(583f) Deoxygenation of Model Biofuel Compounds Over Cs-NaX Zeolite Catalyst

The deoxygenation of methyl octanoate and benzaldehyde over CsNaX zeolite catalyst has been investigated as models for reactions for production of hydrocarbon fuels from bio-oxygenates. The CsNaX zeolite used in the study was prepared by ion exchange of NaX with a CsNO3/CsOH solution to a 50% exchange level. The decarbonylation activity, selectivity, and stability of the CsNaX catalyst were enhanced when methanol was co-fed for the reaction of methyl octanoate. TPD studies suggest that methyl octanoate first decomposes to an octanoate-like species. The decomposition of such species leads to the formation of heptenes and hexenes as major products. Octenes and hydrogenated products are formed in lesser amounts via hydrogenation / hydrogenolysis using hydrogen produced on the surface from methanol decomposition, but not from gas phase H2. In parallel, benzaldehyde can also be decarbonylated to benzene over the CsNaX catalyst; however oxygenated aromatic precursors can be formed on the catalyst surface. These precursors can further decompose/undergo hydrogenolysis to form benzene, toluene and 2-ring compounds. Higher reaction temperature and gas phase H2 reduce the accumulation of the oxygenated aromatic precursors and the formation of non-decomposable coke. An excess of Cs in CsNaX increases the catalyst's basicity leading to higher decarbonylation activity for both methyl octanoate and benzaldehyde. The absence of Cs cation in the zeolite framework (NaX) results in lower decarbonylation activity and the production of undesired products.