The success of the first, second, and third editions of this text has been the primary reason for the decision to publish a fourth edition. In addition, the demand for petroleum products, particularly liquid fuels (gasoline and diesel fuel) and petrochemical feedstocks (such as aromatics and olefins), is increasing throughout the world. Traditional markets such as North America and Europe are experiencing a steady increase in demand whereas emerging Asian markets, such as India and China, are witnessing a rapid surge in demand for liquid fuels. This has resulted in a tendency for existing refineries to seek fresh refining approaches to optimize efficiency and throughput. In addition, the increasing use of heavier feedstock for refineries is forcing technology suppliers and licensors to revamp their refining technologies in an effort to cater to the growing customer base.