Microeactor studies of the cycloaddition of alpha-methylstyrene and isoamylene, and the dimerization of isomylenes

The cycloaddition of isoamylene and alpha-methylstyrene yields indane compounds which are used in the synthesis of musk fragrances. The dimerization of isoamylenes yields an isomeric mixture of diisoamylenes that is used in the synthesis of compounds used in perfumery compositions. The exothermic cycloaddition and dimerization reactions are conventionally carried out in semi-batch reactors using aqueous sulfuric acid catalyst. However, efficient contacting of the reactant and catalyst phases is a major limitation because of the immiscibility of the aqueous catalyst phase and the organic reactant phase, and the high mass and heat transfer resistances of industrial semi-batch reactors. Both reactions could also benefit from the use of solid catalysts since they offer tremendous advantages over the conventional corrosive acid catalyst currently being used. Such advantages include the elimination of the need for expensive separation and purification of the reactor effluent, reduced catalyst disposal costs, and the elimination of the need to use expensive corrosion resistant materials of construction for the reaction vessels and related equipment.;This work reports the development of a microchannel reactor system for the cycloaddition reaction involving two miscible reactants and the immiscible sulfuric acid catalyst phase, both with widely varying liquid densities and viscosities. The replacement of the aqueous catalyst with a solid catalyst for the cycloaddition and dimerization reactions, as well as the development of microreactor systems incorporating the acidic solid catalyst, is investigated. In all cases, performance studies were conducted to optimize the microreactor performance, and comparison studies were also conducted in the batch or semi-batch reactor to compare its performance with that of the microreactor. For the cycloaddition reaction using sulfuric acid catalyst, higher products yields were obtained in the packed bed microreactor and the average reaction rates in the microreactor were three to four orders of magnitude greater than those obtained in the semi-batch reactor. For the cycloaddition reaction with an acidic solid catalyst, Filtrol-24, higher space-time yields were obtained in the microreactor compared to the semi-batch reactor. The space-time yields obtained in the microreactor for the dimerization reaction at optimum conditions were also larger than those obtained in the batch reactor.