阅读说明：本技术 一种提高钛硅分子筛ts-1机械强度的方法 (Method for improving mechanical strength of titanium silicalite TS-1 ) 是由 王向宇 高鑫 温贻强 王妍妍 杨许可 刘杨青 张利岗 高子豪 刘�东 于 2020-10-19 设计创作，主要内容包括：本发明涉及一种提高钛硅分子筛TS-1机械强度的方法,具体为：将硅源、模板剂和水先混合成A溶液,钛酸丁酯和强助剂混合成B溶液,将B溶液缓慢倒入到A溶液混合均匀得到C溶液,加热晶化后,经过抽滤洗涤,烘干,焙烧得到原粉TS-1；在原粉TS-1中加入粘合剂、助挤剂、水混合,捏合,挤条成型后,经过烘干焙烧,得到成型的TS-1。挤条成型的催化剂的机械强度大大提升,并且在丙烯环氧化和氯丙烯环氧化中活性也有所提升。(The invention relates to a method for improving the mechanical strength of a titanium silicalite TS-1, which comprises the following steps: mixing a silicon source, a template agent and water into a solution A, mixing butyl titanate and a strong assistant into a solution B, slowly pouring the solution B into the solution A, uniformly mixing to obtain a solution C, heating for crystallization, performing suction filtration, washing, drying and roasting to obtain raw powder TS-1; adding adhesive, extrusion aid and water into the raw powder TS-1, mixing, kneading, extruding into strips, drying and roasting to obtain the formed TS-1. The mechanical strength of the extruded catalyst is greatly improved, and the activity of the extruded catalyst in propylene epoxidation and chloropropene epoxidation is also improved.)

1. A method for improving the mechanical strength of a titanium silicalite TS-1 is characterized by comprising the following steps: mixing a silicon source, a template agent and water into a solution A, mixing butyl titanate and a strong assistant into a solution B, slowly pouring the solution B into the solution A, uniformly mixing to obtain a solution C, heating for crystallization, performing suction filtration, washing, drying and roasting to obtain raw powder TS-1; adding adhesive, extrusion aid and water into the raw powder TS-1, mixing, kneading, extruding into strips, drying and roasting to obtain the formed TS-1.

2. The method for improving the mechanical strength of the titanium silicalite TS-1 as claimed in claim 1, wherein the silicon source and the template in the solution A are n-butyl silicate and 25% tetrapropyl ammonium bromide; or silica sol or white carbon black and tetrapropylammonium bromide.

3. The method for improving the mechanical strength of the titanium silicalite TS-1 as claimed in claim 1, wherein the strong promoter is an alkaline reagent containing one or more of alkali metals, alkaline earth metals and organic bases of Na or K.

4. The method for improving the mechanical strength of the titanium silicalite TS-1 as claimed in claim 3, wherein the strong assistant is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate and sodium acetate.

5. The method for improving the mechanical strength of the titanium silicalite TS-1 as claimed in claim 1, wherein the molar ratio of the materials in the preparation process is silicon source, titanium source, template agent, strong assistant and water =1:0.01-0.1:0.01-0.2:0.005-0.05: 1-20.

6. The method as claimed in claim 1, wherein the temperature of the solution C is 150 ℃ to 200 ℃ and the crystallization time is 32-72 h.

7. The method of claim 1, wherein the crystallized solution C is filtered, washed, dried, and calcined to obtain raw powder TS-1, wherein the washing is performed at pH =7-8, the drying temperature is 80-120 ℃, the drying time is 4-10h, the calcining temperature is 550-720 ℃, and the calcining time is 6-10 h.

8. The method for improving the mechanical strength of the titanium silicalite TS-1 as claimed in claim 1, wherein the prepared raw powder TS-1, the adhesive, the extrusion aid and the water are mixed and kneaded according to the mass ratio of 1:0.1-0.4:0.02-0.08:0.2-0.4, the kneading time is 1-5h, wherein the adhesive is one or two of silica sol and white carbon black, and the extrusion aid is one or more of soluble starch, corn starch, sesbania powder and polyvinyl alcohol.

9. The method for improving the mechanical strength of the titanium silicalite TS-1 as claimed in claim 1, wherein the kneaded sample is extruded by a twin-screw extruder, and the diameter of the extruded strip is 1.0mm-5 mm.

10. The method as claimed in claim 1, wherein the drying at 60-100 ℃ for 10-20h is performed after extrusion molding, and then the calcination at 600-800 ℃ for 6-10h is performed.

Technical Field

The invention belongs to the technical field of catalyst preparation, and particularly relates to a method for improving the mechanical strength of a titanium silicalite TS-1.

Background

The titanium-silicon molecular sieve is applied to propylene epoxidation and chloropropene epoxidation reactions, and has the outstanding advantages of mild reaction conditions, good atom economy, no pollution to the environment and the like. Only products and water are generated after the reaction, the product yield is high, the process flow is simple, clean and pollution-free, and the method is an internationally recognized environment-friendly production technology. At present, domestic propylene oxide and epichlorohydrin are mainly produced by a fixed bed reactor, and when TS-1 is used for the fixed bed reactor, in order to meet the requirements of the fixed bed on the particle size and the strength of the catalyst, a molded catalyst with a proper shape and good mechanical strength is required to be prepared, and higher catalytic activity and selectivity are kept as far as possible.

US patent 6699812 reports a process for the preparation of an extruded bar-shaped titanium silicalite molecular sieve catalyst and its use in the epoxidation of 3-chloropropene with hydrogen peroxide. The preparation method comprises the steps of mixing the TS-1 titanium silicalite molecular sieve, the adhesive polymethylsiloxane, the plasticizer methylcellulose, the pore-forming agent melamine and the paste forming water into paste, extruding the paste by a strip extruder to obtain strip-shaped formed bodies, drying and roasting the strip-shaped formed bodies to obtain the formed catalyst, and carrying out epoxidation reaction of 3-chloropropene and hydrogen peroxide in a fixed bed loop reactor, wherein the conversion rate of the hydrogen peroxide is only 89%.

In chinese patent CN101371989 (petrochemical science and research institute of china petrochemical corporation), TS-1 powder, nano alumina, alumina sol, pore-forming agent (alkylphenol polyoxyethylene) and extrusion aid (one or a mixture of sesbania powder, starch, polyethylene and polyethylene oxide) are mixed, and the molded SHTS catalyst is prepared through extrusion, granulation, drying, roasting and other steps. When the catalyst is used for catalyzing the reaction of 3-chloropropene and hydrogen peroxide on a fixed bed, the conversion rate of the hydrogen peroxide and the selectivity of epichlorohydrin are high, but the mechanical strength of the catalyst can not meet the requirement of industrial application.

Chinese patent CN200710120615.8 discloses a method for preparing an extruded bar-shaped titanium silicalite molecular sieve catalyst and application thereof in epoxidation reaction of 3-chloropropene and hydrogen peroxide. Mixing TS-1 titanium silicalite molecular sieve, nano alumina, alumina sol, pore-forming agent, extrusion aid and water to obtain a formable object, extruding the formable object by a strip extruder to obtain a wet strip-shaped formed body, drying and roasting the extruded strip-shaped formed body to obtain a formed catalyst, and carrying out epoxidation reaction of 3-chloropropene and hydrogen peroxide in a fixed bed reactor to obtain 99.2% of hydrogen peroxide conversion rate and 96.9% of epoxy chloropropane selectivity, but the mechanical strength of the catalyst is only 20-30N/cm, which is difficult to meet the requirements of an industrial fixed bed reactor.

The above techniques all adopt adding various substances after the molecular sieve raw powder to enhance the extrusion molding strength of the catalyst, and do not improve from the raw powder level.

Disclosure of Invention

The invention aims to provide a method for improving the mechanical strength of a titanium silicalite TS-1, which is characterized in that a strong auxiliary agent is added in the process of preparing raw powder, and after simple adhesive, extrusion aid and water are added into the prepared raw powder, the mechanical strength of the extruded catalyst is greatly improved, and the activity is also improved in propylene epoxidation and chloropropene epoxidation.

In order to achieve the purpose, the invention adopts the technical scheme that:

a method for improving the mechanical strength of a titanium silicalite TS-1 specifically comprises the following steps: mixing a silicon source, a template agent and water into a solution A, mixing butyl titanate and a strong assistant into a solution B, slowly pouring the solution B into the solution A, uniformly mixing to obtain a solution C, heating for crystallization, performing suction filtration, washing, drying and roasting to obtain raw powder TS-1; adding adhesive, extrusion aid and water into the raw powder TS-1, mixing, kneading, extruding into strips, drying and roasting to obtain the formed TS-1.

Further, the silicon source and the template agent in the solution A are n-butyl silicate and 25% tetrapropyl ammonium bromide; or silica sol or white carbon black and tetrapropylammonium bromide.

Further, the strong auxiliary agent is an alkaline reagent and contains one or more of alkali metal, alkaline earth metal and organic alkali of Na or K. Furthermore, the strong auxiliary agent is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate and sodium acetate.

Furthermore, in the preparation process, the molar ratio of the silicon source to the titanium source to the template agent to the strong assistant to the water is 1:0.01-0.1:0.01-0.2:0.005-0.05: 1-20. Furthermore, the molar ratio of the silicon source to the titanium source is 1:0.015-0.05, and the molar ratio of the silicon source to the strong assistant is 1: 0.01-0.04.

Further, the temperature of the heating crystallization C solution is 150-. Furthermore, the temperature of the heating crystallization C solution is 170 ℃, and the crystallization time is 48 h.

Further, filtering, washing, drying and roasting the crystallized solution C to obtain raw powder TS-1, wherein the washing is carried out until the pH value is 7-8, the drying temperature is 80-120 ℃, the drying time is 4-10h, the roasting temperature is 550-720 ℃, and the roasting time is 6-10 h. Furthermore, the drying temperature is 80-100 ℃, the drying time is 6-8h, the roasting temperature is 550-.

Further, mixing and kneading the prepared raw powder TS-1, adhesive, extrusion aid and water according to the mass ratio of 1:0.1-0.4:0.02-0.08:0.2-0.4 for 1-5h, wherein the adhesive is one or two of silica sol and white carbon black, and the extrusion aid is one or more of soluble starch, corn starch, sesbania powder and polyvinyl alcohol. Furthermore, the mass ratio of the raw powder TS-1 to the adhesive is 1: 0.25-0.4. Further, the kneading time is 2 to 3 hours.

Further, extruding the kneaded sample through a double-screw extruder, wherein the diameter of the extruded strip is 1.0mm-5 mm.

Further, drying for 10-20h at 60-100 ℃ after extrusion molding. Furthermore, the extruded strips are dried for 12 to 15 hours at the temperature of between 60 and 80 ℃.

Further, the extruded strip is roasted for 6-10h at the temperature of 600-800 ℃. Furthermore, the extruded strip is roasted for 6-8h at the temperature of 600-720 ℃.

The molded catalyst prepared by the method is applied to propylene epoxidation and chloropropene epoxidation reactions. And cutting the calcined catalyst sample into 1-3mm strips for strength test, and evaluating the synthesis reaction activity of the epoxypropane and the epoxychloropropane.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention advantageously selects alkaline reagents such as sodium carbonate, sodium acetate and the like, and the alkaline reagents are added in the process of preparing the raw powder, so that the preparation steps are reduced, the process of improving the strength after the catalyst is formed is omitted, the strength of the formed catalyst is obviously improved, and the activity and the service life are also improved.

2. The preparation method is simple and rapid, can fundamentally enhance the strength of the formed catalyst, and can meet the requirements of industrial fixed bed reactors.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is an XRD pattern of raw powders of example 1 and example 6 of the present invention; wherein a represents example 1, b represents example 6;

FIG. 2 is an SEM image of raw powder of example 1 of the present invention;

FIG. 3 is an SEM image of raw powder of example 6 of the present invention.

Detailed Description

The present invention will be described in further detail with reference to examples.

Comparative example 1

Uniformly mixing 500g of tetraethoxysilane, 480g of 25 wt% TPAOH and 480g of water, removing alcohol and replenishing water for 3 hours at 70 ℃ to form a transparent solution A, slowly adding 23.33g of butyl titanate into the solution A to form a transparent light yellow solution C, putting the solution C into a high-pressure kettle, crystallizing at 170 ℃ for 48 hours, taking out and filtering, washing until the pH value is 7, putting into a 100 ℃ oven for drying for 6 hours, and roasting at 550 ℃ in a muffle furnace for 6 hours to obtain the raw powder. Taking 100g of prepared raw powder, adding 1.5g of sesbania powder, adding 83.33g of 30 wt% silica sol and 20g of water, uniformly mixing, kneading by a kneader for 1h, extruding into strips with the pore diameter of 1.5mm, putting the extruded samples into an oven at 80 ℃ for drying for 12h, cutting into short strips with the diameter of 2-3mm after drying, and putting into a muffle furnace for roasting at 650 ℃ for 6h to obtain molded samples.

Comparative example 2

480g of 30 wt% silica sol, 157.12g of tetrapropylammonium bromide and 504g of water are uniformly mixed to form a semitransparent solution A, 23.33g of butyl titanate is slowly added into the solution A to form a semitransparent light yellow solution C, the solution C is put into a high-pressure kettle to be crystallized at 170 ℃ for 48 hours, then is taken out to be filtered, is washed until the pH value is 7, is put into a 100 ℃ oven to be dried for 6 hours, and is roasted at 550 ℃ in a muffle furnace for 6 hours, so that the preparation of the raw powder is completed. Taking 100g of prepared raw powder, adding 1.5g of sesbania powder, adding 83.33g of 30 wt% silica sol and 20g of water, uniformly mixing, kneading by a kneader for 1h, extruding into strips with the pore diameter of 1.5mm, putting the extruded samples into an oven at 80 ℃ for drying for 12h, cutting into short strips with the diameter of 2-3mm after drying, and putting into a muffle furnace for roasting at 650 ℃ for 6h to obtain molded samples.

Example 1

The basic procedure is as in comparative example 1, except that 0.96g of sodium carbonate is first dissolved in 23.33g of butyl titanate to form a B solution.

Curve a in FIG. 1 is the XRD characterization result of the TS-1 molecular sieve of example 1, and from XRD, the product has a typical MFI type zeolite molecular sieve structure and has high crystallinity.

Example 2

The basic procedure is as in example 1, except that 0.96g of sodium carbonate is replaced by 1.968g of sodium acetate.

Example 3

The basic procedure is as in example 1, except that 0.96g of sodium carbonate is replaced by 1.92g of sodium carbonate.

Example 4

The basic procedure is as in example 1, except that 1.5g of sesbania powder is replaced by 1.5g of corn starch.

Example 5

The basic procedure was the same as in example 1 except that the molded article obtained in example 1 was baked at 720 ℃ for 6 hours in a muffle furnace.

Example 6

The basic procedure is as in comparative example 2, except that 0.636g of sodium carbonate is first dissolved in 23.33g of butyl titanate to form a B solution.

Curve b in FIG. 1 is the XRD characterization result of the TS-1 molecular sieve of example 6, from which it can be seen that the product has a typical MFI type zeolite molecular sieve structure and has a high crystallinity.

Example 7

The basic procedure is as in example 6, except that 0.636g of sodium carbonate is replaced by 3.18g of sodium carbonate.

The strength of the molded samples fired in the comparative examples and examples was measured, and the radial strength was measured in accordance with HG/T2782-2011.

The continuous reaction test of propylene epoxidation is carried out on the molded samples calcined in the comparative example and the embodiment, the reactor is made of stainless steel and has a two-layer sleeve type design, the outer layer is connected with a constant-temperature water bath device to control the reaction temperature of propylene epoxidation, the inner layer is filled with quartz sand with 40-60 meshes and a catalyst formed by extrusion strips (two ends are quartz sand particles and the middle is the catalyst formed by extrusion strips), the concentration of the catalyst is 0.183g/L, the molar ratio of propylene to hydrogen peroxide is 2.1, the reaction temperature is 42 ℃, the residence time is 10-30 min, and the reaction pressure is 2.5-2.7 MPa. The reaction mixture (methanol and hydrogen peroxide and appropriate amount of ammonia) had a pH of 9.10 and propylene was added via HPLC chromatography pumps, the propylene feed pump requiring a condensing unit for propylene liquefaction. During the reaction, samples were taken at regular intervals, and the reaction products were analyzed by gas chromatography and conventional iodometry. And recording the average conversion rate of the hydrogen peroxide conversion rate of over 99 percent and the service time of the catalyst.

X_H2O2，Y_PO，S_PO，U_H2O2Respectively the conversion rate of hydrogen peroxide, the yield of propylene oxide, the selectivity of propylene oxide and the effective utilization rate of hydrogen peroxide;and n_H2O2The amount of the substance entering the fixed bed hydrogen peroxide and the amount of the substance of the effluent hydrogen peroxide, n_PO，n_PGE，n_PGIs the amount of propylene oxide, propylene glycol monomethyl ether and propylene glycol species in the product. Calculated by the following equation.

Table 1 shows the strength and catalytic propylene epoxidation activity of the formed TS-1 of the comparative examples and examples.

As can be seen from the results in Table 1, the measured values of the intensities in the examples are far higher than those in the comparative example, and meanwhile, the conversion rate of hydrogen peroxide in a fixed bed propylene epoxidation reactor is high, the yield of propylene oxide is high, and the one-way service life of the catalyst is also remarkably prolonged.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.