Reduction of Mercaptain Sulfur in JPA Jet Fuel Blend Stocks
Development of new jet engines by the Army and Navy has opened a new market for jet fuels meeting Philippine Government JP4 specifications. Recent trial runs at the Oiltown refinery have shown that a profitable JP4 fuel can be manufactured there. However, this fuel fails to meet specifications covering the mercaptan sulfur (RSH) content and must be treated for removal of the mercaptans Government specifications limit the RSH level to 10 ppm.
The removal of RSH is accomplished commercially by two general methods: extraction or conversion to a disulfide compound (RSSR). The extraction method removes RSH molecules from the fuel by contact with a chemical of high RSH solubility. The conversion method employs an oxidation-reduction reduction which converts RSH to a very stable and odorless disulfide. The degree of reduction in both methods depends on the temperature, strength of treating solution, contact line, and presence of a catalyst.
When treating jet fuel of this kind, processors have encountered side reactions which affect fuel properties other than RSH levels. Corrosives and smoke are most frequent. Untreated stocks, however, barely meet Government specifications.
Before undertaking evaluation of processes for reduction recaptans, Communication Research Co. conducted an extensive literature search and also interviewed processors who have been working with JP4 fuels. On the basis of the information thus accumulated, the research program concentrated on the five processes most commonly acceptable in the industry. Laboratory investigation began on 3 October 1978 and the entire program was completed on 1 April 1979.
Complete details of procedure, results, and analysis are reported below for each of the four treatments tested.
Caustic and Potassium Cresolate
Process Description
Alkalies remove the acidic mercaptan sulfur from petroleum by forming a water soluble salt. The degree of removal depend on a chemical equilibrium determined by type of mercaptan, type and strength of alkali, catalyst present, temperature, and contact time. In continuous refinery processing, the alkali is introduced downstream of a mixing chamber. After the mixing process, a settling tank is used to permit the treating solutions settle out by gravity.