1. Chemical Engineering Dept.; Universidad Michoacana de San Nicolás de Hidalgo; Morelia Michoacán 58060 México
2. Chemical Engineering Dept.; Texas A&M University; College Station TX 77843
3. Petroleum Engineering Dept.; Texas A&M University; College Station TX 77843
4. Chemical and Materials Engineering Dept.; King Abdulaziz University; Jeddah Saudi Arabia