Description
Xylenes are produced with different processes. When in refineries, oil cuts enter the reforming units, aromatic compounds comprise a great proportion of the outflow material. Separating this flow into its components, accounts for more than 70 percent of global xylene supply. Also in the steam cracking process in olefin units, some quantity of Mixed Xylene is produced. In addition, disproportioning Toluene into Benzene and Xylene and treating Pyrolysis Gasoline are also different ways to produce Mixed Xylene.
Mixed xylenes are the second-most-important aromatic product in terms of world consumption for chemical manufacture, ranking behind benzene and ahead of toluene. Mixed xylenes refers to the equilibrium mixture of four isomers with the same C8H10 chemical formula. The isomers in order of natural occurrence are meta-xylene, ortho-xylene, para-xylene, and ethyl-benzene.
Para-Xylene is made by separating compound xylene, and is a transparent liquid with no color. It is harmful to the body. The product has high value as it is used to produce terephthalic acid, which becomes raw material for polyester, fiber, PET bottles, and films. It is produced separately through the processes of adsorption and desorption wherein PX is selectively adsorbed from the raw material, Mixed Xylene (MX).
o-Xylene (ortho-xylene) is an aromatic hydrocarbon, based on benzene with two methyl substituents bonded to adjacent carbon atoms in the aromatic ring (the ortho configuration). It is a constitutional isomer of m-xylene and p-xylene.
o-Xylene is largely used in the production of phthalic anhydride, and is generally extracted by distillation from a mixed xylene stream in a plant primarily designed for p-xylene production.
MIXED-XYLENE (MX)
Application: Production of paints, Plastic Industries, PTA, etc.
| PARAMETER | TEST METHOD | UNIT | VALUE |
| Density at 15.6 ⁰C | ASTM D4052 | gr/cm3 | TO BE REPORTED |
| Appearance | Visual | – | Clear, Free of haze/sediment |
| Color Pt-Co Scale | ASTM D1209 | – | 10 max |
| Acid Wash Color | ASTM D848 | – | 6 max |
| Acidity | ASTM D847 | mgr NaOH/100ml | no free acid |
| Copper Corrosion | ASTM D849 | – | No.1a |
| H2S & SO2 Content | ASTM D853 | – | free of H2S/SO2 |
| Distillation Range at 670 mmhg | ASTM D850 | ⁰C | 5 max |
| I.B.P | ASTM D850 | ⁰C | 137 min |
| D.P | ASTM D850 | ⁰C | 143 MAX |
| PARA-XYLENE | ASTM D2306 | wt.% | 16.5 MIN |
| ORTHO-XYLENE | ASTM D2306 | wt.% | 15 MIN |
| ETHYL BENZENE | ASTM D2306 | wt.% | 18.5 max |
| METHA XYLENE | ASTMD2306 | wt.% | 49 max |
| BENZENE | ASTM D2360 | wt.% | 0.005 max |
| TOLUENE | ASTM D2360 | wt.% | 0.04 max |
| C9 AROMATICS | ASTM D2360 | wt.% | 0.5 max |
| Non Aromatics | ASTM D2360 | wt.% | 0.05 max |
| TOTAL SULFUR | UOP 727 | wt.ppm | 1 max |
| TOTAL CHLORIDES | IP-AK/81 | wt.ppm | 1 max |
| BROMINE INDEX | IP-129 | mgr/100 gr | 20 max |
PARA-XYLENE (PX)
Applications : Production of paints, Plastic industries, Production of PTA and Chemical industries
| PARAMETER | TEST METHOD | UNIT | VALUE |
| Purity | ASTM D3798 | gr/cm3 | TO BE REPORTED |
| Non-AR | ASTM D3798 | – | Clear, Free of haze/sediment |
| Distillation range | ASTM D850 | – | 10 max |
| T-sulfur | UOP-727 | – | 6 max |
| T-chloride | EP/AK-81 | mgr NaOH/100ml | no free acid |
| Sp.Gr at 60 F/60 F | ASTM D4052 | – | No.1a |
| H2S & SO2 Content | ASTM D853 | – | free of H2S/SO2 |
| Appearance | VISUAL | ⁰C | 5 max |
| TOL+BZ | UOP 720 | ⁰C | 137 min |
| Ethylbenzene | ASTM D3798 | ⁰C | 143 MAX |
| Color (pt-co scale) | ASTM D1209 | wt.% | 16.5 MIN |
| M-XYLENE | ASTM D3798 | wt.% | 15 MIN |
| O-XYLENE | ASTM D3798 | wt.% | 18.5 max |
| Acid wash color | ASTM D848 | wt.% | 49 max |
ORTHO-XYLENE (OX)
Applications: production of phthalic anhydride, etc
| PARAMETER | TEST METHOD | UNIT | VALUE |
| Purity | ASTM D2306 | wt% | 98.5 Min |
| Non-AR | ASTM D2306 | wt% | 0.5 Max |
| BZN+C9 & Heavier Aromatics | ASTM D2306 | wt% | 1 Max |
| Total C8 Aromatics + Toluene + Ethyl Benzene | ASTM D2306 | wt% | 98.5 Min |
| Distillation Range at 760 mmhg | ASTM D850 | °C | 2 Max (Including 144.4) |
| Total sulfur | ASTM D5453 | wt ppm | 1 Max |
| Color (Pt-Co) Scale | ASTM D1209 | — | 20 Max |
| Acidity | ASTM D847 | wt ppm | None detected |
| Hydrocarbon Residue after evaporation | ASTM D1353 | — | 20 Max |
| H2S and SO2 content | ASTM D853 | wt% | None detected |
| Sp.gr @ 15.6/15.6°C | ASTM D4052 | wt% | 0.86-0.89 |
