Title of Invention	"A CATALYST FOR PRODUCTION OF 5H-DIBENZO-(b,f)-AZEPINE AND PROCSS FOR PREPARATION THEREOF"
Abstract	Disclosed herein is a novel catalyst, where the catalyst is devised from carefully selected active metal oxides in appropriate compositions, process for preparing the same and use thereof in the process for producing 5H-dibenzo-(b,f)-azepine by catalytic vapor phase dehydrogenation of 10,1 l-dihydro-5H-dibenzo-(b,f)-azepine.

Full Text

Field of the Invention This invention in general relates to a catalyst for producing 5H-dibenzo-(b,f)-azepine. More particularly the invention provides a novel catalyst comprising carefully selected active metal oxides in appropriate compositions, process for preparing the same and use thereof for producing 5H-dibenzo-(b,f)-azepine by catalytic vapor phase dehydrogenation of 10,11-dihydro-5H-dibenzo-(b,f)-azepine. Background of the Invention 5H-dibenzo-(b,f)-azepine (Iminostilbene) is used as an intermediate for the production of pharmacologically valuable substances such as opipramol or carbamazepine, which is used for epilepsia treatment. The prior arts disclose different conventional chemical processes for producing 5-H-dibenzo-(b,f)-azepine (Iminostilbene). One of the processes is a multistep process for producing iminostilbene from iminodibenzyl by acylation, bromination, dehydrobromination and dealkylation. Also, this process is laborious and involves formation of byproducts, which adversely affects the production capacity. A process involving single step for the production of iminostilbene is also known in the literature. The process involves catalytic dehydrogenation of iminodibenzyl in liquid phase using Pt/C or Pd/C as catalysts. European Patent No. EP 0237952 to Tapani, et al., discloses production of iminostilbene from iminodibenzyl in liquid phase using Pt/C or Pd/C or FeiOs as a catalyst, dimethylaniline or diphenylether used as solvent and O-nitrotoluene or dimethylmaleate used as a hydrogen acceptor. United States Patent No. 5,895,815 to Eichberger, et al., discloses production of iminostilbene from iminodibenzyl in liquid phase using O-nitrotoluene as a solvent and Pd/C as a catalyst. Catalysts used in these processes are very costly and solvents used are highly toxic and hazardous. Thus, iminostilbene obtained by this process consists of a large number of impurities mainly acridine and methylacridine and toluidine, which are difficult to remove economically and thus adversely affect the purity of carbamazepine produced thereafter. United States Patent No. 3,074,931 to Roslyn, discloses an electrically heated column (ID-35 mm) packed with Pd/C catalyst on glass wool. Iminodibenzyl is passed through the column (ID-0.5 mm) by heating until sublimation occurs on the top portion of the column and the yellow sublimate is removed by scratching. The catalyst used in this process is very costiy and this sublimation technology is unattractive for commercial exploitation. Japanese Patent No: 55-017330 to Hidemitsu, discloses the production of iminostilbene from iminodibenzyl through single step catalytic dehydrogenation in vapor phase using a catalyst comprising an oxide of Ce, Mn, Sn or Mg and the reaction is carried out at a temperature of 350-650°C. European Patent No. EP 0570336 to Milos, et al., discloses the production of iminostilbene by high temperature dehydration of iminodibenzyl, using catalyst containing Fe2O3, K2O and Cr2O3. United States Patent No. 3,449,324 to Basel, et al., discloses a catalyst containing Fe2O3, CaO, K2O and Cr2O3 for the production of iminostilbene. British Patent No. GB 1077648, assigned to Degussa, discloses a catalyst containing nickel loaded on kieselguhr for the production of iminostilbene in vapor phase. The reported yield and selectivity are approximately 45% at 600°C. The high reaction temperature may be the cause for low yield of iminostilbene. Moreover, high reaction temperature in this reference is fairly unattractive for commercial exploitation. The processes disclosed in the above-mentioned prior arts consist of various disadvantages, like multi step and laborious processes and high demand on production capacity. For minimizing process steps, catalysts are used, which are very costly, and the major drawback of the processes is the formation of byproducts, which decreases the yield and selectivity of Iminostilbene. Therefore, there is a need to develop an improved process and a novel catalyst for producing 5H-dibenzo(b,f)-azepine, which overcomes the disadvantages associated with the processes disclosed in the prior art. Summary of the Invention It is the principal aspect of the present invention to provide a novel catalyst for use in the production of 5H-dibenzo-(b,f)-azepine by dehydrogenation of 10,ll-dihydro-5H-dibenzo~ (b,f)-azepine in vapor phase, wherein the catalyst comprises multi metal oxides mixed with catalyst support material. Preferred oxides are selected from oxides of metals of group IIIA, IVA, transition metals, alkali metals and alkaline earth metals. Most preferred oxides of the metals are selected from molybdenum, tin, iron, potassium, nickel and cobalt etc. mixed with titania, bentonite, china clay or any similar support material powder in appropriate compositions. Another aspect of the present invention is to provide a low cost catalyst for the production of 5-H-dibenzo-(b,f)-azepine (Iminostilbene) by catalytic vapour phase dehydrogenation of l(),ll-dihydro-5H-dibenzo-(b,f)-azepine (iminodibenzyl) in a single step, which gives good yield and selectivity for the iminostilbene and obviates the formation of by products. Yet another aspect of the present invention is to provide a process for preparing a novel catalyst for use in the production of 5H-dibenzo-(b,f)-azepine by dehydrogenation of 10,11-dihydro-5H-dibenzo-(b,f)-azepine in a vapor phase. Still another aspect of the present invention is to provide a process for producing 5H-diberizo-(b,f)-azepine by dehydrogenation of 10,ll-dihydro-5H-dibenzo-(b,f)-azepine in a vapor phase employing a novel catalyst, which ensures higher equilibrium conversion at lower temperatures of endothermic reaction to obtain better selectivity, wherein the catalyst comprises an active component, consisting of metal oxides of molybdenum, tin and iron, with molar ratios in the range of 1 : 8-16 : 4-16, said active component being supported on powdered titania, bentonite, china clay or similar supports. Optionally potassium, nickel or cobalt etc., can also be used as additives. In one preferred embodiment of the present invention, there is provided a process for producing a multi metal oxide catalyst for use in the production of 5H-dibenzo-(b,f)-azepine (iminostilbene). The catalyst is prepared by adding molybdenum source to solution of a weak organic acid in water and heating the same up to 50-90°C, adding stannic salt or oxide and iron (III) salt or oxide to the resultant solution, heating the same up to 50-90°C and mixing the solution thoroughly to obtain slurry, adding a catalyst support material in the powdered form into the slurry, drying the resultant and calcining the dried mass at a temperature range of 450-600°C to obtain the catalyst. In another preferred embodiment, there is provided a process for producing 5H-dibenzo-(b,f)-azepine (iminostilbene), the process comprising, preparing the feed solution by dissolving 10,1 l-dihydro-5H-dibenzo-(b,f)-azepine (iminodibenzyl) in toluene, vaporizing the same at 300-375°C in a pre-heater and allowing the superheated vapors to pass over a catalyst bed, distilling the reaction mixture to distill out 70% of solvent, cooling the residual mass up to 20°C and filtering the same, washing the obtained precipitate with toluene to remove the unreacted iminodibenzyl to obtain 5H-dibenzo-(b,f)-azepine (iminostilbene). In yet another preferred embodiment, there is provided a process for producing 5H-dibenzo -(b,f)-azepine (iminostilbene), wherein the concentration of feed solution is in the range of 2-60% w/w, preferably 5-35% w/w and flow rate is 10-150 g/h, preferably 20-80 g/h, maintaining WHSV (weight hour space velocity) 0.1-1.0 h"1. In still another preferred embodiment, there is provided a process for producing 5H-dibenzo-(b,f)-azepine (iminostilbene), wherein the catalyst is provided in the form of a fixed catalyst bed, wherein the temperature of the catalyst bed is in the range of 300 -500°C, preferably 350-480°C . Detailed Description of the Invention The present invention provides a novel catalyst and a process for producing 5H-Dibenzo-(b,f)-azepine (iminostilbene) employing the catalyst, which prevents the formation of by-products such as, acridine and methylacridine etc. and provides good yield and selectivity for iminostilbene. After extensive study and analysis, we found that in the preparation of iminostilbene, when catalyst comprising an active component selected from group IIIA, IVA, transition metals, alkali metals and alkaline earth metals, more preferably active metal oxides selected from molybdenum, tin, iron, potassium, nickel and cobalt mixed with titania, bentonite, china clay or any similar support material powder in appropriate compositions is used in catalytic vapor phase dehydrogenation of iminodibenzyl, unwanted reaction products are suppressed and iminostilbene is obtained in good yield and selectivity. The catalyst of the invention also has a good resistance to heat and reduction and is safe in operation. The catalyst used in the present invention is derived from carefully selected active metal oxides and their compositions i.e., molar ratios of active metal oxides, hi such reactions, the concentration of the iminodibenzyl containing solvent solution and feed flow rate is also important. The catalyst of the present invention comprises active metal oxides of molybdenum, tin and iron. Optionally potassium, nickel or cobalt etc., can also be used as additives. The catalyst of the present invention also has a good resistance to heat and reduction and is safe in operation. The feed solution according to the process is prepared by dissolving iminodibenzyl in benzene, toluene or similar solvents in the concentration of 5-30% (w/w). Catalyst activity when reduced (observed as decrease in the conversion rate) can be reactivated by passing air at 450-600°C for 3-8 hrs. The catalyst support material in the process according to the present invention is used in the powdered form. Said active component of the metal mixed oxides according to invention is thoroughly mixed with support material. The presence of active component in the catalyst is in the range of 5 90%, preferably 20-80%, most preferably 30-60%. The molybdenum source disclosed in the process is selected from any of the molybdenum salts or molybdenum oxides. The tin source disclosed in the process is selected from stannic oxide or the salts and iron source is selected from iron (III) oxides or salts respectively. The following examples are illustrative of the invention and should not be construed as limiting the scope of the invention in any manner. It is understood that variation of the process described below are possible without departing from the scope and spirit of the invention. Example 1 Oxalic acid (61.75 g) was taken in 200 g of DM water in a SS vessel with a mechanical stirrer. Ammonium molybdate (61.75 g) was added with stirring. The reaction mixture was heated gradually and temperature was allowed to reach 70-80°C and then 60.24 g of stannic oxide and 31.93 g of iron (III) oxide was added. The resulting reaction mixture was heated to concentrate the solution till thick slurry was obtained. The support material (100 g) in the powdered form was added to the above slurry under constant agitation and heating. The obtained thick mass was carefully dried at 120-130°C for about 2-4 hrs. The dried mass was then calcined in a muffle furnace at 450-600°C for about 5-6 hrs. The calcined mass was pelletized to 3-4 mm size and sieved to remove the powder material. The active material in the catalyst was approximately 40-50% (w/w). Example 2 The same procedure as in example 1 was followed, except that the molar quantities of different metals were adjusted to obtain molar ratio of 1 : 8 : 4 for molybdenum : stannic oxide : iron oxide. The presence of active material in the catalyst was approximately 75-80% (w/w). Example 3 The same procedure as in example 1 was followed, except that the molar quantities of different metals were adjusted to obtain molar ratio of 1 : 16 : 8 for molybdenum : stannic oxide : iron oxide. The presence of active material in the catalyst was approximately 45-50% (w/w). Example 4 The same procedure as in example 1 was followed, except that the molar quantities of different metals were adjusted to obtain molar ratio of 1 : 16 : 16 for molybdenum : stannic oxide : iron oxide. The presence of active material in the catalyst was approximately 45-50% (w/w). The catalysts prepared in the Examples 1-4 were individually used in the preparation of 5H-dibenzo-(b,f)-azepine from 10,ll-dihydro-5H-dibenzo-(b,f)-azepme and satisfactory results were obtained. The following procedure was adopted for evaluating the catalyst and optimizing the process parameters. Example 5 The 10,1 l-dihydro-5H-dibenzo-(b,f)-azepine feed solution was prepared by dissolving it in an aromatic hydrocarbon solvent and was vaporized at 300-375°C in a pre-heater and the superheated vapors were allowed to pass over a catalyst bed, maintained at a temperature in the range of 350-480°C. The reaction is carried out in a steel reactor of one-meter length and 23 mm DD, mounted in a vertical zone tubular furnace. The reactor tube is heated and the temperature is maintained as per the requirement. Reaction is carried out for 4-10 hrs. The reactor bottom outlet is attached to the round bottom flask, which is chilled by ice and maintained at a temperature below 15°C. Condensed product is collected and is worked up for pure product isolation. The reaction mixture was put to distillation and 70% of solvent was distilled out, residual mass was cooled up to 20°C and filtered. Obtained precipitate was thoroughly washed with the solvent to remove the unreacted 10,H-dihydro-5H-dibenzo-(b,f)-azepine. Thus obtained 5H-dibenzo-(b,f)-azepine was of 99.6% purity. The process of the invention for the preparation of 5H-dibenzo-(b,f)-azepine is illustrated below with reference to the following examples: Example 6 A run was carried out over 60 cc of the catalyst prepared in example 1 by following the procedure described in Example 5, keeping the concentration of feed solution as 10% (w/w) and feed flow rate at 52 gh-1 but varying the temperature from 400 to 480°C. Results are tabulated in Table 1. Example 7 The same procedure as in example 6 was followed except varying concentration of feed solution from 5 to 30% (w/w). The feed flow rate was kept same as 52 gh"1 at a temperature of 465°C. The results are summarized in Table 2. Example 8 The same procedure as in example 6 was followed keeping the feed concentration of 10% (w/w) at 465°C but varying the feed flow rate and results obtained are provided in Table 3 Example 9 A run was carried out over 60 cc of the catalyst prepared in example 1 by following the procedure described in example 5, keeping the feed concentration of 10% (w/w) and feed flow rate of 52 gh"1 at 465°C. The obtained yield, conversion and selectivity was 71%, 78% and 91% respectively. Example 10 The same procedure as in example 9 was followed using the catalyst prepared in example 2. The obtained yield, conversion and selectivity were 33%, 70% and 47% respectively. Example 11 The same procedure as in example 9 was followed using the catalyst prepared in example 3. The obtained yield, conversion and selectivity were 55%, 72% and 76% respectively. Example 12 The same procedure as in example 9 was followed using the catalyst prepared in example 4. The obtained yield, conversion and selectivity were 42%, 66% and 64% respectively. Example 13 [he same procedure as in example 9 was followed using the catalyst obtained in example 1 and varying the reaction run time from 4 to 8 hrs. Results are represented in Table 4. Certain modifications and improvements of the disclosed invention will occur to those skilled in the art without departing from the scope of invention, which is limited only by the appended claims. Table 1 (Table Removed) Table 2 (Table Removed) Table 3 (Table Removed) Table 4 (Table Removed) We Claim: 1. A catalyst comprising multi metal oxide mixed with support material powder suitable for production of 5H-dibenzo-(b,f)-azepine, wherein the multi metal oxide comprises an oxide of a metal selected from alkali metals, group IVA and transition metals wherein the ratio of active metal to group IV A metals and transition metals is m the range of 1 : 8-16 : 4-16. 2. The catalyst as claimed in claim 1, wherein the active metal oxides are preferably selected from potassium, sodium, molybdenum, tin, iron or titanium. 3. The catalyst as claimed in claim 1, wherein the active metal oxides are oxides of molybdenum, tin and iron. 4. The catalyst as claimed in claim 1, wherein said catalyst comprises of oxides of molybdenum, tin and iron in the range of 1 : 8-16 : 4-16 5. The catalyst as claimed in claim 1, wherein the support material is selected from a group comprising titania, bentonite, china clay or any such support material powder. 6. A process for the preparation of a multi metal oxide catalyst as claimed in claim 1, comprising: preparing a solution of a weak organic acid in water; adding a molybdenum source to the solution; heating the resulting solution up to 50-90°C; adding stannic salts or oxides and iron salts or oxides to the solution; heating the same up to 50-90°C to obtain slurry; adding, optionally, alkali metal as additives to the slurry; adding a catalyst support material in the powdered form to the slurry wherein the catalyst support material is in the range of 20 to 80% of the slurry; drying the same; and calcining the dried mass up to 450-600°C to obtain the catalyst. 7. The process as claimed in claim 6, wherein the weak organic acid is oxalic acid. 8. The process as claimed in claim 6, wherein said molybdenum source is ammonium molybdate. 9. The process as claimed in claim 6, wherein said tin and iron source is stannic oxide and iron (III) oxide, respectively. 10. The process as claimed in claim 6, wherein the alkali metal additive is selected from potassium or sodium. 11. The process as claimed in claim 10, wherein the alkali metal additive is preferably potassium. 12. The process as claimed in claim 6, wherein the catalyst support matenal is in the range of 30 to 60% of the slurry. 13. The catalyst as claimed in claim 1 used in the process for producing 5H- dibenzo-(b,f)-azepine (iminostilbene).

Documents:

1897-del-2004-abstract.pdf

1897-del-2004-claims.pdf

1897-del-2004-complete specification (granted).pdf

1897-del-2004-correspondence-others.pdf

1897-del-2004-correspondence-po.pdf

1897-del-2004-description (complete).pdf

1897-del-2004-form-1.pdf

1897-del-2004-form-19.pdf

1897-del-2004-form-2.pdf

1897-del-2004-form-26.pdf

1897-del-2004-form-3.pdf

1897-del-2004-form-5.pdf