Alumina reactor

Eigure 31 shows a schematic diagram of a lab-made PEVD reactor for depositing yttria-doped zirconia. The sample tube was placed at the center of a large fully dense alumina reactor tube in an electric furnace. Thus, the sample tube separated the reactor tube into two chambers the air chamber inside the sample tube and the chloride chamber between the sample and reactor tubes. Both chambers were evacuated separately. 

Heavy-particle radiation would be expected to increase the catalytic activity simply because it always produces ionization as well as displacement. In the case of silica gel and silica-alumina, reactor radiation produced large increases in activity (82), but the uncertainties of the dosimetry and of the temperature corrections to the rates make it unwise to speculate on the relative efficiencies of fast neutrons and y-rays. 

The principal general interest in silica and related catalysts has been attached to those reactions which are thought to be catalyzed by acid sites, cracking and isomerization of hydrocarbons. Such reactions have naturally been applied to irradiated silica and silica-aluminas. Reactor irradiation of pure silica was early found by Weisz and Swegler (10) to enhance the activity for n-hexene-1 double bond isomerization, 7.5 X IQi nvt fast neutrons giving a statistically significant increase... 

To avoid classical corrosion mechanisms, ceramics and composite materials have also been tested (some of these materials are also common components in heterogeneous catalysts). An alumina reactor for SCWO was proposed among ceramic materials only a few aluminas and zirconias did not corrode severely, whereas SiC or BN lost up to 90% by weight under SCWO conditions in the presence of HCl. The combination of steel and ceramic coatings should theoretically provide high-pressure stability and improved corrosion resistance, but only slight improvements were reported for stainless steel SS316 coated with sol-gel-prepared Ti, Zr or Hf oxides, stainless steel SUS-304 with TiN or Ni alloys and ceramics. Often the adhesion of the ceramic layer on the steel surface is not sufficient. 

Most A1F. and cryoHte producers have their own HF production faciUties. HF vapor is reacted with alumina trihydrate to form A1F. in a fluid-bed reactor. HF is reacted with sodium hydroxide to form sodium fluoride, which is then used to produce cryoHte. Producers who manufacture these products solely for use in the aluminum industry do not generally install Hquid HF storage and handling faciHties, and do not participate in the merchant HF market. 

This reaction is first conducted on a chromium-promoted iron oxide catalyst in the high temperature shift (HTS) reactor at about 370°C at the inlet. This catalyst is usually in the form of 6 x 6-mm or 9.5 x 9.5-mm tablets, SV about 4000 h . Converted gases are cooled outside of the HTS by producing steam or heating boiler feed water and are sent to the low temperature shift (LTS) converter at about 200—215°C to complete the water gas shift reaction. The LTS catalyst is a copper—zinc oxide catalyst supported on alumina. CO content of the effluent gas is usually 0.1—0.25% on a dry gas basis and has a 14°C approach to equihbrium, ie, an equihbrium temperature 14°C higher than actual, and SV about 4000 h . Operating at as low a temperature as possible is advantageous because of the more favorable equihbrium constants. The product gas from this section contains about 77% H2, 18% CO2, 0.30% CO, and 4.7% CH. ... 

Ethjlben ne Synthesis. The synthesis of ethylbenzene for styrene production is another process in which ZSM-5 catalysts are employed. Although some ethylbenzene is obtained direcdy from petroleum, about 90% is synthetic. In earlier processes, benzene was alkylated with high purity ethylene in liquid-phase slurry reactors with promoted AlCl catalysts or the vapor-phase reaction of benzene with a dilute ethylene-containing feedstock with a BF catalyst supported on alumina. Both of these catalysts are corrosive and their handling presents problems. 

In the Godrej-Lurgi process, olefins are produced by dehydration of fatty alcohols on alumina in a continuous vapor-phase process. The reaction is carried out in a specially designed isothermal multitube reactor at a temperature of approximately 300°C and a pressure of 5—10 kPa (0.05—0.10 atm). As the reaction is endothermic, temperature is maintained by circulating externally heated molten salt solution around the reactor tubes. The reaction is sensitive to temperature fluctuations and gradients, hence the need to maintain an isothermal reaction regime. 

Diphenylamine can also be produced by passing the vapors of aniline over a catalyst such as alumina, or alumina impregnated with ammonium fluoride (17). The reaction is carried out at 480°C and about 700 kPa (7 atm). Conversion per pass, expressed as parts diphenylamine per 100 parts of reactor effluent, is low (18—22%), and the unconverted aniline must be recycled. Other catalysts disclosed for the vapor-phase process are alumina modified with boron trifluoride (18), and alumina activated with boric acid or boric anhydride (19). 

The predominant process for manufacture of aniline is the catalytic reduction of nitroben2ene [98-95-3] ixh. hydrogen. The reduction is carried out in the vapor phase (50—55) or Hquid phase (56—60). A fixed-bed reactor is commonly used for the vapor-phase process and the reactor is operated under pressure. A number of catalysts have been cited and include copper, copper on siHca, copper oxide, sulfides of nickel, molybdenum, tungsten, and palladium—vanadium on alumina or Htbium—aluminum spinels. Catalysts cited for the Hquid-phase processes include nickel, copper or cobalt supported on a suitable inert carrier, and palladium or platinum or their mixtures supported on carbon. 

The OLEFLEX process uses multiple side-by-side, radial flow, moving-bed reactors connected in series. The heat of reaction is suppHed by preheated feed and interstage heaters. The gas-phase reaction is carried out over a catalyst, platinum supported over alumina, under very near isothermal conditions. The first commercial installation of this technology, having an annual capacity of 100,000 t, was made in 1990 by the National Petrochemical Corporation in Thailand. A second unit, at 245,000 t capacity, has been built in South Korea by the ISU Chemical Company (70). 

Ethylene oxide is produced in large, multitubular reactors cooled by pressurized boiling Hquids, eg, kerosene and water. Up to 100 metric tons of catalyst may be used in a plant. Typical feed stream contains about 30% ethylene, 7—9% oxygen, 5—7% carbon dioxide the balance is diluent plus 2—5 ppmw of a halogenated moderator. Typical reactor temperatures are in the range 230—300°C. Most producers use newer versions of the Shell cesium-promoted silver on alumina catalyst developed in the mid-1970s. 

Oxychlorination of Ethylene to Dichloroethane. Ethylene (qv) is converted to dichloroethane in very high yield in fixed-bed, multitubular reactors and fluid-bed reactors by reaction with oxygen and hydrogen chloride over potassium-promoted copper(II) chloride supported on high surface area, porous alumina (84) ... 

Oxychlorination of ethylene to dichloroethane is the first reaction performed in an integrated vinyl chloride plant. In the second stage, dichloroethane is cracked thermally over alumina to give vinyl chloride and hydrogen chloride. The hydrogen chloride produced is recycled back to the oxychlorination reactor. 

The oxychlorination reaction is very exothermic and the catalyst is very active, which makes it necessary to mix the catalyst with an inert diluent to avoid overheating in a fixed-bed reactor. A low surface area, spherically- or ring-shaped alumina or chemical porcelain body can be used as a diluent with the ring-shaped catalyst. The density of the inert material should be similar to the catalyst to avoid segregation during loading, and the size should be slightly different to allow separation of the inert material from the spent catalyst. 

A typical converter is made up of multiple furnaces, each of which contains 8 to 10 reactors. Each reactor is made up of 10 to 30 sintered alumina tubes lined with platinum. The furnaces are direct fired with natural gas to 1200—1300°C. A typical furnace can produce about 125 t per month of hydrogen cyanide. Catalyst life is approximately 10,000 h. 

Butyl slurry at 25—35 wt % mbber continuously overflows from the reactor through a transferline to an agitated flash dmm operating at 140—160 kPa (1.4—1.6 atm) and 55—70°C. Steam and hot water are mixed with the slurry in a nozzle as it enters the dmm to vaporize methyl chloride and unreacted monomers that pass overhead to a recovery system. The vapor stream is compressed, dried over alumina, and fractionated to yield a recycle stream of methyl chloride and isobutylene. Pure methyl chloride is recovered for the coinitiator (AlCl ) preparation. In the flash dmm, the polymer agglomerates as a coarse cmmb in water. Metal stearate, eg, aluminum, calcium, or zinc stearate, is added to control the cmmb size. Other additives, such as antioxidants, can also be introduced at this point. The polymer cmmb at 8—12 wt % in water flows from the flash dmm to a stripping vessel operated under high vacuum to... 

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