Scale-up Production And Forming Of Mo-based Catalysts For Sulfur-resistant Methanation Process

With the decrease of crude oil reserves,natural gas,as an alternative and clean energy,has received considerable attention.The demand for natural gas is increasing these years.To develop the synthetic natural gas by using the abundant coal resources has attracted more and more attention from government.Syngas methanation is key to the technology of coal to natural gas.The most important to the industrialization of methanation process is development and production of methanation catalyst,the catalyst forming process has a great effect on the catalytic performance.In this paper,the forming process of both low and high temperature catalysts was studied.The large-scale production of 25%CeO₂-Al₂O₃ composite support was carried out by co-precipitation method.The produced support was formed by extrusion method,the effects of additives and process on the structure of support and the activity of 20%MoO₃/25%CeO₂-Al₂O₃ catalyst were investigated.The results showed that the optimum water/powder was 0.45-0.55,both the suitable addition amount of pseudo-boehmite and HNO₃ were 10 wt.%.By using 1 wt.%sesbania powder as lubricant,the burrs and cracks on the surface of formed support could be reduced significantly with little damage on the activity of 20%MoO₃/25%CeO₂-Al₂O₃ catalyst.Both the powder and formed support need to be calcined,otherwise the activity of the catalyst will be significantly reduced.When calcined at600 ^oC,the formed support structural was more stable.The low-temperature 25%MoO₃/Zr O₂ catalyst was large-scale produced by co-precipitation method and formed by extrusion method.The forming process investigation results showed that when adding pseudo-boehmite only,the stability of catalyst was increased,the pore structure of catalyst was improved,while the strength of the formed catalyst cannot meet the basic requirements of industrial production.After HNO₃ was added,the strength of the formed catalyst was improved significantly and can be used in industry at the expense of slight decrease of catalytic activity and selectivity.The adding of sesbania powder as lubricant brought a relative high activity of catalyst.The optimum formation conditions of 25%MoO₃/ZrO₂catalyst are as follows:10 wt.%pseudo-boehmite addition,5 wt.%nitric acid addition,1 wt.%sesbania powder addition.The effects of reaction conditions on both the formed 20%MoO₃/25%CeO₂-Al₂O₃ catalyst and formed 25%MoO₃/ZrO₂ catalyst were further investigated,such as temperature,CO₂ and CH₄.The results showed that the adding of CO₂inhibited the water-gas transformation and lead to the decrease of catalytic CO conversion.The rising of reaction temperature contributed to the absorption and decomposition of CO on the surface of 25%MoO₃/ZrO₂ catalyst,then the methanation reaction over 25%MoO₃/ZrO₂ catalyst was promoted,the CO conversion and CH₄ selectivity were increased.On the contrary,the reaction temperature had little effect on the catalytic activity of the 20%MoO₃/25%CeO₂-Al₂O₃ catalyst.The formed catalysts were used to stability study,the results showed that both the two kinds of catalysts are stable during the reaction process.Compared with the commercially available Al₂O₃ forming support,the catalyst prepared by self-made composite support showed a higher activity and selectivity.The self-made support was obviously better than the commercially available support on Mo-based catalysts for sulfur-resistant methanation process.