Carbon content pore distribution

The difference observed in retention on the branched and unbranched phases are caused exclusively by the structure of bonded molecule because other factors can be neglected. The basic features of packings of both types, i.e. carbon content, pore size distribution, coverage, specific surface area, the quality of columns packed with these phases, loadability and rate of equilibration are similar. 

Effectiveness of selective adsorption of phenanthrene in Triton X-100 solution depends on surface area, pore size distribution, and surface chemical properties of adsorbents. Since the micellar structure is not rigid, the monomer enters the pores and is adsorbed on the internal surfaces. The size of a monomer of Triton X-100 (27 A) is larger than phenanthrene (11.8 A) [4]. Therefore, only phenanthrene enters micropores with width between 11.8 A and 27 A. Table 1 shows that the area only for phenanthrene adsorption is the highest for 20 40 mesh. From XPS results, the carbon content on the surfaces was increased with decreasing particle size. Thus, 20 40 mesh activated carbon is more beneficial for selective adsorption of phenanthrene compared to Triton X-100. 

FIGURE 6.4 Variation of pore distribution with carbon content. 

Catalyst Characterization. Carbon contents were determined by the Carlo Erba method and sulfur content by high temperature combustion In O2 (ASTM-D1552-64). Surface area and pore volume distribution were measured via N2 adsorption desorption Isotherms (4). ESR measurements were carried out with a modified Varian Radical Assay Spectrometer at both 77 K and room temperature (3). 

In seawater, the differences between activities and concentrations must always be considered (cf. Sect. 15.1.1). The activity coefficients for monovalent ions in seawater assume a value around 0.75, for divalent ions this value usually lies around 0.2. In most cases of practical importance, the activity coefficients can be regarded with sufficient exactness as constants, since they are, over the whole range of ionic strengths in solution, predominately bound to the concentrations of sodium, chloride, and sulfate which are not directly involved in the calcite-carbonate-equilibrium. The proportion of ionic complexes in the overall calcium or carbonate content can mostly be considered with sufficient exactness as constant in the free water column of the ocean. Yet, this cannot be applied to pore water which frequently contains totally different concentrations and distributions of complex species due to diage-netic reactions. 

FIGURE 9.4 Variation of pore distribution with carbon content. (From Berkowitz, N., An Introduction to Coal Technology, Academic Press, New York, 1979.)... 

The components of the SEI film between the carbon negative electrode and electrolyte depend on the carbon material and the electrolyte. Both the carbon material and the electrolyte determine the species at the surface, the particle shape and size, the surface area and pore distribution, the ratio of open pores, the heteroatoms, and the ash content. The performance of the SEI film affects not only irreversible capacity but also reversible capacity, rate capability, and safety performance. 

The most common characterization techn iques used in refineries to monitor the changes in catalyst activity during commercial operation are textural properties (surface area, pore volume, average pore diameter, and pore size distribution) determined by nitrogen adsorption/desorption metals content (mainly Ni and V) by atomic absorption and carbon content by combustion. There are more advanced characterizations techniques that are mostly employed by researchers for more detailed studies of catalyst deactivation such as Nuclear Magnetic Resonance (NMR), x-ray Photoelectron Spectroscopy... 

In addition to surface area, pore size distribution, and surface chemistry, other important properties of commercial activated carbon products include pore volume, particle size distribution, apparent or bulk density, particle density, abrasion resistance, hardness, and ash content. The range of these and other properties is illustrated in Table 1 together with specific values for selected commercial grades of powdered, granular, and shaped activated carbon products used in Hquid- or gas-phase appHcations (19). 

The physicochemical properties of carbon are highly dependent on its surface structure and chemical composition [66—68], The type and content of surface species, particle shape and size, pore-size distribution, BET surface area and pore-opening are of critical importance in the use of carbons as anode material. These properties have a major influence on (9IR, reversible capacity <2R, and the rate capability and safety of the battery. The surface chemical composition depends on the raw materials (carbon precursors), the production process, and the history of the carbon. Surface groups containing H, O, S, N, P, halogens, and other elements have been identified on carbon blacks [66, 67]. There is also ash on the surface of carbon and this typically contains Ca, Si, Fe, Al, and V. Ash and acidic oxides enhance the adsorption of the more polar compounds and electrolytes [66]. 

The soil-water partition coefficient, soil-water is a conditional and not a fundamental physicochemical compound property. Xsoii-water is included here because of its great practical significance. Its value depends on a number of soil and solution characteristics, such as the organic carbon (OC) or organic matter (OM) content, clay content and type, pore volume, pore size and distribution, and solution conditions. soil—water can be defined as the ratio of the sorbate s mass sorbed per unit volume of soil to the mass dissolved per unit volume of aqueous phase with both phases at equilibrium ... 

A large number of heterogeneous catalysts have been tested under screening conditions (reaction parameters 60 °C, linoleic acid ethyl ester at an LHSV of 30 L/h, and a fixed carbon dioxide and hydrogen flow) to identify a suitable fixed-bed catalyst. We investigated a number of catalyst parameters such as palladium and platinum as precious metal (both in the form of supported metal and as immobilized metal complex catalysts), precious-metal content, precious-metal distribution (egg shell vs. uniform distribution), catalyst particle size, and different supports (activated carbon, alumina, Deloxan , silica, and titania). We found that Deloxan-supported precious-metal catalysts are at least two times more active than traditional supported precious-metal fixed-bed catalysts at a comparable particle size and precious-metal content. Experimental results are shown in Table 14.1 for supported palladium catalysts. The Deloxan-supported catalysts also led to superior linoleate selectivity and a lower cis/trans isomerization rate was found. The explanation for the superior behavior of Deloxan-supported precious-metal catalysts can be found in their unique chemical and physical properties—for example, high pore volume and specific surface area in combination with a meso- and macro-pore-size distribution, which is especially attractive for catalytic reactions (Wieland and Panster, 1995). The majority of our work has therefore focused on Deloxan-supported precious-metal catalysts. 

In these adsorbents an increase in carbon deposit content leads to reduction of the total pore volume, but an enhancement of the specific surface area (Sbet) and contribution of nanopores because the FDA value increases. A noticeable increase in nanoporosity of these carbosils is accompanied by significant changes in the pore size distributions (PSDs) at Rp < 2 nm (Figure 2). 

Analysis of the breakthrough dynamics for TBB and DMMP on carbon beds with different amounts of pre-adsorbed NaCl and different air stream relative humidity, shows that NaCl exhibits deleterious effects at any humidity. However, at low amounts of NaCl these effects are insignificant. This can be caused by the distribution of NaCl at the entrances of pores, reducing penetration of organics into pores. At low NaCl contents, its negative effects are stronger for DMMP than for TBB. 

Figure 6.15. Influence of GDL pore-former content on cell performance of a H2/02 single cell (0) 0 mg/cm2, (o) 3 mg/cm2, ( ) 5 mg/cm2, (A) 7 mg/cm2, and (V) 10 mg/cm2 pore-former loading 5 mg/cm2 carbon loading in the GDL and 0.4 mg Pt/cm2 in the catalyst layer [15]. (Reprinted from Journal of Power Sources, 108(1-2), Kong CS, Kim DY, Lee HK, Shul YG, Lee TH. Influence of pore-size distribution of diffusion layer on mass-transport problems of proton exchange membrane fuel cells, 185-91, 2002, with permission from Elsevier and the authors.)...

Three extraction experiments, runs 11-13, were conducted with carbon dioxide. Run 12 was conducted at a reduced pressure of 0.93 and a reduced temperature of 1.05 for 13 h. The catalyst coke content was reduced from 17.5% to 11%, where the coke was primarily removed from pores of 9.6 nm diameter. This represented a 37% removal of coke from the catalyst and resulted in a bimodal pore size distribution with a pore volume of 0.22 nr/g and a surface area of 137 mz/g. The changes in the pore size distribution are shown in Fig. 1. The other two extractions with carbon dioxide... 

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