Glycols, production

In 1937 the first commercial apphcation of the Lefort direct ethylene oxidation to ethylene oxide [73-21-8] followed by hydrolysis of ethylene oxide became, and remains in the 1990s, the main commercial source of ethylene glycol production (1) (see Ethylene oxide). Ethylene oxide hydrolysis proceeds with... 

An early source of glycols was from hydrogenation of sugars obtained from formaldehyde condensation (18,19). Selectivities to ethylene glycol were low with a number of other glycols and polyols produced. Biomass continues to be evaluated as a feedstock for glycol production (20). 

Although catalytic hydration of ethylene oxide to maximize ethylene glycol production has been studied by a number of companies with numerous materials patented as catalysts, there has been no reported industrial manufacture of ethylene glycol via catalytic ethylene oxide hydrolysis. Studied catalysts include sulfonic acids, carboxyUc acids and salts, cation-exchange resins, acidic zeoHtes, haUdes, anion-exchange resins, metals, metal oxides, and metal salts (21—26). Carbon dioxide as a cocatalyst with many of the same materials has also received extensive study. 

Ethylene Glycol Product Information bulletin. Union Carbide Chemicals and Plastics Co., Danbury, Conn., 1990. 

Membrane Pervaporation Since 1987, membrane pei vapora-tion has become widely accepted in the CPI as an effective means of separation and recovery of liquid-phase process streams. It is most commonly used to dehydrate hquid hydrocarbons to yield a high-purity ethanol, isopropanol, and ethylene glycol product. The method basically consists of a selec tively-permeable membrane layer separating a liquid feed stream and a gas phase permeate stream as shown in Fig. 25-19. The permeation rate and selectivity is governed bv the physicochemical composition of the membrane. Pei vaporation differs From reverse osmosis systems in that the permeate rate is not a function of osmotic pressure, since the permeate is maintained at saturation pressure (Ref. 24). 

Consider the application of chemical reactor technology to a commercial reactor. Figure 5-40 illustrates a simplified flow diagram of ethylene glycol production. Consider the reactions in the formation of glycol ... 

In the following example, ethylene glycol product was manufactured to a specification that limited the diethylene glycol and higher glycol content formation of these materials caused a loss in yield. Reactions... 

The same conclusion was drawn from the results obtained from careful studies of the stereochemistry of the glycol products formed on oxidation of cyclohexene with thallium(III) acetate 3, 83). When dry acetic acid was employed as solvent the product was mainly the tranr-diacetate (XI) in moist acetic acid, however, the mixture of glycol mono- (XII) and diacetates (XIII) which was obtained was mainly cis. These results have been interpreted in terms of initial trans oxythallation, ring inversion. 

Figure 3 Conversion versus Selectivity for Total Glycol Product and EG from Continuous Xylitol Testing, 13g of Ni/Re catalyst, aqueous 20.4% Xylitol 1% NaOH Feed, 35cc catalyst bed, 8,300kPaH2, 5 1 H2 to Xylitol molar ratio.

Although related reactions have also been done under low pressures/ very low rates of product formation are observed (8/10/11). We have found/ however, that a ruthenium carbonyl catalyst is quite active for converting H2/CO to methanol under moderate pressures (below 340 atm). More significantly, we also discovered that an ethylene glycol product could be obtained from this catalyst by use of carboxylic acid promoters or solvents (12) This remarkable and intriguing promoter effect deserved, we felt, further mechanistic investigation... 

Since it is experimentally observed that carboxylic acids are required to promote glycol production by this system and since acid concentration appears in the empirical rate equation for glycol production with a substantial exponent (ca. 1.8) the formation of a metal-carbon bonded intermediate (step 6) may... 

Ethylene glycol industry, 24 270 Ethylene glycol monobutyl ether, acrylamide solubility in, l 290t Ethylene glycol production, economic aspects of, 12 652-653 Ethylene glycols (EGs), 10 664-665 12 113, 644-660. See also Glycols derivatives of, 12 656-660 diethers of, 12 658 from ethylene oxide, 10 596 health, safety, and environmental factors related to, 12 653-655 manufacture of, 12 648-652 monoethers of, 12 656-658 properties of, 12 645-648, 649t uses for, 12 645, 655-656... 

J.W. Lawrie, "Glycerol and the Glycols— Production, Properties and Analyses , Chem. Catalog Co (Reinhold Pubg Co), NY (1928)... 

Also listed in Table II are turnover frequencies to the primary products, in units of moles of product per mole of HCo(CO)4 per hour, which allow a comparison of the relative activity of the catalyst to the primary products under various reaction conditions. It is evident that the activity of this system is quite low under the conditions recorded. The maximum turnover frequency to the glycol product is below 0.05 hr-1, and the highest rate to methanol is slightly above 2 hr-1. 

Catalyst stability in this system is substantially influenced by the characteristics of solvents and promoters. Indeed, the properties of solvents and promoters which improve the catalytic activity for ethylene glycol production (increased dielectric constant, greater cation complexing ability, or... 

The amount of ethylene glycol product formed in acetic acid solvent is usually minor relative to the methanol product. Table XIV, for example, shows examples in which the CJC2 product ratio is within the range of about 35-90. Esters of the three-carbon polyalcohol, glycerol, have also been... 

Reactions of ruthenium catalyst precursors in carboxylic acid solvents with various salt promoters have also been described (170-172, 197) (Table XV, Expt. 7). For example, in acetic acid solvent containing acetate salts of quaternary phosphonium or cesium cations, ruthenium catalysts are reported to produce methyl acetate and smaller quantities of ethyl acetate and glycol acetates (170-172). Most of these reactions also include halide ions the ruthenium catalyst precursor is almost invariably RuC13 H20. The carboxylic acid is not a necessary component in these salt-promoted reactions as shown above, nonreactive solvents containing salt promoters also allow production of ethylene glycol with similar or better rates and selectivities. The addition of a rhodium cocatalyst to salt-promoted ruthenium catalyst solutions in carboxylic acid solvents has been reported to increase the selectivity to the ethylene glycol product (198). 

Methods for the manufacture of raw materials of requisite purity for nitroglycerine, nitroglycol and nitrodiethylene glycol production and for dynamite collodion cotton have already been described (Vol. II, pp. 87, 145, 152 and 409). 

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