Experimental slurry reactors

Calderbank et al. (C6) studied the Fischer-Tropsch reaction in slurry reactors of 2- and 10-in. diameters, at pressures of 11 and 22 atm, and at a temperature of 265°C. It was assumed that the liquid-film diffusion of hydrogen from the gas-liquid interface is a rate-determining step, whereas the mass transfer of hydrogen from the bulk liquid to the catalyst was believed to be rapid because of the high ratio between catalyst exterior surface area and bubble surface area. The experimental data were not in complete agreement with a theoretical model based on these assumptions. 

Hydrogenation of lactose to lactitol on sponge itickel and mtheitium catalysts was studied experimentally in a laboratory-scale slurry reactor to reveal the true reaction paths. Parameter estimation was carried out with rival and the final results suggest that sorbitol and galactitol are primarily formed from lactitol. The conversion of the reactant (lactose), as well as the yields of the main (lactitol) and by-products were described very well by the kinetic model developed. The model includes the effects of concentrations, hydrogen pressure and temperature on reaction rates and product distribution. The model can be used for optinuzation of the process conditions to obtain highest possible yields of lactitol and suppressing the amounts of by-products. 

In 1976 he was appointed to Associate Professor for Technical Chemistry at the University Hannover. His research group experimentally investigated the interrelation of adsorption, transfer processes and chemical reaction in bubble columns by means of various model reactions a) the formation of tertiary-butanol from isobutene in the presence of sulphuric acid as a catalyst b) the absorption and interphase mass transfer of CO2 in the presence and absence of the enzyme carboanhydrase c) chlorination of toluene d) Fischer-Tropsch synthesis. Based on these data, the processes were mathematically modelled Fluid dynamic properties in Fischer-Tropsch Slurry Reactors were evaluated and mass transfer limitation of the process was proved. In addition, the solubiHties of oxygen and CO2 in various aqueous solutions and those of chlorine in benzene and toluene were determined. Within the framework of development of a process for reconditioning of nuclear fuel wastes the kinetics of the denitration of efQuents with formic acid was investigated. 

Kinetic experiments were carried out isothermally in autoclave reactors of sizes 500 ml and 600 ml. The stirring rate was typically 1500 rpm. In most cases, the reactors operated as slurry reactors with small catalyst particles (45-90 micrometer), but comparative experiments were carried out with a static basket using large trilobic catalyst pellets (citral hydrogenation). Samples were withdrawn for analysis (GC for citral hydrogenation and HPLC for lactose hydrogenation). The experimental details as well as qualitative kinetics are reported in previous papers of our group Kuusisto et al. (17), Aumo et al. (5). 

An accurate evaluation of kxa is complicated by the heterogeneous nature and poor definition of contaminant/soil systems. Some success has been achieved in modeling mass transfer from a separate contaminant phase. During degradation these nonaqueous phase liquids (NAPLs) often dissolve under conditions where phase equilibrium is not achieved and dissolution is proportional to k a. Experimental determinations and correlations for k-p depend on interfacial area of the NAPL and liquid velocity at the interface (Geller Hunt, 1993). For adsorbed contaminants, kxa varies with soil composition and structure, concentration and age of contamination, and therefore with time. For example, slurry reactor tests indicate that the rate of naphthalene mass transfer decreases with time, with media size, and with aging of the tar prior to testing (Luthy et al., 1994). 

Figure 1. The concentration of epoxided tetrahydroanthraquinone (left scale) and hydrogenated alkyltetrahydroanthraquinone (right scale) in the slurry reactor at 75 °C experimental data ( ), ( ) and model prediction (—), (—),...

In the case of a stationary basket-type reactor, kLaL correlations proposed for conventional agitated slurry reactors by Ramachandran and Choudhari (1983) can be used. No experimental data for liquid-solid systems are, however, available. 

Figures 21a, b show the 4-CP, 4-CC, and HQ concentrations derived from inserting the estimated parameters in the kinetic model and a comparison with the experimental data under different operating conditions. Symbols correspond to experimental data and solid lines to model predictions calculated with Equations (64)-(66) and Equations (71)-(74). Eor these experimental runs, the RMSE was less than 14.4%. These experimental 4-CC and HQ concentrations are in agreement with the proposed kinetic mechanism of parallel formafion of fhe intermediate species (Figure 16), and also with the series-parallel kinetic model reported by Salaices et al. (2004) to describe the photocatalytic conversion of phenol in a slurry reactor under various operating conditions. ...

Figures 22a, b provides a schematic representation of the pilot scale reactor. Essentially it is a rectangular parallelepiped limited by two parallel windows made of borosilicate glass and operated as a slurry reactor inside the loop of a batch recycling system. Irradiation of one of the reactor faces is obtained using two tubular lamps that were placed along the focal axis of two parabolic reflectors made of specularly finished aluminum (Brandi et al., 1996, 1999, 2002). The specific information concerning the experimental device is presented in Table 9, and more details can be found in Satuf et al. (2007b).

In catalytic slurry reactors the locale of the reaction is the catalyst surface. Hence, in addition to the mass transfer resistance at the gas-liquid interface a further transport resistance may occur at the boundary layer around the catalyst particle. This is characterized by the solid-liquid mass transfer coefficient, kg, which has been the subject of many theoretical and experimental studies. Brief reviews are given by Shah (82). In general, the liquid-solid mass transfer coefficient is correlated by expressions like... 

Methylene chloride was not used in the separation because of concern for its potential catalyst deactivation role in the subsequent series of experiments to be undertaken. Experimental continuous reactor conditions were a 3 1 slurry of tetralin coal to which an iron (278 30 mmol kg dry coal from FeS0i. 7H20) and tin (20 mmol kg dry coal from SnCl2.2H20) catalyst had been added. The reaction temperature was 400 C with a developed pressure of 10 MPa and a residence time from 15 to 40 minutes. 

P12C-2 Use the references given in Ind. Eng. Chem. Prod. Res. Lev. /4, 226 (1975) to define the iodine value, saponification number, acid number, and experimental setup. Use the slurry reactor analysis to evaluate the effects of mass transfer and determine if there are any mass transfer limitations. 

The deactivation of methanol-synthesis catalyst was studied in laboratory and pilot-plant slurry reactors using a concentrated, poison-free, CO-rich feedstream. The extent of catalyst deactivation correlated with the loss of BET surface area. A model of catalyst deactivation as a function of temperature and time was developed from experimental data. The model suggested that continuous catalyst addition and withdrawal, rather than temperature programming, was the best way to maintain a constant rate of methanol production as the catalyst ages. Catalyst addition and withdrawal was demonstrated in the pilot plant. 

One of the surprising results of this study Is the ability of the catalyst to operate with concentrated, CO-rich feed gas without catastrophic catalyst deactivation. The present data show that deactivation of methanol-synthesis catalyst in a slurry reactor is within the range of commercial feasibility. Although the experimental data show that catalyst activity loss correlates with the loss of BET surface area, the relationship between catalyst activity and sintering requires more study. Since commercial methanol-synthesis catalysts are composed primarily of Cu and ZnO, with only smalt amounts of AI2O3, the present data do not discriminate between sintering of the overall surface and sintering of the Cu metal surface, which is believed to provide the actual sites for reaction. 

Experimental studies have demonstrated that conventional methanol-synthesis catalysts deactivate slowly in a slurry reactor, even with a concentrated, CO rich feedstream. The catalyst activity correlates with the BET surface area and the rate of deactivation increases rapidly with temperature. This limits the utility of temperature programming as a means for maintaining a constant methanol production rate as the catalyst ages. Continuous catalyst addition and withdrawal is the preferred means to maintain constant methanol production. The key mechanical and process features of this technique were demonstrated In the pilot plant. 

Isoparaffin alkylation reactions are very fast and they suffer from severe pore diffusion limitations. As a result, when catalyst particle size is increased from 100 pm (for slurry reactors) to 1.6 mm for fixed-bed reactors, the catalyst activity reduces by 10-fold according to basic mass transfer models using experimental values of the intrinsic rate constant, as shown in figure 4. To match the catalyst productivity of a slurry reactor, one would need to build a fixed-bed reactor with ten times the volume - not practical for a commercial scale system. In addition to using a fixed-bed reactor, we wanted to ensure that the solid-acid catalyst was both robust as well as benign (i.e. environmentally fiiendly). 

The activity tests of liquid-phase oxidation of aqueous phenol solution were conducted in a semibatch slurry reactor at operating conditions given in the caption of Figure 1. The experimental apparatus, the procedure of these measurements and the analysis of the reaction samples are described in detail in a preceding paper [6]. Additional kinetic and mechanistic investigations were carried out in an isothermal, differentially operated "liquid-saturated" fixed-bed reactor [8, 9] which was packed with a pretreated EX-1144.3 catalyst (Sfld-Chemie... 

Figure 1. Relative activities of some experimental and commercial catalysts for oxidation of aqueous phenol solutions in a semibatch slurry reactor. Operating conditions T 403 K p(02) ...

The experimental system, Figure 1, comprised a semi-batch slurry reactor with mechanical stirring and gas sparging. The particulars for the reactor include(24) ... 

FIGURE 4.3. Radiative flux distribution in an empty annular reactor (Reprinted from Chem. Eng. Joiirn., 90, M. Salaices, B. Senano and H.I. de Lasa, Experimental evaluation of photon absolution in an aqueous TiOa slurry reactor, 219-229, Copyright 2002, with permission from Elsevier). 

Salaices, M., Senano, B., and de Lasa, H., 2002, Experimental evaluation of photon absorption in an aqueous TI02 slurry reactor, Chem. Eng. J., 90 219-229. 

On the basis of the experimental results, the authors predicted a reactor performance for MBE production of up to 12000kgm h depending on pressure and temperature even at moderate temperature differences in the microstructured heat exchanger. This corresponds to a PI of two orders of magnitude compared to a standard batch slurry reactor with a typical specific productivity of 125 kgm h ... 

Saxena, S.C., Patel, D., Smith, D.N., and Ruether, J.A. (1988), An assessment of experimental techniques for the measurement of bubble size in a bubble slurry reactor as applied to indirect coal liquefaction, Chemical Engineering Communications, 63 87-127. 

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