Production of low sulfur binder pitich from high-sulfur Illinois coals. Quarterly report, 1 March 1995--31 May 1995

The objective of this project is to produce electrode binder pitch with sulfur content below 0.6 wt% from high-sulfur Illinois coal mild gasification liquids. Previously, flash thermocracking (FTC) was used to successfully upgrade the properties of mild gasification pitch, yielding a suitable blending stock for use as a binder in the production of carbon electrodes for the aluminum industry. However, in pitches from high-sulfur (4%) Illinois coal, the pitch sulfur content (2%) was still higher than preferred. In this project two approaches to sulfur reduction are being explored in conjunction with FTC: (1) the use of a moderate-sulfur (1.2%) Illinois coal as mild gasification feedstock, and (2) direct biodesulfurization of the liquids from high-sulfur coal prior to FTC. In Case 1, the liquids are being produced by mild gasification of IBC-109 coal in a bench-scale fluidized-bed reactor, followed by distillation to isolate the crude pitch. In Case 2, biodesulfurization with Rhodococcus Rhodochrous IGTS8 biocatalyst is being performed on crude pitch obtained from Illinois No. 6 coal tests conducted in the IGT MILDGAS PRU in 1990. Following preparation of the crude pitches, pitch upgrading experiments are being conducted in a continuous FTC reactor constructed in previous ICCI-sponsored studies. This quarter, mild gasification of IBC-109 coal was completed, producing 450 g of coal liquids, which were then distilled to recover 329 g of Case 1 crude pitch. Next month, the pitch will be subjected to FTC treatment and evaluated. Biodesulfurization experiments were performed on Case 2 pitch dispersed in l-undecanol, resulting in sulfur reductions of 15.1 to 21.4%. This was marginally lower than the 24.8% desulfurization obtained in l-dodecanol, but separation of pitch from the dispersant was facilitated by the greater volatility of l-undecanol