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
The catalytic cracking of coal tar asphaltene(CTA)pyrolysis vapors was carried out over transition metalion modified zeolites to promote the generation of light aromatic hydrocarbons(L-ArHs)in a pyrolysisgas chromatog...The catalytic cracking of coal tar asphaltene(CTA)pyrolysis vapors was carried out over transition metalion modified zeolites to promote the generation of light aromatic hydrocarbons(L-ArHs)in a pyrolysisgas chromatography/mass spectrometry(Py-GC/MS)micro-reactor system.The effects of ultra stable Y(USY),Co/USY and Mo/USY on the selectivity and yield of L-ArHs products and the extent of deoxygenation(Edeoxygenation),lightweight(Elightweight)from CTA pyrolysis volatiles were investigated.Results showed that the yields of L-ArHs are mainly controlled by the acid sites and specific surface area of the catalysts,while the deoxygenation effect is determined by theirs pore size.The Eligltweight of CTA pyrolysis volatiles over USY is 9.65%,while the Edeoxygenation of CTA pyrolysis volatiles over Mo/USY reaches 20.85%.Additionally,the modified zeolites(Mo/USY and Co/USY)exhibit better performance than USY on L-ArHs production,owing to the synergistic effect of metal ions(Mo,Co)and acid sites of USY.Compared with the non-catalytic fast pyrolysis of CTA,the total yield of L-ArHs obtained over USY(4032 mg·kg^(-1)),Co/USY(4363 mg·kg^(-1))and Mo/USY(4953 mg·kg^(-1))were increased by 27.03%,38.19%and 54.78%,respectively.Furthermore,the possible catalytic conversion mechanism of transition metal ion(Co and Mo)modified zeolites was proposed based on the distribution of products and the characterizations of catalysts.展开更多
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+).
基金financed by the projects of the National Natural Science Foundation of China(21776229,21908180,22078266)the National Key Research&Development Program of China(2018YFB0604603)the Key Research and Development Program of Shaanxi(2020ZDLGY11-02,2018ZDXM-GY-167)。
文摘The catalytic cracking of coal tar asphaltene(CTA)pyrolysis vapors was carried out over transition metalion modified zeolites to promote the generation of light aromatic hydrocarbons(L-ArHs)in a pyrolysisgas chromatography/mass spectrometry(Py-GC/MS)micro-reactor system.The effects of ultra stable Y(USY),Co/USY and Mo/USY on the selectivity and yield of L-ArHs products and the extent of deoxygenation(Edeoxygenation),lightweight(Elightweight)from CTA pyrolysis volatiles were investigated.Results showed that the yields of L-ArHs are mainly controlled by the acid sites and specific surface area of the catalysts,while the deoxygenation effect is determined by theirs pore size.The Eligltweight of CTA pyrolysis volatiles over USY is 9.65%,while the Edeoxygenation of CTA pyrolysis volatiles over Mo/USY reaches 20.85%.Additionally,the modified zeolites(Mo/USY and Co/USY)exhibit better performance than USY on L-ArHs production,owing to the synergistic effect of metal ions(Mo,Co)and acid sites of USY.Compared with the non-catalytic fast pyrolysis of CTA,the total yield of L-ArHs obtained over USY(4032 mg·kg^(-1)),Co/USY(4363 mg·kg^(-1))and Mo/USY(4953 mg·kg^(-1))were increased by 27.03%,38.19%and 54.78%,respectively.Furthermore,the possible catalytic conversion mechanism of transition metal ion(Co and Mo)modified zeolites was proposed based on the distribution of products and the characterizations of catalysts.
