Catalytic reactor internal recycle

The H-Oil reactor (Fig. 21) is rather unique and is called an ebullated bed catalytic reactor. A recycle pump, located either internally or externally, circulates the reactor fluids down through a central downcomer and then upward through a distributor plate and into the ebullated catalyst bed. The reactor is usually well insulated and operated adiabatically. Frequently, the reactor-mixing pattern is defined as backmixed, but this is not strictly true. A better description of the flow pattern is dispersed plug flow with recycle. Thus, the reactor equations for the axial dispersion model are modified appropriately to account for recycle conditions. 

Various experimental methods to evaluate the kinetics of flow processes existed even in the last centuty. They developed gradually with the expansion of the petrochemical industry. In the 1940s, conversion versus residence time measurement in tubular reactors was the basic tool for rate evaluations. In the 1950s, differential reactor experiments became popular. Only in the 1960s did the use of Continuous-flow Stirred Tank Reactors (CSTRs) start to spread for kinetic studies. A large variety of CSTRs was used to study heterogeneous (contact) catalytic reactions. These included spinning basket CSTRs as well as many kinds of fixed bed reactors with external or internal recycle pumps (Jankowski 1978, Berty 1984.)... 

Internally recycled reactor (Berty) High temperature, high pressure catalytic processes High transport rates, intense mixing Limited ease of variation of parameters... 

Catalytic hydrogenation in supercritical carbou dioxide has been studied. The effects of temperature, pressure, and CO2 concentration on the rate of reaction are important. Hydrogenation rates of the two double bonds of an unsaturated ketone on a commercial alumina-supported palladium catalyst were measured in a continuous gra-dient-less internal-recycle reactor at different temperatures, pressures, and C02-to-feed ratios. The accurate control of the organic, carbon dioxide, and hydrogen feed flow rates and of the temperature and pressure inside the reactor provided reproducible values of the product stream compositions, which were measured on-line after separation of the gaseous components (Bertucco et al., 1997). 

The third example (Fig. 4.3-27) is a loop reactor with internal recycle, developed by G. Lull. This reactor can advantageously be used to study kinetics of heterogenous catalytic reactions at pressures up to 40 MPa and temperatures to 500°C. The internal recycle... 

Bertucco, A., Canu, P., Devetta, L. Catalytic Hydrogenation in Supercritical C02 Kinetic Measurements in a Gradientless Internal-Recycle Reactor. Ind. Eng. Chem. Res. 1997, 36, 2626 - 2633. 

Differential internal recycle reactors have become important tools in recent years for the investigation of catalytic processes and a number of such reactors have been reported in literature with the main emphasis on the actual reactor design [1,2]. In this work a similar reactor, which has been developed by the main investigator for gas-phase reactions under low pressure and high temperature, where it proved its suitability, is described. [3]... 

Zwahlen A. G., Agnew J. Modification of an Internal Recycle Reactor of the Berty Type for Low-Pressure High Temperature Catalytic Gas-Phase Reaction CHEMECA 1987, I, 50.1-50.7, Melbourne, Australia. 

Tank reactors for solid-catalyzed gaseous or liquid reactions are seen much less frequently than tubular reactors because of the difficulty in separating the phases and in agitating a fluid phase in the presence of solid particles. One type of CSTR used to study catalytic reactions is the spinning basket reactor, which has the catalyst embedded in the blades of the spinning agitator. Another is the Berty reactor, which uses an internal recycle stream to achieve perfectly mixed behavior." These reactors (see Chapter 5) are frequently used in industry to evaluate reaction mechanisms and determine reaction kinetics. 

Fig. 1-3 Typical reactors (a) tubular-flow recycle reactor, (b) multi tube-flow reactor, (c) radial-flow catalytic reactor, (d) stirred-tank reactor with internal cooling, (e) loop reactor, (f) reactor with intercoolers (opposite)...

PE = polyethylene PP = polypropylene PS = polystyrene ASR = automobile shredder residue VGO = vacuum gas oil LCO = light cycle oil. SA = Si02/ AI2O3 MOR = mordenite. TD/CD = thermal degradation followed by catalytic degradation COMB = mixed polymer and catalyst in a batch reactor COMS = mixed polymer and catalyst in a semibatch reactor FB = fixed bed flow reactor BIRR = Berty internal recycle reactor. 

As in any heterogeneous catalytic reaction (Chapter 7), it is necessary to use a gradientless reactor to obtain precise kinetic data. An internal recycle reactor was recently proposed by Bertucco et al. (1997) for this purpose. The data should be obtained at times shorter than needed for a perceptible onset of deactivation. 

As stated above for catalytic cracking simulation under the reaction conditions of FCCs a bench scale internal recycle batch reactor was proposed by de Lasa (1991, 1992). It has to be pointed out that this objective is not easy nor straight forward considering the complex fluid-dynamic... 

Gas mixing in laboratory internal recycle reactors used for gas-solid catalytic studies may be assessed from pressure drop (Berty, 1974 Berty, 1979), temperature drop measurements across the bed (Mahoney, 1984), or from mass transfer coefficient estimations (Caldwell, 1983). For a given impeller speed, the first method involves comparing the bed pressure drop of the recycle reactor v/iih pressure drop of a calibrated fixed catalyst bed conducted in a separate unit. Then knowing the fluid velocity versus pressure drop for the calibrated bed, the impeller speed versus fluid velocity can be drawn. The recycle rate can also be determined from thermodynamics based on the ratio of the adiabatic temperature change and the measured temperature difference. This method requires the measurements of temperatures across the bed and the mass flow rate. 

The Riser Simulator Reactor is an internal recycle fluidized batch reactor. This patented novel device (de Lasa 1989 de Lasa, 1991), has been developed and successfully tested for the estimation of kinetic parameters of catalytic cracking of heavy oils (Kraemer and de Lasa, 1988). The details of the unit are given in the section entitled "Novel Techniques For FCC Catalyst Selection and Kinetic Modelling" by de Lasa and Kraemer in this NATO-ASI Proceedings. 

A Bertucco, P Canu, L Devetta, AG Zwahlen. Catalytic hydrogenation in supercritical CO2 kinetic measurements in a gradientless internal-recycle reactor. Ind Eng Chem Res 36 2626-2633, 1997. 

The RR developed by the author at UCC was the only one that had a high recycle rate with a reasonably known internal flow (Berty, 1969). This original reactor was named later after the author as the Berty Reactor . Over five hundred of these have been in use around the world over the last 30 years. The use of Berty reactors for ethylene oxide process improvement alone has resulted in 300 million pounds per year increase in production, without addition of new facilities (Mason, 1966). Similar improvements are possible with many other catalytic processes. In recent years a new blower design, a labyrinth seal between the blower and catalyst basket, and a better drive resulted in an even better reactor that has the registered trade name of ROTOBERTY . ... 

The LAB production process (process 1) is mainly developed and licensed by UOP. The N-paraffins are partially converted to internal /z-olefins by a catalytic dehydrogenation. The resulting mixture of /z-paraffins and n-olefins is selectively hydrogenated to reduce diolefins and then fed into an alkylation reactor, together with an excess benzene and with concentrated hydrofluoric acid (HF) which acts as the catalyst in a Friedel-Crafts reaction. In successive sections of the plant the HF, benzene, and unconverted /z-paraffins are recovered and recycled to the previous reaction stages. In the final stage of distillation, the LAB is separated from the heavy alkylates. 

Normal Paraffin-Based Olefins, Detergent range -paraffins are currently isolated from refinery streams by molecular sieve processes (see ADSORPTION, LIQUID separation) and converted to olefins by two methods. In the process developed by Universal Oil Products and practiced by Enichem and Mitsubishi Petrochemical, a -paraffin of the desired chain length is dehydrogenated using the Pacol process in a catalytic fixed-bed reactor in the presence of excess hydrogen at low pressure and moderately high temperature. The product after adsorptive separation is a linear, random, primarily internal olefin. Shell formedy produced olefins by chlorination—dehydrochlorination. Typically, C —C14 -paraffins are chlorinated in a fluidized bed at 300°C with low conversion (10—15%) to limit dichloroalkane and trichloroalkane formation. Unreacted paraffin is recycled after distillation and the predominant monochloroalkane is dehydrochlorinated at 300°C over a catalyst such as nickel acetate [373-02-4]. The product is a linear, random, primarily internal olefin. 

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