(442c) Development of a Highly Integrated Reaction-Distillation Process for the Production of Methylal
Methylal is an important industrial chemical. It is used as a solvent or as an intermediate for other processes like the production of poly(oxymethylene)dimethylethers. In this work, a new process for the production of methylal from an aqueous, methanolic formaldehyde solution was developed. Several process alternatives were evaluated, the most promising of which is a highly integrated reaction-distillation process in which methylal is produced by a heterogeneously catalysed reaction using an acidic ion exchange resin. In order to investigate the kinetics of this reaction, experiments in a tubular fixed-bed reactor were carried out. The parameters of an activity-based pseudo-homogeneous model were fitted to the results of these experiments. As formaldehyde solutions are complex reacting mixtures, their true speciation had to be explicitly taken into account in the modelling. The new process yields highly pure methylal ? in a concentration exceeding that of the methylal-methanol azeotrope. Almost complete conversion of formaldehyde is achieved. Also methanol and water are obtained in reasonably high purity. The new process will be presented and discussed in detail at the conference. It is shown, that the desired specifications can be achieved with reasonable effort. The process development and optimization is based on process simulations. These are extremely demanding for the present system as besides the heterogeneously catalysed formation of methylal the complex reactions in the formaldehyde solutions have to be taken into account - not only in the reactor model but also in the distillation model. Based on previous extensive work of our group both on thermodynamic properties of the complex system studied here and on the simulation of processes with formaldehyde containing reactive mixtures, a reliable model for the new process was developed. It was successfully validated by a comparison to distillation experiments in a laboratory glass column (diameter 50 mm, packing height 4 m) that were carried out in the present project.