Preparation And Characterization Of High Temperature Water-gas Shift Reaction Catalysts In The Pyrolysis Gas

Among a large number of coal chemical process, pyrolysis is one of low rank coal grading effective utilization technologies which can produce large quantity of coal tar,raw gas and coke. While it is hard to deal with the waste water generated during pyrolysis process. This paper want to introduce water gas shift reaction into pyrolysis process and WGSR catalysts were prepared to reduce the waste water and CO among the reaction system.However, the pyrolysis gas has the characteristics of high temperature and complex tar composition. The traditional commercial conversion reaction catalyst is not suitable for this reaction system.The ABO₃ catalysts used for water gas shift reaction were prepared by citric acid method in this paper. The effect of different ratio of citric acid to metal ions and different calcination temperatures on the crystal structure and properties of the catalysts were studied. And then use Fe,Co,Ni to replace the B site of LaBO₃ catalyst to study the influence of different reaction temperature, steam gas ratio, space velocity and pressure on the catalyst activity. Partly substituting LaFeO₃ with Sr?NO₃?₂ Ni?NO₃?3 were also invesgated to find the change of catalyst activity. The catalyst specific surface area were measured by BET and its crystal structure were measured by XRD. The coke deposition on catalyst were examined by thermogravimetric analyzer.The results showed that LaFeO₃ characteristic peaks of perovskite phase were found when the ratio of citric acid and metal ions is 1:1,1.5:1,2:1,and the catalyst activity changed little. When the calcination temperature is 550 "C the catalyst can't prepared perovskite structure.The activity of LaFeO₃ catalyst was low, but its catalytic selectivity was good, and no methane side reaction product was found at any temperature point, and the conversion rate was up to 73.9% at 650?. LaNiO₃ catalytic activity was the highest among the three catalysts, the CO conversion is 94.5%at 500 ?, but it also produce a large number of methane side reaction product, LaCoO₃ catalyst's CO conversion was lowest compared to other catalysts and methane side reaction product was found among the WGSR products.The increase of steam gas ratio can promote the balance of water gas shift reaction turn to the right and restrain the generation of side reaction products.The CO conversion rate of water gas shift reaction increased with the increase of pressure when in 0.2-0.6Mpa and then remained stable. The CO conversion rate decreased significantly when the space velocity was above 6000h-1?The LaFe_1-XNi_xO₃, La?1-X? Sr_xFeO₃ catalysts can be prepared by citric acid sol method, and the increase of the doping content did not destroy the structure of perovskite crystal structure. And the results showed that the shift activity was LaFe_0.5Ni_0.5O₃>LaFe_0.7Ni_0.3O₃> LaFe_0.6Ni_0.4O₃>LaFe_0.8Ni_0.2O₃>LaFe_0.9Ni_0.1O₃, and the methane, ethylene products of side reactions increased with the increase of Ni content. While the content of Sr didn't affect the catalyst side reaction,when x is more than or equal to 0.3, the peak of SrCO₃ can be find from the XRD, the results showed that the shift activity was La_0.3Sr_0.2FeO₃=La_0.6Sr_0.4FeO₃> La_0.5Sr_0.5FeO₃>La_0.8Sr_0.2feO₃>La_0.9Sr_0.1FeO₃.The toluene and naphthalene will cause catalyst deactivation because of carbon deposition. It is also found that the carbon deposition of the catalysts will be burned at 500 ? to 700 ? ?And the catalyst does not have the catalytic hydrogenation of toluene and naphthalene.