Chemical Identification of Surface Groups
TL;DR: The surface properties of a surface are influenced by the surface groups and the knowledge of their existence and of their chemistry are important for many technological processes as mentioned in this paper, which is why it is important to have knowledge of these surface groups.
Abstract: Publisher Summary The properties of a surface are influenced by the surface groups and the knowledge of their existence and of their chemistry are important for many technological processes This chapter examines the surface compounds on carbon—microcrystalline carbon, graphite, and diamond—on silica, on titania, and on alumina and silica–alumina Most important and best known among the surface compounds of carbon are those with oxygen and with sulfur Thus, two kinds of surface oxides are known Basic surface oxides are formed always when a carbon surface is freed from all surface compounds by heating in a vacuum or in an inert atmosphere and comes into contact with oxygen only after cooling to low temperatures Acidic surface oxides are formed when carbon is treated with oxygen a temperatures near its ignition point Unambiguous identification of carboxyl groups has been achieved by two reactions of the acyl chlorides: Friedel–Crafts reaction and Schmidt rearrangement
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TL;DR: Aluminas have been used extensively as adsorbenu and active catalysrs and catalyst supponsm the pas as discussed by the authors, and they are used as catalysts for the larter process LS also caralyzed by molybdena-alumina.
Abstract: Aluminas have been used extensively as adsorbenu and active catalysrs and catalyst supponsm the pas. Already in 1197 the aluminadyzed dehydration of ettllnoi was dtscavered by Dutch chermsts: and S;rbatier [3] remewed the use of dumlnas as active cazaiysrs far vanous reacttons UI the second decade of thu century. She that time the applicazions of aluuuas m dycic pmcesses have mcreased tremendously. In tndustrral cualytic pmcesses, alumuus are mostiy used as catalyst suppons [4]. Oxides a d mued oxides ap well as tracuuion mauls and noble meare supported oa alumma. Thuscb. romaa-elumana catalysts are ktng used for the conversion of parafdns to olailnrc hydrocarbons, 10 hydrodealkplation of aromatics. and to a lesser exzm in catalyzic reforming. The larter process LS also caralyzed by molybdena-alumina, a cavlyst system whid is also active for malang toluene and ocher aromatics from satwed hydrocarc bons. It also dyzes the Isomerhation of pm. Great efions are presently be-made to nudy the surface c...
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TL;DR: The influence of surface modification of activated carbon with gaseous ammonia on adsorption properties toward carbon dioxide (CO2) was reviewed in this paper, where two different methods, heat treatment and ammonia treatment (amination) for producing activated carbon had been compared and amination was found to be suitable modification technique for obtaining efficient CO2 adsorbents.
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TL;DR: In this article, wood origin activated carbon was oxidized and then treated with melamine and urea followed by carbonization at 950 degrees C in an inert atmosphere, and the modified carbons revealed significantly enhanced capacitances in 1 M H2SO4 reaching 300 F/g and the capacitance retention ratio is 86% at the current load of 1 A/g.
755 citations
Cites background from "Chemical Identification of Surface ..."
...The numbers of all acidic sites (of various types) were calculated under the assumption that NaOH neutralizes carboxyl, phenolic and lactonic groups [26]....
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...[26] Boehm HP....
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...The role of nitrogen in catalysis is usually linked to its basicity [3,25] and ability to activate oxygen via formation of O superoxide [26,27], which has tremendous effects on oxidation reactions [27]....
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TL;DR: In this article, the chemical structure of phosphorus species in two series of polymer-based and fruit-stone-based carbons obtained by phosphoric acid activation at 400-1000°C were investigated by XPS and solid state 31 P-NMR and 13 C -NMR.
702 citations
Cites background from "Chemical Identification of Surface ..."
...[7] Boehm HP....
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...Pore size and pore volume are important factors for physical adsorption [2–4], while surface chemistry plays a key role in specific adsorption and surface reactions [4–7]....
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TL;DR: The results suggest that with higher carbonized fractions and loading of chars, heavy metal immobilization by cation exchange becomes increasingly outweighed by other controlling factors such as the coordination by pi electrons (C=C of carbon and precipitation.
Abstract: Chars, a form of environmental black carbon resulting from incomplete burning of biomass, can immobilize organic contaminants by both surface adsorption and partitioning mechanisms. The predominance of each sorption mechanism depends upon the proportion of organic to carbonized fractions comprising the sorbent. Information is currently lacking in the effectiveness of char amendment for heavy metal immobilization in contaminated (e.g., urban and arms range) soils where several metal contaminants coexist. The present study employed sorbents of a common biomass origin (broiler litter manure) that underwent various degrees of carbonization (chars formed by pyrolysis at 350 and 700 degrees C and steam-activated analogues) for heavy metal (Cd(II), Cu(II), Ni(II), and Pb(II)) immobilization in water and soil. ATR-FTIR, (1)H NMR, and Boehm titration results suggested that higher pyrolysis temperature and activation lead to the disappearance (e.g., aliphatic -CH(2) and -CH(3)) and the formation (e.g., C-O) of certain surface functional groups, portions of which are leachable. Both in water and in soil, pH increase by the addition of basic char enhanced the immobilization of heavy metals. Heavy metal immobilization resulted in nonstoichiometric release of protons, that is, several orders of magnitude greater total metal concentration immobilized than protons released. The results suggest that with higher carbonized fractions and loading of chars, heavy metal immobilization by cation exchange becomes increasingly outweighed by other controlling factors such as the coordination by pi electrons (C=C) of carbon and precipitation.
651 citations
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1,637 citations
TL;DR: In this article, the infrared spectrum of pyridine coordinately bonded to the surface of acid solids has been determined and a rough estimate of the strength of surface Lewis sites can be inferred.
1,357 citations
TL;DR: In this article, it was shown that the graphitizing and non-graphitizing carbons form two distinct and well-defined classes, and that the differences in structure are apparent from the earliest stages of carbonization, and may be attributed mainly to the formation at low temperatures, in the nongraphitising carbons, of a strong system of cross-linking uniting the crystallites.
Abstract: An investigation of the structure of carbons of different origin treated at temperatures between 1000 and 3000°C has shown that the graphitizing and non-graphitizing carbons form two distinct and well-defined classes. The differences in structure are apparent from the earliest stages of carbonization, and may be attributed mainly to the formation at low temperatures, in the non-graphitizing carbons, of a strong system of cross-linking uniting the crystallites. This leads to a random orientation of the crystallites in a rigid, finely porous mass. In the graphitizing carbons the cross-linking is much weaker, the structure is more compact, and neighbouring crystallites have a strong tendency to lie in nearly parallel orientation. It is shown that crystallite growth occurs by the gradual displacement of whole layer-planes or even of groups of layer-planes. The pre-orientation existing in the graphitizing carbons facilitates this process, enabling the rearrangement of the layer-planes to take place by small stages. It is the principal factor favouring crystallite growth in the graphitizing carbons. In the non-graphitizing carbons crystallite growth is impeded both by the strong cross-linking between neighbouring crystallites and by their random orientation.
912 citations
TL;DR: In this paper, the surface structures of clean (100) and (110) germanium surfaces were observed and the results indicated that these structures were not due to contamination but to the silicon itself.
Abstract: Diffraction patterns obtained from atomically clean germanium surfaces contained half‐integral order beams in (110) azimuths for both (100) and (110) surfaces and in all azimuths for the (111) surface. These results are considered to be due to displacements of surface atoms from their normal bulk lattice positions in the surface plane. Adsorption of oxygen on all of these surfaces extinguished all of the diffraction beams which were not integral order.In addition to the normal surface lattice spacings of clean (111) and (100) surfaces of silicon, there were surface structures with larger spacings, most of which depended on the conditions of ion bombardment and/or subsequent heat treatment. Two such structures have been observed for the (100) surface of silicon; one is a double‐spaced lattice in the (110) azimuth, similar to that for germanium, and the other has a spacing about 8% greater than that of normal silicon and was obtained only after radiation quenching of the crystal from 1000°C. Two large‐spaced structures were observed for the (111) surface. All of these structures were extinguished by exposure to oxygen. Evidence is presented which indicates that these structures were not due to contamination but to the silicon itself.The method of determining the kinetics of gas adsorption from the low‐energy electron diffraction beams is outlined and the calculations of the fractional coverage and sticking probability are presented for oxygen. For silicon crystals, the calculations of surface coverages and sticking coefficients for oxygen were found to depend on the preceding treatments of the crystals. The rate of adsorption of oxygen was proportional to the pressure, at least for pressures below 10‐6 mm Hg, and depended on the preceding treatments of the crystals. After oxygen adsorption, the clean germanium surface could be regenerated by heating at 500°C for 30 min and for silicon it was regenerated by heating at 900°C for a few minutes. A comparison with results of other observers is given.
660 citations