Shape-selective zeolites(UZ-x/y) were synthesized by a one-pot method using TPAOH(y) and/or MeEt3 N^+I^-(x) as templates.The use of MeEt3 N^+I^- affects the crystal growth and the distribution of acid sites on the ext...Shape-selective zeolites(UZ-x/y) were synthesized by a one-pot method using TPAOH(y) and/or MeEt3 N^+I^-(x) as templates.The use of MeEt3 N^+I^- affects the crystal growth and the distribution of acid sites on the external surface of the zeolites.The catalysts show excellent catalytic activity towards toluene alkylation with CH3 Br.With toluene conversion of 36.3% and p-xylene selectivity of 66.2%,HZ-40/0 is the most effective among the prepared catalysts,showing a p-xylene yield of 21.2%.The improved para-selectivity is mainly due to the decrease of acid sites on the external surface of the catalysts.展开更多
Ammonia(NH_(3)) decomposition to release CO_x-free hydrogen(H_(2)) over non-noble catalysts has gained increasing attention.In this study,three nanostructured CeO_(2) with different morphologies,viz.rod(R).sphere(Sph)...Ammonia(NH_(3)) decomposition to release CO_x-free hydrogen(H_(2)) over non-noble catalysts has gained increasing attention.In this study,three nanostructured CeO_(2) with different morphologies,viz.rod(R).sphere(Sph),and spindle(Spi),were fabricated and served as supports for Ni/CeO_(2) catalyst.The CeO_(2)supports are different in particle sizes,specific surface area and porosity,resulting in the formation of Ni nanoparticles with distinguished sizes and dispersions.The surface properties of the Ni/CeO_(2) catalysts are not only distinct but also influential,affecting the adsorption and desorption of NH_(3),N_(2),and/or H_(2)molecules.The Ni/CeO_(2)-R catalyst shows superior catalytic activity compared to the other two,owing to its smaller Ni crystallite size and larger BET surface area.The most abundant strong basic sites are observed for Ni/CeO_(2)-Spi catalyst based on its exposed CeO_(2)(110) planes,which facilitates the donation of electrons to the Ni particles,benefiting the associative desorption of N atoms.Thus,Ni/CeO_(2)-Spi shows higher catalytic activity than Ni/CeO_(2)-Sph,despite their almost identical Ni crystallite sizes.展开更多
Thiamine derivatives that are cheap, readily available, non-toxic and green are used as heterogeneous catalyst for the generation of cyclic carbonates through cycloaddition of CO_2 to epoxides without the need of co-c...Thiamine derivatives that are cheap, readily available, non-toxic and green are used as heterogeneous catalyst for the generation of cyclic carbonates through cycloaddition of CO_2 to epoxides without the need of co-catalyst and solvent. The interaction between thiamine hydrochloride(VB_1-Cl) and substrates(CO_2 and propylene oxide) was proven by ultraviolet-visible spectroscopy and ~1H nuclear magnetic resonance analysis, and it is deduced that the synergistic action among multi-functional groups(hydroxyl, halide anion and amine) is a favorable factor for cycloaddition reaction. A series of VB_1/GO aerogels were facilely prepared through the addition of aqueous VB_1 derivatives to a suspension of GO in ethanol at room temperature. It was found that the aerogel generated through the interaction of VB_1-Cl with GO shows catalytic activity and stability higher than those of VB_1-Cl. It is because the electrostatic interaction between GO and VB_1-Cl enhances the nucleophilicity and leaving ability of anion. The effects of reaction temperature, catalyst loading, CO_2 pressure and reaction time on CO_2 cycloaddition to propylene oxide were thoroughly studied.展开更多
In this article,we present our research results on chemical fixation of CO_(2) using organobismuth compounds.We fabricated bismuth biphenoate complex,Zn-Mg-Al composite oxides,and SBA-15 or Al-SBA-15 immobilized hydro...In this article,we present our research results on chemical fixation of CO_(2) using organobismuth compounds.We fabricated bismuth biphenoate complex,Zn-Mg-Al composite oxides,and SBA-15 or Al-SBA-15 immobilized hydroxyl ionic liquid for CO_(2) cycloaddition onto epoxides.The hypervalent bismuth compounds show good ability for association and dissociation with CO_(2).The bismuth biphenolate complexes are catalytically effective for the cycloaddition reaction.The heterogeneous catalysts,viz.Zn-Mg-Al oxides and SBA-15 or Al-SBA-15 immobilized ionic liquid,are efficient for the synthesis of cyclic carbonate from CO_(2) and epoxide.It is found that the presence of a trace amount of water can improve the catalytic activity of the immobilized ionic liquid.展开更多
The pure phase of praseodymium orthovanadate (PrVO\-4) has been prepared by the citrate method. The active site of PrVO\-4 was studied by ESR, NO_TPD, O\-2_TPD and 18 O\-2_isotope exchange methods. The results of ESR ...The pure phase of praseodymium orthovanadate (PrVO\-4) has been prepared by the citrate method. The active site of PrVO\-4 was studied by ESR, NO_TPD, O\-2_TPD and 18 O\-2_isotope exchange methods. The results of ESR and NO_TPD confirmed the presence of V 4+ in the catalyst. 18 O\-2_isotope exchange was through a single exchange procedure. From the result of O\-2+TPD and the kinetic study of 18 O\-2_isotope exchange, one can reach a conclusion that the V 4+ species associated with oxygen vacancies are the site for O\-2 activation. The adsorbed O\-2 or O\+- are the active oxygen species in propane oxidative dehydrogenation.展开更多
基金Supported by the National Natural Science Foundation of China(21273067,21476065,21671062,21725602)Program for Changjiang Scholars and Innovative Research Team in University(IRT1238)the Fundamental Research Funds for the Central Universities
文摘Shape-selective zeolites(UZ-x/y) were synthesized by a one-pot method using TPAOH(y) and/or MeEt3 N^+I^-(x) as templates.The use of MeEt3 N^+I^- affects the crystal growth and the distribution of acid sites on the external surface of the zeolites.The catalysts show excellent catalytic activity towards toluene alkylation with CH3 Br.With toluene conversion of 36.3% and p-xylene selectivity of 66.2%,HZ-40/0 is the most effective among the prepared catalysts,showing a p-xylene yield of 21.2%.The improved para-selectivity is mainly due to the decrease of acid sites on the external surface of the catalysts.
基金Project supported by the National Key R&D Program of China (2020YFB1505604)the National Natural Science Foundation of China(22178058,22078062)。
文摘Ammonia(NH_(3)) decomposition to release CO_x-free hydrogen(H_(2)) over non-noble catalysts has gained increasing attention.In this study,three nanostructured CeO_(2) with different morphologies,viz.rod(R).sphere(Sph),and spindle(Spi),were fabricated and served as supports for Ni/CeO_(2) catalyst.The CeO_(2)supports are different in particle sizes,specific surface area and porosity,resulting in the formation of Ni nanoparticles with distinguished sizes and dispersions.The surface properties of the Ni/CeO_(2) catalysts are not only distinct but also influential,affecting the adsorption and desorption of NH_(3),N_(2),and/or H_(2)molecules.The Ni/CeO_(2)-R catalyst shows superior catalytic activity compared to the other two,owing to its smaller Ni crystallite size and larger BET surface area.The most abundant strong basic sites are observed for Ni/CeO_(2)-Spi catalyst based on its exposed CeO_(2)(110) planes,which facilitates the donation of electrons to the Ni particles,benefiting the associative desorption of N atoms.Thus,Ni/CeO_(2)-Spi shows higher catalytic activity than Ni/CeO_(2)-Sph,despite their almost identical Ni crystallite sizes.
文摘Thiamine derivatives that are cheap, readily available, non-toxic and green are used as heterogeneous catalyst for the generation of cyclic carbonates through cycloaddition of CO_2 to epoxides without the need of co-catalyst and solvent. The interaction between thiamine hydrochloride(VB_1-Cl) and substrates(CO_2 and propylene oxide) was proven by ultraviolet-visible spectroscopy and ~1H nuclear magnetic resonance analysis, and it is deduced that the synergistic action among multi-functional groups(hydroxyl, halide anion and amine) is a favorable factor for cycloaddition reaction. A series of VB_1/GO aerogels were facilely prepared through the addition of aqueous VB_1 derivatives to a suspension of GO in ethanol at room temperature. It was found that the aerogel generated through the interaction of VB_1-Cl with GO shows catalytic activity and stability higher than those of VB_1-Cl. It is because the electrostatic interaction between GO and VB_1-Cl enhances the nucleophilicity and leaving ability of anion. The effects of reaction temperature, catalyst loading, CO_2 pressure and reaction time on CO_2 cycloaddition to propylene oxide were thoroughly studied.
基金The financial supports of the National Natural Science Foundation of China(Grant Nos.20507005 and 20873038)Outstanding Young Research Award of National Natural Science Foundation of China(Grant No.E50725825)Hong Kong Baptist University(FRG/08-09/II-09)。
文摘In this article,we present our research results on chemical fixation of CO_(2) using organobismuth compounds.We fabricated bismuth biphenoate complex,Zn-Mg-Al composite oxides,and SBA-15 or Al-SBA-15 immobilized hydroxyl ionic liquid for CO_(2) cycloaddition onto epoxides.The hypervalent bismuth compounds show good ability for association and dissociation with CO_(2).The bismuth biphenolate complexes are catalytically effective for the cycloaddition reaction.The heterogeneous catalysts,viz.Zn-Mg-Al oxides and SBA-15 or Al-SBA-15 immobilized ionic liquid,are efficient for the synthesis of cyclic carbonate from CO_(2) and epoxide.It is found that the presence of a trace amount of water can improve the catalytic activity of the immobilized ionic liquid.
文摘The pure phase of praseodymium orthovanadate (PrVO\-4) has been prepared by the citrate method. The active site of PrVO\-4 was studied by ESR, NO_TPD, O\-2_TPD and 18 O\-2_isotope exchange methods. The results of ESR and NO_TPD confirmed the presence of V 4+ in the catalyst. 18 O\-2_isotope exchange was through a single exchange procedure. From the result of O\-2+TPD and the kinetic study of 18 O\-2_isotope exchange, one can reach a conclusion that the V 4+ species associated with oxygen vacancies are the site for O\-2 activation. The adsorbed O\-2 or O\+- are the active oxygen species in propane oxidative dehydrogenation.
