Adipic acid from butadiene

It has been known since the early 1950s that butadiene reacts with CO to form aldehydes and ketones that could be treated further to give adipic acid (131). Processes for producing adipic acid from butadiene and carbon monoxide [630-08-0] have been explored since around 1970 by a number of companies, especially ARCO, Asahi, BASF, British Petroleum, Du Pont, Monsanto, and Shell. BASF has developed a process sufficiendy advanced to consider commercialization (132). There are two main variations, one a carboalkoxylation and the other a hydrocarboxylation. These differ in whether an alcohol, such as methanol [67-56-1is used to produce intermediate pentenoates (133), or water is used for the production of intermediate pentenoic acids (134). The former is a two-step process which uses high pressure, >31 MPa (306 atm), and moderate temperatures (100—150°C) (132—135). Butadiene,... 

Pure cyclohexanol can also be obtained by the hydrogenation of phenol with a palladium catalyst at 150°C and 10 atm although e process is not widely used. Attempts were made by BASF to synthesize adipic acid from butadiene via a two-step caibonylation process in the presence of methanol. The first step of the synthesis operated at 130°C and 600 bar while the second operated at 170°C and a lower pressure of 160 bar. A typical cobalt catalyst with organic ligands was used, but the process was never developed industrially. 

Adipic acid is prepared commercially by oxidative processes using either benzene or phenol as the raw material base. Since both benzene and phenol prices track with the price of crude oil, future adipic acid price will increase as the oil reserve decreases(j ). Thus, there is a need for a new process to produce adipic acid from cheap, and readily available, raw materials such as butadiene, synthesis gas, and methanol. 

Other starting materials for adipic acid include butadiene and 1,4-disubsti-tuted-2-butene, which involves dicarbonylation with palladium chloride. Polar, aprotic, and nonbasic solvents are preferred for this reaction to avoid unwanted side products from hydrogenolysis or isomerization. 

A most important application of butadiene carbonylations is BASF s development of a three-stage process for the synthesis of adipic acid from the butadiene-containing C4 cut [1] (eqs. (4) and (5)). Cobalt is the catalyst metal of choice for this process. The reaction takes place in two steps the first stage, which involves a lower temperature (100-140 °C), uses a fairly high concentration of HCo(CO)4 and pyridine as catalyst system to ensure rapid carbonylation of butadiene to give methyl pent-3-enoate in 90 % selectivity, thus avoiding typical side reactions such as dimerization and oligomerization. 

Adiponitrile in turn is obtained from processes starting from (a) adipic acid, (b) butadiene, and (c) acrylonitrile. The process starting from adipic add (process 7 in Figure 2.13) is rather well developed and used by most of the major raw material suppliers. It consists of a gas-phase reaction between adipic acid and ammonia at about 270°C at atmospheric pressure. In the presence of dehydration catalysts, such as phosphonic acid or a mixture of phosphoric and boric acids, the reaction proceeds via the formation of adipic add amide to adiponitrile with about 90% yield. 

HDA is commercially produced from adipic acid or butadiene. The catalytic hydrogenation of adiponitrile to HDA is common in both routes. The phosgena-... 

Dodecanedioic acid is prepared from cyclododecene (obtained from butadiene) by methods which are entirely analogous to those used to prepare adipic acid from benzene (section 10.2.2(a)). The cyclododecene is reduced to cyclododecane, which is oxidized firstly to a mixture of cyclododecanol and cyclododecanone and then to dodecanedioic acid. Dodecanedioic acid is a colourless crystalline solid, m.p. 129°C. 

The by-product of this process, pelargonic acid [112-05-0] is also an item of commerce. The usual source of sebacic acid [111-20-6] for nylon-6,10 [9008-66-6] is also from a natural product, ticinoleic acid [141-22-0] (12-hydroxyoleic acid), isolated from castor oil [8001-79-4]. The acid reacts with excess sodium or potassium hydroxide at high temperatures (250—275°C) to produce sebacic acid and 2-octanol [123-96-6] (166) by cleavage at the 9,10-unsaturated position. The manufacture of dodecanedioic acid [693-23-2] for nylon-6,12 begins with the catalytic trimerization of butadiene to make cyclododecatriene [4904-61-4] followed by reduction to cyclododecane [294-62-2] (see Butadiene). The cyclododecane is oxidatively cleaved to dodecanedioic acid in a process similar to that used in adipic acid production. 

The manufacture of hexamethylenediamine [124-09-4] a key comonomer in nylon-6,6 production proceeds by a two-step HCN addition reaction to produce adiponittile [111-69-3] NCCH2CH2CH2CH2CN. The adiponittile is then hydrogenated to produce the desired diamine. The other half of nylon-6,6, adipic acid (qv), can also be produced from butadiene by means of either of two similar routes involving the addition of CO. Reaction between the diamine and adipic acid [124-04-5] produces nylon-6,6. 

In a typical process adiponitrile is formed by the interaction of adipic acid and gaseous ammonia in the presence of a boron phosphate catalyst at 305-350°C. The adiponitrile is purified and then subjected to continuous hydrogenation at 130°C and 4000 Ibf/in (28 MPa) pressure in the presence of excess ammonia and a cobalt catalyst. By-products such as hexamethyleneimine are formed but the quantity produced is minimized by the use of excess ammonia. Pure hexamethylenediamine (boiling point 90-92°C at 14mmHg pressure, melting point 39°C) is obtained by distillation, Hexamethylenediamine is also prepared commercially from butadience. The butadiene feedstock is of relatively low cost but it does use substantial quantities of hydrogen cyanide. The process developed by Du Pont may be given schematically as ... 

Adipic acid may also be produced from butadiene via a carbonylation route (Chapter 9). 

Hexamethylenediamine is now made by three different routes the original from adipic acid, the electrodimerization of acrylonitrile, and the addition of hydrogen cyanide to butadiene. Thus, the starting material can be cyclohexane, propylene, or butadiene. Currently, the cyclohexane-based route from adipic acid is the most costly and this process is being phased out. The butadiene route is patented by DuPont and requires hydrogen cyanide facilities. Recent new hexamethylenediamine plants, outside DuPont, are based on acrylonitrile from propylene, a readily available commodity. 

Hexamethylenediamine (HMDA), a monomer for the synthesis of polyamide-6,6, is produced by catalytic hydrogenation of adiponitrile. Three processes, each based on a different reactant, produce the latter coimnercially. The original Du Pont process, still used in a few plants, starts with adipic acid made from cyclohexane adipic acid then reacts with ammonia to yield the dinitrile. This process has been replaced in many plants by the catalytic hydrocyanation of butadiene. A third route to adiponitrile is the electrolytic dimerization of acrylonitrile, the latter produced by the ammoxidation of propene. 

One process that capitalizes on butadiene, synthesis gas, and methanol as raw materials is BASF s two-step hydrocarbonylation route to adipic acid(3-7). The butadiene in the C4 cut from an olefin plant steam cracker is transformed by a two-stage carbonylation with carbon monoxide and methanol into adipic acid dimethyl ester. Hydrolysis converts the diester into adipic acid. BASF is now engineering a 130 million pound per year commercial plant based on this technology(8,9). Technology drawbacks include a requirement for severe pressure (>4500 psig) in the first cobalt catalyzed carbonylation step and dimethyl adipate separation from branched diester isomers formed in the second carbonylation step. 

An attractive alternative to building a world scale adipic acid plant is to construct a specialty smaller volume oxycarbonylation plant which is capable of exclusively producing the more valuable precursors for pelargonic and sebacic acid. Oxycarbonylation process conditions can be controlled to give methyl, 4-pentadienoate which is the product from butadiene mono-carbonylation(39,40). Methyl, 4-pentadienoate can react in a subsequent step with butadiene to give an unsaturated pelargonic acid precursor in high yield(41). Methyl, 4-pentadienoate... 

Adipic acid historically has been manufactured predominantly from cyclohexane and, to a lesser extent, phenol. During the 1970s and 1980s, however, much research has been directed to alternative feedstocks, especially butadiene and cyclohexene, as dictated by shifts in hydrocarbon markets. All current industrial processes use nitric acid in the final oxidation stage. Growing concern with air quality may exert further pressure for alternative routes as manufacturers seek to avoid NO, abatement costs, a necessary part of processes dial use nitric acid. 

The synthesis of dialkyl hex-3-ene-l,6-dioate from the dioxycarboxylation of butadiene in an alcoholic solvent, and in the presence of a dehydrating agent such as trimethyl orthoformate444 or 1,1-dimethoxycyclohexane,445 provides an economically attractive route for the synthesis of adipic acid (equation 175). 

Hexamethylenediamine [HMDA, EIjEt CEyg-NEy is the principal industrial chemical made from butadiene. EIMDA is polymerized with adipic acid to make a kind of nylon. 

It has a global capacity of 1.3 million tonnes per year. In the United States, production of ADN is based on the hydrocyanation of butadiene or electrochemical conversion from acrylonitrile. In Western Europe, companies produce ADN from adipic acid, butadiene and acrylonitrile. In Japan, the sole producer makes ADN from the electrodimerization of acrylonitrile. Demand for ADN is expected to be around 2% per year through at least 201 (f A comparison of the costs associated with two of the ADN processes are shown in Table 22.1275. 

PVC can be blended with numerous other polymers to give it better processability and impact resistance. For the manufacture of food contact materials the following polymerizates and/or polymer mixtures from polymers manufactured from the above mentioned starting materials can be used Chlorinated polyolefins blends of styrene and graft copolymers and mixtures of polystyrene with polymerisate blends butadiene-acrylonitrile-copolymer blends (hard rubber) blends of ethylene and propylene, butylene, vinyl ester, and unsaturated aliphatic acids as well as salts and esters plasticizerfrec blends of methacrylic acid esters and acrylic acid esters with monofunctional saturated alcohols (Ci-C18) as well as blends of the esters of methacrylic acid butadiene and styrene as well as polymer blends of acrylic acid butyl ester and vinylpyrrolidone polyurethane manufactured from 1,6-hexamethylene diisocyanate, 1.4-butandiol and aliphatic polyesters from adipic acid and glycols. 

Currently the global production of hexamethylenediamine exceeds 1.2 Mt/a and production (e.g. ICI, BASF and Rhone-Poulenc in Europe) is based on the hydrogenation of adiponitrile, largely obtained by catalytic addition of HCN to butadiene. Celanese produced hexamethylenediamine by reaction of ammonia with hexane-1,6-diol, coming from the hydrogenation of adipic acid. However, production by this method was abandoned in 1984. 

Adiponitrile is an important intermediate for the manufacture of hexa-methylenediamine (Section 3.4), which, together with adipic acid, is used to produce nylon 6,6. Although adiponitrile is still largely produced from adipic acid, obtained by vapour phase oxidation of cyclohexane (Section 2.2), it is also manufactured from butadiene by DuPont on the basis of the process first patented in 1970 (Equations 24-26). Conversion is 99% with >90% selectivity to adiponitrile. 

Table 123 gives economic data concerning the manufacture of HMDA from adipic acid, butadiene and acrylonitrile. 

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