Hydrocarbon producing species

Table 13. Oil- and Hydrocarbon-Producing Biomass Species Potentially Suitable for North America ...

The sex pheromones of moths generally are mixtures of two or more chemical components, typically aldehydes, acetates, alcohols, or hydrocarbons, produced in specialized glands by biosynthesis and modification of fatty acids (34). Often, a species-specific blend of components is the message, and males of many moth species, including M. sexta, give their characteristic, qualitatively and quantitatively optimal behavioral responses only when stimulated by the correct blend of sex-pheromone components and not by individual components or partial blends lacking key components (43, 44). 

In a practical HDS process for gas oil, both aromatic species existing in the feed and various types of sulfur compounds compete for the active sites on the catalyst surface. Moreover, H2S and some other hydrocarbons produced in the early stages of the desulfurization appear to inhibit the HDS of the less reactive sulfur species. The reactivities of refractory sulfur compounds and the effects of inhibitors in gas oils need to be fully understood for the development of an improved economical desulfurization process. 

However, if the photochemical reaction is run in the presence of oxygen, then of course, the methyl radicals are oxidized, and one obtains instead methanol, formaldehyde, and their decomposition products. Now, if the vessel is pumped out after a photo-oxidation and once again a normal photolysis of acetone is run, the products in the first 10 or 15 minutes are still oxidation products rather than hydrocarbon products. It takes from 15 to 30 minutes to remove whatever it is that is attached to the wall before the normal photochemical decomposition of pure acetone products are produced. These results should remind us that oxidation system do produce species, some of which are not known or understood. 

Fig. (5). Lepidopteran pheromone biosynthetic pathways utilize fatty acid synthesis, desatiindiun, specific chain-shortening enzymes, and/or functional modification of tlie carbony l carbon to produce species-apecific acetate ester, aldehyde, alcohol, or hydrocarbon pheromone blends. Unsaturated hydrocarbons can be further modified to epoxides (adapted from ref. [21]).

Disubstituted fulvenes are a common source for alkyl-substituted Cp ligand. The reaction of the in-situ generated Bu ZrCV species with 2equiv. of substituted fulvenes in hydrocarbons produces alkyl-substituted zirconocene dichlorides 575 in high yields (Scheme 130).403 6,6-Disubstituted fulvenes were also used to synthesize sterically hindered metallocene dichlorides 576 and 577 via the salt metathesis route.404... 

In the first step, molecular oxygen is adsorbed onto a catalyst surface site, (), forming 02(ads). The molecular oxygen dissociates to produce two adsorbed oxygen species, which may themselves adsorb gas-phase hydrocarbon molecules to form CnHn-O on the catalyst surface, as in step 3. The adsorbed hydrocarbon-oxygen species may further react with adsorbed oxygen to produce, via partially oxidised intermediates, carbon dioxide and water. These are able to dissociate from the catalyst surface into the gas phase. 

Because of the pore structure of ZSM-5, the produced hydrocarbons are composed of low molecular species (4 carbons to about 20) which are in the gasoline, kerosene, and gas oil boiling range. In comparison, the carbon numbers of hydrocarbons produced only by thermal cracking range from 4 to 44. Polystyrene in the feedstock enhances the yield of ethylbenzene, toluene, and benzene, while producing gas that is predominantly propane/propylene. 

Finally, B. braunii presently appears to be the best candidate species for the possible production of renewable hydrocarbons, by large scale culture of photosynthetic organisms. The non-isoprenoid and the iso-prenoid hydrocarbons produced by the different races of B. braunii might thus be used as multipurpose feedstocks, either as such or after chemical transformations. 

First of all, it should be pointed out that the rate of oxidation in the series of normal paraffin hydrocarbons increases rapidly with the length of the hydrocarbon chain. Note also that branched-chain paraffinic hydrocarbons are oxidized more slowly than normal paraffins with the same number of hydrocarbon atoms. This may seem surprising, since the hydrogen atom is more easily separated from a tertiary carbon atom than from a secondary, let alone a primary carbon atom. In this case, the cleavage of the C—H bond is apparently not the limiting step, with the rate of the process being determined by the stability of intermediate oxidation products. The oxidation of normal paraffinic hydrocarbons produces aldehydes, more reactive compoimds, whereas the oxidation of isoparaffinic hydrocarbons yields ketones, more stable species. This dependence of the relative reactivity of paraffins on their structure is directly related to their motor properties (octane number) and explains why branched paraffins exhibit higher antiknock properties [93]. 

The most abundant hydrocarbon in the atmosphere is methane, CH4, released from underground sources as natural gas and produced by the fermentation of organic matter. Methane is one of the least reactive atmospheric hydrocarbons and is produced by diffuse sources, so that its participation in the formation of pollutant photochemical reaction products is minimal. The most significant atmospheric pollutant hydrocarbons are the reactive ones produced as automobile exhaust emissions. In the presence of NO, under conditions of temperature inversion (see Chapter 16), low humidity, and sunlight, these hydrocarbons produce undesirable photochemical smog, manifested by the presence of visibility-obscuring particulate matter, oxidants such as ozone, and noxious organic species such as aldehydes. 

---