Vapor-phase oxidation of β-picoline to nicotinic acid on V2O5 and modified vanadium oxide catalysts

Abstract

Modifi cation of V 2 O 5 with Ti, Sn, Zr, Nb, and Al oxides improves the activity and selectivity of the vanadium oxide catalyst in vapor-phase oxidation of β-picoline to give nicotinic acid. It is shown that the conversion of β-picoline and the yield of nicotinic acid on two-component V 2 O 5 -TiO 2 , V 2 O 5 -SnO 2 , V 2 O 5 -ZtrO 2 , V 2 O 5 -Nb 2 O 5 , and V 2 O 5 -Al 2 O 3 catalysts may be several times those on the V 2 O 5 catalyst. It was found that, on passing from V 2 O 5 to double-component vanadium-containing catalysts, the proton affi nity of active oxygen bonded to vanadium, calculated by the quantum-chemical method, grows simultaneously with the increase in the activity of the catalysts in the oxidation reaction.Pyridine-carboxylic acids and their derivatives possess various physiological properties and fi nd wide application in medicine and agriculture. An important place among carboxylic acids of the pyridine series is occupied by nicotinic acid used to obtain cordiamin, feramide, nicodan, ethiacin, vitamin PP, and other medicinal preparations [1]. Nicotinic acid is also used to prepare premixes in animal breeding. Nicotinic acid is produced by liquid-phase oxidation of β-picoline by inorganic oxidizing agents or by hydrolysis of nicotinic acid nitrile formed in oxidative ammonolysis of the starting methyl pyridine [2].The vapor-phase catalytic oxidation of β-picoline with atmospheric oxygen, which yields nicotinic acid in a single stage, is strongly complicated by the instability of pyridine-carboxylic acids and their rapid decarboxylation at comparatively low temperatures [3]. The conversion of β-picoline on chromium orthovanadate at 350°C was only 19%, and the formation selectivities of pyridine-3-aldehyde and nicotinic acid, 39.5 and 49.1%, respectively. Among the catalysts with general formula Cr 1-x Al x VO 4 , the system Cr 0.5 Al 0.5 VO 4 has the highest activity, with the conversion of 3-methylpyridine at the same reaction temperature being 80% and the overall yield of nicotinic acid and pyridine-3-aldehyde reaching a value of 69% (overall selectivity 86%) [4]. In [5], the mechanism of oxidation of isomeric picolines on this catalyst was studied by the in situ DRIFTS method and the Mars-Van-Krevelen mechanism was substantiated. Among the disadvantages of the cited studies should be mentioned the incomplete conversion of β-picoline, presence of pyridine-3-aldehyde contaminating nicotinic acid in reaction products, and lack of systematic analyses of the effect of various oxides on the catalytic activity of V 2 O 5 .The vapor-phase catalytic oxidation of β-picoline to nicotinic acid has been the subject of a number of publications [6][7][8]. The research has been focused on fi nding effective catalysts providing an increase in the yield of nicotinic acid at comparatively low temperatures. The effect of the composition of a catalyst on its catalytic action in oxidation of β-picoline has been considered [4,9]. A brief review of publications in this fi eld can be found in [10].

Optimization of vanadium oxide catalyst for the oxidation of 3-methylpyridine into nicotinic acid

“…Increasing demands for nicotinic acid and its derivatives have promoted the interest of researchers to study the direct vapor-phase oxidation of 3-methylpyridine into nicotinic acid and to search for efficient catalysts for this process. [3][4][5][6] Thus, on a V 2 O 5 -TiO 2 -Na 2 O catalyst with a V:Ti:Na atomic ratio of 100:20:1.15 at 400 °С, the maximum conversion of 3-methylpyridine into nicotinic acid was up to 94 % with a selectivity of 51 %. 7 The vapor-phase oxidation of 3-methylpyridine was studied on vanadates of Y, Bi, Co, Fe, Mn, 8 and also Cr and Al.…”