高活性铜催化剂无受体乙醇催化脱氢制乙醛研究

相较于Wacker工艺进行乙醛工业化生产,发展多相催化体系实现乙醇直接无氧催化脱氢制乙醛和副产氢气,从生产工艺和经济价值方面无疑是一条更加安全高效的路线.在此,我们发展了一种高效、稳固的Cu/SiO₂催化剂,用于乙醇的无受体催化脱氢.通过氨蒸发法制备得到高度分散的Cu颗粒,在没有任何平衡气体的纯乙醇进料条件下,显示出超强的热稳定性.活性组分Cu和载体SiO₂之间的强相互作用,使其具有优异的催化性能.通过反应条件优化,在250℃下实现了较高的乙醇转化率(>40%)和乙醛选择性(>95%),且催化剂在固定床连续反应过程中可稳定运行超过400 h.

Acceptorless Dehydrogenation of Ethanol to Acetaldehyde using Highly Active Cu Catalyst

As a basic industrial chemical, acetaldehyde is widely used for the production of many kinds of fine chemicals, such as pyridine, acetic acid, acetic anhydride, 1,3-butanediol, and synthetic resins. Beyond the industrial production by Wacker process, the acceptorless dehydrogenation of ethanol to acetaldehyde by heterogeneous catalysts, which is of great interest for the chemical industry to decrease the use of petrochemical reserves, provides a promising alternative with the release of hydrogen. Currently, Cu-based heterogeneous catalysts are extensively studied for this process. However, this Cu-based heterogeneous process faces the problems of low reaction activity and catalyst deactivation caused by copper sintering. Herein, we developed a highly active, stable Cu-based heterogeneous catalyst for the acceptorless dehydrogenation of ethanol to acetaldehyde employing the ammonia evaporation method. The introduction of ammonia has been speculated to be favorable (i) to the formation of a copper-ammonia complex (Cu(NH3)4]2+), affording homogeneous dispersion of Cu species and high distribution of the Cu nanoparticles in the treatment afterwards and (ii) to enhance the formation rate of silica matrixes which acts as cages to confine the Cu nanoparticles, and inhibit the aggregation of the Cu nanoparticles. Applying the typical Cu7.5/SiO2-SG catalyst in the dehydrogenation of ethanol affords excellent ethanol conversion of > 40 %, acetaldehyde selectivity of > 95%, and outperformed thermal stability (up to 400 h) in a fixed-bed reactor without any balance gas.