Reaction calorimeter reduction

Heat-flow calorimetry may be used also to detect the surface modifications which occur very frequently when a freshly prepared catalyst contacts the reaction mixture. Reduction of titanium oxide at 450°C by carbon monoxide for 15 hr, for instance, enhances the catalytic activity of the solid for the oxidation of carbon monoxide at 450°C (84) and creates very active sites with respect to oxygen. The differential heats of adsorption of oxygen at 450°C on the surface of reduced titanium dioxide (anatase) have been measured with a high-temperature Calvet calorimeter (67). The results of two separate experiments on different samples are presented on Fig. 34 in order to show the reproducibility of the determination of differential heats and of the sample preparation. 

Application of the Mettler RC1 Reaction Calorimeter in Optimizing a Process for the Reduction of Methyl (S)-Phenylglycinate. The sodium borohydride reduction of methyl (S )-phenylglydnate (hydrochloride salt) to the corresponding primary amino alcohol (Scheme 4) had been worked out in the laboratory and taken to a pilot plant scale where an unexpected exotherm was observed. 

In order to understand, and avoid, the exotherm observed in the reduction reaction, the following process steps were examined using the Mettler RC-1 reaction calorimeter ... 

The obtained A 7 a() value and the energy equivalent of the calorimeter, e, are then used to calculate the energy change associated with the isothermal bomb process, AE/mp. Conversion of AE/ibp to the standard state, and subtraction from A f/jgp of the thermal corrections due to secondary reactions, finally yield Ac f/°(298.15 K). The energy equivalent of the calorimeter, e, is obtained by electrical calibration or, most commonly, by combustion of benzoic acid in oxygen [110,111,113]. The reduction of fluorine bomb calorimetric data to the standard state was discussed by Hubbard and co-workers [110,111]. 

The bomb calorimeter provides the most suitable and accurate apparatus for determination of the calorific values of solid and liquid fuels. Since the combustion takes place in a closed system, heat transfer from the calorimeter to the water is complete, and since the reaction is one between the fuel and gaseous oxygen, no corrections are necessary for the heat absorbed during the reduction of the oxidizing agent. In addition, the losses due to radiation can be reduced to comparatively small quantities, and more important, can be determined with a considerable degree of accuracy. Corrections due to the heat evolved in the formation of nitric and sulfuric acids under the conditions existing in the bomb can be determined accurately. 

It is interesting to note that the It eat ot this reduction can be found without having to carry out the particular reaction at all—it can be obtained, as shown b the calculation we ha e just made, from measurement of the heat of combustion of ethylene, the heat of combustion of ethane, and the heat of combustion of hydrogen. Heats of combustion are ordinarily reliable to about 0 5 percent, which in this case would be 2 kcah llie molal heat ot hydrogenation of ethylene has been determined directly by carrying out the hydrogenation reaction (in the presence of a catalyst) in a calorimeter. The value 32.8 0.1 kcal was obtained by this direct method. 

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