Acetic acid plants acetaldehyde process

Description Oxygen can be used from air separation plant, as well as, from the cost-effective pressure swing adsorption (PSA) process. The Vinnolit oxychlorination process is also able to handle ethylene and/or anhydrous hydrogen chloride containing vent streams from direct chlorination, acetaldehyde, monochloro acetic acid and other processes. 

Acrolein and condensable by-products, mainly acrylic acid plus some acetic acid and acetaldehyde, are separated from nitrogen and carbon oxides in a water absorber. However in most industrial plants the product is not isolated for sale, but instead the acrolein-rich effluent is transferred to a second-stage reactor for oxidation to acrylic acid. In fact the volume of acrylic acid production ca. 4.2 Mt/a worldwide) is an order of magnitude larger than that of commercial acrolein. The propylene oxidation has supplanted earlier acrylic acid processes based on other feedstocks, such as the Reppe synthesis from acetylene, the ketene process from acetic acid and formaldehyde, or the hydrolysis of acrylonitrile or of ethylene cyanohydrin (from ethylene oxide). In addition to the (preferred) stepwise process, via acrolein (Equation 30), a... 

These two derivatives of the earlier Monsanto technology are the predominant acetic acid processes today and are equally competitive in the market place. Since the advent of the Monsanto Acetic Acid process almost all new acetic acid plants are based on methanol carbonylation and acetaldehyde oxidation has been nearly phased out as a source of acetic acid. The advances in Rh and Ir based methanol carbonylation have recently been reviewed. ... 

Acetaldehyde, first used extensively during World War I as a starting material for making acetone [67-64-1] from acetic acid [64-19-7] is currendy an important intermediate in the production of acetic acid, acetic anhydride [108-24-7] ethyl acetate [141-78-6] peracetic acid [79-21 -0] pentaerythritol [115-77-5] chloral [302-17-0], glyoxal [107-22-2], aLkylamines, and pyridines. Commercial processes for acetaldehyde production include the oxidation or dehydrogenation of ethanol, the addition of water to acetylene, the partial oxidation of hydrocarbons, and the direct oxidation of ethylene [74-85-1]. In 1989, it was estimated that 28 companies having more than 98% of the wodd s 2.5 megaton per year plant capacity used the Wacker-Hoechst processes for the direct oxidation of ethylene. 

Conversion of acetaldehyde is typically more than 90% and the selectivity to acetic acid is higher than 95%. Stainless steel must be used in constmcting the plant. This is an estabHshed process and most of the engineering is weU-understood. The problems that exist are related to more extensively automating control of the system, notably at start-up and shutdown, although even these matters have been largely solved. This route is the most rehable of acetic acid processes. 

Although this process has not been commercialized, Daicel operated a 12,000-t/yr propylene oxide plant based on a peracetic acid [79-21-0] process during the 1970s. The Daicel process involved metal ion-catalyzed air oxidation of acetaldehyde in ethyl acetate solvent resulting in a 30% peracetic acid solution in ethyl acetate. Epoxidation of propylene followed by purification gives propylene oxide and acetic acid as products (197). As of this writing (ca 1995), this process is not in operation. 

It is possible to carry out such oxidation processes as the conversion of acetaldehyde to acetic acid, or methyl alcohol to formaldehyde in aluminum plants, thus avoiding boiling anhydrous acids. The metal is especially valuable for handling delicate chemicals, which must not acquire metallic taste or color. For these reasons, aluminum has found extensive use in the food, dairy, brewing and fishing industries. 

Meanwhile, Wacker Chemie developed the palladium-copper-catalyzed oxidative hydration of ethylene to acetaldehyde. In 1965 BASF described a high-pressure process for the carbonylation of methanol to acetic acid using an iodide-promoted cobalt catalyst (/, 2), and then in 1968, Paulik and Roth of Monsanto Company announced the discovery of a low-pressure carbonylation of methanol using an iodide-promoted rhodium or iridium catalyst (J). In 1970 Monsanto started up a large plant based on the rhodium catalyst. 

Direct Oxidation. Direct oxidation of petroleum hydrocarbons has been practiced on a small scale since 1926 methanol, formaldehyde, and acetaldehyde are produced. A much larger project (29) began operating in 1945. The main product of the latter operation is acetic acid, used for the manufacture of cellulose acetate rayon. The oxidation process consists of mixing air with a butane-propane mixture and passing the compressed mixture over a catalyst in a tubular reaction furnace. The product mixture includes acetaldehyde, formaldehyde, acetone, propyl and butyl alcohols, methyl ethyl ketone, and propylene oxide and glycols. The acetaldehyde is oxidized to acetic acid in a separate plant. Thus the products of this operation are the same as those (or their derivatives) produced by olefin hydration and other aliphatic syntheses. 

The liquid phase processes resembled Wacker-Hoechst s acetaldehyde process, i.e., acetic acid solutions of PdCl2 and CuCl2 are used as catalysts. The water produced from the oxidation of Cu(I) to Cu(II) (Figure 27) forms acetaldehyde in a secondary reaction with ethylene. The ratio of acetaldehyde to vinyl acetate can be regulated by changing the operating conditions. The reaction takes place at 110-130°C and 30-40 bar. The vinyl acetate selectivity reaches 93% (based on acetic acid). The net selectivity to acetaldehyde and vinyl acetate is about 83% (based on ethylene), the by-products being CO2, formic acid, oxalic acid, butene and chlorinated compounds. The reaction solution is very corrosive, so that titanium must be used for many plant components. After a few years of operation, in 1969-1970 both ICI and Celanese shut down their plants due to corrosion and economic problems. 

The low-pressure acetic acid process was developed by Monsanto in the late 1960s and proved successful with commercialization of a plant producing 140 X 10 metric tons per year in 1970 at the Texas City (TX, USA) site [21]. The development of this technology occurred after the commercial implementation by BASF of the cobalt-catalyzed high-pressure methanol carbonylation process [22]. Both carbonylation processes were developed to utilize carbon monoxide and methanol as alternative raw materials, derived from synthesis gas, to compete with the ethylene-based acetaldehyde oxidation and saturated hydrocarbon oxidation processes (cf. Sections 2.4.1 and 2.8.1.1). Once the Monsanto process was commercialized, the cobalt-catalyzed process became noncom-... 

Your company has asked your group to determine whether this new technology should be used in your Gulf Coast plant. Your job is to design a process and plant to produce 100 MM Ib/yr of acetaldehyde from acetic acid, which is available on the site. Based on past experience, you know that you will have to defend any decisions you have made throughout the design, and the best defense is economic justification. 

Acetaldehyde may be prepared from ethylene via the Wacker process, and then oxidized as above. In more recent times, a cheaper, single-stage conversion of ethylene to acetic acid was commercialized by chemical company Showa Denko, which opened an ethylene oxidation plant in Oita, Japan, in 1997. The process is catalysed by a palladium metal catalyst supported on a heteropoly acid such as tungstosilicic acid. It is thought to be competitive with methanol carbonylation for smaller plants (100-250 kt/a), depending on the local price of ethylene. 

The first commercial plant for the chemical production of acetic acid came on line in 1916. Qearly, this was the beginning of the expanding market for acetic add as an important commodity chemical in industry (Agreda and Zoeller 1993). Chemical synthesis of acetic acid is dependent upon petrochemicals from nomenewable crude oil resources. There are three major processes in use today oxidation of acetylene-derived acetaldehyde, catalytic butane oxidation, and the carbonylation of methanol (the Monsanto process Agreda and Zoeller 1993). Production hy the Monsanto process provides the major source of glacial acetic add used in industry worldwide. In the United States, chemical synthesis of acetic acid was reported as 2.34 x 10 t/year in 1995 (Kirschner 1996), which demonstrates the importance of acetic acid as a commodity chemical in industry. 

In 1992, about 6.5 billion lb acetic acid was produced worldwide, of which about 3.6 billion lb was produced in the United States [1]. The current commercial processes for its production include oxidation of ethanol (acetaldehyde), oxidation of butane-butene mixture or naphtha, and carbonylation of methanol or methyl acetate. These are catalytic processes. The last, liquid-phase carbonylation of methanol using a rhodium and iodide catalyst, has become the dominant process since its introduction in the late 1960s, and accounted for about half the production of acetic acid in the United States [2]. That represents a conversion of 1.5 x 106 ton per year of methanol into 2.8 x 106 ton per year of acetic acid. In the United States, 80% of actual plant operation capacity is based on this technology [3]. The reaction is thermodynamically favorable [4], and the theoretical conversion is practicalty 100% at 389 K ... 

The discovoy of methanol carbonylation to acetic acid, with cobalt iodide as the catalyst, goes back to 1913. In 1960 BASF operated a small Co-based methanol carbonylation plant. The Co-catalyzed process requires high pressure and temperature ( 00 bar, 230°C) and is of moderate selectivity. The selectivity with respect to CO and methanol are -70% and -90%, respectively. Acetic acid production is accompanied by unwanted side products such as acetaldehyde, ethanol, and propionic acid. 

The plant began full-scale operation in 1962 and produced acetic, adipic, and propionic acids acetaldehyde butanol hexamethyldiamine vinyl acetate nylon and other chemical products from petroleum-base stocks. The effluent was collected at waste treatment facilities as two separate mixtures. Because mixing two wastestreams produced considerable precipitation, the wastestreams were processed and injected separately into two wells. 

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