Seven transition metal molybdovanadoarsenic heteropoly compounds have been synthesized and characterize d using IR,UV,TG-DTA,pH potential ti tration techniques￡(r)The molecular f ormulae of these compounds are pro-po...Seven transition metal molybdovanadoarsenic heteropoly compounds have been synthesized and characterize d using IR,UV,TG-DTA,pH potential ti tration techniques￡(r)The molecular f ormulae of these compounds are pro-posed to be HxMyAsMO10V2O40·zH2 O￡¨x￡1/21?￡3￡?y￡1/2￡±￡?￡2￡?M￡1/2Cr￡?Mn￡?Fe￡?Co￡?Ni￡?Cu￡?Zn￡(c)￡(r)They are all keggin structure￡(r)Surface nature of these compounds have been investigated by temperature programmed desorption and temperature programmed reducti on techniques￡(r)NH 3 -TPD results show that in TPD profile s of the compounds there are two desorption peaks corre sponding to weak acid sites of desorp tion,respectively￡(r)Desorbing activativon energy and preexponential factor of weak acid site of desorption for comp ounds have been calculated￡(r)H2 -TPR re-sults show that introducting transtion metal to molybdovanarsenic acid,the reduction peak temperatures of H2 -TPR shift regularly with increasing d electron numbers of transition metals￡(r)In addition,Zn and Cu heteropoly com-pounds have yet apparent effect of hydrogen spill over￡(r)展开更多
Pt Sn/MgAl 2O 4 catalysts prepared by co impregnation with nominal 0 35% platinum and varying content of tin (0～2 5%) were characterized by temperature programmed reduction (TPR) and temperature programmed desorption...Pt Sn/MgAl 2O 4 catalysts prepared by co impregnation with nominal 0 35% platinum and varying content of tin (0～2 5%) were characterized by temperature programmed reduction (TPR) and temperature programmed desorption of hydrogen (H 2 TPD). TPR results showed that platinum catalyzed the reduction of tin. However, the average oxidation state of tin after reduction depended upon the concentration of tin on the catalysts. H 2 TPD data indicated that tin addition inhibited the inactivated adsorption of hydrogen but promoted the activated adsorption, implying that tin modified both the ensembles of platinum and metal support interface, thus increasing hydrogen mobility and promoting hydrogen spillover.展开更多
A series of ultrafine Mo Co K catalysts with different Co/Mo ratios but constant potassium content were characterized by TPD technique and their catalytic performance for higher alcohol synthesis was investigated The ...A series of ultrafine Mo Co K catalysts with different Co/Mo ratios but constant potassium content were characterized by TPD technique and their catalytic performance for higher alcohol synthesis was investigated The results indicated that there are two kinds of adsorption sites, ie, low temperature adsorption sites (LTAS) around 90?℃ and high temperature adsorption sites (HTAS) above 400?℃ for H 2 and CO on the surface of the catalysts The desorption temperature of HTAS for H 2 and CO as well as the desorption amount of HTAS for H 2 were strongly influenced by the Co/Mo ratio of the catalysts It was found that the addition of Co into the ultrafine Mo K catalyst resulted in a decrease of the HTAS desorption temperature and an increase of the HTAS desorption amount for H 2 As the Co/Mo ratio increased further, the HTAS desorption amount for H 2 increased accordingly while the HTAS desorption temperature remained constant However, the HTAS desorption temperature for CO was found to be mainly influenced by the Co/Mo ratio, and the HTAS desorption temperature got its minimum at the Co/Mo ratio of 1∶7 It was found that a weaker adsorption of H 2 and CO on the HTAS and an appropriate H 2 adsorption amount were favourable for the formation of higher展开更多
文摘Seven transition metal molybdovanadoarsenic heteropoly compounds have been synthesized and characterize d using IR,UV,TG-DTA,pH potential ti tration techniques￡(r)The molecular f ormulae of these compounds are pro-posed to be HxMyAsMO10V2O40·zH2 O￡¨x￡1/21?￡3￡?y￡1/2￡±￡?￡2￡?M￡1/2Cr￡?Mn￡?Fe￡?Co￡?Ni￡?Cu￡?Zn￡(c)￡(r)They are all keggin structure￡(r)Surface nature of these compounds have been investigated by temperature programmed desorption and temperature programmed reducti on techniques￡(r)NH 3 -TPD results show that in TPD profile s of the compounds there are two desorption peaks corre sponding to weak acid sites of desorp tion,respectively￡(r)Desorbing activativon energy and preexponential factor of weak acid site of desorption for comp ounds have been calculated￡(r)H2 -TPR re-sults show that introducting transtion metal to molybdovanarsenic acid,the reduction peak temperatures of H2 -TPR shift regularly with increasing d electron numbers of transition metals￡(r)In addition,Zn and Cu heteropoly com-pounds have yet apparent effect of hydrogen spill over￡(r)
文摘Pt Sn/MgAl 2O 4 catalysts prepared by co impregnation with nominal 0 35% platinum and varying content of tin (0～2 5%) were characterized by temperature programmed reduction (TPR) and temperature programmed desorption of hydrogen (H 2 TPD). TPR results showed that platinum catalyzed the reduction of tin. However, the average oxidation state of tin after reduction depended upon the concentration of tin on the catalysts. H 2 TPD data indicated that tin addition inhibited the inactivated adsorption of hydrogen but promoted the activated adsorption, implying that tin modified both the ensembles of platinum and metal support interface, thus increasing hydrogen mobility and promoting hydrogen spillover.
文摘A series of ultrafine Mo Co K catalysts with different Co/Mo ratios but constant potassium content were characterized by TPD technique and their catalytic performance for higher alcohol synthesis was investigated The results indicated that there are two kinds of adsorption sites, ie, low temperature adsorption sites (LTAS) around 90?℃ and high temperature adsorption sites (HTAS) above 400?℃ for H 2 and CO on the surface of the catalysts The desorption temperature of HTAS for H 2 and CO as well as the desorption amount of HTAS for H 2 were strongly influenced by the Co/Mo ratio of the catalysts It was found that the addition of Co into the ultrafine Mo K catalyst resulted in a decrease of the HTAS desorption temperature and an increase of the HTAS desorption amount for H 2 As the Co/Mo ratio increased further, the HTAS desorption amount for H 2 increased accordingly while the HTAS desorption temperature remained constant However, the HTAS desorption temperature for CO was found to be mainly influenced by the Co/Mo ratio, and the HTAS desorption temperature got its minimum at the Co/Mo ratio of 1∶7 It was found that a weaker adsorption of H 2 and CO on the HTAS and an appropriate H 2 adsorption amount were favourable for the formation of higher
