Alumina process design

Randolph, A.D. and Tan, C., 1978. Numerical design techniques for staged classified recycle crystallizers Examples of continuous alumina and sucrose crystallizers. Industrial and Engineering Chemistry Process Design and Development, 17(2), 189. 

This is a process designed to cover a catalyst support, such as silica, alumina, mesoporous molecular sieves, or other supports with a metallic catalyst, or other catalytically active materials. The process is carried out by contacting the solid support, for a precise time, with a solution containing the active elements, to introduce a solution of the precursor into the pores of the support. During the impregnation process, the support can be completely free of the solvent when the precursor is dissolved. In this... 

In the late 1960s, Lurgi adopted the CEB for calcination of alumina trihydrate. Design studies have shown that CFBs can be applied for capacities as high as lOOOt/day. A high degree of automation, economy of space, and a simplified process flowsheet are important design criteria. 

W.M.Graven, S.W. Weller, and D.L. Peters, Catalytic Conversion of an Or-ganophosphate Vapor over Pt/alumina , I EC Process Design and Development, Vol. 5, N0.2, April 1966. 

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. 

Ethylene oxide (qv) was once produced by the chlorohydrin process, but this process was slowly abandoned starting in 1937 when Union Carbide Corp. developed and commercialized the silver-catalyzed air oxidation of ethylene process patented in 1931 (67). Union Carbide Corp. is stiU. the world s largest ethylene oxide producer, but most other manufacturers Hcense either the Shell or Scientific Design process. Shell has the dominant patent position in ethylene oxide catalysts, which is the result of the development of highly effective methods of silver deposition on alumina (29), and the discovery of the importance of estabUshing precise parts per million levels of the higher alkaU metal elements on the catalyst surface (68). The most recent patents describe the addition of trace amounts of rhenium and various Group (VI) elements (69). 

Activated alumina and phosphoric acid on a suitable support have become the choices for an iadustrial process. Ziac oxide with alumina has also been claimed to be a good catalyst. The actual mechanism of dehydration is not known. In iadustrial production, the ethylene yield is 94 to 99% of the theoretical value depending on the processiag scheme. Traces of aldehyde, acids, higher hydrocarbons, and carbon oxides, as well as water, have to be removed. Fixed-bed processes developed at the beginning of this century have been commercialized in many countries, and small-scale industries are still in operation in Brazil and India. New fluid-bed processes have been developed to reduce the plant investment and operating costs (102,103). Commercially available processes include the Lummus processes (fixed and fluidized-bed processes), Halcon/Scientific Design process, NIKK/JGC process, and the Petrobras process. In all these processes, typical ethylene yield is between 94 and 99%. 

Referring first of all to the reactions over 0.2% platinum/alumina (Table V) the major features of the product distributions may be explained by a simple reaction via an adsorbed C5 cyclic intermediate. For instance, if reaction had proceeded entirely by this path, 2-methylpentane-2-13C would have yielded 3-methylpentane labeled 100% in the 3-position (instead of 73.4%) and would have yielded n-hexane labeled 100% in the 2-position (instead of 90.2%). Similarly, 3-methylpentane-2-I3C would have yielded a 2-methylpentane labeled 50% in the methyl substituent (instead of 42.6%), and would have yielded n-hexane labeled 50% in the 1- and 3-positions (instead of 43.8 and 49% respectively). The other expectations are very easily assessed in a similar manner. On the whole, the data of Table V lead to the conclusion that some 80% or so of the reacting hydrocarbon reacts via a simple one step process via an adsorbed C5 cyclic intermediate. The departures from the distribution expected for this simple process are accounted for by the occurrence of bond shift processes. It is necessary to propose that more than one process (adsorbed C6 cyclic intermediate or bond shift) may occur within a single overall residence period on the catalyst Gault s analysis leads to the need for a maximum of three. The number of possible combinations is large, but limitations are imposed by the nature of the observed product distributions. If we designate a bond shift process by B, and passage via an adsorbed Cs cyclic intermediate by C, the required reaction paths are... 

NASA conducted studies on the development of the catalysts for methane decomposition process for space life-support systems [94], A special catalytic reactor with a rotating magnetic field to support Co catalyst at 850°C was designed. In the 1970s, a U.S. Army researcher M. Callahan [95] developed a fuel processor to catalytically convert different hydrocarbon fuels to hydrogen, which was used to feed a 1.5 kW FC. He screened a number of metals for the catalytic activity in the methane decomposition reaction including Ni, Co, Fe, Pt, and Cr. Alumina-supported Ni catalyst was selected as the most suitable for the process. The following rate equation for methane decomposition was reported ... 

Isomar [Isomerization of aromatics] A catalytic process for isomerizing xylene isomers and ethylbenzene into equilibrium isomer ratios. Usually combined with an isomer separation process such as Parex (1). The catalyst is a zeolite-containing alumina catalyst with platinum. Developed by UOP and widely licensed by them. It was first commercialized in 1967 by 1992, 32 plants had been commissioned and 8 others were in design or construction. See also Isolene II. 

Zeolites are formed by crystallization at temperatures between 80 and 200 °C from aqueous alkaline solutions of silica and alumina gels in a process referred to as hydrothermal synthesis.15,19 A considerable amount is known about the mechanism of the crystallization process, however, no rational procedure, similar to organic synthetic procedures, to make a specifically designed zeolite topology is available. The products obtained are sensitive functions of the reaction conditions (composition of gel, reaction time, order of mixing, gel aging, etc.) and are kinetically controlled. Nevertheless, reproducible procedures have been devised to make bulk quantities of zeolites. Procedures for post-synthetic modifications have also been described.20 22... 

In this process, propane, and a small amount of hydrogen to control coking, are fed to either a fixed bed or moving bed reactor at 950—1300° F and near atmospheric pressure. Once again the catalyst, this time platinum on activated alumina impregnated with 20% chromium, promotes the reaction. In either design, the catalyst has to be regenerated continuously to maintain its activity. 

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