Patent Application
20060147364
The present invention relates to an improved process for the preparation of porous crystalline aluminophosphate molecular sieves. These molecular sieves are useful as catalysts and adsorbents.
Crystalline aluminosilicate zeolite type molecular sieves are well known in the art and are formed by corner sharing SiO2 and AlO2 tetrahedra and have pore openings of uniform dimensions, have a significant ion exchange capacity and are capable of reversibly desorbing an adsorbed phase which is dispersed throughout the internal voids of the crystal without displacing any atoms which make up the permanent crystal structure.
The most recently synthesized molecular sieves without silica are crystalline aluminophosphate compositions disclosed in U.S. Pat. No. 4,310,440. These materials are formed from AlO2 and PO2 tetrahedra and have electro neutral frameworks as in the case of silica polymorphs. The empirical chemical composition on anhydrous basis is mR(AlxPy)O2 wherein ‘R’ represents at least one organic templating agent present in the intracrystalline pore system, ‘m’ represents the moles of ‘R’ present per mole of (AlxPy)O2 and has a value of from 0.1 to 0.3 and x and y have value from 0.4 to 0.59 and 0.4 to 0.59 respectively.
Unlike the silica molecular sieve, silicalite, which is hydrophobic due to the absence of extra framework cation, aluminophosphate molecular sieves are moderately hydrophilic, apparently due to the difference in the electro negativities of aluminium and phosphorous The intracrystalline pore volumes and pore diameters are comparable to those known for zeolites and silica molecular sieves.
The prior art procedure for synthesis of AlPO-n disclosed in U.S. Pat. No. 4,310,440 involves reaction of aluminium isopropoxide or hydrated aluminium oxide with phosphoric acid and organic templating compounds such as Tripropyl amine or di-n-propyl amine by autoclaving the reaction mixture directly at an elevated temperature of 150° C. to 200° C. for 24 h to 168 h. The major disadvantages of the above prior art method for the synthesis of AlPO-n is lower crystallinity, higher time duration and costly templates.
While carrying out research on use of new templating agents for synthesis of aluminophosphate molecular sieves, we have observed that heating a reaction gel containing the necessary ingredients along with hexamethyleneimine in a controlled manner reduced crystalline time and gave more crystalline samples Based on above studies we have noted that the templating agent hexamethyleneimine crystallized number of aluminophosphates such as AlPO4-5, AlPO4-16, AlPO4-22, AlPO4-31, SAPO-35 and AlPO4-L.
The object of the invention is to provide an improved process for preparing aluminophosphate molecular sieves.
Another object is to provide a process for rapid preparation of aluminophosphate molecular sieves
Yet another object is to prepare more crystalline samples of aluminophosphate molecular sieves.
The present invention provides an improved process for the preparation of a porous crystalline aluminophosphate molecular sieves characterized by the x-ray diffraction pattern as herein described and a chemical composition in terms of the mole ratio of oxides given by the formula mR: Al2O3:nP2O5 wherein R represents at least one organic templating agent present in the intracrystalline pore system; ‘m’ represents moles of ‘R’ present and has a value between 0.02 to 0.3, ‘n’ has a value of from 1.0 to 1.2, the process comprising
In one embodiment of the invention the source of aluminium oxide is pseudoboehmite and aluminium alkoxide, preferably aluminium isopropoxidee
In a preferred embodiment of the invention, the source of aluminium oxide is pseudoboehmite.
In another embodiment of the invention, the source of oxide of phosphorous is orthophosphoric acid.
In another embodiment of the invention the organic templating agent is selected from the group consisting of hexamethyleneimine, hexamethylene tetramine and di-n-propylamine.
In another embodiment of the invention, the reaction mixture is heated in step (b) at a temperature of about 200° C. for a period in the range of 4 h to 24 h.
In another embodiment of the invention, the crystalline material is separated by filtration.
In another embodiment of the invention, the crystals are washed with distilled water and then dried by heating at a temperature in the range of 25° C. to 150° C. at atmospheric pressure.
In another embodiment of the invention, the aluminophosphate molecular sieve is calcined at a temperature in the range of 300° C. to 1000° C. for a period in the range of 1 minute to 20 h.
In yet another embodiment of the invention, the calcination of the crystalline material is effected at a temperature of about 550° C. to remove the organic material occluded in the pore of the crystalline material
In another embodiment of the invention, the crystalline aluminophosphate molecular sieves formed is selected from the group consisting of AlPO4-5, AlPO4-16, AlPO4-22, AlPO4-31, AlPO4-L, SAPO-35, SAPO-15 and VPI-5.
In another embodiment of the invention, a silicon source is added to the reaction mixture to obtain SAPO-35 and SAPO-15.
The present invention also provides a process for synthesising crystalline aluminophosphate molecular sieves selected from the group consisting of AlPO4-5, AlPO4-16, AlPO4-22, AlPO4-31, AlPO4-L, SAPO-35, SAPO-15 and VPI-5, the process comprising
In another embodiment of the invention, the source of silicon oxide is silica sol, fumed silica, tetraethylorthosilicate or mixtures thereof
In one embodiment of the invention the source of aluminium oxide is pseudoboehmite and aluminium alkoxide, preferably aluminium isopropoxidee
In a preferred embodiment of the invention, the source of aluminium oxide is pseudoboehmite.
In another embodiment of the invention, the source of oxide of phosphorous is orthophosphoric acid.
In another embodiment of the invention the organic templating agent is selected from the group consisting of hexamethyleneimine, hexamethylene tetramine and di-n-propylamine.
In another embodiment of the invention, step (b) is carried out in an autoclave and at a temperature of about 200° C. for different time duration
In another embodiment of the invention, the reaction gel is cooled by immersing in cold water.
In yet another embodiment of the invention, the crystalline material is separated by filtration.
In another embodiment of the invention, the crystals are washed with distilled water and then dried by heating at a temperature in the range of 25° C. to 150° C. at atmospheric pressure.
In yet another embodiment of the invention, the crystalline material is dried at a temperature of about 120° C.
In another embodiment of the invention, the aluminophosphate molecular sieve is calcined at a temperature in the range of 300° C. to 1000° C. for a period in the range of 1 minute to 20 h.
In yet another embodiment of the invention, the dried crystalline material is calcined in air at a temperature of about 550° C.
In yet another embodiment of the invention, the aluminophosphates molecular sieve in as-synthesized form has a composition in terms of molar oxide ratio on an anhydrous basis expressed by the formula mR: Al2O3:nP2O5:qSiO2 wherein R represents at least one organic templating agent present in the intracrystalline pore system; ‘m’ represents the moles of ‘R’ present and has a value such that there are 0.02 to 0.3 moles of ‘R’ per mole of alumina, ‘n’ has a value of from 0.9 to 1.2 and ‘q’ has a value of from 0.0 to 1.0.
In another embodiment of the invention, the reaction mixture is essentially free of alkali metal cations and has a composition expressed in terms of mole ratio of oxides as follows aR: Al2O3:0.9-1.2P2O5:0.0-1.0SiO2:bH2O:bEG wherein R is an organic templating agent; ‘a’ has a value of from 0.20 to 2.0 and more preferably about 0.8 to 1.2; ‘b’ has a value between 10 to 45; EG—Ethylene Glycol
In another embodiment of the invention, aqueous or ethylene glycol reaction mixture is formed by combining reactive aluminium and phosphorous sources and thereafter combining the mixture with the organic template followed by a silicon source for SAPO-35 and SAPO-15 formation.
In another embodiment of the invention, the molecular sieve obtained is AlPO4-5 having an X-ray diffraction pattern given in the table below:
In another embodiment of the invention, the molecular sieve obtained is AlPO4-16 having an X-ray diffraction pattern given below:
In yet another embodiment of the invention, the molecular sieve obtained is AlPO4-22 having an X-ray diffraction pattern given in the table below.
In yet another embodiment of the invention, the molecular sieve obtained is AlPO4-22 having an X-ray diffraction pattern given in the table below.
In another embodiment of the invention, the molecular sieve obtained is AlPO4-L having an X-ray diffraction pattern given in the table below.
In another embodiment of the invention, the molecular sieve obtained is SAPO-35 having an X-ray diffraction pattern given in the table below:
In another embodiment of the invention, the molecular sieve obtained is SAPO-15 having an X-ray diffraction pattern given in the table below;
In another embodiment of the invention, the molecular sieve obtained is VPI-5 having an X-ray diffraction pattern given in the table below
The present invention provides an improved process for the preparation of a porous crystalline aluminophosphate molecular sieves characterized by the x-ray diffraction pattern as herein described and a chemical composition in terms of the mole ratio of oxides given by the formula mR: Al2O3:nP2O5 wherein R represents at least one organic templating agent present in the intracrystalline pore system, ‘m’ represents moles of ‘R’ present and has a value between 0.02 to 0.3, ‘n’ has a value of from 1.0 to 1.2. The method of the invention comprises mixing a source of hydrated aluminium oxide and orthophosphoric acid and an organic template (R) which is an amine such as hexamethyleneimine. This mixture is heated under autogeneous conditions at 200° C. for 4 h to 24 h and the reaction mixture then cooled rapidly Crystalline material is then separated by filtration, washed and dried followed by calcination at 550° C. to remove organic material occluded in its pore to get porous crystalline aluminophosphate molecular sieves.
The source of aluminium oxide is preferably pseudoboehmite and source of oxide of phosphorous is orthophosphoric acid The organic template is hexamethyleneimine or hexamethylene tetramine or di-n-propylamine. The aluminophosphate molecular sieves obtained are AlPO4-5, AlPO4-16, AlPO4-22, AlPO4-31, AlPO4-L, SAPO-35, SAPO-15 and VPI-5. In the process of the invention, a reaction gel formed by combining reactive aluminium and phosphorous sources followed by the organic template and the silicon source for SAPO-35 and SAPO-15 was subjected to heating under hydrothermal conditions in an autoclave at 200° C. for various time duration. This was then cooled rapidly by immersing in cold water. The contents were filtered to separate the crystalline solid which is subsequently washed thoroughly and dried at 120° C. and finally calcined in air at 550° C. The AlPO synthesized by the above process is made up of well-crystalline, small and more uniform particles. The aluminophosphates in the as-synthesized form has a composition in terms of molar oxide ratio on an anhydrous basis expressed by the formula mR: Al2O3:nP2O5:qSiO2 where R represents at least one organic templating agent present in the intracrystalline pore system; ‘m’ represents the moles of ‘R’ present and has a value such that there are 0.02 to 0.3 moles of ‘R’ per mole of alumina, ‘n’ has a value of from 0.9 to 1.2 and ‘q’ has a value of from 0.0 to 1.0.
In synthesizing the aluminophosphate composition of the present invention, it is preferred that the reaction mixture be essentially free of alkali metal cations, and accordingly the preferred reaction mixture composition expressed in terms of mole ratio of oxides is as follows aR: Al2O3:0.9-1.2P2O5:0.0-1.0SiO2:bH2O:bEG where in R is an organic templating agent; ‘a’ has preferably a value of from 0.20 to 2.0 and more preferably about 0.8 to 1.2; ‘b’ has a value between 10 to 45, EG—Ethylene Glycol. In the synthesis of the invention an aqueous or ethylene glycol reaction mixture is formed by combining the reactive aluminium and phosphorous sources and thereafter combing the mixture with the template followed by silicon source in SAPO-35 and SAPO-15.
More specifically the synthesis method comprises:
The crystallization is conducted under hydrothermal conditions in an autoclave at autogenous pressure without stirring. Following the crystallization of the aluminophosphate material, the reaction mixture containing the same is filtered and the recovered crystals are washed for example with distilled water and then dried such as by heating at from 25° C. to 150° C. at atmospheric pressure.
The aluminophosphate synthesized by the present method is subjected to thermal treatment to remove the organic templating agent. Thermal treatment is generally performed by heating at a temperature of 300° C. to 1000° C. for at least 1 minute and generally no longer than 20 h. The thermally treated product is particularly useful in the catalysis of certain hydrocarbon conversion reactions.
The improved process of this invention will now be illustrated by examples, which are not to be constructed as limiting the invention in any manner.
7.16 g of catapal B (74.2% Al2O3, Vista Chemicals, USA) was mixed with 20 ml of water. The mixture was stirred well. 11.5 g of orthophosphoric acid (85%, s.d.fine, India) is added drop wise to the mixture and stirred well. A white thick paste was formed. This paste was aged for overnight. 5.82 g of hexamethyleneimine (98%, Aldrich, U.S.A) along with 20 ml of distilled water was mixed well and the active gel (Al2O3:P2O5:1.16HEM:45H2O) was charged into a Teflon lined autoclave. The gel was crystallized for 4 h at 473K. The product is cooled, washed several times with distilled water and dried at 383K and subjected to physicochemical characterization. AlPO4-5 aluminophosphate synthesized by the process of the invention possesses a crystalline structure, the X-ray powder diffraction pattern of the as-synthesized form showing the characteristic peaks listed in Table 1.
6.05 g of finely powdered aluminium isopropoxide was mixed with 45.50 g of ethyleneglycol (EG) 7.27 g of hexamethyleneimine (HEM) was added dropwise to mixture and made into a homogeneous entity 6.024 g of orthophosphoric was added to the gel. The active gel (Al2O3:1.8P2O5:4.5HEM:45EG) was charged into a Teflon lined steel autoclave. Crystallization was carried out at 473K for 15 days. Resulting product was washed well with distilled water and dried at 383K and subjected to physicochemical characterization.
10.86 g of aluminium isopropoxide (98%, Aldrich, U.S.A) is mixed with 20 ml of distilled water. 3.387 g of Hexamethyleneimine was added to the above mixture. The mixture was stirred well A mixture of solution was formed To this solution 5.75 g of orthophosphoric acid was added. The active gel (Al2O3:P2O5:1.16HEM:45H2O) was charged into the Teflon lined autoclave and aloud to crystallize for 2 days The product was cooled and washed, dried at 283K and subjected to physicochemical characterization. The AlPO4-16 aluminophosphate synthesized by the process of the present invention possesses a crystalline structure, the X-ray powder diffraction pattern of the as-synthesized form showing the characteristic peaks listed in Table 2.
3.58 g of pseudoboehmite is mixed well with 10 ml of distilled water. 5.75 g of orthophosphoric acid was added drop wise to the mixture. The resulting white thick paste was aged for overnight. 3.387 g of hexamethyleneimine along with 10 ml of distilled water were added to the paste to make clear gel. The resulting active gel (Al2O3:P2O5:1.35HEM:45H2O) was charged into a Teflon lined steel autoclave. Reaction mixture was crystallized for 48 h. Crystallized products washed with distilled water for several times and dried at ambient temperature and subject to physicochemical characterization. AlPO4-22 aluminophosphate synthesized by this process possesses a crystalline structure, X-ray powder diffraction pattern of as-synthesized form showing the characteristic peaks listed in Table 3.
3.58 g of pseudoboehmite was mixed well with 10 ml of distilled water. 5.75 g of orthophosphoric acid was added drop wise to the above mixture. A thick white paste is formed. The paste is aged for overnight at room temperature. 3.763 g of hexamethyleneimine along with 10 ml of distilled water was thoroughly mixed with the white paste. The resulting active gel (Al2O3:P2O5:1.5HEM:45H2O) was charged into a Teflon lined steel autoclave. Crystallization was carried out for 2 days at 453K. The product was washed well and dried at 383K and subjected to physicochemical characterization.
6.05 g of Aluminium isopropoxide was mixed well with 45.50 g of ethylene glycol. 5.224 g of water is mixed with the above solution. Then 7.27 g of hexamethyleneimine was added to the former mixture. Finally 6.024 g of orthophosphoric acid was added to make an active gel (Al2O3:1.8P2O5:4.5HEM:20H2O:45EG). Gel was charged into a Teflon lined steel autoclave. Crystallization was carried out for 15 days at 453K. Product was washed well with distilled water and dried at 383K and subjected to physicochemical characterization.
6.05 g of aluminium was mixed with 45.50 g of ethyleneglycol 13.06 g of water was added to the above mixture. Further 7.27 g of hexamethyleneimine was added to the above solution. Then 6.024 g of orthophosphoric acid was added to the former gel. The final active gel (Al2O3:1.8P2O5:4.5HEM:50H2O:45EG) charged into a Teflon lined steel autoclave. Crystallization carried out at 453K for 15 days The product removed, washed and dried at 383K and subjected to physicochemical characterization.
6.05 g of finely powdered aluminium isopropoxide was mixed well with 45.50 g of ethylene glycol. 0.526 g of fumed silica was added to the above mixture. 7.27 g of hexamethyleneimine was added to form clear gel. 6.024 orthophosphoric acid along with 0.351 g of sodium hydroxide were added. The final active gel (Al2O3:1.8P2O5:0.25Na2O:4.5HEM:45EG) was charged into a Teflon lined steel autoclave. Crystallization was carried out at 453K for 15 days. The product was washed well with distilled water, and dried at 383K and subjected to physicochemical characterization.
6.05 g of finely powdered aluminium isopropoxide was mixed well with 45.50 g of ethylene glycol 7.27 g of hexamethyleneimine was added slowly to the above mixture and stirred well. 6.024 g of orthophosphoric acid was added slowly to the above gel. The final gel (Al2O3:1.8P2O5:4.5HEM:4.5DPA:45EG) was prepared by adding 7.417 g di-n-propylamine (DPA). The active gel charged into a Teflon lined steel autoclave. Crystallization carried out at 453K for 15 days. The product was washed well with distilled water, and dried at 383K and subjected to physicochemical characterization.
3.58 g of pseudoboehmite was mixed well with 10 ml of distilled water. 5.75 g of orthophosphoric acid was added drop wise to the above mixture. The mixture is stirred well. A thick white paste was formed. The paste is aged for overnight at room temperature Hexamethyleneimine (2.91 g) along with 23.33 g of distilled water was mixed with the white paste. The final active gel (Al2O3:P2O5:1.16HEM:75H2O) was charged into a Teflon lined steel autoclave. Crystallization was carried out at 453K for 24 h. Product was washed well with distilled water and dried at 383K and subjected to physicochemical characterization.
3.58 g of pseudoboehmite is mixed well with 10 g of distilled water. 5.75 g of orthophosphoric acid was added drop wise and the mixture is stirred well A white thick paste was formed which was aged for overnight at room temperature 2.509 g of 5 hexamethyleneimine along with 10 ml of distilled water was mixed with the paste. The final active gel (Al2O3:P2O5:HEM:45H2O) was charged into a Teflon lined steel autoclave. Crystallization was carried out for 3 days at 453K. The product was washed well with distilled water and dried at 383K and subjected to physicochemical characterization.
6.05 g of aluminium isopropoxide was mixed well with 45.50 g of ethylene glycol (99%, s.d.fine, India). To this mixture 7.27 g of hexamethyleneimine was added. The mixture was stirred well to make homogeneous. 6.024 g of orthophosphoric acid was added dropwise to the above gel. The active gel was aged for 8 h under stirring. Final gel charged into a steel autoclave lined with Teflon. Crystallization was carried out at 473K for 15 days. Product was washed, dried and subjected to physicochemical characterization AlPO4-31 aluminophosphate synthesized by this process possesses a crystalline structure, X-ray powder diffraction pattern of as-synthesized form showing the characteristic peaks listed in Table 4.
3.58 g of pseudoboehmite mixed well with 10 ml of distilled water. 5.75 g of orthophosphoric acid was added slowly to the mixture. A thick white paste is formed. This paste was aged overnight. 5.82 g of hexamethyleneimine along with 10 ml of distilled water is mixed with the paste. The mixture stirred well to form an active gel (Al2O3:P2O5:2.32HEM:45H2O). This gel charged into a Teflon lined steel autoclave. Crystallization was carried out at 453K for 8 days The product was washed well with distilled water and dried at 383K and subjected to physicochemical characterization.
The AlPO4-L aluminophosphate synthesized by the process of the present invention possesses a crystalline structure, the X-ray powder diffraction pattern of the as-synthesized form showing the characteristic peaks listed in Table 5.
6.05 g of aluminium isopropoxide was mixed well with 45.50 g of ethylene glycol. 0.526 g fumed silica (>99%, Aldrich, India) was added to the mixture. The mixture was made homogeneous. 7.27 g of hexamethyleneimine was added followed by dropwise addition of 6.024 g of orthophosphoric acid. The homogeneous gel (Al2O3:1.8P2O5:0.3SiO2:4.5HEM:45EG) was thoroughly mixed for 8 h and charged into a Teflon lined steel autoclave. Crystallization was carried out at 473K for 15 days. Product was washed several times with water and dried at 383 k and subjected to physicochemical characterization.
The SAO-35 silicoaluminophosphate synthesized by the process of the present invention possesses a crystalline structure, the X-ray powder diffraction pattern of the as-synthesized form showing the characteristic peaks listed in Table 6.
3.58 g of catapal B was mixed well with 10 ml of distilled water. 5.75 g of orthophosphoric acid was added slowly drop by drop to the mixture The resulting thick white paste was aged over night at room temperature. 4.28 g of hexamethylenetetramine (HMT) along with 10 ml of distilled water along with fumed silica was mixed well with the white paste. The final active gel (Al2O3:P2O5:0.3SiO2:1.16HMT:45H2O) Was charged into a steel autoclave lined with Teflon. Crystallization was carried out at 453K for 2 days. Product was washed well with distilled water and dried at 483K and subjected to physicochemical characterization.
The SAPO-15 aluminophosphate synthesized by the process of the present invention possesses a crystalline structure, the X-ray powder diffraction pattern of the as-synthesized form showing the characteristic peaks listed in Table 7.
3.58 g of pseudoboehmite was mixed well with 10 ml of distilled water. 5.75 g of orthophosphoric acid was added drop wise to the above mixture. The resulting thick white paste was aged overnight at room temperature. 2.969 g of di-n-pripylamine along with 10 ml of distilled water is mixed thoroughly with the white paste. The final active gel (Al2O3:P2O5:1.16DPA:45H2O) charged into a steel autoclave lined with Teflon. Crystallization was carried out for 2 h at 415K. Product was washed several times with distilled water and dried at 383K and subjected to physicochemical characterization.
The VPI-5 aluminophosphate synthesized by the process of the present invention possesses a crystalline structure, the X-ray powder diffraction pattern of the as-synthesized form showing the characteristics peaks listed in Table 8.
