Multifunctional Catalysts for Direct Conversion of Alcohols to Long-Chain Hydrocarbons via Deoxygenative Olefination

Multistep H2-free upgrading of alcohols to liquid hydrocarbons is highly desirable for producing drop-in fuel substitutes, but the limited reports of this process for select substrates require multiple catalysts and bases, resulting in limited applicability. Direct conversion processes that rely on multifunctional catalysts and do not require base are yet to be reported. Here we describe such a Pd-catalyzed deoxygenative coupling of heptanol with heterogeneous catalysts composed of Pd immobilized on acid-base supports, which actively participate in the reaction cascade. The supports include primarily basic MgO, acidic γ-Al2O3, and Mg-Al hydrotalcite (HT), with a combination of Lewis acidic and basic sites. Pd-HTs with 1% and 5 wt % Pd loading afforded the highest overall activity in the multistep cascade, yielding 30% hydrocarbons (tridecene 6-E-tridecene and tridecane) from a neat reaction with heptanol with 0.2 mol % Pd loading. Heterogeneity tests suggest that Pd-HT is operationally heterogeneous. The impact of support selection on the activity and selectivity offers insights into the design principles for next-generation catalysts for this process and related transformations.