Methane ethane

The noncondensable hydrocarbons comprise the hydrocarbons having less than five carbon atoms methane, ethane, propane and butanes encountered in production refining will add the olefins and diolefins ... 

The Reid vapor pressure is generally barely different from the true vapor pressure at 37.8°C if the light gas content —methane, ethane, propane, and butane— of the sample is small, which is usually the case with petroleum products. The differences are greater for those products containing large quantities of dissolved gases such as the crude oils shown in Table 4.13. 

Under standard conditions of temperature and pressure (STP), the first four members of the alkane series (methane, ethane, propane, and butane) are gases. As length of the carbon increases the density of the compound increases (pentane) to C yHgg are liquids, and from C.,gH3g, the compounds exist as wax-like solids at STP. 

Under certain conditions of temperature and pressure, and in the presence of free water, hydrocarbon gases can form hydrates, which are a solid formed by the combination of water molecules and the methane, ethane, propane or butane. Hydrates look like compacted snow, and can form blockages in pipelines and other vessels. Process engineers use correlation techniques and process simulation to predict the possibility of hydrate formation, and prevent its formation by either drying the gas or adding a chemical (such as tri-ethylene glycol), or a combination of both. This is further discussed in SectionlO.1. 

Q-C, Natural gas, methane, ethane, propane, butane, liquefied petroleum gas... 

The structural features of methane ethane and propane are summarrzed rn Ergure 2 7 All of the carbon atoms have four bonds all of the bonds are srngle bonds and the bond angles are close to tetrahedral In the next sectron we 11 see how to adapt the valence bond model to accommodate the observed structures... 

FIGURE 2 7 Structures of methane ethane and propane showing bond distances and bond angles... 

Bonding m n butane and isobutane continues the theme begun with methane ethane and propane All of the carbon atoms are sp hybridized all of the bonds are ct bonds and the bond angles at carbon are close to tetrahedral This generalization holds for all alkanes regardless of the number of carbons they have... 

The lUPAC rules assign names to unbranched alkanes as shown m Table 2 2 Methane ethane propane and butane are retained for CH4 CH3CH3 CH3CH2CH3 and CH3CH2CH2CH3 respectively Thereafter the number of carbon atoms m the chain is specified by a Latin or Greek prefix preceding the suffix ane which identifies the com pound as a member of the alkane family Notice that the prefix n is not part of the lUPAC system The lUPAC name for CH3CH2CH2CH3 is butane not n butane... 

Table 1 7 shows that hydrocarbons are extremely weak acids Among the classes of hydrocarbons acetylene is a stronger acid than methane ethane ethylene or benzene but even its K is 10 ° smaller than that of water... 

Natural gas is an abundant source of methane ethane and propane Petro leum IS a liquid mixture of many hydrocarbons including alkanes A1 kanes also occur naturally m the waxy coating of leaves and fruits... 

Methane ethane and cyclobutane share the common feature that each one can give only a single monochloro derivative All the hydrogens of cyclobutane for example are equivalent and substitution of any one gives the same product as substitution of any other Chlorination of alkanes m which the hydrogens are not all equivalent is more com plicated m that a mixture of every possible monochloro derivative is formed as the chlo rmation of butane illustrates... 

Because of the large price differential between propane and propylene, which has ranged from 155/t to 355 /1 between 1987 and 1989, a propane-based process may have the economic potential to displace propylene ammoxidation technology eventually. Methane, ethane, and butane, which are also less expensive than propylene, and acetonitrile have been disclosed as starting materials for acrylonitrile synthesis in several catalytic process schemes (66,67). 

Many simple systems that could be expected to form ideal Hquid mixtures are reasonably predicted by extending pure-species adsorption equiUbrium data to a multicomponent equation. The potential theory has been extended to binary mixtures of several hydrocarbons on activated carbon by assuming an ideal mixture (99) and to hydrocarbons on activated carbon and carbon molecular sieves, and to O2 and N2 on 5A and lOX zeoHtes (100). Mixture isotherms predicted by lAST agree with experimental data for methane + ethane and for ethylene + CO2 on activated carbon, and for CO + O2 and for propane + propylene on siUca gel (36). A statistical thermodynamic model has been successfully appHed to equiUbrium isotherms of several nonpolar species on 5A zeoHte, to predict multicomponent sorption equiUbria from the Henry constants for the pure components (26). A set of equations that incorporate surface heterogeneity into the lAST model provides a means for predicting multicomponent equiUbria, but the agreement is only good up to 50% surface saturation (9). 

Methane, ethane, and propane are the first three members of the alkane hydrocarbon series having the composition, Selected properties of these... 

Table 1. Selected Properties of Methane, Ethane, and Propane ...

The main commercial source of methane, ethane, and propane is natural gas, which is found ia many areas of the world ia porous reservoirs they are associated either with cmde oil (associated gas) or ia gas reservoirs ia which no oil is present (nonassociated gas). These gases are basic raw materials for the organic chemical industry as well as sources of energy. The composition of natural gas varies widely but the principal hydrocarbon usually is methane (see Gas, natural). Compositions of typical natural gases are Hsted ia Table 2. 

Relatively small amounts of methane, ethane, and propane also are produced as by-products from petroleum processes, but these usually are consumed as process or chemical feedstock fuel within the refineries. Some propane is recovered and marketed as LPG. 

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Helium and Natural-Gas Systems Separation Helium is produced primarily by separation of hehum-rich natural gas. The hemim content of the natural gas from plants operated by the U.S. Bureau of Mines normally has varied from 1 to 2 percent while the nitrogen content of the natural gas has varied from 12 to 80 percent. The remainder of the natural gas is methane, ethane, and heavier hydrocarbons. 

Removal of volatile matter to about 0.5 wt% can be accomplished by calcming in a rotary kiln, rotary hearth, or vertical shaft calcmer All of these processes heat green coke to temperatures in excess of 1000°C where shrinkage and subsequent densification take place. The volatile components are comprised primarily of methane, ethane, hydrogen, and hydi ogen sulfide gases which can be employed as fuel for process heat. 

The example provided in Table 2 is for a four eomponent mixture of hydroearbons (methane, ethane, propane, and n-oetane). The weighting method is a eommon ealeulation procedure that proeess engineers will encounter many times. Computations for simple systems can be easily set up on an Exeel spreadsheet. 

Paraffinic Hydrocarbons Methane Ethane Propane n-Butane 1-Butane n-Pentane n-Hexane... 

Absorption recovers valuable light components such as propane/propylene and butane/ butylene as vapors from fractionating columns. These vapors are bubbled through an absorption fluid, such as kerosene or heavy naphtha, in a fractionating-like column to dissolve in the oil while gases, such as hydrogen, methane, ethane, and ethylene, pass through. Absorption is effectively performed at 100 to 150 psi with absorber heated and distilled. The gas fraction is condensed as liquefied petroleum gas (LPG). The liquid fraction is reused in the absorption tower. 

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