Acetic acid from methanol and carbon monoxide

In homogeneous catalytic systems we witnessed a new process for the production of acetic acid from methanol and carbon monoxide using a transition metal complex, thus displacing the earlier process employing ethylene as the starting material. The use of immobilized enzymes makes possible the commercial conversion of glucose into fructose. 

Catalysts used to convert ethylene to vinyl acetate are closely related to those used to produce acetaldehyde from ethylene. Acetaldehyde was first produced industrially by the hydration of acetylene, but novel catalytic systems developed cooperatively by Farbwerke Hoechst and Wacker-Chemie have been used successfully to oxidize ethylene to acetaldehyde, and this process is now well established (7). However, since the largest use for acetaldehyde is as an intermediate in the production of acetic acid, the recent announcement of new processes for producing acetic acid from methanol and carbon monoxide leads one to speculate as to whether ethylene will continue to be the preferred raw material for acetaldehyde (and acetic acid). 

The novel synthesis required fewer process steps, and this resulted in lower costs and investment. In 1969, another advance was announced—the synthesis of acetic acid from methanol and carbon monoxide with essentially no by-products or co-products.15 16... 

Encouraged by the interesting results obtained in the high-pressure synthesis of acetic acid from methanol and carbon monoxide using nickel, cobalt, and iron halides as catalysts (5-7), the synthesis of glycolic acid from formaldehyde, carbon monoxide and water has been studied using various nickel, cobalt, and iron catalysts. 

Each year the United States produces over 2.5 million tons of acetic acid from methanol and carbon monoxide. The primary use of acetic acid is in the synthesis of vinyl acetate, which is used in paints and adhesives. 

Glacido A process for making acetic acid from methanol and carbon monoxide. 

Presently the number of industrial processes using metal complex catalysts is continuously increasing. They include such classical large-tonnage processes as polymerization on the Ziegler catalysts, olefin oxidation by molecular oxygen to aldehydes, hydroformylation of saturated compounds, preparation of acetic acid from methanol and carbon monoxide, synthesis of adiponitrile fijom butadiene, and others. 

The concept of co-carbonylation of methanol/methyl acetate mixtures was first introduced by BASF in the early 1950s, but the reaction chemistry was not fully developed to commercial realization [75]. Not until the mid-1980s, after the development of carbonylation processes to produce acetic acid and acetic anhydride, were co-carbonylation processes patented using homogeneous rhodium/iodine catalyst systems (Table 2) [2, 56]. The basic process concept is to manufacture acetic acid and acetic anhydride from methanol and carbon monoxide as the only raw materials and to generate methyl acetate within the process. Similiarly, the suitability of dimethyl ether as a raw material for the generation of the anhydride equivalent in addition to or as a substitute for methyl acetate was revealed by Hoechst [76]. To produce a small fraction of acetic acid besides acetic anhydride as the main product, the carbonylation of methyl acetate could be conducted with small amounts of water or methanol. This variant, first demonstrated by Hoechst [56], is practiced by Eastman Kodak [2]. 

Today acetic acid is produced mainly from methanol and carbon monoxide. This process, along with the Tennessee Eastman acetic anhydride plant using syn gas, are the current standards in the industry when considering new expansion regardless of the price of ethylene. The vinyl acetate process described here may achieve this stature if its commercial development is permitted to occur. 

Few chemicals have experienced as long and as successful a career us acetic acid, Acetic acid reluins its importance in (he production of vinyl and cellulose acetates Acetic acid is made industrially by oxidation of acetaldehyde or butane in air, or from methanol and carbon monoxide. 

Takaoka, S., "Acetic Acid Synthesis From Methanol and Carbon Monoxide", Report 37A, SRI Process Economics, March, 1973, pp. 83-107. 

The Monsanto acetic acid process produces acetic acid from methanol and CO gas under fairly mild conditions (I80 C, 30-40 atm). The process utilizes a square planar Rh(l) catalyst. As shown in Figure 19.33, the first step in the catalytic mechanism is the OA of methyl iodide to form an 18-electron compound. In the second step, CO insertion (alkyl migration) occurs, resulting in a 16-electron species. Carbon monoxide adds to the vacant coordination site to r enerate a saturated compound, which then undergoes RE of CH3COI to regenerate the catalyst. The CH3COI product is further processed by reaction with water to make acetic acid and HI. The latter... 

Actual operating capacities of Reppe carbonylation processes are difficult to estimate since only a few data are available in the literature. However, it is known that some of the syntheses are carried out on an industrial scale, e. g. the synthesis of acrylates from acetylene, carbon monoxide and alcohols (BASF) [1004, 1005], the acetic acid synthesis from methanol and carbon monoxide and the synthesis of higher molecular weight saturated carboxylic acids from olefins, carbon monoxide and water. Propionic acid (30,000 tons/year) and to a smaller extent heptadecanoic dicarboxylic acid are manufactured via the carbonylation route at BASF. Butanol is made from propylene in Japan [1003, 1004]. 

Methyl acetate forms as an intermediate in the acetic acid synthesis from methanol and carbon monoxide and is used as a solvent for cellulose, nitrates, esters and ethers. When this ester is produced via esterification of acetic acid with methanol, generally mineral acids like sulfuric acid, hydrogen chloride and aryl sulfonic acid (such as p-toluenesulfonic acid) are used as homogenous acid catalysts, while cation exchange resin and zeolites are used as heterogeneous catalysts. The relevant literature on this subject is summarized in Chapter-1. Some important studies on esterification of acetic acid with methanol are summarized below. 

About half of the wodd production comes from methanol carbonylation and about one-third from acetaldehyde oxidation. Another tenth of the wodd capacity can be attributed to butane—naphtha Hquid-phase oxidation. Appreciable quantities of acetic acid are recovered from reactions involving peracetic acid. Precise statistics on acetic acid production are compHcated by recycling of acid from cellulose acetate and poly(vinyl alcohol) production. Acetic acid that is by-product from peracetic acid [79-21-0] is normally designated as virgin acid, yet acid from hydrolysis of cellulose acetate or poly(vinyl acetate) is designated recycle acid. Indeterrninate quantities of acetic acid are coproduced with acetic anhydride from coal-based carbon monoxide and unknown amounts are bartered or exchanged between corporations as a device to lessen transport costs. 

Acetic acid is also produced hy the oxidation of acetaldehyde and the oxidation of n-hutane. However, acetic acid from the carhonylation route has an advantage over the other commercial processes because both methanol and carbon monoxide come from synthesis gas, and the process conditions are quite mild. 

Methanol process. BASF introduced high-pressure technology way back in I960 to make acetic acid out of methanol and carbon monoxide instead of ethylene. Monsanto subsequently improved the process by catalysis, using an iodide-promoted rhodium catalyst. This permits operations at much lower pressures and temperatures. The methanol and carbon monoxide, of course, come from a synthesis gas plant. 

The third and now preferred method of acetic acid manufacture is the carbonylation of methanol (Monsanto process), involving reaction of methanol and carbon monoxide (both derived from methane). This is discussed in Chapter 12, Section 3. 

The recent dramatic increase in the price of petroleum feedstocks has made the search for high selectivities more urgent. Several new processes based on carbon monoxide sources are currently competing with older oxidation processes.103,104 The more straightforward synthesis of acetic acid from methanol carbonylation (Monsanto process) has made the Wacker process obsolete for the manufacture of acetaldehyde, which used to be one of the main acetic acid precursors. Several new methods for the synthesis of ethylene glycol have also recently emerged and will compete with the epoxidation of ethylene, which is not sufficiently selective. The direct synthesis of ethylene... 

Whereas most of the methanol produced since the thirties until 1980 has been used to produce formaldehyde, a remarkable shift in the pattern of methanol use has occurred. Nowadays, use of methanol for chemical products other than formaldehyde has risen more steeply than for formaldehyde itself. More than all others, the increase of acetic acid production going together with its shifting from ethylene to methanol and carbon monoxide as raw materials has contributed to this increase as well as the production of fuel components such as MtBE. 

Acetic acid is an important petrochemical industrially produced from methane in three steps via the Monsanto process. In this process, methanol and carbon monoxide yield acetic acid with a selectivity of 99% at a pressure of 30-60 bar in the temperature range between 150 and 200 °C. Since these both reactants are... 

The Monsanto process and the hi er pressure BASF processes have been reviewed [3,1012]. In the Monsanto process (Fig. 1) [9], methanol and carbon monoxide are fed to a continuous reactor system. The corrosive nature of iodine in an acid medium requires the use of a highly corrosion-resistant metal reactor (made of such material as Hastelloy C). The acetic acid produced is piuified by conventional distillation. The purified acetic acid is sent to a drying column. The dried acetic acid is removed as the bottom product and sent to the product column to reduce the small concentration of propanoic acid. The typical composition of the acetic acid from this process is [9] as follows ... 

Acetic Acid. Acetic acid used to be derived from ethylene with acetaldehyde as an intermediate. The relatively high price of ethylene compared to methanol and carbon monoxide (raw materials for the currently favored process) has caused a shift away from ethylene as a raw material for acetic acid production, as was discussed earlier in the chapter. 

---