INTRODUCTION

An aromatics complex is a combination of process units that can be used to convert petroleum naphtha and pyrolysis gasoline (pygas) into the basic petrochemical intermediates: benzene, toluene, and xylenes (BTX). Benzene is a versatile petrochemical building block used in the production of more than 250 different products. The most important benzene derivatives are ethylbenzene, cumene, and cyclohexane (Fig. 2.1.1). The xylenes product, also known as mixed xylenes, contains four different C ₈ aromatic isomers: para-xylene, ortho-xylene, meta-xylene, and ethylbenzene. Small amounts of mixed xylenes are used for solvent applications, but most xylenes are processed further within the complex to produce one or more of the individual isomers. The most important C ₈ aromatic isomer is para-xylene, which is used almost exclusively for the production of polyester fibers, resins, and films (Fig. 2.1.2). In recent years, polyester fibers have shown growth rates of 5 to 6 percent per year as synthetics are substituted for cotton. Resins have shown growth rates of 10 to 15 percent per year, corresponding to the emergence of PET (polyethylene terephthalate) containers. Note that benzene can be a significant by-product of para-xylene production, depending on the type of technology being used. A small...