p-Xylene is an aromatic hydrocarbon. It is one among the three isomers of dimethylbenzene known collectively as xylenes. The p- stands for para-, indicating that the 2 methyl groups in p-xylene occupy the diametrically opposite substituent positions 1 and 4.
Para xylene is in the positions of the two methyl groups, their arene substitution pattern, that it differs from the other isomers, o-xylene and m-xylene. All have the same chemical formula C6H4(CH3)2. All xylene isomers are colorless and highly flammable.
Para-Xylene is presently produced almost exclusively from naphtha by catalytic reforming process. The aromatics produced are used as feedstock to aromatics plants. One known method for producing xylenes involves the alkylation of toluene with methanol over a solid acid catalyst. Thus the alkylation of toluene with methanol over cation-exchanged zeolite Y has been described by Yashima et al.
p-Xylene is an important chemical feedstock. Among other industrial applications, it's a staple within the large scale synthesis of varied polymers. In particular it's a component within the production of terephthalic acid for polyesters like polyethylene terephthalate (generally referred to as PET). It also could also be polymerised on to produce Parylene.