Carbon black calorimetric heats

Fig. XVn-21. (a) Differential heat of adsorption of N2 on Graphon, except for Oand , which were determined calorimetrically. (From Ref. 89.) (b) Differential heat of adsorption of N2 on carbon black (Spheron 6) at 78.5 K (From Ref. 124).

Fig. 2.11 Curves of the differential enthalpy of adsorption of nitrogen against surface coverage 0 (= for samples of Sterling carbon black heated at the following temperatures (a) 1500°C (fc) 1700°C (c) 2200 C (d) 2700°C. The curve for 2000°C was similar to (c). but with a lower peak. The calorimetric temperature was 77-5, 77-7, 77-4, 77-4 K in (a), (fc), (c) and (d) respectively.

Fig. 2.13 Adsorption of nitrogen on a carbon black before graphitiz-ation. - The difTerential heat of adsorption Ji, plotted against n/n , was determined calorimetrically at 78 K (O, , A) and was also calculated from the isotherms at 78 6 and 90-1 K (+ ). (Courtesy Joyner and Emmett.)...

The data shown in Figure 9.10 indicate both the kind of data that may be obtained by direct calorimetric study of gas adsorption and some evidence of the effect of preheating on the properties of surfaces. The figure shows the calorimetric heat of adsorption of argon on carbon black. The broken line indicates the behavior of the untreated black, and the solid line is the same adsorbent after heating at 2000°C in an inert atmosphere, a process known as graphitization. The horizontal line indicates the heat of vaporization of argon. 

FIG. 9.10 Calorimetric heats of adsorption as a function of coverage for argon on carbon bis at 78K. The dashed line represents untreated black the solid line is after graphitization at 2000° The horizontal line is the heat of vaporization of argon. (Redrawn with permission from R. Beebe and D. M. Young, J. Phys. Chem., 58, 93 (1954).)... 

Adsorption of oxygen, at room temperature, on samples of NiO(200°) or NiO(260°) containing preadsorbed carbon monoxide changes the color of the oxides to black and increases the electrical conductivity from 10-1 to 1.6 x lO- ohm-i cm-i (2S, 41). Calorimetric heats of adsorption of oxygen are much higher (Table V) (Fig. 16) than in the... 

The same sequence of adsorptions (O2-CO) was also studied on the surface of NiO(250°) [41). As in the case of NiO(200°), adsorption of carbon monoxide on the sample containing preadsorbed oxygen (1.90 cm /gm) (Table II) changes the color of the sample from black to green and decreases its electrical conductivity (1.8 x 10- ohm-i cm- ) to the low initial value. However, this time, carbon dioxide is found in the cold trap placed near the sample. Calorimetric results reported in Table II indicate also that carbon monoxide interacts with preadsorbed oxygen since the heats of adsorption of carbon monoxide are higher on the black sample (Table II) than on the pure surface of NiO(250°) (Fig. 12). 

In this section are reported the results of a calorimetric study of the catal3d)ic oxidation of carbon monoxide on a divided nickel oxide [NiO(200°)] at 200° (84). At this temperature, carbon monoxide reduces the oxide with the formation of gaseous carbon dioxide. As the reduction extent increases, the color of the sample changes from yellowish green to black and the solid becomes ferromagnetic. Differential heats of reduction decrease rapidly from an initial value of 45 to 15 kcal/mole (Fig. 33). Calorimetric curves recorded during the reaction of doses A to G (Pig. 33) are reported in Fig. 34. Differential heats for doses... 

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