Title of Invention

"AN IMPROVED PROCESS FOR THE DEALUMINATION OF ZEOLITE-Y"

Abstract

The present invention relates to an improved process for the dealuminaiton of zeolite Y. The invention more specifically relates to a process for the removal of frame work aluminum form the crystalline alumino silicate, Zeolite - Y by controlled hydro thermal treatment resulting in a product with unit cell size (UCS) of 24.30 A0 and lower with retention of crystallite at minimum 40% level. Such type of dealuminated zeolite-Y is hydro thermally more stable due to increased silica to alumina ratio, suppress hydrogen transfer reaction and produce less coke during cracking reaction due to isolated acid sites. Hydrothermai stability and suppressed hydrogen transfer reaction are the key requirement of any deep catalytic cracking (DCC) catalyst to withstand high severity regeneration conditions and maximization of light olefins yield. During hydrothermai treatment of Zeolite - Y, secondary pores such as super micropores ( 30A°) and mesopores (50- 200 A0) are also generated which are beneficial for the cracking of resid feed stocks.

Full Text

The present invention relates to an improved process for the dealumination of zeolite Y. More particularly'he present invention relates to a process for the controlled dealumination of Y type zeolite. The invention more specifically relates to a process for the removal of frame work aluminum form the crystalline alumino silicate, Zeolite -Y by controlled hydro thermal treatment resulting in a product with unit cell size (UCS) of 24.30 A° and lower with retention of crystallity at minimum 40% level. Such type of dealuminated Zeolite-Y is hydrothermally more stable due to increased silica to alumina ratio, suppress hydrogen transfer reaction and produce less coke during cracking reaction due to isolated acid sites. Hydrothermal stability and suppressed hydrogen transfer reaction are the key requirement of any deep catalytic cracking (DCC) catalyst to withstand high severity regeneration conditions and maximization of light olefins yield. During hydrothermal treatment of Zeolite -Y, secondary pores such as super micropores (~30A°) and mesopores (50- 200 A°) are also generated which are beneficial for the cracking of resid feed stocks^ DCC is the high severity version (over cracking mode of operation) for the conversion of heavier feeds into light olefins such as propylene, iso butylene and iso amylene for important petrochemicals, oxygenates and alkylates. The operating conditions for DCC process are: reactor temperature; catalyst/oil ratio (C/O); and residence time. Higher residence time, although promote deep cracking but simultaneously promote more hydrogen transfer reaction reducing the yield of light olefins product. This makes the selection of process variables more complex. Therefore, there has been an ongoing trend to formulate a catalyst with suppressed hydrogen transfer activity using highly dealuminated Zeolite-Y also known as ultrastablised Zeolite -Y (USY). The primary source of activity of cracking catalyst is zeolite, which actually refers to a large mineral group of crystalline materials. Specifically, the zeolite used in cracking catalyst is faujasite, which is a crystalline three dimensional alumino silicate of the zeolite mineral group with ion exchange capacity. It has pore opening of 8-9 A°. Faujasite is also commonly referred to as molecular sieves or zeolite. Faujasite occurs naturally in nature but due to it's scarcity, it is synthesized commercially in the sodium form. This is not active for cracking reaction due to the absence of surface acidity because of the presence of alkali metals ions. Therefore it is necessary to modify the Y type zeolite to introduce the acidic sites and dealuminate to the appropriate level, suitable for DCC catalyst formulations. It is known in the art that Zeolite -Y can be dealuminated by either chemical or hydrothermal treatment. It is also well known in the art that chemical treatment for dealumination use hazardous chemicals such as fluorine gas, silicon tetrachloride (SiCL4) and ammonium hexa fluroro silicate [(NH4)2SiF6], which pose handling and environmental problems. Also, chemical method of dealumination does not create mesopores. In the alternate method of hydrothermal treatment, the Zeolite -Y, in the ammonium form is heated in presence of steam. During the process, ammonium ions are decomposed driving off ammonia and leaving the protons in the places of the original sodium ions in the crystalline framework. These protons are the source of acidity in the zeolite promoting cracking reaction through the formation of carbenium ion intermediates. Hydrothermal treatment causes the dealumination in the zeolite framework resulting in higher silica to aluminum ratio and shrinkage in crystal lattice leading to the reduction in the unit cell size (UCS). The expelled aluminum ions from the framework, however, remain trapped inside the zeolitic channel and cause diffusional hindrance to the reacting molecules. Non framework aluminum (NFA) also promote non selective cracking reactions due to Lewis acid character and produce more coke and dry gas. Hence there is a need to remove the NFA by acid leaching. However the available hydrothermal method does not define the conditions of temperature and duration in order to achieve the controlled dealumination to get the product with desired UCS and crystallinity level. The known process also invariably includes an intermediate calcination steps during the exchange of Na form of zeolite to NH4 form. This results in excessive crystallinity loss during the exchange process, itself. In carrying out the present invention as a result of extensive investigations carried out by us, the intermediate calcination step has been avoided and achieved the desired level of exchange without any crystallinity loss during the exchange process. As the acid may also attack the framework aluminum during the extraction of NFA, it is essential to use very dilute acid under controlled conditions of temperature and duration for the extraction of NFA. The main object of the present invention is to provide an improved process for the dealuminaiton of zeolite Y which obviates the drawbacks as detailed above. Another objective of the present invention is to provide a process for the controlled hydrothermal treatment to get a product with UCS of 24.30 A0 and lower retaining the crystallinity level of minimum 40%. Still another object of the present invention is to provi9de a method to provide a process to prepare hydrothermally dealuminated zeolite suitable for DCC catalyst formulations with suppressed hydrogen transfer activity, increased hydrothermal stability with creation of mesopores. Accordingly the present invention provides an improved process for the dealumination of zeolite-Y which comprises i) exchanging NaY zeolite to NH4Y zeolite by preparing a slurry of NaY zeolite with an aqueous solution of 1-3N ammonium salt selected from chloride, sulphate and nitrate, preferably NH4NO3 at reflux temperature of 80-100°C, ii) refluxing the slurry for a period of 2 hours and thereafter filtering and washing the zeolite powder obtained with demineralized water 2-3 times to remove the excess NH4NO3 and the sodium salt followed by drying at a temperature of 100- 120°C, iii) repeating the above process three times and finally washing the zeolite powder with deionized water to free all soluble salts followed by drying at a temperature of 100-120°C for a period of 12-16 hours, iv) transferring the above obtained NH4Y zeolite having 95% ammonium in 3 baskets made of inconne 1-600 fitted with perforated switered disc in an inconnel tubular shallow bed reactor, v) heating the reactor by 3 zone furnace while controlling the temperature by a proportional-integral-derivative controller, vi) passing nitrogen at a flow velocity of 3 cm/s and heating the reactor at the rate of 2°C/min to a temperature of 200-275°C followed by feeding of water in absence of nitrogen to get steam at a velocity of 3 cm/sec, vii) further heating at the rate of 3°C/min to a temperature of 450-550°C and after 30 min raising the temperature to 600°C at the rate of about l°C/min and maintaining 600°C temperature for 30 minutes, viii) further heating the bed in presence of steam to a temperature of 650-850°C at the rate of 2°C/min and maintaining the temperature at 650-850°C for 4-7 hours, ix) cooling the reactor to a temperature of 150°C under the flow of nitrogen at the flow velocity of 3 cm/sec and obtaining the dealuminated zeolite from the reactor and x) further treating delaminated zeolite obtained in the step ix with mineral acid such as HNO3, HCl preferably with HCl of 0.1 N to 6 N strength in a controlled manner to remove non frame work aluminum and further reducing the Na content in the zeolite. In an embodiment of the present invention the ammonium salt used is selected from chloride, sulphate and nitrate form preferably NH4NO3. In an another embodiment the NaY zeolite is treated with aqueous solution of NH4NO3, at reflux temperature. In yet another embodiment the NaY zeolite is heated preferably at a temperature in the range of 750°C to 800°C. In yet another embodiment is heated in the presence of steam preferably for a period of 1 to 5 hours. In yet another embodiment the NH4Y zeolite is heated at a temperature of 750°C for 5 hours in the presence of steam to get the dealuminated zeolite with 51.0% crystallinity and unit cell size (UCS) of 24.324 A0. In yet another embodiment the Y zeolite is preferably heated preferably at 800°C for one hour in presence of steam to get dealuminated zeolite with 41.0% crystallinity and unit cell size of 22.334A°. In yet another embodiment the NH4Y zeolite is preferably heated preferably at 800 °C for 1.5 hours in presence of steam to get dealuminated zeolite with 45.0 to 49.0% crystallinity and 24.284 A° to 24.26 A° UCS. In yet another embodiment the HC1 is used for extraction of non framework aluminum. In yet another embodiment by increasing the silica to alumina ratio hydrothermal stability of Zeolite-Y increases. hi yet another embodiment by increasing the silica to alumina ratio the hydrogen transfer activity is suppressed. The invention may be practiced as illustrated by the following examples which should not be construed to limit the scope of the invention. Example 1 60 g of NaY zeolite was slurried in 17.84% aqueous solution of NEL^NOa in demineralized water. The slurry was refluxed for 2 hours filtered and the zeolite powder was washed with demineralised water 2 -3 times to remove the excess NELjNOa and the sodium salt and dried at 110 0 C. The above process was repeated three times. After 4th cycle of the exchange process, the zeolite powder was washed with deionized water free of all soluble salts and dried at 110 ° C for 12 -16 hours. The exchange of sodium ions by ammonium ions was 95%, reducing the sodium content in the zeolite from 9.8% to 0.49%. The crystallinity of NH4Y zeolite thus prepared was 134% and UCS of 24.793 A° as against 100% crystallinity and UCS of 24.68 A° in the original NaY zeolite. (Table-1). 10 g of NH4Y zeolite was placed in each baskets (3Nos) made of inconnel - 600 fitted with perforated switered disc at the bottom (cd 38 mm). These baskets were then placed in an inconnel tubular shallow bed reactor ( 60 mm o.d. and 50.8 mm i.d.). the reactor was heated by 3 zone furnace and temperature controlled by digital PID automatic temperature controller with programming facilities. Nitrogen was passed through the reactor under ambient conditions at the flow rate calculated to give the flow velocity of 3 cm/s and the reactor was heated at the rate of 2°C/min. at 250°C. The nitrogen flow was discontinued and water feeding was started at the rate to give the flow velocity of steam at 3cm/sec and reactor was heated at the rate of 3 °C/min till the temperature attained was 500°C. The temperature was held constant at 500°C for 30 minutes and further raised to 600°C at the rate of l°C/min and was held constant at 600°C for 30 minutes. Then the temperature was raised to 750°C at the rate of 2°C/min and held constant at 750°C for five hours. At the end of five hours the heating was stopped and the reactor was allowed to cool under the flow of nitrogen at the flow velocity of 3 cm/sec till the reactor temperature came down to 150°C. The zeolite sample was withdrawn from the reactor, designated as DAZ -1. and stored in a desiccator. The XRD results presented in the Table 1 show that the % crystallinity of dealuminated zeolite was 51.0% and UCS of 24.324 A°. The physicochemical characteristics such as surface area, pore volume and pore size distribution presented in Table 2 indicate that around 39.14% volume lies in the range of pore diameter of 20-200 A°. The acidity and acid strength distribution presented in the Table -3 indicate that significant persentage (32.65%) of acid site are stronger. 10 g of dealuminated zeolite with 51.0% crystallinity and 24.324 A° of UCS was slurried in 85 ml N HC1 and refluxed for 30 minutes, filtered and washed free of chloride ions with demineralised water and dried at 110 °C for 16 hours. The crystallinity of the zeolite sample was slightly increased and UCS remained intact. Example 2 60 g of NaY zeolite was slurried in 17.84% aqueous solution of NH4NO3 in demineralized water. The slurry was refluxed for 2 hours filtered and the zeolite powder was washed with demineralised water 2 -3 times to remove the excess Nt^NOs and the sodium salt and dried at 110 ° C. The above process was repeated three times. After 4th cycle of the exchange process, the zeolite powder was washed with deionized water free of all soluble salts and dried at 110 °C for 12 -16 hours. The exchange of sodium ions by ammonium ions was 95%, reducing the sodium content in the zeolite from 9.8% to 0.49%. The crystallinity of NH4Y zeolite thus prepared was 134% and UCS of 24.793 A° as against 100% crystallinity and UCS of 24.68 A° in the original NaY zeolite. (Table -1). 10 g of NH4Y zeolite was placed in each baskets (3Nos) made of inconnel - 600 fitted with perforated switered disc at the bottom (cd 38 mm). These baskets were then placed in an inconnel tubular shallow bed reactor ( 60 mm o.d. and 50.8 mm c.d.). The reactor was heated by 3 zone furnace and temperature controlled by digital PID automatic temperature controller with programming facilities. Nitrogen was passed through the reactor under ambient conditions at the flow rate calculated to give the flow velocity of 3 cm/s and the reactor was heated at the rate of 2°C/min. to 250°C. The nitrogen flow was discontinued and water feeding was started at the rate to give the flow velocity of steam at 3cm/sec and reactor was heated at the rate of 3 °C/min till the temperature attained was 500°C. The temperature was held constant at 500°C for 30 minutes and further raised to 600°C at the rate of l°C/min and was held constant at 600°C for 30 minutes. Then the temperature was raised to 800°C. At the rate of 2°C/min. and the flow of steam was continued for 1 hour at the constant temperature of 800°C at the end of the one hour, the heating was stopped, the flow of steam was discontinued and flow of nitrogen was started at the flow velocity of 3 cm/sec till the reactor attained the temperature of 150°C. The zeolite sample was withdrawn from the reactor, designated as DAZ -2 and stored in a desicator. The XRD results presented in the Table -1 show that % crystallinity of dealuminated zeolite was 41.0 and UCS 24.334. Pore size distribution and acid strength presented in the Table 2 and 3 respectively indicated that around 42% volume lies in the range of pore dia of 20 -200 A° and around 30.4% of acid sites are strong. 10 g of dealuminated zeolite with 41.0% crystallinity and 24.334 A° UCS was slurried with 85 ml N HC1 and refluxed for 30 minutes, filtered and washed free of chloride ions with demineralised water and dried at 110 °C for 16 hours. The crystallinity of the acid extracted dealuminated zeolite sample was slightly improved and UCS 24.334 A° remained intact. Example 3 60 g of NaY zeolite was slurried in 17.84% aqueous solution of NfUNOs in demineralized water. The slurry was refluxed for 2 hours filtered and the zeolite powder was washed with demineralised water 2 -3 times to remove the excess NI^NOs and the sodium salt and dried at 110 ° C. The above process was repeated three times. After 4th cycle of the exchange process, the zeolite powder was washed with deionized water free of all soluble salts and dried at 110 ° C for 12 -16 hours. The exchange of sodium ions by ammonium ions was 95%, reducing the sodium content in the zeolite from 9.8% to 0.49%. The crystallinity of NH4Y zeolite thus prepared was 134% and UCS of 24.793 A° as against 100% crystallinity and UCS of 24.68 A° in the original NaY zeolite. (Table-1). 10 g of NH4Y zeolite was placed in each baskets (3Nos) made of inconnel - 600 fitted with perforated sintered disc at the bottom (cd 38 mm). These baskets were then placed in an inconnel tubular shallow bed reactor ( 60 mm o.d. and 50.8 mm i.d.). the reactor was heated by 3 zone furnace and temperature controlled by digital PID automatic temperature controller with programming facilities. Nitrogen was passed through the reactor under ambient conditions at the flow rate calculated to give the flow velocity of 3 cm/s and the reactor was heated at the rate of 2°C/min. to 250°C. The nitrogen flow was discontinued and water feeding was started at the rate to give the flow velocity of steam at 3cm/sec and reactor was heated at the rate of 3 °C/min till the temperature attained was 500°C. The temperature was held constant at 500°C for 30 minutes and further raised to 600°C at the rate of l°C/min and was held constant at 600°C for 30 minutes. Then the temperature was raised to 800°C at the rate of 2°C/min. The flow of steam was continued for 1.5 hour at the constant temperature of 800°C. At the end of 1.5 hour, the heating was stopped, the flow of steam was discontinued and flow of nitrogen was started at the flow velocity of 3cm/ sec till the reactor attained the temperature of 150°C. The zeolite sample was withdrawn from the reactor, designated as DAZ -3 and stored in a desicator. The XRD results presented in the Table -1 show that % crystallinity of dealuminated zeolite was 45.0 and UCS 24.284 A°. Pore size distribution and acid strength presented in the Table 2 and 3 respectively indicated that around 41.64% volume lies in the range of pore dia of 20 -200 A° and around 33.3% of acid sites are strong. The experiment of dealumination was repeated twice under identical conditions of temperature (800°C) and duration of 1.5 hours. The XRD results presented in Table -1 show that % crystallinity and UCS was 49.0, 24.26 A° and 48.0 and 24.27 A° respectively for two sets of dealuminated zeolite (DAZ -4 and DAZ -5 ). The dealuminated zeolite obtained from each sets of experiments were slurried in 85 ml N HC1 and refluxed for 30 minutes, filtered and washed free of chloride ions with demineralised water and dried at 110 °C for 16 hours. The crystallinity of the acid extracted dealuminated zeolite sample was slightly improved without any change in their UCS values. Table 1 (Table Removed) Table 2 Physico -Chemical Characteristics Of Dealuminated Zeolite –Y (Table Removed) Table 3 Acidity and Acid Strength Distribution Of Dealuminated Zeolite –Y (Table Removed) Claim: 1. An improved process for the dealumination of zeolite-Y which comprises: i) exchanging NaY zeolite to NH4Y zeolite by preparing a slurry of NaY zeolite with an aqueous solution of 1-3N ammonium salt selected from chloride, sulphate and nitrate, preferably NH4NO3 at reflux temperature of 80-100°C, ii) refluxing the slurry for a period of 2 hours and thereafter filtering and washing the zeolite powder obtained with demineralized water 2-3 times to remove the excess NH4NO3 and the sodium salt followed by drying at a temperature of 100- 120°C, iii) repeating the above process three times and finally washing the zeolite powder with deionized water to free all soluble salts followed by drying at a temperature of 100-120°C for a period of 12-16 hours, iv) transferring the above obtained NH4Y zeolite having 95% ammonium in 3 baskets made of inconne 1-600 fitted with perforated switered disc in an , inconnel tubular shallow bed reactor, v) heating the reactor by 3 zone furnace while controlling the temperature by a proportional-integral-derivative controller, vi) passing nitrogen at a flow velocity of 3 cm/s and heating the reactor at the rate of 2°C/min to a temperature of 200-275°C followed by feeding of water in absence of nitrogen to get steam at a velocity of 3 cm/sec, vii) further heating at the rate of 3 C/min to a temperature of 450-550°C and after 30 min raising the temperature to 600°C at the rate of about l°C/min and maintaining 600°C temperature for 30 minutes, viii) further heating the bed in presence of steam to a temperature of 650-850°C at the rate of 2°C/min and maintaining the temperature at 650-850°C for 4-7 hours, ix) cooling the reactor to a temperature of 150°C under the flow of nitrogen at the flow velocity of 3 cm/sec and obtaining the dealuminated zeolite from the reactor and x) further treating delaminated zeolite obtained in the step ix with mineral acid such as HNO3, HCl preferably with HCl of 0.1 N to 6 N strength in a controlled manner to remove non frame work aluminum and further reducing the Na content in the zeolite. 2. An improved process as claimed in claim 1, wherein NaY zeolite is treated with aqueous solution of NH4NO3, at relax temperature. 3. An improved process claimed in claim 1 wherein in step viii) NH4Y zeolite is heated preferably at a temperature in the range of 750°C to 800°C, preferably for a period of 1 to 5 hours. 4. An improved process as claimed in claims 1 to 3 wherein the NH4Y zeolite is heated preferably at a temperature of 750° for 5 hours in the presence of steam to get the dealuminated zeolite with 51.0% crystallinity and unit cell size (UCS) of 24.324 A0. 5. An improved process as claimed in claims 1 to 4 wherein the NH4Y zeolite is preferably heated at 800°C for one hour in presence of steam to get dealuminated zeolite with 41.0% crystallinity and unit cell size of 22.334 A . 6. An improved process as claimed in claims 1 to 5, wherien NH4Y zeolite is preferably heated preferably at 800°C for 1.5 hours in presence of steam to get dealuminated zeolite with 45.0 to 49.0% crystallinity and 24.284A0 to 24.26A0 UCS. 7. An improved process as claimed in claims 1 to 6, wherein HCl is used for extraction of non framework aluminum. 8. An improved process as claimed in claims 1 to 7, wherein mesopores are obtained in dealuminated zeolite. 9. An improved process for the dealumination of zeolite-Y substantially as herein described with reference to the examples accompanying this specification.

Documents:

997-DEL-2002-Abstract-(06-11-2008).pdf

997-del-2002-abstract.pdf

997-DEL-2002-Claims-(06-11-2008).pdf

997-del-2002-claims.pdf

997-DEL-2002-Correspondence-Others-(06-11-2008).pdf

997-del-2002-correspondence-others.pdf

997-del-2002-correspondence-po.pdf

997-DEL-2002-Description (Complete)-(06-11-2008).pdf

997-del-2002-description (complete).pdf

997-del-2002-form-1.pdf

997-del-2002-form-18.pdf

997-del-2002-form-2.pdf

997-DEL-2002-Form-3-(06-11-2008).pdf

997-del-2002-form-3.pdf