Hydrocarbon hydrates, naturally occurring

There exists in East Indian sandalwood oil an alcohol, of the formula CjHjgO, which has been named santelol, or santenone alcohol. It is closely allied to, and much resembles, the alcohol obtained by the hydration of the hydrocarbon, santene q.v.), and is probably stereo-isomeric with it. There is some difference of opinion as to the proper nomenclature of the two alcohols. According to Charabot, the naturally occurring alcohol, also obtainable by the reduction of santenone, is analogous to borneol, and should therefore be termed, if that analogy is... 

The solubility of most metals is much higher when they exist as organometallic complexes.4445 Naturally occurring chemicals that can partially complex with metal compounds and increase the solubility of the metal include aliphatic acids, aromatic acids, alcohols, aldehydes, ketones, amines, aromatic hydrocarbons, esters, ethers, and phenols. Several complexation processes, including chelation and hydration, can occur in the deep-well environment. 

Water invariably occurs with petroleum deposits. Thus, a knowledge of the properties of this connate, or interstitial, or formation water is important to petroleum engineers. In this chapter, we examine the composition of oilfield water water density, compressibility, formation volume factor and viscosity solubility of hydrocarbons in water and solubility of water in both liquid and gaseous hydrocarbons and, finally, water-hydrocarbon interfacial tension. An unusual process called hydrate formation in which water and natural gas combine to form a solid at temperatures above the freezing point of water is discussed in Chapter 17. 

As a complement to Table 2.4, size ratios of sH formers are shown in Table 2.7. Although many large sH formers are known, only alkanes and cycloalkanes are of interest, because alkenes and alkynes do not occur in natural hydrocarbons due to their reactivity. A large number of branched alkanes, including methyl butane, all polymethyl butanes, and a number of polymethyl pentanes form sH hydrates. 

Clathrate hydrates have been found to occur naturally in large quantities. Around 120 X 10 m (at STP) of methane is estimated to be trapped in deposits of the deep ocean floor [10]. Clathrate hydrates are also suspected to occur in large quantities on some outer planets, moons, and trans-Neptunian objects [11]. In the petroleum industry, hydrocarbon clathrate hydrates are a cause of problems because they can form inside gas pipelines, often resulting in plugging. Deep sea deposition of carbon dioxide clathrate hydrate has been proposed as a method to remove this greenhouse gas from the atmosphere and control climate change [12]. 

Clathrate hydrates. Chemical systems involving dissolved gases can also form clathrate hydrates at modest pressures and temperatures in a simple low-pressure optical cell. Hydrocarbon clathrate hydrates occur in marine and polar regions where hydrocarbons react with cold water. CO2 hydrates have been reported in seafloor environments near cold CO2 vents. Natural air hydrates occur in ice cores taken from polar ice sheets. Air is trapped and sealed in snow during compaction to form low-porosity ice. 

Some other common monoterpenoid hydrocarbons are shown in Figure 3.4. Citronellene is also known as dihydromyrcene. It does not occur in nature but is prepared by pyrolytic cracking of pinane. Hydration of the trisubstituted bond of citronellene produces dihydro-myrcenol which is used to provide fresh notes in perfumery. Further details of both of these processes are given in Chapter 9. a-Ocimene occurs in various essential oils such as those of basil, catnip and magnolia, while the P-isomer occurs in the leaf oils of lemon, orange and grapefruit and also in narcissus flowers. Allo-ocimene occurs in the leaves of sequoia trees and is the thermodynamically most stable of the three ocimenes since the double bonds are all in conjugation and as heavily substituted as possible. Double bonds can be isomerised under... 

It seemed clear that since only small amounts of water are effective, and if acidity is also involved in the catalytic function, then the nature of the acidity probably is protonic. Removal of water reduces proton availability and also catalyst activity. If protons are indeed involved in the mechanism of hydrocarbon activation and reaction, then it was reasoned that an exchange of hydrogen between catalyst and hydrocarbon might occur. By hydrating the catalyst with D2O it was shown that indeed such exchange does occur ( 7). The ease of exchange was found to follow more or less the expected relative ease of protonation or carbonium ion formation. Thus, the lowest temperature at which exchange was observed for a number of pure hydrocarbons was found to be as follows ... 

The nature of the hydrocarbon and sulfur content is still not clear. However, calculations based on density data would seem to support earlier suggestions that the sulfur must be present as SO, or H O within the silica lattice. The optical characteristics of the mineral show that the organic matter occurs in films between the faces of the crystals. On the other hand, calculations based on the difference in densities of the original mineral and the pyrolyzed silica crystals show that the sulfur compounds at least must be within the crystal lattice. Kamb offers evidence (69) that the silica structure is a clathrate with SO,. HjO, and CH in the lattice analogous to the known 12 A gas hydrates of water, 6X 46HjO, where X is CH , H S, CO SOi, Cl, etc., and in fact the structure is the complete analogue of 6CI - H 0. 

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