Isobutane synthesis

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. 

The forty-eighth volume of Advances in Catalysis includes a description of a new and increasingly well understood class of catalysts (titanosilicates), a review of transmission electron microscopy and related methods applied to catalyst characterization, and summaries of the chemistry and processes of isobutane-alkene alkylation and partial oxidation and C02 reforming of methane to synthesis gas. 

Corma, A., Martinez, A., Arroyo, P.A., Monteiro, J.L.F., and Sousa-Aguiar, E.F. (1996) Isobutane/2-butene alkylation on zeolite beta influence of post-synthesis treatments. Appl. Catal. A, 142,... 

The propylene-butylene fraction constitutes a large part of the useful hydrocarbons produced by synthesis. It differs from similar fractions derived from petroleum refining in its high olefin (over 80%) and low isobutylene content, but this is no handicap in converting it to high octane gasoline by polymerization or by alkylation, if isobutane is available from another source. Polymerization is effected readily over a phosphoric acid on quartz catalyst with high conversion of propylene as well as butylene. The polymer... 

Isosynthesis is a potentially important variation of the Fischer-Tropsch synthesis since it yields mainly branched C4-C8 paraffins.187,188 279 280 Most of the pioneer-ing work was carried out by Pichler and coworkers. They observed that certain nonreducible tetravalent oxides (thoria, zirconia, ceria) exhibited activity in the reaction producing primarily isobutane. The optimum operating conditions... 

The skeletal isomerization of straight-chain paraffins is important for the enhancement of the octane numbers of light petroleum fractions. The isomerization of H-butane to isobutane has attracted much attention because isobutane is a feedstock for alkylation with olefins and MTBE synthesis. It is widely believed that the low-temperature transformation of n-alkanes can be catalyzed only by superacidic sites, and this reaction has often been used to test for the presence of these sites. 

Propylene polymers are relatively stable, but the butylene polymers can be broken down under many conditions. Such a breakdown occurs when butylene polymers are charged to an alkylation unit, when the individual butylene molecules react with the isobutane. The stability of the propylene polymers is one of the reasons why they are preferred as starting materials for such reactions as the synthesis of dodecyl benzene in the manufacture of detergents. 

Other catalytic reactions carried out in fluidized-bed reactors are the oxidation of naphthalene to phthalic anhydride [2, 6, 80] the ammoxidation of isobutane to mcthacrylonitrilc [2] the synthesis of maleic anhydride from the naphtha cracker C4 fraction (Mitsubishi process [81, 82]) or from n-butane (ALMA process [83], [84]) the reaction of acetylene with acetic acid to vinyl acetate [2] the oxychlorination of ethylene to 1,2-di-chloroethane [2, 6, 85, 86] the chlorination of methane [2], the reaction of phenol with methanol to cresol and 2,6-xylenol [2, 87] the reaction of methanol to gasoline... 

A homogeneous catalytic process, developed by Oxirane, uses a molybdenum catalyst that epoxidizes propylene by transferring an oxygen atom from tertiary butyl hydroperoxide. This is shown by 8.28. The hydroperoxide is obtained by the auto-oxidation of isobutane. The co-product of propylene oxide, /-butanol, finds use as an antiknock gasoline additive. It is also used in the synthesis of methyl /-butyl ether, another important gasoline additive. The over-... 

ANHYD1—reaction of acetone and acetic acid to form acetic anhydride BUTAL1—alkylation reaction of butene-1 and isobutane to produce iso-octane Select the new plant design mode and the look at existing flow sheet option, and follow the synthesis steps for one of these processes. Obtain the current flow sheet as output at each level of the synthesis procedure. Also list the heuristics used at each step. 

The facile synthesis of 4,4-dimethyl-2-cyclopentenone by the allylation of isobutanal, followed by the oxidation and aldol condensation of Ae keto aldehyde is another example. ... 

Gavalas et al. [7] prepared ZSM-5 membranes onto porous a-alumina disks by in-situ hydrothermal synthesis at 175°C. The zeolite layers were formed on the bottom face of disks placed horizontally near the air-liquid interface of clear synthesis solutions. The films grown at the optimized conditions were about 10 pm thick and consisted of well-intergrown crystals of about 2 pm in size Pure gas permeation measurements of the best preparations yielded hydrogen isobutane and butane isobutane ratios of 151 and 18 at room temperature and of 54 and 31 at 185°C, respectively. 

Using excess amount of porous silica grains as the Si-source in ZSM-5 synthesis, crystals were grown inside the pores of amorphous silica. The ZSM-5 crystals in the mesopores were very small (0 02-0.035 pm) those in the macropores were somewhat larger (0.5-2 pm), whereas the ones on the outside surface of the particles were between 3 and 5 pm. The composite catalyst was more active in isobutane cracking than conventional H-ZSM-5 [67]. 

The hydrogenation of carbon dioxide was studied using composite catalysts comprised of Fe-Zn-M (M= Cr, Al, Ga, Zr) catalysts and the HY zeolite, where the methanol synthesis and the methanol-to-gasoline(MTG) reaction are combined. The results show that light olefins are important intermediates for iso-butane formation. In all of the cases, the selectivity of isobutane, which can be used as a reactant in subsequent methyl-tert-butyl ether (MTBE) synthesis, was the highest in hydrocarbons. 

The importance of olefins to the distribution of hydrocarbons and the synthesis of isobutane is obvious. In the case of the Cu-Zn-Al/HY composite catalyst, the immediate hydrogenation of the olefins such as ethylene and propylene prevents the oligomerization to higher hydrocarbons. Therefore, C4+ hydrocarbons were scarcely obtained. On the contrary, in the case of the Fe-Zn-Zr/HY composite catalyst (Fig.l, b), the selectivity of methane was... 

Indeed, the reaction was first observed in the synthesis of the hydrides. As mentioned above, when 5 is heated under dry hydrogen to 150 °C for three hours, (=SiO)3ZrH (14) is formed together with nine equivalents of methane and three equivalents of ethane. The formation of methane and ethane rather than neopentane was clear evidence of hydrogenolysis under the synthesis conditions [5, 15, 16]. It was observed that the reaction of neopentane occurred by stepwise formation of firstly isobutane and methane, then conversion of the former to a second equivalent of methane and propane which is further converted to ethane and a third equivalent of methane. The C-C bond of ethane cannot be cleaved by P-methyl elimination because a surface metal-ethyl fragment has no methyl group in the S-position. 

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