The xylene isomers, meta-xylene, ortho-xylene and in particular para-xylene are important chemical intermediates. ortho-xylene is oxidized to make phthalic anhydride which is used to make phthalate plasticizers among other things. meta-Xylene is oxidized to make isophthalic acid, which is used in unsaturated polyester resins (UPR). However, para-xylene has by far the largest market of the three isomers. The largest use of para-xylene is in its oxidation to make terephthalic acid. Terephthalic acid is used in turn to make polymers such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). PET is one of the largest volume polymers in the world. As such the demand for para-xylene is several times that for meta- and ortho-xylene. Xylenes are normally obtained from various sources within a refinery or steam cracker including reformate, pyrolysis gasoline and toluene disproportionation. These sources usually produce a mixture of isomers and are discussed in this section. Technology for the recovery of the various xylene isomers (para-xylene, ortho-xylene and meta-xylene) is available through several licensors, as well as conversion technology to enhance the yield. These include, but are not limited to, UOP (Des Plains, IL), Axens (Rueil-Malmaison, France) and GTC Technology Corp. (Houston, TX). Worldwide para-xylene capacity totaled approximately 21.4 million metric tons per year at the end of 2001. The figure below shows the regional capacities for para-xylene by region. This graph shows that East Asia has the highest percentage of para-xylene capacity followed by the United States and Japan. It is expected that the global average annual para-xylene growth between the year 2000 and 2005 will be 5.5 percent and will decline slightly to about 4.3 percent between 2005 and 2010. The Middle East has the highest growth rate followed by Latin America between 2000 and 2005. During 2005 to 2010 it is expected that Latin America and Eastern Europe will show the highest growth. During the same time periods, Japan will have the lowest growth and, in fact, is expected to shrink between 2000 and 2005. REGIONAL para-XYLENE CAPACITY BREAKDOWN, 2001
 This new report by Nexant Chem Systems reviews the chemistry, process technology, production economics, and markets for xylenes with particular emphasis on para-xylene. |
