Isoprene manufacture

A number of new processes exploiting metathesis have been developed by Phillips. A novel way to manufacture lubricating oils has been demonstrated.145 The basic reaction is self-metathesis of 1-octene or 1-decene to produce Ci4-C28 internal alkenes. The branched hydrocarbons formed after dimerization and hydrogenation may be utilized as lubricating oils. Metathetical cleavage of isobutylene with propylene or 2-butenes to isoamylenes has a potential in isoprene manufacture.136,146 High isoamylene yields can be achieved by further metathesis of C6+ byproducts with ethylene and propylene. Dehydrogenation to isoprene is already practiced in the transformation of isoamylenes of FCC C5 olefin cuts. 

Until the mid-1970s metal-catalyzed propylene dimerization had practical significance in isoprene manufacture. Goodyear developed a process to dimerize propylene in the presence of tri-n-propylaluminum to yield 2-methyl-1-pentene.16,95,96 This was then isomerized to 2-methyl-2-pentene followed by cracking into isoprene and methane. This and other synthetic pocesses, however, are no longer practiced since they are not competitive with isoprene manufactured by cracking of naphtha or gas oil. 

Remark. Several companies have designed techniques derived from the foregoing processes, some of them leading to industrial development These include isoprene manufacture from isobutene and formaldehyde in a single step (British Hydrocarbon Chemical, Japan Institute of Physical and Chemical Research, Marathon, Sun Oil, Tokyo Institute ofTechnology), and the replacement of formaldehyde by methanol and oxygen or by methylether (Idemitsu Petrochemical, Sumitomo etc.). 

Mitsmani, A Kumano, S Recent development on isoprene manufacturing processea in Japan", Chem. Eton, and Engng Rev, 3 (2, 34) 3S-H (19711... 

Coral rubber Cis-l,4-poly(isoprene). Manufactured by Goodrich, USA. 

Butyl Rubber n (1940) A synthetic elastomer produced by copolymerizing isobutylene with a small amount (ca 2%) of isoprene or butadiene. It has good resistance to hear, oxygen, and ozone, and low gas permeability. Thus, it is widely used in inner tubes and to line tubeless tires. Butyl rubber is a vinyl polymer, and is very similar to polyethylene and polypropylene in structure, except that every other carbon is substituted with two methyl groups. It is made from the monomer isobutylene, by cationic vinyl polymerization. It can also go by the name of Polyisobutylene. (1) Generic name for vulcanizable elastic copolymers of isobutylene and small amounts of diolefins. (2) Mixture of isobutylene, 98% and butadiene or isoprene, 2%. (3) Poly (isobutylene) with 2% isoprene. Manufactured by Bayer, Germany. 

Continuous processes have been developed for the alcohols, operating under pressure with Hquid ammonia as solvent. Potassium hydroxide (206) or anion exchange resins (207) are suitable catalysts. However, the relatively small manufacturing volumes militate against continuous production. For a while a continuous catalytic plant operated in Raveima, Italy, designed to produce about 40,000 t/yr of methylbutynol for conversion to isoprene (208,209). 

Chemical Uses. In Europe, products such as ethylene, acetaldehyde, acetic acid, acetone, butadiene, and isoprene have been manufactured from acetylene at one time. Wartime shortages or raw material restrictions were the basis for the choice of process. Coking coal was readily available in Europe and acetylene was easily accessible via calcium carbide. 

Butyl mbber, a copolymer of isobutjiene with 0.5—2.5% isoprene to make vulcanization possible, is the most important commercial polymer made by cationic polymerization (see Elastomers, synthetic-butyl rubber). The polymerization is initiated by water in conjunction with AlCl and carried out at low temperature (—90 to —100° C) to prevent chain transfer that limits the molecular weight (1). Another important commercial appHcation of cationic polymerization is the manufacture of polybutenes, low molecular weight copolymers of isobutylene and a smaller amount of other butenes (1) used in adhesives, sealants, lubricants, viscosity improvers, etc. 

With the avadabihty of polymerization catalysts, extensive efforts were devoted to developing economical processes for manufacture of isoprene. Several synthetic routes have been commercialized. With natural mbber as an alternative, the ultimate value of the polymer was more or less dictated by that market. The first commercial use of isoprene in the United States started in 1940. It was used as a minor comonomer with isobutylene for the preparation of butyl mbber. Polyisoprene was commercialized extensively in the 1960s (6). In the 1990s isoprene is used almost exclusively as a monomer for polymerization (see ELASTOLffiRS,SYNTHETic-POLYisoPRENE). 

Polymers account for about 3—4% of the total butylene consumption and about 30% of nonfuels use. Homopolymerization of butylene isomers is relatively unimportant commercially. Only stereoregular poly(l-butene) [9003-29-6] and a small volume of polyisobutylene [25038-49-7] are produced in this manner. High molecular weight polyisobutylenes have found limited use because they cannot be vulcanized. To overcome this deficiency a butyl mbber copolymer of isobutylene with isoprene has been developed. Low molecular weight viscous Hquid polymers of isobutylene are not manufactured because of the high price of purified isobutylene. Copolymerization from relatively inexpensive refinery butane—butylene fractions containing all the butylene isomers yields a range of viscous polymers that satisfy most commercial needs (see Olefin polymers Elastomers, synthetic-butylrubber). 

Monomers for manufacture of butyl mbber are 2-methylpropene [115-11-7] (isobutylene) and 2-methyl-l.3-butadiene [78-79-5] (isoprene) (see Olefins). Polybutenes are copolymers of isobutylene and / -butenes from mixed-C olefin-containing streams. For the production of high mol wt butyl mbber, isobutylene must be of >99.5 wt % purity, and isoprene of >98 wt % purity is used. Water and oxygenated organic compounds iaterfere with the cationic polymerization mechanism, and are minimized by feed purification systems. 

A partially cross-linked, isobutylene—isoprene—divinylbenzene terpolymer containing some unreacted substituted vinylbenzene appendages is commercially available from Polysar Division, Bayer AG. Because of the residual reactive functionality, it can be cross-linked by peroxides that degrade conventional butyl mbbets. It is employed primarily in the manufacture of sealant tapes and caulking compounds (31). 

Isoprene (2-methyl 1,3-butadiene) is the second most important conjugated diolefin after butadiene. Most isoprene production is used for the manufacture of cis-polyisoprene, which has a similar structure to natural rubber. It is also used as a copolymer in butyl rubber formulations. 

While most isoprene produced today comes from the dehydrogenation of C5 olefin fractions from cracking processes, several schemes are used for its manufacture via synthetic routes. The following reviews the important approaches for isoprene production. 

Ionol is a commercial antioxidant, 2,6-di-/cr/-butyl- -cresol, manufactured by Shell Chemical Corp. Inhibitors appear to minimize formation of polymeric side products, although with isoprene the effect is often small. 

Conjugated dienes are among the most significant building blocks both in laboratories and in the chemical industry [1], Especially, 1,3-butadiene and isoprene are key feedstocks for the manufacture of polymers and fine chemicals. Since the discovery of the Ziegler-Natta catalyst for the polymerizations of ethylene and propylene, the powerful features of transition metal catalysis has been widely recognized, and studies in this field have been pursued very actively [2-7]. 

In 1994, the worldwide consumption of rubber was approximately 14.5 million tons a year, of which about 40% consisted of natural rubber. Natural rubber is produced as latex by tropical rubber trees (Hevea brasiliensis). It is processed locally and therefore the quality of natural rubber fluctuates remarkably [ 140]. Due to increasing demand for rubbers, combined with a decreasing production capacity in Asia and a vast increase in labor costs, the price of natural rubber is still rising sharply. In 1990-1994, the average price of natural rubber was about 0.38 /lb, while in 1996 it was already over 0.80 /lb. The remaining 60% of the articles were manufactured from synthetic petroleum-based rubbers such as isoprene rubber, styrene-butadiene rubber, chloroprene rubber and polyurethanes. The quality of synthetic rubbers is constant, and their price varies between 2 and 5 US per kilogram [137-140]. 

Polymerised isoprene. Naturally-occurring polyisoprenes are natural rubber (cA-form) and gutta percha (trans- form). The use of stereo specific catalysts has made possible the manufacture of synthetic cA-polyisoprene and fraws-polyisoprene both of which are now available commercially. 

Isoprene, the most abundant hydrocarbon emitted to the atmosphere by plants, can also be measured using ozone chemiluminescence. As discussed above, al-kenes react with ozone to produce formaldehyde in its A2 electronic state, in addition to several other chemiluminescent products. In a fast isoprene detector manufactured by Hills Scientific (Boulder, CO), the chemiluminescence is detected using a blue-sensitive PMT to maximize the sensitivity for isoprene detec-... 

IDAS A process for making isoprene (for the manufacture of a synthetic rubber) by the oxidative dehydrogenation of isopentene. Iodine is the initial reactant the hydrogen iodide produced in the reaction is reconverted to elemental iodine via nickel iodide. 

They are not found to any extent in natural products, but are produced in the destructive distillation of complex natural substances, such as coal, and are formed in large amounts in petroleum refining, particularly in the cracking process. The first member of the series is ethylene, C2H4. The dienes contain two double bonds between pairs of carbon atoms in the molecule. They are related to the complex hydrocarbons in natural rubber and are important in the manufacture of synthetic rubber and plastics. The most important members of this series are butadiene, C4H5 and isoprene, CsHg. 

The mechanical properties at low strain rates, dynamic mechanical properties, creep-recovery behaviour, thermal expansion and thermal conductivity of foams manufactured from blends of LDPE with an EVA and with an isoprene-styrene block copolymer were studied as a function of the LDPE content in the blends. The experimental results demonstrated important aspects related to the modification of the foam properties by blending. 16 refs. 

It was a good idea, but it didn t work. No microbe that Weizmann tried yielded isoprene. But Clostridium aceto-butylium did convert starch into a mixture of ethanol, acetone, and butanol, a blend that did not particularly interest Weizmann. It certainly interested Lloyd George, however he heard the whole account from Weizmann himself. Here, pehaps, was a way to produce the acetone that they sorely needed for the manufacture of cordite. Weizmann was asked to scale up his experimental process, and within a short time he d converted a gin distillery into a factory to make his mixture. He easily separated the acetone through distillation, and soon mass production was under way. There was no need for butanol, and huge stocks built up. But after the war the... 

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