Controlled semi-batch solution

Controlled and Uncontrolled Semi-batch Solution Copolymerization of Styrene with Methyl Acrylate... 

All polymerisations were carried out in nitrogen purged xylene solutions in a thermostatically controlled one litre glass reactor. Semi-batch processes were carried out in a similar reactor which was provided with calibrated peristaltic pumps (computer controlled when necessary) for delivering the monomer feeds. Typically, experiments were carried out at 80°C with monomer concentrations which gave solids contents in the range 10 - 60% at 100% conversion. 

In semi-batch operation, the SCISR is first filled with a solution of sodium silicate with certain concentration, and then a sulfuric acid solution of a given concentration is dripped at a certain rate into the reactor to react with the sodium silicate at a controlled temperature. The reaction continues for a certain interval of time after the dripping has finished. Stirring is then stopped for ageing of the precipitate for a term, and then the precipitate is sampled and the sample is measured with a laser particle-measuring instrument of FAM type to obtain the sizes and size distribution of the particles in the wet product. 

A solution of the semi-batch reactor model equations yields the results that would be expected from a real reactor. If the control action has been effective, p should remain constant. Any error in the computation of the exact amount of the required... 

The experiments were carried out in a semi-batch stirred reactor with continuous oxygen feed. The reactor is a one liter Pyrex flask with flattened bottom and baffles which is fitted with five standard 24/40 necks to accomodate the gas inlet, gas vent, sampling tube, and pH electrode. The reactor is immersed in a standard water bath for temperature control. Gas is fed at a flow rate of 3.0 + 0.1 1/min through a rotameter. The solution is stirred at 1620 rpm. 

Gladkii(16) at the State Scientific Research Institute of Industrial and Sanitary Gas Cleaning at Moscow did work on the three-phase calcium sulfite slurry oxidation system, finding that the liquid phase oxidation (pH 3.6-6) is first order with respect to the sulfite species. He pointed out, on the basis of pH versus time data from his semi-batch reaction, that the slurry oxidation had different periods in which either reaction kinetics or solid-liquid mass transfer controlled the oxidation rate. He also presented an omnibus empirical correlation between pH, temperature, and the liquid phase saturation concentration of calcium sulfite solution for predicting the slurry oxidation rate. The catalytic effect of manganese... 

A number of laboratory studies have been recorded recently aimed at characterizing the kinetics of both the chemical reaction and crystallization steps in a reaction crystallization process. Examples of liquid phase reactions studied for this purpose are the crystallization of salicylic acid from aqueous solutions of sodium salicylate using dilute sulphuric acid (Franck et al, 1988) and the crystallization of various calcium phosphates by reacting equimolar aqueous solutions of calcium nitrate and potassium phosphate (Tsuge, Yoshizawa and Tsuzuki, 1996). Several aspects of crystal size distribution control in semi-batch reaction crystallization have been considered by Aslund and Rasmuson (1990) who studied the crystallization of benzoic acid by reacting aqueous solutions of sodium benzoate with HCl. An example of crystallization arising from a gas-liquid reaction in an aqueous medium is the precipitation of calcium carbonate from the reaction between calcium hydroxide and CO2 (Wachi and Jones, 1995). 

The ratio of API/polymer solution (solvent) to antisolvent is one of the most important factors for the success of the precipitation process. For continuous process, it is controlled by the feed rates of the APFpolymer solution and the antisolvent into the high-shear mixing chamber and is generally constant for the process. For semi-batch... 

After these estimates, it would be advisable to do bench scale experiments in a semi-batch reactor under well controlled conditions. One should measure the concentrations of the main product P and the byproduct X as functions of time, for various feed rates. From these data one may find the additional information require to predict more accurately the maximum feed rate that can be allowed to obtain a given selectivity. One will need a numerical solution of s. (3.25a) and (3.25b) now. One can also proceed in a purely empirical manner. Since Ais process is apparently not very sensitive to scale-dependent factors, the bench scale results may be applied with confidence on the commercial scale. 

The two solutions are identical. Hence, for a long time no importance was attributed to the use of a kinetic approach for describing batch polycondensations starting from monomers, and the statistical approach was preferred. Of course, chemical engineers had to deal with semi-batch and continuous stirred tank reactors where the statistical approach, although possible, is cumbersome and error-prone, so a few papers appeared in the 1960s dealing with kinetically controlled linear polycondensations [274—276]. 

Copolymers from styrene and butadiene (SBRs) with a more or less random comonomer distribution are produced either in an emulsion polymerization process (cold or hot E-SBR), a free-radical polymerization, which however gives crosslinked polymers, or in a solution process using lithium initiators (S-SBR). There are continuous processes [157,158,160-166] as well as (semi-) batch processes (167,168) with a controlled feed of butadiene [133, 169] to maintain a constant monomer ratio. Randomizers are often used [131, 170] to control the comonomer distribution. 

Previous studies have shown that a strict control of the preparation conditions is necessary to control the crystals morphology of heteropolycompounds (HPC) and therefore their textural properties (i.e. specific area, porous volume and pore size distribution) [1,2]. In this work we try to clarify this point using a perfectly stirred instrumented semi-batch reactor in order to prepare a series of CS3PM012O40 Keggin heteropolysalts starting from aqueous solutions of H3PM012O40 and CS2CO3. 

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