Identifying desulfurization experts can be time consuming ... but worth the effort. The first step is to use Google, Yahoo!, or some other search engine, for technical articles that discuss desulfurization.
The second step is to browse ... browse page after page, downloading the occasional article or abstract that addresses your particular concern.
The third step is to identify the author(s) of the articles you have found ... and search Google, Yahoo! or some other search engine for items that provide you some sense of how good a fit a given author is in addressing your need.
All of this takes time ... lots of it. If you don't have that kind of time, contact Jean Steinhardt at letters@jeansteinhardt.com. As a professional searcher with 13 years of experience in the oil and gas industry, he may be able to help.
