Acetic acid plants butane process

Hoechst Celanese officials said it was too early to decide whether to rebuild the butane reactor, install a newer methanol-to-acetic acid process, or start up a standby acetic acid facility at Hay City, TX, to replace the idled 350-million-lb per year acetic acid plant. 

Even though methanol carbonylation is the favored process for new acetic acid capacity today, existing paraffin oxidation plants remain quite competitive where coproducts can be marketed successfully [2, 3]. Over half the original capacity of acetic acid plants based on paraffin oxidation remains in use today. In North America, Hoechst Celanese operates two facilities using the butane oxidation process to make acetic acid. The reported 1994 capacity at Pampa, Texas, is 250000 metric tons/year, while that at monton, Alberta, is 75 000 metric tons/year [4]. There are two plants believed to be using the naphtha oxidation process to make acetic acid BP Chemicals in Hull, England, with a capacity of 210000 metric tons/year [5] and a state complex in Armenia (in the former USSR) with a capacity reported to be 35 000 metric tons/year [6]. 

Butane. Butane LPO has been a significant source for the commercial production of acetic acid and acetic anhydride for many years. At various times, plants have operated in the former USSR, Germany, Holland, the United States, and Canada. Only the Hoechst-Celanese Chemical Group, Inc. plants in Pampa, Texas, and Edmonton, Alberta, Canada, continue to operate. The Pampa plant, with a reported aimual production of 250,000 t/yr, represents about 15% of the 1994 installed U.S. capacity (212). Methanol carbonylation is now the dominant process for acetic acid production, but butane LPO in estabhshed plants remains competitive. 

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 significant reductions in acetic acid capacity based on paraffin oxidation that have occurred include those at (1) the butane oxidation plant operated by Union Carbide at Brownsville, Texas, (2) butane oxidation processes in the Netherlands and Germany, and (3) a Russian naphtha oxidation plant. 

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 ... 

Since the temperature and by-products are different for processes starting with benzene and C4 hydrocarbons, the construction materials of various plant equipment may vary. For the benzene-based process carbon steel is considered adequate. On the other hand, in C4-based processes, lower acids (acetic, acrylic, crotonic, etc.) are coproduced and hence suitable acid-resistant reactor tubes may be needed. /t-Butane oxidation is run at higher temperature, and so steel suitable for higher temperature is necessary. It has been sug-gested that a butane-based MA reactor can be easily converted to a benzene-based process but not vice-versa. 

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