Published August 2018
Mixed xylenes are the second-most-important aromatic product in terms of world consumption for chemical manufacture, ranking behind benzene but ahead of toluene. The term mixed xylenes refers to the equilibrium mixture of four isomers with the same C8H10 chemical formula—para-xylene (PX), ortho-xylene (OX), meta-xylene (MX), and ethylbenzene. Mixed xylenes are produced by several methods but petroleum is by far the major source; petroleumderived mixed xylenes are produced primarily from catalytic reformate in refineries and, to a lesser extent, from pyrolysis gasoline and toluene disproportionation. However, large volumes of the mixed xylenes produced during petroleum refining are not isolated but rather left in the refinery stream for use in the gasoline pool as an octane value enhancer. This application, which is estimated to account for more than half of the reformate stream globally, is not captured in this report. However, mixed xylenes markets can be greatly influenced by this alternative use. A strong gasoline and octane market can increase the blend value for mixed xylenes, which reduces the incentives for refiners to isolate the product. A high mixed xylenes price can also make nonintegrated para-xylene producers unable to compete, which negatively impacts the demand.
Mixed xylenes serve as the feedstock from which the three xylene isomers are isolated. The composition may vary, but typically is rich in meta-xylene, the least valuable component. By isolating the desired components from the mixed xylenes stream via distillation, crystallization or selective adsorption processes, then isomerizing and recycling the balance of the stream, the mixed xylenes stream can be processed to extinction to produce only the component(s) needed to satisfy demand for each of the isomers.
The following pie chart shows world consumption of xylenes:
The past 15 years have seen substantial investment in mixed xylenes capacity, primarily for use in para-xylene. These investments have been located mainly in Northeast Asia, which has a well-developed, integrated polyester industry as well as access to raw materials. Asian polyester producers have moved to back-integrate their business into purified terephthalic acid (PTA), PX, and mixed xylenes to improve their cost-competitiveness. As a result, more than 70% of global mixed xylenes capacity is now found in Asia.
The Asian market, with its large population, growing demand for polyester fiber (fibers, fabrics, and floor coverings) and polyester resins (beverage containers) and corresponding growth in the polyester industry, is solidifying its position as the center of influence for the mixed xylenes market. Within the region, China is a major producer and consumer, owing to its vertically integrated polyester value chain. However, China’s mixed xylenes capacity development has been partially hindered by the shortage of heavy naphtha available for reforming in the country, as well as public resistance to the construction of PX plants because of safety concerns.
PX is the most widely used of the three xylene isomers. The major application for PX is, by far, the production of PTA, which itself is used almost exclusively for the production of polyethylene terephthalate (PET) polymer for the manufacture of polyester fibers, PET solid-state resins, and PET film. ortho-Xylene is isolated primarily to produce phthalic anhydride, which is used as a plasticizer in the manufacture of PVC products, including cable, flooring, pipe, shoes, and packaging film. meta-Xylene is isolated and used to produce isophthalic acid, which is used as a comonomer in PET production to manufacture plastic bottles.
In the next five years, mixed xylenes capacity is expected to increase at an average of 4–5% per year, driven primarily by new investments in China, Southeast Asia, and the Middle East, while consumption will grow at an average of 3–4% per year.