Butane Chemicals

Like propane, n-hutane is mainly obtained from natural gas liquids. It is also a hy-product from different refinery operations. Currently, the major use of n-hutane is to control the vapor pressure of product gasoline. Due to new regulations restricting the vapor pressure of gasolines, this use is expected to he substantially reduced. Surplus n-butane could be isomerized to isobutane, which is currently in high demand for producing isobutene. Isobutene is a precursor for methyl and ethyl tertiary butyl ethers, which are important octane number boosters. Another alternative outlet for surplus n-butane is its oxidation to maleic anhydride. Almost all new maleic anhydride processes are based on butane oxidation. 

The chemistry of n-butane is more varied than that of propane, partly because n-butane has four secondary hydrogen atoms available for substitution and three carbon-carbon bonds that can be cracked at high temperatures  

Like propane, the noncatalytic oxidation of butane yields a variety of products including organic acids, alcohols, aldehydes, ketones, and olefins. Although the noncatalytic oxidation of butane produces mainly aldehydes and alcohols, the catalyzed oxidation yields predominantly acids. 

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Chemical Designations - Synonyms n-Butane Chemical Formula n-C4Hio... 

Common Name n-Butane Synonym 1-butane Chemical Name n-butane CAS Registry No 106-97-8 Molecular Formula C4H10 Molecular Weight 58.122 Melting Point (°C) ... 

The i-butane chemical ionization mass spectra of a number of saturated mono-hydroxylic alcohols have been determined to establish the general patterns of the spectra of this class of compounds. The spectrum of 2-hexanol is given as a typical example in Table X, and it may be seen that the following ion types comprise large fractions of the spectra of alcohols the alkyl ion formed from the hydrocarbon portion of the molecule R ) the ion formed by abstraction of the hydride from the molecule, (M l)" the protonated molecule, (M + 1) the association complex of the molecule with the mje = 39 ion of the i-butane plasma, (M -h 39) the association complex of the molecule with the mje = 57 ion of the /-butane plasma, (M -h 57) and the protonated dimer of the molecule, (2M -h 1). The intensity of this ion in the spectrum of 2-hexanol is so small that it is not included in Table X. 

In the course of determining the i-butane chemical ionization mass spectra of acetate esters it was observed that the spectra obtained are very sensitive to the temperature of the ionization chamber of the mass spectrometer. This is illustrated in Table XII, which gives the i-butane chemical ionization spectra of benzyl acetate at three temperatures. As the temperature is increased, the intensities of all the ions change, and indeed some so extensively that the whole character of the spectrum changes. At the two lower temperatures the protonated ester mje =151) constitutes more than half of the total ionization of the ester, but at the highest temperature the spectrum is dominated by the C7H7 ion (mje = 91). 

The /-butane chemical ionization spectra of benzyl acetate and t-amyl acetate have been investigated at a number of temperatures, and the rate constants for the decomposition of the protonated esters to benzyl and r-amyl ions, respectively, have been obtained at the several temperatures from (41) to (42). It is found that the rate constants obey the Arrhenius relationship, and this is illustrated in Fig. 5. Activation energies and frequency factors obtained from the Arrhenius plots are given in Table XIV. 

While most of the features of the /-butane chemical ionization spectra of the sulfur compounds are similar to those of their oxygen analogs (Table XVI), an important difference exists namely methylthiomethyl ion is produced in good abundance,... 

There are two major areas of commercial application of acetic add today food-grade vinegar, which is largely the product of bacterial oxidative conversion of diluted purified alcohol or alcoholic mashes from various fruits and grains, and chemically synthesized industrial acetic acid, 62 % of which is produced by carbonylation of methanol and the rest by oxidation of -butane. Chemically synthesized acetic acid is a commodity chemical that has become a major feedstock for the United States and worldwide chemical industry. O Figure 1.5 displays the major chemicals derived from acetic acid and their commercial applications. 

Assabumrungrat, S., Rienchalanusarn, T, Praserthdam, P. and Goto, S. (2002) Theoretical study of the application of porous membrane reactor to oxidative dehydrogenation of w-butane. Chemical Engineering Journal, 85,69-79. 

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. 

Figure 7.13 reprinted with permission from Jorgensen W L, R C Binning Jr and B Bigot. Structures md Properties of Organic Liquids u-Butane and 1,2-Dichloroethane and Their Conformational Equilibria. The Journal of the American Chemical Society 103 4393-4399. 1981 American Chemical Society. 

Butadiene is an industrial chemical and is prepared by dehydrogena tion of butane Elimination reactions such as dehydration and dehydro halogenation are common routes to alkadienes... 

Natural gas Hquids represent a significant source of feedstocks for the production of important chemical building blocks that form the basis for many commercial and iadustrial products. Ethyleae (qv) is produced by steam-crackiag the ethane and propane fractions obtained from natural gas, and the butane fraction can be catalyticaHy dehydrogenated to yield 1,3-butadiene, a compound used ia the preparatioa of many polymers (see Butadiene). The / -butane fractioa can also be used as a feedstock ia the manufacture of MTBE. 

Commercial VPO of propane—butane mixtures was in operation at Celanese Chemical Co. plants in Texas and/or Canada from the 1940s to the 1970s. The principal primary products were acetaldehyde, formaldehyde, methanol, and acetone. The process was mn at low hydrocarbon conversion (3—10%) and a pressure in excess of 790 kPa (7.8 atm). These operations were discontinued because of various economic factors, mainly the energy-intensive purification system required to separate the complex product streams. 

Butane. Butane LPO has been a significant source for the commercial production of acetic acid and acetic anhydride for many years. At various times, plants have operated in the former USSR, Germany, Holland, the United States, and Canada. Only the Hoechst-Celanese Chemical Group, Inc. plants in Pampa, Texas, and Edmonton, Alberta, Canada, continue to operate. The Pampa plant, with a reported aimual production of 250,000 t/yr, represents about 15% of the 1994 installed U.S. capacity (212). Methanol carbonylation is now the dominant process for acetic acid production, but butane LPO in estabhshed plants remains competitive. 

The properties of butane and isobutane have been summarized ia Table 5 and iaclude physical, chemical, and thermodynamic constants, and temperature-dependent parameters. Graphs of several physical properties as functions of temperature have been pubUshed (17) and thermodynamic properties have been tabulated as functions of temperature (12). 

The alkanes have low reactivities as compared to other hydrocarbons. Much alkane chemistry involves free-radical chain reactions that occur under vigorous conditions, eg, combustion and pyrolysis. Isobutane exhibits a different chemical behavior than / -butane, owing in part to the presence of a tertiary carbon atom and to the stability of the associated free radical. 

Ma.leic Anhydride. The largest chemical use for / -butane is as feedstock for maleic anhydride. A dilute air—butane mixture is passed over a vanadium—phosphoms catalyst 400—500°C to produce maleic anhydride [108-31-6] in good yield. Formerly benzene was used as feedstock, but in the last few years nearly all maleic anhydride in the United States, and an increasing proportion worldwide, is made from butane. 

Production of maleic anhydride by oxidation of / -butane represents one of butane s largest markets. Butane and LPG are also used as feedstocks for ethylene production by thermal cracking. A relatively new use for butane of growing importance is isomerization to isobutane, followed by dehydrogenation to isobutylene for use in MTBE synthesis. Smaller chemical uses include production of acetic acid and by-products. Methyl ethyl ketone (MEK) is the principal by-product, though small amounts of formic, propionic, and butyric acid are also produced. / -Butane is also used as a solvent in Hquid—Hquid extraction of heavy oils in a deasphalting process. 

About 35% of total U.S. LPG consumption is as chemical feedstock for petrochemicals and polymer iatermediates. The manufacture of polyethylene, polypropylene, and poly(vinyl chloride) requires huge volumes of ethylene (qv) and propylene which, ia the United States, are produced by thermal cracking/dehydrogenation of propane, butane, and ethane (see Olefin polymers Vinyl polymers). 

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