3-picoline ammoxidation

Reddy, B.N., Reddy, B.M. and Subrahmanyam, M. (1991) Dispersion and 3-picoline ammoxidation investigation of vanadium oxide/ aluminum oxide (V205/a-A1203) catalysts. Journal of the Chemical Society, Faraday Transactions, 87 (10), 1649-55. 

Nicotinonitrile is a precursor to nicotinic acid (Niacin) and nicotinamide, both of which are important B-complex vitamins. High selectivities to nicotinonitrile by ammoxidation of 3-picoline are possible with a variety of supported and promoted vanadium oxide catalysts. Particularly effective is V2O5 supported on titania. Merck Co., Inc., U.S.A. disclosed the use of V205/Ti02 catalysts promoted with M0O3, P2O5, and MnS04 for 3-picoline ammoxidation. The reaction was conducted at a relatively low temperature for ammoxidation in order to... 

Much of the Vertellus picoline ammoxidation technology was developed by its precursor companies (Reilly, Nepera, and Degussa) based on fixed and fluid-bed reactors. In addition to 3CP and 4CP, the ammoxidation of 2-picoline to 2-cyanopyridine (2CP) has been practiced since 1970s. 

The reaction scheme for the ammoxidation of 2-picoline to 2-cyanopyridine is shown in Scheme 7.5. In general, this reaction can be carried out in fixed bed or fluidized bed reactors in the temperature range from 300 to 450°C. Among the three isomers, 2-picoline ammoxidation is less investigated. The first studies on this reaction appeared in the literature in the late 1960s and early 1970s by Russian researchers [e.g., 27,28] using V-W-0 and V Oj/TiO catalysts at reaction temperatures of 380 05°C. 

Cyanopyridines are usually manufactured from the corresponding picoline by catalytic, vapor-phase ammoxidation (eq. 7) in a fixed- or fluid-bed reactor (28). 3-Cyanopyridine (25) is the most important nitrile, as it undergoes partial or complete hydrolysis under basic conditions to give niacinamide... 

Nicotinic acid and nicotinamide, members of the vitamin B group and used as additives for flour and bread enrichment, and as animal feed additive among other applications, are made to the extent of 24 million pounds (nearly 11 million kilograms) per year throughout the world. Nicotinic acid (pyridine-3-caiboxylic acid), also called niacin, has many uses. See also Niacin. Nicotinic acid is made by the oxidation of 3-picolme or 2-mcthyl-5-cthylpyridine (the isocinchomcnc acid produced is partially deearboxylated). Alternatively, quinoline (the intermediate quinolinic acid) is partially deearboxylated with sulfuric add in the presence of selenium dioxide at about 300° C or with nitric acid, or by electrochemical oxidation. Nicotinic acid also can be made from 3-picoline by catalytic ammoxidation to 3-cyanopyridine, followed by hydrolysis. 

A new route to prepare nicotinic acid starts from 2-methylglutaronitrile, a major side-product in the adiponitrile process and, as such, a readily available starting-material. It is easily hydrogenated to 2-methylpentanediamine, which is then condensed to methyl piperidine and dehydrogenated to 3-picoline. The gas-phase ammoxidation of the latter to cyanopyridine is followed by hydrolysis to either nicotinamide or nicotinic acid (Scheme 20.4). The cyanopyridine route for the production of nicotinic acid has the advantage of a significantly better selectivity with respect to the direct oxidation route from 3-picoline owing to the easy decar-... 

Scheme 20.4 Ammoxidation of 3-picoline and hydrolysis of cyanopyridine to niacinamide (nicotinamide) and niacin (nicotinic acid). Adapted from [106].

Other applications of the ammoxidation include the reactions of isobutene (—> a-methacrylonitrile), a-methylstyrene (- atropanitrile), y5-picoline nicotine nitrile and nicotinamide), toluene benzonitrile), and xylenes (—> phthalo-nitrile, terephthalonitrile, and isophthalonitrile on the way to fiber- grade diamines). 

The ammoxidation step (Scheme 15.7) utilizes a catalyst that selectively converts picoline in the presence of oxygen and ammonia into 3-cyanopyridine. Even at... 

Scheme 15.7 Ammoxidation of 3-picoline and hydrolysis to niacinamide and niacin.

The energy-neutral picoline route and the resourceful recuperation and reutili-zation of energy in the exothermic ammoxidation contribute to low-energy requirements in the process. 

The reagents used (3-picoline, water, air) are not particularly toxic (picoline LD50 = 420 mg kg ). The ammonia necessary for the ammoxidation is predominantly obtained as a by-product in the production of 3-picoline. Any toxic by-products are catalytically converted into benign material. 

Other examples found in the literature can be interpreted in the same way. In the ammoxidation of 3-picoline (81) on N (rutile), the maximum activity and selectivity are obtained in nearly the same composition range as for oxidation of o-xylene The catalyst was prepared by heating V O... 

Activity measurements. The measurements were performed at atmospheric pressure in a glass reactor. A thermocouple was positioned in the center of the reactor. In the ammoxidation of 3-picoline, the inlet reaction mixture was admitted at a rate of 32 liters/hr and contained 232-254 moles of air, 13-14 moles of ammonia, and 56-62 moles of water vapor for each mole of 3-picoline. The reaction was usually performed in the temperature interval 300-400 C. In the oxidation of MEP (2-methyl-5-ethylpyridlne) the molar ratios of O /MEP and steam/MEP were 75 and 175 respectively, and the space velocity was 7000 h. In ammoxidation studies prereduced catalysts were used and the measurements extrapolated in time to give data at the start of the reaction. In oxidation studies unreduced catalysts were used and the data were obtained at the steady state. 

Ammoxidation of 3-picoline. ESCA results indicated that the surfaces of the catalysts were composed mainly of and... 

Physico-Chemical Characterisation of V2O5- Ti02 ( anatase ) Catalysts for Ammoxidation of 3- Picoline... 

Figure 14.9 shows the flow diagram for ammoxidation of P-picoline. 

Ammoxidation of Picolines. Selective catal3d ic ammoxidation of picol-ines produces cyanopyridines. The most important process of this type, industrially, is ammoxidation of 3-picoline to give 3-cyanop3rridine or nicotinonitrile. 

An economically advantaged alternative to 3-picoline is 2-methyl-5-ethyl pyridine (MEP), which is a less expensive and more readily available feedstock. MEP is thus a preferred starting material for producing nicotinic acid whether by a direct oxidation or ammoxidation route. For direct conversion of MEP to nicotinonitrile, an added requirement of the catalyst and process is the dealkylation that must occur concurrently with the selective ammoxidation reaction. 

Fig. 6. Relationship between selectivity in ammoxidation of 3-picoline to nicotinonitrile and concentration of reduced vanadium cations. Reprinted with permission from Ref (92)., Copyright (1985), American Chemical Society.

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