Catalytic deoxygenation of fatty acids via ketonization and α-carbon scissions over layered alkali titanate catalysts under N(2)

The ketonization of fatty acid with subsequent McLafferty rearrangement of the fatty ketone allows the deoxygenation to hydrocarbons. Here, we report the cascade reaction of palmitic acid (C(16)) to hydrocarbons (≤C(14)) over lepidocrocite-type alkali titanate K(0.8)Zn(0.4)Ti(1.6)O(4), K(0.8)Mg(0.4)Ti(1.6)O(4), and K(0.8)Li(0.27)Ti(1.73)O(4) and the reassembled TiO(2) catalysts at ≤400 °C under atmospheric N(2) in a continuous fixed-bed flow reactor. The C(16) acid is coupled to C(31) ketone prior to the scissions mostly to a C(17) methyl ketone and C(14) hydrocarbons (i.e., the McLafferty rearrangement). The hydrocarbons yield increases with temperature and is proportional to partial charge at the O atom, suggesting that basic sites are responsible for C(31) ketone scissions. The layered alkali titanate catalysts with two-dimensional (2D) space inhibit diffusion of the ketone primarily formed and promote its scissions to hydrocarbons within the confined space. Otherwise, low hydrocarbons yield (but high ketone yield) is obtained over TiO(2) and the Mg/Al mixed oxide catalysts possessing no interlayer space. Meanwhile, the semi-batch experiment with pre-intercalated palmitic acid favors a direct deoxygenation, demonstrating the essential role of reaction mode toward ketone scission reaction pathway. Over K(0.8)Li(0.27)Ti(1.73)O(4), the complete palmitic acid conversion leads to ∼47% hydrocarbons yield, equivalent to ∼80% reduction of the oxygen content in the feed under N(2).