Hydrogen to Carbon Ratio

Hydrocarbon resources can be classified as organic materials which are either mobile such as cmde oil or natural gas, or immobile materials including coal, lignite, oil shales, and tar sands. Most hydrocarbon resources occur as immobile organic materials which have a low hydrogen-to-carbon ratio. However, most hydrocarbon products in demand have a H C higher than 1.0. 

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. 

The higher the hydrogen to carbon ratio in the polymer the greater is the tendency to burning (other factors being equal). 

Cracking and isomerization reactions occur readily in acidic chloroaluminate(III) ionic liquids. A remarkable example of this is the reaction of poly(ethene), which is converted into a mixture of gaseous alkanes of formula (C Ff2n+2, where n = 3-5) and cyclic alkanes with a hydrogen to carbon ratio of less than two (Figure 5.1-4, Scheme 5.1-68) [99]. 

The major chemical difference between natural gas, crude oil, and coal is their hydrogen-to-carbon ratios. Coal is carbon-rich and hydrogen-poor, so to produce a synthetic liquid or gas from coal requires an increase in the hydrogen-to-carbon ratio. Coal s ratio of about 0.8 has to be raised to 1.4 to 1.8 for a... 

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. 

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. 

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... 

The most important pretreatment steps of the feed are proper desalting and hydroprocessing. The latter step will reduce the content of heteroatoms, asphaltenes and metals, and raise the hydrogen to carbon ratio of the feed. In other words, hydroprocessing significantly reduces the heavy oil character of the feed oil. 

The bitumen in its raw state has an API gravity of 8.3 and is characterized by low hydrogen to carbon ratios, 1.5, and high sulphur content,... 

However, hydrogen is in effect wasted in both the gas generation and synthesis steps— in the former by combustion to water and in the latter by production of compounds of higher average hydrogen to carbon ratio than olefins and by loss of hydrogen gas in the reactor effluent. It is therefore necessary to provide additional hydrogen from some source this source is the equivalent of the water gas reaction ... 

Solvent extraction is used extensively in the petroleum industry to refine lubricating oils, kerosene, and specialty oils for medicinal and agricultural purposes. It is a process that separates hydrocarbons into two phases—a raffinate which contains substances of high hydrogen to carbon ratio and an extract which contains substances of low hydrogen to carbon ratio. 

The research into energetic molecules which produce a large amount of gas per unit mass, led to molecular structures which have a high hydrogen to carbon ratio. Examples of these structures are hydrazinium nitroformate (HNF) and ammonium dinitramide (ADN). The majority of the development of HNF has been carried out in The Netherlands whereas the development of ADN has taken place in Russia, USA and Sweden. ADN is a dense non chlorine containing powerful oxidiser and is an interesting candidate for replacing ammonium perchlorate as an oxidiser for composite propellants. ADN is less sensitive to impact than RDX and HMX, but more sensitive to friction and electrostatic spark. 

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... 

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