Tailoring olefin distribution via tuning rare earth metals in bifunctional Cu-RE/beta-zeolite catalysts for ethanol upgrading

Bioethanol to middle distillate technologies have offered a unique solution to produce renewable aviation fuel for decarbonizing the hard-to-electrify sectors. Here, we have developed the series of bimetallic Cu- and rare earth-containing (RE) Beta zeolite catalysts that yield high C3+ alkene selectivity from ethanol upgrading (>80% selectivity at ∼100% conversion, 623 K). The formation rates of butene isomers to C5+ alkenes are linearly correlated with the strength of Lewis acidic RE identity, which follows the sequence of Yb12/Beta >Y7/Beta > Gd12/Beta > Ce10/Beta > La12/Beta. Rate measurements indicate that the RE selection plays the vital role in altering the rate of the key competitive reactions within the ethanol-to-alkenes reaction network, namely C4 alcohol dehydration and C-C chain growth, which dictate alkene product distributions. These findings indicate a feasible and promising method for tailoring alkene product distributions from ethanol upgrading, which is of notable significance to the generation of renewable middle distillates.