Experimental and computational optimisation of methanol dehydration to dimethyl ether†

Meeting the International Maritime Organization's net-zero target by 2050 necessitates the replacement of marine fossil fuels with sustainable alternatives, such as dimethyl ether (DME). Silicon-doped aluminophosphate (SAPO) solid acid catalysts, particularly the weakly-acidic SAPO-11, can catalyse the selective dehydration of methanol-to-DME with exceptional stability. Herein, we present a combined experimental, computational fluid dynamics, and design of experiments study to augment catalyst efficiency and DME production, and to support scale-up endeavours. Using a four-dimensional design surface, it was found that longer catalyst beds and higher operating temperature increase DME yields, with the catalyst bed length having a more pronounced influence. In contrast, the use of highly concentrated methanol reactant streams had a detrimental effect and this was ascribed to a saturation of the active sites in the SAPO-11 catalyst. Improved single-pass conversions and catalyst longevity on industrial scales can thus be achieved by optimising both the number of acid sites in SAPO-11 and reaction parameters.