Atomic hydrogen to carbon ratio

Coal Hquefaction iavolves raising the atomic hydrogen-to-carbon ratio from approximately 0.8/1.0 for a typical bituminous coal, to 2/1 for Hquid transportation fuels or 4/1 for methane (4). In this process, molecular weight reduction and removal of mineral matter and heteroatoms such as sulfur, oxygen, and nitrogen may need to be effected. 

Figure 4. Dependence of tar yield, determined by low-temperature Gray-King carbonization assay, n atomic hydrogen-to-carbon ratio for a wide range of Australian coals. Tar yield = 50.4 X H/C — 25.9 correlation coefficient, 0.95.

Figure 6. Dependence of maximum tar yields and corresponding total volatile matter yields during flash pyrolysis on atomic hydrogen-to-carbon ratio for some Australian and V.S.A. coals (O, 9), black coals (X), brown coals (A), Pittsburgh No. 8 (USA.) ( ), Montana lignite (USA).

For each ton of hydrogen produced from hydrocarbons, approximately 2.5 t of carbon is vented to the atmosphere [44-47], However, for each ton of hydrogen produced from current coal technology, approximately 5 t of carbon is emitted to the atmosphere. Principally, C02 capture and sequestration is a precondition for use of these fossil fuels. However, the sequestration necessity varies, because the relative atomic hydrogen-to-carbon ratios are 1 2 4 for coal oil natural gas. There are two basic approaches to C02 sequestration either at the point of emission (in situ capture) or from the air (direct capture). In either case, C02 must be disposed off safely and permanently. With the capture and sequestration of C02, hydrogen is one path for coal, oil, and natural gas to remain viable energy resources [46]. Carbon sequestration technologies are discussed in detail in Chapter 17. 

H/C = atomic hydrogen-to-carbon ratio V = vitrinite content of coal VM volatile matter St = total sulfur TRM = total reactive macerals The adequacies of these reactivity correlations, expressed as a percentage of the total variation in the data set explained by the model, were 80.0%, 79.2%, and 47.5% respectively. A later paper in the series (21) concentrated on the development of reactivity correlations for a set of 26 high volatile bituminous coals with high sulfur contents, and extended the models previously developed in include analyses of the liquefaction products and coal structural features. These structural features included the usual... 

It is appropriate now to re-emphasize just what reasonably quantitative data one can derive from the proton and C13 spectra. In this early work we assume that atoms other than carbon and hydrogen are present in only negligible amounts. The atomic hydrogen to carbon ratios can be evaluated from the elemental analyses of the materials and can be used to normalize the hydrogen and carbon NMR measurements so that they add to unity. The proton spectrum gives, after this minor modification, three items of information hnr, the fraction of total atoms in the material which is present as hydrogen atoms directly bonded to aromatic carbons hay the fraction bonded to carbons situated a to aromatic rings and hp, the fraction bonded to other nonaromatic carbons. The carbon spectrum in conjunction with the aromaticity calibration curve yields c.r, the fraction of total atoms in the material... 

Three of the more important structural parameters which can be derived from the H1 and C13 data are the aromaticity, / , degree of aromatic ring substitution, atomic hydrogen to carbon ratio for the hypothetical... 

These observations can be put on a more chemical basis by examining the variation of AHpp with the atomic hydrogen-to-carbon ratio (Figure 4). Here, the clustering of exinite properties is even more prominent. The single deviant exinite point comes from a very different organic matter type—alginite, rath-... 

Shale oil is not a uniquely hydrogen deficient feedstock vis-a-vis petroleum crudes. As can be seen from the representative data presented in Table II, its atomic hydrogen to carbon ratio is within the range of some mid-continent crude oils. Its atomic H/C ratio is that of a naphthenic base petroleum crude. 

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. 

Table IV. Atomic hydrogen to carbon ratios (H C) for raw foams and humic substances isolated from stream, foam, and foam-extract samples from Como Creek and the Suwannee...

The calorific value (heat of combustion) of residual fuel oil (ASTM D-240, IP 12) is lower than that of lower-boiUng fuel oil (and other liquid fuels) because of the lower atomic hydrogen-to-carbon ratio and the incidence of greater amounts of less combustible material, such as water and sediment, and generally higher levels of sulfur. 

Elemental analysis of fuel oil often plays a more major role that it may appear to do in the lower-boiling products. Aromaticity (through the atomic hydrogen-to-carbon ratio), sulfur content, nitrogen content, oxygen content, and metals content are all important features that can influence use of residual fuel oil. 

Figure la Atomic hydrogen to carbon ratio (H/C) on USHY versus the reaction temperature (T, °C). Reactants propene [7], cyclohexene [8] toluene [91. ... 

Figure lb Atomic hydrogen to carbon ratio (H/C) of coke deposited on USHY at 450 C versus the coke percentage (%C). n-heptane toluene... 

The difference in the hydrogen to carbon ratios of the extract and O-alkylated extract was used to establish the number of hydroxyl groups that had reacted. The results are shown in Table I. The predicted H/C ratio is calculated based on the assumption that 4 hydroxyl groups per 100 carbon atoms were alkylated. The agreement between calculated and observed H/C ratio is very good. 

Analytical data obtained from elemental combustion analysis for Fraction 30 of the five SRC samples are presented in Table IV. The relatively constant molecular size of each Fraction 30 sample with 22-28 carbon atoms per average molecule is noteworthy. The only exception which has been noted previously in terms of the mol wt data is the Monterey Fraction 30 sample with 38 carbon atoms per average molecule. The total hydrogen to carbon ratio (H/C)tot is lower for each Fraction 30 sample than (H/C)tot obtained for the non-chromatographed THF-soluble SRC sample. Perhaps one of the more significant trends is the consistently lower (H/C)tot values for the western SRC Fraction 30 (Amax, 0.77 Monterey, 0.79) relative to the other Fraction 30 samples (0.86-0.90). 

Conversion processes are, in essence, processes that change the number of carbon atoms per molecule, alter the molecular hydrogen-to-carbon ratio, or change the molecular structure of the material without affecting the number of carbon atoms per molecule (Fig. 2.2). These latter processes isomerization processes) essentially change the shape of the molecule(s) and are used to improve the quality of the product (Speight, 1999 Speight and Ozum, 2002). 

FIGURE 11 Relationship of resource to end products on the basis of the ratio of atomic hydrogen to carbon. 

As more and more aromatic compounds were isolated and studied, chemists gradually realized that aromatics contained at least six carbon atoms, had low hydrogen-to-carbon ratios (relative to other organic hydrocarbons), and were related to benzene (C5H5). For example, toluene, an aromatic compound from the bark of the South American tolu tree, has the formula C7H8. 

Ion series separated by CH and C. Compounds with a hydrogen-to-carbon ratio much less than two cannot show a significant series of ions spaced at CH2 intervals (see Unknown 5.1, naphthalene, CioHg). The low-mass ions of such compounds can still show characteristic series. A very important series is that shown by aromatic hydrocarbons at m/z 38-9, 50-2, 63-5, and 75-8 (C Ho,5 to C H ). Heterocyclic compounds containing oxygen and nitrogen atoms and... 

The results of the CHN Test are listed in Table 2. The quoted accuracy of the CHN test is 3=0.3% by weight. The hydrogen to carbon atomic ratio was... 

The ratio of hydrogen to carbon atoms is a maximum in alkanes, hence the term saturated hydrocarbon. The general formula of an alkane containing n carbon atoms is... 

A compound of carbon and hydrogen is known that contains 1.0 gram of hydrogen for every 3.0 grams of carbon. What is the atomic ratio of hydrogen to carbon in this substance ... 

Figure 7. Dependence of yields of hydrogenation products on the atomic hydro-gen-to-carbon ratio (a) Australian coals—noncatalytic conditions (10) (b) Canadian coals—catalytic conditions.

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