Catalytic fluid

Abedi, J., Yeboah, Y.D., Howard, J., and Bota, KB. (2001) Development of a catalytic fluid bed steam reformer for production of hydrogen from biomass, 5th Biomass Conference of the Americas, Orlando, FL (Cancelled). Abstracts to be published on CD/ROM. 

The subject of the movement of particles in a stream of gas arises in connection with pulverized coal, catalytic fluid cracking, etc. Khudyakov and Chukhanov 5P) derive equations and present an experiment using sand particles ranging between 70 and 845 microns. The particles are introduced into a stream of air flowing vertically down through glass tubes of varying diameter. 

Figure 1. Individual steps of a simple, heterogeneous catalytic fluid-solid reaction A — A2 carried out on a porous catalyst...

Figure 2. Stationary concentration (reactant) and temperature profiles inside and around a porous catalyst pellet during an exo thermic, heterogeneous catalytic fluid-solid reaction (a) without transport influence, (b) limited only by intraparticle diffusion, (0 limited by lntcrphase and intraparticle diffusion, (d) limited only by interphase diffusion (dense pellet)...

A chemical reactor is a vessel in which reactants are converted to products through chemical reactions. This vessel takes many shapes and sizes depending upon the nature of the chemical reaction. The choice of a suitable laboratory reactor depends upon the nature of the reaction system (fluid-solid catalytic, fluid-solid noncatalytic, fluid-fluid, etc.), the nature of the required kinetic or thermodynamic data, or the feasibility of operation. The important parameters for a successful reactor design are the following ... 

The work just cited refers to beds of small diameter. Designers and operators of large-scale catalytic fluid beds of Group A powders now appreciate that all of these beds function beyond the Lanneau-Kehoe-Davidson transition (Avidan, 1982 Squires et al., 1985). Most are turbulent beds Sasol reactors and some fluid catalytic cracking regenerators are fast beds. Sasol engineers reported successful development of a turbulent bed for hydrocarbon synthesis (Steynberg et al., 1991). 

Figure 4. Catalytic Fluid Bed Steam Reforming Reactor...

A schematic and photograph of the pilot-scale catalytic fluid bed reformer are shown in Figure 4. The 30-cm catalytic steam reforming reactor was successfully operated on peanut pyrolysis vapor at a feed rate of 7 kg/hour of vapors. The results are in agreement with those obtained from the 5-cm bench-scale reactor used for the reforming of the aqueous fraction of pyrolysis oil. Typical gas compositions at the outlet of the reformer are shown in Figure 5. These data show that the yield of hydrogen is approximately 90% of maximum. 

The aqueous phase product from the catalytic fluid bed was separated and analyzed by gas chromatography for oxygenates from which conversion could be... 

The low total carbon conversion of the gas-phase reaction resulted from the highly exothermic reaction from which heat and product cannot be removed rapidly from the catalyst bed. The heat and product removal from the catalyst bed, which would improve the reaction activity, was achieved when SC n-hexane was introduced into the reaction. The highest total carbon conversion was obtained by using the alcohols as SC catalytic fluids. SC alcohol improved the conversion by promoting the reaction not only by the SCF advantage, but also by the catalytic effect as behaved in the low temperature methanol synthesis. The methanol synthesis could significantly be improved by the combination of SCF advantage and catalytic effect when alcohol was used as an... 

Cracking Catalytic Deep catalytic Fluid catalytic (6) Hydrocracking (6)... 

Wiese, K.-D., Moeller, O., Protzmann, G., and Trocha, M. (2003) A new reactor design for catalytic fluid-fluid multiphase reactions. Catal. Today, 79-80,97-103. 

As indicated above, the principal difference between reactor design calculations involving homogeneous reactions and those involving catalytic (fluid-solid) heterogeneous reactions is that for the latter the reaction rate is based on the mass of solid, W, rather than on reactor volume V. For a fluid—solid heterogeneous system the rale of reaction of species A is then defined as — with the aforementioned units of (mols A reacted)/(mass catalyst) (time). 

I would like to add here another, less known, example - the design of a catalytic fluid bed reactor At low flow velocities such reactors are hard to scaleup Large bubbles are formed and the exact behavior of the bed is hard to predict (28, 39) This is well illustrated by the available data In Fig 5 conversion is plotted for a first order reaction as a function of bubble size for a specific case (40). It is very sensitive to bubble size In that sense bubble models are learning models and not predictive models, inasmuch as we cannot predict bubble size that accurately At higher velocities bubbles become less distinct and gas solid contact improves considerably (, 42) The risk of scaleup decreases ... 

However, before extrapolating the arguments from the gross patterns through the reactor for homogeneous reactions to solid-catalyzed reactions, it must be recognized that in catalytic reactions the fluid in the interior of catalyst pellets may diSer from the main body of fluid. The local inhomogeneities caused by lowered reactant concentration within the catalyst pellets result in a product distribution different from that which would otherwise be observed. 

Fluidized-bed catalytic reactors. In fluidized-bed reactors, solid material in the form of fine particles is held in suspension by the upward flow of the reacting fluid. The effect of the rapid motion of the particles is good heat transfer and temperature uniformity. This prevents the formation of the hot spots that can occur with fixed-bed reactors. 

Ecole Nationale Superieure du Petrole et des Moteurs Formation Industrie end point (or FBP - final boiling point) electrostatic precipitation ethyl tertiary butyl ether European Union extra-urban driving cycle volume fraction distilled at 70-100-180-210°C Fachausschuss Mineralol-und-Brennstoff-Normung fluid catalytic cracking Food and Drug Administration front end octane number fluorescent indicator adsorption flame ionization detector... 

Catalysis in a single fluid phase (liquid, gas or supercritical fluid) is called homogeneous catalysis because the phase in which it occurs is relatively unifonn or homogeneous. The catalyst may be molecular or ionic. Catalysis at an interface (usually a solid surface) is called heterogeneous catalysis, an implication of this tenn is that more than one phase is present in the reactor, and the reactants are usually concentrated in a fluid phase in contact with the catalyst, e.g., a gas in contact with a solid. Most catalysts used in the largest teclmological processes are solids. The tenn catalytic site (or active site) describes the groups on the surface to which reactants bond for catalysis to occur the identities of the catalytic sites are often unknown because most solid surfaces are nonunifonn in stmcture and composition and difficult to characterize well, and the active sites often constitute a small minority of the surface sites. 

CATALYSTS - REGENERATION - FLUID CATALYTIC CRAC KING UNITS] (Vol 5) [CONTROLLED RELEASE TECHNOLOGY - PHARMACEUTICAL] (Vol 7)... 

The enhanced concentration at the surface accounts, in part, for the catalytic activity shown by many solid surfaces, and it is also the basis of the application of adsorbents for low pressure storage of permanent gases such as methane. However, most of the important applications of adsorption depend on the selectivity, ie, the difference in the affinity of the surface for different components. As a result of this selectivity, adsorption offers, at least in principle, a relatively straightforward means of purification (removal of an undesirable trace component from a fluid mixture) and a potentially useflil means of bulk separation. 

Eriedel-Crafts reaction of naphthalene or tetrahydronaphthalene derivatives with those of styrene or alkylbenzenes has been used in the preparation of high viscous fluids for traction drive (195). Similarly, Eriedel-Crafts reaction of tetraline and a-methylstyrene followed by catalytic hydrogenation provided l-(l-decalyl)-2-cyclohexyl propane, which is used as a highly heat resistant fluid (196). 

Thermochemical Liquefaction. Most of the research done since 1970 on the direct thermochemical Hquefaction of biomass has been concentrated on the use of various pyrolytic techniques for the production of Hquid fuels and fuel components (96,112,125,166,167). Some of the techniques investigated are entrained-flow pyrolysis, vacuum pyrolysis, rapid and flash pyrolysis, ultrafast pyrolysis in vortex reactors, fluid-bed pyrolysis, low temperature pyrolysis at long reaction times, and updraft fixed-bed pyrolysis. Other research has been done to develop low cost, upgrading methods to convert the complex mixtures formed on pyrolysis of biomass to high quaHty transportation fuels, and to study Hquefaction at high pressures via solvolysis, steam—water treatment, catalytic hydrotreatment, and noncatalytic and catalytic treatment in aqueous systems. 

Catalytic Processes. A second group of refining operations which contribute to gas production are the catalytic cracking processes, such as fluid-bed catalytic cracking, and other variants, in which heavy gas oils are converted into gas, naphthas, fuel oil, and coke (5). 

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