Butane oxidation, pressure

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. 

Other methods for the preparation of acetic acid are partial oxidation of butane, oxidation of ethanal -obtained from Wacker oxidation of ethene-, biooxidation of ethanol for food applications, and we may add the same carbonylation reaction carried out with a cobalt catalyst or an iridium catalyst. The rhodium and iridium catalysts have several distinct advantages over the cobalt catalyst they are much fester and fer more selective. In process terms the higher rate is translated into much lower pressures (the cobalt catalyst is operated by BASF at pressures of 700 bar). For years now the Monsanto process (now owned by BP) has been the most attractive route for the preparation of acetic acid, but in recent years the iridium-based CATTVA process, developed by BP, has come on stream. 

Caprio et al. [18] measured heat release rates from i-butane oxidation at 100 kPa in the reactant mixture [i-C4Hio] [O2] [N2] = 1 2 1 (Fig. 6.6). A considerably higher heat release rate than that from propane occurred in this system despite the lower partial pressure of reactant. It seems likely that the differences in residence times in the respective experiments is contributory since variations in the heat release rate from i-butane oxidation were obtained when the mean residence time was changed [18]. However, Lignola et al. [47] showed that, at constant tres, the heat release rate from primary reference fuel mixtures, comprising i-CgHig and n-C7H16, depended on the proportions of the fuel components (Fig. 6.6). 

The inclusion of reactions to represent the low-temperature chemistry in a detailed model for n-butane oxidation at high pressures, that is appropriate to temperatures down to about 600 K began in 1986 [225]. At the present time, models which include around 500 species and more than 2000 reversible reactions to represent alkane isomers up to heptane, are in use [219] and still larger schemes are under development [220]. Progress in the validation and application of these models, and kinetic representations for propane and propene oxidation, are discussed in the next subsection. Modelling of the low-temperature combustion of ethene has also been undertaken more recently [20]. 

Following this study, Wilk et al. [230] simulated the composition-time profiles for selected alkenes and oxygenated products that were formed from n-butane and i-butane combustion, and also mixtures of these fuels, in a motored engine. An engine cycle was simulated within a spatially uniform zone of varying volume. The volume history was specified in such a way that the predicted pressure history matched the measured polytropic pressure history in non-reactive conditions. Composition profiles were compared with those measured experimentally. Some of the kinetic features that distinguish the reactivities of the two fuels and their modes of reaction involving alkylperoxy and dialkylperoxy radicals were elucidated in this work. The n-butane oxidation model had also been applied to the... 

In what concerns to products distribution, the effect of temperature is similar with both catalysts and corresponds to an increase in butane conversion the butenes selectivity decreases as the butadiene selectivity increases and the carbon oxides formation also increases, specially CO. These effects are more pronounced with the Cs doped sample. Butane partial pressure does not affect the products distribution with NiMo04 but increases the C4 s selectivity (specially butenes) decreasing mainly the CO2 formation with the 3% Cs doped catalyst. The effects of increasing P02 are the same for both catalysts. A decrease of C4 S selectivities and an increase of COx formation at low pressures is mainly observed. It is noteworthy that the main effects of Cs doping in the selectivities are increase in I-butene selectivity and decrease in CO formation. 

In the work of Baumgartner, isobutane is oxidized at conditions significantly higher than the and Pc of isobutane and also above the critical pressure of the reaction mixture. The reactor operating variables must be carefully optimized and controlled to attain enhanced TBHP selectivities. Also, as with the case of -butane oxidation, enhanced TBHP formation is observed when the reaction is run homogeneously in the dense phase, compared with the corresponding formation obtained when the reaction is run in the liquid phase (Baumgartner, 1983). 

In many chemical or petrochemical processes, economy dictates that superfluous exotherms be utilized to generate steam as an energy conservation measure. Examples are the cooling of a butane oxidation reaction or the condensation of hot sulfur vapors, steam pressure being generated on the shell side of specially designed heat exchangers. 

The effect of temperature on the yield of the main groups of butane oxidation products is shown in Fig. 10.15. The yield of oxygenates is promoted by a temperature reduction, whereas temperature rise increases the yield of olefins, first primary and then lower ones [248]. It is interesting that the composition of the gas-phase butane oxidation products is strikingly different from that of the liquid-phase oxidation products obtained at high pressure, when mainly acetic acid and methyl ethyl ketone are produced, with alcohols being present in small amounts [249]. 

FIGURE 10.15 Effect of temperature on the distribution of products for butane oxidation at atmospheric pressure and constant reactant ratio [248]. 

FIGURE 10.16 Effect of pressure on the yield of the butane oxidation products at T = 386 °C, reaction time of... 

Furman MS, Badrian AS, Gol tyaeva NA, Savchuk SN. Gas-phase oxidation of n-butane under pressure. Gazov Prom 1958 (10) 36—43 [in Russian]. 

Manufactured by the liquid-phase oxidation of ethanal at 60 C by oxygen or air under pressure in the presence of manganese(ii) ethanoate, the latter preventing the formation of perelhanoic acid. Another important route is the liquid-phase oxidation of butane by air at 50 atm. and 150-250 C in the presence of a metal ethanoate. Some ethanoic acid is produced by the catalytic oxidation of ethanol. Fermentation processes are used only for the production of vinegar. 

Isobutane shows the usual NTC and cool flame phenomena (78,154,157,158). As the pressure is iacreased, the expected iacrease ia oxygenated products retaining the parent carbon skeleton is observed (96). Under similar conditions, isobutane oxidizes more slowly than / -butane (159). There are stUl important unresolved questions concerning isobutane VPO (160). 

Oxidation of Hydrocarbons. Ethanol is one of a variety of oxygen-containing compounds produced by the oxidation of hydrocarbons. Ethanol is reported to be obtained in a yield of 51% by the slow combustion of ethane (158,159). When propane is oxidi2ed at 350°C under a pressure of 17.2 MPa (170 atm) (160,161), 8% of the oxygen is converted to ethanol. Lower conversions to ethanol are obtained by oxidi2ing butane. Other oxidation systems used to produce ethanol and acetaldehyde (162—164) and methods for separating the products have been described in the patent Hterature. 

During World War II, production of butadiene (qv) from ethanol was of great importance. About 60% of the butadiene produced in the United States during that time was obtained by a two-step process utilizing a 3 1 mixture of ethanol and acetaldehyde at atmospheric pressure and a catalyst of tantalum oxide and siHca gel at 325—350°C (393—397). Extensive catalytic studies were reported (398—401) including a fluidized process (402). However, because of later developments in the manufacture of butadiene by the dehydrogenation of butane and butenes, and by naphtha cracking, the use of ethanol as a raw material for this purpose has all but disappeared. 

Explosion prevention can be practiced by mixing decomposable gases with inert diluents. For example, acetylene can oe made nonexplosive at a pressure of 100 atm (10.1 MPa) by including 14.5 percent water vapor and 8 percent butane (Bodurtha, 1980). One way to prevent the decomposition reaction of ethylene oxide vapor is to use methane gas to blanket the ethylene oxide hquid. 

On the other hand, the catalytic oxidation of a n-butane, using either cobalt or manganese acetate, produces acetic acid at 75-80% yield. Byproducts of commercial value are obtained in variable amounts. In the Celanese process, the oxidation reaction is performed at a temperature range of 150-225°C and a pressure of approximately 55 atmospheres. ... 

Light naphtha containing hydrocarbons in the C5-C7 range is the preferred feedstock in Europe for producing acetic acid by oxidation. Similar to the catalytic oxidation of n-butane, the oxidation of light naphtha is performed at approximately the same temperature and pressure ranges (170-200°C and =50 atmospheres) in the presence of manganese acetate catalyst. The yield of acetic acid is approximately 40 wt%. 

Raffinate-II typically consists of40 % 1-butene, 40 % 2-butene and 20 % butane isomers. [RhH(CO)(TPPTS)3] does not catalyze the hydroformylation of internal olefins, neither their isomerization to terminal alkenes. It follows, that in addition to the 20 % butane in the feed, the 2-butene content will not react either. Following separation of the aqueous catalyts phase and the organic phase of aldehydes, the latter is freed from dissolved 2-butene and butane with a counter flow of synthesis gas. The crude aldehyde mixture is fractionated to yield n-valeraldehyde (95 %) and isovaleraldehyde (5 %) which are then oxidized to valeric add. Esters of n-valeric acid are used as lubricants. Unreacted butenes (mostly 2-butene) are hydroformylated and hydrogenated in a high pressure cobalt-catalyzed process to a mixture of isomeric amyl alcohols, while the remaining unreactive components (mostly butane) are used for power generation. Production of valeraldehydes was 12.000 t in 1995 [8] and was expected to increase later. 

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