Aliphatic content

D A solid insoluble in ethanol/ benzene azeotrope 25 Predominantly diaromatic and polynuclear perhaps combined through naphthenic bridges, with negligible aliphatic content. 

The nmr analyses of the bottoms products given in Table IV show the material to have a large aliphatic content. The aromatic/aliphatic ratios of the fractions are higher than for the whole coal because of the presence of combined phenol reaction with Tetralin reduces these ratios considerably, presumably by transfer of much of this material to the solvent-range product, but some of it must remain in the bottoms as the aromatic/aliphatic ratio of the composite bottoms product from the fractions is higher than that from the whole coal. It was not possible to calculate the contribution that the diluents, excess solvent and combined phenol, made to the aromatic H, but the large monoaromatic content of the bottoms product must be due, in part, to these. 

With regard to the results of our infrared study, a word of caution is appropriate. The large decreases in the concentration of the aliphatic bridges after oxidation, as measured by transalkylation (Table III), cannot be expected to match those indicated in the difference infrared spectra between oxidized and fresh coals. This is because the spectra measure the total aliphatic content of the samples, namely aliphatic bridges, hydroaromatics, and aliphatic side chains. In contrast, results in Table II show differences in relative concentrations of the aliphatic bridges, which represent only a part of the total aliphatics. Furthermore, concentrations measured by transalkylation correspond to only the soluble fractions of the reaction products some of the more complex transalkylation products may be retained in the residue itself. 

There have been some attempts to find chemical or physical correlates of short-term consumption that can be used as indices of biological lability (Amon et al., 2001). For example, there is indication that bioavailability (i.e., in terms of milligrams bacterial biomass per milligrams of DOC consumed) is correlated to the elemental composition in terms of C, N, H, and O, to the aliphatic contents, and to the overall degree of reduction of the DOM (Sun et al., 1997 Hopkinson et al., 1998 Hunt et al., 1999). However, there is still no general index that is applicable to all different aquatic systems, and it is unlikely that a single index will be able to account for variation in the multiple factors that simultaneously determine DOM... 

The remaining significant correlations are low and suggest only a slight increase in aliphatic content as coalification increases. 

Alkylation of solvent represents still another pathway for changing the properties of a recycle solvent. If we consider alkylation in terms of the transfer to methyl groups from coal to solvent components, then there are several structural and physical changes that occur to the solvent. Alkylation will increase the hydrogen content of the solvent at the expense of coal since the solvent molecule will have a C-H replaced by C-CH. This represents an increase in the aliphatic content and conversely a decrease in the aromatic content of the solvent. Kleinpeter (7) has indicated that alkylation of condensed aromatics is a problem. High aliphatic character will decrease the ability of the solvent to act as a physical solvent for coal liquefaction products. 

The glass temperatures of all products fall within the range 130°-160 °C. The partially aromatic polycarbonate has a glass temperature of 150 °C. the partially aromatic PETP has a glass temperature of 75 °C. To determine the ratio of the aromatic to the aliphatic content, we assume four chain links for the benzene rings. Then the polycarbonate has the ratio aromatic/aliphatic links = 4 6, the polyester has a ratio 4 2, and the polyamides (Table I) have a ratio 4 10. Despite the lower aromatic content the glass temperatures of some of the amorphous polyamide are... 

Ouchi also showed that the aliphatic content of benzene-alcohol extracts increased during successive cycles of depolymerization and the residues showed an increasingly dense network of aromatic structures. Increased aliphatic content implies alkylation has occurred. On-going work at Battelle Northwest is in general agreement with the results of Ouchi (10). 

Figure 9. Comparison of tar and heavy aliphatic evolution with diminishing char aliphatic content products from 20-sec vacuum pyrolysis run ofPSOC 170 coal ((H) tar released (O) hydrocarbons released (k) aliphatic C-H in char)...

A ratio commonly used as an indication of the aliphaticity of a sample is the atomic hydrogen to carbon ratio (H C). An increase in the ratio reflects an increased aliphatic content (-CH2-) over aromatic carbon (-C=C-). The values of the atomic hydrogen to carbon ratios for each fulvic and humic acid and for typical humic substances are shown in Table IV (25). The H C ratios for stream and foam samples follow a trend of increasing from stream (1.06 to 1.3) to foam and foam-extract fractions (1.1 to 1.4) for both Como Creek and the Suwannee River, indicating an increase in aliphatic character from stream to foam humic substances. 

The lack of color in humic substances from groundwater indicates that they contain fewer chromophores, such as conjugated double bonds, aromatic rings, and phenolic functional groups. It has been suggested that these groups serve as color centers in humic substances (Schnitzer and Khan, 1972 Oliver and Thurman, 1982). The increased aliphatic content (thus lower aromatic content) of humic substances from groundwater is also consistent with decreased color. 

Spectra of fulvic acids must be interpreted carefully purification of this fraction leads to losses that can reach 50%. Comparison of spectra of different humic fractions of the same sample, such as a sediment from the Oman Sea (Fig. 6) illustrates several differences. Oxygenated functional groups are more important in fulvic and humic acids than in stable residues. Particularly important are the absorption bands at 3400 cm (OH from alcohols, acids, etc.), 1710 cm (C==0 from quinones, ketones, carboxylic acids), 1250 cm (C—O from alcohols, esters, ethers) and 1050 cm (C—O from carbohydrates). Absorption at 1050 cm is nearly absent in stable residues. Aliphatic content increases from fulvic acids to humic acids and stable residues (bands between 2870 and 2960 cm ) and the shape of the aliphatic bands (2900-2950 1450 1375) indicates that fulvic acids contain mainly CH groups. 

HA can be precipitated from natural waters by lowering the pH value to 1,0, while the FA remains in solution (Bourbonniere and van Haldeten (1989)). FA has an increased carboxyl and decreased aliphatic content which explains its higher solubility in water than HA (Rasyid et al. (1992)). The acidification step used to precipitate HA, hydrolysed the carbohydrates and altered the subsequent analysis (Clair et al (1996)). 

Salame and Bandosz employed the FTTR spectroscopy to elucidate the twofold mechanism of interaction of nitric acid with carbon surfaces. In addition to the formation of oxygen-containing functionalities, the results corroborated the nitration mechanism during oxidation of carbon surfaces with HNO3 solutions [201], The presence of nitro groups on the carbonaceous aromatic structure was detected by absorption bands at 1530 and 1330 cm. Nitro groups were mainly incorporated to the carbon matiix with high aliphatic contents (i.e., low-temperature carbonized materials), and could not be detected by other techniques such as titration methods, due to their inability to dissociate. 

The soft (chloroform-extractable) and hard coke fractions fi om a suite of deactivated Co/Mo hydrodesulfurisation (HDS) catalysts with carbon contents ranging from 5 to 18% have been characterised. The hard coke accounted for between 50 and 70% of the total carbon, but was responsible for much less of a reduction in BET surface area as the carbon content increased. Indeed, significant variations in hard coke structure were revealed by solid state C NMR with the aromaticity ranging from 0.6 to over 0.9 with increasing carbon content and time on stream. The relatively high aliphatic contents and atomic H/C ratios for the hard cokes obtained at low levels of carbon deposition (5-7%) suggested that much of the carbon should be removed under reductive conditions. Indeed, hydropyrolysis, in which the deactivated catalysts were heated from ambient to 500°C under a hydrogen pressure of 15 MPa, removed over 90% of the carbon and recovered 70% of the BET surface that had been lost. 

Moisture sorption in PLA depends on the molecular weight and the aliphatic content via end group modification [64]. The primary petroleum-based polymers are nonpolar, where-... 

V. M. Singh,Synthesis of polylactide with varying molecular weight and aliphatic content effect on moisture sorption, MS thesis, Drexel University, 2008. 

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