The structures and catalytic performances of V_2O_5, Mg_3V_2O_8 and V/MgO catalysts have been correlated by means of XRD, FTIR, TPR and flow micro-reactor tests. The postulation about active site has been made. Based ...The structures and catalytic performances of V_2O_5, Mg_3V_2O_8 and V/MgO catalysts have been correlated by means of XRD, FTIR, TPR and flow micro-reactor tests. The postulation about active site has been made. Based on it, better catalysts have been first prepared via grafting and modification with Sb which are better than that via impregnation.展开更多
Dehydrogenation of ethylbenzene （EB） to styrene （ST） in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift （RWGS）, was investigated extensively through both theoretical ...Dehydrogenation of ethylbenzene （EB） to styrene （ST） in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift （RWGS）, was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process. The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3, while the one-step pathway dominates the reaction over V/Al2O3. Coke deposition and deep reduction of active components are the major causes of catalyst deactivation. CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.展开更多
The selective synthesis of p-diethylbenzene （p-DEB） by disproportionation of ethylbenzene （EB） in the presence of aromatics like m- and p- xylene isomers has been studied over a pore size regulated HZSM-5 catalyst...The selective synthesis of p-diethylbenzene （p-DEB） by disproportionation of ethylbenzene （EB） in the presence of aromatics like m- and p- xylene isomers has been studied over a pore size regulated HZSM-5 catalyst. The industrial feed having different compositions of ethylbenzene and xylene isomers was used for the experimentation. Hence, they were expected to hinder the movement of reactant molecules both on the external surface and within the zeolite channels. It was observed that irrespective of the different feed compositions the concentration of the xylene isomers was intact in the product. There is no other byproducts formation like para-ethylmethyl benzene. The effects of varying the concentration of aromatic compounds in the feed on ethylbenzene conversion and product distribution over the parent and modified H-ZSM-5 catalyst have been discussed. Ethylbenzene disproportionation reaction follows the pseudo first order reaction with an activation energy of 8.6 kcal/mol.展开更多
The PdPtVO_(x)/CeO_(2)-ZrO_(2)(PdPtVO_(x)/CZO)catalysts were obtained by using different approaches,and their physical and chemical properties were determined by various techniques.Catalytic activities of these materi...The PdPtVO_(x)/CeO_(2)-ZrO_(2)(PdPtVO_(x)/CZO)catalysts were obtained by using different approaches,and their physical and chemical properties were determined by various techniques.Catalytic activities of these materials in the presence of H_(2)O or SO_(2)were evaluated for the oxidation of ethylbenzene(EB).The PdPtVO_(x)/CZO sample exhibited high catalytic activity,good hydrothermal stability,and reversible sulfur dioxide-poisoning performance,over which the specific reaction rate at 160℃,turnover frequency at 160℃(TOF_(Pd or Pt)),and apparent activation energy were 72.6 mmol/(g_(Pt)·sec)or 124.2 mmol/(g_(Pd)·sec),14.2 sec^(-1)(TOF_(Pt))or 13.1 sec^(-1)(TOF_(Pd)),and 58 k J/mol,respectively.The large EB adsorption capacity,good reducibility,and strong acidity contributed to the good catalytic performance of PdPtVO_(x)/CZO.Catalytic activity of PdPtVO_(x)/CZO decreased when 50 ppm SO_(2)or(1.0 vol.%H_(2)O+50 ppm SO_(2))was added to the feedstock,but was gradually restored to its initial level after the SO_(2)was cut off.The good reversible sulfur dioxide-resistant performance of PdPtVO_(x)/CZO was associated with the facts:(i)the introduction of SO_(2)leads to an increase in surface acidity;(ii)V can adsorb and activate SO_(2),thus accelerating formation of the SO_(x)^(2-)(x=3 or 4)species at the V and CZO sites,weakening the adsorption of sulfur species at the PdPt active sites,and hence protecting the PdPt active sites to be not poisoned by SO_(2).EB oxidation over PdPtVO_(x)/CZO might take place via the route of EB→styrene→phenyl methyl ketone→benzaldehyde→benzoic acid→maleic anhydride→CO_(2)and H_(2)O.展开更多
The oxidation of hydrocarbons to produce high value-added compounds(ketones or alcohols)using oxygen in air as the only oxidant is an efficient synthetic strategy from both environmental and economic views.Herein,we s...The oxidation of hydrocarbons to produce high value-added compounds(ketones or alcohols)using oxygen in air as the only oxidant is an efficient synthetic strategy from both environmental and economic views.Herein,we successfully synthesized cobalt single atom site catalysts(Co SACs)with high metal loading of 23.58 wt.%supported on carbon nitride(CN),which showed excellent catalytic properties for oxidation of ethylbenzene in air.Moreover,Co SACs show a much higher turn-over frequency(19.6 h^(−1))than other reported non-noble catalysts under the same condition.Comparatively,the as-obtained nanosized or homogenous Co catalysts are inert to this reaction.Co SACs also exhibit high selectivity(97%)and stability(unchanged after five runs)in this reaction.DFT calculations reveal that Co SACs show a low energy barrier in the first elementary step and a high resistance to water,which result in the robust catalytic performance for this reaction.展开更多
Through screening Ce precursors and pyrolysis temperatures[Ce(acac)3 as Ce precursors and pyrolysis at 900°C],zeolitic imidazolate framework-8(ZIF-8)derived nitrogen-doped carbon supported cerium single atom cata...Through screening Ce precursors and pyrolysis temperatures[Ce(acac)3 as Ce precursors and pyrolysis at 900°C],zeolitic imidazolate framework-8(ZIF-8)derived nitrogen-doped carbon supported cerium single atom catalyst(Ce_(1)/NC)is successfully prepared by ball milling method.The Ce_(1)/NC catalyst exhibits exceptional catalytic performance in the selective oxidation of saturated C―H bonds in aromatic compounds,e.g.,91%conversion and 99%selelctivity can be achieved in the oxidation of ethylbenzene to acetophenone under mild reaction conditions.展开更多
文摘The structures and catalytic performances of V_2O_5, Mg_3V_2O_8 and V/MgO catalysts have been correlated by means of XRD, FTIR, TPR and flow micro-reactor tests. The postulation about active site has been made. Based on it, better catalysts have been first prepared via grafting and modification with Sb which are better than that via impregnation.
基金The authors are grateful for the financial support of The Sate Key Fundamental Research Project and the Natural Science Foundation of China.
文摘Dehydrogenation of ethylbenzene （EB） to styrene （ST） in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift （RWGS）, was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process. The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3, while the one-step pathway dominates the reaction over V/Al2O3. Coke deposition and deep reduction of active components are the major causes of catalyst deactivation. CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.
文摘The selective synthesis of p-diethylbenzene （p-DEB） by disproportionation of ethylbenzene （EB） in the presence of aromatics like m- and p- xylene isomers has been studied over a pore size regulated HZSM-5 catalyst. The industrial feed having different compositions of ethylbenzene and xylene isomers was used for the experimentation. Hence, they were expected to hinder the movement of reactant molecules both on the external surface and within the zeolite channels. It was observed that irrespective of the different feed compositions the concentration of the xylene isomers was intact in the product. There is no other byproducts formation like para-ethylmethyl benzene. The effects of varying the concentration of aromatic compounds in the feed on ethylbenzene conversion and product distribution over the parent and modified H-ZSM-5 catalyst have been discussed. Ethylbenzene disproportionation reaction follows the pseudo first order reaction with an activation energy of 8.6 kcal/mol.
基金supported by the National Natural Science Foundation Committee of China-Liaoning Provincial People’s Government Joint Fund(No.U1908204)the National Natural Science Foundation of China(21976009)+2 种基金the National Key R&D Program of China(Nos.2022YFB3506200 and 2022YFB3504100)the Beijing Natural Science Foundation(J210006)the R&D Program of Beijing Municipal Education Commisson(No.KZ202210005011)。
文摘The PdPtVO_(x)/CeO_(2)-ZrO_(2)(PdPtVO_(x)/CZO)catalysts were obtained by using different approaches,and their physical and chemical properties were determined by various techniques.Catalytic activities of these materials in the presence of H_(2)O or SO_(2)were evaluated for the oxidation of ethylbenzene(EB).The PdPtVO_(x)/CZO sample exhibited high catalytic activity,good hydrothermal stability,and reversible sulfur dioxide-poisoning performance,over which the specific reaction rate at 160℃,turnover frequency at 160℃(TOF_(Pd or Pt)),and apparent activation energy were 72.6 mmol/(g_(Pt)·sec)or 124.2 mmol/(g_(Pd)·sec),14.2 sec^(-1)(TOF_(Pt))or 13.1 sec^(-1)(TOF_(Pd)),and 58 k J/mol,respectively.The large EB adsorption capacity,good reducibility,and strong acidity contributed to the good catalytic performance of PdPtVO_(x)/CZO.Catalytic activity of PdPtVO_(x)/CZO decreased when 50 ppm SO_(2)or(1.0 vol.%H_(2)O+50 ppm SO_(2))was added to the feedstock,but was gradually restored to its initial level after the SO_(2)was cut off.The good reversible sulfur dioxide-resistant performance of PdPtVO_(x)/CZO was associated with the facts:(i)the introduction of SO_(2)leads to an increase in surface acidity;(ii)V can adsorb and activate SO_(2),thus accelerating formation of the SO_(x)^(2-)(x=3 or 4)species at the V and CZO sites,weakening the adsorption of sulfur species at the PdPt active sites,and hence protecting the PdPt active sites to be not poisoned by SO_(2).EB oxidation over PdPtVO_(x)/CZO might take place via the route of EB→styrene→phenyl methyl ketone→benzaldehyde→benzoic acid→maleic anhydride→CO_(2)and H_(2)O.
基金This work was supported by the National Key R&D Program of China(Nos.2018YFA0702003 and 2016YFA0202801)the National Natural Science Foundation of China(Nos.21890383,21671117,21871159,and 21901135)+2 种基金Science and Technology Key Project of Guangdong Province of China(No.2020B010188002)Beijing Municipal Science&Technology Commission(No.Z191100007219003)China Postdoctoral Science Foundation(No.2018M640114).
文摘The oxidation of hydrocarbons to produce high value-added compounds(ketones or alcohols)using oxygen in air as the only oxidant is an efficient synthetic strategy from both environmental and economic views.Herein,we successfully synthesized cobalt single atom site catalysts(Co SACs)with high metal loading of 23.58 wt.%supported on carbon nitride(CN),which showed excellent catalytic properties for oxidation of ethylbenzene in air.Moreover,Co SACs show a much higher turn-over frequency(19.6 h^(−1))than other reported non-noble catalysts under the same condition.Comparatively,the as-obtained nanosized or homogenous Co catalysts are inert to this reaction.Co SACs also exhibit high selectivity(97%)and stability(unchanged after five runs)in this reaction.DFT calculations reveal that Co SACs show a low energy barrier in the first elementary step and a high resistance to water,which result in the robust catalytic performance for this reaction.
基金National Key Research and Development Program Nanotechnology Specific Project,China(No.2020YFA0210900)Science and Technology Key Project of Guangdong Province,China(No.2020B010188002)+5 种基金Guangdong Natural Science Funds for Distinguished Young Scholar,China(No.2022B1515020035)Guangdong Provincial Key R&D Programme,China(No.2019B110206002)National Natural Science Foundation of China(Nos.22078371,21938001,21961160741)Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program,China(No.2017BT01C102)Natural Science Foundation of Guangdong Province,China(No.2020A1515011141)Science and Technology Project of Guangzhou City,China(No.202102020461).
文摘Through screening Ce precursors and pyrolysis temperatures[Ce(acac)3 as Ce precursors and pyrolysis at 900°C],zeolitic imidazolate framework-8(ZIF-8)derived nitrogen-doped carbon supported cerium single atom catalyst(Ce_(1)/NC)is successfully prepared by ball milling method.The Ce_(1)/NC catalyst exhibits exceptional catalytic performance in the selective oxidation of saturated C―H bonds in aromatic compounds,e.g.,91%conversion and 99%selelctivity can be achieved in the oxidation of ethylbenzene to acetophenone under mild reaction conditions.
