Chromia-alumina reactor

Solution Polymerization These processes may retain the polymer in solution or precipitate it. Polyethylene is made in a tubular flow reactor at supercritical conditions so the polymer stays in solution. In the Phillips process, however, after about 22 percent conversion when the desirable properties have been attained, the polymer is recovered and the monomer is flashed off and recyled (Fig. 23-23 ). In another process, a solution of ethylene in a saturated hydrocarbon is passed over a chromia-alumina catalyst, then the solvent is separated and recyled. Another example of precipitation polymerization is the copolymerization of styrene and acrylonitrile in methanol. Also, an aqueous solution of acrylonitrile makes a precipitate of polyacrylonitrile on heating to 80°C (176°F). 

As deseribed earlier, the Houdry Catadiene process, the Houdry Catofln proeess, and other similar eyclical processes make use of parallel reactors that contain a shallow bed of chromia-alumina catalyst. Fig. 11 illustrates a schematic of such a process. 

The cited article does not give operating conditions for propylene. The catalyst is chromia-alumina. Because of equilibrium, vacuum operation and hence short catalyst beds are required, as suggested by the compressors shown in Figure 6. Reactor effluents, after being quenched quickly, are compressed and separated conventionally. 

Reactor Apparatus. The reactor systems used for obtaining data on n-dodecane dehydrogenation over molybdena-alumina and platinum-alumina catalysts and the data on reaction of bare supports with -dodo-cene have been described previously (12). The reactors used for obtaining data on n-dodecane dehydrogenation over chromia-alumina and... 

In a fundamental study of coke formation on a chromia-alumina dehydrogenation catalyst, the catalyst activity and coke formation rate were measured in a differential reactor [20]. The equation for the rate of coking allowed for the decrease in rate with increase in coke level and the effects of reactants and products ... 

Butane was also dehydrogenated, usually to butene, by the Phillips and UOP processes. Both processes used the same sort of chromia/alumina catalysts, loaded in tubular reactors, but were able to operate at atmospheric pressure because less hydrogen was produced during the reaction. In some cases the butene produced was subsequently dehydrogenated to butadiene in a separate unit... 

Catadiene [Catalytic butadiene] Also spelled Catadien. A version of the Houdry process for converting mixtures of butane isomers into butadiene by dehydrogenation over an alumina/chromia catalyst. Another version converts propane to propylene. Rapid coking of the catalyst necessitates use of several reactors in parallel, so that reactivation can be carried out continuously. Developed by Houdiy and first operated at El Segundo, CA, in 1944. By 1993, 20 plants had been built worldwide. Now licensed by ABB Lummus Crest. 

The reactor equipment used for solution polymerizations is typically glass-lined stainless steel. An example of solution polymerization is the reaction of ethylene in isooctane with a chromia silica alumina catalyst initiator (see Figure 3.23) to form polyethylene. Typical reaction conditions for this polymerization are 150-180°C and 2.1-4.8 MPa (300-700 psi). 

Thermofor catalytic reforming a reforming process in which the synthetic, bead-type catalyst of coprecipitated chromia (Cr2Ot) and alumina (A1203) flows down through the reactor concurrent with the feedstock. 

FBD [Fluidized Bed Dehydrogenation] A catalytic process for converting alkanes to alkenes. Two fluidized beds are used a reactor and a regenerator. The catalyst beads are recirculated from the regenerator to the reactor, providing heat to the reactor. The catalyst is chromia on alumina. 

There have been two recent kinetic studies of the dismutation behaviour of CHC12F, CHC1F2 and other members of the CHC13 F series, in one case over activated y-alumina under conventional flow conditions [105] in the other, over activated chromia using plug-flow and temporal analysis of products (TAP) reactors... 

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