Chrome-alumina catalysts

A schematic of a palladium membrane reactor is shown in figure 1. The reversible reaction of 1-butene dehydrogenation occurs on the reaction side of the membrane in which the chrome-alumina catalyst is uniformly packed. The oxidation of hydrogen with oxygen in air occurs in the permeation or separation side on the palladium membrane surface. The... 

Alkali salts from combustion air at coastal installations or low-heating value fuels originating from gasification of biomass may be present in the fuel or combustion air. Salt deposition could be a problem at coastal or offshore installations. Chlorine deactivation was studied by Agarwal and co-workers, with respect to catalytic combustion of mixed chlorohydrocarbons over chrome-alumina catalysts. A decline in catalyst activity downstream of the catalyst bed was observed after 153 days-on-stream. 

Similarly, Manning 08 reports deactivation of a chromia alumina catalyst during oxidation of chlorinated hydrocarbons. He observed chromium loss from the catalyst after deactivation. MichalowiczlOS measured a loss of chromium, thought due to the formation of a volatile chlorine-chrome complex. 

The dehydrogenation of butene to butadiene over a 20% chrome on alumina catalyst is an important industrial process. This catalytic reaction, that is deactivated by coke deposition, has been extensively studied by Froment et al. [10,11]. Faccio et al. [7] have simulated this process using a site-bond-site model on a Bethe network. 

The reaction is cataly2ed by all but the weakest acids. In the dehydration of ethanol over heterogeneous catalysts, such as alumina (342—346), ether is the main product below 260°C at higher temperatures both ether and ethylene are produced. Other catalysts used include siUca—alumina (347,348), copper sulfate, tin chloride, manganous chloride, aluminum chloride, chrome alum, and chromium sulfate (349,350). 

Vapor-phase processes using vinyl fluoride employ a wide variety of catalysts as well. For example, fluorided alumina or aluminum fluoride has been widely used. The conventional chrome-based systems have also been used with success. Carbon-supported VCI3 appears to be (74) a selective catalyst for this synthesis. 

The base material of construction is a ferritic stainless steel alloy having iron/chrome/aluminum/rare earths. Typical monoliths have between 400 and 600 cpsi, with 0.002-in. wall thickness. The metallic monoliths are heat treated to provide an alumina-rich surface and then the structure is coated with catalysts similar to their ceramic counterparts (10). 

Several analyses are indicated in Table 20-19. The other type of catalyst, i.e., chromia-alumina, appears to be most useful for the dehydrogenation of propane and the butanes. Alumina prepared by calcining specially crystallized alumina trihydrate is used at 600 to 650 C for propane or isobutane. Chromium oxide in the form of its active gel is highly selective in its action but is destroyed by temperatures exceeding 500 C. If alumina is used as the carrier for 10 to 20 per cent chromium oxide, the dehydrogenation reaction proceeds at even 50 to 70 C but the life of the catalyst is short. Both the activated alumina and the alumina-chrome catalysts may be regenerated by careful oxidation of the impurities in a... 

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