Ethylene glycol plant process

Ethylene is rather inert, but it is metabolized slowly, some of it to ethylene glycol. Plants store Af-malonyl-ACC as a metabolically inert pool. Excess ACC can be deaminated in a PLP-dependent reaction to 2-oxobutyrate (step k, Pig. 24-16), a process that also occurs in bacteria able to subsist on ACC. There may also be other mechanisms for ethylene formation, e.g., peroxidation of lipids during scenescence of leaves. See also Chapter 31, Section G. 

Ethylene glycol is the most common recoverable inhibitor. It is less soluble in hydrocarbons and has less vaporization loss than methanol. This is common on the inlet to gas processing plants. 

Hydrolysis, although a simple method in theory, yields terephthalic acid (TPA), which must be purified by several recrystallizations. The TPA must be specially pretreated to blend with ethylene glycol to form premixes and slurries of the right viscosities to be handled and conveyed in modern direct polyesterification plants. Hie product of the alkaline hydrolysis of PET includes TPA salts, which must be neutralized with a mineral acid in order to collect the TPA. That results in the formation of large amounts of inorganic salts for which commercial markets must be found in order to make the process economically feasible. There is also the possibility that the TPA will be contaminated with alkali metal ions. Hydrolysis of PET is also slow compared to methanolysis and glycolysis.1... 

Two options are being developed at the moment. The first is to produce 1,2-propanediol (propylene glycol) from glycerol. 1,2-Propanediol has a number of industrial uses, including as a less toxic alternative to ethylene glycol in anti-freeze. Conventionally, 1,2-propanediol is made from a petrochemical feedstock, propylene oxide. The new process uses a combination of a copper-chromite catalyst and reactive distillation. The catalyst operates at a lower temperature and pressure than alternative systems 220°C compared to 260°C and 10 bar compared to 150 bar. The process also produces fewer by-products, and should be cheaper than petrochemical routes at current prices for natural glycerol. The first commercial plant is under construction and the process is being actively licensed to other companies. 

SOLINOX SO,. Linde NO,] A process for removing both NOx and SOx from fluegases. The SOx is removed by scrubbing with tetra-ethylene glycol dimethyl ether, circulated in a packed tower (the Selexol process). The NOx is destroyed by Selective Catalytic Reduction ( SCR). The sorbent is regenerated with steam the SOx is recovered for conversion to sulfuric acid. Developed by Linde in 1985 and used in a lead smelter in Austria and several power stations in Germany. In 1990 it was announced that it would be used at the titanium pigment plant in The Netherlands operated by Sachtleben. 

By adding up to 36% ethylene glycol to the aqueous catalyst phase, the space-time yield could be boosted up to approx. 3 mt m-3 h-1 for propene hydroformylation, a factor of 20 in comparison to the conventional two-phase process without changing the reaction conditions. Because of this surprising speed-up, higher alpha-olefins up to 1-octene are converted with high to acceptable space-time yield (Fig. 22). Up to date this process is not commercialized, but has been tested in a continuous pilot plant. 

PET is manufactured in a two-step process. In the first step terephthalic acid (TPA) is esterified with ethylene glycol (EG) to form bis-2-hydroxyethylene terephthalate (BHET) and oligomers up to a molar mass of 2000 g/mol. Older plants use the transesterificafion of dimethylterephthalate (DMT) with EG, because for a long time it was difficult and... 

Important applications of chemical reaction engineering (CRE) of all kinds can be found both inside and outside the chemical process industries (CPI). In this text, examples from the chemical process industries include the manufacture of ethylene oxide, phthaiic anhydride, ethylene glycol, metexylene, styrene, sul fur trioxide, propylene glycol, ketene, and i-fautane just to name a few. Also, plant safety in the CPI is addressed in both example problems and homework problems. These are real industrial reactions with aaua data and reaction rate law parameters. 

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