邢鹏 王淑芳 王延吉

摘要 以不同材质的活性炭为载体，制备了一系列VOx/AC催化剂。考察了载体结构和焙烧温度对催化剂表面活性物种、酸性、甲醇氧化反应活性及产物分布的影响。结果表明，煤质球形炭（AC-1）与果壳炭（AC-3）载体表面能够形成高度分散的以四面体型VO4存在的单钒氧化物物种，使甲醇氧化活性明显高于其他活性炭载体;催化剂表面酸量影响产物选择性，酸量大的载体有利于甲酸甲酯和甲缩醛的生成;高温焙烧的VOx/AC-3催化剂表面有更多的V2O3生成，能提高反应活性和甲醛选择性，降低甲缩醛和甲酸甲酯选择性;高温、高空速及高醇/氧进料比提高了甲醛的选择性;低温、低醇/氧进料比有利于甲缩醛合成;高压、低醇/氧进料比有利于甲酸甲酯的生成。

关 键 词 活性炭;钒氧化物;催化剂;甲醇;选择性氧化

中图分类号 O622.4     文献标志码 A

Effect of supports and calcinations temperatures on VOx/AC catalyzed methanol oxidation

XING Peng， WANG Shufang， WANG Yanji

（School of Chemical Engineering， Hebei University of Technology， Tianjin 300130， China）

Abstract A series of VOx/AC catalysts were prepared with various AC supports. The effects of support structure and calcination temperatures on the catalyst surface active species， acidity， methanol oxidation activity and products distribution were studied. The result show that when AC-1（coal sphere） and AC-3 （shell） were taken as supports， active components were highly dispersed， and more isolated VO4 tetrahedron monovanadate specie was formed， which is benefited to methanol oxidation process. Acid quantity on catalyst surface has effect on products distribution. Its increase has obvious promotion effect on the formation of methyl formate （MF） and dimethoxymethane（DMM）. The formation of V2O3 on the catalyst surface after calcination at a high temperature has a promotion effect on methanol conversion and formaldehyde （FA） selectivity， while decreasing MF and DMM selectivity. It is a good way to increase formaldehyde selectivity and reduce the competitive reaction of FA deep oxidation to MF by increasing reaction temperature， reducing space velocity and oxygen concentration in the feed gas. While lowering temperature and increasing methanol feed ratio can apparently promote the reaction of FA condensation to DMM， high pressure and low methanol feed ratio benefit to synthesize more MF.

Key words activated carbon; vanadium oxide; catalyst; methanol; selective oxidation

0 引言

甲醇是重要的化工原料。近年來，对甲醇的下游产物开发受到了越来越广泛的关注[1]。甲醇的选择性氧化反应是甲醇深度加工过程的基本步骤，通过选择性氧化，甲醇可转化为甲醛（FA）、甲酸甲酯（MF）、甲缩醛（DMM）等重要的化工产品或中间体，进一步反应还可得到高附加值产品[2-3]。甲醇选择性催化氧化反应存在的主要问题是目标产物收率低、副产物多。因此，为了开发出高转化率、高选择性的催化剂，对催化剂性质、操作条件和反应性能的关系进行研究是十分必要的。

负载氧化钒催化剂是常用的氧化还原反应催化剂，具有良好的活性和选择性，广泛应用于邻二甲苯氧化制苯酐、烃类选择性氧化和氮氧化物选择性还原等反应[4-6]。……