CN102190312A - Method for recycling molecular sieve mother solution - Google Patents

Abstract

The invention discloses a method for recycling a molecular sieve crystallization mother liquor, comprising the steps of: (1) preparing a material for synthesizing molecular sieves, gelling, crystallizing and filtering, and collecting all the molecular sieve crystallization mother liquors; (2) preparing the obtained molecular sieve crystallization mother liquor; All the molecular sieve crystallization mother liquors are directly used in the synthesis of molecular sieves, which are mixed with solid silicon sources, aluminum sources and alkalis, with or without molecular sieve crystal seeds and templates, to make reaction mixtures; (3) the resulting reaction mixtures Carry out crystallization by conventional hydrothermal method, the filter cake of gained is molecular sieve product, filter and collect simultaneously and obtain all molecular sieve crystallization mother liquors; Wherein, can with gained all molecular sieve crystallization mother liquors, according to steps (2), (3) Sequential, multiple recycling. According to the invention, there is basically no discharge of alkaline waste liquid in the synthesis of molecular sieves, the overall silicon utilization rate is more than 90%, and the yield of molecular sieve products is higher than 90%.

Description

A kind of recycling method of molecular sieve crystallization mother liquor

technical field

The invention relates to the technical field of molecular sieve synthesis, and more specifically relates to a method for recycling molecular sieve synthesis by using the molecular sieve crystallization mother liquor synthesized by silicon-aluminum molecular sieves.

Background technique

Molecular sieves are important catalysts or catalyst active components in petroleum refining and chemical processes. In the prior art, when synthesizing silica-alumina molecular sieves, silicon-containing compounds (water glass, silica sol, and organosilicon ester, etc.), aluminum-containing compounds (hydrated alumina, aluminum salts, etc.), alkalis (sodium hydroxide, potassium hydroxide, etc.) ) and water in an appropriate proportion, adding or not adding an organic template and heating in an autoclave for a certain period of time to obtain molecular sieve crystals. Under alkaline conditions, some silicon will remain in the mother liquor and not be fully utilized. If the mother liquor after synthesis is directly used as sewage in the factory, it will not only increase the total amount of sewage treatment, but also cause a lot of waste and reduce the utilization rate of silicon. Due to the large amount of silicon in the mother liquor and the free silica is not easy to settle, it is very easy to cause the suspended solids in the sewage to exceed the standard, thus increasing the difficulty of sewage treatment; and the Na ₂ O in the crystallization mother liquor is high, which increases the treatment of filter residues. cost.

Usually, when NaY molecular sieve is synthesized, the silicon-aluminum ratio of the feed is generally 8-12, and the silicon-aluminum ratio of the product is generally 4.5-5.5. Therefore, the utilization rate of silicon in raw materials is only about 60%. There are also some research reports on the recycling of NaY mother liquor in the prior art. For example, DD 227416A discloses the use of the mother liquor of synthetic Y-type zeolite or mordenite to synthesize X-type zeolite; SU975573A, CN 1634764 and CN 1854066 disclose the use of NaY mother liquor to prepare silicon (aluminum) glue, and then use this silicon (aluminum) Glue is used as a raw material for synthesizing NaY zeolite; CN 1631780 relates to a method for producing 4A molecular sieve by utilizing the crystallization mother liquor of NaY molecular sieve and sodium aluminate solution. CN 1057067 discloses a method for synthesizing ZSM-5 using silica-alumina microspheres prepared from NaY mother liquor. In most cases in the prior art, it is necessary to settle down the silicon in the mother liquor in the form of silica gel or silica-alumina gel, and the prepared silica (aluminum) gel also needs to be filtered and/or washed. , can be used in the synthesis of molecular sieves. In addition, CN 1217232 proposes a method for synthesizing titanium-silicon molecular sieves using the template in the mother liquor of molecular sieves; CN1500722 discloses a method for using the template in the crystallization mother liquor of MCM-22 molecular sieves as part or all of the templates synthesized by molecular sieves.

Usually, the SiO ₂ content in the molecular sieve crystallization mother liquor is 30-70g/L, and the Na ₂ O content is 20-45g/L, which is equivalent to dilute water glass with a modulus of 1.65-2.58. If more water-containing silicon source, aluminum source or template solution is added to the molecular sieve synthesis feed, the water-to-silicon ratio of the system will increase, thereby reducing the single-pot yield of molecular sieve synthesis.

The present invention provides a new method for synthesizing molecular sieves, that is, a method for recycling molecular sieve crystallization mother liquors. All the molecular sieve mother liquors are directly fed, and the molecular sieve mother liquors obtained in each step are repeatedly recycled to make full use of the OH in the mother liquors. ^- , silicate and water, and comprehensively utilize the crystallization mother liquor of molecular sieves to overcome the defects of the prior art and ensure a higher single-pot yield.

Contents of the invention

The object of the present invention is to provide a kind of recycle method of molecular sieve crystallization mother liquor, comprises the steps:

(1) Prepare a material for synthesizing molecular sieves, gel, crystallize and filter, and collect all the crystallization mother liquors of molecular sieves;

(2) All the molecular sieve crystallization mother liquor obtained in step (1) is directly used for the synthesis of molecular sieves without any treatment, that is, it is mixed with solid silicon source, aluminum source and alkali, with or without molecular sieve seed crystals and Templating agent, make reaction mixture;

(3) The reaction mixture obtained in step (2) is crystallized by a conventional hydrothermal method, and the resulting filter cake is a molecular sieve product, and is filtered and collected to obtain all the molecular sieve crystallization mother liquors;

Wherein, all the molecular sieve crystallization mother liquid obtained in step (3) can be recycled multiple times according to the sequence of steps (2) and (3).

The method for recycling molecular sieve crystallization mother liquor of the present invention, wherein, the molecular sieve described in the step (1) is a silica-alumina molecular sieve, including NaY, ZSM-5, ZSM-11, TS-1, MCM-22, Beta or mordenite . The preferred molecular sieve is ZSM-5, TS-1, MCM-22 or Beta. Wherein, the technologies such as materials, gelation, crystallization, and filtration of the synthetic molecular sieve described in step (1), its preparation conditions, etc. are all known conventional technologies, and details can be found in references: Verified Syntheses of ZeoliticMaterials, Ed.By H. Robson, Elsevier, 2001, Amsterdam.

The method for recycling molecular sieve crystallization mother liquor of the present invention, wherein, all the crystallization mother liquors described in step (2) include the mother liquor collected by filtration after molecular sieve crystallization, and the washing liquid obtained after the molecular sieve filter cake is washed with a small amount of water . Wherein said "a small amount of water washing" means that the washing liquid is about 10-20 weight percent of the mother liquor. The invention directly recycles and utilizes all the crystallization mother liquid of the molecular sieve, so that there is no discharge of silicon and alkali in the synthesis of the molecular sieve.

The molecular sieve crystallization mother liquor of the present invention is directly used in the synthesis of molecular sieves without any treatment, and this technology has not been reported so far. Wherein, all crystallization mother liquors described in step (2) can be mixed with solid silicon source, aluminum source and alkali in any order. Wherein, the "molecular sieve seed crystal" in step (2) refers to any solid and colloidal solution containing silicon and aluminum that can accelerate the synthesis of molecular sieves, and the "template agent" refers to organic matter directed to a certain molecular sieve structure.

The method for recycling molecular sieve crystallization mother liquor of the present invention, wherein, the solid silicon source described in step (2) includes any silicon-containing solid compound or natural mineral, including solid silica gel, silicon (aluminum) gel, precipitated silica gel, white carbon black , kaolin, montmorillonite. Wherein, the solid silicon source described in step (2) is preferably solid silica gel, silica (aluminum) gel, precipitated silica gel, and white carbon black. The reaction mixture with a certain molar ratio made in the step (2), the molar ratio can be the same or different from the molar ratio synthesized in the step (1), and the molar ratio in the step (2) meets the target synthetic molecular sieve. Just ask.

In the method for recycling the crystallization mother liquor of molecular sieves of the present invention, the molecular sieves synthesized in steps (2) and (3) may be the same as or different from the molecular sieves in step (1). For example, the crystallization mother liquor using ZSM-5 molecular sieve can be directly used in the synthesis of molecular sieves such as Beta, MCM-22 or mercerized, and the crystallization mother liquor of NaY molecular sieve can be used in the synthesis of molecular sieves such as ZSM-5 or Beta. Example 4 of the present invention illustrates that the crystallization mother liquor of NaY molecular sieve is used for the synthesis of ZSM-5 molecular sieve.

The conventional hydrothermal method mentioned in the method step (3) provided by the present invention refers to the same crystallization method as when the crystallization mother liquor is not added to carry out molecular sieve synthesis, which is a well-known conventional technology.

The innovation of the method for recycling the crystallization mother liquor of molecular sieves of the present invention is that all crystallization mother liquors synthesized by molecular sieves are directly fed to synthesize molecular sieves without any treatment, so that there is no silicon and alkali in the synthesis of molecular sieves discharge; again, the mixture of solid silicon source and crystallization mother liquor is used as the silicon source for molecular sieve synthesis; especially, the molecular sieve crystallization mother liquor collected by filtration is repeatedly recycled, making full use of the OH- and silicate radicals in the mother liquor With water, comprehensively utilize the crystallization mother liquor of molecular sieves. These technical innovations have not yet been reported and disclosed in the prior art.

The method for recovering and utilizing the crystallization mother liquid of the molecular sieve of the present invention basically avoids the discharge of alkaline waste liquid during the synthesis of the molecular sieve and the discharge of waste liquid during the crystallization process of the molecular sieve, and the utilization rate of the overall silicon is more than 90%. If there is discharge, silicon oxide and sodium oxide in the mother liquor cannot be utilized. In prior art ZSM-5 molecular sieve synthesis, the crystallization mother liquor usually contains 15-20% by weight of SiO ₂ , and the method of the present invention can recycle all these crystallization mother liquors to synthesize molecular sieves. After the second cycle, the yield of using the obtained molecular sieve product is higher than 90%. For every ton of molecular sieve produced, the crystallization process can reduce water consumption by 1.5-2.0 tons and save about 40% of NaOH consumption. Moreover, the present invention simultaneously uses two silicon sources, the silicon in the mother liquor and the solid silicon source, to ensure that the ratio of water to silicon synthesized by molecular sieves during the recycling of the mother liquor will not gradually increase.

Description of drawings

Figure 1: is the X-ray diffraction (XRD) crystal phase diagram of the sample obtained in Comparative Example 1, which is a typical ZSM-5 molecular sieve without heterocrystalline phase.

Figure 2: is the X-ray diffraction (XRD) crystal phase diagram of the sample obtained in Example 2, which is a typical ZSM-5 molecular sieve without heterocrystalline phase. Compared with Comparative Example 1, the relative crystallinity is 102%.

Figure 3: is the X-ray diffraction (XRD) crystal phase diagram of the sample obtained in Example 5, which is a typical Beta molecular sieve without a heterocrystalline phase.

Detailed ways

In conjunction with the following examples, the present invention will be further described. The present invention is not limited to the following specific examples.

In the following examples and comparative examples, the relative crystallinity of molecular sieves is measured by X-ray powder diffraction method, and the comparative sample is the corresponding sample synthesized without crystallization mother liquor; the BET surface area of the sample adopts GB/T 5816-1995 Determination by standard method; the analysis of silicon oxide and sodium oxide in the mother liquor adopts the chemical industry standard HC/T 2830-1997 of the People's Republic of China.

Comparative example 1

55.0 grams of sodium hydroxide, 31.5 grams of sodium metaaluminate (Sinopharm Chemical Reagent Company, Al ₂ O ₃ content 41% by weight) and 12.5 grams of tetrapropylammonium bromide were dissolved in 1200 milliliters of water, and 22.8 grams of NaY ( Changling Oil Refinery Chemical Plant Catalyst Plant) and 500 grams of silica gel (Qingdao Ocean Chemical Plant, 40-120 mesh, solid content of burnt residue is 95%), stirred evenly, transferred to a 2-liter autoclave, and crystallized at 175 ° C for 24 hour, filtered after cooling, washed and dried, the XRD crystal phase diagram of the product obtained as shown in Figure 1, is a ZSM-5 structure, its crystallinity is set to 100%, and the BET surface area is 324m2/g. The filtered crystallization mother liquor was collected for the synthesis in Example 1. The yield of the obtained ZSM-5 molecular sieve sample is about 84% relative to the solid silicon source.

Example 1

Mix 790 milliliters of the crystallization mother liquor in Comparative Example 1 (SiO ₂ : 65.0 g/L; Na ₂ O: 38.8 g/L) with 500 milliliters of water, add 4.7 grams of sodium hydroxide, 22.8 grams of sodium metaaluminate and 8.8 Dissolve 1 gram of tetrapropylammonium bromide, add 360 grams of silica gel (Qingdao Ocean Chemical Factory, 40-120 mesh, and the solid content of burnt residue is 95%), transfer to a 2-liter autoclave after stirring evenly, and crystallize at 175 ° C After 24 hours, filter, wash and dry after cooling, the XRD crystal phase diagram of the product obtained is shown in Figure 2, which is a ZSM-5 structure, its relative crystallinity is 102%, and the BET surface area is 340m2/g. The filtered crystallization mother liquor was collected for the synthesis in Example 2. The yield of the obtained ZSM-5 molecular sieve sample is about 92% relative to the solid silicon source.

Example 2

Mix 898 milliliters of the crystallization mother liquor in Example 1 (SiO ₂ : 46.9 g/L; Na ₂ O: 23.5 g/L) with 300 milliliters of water, add 14.4 grams of sodium hydroxide, 22.8 grams of sodium metaaluminate and 8.8 Dissolve 1 gram of tetrapropylammonium bromide, add 360 grams of silica gel (Qingdao Ocean Chemical Factory, 40-120 mesh, and the solid content of burnt residue is 95%), transfer to a 2-liter autoclave after stirring evenly, and crystallize at 175 ° C After cooling for 24 hours, filter, wash and dry, the XRD crystal phase diagram of the product obtained is similar to that in Figure 2, which is a ZSM-5 structure with a relative crystallinity of 105%. The filtered crystallization mother liquor was collected for the synthesis of ZSM-5. The yield of the obtained ZSM-5 molecular sieve sample is about 93% relative to the solid silicon source.

Example 3

Mix 820 milliliters of the crystallization mother liquor in Example 2 (SiO ₂ : 46.0 g/L; Na ₂ O: 39.8 g/L) with 400 milliliters of water, add 14.4 grams of sodium hydroxide, 22.8 grams of sodium metaaluminate and 8.8 Dissolve 1 gram of tetrapropylammonium bromide, add 360 grams of silica gel (Qingdao Ocean Chemical Factory, 40-120 mesh, and the solid content of burnt residue is 95%), transfer to a 2-liter autoclave after stirring evenly, and crystallize at 175 ° C After cooling for 24 hours, filter, wash and dry, the XRD crystal phase diagram of the product obtained is similar to that in Figure 2, which is a ZSM-5 structure with a relative crystallinity of 105%. The filtered crystallization mother liquor was collected for the synthesis of ZSM-5. The yield of the obtained ZSM-5 molecular sieve sample is about 93% relative to the solid silicon source.

Example 4

NaY was synthesized according to the molar ratio of SiO2:Al2O3:Na2O:H2O=9.4:3.0:1:210, and the _SiO2 in the obtained NaY crystallization mother liquor was 56.6g/L; _Na2O : 24.8g/L. Mix 900 milliliters of NaY crystallization mother liquor with 300 milliliters of water, add 13.8 grams of sodium hydroxide, 22.8 grams of sodium metaaluminate and 8.8 grams of tetrapropylammonium bromide to dissolve, add 360 grams of silica gel (Qingdao Ocean Chemical Factory, 40-120 mesh , the solid content of the burnt residue is 95%), stir evenly and transfer to a 2-liter autoclave, crystallize at 175°C for 24 hours, filter, wash and dry after cooling, the obtained product is a typical ZSM-5 molecular sieve, its crystallization The degree is 110%. The filtered crystallization mother liquor can continue to be used for the synthesis of ZSM-5 after being collected. It shows that the mother liquor of molecular sieve can be used for the synthesis of molecular sieves with different structures.

Comparative example 2

3.49 grams of sodium hydroxide and 0.953 grams of sodium metaaluminate (Al2O3: 53.52%, Na2O: 40.52%) were dissolved in 50.4 milliliters of water, and 1.20 grams of roasted Beta molecular sieves (Changling Oil Refinery Chemical Plant Catalyst Factory) and 12.0 grams were added successively. gram of freshly precipitated silica gel, stirred evenly, transferred to a 100 ml autoclave, crystallized at 145°C for 24 hours, filtered, washed and dried after cooling, the resulting product was a pure phase BETA molecular sieve with a crystallinity of 100 %. The filtered crystallization mother liquor was collected for the synthesis in Example 5. Relative to the solid silicon source, the yield of BETA molecular sieve is 30%.

Example 5

Mix 30 ml of crystallization mother liquor (SiO ₂ : 54.2 g/L; Na ₂ O: 25.8 g/L) in Comparative Example 2 with 20 ml of water, add 2.72 g of sodium hydroxide and 0.953 g of sodium metaaluminate to dissolve, Add 10.4 grams of white carbon black and 1.2 grams of roasted Beta molecular sieve, stir evenly, transfer to a 100 ml autoclave, crystallize at 145°C for 24 hours, filter, wash and dry after cooling, the XRD crystal phase diagram of the obtained product As shown in Figure 3, it is a BETA molecular sieve with a crystallinity of 110%. The filtered crystallization mother liquor can continue to be used for the synthesis of Beta molecular sieves after collection. Relative to the solid silicon source, the yield of BETA molecular sieve is 81%.

Claims (7)

1. the recoverying and utilizing method of a molecular sieve crystallization mother liquor is characterized in that, comprises the steps:

(1) whole molecular sieve crystallization mother liquors is collected in the material of a kind of synthesis of molecular sieve of preparation, one-tenth glue, crystallization and filtration;

(2) the whole molecular sieve crystallization mother liquor of step (1) gained is directly used in the synthetic of molecular sieve, it is mixed with solid silicon source, aluminium source and alkali, add or do not add molecular sieve crystal seed and template, make reaction mixture;

(3) with the reaction mixture of step (2) gained routinely hydrothermal method carry out crystallization, the filter cake of gained is a zeolite product, filters simultaneously to collect to obtain whole molecular sieve crystallization mother liquors;

Wherein, can be with the whole molecular sieve crystallization mother liquor of step (3) gained, according to the order of step (2), (3), recycled for multiple times.

2. recoverying and utilizing method as claimed in claim 1 is characterized in that, molecular sieve is a Si-Al molecular sieve described in the step (1), is NaY, ZSM-5, ZSM-11, TS-1, MCM-22, Beta or mordenite.

3. recoverying and utilizing method as claimed in claim 2 is characterized in that, molecular sieve is ZSM-5, TS-1, MCM-22 or Beta described in the step (1).

4. recoverying and utilizing method as claimed in claim 1 is characterized in that, whole crystallization mother liquors described in the step (2) comprise mother liquor and the molecular sieve filter cake a small amount of washing resulting water lotion afterwards that molecular sieve crystallization after-filtration is collected.

5. recoverying and utilizing method as claimed in claim 1 is characterized in that, solid silicon source comprises any silicon-containing solid compound or natural mineral described in the step (2), is solid silicone, silicon (aluminium) glue, precipitation silica gel, white carbon black, kaolin or polynite.

6. recoverying and utilizing method as claimed in claim 5 is characterized in that, solid silicon source described in the step (2) is solid silicone, silicon (aluminium) glue, precipitation silica gel, white carbon black.

7. recoverying and utilizing method as claimed in claim 1 is characterized in that, the described molecular sieve of synthetic can be identical or different with the described molecular sieve in the step (1) in step (2) and (3).

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