Cr/MgO催化剂上乙腈和甲醇选择性合成丙烯腈的研究

A Study on Cr/MgO Catalysts for Acrylonitrile Synthesis from Acetonitrile and Methanol

用浸渍法制备了系列MgO负载过渡金属氧化物催化剂,比较了这些催化剂的催化性能.详细考察了Cr/MgO催化剂的活性组份含量、焙烧温度及反应温度等因素对乙腈和甲醇选择性合成丙烯腈的影响.结果表明,对于Cr/MgO催化剂,当负载量3%时催化性能最佳,过高的负载量对生成丙烯腈的选择性影响不大,但乙腈转化率呈下降趋势.焙烧温度对生成丙烯腈选择性的影响不大,但经600℃焙烧的催化剂乙腈转化率最高.随着反应温度提高,乙腈转化率提高,而生成丙烯腈选择性400℃左右出现最高值.CO2-TPD表明,催化剂强吸附碱中心越多,越有利于乙腈和甲醇选择性合成丙烯腈反应.Cr/MgO催化剂中引入Na2O后,提高了乙腈的转化率,而生成丙烯腈的选择性降低.

A series of transition metal(Cr, Mn, Fe, Co, Ni, Cu, Ag) oxide catalysts supported on MgO were prepared by impregnation method. Catalytic synthesis of acrylonitrile from acetonitrile and methanol was carried out in a conventional flow reactor system. The effects of Cr loading, calcination temperature and reaction temperature on the catalytic properties of Cr/MgO were studied. Experimental results show that the activity of MgO was very poor, however, it was evidently enhanced with 3% Cr, As for Cr loading. A highest conversion of acetonitrile was 21.4% with 92.6% selectivity of acrylonitrile. In addition, the effect of calcination temperature(300～800 ℃) on selectivity to acrylonitrile was less, while the catalyst calcined at 600 ℃ has a highest conversion of acetonitrile. It was found that the acetonitrile conversion increases with reaction temperature, while a highest selectivity to acrylonitrile at 380~400 ℃. C_2-TPD shows that the more of stronger base sites on the surface of catalysts, which was much more favorable for the reaction. It is also found that the introduction of Na or K to Cr/MgO was favorable for the improvement of acetonitrile conversion, but should decrease selectivity to acrylonitrile.