Dealkylation of alkyl polycyclic aromatic hydrocarbon over silica monolayer solid acid catalyst

Abstract

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.

Removal of Basic Compounds and Dealkylation of Alkyl Polycyclic Aromatic Hydrocarbons in Vacuum Gas Oil

“…Addition of 5 wt% of dibenzothiophene, a sulfur-containing aromatic, also did not affect the reactivity. Our previous study also found no influence of aromatic hydrocarbons with larger number of aromatic rings or of sulfur-containing compounds 8) . Then various nitrogen-containing compounds were tested; basic nitrogen-containing aromatic hydrocarbons were removed from VGO-sol, but nonbasic compounds such as carbazole, indole and the 297 J. Jpn.…”

“…The reaction was prohibited by basic nitrogen compounds which poisoned the acid sites 16) 19) . In the first stage of the study, we demonstrated that removal of basic substances from the reactant oil resulted in high reactivity for the subsequent dealkylation 8) . However, we employed a strongly acidic cation exchange resin as the solid acid.…”

“…Hydrogen was introduced for the hydro-genation of alkene into alkanes over a solid acid 6) 8) . The silica monolayer catalyst has comparably large mesopore size (10-30 nm) or, more exactly, non-porous nature, which are the important features for the high activity for the desired reaction, resulting in the high selectivity, because the dealkylation requires the formation of carbenium cations with high steric hindrance 8) . This dealkylation process minimizes the formation of unnecessary light alkanes and maximizes the yield of alkane fractions usable for gasoline and diesel fuel.…”

Selective dealkylation of alkyl polycyclic aromatic hydrocarbons towards innovative upgrading process of practical heavy oil

“…SMA-3 exhibited high activity and selectivity in the model reaction of HDN as previously reported 6 , and was thus compared with various aluminosilicates as solid acids in this section. Hexadecylnaphthalene (HDN) was added to VGO as an index reactant, and the reactivity was assessed by the conversion of this compound.…”

“…Thus, this alternative process to the conventional processes can maximize the amounts of long-chain alkanes and benzene derivatives with the minimum consumption of hydrogen, compared to the hydrocracking process. We have previously reported the dealkylation as a model reaction, in which only the C16 and 18 alkylnaphthalenes were fed as the reactant 6 . The next report revealed the influence of coexisting substances in VGO as real heavy oil on the conversion of C16 alkylnaphthalene added as an index reactant 7 .…”