Highly-dispersed Ni on BEA catalyst prepared by ion-exchange-deposition-precipitation for improved hydrodeoxygenation activity

BEA zeolite-supported nickel is a promising catalyst for the hydrodeoxygenation reaction. In this study, highly dispersed Ni/BEA catalysts prepared via ion-exchange-deposition-precipitation (IDP) utilising careful pH control were investigated in the hydrodeoxygenation of guaiacol. In comparison, catalysts prepared by incipient wetness impregnation (IWI) and deposition-precipitation (DP) methods were also studied and IDP catalysts were shown to have higher dispersion. Over these carefully prepared catalysts significantly increased selectivity toward hydrocarbons was observed. The presence of nickel hydrides was confirmed by H2-TPD and H2-FTIR. IDP catalyst displays a higher metal dispersion and higher concentration of nickel hydrides than impregnated and DP catalysts, while bigger Ni nanoparticles formed in impregnated catalysts exhibit a higher concentration of nickel hydrides per surface Ni. The guaiacol conversion was not significantly affected by the catalyst preparation method, while the product selectivity was altered. Higher cyclohexane formation rate was detected over IDP catalysts compared to DP and impregnated catalysts. Besides, cyclohexane formation rate displays a positive linear correlation with the concentration of nickel hydrides, suggesting nickel hydrides play a crucial role in the hydrodeoxygenation reaction.