Light olefins is the incredibly important materials in chemical industry.Methanol to olefins(MTO),which provides a non-oil route for light olefins production,received considerable attention in the past decades.However...Light olefins is the incredibly important materials in chemical industry.Methanol to olefins(MTO),which provides a non-oil route for light olefins production,received considerable attention in the past decades.However,the catalyst deactivation is an inevitable feature in MTO processes,and regeneration,therefore,is one of the key steps in industrial MTO processes.Traditionally the MTO catalyst is regenerated by removing the deposited coke via air combustion,which unavoidably transforms coke into carbon dioxide and reduces the carbon utilization efficiency.Recent study shows that the coke species over MTO catalyst can be regenerated via steam,which can promote the light olefins yield as the deactivated coke species can be essentially transferred to industrially useful synthesis gas,is a promising pathway for further MTO processes development.In this work,we modelled and analyzed these two MTO regeneration methods in terms of carbon utilization efficiency and technology economics.As shown,the steam regeneration could achieve a carbon utilization efficiency of 84.31%,compared to 74.74%for air combustion regeneration.The MTO processes using steam regeneration can essentially achieve the near-zero carbon emission.In addition,light olefins production of the MTO processes using steam regeneration is 12.81%higher than that using air combustion regeneration.In this regard,steam regeneration could be considered as a potential yet promising regeneration method for further MTO processes,showing not only great environmental benefits but also competitive economic performance.展开更多
CO_(2)hydrogenation has been considered to be a highly promising route for the production of high-value olefins(HVOs)while also mitigating CO_(2)emissions.However,it is challenging to achieve high selectivity and main...CO_(2)hydrogenation has been considered to be a highly promising route for the production of high-value olefins(HVOs)while also mitigating CO_(2)emissions.However,it is challenging to achieve high selectivity and maintain stable performance for HVOs(ethylene,propylene,and linear a-olefins)over a prolonged reaction time due to the difficulty in precise control of carbon coupling and rapid catalyst deactivation.Herein,we present a selective Ba and Na co-modified Fe catalyst enriched with Fe_(5)C_(2)and Fe_(3)C active sites that can boost HVO synthesis with up to 66.1%selectivity at an average CO_(2)conversion of 38%for over 500 h.Compared to traditional NaFe catalyst,the combined effect of Ba and Na additives in the NaBaFe-0.5 catalyst suppressed excess oxidation of FeCxsites by H_(2)O.The absence of Fe3O4phase in the spent NaBaFe-0.5 catalyst reflects the stabilization effect of the co-modifiers on the FeCxsites.This study provides a strategy to design Fe-based catalysts that can be scaled up for the stable synthesis of HVOs from CO_(2)hydrogenation.展开更多
To produce low olefin gasoline with high octane number by Fischer-Tropsch (F-T) wax fluid catalytic cracking (FCC) process, operating conditions optimization were carried out in the pilot-scale riser and turbulent flu...To produce low olefin gasoline with high octane number by Fischer-Tropsch (F-T) wax fluid catalytic cracking (FCC) process, operating conditions optimization were carried out in the pilot-scale riser and turbulent fluidized bed (TFB) FCC unit. The experimental results in the riser indicated that under the condition of low reaction temperature and regenerated catalyst temperature, large catalyst-to-oil weight ratio (C/O) and long reaction time, the gasoline olefin content could be reduced to 20.28 wt%, but there is large octane number loss owing to a great loss in high octane number olefin. Therefore, a novel FCC process using the TFB reactor was proposed to strengthen the aromatization reaction. The reaction performance of TFB reactor were investigated. The result demonstrated that the TFB reactor has more significant effect in reducing olefins and improving aromatics. At the expense of certain gasoline yield, the gasoline olefin content reduced to 23.70 wt%, aromatics content could increase to 26.79 wt% and the RON was up to 91.0. The comparison of reactor structure and fluidization demonstrated that the TFB reactor has higher catalyst bed density. The reaction heat and coke combustion heat was calculated indicating the feasibility of its industrial application of the TFB process.展开更多
When converting C_(5) hydrocarbons to light olefins by catalytic pyrolysis,the generation of low value-added methane will affect the atomic utilization efficiency of C_(5) hydrocarbons.To improve the atomic utilizatio...When converting C_(5) hydrocarbons to light olefins by catalytic pyrolysis,the generation of low value-added methane will affect the atomic utilization efficiency of C_(5) hydrocarbons.To improve the atomic utilization efficiency,different generation pathways of light olefins and methane in the catalytic pyrolysis of C_(5) hydrocarbons were analyzed,and the effects of reaction conditions and zeolite types were inves-tigated.Results showed that light olefins were mainly formed by breaking the C_(2)-C_(3) bond in the middle position,while methane was formed by breaking the C_(1)-C_(2) bond at the end.Meanwhile,it was discovered that the hydrogen transfer reaction could be reduced by about 90%by selecting MTT zeolite with 1D topology and FER zeolite with 2D topology under high weight hourly space velocity(WHSV)and high temperature operations,thus leading to the improvement of the light olefins selectivity for the catalytic pyrolysis of n-pentane and 1-pentene to 55.12% and 74.60%,respectively.Moreover,the fraction ratio of terminal C_(1)-C_(2) bond cleavage was reduced,which would reduce the selectivity of methane to 6.63%and 1.83%.Therefore,zeolite with low hydrogen transfer activity and catalytic pyrolysis process with high WHsV will be conducive to maximize light olefins and to decrease methane.展开更多
Selective epoxidation of olefins is an important field in chemical industry.In this work,we developed a new phosphotungstic acid catalyst{[(C_8H_(17))(CH_(3))_(2)N]_(2)(CH_(2))_(3)}_(1.5){PO_(4)[WO(O_(2))_(2)]_(4)}wit...Selective epoxidation of olefins is an important field in chemical industry.In this work,we developed a new phosphotungstic acid catalyst{[(C_8H_(17))(CH_(3))_(2)N]_(2)(CH_(2))_(3)}_(1.5){PO_(4)[WO(O_(2))_(2)]_(4)}with long carbon chain and biquaternary ammonium cation.Cyclohexene could be epoxidized to cyclohexene oxide in 96.3%conversion and 98.2%selectivity.The catalyst type,solvent type,catalyst loading,initial molar ratio,temperature,cycle performance and substrate extensibility were studied and optimized,the kinetic parameters about overall reaction and unit reaction were also calculated.Dynamic light scattering analysis was carried out to explain the different catalytic performance between catalysts with different carbon chain length.This novel catalyst and the corresponding dynamics and mechanism study could probably help the industrial application on the epoxidation of cyclohexene with H_(2)O_(2).展开更多
Light olefins are important organic building blocks in the chemicals industry.The main low-carbon olefin production methods,such as catalytic cracking and steam cracking,have considerable room for improvement in their...Light olefins are important organic building blocks in the chemicals industry.The main low-carbon olefin production methods,such as catalytic cracking and steam cracking,have considerable room for improvement in their utilization of hydrocarbons.This review provides a thorough overview of recent studies on catalytic cracking,steam cracking,and the conversion of crude oil processes.To maximize the production of light olefins and reduce carbon emissions,the perceived benefits of various technologies are examined.Taking olefin generation and conversion as a link to expand upstream and downstream processes,a targeted catalytic cracking to olefins(TCO)process is proposed to meet current demands for the transformation of oil refining into chemical production.The main innovations of this process include a multiple feedstock supply,the development of medium-sized catalysts,and a diameter-transformed fluidizedbed reactor with different feeding schemes.In combination with other chemical processes,TCO is expected to play a critical role in enabling petroleum refining and chemical processes to achieve low carbon dioxide emissions.展开更多
The Fischer–Tropsch to olefins(FTO) process is a method for the direct conversion of synthesis gas to lower C_2–C_4olefins. Carbon-supported iron carbide nanoparticles are attractive catalysts for this reaction.The ...The Fischer–Tropsch to olefins(FTO) process is a method for the direct conversion of synthesis gas to lower C_2–C_4olefins. Carbon-supported iron carbide nanoparticles are attractive catalysts for this reaction.The catalytic activity can be improved and undesired formation of alkanes can be suppressed by the addition of sodium and sulfur as promoters but the influence of their content and ratio remains poorly understood and the promoted catalysts often suffer from rapid deactivation due to particle growth. A series of carbon black-supported iron catalysts with similar iron content and nominal sodium/sulfur loadings of 1–30/0.5–5 wt% with respect to iron are prepared and characterized under FTO conditions at 1and 10 bar syngas pressure to illuminate the influence of the promoter level on the catalytic properties.Iron particles and promoters undergo significant reorganization during FTO operation under industrially relevant conditions. Low sodium content(1–3 wt%) leads to a delay in iron carbide formation. Sodium contents of 15–30 wt% lead to rapid loss of catalytic activity due to the covering of the iron surface with promoters during particle growth under FTO operation. Higher activity and slower loss of activity are observed at low promoter contents(1–3 wt% sodium and 0.5–1 wt% sulfur) but a minimum amount of alkali is required to effectively suppress methane and C_2–C_4paraffin formation. A reference catalyst support(carbide-derived carbon aerogel) shows that the optimum promoter level depends on iron particle size and support pore structure.展开更多
Most olefins （e.g., ethylene and propylene） will continue to be produced through steam cracking （SC） ofhydrocarbons in the coming decade. In an uncertain commodity market, the chemical industry is investingvery li...Most olefins （e.g., ethylene and propylene） will continue to be produced through steam cracking （SC） ofhydrocarbons in the coming decade. In an uncertain commodity market, the chemical industry is investingvery little in alternative technologies and feedstocks because of their current lack of economic viability,despite decreasing crude oil reserves and the recognition of global warming. In this perspective, some of themost promising alternatives are compared with the conventional SC process, and the major bottlenecks ofeach of the competing processes are highlighted. These technologies emerge especially from the abundanceof cheap propane, ethane, and methane from shale gas and stranded gas. From an economic point of view,methane is an interesting starting material, if chemicals can be produced from it. The huge availability ofcrude oil and the expected substantial decline in the demand for fuels imply that the future for proventechnologies such as Fischer-Tropsch synthesis （FFS） or methanol to gasoline is not bright. The abundance ofcheap ethane and the large availability of crude oil, on the other hand, have caused the SC industry to shiftto these two extremes, making room for the on-purpose production of light olefins, such as by the catalyticdehydrogenation of orooane.展开更多
As a sustainable and short-flow process, iron-catalyzed direct conversion of CO-rich syngas to lower olefins without intermediate steps, i.e., Fischer–Tropsch-to-Olefins(FTO), has received increasing attention. Howev...As a sustainable and short-flow process, iron-catalyzed direct conversion of CO-rich syngas to lower olefins without intermediate steps, i.e., Fischer–Tropsch-to-Olefins(FTO), has received increasing attention. However, its fundamental understanding is usually limited by the complex crystal phase composition in addition to the interferences of the promoter effects and inevitable catalyst deactivation. Until recently,the combination of multiple in-situ/ex-situ characterizations and theoretical studies has evidenced H?gg iron carbide(χ-Fe_5C_2) as the dominant active phase of iron-based Fischer–Tropsch catalysts. This perspective attempts to review and discuss some recent progresses on the nature of χ-Fe_5C_2 catalyst and the crucial effects of promoters on the FTO performance from theoretical and experimental viewpoints,aiming to provide new insights into the rational design of iron-based FTO catalysts.展开更多
Catalytic cracking of cyclohexane(CHA) over ZSM-5, Beta, and USY zeolite catalysts was examined in a fixed fluidized bed reactor(ACE) at 773 K. The adsorption of cyclohexane in ZSM-5, Beta, and USY catalysts was inves...Catalytic cracking of cyclohexane(CHA) over ZSM-5, Beta, and USY zeolite catalysts was examined in a fixed fluidized bed reactor(ACE) at 773 K. The adsorption of cyclohexane in ZSM-5, Beta, and USY catalysts was investigated by IR spectroscopy. The IR results demonstrated that the zeolite structure has a remarkable influence on adsorption. Beta zeolite has stronger adsorption of cyclohexane than ZSM-5 and USY zeolites. During the cracking of cyclohexane, path Ⅰ(cyclohexane →methycyclopentane →light olefins) and path Ⅱ(cyclohexane → cyclohexene → light olefins) were found as two important reaction pathways to produce light olefins. A mixture of ZSM-5 and Beta zeolites is better suited for path Ⅰ, and a combination of ZSM-5 and USY zeolites is suitable for path Ⅱ. When pathway Ⅰ and pathway Ⅱ had the same proportion in cyclohexane conversion, pathway Ⅱ would be a better choice for light olefins production.展开更多
A novel thermoregulated phosphine ligand Ph<sub>2</sub>P（CH<sub>2</sub>CH<sub>2</sub>O）<sub>n</sub>CH<sub>3</sub>（n=22） was synthesized and used for the ...A novel thermoregulated phosphine ligand Ph<sub>2</sub>P（CH<sub>2</sub>CH<sub>2</sub>O）<sub>n</sub>CH<sub>3</sub>（n=22） was synthesized and used for the Rh-catalyzed hydroformylation of mixed C<sub>11-12</sub> olefins in aqueous/organic biphasic system.Under the optimized conditions,pressure =5 MPa （H<sub>2</sub>:CO=1:1）,phosphine/Rh =13（molar ratio）,reaction time =6 h and temperature =130℃,the conversion of C<sub>11-12</sub> olefins and the yield of aldehyde are 99%and 94%,respectively.The catalyst retained in aqueous phase can be easily separated from the product-containing organic phase by simple phase separation and the catalytic activity remains almost constant after four consecutive cycles.展开更多
A ZSM-5/MAPO composite catalyst was prepared by adding ZSM-5 zeolite powder to a conventional molecular sieve synthesis system, followed by modification with NH_4H_2PO_4. The samples were characterized by XRD, SEM, IR...A ZSM-5/MAPO composite catalyst was prepared by adding ZSM-5 zeolite powder to a conventional molecular sieve synthesis system, followed by modification with NH_4H_2PO_4. The samples were characterized by XRD, SEM, IR, NH_3-TPD, and BET analyses. The catalytic property of the samples toward the methanol-to-olefin(MTO) reaction was evaluated in a connected in series two-stage unit equipped with a continuous flow(once-through) fixed-bed tubular reactor similar to an industrial reactor. The first reactor mainly converted methanol into dimethyl ether and water, followed by being subject to continuous reaction in the second reactor, in which DME was converted to hydrocarbons. The composites exhibited the typical framework topology of MFI, AEI and AFI, which represented the ZSM-5 zeolite, the molecular sieves AlPO-18 or SAPO-18, AlPO-5 or SAPO-5, respectively. The composites showed several advantages for optimizing the zeolite acidity, enhancing the mass transfer, and restraining the side reactions. Catalytic reaction results showed that the composites exhibited higher selectivity to light olefins(84.0%) and lower selectivity to C_2―C_4 alkanes and C_5^+ hydrocarbons than pure ZSM-5. Moreover, the composite zeolite loaded with 3% of P demonstrated improved catalytic activity and stability for the conversion of methanol to propylene, because the coking rate was obviously suppressed.展开更多
A comprehensive economic analysis of twenty light olefin production pathways has been performed,covering current and promising processes from fossil(petroleum,coal and natural gas)and renewable resources(biomass and C...A comprehensive economic analysis of twenty light olefin production pathways has been performed,covering current and promising processes from fossil(petroleum,coal and natural gas)and renewable resources(biomass and CO_(2)).Taking steam cracking of naphtha as the benchmark,this study gives an economic perspective and points out the bottleneck in different olefin production pathways.The assessment indicates that nearly all renewable pathways are economically unattractive currently and the raw material cost accounts for dominant contribution in most pathways,especially in the oil-,natural gas-and CO_(2)-derived pathways.For the ways of methanol-to-olefins and methanol-to-propylene,fossil pathways are cost-competitive according to the date of current Chinese market prices.However,the price of feedstock hydrogen needs to be lowered by 55%to fill the cost gap between CO_(2)-derived pathways and the benchmark.For the ways of oxidative coupling of methane and Fischer-Tropsch synthesis to olefins,fossil pathways enable cost-competitive processes by feedstock price fall,but further process improvement is required to approach benchmark in renewable pathways.Conditionally,a decrease in ethanol price by45%can make ethanol dehydration pathway profitable.In addition,costs can reduce by 4%-23%in different pathways as the production scales expand from 100 to 1000 kt/a,resulting in a change from high cost to economic profit for some of the pathways.The results quantify the need for improvements on feedstock price,scale size and process improvement to achieve competitive production costs.展开更多
Single-event microkinetic(SEMK) model of the catalytic cracking of methylcyclohexane admixed with 1-octene over REUSY zeolites at 693 K—753 K in the absence of coke formation is enhanced. To keep consistency with the...Single-event microkinetic(SEMK) model of the catalytic cracking of methylcyclohexane admixed with 1-octene over REUSY zeolites at 693 K—753 K in the absence of coke formation is enhanced. To keep consistency with the wellknown carbenium ion chemistry, hydride transfer forming and consuming allylic carbenium ions in the aromatization of cycloparaffins are further investigated and differentiated. The reversibility of endocyclic β-scission and cyclization reactions is refined by accounting explicitly for the reacting olefins and resulting cycloparaffins in the corresponding thermodynamics. 24 activation energies for the reactions involved in the cracking of cycloparaffins are obtained by the regression of 15 sets of experimental data upon taking the resulting 37 main cracking products, i. e., responses into account. The enhanced SEMK model can adequately describe the catalytic behavior of 37 main products with conversion and temperature.展开更多
The effects of the substituents on the cyclopentadienyl ring and the reducing agents on the catalytic activity and the stability of titanocene/NaH or n BuLi systems for the hydrogenation of olefins were investigated. ...The effects of the substituents on the cyclopentadienyl ring and the reducing agents on the catalytic activity and the stability of titanocene/NaH or n BuLi systems for the hydrogenation of olefins were investigated. For the catalyst systems composed of titanocene/NaH or n BuLi, the nature and the number of the substituents on the cyclopentadienyl ring control the catalytic behavior of those two systems. The effect of the reducing agent on the catalytic activity is relatively small. In addition, the characters of the hydrogenation of various olefins catalyzed respectively by Cp 2TiCl 2/NaH or n BuLi systems were compared.展开更多
Precise,efficient copolymerizations of ethylene with cyclic olefins[norbornene(NBE),cyclopentene(CPE)]using nonbridged half-titanocenes of type,Cp'TiCl_2(L)(Cp'=cyclopentadienyl group,L=aryloxo,ketimide)-MAO c...Precise,efficient copolymerizations of ethylene with cyclic olefins[norbornene(NBE),cyclopentene(CPE)]using nonbridged half-titanocenes of type,Cp'TiCl_2(L)(Cp'=cyclopentadienyl group,L=aryloxo,ketimide)-MAO catalyst systems have been summarized.CpTiCl_2(N=C'Bu_2)exhibited both remarkable catalytic activity and efficient NBE incorporation for ethylene/NBE copolymerization:the NBE incorporation by Cp'TiCl_2(X)(X=N=C'Bu_2,O-2,6-'Pr_2C_6H_3; Cp'=Cp,C_5Me_5,indenyl)was related to the calculated coordination ...展开更多
Through the hydrogenation experiments for removal of olefin impurities in effluent mixture obtained from alkylation reactor for linear alkylbenzene synthesis, the reaction kinetics was studied. The experimental result...Through the hydrogenation experiments for removal of olefin impurities in effluent mixture obtained from alkylation reactor for linear alkylbenzene synthesis, the reaction kinetics was studied. The experimental results showed that the catalytic activity of Pd/Al2 O3 among four kinds of catalysts was the highest, and the olefin conversion reached 100%when the reaction temperature was higher than 140 ℃. The kinetic model was established through parameters estimation.The experimental validation of the kinetic model showed that the kinetic model had higher simulation accuracy. The results of prediction by the kinetic model indicated that with the intensification of reaction conditions, the olefin conversion would increase and the bromine index of the linear alkyl benzene would decrease. Under the conditions covering a WHSV of 2.0 h^(-1),a temperature of 90 ℃, and a hydrogen partial pressure of 1.5 MPa, the olefin conversion was 99.67%, and the bromine index of the linear alkyl benzene could be reduced to less than 20.00 mgBr/(100 g).展开更多
基金the financial support from the Strategic Priority Research Program of Chinese Academy of Sciences(XDA21010100)。
文摘Light olefins is the incredibly important materials in chemical industry.Methanol to olefins(MTO),which provides a non-oil route for light olefins production,received considerable attention in the past decades.However,the catalyst deactivation is an inevitable feature in MTO processes,and regeneration,therefore,is one of the key steps in industrial MTO processes.Traditionally the MTO catalyst is regenerated by removing the deposited coke via air combustion,which unavoidably transforms coke into carbon dioxide and reduces the carbon utilization efficiency.Recent study shows that the coke species over MTO catalyst can be regenerated via steam,which can promote the light olefins yield as the deactivated coke species can be essentially transferred to industrially useful synthesis gas,is a promising pathway for further MTO processes development.In this work,we modelled and analyzed these two MTO regeneration methods in terms of carbon utilization efficiency and technology economics.As shown,the steam regeneration could achieve a carbon utilization efficiency of 84.31%,compared to 74.74%for air combustion regeneration.The MTO processes using steam regeneration can essentially achieve the near-zero carbon emission.In addition,light olefins production of the MTO processes using steam regeneration is 12.81%higher than that using air combustion regeneration.In this regard,steam regeneration could be considered as a potential yet promising regeneration method for further MTO processes,showing not only great environmental benefits but also competitive economic performance.
基金supported by the National Natural Science Foundation of China(21802138,21773234 and 22078315)the‘‘Transformational Technologies for Clean Energy and Demonstration’’,Strategic Priority Research Program of the Chinese Academy of Sciences(XDA 21090203)+3 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(2020189)the Natural Science Foundation of Liaoning Province(2022-MS-027)the Youth Science and Technology Star Project Support Program of Dalian City(2021RQ123),DICP(Grant:DICP I202138)the University of Chinese Academy of Sciences(UCAS)for UCAS Scholarship。
文摘CO_(2)hydrogenation has been considered to be a highly promising route for the production of high-value olefins(HVOs)while also mitigating CO_(2)emissions.However,it is challenging to achieve high selectivity and maintain stable performance for HVOs(ethylene,propylene,and linear a-olefins)over a prolonged reaction time due to the difficulty in precise control of carbon coupling and rapid catalyst deactivation.Herein,we present a selective Ba and Na co-modified Fe catalyst enriched with Fe_(5)C_(2)and Fe_(3)C active sites that can boost HVO synthesis with up to 66.1%selectivity at an average CO_(2)conversion of 38%for over 500 h.Compared to traditional NaFe catalyst,the combined effect of Ba and Na additives in the NaBaFe-0.5 catalyst suppressed excess oxidation of FeCxsites by H_(2)O.The absence of Fe3O4phase in the spent NaBaFe-0.5 catalyst reflects the stabilization effect of the co-modifiers on the FeCxsites.This study provides a strategy to design Fe-based catalysts that can be scaled up for the stable synthesis of HVOs from CO_(2)hydrogenation.
基金supported by the National Key Research and Development Program of China(2017YFB0602504)the General Program of National Natural Science Foundation of China(22178385).
文摘To produce low olefin gasoline with high octane number by Fischer-Tropsch (F-T) wax fluid catalytic cracking (FCC) process, operating conditions optimization were carried out in the pilot-scale riser and turbulent fluidized bed (TFB) FCC unit. The experimental results in the riser indicated that under the condition of low reaction temperature and regenerated catalyst temperature, large catalyst-to-oil weight ratio (C/O) and long reaction time, the gasoline olefin content could be reduced to 20.28 wt%, but there is large octane number loss owing to a great loss in high octane number olefin. Therefore, a novel FCC process using the TFB reactor was proposed to strengthen the aromatization reaction. The reaction performance of TFB reactor were investigated. The result demonstrated that the TFB reactor has more significant effect in reducing olefins and improving aromatics. At the expense of certain gasoline yield, the gasoline olefin content reduced to 23.70 wt%, aromatics content could increase to 26.79 wt% and the RON was up to 91.0. The comparison of reactor structure and fluidization demonstrated that the TFB reactor has higher catalyst bed density. The reaction heat and coke combustion heat was calculated indicating the feasibility of its industrial application of the TFB process.
基金supported by Program of China National Petroleum Corporation(2020B-20122022zS27)the General Program of National Natural Science Foundation of China(22178385).
文摘When converting C_(5) hydrocarbons to light olefins by catalytic pyrolysis,the generation of low value-added methane will affect the atomic utilization efficiency of C_(5) hydrocarbons.To improve the atomic utilization efficiency,different generation pathways of light olefins and methane in the catalytic pyrolysis of C_(5) hydrocarbons were analyzed,and the effects of reaction conditions and zeolite types were inves-tigated.Results showed that light olefins were mainly formed by breaking the C_(2)-C_(3) bond in the middle position,while methane was formed by breaking the C_(1)-C_(2) bond at the end.Meanwhile,it was discovered that the hydrogen transfer reaction could be reduced by about 90%by selecting MTT zeolite with 1D topology and FER zeolite with 2D topology under high weight hourly space velocity(WHSV)and high temperature operations,thus leading to the improvement of the light olefins selectivity for the catalytic pyrolysis of n-pentane and 1-pentene to 55.12% and 74.60%,respectively.Moreover,the fraction ratio of terminal C_(1)-C_(2) bond cleavage was reduced,which would reduce the selectivity of methane to 6.63%and 1.83%.Therefore,zeolite with low hydrogen transfer activity and catalytic pyrolysis process with high WHsV will be conducive to maximize light olefins and to decrease methane.
基金supported by Natural Science Foundation of Jiangsu Province(BK20210185)National Natural Science Foundation of China(21776122)。
文摘Selective epoxidation of olefins is an important field in chemical industry.In this work,we developed a new phosphotungstic acid catalyst{[(C_8H_(17))(CH_(3))_(2)N]_(2)(CH_(2))_(3)}_(1.5){PO_(4)[WO(O_(2))_(2)]_(4)}with long carbon chain and biquaternary ammonium cation.Cyclohexene could be epoxidized to cyclohexene oxide in 96.3%conversion and 98.2%selectivity.The catalyst type,solvent type,catalyst loading,initial molar ratio,temperature,cycle performance and substrate extensibility were studied and optimized,the kinetic parameters about overall reaction and unit reaction were also calculated.Dynamic light scattering analysis was carried out to explain the different catalytic performance between catalysts with different carbon chain length.This novel catalyst and the corresponding dynamics and mechanism study could probably help the industrial application on the epoxidation of cyclohexene with H_(2)O_(2).
基金financially supported by a research grant from the National Key Research and Development Program of China(2021YFA1501204)China Petroleum and Chemical Corporation(Sinopec Corp.),China(ST22001)。
文摘Light olefins are important organic building blocks in the chemicals industry.The main low-carbon olefin production methods,such as catalytic cracking and steam cracking,have considerable room for improvement in their utilization of hydrocarbons.This review provides a thorough overview of recent studies on catalytic cracking,steam cracking,and the conversion of crude oil processes.To maximize the production of light olefins and reduce carbon emissions,the perceived benefits of various technologies are examined.Taking olefin generation and conversion as a link to expand upstream and downstream processes,a targeted catalytic cracking to olefins(TCO)process is proposed to meet current demands for the transformation of oil refining into chemical production.The main innovations of this process include a multiple feedstock supply,the development of medium-sized catalysts,and a diameter-transformed fluidizedbed reactor with different feeding schemes.In combination with other chemical processes,TCO is expected to play a critical role in enabling petroleum refining and chemical processes to achieve low carbon dioxide emissions.
基金supported by a Post Doc grant of the German Academic Exchange Service(Deutscher Akademischer Austauschdienst,DAAD grant no.91552012)by the European Research Council(EU FP7 ERC advanced grant no.338846)
文摘The Fischer–Tropsch to olefins(FTO) process is a method for the direct conversion of synthesis gas to lower C_2–C_4olefins. Carbon-supported iron carbide nanoparticles are attractive catalysts for this reaction.The catalytic activity can be improved and undesired formation of alkanes can be suppressed by the addition of sodium and sulfur as promoters but the influence of their content and ratio remains poorly understood and the promoted catalysts often suffer from rapid deactivation due to particle growth. A series of carbon black-supported iron catalysts with similar iron content and nominal sodium/sulfur loadings of 1–30/0.5–5 wt% with respect to iron are prepared and characterized under FTO conditions at 1and 10 bar syngas pressure to illuminate the influence of the promoter level on the catalytic properties.Iron particles and promoters undergo significant reorganization during FTO operation under industrially relevant conditions. Low sodium content(1–3 wt%) leads to a delay in iron carbide formation. Sodium contents of 15–30 wt% lead to rapid loss of catalytic activity due to the covering of the iron surface with promoters during particle growth under FTO operation. Higher activity and slower loss of activity are observed at low promoter contents(1–3 wt% sodium and 0.5–1 wt% sulfur) but a minimum amount of alkali is required to effectively suppress methane and C_2–C_4paraffin formation. A reference catalyst support(carbide-derived carbon aerogel) shows that the optimum promoter level depends on iron particle size and support pore structure.
基金supported by the Long-Term Structural Methusalem Funding (BOF09/01M00409)by the Flemish Government and the European Union’s Horizon H2020 Programme (H2020SPIRE-0 4-2016) under grant agreement No. 72370 6+2 种基金financial support from SABIC Geleenfinancial support from a doctoral fellowship from the Fund for Scientific Research Flanders (FWO)
文摘Most olefins （e.g., ethylene and propylene） will continue to be produced through steam cracking （SC） ofhydrocarbons in the coming decade. In an uncertain commodity market, the chemical industry is investingvery little in alternative technologies and feedstocks because of their current lack of economic viability,despite decreasing crude oil reserves and the recognition of global warming. In this perspective, some of themost promising alternatives are compared with the conventional SC process, and the major bottlenecks ofeach of the competing processes are highlighted. These technologies emerge especially from the abundanceof cheap propane, ethane, and methane from shale gas and stranded gas. From an economic point of view,methane is an interesting starting material, if chemicals can be produced from it. The huge availability ofcrude oil and the expected substantial decline in the demand for fuels imply that the future for proventechnologies such as Fischer-Tropsch synthesis （FFS） or methanol to gasoline is not bright. The abundance ofcheap ethane and the large availability of crude oil, on the other hand, have caused the SC industry to shiftto these two extremes, making room for the on-purpose production of light olefins, such as by the catalyticdehydrogenation of orooane.
基金supported by the Natural Science Foundation of China (21306046)the Open Project of State Key Laboratory of Chemical Engineering (SKL-Che-15C03)+2 种基金the Fundamental Research Funds for the Central Universities (WA1514013)the 111 Project of Ministry of Education of China (B08021)supported by the China Scholarship Council (CSC) for the research at Norwegian University of Science and Technology (NTNU)
文摘As a sustainable and short-flow process, iron-catalyzed direct conversion of CO-rich syngas to lower olefins without intermediate steps, i.e., Fischer–Tropsch-to-Olefins(FTO), has received increasing attention. However, its fundamental understanding is usually limited by the complex crystal phase composition in addition to the interferences of the promoter effects and inevitable catalyst deactivation. Until recently,the combination of multiple in-situ/ex-situ characterizations and theoretical studies has evidenced H?gg iron carbide(χ-Fe_5C_2) as the dominant active phase of iron-based Fischer–Tropsch catalysts. This perspective attempts to review and discuss some recent progresses on the nature of χ-Fe_5C_2 catalyst and the crucial effects of promoters on the FTO performance from theoretical and experimental viewpoints,aiming to provide new insights into the rational design of iron-based FTO catalysts.
基金Thanks for the financial support of Sinopec Research Institute of Petroleum Processing(RIPP R17022).
文摘Catalytic cracking of cyclohexane(CHA) over ZSM-5, Beta, and USY zeolite catalysts was examined in a fixed fluidized bed reactor(ACE) at 773 K. The adsorption of cyclohexane in ZSM-5, Beta, and USY catalysts was investigated by IR spectroscopy. The IR results demonstrated that the zeolite structure has a remarkable influence on adsorption. Beta zeolite has stronger adsorption of cyclohexane than ZSM-5 and USY zeolites. During the cracking of cyclohexane, path Ⅰ(cyclohexane →methycyclopentane →light olefins) and path Ⅱ(cyclohexane → cyclohexene → light olefins) were found as two important reaction pathways to produce light olefins. A mixture of ZSM-5 and Beta zeolites is better suited for path Ⅰ, and a combination of ZSM-5 and USY zeolites is suitable for path Ⅱ. When pathway Ⅰ and pathway Ⅱ had the same proportion in cyclohexane conversion, pathway Ⅱ would be a better choice for light olefins production.
基金the financial support from the Program for New Century Excellent Talents in University (No.NCET-07-0138)the Science and Technology Project in Universities from the Education Department of Liaoning Province(No.2008T233).
文摘A novel thermoregulated phosphine ligand Ph<sub>2</sub>P（CH<sub>2</sub>CH<sub>2</sub>O）<sub>n</sub>CH<sub>3</sub>（n=22） was synthesized and used for the Rh-catalyzed hydroformylation of mixed C<sub>11-12</sub> olefins in aqueous/organic biphasic system.Under the optimized conditions,pressure =5 MPa （H<sub>2</sub>:CO=1:1）,phosphine/Rh =13（molar ratio）,reaction time =6 h and temperature =130℃,the conversion of C<sub>11-12</sub> olefins and the yield of aldehyde are 99%and 94%,respectively.The catalyst retained in aqueous phase can be easily separated from the product-containing organic phase by simple phase separation and the catalytic activity remains almost constant after four consecutive cycles.
基金financially supported by the National International Cooperation S & T Project of China (No.2015DFA40660)
文摘A ZSM-5/MAPO composite catalyst was prepared by adding ZSM-5 zeolite powder to a conventional molecular sieve synthesis system, followed by modification with NH_4H_2PO_4. The samples were characterized by XRD, SEM, IR, NH_3-TPD, and BET analyses. The catalytic property of the samples toward the methanol-to-olefin(MTO) reaction was evaluated in a connected in series two-stage unit equipped with a continuous flow(once-through) fixed-bed tubular reactor similar to an industrial reactor. The first reactor mainly converted methanol into dimethyl ether and water, followed by being subject to continuous reaction in the second reactor, in which DME was converted to hydrocarbons. The composites exhibited the typical framework topology of MFI, AEI and AFI, which represented the ZSM-5 zeolite, the molecular sieves AlPO-18 or SAPO-18, AlPO-5 or SAPO-5, respectively. The composites showed several advantages for optimizing the zeolite acidity, enhancing the mass transfer, and restraining the side reactions. Catalytic reaction results showed that the composites exhibited higher selectivity to light olefins(84.0%) and lower selectivity to C_2―C_4 alkanes and C_5^+ hydrocarbons than pure ZSM-5. Moreover, the composite zeolite loaded with 3% of P demonstrated improved catalytic activity and stability for the conversion of methanol to propylene, because the coking rate was obviously suppressed.
基金financially supported by the National Natural Science Foundation of China(21721004,21961130378,21711530020)the Ministry of Science and Technology of the People’s Republic of China(2018YFE0117300)Dalian Science and Technology Innovation Fund(2019J11CY009)。
文摘A comprehensive economic analysis of twenty light olefin production pathways has been performed,covering current and promising processes from fossil(petroleum,coal and natural gas)and renewable resources(biomass and CO_(2)).Taking steam cracking of naphtha as the benchmark,this study gives an economic perspective and points out the bottleneck in different olefin production pathways.The assessment indicates that nearly all renewable pathways are economically unattractive currently and the raw material cost accounts for dominant contribution in most pathways,especially in the oil-,natural gas-and CO_(2)-derived pathways.For the ways of methanol-to-olefins and methanol-to-propylene,fossil pathways are cost-competitive according to the date of current Chinese market prices.However,the price of feedstock hydrogen needs to be lowered by 55%to fill the cost gap between CO_(2)-derived pathways and the benchmark.For the ways of oxidative coupling of methane and Fischer-Tropsch synthesis to olefins,fossil pathways enable cost-competitive processes by feedstock price fall,but further process improvement is required to approach benchmark in renewable pathways.Conditionally,a decrease in ethanol price by45%can make ethanol dehydration pathway profitable.In addition,costs can reduce by 4%-23%in different pathways as the production scales expand from 100 to 1000 kt/a,resulting in a change from high cost to economic profit for some of the pathways.The results quantify the need for improvements on feedstock price,scale size and process improvement to achieve competitive production costs.
基金financial support from the China Scholarship Councilthe Long Term Structural Methusalem Funding by the Flemish Government
文摘Single-event microkinetic(SEMK) model of the catalytic cracking of methylcyclohexane admixed with 1-octene over REUSY zeolites at 693 K—753 K in the absence of coke formation is enhanced. To keep consistency with the wellknown carbenium ion chemistry, hydride transfer forming and consuming allylic carbenium ions in the aromatization of cycloparaffins are further investigated and differentiated. The reversibility of endocyclic β-scission and cyclization reactions is refined by accounting explicitly for the reacting olefins and resulting cycloparaffins in the corresponding thermodynamics. 24 activation energies for the reactions involved in the cracking of cycloparaffins are obtained by the regression of 15 sets of experimental data upon taking the resulting 37 main cracking products, i. e., responses into account. The enhanced SEMK model can adequately describe the catalytic behavior of 37 main products with conversion and temperature.
基金Supported by the Educational Com mittee of L iaoning Province
文摘The effects of the substituents on the cyclopentadienyl ring and the reducing agents on the catalytic activity and the stability of titanocene/NaH or n BuLi systems for the hydrogenation of olefins were investigated. For the catalyst systems composed of titanocene/NaH or n BuLi, the nature and the number of the substituents on the cyclopentadienyl ring control the catalytic behavior of those two systems. The effect of the reducing agent on the catalytic activity is relatively small. In addition, the characters of the hydrogenation of various olefins catalyzed respectively by Cp 2TiCl 2/NaH or n BuLi systems were compared.
基金Grant-in-Aid for Scientific Research(B)from the Japan Society for the Promotion of Science(JSPS,No.18350055).
文摘Precise,efficient copolymerizations of ethylene with cyclic olefins[norbornene(NBE),cyclopentene(CPE)]using nonbridged half-titanocenes of type,Cp'TiCl_2(L)(Cp'=cyclopentadienyl group,L=aryloxo,ketimide)-MAO catalyst systems have been summarized.CpTiCl_2(N=C'Bu_2)exhibited both remarkable catalytic activity and efficient NBE incorporation for ethylene/NBE copolymerization:the NBE incorporation by Cp'TiCl_2(X)(X=N=C'Bu_2,O-2,6-'Pr_2C_6H_3; Cp'=Cp,C_5Me_5,indenyl)was related to the calculated coordination ...
文摘Through the hydrogenation experiments for removal of olefin impurities in effluent mixture obtained from alkylation reactor for linear alkylbenzene synthesis, the reaction kinetics was studied. The experimental results showed that the catalytic activity of Pd/Al2 O3 among four kinds of catalysts was the highest, and the olefin conversion reached 100%when the reaction temperature was higher than 140 ℃. The kinetic model was established through parameters estimation.The experimental validation of the kinetic model showed that the kinetic model had higher simulation accuracy. The results of prediction by the kinetic model indicated that with the intensification of reaction conditions, the olefin conversion would increase and the bromine index of the linear alkyl benzene would decrease. Under the conditions covering a WHSV of 2.0 h^(-1),a temperature of 90 ℃, and a hydrogen partial pressure of 1.5 MPa, the olefin conversion was 99.67%, and the bromine index of the linear alkyl benzene could be reduced to less than 20.00 mgBr/(100 g).
