The Study On The Catalysts Preparation And Dual Bed Reactor For Oxidative Coupling Of Methane

The oxidative coupling of methane (OCM) reaction is a non-petroleum route to produce ethylene, which has significance and applications in industry. The development of new high activity catalyst and reaction process has been to the priority and difficulty for oxidative coupling of methane. In this paper, the OCM performances over the Li/MgO and Na2SO4/SiO2 series catalysts were evaluated and the dual bed reactor for OCM was studied, the main research works and results in this paper were listed as follows.The Ce modified 4%Li/MgO catalysts were prepared by impregnation. The catalytic activity results showed that, Ce additives helped to improve the C2 selectivity of the catalyst, and the catalyst that added 3%Ce had a good OCM activity. The Li/MgO/cordierite (D) series monolithic catalysts were prepared for OCM, and the effects of silica sol, aluminum sol and mixed colloid as interlayer on the OCM performance of Li/MgO/cordierite (D) ceramic-based monolithic catalysts were investigated. The experimental data showed that the scatter supporter could improve the catalytic activity at high temperature and enhanced the selectivity of C2 especially for ethane. Compared to other scatter supporter,7% Li/MgO/SiO2/D monolithic catalysts which used silica sol as a transition layer had a better OCM performance.With the acidic silica sol as silica source, the Na2SO4/SiO2 catalysts were prepared by sol-gel method, and the OCM performances of Mn, Fe, Co, La transition metal-doped Na2SO4/SiO2 catalysts were studied. The results indicated that different metals had varying degrees of change in the OCM catalyst performance, in which Mn additives significantly increased Na2SO4/SiO2 catalytic activity, and the 34.5% methane conversion and 56.6% C2 selectivity were obtained over the 2%Mn-5%Na2SO4/SiO2. With the cordierite as a substrate, the silica sol as silica source, a series of Mn-Na2SO4/SiO2/D monolithic catalysts were prepared, and the OCM performances of the catalyst were investigated. The results revealed that the Mn and Na2SO4 were benefit for OCM, and the 7%Na2SO4-3%Mn/SiO2/D catalyst had better activity. For the 7%Na2SO4-3%Mn/SiO2/D catalyst, Ce additives can increase the trend of C2 selectivity increased with temperature clearly; an appropriate amount of Ce additives can inhibit C2 oxidation at high-temperature to improve the performance of the catalyst OCM reaction. The 3%Ce-7%Na2SO4-3% Mn/SiO2/D catalyst has good performance of OCM reaction.The particle/metal based monolithic catalysts dual bed reactor was built by 5%Na2WO4-2%Mn/SiO2 particle catalysts and 3%Ce-5%Na2WO4-2%Mn/ SBA-15/Al2O3/FeCrAl monolithic catalyst and the particle/ceramic based monolithic catalysts dual bed reactor was built by 5%Na2WO4-2%Mn/SiO2 particle catalysts and 4%Ce-5%Na2WO4-2%Mn/SiO2/cordierite monolithic catalyst. The performances of the oxidative coupling of methane over the dual bed reactor were evaluated. The results indicated that particle/monolithic catalyst dual bed reactor that the feed gas passed firstly through the particle bed and then to the monolithic bed can effectively inhibit the deep oxidation of products and partial oxidation of methane, and have a positive influence on the ethylene selectivity. When the height of 5%Na2WO4-2%Mn/SiO2 particle catalyst was 10 mm, the height of 4%Ce-5%Na2WO4-2%Mn/SiO2/cordierite monolithic catalyst was 50 mm, the particle/ceramic based monolithic dual catalysts bed reactor exhibited the best performance for the oxidative coupling of methane.37.3% of CH4 conversion and 43.0% of C2H4 selectivity could be obtained,3% of CH4 conversion and 11.9% of C2H4 selectivity were improved compared with 5%Na2WO4-2%Mn/SiO2 particle single bed and 13.4% of CH4 conversion and 23.1% of C2H4 selectivity were improved compared with 4%Ce-5%Na2WO4-2%Mn/SiO2/cordierite monolithic catalysts single bed.