnation method. The catalysts were characterized by XRD, BET, NH_3-TPD and Py-IR to reveal the microstructure and acid property. The catalysis performances of methanol aromatization of catalysts were investigated in a fixed-bed reactor. The results show that the strength and distribution of acid center of these catalysts are significantly influenced by the species of transition metal. There are more mediate strong Lewis acid center in Zn modified HZSM-5 catalyst and therefore exhibits higher selectivity to aromatic, benzene, toluene and xylenes in the MTA reaction..
基金supported by the "Action Plan of CAS to Support China’s New and Strategic Industries with Science and Technology(2012-2014)"the "Knowledge Innovation Program of the Chinese Academy of Sciences(S201041)""Youth Innovation Promotion Association CAS(2012-2015)"
文摘The aromatization of light alkenes in liquefied petroleum gas (LPG) with and without dimethyl ether (DME) addition in the feed was investigated on a modified ZSM-5 catalyst.The results showed that under the given reaction conditions the selectivity of alkenes to high-octane gasoline blending components was markedly enhanced and the formation of propane and butanes was greatly suppressed with the addition of DME.It was also found that the distribution of C5+ components was changed a lot with DME addition into the LPG feed.The formation of branched hydrocarbons (mainly C6 C8 i-paraffin) and multi-methyl substituted aromatics,which are high octane number gasoline blending components,was promoted significantly,while the content of n-paraffins and olefins in C5+ components was decreased obviously,indicating that in addition to the oligomerization,cracking,hydrogen-transfer and dehydrogenation-cyclization of alkenes,the methylation of the formed aromatics and olefins intermediates also plays an important role in determining the product distribution due to the high reactivity of surface methoxy groups formed by DME.And this process,in combination with the syngas-to-methanol/DME technology,provides an alternative way to the production of high-octane gasoline from coal,natural gas or renewable raw materials.
文摘The influence of adding Fe, Cr, Co, and Ga into 3%Mo/HZSM-5 catalyst on methane aromatization, and the influence of additives ratio on methane conversion, selectivity to hydrocarbons and coke, as well as distribution of aromatics were investigated. The experimental results showed that the addition of Fe, Cr, Co and Ga promoted the dehydrogenation and dissociation of methane. The results of NH3-TPD indicated that the acidity of HZSM-5 was changed by adding Fe and Co components, consequently the catalytic properties of Mo/HZSM-5 were changed. It was also revealed that strong acid sites were the center of methane aromatization. The results of XRD characterization showed that the crystallinity of Mo on ZSM-5 zeolite was increased after adding Fe, Co additives.
