Fluid catalysts mechanical properties

Such tailoring of properties is feasible for many catalyst-carrier formulations, bnt drying processes, for instance, may be restricted by other considerations. Fluidization of difficult materials can be maintained by mechanical or ultrasonic vibration of the vessel, or pulsation of the supply of the fluid, or mechanical agitation of the contents of the vessel, or by addition of fluidization aids such as fine foreign solids. 

In evaluating the transport properties in fluid catalyst beds during reaction, it is necessary to utilize reaction data obtained at relatively high reaction rate. The reactor models of different mechanisms have been reduced to the form of Eq. (7-35), as shown in Table VII, including the bubbling bed model when k a, ATor- Eq. (7-35) is equivalent to one developed by Lewis et al. (LI2) for their direct contact model of vertically unmixed emulsion (VUE). As a consequence, Eq. (7-35) is transformed (LI2) to ... 

Another patent by BP America (29) deals with the preparation of an attrition-resistant fluid-bed catalyst based on unsupported vanadium hosphorus mixed oxide. The mechanical properties are given to the catalyst only by the special pr aration procedure. The procedure is summarized in Scheme 10. Key-features of this procedure are i) densification of the catalyst precursor by tabletting or pdleting, followed by dry ball milling, ii) preparation of an aqueous slurry with the uncalcined comminuted catalyst, because the calcined catalyst (and the oxidized precursor, also) may be altered by water, and iii) activation of the particles in the fluid-bed which gives higher attrition resistance than static calcination. 

The effectiveness of these components can be enhanced by co-catalysts, coreactants or surface active fluids. While the precise chemistry is not always clear, noticeable improvements in morphology and mechanical properties are reported. Some of the cases described are early examples of what may be a new approach to reactive blend compatibilization. 

The resistance to attrition is an important characteristic of catalysts used in fluid beds (5). This mechanical property is evaluated with an air jet Gwyn-type-apparatus (17). 

Fluidized-bed catalytic cracking units (FCCUs) are the most common catalytic cracking units. In the fluidized-bed process, oil and oil vapor preheated to 500 to SOOT is contacted with hot catalyst at about 1,300°F either in the reactor itself or in the feed line (called the riser) to the reactor. The catalyst is in a fine, granular form which, when mixed with the vapor, has many of the properties of a fluid. The fluidized catalyst and the reacted hydrocarbon vapor separate mechanically in the reactor and any oil remaining on the catalyst is removed by steam stripping. 

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