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

Abstract

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.

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

“…Decline in the reaction rate was in the order of N631-L < SMA-3 < USY << ZSM-5. Here it is noted that the previous studies have revealed the highest activity of SMA for the conversion of HDN at 673 K among the solid acids which were tested also in the present study 6,7 . The present experiments were performed at 723 K for evaluation of the catalytic performances under practical conditions, and therefore the apparent order of conversion was somewhat different.…”

“…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 . However, the reactivity of original hydrocarbons in VGO has not been apparent.…”

“…The resulting mixture was stirred at room temperature for 1 h, and then the Amberlyst-15DRY was removed by filtration. The above cation exchange resin treatment was repeatedly carried out (usually 2-3 times) until the pH trend indicated the neutralization point as observed using an automatic neutralization titrator (916Ti-Touch, Metrohm AG) 7,8 .…”

“…However, the solid acids are poisoned by basic nitrogen-containing compounds in the original VGO. Before the dealkylation, the basic nitrogen-containing aromatic hydrocarbons were removed by acidic ion-exchanged resins (containing a SO3H group) 7 . The industrial utilization of this resin may be difficult due to the expensiveness and the laborious regeneration, but we have recently found that the alternative to the resin was inexpensive amorphous silica-alumina, which could be simply regenerated by heating 8 .…”

“…In the reaction, a small amount of hydrogen is fed for hydrogenation of the alkenes, which are produced by the dealkylation and contained in the practical oil, because formation of coke from the alkenes deactivates the solid acid. The previous study mainly reported the reactivity of C16, 18 alkylnaphthalene, as a model reactant for indexing the dealkylation rate, in the coexistence of VGO components to quantitatively show the activity of SMA catalyst 7 , and here the reactivity and selectivity of dealkylation of practical VGO components are evaluated with the aid of the two-dimensional GC (2D-GC) technique, in order to clarify changes in compositions of existing hydrocarbons in VGO. The high dealkylation activity and selectivity of long-chain alkanes of SMA, due to weak Brønsted acidity and large pore size, will be focused on.…”