CN1235875A - Synthetic method for high silicon ZSM-5 zeolite - Google Patents

Abstract

The invention provides a method for synthesizing high-silicon ZSM-5 zeolite, which uses solid silica-alumina colloid as a raw material, alkylamine organic matter (Q) as a template, and adding sodium hydroxide and water to prepare a molar ratio SiO ₂ /Al ₂ O ₃ =100～1000, Na ₂ O/SiO ₂ =0.02～0.3, Q/SiO ₂ =0.02～0.5, H ₂ O/SiO ₂ =1～9.5 reaction mixture, and then the The reaction mixture is hydrothermally crystallized according to the conventional method, and the crystallized product is filtered, and the filtered solid is used as a high-silicon ZSM-5 zeolite product, and the obtained filtrate is used as a raw material for the next synthesis to replace the required product of the reaction mixture. Part of the water, templating agent, alkali and silicon-aluminum sources are recycled in this way. The method of the invention can reduce the consumption of organic templates and silicon-alumina, thereby reducing the cost of the product, while avoiding the discharge of filtrate and reducing the pollution to the environment without affecting the performance of the product.

Description

A kind of synthetic method of high silicon ZSM-5 zeolite

The invention relates to a method for synthesizing ZSM-5 zeolite with high silicon-aluminum ratio.

The ZSM-5 molecular sieve (USP3702886, 1972) invented by Mobil Petroleum Company of the United States has been widely used in petrochemical processes such as shape-selective cracking, alkylation, isomerization, disproportionation, dewaxing, and etherification of hydrocarbons. application. The method of USP3702886 can only synthesize the ZSM-5 molecular sieve that silicon aluminum ratio is less than 100, and will use expensive tetrapropyl ammonium hydroxide organic template.

ZSM-5 molecular sieve with high silicon-aluminum ratio is more useful than ZSM-5 molecular sieve with low silicon-aluminum ratio in many chemical processes. ZSM-5 molecular sieves with a low silicon-aluminum ratio can be synthesized by a reaction mixture without an organic template, but ZSM-5 zeolites with a high silicon-aluminum ratio generally require the use of an organic template to be synthesized, that is to say, high silicon ZSM-5 The synthesis is relatively difficult. USP3941871 and USP4061724 reported the synthesis of ZSM-5 molecular sieves with a silicon-aluminum ratio greater than 200, but the organic templates used are still quaternary ammonium compounds or organic phosphorus compounds, which are expensive. In addition, in USP4528172, organophosphorus compounds are also used as templates to synthesize ZSM-5.

In the synthetic method of ZSM-5 molecular sieve reported in USP4526879, adopt the mixture of alkylamine and haloalkane as template agent (R), and add a kind of miscible solvent, the molar proportion of its reaction mixture is SiO ₂ /Al ₂ O ₃ =10-500, H ₂ O/SiO ₂ =10-100, Na ₂ O/SiO ₂ =0.1-2.0, R/SiO ₂ =0.05-1.0.

Zeolite molecular sieves are mostly prepared by hydrothermal crystallization. As a method for preparing zeolite, hydrothermal crystallization plays an important role, but the conventional hydrothermal crystallization method has certain deficiencies, which are mainly manifested in: (1) The ratio of water to silicon in the original feed is very large. The yield of the still is low, and on the other hand, the filtrate is discharged in large quantities, causing environmental pollution. (2) When organic nitrogen-containing compounds are used as templates, part of them acts as a template to form the molecular sieve skeleton, and the other part enters the mother liquor and is discharged, resulting in waste of raw materials and environmental pollution, and the cost of molecular sieves depends mostly on The amount of the template agent increases the synthesis cost of the molecular sieve. Based on the above reasons, both at home and abroad have been devoting themselves to developing a new zeolite molecular sieve synthesis method that reduces the above two unfavorable factors for many years.

People such as Li Jianquan proposed a kind of method for preparing zeolite molecular sieve in CN1082510A, this method is to mix sodium hydroxide and water glass earlier, react with aluminum sulfate to form gel immediately, then after the gained silica-alumina gel is dried, at 450～600 ℃ roasting, and then add a small amount of ethylenediamine and water to the above-mentioned roasted silica-alumina gel, and crystallize at 150-200 °C; the products of this method are all solid, and there is no mother liquor discharge, but roasting is required to prepare silicon The raw material of aluminum gel increases the production cost, and there is no specific description on the preparation of ZSM-5 in this publication.

Li Jianquan et al. (Zeolites and Related Microporous Materials: State of the Art 1994, Studies in Surface Science and Catalysis, Volume 84, Page 195) also proposed a method for synthesizing ZSM-5 molecular sieves in an ultra-concentrated system. Silica-alumina gel, sodium hydroxide and 1,6-hexanediamine are used as raw materials, and a small amount of water is added to crystallize at 110-200°C. After crystallization, the product does not need to be filtered, and there is no mother liquor discharge, but the crystallization method The time is too long, it takes more than 7 days for crystallization at 110°C, and more than 2 days for crystallization at 200°C, which is very unfavorable for industrial production.

The purpose of the present invention is to provide a method for synthesizing high-silicon ZSM-5 zeolite, so as to reduce the cost and reduce the pollution to the environment caused by the discharge of mother liquor.

The synthesis method of the high-silicon ZSM-5 zeolite provided by the present invention is to use solid silica-alumina colloidal microspheres as raw materials, use alkylamine organic matter (Q) as a template, and add sodium hydroxide and water to prepare a molar compound Ratio of SiO ₂ /Al ₂ O ₃ =100～1000, Na ₂ O/SiO ₂ =0.02～0.3, Q/SiO ₂ =0.02～0.5, H ₂ O/SiO ₂ =1～9.5 reaction mixture, and then The reaction mixture is hydrothermally crystallized according to a conventional method, and the crystallized product is filtered, and the filtered solid is used as a high-silicon ZSM-5 zeolite product, and the obtained filtrate is used as a raw material for the next synthesis to replace the product of the reaction mixture. Part of the water, templating agent, alkali and silicon-aluminum sources needed are recycled in this way.

In the method provided by the present invention, the silicon-aluminum ratio of the solid silica-alumina colloidal microspheres is determined according to the feed-silicon-alumina ratio of the reaction mixture, and its particle size is less than 800 microns. The present invention has no special requirements on its surface area and pore volume.

In the method provided by the present invention, the template agent is an alkylamine with the general formula R(NH ₂ ) _n , wherein R is an alkyl or alkylene group with 1-6 carbon atoms, and n is 1 or 2.

Said crystallization in the method provided by the present invention is carried out according to conventional conditions, the general condition is crystallization at 110～220°C for 8 hours to 10 days, wherein the preferred conditions are that the temperature is 130～200°C, and the time is 1～200°C. 6 days.

In the method provided by the present invention, the prepared reaction mixture can also be aged at 20-110°C for 4-48 hours before crystallization, preferably at 30-100°C for 8-24 hours, and then Hydrothermal crystallization by conventional methods.

The filtrate in the method provided by the present invention may also include the washing liquid obtained when the molecular sieve is washed.

The method for synthesizing high silicon ZSM-5 zeolite provided by the invention is characterized in that the filtrate is recycled. In the molecular sieve synthetic filtrate, most of it is water, and there is also a part of unutilized organic template and silicon aluminum (wherein aluminum is very little), so the composition of the filtrate can be reduced in the next feeding. The amount of silicon and aluminum is reduced, thereby reducing the cost of the product, avoiding the discharge of the filtrate at the same time, reducing the pollution to the environment, and has no effect on the performance of the product.

FIG. 1 is an X-ray diffraction (XRD) pattern of a sample synthesized in Comparative Example 1.

The following examples will further illustrate the present invention, but do not limit the present invention. In each embodiment and comparative example, the relative crystallinity is represented by the ratio of the sum of the peak heights of five XRD diffraction peaks whose 2θ angles of X-ray diffraction (XRD) of the product and the standard sample are between 22.5～25° , the standard sample (regulating its crystallinity as 100%) here is the sample obtained in Comparative Example 1.

In each embodiment and comparative example, the used silica-alumina colloidal microsphere adopts following method to prepare: the aluminum sulfate solution of calculated amount is added in the water glass (its silica-alumina ratio is determined according to the needs of each example) under stirring ), stirred evenly, then added dropwise 25% by weight of H ₂ SO ₄ aqueous solution to adjust the pH value of the mixture to 5-6, aged for 30 minutes, then spray-dried into silica-alumina microspheres of 50-800 microns, washed with water Until the content of Na ₂ O is less than 0.1% by weight, and the content of SO ₄ ⁼ is less than 1.0% by weight, and then dried at 110° C. for 7 hours to obtain the required silica-alumina gel microspheres.

Comparative example 1

Mix 95 grams of silica-alumina microspheres with a particle size of 120-175 microns and a _SiO2 / _Al2O3 molar ratio of ₃₀₀ with a solution composed of 6.7 grams of NaOH, 24 grams of n-butylamine, and 230 grams of water. The molar ratio of the obtained reaction mixture is: SiO ₂ /Al ₂ O ₃ =300, H ₂ O/SiO ₂ =7.8, Na ₂ O/SiO ₂ =0.05, n-butylamine/SiO ₂ =0.2.

The above reaction mixture was put into a sealed stainless steel reactor and crystallized at 170°C for 24 hours. After the reaction, the reactor was cooled, and the product was filtered (the filtrate was collected for the synthesis of the following examples), washed and dried. XRD analysis showed that It has a crystal phase structure of ZSM-5 (see Figure 1), and its crystallinity is specified to be 100%, and the product SiO ₂ /Al ₂ O ₃ =245.

Example 1

Get 4.7 grams of gained mother liquor after comparative example 1 is filtered ( _SiO content 4.0 weight %, n-butylamine content 4.5 weight %, Na _O content 2.6 weight %) and by 0.59 gram NaOH, 2.2 gram n-butylamine, 18.8 gram water The resulting solution is mixed evenly, and then 9.5 grams of silica-alumina gel microspheres with a particle size of 120-350 microns and a silica-alumina ratio of 300 are added. The molar ratio of the resulting reaction mixture is: SiO ₂ /Al ₂ O ₃ =305,H ₂ O/SiO ₂ =8.1, Na ₂ O/SiO ₂ =0.05, n-butylamine/SiO ₂ =0.2.

The above reaction mixture was put into a sealed stainless steel reactor and crystallized at 170°C for 24 hours. After the reaction, the reactor was cooled, and the product was filtered (the filtrate was collected for the synthesis of Example 2), washed, and dried. XRD analysis showed that It has a crystal phase structure of ZSM-5 (the peak shape of the XRD pattern is similar to that in Figure 1), the relative crystallinity is 105%, and the product SiO ₂ /Al ₂ O ₃ =250.

Example 2

Get 10 grams of the mother liquor that embodiment 1 filters gained ( _SiO content 4.2 weight %, n-butylamine content 3.8 weight %, Na _O content 2.2 weight %) and by 0.5 gram NaOH, 1.95 gram n-butylamine, 14 grams water The resulting solution was mixed evenly, and then 9.5 grams of silica-alumina gel microspheres with a particle size of 120-350 microns and a silica-aluminum ratio of 300 were added. The molar ratio of the resulting reaction mixture was: SiO ₂ /Al ₂ O ₃ =310, H ₂ O/SiO ₂ =8.1, Na ₂ O/SiO ₂ =0.05, n-butylamine/SiO ₂ =0.2.

The above mixture was put into a sealed stainless steel reactor and crystallized at 170°C for 24 hours. After the reaction, the reactor was cooled, and the product was filtered (the filtrate was collected for the synthesis of Example 3), washed and dried. XRD analysis showed that it had The crystal phase structure of ZSM-5 (the peak shape of the XRD pattern is similar to that in Figure 1), the crystallinity is 99%, and the product SiO ₂ /Al ₂ O ₃ =255.

Example 3

Get 4.7 gram of the mother liquor that embodiment ₂ filters gained (SiO content 3.9 weight %, n-butylamine content 4.6 weight %, Na _O content 2.3 weight %) and by 1.9 gram NaOH, 1.42 gram ethylenediamine, 18 gram water The resulting solution was mixed evenly, and then 9.5 grams of silica-alumina microspheres with a particle size of 70-150 microns and a silica-alumina ratio of 400 were added. The molar ratio of the resulting reaction mixture was: SiO ₂ /Al ₂ O ₃ =404, H ₂ O/SiO ₂ =7.8, Na ₂ O/SiO ₂ =0.16, ethylenediamine/SiO ₂ =0.15.

The above reaction mixture was put into a sealed stainless steel reactor and aged at 90°C for 4 hours, then crystallized at 170°C for 20 hours, after the reaction was completed, the reactor was cooled, and the product was filtered, washed and dried, and XRD analysis showed that it had ZSM The crystal phase structure of -5 (the peak shape of the XRD pattern is similar to that in Figure 1), the crystallinity is 96%, and the product SiO ₂ /Al ₂ O ₃ =355.

Example 4

Get 25.8 grams of the mother liquor obtained by filtering Comparative Example ₁ (SiO 4.0 weight percent content, 4.5 weight percent n-butylamine content, Na ₂ O content 2.6 weight percent) mixed with a solution composed of 0.27 gram NaOH and 2.44 gram n-butylamine uniform, and then add 9.5 grams of silica-alumina gel microspheres with a particle size of 70-150 microns and a silica-aluminum ratio of 650. The molar ratio of the resulting reaction mixture is: SiO ₂ /Al ₂ O ₃ =661, H ₂ O/SiO ₂ =8.2, Na ₂ O/SiO ₂ =0.05, n-butylamine/SiO ₂ =0.3.

Put the above mixture into a sealed stainless steel reactor and age at 40°C for 11 hours, and then crystallize at 150°C for 20 hours. After the reaction, the reactor is cooled. After the product is filtered, washed and dried, it is detected by XRD that it has ZSM-5 The crystal phase structure (XRD pattern peak shape is similar to that in Figure 1), the crystallinity is 98%, and the product SiO ₂ /Al ₂ O ₃ =546.

Example 5

Get 10 grams of the mother liquor (SiO content 4.0 weight % of comparative example ₁ filtration gained, n-butylamine content 4.5 weight %, Na _O content 2.6 weight %) and by 0.5 gram NaOH, 0.75 gram n-butylamine, 10 grams water The resulting solution was mixed evenly, and then 9.5 grams of silica-alumina gel microspheres with a particle size of 70-150 microns and a silica-alumina ratio of 400 were added. The molar ratio of the resulting reaction mixture was: SiO ₂ /Al ₂ O ₃ =411, H ₂ O/SiO ₂ =6.6, Na ₂ O/SiO ₂ =0.05, n-butylamine/SiO ₂ =0.1.

Put the above mixture into a sealed stainless steel reactor and age it at 110°C for 16 hours, and then crystallize it at 150°C for 10 hours. After the reaction, the reactor is cooled. After the product is filtered, washed and dried, it is detected by XRD that it has ZSM-5 The crystal phase structure (XRD pattern peak shape is similar to that in Figure 1), the crystallinity is 99%, and the product SiO ₂ /Al ₂ O ₃ =330.

Example 6

Get 10 grams of the mother liquor (SiO ₂ content 4.0 weight %, n-butylamine content 4.5 weight %, Na ₂ O content 2.6 weight %) obtained from filtering of 10 grams of comparative example 1 and by 0.5 gram NaOH, 0.75 gram n-butylamine, 5.4 gram water The resulting solution was mixed evenly, and then 9.5 grams of silica-alumina gel microspheres with a particle size of 70-150 microns and a silica-alumina ratio of 400 were added. The molar ratio of the resulting reaction mixture was: SiO ₂ /Al ₂ O ₃ =411, H ₂ O/SiO ₂ =5, Na ₂ O/SiO ₂ =0.05, n-butylamine/SiO ₂ =0.1.

Put the above mixture into the reactor and age at 110°C for 10 hours, and then crystallize at 150°C for 10 hours. After the reaction, the reactor is cooled. After the product is filtered, washed and dried, it has the crystal phase structure of ZSM-5 as detected by XRD (The peak shape of the XRD pattern is similar to that in Figure 1), the crystallinity is 95%, and the product SiO ₂ /Al ₂ O ₃ =340.

Example 7

Get 10 gram of the mother liquor that embodiment 6 filters gained ( _SiO Content 3.5 weight %, n-butylamine content 3.6 weight %, _Na O content 2.2 weight %) and by 1.2 gram NaOH, 7.1 gram ethylamine aqueous solution (30m%), Mix the solution composed of 3.2 grams of water evenly, then add 9.5 grams of silica-alumina colloidal microspheres with a particle size of 70-150 microns and a silicon-aluminum ratio of 180. The molar ratio of the resulting reaction mixture is: SiO ₂ /Al ₂ O ₃ = 186. H ₂ O/SiO ₂ =6, Na ₂ O/SiO ₂ =0.1, Ethylamine/SiO ₂ =0.3.

Put the above mixture into a sealed stainless steel reactor and age at 90°C for 16 hours, then crystallize at 160°C for 16 hours. After the reaction, the reactor is cooled. After the product is filtered, washed and dried, it is detected by XRD that it has ZSM-5 The crystal phase structure (XRD pattern peak shape is similar to that in Figure 1), the crystallinity is 90%, and the product SiO ₂ /Al ₂ O ₃ =153.

Claims (6)

1. A kind of synthetic method of high silicon ZSM-5 zeolite, it is characterized in that this method is to be raw material with solid silica-alumina colloidal microsphere, is template agent with alkylamine organic matter (Q), and adds sodium hydroxide and water, prepares Form a reaction mixture with a molar ratio of SiO ₂ /Al ₂ O ₃ =100-1000, Na ₂ O/SiO ₂ =0.02-0.3, Q/SiO ₂ =0.02-0.5, H ₂ O/SiO ₂ =1-9.5 , and then the reaction mixture is hydrothermally crystallized according to conventional methods, and the crystallized product is filtered, and the filtered solid is used as a high-silica ZSM-5 zeolite product, and the resulting filtrate is used as a raw material for the next synthesis to replace Part of the water, templating agent, alkali and silicon-aluminum sources required by the reaction mixture are recycled in this way. 2. The method according to claim 1, wherein the silicon-aluminum ratio of said solid silica-alumina colloidal microspheres is determined according to the feed-silicon-alumina ratio of said reaction mixture, and its particle size is less than 800 microns. 3. The method according to claim 1, wherein said templating agent is an alkylamine having a general formula of R(NH ₂ ) _n , wherein R is an alkyl or alkylene group having 1 to 6 carbon atoms, and n is 1 or 2 . 4. The method according to claim 1, characterized in that the method further comprises aging said reaction mixture at 20-110° C. for 4-48 hours before crystallization, and then hydrothermal crystallization according to a conventional method. 5. The method according to claim 1 or 4, wherein the condition of said hydrothermal crystallization is crystallization at 110-220° C. for 8 hours to 10 days. 6. The method according to claim 5, wherein the condition of said hydrothermal crystallization is crystallization at 130-200° C. for 1-6 days.

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