Nanosized Ga-containing ZSM-5 zeolites were prepared via isomorphous substitution and impregnation followed by characterized using various techniques. The catalytic performance of the zeolites for the aromatization of...Nanosized Ga-containing ZSM-5 zeolites were prepared via isomorphous substitution and impregnation followed by characterized using various techniques. The catalytic performance of the zeolites for the aromatization of 1-hexene was investigated. The results indicate that isomorphous substitution promotes the incorporation of Ga heteroatoms into the framework along with the formation of extra-framework GaO;species（[GaO;]a） that have stronger interactions with the negative potential of the framework. In addition, based on the Py-IR results and catalytic performance, the [GaO;]aspecies with stronger Lewis acid sites produced a better synergism with moderate Br?nsted acid sites and thus improved the selectivity to aromatic compounds. However, the impregnation results in the formation of Ga;O;phase and small amounts of GaO;species that are mainly located on the external surface（[GaO;];）, which contribute to weaker Lewis acid sites due to weaker interactions with the zeolite framework. During 1-hexene aromatization, the nanosized Ga isomorphously substituted ZSM-5 zeolite samples（Gax-NZ5） exhibited better catalytic performance compared to the impregnated samples, and the highest aromatic yield（i.e.,65.4 wt%） was achieved over the Ga4.2-NZ5 sample, which contained with the highest Ga content.展开更多
The development of highly effective metal-zeolite bifunctional catalysts for the hydroisomerization of n-alkanes is a paramount strategy to produce second-generation biofuels with high quality.In this study,polyhexame...The development of highly effective metal-zeolite bifunctional catalysts for the hydroisomerization of n-alkanes is a paramount strategy to produce second-generation biofuels with high quality.In this study,polyhexamethylene biguanide hydrochloride(PHMB)is precisely added to the initial gel to synthesize nanosized ZSM-23 zeolites(Z23-x PH).Due to orientation adsorption and steric hindrance effects of PHMB,each sample of Z23-x PH demonstrates enhanced mesoporosity in comparison with the conventional Z23-C zeolite.Furthermore,the Bronsted acid density of the Z23-x PH samples is also signifi cantly reduced due to a reduction in the distribution of framework Al at T2-T5 sites.The corresponding Pd/23-C and Pd/Z23-x PH bifunctional catalysts with 0.5 wt%Pd loading for n-hexadecane hydroisomerization are prepared by incorporating ZSM-23 zeolites as acid supports.According to the catalytic test results,the suitable addition of PHMB can effectively promote the iso-hexadecane yield.The Pd/Z23-2PH catalyst with an n_(PHMB)/n(_Si)molar ratio of 0.002 demonstrates the highest maximum iso-hexadecane yield of 74.1%at an n-hexadecane conversion of 88.3%.Therefore,the employment of PHMB has provided a simple route for the development of highly effective Pd/ZSM-23 catalysts for n-alkane hydroisomerization.展开更多
The production of H_2 and O_2 from solar-light photocatalytic water splitting has attracted significant research attention as a clean and renewable source of energy.In this study,hydrogenated TiO_2/SrTiO_3 porous micr...The production of H_2 and O_2 from solar-light photocatalytic water splitting has attracted significant research attention as a clean and renewable source of energy.In this study,hydrogenated TiO_2/SrTiO_3 porous microspheres were prepared as a high-performance photocatalyst.Titanium glycerolate and then strontium complex precursors were first prepared via a two-step solvothermal process,then,after calcination in air and subsequent H_2/Ar reduction treatments,hydrogenated TiO_2/SrTiO_3 porous microspheres with controllable defects and band positions were prepared.Several characterization techniques were used to demonstrate that the catalyst heterostructures,the oxygen-vacancy content,and the unique porous structures synergistically enhanced the visible-light harvesting abilities and photogenerated charge separation,and resulted in improved photocatalytic efficiency for H_2 and O_2 evolution.As expected,the optimum treatment conditions provided hydrogenated TiO_2/SrTiO_3 porous microspheres that showed excellent photocatalytic activity with H_2 and O_2 evolution rates of 239.97 and 103.79μmol h^(-1)(50 mg catalyst,under AM 1.5 irradiation),respectively,which were ca.5.9 and 6.6times higher,respectively,than those of solid TiO_2/SrTiO_3materials.Thus,this type of hydrogenated TiO_2/SrTiO_3porous microsphere catalyst shows great potential as a photocatalyst for solar-energy conversion applications.展开更多
Chemoselective hydrodeoxygenation of vanillin is of great importance in converting biomass into high value-added chemicals.Herein,we describe a facile photochemical route to access palladium single atoms and clusters ...Chemoselective hydrodeoxygenation of vanillin is of great importance in converting biomass into high value-added chemicals.Herein,we describe a facile photochemical route to access palladium single atoms and clusters supported on silicoaluminophosphate-31(SAPO-31)as a highly active,chemoselective,and reusable catalyst for hydrodeoxygenation of vanillin.Characterizations by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy,extended X-ray absorption fine structure measurement,and CO-absorbed diffuse reflectance infrared Fourier transform spectroscopy reveal the atomically dispersed palladium single atoms and clusters are loosely bonded and randomly dispersed,without forming strong palladium-palladium metallic bonding,over the SAPO-31 support.This catalyst,with a full metal availability to the reactants,exhibits exceptional catalytic activity(TOF:3,000 h^(−1),Yield:>99%)in the hydrodeoxygenation of vanillin toward 2-methoxy-4-methylphenol(MMP)under mild conditions(1 atm,80°C,30 min),along with excellent stability,scalability(up to 100-fold),and wide substrate scope.The superior catalytic performance can be attributed to the synergistic effect of the positively charged palladium single atoms and fully exposed clusters,as well as the strong metal-support interactions.This work may offer a new avenue for the design and synthesis of fully exposed metal catalysts with targeted functionalities.展开更多
The hydroisomerization of n-hexadecane over Pt-Pd bimetallic catalysts is an effective way to produce clean fuel oil.This work reports a useful preparation method of bimetallic bifunctional catalysts by a co-impregnat...The hydroisomerization of n-hexadecane over Pt-Pd bimetallic catalysts is an effective way to produce clean fuel oil.This work reports a useful preparation method of bimetallic bifunctional catalysts by a co-impregnation or sequential impregnation process.Furthermore,monometallic catalysts with loading either Pt or Pd are also prepared for comparison.The effects of the metal species and impregnation order on the characteristics and catalytic performance of the catalysts are investigated.The catalytic test results indicate that the maximum iso-hexadecane yield over different catalysts increases as follows:Pt/silicoaluminophosphate SAPO-41<Pd/SAPO-41<Pt^(*)-Pd/SAPO-41(prepared by sequential impregnation)<Pt-Pd/SAPO-41(prepared by co-impregnation).Owing to the synergic effects between Pt and Pd,the Pt-Pd/SAPO-41 catalyst prepared by the co-impregnation method demonstrates the effective promotion of(de)hydrogenation activity.Therefore,this catalyst exhibits the highest iso-hexadecane yield of 89.4%when the n-hexadecane conversion is 96.3%.Additionally,the Pt-Pd/SAPO-41 catalyst also presents the highest catalytic activity and best stability even after 150 h long-term tests.展开更多
基金supported by the National Natural Science Foundation of China(Nos.21276067 and 21676074)Programs of International S&T cooperation(No.2014DFR41110)
文摘Nanosized Ga-containing ZSM-5 zeolites were prepared via isomorphous substitution and impregnation followed by characterized using various techniques. The catalytic performance of the zeolites for the aromatization of 1-hexene was investigated. The results indicate that isomorphous substitution promotes the incorporation of Ga heteroatoms into the framework along with the formation of extra-framework GaO;species（[GaO;]a） that have stronger interactions with the negative potential of the framework. In addition, based on the Py-IR results and catalytic performance, the [GaO;]aspecies with stronger Lewis acid sites produced a better synergism with moderate Br?nsted acid sites and thus improved the selectivity to aromatic compounds. However, the impregnation results in the formation of Ga;O;phase and small amounts of GaO;species that are mainly located on the external surface（[GaO;];）, which contribute to weaker Lewis acid sites due to weaker interactions with the zeolite framework. During 1-hexene aromatization, the nanosized Ga isomorphously substituted ZSM-5 zeolite samples（Gax-NZ5） exhibited better catalytic performance compared to the impregnated samples, and the highest aromatic yield（i.e.,65.4 wt%） was achieved over the Ga4.2-NZ5 sample, which contained with the highest Ga content.
基金funded by the National Key Research and Development Project,Intergovernmental International Science and Technology Innovation Cooperation Key Project(No.2018YFE0108800)National Natural Science Foundation of China(No.22278115)Heilongjiang Province Natural Science Foundation(No.YQ2021B010).
文摘The development of highly effective metal-zeolite bifunctional catalysts for the hydroisomerization of n-alkanes is a paramount strategy to produce second-generation biofuels with high quality.In this study,polyhexamethylene biguanide hydrochloride(PHMB)is precisely added to the initial gel to synthesize nanosized ZSM-23 zeolites(Z23-x PH).Due to orientation adsorption and steric hindrance effects of PHMB,each sample of Z23-x PH demonstrates enhanced mesoporosity in comparison with the conventional Z23-C zeolite.Furthermore,the Bronsted acid density of the Z23-x PH samples is also signifi cantly reduced due to a reduction in the distribution of framework Al at T2-T5 sites.The corresponding Pd/23-C and Pd/Z23-x PH bifunctional catalysts with 0.5 wt%Pd loading for n-hexadecane hydroisomerization are prepared by incorporating ZSM-23 zeolites as acid supports.According to the catalytic test results,the suitable addition of PHMB can effectively promote the iso-hexadecane yield.The Pd/Z23-2PH catalyst with an n_(PHMB)/n(_Si)molar ratio of 0.002 demonstrates the highest maximum iso-hexadecane yield of 74.1%at an n-hexadecane conversion of 88.3%.Therefore,the employment of PHMB has provided a simple route for the development of highly effective Pd/ZSM-23 catalysts for n-alkane hydroisomerization.
基金supported by the National Natural Science Foundation of China(51272070,21631004,21371053,and 21376065)the Project for Foshan Innovation Group(2014IT100062)+4 种基金the Application Technology Research and Development Projects in Harbin(2013AE4BW051)the International Science&Technology Cooperation Program of China(2014DFR41110)the Natural Science Foundation of Heilongjiang province(E201455)the Postdoctoral Science-research Developmental Foundation of Heilongjiang province(LBH-Q13136)the Special Fund of Technological Innovation Talents in Harbin City(2015RAQXJ003)
文摘The production of H_2 and O_2 from solar-light photocatalytic water splitting has attracted significant research attention as a clean and renewable source of energy.In this study,hydrogenated TiO_2/SrTiO_3 porous microspheres were prepared as a high-performance photocatalyst.Titanium glycerolate and then strontium complex precursors were first prepared via a two-step solvothermal process,then,after calcination in air and subsequent H_2/Ar reduction treatments,hydrogenated TiO_2/SrTiO_3 porous microspheres with controllable defects and band positions were prepared.Several characterization techniques were used to demonstrate that the catalyst heterostructures,the oxygen-vacancy content,and the unique porous structures synergistically enhanced the visible-light harvesting abilities and photogenerated charge separation,and resulted in improved photocatalytic efficiency for H_2 and O_2 evolution.As expected,the optimum treatment conditions provided hydrogenated TiO_2/SrTiO_3 porous microspheres that showed excellent photocatalytic activity with H_2 and O_2 evolution rates of 239.97 and 103.79μmol h^(-1)(50 mg catalyst,under AM 1.5 irradiation),respectively,which were ca.5.9 and 6.6times higher,respectively,than those of solid TiO_2/SrTiO_3materials.Thus,this type of hydrogenated TiO_2/SrTiO_3porous microsphere catalyst shows great potential as a photocatalyst for solar-energy conversion applications.
基金The authors greatly acknowledge the financial support from the China Postdoctoral Science Foundation(Nos.2019M661247 and 2020T130091)Postdoctoral Science Foundation of Heilongjiang Province(LBH-Z19047)+1 种基金Scientific Research Foundation for Returned Scholars of Heilongjiang Province of China(719900091)Key Laboratory of Functional Inorganic Material Chemistry(Heilongjiang University),Ministry of Education.
文摘Chemoselective hydrodeoxygenation of vanillin is of great importance in converting biomass into high value-added chemicals.Herein,we describe a facile photochemical route to access palladium single atoms and clusters supported on silicoaluminophosphate-31(SAPO-31)as a highly active,chemoselective,and reusable catalyst for hydrodeoxygenation of vanillin.Characterizations by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy,extended X-ray absorption fine structure measurement,and CO-absorbed diffuse reflectance infrared Fourier transform spectroscopy reveal the atomically dispersed palladium single atoms and clusters are loosely bonded and randomly dispersed,without forming strong palladium-palladium metallic bonding,over the SAPO-31 support.This catalyst,with a full metal availability to the reactants,exhibits exceptional catalytic activity(TOF:3,000 h^(−1),Yield:>99%)in the hydrodeoxygenation of vanillin toward 2-methoxy-4-methylphenol(MMP)under mild conditions(1 atm,80°C,30 min),along with excellent stability,scalability(up to 100-fold),and wide substrate scope.The superior catalytic performance can be attributed to the synergistic effect of the positively charged palladium single atoms and fully exposed clusters,as well as the strong metal-support interactions.This work may offer a new avenue for the design and synthesis of fully exposed metal catalysts with targeted functionalities.
基金the financial supports from the National Key R&D Program of China,Intergovernmental International Science and Technology Innovation Cooperation Key Project(Grant No.2018YFE0108800)the National Natural Science Foundation of China(Grant Nos.21676074 and 21706053)National Key Research and Development Project,National Ministry of Education“Silk Road 1+1”Research Cooperation Project.
文摘The hydroisomerization of n-hexadecane over Pt-Pd bimetallic catalysts is an effective way to produce clean fuel oil.This work reports a useful preparation method of bimetallic bifunctional catalysts by a co-impregnation or sequential impregnation process.Furthermore,monometallic catalysts with loading either Pt or Pd are also prepared for comparison.The effects of the metal species and impregnation order on the characteristics and catalytic performance of the catalysts are investigated.The catalytic test results indicate that the maximum iso-hexadecane yield over different catalysts increases as follows:Pt/silicoaluminophosphate SAPO-41<Pd/SAPO-41<Pt^(*)-Pd/SAPO-41(prepared by sequential impregnation)<Pt-Pd/SAPO-41(prepared by co-impregnation).Owing to the synergic effects between Pt and Pd,the Pt-Pd/SAPO-41 catalyst prepared by the co-impregnation method demonstrates the effective promotion of(de)hydrogenation activity.Therefore,this catalyst exhibits the highest iso-hexadecane yield of 89.4%when the n-hexadecane conversion is 96.3%.Additionally,the Pt-Pd/SAPO-41 catalyst also presents the highest catalytic activity and best stability even after 150 h long-term tests.
