Characteristics and catalytic properties of WO3 supported on zeolite A-derived from fly ash of sugarcane bagasse via esterification of ethanol and lactic acid

Abstract

In the current trend of industrial manufacturing processes, an interest in utilization of industrial and agricultural wastes for producing green chemistry, eco-friendly product, has been increased. Therefore, this study aimed to produce ethyl lactate using solid-acid catalyst WO3/zeolite-A via esterification. Various analytical techniques, including XRF, BET, XPS, FTIR, NH3-IR, NH3-TPD, SEM-EDX, ICP-OES, XRD, TGA-DTA, and TEM, were employed to analyze the physical and chemical properties of zeolite-A and tungsten-supported on zeolite-A. The results revealed that after five reuse cycles, the lactic acid conversion rates were 20.1 % and 10.3 % for WO3/zeolite-A and Amberlyst-15, respectively. The spent WO3/zeolite-A exhibited a reduction in surface acid site, declining from 1,591.8 μmol/g in the first run to 690.1 μmol/g in the fifth run. The decline in efficiency was attributed to impurities blocking of active sites, structural alterations, and partial leaching of active species. XRD and FTIR analyses confirmed decreased crystallinity and structural changes in spent catalysts. TEM, SEM-EDS, and ICP-OES analyses showed the loss of active tungsten species and the deposition of reaction intermediates leading to a decrease in ethyl lactate yield (decreased from ca. 44 to 20 %). Despite structural changes affecting catalytic performance, WO3/zeolite-A demonstrated a good promising catalyst for ethyl lactate production over five successive cycles (with ca. 50 % decrease).