Title of Invention | AN IMPROVED PROCESS FOR THE PREPARATION OF CYANOPYRIDINES |
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Abstract | An improved process for the preparation of cyanopyridines which comprises passing a feed consisting of respective picolines and ammonia ranges from 1:1 to 1:20 water and air/oxygen in a feed ratio of 30 to 100 cc per minute over a vanadium-alumino-phosphate (VAPO) catalyst prepared by the process such as herein described at a temperature in the range of 300-450°C and weight hourly space velocity of liquid feed products in the range of 0.25 to 1.0 per hour and recovering the cyanopyridines formed by known methods. |
Full Text | This invention relates to an improved process for the preparation of cyanopyridines. This invention particularly relates to an improved process for the preparation of nitriles such as 3-cyanopyridine and 4-cyanopyridine from 3-picoline and 4-picoline respectively. According to the process of the present invention 3- and 4- picolines are reacted with ammonia and air in the presence of a catalyst selected from crystalline, porous vanadium aluminophosphates(VAPO). The process of preparing the above catalyst has been described and claimed in our copending application number 1459/Del/95. In the presently known process, 3- and 4- cyanopyridines can be synthesized from ammoxidation of 3- and 4-picolines over amorphous V 0 or VOPO supported 2 5 4 over various supports like Al 0 , Al 0 ,Cr 0 ,TiO . 2 3 2 3 2 3 2 The conventional catalysts have been amorphous in nature and not shape selective catalysts. These catalysts have been employed in mostly fixed bed reactors. The following patents have discussed the preparation of nitriles of present interest, e.g. Eur.Pat; Appl. EP 37173 (1981), US Patent 4876348 (1989),US Patent 4603 207 (1986), Eur. Pat 0037123A1 (1981), Brit. Patent 77746 (1957), Ger. (East) DDPatent 241903 (1985), US Patent 3981879 (1976), US Patent 2839535 (1958), US Patent 2510605 (1950) , US Patent 3981879 (1976) . In these inventions the yield of nitrile may or may not be highly selective. Particularly high-boiling products, CO,CO were formed, due to the amorphous nature of the 2 catalysts. The high-boling products create environmental and disposal problems. The reaction of 3-picoline or 4-picoline was carried out over V O -Al O ,mixed oxides of 2 5 2 3 V,Cr,Ti,Sb,Al or Si.The yield of 3-cyanopyridine varied from 50 to 85%; while the yield of 4-cyanopyridine was 70 to 90%.The other products were the high boiling compounds,CO and CO . 2 The object of the present invention is to provide an improved process for the preparation of cyanopyri-dines employing porous active catalytic materials. The other objective of the invention is to provide a process for the preparation of nitriles wherein the formation of CO, CO and high-boiling products are mini- 2 mized. The present invention provides an improved process for the preparation of cyanopyridines from respective picolines in 50-85% yields of by ammoxidation in one step with very high selectivity over VAPO(TPA-B) o catalysts at a temperature in the range of 350 to 450 C and weight hourly space velocity in the range of 0.2 5 to 1.0 per hour. Accordingly, the present invention provides an improved process for the preparation of cyanopyridines from respective picolines which comprises ; passing a feed consisting of respective picolines, ammonia, water and air/ oxygen over a crystalline , vanadium - alumi- no phosphate (VAPO) catalyst prepared by the process described & claimed in our copending application no. 1459/del/95 at a temperature in the range of 300 - 450 o C, and weight hourly space velocity of liquid feed products in the range of 0.25 to 1.0 per hr and recovering the cyanopyridine formed by known methods. The molar ratio of picolines and ammonia may be in the range of 1:1 to 1:20. The feed ratio of air / oxygen gas may be in the range of 3 0 - 100 cc. per minute. The catalysts are prepared in general in the fol lowing way. Al (SO ) , H PO , with or without NaCl,V 0 2 4 3 3 4 2 5 and tetrapropylammonium bromide (TPA) or tetrabutylam-monium bromide (TBA) used as a template,are mixed in distilled water in the pH range of 7.0 to 12.0. The slurry is mixed for atleast 2 hrs at room temperature with constant stirring and the pH is adjusted by aqueous ammonia. The slurry was put into an autoclave for autoclaving under autogeneous pressure in the tempera- o ture range of 150 to 220 C for 24 hrs to 80 hrs till complete crystallization was achieved. The mixture was filtered and washed with distilled water.The solid o catalyst was dried in oven at 120 C over night. The organic template was removed by the activation of the o catalyst at 400-550 C for 5-15 hrs. Then the calcined material was modified by promoters like Sb O or oxides 2 3 of the elements active as promoters in the respective reactions. Basically in aluminophosphate molecular sieves the Al:P atomic ratio is 1:1. We have substituted P partially by V as discussed and claimed in the copending patent number : 1459/del/95. Al also may be substituted partially by V ; with the corresponding variation in the atomic ratio. The above said reactions were carried out in a tubular,down-flow, pyrex reactor with 20 mm internal diameter. The reaction mixture was fed from top using syringe pump(Sage Instruments,USA). The product was cooled by using ice-cooled water and collected at the bottom. The required number of ice-cooled traps were used to collect the total amount of products. The products were analysed by using SE-30 (5%) and OV-17 columns.The analysis was confirmed by mass spectra and GC-mass. The ammoxidation of 4-picoline with ammonia was o carried out in presence of air (O ) at 420 C with 0.5 2 -1 hr W.H.S.V. and 4 gm of catalyst like VAPO(B), VAPO(C),VAPO(D) (18-30 mesh). 4-Picoline was diluted with water in 1:3 volume ratio. The feed rate of ammonia was 30-35 cc per min and the rate of air was 6 0 cc per min. The following reaction parameters were varied,reaction temperature, 4-picoline : NH , 4-pico- 3 line:H O, W.H.S.V., etc. 2 The ammoxidation of 3-picoline with ammonia was o carried out in presence of air (O ) at 420 C with 2 -1 0.5hr W.H.S.V. and 4gm of catalyst. 3-Picoline was diluted with water using 1:3 by volume ratio. The feed rate of ammonia gas was 3 5 cc per min and rate of air was 60 cc per min. With the increase of ammonia in the feed there was increase in the yield of 3-cyanopyridine to about 60.8 wt%. The various reaction parameters like reaction temperature, weight hourly space velocity, picoline to ammonia and water ratio in the feed were varied. The following examples are given to illustrate the process of the present invention,however these should not be construed to limit the scope of invention. EXAMPLE - 1 0.477 gm per hr 4-Picoline, 1.50 gm of water per hour,0.228 gm( 3 0 cc per min)of ammonia and 6 0.0 cc per o -1 min air over VAPO(TPA-B) at 420 C and 0.5 hr weight hourly space velocity of liquid feed. The 4-Picoline to ammonia mole ratio was 1:5. The yield of 4-cyanopyridine was 49.7% based on 4-picoline at 65.4% conversion of 4-picoline.No deactivation was observed for more than 6 hrs time on stream. The template TPA (tetra propyl ammonium bromide) was removed before the rec-tion. The activity can be regenerated. EXAMPLE - 2 In the reaction of 0.477 gm per hr of 4- picoline,0.228 gm (30 cc per min) ammonia,1.5 gm of water per hr and 60 cc per min air over 4 gm VAP0(TPA- o -1 C) at 420 C, 0.5 hr W.H.S.V. of liquid feed; the yield of 4- cyanopyridine was 59.3% based on 4-picoline at 67.2% conversion of 4-picoline. EXAMPLE - 3 In the reaction of 0.477 gm per hr of 3-picoline, 0.228 gm (30 cc per min) ammonia, 1.5 gm of water per o hr and 60 cc per min air over 4 gm VAPO(TPA-B) at 420 -1 C, 0.5 hr W.H.S.V. of liquid feed; the yield of 3- cyanopyridine was 58.8% based on 3-picoline at 63.3% conversion of 3-picoline. WE CLAIM: 1. An improved process for the preparation of cyanop- yridines which comprises passing a feed consisting of respective picolines and ammonia ranges from 1:1 to 1:20 water and air / oxygen in a feed ratio of 3 0 to 100 cc per minute over a vanadium - alumino - phosphate (VAPO) catalyst prepared by the process such as herein o described at a temperature in the range of 300-450 C and weight hourly space velocity of liquid feed products in the range of 0.25 to 1.0 per hour and recovering the cyanopyridines formed by known methods. 2. An improved process for the preparation of cyanop yridines substantially as herein described with refer ence to the example. |
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Patent Number | 190238 | |||||||||||||||||||||
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Indian Patent Application Number | 957/DEL/1995 | |||||||||||||||||||||
PG Journal Number | 27/2003 | |||||||||||||||||||||
Publication Date | 05-Jul-2003 | |||||||||||||||||||||
Grant Date | 03-Mar-2004 | |||||||||||||||||||||
Date of Filing | 25-May-1995 | |||||||||||||||||||||
Name of Patentee | COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH | |||||||||||||||||||||
Applicant Address | RAFI MARG, NEW DELHI-100 001,INDIA | |||||||||||||||||||||
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PCT International Classification Number | C07C 121/00 | |||||||||||||||||||||
PCT International Application Number | N/A | |||||||||||||||||||||
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