Hurdles and solutions for reactions between gas and liquid in a monolithicreactor

In this paper, proof of principle experiments and exploratory work that sol ves the problem of ensuring that a gaseous and a liquid reactant are availa ble at the catalytically active site at the same time by separating the rea ction and the transport of the gaseous reactant. The equipment consisted of an autoclave in which a feed was saturated with hydrogen, a reactor with a catalyst coated on a monolith, a pump to circulate the feed/product stream , and devices to control and monitor the process. A lot of information of how the process can be practised was gathered durin g the work. Conversion per pass should be below the amount of hydrogen that can be dissolved in the liquid to avoid coke deposition (and hence deactiv ation) of the catalyst. The effectiveness of the catalyst coated on the mon olith was found to be 100%. Several variations of the process design and catalysts used were explored. Integration of the monolith with a heat exchanger will obviously allow for the use of the process for very exothermic reactions like (nitro)benzene hy drogenation. A monolith to which Rh-cyclooetadiene-1,2-bis-diphenylfosfino- ethane (a homogeneous catalyst) was tethered was equally active in hydrogen ation of 1-hexene as Rh-cyclooetadiene-1,2-bis-diphenylfosfino-ethane tethe red to a standard alumina. This allows (fine)chemical producers to repeated ly use the expensive homogeneous catalysts without the need for separation of the catalyst from the reaction mixture. (C) 2001 Elsevier Science B.V. A ll rights reserved.