Study On Preparation Of Cerium Oxide Supported Molybdenum-based Catalyst And Its Sulfur-resistant Methanation Performance

Natural gas is an important clean fuel for the transformation and upgrading of China's energy structure.In recent years,the demand has increased year by year.The vigorous development of coal-to-natural gas technology have a great significance to accelerate the transformation of China's energy structure.Sulfur-tolerant methanation technology can shorten the coal-to-natural gas process and has certain cost advantages,and the development of efficient sulfur-resistant methanation catalyst is the key to develop sulfur-resistant methanation technology.In this paper,a cerium oxide-supported molybdenum-based catalyst is used as a sulfur-tolerant methanation catalyst to investigate its sulfur-tolerant methanation performance and optimize the preparation conditions.The effect of the morphology of cerium oxide carrier on the sulfur methanation resistance of the catalyst was investigated.The results showed that the nanorods cerium oxide as the carrier of molybdenum-based catalyst exhibited the best methanation activity.This is because the nanorods cerium oxide have a larger specific surface area and pore volume,a smaller grain size,and a higher content of oxygen vacancies.In addition,the interaction force between the nanorods cerium oxide carrier and the molybdenum species of the active component is weak,and the curved surface advantage of the nanorods is beneficial to improve the contactability of the active component,exposing more active sites of catalytic reaction.The effect of hydrothermal temperature on the preparation of cerium oxide carrier by hydrothermal method is further investigated.The results show that the effect is best when the hydrothermal temperature is 100~oC,the CO conversion rate is 63.4%,the methane selectivity is 53.1%.The cerium oxide prepared at this temperature has a large specific surface area,pore volume,and grain size is small and the relative content of trivalent cerium and defective oxygen is high,providing more adsorption sites for active components.The effects of different preparation methods on the sulfur-tolerant methanation performance of cerium oxide-supported molybdenum-based catalysts were investigated.The results showed that the molybdenum-based catalysts prepared by the co-precipitation method showed better sulfur-tolerant methanation activity than the impregnation method and the direct roasting method.The characterization found that the catalyst prepared by co-precipitation method had more hexavalent molybdenum species on the surface.The preparation conditions of the co-precipitation method were optimized,and the catalytic effect is better when sodium hydroxide is used as the precipitant.The obtained catalyst has larger specific surface area and pore volume,more hexavalent molybdenum species content,and better dispersibility of molybdenum material.Using sodium hydroxide as precipitant,the effect of molybdenum oxide loading was investigated.The results showed that the optimal molybdenum oxide loading was 10%.The catalyst has a large specific surface area and the active component content is close to the monolayer saturated loading.In addition,a suitable p H value for preparing a cerium oxide-supported molybdenum-based catalyst using sodium hydroxide as a precipitation agent is 11.The CO conversion of the catalyst prepared under the best preparation conditions is 76.0%,and the methane selectivity is50.6%.