| China's energy structure which is“rich in coal,meager oil and litter gas”determines coal is one of China's main energy.With the burning of large amounts of coal,the environmental pollutants emissions,such as carbon dioxide,nitrogen oxides and dust,increased year by year,which brought a lot of serious environmental problems.And the increasingly serious environmental problems have become one of the factors that restrict economic and social better and faster development.If we can't solve the contradiction between rapid economic development and environmental problems,we can't achieve the national sustainable development strategy.And people's living conditions and quality of life will also be greatly affected.This requires us to find a clean,renewable alternative energy as soon as possible.China is an agricultural country with vast territory and abundant resources,which is especially rich in biomass energy.More and more scientists pay attention to the research and development of biomass energy due to it's a renewable clean energy.But the traditional use of biomass energy is just directly burning of the dead branches,dead rods,leaves and so on.Rural cooking with the firewood is one of this form.In this way not only cause low utilization rate of calorific value,but also will produce dust and other small particles to pollute the environment,so how to rationally and effectively use the biomass energy to alleviate the current energy crisis and environmental crisis is the problem that vast number of scientific research workers faced.We can see scientific research workers are indeed more research for methanation catalyst in the low carbon hydrogen ratio in recent years.The CO concentration of raw gas from coal-based natural gas or biomass synthesis is relatively high and hydrocarbon ratio is close to 1,which will cause many side effects.The general catalyst in the reaction process is easy to produce a lot of problems,including carbon deposition,sintering of the situation,which will result in catalyst deactivation.This poses a higher demand for the performance of the catalyst.In this paper,by appropriately modifying the reaction apparatus,the methanation reaction is designed to be combined with the water gas shift reaction in order to adjust the hydrocarbon ratio before the feed gas enters the methanation catalytic bed,which will finally increase CO conversion and CH4 yield.The basic Ni-based methanation catalysts are also modified appropriately to enhance its high temperature stability and catalytic performance.In this way can not only effectively utilize the biomass energy,but also alleviate the environmental problem and energy shortages of our country to a certain extent.Based on the preparation of Ni/Al2O3 by impregnation method,Ni/4Al2O3-6CeO2was prepared by adding CeO2 on the carrier.Based on the bonding device of the water gas shift reaction and the methanation reaction,we investigated the influence of the ratio of the composite support Al2O3-CeO2,the content of Ni,the calcination temperature,the reduction temperature,the content of water vapor and the space velocity.And we selected the optimal conditions.Finally,the catalyst was characterized by XRD,TPR,SEM,BET,TG.The selectivity and yield of CH4 were improved by the combination of water gas shift reaction and methanation reaction,which effectively adjusted the hydrocarbon ratio before the feed gas enters the methanation catalytic bed.The results showed that the high temperature stability and carbon deposition resistance of the modified methanation catalyst by adding CeO2 were obviously improved,and the addition of CeO2 can improve the dispersibility of the active component Ni on the support surface,restrain the formation of NiAl2O4.The catalyst 10Ni/4Al2O3-6CeO2 showed the best catalytic activity.It was found that CO conversion reach to 100%,CH4 selectivity and yield were both increased by 10%at 300?when catalyst 10Ni/4Al2O3-6CeO2 were tested under the condition of reducing temperature at 500?,calcination temperature at 500?,space velocity at 10000 h-1 and steam velocity at 0.02 ml/min.Under 33 h life experiment,the yield of catalyst 10Ni/Al2O3decreased by 3.8%,while the yield of catalyst 10Ni/4Al2O3-6CeO2 decreased by only0.8%. |
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