Systematic Catalyst Screening of Zeolites with Various Frameworks and Si/Al Ratios to Identify Optimum Acid Strength in OME Synthesis

Oxymethylene dimethyl ethers (OME(x)oligomers with the chain length x) present a promising emission reducing diesel additive, which can potentially be produced based on renewable resources. In this work, the OME(x)synthesis catalysed by zeolites was investigated starting from paraformaldehyde and methanol. The catalytic performance of zeolites with different framework types (BEA, FAU, MFI, MOR) and various Si/Al ratios was comparatively studied. The zeolites were characterised by means of NH3-TPD, ICP-OES, XRD and N(2)physisorption. A relationship between catalytic activity and Si/Al ratio was established demonstrating the highest turnover frequency for zeolites with high Si/Al ratios. HZSM-5 114 with a TOF of 3375 mol(OME3-5) mol(AcidSites)(-1) h(-1)was determined as the best-performing zeolite which indicates that the OME(x)synthesis requires a moderately strong acid strength.