Bimetallic Ni-Co/γ-Al2O3 catalyst for vapour phase production of γ-valerolactone: Deactivation studies and feedstock selection

Abstract

With an aim to establish supported non-noble Co metal catalysts for production of a promising fuel and fuel additive γ-valerolactone (GVL) at ambient pressure in continuous mode, Co/γ-Al2O3 and bimetallic Ni-Co/γ-Al2O3 catalysts were prepared and their catalytic activities vs. catalytic features were correlated. Ni-Co/γ-Al2O3 catalyst exhibited GVL productivity of 1.125 kgGVL.kgcatalyst−1h−1 which is relatively higher than Co/γ-Al2O3 catalyst. Ni-Co/γ-Al2O3 catalyst is stable during 12 h time-on-stream studies while Co/γ-Al2O3 catalyst suffers from deactivation. The addition of Ni to Co/γ-Al2O3 augments the resultant bimetallic catalyst activity and coke resistance capacity. As evidenced from XRD, H2-TPR, XPS analyses the addition of Ni to Co/γ-Al2O3 results in formation of Ni-Co alloy in the bimetallic catalysts. H2-pulse chemisorption studies and TEM analyses illustrate formation of smaller particles in bimetallic Ni-Co/γ-Al2O3 catalyst which in turn influenced the rate of formation of GVL. From TGA of spent catalysts, the carbon deposition rate is found to be decreased in the case of Ni-Co/γ-Al2O3 catalyst (0.43 mmol.gcat−1.h−1) than Co/γ-Al2O3 catalyst (1.014 mmol.gcat−1.h−1). Among the feedstocks of GVL i.e. levulinic acid, methyl levulinate, ethyl levulinate, ethyl levulinate is found to be prominent in constantly yielding GVL during 24 h study over bimetallic Ni-Co/γ-Al2O3 catalyst.