Commercial Oxirane Processes

In the isobutane process the f-butanol (TBA) co-product is converted to the gasoline additive, methyl t-butyl ether (MTBE), via dehydration to isobutene and reaction with methanol. The theoretical weight ratio of TBA/PO is 1.32 1 but commercial plants produce 2-3 kg TBA per kg, depending on demand. Because of the very large gasoline pool, marketing 2-3 kg of TBA per kg PO is not a problem. 

Isobutane oxidation is performed in the liquid phase at 130-160 °C and elevated pressures. Since this exceeds the critical temperature of isobutane (134 °C), products (TBA, t-butyl hydroperoxide (TBHP)) must be present to maintain a liquid phase. The epoxidation step is performed at 100-130 °C using 10-300 ppm of Mo. Since propene is a rather unreactive olefin, a high propene/TBHP molar ratio is used to suppress nonproductive decomposition of TBHP. The high propene concentration leads to very high operating pressures and high recycle costs. The PO and TBA products are purified by a combination of direct and extractive distillation. TBHP conversion and PO selectivity are in excess of 90 %. 

In the ethylbenzene process the 1-methylbenzyl alcohol (MBA) co-product is dehydrated to monomeric styrene (SM). The theoretical SM/PO ratio is 1.8 1 and commercial plants operate in the range 2.2-2.7 l, indicating that the selectivity of ethylbenzene hydroperoxide (EBHP) formation is much higher than that of 

TBHP vide supra). The autoxidation of EB is performed at 120-160 °C and 1- bar. MBA and acetophenone (ACP) are formed as by-products via the facile termination of the secondary 1-methylbenzylperoxy radicals. In order to minimize by-product formation by further oxidation of MBA and ACP, the autoxidation is carried out to only low conversions ( 12 %). This solution (ca. 10 %) of EBHP in EB is used in the epoxidation step, i.e., EB is the solvent for the latter step. A high propene/EBHP molar ratio is used and reaction conditions are similar to those of the TBHP process vide supra). The PO selectivity is reported to be 90 % at 92 % EBHP conversion [30] but in practice it may be higher. For comparison the heterogeneous Ti /SiOa catalyst in fixed-bed operation reportedly gives 93-94 % PO selectivity at 96 % EBHP conversion [11]. The products are separated by distillation and MBA is dehydrated to styrene in the vapor phase over a Ti02 catalyst. 

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It is carried out in the Hquid phase at 100—130°C and catalyzed by a soluble molybdenum naphthenate catalyst, also in a series of reactors with interreactor coolers. The dehydration of a-phenylethanol to styrene takes place over an acidic catalyst at about 225°C. A commercial plant (50,51) was commissioned in Spain in 1973 by Halcon International in a joint venture with Enpetrol based on these reactions, in a process that became known as the Oxirane process, owned by Oxirane Corporation, a joint venture of ARCO and Halcon International. Oxirane Corporation merged into ARCO in 1980 and this process is now generally known as the ARCO process. It is used by ARCO at its Channelview, Texas, plant and in Japan and Korea in joint ventures with local companies. A similar process was developed by Shell (52—55) and commercialized in 1979 at its Moerdijk plant in the Netherlands. The Shell process uses a heterogeneous catalyst of titanium oxide on siHca support in the epoxidation step. Another plant by Shell is under constmction in Singapore (ca 1996). 

There are other commercial processes available for the production of butylenes. However, these are site or manufacturer specific, eg, the Oxirane process for the production of propylene oxide the disproportionation of higher olefins and the oligomerisation of ethylene. Any of these processes can become an important source in the future. More recentiy, the Coastal Isobutane process began commercialisation to produce isobutylene from butanes for meeting the expected demand for methyl-/ rZ-butyl ether (40). 

Company was the largest producer. In that year, Oxirane brought on stream the first peroxidation process involving catalyzed epoxidation of propylene with tert-butyl hydroperoxide. In 1977, Oxirane (later Arco Chemical) commercialized a process which employed ethylbenzene hydroperoxide as the epoxidizing agent and produced PO and styrene (Fig. 10.23). 

Two variants of the Oxirane process are used (Figure 1) for the commercial production of propene oxide (PO) [29]. They differ in the hydrocarbon (isobutane or ethylbenzene (EB)) that is the precursor of the hydroperoxide, and, hence, in the alcohol co-product. ARCO operates both processes using a homogeneous molybdenum catalyst. Shell, in contrast, operates only the EB variant and uses a heterogeneous Ti /Si02 catalyst. 

The Oxirane process is a mature technology that has stood the test of time. Both ARCO and Shell have been successfully operating for more than two decades. More recently a heterogeneous titanium-substituted silicalite (TS-1) catalyst was developed by Enichem [43, 44]. In contrast to the Shell Ti /Si02 catalyst, TS-1 has a hydrophobic surface and is a remarkably effective catalyst for a variety of liquid-phase oxidations with 30 % aqueous hydrogen peroxide, including epoxidation [44]. It has been commercialized for the hydroxylation of phenol to... 

The derivatives are hydroxyethyl and hydroxypropyl cellulose. AH four derivatives find numerous appHcations and there are other reactants that can be added to ceUulose, including the mixed addition of reactants lea ding to adducts of commercial significance. In the commercial production of mixed ethers there are economic factors to consider that include the efficiency of adduct additions (ca 40%), waste product disposal, and the method of product recovery and drying on a commercial scale. The products produced by equation 2 require heat and produce NaCl, a corrosive by-product, with each mole of adduct added. These products are produced by a paste process and require corrosion-resistant production units. The oxirane additions (eq. 3) are exothermic, and with the explosive nature of the oxiranes, require a dispersion diluent in their synthesis (see Cellulose ethers). 

Oxirane A general process for oxidizing olefins to olefin oxides by using an organic hydroperoxide, made by autoxidation of a hydrocarbon. Two versions are commercial. The first to be developed oxidizes propylene to propylene oxide, using as the oxidant f-butyl hydroperoxide made by the atmospheric oxidation of isobutane. Molybdenum naphthenate is used as a... 

Polymerization of the oxiranes is typically propagated from a starter molecule that is chosen to define the functionality if) of the final polyol. The functionality and the molecular weight of polyols are the main design features that define the polyurethane properties in the end-use applications. Additionally, the balance of EO and PO in the polyether polyols, mainly for flexible foam polyols, is tailored to enhance the compatibility of formulations and the processability of the foam products. The exact composition of the polyols defines the crucial performance features of the final polyurethane product. Even seemingly small differences in polyol composition can result in changes to polyol processabihty and polyurethane performance. This becomes a crucial issue when replacing conventional petrochemical polyols with polyols from different feedstocks. To demonstrate the sensitivity of commercial formulations to changes in feedstocks, a simple example is offered below. 

Styrene, one of the world s major organic chemicals, is derived from ethylene via ethylbenzene. Several recent developments have occurred with respect to this use for ethylene. One is the production of styrene as a co-product of the propylene oxide process developed by Halcon International (12). In this process, benzene is alkylated with ethylene to ethylbenzene, and the latter is oxidized to ethylbenzene hydroperoxide. This hydroperoxide, in the presence of suitable catalysts, can convert a broad range of olefins to their corresponding oxirane compounds, of which propylene oxide presently has the greatest industrial importance. The ethylbenzene hydroperoxide is converted simultaneously to methylphenyl-carbinol which, upon dehydration, yields styrene. Commercial application of this new development in the use of ethylene will be demonstrated in a plant in Spain in the near future. 

Polyethylene oxide)macromonomers have thus been synthesized by two-step processes. Poly(oxyethylene)mo nomethyl ethers with widely varying molecular weights are commercially available. They are obtained by anionic polymerization of oxirane initiated by monofunctional alkoxides261 such as potassium 2-methoxyethanol. 

This process was originally developed and commercialized by Oxirane (a joint venture company between ARCO Chemical, now Lyondell, and Halcon) and independently by Shell Petrochemical Company. At present, this is one of the main processes for the commercial manufacture of propylene oxide (the other is a variant of the same that starts with isobutane instead of ethylbenzene, and produces propylene oxide together with tert-butyl alcohol, isobutylene, and... 

Synthesis of Oxirans by Halohydrin Cyclizations and Related Reactions. One of the oldest commercial methods for the production of ethene oxide is the chlorohydrin route, involving chlorohydration of ethene followed by dehydrochlorination. An improved procedure for the second stage of this process has been reported in which a basic ion-exchange resin is used to... 

Sumitomo developed a recirculation process for manufacture of PO using CHP as oxidant (196). The company developed both a new catalyst and a new process for PO production. The production method is fundamentally similar to known methods involving organic peroxides as oxidants the major difference is that cumene is used as the reaction medium and hence the process is referred to as the cumene PO-only process. Laboratory tests started in 2000 and pilot plant testing in 2001. A plant was completed in 2002 and started up in 2003. This commercial plant was the first PO-only plant in Japan, producing PO by oxidation of propylene with cumene hydroperoxide without a significant formation of coproducts. The plant is located in the Chiba prefecture, operated by a joint venture between Nihon Oxirane Co. and Lyondell, and produces aroimd 200,000 t of PO/year. A second plant was started in May 2009 in Saudi Arabia, as a joint project of Sumitomo with Saudi Arabian Oil Co. 

Methylphenylcarbinol is also an intermediate in the Halcon process, in which ethylbenzene is oxidized to a hydroperoxide at around 130 °C with air, then converted with propylene into propylene oxide and carbinol. The carbinol is subsequently dehydrated on a titanium catalyst at 180 to 280 °C to styrene. This process, first commercialized by Atlantic Richfield, has found large-scale application in a few isolated cases (e.g. Shell (Netherlands), Alcudia (Spain) and Nihon Oxirane (Japan)) it is only viable if there is sufficient demand for propylene oxide. 

According to Scheme 21.12, the multistep process involves first ethylene carbonate production from oxirane (EO) and carbon dioxide, the commercial catalytic technology. The carbon dioxide utilised herein is the byproduct from a nearby oxirane plant. Then, step A produces dimethyl carbonate and monoethyleneglycol (MEG) by catalytic transesterification of ethylene... 

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