Acrolein/acrylonitrile propylene oxidation

Acrolein and condensable by-products, mainly acrylic acid plus some acetic acid and acetaldehyde, are separated from nitrogen and carbon oxides in a water absorber. However in most industrial plants the product is not isolated for sale, but instead the acrolein-rich effluent is transferred to a second-stage reactor for oxidation to acrylic acid. In fact the volume of acrylic acid production ca. 4.2 Mt/a worldwide) is an order of magnitude larger than that of commercial acrolein. The propylene oxidation has supplanted earlier acrylic acid processes based on other feedstocks, such as the Reppe synthesis from acetylene, the ketene process from acetic acid and formaldehyde, or the hydrolysis of acrylonitrile or of ethylene cyanohydrin (from ethylene oxide). In addition to the (preferred) stepwise process, via acrolein (Equation 30), a... 

In 1957 Standard Oil of Ohio (Sohio) discovered bismuth molybdate catalysts capable of producing high yields of acrolein at high propylene conversions (>90%) and at low pressures (12). Over the next 30 years much industrial and academic research and development was devoted to improving these catalysts, which are used in the production processes for acrolein, acryUc acid, and acrylonitrile. AH commercial acrolein manufacturing processes known today are based on propylene oxidation and use bismuth molybdate based catalysts. 

Both fixed and fluid-bed reactors are used to produce acrylonitrile, but most modern processes use fluid-bed systems. The Montedison-UOP process (Figure 8-2) uses a highly active catalyst that gives 95.6% propylene conversion and a selectivity above 80% for acrylonitrile. The catalysts used in ammoxidation are similar to those used in propylene oxidation to acrolein. Oxidation of propylene occurs readily at... 

ETHYLENE GLYCOL ETHYL MERCAPTAN DIMETHYL SULPHIDE ETHYL AMINE DIMETHYL AMIDE MONOETHANOLAMINE ETHYLENEDIAMINE ACRYLONITRILE PROPADIENE METHYL ACETYLENE ACROLEIN ACRYLIC ACID VINYL FORMATE ALLYL CHLORIDE 1 2 3-TRICHLOROPROPANE PROPIONITRILE CYCLOPROPANE PROPYLENE 1 2-DICHLOROPROPANE ACETONE ALLYL ALCOHOL PROPIONALDEHYDE PROPYLENE OXIDE VINYL METHYL ETHER PROPIONIC ACID ETHYL FORMATE METHYL ACETATE PROPYL CHLORIDE ISOPROPYL CHLORIDE PROPANE... 

Propellant 12, see Dichlorodifluoromethane Propenal, see Acrolein Prop-2-en-l-al, see Acrolein 2-Propenal, see Acrolein Propenamide, see Acrylamide 2-Propenamide, see Acrylamide Propenenitrile, see Acrylonitrile 2-Propenenitrile, see Acrylonitrile Propene oxide, see Propylene oxide Propenitrile, see Acrylonitrile... 

Acrylic acid is made by the oxidation of propylene to acrolein and further oxidation to acrylic acid. Another common method of production is acrylonitrile hydrolysis. 

Light hydrocarbons consisting of oxygen or other heteroatoms are important intermediates in the chemical industry. Selective hydrocarbon oxidation of alkenes progressed dramatically with the discovery of bismuth molybdate mixed-metal-oxide catalysts because of their high selectivity and activity (>90%). These now form the basis of very important commercial multicomponent catalysts (which may contain mixed metal oxides) for the oxidation of propylene to acrolein and ammoxidation with ammonia to acrylonitrile and to propylene oxide. 

Acrolein and Acrylic Acid. Acrolein and acrylic acid are manufactured by the direct catalytic air oxidation of propylene. In a related process called ammoxida-tion, heterogeneous oxidation of propylene by oxygen in the presence of ammonia yields acrylonitrile (see Section 9.5.3). Similar catalysts based mainly on metal oxides of Mo and Sb are used in all three transformations. A wide array of single-phase systems such as bismuth molybdate or uranyl antimonate and multicomponent catalysts, such as iron oxide-antimony oxide or bismuth oxide-molybdenum oxide with other metal ions (Ce, Co, Ni), may be employed.939 The first commercial process to produce acrolein through the oxidation of propylene, however, was developed by Shell applying cuprous oxide on Si-C catalyst in the presence of I2 promoter. 

In 1959, Idol (2), and in 1962, Callahan et al. (2) reported that bismuth/molybdenum catalysts produced acrolein from propylene in higher yields than that obtained in the cuprous oxide system. The authors also found that the bismuth/molybdenum catalysts produced butadiene from butene and, probably more importantly, observed that a mixture of propylene, ammonia, and air yielded acrylonitrile. The bismuth/molybdenum catalysts now more commonly known as bismuth molybdate catalysts were brought to commercial realization by the Standard Oil of Ohio Company (SOHIO), and the vapor-phase oxidation and ammoxidation processes which they developed are now utilized worldwide. 

Epichlorohydrin Acrolein Propylene oxide Acrylonitrile Methyl isothiocyanate Butylene oxide... 

Bismuth Molybdate Catalysts. The Raman spectra of the bismuth molybdates, with Bi/Mo stoichiometric ratios between 0.67 and 14, have been examined using the FLS approach (see Section 3.2). " The bismuth molybdates fall into an unusual class of compounds, the ternary bismuth oxide systems Bi-M-0 (where M = Mo, W, V, Nb, and Ta) which exhibit a variety of interesting physical and chemical properties. Of commercial importance, the bismuth molybdates are heterogeneous catalysts for selective oxidations and ammoxidations (the Sohio process), for example, propylene ( 311 ) to acrolein (C3H4O) by oxidation or to acrylonitrile (C3H3N) by arrunoxidation. ... 

Derivation (1) Condensation of ethylene oxide with hydrocyanic acid followed by reaction with sulfuric acid at 320F (2) acetylene, carbon monoxide, and water, with nickel catalyst (3) propylene is vapor oxidized to acrolein, which is oxidized to acrylic acid at 300C with molybdenum-vanadium catalyst (4) hydrolysis of acrylonitrile. 

Next, we performed experimental testing of TIC s on the following hquids carbon disulfide, acrylonitrile, acrolein, nitric acid, propylene oxide, allyl alcohol, and phosphoras trichloride. The measurements were taken in vials containing three milliliters of hquid. Five spectra from 1100 to 2300 mn were taken of each liquid with 200 scans per spectra. The gain setting was two. The first derivative spectral graph for all of the liquids is shown in Figure 3. 

All selective oxidation and ammoxidation catalysts possess redox properties. They must be capable not only of reduction during the formation of acrolein or acrylonitrile, but also subsequent catalyst reoxidation in which gaseous oxygen becomes incorporated into the lattice as to replenish catalyst vacancies (Scheme 2). As mentioned earlier, the incorporation of such redox properties into solid state metal oxides was one of the salient working hypotheses on which the development of the Sohio ammoxidation process was based (2). Later, Keulks (70) confirmed the involvement of lattice oxygen in propylene oxidation by using as a vapor phase oxidant. The results showed that the incorporation of O into the acrolein (and CO2) increases with time (Fig. 11), which is consistent with the above redox mechanism. 

N-allyl species and two hydrogen abstractions account for acrylonitrile formation. Thus, although allyl radicals are probably not the selective intermediate in propylene oxidation and ammoxidation, they can form acrolein or acrylonitrile via these selective O- or N-allyl intermediates. 

Industrial catalytic formulations for the oxidation of propylene to acrolein and ammo-oxidation to acrylonitrile are based on the bismuth molybdate phases modified by the above-mentioned metal oxide components. The conversion and selectivity are excellent over the temperature range of 250-450°C, as shown in Table 5.4. 

The modern beginning of the heterogeneous catalytic oxidation of olefins to aldehydes may be taken as the discovery of the oxidation of propylene to acrolein over cuprous oxide by Hearne and Adams (5 ). This reaction has been carried to commercial operation by Shell Chemical Company. More recently, the use of bismuth phosphomolybdate has been demonstrated for the oxidation of propylene to acrolein by Veatch and co-workers (88), and, in the presence of ammonia, to acrylonitrile by Idol (89). It was also shown, by Heame and Furman (90), that diolefins could be made from C4 and higher olefins by oxidative dehydrogenation over a bismuth molybdate catalyst. From these beginnings, information on olefin oxidation has increased very rapidly, both in journal and patent literature. We shall make no attempt to review the large number of patents that have issued, but shall limit ourselves mainly to journal literature. 

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