Hydrocarbons higher molecular weight

Almost any hydrocarbon can serve as a starting material for production of ethylene and propene Cracking of petroleum (Section 2 16) gives ethylene and propene by processes involving cleavage of carbon-carbon bonds of higher molecular weight hydrocarbons... 

Higher molecular weight hydrocarbons present in natural gases are important fuels as well as chemical feedstocks and are normally recovered as natural gas liquids. For example, ethane may be separated for use as a feedstock for steam cracking for the production of ethylene. Propane and butane are recovered from natural gas and sold as liquefied petroleum gas (LPG). Before natural gas is used it must be processed or treated to remove the impurities and to recover the heavier hydrocarbons (heavier than methane). The 1998 U.S. gas consumption was approximately 22.5 trillion ft. ... 

For more aromatics yield, the end point of the feed may be raised to include higher molecular weight hydrocarbons in favor of hydrocracking and dehydrocyclization. However, excessive hydrocracking is not desirable because it lowers liquid yields. 

Although ethylene is more readily hydrogenated than the other alkenes, it has been reported 2A) to participate to the formation of higher molecular weight hydrocarbons under F-T conditions. This is observed too for Fe (CO)- 2-NaY catalysts. 

Liquefied petroleum gas, natural gas, and refinery gas are mixtnres of products or naturally occurring materials and, fortunately, are relatively simple mixtures and do not suffer the complexities of the isomeric variations of the higher-molecular-weight hydrocarbons (Drews, 1998 Speight, 1999). 

In the hydrocracking process, this phenomenon is exploited to shift catalyst selectivity from the naphtha to the distillate products. Here the wide separation of sites is exploited to minimize the potential for secondary cracking in initial products and intermediates. This, along with the introduction of escape routes for the primary product tends to preserve the higher molecular weight hydrocarbons, thereby producing more dishllates [49, 61, 62]. 

About 98% of gas formed during radiolysis of natural rubber and polyiso-prene is hydrogen, the rest consists of methane and higher-molecular-weight hydrocarbons. The yield of hydrogen is directly proportional to dose up to 200 Mrad (2,000 kGy). Moreover, it is independent of dose rate and the type of radiation (gamma, electron beam).i ... 

Alkylation processes usually combine isobutane with an alkene or with mixed alkene streams (C3-C5 olefins from FCC units). The best octane ratings are attained when isobutane is alkylated with butylenes. Alkylation of higher-molecular-weight hydrocarbons (>C5) is less economic because of increased probability of side reactions. Phillips developed a technology that combines its triolefin process (metathesis of propylene to produce ethylene and 2-butenes) with alkylation since 2-butenes yield better alkylate than propylene.290 Since ethylene cannot be readily used in protic acid-catalyzed alkylations, a process employing AICI3 promoted by water was also developed.291... 

Of the substances studied the most abundant in the Paleozoic rocks of the area are furfurals presumably derived from carbohydrates, higher molecular weight hydrocarbons, and in a few samples, amino acids. Acid and base soluble, low boiling substances having some properties of heterocyclic compounds, phenols, and organic acids exist in smaller amounts. 

This reaction in turn led to the discovery that aldehydes were formed by the further addition of carbon monoxide and hydrogen to alkenes, and was further developed as the oxo process for production of alcohols. The combination CO + H2 often is called synthesis gas. It is prepared by the reduction of water under pressure and at elevated temperatures by carbon (usually coke), methane, or higher-molecular-weight hydrocarbons ... 

The hydrate produced gas of 98.43% CH4 and 1.57% CO2. Ethane and propane were at 196 and 3.8 ppmv, respectively, and the C1/C2 ratio (4936) was between the ratios of gas in the headspace (1880) and free gas (6748). All above indicators suggested the gas was biogenic. However, microscopically visible oil occurred from approximately 500-620 mbsf, which suggested migration of some oil and gas, when coupled with the occurrence of higher molecular weight hydrocarbons. 

Such a situation may arise, for example, in the combustion sensor in which the species of interest is methane and the other combustibles are different higher molecular weight hydrocarbons. The catalyst, in this case, can be Pt and the preferentially catalyzed reaction is as follows. 

Steam-naphtha reforming a process that is essentially similar in nature to the steam-methane reforming process (q.v.) but which used higher molecular weight hydrocarbons as the feedstock. 

Steam is added and the mixture is heated in the furnace at 760 to 980°C and 600 psi over a nickel catalyst. When higher-molecular-weight hydrocarbons are the feedstock, potassium oxide is used along with nickel to avoid larger amounts of carbon formation. 

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