Dealkylation of alkylnaphthalene, as a model of alkyl polycyclic aromatic hydrocarbon compounds in heavy oils, proceeded selectively on a silica monolayer solid acid catalyst. The activity was generated by the deposition of silica on alumina with generation of Brønsted acidity. The activity and Brønsted acid amount showed the maximum where the monolayer covered the surface, indicating that the Brønsted acid site generated on the silica monolayer was the active species. The activity and selectivity on the silica monolayer were high compared to other aluminosilicate catalysts, and high activity was observed even after calcination at 973-1173 K.

We propose a novel method to upgrade heavy oil. This method utilizes dealkylation of alkyl polycyclic aromatic hydrocarbons on a silica monolayer solid acid catalyst to produce alkanes with preserved alkyl chain length and aromatic hydrocarbons without alkyl groups, resulting in maximization of the yields of value-added products, alkanes suitable for diesel fuel and alkylbenzenes suitable for gasoline and chemical feedstocks. Basic compounds in vacuum gas oil were found to inhibit the reaction, but were removed by treatment with solid acids such as strongly acidic cation exchange resin and amorphous silica _ alumina. Drying of the silica _ alumina significantly enhanced the removal rate. The silica _ alumina was repeatedly usable by calcination in an oxygen flow. After the treatments for the removal of basic compounds, dealkylation of alkyl polycyclic aromatic hydrocarbons proceeded at 673 K. However, rapid catalyst deactivation was observed. Higher reaction temperature of 723 K suppressed deactivation of the catalyst and maintained the high selectivity. Even in the optimized conditions, slow deactivation of the catalyst was observed, but the catalyst was regenerated by calcination at 773 K in oxygen, and the catalytic performance was repeatedly demonstrated.