Highly dispersed Ga2O3 integrated mesoporous γ-Al2O3 nanocomposites (Al10GaxOy) for enhanced hydrogen production by dimethyl ether steam reforming reaction

Abstract

The present work demonstrates a one-pot sol-gel process for producing highly dispersed Ga2O3 integrated mesoporous γ-Al2O3 catalysts with the composition Al10GaxOy (x = 0.25, 0.5, 1 and 2), and their high efficacy as bifunctional catalysts for H2 production by DME steam reforming (SR) reaction. The sol-gel synthesis of mesoporous Al10GaxOy (m-Al10GaxOy) catalysts were accomplished by using ethylenediamine tetraacetic acid (EDTA) and ethylene diamine (ED) as organic gelators. XRD, FESEM-EDX, TEM, N2 adsorption analysis, XANES and EXAFS studies revealed that m-Al10GaxOy catalysts have a disordered mesoporous structure with good chemical homogeneity, well distributed Ga2O3 species in γ-Al2O3 lattice, and strong interfacial interaction between Ga2O3 and γ-Al2O3. DME SR reaction revealed that Ga addition in γ-Al2O3 significantly improve the DME SR reaction by regulating the carbonaceous product selectivity, and the rate of H2 production increases with increase of Ga content in γ-Al2O3. Among all mesoporous Al10GaxOy catalysts, Al10Ga2 showed the highest performance in DME SR, which showed 100% DME conversion with a H2 yield of 62% at 673 K. Mesoporous Al10GaxOy catalyst with 16.7% Ga (Al10Ga2) could produce an amount of H2 yield very close to that of pure mesoporous Ga2O3 (66% at 673 K), which is promising by considering the relatively high cost of Ga2O3. Mesoporous Ga2O3 integrated γ-Al2O3 catalysts exhibited distinctly high H2 production rate compared to mesostructured 3d transition metal ion integrated γ-Al2O3 catalysts and non-mesoporous Ga2O3-Al2O3 catalysts. The formation of highly dispersed Ga2O3 species with catalytically active Ga atoms located at the surface atomic sites and its strong interaction with γ-Al2O3 lattice makes Al10GaxOy catalysts highly performing in DME SR reaction.