Propene oxide production

Attempts to produce propene oxide selectively by gas phase oxidation have been plentiful but not successful. 

The formation of propene oxide as a side product of the acrolein formation or dimerization reactions is reported by many authors. Daniel et al. [95,96] demonstrated that propene oxide is formed by surface-initiated homogeneous reactions which may involve peroxy radical intermediates. The epoxidation is increased by a large void fraction in the catalyst bed or a large postcatalytic volume. In view of these results, the findings of Centola et al. [84] are understandable, as the wall of the empty reactor may have been sufficiently active to initiate the reaction. 

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The epoxidation of propene with tert-butylhydroperoxide (TBHP) or ethylbenzene hydroperoxide (EBHP), for example, accounts for more than one million tons of propene oxide production on an annual basis (Fig. 4.19). 

The selectivity depends on the anion present, but can be as high as 70—80%. The reaction is a co-oxidation of copper and propene rather than a catalytic system and the propene oxide production rate rapidly falls as the copper catalyst is re-oxidized. This effect demonstrates that the oxygen chemistry occurring on copper(i) oxide is closer to that occurring on silver, rather than on mixed oxides such as bismuth molybdate, despite the difference in the partial oxidation product. 

Introduction Current Industrial Propene Oxide Production... 

Scheme 14.2 Future propene oxide production processes.

The direct vapor phase epoxidation of propene using dioxygen (O2) and dihydrogen (H2) can be achieved using supported gold catalysts and is expected to contribute to future industrial processes for propene oxide production. At present, the following conclusions can be drawn ... 

Fig. 12-5. Ozone-propene reaction pathways showing oxidation products.

Group C are catalysts that had high activity but low C.F. s. The NO conversions reached the maximum values at much lower temperatures of 623-643 K. The propene conversion was 100% at this point, and COj was the only deteaable oxidation product. In addition, significant amounts of NjO were detect. For some catalysts (such as catalyst B-1 OB), NjO was observed under the conditions used in Table 1. For others (such as catalyst B-15), it was observed at higher space velocities (see Table 2). 

Examples for necessary process improvements through catalyst research are the development of one-step processes for a number of bulk products like acetaldehyde and acetic acid (from ethane), phenol (from benzene), acrolein (from propane), or allyl alcohol (from acrolein). For example, allyl alcohol, a chemical which is used in the production of plasticizers, flame resistors and fungicides, can be manufactured via gas-phase acetoxylation of propene in the Hoechst [1] or Bayer process [2], isomerization of propene oxide (BASF-Wyandotte), or by technologies involving the alkaline hydrolysis of allyl chloride (Dow and Shell) thereby producing stoichiometric amounts of unavoidable by-products. However, if there is a catalyst... 

Catalysis is a special type of closed-sequence reaction mechanism (Chapter 7). In this sense, a catalyst is a species which is involved in steps in the reaction mechanism, but which is regenerated after product formation to participate in another catalytic cycle. The nature of the catalytic cycle is illustrated in Figure 8.1 for the catalytic reaction used commercially to make propene oxide (with Mo as the catalyst), cited above. 

The disappearance of the propene bands was not noticed when H202 (and consequently TiOOH) was not present. After 80 min, the product spectrum included bands at 830, 895, 1372, 1409, 1452, 1460 and 1493 cm-1. The product spectrum was similar to that obtained when a sample of propene oxide was loaded onto TS-1. The rate of decay of the 837-cm-1 absorption (0-0 vibration of TiOOH) was accompanied by the growth of the infrared bands of the product. These observations led Lin and Frei to conclude that the TiOOH group was... 

The production of propene oxide catalytic processes and recent developments. Ind. Eng. Chem. Res., 45, 3447-3459. 

Uses. In the production of polypropylene, acrylonitrile, isopropyl alcohol, and propene oxide, as well as gasoline and synthetic rubber as an aerosol propellant or component... 

Laboratory studies have indicated an increasing number of further processes for which iron oxides may be used as catalysts. A sodium promoted iron oxide on a support of Si02 catalyses the gas phase oxidation (377-427 °C) by nitrous oxide, of pro-pene to propene oxide (Duma and Honicke, 2000). Ferrihydrite or akaganeite can be used to catalyse the reduction (at 55-75 °C) by hydrazine, of aromatic nitro compounds to aromatic amines (which are the starting materials for a huge range of chemicals) these Fe oxides have the potential to provide a safe and economical pathway to the production of these important organics (Lauwiner et al., 1998). 

Isopropanol [67-63-0] M 60.1, b 82.5°, d 0.783, n25-8 1.3739. Isopropyl alcohol is prepared commercially by dissolution of propene in H2SO4, followed by hydrolysis of the sulphate ester. Major impurities are water, lower alcohols and oxidation products such as aldehydes and ketones. Purification of isopropanol follows substantially the same procedure as for n-propyl alcohol. 

The allylic oxidation of propene is catalyzed by (compound) metal oxides, which essentially contain metal ions of variable valency. It is commonly accepted that a redox mechanism is operative in such a way that the catalyst acts as the oxidizer and that lattice oxygen is incorporated in the oxidation products. The assumptions have been proved for several catalysts by the analysis of cation valency changes and by experiments with labelled oxygen. 

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