Conversion of the rosin acid fraction of crude tall oil into fuels and chemicals

Tall oil rosin acid, a forest product industry residue, has been converted into a diesel fuel additive in a single step process. Fractionation of crude tall oil produces an excess of rosin acids. This material is an abundant, inexpensive and chemically desirable feedstock. Two components, abietic acid and dehydroabietic acid, comprise about 70% of the rosin acid fraction of tall oil, The carboxylic acid functionality of these compounds must be removed and double bonds in the ring structure hydrogenated to obtain diesel fuel additives. Hydrotreatment of the rosin acid fraction achieves both goals. The experiments were performed in a laboratory-scale batch reactor using three commercial sulfided Ni-Mo and Co-Mo catalysts. For each of the catalysts, three different factors were studied: temperature, hydrogen pressure, and reaction time. Experiments probe the effects of these variables on liquid product yield, cetane index, hydrogen-to-carbon ratio, and degree of cracking. The liquid products, mainly saturated tricyclic ring compounds, were analyzed by elemental analysis (C, H, S, and O) and by GC-MS. Boiling point distributions and densities were also determined. From these data, cetane indexes were calculated.