Abstract:

In order to overcome the shortcomings of particulate catalyst for oxidative esterification of methacrolein in slurry reactor, the monolithic catalyst(Pd_xPb_y/Al₂O₃-MgO/nickel alloy foam)for direct oxidative esterification of methacrolein (MAL) with methanol to methyl methacrylate (MMA) was prepared using dipping methods. The porous Al₂O₃-MgO with high surface area on nickel alloy foam support was synthesized using electro-deposition method. The effects of preparation parameters on Al₂O₃ coating were studied, and the optimum coating was achieved when the volume content of aluminum sol was 35%—40%, the Al₂O₃ content was 25—30 g·L^-1, the stirring speed was 200—250 r·min^-1, the deposition voltage was 10—12 V, and the deposition time was 8—12 min. Furthermore, the coating and catalyst were characterized using BET, XRD, SEM, ICP as well as TEM and the catalytic performance of Pd₅Pb₅/Al₂O₃-MgO/nickel alloy foam was investigated in a fixed bed reactor. The optimal reaction conditions were determined as:T=80℃, p=0.3 MPa, methanol:MAL molar ratio=8:1, liquid materials flux rate =0.5 ml·min^-1, oxygen flux rate=35 ml·min^-1 and reaction time=2 h. Under these conditions, MAL conversion and MMA selectivity reached 76.1% and 81.2%,respectively. The results can provide scientific basis for the optimization of methacrolein to methyl methacrylate production process.

Key words: methacrolein, monolithic catalyst, esterification, heterogeneous reaction, methyl methacrylate

摘要：

针对甲基丙烯醛氧化酯化浆态床反应过程中颗粒催化剂易破碎、活性组分易流失等缺点,采用浸渍法在电沉积到泡沫镍合金表面的氧化铝-氧化镁涂层上负载活性组分,制备了Pd_xPb_y/Al₂O₃-MgO/泡沫镍合金整体式催化剂。研究分析了铝溶胶含量、Al₂O₃含量、沉积电压和沉积时间等条件对涂层负载的影响,并对载体和催化剂进行了BET、XRD、SEM、ICP和TEM表征和气-液-固固定床反应性能评价。结果表明,当铝溶胶的体积含量为35%～40%,Al₂O₃含量为25～30 g·L^-1,沉积电压为10～12 V,沉积时间为8～12 min,搅拌速度为200～250 r·min^-1时可得到稳定的涂层。在温度为80℃、压力为0.3 MPa、醇醛摩尔比为8:1、液相物料进口流量为0.5 ml·min^-1、氧气进口流量为35 ml·min^-1、反应时间为2 h条件下,整体式催化剂上甲基丙烯醛转化率最高为76.1%,甲基丙烯酸甲酯选择性为81.2%。研究结果可为甲基丙烯醛氧化酯化制甲基丙烯酸甲酯的生产工艺优化提供科学数据。

关键词: 甲基丙烯醛, 整体式催化剂, 酯化, 多相反应, 甲基丙烯酸甲酯