Intercalation of sulfuric acid

In the case of intercalation reactions, the nanotexture of the host carbon materials has a strong effect. The intercalation of sulfuric acid into natural graphite can proceed at room temperature in concentrated sulfuric acid with a small amount of oxidant, such as nitric acid. The resulting intercalation compound is commonly used in industry for the preparation of exfoliated graphite [32], However, in order to intercalate sulfuric acid into carbon fibers, electrolysis is needed [145,146], Potassium as a vapor, on the other hand, can be easily intercalated in various carbon materials, even in low-temperature-treated carbon fibers [147],... 

Starting natural graphite from Zavalie deposit in, Ukraine was chemically intercalated in sulfuric acid. Potassium persulphate was used as an oxidizer. Thermal expansion of graphite was performed at 900°C [3], Carbon content in the experimental samples was of about 99.0%. 

In order to evaluate the total acidity, TPD- NH3 was carried out. The desorbed amount of NH3 was also compared in Table 1. In the case of S-xTi series, it is evidenced that the amount of desorbed ammonia increases with the added amount of sulfate ion during the preparation. In other words, the different Ti/clay ratio also induced the different amount of sulfuric acid added. This result shows that the different amount of sulfate intercalated contributes to the increase of the acidity. 

To decrease the peak widths of H NMR spectra of substances adsorbed on graphite surface (Turov et al. 1991a-c), water, benzene, and acetonitrile were adsorbed on the surface of EG (Figure 3.47) produced by fast heat treatment of a crystalline graphite powder intercalated with sulfuric acid. 

TABLE 12.2 Values of molar enthalpies and entropies of formation of sulfuric acid-graphite intercalation compounds according to the reaction [139] ... 

Historically, the chemistry of layered intercalates began in 1840 with the report that graphite was able to intercalate sulfuric acid between successive layers of its chicken wire mesh. It was not until after the 1960s that serious interest was aroused by intercalates, following the realisation that guest intercalation may significantly alter the host s chemical, catalytic, electronic and optical properties. This is especially true when the host properties are dependent on its layered structure. In the case of graphite, for example, its use as a dry , low-temperature lubricant has come about because of the ease... 

GICs have been first discovered from the reaction of graphite with sulfuric acid more than 150 years ago.30 In the long history of GICs research, a huge number of compounds have been yielded with a large variety of donors and acceptors, in which alkali metals, alkaline earth metals, transition metal chlorides, acids, and halogens are involved as typical intercalates. 

The orthophosphates M(HP04)2 are practically insoluble in mineral acids (except HF) and can be precipitated from strong acid solutions as hydrates with one or two water molecules. This is a method for separating Zr and Hf from other metals (except Pa). The Hf salts are less soluble than those of Zr and accumulate in the precipitate from sulfuric acid solution. Both Zr(HP04)2 H20 phases have a layered structure and can be intercalated by quite large molecules, such as phen or aminoferrocene. " The pillared materials so obtained have pore dimensions approaching those found in... 

Ihble 5. Relationship of intercalation potentials U (vs. SHE) to sulfuric acid molarity for three host lattices. 

Due to the action of an oxidizing agent electrons are drawn from the graphite lattice and anions beside neutral species are intercalated. These processes can be driven in a direct reversible electrochemical way, as has been demonstrated for carbon in concentrated sulfuric acid [39]. 

---