Hurdles and solutions for reactions between gas and liquid in a monolithic reactor

• Published in: Catalysis today 2001-09, Vol.69 (1-4), p.131-135
• Main Authors: Vaarkamp, Marius, Dijkstra, Willem, Reesink, Bennie H.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Exact sciences and technology; Gas-liquid mixing; General and physical chemistry; Homogeneous catalyst; Hydrogenation; Monolithic reactor; Tethering; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/S0920-5861(01)00363-7

In this paper, proof of principle experiments and exploratory work that solves the problem of ensuring that a gaseous and a liquid reactant are available at the catalytically active site at the same time by separating the reaction 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 during 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 deactivation) of the catalyst. The effectiveness of the catalyst coated on the monolith 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 hydrogenation. A monolith to which Rh-cyclooctadiene-1,2-bis-diphenylfosfino-ethane (a homogeneous catalyst) was tethered was equally active in hydrogenation of 1-hexene as Rh-cyclooctadiene-1,2-bis-diphenylfosfino-ethane tethered to a standard alumina. This allows (fine)chemical producers to repeatedly use the expensive homogeneous catalysts without the need for separation of the catalyst from the reaction mixture.