Batch screening reactors

Figure 11.26 Plot of the position sensitivity of the degree of conversion for a set of 48 bismuth-molybdate catalysts (same batch) in propylene to acrolein conversion in a Stage II 48-fold-screening reactor (reaction conditions 2% hydrocarbon in air at GHSV of 3000 h-1, column no. 8 contains only inert carrier material).

The mini multi-well batch reactors presented by Desrosiers et al. [45] (Figure 3.12) were applied to the direct amination of benzene to aniline. The screening reactor... 

Information on specific production methods can be found in the literature [Pinna 1998]. Impregnated catalysts are mainly produced batchwise with discontinuous process steps. Therefore, continuous quality control of the individual catalyst batches is vital (e.g., testing of mechanical strength, performance tests in screening reactors). The process developer must pay special attention to transferring the laboratory recipe to industrial catalyst production. Test production should be carried out relatively early... 

To select the most suitable solvent for a desired reaction, screening of various solvents is usually necessary, since the prediction of the best solvents by the simulation is still difficult. The screening has to be condurted to optimize the reaction conditions with respect to (1) the type and scale of the reaction, (2) the stability of the biocatalyst, (3) the hydrophobicity of the solvents, (4) the solubilities of the substrate and product, (5) the recovery of the product and enzyme, (6) environmental and safety concerns, and (7) the cost of the biocatalyst, substrate, and product. For example, to conduct a dehydration reaction using hydrolytic enzyme, a water-free nonaqueous solvent must be selected instead of water. On the other hand, the level of the dehydration should not be too much, as noted previously, to take away the water from enzyme necessary for its activity. Supercritical CO is better to be used in relatively large scale using a flow reactor than using in the very small-scale batch reaction because product recovery in the small-scale reaction in batch CO reactor needs extraction with organic solvents. 

Figure 4.63 Comparison between the results of the screening of different substrates against one catalyst in a batch reactor (white columns) and micro reactor set-up (gray columns) [llOj.

Batchwise operating three-phase reactors are frequently used in the production of fine and specialty chemicals, such as ingredients in drags, perfumes and alimentary products. Large-scale chemical industry, on the other hand, is often used with continuous reactors. As we developed a parallel screening system for catalytic three-phase processes, the first decision concerned the operation mode batchwise or continuous. We decided for a continuous reactor system. Batchwise operated parallel sluny reactors are conunercially available, but it is in many cases difficult to reveal catalyst deactivation from batch experiments. In addition, investigation of the effect of catalyst particle size on the overall activity and product distribution is easier in a continuous device. 

We would like to thank Battelle Memorial Institute for supporting this work and also to the U.S. DOE(OIT) under whose sponsorship this work was begun. We would also like to acknowledge Mr.Todd Hart who conducted most of the batch reactor screening runs and also Mr. Mark Butcher who performed the product analyses. Our deepest appreciation goes to Dr. James F. White for his assistance in the preparation of this paper. 

We evaluated a number of potential catalysts and conditions using xylitol as a model compound in a batch reactor. A catalyst was selected from this initial screening and examined in a continuous trickle-bed reactor to develop operating conditions. Finally, as resources allowed, the catalyst was evaluated in a trickle bed reactor to gain a concept of potential catalyst lifetime. 

Catalyst Screening with Xylitol - Batch Reactor... 

The C-5 sugar alcohols produced from the hydrolysis of hemicellulose are both xylitol and arabitol [6], Equivalence testing was performed with Ni/Re catalyst in the batch reactor to verily similar performance between xylitol and arabitol feedstocks. The operating conditions were 200°C and 8300kPa H2 using the procedure outlined in section Catalyst Screening section. 

Selected conditions and results are shown in Table 2 that are representative of the catalyst performance. Continuous testing of the Ni/Re catalyst compared favorably with the baseline data generated for this catalyst in the batch reactor screening. At 200°C, the overall activity of the catalyst appeared slightly higher in the continuous reactor, achieving 94% conversion at a weight hourly space velocity of 2.5hr 1 (g xylitol/g catalyst/h) and 200°C compared to 88% conversion at an equivalent exposure in the batch reactor of 2.1 hr"1 (g xylitol/g catalyst/h) achieved at the 4 hour sample at 200°C. 

The initial screening of the resin catalysts was done in a batch reactor at supercritical for butene-1 conditions of temperature 155 °C, pressure of 1000 psig and at molar ratio of 1-butene water of 5.5. The reaction was stopped after predetermined period of time and the products analyzed. It was found that under the standard reaction conditions, for all of the catalysts studied, a constant concentration in the sec-butanol concentration was achieved within a 1-2 hour reaction time. Using only the linear section of the concentration-time plot, the one hour result was used to evaluate the catalyst activity, which was normalized as mmol of SBA/ per proton/ per hour (a), as mmol of product/ per gram of dry catalyst/ per hour (b) and mmol of product/ per ml of wet catalyst/ per hour (c). 

A new alternative approach for Stage I screening in liquid phase is the use of bubble column-type reactors. These parallel bubble columns can operate in batch and fed-batch mode regarding the reaction mixture, while a continuous stream of gas is used as reactant (H2, 02, or others) as well as for the intense agitation of the reaction mixture (Figure 11.39). 

The catalytic screening was carried out with high-pressure acetylene in a batch reactor (see Section IV). The range of results are shown in Table I. 

The fulminate is precipitated in the form of greyish needles. When the reaction is complete, the reactor is allowed to stand for approximately 30 min while the contents are cooled. 1-2 1. of water are then poured in and the liquid is decanted from above the precipitated crystals. The precipitate is transferred to a cloth filter and washed with distilled water until completely free of acid. The product is then screened on a silk sieve (approximately 100 mesh/cm2) which retains the larger crystals. The smaller crystals are collected for direct use. The large ones are ground under water, passed through the same sieve and added to the previous batch. 125 parts of fulminate are obtainable from 100 parts of mercury, which corresponds to a yield of 88%. 

Compeau et al. (1990) reported a full-scale slurry-phase PCP remediation. The system consisted of soil washing and screening and resulted in clean soil and wash solution. The wash solution was a slurry containing PCP and < 60-mesh-size soil particles at approximately 20% solids concentration. Slurry was treated subsequently in on-site slurry-phase bioreactors. A 50 m3 slurry reactor was operated in batch mode and inoculated by an uncharacterized PCP-mineralizing culture (107 cells/ml of slurry). After 14 days, 370mg PCP/kg slurry had been degraded to below 0.5 mg/kg. For effective biogradation to occur, inoculation was required. 

Batch-stirred-tank reactors [12-21] are usually used for screening enzymatic reactions in dense gases. The design of the system is shown in Figure 9.2-1. Initially, the reaction mixture was pumped into the reactor and then the enzyme-preparation was added. Finally, dry gas was pumped into the reactor, up to the desired pressure. The initial concentration of the reactant never exceeded its solubility-limit in the gas. 

An important parameter in a number of fields is the study of inorganic phosphate. Recently, Kwan et al. [206,207] have reported on a screen-printed phosphate biosensor based on immobilised pyruvate oxidase (PyOD) for monitoring phosphate concentrations in a sequencing batch reactor system [206] and in human saliva [207]. The enzyme was immobilised by drop-coating a Nation solution onto the working electrode surface this was then covered by a poly(carbamoyl) sulfonate (PCS) hydrogel membrane. 

Then, a survey of micro reactors for heterogeneous catalyst screening introduces the technological methods used for screening. The description of microstructured reactors will be supplemented by other, conventional small-scale equipment such as mini-batch and fixed-bed reactors and small monoliths. For each of these reactors, exemplary applications will be given in order to demonstrate the properties of small-scale operation. Among a number of examples, methane oxidation as a sample reaction will be considered in detail. In a detailed case study, some intrinsic theoretical aspects of micro devices are discussed with respect to reactor design and experimental evaluation under the transient mode of reactor operation. It will be shown that, as soon as fluid dynamic information is added to the pure experimental data, more complex aspects of catalysis are derivable from overall conversion data, such as the intrinsic reaction kinetics. 

Figure 3.12 High-throughput batch reactor used as primary screen for the discovery of aniline cataloreactants. The reactor consists of a circular block with an array of 15 x 10 catalysts [45] (by courtesy of Elsevier Ltd ).

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