Hydrogen-deficient feedstocks

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. 

The trend in pyrolysis over the last decade has been toward higher temperatures and shorter residence times. In the case of utilization of heavier hydrogen-deficient feedstocks, short residence time is the prime means of maximizing olefin and minimizing coke yields. 

The relationship between coal composition and hydrogenation reactivity has been studied extensively and coal with less than 85% w/w carbon (daf) made poor liquefaction feedstocks. It has been suggested that coal reactivity is related to rank (Francis, 1961). Coal is, in actual fact, a hydrogen-deficient organic natural product having an atomic hydrogen/carbon ratio of approximately 0.8 compared with an atomic hydrogen/carbon atomic ratio of 1.4 1.8 for various crude oils, heavy oil, and bitumen (Table 12.1). 

Conradson coke - hydrogen deficient, high coking tendency feed components which correlates directly with the basic nitrogen and average molecular weight of the feedstock, as well as the Conradson carbon analysis... 

The elemental composition of the three maceral groups varies. The vitrinite, which frequently is about 85% of the sample in the United States, is similar to the patent coal. The liptinites are richer in hydrogen, whereas the inertinites are relatively deficient in hydrogen and richer in carbon. The liptinites also contain more aliphatic materials the inertinites are richer in aromatics. The term inertinite refers to the relative chemical inertness of this material, making it especially undesirable for Hquefaction processes because it tends to accumulate in recycled feedstock streams. 

The demand for aviation gasoline during World War II was so great that isobutanc from alkylation feedstock was insufficient. This deficiency was remedied by isomerization of abundant normal butane into isobutane using the isomerization catalyst aluminum chloride on alumina promoted by hydrogen chloride gas. 

Methane, also referred to as marsh gas, is a gas composed of carbon and hydrogen with a chemical formula of CH4. It is the first member of the paraffin or alkane series of hydrocarbons. It is lighter than air, colorless, odorless, tasteless and is flammable. It occurs in natural gas and as a by-product of petroleum refining. In atmospheric burning no smoke production normally occurs. In air methane bums with a pale, faintly luminous flame. With excess air carbon dioxide and water vapor is formed during combustion, with an air deficiency carbon monoxide and water is formed. It forms an explosive mixture with air over a moderate range. Its primary uses are as a fuel and raw feedstock for petrochemical products. 

Sulfur impurities in the feedstock are converted to hydrogen sulfide and carbonyl sulfide, from which sulfur can be easily extracted, typically as elemental sulfur or sulfuric acid, both valuable by-products. Nitrogen oxides, potential pollutants, are not formed in the oxygen-deficient (reducing) environment of the gasifier instead, ammonia is created by nitrogen-hydrogen reactions. The ammonia can be easily washed out of the gas stream. 

Because heavy oil is deficient in hydrogen compared with conventional crude oil, either hydrogen must be added to the molecules or carbon removed to render it useful as a feedstock for a conventional refinery. 

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