2-Ethylhexanol applications

A detailed discussion on surfactants from secondary alcohols which are relatively little known in the U.S. is included, together with a review of linear alcohol processes (Oxo and Ziegler) and detergent applications of the Ziegler alcohols. Also covered is a discussion of the revolutionary rhodium oxo process which has already resulted in a number of new plants—announced, under construction, or in operation, worldwide—for the manufacture of n-butanol and 2-ethylhexanol. Applications of these alcohols are also discussed. 

The triester of ethylene chlorohydrin readily undergoes ester interchange with higher alcohols, e.g., 2-ethylhexanol. The formed ethylene chlorohydrin is distilled off. The reaction is applicable to all alcohols having a higher boiling point than ethylene chlorohydrin. 

Considering the promising results with 2-ethylhexanol, we tested the applicability of SZ also for esterification with methanol. High conversions can be reached even at 140°C providing that an increased amount of catalyst is used (Figure 33.2). It is worthwhile noting that the esterification with methanol takes place at the highest rates. This can be explained by the alcohols relative sizes. 

The principal product of the hydroformylation which is most desired in industrial applications is a linear aldehyde. The unmodified, cobalt-catalyzed processes produce a mixture of linear and branched aldehydes, the latter being mostly an a-methyl isomer. For the largest single application—propylene to butyraldehydes—the product composition has an isomer ratio (ratio of percent linear to percent branched) of (2.5 t.0)/l. The isobutyraldehyde cannot be used to make 2-ethylhexanol, and iso-... 

In our experiments we screened zeolites, ion-exchange resins, heteropoly compounds and mixed metal oxides. Several alcohols were used to show the range of applicability. The selectivity was assessed by testing the formation of side products in a suspension of catalyst in alcohol (e.g. SZ in 2-ethylhexanol) under reflux for 24 hours. Under the reaction conditions, no by-products were detected by GC analysis. 

More recent developments in this country have included synthesis of relatively stable oils of low volatility, low pour point, and high viscosity index by esterification of octyl alcohols, such as 2-ethylhexanol, with dibasic acids such as adipic acid and sebacic acid (3). Octyl alcohols may be synthesized from petroleum hydrocarbons via the oxo process. Although of relatively high cost, these synthetic oils find general application in making greases for lubrication of antifriction bearings and instruments in aircraft. 

One exception to the general application of these ketone syntheses was failure of compounds having an alpha-substituted carbon atom such as isobutyl alcohol or 2-ethylhexanol to undergo the dehydrogenation (7) condensation reaction. This failure of alpha-substituted reactants to undergo the ketone synthesis was unexpected as the aldol condensation of alpha-substituted aldehydes with one labile hydrogen atom occurs readily. 

Manufacture of /i-Butanol and 2-Ethylhexanol by the Rhodium Oxo Process and Applications of the Alcohols... 

The key industrial applications and markets for normal and isobutanol and 2-ethylhexanol are discussed. As will be noted, the C4 oxo alcohols find use primarily within the coatings industry, either as solvents, per se, or as intermediates to manufacture solvents or protective coatings chemicals. Applications for 2-ethylhexanol, while numerous and varied, are basically oriented toward the manufacture of plasticizers for polyvinyl chloride. Total U.S. consumption of these alcohols in 1979 was approximately 1.3 billion pounds -730 million pounds of n-butanol, 190 million pounds of isobutanol, and 380 million pounds of 2-ethylhexanol. The consumption pattern is summarized in Table II and described in the following sections ... 

Isobutanol use in the manufacture of zinc dialkyl dithiophosphates (ZDDP), anti-wear lube oil additives, represented 13 percent of domestic consumption. Other alcohols used in this application include methylamyl alcohol, primary amyl,alcohol, n-butanol, 2-ethylhexanol and isooctanol. 

Ethylhexanol. Use of 2-ethylhexanol in the manufacture of PVC plasticizers, most notably DOP (di-2-ethylhexyl phthalate), has historically accounted for over 70 percent of U.S. demand for this alcohol. DOP has been the most widely used general purpose PVC plasticizer for close to half a century and is considered the "workhorse" of the industry. The material is used in a wide variety of PVC resin applications including flooring, wire and cable, packaging and coated fabrics. In the past, DOP has represented the industry cost/ performance standard against which all competing plasticizers were measured. 

Shutdown of Oxochem s 2-ethylhexanol unit in 1978 eliminated 300 million pounds of capacity overnight. As a result, DOP users began a crash reformulation effort on alternative plasticizers. Linear alcohol and Cg and Ciq branched chain alcohol based phthalates as well as butyl benzyl phthalate, for example, were found to be wholly or partially substitutable plasticizers in many DOP applications. New 2-ethylhexanol capacity available starting in 1981 is expected... 

Other 2-ethylhexanol based plasticizers include di-2-ethylhexyl adipate for vinyl food wrap application, tri-2-ethylhexyl trimellitate, di-2-ethylhexyl azelate, and di-2-ethylhexyl sebacate. 

Diester synthetic base stock lubricants formulated with 2-ethylhexanol (e.g., di-2-ethylhexyl adipate) provide excellent low temperature starting properties in automotive crank case applications and are also employed as lubricants for industrial machinery such as compressors and turbines. 

Shell s version of the Oxo process is in use in several foreign countries as well as in the U.S. The first commercial use of this catalyst system was for the production of normal butanol and 2-ethylhexanol in 1963. It is ejected to continue to be Shell s primary process for the conversion of olefins to alcohols. This process has produced higher alcohols efficiently since its first commercial application in 1965. This is due to its simplicity, its high quality products and its flexibility to utilize many different feedstocks. 

Other 2-ethylhexanol based plasticizers were introduced, including some which imparted outstanding low temperature flexibility—dioctyl adipate (DOA), dioctyl azelate (DOZ), dioctyl sebacate (DOS), and trioctyl phosphate (TOF). In addition, TOF showed high resistance to microorganisms which was important in military applications. Furthermore, TOF improved flame resistance. However, the mixed ester—octyl diphenyl phosphate—also introduced in the forties—was far superior and showed a better balance of low temperature performance and flame resistance than either TOF or the well-established plasticizer—tricresyl phosphate (TCP). Each of these found a market as a specialty plasticizer because of these specific performance attributes. None, however, was a serious threat to DOP on an overall price-performance basis. Rather, they were used to supplement the properties of DOP where its performance was inadequate. 

Meanwhile, Rohm and Haas introduced the first of the polymeries - polyesters based on the reaction of a dibasic acid with a glycol and with a monohydric alcohol or monobasic acid as chain terminator(j>). These plasticizers were developed as highly permanent, extraction and migration resistant types for specialty applications. 2-Ethylhexanol and isodecyl alcohol are examples of monohydric alcohols used as chain terminators in today s polymeries. 

Oxo chemicals include butyraldehyde (normal- and iso-) and the corresponding alcohols, 2-ethylhexanol (from n-butyraldehyde), propionaldehyde, and n-propyl alcohol, and lesser amounts of higher aldehydes and alcohols derived from C5 through C]7 olefins. The total volume of products derived from oxo chemistry exceeds a billion pounds a year. Volumes and applications are given later in this chapter for the most important products. 

Table 3 further outlines the estimated capacities for 2-ethylhexanol (2-EH) production. In total, about 60 % of the C4 capacity (or about 70 % of the w-butanal capacity) is required to produce 2-EH. However, regional deviations in C4/2-EH capacities are obvious, indicating that n-butanal is to be considered a commodity with worldwide availability. Bearing in mind that 2-EH and the C9/C10 alcohols are nearly quantitatively absorbed in plasticizer production, the enormous significance of hydroformylation for the polymer industry, especially for PVC, is underlined. In contrast to repeatedly published predictions, a decrease in the application of 2-EH as plasticizer alcohol has not been observed to date. 

The percentage of solids in the dispersion adhesives is 35-55%, in some cases as much as 70%, the rest is water, which after the adhesive application must either be completely evaporated (ventilation time) or diffuse into the joined parts (wood, textiles, concrete, foams, leather). The film formation temperature in types containing plasticizers and flexibilizing additives is lower than in types that are free of plasticizers. Additives, so-called high boilers (ethyl glycol, ethyl glycol acetate, ethylhexanol), are used to bring the film formation temperature down. 

The most important and oldest application of aqueous biphasic, homogeneous catalysis is hydroformylation (oxo process, Roelen reaction). This process is used to produce n-butyraldehyde, the desired main product of the reaction of propylene, which is converted by aldolization into 2-ethyUiexenal and this is finally hydrogenated to give 2-ethylhexanol (2-EH), the most economically important plasticizer alcohol (Scheme 1) ... 

There are primarily two types of C8 alcohols (octanols) that bear commercial significance 2—ethylhexanol, and isooctanol. The total U.S. demand for these two octanols in 1965 was 285 million pounds. The industrial applications of octanols are as follows ... 

Other Applications. The alcohols through Cg have applications as specialty solvents, as do derivatives of linear and branched hexanols. Inks, coatings, and dyes for polyester fabrics are other application areas for 2-ethylhexanol (63). Di(2-ethylhexyl) phthalate is used as a dielectric fluid to replace polychlorinated biphenyls. Trialkyl amines of the linear alcohols are used in solder fluxes, and hexanol is employed as a solvent in a soldering flux (64). Quaternary ammonium compounds of the plasticizer range alcohols are used as surfactants and fungicides, similarly to those of the detergent range alcohols. 

Application of solid-liquid extraction in the field of Inorganic Chemistry can be illustrated by taking the examples of separation of (i) lithium chloride from the chlorides of other members of the alkali metal group and (ii) calcium nitrate from the nitrates of other members of the alkaline earth group. The solubilities of sodium chloride and potassium chloride are very small in -hexanol and 2-ethylhexanol, whereas the solubility of lithium chloride is large enough so that it can be separated from a mixture of the three chlorides by extraction with these solvents. Similarly, using a 50-50 per cent mixture of absolute ethanol and ether calcium nitrate can be removed from a mixture of the anhydrous nitrates of calcium, barium and strontium. 

The recovery of actinides from such solutions by acidification with HNO3 followed by solvent extraction is hampered by the accumulation of H2MBP and HDBP in the solvent. This problem may be overcome by extracting the H2MBP and HDBP from the acidified carbonate solutions with 2-ethylhexanol, EHOH, prior to acidification. Laboratory trials indicated that such a process was potentially applicable to Purex waste streams. Problems identified were the formation of precipitates of H MBP or HDBP complexes on neutralization of the carbonate solutions and the transfer of some EHOH through the process into the actinide extractant used. The extraction of oxidation state (IV) and (VI) actinides could be accomplished using TBP while DHDECMP could be used to extract oxidation state (III) actinides and lanthanides also. 

The principal industrial application is the hydroformylation of propene, where the primary product n-butyraldehyde may be converted via an aldol condensation followed by hydrogenation to give 2-ethylhexanol which is used as a plasticiser alcohol in dialkylphthalate formulations. Alternatively butyraldehyde is converted to butanol which is used as a solvent. 

Rhodium Catalysts. - The hydroformylation of propene with a Rh/triphenyl-phosphine catalyst is now an established industrial process which will consume over a million tonnes per annum of propene when all licensed plants are operational. Most of the product n-butyraldehyde is converted to 2-ethylhexanol for plasticiser applications. The process is also applicable to the hydroformylation of C2, C4, and C5 alkenes. The process is remarkable for the long lifetime of the Rh catalyst but by-products are formed which deactivate the catalyst and have to be removed. The formation of triphenyl-phosphine oxide, benzaldehyde, and propyldiphenylphosphine under hydroformylation conditions has been investigated where benzaldehyde is produced by or /zo-metallation of triphenylphosphine followed by CO insertion and P-C bond cleavage and propyldiphenylphosphine was assumed to result from reaction of propene with the co-ordinated diphenylphosphine group remaining after benzaldehyde formation. The same authors have also studied the kinetics of the formation of heavy by-products which are dependent on... 

Berberich et al. used salt hydrate pairs to control water activity in [BMIM][PF6]. The results were in good agreement with that obtained for water activity control using saturated salt solutions. The advantage of pre-equilibration is that the contact of the enzyme with the used salt and thus enzyme deactivation can be avoided. On the other hand it is only applicable for initial rate measurements. This disadvantage can be overcome by controlling water activity with salt hydrate pairs. Berberich et al. measured initial rate - water activities for the transesterification reaction of methyl methacrylate with 2-ethylhexanol in either hexane or [BMIM][PF6]. Both reaction systems gave similar profiles [72],... 

The rate of the reaction changes depending upon the partial pressure of CO it reaches a maximum at ca 3 MPa. The yield of the reaction decreases as the temperature increases. At low temperatures the rate of the hydroformylation is small and therefore higher temperatures are applied. Hydroformylation allows the preparation of various valuable products because the oxo synthesis may utilize different compounds containing a carbon-carbon double bond, for example, dienes, polyenes, and unsaturated aldehydes, ketones, nitriles, alcohols, esters, etc. For example, dienes may afford dialdehydes. A substantial amount of aldehydes is converted to alcohols which find considerable application in the preparation of detergents, plasticizers, and lubricants. The aldol condensation generally is not desired in hydroformylation processes. Nevertheless, via aldol condensation followed by hydrogenation, 2-ethylhexanol is obtained from n-butyraldehyde see equation (13.117). 

These plasticizers can be further grouped in a number of ways one convenient distinction is into general purpose and speciality plasticizers. General purpose types include the three phthalates di-2-ethylhexyl phthalate (DEHP or DOP), di-isononyl phthalate (DINP) and di-isodecyl phthalates (DIDP). These are the esters of phthalic anhydride with the alcohols 2-ethylhexanol, iso-nonanol and isodeconal respectively, and they account for about 75% of plasticizer usage in Western Europe. Other phthalates are also manufactured, but find use more in applications where specific properties are required. 

Many of the acrylates are also made by free radical polymerization. By varying the alcohol portion, such as methanol as in methyl acrylate or butanol for butyl acrylate or 2-ethylhexanol as in octyl acrylate, the Tg and other polymeric properties can be varied. As the side chain increases in length, the Tg decreases. Going from a one carbon alcohol as in methyl acrylate to an eight carbon alcohol results in a lowering of the Tg by about 60 °C. However, the cost increases. Often copolymers are made such as in the copolymerization of methyl acrylate with butyl acrylate to optimize properties needed for particular applications. The acrylates are commonly used as pressure-sensitive adhesives. 

Examples of common plasticizers include phthalate esters such as dioctyl phthalate (DOP), more properly called di-2-ethylhexyl phthalate (DEHP), and used as an inexpensive general purpose plasticizer. This is made by reacting phthahc anhydride with 2-ethylhexanol. Another example is diisodecyl phthalate (DIDP). DIDP has lower volatihty and improved resistance to soapy water extraction. It has many applications in PVC used for wire and cable coating. Phthalate plasticizers are also made from linear alcohols such as 1-hydroxyheptane, 1-hydroxynonane, and 1-hydroxyundecane. They are often used when superior low temperature properties, lower volatility, or outdoor weathering is required. 

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