Alkylation of Asphaltenes Using a FeCl3Catalyst

Abstract

Friedel–Crafts alkylation as a strategy to convert asphaltenes to maltenes was investigated. It was postulated that conversion of polar hydroxyl groups in the asphaltenes would make the product more soluble in light hydrocarbons. Reactions were performed with oilsands bitumen-derived materials using FeCl3 as a catalyst and o-xylene and methanol, separately. Only the reaction of o-xylene with asphaltenes was mildly beneficial; it resulted in 6% conversion of asphaltenes to maltenes and an increase of 9% in straight-run distillate and vacuum gas oil. The reactions of o-xylene with maltenes and bitumen were detrimental, as was all alkylation reactions with methanol. To better understand the nature of the conversion, the reactions were repeated with model compounds. With 2-naphthol, it was found that dimerization of 2-naphthol to produce (1,1′-binaphthalene)-2,2′-diol (BINOL) and the subsequent coordination with iron were the two dominant reactions. The adverse consequences of FeCl3-catalyzed conversion could be explained by such intermolecular addition reactions. The reaction of 2-naphthol with methanol and FeCl3 also caused some chlorination of the product. The possibility that FeCl3 as a catalyst affected ethers was explored by performing the reaction with dibenzyl ether as feed. It was found that the ether bonds were cleaved. In the presence of o-xylene, ether cleavage was followed by C-alkylation. The increase in maltenes after the reaction of o-xylene with asphaltenes was better explained by C-alkylation following ether cleavage than the reaction between o-xylene and the hydroxyl groups in the asphaltenes. The reaction of dibenzyl ether with methanol produced benzaldehyde, rearrangement products, and heavy gums.