Surface area activity

Liquid-solid chromatography (LSC). This process, often termed adsorption chromatography, is based on interactions between the solute and fixed active sites on a finely divided solid adsorbent used as the stationary phase. The adsorbent, which may be packed in a column or spread on a plate, is generally a high surface area, active solid such as alumina, charcoal or silica gel, the last... 

For their experimental investigation of flow interruption, Haure et al. (1989) chose the catalytic oxidation of S02 over a high-surface-area activated carbon catalyst. Several research groups have studied this catalytic reaction and kinetics are available. It proceeds rapidly at 25°C and is controlled, at least partially, by 02 transport through the liquid phase. 

Enter the pores of the high-surface area activated carbons ... 

Hirano, S., K.S. Young, A. Kwabena and J.A. Schwarz, The high surface area activated carbon hydrogen storage system. Frontiers Sci. Ser., 7 (New Energy Systems and Conversions), 67-72, 1993. 

Otowa, T., Development and application of high surface area activated carbon. Hyoumen (Surface), 34(2), 62-65 (1996). 

The measured uptake of CPA and PTA over the three activated carbons [55] is shown in Figure 6.28, and the trends predicted by the RPA model in Figure 6.27 are at least qualitatively observed. However, at high pH, over the two highest-surface-area carbons (CA and KB), uptake is about half of that predicted by the RPA model. The discrepancy was explained [55] by steric exclusion of the large Pt ammine complexes, believed to retain two hydration sheaths [15,19], from the smallest micropores of the high-surface-area activated carbon. 

Reaction between metal oxide vapor and solid carbon. A novel method of preparation of ultra-high surface area carbides55-59 involves the reaction of solid carbon with vaporized metal oxide precursors like Mo03 or WO2. The synthesis uses high specific surface area activated carbons and the final product appears to retain a memory of the porous structure of the starting material. The carbon acts like a skeleton around which the carbides are formed, and catalytically active samples with surface areas between 100 and 400 m2g 1 are generated. Materials prepared by this method are described by Ledoux et al. (chapter 20). 

Owing to its large surface area, activated charcoal can adsorb many drugs and poisons. It is most effective if given in a ratio of at least 10 1 of charcoal to estimated dose of toxin by weight. 

Figure 10 shows the comparison of the surface activities of the two catalysts on the heavier feedstock, Synthoil liquid. In this case the unit surface area activity of the Monolith catalyst is greater than that of the Nalcomo 474 catalyst. This behavior is different from that observed on the Raw Anthracene Oil, and as further discussion will show, this difference in the superiorities of the Monolith catalyst on the two feedstocks throws light on some interesting observations of this study. 

To have a quantitative idea of the higher unit surface area activity of the Monolith catalyst, rate constants based on surface area were considered essential to know. To accomplish this, the global reaction kinetics of desulfurization and denitrogen-ation were determined. For the desulfurization the following three kinetic models, as suggested in the literature, were tested to determine which best represented the data of this study. 

Reasons for the Higher Observed Unit Surface Area Activity of the Monolith Catalyst. There can be three main reasons ... 

Activity per Unit Surface Area for Gas Oil Cracking. A second order kinetic conversion parameter (conversion + 100 - conversion) was used (13) to monitor gas oil cracking activity. The activity relationship as a function of surface area and catalyst composition is described in Figure 4. As expected, activity increased linearly with surface area. Activity per unit surface area depended on composition and increased with increasing alumina content. 

Type I isotherms are characteristic of microporous solids having relatively small external surface area (activated carbons, molecular sieve zeolites, metal organic frameworks, etc.). They are usually obtained by most gases and vapors on activated carbons. 

The weighed amount of catalysts and the gas flow should be adjusted to the essential features of the catalyst, assigned to the catalytic activity (e.g. surface area, active component, dopant, etc.). 

O GRADY AND WENNERBERG High-Surface-Area Active Carbon... 

Figure 1. High surface area active carbon.

Table II. Typical Adsorptive Properties High Surface Area Active Carbons ...

Figure 3. High surface area active carbon. Total magnification x 145,480.

TOTAL SURFACE AREA, ACTIVE SURFACE AREA, POROSITY,... 

The use of large-surface area activated charcoal or carbon (approximately 500-1500 m2/g), either as powder activated carbon (PAC) or granular activated carbon (GAC), is the most popular adsorption technique. It is a relatively simple, low-cost, and widely applicable method of pollutant removal, and the literature is replete with descriptions of applications. The GAC version is mostly used in effluents that have already received normal biological treatment... 

Hu, Z., and Srinivasan, M. P., Mesoporous high-surface-area activated carbon, Microporous and Mesoporous Materials 43 (2001) pp.267-275. 

The two-stage process was licensed by Mitsui Mining Company (MMC) in Japan in 1982, and by 1993 a modified form of the process was installed in four commercial plants in Japan and Germany [58]. The granular carbon or activated coke used in this process has a surface area of initially 150 to 250 mVg, which is much lower than that of commercial activated carbons. It is produced from a bituminous coal and a pitch binder. Low surface area carbons have been found to be the most effective in this process they are cheaper than high surface area activated carbons, they retain their SO2 adsorption capacity more efficiently on repeated cycling, and their relatively low porosity contributes to strength and abrasion resistance. 

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