Vapor phase catalytic reactions

In the dyestuff industry, anthraquinone still ranks high as an intermediate for the production of dyes and pigments having properties unattainable by any other class of dyes or pigments. Its cost is relatively high and will remain so because of the equipment and operations involved in its manufacture. As of May 1991, anthraquinone sold for 4.4/kg in ton quantities. In the United States and abroad, anthraquinone is manufactured by a few large chemical companies (62). At present, only two processes for its production come into consideration manufacture by the Friedel-Crafts reaction utilizing benzene, phthahc anhydride, and anhydrous aluminum chloride, and by the vapor-phase catalytic oxidation of anthracene the latter method is preferred. 

The production of acetic acid from n-butene mixture is a vapor-phase catalytic process. The oxidation reaction occurs at approximately 270°C over a titanium vanadate catalyst. A 70% acetic acid yield has been reported. The major by-products are carbon oxides (25%) and maleic anhydride (3%) ... 

This application was performed on a lab-scale reactor and later in a miniplant-scale reactor. The reaction studied was the vapor phase catalytic amidation/cyclization step in a pesticide process. As shown in Figure 2, two reactions are taking place on the catalyst bed. 

Figure 2 Vapor phase catalytic amidation/cyclization reaction in a pesticide process monitored by on-line HPLC.

In the 1960s, like almost all acetylene technology, the HCN/C2H2 route to acrylonitrile gave way to ammoxidation of, propylene. Thar word, ammoxidation, looks suspiciously like the contraction of two more familiar terms, ammonia and oxidation, and it is. When Standard of Ohio (Sohio) was still a company they developed a one-step vapor phase catalytic reaction of propylene with ammonia and air to give acrylonitrile. 

Ammonoxidation. The contraction of two terms, ammonia and oxidation, ammonoxidation is a one-step process involving vapor phase, catalytic reaction of propylene with ammonia and the,oxygen portion of air to give acrylonitrile. The ammonoxidation reaction is carried out at about 800°F and 30 psi. 

Benzo[c]thiophene may be prepared by low-pressure (20 mm) vapor-phase catalytic dehydrogenation of l,3-dihydrobenzo[c]thio-phene (Section III,A) at 330° under nitrogen,5,8 by decarboxylation of benzo[c]thiophene-1 -carboxylic acid (Section III,C) with copper in quinoline16,38 or by dehydration of l,3-dihydrobenzo[c]thiophene 2-oxide (Section VI,A) in acetic anhydride or over aluminum oxide at 20 mm Hg and 100°-125° in a sublimation tube.52 A trace of water appears to be beneficial to the first reaction, and it has been suggested53... 

Catalytic reactions can be run over large, massive metal particles as well as the much smaller, dispersed metal crystallites. The massive metal catalysts can be the single crystal catalysts such as those shown in Fig. 3.2 or polycrystalline forms of bulk metal such as wires, foils or ribbons. These latter materials were used somewhat routinely in the early catalytic research efforts that were involved with developing the mechanisms of vapor phase catalytic processes. These materials were considered to be analogs of the supported catalysts in which the effect of the support, if any, was eliminated. 

Arylation involves the reaction between amines and phenols, aryl halides and aryl amines, including aniline. In arylation, one reactant acts as solvent acidic catalysts and high temperatures are employed. Diphenylamine (A-phenylbenzeneamine, /V-phenylani-line) (8) is made by condensation of aniline in the presence of a small amount of mineral acid catalyst at around 300 °C catalytic reaction of chlorobenzene with aniline at high temperature and pressure and continuous vapor-phase catalytic condensation of aniline. It is a useful intermediate in azo dye manufacture. Crompton is the main US manufacturer of 8, producing 1.3 billion lbs. in 2000. Applications include as lube additives... 

Design a reactor system to produce styrene by the vapor-phase catalytic dehydrogenation of ethyl benzene. The reaction is endothermic, so that elevated temperatures are necessary to obtain reasonable conversions. The plant capacity is to be 20 tons of crude styrene (styrene, benzene, and toluene) per day. Determine the bulk volume of catalyst and number of tubes in the reactor by the one-dimensional method. Assume that two reactors will be needed for continuous production of 20 tons/day, with one reactor in operation while the catalyst is being regenerated in the other. Also determine the composition of the crude styrene product. 

The vapor phase catalytic oxidation of toluene to benzaldehyde has been studied over V20s-K2S04-Si02 catalysts in an isothermal differential reactor. The experiments were carried out at atmospheric pressure, temperatures from 410 C to 470 C and the modified spatial time (W/Fto) ranging from 0 to 180 g cat/mol toluene/h. The experimental tests showed the best performance for the catalyst obtained by co-precipitation. These results may be due to a crystalline phase identified in the process of catalyst characterization. Reaction kinetics was determined using the Mars and van Krevelen model. 

Removal of heat from the reaction. In the vapor phase catalytic oxidation of naphthalene to phthalic anhydride, the heat of reaction is so great that unless it is rapidly and thoroughly dissipated the temperature of the catalyst mass rises to a point where complete combustion only occurs. Further, there is a tendency for the pentoxide of vanadium to be reduced to lower oxides at the high temperatures used, particularly if the oxygen supply is limited. These lower oxides tend to combine with the phthalic anhydride and subsequently decompose to destroy the anhydride, so that simple limitations of the oxygen supply to prevent further oxidation of the hydrocarbon is not effective. 

Vapor phase catalytic alkylation of phenols with methanol was carried out on various phosphates as catalysts. The best activity and selectivity was observed on boron, rare-earth and niobium phosphate. With boron phosphate, the reaction is very selective for O-alkylation even at high temperature. On this catalyst o-methoxy-phenol is selectively obtained from 1-2-dihydroxybenzene. With rare-earth phosphate calcinated at 400°C and with niobium phosphate, O-alkylation selectivity decreases with an increase of reaction temperature. For rare-earth phosphates it is possible to improve the selectivity by calcination at higher temperature or by a wetness impregnation of cesium hydrogenophosphate. An explanation of these results is proposed. 

Vapor-phase Catalytic Reactions. When a gaseous reaction is promoted by a catalyst, the reactants are first adsorbed upon the catalyst surface. The actual transformation from reactants to products takes place in the adsorbed phase. Therefore, the adsorption characteristics of the catalyst toward each of the reactants and products are important factors in rate determination. 

The most common heterogeneous reactors are the fixed-, momng, and fiuldized-hed catalytic reactors. One example of vapor-phase catalytic reactions is in the catalytic vapor-phase reduction of nitroxylene to xylidene. This process is discussed in Chap. 5 (Figs. 5-16 and 5-17). 

Since there are so many applications of vapor-phase catalytic reactions in carrying out unit processes, the kinetics of this type of reaction are very important. 

In previous publications [1-4], the vapor phase catalytic hydrodechlorination (HDC) of 1,1,1-trichloroethane (111 TCA) and its reaction intermediates was studied. Various catalysts were evaluated, including Pt/T)-alumina. The Pt/ri-alumina catalyst deactivated rapidly during the HDC of saturated chlorocarbons such as 111 TCA, but remained stable during the HDC of unsaturated chlorocarbons such as 1,1-dichloroethylene (11 DCE). At 523K and higher, large quantities of coke were deposited on the Pt/rj-alumina during the HDC of 111 TCA. However, very little coke was observed on the catalyst after the HDC of any other compound. In this paper, a mathematical model is developed for the deactivation of Pt/q-alumina catalyst for the HDC of 111 TCA in a fixed-bed reactor. Model predictions are compared to experimental data. 

A large number of liquid-phase organic reactions are carried out in batch or semibatch reactors. For large volume, liquid-phase reactions, the use of a series of CSTRs is quite common. For large volume, vapor-phase catalytic reactions, tubular reactors are often the reactors of choice. 

Deacon was awarded the first patents in 1868 [7]. The Deacon process was the first vapor-phase catalytic reaction put into large-scale commercial use. While the reaction... 

For most vapor-phase catalytic reactions, use a gradientless reactor like the back-mixed catalyst autoclave developed by J. M. Berty (1). This reactor permits the independent variation of mass- and space-velocities and the direct observation of reaction rates. 

Vapor-phase catalytic transformations of chlorobenzene were performed at 50-300°C, 0.1 MPa in a quartz fix-bed flow-type reactor. Chlorobenzene was fed to the reactor in H2 flow at molar ratio H2 C6H5C1 =55 1. Reaction products were analyzed by GC (Agilent 6890N DB-WAX colirrrm 30 m, flame ionization detector). For each analysis a gas probe was taken directly after the reactor by syringe. Each point on conversion vs time curves is the average value for 4-5 measurements at the stable woik period. 

Mercaptals, CH2CH(SR)2, are formed in a like manner by the addition of mercaptans. The formation of acetals by noncatalytic vapor-phase reactions of acetaldehyde and various alcohols at 35°C has been reported (67). Butadiene [106-99-0] can be made by the reaction of acetaldehyde and ethyl alcohol at temperatures above 300°C over a tantala—siUca catalyst (68). Aldol and crotonaldehyde are beheved to be intermediates. Butyl acetate [123-86-4] has been prepared by the catalytic reaction of acetaldehyde with 1-butanol [71-36-3] at 300°C (69). 

The catalytic vapor-phase oxidation of propylene is generally carried out in a fixed-bed multitube reactor at near atmospheric pressures and elevated temperatures (ca 350°C) molten salt is used for temperature control. Air is commonly used as the oxygen source and steam is added to suppress the formation of flammable gas mixtures. Operation can be single pass or a recycle stream may be employed. Recent interest has focused on improving process efficiency and minimizing process wastes by defining process improvements that use recycle of process gas streams and/or use of new reaction diluents (20-24). 

Equation 11 predominates in uncatalyzed vapor-phase decomposition and photo-chemicaHy initiated reactions. In catalytic reactions, and especially in solution, the nature of the reactants determines which reaction is predominant. 

Tetrahydronaphthalene is produced by the catalytic treatment of naphthalene with hydrogen. Various processes have been used, eg, vapor-phase reactions at 101.3 kPa (1 atm) as well as higher pressure Hquid-phase hydrogenation where the conditions are dependent upon the particular catalyst used. Nickel or modified nickel catalysts generally are used commercially however, they are sensitive to sulfur, and only naphthalene that has very low sulfur levels can be used. Thus many naphthalene producers purify their product to remove the thionaphthene, which is the principal sulfur compound present. Sodium treatment and catalytic hydrodesulfuri2ation processes have been used for the removal of sulfur from naphthalene the latter treatment is preferred because of the ha2ardous nature of sodium treatment. 

Thermal polymerization is not as effective as catalytic polymerization but has the advantage that it can be used to polymerize saturated materials that caimot be induced to react by catalysts. The process consists of the vapor-phase cracking of, for example, propane and butane, followed by prolonged periods at high temperature (510—595°C) for the reactions to proceed to near completion. Olefins can also be conveniendy polymerized by means of an acid catalyst. Thus, the treated olefin-rich feed stream is contacted with a catalyst, such as sulfuric acid, copper pyrophosphate, or phosphoric acid, at 150—220°C and 1035—8275 kPa (150—1200 psi), depending on feedstock and product requirement. 

Catalytic hydrogenations can be carried out ia the vapor phase or ia the Hquid phase, either with or without the use of a solvent. The vapor phase reaction is limited to compounds which are thermally stable and relatively volatile. High boiling compounds and those which are thermally unstable must be hydrogenated ia the Hquid phase. 

The sulfur trioxide produced by catalytic oxidation is absorbed in a circulating stream of 98—99% H2SO4 that is cooled to approximately 70—80°C. Water or weaker acid is added as needed to maintain acid concentration. Generally, sulfuric acid of approximately 98.5% concentration is used, because it is near the concentration of minimum total vapor pressure, ie, the sum of SO, H2O, and H2SO4 partial pressures. At acid concentrations much below 98.5% H2SO4, relatively intractable aerosols of sulfuric acid mist particles are formed by vapor-phase reaction of SO and H2O. At much higher acid concentrations, the partial pressure of SO becomes significant. 

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