Tuning the acidity of W-Cu/Beta bifunctional catalysts for selective isobutane hydroisomerization to n-butane

The hydroisomerization of isobutane is of considerable practical significance for the development of low-carbon and high-efficiency ethylene production technologies. However, conventional noble metal-solid superacid catalysts used for this reaction suffer from drawbacks including high cost and catalyst deactivation caused by the loss of halogen species and other active components. Herein, a series of highly dispersed W-Cu/Beta catalysts were designed and prepared via a facile ion-exchange method, and their catalytic performances toward isobutane hydroisomerization were systematically investigated. The results show that the introduction of WO x species effectively suppresses strong Brønsted acid sites of the Beta zeolite and modifies the Brønsted/Lewis acid balance of W-Cu/Beta catalysts. Although both Brønsted and Lewis acid site concentrations decrease with increasing W loading, Brønsted acidity is reduced to a greater extent, resulting in a lower Brønsted/Lewis acid site ratio. This acidity regulation is associated with suppression of undesired cracking reactions and improved selectivity toward n-butane. Under reaction conditions of 2 MPa, 380°C, and a weight hourly space velocity of 2.0 h ‒1 , the 5%W-Cu/Beta catalyst exhibits the best catalytic performance with isobutane conversion of 62.3% and n-butane yield of 32.4%. This enhanced catalytic behavior is attributed to optimized acidity and an appropriate distribution of catalytic active sites. Kinetic analyses indicate that WO x introduction alters the apparent kinetic behavior of the catalysts and is accompanied by an increase in apparent activation energy. The improved catalytic selectivity is correlated with changes in acidity distribution and suppression of cracking pathways rather than direct evidence of carbocation stabilization.