Styrene monomer/propylene oxide process

EB/SM (ethylbenzene/styrene monomer) process. Styrene can also be made by PO/SM (propylene oxide/styrene monomer) process). This process starts by oxidizing ethylbenzene (C6H5CH2CH2) to its hydroperoxide (C6H5CH(OOH)CH3), which is then used to oxidize propylene (CH3CH = CH2) to produce propylene oxide (CH3CH2CHO) and phenylethanol (C6H5CH(OH)CH3). The phenylethanol is then dehydrated to give... 

W. S. Dubner, R. N. Cochran, Propylene oxide-styrene monomer process, U.S. Patent No. 5,210,354,1993, Assigned to ARCO Chemical Technology. 

POSM [Propylene Oxide Styrene Monomer] A process for making propylene oxide from ethylbenzene. The ethylbenzene is reacted with oxygen and propylene in the presence of a proprietary catalyst. Developed in Russia by JSC Nizkhnekamskneftkheim and licensed exclusively by Dow Chemical Company. In 2006, 36% of the world production of propylene oxide was made by this process. See also SMPO. 

Aerobic selective oxidation of alkylaromatics, including cumene (CU), ethylbenzene (EtB), and cyclohexylbenzene (CyB), to the corresponding hydroperoxides (CHPs) represents a key step for several large-scale productions, including the Hock process for the synthesis of phenol (see Chapter 2) [15] and the Shell styrene monomer/propylene oxide (SM/PO) process for the production of propylene oxide (PO) and styrene monomer (SM) [16]. 

SMPO [styrene monomer propylene oxide] A process for making propylene oxide by the catalytic epoxidation of propylene. The catalyst contains a compound of vanadium, tungsten, molybdenum, or titanium on a silica support. Developed by Shell and operated in The Netherlands since 1978. 

Olefin epoxidation is an important industrial domain. The general approach of SOMC in this large area was to understand better the elementary steps of this reaction catalyzed by silica-supported titanium complexes, to identify precisely reaction intermediates and to explain catalyst deachvahon and titanium lixiviation that take place in the industrial Shell SMPO (styrene monomer propylene oxide) process [73]. (=SiO) Ti(OCap)4 (OCap=OR, OSiRs, OR R = hydrocarbyl) supported on MCM-41 have been evaluated as catalysts for 1-octene epoxidation by tert-butyl hydroperoxide (TBHP). Initial activity, selechvity and chemical evolution have been followed. In all cases the major product is 1,2-epoxyoctane, the diol corresponding to hydrolysis never being detected. 

A process to produce styrene monomer and propylene oxide simultaneously was introduced in 1969. 

Monomers devoid of polar groups generally undergo anionic polymerization in a predictable manner. With polar monomers sometimes side reactions occur during the process transfer reactions in the case of acrylonitrile, or propylene oxide, and even more so with alkylacrylates deactivations (or "killing") reactions in the case of halogen substituted styrene or dienes. 

All the styrene monomer (bpi.oia - 145.2 C, s/J == 0.906. ) produced throughout the world is obtained directly or indiiectly from etbylbenzeoe. Most is product by dehydrogenation, while a certain amount is also obtained as a co-product of Ae manu- ctuie of propylene oxide. Some attempts have been made to extract styrene from liyrolysis C5- gasolines (Stex process by Toray, deserflied in Section 4.2J), but they have. not culminated in commercial plants. 

Styrene is an important monomer or comonomer in the manufacture of a number of polymers polystyrene, acrylonitrile/butadiene/styrene, styrene/acrylonitrile, etc. There are two main processes for the manufacture of styrene. In one process styrene is made a coproduct with propylene oxide ... 

Shell has coproduced propylene oxide (PO) and styrene using its proprietary styrene monomer propylene oxide (SMPO) process for three decades. Research, development, and plant trials have been performed on a continuous basis in order to improve its efficiency and cost competitiveness. We report here some of the key fundamental and technological learnings gathered over various parts of the process. 

Propylene oxide (PO) is a versatile chemical intermediate used in a wide range of industrial and commercial products. Current world production is over 6 million metric torts a year. While several processes exist, the Shell Chemicals companies have derived a strong competitive advantage by using and continually developing their proprietary styrene monomer propylene oxide (SMPO) technology, a process in which propylene and ethylbenzene (EB) are converted into PO and styrene monomer (SM), respectively. Worldwide, there are now five world-scale SMPO plants based on Shell technology, the most recent one started up in 2006 in China. 

Scheme 4.51 shows the process known to the bulk chemicals industry as SMPO, the styrene monomer-propylene oxide process. Styrene is used in polymers, and propylene oxide derivatives have a wide variety of uses, including as surfactants and in anti-freeze. For the bulk industry, the process is as follows. Addition of ethylene to benzene gives ethylbenzene, which undergoes air oxidation to give the hydroperoxide. Reaction of this with propylene, in the presence of a suitable catalyst, gives styrallyl alcohol and propylene oxide. Styrallyl alcohol is readily dehydrated to styrene. 

A variety of hydrocarbons can be used to form hydroperoxides in situ which can then be used to make propylene oxide however, in each case, a coproduct is formed. The quantity of the coproduct, on a weight basis, is larger than the propylene oxide produced therefore, the economics of the processes are sensitive to the market and price for both propylene oxide and the coproduct. Two hydrocarbon feedstocks have been commercialized isobutane which yields tert-butyl alcohol as coproduct and ethylbenzene which yields styrene as coproduct. Both of these feedstocks are readily available and there are large established markets for both coproducts. Styrene is a large volume and well established petrochemical monomer and tert-butyl alcohol can be easily dehydrated to isobutylene which can be used as a feedstock for the gasoline additive methyl-tert-butyl ether (MTBE). 

Dubner, W. S. Improved Process for the Co-Production of Propylene Oxide and Styrene Monomer. 199300569248, 1993. 

The styrene is separated from the product mix, which also contains unreacted ethylbenzene and other impurities, by vacuum distillation. The monomer can easily autopolymerize into a hard solid and is therefore inhibited from polymerization during storage by mixing in a few parts per milhon of a free-radical reaction inhibitor (generally f-butyl catechol). A relatively small amount of styrene is also made by the oxidation of ethyl benzene in a process introduced by Union Carbide. The ethylbenzene hydroperoxide formed by oxidation is reacted with propylene to form propylene oxide and 2-phenyl ethanol. The latter compound is dehydrated to obtain styrene. 

Ethylene oxide is manufactured hy direct oxidation of ethylene, in contrast PO is only obtained in coproduct processes. The classical process, chlorination of propylene, is still used by Dow, one of the world s largest producer of polyether polyols. In contrast, all other producers use the Halcon process, based on the simultaneous production of PO and styrene monomer or t-butyl alcohol. In view of the demise of AITBE (methyl-f-butyl ether based on t-butyl alcohol) as a fuel additive, the styrene coproduct process (POSM) will remain as the economically viable route to PO. A recent example is the new (SMPO) plant of Basell at Moerdijk in the Netherlands. The largest producer of PO, the former Arco (now Lyondell), has sold its global polyol business to Bayer in 1999. Lyondell will also provide Bayer a long-term, low cost supply of PO. Recently, Dow annoimced that it also will use the POSM route to PO in a new facility. 

Styrene. Global consumption of styrene monomer in 1998 was 17.9 million metric tons (2). While polystyrene was the largest outlet, SB copolymers (including latexes) consumed a total of 1.95 million metric tons. Styrene monomer is produced by two processes. Ethylbenzene dehydrogenation is the most widespread process used for styrene manufacture, followed by the propylene oxide coproduct route. 

The indirect propylene oxidation process via ethylbenzene hydroperoxide (Halcon process) is displayed in Eq. (6.12.12). Ethylbenzene, obtained by the acid-catalyzed Friedel-Crafts alkylation of benzene with ethylene, is converted with air into ethylbenzene hydroperoxide. The hydroperoxide epoxidizes propylene and generates the co-product a-phenylethanol that is later dehydrated to styrene. Styrene is a major industrial chemical used mainly as monomer for polymers such as polystyrene or styrene-containing copolymers ... 

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