Carbon gravimetric factors

Ash and Inorganic Constituents. Ash may be measured gravimetdcaHy by incineration in the presence of sulfudc acid or, more conveniendy, by conductivity measurement. The gravimetric result is called the sulfated ash. The older carbonate ash method is no longer in use. Ash content of sugar and sugar products is approximated by solution conductivity measurements using standardized procedures and conversion factors. 

Rostrup-Nielsen and Pedersen (209) recently studied sulfur poisoning of supported nickel catalysts in both methanation and Boudouard reactions by means of gravimetric and differential packed-bed reactor experiments. In their gravimetric experiments a synthesis mixture (H2/CO/He = 5/7/3) containing 1-2 ppm H2S was passed over a catalyst pellet of 13% Ni/Al203-MgO at 673 K and 1 atm. The rates of Boudouard and methanation reactions were determined from weight increases and exit methane concentrations respectively. In the presence of 2 ppm H2S a factor of 20 decrease was observed in both methanation and Boudouard rates over a period of 30-60 min. However, the selectivity or ratio of the rates for Boudouard and methanation reactions was constant with time. From these results the authors concluded that the methanation and Boudouard reactions involve the same intermediate, carbon, and that sulfur blocks the sites for the formation of this intermediate. 

In this expression, bd and bc refer to the appropriate anodic and cathodic Tafel constants. Comparison of weight loss data collected as a function of exposure time determined from R , Rf from EIS, and gravimetric measurements of mild steel exposure to 0.5 M H2S04 are often within a factor of two. This suggests that use of Rn in the Stern-Geary equation may be appropriate for the estimation of corrosion rate (147-150). However, Rn measurements may underestimate corrosion rates. / p is often measured at effective frequencies of 1(T2 Hz or less in linear polarization or EIS measurements, while Rn is measured at 1 Hz or greater. An example of this is provided in Fig. 57, which shows the corrosion rate of carbon steel in 3% NaCl solution as a function of exposure time determined by EIS, linear polarization, noise resistance, and direct current measurement with a ZRA. Among these data, the corrosion rates determined by noise resistance are consistently the lowest. 

In the literature, there are reports of work concerned with the measurement of oxoacidic properties of ionic melts by gravimetric measurements of the solubility of acidic gases in these media [76, 77], The solubility of sulfur(VI) oxide in molten sodium phosphates was determined by the gravimetric method [76], A correlation was obtained between the melt basicities and the solubility of gaseous acid S03 in them. Iwamoto reported the estimation of the basic properties of molten salt by measurements of acidic gas solubilities (carbon dioxide and water) in them [77], However, similar methods cannot be used widely, owing to two factors. The first of these consists in the fact that the solubility of any gas in a liquid phase obeys Henry s law. Let us consider the following system of reactions ... 

Yaghi and coworkers have shown that MOF-177 exhibits a CO2 sorption capacity of up to 33.5 mmol CO2 per gram of sorbent material at room temperature and 42 bar, surpassing the benchmark materials zeolite 13X and activated carbon MAXSORB by a factor of over 1.5 in both gravimetric and volumetric capacities (Figure 4a). ° Significantly, under the same conditions of temperature and... 

Besides the gravimetric dehvery an important measure of the effectiveness of the storage cycle is the enhancement factor, defined as the ratio of dehvery from an adsorbent-packed container to that from an identical one filled with bnlk gas, operating between 30 and 1.5 bar. To determine this factor we consider a container packed with activated carbon with a bed voidage of 0.26 (the close packed value), and assume the carbon to comprise of macroporosily 0.26, in which the fluid phase density is that of the bulk fluid. Figure 4 (a) depicts the... 

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