Oxidative Route 'Cleans Up' Diesel

Description and Advantages

A novel, low-emission technology uses an oxidative chemistry to desulfurize crude oil or refined products. The process - UniPure ASR-2-has been developed by UniPure Corp. in cooperation with Texaco and Mustang Engineering. It is an alternative ultra-low desulfurization process that readily converts highly substituted thiophenic compounds into sulfones; it does not consume hydorgen.

UniPure ASR-2, is a two step process. The sulphur species are oxidized into sulphones using an oxidantcarried in the aqueous phase with a liquid catalyst. The reaction occurs at near atmospheric pressure and mild temperatures.

This reaction consumes insignificant amounts of oxidant; conversion of sulphur compounds into sulphones occurs quickly- with a 5 min. reactor residence time. After separation from the oil, the aqueous phase - containing spent catalyst and some sulphones - is sent to a recovery section. At recovery, the sulphones are removed, and the catalyst is regenerated.

The oil phase, which also carries some sulphones, is forwarded to an extraction step that uses a solid adsorbent. Methanol is used to regenerate this adsorbent. The final product is diesel with 5 ppm of sulphur. Recovered sulphones can be disposed off in the refinery coker. One tpd of sulphone is extracted for each 1,000 bpd of diesel (500 ppm sulphur) processed.

The process is claimed to be simple to operate and have low energy consumption with nearly zero emission. This new oxidative technology is an alternative processing route to high pressure hydrotreaters. Smaller ARS-2 units can be combined with existing hydrotreaters to meet lower sulphur specifications and debottleneck present equipment configurations for low sulphur specifications.

Source: Hydrocarbon Processing, May 2001