CN103041850B - A kind of extrusion forming method of high-strength TS-1 titanium-silicon molecular sieve catalyst - Google Patents

Abstract

The present invention provides a method for extrusion molding of high-strength TS-1 titanium silicon molecular sieve catalyst, which is characterized in that TS-1 raw powder, silica sol, extrusion aid, activated carbon fiber and boric acid are kneaded into a wet plastic body in proportion; then dried and calcined to obtain an extruded TS-1 catalyst. The activated carbon fiber introduced in the molding forms a diffusion channel that runs through the entire particle after calcination, which improves the heat transfer and mass transfer efficiency, avoids secondary side reactions and catalyst deactivation caused by product retention, and prevents catalyst particles from sintering due to unfavorable heat dissipation. At the same time, the boric acid introduced in the molding process improves the mechanical strength of the molded catalyst after calcination, which can effectively resist the impact generated during transportation, loading and use and the wear caused by fluid flow, which is beneficial to prolonging the service life of the catalyst.

Description

A kind of extrusion forming method of high-strength TS-1 titanium-silicon molecular sieve catalyst

technical field

The invention belongs to the technical field of petrochemical catalysts, and relates to a molding method of a high-strength titanium-silicon molecular sieve catalyst.

Background technique

Titanium silicalite-1 is a new heteroatom molecular sieve with MFI structure developed in the early 1980s, referred to as TS-1. TS-1 molecular sieve has great application potential in the field of selective oxidation. The following patents and publications describe applications of TS-1:

Such as CN1376151A(2000-08-08), CN1314348A(2001-03-30), CN1387948A(2002-02-05), CN1534030A(2003-03-28), CN1651405A(2004-11-04), CN1769277A(2005- 11-14), CN1810772A(2006-01-24), CN101172970A(2007-10-12), Acta Catalysis, 25(2004)49-54; Molecular Catalysis, 19(2005)7-11; Acta Petroleum Sinica (Petroleum Processing ), 22(2006) 72-77; Applied catalysis A: General, 246(2003) 69-77; Journal of molecular catalysis A: chemical, 210(2004) 171-178; Journal of molecular catalysis A: chemical, 229(2005 ) 71-75; Chemical engineering journal, 116 (2006) 179-186; Journal of catalysis, 253 (2008) 148-158, etc.

The forming process of TS-1 molecular sieve is an important part of its application. Due to the special requirements of TS-1 molecular sieve for selective oxidation, the molding process of TS-1 molecular sieve is different from that of silica-alumina molecular sieve, and special molding technology needs to be developed. The following patents and publications describe the preparation of TS-1 shaped catalysts:

Patent CN 1419475 (application number 01807020.5 application date 2001-03-21) discloses a method for preparing titanosilicate molded body. Its technical feature is to firstly form a moldable composition of titanosilicate, binder and a paste-forming agent to form a raw molded body, which is dried and calcined under different conditions to form the desired molded body.

Patent CN 1346705 (application number 01140509.0 application date 2001-09-13) discloses a method for preparing a composite catalyst. Its technical feature is that the catalyst is composed of 2.0-95.0wt% MFI structure titanium-silicon molecular sieve and 5.0-98.0wt% inorganic oxide. Titanium-silicon molecular sieves are prepared by formulating silicon source, titanium source, template agent, alkali and distilled water in a certain molar ratio, mixing them, and hydrothermal crystallization. The inorganic oxides are selected from TiO ₂ , SiO ₂ , ZrO ₂ , Al ₂ O ₃ , Na ₂ O, K ₂ O, CaO, PbO or their complexes or mixtures. Composite catalyst with spherical or irregular particles made by extrusion or spray molding.

Patent CN 1398674 (application number 02126775.8 application date 2002-07-25) discloses a composite titanium silicon catalyst and its in-situ forming preparation method. Its technical feature is that it is composed of 1.0-80.0% (weight) of MFI structure titanium-silicon molecular sieve (TS-1) and 20.0-99.0% (weight) of inorganic oxides. The composite titanium-silicon catalyst adopts the preparation method of in-situ forming, that is, the inorganic oxide is introduced into the titanium-silicon molecular sieve hydrothermal synthesis system composed of silicon source, titanium source, template agent, alkali and distilled water, so that the titanium-silicon molecular sieve is oxidized in the inorganic grow in situ. The obtained composite titanium-silicon catalyst is spherical or irregular particles and can be directly used in a fixed bed, a moving bed or a catalytic rectification reaction device.

Patent CN 1600428 (application number 03126438.7 application date 2003-09-28) discloses a preparation method of a molecular sieve catalyst containing MFI structure. The method is to combine MFI structural molecular sieves with alkaline silica gel at pH 8-10, use ammonia water or tetraethylammonium hydroxide as a gelling agent, and astragalus powder as an auxiliary agent to extrude or press into tablets, and dry, 500-650 Baking at ℃ for 4-24 hours. The crushing strength of the prepared catalyst can meet the requirements of the fixed-bed process, and the catalyst has good regeneration performance and can meet the requirements of industrial use.

Patent CN 1554483 (application number 200310120868.7 application date 2003-12-27) discloses a composite titanium silicon catalyst and its preparation method. Its technical feature is that it is prepared by in-situ forming method, and the graphite powder is introduced into the titanium-silicon molecular sieve hydrothermal synthesis system composed of silicon source, titanium source, template agent, alkali and distilled water, so that the titanium-silicon molecular sieve grows in situ on the graphite powder , and then the composite material is separated from the mother liquor, dried and roasted.

Patent CN 101371989 (application number 200710120615.8 application date 2007-08-22) discloses a titanium silicon molecular sieve catalyst and its preparation method and application. Its technical feature is that the titanium-silicon molecular sieve with MFI structure is mixed with nano-alumina, aluminum sol, pore-forming agent and auxiliary agent, and the catalyst with high mechanical strength is prepared by extruding.

Patent CN 101264453 (application number 200810034431.4 application date 2008-03-10) discloses a titanium silicon molecular sieve/diatomite composite catalyst and its preparation method. Its technical feature is that titanium-silicon molecular sieves (such as TS-1, TS-2, etc.) sex. Said preparation method is to carry out acid solution and alkali solution treatment to diatomite, to carry out high-temperature heat treatment on it to make it have specific chemical properties; Oxide (such as lanthanum, nickel, etc.) for chemical modification.

Patent CN 101890376A (application number 200910206227.0 application date 2009-10-18) discloses a method for preparing a titanium-silicon composite oxide carrier. Its technical feature is that the titanium hydroxide-silicon hydroxide gel prepared by the supersolubilization micelle method is used as the raw material. Since the gel contains surfactants and hydrocarbon components, after molding and roasting, the polymerized hydrogen The nano titanium oxide and silicon oxide particles formed after dehydration of titanium oxide and silicon hydroxide still have a rod-shaped basic structure, and a frame structure carrier with disordered stacking is obtained. The carrier has large pore volume, large pore diameter, high porosity, large pores on the outer surface, and good pore penetration, especially for macromolecules. Active, it is beneficial to increase the deposition of impurities and prolong the operation period of the catalyst.

Patent CN 102049304A (application number 200910188161.7 application date 2009-10-27) discloses a titanium silicon molecular sieve and resin composite catalyst and its preparation method. Its technical feature is to fully mix titanium-silicon molecular sieve powder, polymerized monomer for resin preparation and pore-forming agent, and then carry out polymerization reaction in the presence of initiator, break the obtained block solid catalyst, and then add it to halogen After being swelled in a hydrocarbon, solvent extraction was used to obtain a shaped catalyst. The pore-forming agent is one or more of gasoline, C ₅ ~C ₁₃ normal alkanes, and C ₄ ~C ₁₂ fatty alcohols, and the initiator is benzoyl peroxide/or azobisisobutanol . The obtained catalyst solves the problem that the titanium-silicon catalyst powder and the reaction liquid are difficult to separate, and improves the reaction efficiency.

Patent CN 102049305A (application number 200910188162.1 application date 2009-10-27) discloses a method for preparing a titanium-silicon molecular sieve catalyst. Its technical feature is that the titanium-silicon molecular sieve powder, polymerized monomer styrene, polymerized monomer polyene compound and pore-forming agent are fully mixed, and then polymerized in the presence of an initiator, and the obtained block solid catalyst is Crushed, then added to halogenated hydrocarbons to swell, and then extracted with a solvent to obtain a shaped titanium-silicon molecular sieve catalyst. The pore-forming agent is one or more of gasoline, C ₅ ~C ₁₃ normal alkanes, and C ₄ ~C ₁₂ fatty alcohols, and the initiator is benzoyl peroxide/or azobisisobutanol . The obtained catalyst solves the problem that the titanium-silicon catalyst powder and the reaction liquid are difficult to separate, and improves the reaction efficiency.

Patent CN 102259023A (application number 201010184391.9 application date 2010-05-27) discloses a method for forming a titanium-silicon molecular sieve catalyst. Its technical feature is to mix and knead titanium-silicon molecular sieve powder with MFI topological structure, aluminum hydroxide powder, aluminum sol, porogen, extrusion aid and water to obtain a formable plastic body, which is extruded by extruder The moldable product is obtained as a wet strip-shaped body, dried and calcined to obtain a strip-shaped catalyst. The aluminum oxide is derived from aluminum hydroxide powder and aluminum sol, and the lateral crushing strength is 70-150 N/cm. The porogen is alkylphenol polyoxyethylene ether, and the extruding aid is one or more of safflower powder, starch and citric acid.

Patent CN 101935064A (application number 201010275332.2 application date 2010-09-07) discloses a method for synthesizing an easily formed ordered mesoporous titanium silicon material. Its technical feature is to use newly synthesized mesoporous silica as the silicon source, and use post-grafting technology to introduce organic or inorganic titanium sources into the mesoporous silica system under the condition of water or ethanol as the solvent. After ultrasonication, drying, Volatilize, and then use roasting to remove the surfactant, and then prepare a mesoporous titanium-silicon material that is easy to form, has a high degree of order, a large specific surface area, a large pore size, a large pore volume, a high titanium content, and an adjustable silicon-to-titanium ratio.

Patent CN 102441429A (application number 201010511564.3 application date 2010-10-11) discloses a molding method of titanium silicon molecular sieve. Its technical feature is that the mixture of titanium-silicon molecular sieve, amorphous silicon dioxide, alkaline earth metal oxide and water is formed to obtain a molded body, and the molded body is dried and calcined.

Patent CN 102451763A (application number 201010522141.1 application date 2010-10-15) discloses a titanium-silicon molecular sieve composite catalyst and a preparation method thereof. Its technical feature is to fully mix titanium-silicon molecular sieve, acidic molecular sieve, polymerized monomer polyene compound and pore-forming agent, and then carry out polymerization reaction in the presence of initiator, break the obtained block solid catalyst, and then add it to After swelling in halogenated hydrocarbon, it is activated by solvent extraction to obtain a formed titanium-silicon molecular sieve composite catalyst. The pore-forming agent is one or more of gasoline, C ₅ ~C ₁₃ normal alkanes, and C ₄ ~C ₁₂ fatty alcohols, and the initiator is benzoyl peroxide/or azobisisobutanol . The catalyst obtained in the invention can realize the one-step reaction of olefin epoxidation and hydration to prepare the corresponding diol compound, and can also solve the problem that the titanium silicon catalyst powder and the reaction liquid are difficult to separate, and improve the reaction efficiency.

Patent CN 102091651A (application number 201010597078.8 application date 2010-12-10) discloses a method for TS-1 extrusion molding. Its technical features are: uniformly mix TS-1 powder with squash powder, silica sol, and liquid paraffin, knead, extrude, dry and roast, excessively impregnate nickel or cobalt salt solution, dry roast, and excessively impregnate molybdenum or tungsten salt Solution, dry and roast.

Patent CN 102614911A (application number 201210042471.X application date 2012-02-23) discloses a one-time molding method of titanium-silicon molecular sieve. Its technical feature is that after hydrothermally synthesized titanium-silicon molecular sieves are crystallized, separation, washing, and roasting are omitted, but matrix materials, adhesives, peptizers, polyethylene glycol or safflower powder are directly added to form The pore-enlarging agent is subjected to spray molding after beating, and the formed microspheres are then roasted to remove the template agent, and then large particles of shaped titanium-silicon molecular sieve particles are obtained.

At the same time, in the existing TS-1 molding method, after introducing the above-mentioned pore-forming agent, the mechanical strength of the shaped catalyst is reduced, and it is more likely to be worn or broken during use.

Contents of the invention

The invention provides a extrusion forming method of a high-strength TS-titanium silicate molecular sieve catalyst. The method is to introduce activated carbon fibers of appropriate length and an appropriate amount of boric acid during the extruding process, the activated carbon fibers are calcined and removed to form a diffusion channel through the entire particle, and the boric acid is calcined to form boron oxides to enhance the mechanical strength of the molded catalyst. Technical scheme of the present invention is as follows:

In the first step, the TS-1 titanium-silicon molecular sieve raw powder and activated carbon fiber were stirred in a mixer for 5-300 minutes, and then silica sol, extrusion aid and strength aid were added to knead into a wet plastic body, kneaded for 5 -300min to obtain a molded plastic body that can be extruded.

Wherein said silica sol is alkaline silica sol with aluminum content lower than 1000ppm, and its SiO ₂ mass percentage is 20-40%, preferably 25-35%. The mass percent of silica sol (calculated as SiO ₂ ) in the wet plastomer after kneading is 5-30%, preferably 10-25%.

Said activated carbon fiber can be artificial activated carbon fiber or natural fiber, artificial activated carbon fiber adopts viscose base, phenolic base, polyacrylonitrile base, pitch base activated carbon fiber, polyvinylidene chloride, polyimide fiber, polystyrene Fiber, polyvinyl alcohol fiber, lignin fiber or a mixture of several. The mass percentage of activated carbon fiber in the wet plastic body after kneading is 0.5-20%, preferably 1-10%. Activated carbon fiber length ranges from 0.5-10mm, preferably 1-5mm

Said strength aid is boric acid, and its addition accounts for 0.1-15% of the mass percent of the wet plastic body after kneading, preferably 0.2-10%.

Said extrusion aid is selected from one or more of liquid paraffin, glycerin, starch and polycarboxylic acid. The mass percentage of the extrusion aid in the wet plastomer after kneading is 0.2-15%, preferably 0.5-10%.

In the second step, extrude the prepared above-mentioned wet shaped plastic body in an extruder at a suitable speed to obtain a wet strip-shaped shaped catalyst in a desired shape. In addition, according to the difference in the size of the orifice plate, a shaped catalyst with a diameter of 0.5-10mm can be prepared, and the diameter is preferably 1-6mm. catalyst. The extrusion length is preferably 1-600mm, which is convenient for drying and roasting.

The third step is to dry the wet molded catalyst obtained in the second step in the air not exceeding 80°C for 1-48h, preferably 5-35h; then dry the catalyst in the air at 100-200°C for 1-24h, It is preferably dried in air at 100-150°C for 1-12h.

In the fourth step, the dried shaped catalyst obtained in the third step is calcined at 200-800°C for 5-48h, preferably at 350-700°C for 6-24h; the heating rate from room temperature to the set calcining temperature is 10 -100°C/min, the calcination atmosphere is a temperature-programmed calcination in a nitrogen atmosphere containing oxygen, and the extruded catalyst is obtained.

The oxygen content of said oxygen-containing nitrogen gas is 0.2-21%; said temperature-programmed roasting temperature is 200-800°C, preferably 350-600°C; said heating rate is 10-100°C/hour, preferably 20- 50°C/hour.

The beneficial effect of the present invention is that, by introducing activated carbon fibers of appropriate length and appropriate amount of boric acid in the molding process, the calcined molded catalyst has a relatively large channel through the entire particle, and has strong mechanical strength at the same time. On the one hand, it can improve the mass transfer and heat transfer efficiency in the catalytic oxidation process, avoid secondary side reactions and catalyst deactivation caused by product retention, and prevent catalyst particles from sintering due to unfavorable heat dissipation; Shock during filling and use, as well as abrasion caused by fluid flow, help prolong catalyst life.

Detailed ways

The following examples will further illustrate the present invention, but do not limit the present invention. The mechanical strength of the shaped catalyst was tested by ZQJ-Ⅱ intelligent particle strength testing machine.

Comparative Example 1

According to the method disclosed in the literature Catalysis Today 74 (2002) 65-75, the micron TS-1 molecular sieve powder was synthesized, the silicon-titanium ratio was 33, and the grain size was 6 μm×2 μm×1 μm.

The micron TS-1 powder is fully mixed with 3% citric acid and 10% polyacrylonitrile-based activated carbon fibers with a fiber length of 3mm in the mass percentage of the wet plastomer after kneading, and then the accounted for molding catalyst (Dry basis) Silica sol solution with a mass fraction of 25% (SiO ₂ content is 30%) is fully stirred and kneaded to obtain a plastic molding; use an all-stainless steel kneading extruder to extrude into wet strips through a Φ1.5mm orifice plate Shaped solid cylinders were baked in an oven at 40°C for 10 hours, and then heated to 120°C for 5 hours, then heated at a rate of 2°C/min to 550°C, and then calcined at 550°C for 12 hours to obtain cylindrical strip-shaped catalyst sample A. .

Comparative Example 2

Nano TS-1 molecular sieve powder was synthesized according to the method disclosed in the literature "Acta Catalytica Sinica" (2001, 22(6):513~514), the silicon-titanium ratio was 41, and the grain size was 0.2 μm.

Repeat Comparative Example 1, but replace the micron TS-1 molecular sieve powder with nanometer TS-1 molecular sieve powder to obtain shaped catalyst sample B.

Example 1

The mass percent of the micron TS-1 powder and the wet plastomer after kneading is respectively 3% citric acid, 5% polyacrylonitrile-based activated carbon fibers with a fiber length of 3 mm and 0.2% boric acid. After kneading, the mass percentage of the wet plastic body is 25% of the silica sol solution (SiO ₂ content is 30%), which is fully stirred and kneaded to obtain a plastic molding; use a full stainless steel kneading extruder to extrude through a Φ1.5mm orifice plate into a wet The elongated solid cylinder was baked in an oven at 40°C for 10h, then heated at a rate of 2°C/min to 550°C, and fired at 550°C for 12h to obtain a cylindrical strip-shaped catalyst sample C, whose mechanical strength was comparable to that of An increase of 80.5% compared to sample A.

Example 2

Repeat Example 1, but replace the micron TS-1 molecular sieve powder with nanometer TS-1 molecular sieve powder to obtain shaped catalyst sample D, whose mechanical strength is increased by 82.4% compared with sample B.

Example 3

Repeat Example 1, but change the addition of boric acid to 5% and 10%, and then obtain samples E and F, and their mechanical strengths are respectively increased by 101.4% and 120.1% compared with sample A.

Example 4

Repeat Example 1, but the length of the acrylonitrile-based activated carbon fiber is changed to 1mm, 5mm, the addition remains constant, and samples G and H are obtained successively, and the mechanical strength of the obtained sample is all equivalent to the C sample.

Example 5

Repeat embodiment 1, but change polypropylene-based activated carbon fiber into viscose base, phenolic base, pitch-based activated carbon fiber, and with polyvinylidene chloride, polyimide fiber, polystyrene fiber, polyvinyl alcohol fiber, For lignin fibers and natural fibers, the addition amount and fiber length remained unchanged, consistent with Example 1, and shaped catalyst samples were sequentially obtained, and the mechanical strength of the obtained samples was equivalent to that of the C sample.

Example 6

Repeat Example 1, but replace the silica sol wherein the _SiO2 content is 10% and 15%, respectively, the proportion remains unchanged, and the shaped catalyst samples are obtained successively, and the mechanical strength of the obtained samples is equivalent to that of the C sample.

Example 7

Repeat embodiment 1, but change according to the add-on of acrylonitrile-based activated carbon fiber into 1%, 3% and 6%, add-on remains constant, obtain sample successively, the mechanical strength of gained sample increases respectively 123.8%, 123.8%, 80.9% and 30.6%.

Example 8

Repeat Example 1, but change the addition of citric acid to 3%, 7% and 9% respectively, and obtain shaped catalyst samples successively, and the mechanical strength of the obtained samples is all equivalent to the C sample.

Example 9

Repeat Example 1, but the extruding aid wherein is changed into glycerol, liquid paraffin and starch, and the addition amount remains unchanged, and the molded catalyst samples are obtained successively, and the mechanical strength of the obtained samples is all equivalent to the C sample.

Example 10

Repeat Example 1, but change the drying temperature to 50°C, 65°C, and 80°C, and change the further heating temperature to 100°C and 150°C at each drying temperature, and the drying time remains unchanged, and the shaped catalyst samples are sequentially obtained , the mechanical strength of the obtained samples is equivalent to that of the C sample.

Example 11

Repeat Example 1, but change the calcination temperature to 450°C, 500°C and 600°C, and change the ascending heating rate to 20°C/hour, 30°C/hour and 40°C/hour at each calcination temperature respectively, sequentially A shaped catalyst product is obtained, the mechanical strength of which is comparable to product C.

Claims (4)

1. A method for extruding a high-strength TS-1 titanium-silicon molecular sieve catalyst, characterized in that it comprises the steps: In the first step, the TS-1 titanium-silicon molecular sieve raw powder and activated carbon fiber were stirred in a mixer for 5-300 minutes, and then silica sol, extrusion aid and strength aid were added to knead into a wet plastic body, kneaded for 5 -300min obtains the molding plastomer for extruding; Wherein said silica sol is the alkaline silica sol that aluminum content is lower than 1000ppm, and its SiO _The mass percentage composition is at _20-40 %; The mass percent of the wet plastomer after kneading is 5-30%; The mass percentage of activated carbon fiber in the wet plastic body after kneading is 0.5-20%, and the length of activated carbon fiber is 0.5-10 mm; The strength aid is boric acid, and its addition accounts for 0.1-15% of the mass percent of the wet plastic body after kneading; The extrusion aid is selected from one or more of liquid paraffin, glycerin, starch and polycarboxylic acid, and the extrusion aid accounts for 0.2-15% by mass of the wet plastic after kneading; In the second step, the prepared above-mentioned shaped plastic body is extruded at a suitable speed in an extruder to obtain a wet strip-shaped shaped catalyst of the desired shape; The third step is to dry the wet shaped catalyst obtained in the second step in the air not exceeding 80°C for 1-48h; then dry the catalyst in the air at 100-200°C for 1-24h; In the fourth step, the dried shaped catalyst obtained in the third step is calcined at 200-800°C for 5-48h; In a nitrogen atmosphere, the temperature is programmed to rise and roasted, and the extruded catalyst is obtained by processing; The oxygen content of the oxygen-containing nitrogen gas is 0.2-21%, the temperature-programmed calcination temperature is 200-800°C, and the heating rate is 10-100°C/hour. 2. The extruded molding method according to claim 1, characterized in that, the activated carbon fiber is artificial activated carbon fiber or natural fiber, and the artificial activated carbon fiber is viscose base, phenolic base, polyacrylonitrile base, pitch base activated carbon Fiber, polyvinylidene chloride, polyimide fiber, polystyrene fiber, polyvinyl alcohol fiber or a mixture of several. 3. The extrusion forming method according to claim 1 or 2, characterized in that, the length of the activated carbon fiber is in the range of 1-5 mm. 4. The extrusion molding method according to claim 1 or 2, characterized in that, the silica sol is one or a mixture of white carbon black, solid silica gel, and precipitated silica spheres.