Comparative study of the effects of reactor system and catalysts on glycerol valorisation via aqueous-phase reforming

The conversion of glycerol through aqueous phase reforming (APR) presents an important opportunity for sustainable chemical and fuel production. This study explores the APR of glycerol using three catalysts (nickel supported on alumina (NiAl), copper supported on alumina (CuAl), and bimetallic nickel-iron supported on alumina (NiAlFe)), synthesised via the coprecipitation method. The APR experiments were conducted in both batch and fixed-bed reactors. In the batch reactor, a 75 mL Parr reactor was utilised, operating at 238 °C and 5 bar initial nitrogen pressure with 20 mL of a 5 wt% glycerol solution and 0.3 g of catalyst (catalyst/glycerol mass ratio = 0.3). The fixed-bed reactor was made of a stainless steel tube loaded with 2 g of catalyst, operating at 238 °C and 37 bar, with a continuous feed of 5 wt% glycerol solution, equivalent to catalyst/glycerol mass ratio of 0.33. NiAl produced the highest conversion of glycerol to gases and the highest yield of hydrogen (230 mg H2/mol C fed). However, among the tested catalysts, NiAlFe demonstrated superior performance, achieving a carbon yield to total products (liquid and gases) of approximately 80% in the batch reactor as well as a relatively high hydrogen yield (141 mg H2/mol C fed). These results underscore the promising potential of the NiAlFe catalyst for efficient glycerol conversion in APR processes, paving the way for advancements in sustainable fuel and chemical production.