Catalytic decomposition of 1,3-diphenoxybenzene to monomeric cyclic compounds over palladium catalysts supported on acidic activated carbon aerogels

Activated carbon aerogel (ACA) was prepared by a chemical activation of carbon aerogel using phosphoric acid (H3PO4). Activated carbon aerogel bearing sulfonic acid (ACA-SO3H), Cs2.5H0.5PW12O40-impregnated activated carbon aerogel (Cs2.5H0.5PW12O40/ACA), and Cs2.5H0.5PW12O40-impregnated activated carbon aerogel bearing sulfonic acid (Cs2.5H0.5PW12O40/ACA-SO3H) were prepared in order to provide acid sites to ACA. Palladium catalysts were then supported on ACA, ACA-SO3H, Cs2.5H0.5PW12O40/ACA, and Cs2.5H0.5PW12O40/ACA-SO3H by an incipient wetness impregnation method. The prepared Pd/ACA, Pd/ACA-SO3H, Pd/Cs2.5H0.5PW12O40/ACA, and Pd/Cs2.5H0.5PW12O40/ACA-SO3H catalysts were applied to the decomposition of 1,3-diphenoxybenzene. 1,3-Diphenoxybenzene was used as a trimeric lignin model compound for representing C-O bond in lignin. Cyclohexanol, benzene, and phenol were mainly produced by the decomposition of 1,3-diphenoxybenzene. 4-Phenoxyphenol was also produced as an intermediate by the decomposition of 1,3-diphenoxybenzene. Conversion of 1,3-diphenoxybenzene and total yield for main products (cyclohexanol, benzene, and phenol) increased with increasing acidity of the catalysts. Among the catalysts tested, Pd/Cs2.5H0.5PW12O40/ACA-SO3H with the largest acidity showed the highest conversion of 1,3-diphenoxybenzene and total yield for main products. Pd/Cs2.5H0.5PW12O40/ACA-SO3H also served as a stable and reusable catalyst in the decomposition of 1,3-diphenoxybenzene.

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► Pd catalysts supported on acidic ACAs (activated carbon aerogels) were prepared.
► Catalytic decomposition of 1,3-diphenoxybenzene was conducted.
► Acidity of the catalysts played an important role in the reaction.
► Total yield for monomeric cyclic compounds increased with increasing catalyst acidity.