溶胶-凝胶法制备NiFe 2O 4载氧体及其化学链制氢反应性能

Performance of NiFe2O4 Oxygen Carriers Prepared by Sol-Gel Method in Chemical Looping Process of Hydrogen Production

采用溶胶-凝胶法制备了NiFe 2O 4载氧体,并应用于化学链制氢(CLH)反应过程,通过正交实验方法考察了原料配比、溶液pH值、凝胶温度等制备条件对载氧体物化特性和制氢性能的影响。结果表明:柠檬酸与金属离子摩尔比(R CAMI)是影响载氧体前驱体空间结构的主要因素,进而影响载氧体晶型构成、比表面积及其化学链制氢性能;溶液pH值影响柠檬酸络合物水解缩聚速率,并通过强化或抑制热解气反应阶段CH 4裂解积炭来影响制氢过程H 2纯度;凝胶温度提高可强化载氧体前驱体离子成核速率,但会导致生成溶胶不稳定,影响制备载氧体晶型结构及比表面积,较低凝胶温度有利于载氧体晶格氧释放。适用于化学链制氢的NiFe 2O 4载氧体制备条件为:R CAMI为1,pH值为7,凝胶温度为60℃;制得H 2纯度接近100%。

NiFe 2O 4oxygen carriers were prepared by the sol-gel method and used in chemical looping hydrogen(CLH).The effects of preparation parameters,such as the molar ratio of citric acid to metal ions(R CAMI),solution pH value and gelation temperature,on physicochemical properties and CLH performance of oxygen carriers were investigated by orthogonal experiments.Experimental results indicate that the CAMIR is the main factor to form the spatial structure of precursor,which affects the crystal phase,specific surface area and CLH performance.The solution pH value is related to the hydrolytic polycondensation of citric acid complex,which affects the purity of H 2 product by strengthening or inhibiting the carbon deposition of CH 4 in reaction process of biomass pyrolysis gas.The increase of gelation temperature can enhance the nucleation rate of precursor,but it will lead to the instability of sol,affecting the crystal structure and specific surface area of oxygen carrier subsequently.Lower gelation temperature is conducive to the release of lattice oxygen.The optimized preparation conditions of NiFe 2O 4 oxygen carriers for CLH are as follows:R CAMI of 1,pH value of 7 and gelation temperature of 60℃with maximum H 2 purity nearly 100%in CLH process.