CATALYTIC HYDROTREATING OF BLACK LIQUOR OILS

Laboratory-scale batch experiments have been completed for testing catalytic hydrotreating as a means of upgrading an oil product produced from kraft black liquor. The experiments show that sulfided cobalt-molybdenum and nickel-molybdenum catalysts can be used to convert the viscous, low-volatility oil into a mixture of hydrocarbons and phenolics at 380-degrees-C and about 1 h residence time. Removal of the sodium in the oil by an acid wash before the experiment results in a more effective reaction and a higher quality product. Addition of water to the hydrotreating experiment can be used as a means to separate the sodium from the upgraded product into a byproduct aqueous stream. The upgraded product contains less oxygen and sodium than the black liquor oil and contains a larger volatile fraction (distillable under vacuum). Comparison of the operating results and the product composition with earlier results in wood-derived oil upgrading shows many similarities.