A few companies, such as Royal Dutch Shell PLC, have developed a new generation of catalysts to help refiners use the same equipment to meet new fuel specifications, such as the U.S. mandate to reduce the level of sulfur in diesel. "You can consider the catalysts like the software and the hydrocracker like your PC," says Carl Mesters, Shell's chief scientist for chemistry and catalysis. The catalysts allow companies to update their refining process without investing in new hardware.