Study On Hydrogen Production By Steam Reforming Of Glycerol With Attapulgite Supported Transition Metal Catalyst

With the increasingly prominent environmental problems caused by the use of fossil fuels,hydrogen,as an important energy substitute for the future energy transformation,has been paid more and more attention.As a result,the by-products of glycerol produced by the development of biodiesel industry have been studied deeply in the raw materials for hydrogen production,and the by-products of glycerol produced by the development of biodiesel industry are gradually applied in hydrogen production process.As a kind of renewable clean energy,glycerol has a very broad application prospect in the future.According to the current research progress,the catalytic performance of attapulgite（ATP）as supported catalyst in hydrogen production from steam reforming of glycerol was investigated in this paper.The optimum process conditions for hydrogen production from steam reforming were explored in a fixed-bed reactor.（1）ATP was pretreated with nitric acid,and supported catalysts of different transition metals（Ni,Cu,Co,Fe）were prepared by precipitation method.The dispersion of different transition metals on ATP surface,the crystal structure of active metals,the surface area carbon of the catalyst,the interaction between the metal and the support,and the pore channels on the surface of the catalyst were studied by TEM,XRD,TG-DSC,H₂-TPR,and N₂ adsorption and desorption analysis,respectively.The effects of different catalysts,reaction temperature,water-carbon ratio and reaction time on hydrogen production by steam reforming of glycerol were discussed.The experimental results showed that compared with Cu/ATP and Fe/ATP,Ni/ATP and Co/ATP catalysts have higher ability to break bonds and promote the shift reaction of water vapor,so the conversion of glycerol and the selectivity of hydrogen are higher.The conversion of glycerol and selectivity of hydrogen for Ni/ATP catalyst were 78.2%and 68.3%,respectively.（2）Ni/ATP-P and Ni/ATP-I catalysts were prepared by precipitation method and impregnation method respectively.The catalysts were characterized by N2 adsorption desorption,XRD,TPR,TEM,etc.The effects of catalyst preparation methods on the dispersion of active metals,catalytic stability and the effect of water-carbon ratio on catalytic reforming of Ni/ATP-I catalysts were investigated.The results show that the Ni/ATP-I catalyst prepared by impregnation method is beneficial to metal dispersion.From TEM and XRD,it can be seen that Ni metal particles show smaller metal size on the surface of ATP.The results of TPR analysis show that the Ni oxide prepared by impregnation method has a strong interaction with the support,and the migration and aggregation of metals are inhibited during the calcination and activation process of the catalyst.In the stability test,the conversion of glycerol and selectivity of hydrogen for Ni/ATP-I catalyst were 93.7%and 66.9%,respectively.（3）The Ni/ATP-I catalyst modified by CaO as an auxiliary agent were applied in the research on the hydrogen production from the catalytic reforming of the glycerol.The XRD,TPR,TPR and etc showed that the addition of CaO could change the pore channel distribution of the catalyst surface and enhanced the interaction between the nickel metal particles and the ATP,and at the same time,the surface acidity of the catalyst was reduced,so that the catalyst anti-product carbon performance was enhanced.The research of steam reforming process showed that the conversion of glycerol and the selectivity of hydrogen were the highest under the conditions of600^oC and 5 of water-to-carbon ratio about the Ni-3%Ca/ATP-I catalyst,reaching96.5%and 82.4%,respectively.