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Energy & Fuels 2001, 15, 1166-1172
Conversion of the Rosin Acid Fraction of Crude Tall Oil into Fuels and Chemicals Robert Coll, Siddharth Udas, and William A. Jacoby* Department of Chemical Engineering, University of MissourisColumbia, W2033 Engineering Building East, Columbia, Missouri 65211 Received January 29, 2001. Revised Manuscript Received June 22, 2001
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.
Introduction The use of gasoline and diesel fuel additives is increasing. A decline in crude oil quality, more restrictive environmental regulations, and the interest of vehicle manufacturers in improving engine performance and fuel economy are driving the increase. Environmental issues related to burning fossil fuels are also assuming greater importance in the scientific community and society as a whole. Biomass-derived fuels balance carbon dioxide release during burning with fixation during growth. Ethanol is widely used as a gasoline additive and can be produced from biomass. Bio-diesel fuel, obtained from esterification of vegetable oils, is also available. In general, however, biomassderived fuels are more expensive than fossil fuels. A widely available, low cost and chemically desirable feedstock could form the basis for an economically feasible process for converting a forest product industry residue into diesel fuel additives. Tall oil meets these criteria. It comes from pine trees, a byproduct of paper production via the Kraft process. Tall oil is composed of the ether extractable, nonlignin, noncellulosic portion of the pine tree, and it must be fractionated via steam-vacuum distillation for commercial use. Fractionation of one metric ton of crude tall oil produces about 350 kg of rosin acids, 300 kg of fatty acids, and 350 kg of distillated tall oil, head and pitch.1 Tall oil rosin production has recently been driven by demand for its coproduct, tall oil fatty acid. In 1992, tall oil rosin production was so far in excess of demand that * To whom correspondence should be addressed. E-mail: Jacoby@ missouri.edu. (1) North American Pulp and Paper Fact Book.
it was being burned to save storage costs.2 United States production of tall oil rosin in 1994 was 265,000 metric tons, exceeding consumption by nearly 50000 metric tons. The rosin acid fraction of crude tall oil is in abundant supply and has attractive characteristics as a precursor to high value chemicals. Despite its low cost and abundance, tall oil has only recently been considered as a potential fuel source. Initial studies have focused on the unfractionated material.3-9 Direct use of tall oil is not possible since it produces excessive corrosion, has deficient rheological properties at low temperatures, and produces unacceptable contamination of the lubricating oil and coking in the engine.7 Tall oil rosin is made up of a number of different diterpenoid (resin) acids, diterpene alcohols, aldehydes and hydrocarbons.16 The resin acids comprise nearly 85% of the tall oil rosin (Table 6). As a result of exposure (2) Chemical Economics Handbook; SRI International: Menlo Park, CA, 1995. (3) Sharma, R. K.; Bakhshi, N. N. Catalytic Conversion of Crude Tall Oil to Fuels and Chemicals over HZSM-5: Effect of Co-feeding Steam. Fuel Process. Technol. 1991, 27, 113-130. (4) Sharma, R. K.; Bakhshi, N. N. Upgrading of Wood-derived Biooil Over HZSM-5. Bioresour. Technol. 1991, 35, 57-66. (5) Sharma, R. K.; Bakhshi, N. N. Upgrading of Tall Oil to Fuels and Chemicals Over HZSM-5 Catalyst Using Various Diluents. Can. J. Chem. Eng. 1991, 69. (6) Sharma, R. K.; Bakhshi, N. N. Catalytic Upgrading of Biomassderived Oils to Transportation Fuels and Chemicals. Can. J. Chem. Eng. 1991, 69. (7) Wong, A. Tall Oil-based Cetane Enhancer for Diesel Fuel. Pulp Pap. Can. 1995, 96 (11), 37-40,. (8) Stumborg, M.; Wong, A.; Hogan, E. Hydroprocessed Vegetable Oils for Diesel Fuel Improvement. Bioresour. Technol. 1996, 56, 1318. (9) Liu, D. D. S.; Monnier, J.; Tourigny, G.; Kriz, J.; Hogan, E.; Wong, A. Production of High Quality Cetane Enhancer from Depitched Tall Oil. Pet. Sci. Technol. 1998, 16 (5,6), 597-609.
10.1021/ef010018a CCC: $20.00 © 2001 American Chemical Society Published on Web 08/09/2001
Rosin Acid Fraction of Crude Tall Oil
Energy & Fuels, Vol. 15, No. 5, 2001 1167
Figure 1. Obtaining fuel additives from tall oil rosin acid fraction Table 1. Characteristic Properties of Catalysts Used Industrial Application Areas Hydrocracker pretreat service and applications requiring maximum HDN. Heavy oil hydrotreaters at severe conditions where diffusion limitsare expected to be a problem, e.g., first stage hydrocracker, VGO hydrotreater or lube oil hydrotreater.
TK-555 (NiMo) C-424 (NiMo)
C-448 (CoMo)
multipurpose catalyst used for deep desulfurization of distillate feedstocks. Can also be used for the desulfurization of lighter (kero/naphtha) feedstocks if significant debottlenecking is required.
Figure 2. Chemical structures of abietic acid and dehydroabietic acid.
Physical Properties
shape
size mm (i)n
bulk surface pore density area volume g/cm3 m2/g mL/g (H2O) (lb/ft3)
TK-555 TRILOBE 1.3 (1/20) (NiMo) C-424 TRILOBE 1.3 (1/20) (NiMo) C-448 TRILOBE 1.3 (1/20) (CoMo)
155
0.45
265
0.54
0.95 (59) 0.81 (50) 0.71 (44)
Table 2. Approximate Composition of Catalysts Used % w/w TK-555 2-5 20-30 68-80 5-10 C-424a
