Effect of surface acidity of Al₂O₃ supported metal catalysts on catalytic activity and carbon deposition during SCWG of glucose

In this study, the impact of a catalyst's surface acidity on supercritical water gasification (SCWG) of glucose is investigated. Four different catalysts including Ni, Ru^0·2Ni, Ru^0·5Ni and NiLa were prepared on an Al₂O₃ support via an incipient impregnation method. NH₃-TPD and pyridine-FTIR results of the fresh catalysts showed that NiLa was the least acidic amongst the four investigated catalysts. Although the BET surface area for all four catalysts were similar, the NiLa and Ru^0·5Ni catalysts were found to significantly reduce carbon deposition during SCWG of glucose, attributed to their lower acidic nature. Production of H₂ was also increased by 1.52 and 1.21 × using the NiLa and Ru^0·5Ni compared to Ni. The carbon deposition was characterized by TG-DTA, TPO, XRD and Raman spectroscopy, showing that the higher the acidic nature of the catalyst, the higher the tendency for carbon deposition. Using a lower acidic catalyst for SCWG helped minimize the catalyst's deactivation, while improving the catalyst lifetime This study shows that the acidic nature of the catalyst is an important consideration towards a better understanding of the SCWG mechanism.