Preparation And Reaction Characteristics Of Catalysts For APR Hydrogen Production From Ethylene Glycol

In view of the shortage and high pollution of fossil energy,hydrogen produced using biomass as raw material is an ideal alternative energy sources with sustainable development and extremely potential.Comparing with the traditional hydrogen production methods with disadvantages including low H₂ yield and complex equipment,the aqueous phase reforming shows more advantages due to its simple reaction process and the one-step production of H₂.Among the catalyst in the aqueous phase reforming reaction,on the Pt-based noble metal catalysts show high conversion,whereas the H₂ production rate is low.Meanwhile,the high cost limits the application of this catalyst.For the Ni-based non-noble metal catalyst,it shows high C-C bond,however,it is easy to be deactivated.In view of what stated above,the wet impregnation method,co-precipitation method,deposition-precipitation method and citric acid sol-gel method are employed to prepare the Pd,NiFeCo and NiFe/CeO₂ series catalysts in this paper,and their structural characteristics and catalytic activity in the aqueous phase reforming of ethylene glycol were investigated.The main obtained research results are showing as follows.1.Pd/γ-Al₂O₃,PdNi/γ-Al₂O₃ and Ni/γ-Al₂O₃ catalysts were prepared with wet impregnation method and the effect of Ni doping on their catalytic activity were investigated.The experimental results showed that H₂ selectivity and ethylene glycol conversion on the Pd/γ-Al₂O₃ were 38.9% and 13.7% respectively,whereas the alkane selectivity was only 11.3%.With the doping of Ni metal,a PdNi alloy was formed on the Pd/γ-Al₂O₃ catalyst,and the Pd and Ni showed a strong interaction,which promoted desorption of CO from active sites and improved the metal dispersion.In addition,the H₂ selectivity and ethylene glycol conversion rose up to 49.5% and 49.5% respectively.2.Citric acid sol-gel method was utilized to prepare NiFeCo catalysts.Effects of Fe/Co mole ratio and reduction temperature on catalytic activity were investigated.It was found that the Ni improved C-C bond cleavage ability,but it resulted in a high methanation.The Fe could promote the WGS reaction process,however,its catalytic activity was low.Additionally,the Co showed a promoting effect on the formation of FeNi alloy,which improved the WGS reaction activity.After the reduction at 660℃,the H₂ selectivity and ethylene glycol conversion could reach up to 99.8% and 95.1% respectively,and alkane selectivity decreased to 1.3%.Fe/Ni mole ratio in FeNi alloy showed a great influence on the catalytic activity of the catalyst and the deactivation of NiFeCo catalyst was obvious.3.Effects of the preparation methods on the catalytic activity of the NiFe/CeO₂ catalysts in the aqueous phase reforming of ethylene glycol for hydrogen production were investigated.On the cal-NiFe/CeO₂ catalyst,a 75.5% H₂ selectivity,a 76.3% ethylene glycol conversion and a 12.5% alkane selectivity were obtained.In the structure of the prepared catalyst,the better pore structure and larger specific surface area were benefit for the free access of reactants and products.It was found that there was a strong interaction between FeNi alloy and CeO₂ support,which improved the catalytic activity.4.The NiFe/CeO₂ catalysts were prepared with deposition precipitation method,and the Ni/Fe mole ratio on the reaction activity was investigated.It was shown that the interaction between Fe and Ni promoted improved the dispersion of the formed FeNi alloy on the surface of CeO₂ support,and which also improved the H₂ selectivity and ethylene glycol conversion.The CeO₂ support eliminated the carbon deposition on the surface of active sites,suppressed the particle sintering,and enhanced the stability of Ni Fe/CeO₂ catalyst.The H₂ selectivity and polyols conversion of four kinds of polyols decreased in the following order: methanol>ethylene glycol>glycerol>sorbitol.