Progress in natural gas conversion in China is presented in this paper, including processes of natural gas to synthesis gas （syngas）, syngas to liquid hydrocarbons, oxygenates synthesis, methanol to olefins （MTO）,...Progress in natural gas conversion in China is presented in this paper, including processes of natural gas to synthesis gas （syngas）, syngas to liquid hydrocarbons, oxygenates synthesis, methanol to olefins （MTO）, methane to aromatics and oxidative coupling of methane （OCM）.展开更多
Avery wide range of the C3^=/C2^= ratio from 0.72 to 7.56 with high C2^= ＋ C3^= selectivity of around 66%in the methanol-to-hydrocarbons process can be realized over ZSM-5 catalyst in a fixed-bed reactor.We firstly c...Avery wide range of the C3^=/C2^= ratio from 0.72 to 7.56 with high C2^= ＋ C3^= selectivity of around 66%in the methanol-to-hydrocarbons process can be realized over ZSM-5 catalyst in a fixed-bed reactor.We firstly conduct a single factor experiment of acidity,demonstrating that the acidity control of MTH catalyst is crucial to adjusting light olefins selectivity.Weak Bronsted acid sites favor to high C3^= selectivity（59.0%）due to the suppression of the conversion reactions from the alkene-based to arene-based cycle,while Lewis acid sites conduce to high C2^= selectivity（39.6%） due to the promotion of the conversion reactions for the aromatics formation and steric constraints of Lewis acid sites making the aromatics crack more efficiently to C2^=.展开更多
The influence factors and paths of methane formation during methanol to hydrocarbons （MTH） reaction were studied experimentally and thermodynamically. The fixed-bed reaction results show that the formation of methan...The influence factors and paths of methane formation during methanol to hydrocarbons （MTH） reaction were studied experimentally and thermodynamically. The fixed-bed reaction results show that the formation of methane was favored by not only high temperature, but also high feed velocity, low pressure, as well as weak acid sites dominated on deactivated catalyst. The thermodynamic analysis results indicate that methane would be formed via the decomposition reactions of methanol and DME, and the hydrogenolysis reactions of methanol and DME. The decomposition reactions are thermal chemistry processes and easily occurred at high temperature. However, they are influenced by catalyst and reaction conditions through DME intermediate. By contrast, the hydrogenolysis reactions belong to catalytic processes. Parallel experiments suggest that, in real MTH reactions, the hydrogenolysis reactions should be mainly enabled by surface active H atom which might come from hydrogen transfer reactions such as aromatization. But H2 will be involved if the catalyst has active components like NiO.展开更多
Low-carbon process for resource utilization of polycyclic aromatic hydrocarbons(PAHs)in zeolitecatalyzed processes,geared to carbon neutrality-a prominent trend throughout human activities,has been bottlenecked by the...Low-carbon process for resource utilization of polycyclic aromatic hydrocarbons(PAHs)in zeolitecatalyzed processes,geared to carbon neutrality-a prominent trend throughout human activities,has been bottlenecked by the lack of a complete mechanistic understanding of coking and decoking chemistry,involving the speciation and molecular evolution of PAHs,the plethora of which causes catalyst deactivation and forces regeneration,rendering significant CO_(2) emission.Herein,by exploiting the high-resolution matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry(MALDI FT-ICR MS),we unveil the missing fingerprints of the mechanistic pathways for both formation and decomposition of cross-linked cage-passing PAHs for SAPO-34-catalyzed,industrially relevant methanol-to-olefins(MTO)as a model reaction.Notable is the molecule-resolved symmetrical signature:their speciation originates exclusively from the direct coupling of in-cage hydrocarbon pool(HCP)species,whereas water-promoted decomposition of cage-passing PAHs initiates with selective cracking of inter-cage local structures at 8-rings followed by deep aromatic steam reforming.Molecular deciphering the reversibly dynamic evolution trajectory(fate)of full-spectrum aromatic hydrocarbons and fulfilling the real-time quantitative carbon resource footprints advance the fundamental knowledge of deactivation and regeneration phenomena(decay and recovery motifs of autocatalysis)and disclose the underlying mechanisms of especially the chemistry of coking and decoking in zeolite catalysis.The positive yet divergent roles of water in these two processes are disentangled.These unprecedented insights ultimately lead us to a steam regeneration strategy with valuable CO and H_(2) as main products,negligible CO_(2) emission in steam reforming and full catalyst activity recovery,which further proves feasible in other important chemical processes,promising to be a sustainable and potent approach that contributes to carbon-neutral chemical i展开更多
The external surface of HZSM-5 zeolite was passivated by liquid siliceous deposition and by acidic sites poisoning with lepidine, respectively. Then methanol-to-hydrocarbons （MTH） reaction was investigated over the ...The external surface of HZSM-5 zeolite was passivated by liquid siliceous deposition and by acidic sites poisoning with lepidine, respectively. Then methanol-to-hydrocarbons （MTH） reaction was investigated over the above as-prepared catalysts and the dissoluble coke on these used catalysts was analyzed by GC-MS, to study the role of the external surface of HZSM-5 in the catalytic reaction. Comparison with the experi- mental results based on parent ZSM-5 showed that the product distribution of MTH reaction was obviously influenced by the external surface. Evidences were listed as follows： （1） the final product on parent HZSM-5 showed higher aromatic selectivity, lower olefin selectivity, lower ra- tio of C2/C3＋ aliphatics and higher ratio of C3/C4＋ aliphatics than the reaction mixture produced by the sole catalysis of acidic sites in HZSM-5 channel; （2） a little of pentamethylbenzene and hexamethylbenzene in the product on parent HZSM-5, was produced via multi-methylation of methylbenzene on the external surface. The above conclusion may also be suitable for MTH reaction over other zeolites with 10-ring channel.展开更多
Five kinds of BZSM-5 molecular sieve with different Si/B ratio and a SiZSM-5 molecular sieve were prepared by hydrothermal synthesis method followed by acid exchange and pelletization.The samples were characterized by...Five kinds of BZSM-5 molecular sieve with different Si/B ratio and a SiZSM-5 molecular sieve were prepared by hydrothermal synthesis method followed by acid exchange and pelletization.The samples were characterized by XRD,SEM,FT-IR,ICP,low temperature N_(2) physical adsorption and desorption,NH3-TPD and Py-IR.The catalytic performance in the reaction of methanol to hydrocarbons was evaluated in the fixed bed reactor.Compared with SiZSM-5,the amount and strength of Bronsted(B)acid were enhanced by introducing skeleton boron and the activity of the catalyst was greatly improved.The characterization and evaluation results indicated that the BZSM-5 catalyst synthesized from the gel of SiO_(2)/B2 O320 with Si/B ratio 74.48 had modest acidity strength,acid amount of 0.18 mmol NH3·g^(-1) and large mesopore volume of 0.23 cm3·g^(-1).The B acid ratio was higher and the acid strength of BZSM-5 was weaker than that of AIZSM-5,which could inhibit the deep coke formation and increase the activity stability.B-2 had the best lifetime which could reach 672 h under the same evaluation reaction conditions,due to the best matching of moderate acidity and good diffusion properties.展开更多
Understanding the complete reaction network and mechanism of methanol to-hydrocarbons remains a key chal-lenge in the field of zeolite catalysis and C1 chemistry.Inspired by the identification of the reactive surface ...Understanding the complete reaction network and mechanism of methanol to-hydrocarbons remains a key chal-lenge in the field of zeolite catalysis and C1 chemistry.Inspired by the identification of the reactive surface methoxy species on solid acids,several direct mechanisms associated with the formation of the first C-C bond in methanol conversion have been recently disclosed.Identifying the stepwise involvement of the initial intermedi-ates containing the first CC bond in the whole reaction process of methanol to-hydrocarbons conversion becomes possible and attractive for the further development of this important reaction.Herein,several initial unsaturated aldehydes/ketones containing the C-C bond are identified via complementary spectroscopic techniques.With the combination of kinetic and spectroscopic analyses,a complete roadmap of the zeolite catalyzed methanol-to-hydrocarbons conversion from the initial CC bonds to the hydrocarbon pool species via the oxygen-containing unsaturated intermediates is clearly ilustrated.With the participation of both Bronsted and Lewis acid sites in H-ZSM-5 zeolite,an initial aldol-cycle is proposed,which can be closely connected to the well-known dual-cycle mechanism in the methanol-to-hydrocarbons conversion.展开更多
采用直接水热合成和后合成两种方法制备Al-ITQ-13分子筛,用于催化甲醇转化制备烃类化合物。采用XRD、27Al M AS NM R、NH3-TPD、Py-FTIR和SEM等技术对所合成样品进行了表征。结果表明,两种方法制备的Al-ITQ-13结晶度都较高,且晶体形貌...采用直接水热合成和后合成两种方法制备Al-ITQ-13分子筛,用于催化甲醇转化制备烃类化合物。采用XRD、27Al M AS NM R、NH3-TPD、Py-FTIR和SEM等技术对所合成样品进行了表征。结果表明,两种方法制备的Al-ITQ-13结晶度都较高,且晶体形貌为薄片。与ZSM-5相比,Al-ITQ-13在甲醇转化反应中显示出较高的丙烯选择性、较高的丙烯/乙烯产物比以及较好的催化稳定性。同时,由于后合成所得到的Si Al(B)-ITQ-13强酸量减少,其催化性能优于直接合成的Si Ge Al-ITQ-13。展开更多
基金the National Natural Science Foundation of China (20490201,20306016)
文摘Progress in natural gas conversion in China is presented in this paper, including processes of natural gas to synthesis gas （syngas）, syngas to liquid hydrocarbons, oxygenates synthesis, methanol to olefins （MTO）, methane to aromatics and oxidative coupling of methane （OCM）.
基金the National Natural Science Foundation of China(Nos.U1462106 and 21673076)the National Key Research and Development Program of China(No.2016YFB0701100)
文摘Avery wide range of the C3^=/C2^= ratio from 0.72 to 7.56 with high C2^= ＋ C3^= selectivity of around 66%in the methanol-to-hydrocarbons process can be realized over ZSM-5 catalyst in a fixed-bed reactor.We firstly conduct a single factor experiment of acidity,demonstrating that the acidity control of MTH catalyst is crucial to adjusting light olefins selectivity.Weak Bronsted acid sites favor to high C3^= selectivity（59.0%）due to the suppression of the conversion reactions from the alkene-based to arene-based cycle,while Lewis acid sites conduce to high C2^= selectivity（39.6%） due to the promotion of the conversion reactions for the aromatics formation and steric constraints of Lewis acid sites making the aromatics crack more efficiently to C2^=.
文摘The influence factors and paths of methane formation during methanol to hydrocarbons （MTH） reaction were studied experimentally and thermodynamically. The fixed-bed reaction results show that the formation of methane was favored by not only high temperature, but also high feed velocity, low pressure, as well as weak acid sites dominated on deactivated catalyst. The thermodynamic analysis results indicate that methane would be formed via the decomposition reactions of methanol and DME, and the hydrogenolysis reactions of methanol and DME. The decomposition reactions are thermal chemistry processes and easily occurred at high temperature. However, they are influenced by catalyst and reaction conditions through DME intermediate. By contrast, the hydrogenolysis reactions belong to catalytic processes. Parallel experiments suggest that, in real MTH reactions, the hydrogenolysis reactions should be mainly enabled by surface active H atom which might come from hydrogen transfer reactions such as aromatization. But H2 will be involved if the catalyst has active components like NiO.
基金financial support from the National Natural Science Foundation of China(21991092,21991090,22022202,21972142,21902153,21974138)the Chinese Academy of Sciences(QYZDY-SSW-SC024)the Dalian Institute of Chemical Physics(DICP I201926,DICP I201947)。
文摘Low-carbon process for resource utilization of polycyclic aromatic hydrocarbons(PAHs)in zeolitecatalyzed processes,geared to carbon neutrality-a prominent trend throughout human activities,has been bottlenecked by the lack of a complete mechanistic understanding of coking and decoking chemistry,involving the speciation and molecular evolution of PAHs,the plethora of which causes catalyst deactivation and forces regeneration,rendering significant CO_(2) emission.Herein,by exploiting the high-resolution matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry(MALDI FT-ICR MS),we unveil the missing fingerprints of the mechanistic pathways for both formation and decomposition of cross-linked cage-passing PAHs for SAPO-34-catalyzed,industrially relevant methanol-to-olefins(MTO)as a model reaction.Notable is the molecule-resolved symmetrical signature:their speciation originates exclusively from the direct coupling of in-cage hydrocarbon pool(HCP)species,whereas water-promoted decomposition of cage-passing PAHs initiates with selective cracking of inter-cage local structures at 8-rings followed by deep aromatic steam reforming.Molecular deciphering the reversibly dynamic evolution trajectory(fate)of full-spectrum aromatic hydrocarbons and fulfilling the real-time quantitative carbon resource footprints advance the fundamental knowledge of deactivation and regeneration phenomena(decay and recovery motifs of autocatalysis)and disclose the underlying mechanisms of especially the chemistry of coking and decoking in zeolite catalysis.The positive yet divergent roles of water in these two processes are disentangled.These unprecedented insights ultimately lead us to a steam regeneration strategy with valuable CO and H_(2) as main products,negligible CO_(2) emission in steam reforming and full catalyst activity recovery,which further proves feasible in other important chemical processes,promising to be a sustainable and potent approach that contributes to carbon-neutral chemical i
基金supported by Shanghai Key Basic Research(Grant No.11JC1412500)the National Natural Science Foundation of China(Grant No.51174277)
文摘The external surface of HZSM-5 zeolite was passivated by liquid siliceous deposition and by acidic sites poisoning with lepidine, respectively. Then methanol-to-hydrocarbons （MTH） reaction was investigated over the above as-prepared catalysts and the dissoluble coke on these used catalysts was analyzed by GC-MS, to study the role of the external surface of HZSM-5 in the catalytic reaction. Comparison with the experi- mental results based on parent ZSM-5 showed that the product distribution of MTH reaction was obviously influenced by the external surface. Evidences were listed as follows： （1） the final product on parent HZSM-5 showed higher aromatic selectivity, lower olefin selectivity, lower ra- tio of C2/C3＋ aliphatics and higher ratio of C3/C4＋ aliphatics than the reaction mixture produced by the sole catalysis of acidic sites in HZSM-5 channel; （2） a little of pentamethylbenzene and hexamethylbenzene in the product on parent HZSM-5, was produced via multi-methylation of methylbenzene on the external surface. The above conclusion may also be suitable for MTH reaction over other zeolites with 10-ring channel.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(XDA21020500)。
文摘Five kinds of BZSM-5 molecular sieve with different Si/B ratio and a SiZSM-5 molecular sieve were prepared by hydrothermal synthesis method followed by acid exchange and pelletization.The samples were characterized by XRD,SEM,FT-IR,ICP,low temperature N_(2) physical adsorption and desorption,NH3-TPD and Py-IR.The catalytic performance in the reaction of methanol to hydrocarbons was evaluated in the fixed bed reactor.Compared with SiZSM-5,the amount and strength of Bronsted(B)acid were enhanced by introducing skeleton boron and the activity of the catalyst was greatly improved.The characterization and evaluation results indicated that the BZSM-5 catalyst synthesized from the gel of SiO_(2)/B2 O320 with Si/B ratio 74.48 had modest acidity strength,acid amount of 0.18 mmol NH3·g^(-1) and large mesopore volume of 0.23 cm3·g^(-1).The B acid ratio was higher and the acid strength of BZSM-5 was weaker than that of AIZSM-5,which could inhibit the deep coke formation and increase the activity stability.B-2 had the best lifetime which could reach 672 h under the same evaluation reaction conditions,due to the best matching of moderate acidity and good diffusion properties.
基金This work was supported by the National Natural Science Foundation of China(Grants No.21972069,22025203)the Fundamental Research Funds for the Central Universities,and Frontiers Science Center for New Organic Matter,Nankai University(Grant No.63181206).
文摘Understanding the complete reaction network and mechanism of methanol to-hydrocarbons remains a key chal-lenge in the field of zeolite catalysis and C1 chemistry.Inspired by the identification of the reactive surface methoxy species on solid acids,several direct mechanisms associated with the formation of the first C-C bond in methanol conversion have been recently disclosed.Identifying the stepwise involvement of the initial intermedi-ates containing the first CC bond in the whole reaction process of methanol to-hydrocarbons conversion becomes possible and attractive for the further development of this important reaction.Herein,several initial unsaturated aldehydes/ketones containing the C-C bond are identified via complementary spectroscopic techniques.With the combination of kinetic and spectroscopic analyses,a complete roadmap of the zeolite catalyzed methanol-to-hydrocarbons conversion from the initial CC bonds to the hydrocarbon pool species via the oxygen-containing unsaturated intermediates is clearly ilustrated.With the participation of both Bronsted and Lewis acid sites in H-ZSM-5 zeolite,an initial aldol-cycle is proposed,which can be closely connected to the well-known dual-cycle mechanism in the methanol-to-hydrocarbons conversion.
基金supported by Doctoral Scientific Research Foundation of Shanxi Datong University (2015-B-02)
文摘采用直接水热合成和后合成两种方法制备Al-ITQ-13分子筛,用于催化甲醇转化制备烃类化合物。采用XRD、27Al M AS NM R、NH3-TPD、Py-FTIR和SEM等技术对所合成样品进行了表征。结果表明,两种方法制备的Al-ITQ-13结晶度都较高,且晶体形貌为薄片。与ZSM-5相比,Al-ITQ-13在甲醇转化反应中显示出较高的丙烯选择性、较高的丙烯/乙烯产物比以及较好的催化稳定性。同时,由于后合成所得到的Si Al(B)-ITQ-13强酸量减少,其催化性能优于直接合成的Si Ge Al-ITQ-13。
