Ethylbenzene hydroperoxide conversion

Ethylbenzene Hydroperoxide Process. Figure 4 shows the process flow sheet for production of propylene oxide and styrene via the use of ethylbenzene hydroperoxide (EBHP). Liquid-phase oxidation of ethylbenzene with air or oxygen occurs at 206—275 kPa (30—40 psia) and 140—150°C, and 2—2.5 h are required for a 10—15% conversion to the hydroperoxide. Recycle of an inert gas, such as nitrogen, is used to control reactor temperature. Impurities ia the ethylbenzene, such as water, are controlled to minimize decomposition of the hydroperoxide product and are sometimes added to enhance product formation. Selectivity to by-products include 8—10% acetophenone, 5—7% 1-phenylethanol, and <1% organic acids. EBHP is concentrated to 30—35% by distillation. The overhead ethylbenzene is recycled back to the oxidation reactor (170—172). 

Epoxidation of propylene with ethylbenzene hydroperoxide is carried out at approximately 130°C and 35 atmospheres in presence of molybdenum catalyst. A conversion of 98% on the hydroperoxide has been reported ... 

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... 

FIGURE 14.1 Influence of TiCU deposition time on ethylbenzene hydroperoxide (EBHP) conversion and propylene oxide yield for Ti/Si02 catalysts. 

We have developed an effective method for the selective autoxidation of alky-laromatic hydrocarbons to the corresponding benzylic hydroperoxides using 0.5 mol% NHPI as a catalyst and the hydroperoxide product as an initiator. Using this method we obtained high selectivities to the corresponding hydroperoxides, at commercially viable conversions, in the autoxidation of cyclohexylbenzene, cumene and ethylbenzene. The highly selective autoxidation of cyclohexylbenzene to the 1-hydroperoxide product provides the basis for a coproduct-free route to phenol and the observed inq)rovements in ethylbenzene hydroperoxide production provide a basis for in roving the selectivity of the SMPO process for styrene and propene oxide manufacture. 

Figure 7.16. Reduced value contributions of individual steps over the induction period for liquid-phase oxidation of ethylbenzene inhibited by BHT at different initial concentrations lO M, 10 M and 10 M, T=60 °C. The initial concentration of ethylbenzene hydroperoxide was 10 M. Step contributions are numbered according to the steps. Conversion of BHT makes up 7-10%.

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%). 

Hydroperoxide Process. The hydroperoxide process to propylene oxide involves the basic steps of oxidation of an organic to its hydroperoxide, epoxidation of propylene with the hydroperoxide, purification of the propylene oxide, and conversion of the coproduct alcohol to a useful product for sale. Incorporated into the process are various purification, concentration, and recycle methods to maximize product yields and minimize operating expenses. Commercially, two processes are used. The coproducts are / fZ-butanol, which is converted to methyl tert-huty ether [1634-04-4] (MTBE), and 1-phenyl ethanol, converted to styrene [100-42-5]. The coproducts are produced in a weight ratio of 3—4 1 / fZ-butanol/propylene oxide and 2.4 1 styrene/propylene oxide, respectively. These processes use isobutane (see Hydrocarbons) and ethylbenzene (qv), respectively, to produce the hydroperoxide. Other processes have been proposed based on cyclohexane where aniline is the final coproduct, or on cumene (qv) where a-methyl styrene is the final coproduct. 

Several solvents have been tested in the epoxidation of a- isophorone with t-butyl hydroperoxide (TBHP). The best performance of the aerogel was observed in low polarity solvents such as ethylbenzene or cumene (Table 1). In these solvents 99 % selectivity related to the olefin converted was obtained at 50 % peroxide conversion, independent of the temperature. Rasing temperature resulted in increasing initial rate and decreasing selectivity related to the peroxide. The low peroxide efficiency is explained by the homol5d ic peroxide decomposition. Protic polar solvents were detrimental to the reaction due to their strong coordination to the active sites. There was no epoxide formation in water. 

We discovered phenomenon of the considerable increase in the efficiency of selective ethylbenzene oxidation reaction into a-phenylethylhydroperoxide with dioxygen in the presence of triple systems Ni(II) (acac)2+LHPhOH, parameters S C, the conversion degree C (at -85-90%), and the hydroperoxide contents ([PEH] ), in comparison with catalysis by binary systems Ni(II)(acac)2+L. The obtained synergetic effects of increase in S C under catalysis by Ni(II)(acac)2 +... 

Based on the established (for Ni complexes) and h q)othetical (for Fe complexes) mechanisms of formation of catalytically active species and their operation, efficient catalytic systems ML + L (L are crown ethers or quaternary ammonitrm salts) of ethylbenzene oxidation to a-phe-nyl ethyl hydroperoxide were modeled. Selectivity conversion,... 

Figure 7.9. Reduced value contributions depending on Dqk in liquid-phase oxidation of ethylbenzene inhibited by efficient antioxidants /lura-iV-diniethylaininophenol (R =N(CH3)2, 79oh=355 kJ/mol) and / ara-methylphenol (R Hs, Z)oh=365 kJ/mol) at r= 60 C. Initial concentrations of the antioxidant and the hydroperoxide of ethylbenzene were 10 and 10 M, respectively. Conversion of ethylbenzene ...

The phenomenon of a substantial increase in the seleetivity (S) and conversion (C) of the ethylbenzene oxidation to the to a-phenyl ethyl hydroperoxide upon addition of PhOH together with alkali metal stearate M St (NT = Li, Na) as ligands to metal complexes NiII(acac)2 was discovered in our works [1, 2, 4]. 

FIGURE 1 Values of conversion C (%) (I row), maxinimn values of hydroperoxide concentrations (mass.%) (II row) in reactions of ethylbenzene oxidation in the... 

The catalytic activity of several metal a-thiopicolinamide polymers for chemical reactions has been determined. The decomposition of hydrazine (12, 18), isopropanol (6), formic acid (6), hydrogen peroxide (19), and the oxidation of cumene (17, 21) and ethylbenzene (21) to their hydroperoxides have been investigated. The copper(II) chelate of bis(a-thiopicolinamido)-diphenyl catalyzes a 94-96% conversion of cumene to its hydroperoxide in 5 hours at 80°-95°C (17). 

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