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p-Xylene is the principal precursor to terephthalic acid and dimethyl terephthalate, both monomers used in the production of polyethylene terephthalate (PET) plastic bottles and polyester clothing. 98% of p-xylene production, and half of all xylenes produced is consumed in this manner.
The production of p-xylene is industrially significant, with annual demand estimated at 37 million tons in 2014, and still on the increase. [12] [13] p-Xylene is produced by catalytic reforming of petroleum naphtha as part of the BTX aromatics (benzene, toluene and the xylene isomers) extracted from the catalytic reformate.
The xylene isomers are distinguished by the designations ortho – (or o –), meta – (or m ... Benzene, toluene, and xylenes can be made by various processes.
Xylene is among the 30 most produced chemicals in the country. It is described as a colorless, flammable liquid with a sweet odor, ...
o-Xylene (ortho-xylene) is an aromatic hydrocarbon with the formula C 6 H 4 (CH 3) 2, with two methyl substituents bonded to adjacent carbon atoms of a benzene ring (the ortho configuration). It is a constitutional isomer of m -xylene and p -xylene , the mixture being called xylene or xylenes.
Transalkylation of toluene and trimethylbenzene to produce xylene. In this example, the M/R ratio is 2. This type of reaction can also be performed with toluene and trimethylbenzene to produce xylene. The reaction occurs via equilibrium, so the product is not pure xylene. Many products are produced with varying numbers of methyl groups.
α,α'-dimethoxy-p-xylene. A similar synthesis for parylene N uses the precursor α,α'-dimethoxy-p-xylene. [28] The methoxy group H 3 CO − is the leaving group; while it condenses in the deposition chamber, it does not interfere with the deposition of the polymer. [23] This precursor is much less expensive than [2.2]para-cyclophane.
In many petroleum refineries, the net hydrogen produced in catalytic reforming supplies a significant part of the hydrogen used elsewhere in the refinery (for example, in hydrodesulfurization processes). The hydrogen is also necessary in order to hydrogenolyze any polymers that form on the catalyst.