Synthesis Of 3-Cyanopyridine From Ammoxidation Of 3-Picoline Over V₂O₅/TiO₂ Catalysts

Nicotinic acid and nicotinic amide are important organic intermediates.They are widely used in medicine, feedstuff additive, plate brightness and soon. At present, the supply of nicotinic acid and nicotinic amide in the worldmarket is insufficient, and this situation in China is more serious. Therefore,the production of nicotinic acid and nicotinic amide should be enhancedurgently.Nicotinic acid and nicotinic amide can be produced by ammoxidation of3-picoline then the produced nicotinonitrile is hydrolyzed into nictinic acidand nicotinic amide. This process is most commonly used in the production ofnicotinic acid and nicotinic amide. The most crucial step in theabove-mentioned process is ammoxidation of 3-picoline, in which thedevelopment of a catalyst with high activity and selectivity is of utmostimportance.V₂O₅/TiO₂ catalysts are commonly used in selective oxidation andammoxidation. In the current study, some self-prepared V₂O₅/TiO₂ catalystswere used in ammoxidation of 3-picolirie, and the main results in terms ofcatalyst characterization and performance aresummarized as follows:(1) Anatase TiO₂ with a surface area of 13 m²/g, referred to asTiO₂(13), was used as a support, a series of V₂O₅/TiO₂(13)catalysts withdifferent V₂O₅ loadings were prepared by wet impregnation.The effects ofV₂O₅ loading, precursor, calcination temperature, amount of oxalic acid on thecatalytic performance of V₂O₅/TiO₂(13)were investigated. The 5 wtï¼…V₂O₅loaded on TiO₂(13) catalyst, referred to as V₂O₅(5)/TiO₂(13), shows the bestperformance, i.e. the highest activity and selectivity for nicotinonitrile. The XRD and Raman results indicate that when V₂O₅ loading is 5 wtï¼…, just a VO_xmonolayer on the anatase surface forms. This indicates that the fromed VO_xmonolayer is an active phase for ammoxidation of 3-picoline. When the otherfactors are the same, the catalysts prepared using different precursors showalmost the same conversion and selectivity. Thus the effect of the precursor onthe performance of the V₂O₅/TiO₂(13) catalysts is very minor. Whencalcination temperature is 450℃, the V₂O₅(5)/TiO₂(13) shows the bestperformance.The amount of H₂C₂O₄ which was used in the preparation ofV₂O₅/TiO₂ catalysts has influence the performance of the catalysts; whenH₂C₂O₄:V₂O₅ (mol) is 10:1, the prepared V₂O₅(5)/TiO₂(13) catalyst shows thebest performance. The temperature ramp for catalyst calcinations hardlyaffects the performance of V₂O₅/TiO₂ catalysts.(2) Anatase TiO₂ with a high surface area of 328 m²/g, referred to asTiO₂(328), was used as a support, a series of V₂O₅/TiO₂(328)catalysts withdifferent V₂O₅ loadings were prepared by wet impregnation, The effects ofV₂O₅ loading and calcination temperature on the catalytic performance ofV₂O₅/TiO₂(328) were investigated. The 10 wtï¼…V₂O₅ loaded on TiO₂(328)catalyst, referred to as V₂O₅(10)/TiO₂(328), shows the best performance, i.e.the highest activity and the highest selectivity for nicotinonitrile. The XRDresults indicate that when V₂O₅ loading is 10 wtï¼…, just a VO_x monolayer onthe anatase surface forms.The effect of calcination temperature on thecatalytic performance of V₂O₅(10)/TiO₂(328) is very notably, because theporous structure of TiO₂(328) can be changed with temperature. The surfacearea of catalyst calcined at 450℃is smaller than that calcined at 350℃. Theconversion of the prob reaction over the catalyst calcined at 450℃is lowerthan that over the calcined at 350℃. On the other hand, the selectivity over the catalyst calcined at 450℃is higher than that over the catalyst calcined at350℃.(3) Under the same reaction conditions and V₂O₅ loadings, a comparisonof the catalytic performances of V₂O₅/TiO₂(13) and V₂O₅/TiO₂(328) catalystsshows that the conversions over V₂O₅/TiO₂(328) catalysts are much higherthan those over V₂O₅/TiO₂(13) catalysts, but selectivities over V₂O₅/TiO₂(328)catalysts are much lower than those V₂O₅/TiO₂(13) catalysts.