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采用浸渍法制备了不同V2O5担载量的V2O5/MO-Al2O3(M=Mg,Ca,Sr,Ba)催化剂,钒物种的前驱体为偏钒酸铵.对制备的催化剂进行了一系列表征,并对催化剂上正丁烷选择性氧化脱氢制取丁烯进行了反应研究.表征结果(包括比表面积、X射线衍射、傅里叶红外光谱、氢气程序升温还原和拉曼光谱)显示,不同碱土金属元素掺杂的催化剂显示不同的钒价态信息和催化性能.其中掺杂Ca,Sr,Ba的催化剂,正钒酸盐相很难被还原,因此催化剂的氧化还原循环难以建立,导致以上三种催化剂在正丁烷氧化脱氢反应中活性较低.然而,Mg掺杂的催化剂却显示出较高的催化活性和选择性.实验结果表明:在Mg掺杂的载体上担载5%V2O5的催化剂上600°C时可获得高达30.3%的正丁烷转化率和64.3%的烯烃总选择性.这与V2O5担载量为5%时,在获得高度分散的钒氧化合物物种时可使MgO晶相稳定存在密切相关.
The V2O5 / MO-Al2O3 (M = Mg, Ca, Sr, Ba) catalysts with different V2O5 loadings were prepared by impregnation method, and the precursor of vanadium species was ammonium metavanadate.The catalysts were characterized by a series of methods, The selective oxidation of n-butane to butene on the catalyst was also studied. The characterization results (including specific surface area, X-ray diffraction, Fourier transform infrared spectroscopy, hydrogen temperature programmed reduction and Raman spectroscopy) Alkaline earth metal doped catalysts show different vanadium valence information and catalytic properties, in which the catalysts doped with Ca, Sr and Ba are very hard to be reduced, so the redox cycle of the catalyst is difficult to establish, resulting in the above However, the Mg-doped catalysts show higher catalytic activity and selectivity.The experimental results show that the catalysts supported on Mg-doped carriers have 5% V2O5 catalyst achieves up to 30.3% n-butane conversion and 64.3% olefinic selectivity at 600 ° C. This is in contrast with the V2O5 loading of 5%, when highly dispersed vanadoxy species are available MgO crystal phase stability is closely related.