Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF CYANOPYRIDINES

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.

Documents:


Patent Number 190238
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
Inventors:
# Inventor's Name Inventor's Address
1 PANJA KANTA RAO INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, INDIA
2 SURESH FARSINAVIS INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, INDIA
3 SHIVANAND JANARDAN KULKARNI INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, INDIA
4 REVUR RAMCHANDRA RAO INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, INDIA
5 MACHIRAJU SUBRAHMANYAM INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, INDIA
6 ALLA VENKAT RAMA RAO INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, INDIA
PCT International Classification Number C07C 121/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA