Batch experiments

Usually, diffusivity and kinematic viscosity are given properties of the feed. Geometiy in an experiment is fixed, thus d and averaged I are constant. Even if values vary somewhat, their presence in the equations as factors with fractional exponents dampens their numerical change. For a continuous steady-state experiment, and even for a batch experiment over a short time, a very useful equation comes from taking the logarithm of either Eq. (22-86) or (22-89) then the partial derivative ... 

Several authors have presented methods for the simultaneous estimation of crystal growth and nucleation kinetics from batch crystallizations. In an early study, Bransom and Dunning (1949) derived a crystal population balance to analyse batch CSD for growth and nucleation kinetics. Misra and White (1971), Ness and White (1976) and McNeil etal. (1978) applied the population balance to obtain both nucleation and crystal growth rates from the measurement of crystal size distributions during a batch experiment. In a refinement, Tavare and... 

Gutwald, T. and Mersmann, A., 1990. Determination of crystallization kinetics from batch experiments. In Industrial crystallization 90. Gamiiscli-Partenkirclien, September 1990. Ed. A. Mersmann, Dtisseldorf GVC-VDI, p. 331. 

Nyvlt, J., 1989. Calculation of crystallization kinetics based on a single batch experiment. Collection of Czechoslovakian Chemical Communications, 54, 3187-3197. 

Tavare, N.S. and Garside, J., 1986. Simultaneous estimation of crystal nucleation and growth kinetics from batch experiments. Chemical Engineering Research and Design, 64, 109. 

The distribution coefficient can be determined by batch experiments in which a small known quantity of resin is shaken with a solution containing a known concentration of the solute, followed by analysis of the two phases after equilibrium has been attained. The separation factor, a, is used as a measure of the chromatographic separation possible and is given by the equation,... 

Despite the advantages of continuous cultures, the technique has found little application in the fermentation industry. A multi-stage system is the most common continuous fermentation and has been used in the fermentation of glutamic add. The start-up of a multi-stage continuous system proceeds as follows. Initially, batch fermentation is commenced in each vessel. Fresh medium is introduced in the first vessel, and the outflow from this proceeds into the next vessel. The overall flow rate is then adjusted so that the substrate is completely consumed in the last vessel, and the intended product accumulated. The concentration of cells, products and substrate will then reach a steady state. The optimum number of vessels and rate of medium input can be calculated from simple batch experiments. 

It is very simple to perform batch fermentation in a small flask with a volume of say 200 ml. Now our target is to use a 2 litre B. Braun fermenter. All accessories are shown in Figure 10.5. The fermentation vessel only, as shown in Figure 10.6, with about 250 ml of media without any accessories but with some silicon tubing attached with a filter for ventilation is autoclaved at a 131 °C for 10 minutes at 15psig.9 After that, the system is handled with special care and all accessories attached. Media is separately sterilised and pumped into the vessel. Inoculum is transferred and the batch experiment is started right after the inoculation of seed culture. An initial sample is withdrawn for analysis. 

The batch experiment had neither incoming fresh media nor any product stream leaving the fermentation vessel. A complete experimental set up with a B. Braun Biostat, is shown in the above laboratory experimental set up. The continuous flow of media requires a feed tank and product reservoir. The batch process has many disadvantages such as substrate and product inhibition, whereas in the continuous process the fresh nutrients may remove any toxic by-product formed. 

Example 2.8 Most polymers have densities appreciably higher than their monomers. Consider a polymer having a density of 1040 kg/m that is formed from a monomer having a density of 900 kg/m. Suppose isothermal batch experiments require 2h to reduce the monomer content to 20% by weight. What is the pseudo-first-order rate constant and what monomer content is predicted after 4h ... 

The hrst step is to obtain a good kinetic model for the reaction. To this end, the following batch experiments were conducted in laboratory glassware ... 

A massive but readable classic on chemical kinetics and the extraction of rate data from batch experiments is... 

Example 13.6 The following data were obtained using low-conversion batch experiments on the bulk (solvent-free), free-radical copol)mierization of styrene (X) and acrylonitrile (Y). Determine the copolymer reactivity ratios for this pol5Tnerization. 

Preliminary kinetic studies revealed that the catalyst deactivated it was difficult to achieve a complete conversion of the substrate (sitosterol) in a batch experiment, but the conversion approached a limiting value, depending on the amount of catalyst added. By the addition of higher amounts of the catalyst, higher conversions were obtained even so the standard plots of the substrate conversion versus the mass... 

Bandstra JZ, R Miehr, RL Johnson, PG Tratnyek (2005) Reduction of 2,4,6-trinitrotoluene by iron metal kinetic controls on product distributions in batch experiments. Environ Sci Technol 39 230-238. 

Platinum catalysts were prepared by ion-exchange of activated charcoal. A powdered support was used for batch experiments (CECA SOS) and a granular form (Norit Rox 0.8) was employed in the continuous reactor. Oxidised sites on the surface of the support were created by treatment with aqueous sodium hypochlorite (3%) and ion-exchange of the associated protons with Pt(NH3)42+ ions was performed as described previously [13,14]. The palladium catalyst mentioned in section 3.1 was prepared by impregnation, as described in [8]. Bimetallic PtBi/C catalysts were prepared by two methods (1) bismuth was deposited onto a platinum catalyst, previously prepared by the exchange method outlined above, using the surface redox reaction ... 

In this context, the esterification of 4-(l-pyrenyl)butyric acid with an alcohol to the corresponding ester was investigated [171]. Without the presence of sulfuric acid no reaction to the ester was foimd in the micro reactor. On activating the surface by a sulfuric acid/hydrogen peroxide mixture, however, a yield of 9% was achieved after 40 min at 50 °C. On making the surface hydrophobic by exposure to octadecyltrichlorosilane, no product formation was observed. Using silica gel in a laboratory-scale batch experiment resulted in conversion, but substantially lower than in the case of the micro reactor. The yield was no higher than 15% (40 min ... 

The conversions observed followed the sequence of reactivity known from batch experiments carried out in advance. For example, only 15% conversion was found for the less reactive reagent benzoylacetone in the micro reactor experiment, while 56% was determined when using the more reactive 2,4-pentanedione (batch syntheses 78% and 89%, respectively) [8]. Using the stopped-flow technique (2.5 s with field applied 5.0 s with field turned off) to enhance mixing, the conversions for both syntheses were increased to 34 and 95%, respectively. Using a further improved stopped-flow technique (5.0 s with field applied 10.0 s with field turned off), the conversion could be further enhanced to 100% for the benzoylacetone case. For the other two substrates, diethyl malonate and methyl vinyl ketone, similar trends were observed. 

OS 63] [R 27] ]P 46] A 43% conversion was achieved by micro-channel processing, while both batch experiments and expectation from intrinsic kinetics indicated conversions close to 90% [117] 80% was achieved by micro-channel processing with an additional micro mixer (see the Section Setting micro mixing prior to reaction, below). 

Batch Experiments with Thermomorphic Systems. As a reference, we tested the hydroformylation of 1-octene in a completely homogeneous system using the same rhodium triphenylphosphine catalyst that is used for hydroformylation of lower aldehydes. This is sample R39 in Table 28.1, and gives us a baseline to compare the performance of our systems in terms of conversion and selectivity. To maintain consistency, we performed all the reactions at 100°C using the same amounts of reactants, catalysts and solvents. Under these conditions we only detected aldehyde products no alcohol or alkene isomers were formed. 

Of particular note we found improved selectivity with certain extiuded carbon supports versus granular carbons, graphitic carbons, metal oxides (titaiua and zircoitia), and carbon treated with zircoiua. Data shown in Figures 34.6 and 34.7 were generated in batch experiments using Ni/Re as catalytic metals. In Figure 34.6a,... 

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. 

A much better approach for the estimation of specific rates in biological systems is through the use of the integral method. Let us first start with the analysis of data from batch experiments. 

The aerobic degradation of formaldehyde in wastewater has been studied by different authors in both continuous22 and batch experiments.23 25 The degradation can occur by two possible paths (see Equations 19.10 and 19.11) ... 

Experimental data are available using an ion-exchange resin catalyst based on batch experiments at 60°C10. These data are presented in Table 5.710. 

The following temperature-time-con version data was obtained for the batch experiments in the gas phase for the isomerization of reactant A to product B. The equilibrium constant for the reaction is large over the temperature range concerned in Table 6.17. 

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