An investigation of continuous hydrogenation

Abstract

Heterogeneous catalysis is one of the key processes for the synthesis of pharmaceuticals, fine chemicals, petrochemicals, polymers, agrochemicals, among others and often involves three phases where a gaseous reactant needs to diffuse through the solvent (liquid) onto the surfaces of catalyst particles (solid) in order for catalytic reaction to take place. Traditionally stirred tank and packed bed reactors are the workhorse for heterogeneous catalysis, as such, interphase mass transfer limits the overall efficiency for this type of operation. This PhD project focuses on the study of a multiphase catalytic hydrogenation in an alternative reactor platform, i.e. oscillatory baffled reactor (OBR), due to its reported uniform mixing and enhanced mass transfer rate. The chosen model reaction is the hydrogenation of 3-butyn-2-ol over Pd/Al2O3. A comprehensive and systematic comparable evaluation of the OBR vs a commercial stirred tank PARR reactor was for the first time undertaken in this project by assessing reactor efficiency (power consumption), hydrogen feed mode and hydrogen utilization (H2 efficiency). Our investigation demonstrates • enhanced reaction performance is obtained when hydrogen-on-demand is operated; • H2 efficiency is significantly improved and the residence time reduced in the OBR in comparison to the PARR reactor at both ambient and pressurized conditions due to its enhanced and uniform mixing; • the OBR has also displayed better reactor efficiency than the PARR reactor. One of the objectives of this PhD work was to investigate the possibility of performing heterogeneous catalysis continuously in the OBR, this has been achieved. The model hydrogenation reaction was successfully run for 8 hrs continuously, the catalyst stability and usability were consistent for the 8 hrs achieving the target conversion of 95 % and selectivity > 97%. This work is again the first of its kind in this field.