Mg修饰锌孔雀石催化甲醇合成的性能研究

Effect of Mg modification on the catalytic performance of zinc malachite for methanol synthesis

焦炉煤气制甲醇的复杂工况给铜基甲醇合成催化剂的稳定性和寿命带来挑战。本工作制备了一系列不同镁含量的锌孔雀石样品,采用原位X射线衍射、热重-质谱、N_(2)物理吸附、H_(2)程序升温还原、CO_(2)程序升温脱附等方法对锌孔雀石及焙烧后的样品进行表征,考察镁元素的添加对锌孔雀石结构和甲醇合成催化性能的影响。结果发现,镁元素的添加提高了锌孔雀石结构内部的铜取代程度,促进了焙烧后催化剂内部高温碳酸盐的形成。随着镁含量的增加,焙烧后催化剂的比表面积逐渐增大,还原后的单质铜晶粒尺寸逐渐减小。原位XRD结果表明,少量镁元素在催化剂热处理过程中能有效抑制单质铜晶粒尺寸生长。评价显示催化剂的初始活性随着镁元素的添加呈现先升高后降低的趋势,热处理后含镁催化剂活性仍保持在相对较高的水平。镁元素的适量添加有助于提高铜基甲醇合成催化剂初始活性和热稳定性。

The complex conditions of methanol production from coke-oven gas have brought challenges to the copper-based methanol synthesis catalyst.In this work,a series of zinc-malachite samples with different Mg contents were prepared.The zinc-malachite and calcined samples were characterized by in-situ X-ray diffraction(XRD),thermogravimetry-mass spectrometry(TG-MS),N_(2) physical adsorption,H_(2) programmed temperature reduction(H2-TPR),CO_(2) programmed temperature desorption(CO_(2)-TPD)and other methods.The effects of Mg addition on the structure of zinc-malachite and its catalytic performance of methanol synthesis were investigated.The results showed that the addition of Mg increased the degree of Cu substitution inside the zinc-malachite structure and promoted the formation of high temperature carbonates in the catalyst after roasting.With the increase of Mg content,the specific surface area of the calcined catalyst increased gradually,and the Cu grain size decreased simultaneously.In-situ XRD results showed that a small amount of Mg could effectively inhibit the growth of copper grain size during the heat treatment.The evaluation showed that the initial activity of the catalyst increased first and then decreased with Mg addition,and the activity of the Mg-doped catalyst remained at a relatively high level after heat treatment.The appropriate Mg addition is beneficial to the initial activity and thermal stability of Cu-based methanol synthesis catalyst.