Effect of Fe/Zn ratio in composite catalyst for synthesizing polyoxymethylene dimethyl ethers

Abstract

AbstractPolyoxymethylene dimethyl ethers (PODEn) are extremely effective diesel additives to reduce soot formation during combustion. We introduce a series of Fe‐Zn composite solid acid catalysts (SO42−/xFe2O3‐yZnO), for the condensation reaction of methanol and paraformaldehyde (PF) with a cheap and feasible route to efficiently synthesize PODEn. These catalysts were characterized by different characterization techniques, namely BET, XRD, SEM, EDS, FTIR, and NH3‐TPD and the results showed that Fe/Zn molar ratios strongly influenced the physicochemical characteristics of catalysts, thus affecting the methanol conversion and PODE1‐6 and PODE3‐6 selectivity. Accordingly, the methanol conversion was decreased and the selectivity of PODE3‐6 was increased after increasing the Zn molar content. Comparatively, SO42−/Fe2O3‐2ZnO exhibited superior catalytic activity among the various investigated catalysts due to the high acid density of strong acid sites. The optimal reaction conditions were observed to be at a 3.0 wt% catalyst loading (catalyst/reactant mass ratio), 2.5 hours ours of reaction time, a reaction temperature of 403 K, and a molar ratio of 3:1 of CH2O to methanol, achieving a high selectivity of 99.09% PODE1‐6 and 28.23% PODE3‐6 with 55.16% methanol conversion during the reaction.