| As a high-polluting,high-carbon energy,coal has accelerated China's rapid economic development in the past few decades.However,it has also caused increasing environmental pollution and speeded up emissions of gases that contribute to global warming.Taking into account the stringent air pollution control policies and the shortage in the supply of natural gas at present in China,it is necessary for pyrolysis gas preparing natural gas to realize the clean and efficient utilization of energy and balance the supply and demand of natural gas.Some of the catalysts made of perovskite precursor have good catalytic activity for WGSR and methanation and high temperature resistance,using them in pyrolysis gas atmosphere which has high temperature and complex tar components will reduce pyrolysis effluent and enhance methane content,thus improve the quality of original gas.The composition of pyrolytic gas of a typical lignite from Hesigewula was researched firstly.When pyrolyzing it in rotary kiln with ceramic sphere as the heat carrier at 520550?,the molar ratio value of CO and H2 in pyrolytic gas is about 2,while the molar ratio value of?CO+H2?and H2O is about 1.2.Meanwhile,there is a lot of aromatics,tiny amounts of sulfocompound and other tar components in the high temoerature pyrolytic gas.Based on this standard,a simulated raw gas was prepared for catalyst performance evaluation.Secondly,the LaNiO3 catalyst was prepared by citric acid complex method and the effect of different preparation conditions on the performance of the catalyst was investigated.The experimental results showed that when the pH value was 2.5,the degree of hydrolysis of citric acid was moderate,and a pure perovskite structure could be obtained and has high CO2selectivity?68.6%?.From the results of thermogravimetric analysis and differential thermal analysis combined with XRD results,it was found that when the calcination temperature was800°C,Ni-Co B-site diatomic perovskite with a high degree of crystallization could be formed.Higher calcining temperatures can lead to agglomeration of the catalyst particles and thus affect the catalytic activity.Pre-reduction of H2 at 600°C can form a Ni/La2O3 supported structure with good stability and high dispersity,and the reaction can achieve a smooth high conversion rate in a short time?95.18%?.La2O2?CO3?is an important stable intermediate product of the water gas shift reaction.Finally,the catalytic performance of the B-site diatomic perovskite catalysts and nonstoichiometric perovskite catalysts under simulated gas conditions was studied.Under the experimental conditions,the order of activity of the catalysts per unit mass is La NiO3>LaCoO3>La Fe O3;the order of selectivity for CO2 is LaNi O3<LaCoO3<LaFeO3;the order of resistance to carbon deposition is LaFe O3>LaCoO3>La Ni O3.After the reduction,A site surplus perovskite could gain more La2O3 which is favored to increase the selectivity of CO2,and the La1.1Ni0.33Co0.66O3+?catalyst has the highest water removal rate,the CO conversion rate was 88.4%,and the selectivity of CO2 was 79.4%.The macroscopic reaction equation on the catalyst is:4.84CO+2.842?3.842+4+0.842.With the increase of H2 concentration,the H2O participating in the reaction gradually decreases.When n?CO?/n?H2?=2/7,the water content in the system no longer decreases,it means the catalyst is not suitable for the atmosphere with High concentration of H2.When the toluene solution of naphthalene was introduced into the reaction atmosphere,the catalytic activity slightly decreased.However,when the toluene solution of 5%naphthalene+1%thiophene was introduced,the conversion rate of CO dropped drastically within 1 h and there was a clear phenomenon of sulfur poisoning,that is,the catalyst was not suitable for the gas atmosphere with high sulfur content. |
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