CN1332761C - Process for preparing load type silicon phoshporus aluminium molecular sieve - Google Patents

Abstract

The invention discloses a preparation method of a SAPO-34 coated silicon-phosphorus-aluminum molecular sieve which can be directly used in a fluidized bed and belongs to the field of molecular sieve preparation. The technical scheme to realize the preparation method of the covered silicon phosphorus aluminum molecular sieve is as follows: use silica sol as the silicon source, phosphoric acid as the phosphorus source, pseudo-boehmite as the aluminum source, use nitrogen-containing compound triethylamine as the template, and use oxidation Silicon, alumina, titanium oxide or magnesium oxide and other small balls with a diameter of 20-200 microns are used as carriers, and then mixed according to a certain weight ratio, and an appropriate amount of _H2O is added to evenly mix, stir, crystallize, and dry to obtain the molecular sieve powder; Then the raw powder of molecular sieve is impregnated and roasted by silica sol or aluminum sol, and the synthesized molecular sieve is a coated silicon phosphorus aluminum molecular sieve, which can be directly used in a fluidized bed. The SAPO-34 coated silicon-phosphorus-aluminum molecular sieve prepared by this method saves production links such as spray granulation, shortens the process, and saves production costs. It can be used in the reaction of methanol or dimethyl ether cracking to produce low-carbon olefins .

Description

Preparation method of covered silicon phosphorus aluminum molecular sieve

technical field

The invention belongs to the field of molecular sieve preparation, in particular to a preparation method of a SAPO-34 coated silicon-phosphorus-aluminum molecular sieve that can be directly used in a fluidized bed.

Background technique

Low-carbon olefins such as ethylene and propylene are important chemical raw materials. The traditional production method of ethylene and propylene is prepared by cracking light oil. Compared with the scarce oil resources, my country has abundant coal resources and natural gas resources. From coal and natural gas we can get cheap synthesis gas to make methanol or dimethyl ether. Using silicon phosphorus aluminum (SAPO-34) molecular sieves to produce light olefins from methanol or dimethyl ether is a promising alternative route for petroleum to olefins.

U.S. Patent No. 4,440,871 discloses a method for preparing silicon-phosphorus-aluminum molecular sieves by using tetraethylammonium hydroxide as a template, but the template used is expensive and not practical.

Chinese patent CN1037334C adopts triethylamine as template to prepare the method for silicon phosphorus aluminum (SAPO-34) molecular sieve. The particle size of the molecular sieve produced by this method is about 10 microns, and the silicon phosphorus aluminum (SAPO-34) molecular sieve can be prepared cheaply. In Chinese patent CN1467155A, a method for synthesizing silicon phosphorus aluminum (SAPO-34) molecular sieves is disclosed by using triethylamine and fluoride as composite templates.

The production of light olefins from methanol or dimethyl ether generally uses a fluidized bed reactor. The silicon phosphorus aluminum (SAPO-34) molecular sieve catalyst produced in the above three methods cannot be fluidized because of its small particle size, so it cannot be directly used in a fluidized bed reactor. It is necessary to use a binder, and use a spray granulation method to make a microsphere catalyst that can be used in a fluidized bed.

Contents of the invention

The invention provides a method for preparing a coated silicon-phosphorus-aluminum molecular sieve that can be directly used in a fluidized bed.

In order to solve the above-mentioned technical problems, the technical scheme for realizing the preparation method of the covered silicon-phosphorus-aluminum molecular sieve is as follows: use silica sol as the silicon source, phosphoric acid as the phosphorus source, pseudo-boehmite as the aluminum source, and use the nitrogen-containing compound triethyl Amine is used as a template, and small balls with a diameter of 20-200 microns such as silicon oxide, aluminum oxide, titanium oxide or magnesium oxide are used as a carrier, and then weighed according to the following weight ratio: Al ₂ O ₃ is 0.8-5; P ₂ O ₅ 0.2~8 for _SiO2 ; 0.5~7 for SiO2; 1~10 for triethylamine, add 20~30 of water, 15~40 of carrier pellets, mix evenly, stir, crystallize, dry, and then sieve the obtained The original powder is impregnated and roasted by the binder to prepare the covered silicon phosphorus aluminum molecular sieve; the specific process is as follows:

1) According to the above ratio, take phosphoric acid, pseudoboehmite, silica sol, triethylamine and carrier pellets, add water, and carry out a mixed reaction for 0.5 to 8 hours;

2) Transfer to a closed reaction kettle for crystallization reaction at 180-200°C for 12-72 hours;

3) filtering the crystallized product, washing the solid product and drying at 110° C. to obtain the molecular sieve powder;

4) The prepared molecular sieve raw powder is immersed in the binder at a weight ratio of 1:10 to 100 for 5 to 30 minutes;

5) Calcining the raw molecular sieve powder impregnated in the binder at 500-650° C. for 3-6 hours to obtain a coated silicon-phosphorus-aluminum molecular sieve.

The adhesive is silica sol or aluminum sol.

The beneficial effect of the invention is that it overcomes the process that the molecular sieve raw powder generated in the past must use a binder to carry out spray granulation. Silicon phosphorus aluminum (SAPO-34) molecular sieves can be prepared cheaply. The particle size of the molecular sieve produced by the present invention is within the size range required by the fluidized bed, and can be directly used in the fluidized bed, eliminating the need for spray granulation and other production links, shortening the process, and saving production. cost, the synthesized molecular sieve catalyst can be used in the reaction of methanol or dimethyl ether cracking to produce light olefins.

Detailed ways

The invention provides a method for preparing a coated silicon-phosphorus-aluminum molecular sieve that can be directly used in a fluidized bed. In this method, silica sol is used as silicon source, phosphoric acid is used as phosphorus source, pseudoboehmite is used as aluminum source, nitrogen-containing compound triethylamine is used as template, and silicon oxide, aluminum oxide, titanium oxide or magnesium oxide with a diameter of 20 - 200 micron pellets as carrier. Then weigh according to the following weight ratio: Al ₂ O ₃ is 0.8-5; P ₂ O ₅ is 0.2-8; SiO ₂ is 0.5-7; triethylamine is 1-10, add 20-30 40 carrier pellets, uniformly mixed and stirred, crystallized, dried, impregnated, and roasted to obtain a covered silicon-phosphorus-aluminum molecular sieve; the specific process is as follows:

1) According to the above ratio, take phosphoric acid, pseudoboehmite, silica sol, triethylamine and carrier pellets, add water, and carry out a mixed reaction for 0.5 to 8 hours;

2) Transfer to a closed reaction kettle for crystallization reaction at 180-200°C for 12-72 hours;

3) filtering the crystallized product, washing the solid product, and drying at 110° C. to obtain a molecular sieve powder;

4) The prepared molecular sieve powder and the binder are immersed in the binder silica sol or aluminum sol for 5 to 30 minutes at a weight ratio of 1:10 to 100;

5) Calcining the raw molecular sieve powder impregnated in the binder at 500-650° C. for 3-6 hours to obtain a coated silicon-phosphorus-aluminum molecular sieve.

The invention is now further illustrated by examples.

Example 1

Preparation of molecular sieve catalyst a (conventional method synthesis)

4.5 grams of pseudo-boehmite are mixed evenly with 10 grams of deionized water, add 15g of phosphoric acid with a concentration of 85% by weight and dilute with 15g of water, add 4 grams of silica sol with a concentration of 20% by weight after stirring, add pure 8 g of triethylamine and 10 g of deionized water were stirred at room temperature for 3 hours; the mixed solution was transferred into a closed reactor lined with polytetrafluoroethylene, and crystallized at 200 ° C for 40 hours; the product was pumped After filtering and washing, dry at 110°C for 6 hours, and bake the dried product at 600°C for 4 hours to remove the template agent and obtain the original molecular sieve SAPO-34 powder. Mix SAPO-34 raw powder and silica sol at a ratio of 1:4 (dry basis weight of silica sol), and spray dry to obtain microspherical molecular sieve catalyst a with an average particle size of 75 microns.

Example 2

Preparation of Covered Silicon-Phosphorus-Aluminum Molecular Sieve

15g of microspherical α particles were ultrasonically cleaned for 10min, then soaked in concentrated nitric acid for 10 hours, filtered, washed and dried, and used as a carrier for later use; 5g of deionized water was added to 2.25g of pseudoboehmite and stirred, then added 16g of phosphoric acid with a concentration of 40% by weight and 4g of silica sol with a concentration of 20% by weight were stirred evenly, and 4g of pure triethylamine was added to continue stirring. Mix the treated alumina pellets or silicon oxide with 20 g of water and add to the above reaction solution, transfer the mixed solution into the reactor of Example 1, turn the reactor over at a low speed, and conduct the crystallization reaction at 200° C. for 12 hours. The product was suction filtered, washed, and dried at 110°C for 6 hours. Immerse the obtained powder in 10% silica sol for 20 minutes, suction filter, dry the powder, and calcinate at 600° C. for 4 hours to obtain a coated molecular sieve b.

Example 3

Preparation of Covered Silicon-Phosphorus-Aluminum Molecular Sieve

15g of microspherical α particles were ultrasonically cleaned for 10min, then soaked in concentrated nitric acid for 10 hours, filtered, washed, dried, and used as a carrier for later use; 5g of deionized water was added to 3.50g of pseudoboehmite and stirred, and then 20g of Phosphoric acid with a concentration of 40% by weight and 20g of silica sol with a concentration of 20% by weight are stirred evenly, and 4g of pure triethylamine is added to continue stirring, and the processed magnesium oxide or titanium oxide pellets are mixed with 30g of water and added to the above reaction solution, the mixed solution was transferred to the reactor of Example 1, and the reactor was turned over at a low speed, and the crystallization reaction was carried out at 180° C. for 48 hours. The product was filtered by suction, washed, and dried at 110° C. for 6 hours. Immerse the obtained powder in 10% silica sol for 10 minutes, filter with suction, dry the powder, and bake at 600° C. for 4 hours to obtain a coated molecular sieve c.

Example 4

Catalytic Performance Evaluation of Molecular Sieves

Component analysis of molecular sieves determined by x-ray fluorescence: as shown in Table 1

Table 1

Substance Al ₂ O 3 P ₂ O ₅ SiO ₂ example 1 0.805 0.111 0.083 Example 2 0.835 0.131 0.033 Example 3 0.845 0.225 0.853

A fixed bed reaction device is adopted, and the reactor is a quartz glass tube, and the molecular sieve catalyst a, molecular sieve b and molecular sieve c prepared in Examples 1 to 3 are used. 20 mg of molecular sieves were loaded into the reactor, and the temperature was raised to 500° C. in a nitrogen atmosphere with a flow rate of 30 ml/min and kept at a constant temperature for 1 hour for activation. Pure dimethyl ether enters the reactor in pulses as a raw material, each pulse is 0.5ml, and the weight space velocity of dimethyl ether is WHSV=172h ^-1 . The conversions of the reactions and product distributions of hydrocarbon products in the products are listed in Tables 2 and 3 below.

Table 2

  Molecular sieve catalyst a Molecular sieve b Molecular sieve c Conversion rate 0.98 0.98 0.99

Table 3 Distribution of hydrocarbon products, (carbon-based)

CH ₄ C ₂ H ₆ C ₂ H ₄ C ₃ H ₈ C ₃ H ₆ C ₄ H ₁₀ C ₄ H ₈ C ₅ Molecular sieve catalyst a 0.029 0.008 0.519 0.032 0.317 0.002 0.046 0.047 Molecular sieve b 0.049 0.012 0.484 0.028 0.317 0.011 0.043 0.056 Molecular sieve c 0.039 0.002 0.501 0.028 0.325 0.007 0.045 0.053

Claims (2)

1. the preparation method of a load type silicon phoshporus aluminium molecular sieve, it is characterized in that: be the silicon source with the Ludox, phosphoric acid is the phosphorus source, boehmite is the aluminium source, the employing triethylamine is a template, the employing diameter is that bead silica, aluminium oxide, titanium oxide or the magnesia of 20-200 micron is carrier, takes by weighing by following part by weight then: Al ₂O ₃Be 0.8～5; P ₂O ₅Be 0.2～8; SiO ₂Be 0.5～7; Triethylamine is 1～10, adds 20～30 water, 15～40 carrier beads, and evenly mixing, stirring, crystallization, drying obtain molecular screen primary powder, and then, molecular screen primary powder makes molecular sieve after bonding agent dipping, roasting; Concrete technology is as follows:

1) by said ratio, takes Ludox, phosphoric acid, boehmite, triethylamine and carrier beads, add entry, carried out hybrid reaction 0.5～8 hour;

2) carry out in the immigration closed reactor, under 180～200 ℃, carried out crystallization 12～72 hours;

3) crystallization product is filtered, solid product is washed, carries out drying under 110 ℃, obtain molecular screen primary powder;

4) molecular screen primary powder that makes flooded in bonding agent 5～30 minutes with weight ratio 1: 10～100;

5) will be in bonding agent impregnated molecular screen primary powder, 500～650 ℃ of following roastings 3～6 hours, obtain load type silicon phoshporus aluminium molecular sieve.

2. according to the preparation method of the described load type silicon phoshporus aluminium molecular sieve of claim 1, it is characterized in that: described bonding agent is Ludox or aluminium colloidal sol.