A composite lithium phosphate catalyst, its preparation method and application, and a method for preparing allyl alcohol

Abstract

The present invention relates to the field of catalytic technology, and provides a composite lithium phosphate catalyst, a preparation method and application thereof, and a method for preparing allyl alcohol. The composite lithium phosphate catalyst provided by the present invention comprises a silica carrier, lithium phosphate crystals loaded in the silica carrier, and copper oxide doped in the lithium phosphate crystals. By adding a carrier and tetraethyl orthosilicate during the crystallization process of lithium phosphate in the present invention, the specific surface area and roughness of the catalyst can be increased, and the catalytic activity can be improved; by introducing copper oxide, the anti-coking performance of the catalyst can be improved, and the service life can be prolonged. By purging the catalyst slurry before the reaction in the present invention, the generation of n-propanol can be effectively reduced, and the selectivity of the reaction can be improved. The results of the examples show that when allyl alcohol is prepared by the method of the present invention, the selectivity can reach more than 95%, and the service life of the catalyst exceeds 600 h.

Description

Technical Field

[0001] The present invention relates to the field of catalytic technology, and in particular to a composite lithium phosphate catalyst, a preparation method and application thereof, and a method for preparing allyl alcohol. Background Art

[0002] Allyl alcohol, also known as propenol and garlic alcohol, is an important fine chemical intermediate. Due to the presence of two functional groups, double bond and hydroxyl group, in its molecular structure, its chemical properties are very active and it can participate in chemical reactions such as oxidation, reduction, esterification, etherification, and addition. Allyl alcohol and its derivatives, as basic chemical raw materials, can be used to synthesize many important downstream products and have very wide applications in pharmaceuticals, fragrances, and other organic syntheses.

[0003] Currently, there are many methods for preparing allyl alcohol. Among them, the isomerization of propylene oxide is a simple process with the advantages of high atom economy, high yield, no corrosion, and no three wastes. However, this method has two obvious problems: First, the selectivity of the reaction is relatively low. When propylene oxide is isomerized to allyl alcohol, a part of propionaldehyde, acetone, and n-propanol will be produced. The boiling point of n-propanol (97.2 °C) is less than 1 °C different from that of allyl alcohol (96.9 °C), making the post-treatment difficult. Second, during the isomerization process, due to factors such as carbon deposition poisoning and different physical and chemical conditions, the activity of the catalyst is easily reduced with the increase of the use time, resulting in catalyst deactivation. For example, in the related technology for preparing allyl alcohol by the liquid phase method, the catalyst used is fine powder lithium phosphate, which is dissolved in a high boiling point solvent and the reaction temperature is about 280 °C. The selectivity of this method is less than 90%, the loss of the high boiling point solvent and the catalyst is very serious, and the single-pass life of the catalyst is less than 200 h.

[0004] In summary, how to improve the selectivity of propylene oxide isomerization and the service life of the catalyst is an urgent problem to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides a composite lithium phosphate catalyst, a preparation method and application thereof, and a method for preparing allyl alcohol. The composite lithium phosphate catalyst prepared by the present invention has high catalytic activity and long service life. When it is applied to the isomerization of propylene oxide to prepare allyl alcohol, it can improve the selectivity of the reaction and realize the large-scale continuous production of allyl alcohol.

[0006] In order to achieve the above invention object, the present invention provides the following technical solutions:

[0007] A preparation method of a composite lithium phosphate catalyst, comprising the following steps:

[0008] Mix an aqueous phosphoric acid solution with a catalyst support to obtain a phosphoric acid - support mixture solution; the catalyst support is silica; the mass of the catalyst support is 1.1 - 1.5 times the mass of phosphoric acid in the aqueous phosphoric acid solution;

[0009] Mix a lithium hydroxide solution with lithium phosphate seeds to obtain a lithium hydroxide - seeds mixture solution;

[0010] Mix the lithium hydroxide - seeds mixture solution, tetraethyl orthosilicate alcohol solution, copper oxide, and the phosphoric acid - support mixture solution for crystallization to obtain a crystallization solution; age the crystallization solution to obtain a catalyst precursor; the temperature of the crystallization is 60 - 80 °C, and the final pH value is 12 - 12.5;

[0011] Dry the catalyst precursor and then calcine it to obtain a composite lithium phosphate catalyst.

[0012] Preferably, the concentration of the aqueous phosphoric acid solution is 40 - 50 wt%; the mass of the catalyst support is 1.1 - 1.5 times the mass of phosphoric acid in the aqueous phosphoric acid solution; the average particle size of the lithium phosphate seeds is 0.4 - 0.8 μm.

[0013] Preferably, the concentration of the lithium hydroxide solution is 5 - 12.4 wt%; the molar ratio of lithium hydroxide in the lithium hydroxide solution to phosphoric acid in the aqueous phosphoric acid solution is 3 - 3.5:1;

[0014] The dosage ratio of lithium hydroxide in the lithium hydroxide solution to lithium phosphate seeds is (3 - 3.5) mol:(0.2 - 5) g;

[0015] The concentration of the tetraethyl orthosilicate alcohol solution is 10 - 30 wt%, and the molar ratio of tetraethyl orthosilicate in the tetraethyl orthosilicate alcohol solution to phosphoric acid in the aqueous phosphoric acid solution is 0.01 - 0.1:1;

[0016] The particle size of the copper oxide is 5 - 10 μm, and the mass ratio of copper oxide to phosphoric acid in the aqueous phosphoric acid solution is 0.1 - 0.5:1.

[0017] Preferably, the crystallization includes: at 60 - 80 °C, simultaneously drop the tetraethyl orthosilicate alcohol solution and a part of the lithium hydroxide - seeds mixture solution into the phosphoric acid - support mixture solution, after dropping, mix with copper oxide, and then continue to drop the remaining part of the lithium hydroxide - seeds mixture solution. When the pH value of the system reaches 12 - 12.5, stop dropping.

[0018] Preferably, the temperature of the aging is 60 - 80 °C, and the time is 0.5 - 1.5 h; the temperature of the drying is 70 - 110 °C, and the time is 1 - 2 h; the temperature of the calcination is 250 - 380 °C, and the time is 0.5 - 4 h.

[0019] The present invention also provides a composite lithium phosphate catalyst prepared by the preparation method described in the above solution, which includes a silica carrier, lithium phosphate crystals loaded in the silica carrier, and copper oxide doped in the lithium phosphate crystals.

[0020] The present invention also provides the application of the composite lithium phosphate catalyst described in the above solution in the isomerization of propylene oxide to prepare allyl alcohol.

[0021] The present invention also provides a method for the isomerization of propylene oxide to prepare allyl alcohol, which includes the following steps:

[0022] Mix the composite lithium phosphate catalyst described in the above solution with a dispersion medium to obtain a catalyst slurry;

[0023] Purge the catalyst slurry with an inert gas, and then jointly introduce propylene oxide vapor and the inert gas into the catalyst slurry for isomerization reaction to obtain allyl alcohol.

[0024] Preferably, the device used for the isomerization reaction is a slurry bed reactor;

[0025] The propylene oxide vapor is obtained by vaporizing propylene oxide liquid, and the dosage of the propylene oxide liquid is 121.2 - 206.4 g / h / L catalyst slurry;

[0026] The dispersion medium is an inert liquid; the mass ratio of the composite lithium phosphate catalyst to the dispersion medium is 1:1 - 10;

[0027] The temperature of the catalyst slurry during purging is 230 - 280 °C; the temperature of the isomerization reaction is 230 - 280 °C;

[0028] During purging, the per-minute introduction amount of the inert gas is 8 - 13 times the volume of the catalyst slurry;

[0029] During the isomerization reaction, the per-minute introduction amount of the inert gas is 1.5 - 2.5 times the volume of the catalyst slurry.

[0030] The present invention provides a method for preparing a composite lithium phosphate catalyst, comprising the following steps: mixing an aqueous phosphoric acid solution and a catalyst support to obtain a phosphoric acid-support mixed solution; the catalyst support is silica; the mass of the catalyst support is 1.1 to 1.5 times the mass of phosphoric acid in the aqueous phosphoric acid solution; mixing a lithium hydroxide solution and lithium phosphate seeds to obtain a lithium hydroxide-seed mixed solution; mixing the lithium hydroxide-seed mixed solution, tetraethyl orthosilicate alcohol solution, copper oxide and the phosphoric acid-support mixed solution for crystallization to obtain a reaction solution; aging the reaction solution to obtain a catalyst precursor; the temperature of the crystallization reaction is 60 to 80 °C, and the end point pH value is 12 to 12.5; calcining the catalyst precursor to obtain a composite lithium phosphate catalyst. In the process of lithium phosphate crystallization in the present invention, a support is added to guide nucleation, making the catalyst particles finer and the specific surface area larger, thereby improving the catalytic activity; in the process of lithium phosphate crystallization in the present invention, tetraethyl orthosilicate is added, and tetraethyl orthosilicate hydrolyzes to produce small particles of silica, which can make the catalyst morphology rougher, and the remaining tetraethyl orthosilicate decomposes during calcination, which can play a role in secondary pore formation, further increasing the specific surface area of the catalyst and improving the catalytic activity; copper oxide is introduced into the composite lithium phosphate catalyst in the present invention, which can improve the anti-coking performance of the catalyst and extend the service life.

[0031] The present invention also provides a method for preparing allyl alcohol by isomerization of propylene oxide, comprising the following steps: mixing the composite lithium phosphate catalyst described in the above scheme and a dispersion medium to obtain a catalyst slurry; purging the catalyst slurry with an inert gas, and then co-introducing propylene oxide and an inert gas into the catalyst slurry for isomerization reaction to obtain allyl alcohol. In the present invention, the catalyst slurry is purged before the isomerization reaction to remove residual crystal water, thereby effectively reducing the formation of n-propanol and improving the selectivity of the reaction; further, the present invention uses a slurry bed reactor for the isomerization reaction of propylene oxide, and the residence time of the raw materials is short, which can reduce the side reaction of allyl alcohol generating n-propanol, thereby improving the selectivity. The results of the examples show that when using the method of the present invention to prepare allyl alcohol, the selectivity can reach more than 95%, the conversion rate of n-propanol reaches more than 50%, and the service life of the catalyst exceeds 600 h. Detailed embodiments

[0032] The present invention provides a method for preparing a composite lithium phosphate catalyst, comprising the following steps:

[0033] Mixing an aqueous phosphoric acid solution and a catalyst support to obtain a phosphoric acid-support mixed solution; the catalyst support is silica; the mass of the catalyst support is 1.1 to 1.5 times the mass of phosphoric acid in the aqueous phosphoric acid solution;

[0034] Mixing a lithium hydroxide solution and lithium phosphate seeds to obtain a lithium hydroxide-seed mixed solution;

[0035] Mix the lithium hydroxide-seed mixture solution, tetraethyl orthosilicate alcohol solution, copper oxide, and phosphoric acid-carrier mixture solution for crystallization to obtain a reaction solution; age the reaction solution to obtain a catalyst precursor; the temperature of the crystallization is 60-80°C, and the final pH value is 12-12.5;

[0036] Dry the catalyst precursor and then calcine it to obtain a composite lithium phosphate catalyst.

[0037] In the present invention, an aqueous phosphoric acid solution and a catalyst carrier are mixed to obtain a phosphoric acid-carrier mixture solution. In the present invention, the catalyst carrier is silica, preferably white carbon black; the concentration of the aqueous phosphoric acid solution is preferably 40-50 wt%, more preferably 45.5 wt%; the mass of the catalyst carrier is 1.1-1.5 times the mass of phosphoric acid in the aqueous phosphoric acid solution, preferably 1.184-1.549 times, and further preferably 1.2 times.

[0038] In the present invention, a lithium hydroxide solution and lithium phosphate seeds are mixed to obtain a lithium hydroxide-seed mixture solution. In the present invention, the concentration of the lithium hydroxide solution is preferably 5-12.4 wt%; the solvent of the lithium hydroxide solution is preferably water; in a specific embodiment of the present invention, preferably add lithium hydroxide to water and heat to 80°C to completely dissolve lithium hydroxide; the lithium hydroxide is preferably lithium hydroxide monohydrate; the molar ratio of lithium hydroxide in the lithium hydroxide solution to phosphoric acid in the aqueous phosphoric acid solution is preferably 3-3.5:1, more preferably 3.2:1; in the present invention, the average particle size of the lithium phosphate seeds is preferably 0.4-0.8 μm, more preferably 0.52 μm; the dosage ratio of lithium hydroxide in the lithium hydroxide solution to lithium phosphate seeds is preferably (3-3.5) mol:(0.2-5) g, more preferably 3.2 mol:1 g.

[0039] In the present invention, the preparation method of the lithium phosphate seeds preferably includes: stirring and mixing a dilute lithium hydroxide solution and a phosphoric acid alcohol solution to precipitate lithium phosphate seeds; the concentration of the dilute lithium hydroxide solution is preferably 0.15 mol / L, and the solvent of the dilute lithium hydroxide solution is preferably water; the concentration of the phosphoric acid alcohol solution is preferably 0.1 mol / L; the solvent of the phosphoric acid alcohol solution is preferably ethanol; the molar ratio of lithium hydroxide in the dilute lithium hydroxide solution to phosphoric acid in the phosphoric acid alcohol solution is preferably 14-16:1, more preferably 15:1; the temperature of the stirring and mixing is preferably 60-80°C, and the time is preferably 15 min; in a specific embodiment of the present invention, preferably heat the dilute lithium hydroxide solution to 60-80°C first, and then quickly add the phosphoric acid alcohol solution for stirring. After precipitating the lithium phosphate seeds, the present invention preferably filters the obtained slurry by suction and dries the obtained solid product to obtain the lithium phosphate seeds; the drying temperature is preferably 90°C.

[0040] After obtaining the lithium hydroxide-seed mixture solution and the phosphoric acid-carrier mixture solution, the present invention mixes the lithium hydroxide-seed mixture solution, the tetraethyl orthosilicate alcohol solution, copper oxide, and the phosphoric acid-carrier mixture solution for crystallization to obtain a reaction solution. In the present invention, the concentration of the tetraethyl orthosilicate alcohol solution is preferably 10-30 wt%, more preferably 15-25 wt%; the solvent of the tetraethyl orthosilicate alcohol solution is preferably ethanol; the molar ratio of tetraethyl orthosilicate in the tetraethyl orthosilicate alcohol solution to phosphoric acid in the phosphoric acid aqueous solution is preferably 0.01-0.1:1, specifically 0.01:1, 0.03:1, 0.05:1 or 0.1:1; the copper oxide is specifically copper oxide powder, the particle size of the copper oxide is preferably 5-10 μm, and the purity of the copper oxide is preferably above 99%; the mass ratio of the copper oxide to phosphoric acid in the phosphoric acid aqueous solution is 0.1-0.5:1, specifically 0.2:1, 0.25:1, 0.3:1 or 0.5:1.

[0041] In the present invention, the temperature of the crystallization is preferably 60-80 °C, and the end point pH value is preferably 12-12.5, specifically 12 or 12.5, more preferably 12. By controlling the temperature and pH value of the crystallization, the present invention can control the precipitation rate of lithium phosphate crystals, not only making the precipitation of lithium phosphate more complete, but also reducing the deposition of lithium phosphate on the surface of large crystals, and obtaining lithium phosphate crystals with more uniform morphology.

[0042] In the present invention, the crystallization preferably includes: at 60-80 °C, simultaneously dripping the tetraethyl orthosilicate alcohol solution and a part of the lithium hydroxide-seed mixture solution into the phosphoric acid-carrier mixture solution, after the dripping is completed, mixing with copper oxide, and then continuing to drip the remaining part of the lithium hydroxide-seed mixture solution. When the pH value of the system reaches 12-12.5, stop dripping; in the present invention, the time for simultaneously dripping the tetraethyl orthosilicate alcohol solution and a part of the lithium hydroxide-seed mixture solution is preferably 0.5-3 h, specifically 1 h, 2 h or 3 h; the volume of the part of the lithium hydroxide-seed mixture solution is preferably 93-95% of the total volume of the lithium hydroxide-seed mixture solution, more preferably 93.75%; when simultaneously dripping the tetraethyl orthosilicate alcohol solution and a part of the lithium hydroxide-seed mixture solution, adding copper oxide, and dripping the remaining part of the lithium hydroxide-seed mixture solution, it is all preferably carried out under stirring conditions; the present invention first drips a part of the lithium hydroxide-seed mixture solution, and then continues to drip after adding copper oxide, which can make the copper oxide evenly doped in the lithium phosphate crystals.

[0043] After the pH value reaches the requirement, the addition of the lithium hydroxide-seed mixture solution is stopped, and then the obtained reaction solution is aged. The temperature of the aging is preferably 60-80°C, the time is preferably 0.5-1.5 h, more preferably 1 h, and the aging is preferably carried out under stirring conditions. After the aging is completed, it is preferred to filter the obtained slurry, and the obtained solid is the catalyst precursor.

[0044] After obtaining the catalyst precursor, in the present invention, the catalyst precursor is dried and then calcined to obtain the composite lithium phosphate catalyst. In the present invention, the temperature of the drying is preferably 70-110°C, specifically it can be 90°C or 100°C, the time of the drying is preferably 1-2 h, more preferably 1.5 h. After the drying, it is preferred to grind the dried material and then carry out the calcination. The temperature of the calcination is preferably 250-380°C, specifically it can be 300°C, 330°C or 350°C, the time of the calcination is preferably 0.5-4 h, specifically it can be 2 h, 3 h or 4 h. During the calcination process, the residual solvent in the catalyst is removed, and at the same time, the incompletely decomposed tetraethyl orthosilicate is further hydrolyzed and condensed, realizing the function of secondary pore formation of tetraethyl orthosilicate on the surface of the catalyst, and improving the specific surface area of the catalyst. After the calcination is completed, in the present invention, it is preferred to screen the obtained calcined material to obtain a product with a particle size of less than 50 μm, which is the composite lithium phosphate catalyst of the present invention. The product with a particle size greater than 50 μm is preferably ground until the particle size meets the requirements. The mesh number of the sieve used for the screening is preferably 300 mesh.

[0045] The present invention also provides a composite lithium phosphate catalyst prepared by the preparation method described in the above scheme, including a silica carrier, lithium phosphate crystals loaded in the silica carrier, and copper oxide doped in the lithium phosphate crystals. In the present invention, the particle size of the composite lithium phosphate catalyst is preferably less than 50 μm, the specific surface area is preferably 135-162 m 2 / g, the lithium phosphate content is preferably 38-50 wt%, preferably 45-50 wt%, and further preferably 48.5 wt%.

[0046] The present invention also provides the application of the composite lithium phosphate catalyst described in the above scheme in the isomerization of propylene oxide to prepare allyl alcohol.

[0047] The present invention also provides a method for preparing allyl alcohol by isomerization of propylene oxide, including the following steps:

[0048] Mix the composite lithium phosphate catalyst described in the above scheme with a dispersion medium to obtain a catalyst slurry;

[0049] Purge the catalyst slurry with an inert gas, and then co-feed propylene oxide vapor and an inert gas into the catalyst slurry for isomerization reaction to obtain allyl alcohol.

[0050] In the present invention, the apparatus used for the isomerization reaction is preferably a slurry bed reactor; a stirrer paddle is preferably provided in the slurry bed reactor, and the stirrer paddle preferably includes a stirring shaft and blades provided on the stirring shaft; an inlet for propylene oxide vapor is preferably provided at the bottom of the slurry bed reactor; in a specific embodiment of the present invention, an inert gas can be introduced into the slurry bed reactor from the same inlet as the propylene oxide vapor, or an additional inlet for the inert gas can be provided at the bottom of the slurry bed reactor; the apparatus used for the isomerization reaction preferably further includes a raw material tank, a vaporizer, a condensation device, and a storage tank; the raw material tank is used for storing liquid propylene oxide; the vaporizer is used for vaporizing the liquid propylene oxide; the condensation device is used for condensing the gaseous products generated by the isomerization reaction; the storage tank is used for storing the condensed products; the inlet for propylene oxide vapor of the slurry bed reactor is preferably connected to the vaporizer; the inlet of the vaporizer is preferably connected to the raw material tank; the gas outlet of the slurry bed reactor is preferably connected to the condensation device; the inlet of the storage tank is preferably communicated with the outlet of the condensation device.

[0051] In the present invention, the dispersion medium is preferably an inert liquid, specifically it can be therminol 55 heat transfer oil; the mass ratio of the composite lithium phosphate catalyst to the dispersion medium is preferably 1:1 to 10, specifically it can be 1:1, 1:3, 1:5, 1:6, 1:6.4, 1:7, or 1:10; in the present invention, the dispersion medium and the composite lithium phosphate catalyst are preferably added to the slurry bed reactor and stirred by the stirrer paddle in the slurry bed reactor to enable uniform distribution of the catalyst slurry.

[0052] In the present invention, the inert gas is preferably nitrogen or an inert gas, more preferably nitrogen; the temperature of the catalyst slurry during purging is preferably 230 to 280 °C, more preferably 250 °C; during purging, the amount of the inert gas introduced per minute is preferably 8 to 13 times the volume of the catalyst slurry, more preferably 10 times; the purging time is preferably 1 to 2 h, more preferably 1.5 h; in a specific embodiment of the present invention, it is preferably to first heat the catalyst slurry to the target temperature, and then introduce nitrogen from the bottom of the slurry bed reactor to purge the catalyst slurry; through high-temperature purging in the present invention, low-boiling components in the catalyst slurry can be removed, and crystal water can be removed, thereby reducing the formation of n-propanol and improving the selectivity of the reaction.

[0053] In the present invention, the temperature of the isomerization reaction is preferably 230-280 °C, more preferably 250 °C; in the isomerization reaction, the feeding rate of the inert gas per minute is preferably 1.5-2.5 times the volume of the catalyst slurry, more preferably 2 times; the propylene oxide vapor is obtained by vaporizing the propylene oxide liquid, and the dosage of the propylene oxide liquid is preferably 121.2-206.4 g / h / L of the catalyst slurry, more preferably 121.2-182.4 g / h / L of the catalyst slurry. In the specific embodiments of the present invention, preferably, the propylene oxide liquid in the raw material tank is introduced into the vaporizer to be vaporized into propylene oxide gas, and then together with the inert gas, it is bubbled into the catalyst slurry from the bottom of the slurry bed reactor; the feeding rate of the propylene oxide liquid is preferably controlled by a metering pump.

[0054] After the propylene oxide gas and the inert gas enter the catalyst slurry in the form of bubbles and react, the resulting gas product enters the condensation device from the gas outlet at the top of the slurry bed reactor for condensation, and the resulting condensate enters the storage tank for storage.

[0055] In the present invention, the composite lithium phosphate catalyst in the slurry bed reactor is suspended in the dispersion medium, and the propylene oxide gas is bubbled into the liquid for reaction. In specific implementation, an opening can be made on the side wall of the slurry bed reactor, and a pump is used to pump out the catalyst slurry and enter the regeneration device for activation and regeneration. At the same time, the activated catalyst slurry is continuously replenished into the reactor, so as to achieve large-scale continuous production. In the present invention, the method of activation and regeneration is preferably calcination activation or polar solvent immersion activation, and the activity of the catalyst is restored by removing carbon deposits through activation and regeneration; specifically, the calcination activation preferably includes: filtering the used catalyst slurry to obtain the catalyst solid, passing steam into the catalyst solid to remove carbon deposits, and then calcining under air conditions; the temperature of the steam is preferably 270 °C, and the temperature of the calcination is preferably 300-400 °C; the polar solvent immersion activation preferably includes: filtering the used catalyst slurry, immersing the obtained catalyst solid in a polar solvent, and then filtering out the catalyst for drying and roasting; the polar solvent used for the polar solvent immersion is preferably acetone, and the tar on the surface layer of the catalyst is dissolved by the polar solvent immersion; the temperature of the roasting is preferably 300-400 °C, and the roasting atmosphere is preferably air. The polar solvent immersion method causes less damage to the catalyst, and the present invention preferably uses the polar solvent immersion method to activate and regenerate the catalyst.

[0056] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0057] Example 1

[0058] 2.3 g of phosphoric acid with a concentration of 85 wt% (0.02 mol) was added to 200 g of ethanol and dissolved to obtain a phosphoric acid-ethanol solution for standby. In a flask, 12.6 g of lithium hydroxide monohydrate was added to 2 L of water and dissolved to obtain a dilute lithium hydroxide solution (0.15 mol / L); the dilute lithium hydroxide solution was heated to 60 °C, and the phosphoric acid-ethanol solution was quickly added to the flask. After stirring for 15 min, the turbid slurry was filtered by suction, and the filter cake was dried at 90 °C to obtain a white solid powder, which was the lithium phosphate seed crystal. Tested by an X-ray powder diffractometer (model RIGAKU Ultima IV), the average particle size of the lithium phosphate seed crystal was 0.52 μm.

[0059] 134.4 g of lithium hydroxide monohydrate (3.2 mol) was added to 544 mL of water and heated to 80 °C (saturated) for dissolution, then 1.0 g of lithium phosphate seed crystal was added and stirred evenly to obtain a lithium hydroxide-seed crystal mixed solution for standby. 10.4 g of tetraethyl orthosilicate was dissolved in 50 g of ethanol to obtain a tetraethyl orthosilicate-ethanol solution for standby.

[0060] 115.3 g of phosphoric acid with a concentration of 85 wt% (1 mol) was added to the reaction kettle, diluted with 100 g of water, and 116 g of white carbon black was added and quickly stirred evenly to obtain a phosphoric acid-carrier mixed solution. The prepared lithium hydroxide-seed crystal mixed solution was slowly and evenly added to the reaction kettle. During this period, the temperature of the reaction kettle was maintained at 80 °C by heating, and continuous stirring was carried out. 636 g of the lithium hydroxide-seed crystal mixed solution was added within 1 h. While dropping the lithium hydroxide-seed crystal mixed solution, the tetraethyl orthosilicate-ethanol solution was also slowly added, and the dropping rate was controlled to be completed within 1 h. Then 30 g of powdered copper oxide was added to the kettle, stirred, and the pH value of the solution in the kettle was detected with a pH meter. The lithium hydroxide-seed crystal mixed solution was continuously dropped until the pH value of the reaction solution in the kettle reached 12.0. Then the reaction solution was kept warm at 80 °C and continuously stirred for 1 h. The solid in the kettle was filtered out under pressure, and the solid was placed in an oven and dried at 100 °C for 1.5 h. The dried solid was transferred to a grinder and ground for 30 min, and then the solid was transferred to a muffle furnace and calcined at 330 °C for 2 h. The obtained solid product was sieved through a 300-mesh sieve to separate out particles with a particle size below 50 microns as the composite lithium phosphate catalyst of the present invention, and the remaining solid was returned to the grinder for further crushing. Elemental analysis of the obtained composite lithium phosphate catalyst was carried out using an inductively coupled plasma optical emission spectrometer (model Optima-7000 DV). The results showed that the lithium phosphate content was 48.5 wt%; measurement was carried out using a specific surface area and porosity analyzer (model Quadrasorb SI-MP). The results showed that the specific surface area of the composite lithium phosphate catalyst was 162 m 2 / g.

[0061] Example 2

[0062] The reaction device includes a raw material tank, a vaporizer, a slurry bed reactor, a condensation device and a storage tank. The slurry bed reactor is 0.5 m high and 4 cm in inner diameter, and is stirred by multiple groups of blades on the stirring shaft. An inlet for propylene oxide vapor is provided at the bottom of the slurry bed reactor, which is connected to the propylene oxide vaporizer, and the inlet of the vaporizer is connected to the raw material tank; a gas outlet is provided at the top of the slurry bed reactor, which is connected to the condensation device, and the outlet of the condensation device is connected to the storage tank.

[0063] Take 50 g of catalyst powder and mix it with 320 g (volume about 0.45 L) of the dispersing medium therminol 55 heat transfer oil, and load them into the slurry bed reactor. Start stirring to mix the catalyst solid and the heat transfer oil to obtain a catalyst slurry, and start heating to raise the temperature of the slurry to 250 °C. Nitrogen is introduced at a rate of 5 L / min for 90 min to activate the catalyst and remove the crystal water remaining in the catalyst. Reduce the nitrogen rate to 1 L / min, and feed liquid propylene oxide into the vaporizer at a rate of 1.01 g / min to be converted into propylene oxide vapor, and introduce it into the catalyst slurry through the feed port at the bottom of the kettle. The condensation device at the top of the reactor cools the reaction products and the remaining raw materials together and stores them in the storage tank. After the device runs for 10 min, the reaction proceeds stably. A small amount of condensate is taken from the condenser and analyzed by gas chromatography for the composition of the condensate material, which contains 47.9 wt% of propylene oxide, 49.7 wt% of allyl alcohol, 0.90 wt% of acetone, 1.29 wt% of propionaldehyde, and 0.21 wt% of n-propanol.

[0064] After the reactor runs continuously for 400 h, a small amount of condensate is taken again for gas chromatography analysis: it contains 48.3 wt% of propylene oxide, 49.3 wt% of allyl alcohol, 1.17 wt% of acetone, 1.03 wt% of propionaldehyde, and 0.20 wt% of n-propanol, and the catalyst activity does not decrease significantly.

[0065] After the reactor runs continuously for 600 h, a small amount of condensate is taken again for gas chromatography analysis: it contains 53.3 wt% of propylene oxide, 44.5 wt% of allyl alcohol, 0.88 wt% of acetone, 1.13 wt% of propionaldehyde, and 0.19 wt% of n-propanol, and the catalyst activity decreases slightly.

[0066] Example 3

[0067] According to the same scheme as in Example 1, only when adding the lithium hydroxide-seed mixture liquid, the pH of the reaction liquid is finally stabilized at 12.5. Other subsequent preparation conditions are the same as those in Example 1 to obtain a composite lithium phosphate catalyst. Sampling and testing show that the specific surface area of the catalyst is 144 m 2 / g. The isomerization reaction of propylene oxide was carried out using the composite lithium phosphate catalyst prepared in Example 3 according to the same scheme as in Example 2. After the reaction was stabilized, the material composition of the condensate was analyzed by gas chromatography.

[0068] Comparative Example 1

[0069] According to the same scheme as in Example 1, only when adding the lithium hydroxide-seed mixture solution, the pH of the reaction solution was finally stabilized at 13. Other subsequent preparation conditions were the same as those in Example 1, and a composite lithium phosphate catalyst was obtained. Sampling and testing showed that the specific surface area of the catalyst was 102 m 2 / g. The isomerization reaction of propylene oxide was carried out using the lithium phosphate catalyst prepared in Comparative Example 1 according to the same scheme as in Example 2. After the reaction was stabilized, the material composition of the condensate was analyzed by gas chromatography.

[0070] Example 4

[0071] According to the same scheme as in Example 1, when adding the lithium hydroxide-seed mixture solution, tetraethyl orthosilicate ethanol solution and copper oxide, the heating temperature was controlled at 70 °C; after dropping the lithium hydroxide solution, it was kept at 70 °C for 1 h. Other subsequent preparation conditions were the same as those in Example 1, and a composite lithium phosphate catalyst was obtained. Sampling and testing showed that the specific surface area of the catalyst was 144 m 2 / g. Sampling the catalyst for elemental analysis, the lithium phosphate content was 44.1 wt%. The isomerization reaction of propylene oxide was carried out using the lithium phosphate catalyst prepared in Example 4 according to the same scheme as in Example 2. After the reaction was stabilized, the material composition of the condensate was analyzed by gas chromatography.

[0072] Example 5

[0073] According to the same scheme as in Example 1, when adding the lithium hydroxide-seed mixture solution, tetraethyl orthosilicate ethanol solution and copper oxide, the heating temperature was controlled at 60 °C; after dropping the lithium hydroxide solution, it was kept at 60 °C for 1 h. Other preparation conditions were the same as those in Example 1, and a composite lithium phosphate catalyst was obtained. Sampling and testing showed that the specific surface area of the catalyst was 135 m 2 / g. Sampling the catalyst for elemental analysis, the lithium phosphate content was 42.6 wt%. The isomerization reaction of propylene oxide was carried out using the lithium phosphate catalyst prepared in Example 5 according to the same scheme as in Example 2. After the reaction was stabilized, the material composition of the condensate was analyzed by gas chromatography.

[0074] Comparative Example 2

[0075] According to the same scheme as in Example 1, when adding the lithium hydroxide-seed mixture solution, tetraethyl orthosilicate ethanol solution, and copper oxide, the heating temperature was controlled at 50 °C; after dropping the lithium hydroxide solution, it was kept warm at 50 °C for 1 h. Other subsequent preparation conditions were the same as those in Example 1, and a composite lithium phosphate catalyst was obtained. Sampling and testing showed that the specific surface area of the catalyst was 113 m 2 / g. Sampling the catalyst for elemental analysis, the lithium phosphate content was 38.4 wt%. According to the same scheme as in Example 2, the lithium phosphate catalyst prepared in Comparative Example 2 was used for the isomerization reaction of propylene oxide. After the reaction was stable, the material composition of the condensate was analyzed by gas chromatography.

[0076] Example 6

[0077] According to the same scheme as in Example 1, only the amount of silica white was changed to 143 g. Other subsequent preparation conditions were the same as those in Example 1, and a composite lithium phosphate catalyst was obtained. Sampling for elemental analysis, the lithium phosphate content was 38.7 wt%. According to the same scheme as in Example 2, the lithium phosphate catalyst prepared in Example 6 was used for the isomerization reaction of propylene oxide. After the reaction was stable, the material composition of the condensate was analyzed by gas chromatography.

[0078] Comparative Example 3

[0079] According to the same scheme as in Example 1, only the amount of silica white was changed to 190 g. Other subsequent preparation conditions were the same as those in Example 1, and a composite lithium phosphate catalyst was obtained. Sampling for elemental analysis, the lithium phosphate content was 21.2 wt%. According to the same scheme as in Example 2, the lithium phosphate catalyst prepared in Comparative Example 3 was used for the isomerization reaction of propylene oxide. After the reaction was stable, the material composition of the condensate was analyzed by gas chromatography.

[0080] Example 7

[0081] According to the same scheme as in Example 2, the composite lithium phosphate catalyst prepared in Example 1 was used for the isomerization experiment of propylene oxide. The metering valve was controlled to control the addition amount of propylene oxide at 1.52 g / min. Other subsequent reaction conditions were the same as those in Example 2. After the reaction was stable, the material composition of the condensate was analyzed by gas chromatography.

[0082] Example 8

[0083] According to the same scheme as in Example 2, the composite lithium phosphate catalyst prepared in Example 1 was used for the isomerization experiment of propylene oxide. The metering valve was controlled to control the addition amount of propylene oxide at 1.72 g / min. Other subsequent reaction conditions were the same as those in Example 2. After the reaction was stable, the material composition of the condensate was analyzed by gas chromatography.

[0084] Comparative Example 4

[0085] According to the same scheme as in Example 2, the isomerization experiment of propylene oxide was carried out using the composite lithium phosphate catalyst prepared in Example 1. The metering valve was controlled to control the addition amount of propylene oxide at 0.81 g / min, and other subsequent reaction conditions were the same as those in Example 2. After the reaction was stable, the material composition of the condensate was analyzed by gas chromatography.

[0086] Example 9

[0087] According to the same scheme as in Example 2, the isomerization experiment of propylene oxide was carried out using the composite lithium phosphate catalyst prepared in Example 1. Before the start of the reaction, the catalyst dosage was changed to 100 g, and the amount of heat transfer oil was 300 g. Other subsequent reaction conditions were the same as those in Example 2. After the reaction was stable, the material composition of the condensate was analyzed by gas chromatography.

[0088] Example 10

[0089] According to the same scheme as in Example 2, the isomerization experiment of propylene oxide was carried out using the composite lithium phosphate catalyst prepared in Example 1. Before the start of the reaction, the catalyst dosage was changed to 200 g, and the amount of heat transfer oil was 200 g. Other subsequent reaction conditions were the same as those in Example 2. After the reaction was stable, the material composition of the condensate was analyzed by gas chromatography.

[0090] Example 11

[0091] According to the same scheme as in Example 2, the isomerization experiment of propylene oxide was carried out using the composite lithium phosphate catalyst prepared in Example 1. Before the start of the reaction, the catalyst dosage was changed to 40 g, and the amount of heat transfer oil was 400 g. Other subsequent reaction conditions were the same as those in Example 2. After the reaction was stable, the material composition of the condensate was analyzed by gas chromatography.

[0092] The variable summaries of each example are shown in Table 1:

[0093] Table 1 Summary of experimental condition variables for Examples 2 - 11 and Comparative Examples 1 - 4

[0094]

[0095] Comparative Example 5

[0096] Using the composite lithium phosphate catalyst prepared in Example 1, the catalyst and heat transfer oil were mixed to prepare a catalyst slurry. Without purging the catalyst slurry with nitrogen, it was directly applied to the experiment of preparing allyl alcohol by isomerization of propylene oxide. Other subsequent steps were carried out according to the same scheme as in Example 2. After the reaction was stable, the material composition of the condensate was analyzed by gas chromatography.

[0097] Comparative Example 6

[0098] Prepare the composite lithium phosphate catalyst according to the scheme in Example 1. Only change the dosage of silica to 0, and keep other preparation steps the same as those in Example 1 to obtain a carrier-free composite lithium phosphate catalyst. According to the same scheme as in Example 2, use 50 g of the above carrier-free lithium phosphate catalyst for the isomerization reaction of propylene oxide. After the reaction is stable, use gas chromatography to analyze the material composition of the condensate.

[0099] Comparative Example 7

[0100] Prepare the composite lithium phosphate catalyst according to the scheme in Example 1. Only change the dosage of copper oxide powder to 0, and keep other preparation steps the same as those in Example 1 to obtain a copper-oxide-free composite lithium phosphate catalyst. According to the same scheme as in Example 2, use the above copper-oxide-free lithium phosphate catalyst for the isomerization reaction of propylene oxide. After the reaction is stable, use gas chromatography to analyze the material composition of the condensate. After the reactor runs continuously for 400 h and 600 h, take a small amount of condensate again for gas chromatography analysis.

[0101] The analysis data of the product components in each example and comparative example are shown in Table 2.

[0102] Table 2 Analysis results of product components in Examples 2-11 and Comparative Examples 1-7

[0103]

[0104] From the results of Examples 2-3 and Comparative Example 1, Examples 4-5 and Comparative Example 2, it can be seen that during the preparation of the composite lithium phosphate catalyst, the temperature and pH value during the precipitation of lithium phosphate crystals have an obvious influence on the catalyst performance. Excessive pH value will affect the crystallization process of lithium phosphate, causing lithium phosphate crystals to agglomerate into large particles too much, and also affecting the combination of lithium phosphate and the carrier, reducing the effective area of the catalyst, and resulting in a low reaction conversion rate during the use of the catalyst. At the same time, since the lithium phosphate catalyst contains more basic centers, the reaction selectivity is reduced, and the by-products acetone and propionaldehyde increase. The temperature during crystallization affects the precipitation rate of lithium phosphate and the self-repair process of lithium phosphate crystals during the aging process. A higher temperature can not only make the precipitation of lithium phosphate more complete, but also reduce the deposition of lithium phosphate on the surface of large crystals, and lithium phosphate with more uniform morphology can be obtained. The results of Example 6 and Comparative Example 3 show that the change in the carrier content during the catalyst preparation process will affect the reaction conversion rate during the use of the catalyst, and has no obvious influence on the reaction selectivity.

[0105] The results in Examples 7-8, Comparative Example 4, and Examples 9-11 show that when the composite lithium phosphate catalyst is used to catalyze the isomerization reaction of propylene oxide, changing the raw material feeding rate and the catalyst dosage will affect the conversion rate and selectivity of the reaction. When the feeding rate is too low or the catalyst dosage increases, the catalyst in the catalyst slurry can act more effectively on the propylene oxide molecules, increasing the reaction conversion rate, but also slightly reducing the reaction selectivity. Therefore, an appropriate catalyst dosage and feeding rate need to be selected for the reaction to balance the conversion rate and selectivity.

[0106] In Comparative Example 5, the step of purging the catalyst slurry was omitted. Compared with Example 2, the reaction selectivity decreased significantly, demonstrating the necessity of using nitrogen to purge the catalyst slurry before the reaction. By promoting the departure of the crystal water in the catalyst, the influence of moisture on the reaction during the subsequent reaction process was reduced, effectively reducing the formation of the by-product n-propanol.

[0107] In Comparative Example 6, a carrier-free composite lithium phosphate catalyst was used. Compared with Example 2, the reaction conversion rate was lower. This is because lithium phosphate precipitated on the surface of the carrier during the precipitation process. By adding a carrier, the amount of lithium phosphate used was reduced to save costs, and the addition of the carrier not only did not reduce the active components of the catalyst, but instead provided more nucleation centers when lithium phosphate precipitated, making the catalyst particles smaller and more uniform in size. Combining Example 6 and Comparative Example 3, it can be seen that the addition amount of the carrier within a certain range is beneficial to the overall catalytic effect of the catalyst.

[0108] In Comparative Example 7, the addition of copper oxide was omitted. Compared with Example 2, the service life of the catalyst decreased significantly, demonstrating the role of the added copper oxide in the composite catalyst in delaying carbon deposition and extending the service life of the catalyst. The single-pass service life of the conventional lithium phosphate catalyst is about 200 h. In Comparative Example 7, the reaction conversion rate decreased significantly after the catalyst was used for 400 h and was almost completely deactivated after 600 h. However, the catalyst in Example 2 could still maintain a high conversion rate and selectivity after being used for 600 h, reducing the frequency of catalyst regeneration. Combining this with the characteristics of the slurry bed reactor used in the present invention, which can continuously extract the slurry into the regeneration process and supplement new catalyst slurry, enables the large-scale continuous production of the propylene oxide isomerization reaction.

[0109] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a composite lithium phosphate catalyst, characterized in that, It includes the following steps: Mix an aqueous phosphoric acid solution and a catalyst support to obtain a phosphoric acid - support mixed solution; the catalyst support is silica; the mass of the catalyst support is 1.1 - 1.5 times the mass of phosphoric acid in the aqueous phosphoric acid solution; Mix a lithium hydroxide solution and lithium phosphate seeds to obtain a lithium hydroxide - seeds mixed solution; Mix the lithium hydroxide - seeds mixed solution, tetraethyl orthosilicate alcohol solution, copper oxide and the phosphoric acid - support mixed solution for crystallization to obtain a reaction solution; age the reaction solution to obtain a catalyst precursor; the temperature of the crystallization is 60 - 80 °C, and the end - point pH value is 12 - 12.5; Dry the catalyst precursor and then calcine it to obtain a composite lithium phosphate catalyst.

2. The preparation method according to claim 1, characterized in that, The concentration of the aqueous phosphoric acid solution is 40 - 50 wt%; the average particle size of the lithium phosphate seeds is 0.4 - 0.8 μm.

3. The preparation method according to claim 1, characterized in that, The concentration of the lithium hydroxide solution is 5 - 12.4 wt%; the molar ratio of lithium hydroxide in the lithium hydroxide solution to phosphoric acid in the aqueous phosphoric acid solution is 3 - 3.5:1; the dosage ratio of lithium hydroxide in the lithium hydroxide solution to lithium phosphate seeds is (3 - 3.5) mol:(0.2 - 5) g.

4. The preparation method according to claim 1, characterized in that, The concentration of the tetraethyl orthosilicate alcohol solution is 10 - 30 wt%, and the molar ratio of tetraethyl orthosilicate in the tetraethyl orthosilicate alcohol solution to phosphoric acid in the aqueous phosphoric acid solution is 0.01 - 0.1:1; The particle size of the copper oxide is 5 - 10 μm, and the mass ratio of copper oxide to phosphoric acid in the aqueous phosphoric acid solution is 0.1 - 0.5:

1.

5. The preparation method according to claim 1, 3 or 4, characterized in that, The crystallization includes: at 60 - 80 °C, simultaneously drip the tetraethyl orthosilicate alcohol solution and a part of the lithium hydroxide - seeds mixed solution into the phosphoric acid - support mixed solution, after the dripping is completed, mix with copper oxide, and then continue to drip the remaining part of the lithium hydroxide - seeds mixed solution, and stop dripping when the pH value of the system reaches 12 - 12.

5.

6. The preparation method according to claim 1, wherein The temperature of the aging is 60 - 80 °C, and the time is 0.5 - 1.5 h; the temperature of the drying is 70 - 110 °C, and the time is 1 - 2 h; the temperature of the calcination is 250 - 380 °C, and the time is 0.5 - 4 h.

7. The composite lithium phosphate catalyst prepared by the preparation method according to any one of claims 1 to 6, characterized in that It includes a silica support, lithium phosphate crystals loaded in the silica support, and copper oxide doped in the lithium phosphate crystals.

8. Use of the composite lithium phosphate catalyst according to claim 7 in the isomerization of propylene oxide to prepare allyl alcohol.

9. A method for preparing allyl alcohol by isomerization of propylene oxide, characterized in that, It includes the following steps: Mix the composite lithium phosphate catalyst according to claim 7 and a dispersion medium to obtain a catalyst slurry; Purge the catalyst slurry with an inert gas, and then co - feed propylene oxide vapor and the inert gas into the catalyst slurry for isomerization reaction to obtain allyl alcohol.

10. The method according to claim 9, wherein The device used for the isomerization reaction is a slurry - bed reactor; The propylene oxide vapor is obtained by vaporizing propylene oxide liquid, and the dosage of the propylene oxide liquid is 121.2 - 206.4 g / h / L catalyst slurry; The dispersion medium is an inert liquid; the mass ratio of the composite lithium phosphate catalyst to the dispersion medium is 1:1 - 10; The temperature of the catalyst slurry during purging is 230~280°C; the temperature of the isomerization reaction is 230~280°C; During purging, the per-minute feeding amount of the inert gas is 8~13 times the volume of the catalyst slurry; During the isomerization reaction, the per-minute feeding amount of the inert gas is 1.5~2.5 times the volume of the catalyst slurry.

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