Nanoscale coupling of acidic sites and metal sites on Cu/Al2O3 catalysts boosting dimethyl ether steam reforming

Abstract

Dimethyl ether steam reforming (DME SR) is a tandem reaction involving DME hydrolysis over acidic sites and then methanol steam reforming (MSR) over metal sites. However, developing bifunctional catalysts with highly efficient relay effect of the two-step reaction remains a great challenge. Herein, we facilely synthesize a Cu/Al2O3 catalyst (CuAl-AC) with nanoscale-coupled acidic sites and metal sites, which increases DME SR reaction rate 3-fold compared with the catalyst with micron-scale coupled acidic sites and metal sites. Compared with the traditional Cu/Al2O3 catalyst typically prepared by alkaline carbonate coprecipitation, the CuAl-AC catalyst eliminates the toxic effect of alkali metal cations on acidic sites, improves DME hydrolysis activity, and thus increases DME SR activity 5-fold. Additionally, compared with the CuAl-IM catalyst prepared by impregnation, the CuAl-AC catalyst exhibits strengthened metal-support interactions, significantly improving the stability. Furthermore, the efficient relay effect, high Cu+ content and small Cu particle sizes of the CuAl-AC catalyst result in ultrahigh H2 space-time yield of 0.95 mol gcat−1 h−1 compared with catalysts reported in literatures, and low CO selectivity of ∼4% when the DME conversion reaches 95%. In-situ infrared spectroscopy results suggest that MSR over the CuAl-AC catalyst follows the HCOOCH3* pathway over Cu sites.