Ethanol dehydrogenation processes

Traditionally, ethanol has been made from ethylene by sulfation followed by hydrolysis of the ethyl sulfate so produced. This type of process has the disadvantages of severe corrosion problems, the requirement for sulfuric acid reconcentration, and loss of yield caused by ethyl ether formation. Recently a successful direct catalytic hydration of ethylene has been accomplished on a commercial scale. This process, developed by Veba-Chemie in Germany, uses a fixed bed catalytic reaction system. Although direct hydration plants have been operated by Shell Chemical and Texas Eastman, Veba claims technical and economic superiority because of new catalyst developments. Because of its economic superiority, it is now replacing the sulfuric acid based process and has been licensed to British Petroleum in the United Kingdom, Publicker Industries in the United States, and others. By including ethanol dehydrogenation facilities, Veba claims that acetaldehyde can be produced indirectly from ethylene by this combined process at costs competitive with the catalytic oxidation of ethylene. 

Further, oxides that are characterized by the possibility of metal ion reduction without oxide state modification have the greatest ability to promote oxidizing dehydrogenation processes. Oxide such as Iu203 is inclined to the changing of the metal ion oxidizing state In(III) In(II), while the oxide phase remains original. Due to this fact, sensors based on heterojunction oxide composites show considerable response to alcohol vapors (methanol, ethanol). The heterojunction between an oxide and solid solution phases appears to be very active in both adsorption and oxidation of alcohol. 

The feedstock picture further diversified in 1920 with the commercialization of ethanol dehydrogenation to generate acetaldehyde. (The process was conducted in the vapor phase at 260-290°C using copper-chromite catalysts.) While the process was known as early as 1886 the development of adequate catalysts for the endothermic process would take nearly 35 years. Subsequent oxidation to acetic acid provided an additional source of acetic acid. These technologies would largely stay in place with only minor modification until the 1950 s. A summary of the chemical routes to the various acetyls in 1920 is shown in Figure 1. 

Over the next 30 years, wood distillation declined relative to ethanol dehydrogenation and acetylene based processes as a source of acetyls, but all three would contribute to the acetyl supply chain required to generate the acetic anhydride needed to meet the market demands for cellulose acetate as the product grew and matured over the period 1920-1940. However, while cellulose acetate and cellulose ester markets would grow, improvements in technology for the basic acetyl products were limited during this time period. 

Fundamentals on the physical properties of the substrates and on the microfabrication technologies can be found elsewhere [23-25]. First, it has to be considered that the metallic surfaces contacting the process fluids do not catalyze reactions at any appreciable rate. Mills and Nicole [26,27] have shown that the natme of the metal substrate affects combustion reactions. AISI 316 stainless steel, titanium or iron, results in hydrocarbon and oxygen conversions of up to 50% depending on the natme of the metallic material. Similar effects have been found using Cu-based alloys. For these alloys the oxide layer formed upon brass pretreatment results in active ethyl acetate combustion or ethanol dehydrogenation [28,29]. 

In a widely used industnal process the mixture of ethylene and propene that is obtained by dehydrogenation of natural gas is passed into concentrated sulfunc acid Water is added and the solution IS heated to hydrolyze the alkyl hydrogen sulfate The product is almost exclusively a sin gle alcohol Is this alcohol ethanol 1 propanol or 2 propanoH Why is this particular one formed almost exclusively" ... 

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. 

Some isopentane is dehydrogenated to isoamylene and converted, by processes analogous to those which produce methyl /-butyl ether [1634-04-4] (MTBE) to /-amyl methyl ether [994-05-8] (TAME), which is used as a fuel octane enhancer like MTBE. The amount of TAME which the market can absorb depends mostly on its price relative to MTBE, ethyl /-butyl ether [637-92-3] (ETBE), and ethanol, the other important oxygenated fuel additives. 

The pattern of commercial production of 1,3-butadiene parallels the overall development of the petrochemical industry. Since its discovery via pyrolysis of various organic materials, butadiene has been manufactured from acetylene as weU as ethanol, both via butanediols (1,3- and 1,4-) as intermediates (see Acetylene-DERIVED chemicals). On a global basis, the importance of these processes has decreased substantially because of the increasing production of butadiene from petroleum sources. China and India stiU convert ethanol to butadiene using the two-step process while Poland and the former USSR use a one-step process (229,230). In the past butadiene also was produced by the dehydrogenation of / -butane and oxydehydrogenation of / -butenes. However, butadiene is now primarily produced as a by-product in the steam cracking of hydrocarbon streams to produce ethylene. Except under market dislocation situations, butadiene is almost exclusively manufactured by this process in the United States, Western Europe, and Japan. 

In a process which is now largely of historical interest, 1-butanol has been produced from ethanol [64-17-5] via successive dehydrogenation (to acetaldehyde [75-07-0]) condensation (to crotonaldehyde [4170-30-3]) and hydrogenation. 

The earhest commercial route to -butyraldehyde was a multistep process starting with ethanol, which was consecutively dehydrogenated to acetaldehyde, condensed to crotonaldehyde, and reduced to butyraldehyde. In the late 1960s, production of -butyraldehyde (and isobutyraldehyde) in Europe and the United States switched over largely to the Oxo reaction of propylene. 

During World War II, production of butadiene (qv) from ethanol was of great importance. About 60% of the butadiene produced in the United States during that time was obtained by a two-step process utilizing a 3 1 mixture of ethanol and acetaldehyde at atmospheric pressure and a catalyst of tantalum oxide and siHca gel at 325—350°C (393—397). Extensive catalytic studies were reported (398—401) including a fluidized process (402). However, because of later developments in the manufacture of butadiene by the dehydrogenation of butane and butenes, and by naphtha cracking, the use of ethanol as a raw material for this purpose has all but disappeared. 

Acetaldehyde may be made (1) from ethylene by direct oxidation, with the Wacker-catalyst containing copper(II) and palladium(II) salts (2) from ethanol by vapor-phase oxidation or dehydrogenation or (3) from butane by vapor-phase oxidation. The direct oxidation of ethylene is the most commonly used process, accounting for 80% of acetaldehyde production. 

Acetaldehyde. The industrial production of acetaldehyde by the hydration of acetylene has lost its importance with the introduction of more economical petrochemical processes (dehydrogenation of ethanol, oxidation of ethylene see Section 9.5.2). At present it is practiced only in a few European countries where relatively cheap acetylene is still available.86-88... 

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