Jeannette Aumo

Hydrogenation of Citral Over a Polymer Fibre Catalyst

A polymer-supported Pd catalyst was investigated in hydrogenation of citral (3,7-dimethyl-2,6-octadienal), which is a stereoisomer with an isolated and a conjugated double bond as well as a carbonyl group. The catalyst was a fibrous polymer-supported catalyst modified with functional groups and immobilized metals. A comparison of the polymer-supported catalyst with conventional catalysts was made.

Residence time distributions from CFD in monolith reactors-combination of avant-garde and classical modelling

Abstract Computational fluid dynamics (CFD) was used to investigate the flow pattern and flow distribution in a recirculating monolith reactor system designed for catalytic three-phase processes. The information from the CFD model was transferred to a simplified simulation model, where the monolith and the mixing system were described by parallel tubular reactors coupled to a mixing space. The model was based on the following principles: the mixing space and the monoliths were in fully dynamic states, but the concept of differential reactors was applied on the monolith channels. Thus the simplified model consisted of ordinary differential equations for the gas and liquid phases. The modelling concept was successfully illustrated by a case study involving complex reaction kinetics: hydrogenation of citral to citronellal, citronellol and 3,7-dimethyloctanol over cordeorite-supported nickel on alumina washcoat. A comparison of experimental results with the model predictions revealed that the proposed approach is reasonable for the description of three-phase monolith reactors.

Studies on The Ultrasonic Enhancement of The Catalytic Activity in The Hydrogenation of Citral

Acoustic energy is mechanical by its nature. Cavitation bubbles are formed, provided that the intensity of ultrasonic field is sufficiently high. Cavitation close to the liquid-solid interface differs from that in pure liquid. Different mechanisms for the effects of cavitation close to the surfaces have been proposed: microjet impact and Shockwave damage (Suslick, 1990, Suslick et al. 1987). Heterogeneous catalysis involving suspended solid particles in liquid is accelerated by the use of acoustic irradiation. However, studies in the regenerating effect of acoustic irradiation in catalysts are sparse. The localized erosion and grinding caused by these phenomena are responsible for ultrasonic cleaning, generating newly exposed, highly active surface. In this work, we studied on-line acoustic irradiation in batchwise, three-phase hydrogenation of citral to citronellal and citronellol over a Raney nickel catalyst. Citral can be used in the preparation of citronellol (referred as OL hereafter) or citronellal (referred as AL hereafter), to be utilized by parfume industry etc. due to their pleasant odor (Maki-Arvela et al, 1997; Salmi et al, 2000).

Hydrogenation of Citral Over Ni on Monolith

Citral was hydrogenated over Ni on alumina wash-coated cordierite monoliths in a screw impeller batch reactor. The prepared catalyst was characterized by means of nitrogen adsorption (BET), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The performance of the monolith reactor configuration at different temperatures and pressures was compared. Reasonable reaction rate was obtained even after 18 consecutive experiments without regeneration of the catalyst. At temperatures up to 80°C and 5 bar pressure the selectivity to citronellal was ca. 93 %. Increasing the temperature to 100°C decreased the selectivity of citronellal to 65 %. At 100°C and 40 bar pressure the selectivity of citronellal was diminished to 1.4 % due to the formation of the fully hydrogenated product 3,7-dimethyloctanol with a selectivity of 93 %.