PREPARATION METHOD FOR PROPYLENE EPOXIDATION CATALYST AND USE THEREOF

Abstract

Provided are a preparation method for a propylene epoxidation catalyst, and a use thereof. During the preparation, an alkoxide solution of a prepared active component and a silica gel support are mixed, then a rotary evaporation treatment is performed on the mixture to remove a low-carbon alcohol to obtain a catalyst precursor, and then the obtained catalyst precursor is subjected to calcination and silylation treatments to obtain the propylene epoxidation catalyst. The catalyst is prepared in a simple process, can be applied to the chemical process of preparing propylene oxide by propylene epoxidation, has high average selectivity to propylene oxide, and has industrial application prospect.

Claims

1-15. (canceled)

16. A preparation method of a propylene epoxidation catalyst, comprising the following steps: (1) titanate and ammonium molybdate are dissolved in a low-carbon alcohol, and mixed with a silica gel support to perform a rotary evaporation treatment to remove the low-carbon alcohol to obtain a catalyst precursor; (2) a calcination treatment is performed on the catalyst precursor obtained in step (1) at elevated temperature to obtain an oxide catalyst; and (3) a silylation treatment is performed on the oxide catalyst obtained in step (2) using a silylating reagent to obtain the propylene epoxidation catalyst.

17. The preparation method according to claim 16, wherein in step (2), the catalyst precursor is calcined at elevated temperature under an ammonia atmosphere.

18. The preparation method according to claim 16, wherein in step (1), the amount of Ti in the titanate is 2 to 5 wt % of the mass of the silica gel support in step (1), and the concentration of the titanate in the low-carbon alcohol is 1 to 10 wt %.

19. The preparation method according to claim 16, wherein the titanate in step (1) is one or more selected from the group consisiting of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, tetrabutyl titanate, and tetraisobutyl titanate.

20. The preparation method according to claim 18, wherein in step (1), the amount ratio of titanate to ammonium molybdate is such that the molar ratio of Mo to Ti is 0.05:1 to 0.2:1.

21. The preparation method according to claim 16, wherein the silica gel support in step (1) has an equivalent spherical diameter of 0.5 to 3 mm and a specific surface area of 800 to 900 m.sup.2/g.

22. The preparation method according to claim 16, wherein the silica gel support in step (1) has an average pore size of 2 to 3 nm.

23. The preparation method according to claim 17, wherein in step (2), calcination process conditions are: a calcination atmosphere is ammonia gas, and a two-stage temperature programming is adopted, in which in a first stage, a calcination temperature is 140° C. to 160° C., a calcination duration is 1 to 3 h, and a space velocity of the ammonia gas is 2 to 5 h.sup.−1, and in a second stage, a calcination temperature is 450° C. to 600° C., a calcination duration is 3 to 5 h, and a space velocity of the ammonia gas is 0.4 to 2 h.sup.−1.

24. The preparation method according to claim 17, wherein in step (2), the content of N in the oxide catalyst obtained after the calcination treatment is greater than 0.2 wt %.

25. The preparation method according to claim 16, wherein the silylating reagent in step (3) is hexamethyldisilazane, and the temperature of the silylation treatment is 200° C. to 300° C.

26. The preparation method according to claim 16, wherein the amount of the silylating reagent in step (3) is 5 to 15 wt % of the mass of the silica gel support, and the duration of the silylation treatment is 60 to 180 min.

27. The preparation method according to claim 21, wherein during the rotary evaporation treatment in step (1), a rotary evaporation speed is 10 to 100 rpm, a rotary evaporation temperature is 50° C. to 70° C., and a pressure is 50 to 100 KPa.

28. A preparation method of propylene oxide, wherein the method uses the propylene epoxidation catalyst prepared by the preparation method according to claim 16 in catalyzing a propylene epoxidation reaction.

29. The preparation method according to claim 28, wherein the propylene epoxidation reaction is a reaction in which propylene is reacted with cumene hydroperoxide as an oxidizing agent to prepare propylene oxide.

30. The preparation method according to claim 29, wherein the molar ratio of the propylene to the cumene hydroperoxide is 5:1 to 7:1, and a weight hourly space velocity is 2 to 3.5 h.sup.−1.

Description

DETAILED DESCRIPTION

[0027] For a better understanding of the present disclosure, the content of the present disclosure will be further illustrated below in conjunction with examples, but is not limited to the examples set forth below.

[0028] In the present disclosure, unless otherwise specified, the percentages used are all percentages by mass.

[0029] The specific surface area and pore structure in the examples of the present disclosure were determined by the BET method (N.sub.2 physical adsorption method) with the instrument No. ASP2020 manufactured by Micromeritics Instrument Corporation, USA.

[0030] The content of N in the catalyst in the examples of the present disclosure was determined by using an oxygen/nitrogen/hydrogen determinator No. ONH836 manufactured by LECO Corporation, USA.

[0031] The content of PO in the reaction liquid and tail gas absorption liquid was analyzed by gas chromatography in the examples of the present disclosure, and the conversion rate of CHP was analyzed by iodometry. The chromatographic analysis conditions are shown in Table 1.

TABLE-US-00001 TABLE 1 Operating conditions for chromatography Chromatographic column Agilent 19091N-133 (30 m*250 μm*0.25 μm) H.sub.2 flow rate 35 mL/min Air flow rate 350 mL/min Tail-blowing flow rate 25 mL/min (N.sub.2) Heater 270° C. Column oven 250° C. Temperature Initial temperature 50° C. programming Temperature programmed 50° C. to 100° C. 15° C./min maintain for 0 min 100° C. to 250° C. 20° C./ min maintain for 2 min Injection port split ratio 30:1 FID detector temperature 270° C.

[0032] The content of PO was determined by internal standard method. The liquid concentration was determined using DMF as the solvent and dioxane (DT) as the internal standard, and the standard curve of internal standard of PO and DT was determined to be y=0.6985x−0.0046, R2=0.999. The concentration of PO in the gas-phase absorption liquid was determined using toluene as the internal standard, and the standard curve of internal standard of PO and toluene was determined to be y=2.161x+0.0002, R2=0.999.

[0033] Liquid PO concentration=(0.6985×(A.sub.PO/A.sub.DT)−0.0046)×0.01×dilution scale

[0034] Liquid PO content=liquid PO concentration×liquid sampling mass

[0035] Gas PO concentration=(2.162×(A.sub.PO/A.sub.toluene)+0.0002)×toluene mass

[0036] Gas PO content=gas PO concentration×total absorption liquid/gas-phase sampling mass

[0037] Total PO production=gas PO content+liquid PO content

[0038] PO selectivity=Total PO production/theoretical amount of PO produced by propylene capable of being oxidized by CHP×100%

[0039] The CHP conversion was titrated by iodometry and determined using a titrator.

[0040] CHP conversion=(CHP initial value−CHP remaining amount)/CHP initial value

[0041] CHP remaining amount=(titration end-point−blank)×CNa.sub.2S.sub.2O.sub.3×0.001×0.5×142×total liquid sampling amount/titration sampling amount

[0042] The titanate used in the examples was tetrabutyl titanate, and the low-carbon alcohol was anhydrous ethanol.

[0043] The silica gel support used in the examples of the present disclosure was manufactured by Bokai Silica Gel Co., Ltd. The silica gel support had an equivalent spherical diameter of 1.2 mm, a specific surface area of 852 m.sup.2/g, an average pore size of 2.6 nm, a Na content of about 30 ppm, and an iron content of 27 ppm.

[0044] The catalyst in the Examples and Comparative Examples was used for preparing propylene oxide by propylene epoxidation under the following conditions: the oxidizing agent was cumene hydroperoxide (CHP), the reaction tube was a fixed bed reactor with an inner diameter of 24 mm, the loading volume of the catalyst was 20 g, the molar ratio of propylene to CHP was 7:1, the weight hourly space velocity was 3.5 hr.sup.−1, and the reaction temperature was gradually increased according to the CHP conversion (ensuring that the CHP conversion is greater than 99%) with the initial reaction temperature of 50° C.

EXAMPLE 1

[0045] 7.08 g of tetrabutyl titanate and 0.21 g of ammonium molybdate were dissolved in 200 g of ethanol which was denoted as solution a. Then 40 g of silica gel and the solution a were mixed and added to a rotary evaporation flask. The flask was heated and rotated by rotary evaporation at a heating temperature of 50° C. and a rotation speed of 30 rpm, and then vacuumized by a vacuum pump at a pressure of 50 KPa. The rotary evaporation impregnation was performed until the silica gel surface was dried to obtain a catalyst precursor. The catalyst precursor was added to a tubular furnace, and the temperature elevation rate was set to 2° C./min. The catalyst precursor was calcined at 150° C. for 3 h at a flow rate of NH.sub.3 of 100 g/h, and then calcined at an elevated temperature of 450° C. for 3 h at a flow rate of NH.sub.3 of 20 g/h. The sample obtained after calcination was subjected to gas-phase silylation treatment: 6 g of hexamethyldisilazane was added to a vaporization tank and heated at a heating temperature of 130° C., and the steam of hexamethyldisilazane was carried into a reaction tube by N.sub.2 and reacted with the sample obtained after calcination, in which the linear velocity of N.sub.2 in the reaction tube was 1 cm/s, the silylation temperature was 200° C., and the silylation duration was 180 min. The resulting catalyst was denoted as TM-01.

[0046] The average pore size of the TM-01 catalyst was determined by the BET method to be 8.9 nm. The content of N in the catalyst was determined by an oxygen/nitrogen/hydrogen determinator to be 0.29%. TM-01 was evaluated by continuous operation for 680 hr with the reaction temperature elevated from initially 50° C. to 60° C. The sample was analyzed by gas chromatography. The CHP conversion was greater than 99.9%, and the selectivity to PO was up to 97.9%, with an average of 96.9%.

EXAMPLE 2

[0047] 9.92 g of tetrabutyl titanate and 0.57 g of ammonium molybdate were dissolved in 200 g of ethanol which was denoted as solution a. Then 40 g of silica gel and the solution a were mixed and added to a rotary evaporation flask. The flask was heated and rotated by rotary evaporation at a heating temperature of 50° C. and a rotation speed of 50 rpm, and then vacuumized by a vacuum pump at a pressure of 60 KPa. The rotary evaporation impregnation was performed until the silica gel surface was dried to obtain a catalyst precursor. The catalyst precursor was added to a tubular furnace, and the temperature elevation rate was set to 2° C./min. The catalyst precursor was calcined at 150° C. for 3 h at a flow rate of NH.sub.3 of 150 g/h, and then calcined at an elevated temperature of 550° C. for 4 h at a flow rate of NH.sub.3 of 40 g/h. The sample obtained after calcination was subjected to gas-phase silylation treatment: 4 g of hexamethyldisilazane was added to a vaporization tank and heated at a heating temperature of 140° C., and the steam of hexamethyldisilazane was carried into a reaction tube by N.sub.2 and reacted with the sample obtained after calcination, in which the linear velocity of N.sub.2 in the reaction tube was 0.5 cm/s, the silylation temperature was 250° C., and the silylation duration was 120 min. The resulting catalyst was denoted as TM-02.

[0048] The average pore size of the TM-02 catalyst was determined by the BET method to be 10.1 nm. The content of N in the catalyst was determined by an oxygen/nitrogen/hydrogen determinator to be 0.39%. TM-02 was evaluated by continuous operation for 1200 hr with the reaction temperature elevated from initially 50° C. to 70° C. The sample was analyzed by gas chromatography. The CHP conversion was greater than 99.9%, and the selectivity to PO was up to 98.2%, with an average of 98%.

EXAMPLE 3

[0049] 11.33 g of tetrabutyl titanate and 0.98 g of ammonium molybdate were dissolved in 200 g of ethanol which was denoted as solution a. Then 40 g of silica gel and the solution a were mixed and added to a rotary evaporation flask. The flask was heated and rotated by rotary evaporation at a heating temperature of 60° C. and a rotation speed of 70 rpm, and then vacuumized by a vacuum pump at a pressure of 80 KPa. The rotary evaporation impregnation was performed until the silica gel surface was dried to obtain a catalyst precursor. The catalyst precursor was added to a tubular furnace, and the temperature elevation rate was set to 2° C./min. The catalyst precursor was calcined at 150° C. for 2 h at a flow rate of NH.sub.3 of 180 g/h, and then calcined at an elevated temperature of 600° C. for 2 h at a flow rate of NH.sub.3 of 50 g/h. The sample obtained after calcination was subjected to gas-phase silylation treatment: 3.2 g of hexamethyldisilazane was added to a vaporization tank and heated at a heating temperature of 150° C., and the steam of hexamethyldisilazane was carried into a reaction tube by N.sub.2 and reacted with the sample obtained after calcination, in which the linear velocity of N.sub.2 in the reaction tube was 0.6 cm/s, the silylation duration was 100 min, and the silylation temperature was 300° C. The resulting catalyst was denoted as TM-03.

[0050] The average pore size of the TM-03 catalyst was determined by the BET method to be 11.1 nm. The content of N in the catalyst was determined by an oxygen/nitrogen/hydrogen determinator to be 0.44%. TM-03 was evaluated by continuous operation for 980 hr with the reaction temperature elevated from initially 50° C. to 90° C. The sample was analyzed by gas chromatography. The CHP conversion was greater than 99.9%, and the selectivity to PO was up to 97.9%, with an average of 96.5%.

EXAMPLE 4

[0051] 14.16 g of tetrabutyl titanate and 1.63 g of ammonium molybdate were dissolved in 200 g of ethanol which was denoted as solution a. Then 40 g of silica gel and the solution a were mixed and added to a rotary evaporation flask. The flask was heated and rotated by rotary evaporation at a heating temperature of 70° C. and a rotation speed of 100 rpm, and then vacuumized by a vacuum pump at a pressure of 100 KPa. The rotary evaporation impregnation was performed until the silica gel surface was dried to obtain a catalyst precursor. The catalyst precursor was added to a tubular furnace, and the temperature elevation rate was set to 2° C./min. The catalyst precursor was calcined at 150° C. for 2 h at a flow rate of NH.sub.3 of 200 g/h, and then calcined at an elevated temperature of 550° C. for 5 h at a flow rate of NH.sub.3 of 80 g/h. The sample obtained after calcination was subjected to gas-phase silylation treatment: 2.6 g of hexamethyldisilazane was added to a vaporization tank and heated at a heating temperature of 140° C., and the steam of hexamethyldisilazane was carried into a reaction tube by N.sub.2 and reacted with the sample obtained after calcination, in which the linear velocity of N.sub.2 in the reaction tube was 0.5 cm/s, the silylation temperature was 250° C., and the silylation duration was 120 min. The resulting catalyst was denoted as TM-04.

[0052] The average pore size of the TM-04 catalyst was determined by the BET method to be 11.8 nm. The content of N in the catalyst was determined by an oxygen/nitrogen/hydrogen determinator to be 0.47%. TM-04 was evaluated by continuous operation for 600 hr with the reaction temperature elevated from initially 60° C. to 75° C. The sample was analyzed by gas chromatography. The CHP conversion was greater than 99.9%, and the selectivity to PO was up to 97.8%, with an average of 97.1%.

COMPARATIVE EXAMPLE 1

[0053] The difference of Comparative example 1 from Example 2 lied in that the calcination was performed under a nitrogen atmosphere and the resulting catalyst was denoted as TS-21.

[0054] The average pore size of the TS-21 catalyst was determined by the BET method to be 2.5 nm. TS-21 was evaluated by continuous operation for 200 hr with the reaction temperature elevated from initially 50° C. to 80° C. The sample was analyzed by gas chromatography. The CHP conversion was greater than 99.9%, and the selectivity to PO was up to 13.9%, with an average of 11%.

COMPARATIVE EXAMPLE 2

[0055] 9.92 g of tetrabutyl titanate and 0.57 g of ammonium molybdate were dissolved in 200 g of ethanol which was denoted as solution a. Then 40 g of silica gel and the solution a were mixed and added to a rotary evaporation flask. The flask was heated and rotated by rotary evaporation at a heating temperature of 50° C. and a rotation speed of 50 rpm, and then vacuumized by a vacuum pump at a pressure of 60 KPa. The rotary evaporation impregnation was performed until the silica gel surface was dried to obtain a catalyst precursor. The catalyst precursor was added to a tubular furnace, and the temperature elevation rate was set to 2° C./min. The catalyst precursor was calcined at 150° C. for 3 h at a flow rate of NH.sub.3 of 150 g/h, and then calcined at an elevated temperature of 550° C. for 4 h at a flow rate of N.sub.2 of 40 L/h. The sample obtained after calcination was subjected to gas-phase silylation treatment: 4 g of hexamethyldisilazane was added to a vaporization tank and heated at a heating temperature of 140° C., and the steam of hexamethyldisilazane was carried into a reaction tube by N.sub.2 and reacted with the sample obtained after calcination, in which the linear velocity of N.sub.2 in the reaction tube was 0.5 cm/s, the silylation temperature was 250° C., and the silylation duration was 120 min. The resulting catalyst was denoted as TM-22.

[0056] The average pore size of the TM-22 catalyst was determined by the BET method to be 10.1 nm. No N was detected in the catalyst by an oxygen/nitrogen/hydrogen determinator. TM-22 was evaluated by continuous operation for 200 hr with the reaction temperature elevated from initially 50° C. to 70° C. The sample was analyzed by gas chromatography. The CHP conversion was greater than 99.8%, and the selectivity to PO was up to 95.9%, with an average of 94.4%.