EP1565439A1

EP1565439A1 - Process for the preparation of vinylpyridine from picoline over modified zeolites

Info

Publication number: EP1565439A1
Application number: EP02779826A
Authority: EP
Inventors: Shivanand Janardan Kulkarni; Gangapuram Madhavi; Venkataraman Viswanathan; Kondapuram Vijaya Raghavan
Original assignee: Council of Scientific and Industrial Research CSIR
Current assignee: Council of Scientific and Industrial Research CSIR
Priority date: 2002-11-06
Filing date: 2002-11-06
Publication date: 2005-08-24
Also published as: JP2006515569A; AU2002343158A1; JP4545593B2; WO2004041785A1

Abstract

The present invention relates to an improved eco-friendly process for the preparation of vinylpyridine from corresponding picoline over modified zeolite catalyst in vapour phase which comprises reacting picoline with formaldehyde with a molar ratio of formaldehyde to picoline in the range of 1:1 to 4:1, at a temperature ranging between 200°C to 450°C, at a weight hourly space velocity in the range of 0.25 hr?-1¿ - 1.00 hr?-1¿ over a modified commercial zeolite catalyst to obtain a high yield and selectivity of the desired product.

Description

P_ROC_ESS FOR THE PREPARATION OF VINY PYRIDINE FROM PICOLINE OVER MODIFIED ZEOLITES

TECHNICAL FIELD The present invention relates to an improved process for preparing vinylpyiϊdine from corresponding picoline. The present invention relates to a process for the preparation of 2-vinylpyridine or 4-vinylpyridine over modified zeolite catalysts. In particular, it relates to method for the synthesis of vinylpyridine from corresponding picoline with formaldehyde in vapour phase in an eco-fπendly method with high yield and selectivity. This invention provides a non-corrosive, eco-friendly process, where the catalyst can be recycled and reused for many times. 2-vinylpyridine and 4-vinylpyridine are useful starting material iώ poliyrm r industry.

BACKGROUND ART 2-vinylpyridine (2-VP) is an important monomer used in synthesizing various polymers. Butadiene and styrene monomers were used with 2-vinylpyridine to form latex terpolymer that bonded fabric cords to the rubber matrix of tires. The addition product of methanol and 2-vinylpyridine, 2-(2-methoxy-ethyl) pyridine is a veterinary anthelmintic. Thisi monomer is prepared commercially by autoclaving acetylene, acrylonitrile using cobaltocene catalyst or oxidative dehydrogenation of 2-ethylpyridine on Cr-Nb catalyst (Y. Wakatsuki, synthesis, l,ι 26 (1976)). ("Heterocyclic compounds: Pyridine and Pyridine derivatives part 2, Ed. E. Klingsberg, Chapt. V, p 203). Generally in most of the processes, the synthesis of 2-vinylpyridine is practiced by a two-step procedure, which involves a base catalyzed addition of 2-picoline to formaldehyde to give 2-(2-hydroxy ethyl) pyridine followed by, dehydration ! to 2-vinylpyridine monomer. (S. Yasuda, H. Niwa and O. Tagano, Jpn. Kokai Tokyo, Koho 78, 141281 (1978)). 2-vinylpyridine was prepared with 70.8% selectivity at 35.8% conversion over ZrO₂ catalyst (Reddy B.N. and Subrahmanyam M, Catalysis Present & iFuture, Eds. Kanta Rao P. & Beniwal R.S. p. 304(1995)). The synthesis of vinylpyridines are also reported by the dehydrogenation of alkyl pyridines overj V₂O5/MgO and ^■ MoO₃/MgO catalysts in the presence of O₂. The alkylation of pyridine, 2,3, and 4-picolines with methanol as alkylating agent over alkali metal ion exchanged X and Y typei zeolites in N₂ atmosphere resulted in the formation of side-chain alkylated products like ethylpyridines and vinylpyridines were 22.2, and 5.3% at 82.0% conversion over CsY , catalyst from 2-picoline and methanol at 450°C. However considerable amounts of ring-alkylated derivatives (lutidines) were formed simultaneously. (Ksh'iwagi H., EnoiriotbiS.j Chem. Pharm. Bull, 30(2), 404(1982)).

The alkylation of picolines with methanol was studied over modified X and Y zeolites in which the major products were ethylpyridine and vinylpyridine (Chem. Pharm. Bull., 30(2), 404, 1982). The yields of ethylpyridine were more when the CsY zeolite was used at 450°C. On the other hand the yields of vinylpyridines were more over CsX zeolite at a^:bout 425°C. The (yields of vinylpyridines were <20-25%. The syntheses of vinylpyridines were also reported by the dehydrogenation of alkylpyridines over N₂θ₅/MgO and MoO₃/MgO catalysts in the presence of oxygen. However the yields and selectivities of 4-vinylpyridine were lower

OBJECTIVES OF THE INVENTION

The main objective of the present invention is to provide a process for the synthesis of vinylpyridines over modified zeolites in a heterogeneous eco-friendly method. Another objective ι of the present invention is to provide a process for the preparation of 2-vinylpyridine in high yield and high selectivity.

Another object of the present invention is to provide a process for the preparation of 4-vinylpyridine in high yield and high selectivity.

Another object of the present invention is to provide a process for the preparation of 2-vinylpyridine from , 2-picoline and formaldehyde in the presence of catalyst which comprises ZSM-5 containing one or two element(s) from alkali and/or alkaline earth metal ions_? like Na , K , Rb , Cs , Mg , Ca , Sr , etc., which can be recycled and reused for several times.

Still another object of the present invention is to provide a process for the preparation of 4-vinylpyridine from 4-picoline and formaldehyde in the presence of a catalyst which comprises ZSM-5 containing one or two element(s) from alkali and alkaline earth metal ions, like Na, K, Rb, Cs, Mg, Ca, Sr, Ba etc., which can be recycled and reused for several times., :« j SUMMARY OF THE INVENTION

Accordingly, the present invention provides a process for the preparation of 2- vinylpyridine from 2-picoline and formaldehyde in vapour phase over 2-picoline and formaldehyde in vapour phase over modified zeolite/molecular sieve. The catalyst comprises of particularly ZSM-5 modified with sodium, potassium, rubidium, cesium, magnesium, calcium, and/or barium, etc as cation or species.

I I The present invention also provides a process for the preparation of 4-vinylpyrdine from 4-picoline and formaldehyde in_. vapour phase over modified zeolite/molecular sieve. The catalyst comprises of ZSM-5 modified with sodium, potassium, rubidium, cesium, magnesium,, calcium or barium. DETAILED DESCRIPTION OF THE INVENTION

Accordingly, the present invention provides an improved process for the preparation of vinylpyridine from corresponding picoline over modified zeolite catalyst in vapour phase which comprises reacting picoline with formaldehyde with a molar ratio of formaldehyde to . picoline in the range of 1:1. to 4:1, at a temperature ranging between 200°|C to 450°C, at a weight hourly space velocity in the range of 0.25 hr^"1 - 1.00 l r^"1 over a modified commercial zeolite catalyst to obtain the desired product.

' In an embodiment of the present invention provides a process wherein, the vinylpyridine obtained is either 2-vinylpyridine or 4-vinylpyridine.

Still another embodiment, one of the reactant picoline: is selected from 2-picoline and 4-picoline.

Still another embodiment, one of the catalyst is prepared by varying alkali and alkaline earth modified with a zeolite catalyst selected from a group consisting of ZSM-5, X, Y, mordenit iand'MCJyHl-

In yet another embodiment, the catalyst used is preferably ZSM-5 pentasil type zeolite. i Yet another embodiment, the modification of the catalyst is carried out by alkali or alkaline earth metal ion selected from the group consisting of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg⁺², Ca⁺²j, Sr⁺², Ba⁺² or twoj cation modified ZSM-5 like Cs-K-ZSM-5.

I Still another embodiment the present invention provides a process , wherein the weight percent of the alkali or alkaline earth metal cation in ZSM-5 is varied from 1 weight percent to 4 weight percent.

Still another embodiment, the precursor to modify ZSM-5 catalyst by potassium ion or other elements is varied like KO^lBu, KOH, KF, KNO₃, K₃PO₄ and KOAc to improve the yield ,and selectivity of vinylpyridine. Still another embodiment, the calcination temperature of modified zeolite is varied from 400°C toι7:0Q?C.' | , | |.

Still another embodiment the reaction temperature of the catalytic zone in the process is varied from 20.0°C to 450°C. ¹ Still another embodiment the weight hourly space velocity (WHSN) is in the range of 0J25 to l.0 hr^"1. I

' The following catalysts were used in the present process development HZSM-5 (SiO₂/Al₂O₃ = 30), ΝaY (SiO₂/Al₂O₃= 5.0), H-Mordenite (SiO₂/Al₂O₃= 12), and H-MCM- 41 (SiO₂/Al₂O₃= 31). Each zeolite was pelleted without binder, crushed and sized 18-30 mesh before the impregnation. The catalysts were modified by using required amount of alkali or alkaline earth cation nitrate by an impregnation method. In the case of potassium, different precursors 'like KO'Bu, KF, KOAC, K₃PO₄ and KOH were used to modify ZSM-5 (30) catalyst. The required amount of precursor was taken in the form of nitrate or other soluble salts in 30 ml of distilled water. 4.0 g of the meshed catalyst was added to it and kept for soaking for 12 hi Then it was dried at 110°C overnight and calcined at 420°C for 4 h before using for the reaction. In a typical procedure for the synthesis of KO'Bu modified ZSΪ^-5 (30) catalyst is as follows, 7 g of HZSM-5 (30) was taken in 250 ml two-necked round bottom flask. Prior! to the modification the catalyst was predried in oven at 100°C for

! I 1 h followed by flushing¹ with nitrogen gas to remove the water present in the channels of the catalyst. In another round bottom flask required amount of KO^lBu was dissolved in dry

DMSO solvent. This solution was added to HZSM-5 (30) catalyst and kept stirring for 24 h in presence of nitrogen atmosphere. After 24 h stirring the resultant mixture was filtered, dried at 120°C overnight and calcined at 400°C for 4 h. The reactions were carried out in a fixed bed, continuous, . down-flow pyrex reactor with 20 mm internal diameter at atmospheric pressure. I AU| the catalysts were activated by calcination in a flow of air at 420°C for 4 h and brought to the reaction temperature in situ. The catalyst temperature was measured with a thermocouple placed in the middle of the catalyst bed. A mixture of 2- picoline and formaldehyde were fed from a syringe pump at a rate of 2 ml.h^"1. The products from the reactor was cooled by circulating ice-cooled water and periodically collected. The quantitative analysis of product was carried out by gas chromatography (G.C.). The samples were analyzed by G.C. (Schimadzu-17A and 14B) fixed with an ON-

I

17 (2mmXl/8"OD) on lchromosorb W-HP column and flame ionization detector. The retention times were compared with the authentic compounds. The products were confirmed by mass spectra, GC-mass and ΝMR techniques. The mass balance was >90- 95%. ,

The following catalysts were used in the present process development HZSM-5 (SiO₂/Al₂O₃= 30), ΝaY (SiO₂/Al₂O₃= 5.0), H-Mordenite (SiO₂/Al₂O₃= 12), and H-MCM-

41 (SiO₂/Al2θ3F,3'l). Eac h! zeolite was pelleted without binder, crushed and sized 18-30 mesh before the impregnation. The catalysts were modified by using required amount of alkali or alkaline earth cation nitrate by an impregnation method. In the case of potassium, different precursors like KOT^u, KF, KOAc, K₃PO₄ and KOH were used to modify ZSM-5 (30)| catalyst. The required amount of precursor was taken in the form of nitrate or other soluble salts in 30 ml ofj distilled water. 4.0 g of the meshed catalyst was added to it and kept|for soaking for 12 h. Then it was dried at 110°C overnight and calcined at 420°C for 4 h before using for the reaction. In a typical procedure for the synthesis of KO^lBu modified ZSM-5 (30) catalyst is as follows, 7 g of HZSM-5 (30) was taken in 250-ml two-necked round bottom flask. Prior to the modification the catalyst was predried in oven at 100°C for 1 h followed by flushing with nitrogen gas to remove the water present in the channels of the catalyst. In_lian,othei] rcjund bottom flask required amount of KO Bu was dissolved in dry DMSO solvent. This solution was added to HZSM-5 (30) catalyst and kept stirring for 24 h in presence of nitrogen atmosphere. After 24 h stirring the resultant mixture was filtered, dried at 120°C overnight ι and calcined at 400°C for 4 h. The reactions were carried out in a fixed bed, continuous down-flow pyrex reactor with 20 mm internal diameter at atmospheric pressure. _r ll, the catalysts was activated by calcination in a flow of air at 420^ for 4 h and brought to the reaction temperature in situ. The catalyst temperature was measured with a thermocouple placed in the middle of the catalyst bed. A mixture of 4- picoline and formaldehyde were fed from a syringe pump at a rate of 2 ml.h^"1. The products from the reactor was cooled by circulating ice-cooled water and periodically collected. The quantitative analysis of product was carried out by gas chromatography (G.C.). The samples were analyzed by G.C. (Schimadzu-17A and 14B) fixed with an ON-17 (2mmXl/8"OD) on chromosorb W-HP column and flame ionization detector. The, times were compared with the authentic compounds. The products were confinned by mass, spectra, GC-mass and ΝMR techniques. The mass balance was >90-95%.

, i EXAMPLES

The present invention will be explained in more detail by the following examples, which do not limit the scope of the invention in any way. I ' ! EXAMPLE-1

Synthesis of potassium modified ZSM-5,

Four grams of calcined HZSM-5 having SiO₂/Al₂O₃ molar ratio of 30 was taken in the form of 18-30 mesh size and soaked in 30 ml of the solution of potassium nitrate containing 0.4tig:.pJ( tassiu!hτj'(K) for 12 h. Then it was dried at 110°C overnight and calcined at ~420°C for 4 h before using for the reaction.

EXAMPLE-2:

Synthesis of cesium modified ZSM-5 j The same (procedure as given in Example- 1 was used for the preparation of other metal ion ZSM-5 catalyst by using their inorganic salts as precursors. Cesium nitrate was used for Cs-ZSM-5. ;

I - i

! EXAMPLE-3 i The modified ZSM-5 was used in the following reactipn for the preparation of 2- vinylpyridine. j

Cs-ZSM-5 (SiO₂/Al₂O₃ = 30) catalyst was packed in a pyrex reactor having an inner diameter of 20 mm with the length of 30-40 cms and the catalytic zone was heated at 300ι1C. and formaldehyde in a molar ratio of 1:2 was fed from the top of the reactor at a weight hourly space velocity of o.5 h^"1. The liquid product selectivity of 2-vinylpyridine was 92.8% at 40.4% conversion of 2-picoline at 4^th hour on stream. The conversion j of 2-picoline was in the range of 4- >10% with 30 -81.5%ι selectivity of 2-picoline at 300°C over CsY, Cs-mordenite and Cs-MCM-41.

EXAMPLE 4

The reaction of ^! 2-picoline and formaldehyde was carried out over K-ZSM-5 (Siθ[₂/Al₂O₃ = 30) at 300°C with 0.5 h^"1 weight hourly space velocity (W.H.S.N). The catalyst was 4 g with 18-30 mesh size and feed rate was 2 ml.hr^"1. 2-Picoline to formaldehyde was 1 :2^' molar. The liquid product selectivity of 2-vinylpyridine was 81.1% at 65.7% conversion of 2-picoline. 2-Ethylpyridine and other products were less than 18.9% selectivity. The reactor design and the other experimental details were as explained in Example-3 and the text.

^'" i ^' ' W 'H l EXAMPLE-5

The reaction of 2-picoline and formaldehyde was carried out over Rb-ZSM-5 (SiO₂/Al₂O₃ = 30) at 300°C with 0.5 h^"1 W.H.S.N. The experimental conditions are as explained in Example^. The weight of the rubidium was 3 wt% in ZSM-5 catalyst. The percent liquid product selectivity of 2-vinylpyridine was 86.1% at 61.0% conversion of 2-

J ^' i I , picoline. The conversion :of formaldehyde was ~100%. i '

EXAMPLE-6

The reaction of 2-picoline and formaldehyde was carried out over Na-ZSM-5

(SiO₂/Al₂O₃ = 30) at 300°C and 0.5 h^"1 W.H.S.N. The experimental conditions are as explained in Example-3l|τfhe weight of sodium was 3 wt% in ZSM-5 catalyst. The liquid product selectivity of 2-vinylpyridine was 99.7% at 35.0% conversion of 2-picoline during

4^th hour on stream.

_I EXAMPLE-7

, The reaction of 2-picoline and formaldehyde was carried out over CaZSM-5 (Si ₂/Al₂O₃ = 30) at ^!3Θ0°C and 0.5 h^"1 W.H.S.N. The experimental conditions are as

I ! explained in Example-3. [The weight of calcium was 3 wt% in ZSM-5 catalyst. The liquid product selectivity of 2-Vinylpyridine was 72.2% at 57.2% conversion of 2-picoline during 4^th hour on stream. Mg-ZSM-5, Sr-ZSM-5 and Ba-ZSM-5 were also tested with lower yields.

EXAMPLE-8 The ZSM-5 was modified using two cations like potassium (K) and cesium (Cs).

The reaction of 2-picoline and formaldehyde was carried out over Cs-K-ZSM-5 (1 wt% Cs & 3 wt% K) at 300°C and 0.5 h^"1 W.H.S.N. The experimental conditions were as given in Example-3. The liquid product selectivity of 2-vinylpyridine was 96.4% at 47.8% conversion of 2-picoline during 4^th hour on stream. EXAMPLE-9

The liquid product selectivities of 2-vinylpyridine were 96.2, 99.7, 99.8, 81.1, 98.9 and 99 % at 82.4, 72.17, 54.3, 65.7, 56.8, and 61.8 % conversions of 2-picoline when

KO pu, KOH, KF, KΝO|₃, K PO₄ and KOAc were used as precursors or as a potassium- source to prepare K-ZSM-5 (3 wt% K, SiO₂/Al₂O₃ = 30), respectively. The experimental conditions were as given lin Example-3.

EXAMPLE-10

The liquid product selectivities of 2-vinylpyridine were 93.3, 87.6, 81.1, and 80.7% at 49.1, 49.9, 65.7, and 66.4% conversions of 2-picoline over lwt% K-ZSM-5 (SiO₂/Al₂O₃ = 30), 2 wt% l£-ZSMi5 '1(30), 3 wt% K-ZSM-5 (30) and 4 wt% K-ZSM-5 (30) catalysts, respectively. The experimental conditions were as given in Example-3. Similarly the weight percent of cesium (Cs) was varied and conversions and selectivities were studied. The activity for Cs-ZSM-5 was lower than that for K-ZSM-5 catalysts. EXAMPLE-11

: The liquid product! selectivities of 2-vinylpyridine were 88.1, 57.6, 92.8, 75.9 and i

84.4% at 19.4, 28,3, 40.4< 61.5, and 37.8% conversions of 2-picoline at 200, 250, 300, 350, and 400°C reaction temperatures over 3wt% Cs-ZSM-5 (SiO₂/Al₂O₃ = 30) respectively. The other experimental conditions were as given in Example-3.

'i were 73.6, 92.1, 74.6, and 74.0% at 60.3, 40.7, 63.9, and 62.7% conversions of 2-picoline with 1:1, 1:2, 1:3, and 1:4 molar ratio of 2-picoline/formaldehyde respectively. The catalyst was 3 wt% Cs-ZSM-5

(Si ₂/Al₂O₃ = 30). The other experimental conditions were as given in Example-3.

EXAMPLE-13

The liquid product selectivities of 2-vinylpyridine were^:90.5, 92.1, 73.0, and 75.5% at 40.9, 40.7, 54.9, and |57.1% conversions of 2-picoline at 0.25, 0.5, 0.75, and. 1.0 h^"1 weight hourly space velocities (at A hour on stream) respectively. The catalyst was 3 wt%

Cs-ZSM-5 (SiO^Ahβi {-, 30) and formaldehyde /2-picoline is 2 molar. The reaction temperature was 300 o C. T ' he other experimental conditions were as given in Example-3.

EXAMPLE-14

! details' as given in Example-3, the time on stream was studied and steady states 'activity and yields were obtained for > 8 hours on stream.

_; EXAMPLE 15 i i ⁱ ' The modified ZSM-5 was used in the following reaction for the preparation of 4-

45% with 40-62% selectivity of 4-vinylpyridine at 300°C over CsY, Cs-mordenite and Cs-

MCM :^M-"41 ! " - EXAMPLE 16

3% s I electivity. The react ior ' design and the other experimental details were as explained in

Example-15 and the text.

EXAMPLE 17 of 4-picoline and formaldehyde was carried out over Rb-ZSM-5 300^olC with 0.5 h^"1 W.H.S.N. The experimental conditions are as explained in Example-15. The weight of the rubidium was 3 wt% in ZSM-5 catalyst. The percent liquid product selectivity of 4-vinylpyridine was 96.2% at 85.2%) conversion of 4-

I J picoline. The formaldehyde conversion was 100%.

liquijd product selectivity of 4-vinylpyridine was 99.3% at 76.9% conversion of 4-picoline during 4^th hour on stream.

EXAMPLE 19 The reaction of 4-picoline and formaldehyde was carried out over Ca-ZSM-5 (SiCj₂/Al₂O₃= ,₁3,0 at |30jOJ^,C and 0.5h W.H.S.N. The experimental conditions are as explained in Example-15. The weight of calcium was 3wt% in ZSM-5 catalyst. The liquid product selectivity of 4-vinylpyridine was 83.9% at 37.2% conversion of 4-picoline during i

4^th hour on stream. Mg-ZSM-5, Sr-ZSM-5 and Ba-ZSM-5 were also tested with lower yield.

EXAMPLE 20 The ZSM-5 was ι modified using two cations like K and Cs. The reaction of 4- picoline and formaldehyde was carried out over Cs-K-ZSM-5 (lwt%Cs & 3wt% K) at 300°|C and 0.5 h^"1 W.H.S.N. The experimental conditions were as given in Example-15. The [liquid product selectivity of 4-vinylpyridine was 96.1% at 69.8% conversion of 4- picoline during 4^th hour q stream. EXAMPLE 21

The liquid product selectivities of 4-vinylpyridine were 78.2, 99.3, 96.8, 97.3, and

95.3% at 80.2, 85.1, 91.9, 90.0, and 91.5% conversion of 4-picoline when KO^lBu, KOH,

KF, K₃PO₄ and KOAc were used as precursors or as a potassium- source to prepare K- 30), respectively. The experimental conditions were as

EXAMPLE 22

The liquid product selectivities of 4-vinylyridine were 87.8, 89.1, 97.0, and 68.7% at 63.3, 64.4, 77.6, and 76.6% conversion of 4-picoline over lwt% K-ZSM-5 (SiO₂/Al₂O₃= 30), 2wt%K-ZSM-5 (3,0), 3wt%K-ZSM-5 (30) and 4wt%K-ZSM-5 (30) catalysts respectively. The experimental conditions were as given in Example-15. Similarly the weight percent of cesium (Cs) was varied and conversion and selectivities were studied (dete irmined). T i el i' activ I i Ity i fo I r Cs-ZSM-5 was lower than that for K-ZSM-5 catalysts.

EXAMPLE 23 The liquid product selectivities of 4-vinylpyridine were 73.4, 63.9, 96.8, 59.9, and

51.6% at 28.8, 57.4, 49.3, 66.2, and 65.3% conversion of 4-picoline at 200, 250, 300, 350 and 400°C reaction temperature over 3wt% Cs-ZSM-5 (SiO₂/Al₂O₃= 30) respectively. The othe' experimental conditions were as given in Example-15.

; I EXAMPLE 24 . The liquid product selectivities of 4-vinylpyridine were 79.8, 96.8, 89.9, and 66.3% at 53.5, 49.3, 52.3, and 54.9% conversions of 4-picoline with 1:1, 1:2, 1:3, and 1:4 molar ratio¹ of 4-picoline/fόrmaldehyde respectively. The catalyst was 3wt% Cs-ZSM-5 (Siθ₂/A-₂θ₃= 30). The other experimental conditions were as given in Example-15. ' EXAMPLE 25

I The liqu^dlproduct selectivities of 4-vinylpyridine were, 80.3, 96.8, 96.2, and 93.5% at 66.4, 49.3, 39.2, and 37.1% conversion of 4-picoline at 0.25, 0.5, 0.75 and 1.0 h^"1 weight hourly space velocities respectively. The catalyst was 3wt% Cs-ZSM-5 (Siθ₂/Al₂O₃= 30) and ιformaldehyde/4picoline = 2 molar. The reaction temperature was 300°C. The other experimental conditions were as given in Example-15. j , I , EXAMPLE 26

With the experimental details as given in Example-15, the time on stream was studied and steady state activity and yields were obtained for > 8 hours on stream.

Claims

Claims:

1. An improved process for the preparation of vinylpyridine from corresponding picoline overijjmOdifi d' zeolite catalyst in vapour phase 'which comprises reacting picoline with formaldehyde with a molar ratio of formaldehyde to picoline in the range of 1:1 to 4:1, at a temperature ranging between 200°C to 450°C, at a weight hourly space velocity in the Irange of 0.25 hr^"1 - 1.00 hr^"1 over a modified commercial zeolite catalyst to obtain the desired product.

2. An improved .procjess as claimed in claim 1, wherein the vinylpyridine obtained is either 2-vinylpyridine or 4-vinylpyridine.

3. . _α improved process as claimed in claim 1, wherein picoline used is selected from 2- p icoline and 4_rpicoline.

4. An improved process as claimed in claim 1, wherein the I catalyst used is a modified zeolite selected from the group consisting of ZSM-5, X, Y, imordenite and MCM-41.

5. An improved process ι as claimed in claim 1, wherein the catalyst used is zeolite modified by one or two element(s) from alkali and alkaline earth metal ions.

6. An improvied'iprocps^ 'as claimed in claim 1, wherein the modification of the catalyst, preferably ZSM-5 is carried out by alkali or alkaline earth metal ion selected from the group consisting of iLi , Na , K , Rb , Cs , Mg , Ca , Sr , Ba or two cation modified ZSM-5 like,Cs-K-ZSM-5.

7. An improved process as claimed in claim 1, wherein the weight percent of the alkali or alkaline earth metal potion in ZSM-5 catalyst used is in the range of 1 to 4 wt%.

8. n improved process as claimed in claim 1, wherein the precursor used tp modify ZSM-5 catalyst by₍potassium ion or other elements, wherein potassium ions is selected from the group consisting of KOtBu, KOH, KF, KNO3, K3PO4 and KOAc to improve the yield and selectivity of vinylpyridine.

9. An improved process as claimed in claim 1, wherein the calcination temperature of modified zeolite used is varied between 400°C to 700°C.

10. An improved process as claimed in claim 1, wherein the reaction temperature of the fatalyticiZQnellμsedjiijsjipjreferably in the range of 300°C to 400°C.

11. A process accordingi to claim 1, wherein the preferable mole ratio of 2-picoline to formaldehyde is 1:2. ,

12. A process according! to claim 1, wherein K or Rb modified zeolite catalyst provide better yield of 2-vinyl pyridine. !

13. ^ process according to claim 1, wherein K or Rb modified zeolite catalyst provide better selectivity of 2-vinyl pyridine.

14. A process according! to claim 1, wherein K or Rb modified zeolite catalyst provides better yield of 4-vinyl pyridine.

15. A process according to claim 1, wherein K or Rb modified zeolite catalyst provide better selectivity of,4f vinyl pyridine.

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