Vapor phase process, commercial

The vapor-phase process commercialized by Exxon-Mobil uses a zeolite catalyst designated as ZSM-5 (44,45). The temperature of the catalyst bed varies from about 400° C near its entrance to about 450° C near the outlet. Pressures vary from approximately 14 to 26 atm (2-3 MPa). Water is used as the coolant for the exit product stream resulting in the production of low pressure steam. Since the catalyst deactivates rather quickly, two reactors are provided. One is on-stream while the second is being reactivated. Rather, low purity feedstreams can be employed with the process. 

Liquid- and vapor-phase processes have been described the latter appear to be advantageous. Supported cadmium, zinc, or mercury salts are used as catalysts. In 1963 it was estimated that 85% of U.S. vinyl acetate capacity was based on acetylene, but it has been completely replaced since about 1982 by newer technology using oxidative addition of acetic acid to ethylene (2) (see Vinyl polymers). In western Europe production of vinyl acetate from acetylene stiU remains a significant commercial route. 

Vinyl ethers are prepared in a solution process at 150—200°C with alkaH metal hydroxide catalysts (32—34), although a vapor-phase process has been reported (35). A wide variety of vinyl ethers are produced commercially. Vinyl acetate has been manufactured from acetic acid and acetylene in a vapor-phase process using zinc acetate catalyst (36,37), but ethylene is the currently preferred raw material. Vinyl derivatives of amines, amides, and mercaptans can be made similarly. A/-Vinyl-2-pyrroHdinone is a commercially important monomer prepared by vinylation of 2-pyrroHdinone using a base catalyst. 

Commercial Manufacture of Pyridine. There are two vapor-phase processes used in the industry for the synthesis of pyridines. The first process (eq. 21) uti1i2es formaldehyde and acetaldehyde as a co-feed with ammonia, and the principal products are pyridine (1) and 3-picoline (3). The second process produces only alkylated pyridines as products. 

Polyethylene (PE) was a commercial LD type (without additives) with a density of 0.92 and polypropylene (PP) was also a commercial material with a density of 0.91. The polvolefin samples were melt pressed to 1 mm thick sheets (plates) which were wiped clean with acetone and used directly for the grafting experiments with the vapor-phase process. 

Xyloflning [Xylol refining] A process for isomerizing a petrochemical feedstock containing ethylbenzene and xylenes. The xylenes are mostly converted to the equilibrium mixture of xylenes the ethylbenzene is dealkylated to benzene and ethylene. This is a catalytic, vapor-phase process, operated at approximately 360°C. The catalyst (Encilite-1) is a ZSM-5-type zeolite in which some of the aluminum has been replaced by iron. The catalyst was developed in India in 1981, jointly by the National Chemical Laboratory and Associated Cement Companies. The process was piloted by Indian Petrochemicals Corporation in 1985 and commercialized by that company at Baroda in 1991. 

Butane Isomerization. Five processes for butane isomerization were in commercial use by the end of World War II. These processes differ primarily in the method of contacting the hydrocarbon with the catalyst. Two are vapor-phase processes, which require periodic discard and replacement of the catalyst bed the other three are carried out in the liquid phase and are continuous with respect to catalyst addition and withdrawal. 

Processes for Paraffin Nitrations. Propane is thought to be the only paraffin that is commercially nitrated by vapor-phase processes. Temperature control is a primary factor in designing the reactor, and several approaches have been investigated. A spray mtrator in which liquid nunc acid is spiayed into hoi propane is used industiially. Relatively small-diameter tubular reactors, fluidized-bed reactors, and molten salt reactors have all been successfully used in laboratory units. 

Adiponitrile is made commercially by several different processes utilizing different feedstocks. The reaction of adipic acid with ammonia in either liquid or vapor phase produces adipamide as an intermediate, which is subsequently dehydrated to adiponitrile. The most widely used catalysts are based on phosphorus-containing compounds. Vapor-phase processes involve the use of fixed catalyst beds whereas, in liquid-gas processes, the catalyst is added to the feed. DuPont currently practices a buiadiene-to-adiponitdle route based on direct addition of HCN to butadiene. 

There are two main process categories for the direct hydration of ethylene to ethanol. Vapor-phase processes contact a solid or liquid catalyst with gaseous reactants. Mixed-phase processes contact a solid or liquid catalyst with liquid and gaseous reactants. Generally, ethanol is produced by a vapor-phase process mixed-phase processes are used for the analogous hydration of propylene to 2-propanol. Important exceptions to these two generalizations exist, but the discussion that follows emphasizes technology associated with the commercially important vapor-phase direct hydration of ethylene. 

To oxidize ethylene to acetaldehyde technically, two major approaches seem feasible (a) vapor-phase heterogeneous catalysis, and (b) liquid-phase homogeneous catalysis. The most pertinent references on the vapor-phase process are summarized in Table VI. However, neither this approach nor the electrolytic oxidation of ethylene (14) appears to have gained any commercial importance. Liquid-phase homogeneous catalysis is the approach practiced commercially, and this is understood when one talks about the Wacker process. The latter has been carried out in two principal ways ... 

Air is sufficient to oxidize the methyl groups of o-xylene, under the right conditions, like it is with p-, or w-xylene just described. However, here the similarity ends since commercial o-xylene oxidation is a vapor phase process [27]. ortf o-Xylene vapor, mixed with a large excess of air to ensure operation outside the explosive range, is fed to a reactor containing a supported vanadium pentoxide catalyst and heated to about 550°C. Using about a 0.1-second contact time under these conditions produces exit gases composed of phthalic anhydride, water, and carbon dioxide (Eq. 19.68). 

The first commercial plant based on the Mobil/Badger vapor phase technology was commissioned in 1980. From 1980 until the early 1990s, use of the vapor phase process gained in popularity because it offered several advantages over the aluminum chloride process. A major benefit of the vapor phase process was the use of a zeolite catalyst that eliminated the issues associated with corrosion and waste disposal of aluminum chloride. 

The liquid phase vinyl acetate process dominated new installations until 1970 when Hoechst and Bayer commercialized a jointly developed heterogeneous vapor phase process for the addition of acetic acid to ethylene in the presence of oxygen (Equation [19]) in 1970. National Distillers (now Quantum Chemical) developed a similar process about the same time and commercialized the process rapidly thereafter. The processes (which were developed during the late 1960 s) used a Pd-Au or Pd/Cd catalyst with an alkali... 

For the production of ethylbenzene with solid catalysts, both liquid-phase and vapor-phase processes have been commercialized. Somewhat higher temperatures are employed with the gas-phase processes. Hence, the exit gas stream from the reactor can be employed to produce steam. 

Vinyl acetate is the most available and widely used member of the vinyl ester family. This colorless, flammable liquid was first prepared in 1912. Liquid-phase processes were commercialized early in Germany and Canada, but these have been replaced generally by vapor-phase processes. Earlier commercial processes were based on the catalyzed reaction of acetylene with acetic acid. The more recent technical development is the production of vinyl acetate monomer from ethylene and acetic acid. Palladium catalyst is used for the vapor phase process. The ethylene route is the dominant route worldwide. 

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