Evaluation of the Efficiency of Polydecylmethylsiloxane in the Separation of a 1-Hexene–Heptanal Mixture

Abstract

Hydroformylation (or oxo synthesis) is currently one of the most important processes of organic synthesis. Increasing the degree of conversion of this process as well as reducing operating costs seems to be an important direction for its development. A hydroformylation membrane reactor is proposed as an in situ method for separating the catalyst and reaction mixture from the reaction products (aldehydes). This work considers the potential of application of a membrane based on polydecylmethylsiloxane (PDecMS) for a membrane reactor for the hydroformylation of 1-hexene to heptanal. To evaluate the interaction of 1-hexene and heptanal with PDecMS, the sorption of the individual substances and their mixtures at 30 up to 60°C is studied. Sorption isotherms are also obtained for a mixture containing 1-hexene and heptanal which demonstrate selective sorption of heptanal in PDecMS. The transport of 1-hexene and heptanal through a membrane based on PDecMS is studied in the vacuum pervaporation mode at 30 up to 60°C. Based on the obtained experimental data, the temperature dependences of the permeability of 1-hexene and heptanal are plotted. It is shown that the activation energy of transport through a PDecMS membrane is −11.5 kJ/mol for heptanal and −16.4 kJ/mol for 1-hexene. Extrapolation of the temperature dependence of permeability to the operating temperature of hydroformylation (130°C) at a conversion of ~80% shows that, at the permeability of heptanal of 740 mol m⁻² h⁻¹ bar⁻¹ and of 1-hexene, 55 mol m⁻² h⁻¹ bar⁻¹, the flux of heptanal will be 37 kg m⁻² h⁻¹ and of 1-hexene, 5 kg m⁻² h⁻¹. Thus, the permeate will be enriched with the aldehyde.