Adipic selectivity

Cyclohexane. The LPO of cyclohexane [110-82-7] suppUes much of the raw materials needed for nylon-6 and nylon-6,6 production. Cyclohexanol (A) and cyclohexanone (K) maybe produced selectively by using alow conversion process with multiple stages (228—232). The reasons for low conversion and multiple stages (an approach to plug-flow operation) are apparent from Eigure 2. Several catalysts have been reported. The selectivity to A as well as the overall process efficiency can be improved by using boric acid (2,232,233). K/A mixtures are usually oxidized by nitric acid in a second step to adipic acid (233) (see Cyclohexanol and cyclohexanone). 

Plasticizers and Processing Aids. Petroleum-based oils are commonly used as plasticizers. Compound viscosity is reduced, and mixing, processing, and low temperature properties are improved. Air permeabihty is increased by adding extender oils. Plasticizers are selected for their compatibihty and low temperature properties. Butyl mbber has a solubihty parameter of ca 15.3 (f /cm ) [7.5 (cal/cm ) ], similar to paraffinic and naphthenic oils. Polybutenes, paraffin waxes, and low mol wt polyethylene can also be used as plasticizers (qv). Alkyl adipates and sebacates reduce the glass-transition temperature and improve low temperature properties. Process aids, eg, mineral mbber and Stmktol 40 ms, improve filler dispersion and cured adhesion to high unsaturated mbber substrates. 

The reasons why a tubular reactor was selected for the production of adipic acid nitrile from adipic acid and ammonia are discussed by Weikard (in Ullmann, Enzyldopaedie, 4th ed., vol. 3, Verlag Chemie, 1973, p. 381). 

Hexaammonium macrocycles [32]aneN6 and [38]aneN6 were designed as selective ditopic receptor molecules for dicarboxylates -02C—R—C02- such as succinate, glutarate, or adipate 51). Highest stability of the complex corresponds to the best fit between the substrate R length and the site separation of the receptor II. 

The epoxidation method developed by Noyori was subsequently applied to the direct formation of dicarboxylic acids from olefins [55], Cyclohexene was oxidized to adipic acid in 93% yield with the tungstate/ammonium bisulfate system and 4 equivalents of hydrogen peroxide. The selectivity problem associated with the Noyori method was circumvented to a certain degree by the improvements introduced by Jacobs and coworkers [56]. Additional amounts of (aminomethyl)phos-phonic acid and Na2W04 were introduced into the standard catalytic mixture, and the pH of the reaction media was adjusted to 4.2-5 with aqueous NaOH. These changes allowed for the formation of epoxides from ot-pinene, 1 -phenyl- 1-cyclohex-ene, and indene, with high levels of conversion and good selectivity (Scheme 6.3). 

In one approach cyclohexane is autoxidized to a mixture of cyclohexanol and cyclohexanone in the presence of a Co or Mn naphthenate catalyst. This mixture is subsequently oxidized to adipic acid using nitric acid as the oxidant in the presence of a Cu Vv catalyst. An alternative method using dioxygen in combination with Co or Mn in HOAc gives lower selectivities to adipic acid (70% vs 95%). Alternatively, autoxidation in the presence of stoichiometric amounts of boric acid produces cyclohexanol as the major product, which is subsequently oxidized to adipic acid using HNO3 in the presence of Cu Vv. The latter step produces substantial amounts of N2O as a waste product. 

Interestingly, Tanaka (ref. 27) has reported the cooxidation of cyclohexane with acetaldehyde in the presence of a Co(OAc)2 catalyst in acetic acid at 90 °C (3). Adipic acid was obtained in 73% selectivity at 88% cyclohexane conversion. 

Nitrous oxide has received increasing attention the last decade, due to the growing awareness of its impact on the environment, as it has been identified as an ozone depletion agent and as a Greenhouse gas [1]. Identified major sources include adipic acid production, nitric acid and fertilizer plants, fossil fuel and biomass combustion and de-NOx treatment techniques, like three-way catalysis and selective catalytic reduction [2,3]. 

Numerous chemical intermediates are oxygen rich. Methanol, acetic acid and ethylene glycol show a O/C atomic ratio of 1, as does biomass. Other major chemicals intermediates show a lower O/C ratio, typically between 1/3 and 2/3. This holds for instance for propene and butene glycols, ethanol, (meth)acrylic acids, adipic acid and many others. The presence of some oxygen atoms is required to confer the desired physical and chemicals properties to the product. Selective and partial deoxygenation of biomass may represent an attractive and competitive route compared with the selective and partial oxidation of hydrocarbon feedstock. 

On the other hand, the methoxyester results from MeOH attack on coordinated double bond, followed by methoxycarbonylation (Scheme 11). In both cases, the formation of 7r-allylpalladium complexes directs the regio-chemistry of the process. By optimizing the reaction conditions, it has been possible to obtain the unsaturated diester selectively. The latter compound is particularly important, since it can be easily transformed after hydrolysis and hydrogenation into adipic acid [52-54], Selective alkoxy-alkoxycarbonylation of 1,3-dienes has also been achieved [55]. 

Receptor [86] (Fig. 44) forms extremely stable 1 1 anion complexes with chloride, bromide and H2PC>4 in dimethyl sulfoxide solutions and with the adipate anion in acetone solutions. Interestingly, this receptor displays selectivity for chloride over dihydrogenphosphate. 

J. M. Thomas, R. Raja, G. Sankar, and R. G. Bell, Molecular-sieve catalysts for the selective oxidation of linear alkanes by molecular oxygen. Nature 398,227 (1999) J. M. Thomas, Designing a molecular sieve catalyst for the aerial oxidation of n-hexane to adipic acid, Angew. Chem. Int. 

D-Glucaric acid, directly produced by nitric oxidation of glucose or starch, is usually isolated as its 1,4-lactone. The technical barrier to its large-scale production mainly includes development of an efficient and selective oxidation technology to eliminate the need for nitric acid as the oxidant. Because it represents a tetrahydroxy-adipic acid, D-glucaric acid is of similar utility as adipic acid for the generation of polyesters and polyamides (see later in this chapter). 

The use of zeolites can overcome many of these limitations and provide new controlled entries into these oxidized hydrocarbons and new materials. For example, some of the most valuable industrial intermediates are terminally oxidized hydrocarbons, snch as n-hexanol or adipic acid, that are not readily available in free-radical chain processes. The ability of zeolites to function as shape-selective catalysts can, in principle, be used to restrict access, by reactant or transition state selectivity, to sites not normally attacked by oxidants [3]. 

The selective oxidations of the terminal positions of -alkanes are an example of substrate-shape selectivity. Product-shape selectivity has been used to enhance the selectivity of the type IIaRH oxidation of cyclohexane [66-68], For example, oxidation of cyclohexane at 373 K for 8 hr using FeAlPO-31 (pore aperture 5.4 A) as a catalyst resulted in 2.5% conversion to a mixture which contained 55.3% of adipic acid and 37.3% of a mixture of cyclohexanol and cyclohexanone [68]. In contrast, oxidation under identical conditions using FeAlPO-5 (pore aperture 7.3 A) resulted in only 9.2% of adipic acid and 89.5%... 

Effect of 6- Caprolactone and Adipic Acid Molar Ratio for Copolyester III on the Hydrolysis by R. delemar Lipase. The hydrolysis of various copolymers by R. delemar lipase was exam ed to see whether there was an optimum chemical structure or not. Mn of those copolyesters was selected from 17 0 to 2220, to diminish the effect of molecular weight. Optimum molar ratio of e- caprolactone and adipic acid was about from 90 10 to 70 30 (Figure 5). The Tm at the optimum molar ratio was the lowest of all. So it seemed that the existence of optimum molar ratio came from the lowest Tm, which would show the most amorphous material, rather than the optimum chemical structure. 

Following hydrogenation over palladium on carbon(33), dimethyl adipate hydrolysis to adipic acid is carried out using a strong mineral acid such as sulfuric acid. Hydrolysis is nearly quantitative with a selectivity of 99.5%. Since the adipic acid from the oxycarbonylation process contains no branched by-product acids, as is the case with the commercial oxidation process, extensive recrystallization is not required to produce a polymer grade material. Results indicate that the dried adipic acid crystals contain less than. 5 weight % moisture and are 99.95 weight % pure on a dry basis. 

In Japan the need for new technology was answered by the development of an electrolytic route to sebacic acid(33). The Kolbe type electrolytic process developed by Asahi involves dimerization of adipic acid half methyl ester salt to give dimethyl sebacate(34). The dimerization proceeds in 92% yield with 90% selectivity based on the adipate half ester. The main drawbacks of this process are the cost of energy utilized by the electrolytic process and the cost of adipic acid. A Chem Systems report indicates a small advantage for the Asahi electrolytic process with ample room for new technology development(35). 

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