Title of Invention	AN IMPROVED PROCESS FOR THE PREPARATION OF PICOLINES
Abstract	An improved process for the preparation of picolines by passing a feed consisting of acetaldehyde, acetonitrile, ammonia and water over modified pentasil ZSM-5 catalyst with various Si/AI ratios in the range of 30 to 280 at a temperature in the range of 300 to 450°C and weight hourly space velocity in the range of 0.25 to 1.0 per hr, collecting the picolines by known methods.

Full Text

The present invention relates to an improved process for the preparation of picolines. This invention particularly relates to a process for the simultaneous preparation of 2-picoline and 4-picoline from acetaldehyde, acetonitrile and ammonia. The invention particularly relates to a process for synthesizing 2-picoline and 4-picoline selectively from acetaldehyde, acetonitrile and ammonia. The reaction of this feed was carried out over modified ZSM-5 type pentasil catalysts. In the presently known processes, the reaction of acetaldehyde with ammonia has been carried out over amorphous and crystalline aluminosilicates to get 2-picoline and 4-picoline. On the other hand, the reaction of acetaldehyde, formaldehyde with ammonia leads to pyridine and 3-picoline. The conventional catalysts for all these reactions have been amorphous in nature. These catalysts have been employed in the fixed bed or fluidized bed reactors. There are patents which describes the reaction of acetaldehyde with ammonia, see e.g., U.S. Patent 3932421(1976), U.S.Patent 4675410(1987), U.S.Patent 378192(1973), U.S.Patent 3417092(1968), U.S.Patent 3829428(1974), British Patent No.1579473 (1980) , Japanese patent Nos.76-63176 and 80-151558. In these inventions the yield of a desired product may or may not be highly selective among pyridine and picolines. Along with 2-picoline, invariably 4-picoline was obtained. Particularly high boiling products above picolines like lutidines, collidines were dominant for amorphous silica-alumina, presently commercially used catalysts. The conversion with respect to acetaldehyde is about 100%, while the high boilers obtained were >30-40%. Though lutidines are useful products, the high boilers above lutidines create environmental and disposal problems. The reaction of acetaldehyde and ammonia with or without formaldehyde was carried out over silica-alumina promoted by oxides or phosphates of Co, Mg, Ca, Ni, Pb and Zn or a mixture of some of these oxides, in the above mentioned patents. In the formation of 2-picoline and 4-picoline from acetaldehyde and ammonia, the total yield of picolines was less than 50%. We have described the preparation of pyridine and pyridine derivatives from ethanol over various modified ZSM-5 catalysts in our co-pending patent (699/DEL/94) and preparation of pyridine and picolines over modified ZSM-5 and silica-alumina catalysts from acetaldehyde in our copending patent (703/DEL/93). The main object of the present invention is to provide an improved process for the preparation of picolines. Another object of present invention is to increase the yield and selectivity of 2-picoline and 4-picoline by using additive to acetaldehyde. Yet another objective is to decrease the dilution effect. If we use only acetaldehyde, water should be added to it so as to decrease the side reactions and coking. The addition of more water may reduce conversion and yields. To overcome this we are using acetonitrile as additive which is also a cheaper feed. Accordingly, the present invention provides an improved process for the preparation of picolines which comprises; passing a feed consisting of acetaldehyde, acetonitrile, ammonia and water over modified pentasil ZSM-5 catalyst with various Si/AI ratios in the range of 30 to 280 at a temperature in the range of 300 to 450°C and weight hourly space velocity in the range of 0.25 to 1.0 per hr, collecting the picolines by known methods. The catalysts used in the present invention were modified pentasil ZSM-5 type with various Si/AI ratios in the range 30 to 280 as described and claimed in our other patents as given above. The ZSM-5 catalysts were modified by respective nitrates with 1 wt% of that metal atom. The zeolite was mixed with the required amount of that salt in distilled water, stirred for 2 hrs and dried in the oven at 120°C. The catalyst was activated at 420°C for 4 hrs before use. The reactions were carried out in a tubular down-flow pyrex reactor with 20 mm internal diameter. The reaction mixture was fed from top using B.Braun syringe pump. The product was cooled by using ice-cooled water and collected at the bottom. The products were analysed by using 5% SE-30 and 30% SE-30 columns. The analysis was confirmed by mass spectra and GC-mass. The reaction of acetaldehyde, acetonitrile and ammonia was carried out over various modified ZSM-5 catalysts. The feed composition used was 1:1:5 molar of acetaldehyde:acetonitrile:ammonia. The reaction was carried out in the temperature range of 300 to 420°C and 0.25 to 1 hr-1 weight hourly space velocity. The reaction was carried out over various zeolites like HZSM-5(30), HZSM-5(280) and HY catalysts to compare the activity of the catalysts. Bracketed figures indicate the ratio of silica to alumina. HZSM-5(30) was observed as the better catalyst compared to others. The reaction temperature is also varied from 3 00 to 400°C for all these catalysts. In the case of PbZSM-5, MoZSM-5, LaZSM-5 and PdZSM-5 the conversions of acetaldehyde were 78.8, 56.6, 53.4 and 60.5 wt% respectively. The yields of picolines (both 2&4 picolines) were 71.7,30.0, 26.3 and 40.3 wt% respectively. The raection temperature and WHSV were 4 0 0°C and 0.5 hr_1 respectively. The effect of molar ratio of acetaldehyde and acetonitrile was studied over PbZSM-5 catalyst at reaction temperature 400°C and 0.5 hr"1 WHSV. With the increase of acetonitrile from 0.25 to 1 molar ratio the conversion and yield of picolines increased. With further increase of the acetonitrile mole ratio,the yield of picolines started decreasing. The maximum yield of picolines 71.7 wt% was observed at 1:1 molar ratio of acetaldehyde and acetonitrile. The reaction of acetaldehyde, acetonitrile and ammonia was carried out over PbZSM-5 catalyst at 0.5 hr"1 WHSV in the temperature range of 250-400°C. At reaction temperatures 250, 300 and 400°C, the conversions with respect to acetaldehyde were 61.9, 73.5 and 79.0 wt% and yields of picolines (2&4-Picoline) were 53.8, 67.0 and 71.7 wt% respectively. The ratio of 2-picoline to 4-picoline varies from 0.8 to 1.1. The effect of different additives to acetaldehyde in addition to acetonitrile were also studied. The reaction of acetaldehyde, additive and ammonia was carried out over PbZSM-5 catalyst at 400°C with 0.5 hr"1 WHSV. When Methylamine is used as additive, the yield of pyridine was enhanced, with 63.7 wt% conversion of acetaldehyde. Similarly when formaldehyde and acetonitrile were used as additives the yield of pyridine and 3-picoline were 31.6 and 23.8 wt% respectively with 68.2 wt% conversion of acetaldehyde.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 : 0.3 0 gm per hr of acetaldehyde, 0.7 8 gm per hr of acetonitrile, 0.70 gm per hr of water and 0.13 gm per hr of ammonia was passed over HZSM-5(30), the yields of 2-picoline and 4-picoline obtained were 33.6 and 36.4 wt% at 80.1 wt% conversion of acetaldehyde. The reaction was carried out at 350°C with 0.5 hr" 1 WHSV. The other major products were pyridine (5.7%) and lutidines (4.4%). EXAMPLE 2 : 0.3 0 gm per hr. of acetaldehyde, 0.7 8 gm per hr of acetonitrile, 0.70 gm per hr of water and 0.13 gm per hr of ammonia was passed over HZSM-5(30), the yields of 2-picoline and 4-picoline obtained were 36.8 and 35.8 wt% at 93.6 wt% conversion of acetaldehyde.The reaction was carried out at 400°C with 0.5 hr'1 WHSV. The other major products were pyridine (6.4%) and lutidines (14.6%) . EXAMPLE 3 : 0.3 0 gm per hr of acetaldehyde, 0.78 gm per hr of acetonitrile, 0.70 gm per hr of water and 0.13 gm per hr of ammonia was passed over HZSM-5(280) , the yields of 2-picoline and 4-picoline obtained were 29.6 and 20.9 wt% at 52.0 wt% conversion of acetaldehyde. The reaction was carried out at 400°C with 0.5 hr" 1 WHSV. The other major products were pyridine (1.5%) and lutidines (4.6%) . EXAMPLE 4 : 0.3 0 gm per hr of acetaldehyde, 0.78 gm per hr of acetonitrile, 0.70 gm per hr of water and 0.13 gm per hr of ammonia was passed over HY, the yields of 2-picoline and 4-picoline obtained were 25.1 and 20.4 wt% at 72.6 wt% conversion of acetaldehyde. The reaction was carried out at 300°C with 0.5 hr"1 WHSV. The other major products were pyridine (1.5%) and lutidines (26.5%) . EXAMPLE 5 : 0.3 0 gm per hr of acetaldehyde, 0.78 gm per hr of acetonitrile, 0.70 gm per hr of water and 0.13 gm per hr of ammonia was passed over PbZSM-5(30), the yields of 2-picoline and 4-picoline obtained were 37.7 and 34.0 wt% at 78.8 wt% conversion of acetaldehyde. The reaction was carried out at 400°C with 0.5 hr"1 WHSV. The other major products were pyridine (3.2%) and lutidines (3.9%). EXAMPLE 6 : 0.3 0 gm per hr of acetaldehyde, 0.78 gm per hr of acetonitrile, 0.70 gm per hr of water and 0.13 gm per hr of ammonia was passed over MoZSM-5(30), the yields of 2-picoline and 4-picoline obtained were 19.2 and 10.8 wt% at 56.6 wt% conversion of acetaldehyde. The reaction was carried out at 400°C with 0.5 hr"1 WHSV. The other major products were pyridine (16.5%) and lutidines (10.1%). EXAMPLE 7 : 0.30 gm per hr of acetaldehyde, 0.78 gm per hr of acetonitrile, 0.70 gm per hr of water and 0.13 gm per hr of ammonia was passed over LaZSM-5(30), the yields of 2-picoline and 4-picoline obtained were 21.8 and 4.5 wt% at 53.4 wt% conversion of acetaldehyde. The reaction was carried out at 400°C with 0.5 hr"1 WHSV. The other major products were pyridine (18.7%) and lutidines (8.4%). EXAMPLE 8 : 0.3 0 gm per hr of acetaldehyde, 0.78 gm per hr of acetonitrile, 0.70 gm per hr of water and 0.13 gm per hr of ammonia was passed over PdZSM-5(30), the yields of 2-picoline and 4-picoline obtained were 20.3 and 20.0 wt% at 60.5 wt% conversion of acetaldehyde. The reaction was carried out at 400°C with 0.5 hr"1 WHSV. The other major products were pyridine (4.3%) and lutidines (15.9%). EXAMPLE 9 : 0.40 gm per hr of acetaldehyde, 0.47 gm per hr of acetonitrile, 0.93 gm per hr of water and 0.13 gm per hr of ammonia was passed over PbZSM-5(30), the yields of 2-picoline and 4-picoline obtained were 32.0 and 28.0 wt% at 72.8 wt% conversion of acetaldehyde. The reaction was carried out at 400°C with 0.5 hr"1 WHSV. The other major products were pyridine (2.3%) and lutidines (10.5%). EXAMPLE 10 : 0.19 gm per hr of acetaldehyde, 1.04 gm per hr of acetonitrile, 0.47 gm per hr of water and 0.13 gm per hr of ammonia was passed over PbZSM-5(30), the yields of 2-picoline and 4-picoline obtained were 21.9 and 2 5.1 wt% at 52.2 wt% conversion of acetaldehyde. The reaction was carried out at 400°C with 0.5 hr"1 WHSV. The other major products were pyridine (3.4%) and lutidines (1.8%) . EXAMPLE 11 : 0.30 gm per hr of acetaldehyde, 0.78 gm per hr of acetonitrile, 0.70 gm per hr of water and 0.13 gm per hr of ammonia was passed over PbZSM-5(30), the yields of 2-picoline and 4-picoline obtained were 24.4 and 29.4 wt% at 61.9 wt% conversion of acetaldehyde. The reaction was carried out at 250°C with 0.5 hr-1 WHSV. The other major products were pyridine (3.6%) and lutidines (4.5%). EXAMPLE 12 : 0.30 gm per hr of acetaldehyde, 0.78 gm per hr of acetonitrile, 0.70 gm per hr of water and 0.13 gm per hr of ammonia was passed over PbZSM-5(30), the yields of 2-picoline and 4-picoline obtained were 34.1 and 32.9 wt% at 73.5 wt% conversion of acetaldehyde. The reaction was carried out at 300°C with 0.5 hr"1 WHSV. The other major products were pyridine (2.2%) and lutidines (4.3%). EXAMPLE 13 : 0.3 0 gm per hr of acetaldehyde, 1.0 gm per hr of methylamine, 0.70 gm per hr of water and 0.13 gm per hr of ammonia was passed over PbZSM-5(30), the yields of 2-picoline and 4-picoline obtained were 12.3 and 19.2 wt% at 63.7 wt% conversion of acetaldehyde. The reaction was carried out at 400°C with 0.5 hr"1 WHSV. The other major products were pyridine (23.9%) and lutidines (8.3%). We claim: 1. An improved process for the preparation of picolines which comprises; passing a feed consisting of acetaldehyde, acetonitrile, ammonia in a ratio of 1:1:5 molar and water over modified pentasil ZSM-5 catalyst with various Si/AI ratios in the range of 30 to 280 at a temperature in the range of 300 to 450°C and weight hourly space velocity in the range of 0.25 to 1.0 per hr, collecting the picolines by known methods. 2. An improved process as claimed in claims 1 & 2 wherein the weight ratio of acetaldehyde per hr to the catalyst used in the range 1:4 to 4:4. 3. An improved process for the preparation of picolines catalysts substantially as herein described with reference to the examples.

Documents:

573-del-2000-abstract.pdf

573-del-2000-claims.pdf

573-del-2000-complete specification(granted).pdf

573-del-2000-correspondence-others.pdf

573-del-2000-correspondence-po.pdf

573-del-2000-description (complete).pdf

573-del-2000-form-1.pdf

573-del-2000-form-19.pdf

573-del-2000-form-2.pdf