Molybdenum naphthenate

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). 

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... 

The reaction sequence is summarized below using isobucane as the hydrocarbon. The crucial and nearly incredible part of the process is in two parts itself but only shows as one. It is the second equation where the oxygen molecule transfers to the propylene molecule and the ring closes to form the epoxide. (Thats why they call it epoxidation). The magic that causes all that to happen is in the metal catalysts, molybdenum naphthenate or the soluble salts of titanium, vanadium, or tungsten. This molecular fancy-dance is but one of nniany examples in chemistry where catalysts can cause atoms to slide around molecules in unlikely ways. 

The second manufacturing method for propylene oxide is via peroxidation of propylene, called the Halcon process after the company that invented it. Oxygen is first used to oxidize isobutane to r-butyl hydroperoxide (BHP) over a molybdenum naphthenate catalyst at 90°C and 450 psi. This oxidation occurs at the preferred tertiary carbon because a tertiary alkyl radical intermediate can be formed easily. 

In the C4 coproduct route isobutane is oxidized with oxygen at 130-160°C and under pressure to tert-BuOOH, which is then used in epoxidation. In the styrene coproduct process ethylbenzene hydroperoxide is produced at 100-130°C and at lower pressure (a few atmospheres) and is then applied in isobutane oxidation. Epoxidations are carried out in high excess of propylene at about 100°C under high pressure (20-70 atm) in the presence of molybdenum naphthenate catalyst. About 95% epoxide selectivity can be achieved at near complete hydroperoxide and 10-15% propylene conversions. Shell developed an alternative, heterogeneous catalytic system (T1O2 on SiOi), which is employed in a styrene coproduct process.913 914... 

The process also offers the attractive option of reducing the coke yield by slurrying the feedstock with less than 10 ppm of catalyst (molybdenum naphthen-ate) and sending the slurry to a hydroconversion zone to produce low-boiling products (Kriz and Teman, 1994). 

Epoxidation of propylene by a hydroperoxide is commercially viable for those hydroperoxides which, when spent, can easily give another commercial product. One option is to produce -butyl hydroperoxide (plus some -buta-nol) by the air oxidation of isobutane at 90°C and ca. 30 atm in the presence of molybdenum naphthenate (Arco and Texaco). The separated hydroperoxide is then used to oxidize propylene to propylene oxide with yields on hydroperoxide of over 90% (Eqs. 19.39 and 9.40). 

L. Siimegi, I. P. Hajdu, I. Nemes, A. Gedra, On the mechanism of propylene epoxidation catalyzed by molybdenum naphthenate. React. Kinet. Catal. Lett. 12 (1979) 57. 

Epoxidation takes place in the liqnd phase. The catalyst employed for the purpose is generally a 5 per cent weight solution of molybdenum naphthenate in a mixture of... 

Epoxidation. In the Oxirane homogeneous phase technique, epoxidation is catalyzed by molybdenum naphthenate, introduced in a solution in phenyi-1 ethanol at the rate of... 

Mixed plastics waste, coal Sulfided molybdenum naphthenate, sulfided iron naphthenate, Low Alumina, HZSM-5 TD/CD Yes... 

A group of Russian workers has produced a series of technical reports, currently to number 11, that deal with the epoxidation of cyclohexene by ethylbenzene hydroperoxide, using molbydenum catalysts. The reports explore the effects of modifications of the catalyst on reaction efficiency. The use of molybdenum catalysts in the oxidation of cyclohexene by cumyl peroxide has been studied, using i.r. and e.s.r. spectroscopyE.s.r. spectroscopy has also been used to investigate the decomposition of ethylbenzene hydroperoxide in the presence of molybdenum naphthenate. ... 

Experiments were run using 0.9%, 2.0%, 3.0%, and 5.0% sulfided molybdenum naph-thenate (as the percent of molybdenum in the resid) to select a catalyst level. Standard conditions of 30 min at 420°C at a 3 1 tetralin/resid ratio, 3 wt % sulfided molybdenum naphthenate catalyst, and 1500 psi of hydrogen pressure were selected for determination of the relative reactivity to hydroconversion of the coal-derived vacuum resids. It was found that both catalyst concentration and hydrogen pressure have strong effect on the conversion of coal to hydrocarbon. 

The yield of propylene oxide is about 94% and approximately 2.2 mol of the co-product tert-butanol is produced per mol of propylene oxide. From this ratio it becomes immediately understandable that it is essential for an economic indirect propylene oxidation process to find a good market for the coupling product, here tert-butanol. For the isobutane hydroperoxidation reaction propylene is converted with pure oxygen at 120-140 °C, applying pressures of 25-35 bar. The non-catalyzed reaction takes places in the liquid-phase and acetone is formed as a minor by-product. The subsequent epoxidation is carried out in the liquid phase at 110-135 °C under 40-50 bar pressure in five consecutive reactors. The reaction is catalyzed by a homogeneous molybdenum naphthenate catalyst. The co-product tert-butanol can be dehydrated and is afterwards converted into methyl tert-butyl ether (MTBE), an important fuel additive for lead-free gasoline. 

In the peroxidation reactor ethylbenzene is converted with air at 146 °C and 2 bar to form a 12-14 wt% solution of ethylbenzene hydroperoxide in ethylbenzene. The reaction takes place in the liquid phase and conversion is limited to 10% for safety reasons. The reactor is a bubble tray reactor with nine separate reaction zones. To avoid decomposition of the formed peroxide the temperature is reduced from 146 °C to 132 °C over the trays. In the epoxidation reactor the reaction solution is mixed with a homogeneous molybdenum naphthenate catalyst. Epoxidation of propylene in the liquid phase is carried out at 100-130 °C and 1-35 bar. The crude product stream (containing PO, unreacted propylene, a-phenylethanol, acetophenone, and other impurities) is sent to the recycle column to remove propylene. The catalyst can be removed by an aqueous alkali wash and phase separation. The crude PO, obtained as head stream in the crude PO column, is purified by distillations. The unconverted reactant ethylbenzene can be recycled in the second recycle column. The bottom stream containing a-phenylethanol is sent to the dehydration reactor. The vapor-phase dehydration of a-phenylethanol to styrene takes place over a titanium/alumina oxide catalyst at 200-280 °C and 0.35 bar (conversion 85%, selectivity 95%). 

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