Wang Yuchun, Liu Zhaorong, Tan Chao, Sun Hong, Li Zhong
Department of Applied Chemistry, Yuncheng University Fudan Street 1155 Yuncheng 044000 Shanxi China
Key Lab of Process Analysis and Control of Sichuan Universities, Yibin University Yibin 644000 Sichuan China.
RSC Adv. 2020 Jan 20;10(6):3293-3300. doi: 10.1039/c9ra10501h. eCollection 2020 Jan 16.
CuY catalysts were prepared by high temperature anhydrous interaction between NHY zeolite and copper(ii) acetylacetonate Cu(acac) and the activities were measured for the oxidative carbonylation of methanol to dimethyl carbonate under atmospheric pressure. The bulk and surface properties of the as-prepared catalyst were characterized by XRD, H-TPR and XPS techniques. The activation atmosphere of the CuY catalyst and the testing temperature of the catalytic activity was systematically studied. During activation, nitrogen promotes the auto-reduction of Cu to form the Cu active center, but deposited carbon on the surface of the CuY catalyst covers the active center, even plugging the channel, resulting in lower catalytic activity. Oxygen eliminates deposited carbon, but is not so good for the auto-reduction of Cu. Nitrogen doped with a small amount of oxygen not only eliminates the deposited carbon, but also promotes the auto-reduction of Cu to form more Cu active centers. With the testing temperature increasing, the catalytic activity increases first and then decreases. When the testing temperature is 170 °C, the CuY catalyst with satisfactory activity and stability showed an excellent catalytic activity with 525.1 mg g h space time yield of DMC (STY) and 18.9% methanol conversion. Then the longevity was investigated at 170 °C for 150 h. During the initial reaction period of 40 h, the STY value was constant. In the next 20 h, the catalytic activity slightly decreased. But in the last 90 h, the catalytic performance is very stable and the STY value remains 480 mg g h. The main cause of deactivation is the growth of the particles.
通过NHY沸石与乙酰丙酮铜（II）（Cu(acac)）之间的高温无水相互作用制备了CuY催化剂，并在常压下测定了其用于甲醇氧化羰基化制碳酸二甲酯的活性。采用XRD、H-TPR和XPS技术对所制备催化剂的体相和表面性质进行了表征。系统研究了CuY催化剂的活化气氛和催化活性测试温度。在活化过程中，氮气促进Cu的自还原形成Cu活性中心，但CuY催化剂表面沉积的碳覆盖了活性中心，甚至堵塞了孔道，导致催化活性降低。氧气能消除沉积的碳，但对Cu的自还原不利。掺杂少量氧气的氮气不仅能消除沉积的碳，还能促进Cu的自还原形成更多的Cu活性中心。随着测试温度的升高，催化活性先增加后降低。当测试温度为170℃时，具有良好活性和稳定性的CuY催化剂表现出优异的催化活性，碳酸二甲酯的时空产率（STY）为525.1 mg g h，甲醇转化率为18.9%。然后在170℃下考察了其寿命150 h。在最初的40 h反应期内，STY值保持恒定。在接下来的20 h内，催化活性略有下降。但在最后的90 h内，催化性能非常稳定，STY值保持在480 mg g h。失活的主要原因是颗粒的生长。
