Pretreatment compensation effect

In some cases the estimated temperature of preparation of solid catalysts seems to be close to 0 and therefore in accordance with the foregoing working hypothesis moreover, adsorption measurements on some catalysts show a dependence on the temperature of catalyst pretreatraent in accordance with a Boltzmann distribution of their surface centers. However for catalysts such as chlorides (15) and oxides of the type Me2O3 (7), which were first considered to be suitable objects for rationalizing the compensation effect, Equations (10) and (17), which interrelate the overall rate constant k with the temperature 9 of the pretreatment of the catalyst, did not fit the experimental data. 

In many cases a compensation effect is indicated on comparison of the rates of the same reaction at the same type of catalyst after the latter has undergone special pretreatments or has been changed in its composition. In such cases the occurrence of a compensation effect may be expected if different kinds of active surface centers act simultaneously as sites of the catalytic reaction and if the proportions of these different active centers (involving different activation energies) are shifted by means of special pretreatments of the catalyst or by changes in its composition. 

For the other combinations of planes, occurring after pretreatment under other conditions, analogous equations will hold. Cremer (41) has shown that for different distributions of a and E values, equations of the shape of (23) lead to the conclusion that the compensation effect is involved, as did equation (22). 

Figure 14.13. Compensation effects for the Arrhenius parameters of MCP hydrogenolysis on R/Ti02 variously pretreated (see text) , 2-methylpentane A, 3-methylpentane v> n-hexane O, C1-C5 alkanes.

Industrial application of plasma treatment for cotton gray fabric pretreatment results in poorer hand feel and sofmess, but these adverse effects can be compensated by the subsequent finishing process. Plasma treatment can reduce effluents and cost of energy compared with conventional pretreatment processes. In terms of energy use, plasma treatment consumes about 9.8 ml of gasoline per meter of fabric while conventional pretreatment method consumes 62.5 ml of gasoline. In addition, the residues that remain after plasma treatment can be removed easily by the subsequent washing process. The plasma treatment shortens the treatment time when compared with conventional pretreatment with chemicals, but similar results can be achieved (Chen, 2005). 

Preparation of standards If NaHCOa pretreatment is used, add to the standards (approximately 45 mL total volume) 200 mg NaHCC and 2.4 mL of 1 N H2SO4 to compensate both for the slight amoimt of silica introduced by the reagents and for the effect of the salt on color intensity. Dilute to 50.0 mL. 

---