(442b) Process Intensification in Reactive Distillation: Design of a Diabatic Microwave Heated Column for the Synthesis of n-Propyl Propionate
Process intensification (PI) is a good example of how innovation is driving development in chemical engineering. Completely new approaches are being reported every year to perform conventional chemical processes with improved efficiency. Although the application of electromagnetic radiation as an alternative energy form in chemical syntheses has been studied extensively and the literature regarding intensification effects is remarkably rich, no successful commercial implementations in chemical plants have been reported. In addition to reactions, distillation processes benefit from microwave radiation (MW) with improved molecular separations. We have reported that when the vapor-liquid interface is exposed to microwaves, the system can be disturbed from conventional equilibrium conditions and a positive deviation in phase composition can be achieved, as the vapor phase becomes richer in the component with the lower boiling temperature; the extent of separation improvement depends on the boiling points and the dielectric properties of the mixture components. Since the two processes (reaction and distillation) separately can be enhanced by microwave radiation, the synergy gained by the integration of both operations in terms of chemical equilibrium shift and heat exchange can be additionally improved. In this investigation, we take a step further with the design and construction of a laboratory-scale diabatic RD unit using MW energy (f = 2.45 GHz). As a test system the heterogeneously catalyzed reaction of n-propyl propionate (ProPro) from 1-propanol (ProOH) and propionic acid (ProAc) is used. The MW heated column comprises a modified version of an Armfield UOP3 distillation column (DN-50) coupled with a specially designed mono-mode MW cavity from Sairem. The research is divided in two parts. First, experimental results of three out of the six constituent binary systems (ProOH/ProPro, ProPro/ProAc, ProOH/ProAc) are compared to the conventional heated process in the diabatic column using glass sieve plates and structured packing transparent to MW. In the second part of the research screening for a suitable catalyst including a BEA zelite, an acidic MOF and metal oxides is performed. The selected catalyst is coated upon the structured packing and tried in reactive distillation experiments.