超临界多相催化反应的应用研究进展

超临界流体具有似气似液的独特物性,在超临界条件下进行化学反应,有可能在控制反应速率、提高转化率和目的产物选择性、延缓催化剂失活、提高传热传质效率、改进产物分离与溶剂回收操作过程等方面取得较好的效果。以超临界条件下的甲醇和低碳醇的合成、烷基化和烷烃选择氧化等几类多相催化反应为例,对在超临界溶剂效应以及反应条件和相态变化对反应特性和催化剂寿命的影响等方面的研究进展进行了评述,对如何在催化反应中更充分地发挥超临界流体的优异性能提出了一些看法和建议。在超临界反应过程的设计和操作中,为确保反应在所需的超临界相区进行,须以反应混和物的临界性质为依据,并在确定超临界反应条件时,考虑反应体系临界性质随反应进程的变化。

Progresses in Research of Heterogeneous Catalytic Reactions Under Supercritical Conditions

Supercritical fluid is provided with both liquid-like and gas-like properties and can exhibit special performance as a reaction medium.Performing reactions under supercritical conditions rather than in gas or liquid phase can be an interesting option for improving equilibrium conversion,enhancing reaction rate,increasing throughput,prolonging catalyst lifetime and making the process more environmentally benign.In this work,taking synthesis of methanol and higher alcohols from syngas,alkylations of benzene/propene and isobutane/butene,and selective oxidation of alkanes as examples,recent research progress concerning effects of additive solvent,phase variances and reaction conditions on catalytic reaction behavior under supercritical conditions were reviewed.Some suggestions were stated for measures to make use most of the special properties of supercritical fluids in catalytic reactions.It is illuminated that supercritical reaction conditions should be determined on basis of critical properties of a real reacting mixture with consideration of their changes along reaction course,to ensure that reaction is carried out under proper supercritical conditions approaching critical region.