Glycerol oxi-dehydration to acrylic acid experimental assessment: Effect of catalyst properties, reaction parameters, and bed configurations

This study presents the proof-of-principle and sensitivity analysis of a dual-bed catalytic system achieving exceptional acrylic acid yield (up to 67.2%) from glycerol oxi-dehydration - among the highest reported in the literature. A systematic investigation was carried out to boost the catalytic performance by investigating several variables, including type of catalysts, reaction parameters, and bed configurations. The reaction process involved the dehydration of glycerol to acrolein over HZSM-5 zeolites, followed by further oxidation to acrylic acid using vanadium-molybdenum mixed oxide catalysts having orthogonal (Ortho-MoVO) or amorphous structure (Amor-MoVO). HZSM-5 zeolites with Si/Al ratios ranging from 23 to 500 were evaluated in the presence and absence of the air at 280 °C for the glycerol dehydration, with HZSM-5 (200) showing optimal performance. The dual-bed configuration (HZSM-5/MoVO) significantly outperformed the mixed-bed system, with Amor-MoVO achieving the highest yield of 67.2% at 280 °C. When using Ortho-MoVO under optimized conditions (280 °C, 4972 h⁻¹ GHSV, oxygen-to-glycerol ratio of 9.5), the system maintained high acrylic acid yield of 58.8%. The superior performance of the dual-bed system was attributed to the spatial separation of reaction zones, enabling controlled oxygen exposure and minimizing undesired oxidation pathways. The main by-products from the oxi-dehydration reaction in the dual-bed system were acetic acid, propanoic acid, formic acid and COx, however, additional by-products such as acetaldehyde, propanal and acrolein were observed in the case of a mixed-bed system. This study demonstrates the feasibility of a promising route for the sustainable acrylic acid production from renewable feedstocks, with a perspective on industrial implementation.