Isobutylene solvent extraction

Isobutylene is the most chemically reactive of the butylene isopiers. If the objective is just to get the isobutylene out of the C4 stream, it can be removed by reaction with methanol (CH3OH) to make MTBE (methyl tertiary butyl ether), by reaction with water to make TBA (tertiary butyl alcohol), by polymerization, or by solvent extraction. After that, butene-1 can be removed by selective adsorption or by distillation. That leaves the butene-2 components, together with iso- and normal butane, which are generally used as feed to an alkylation plant. 

Solvent extraction. Isobutylene can also be segregated by extractive distillation in the same way as butadiene. In this case, the solvent is cold sulfuric acid. One problem occurs if there is any butadiene left in the stream—sulfuric acid will cause it to polymerize. But if the butadiene has been first extracted, a 99" % isobutylene stream can be recovered. 

Solvent Extraction Performance in Petroleum Refining Industry (Lube Oil Refining Subcategory) Using Extractor (Spray Column Contactor and Stripping Column) and Solvent (Isobutylene)... 

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. 

Separation and Purification of Isomers. 1-Butene and isobutylene caimot be economically separated into pure components by conventional distHlation because they are close boiling isomers (see Table 1 and Eig. 1). 2-Butene can be separated from the other two isomers by simple distHlation. There are four types of separation methods avaHable (/) selective removal of isobutylene by polymeriza tion and separation of 1-butene (2) use of addition reactions with alcohol, acids, or water to selectively produce pure isobutylene and 1-butene (3) selective extraction of isobutylene with a Hquid solvent, usuaHy an acid and (4) physical separation of isobutylene from 1-butene by absorbents. The first two methods take advantage of the reactivity of isobutylene. Eor example, isobutylene reacts about 1000 times faster than 1-butene. Some 1-butene also reacts and gets separated with isobutylene, but recovery of high purity is possible. The choice of a particular method depends on the product slate requirements of the manufacturer. In any case, 2-butene is first separated from the other two isomers by simple distHlation. 

Schoenmakers et al. [72] analyzed two representative commercial rubbers by gas chromatography-mass spectrometry (GC-MS) and detected more than 100 different compounds. The rubbers, mixtures of isobutylene and isoprene, were analyzed after being cryogenically grinded and submitted to two different extraction procedures a Sohxlet extraction with a series of solvents and a static-headspace extraction, which entailed placing the sample in a 20-mL sealed vial in an oven at 110°C for 5,20, or 50 min. Although these are not the conditions to which pharmaceutical products are submitted, the results may give an idea of which compounds could be expected from these materials. Residual monomers, isobutylene in the dimeric or tetrameric form, and compounds derived from the scission of the polymeric chain were found in the extracts. Table 32 presents an overview of the nature of the compounds identified in the headspace and Soxhlet extracts of the polymers. While the liquid-phase extraction was able to extract less volatile compounds, the headspace technique was able to show the presence of compounds with low molecular mass... 

Altenau and co-workers [26,27] used MS to identify quantitatively volatile antioxidants in 0.02-0.03 inch thick samples of synthetic styrene-butadiene rubbers and rubber-type vulcanisates. They extracted the polymer with acetone in a Soxhlet apparatus, removed excess solvent, and dissolved the residue in benzene. Substances identified and determined by this procedure include N-phenyl-P-napthylamine, 6-dodecyl-2,2,4-trimethyl-l,2-dihydroquinolines, trisnonylphenylphosphate, isobutylene-bisphenol, 2-mercaptobenzothiazole sulfenamide (accelerator), N-cyclohexyl-2-benzothiazole... 

Countercurrent extraction should be the answer to the problem and has indeed been suggested by a number of authors [18-20]. Calculations by Englert and Tompa [21] have demonstrated that truly impressive results should be obtainable, provided some experimental problems could be solved. The latter relate to the extremely slow phase segregation caused by the high viscosity of the concentrated phase which is a handicap for continuous operation. Further, a binary solvent system in whieh the solvent power of the two phases is different, though not too much, is not easy to find. It has been a fairly reeent accomplishment of Wolf et al. [22 24] to overeome these practical problems and realize large-seale fractionation by continuous liquid liquid extraction. They included poly(isobutylene) in their studies and also sueeeeded in applying the method succesfully to linear poly(ethylene) [25]. 

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