Hydrogen glass model

Glass model studies (14) with an upflow air-water system have shown that gas flow plays a significant role in achieving axial mixing in the open spaces between the catalyst tubes and radial mixing within the catalyst tubes both axial and radial mixing increased with an increase in the hydrogen flow rate. 

In the present study, the gas-liquid mass transfer coefficients under the prevailing experimental conditions were estimated using the correlations of Akita and Yoshida (17). The radial dispersion coefficients within the catalyst tubes were measured as a function of gas flow rate in a glass model of the reactor. The details of these measurements will be released in a subsequent publication. Based on this knowledge and an estimated value of the catalytic kinetic constant for solvent hydrogenation at the highest temperature and pressure conditions examined in this study, the minimum gas flow rate required to permit neglecting mass transfer resistances was obtained. Ibis value of the gas flow rate was used in all experiments. 

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As a consequence, the overall penetrant uptake cannot be used to get direct informations on the degree of plasticization, due to the multiplicity of the polymer-diluent interactions. The same amount of sorbed water may differently depress the glass transition temperature of systems having different thermal expansion coefficients, hydrogen bond capacity or characterized by a nodular structure that can be easily crazed in presence of sorbed water. The sorption modes, the models used to describe them and the mechanisms of plasticization are presented in the following discussion. 

Figure 10 shows the instrumental setup used to implement the APP-CLS approach. It consists of (a) a CSTR that is a thermostated 10-mL glass reaction vessel accommodated in a commercially available spectrofluorimeter (a Hitachi F2000 model in this case) (b) a four-channel peristaltic pump with three channels used to dispense the reagent solutions and the fourth to keep the volume of the reaction mixture in the CSTR constant the three reagent solutions are as follows (1) 0.15 M hydrogen peroxide (2) 0.15 M sodium thiocyanate, 0.15 M sodium hydroxide, and 1.95 x 10 3 M luminol and (3) 6.0 x 10 4 M copper(II) sulfate ... 

At the turn of the century, considerable attempts were being made to find suitable membrane models. These models fall into two groups compact, usually liquid ( oil ) and soUd membranes [10, 33, 62, 75] and porous membranes [9]. At the very beginning of the study of compact membranes, the glass electrode was discovered [ 18, 34], whose membrane represented the first observation of marked selectivity for a particular type of ion, here the hydrogen ion. It is interesting that this first ion-selective electrode remains the best and most widely used of all such electrodes. 

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