Exploring Heterogeneous Pd Nanocatalysts for Upgrading Acetone-Butanol Mixtures to Sustainable Aviation Fuel Precursors

Abstract

The catalytic conversion of fermentation-derived short-chained oxygenates into longer-chained hydrocarbons offers a promising solution to obtain sustainable aviation fuel (SAF) with a low carbon footprint and maximum utilization of renewable resources. This study explores the alkylation of acetone-butanol (AB) mixtures using Pd supported on high-surface area materials with varying inherent properties, aiming to optimize selectivity toward higher ketones. To elucidate the nature of the active catalyst, all synthesized catalysts were thoroughly characterized and tested under the optimized reaction conditions for the AB alkylation. A 5 wt % Pd/MgO-HS (HS: high surface) catalyst was found to exhibit the highest selectivity (81%) for 6-undecanone, C₁₁(═O), which was attributed to an optimal balance of catalytically active sites and surface properties. Despite the absence of Pd leaching, the catalyst showed reduced activity in consecutive reaction runs. Comprehensive analysis of the spent catalyst identified the primary cause to be a transformation of the MgO support to MgKPO₄ in the presence of the K₃PO₄ base additive under the reaction conditions. The restructuring of the catalyst support led to entrapment of the accessible Pd sites, reducing their availability for catalytic reactions. The insights from the study provide a robust framework for future SAF development, particularly in the design and optimization of catalysts for higher ketone production from renewable resources.