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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)
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 £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ © (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 Both 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 compounds 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 el ectron numbers of transition metals £ (r) In addition, Zn and Cu heteropoly com-pounds have yet apparent effect of hydrogen spill over £ (r)