Catalyst for preparing isobutene by dissociation of methyl tert-butyl ether, preparation method and use thereof

Abstract

Disclosed is a catalyst for preparing isobutene by dissociation of methyl tert-butyl ether, the catalyst comprising amorphous silica alumina and a silicalite-1 molecular sieve, wherein the total IR acid amount of weak acids in the catalyst is in a range from 0.020 to 0.080 mmol/g, and the ratio of B acid/L acid of the weak acids is in a range from 2.5:1 to 4.0:1. Also provided is a method of preparing the catalyst and the use thereof. The catalyst has a high selectivity with respect to isobutene, and high conversion of methyl tert-butyl ether, and can also effectively inhibit formation of the by-product dimethyl ether.

Claims

1. A method for preparing isobutene by a dissociation reaction of methyl tert-butyl ether (MTBE), comprising: contacting a feedstock with a catalyst in a reactor; and obtaining an effluent from the reactor, wherein the feedstock comprises MTBE and water, wherein the effluent comprises an isobutene product stream, and wherein the catalyst comprises amorphous silica alumina and a silicalite-1 molecular sieve.

2. The method of claim 1, wherein a liquid hourly space velocity of MTBE in the reactor is in a range from 0.7 to 6.0 h.sup.1, a liquid hourly space velocity of water in the reactor is in a range from 0 to 1.0 h.sup.1, a temperature in the reactor is in a range from 180 to 360 C., and a pressure in the reactor is in a range from the atmospheric pressure to 1.0 MPa.

3. The method of claim 2, wherein the liquid hourly space velocity of MTBE is in a range from 2.0 to 4.0 h.sup.1, the liquid hourly space velocity of water is in a range from 0.1 h.sup.1 to 0.5 h.sup.1, the temperature is in a range from 210 to 270 C., and the pressure is in a range from the atmospheric pressure to 0.6 MPa.

4. The method of claim 1, wherein the catalyst has a total IR acid amount of weak acids in a range from 0.020 to 0.080 mmol/g, and a ratio of B acid/L acid of the weak acids is in a range from 2.5:1 to 4.0:1.

5. The method of claim 1, wherein the catalyst a mass ratio of the amorphous silica-alumina to the silicalite-1 is in a range from 9.5:1 to 1:1.

6. The method of claim 5, wherein the mass ratio of the amorphous silica-alumina to the silicalite-1 is in a range from 8:1 to 4:1.

7. The method of claim 1, wherein in said amorphous silica-alumina, a content of SiO.sub.2 is in a range from 60 wt % to 99 wt %, and a content of Al.sub.2O.sub.3 is in a range from 1 wt % to 40 wt %.

8. The method of claim 7, wherein in said amorphous silica-alumina, the content of silica is in a range from 80 wt % to 95 wt %, and the content of alumina is in a range from 5 wt % to 20 wt %.

9. The method of claim 1, wherein the catalyst further comprises an active metal component selected from the group consisting of Group IIA metals and Group VIII metals.

10. The method of claim 9, wherein a content of said active metal component, calculated based on elemental metal, is in a range from 0.3 wt % to 2.0 wt % of a total weight of the catalyst.

11. The method of claim 10, the active metal component is selected from the group consisting of Be, Mg, Ca, Ni, Pd, and Pt.

12. The method of claim 1, wherein the isobutene product comprises less that 0.30 wt % of dimethyl ether.

13. The method of claim 1, wherein a selectivity of isobutene of the MTBE dissociation reaction is about 99.9%.

14. The method of claim 1, wherein a conversion of MTBE in the MTBE dissociation reaction is about 99.9%.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

(1) The present disclosure will be explained in detail in connection with the following examples, which are not to restrict the scope of the present disclosure in any manner.

(2) Specific measurement of a total IR acid, B acid, and L acid of the present disclosure is performed according to an existing IR acidity measurement method (see Catalyst Analysis, pages 90 to 92, published by Northeastern University Press in July, 2000). Specific steps are as follows:

(3) 1. Preparation of a sample: 20 mg of a finely grinded sample (particle size lower than 200 mesh) is measured, crushed into a sheet with a diameter of 20 mm, and placed into an infrared absorption cell; another 200 mg of the sample (sheet) is loaded into a hanging cup at a lower end of a quartz spring; the system is evacuated to 110.sup.2 Pa, heated to 500 C., and maintained for 1 h; the sample is purified, removed of adsorbates, water, and so on that cover the surface of the sample.

(4) 2. The system is cooled down to room temperature under the above evacuated conditions, and after absorbing pyridine for 5 min, is heated up to 160 C., and balanced for 1 h; the pyridine physically absorbed is desorbed; the total acid amount is acquired by utilizing the pyridine gravimetric absorption method, and the infrared spectrum obtained under the above-mentioned method is recorded, wherein the band that corresponds to B acid is 1,545 cm.sup.1, and the band that corresponds to L acid is 1,455 cm.sup.1; therefore the total acid amount, B acid amount, and L acid amount at 160 C. can be obtained.

(5) 3. The temperature is kept raising till 250 C., and balanced for 1 h; the pyridine physically absorbed is desorbed, and the infrared spectrum obtained under the above-mentioned method is recorded; the total acid amount is acquired by utilizing the pyridine gravimetric absorption method, and the infrared spectrum obtained under the above-mentioned method is recorded, wherein the band that corresponds to B acid is 1,545 cm.sup.1, and the band that corresponds to L acid is 1,455 cm.sup.1; therefore, the total acid amount, B acid amount, and L acid amount at 250 C. can be obtained.

Example 1

(6) Preparation of the Catalyst

(7) Silica-alumina gel with a silicon-alumina weight ratio of 92.0:8.0 based on SiO.sub.2 and Al.sub.2O.sub.3 is used as the raw material, which is calcined for 4 h under 450 C. to obtain amorphous silica-alumina SA, with a specific surface area of 277 m.sup.2/g, a pore volume of 0.59 mL/g, a SiO.sub.2 content of 92.0 wt %, and an Al.sub.2O.sub.3 content of 8.0 wt %.

(8) At room temperature, a TPAOH (tetrapropylammonium hydroxide) solution with a concentration of 30 wt % is added to tetraethyl orthosilicate. The resulting mixed slurry is stirred at 80 C. for 3 h and taken out after being crystallized for 48 h at 150 C. The crystallized resultant is then calcined for 4 h at 550 C. to obtain an all-silicon molecular sieve, i.e., silicalite-1, with a specific surface area of 333 m.sup.2/g and a pore volume of 0.17 mL/g.

(9) The amorphous silica-alumina SA is mixed with the silicalite-1 molecular sieve in a weight ratio of 9:1, ball-rolled for molding, dried under 110 C. for 3 h, and then calcined at 500 C. for 4 h. After that, the resulting materials are treated with saturated steam at 200 C. for 5 h, dried at 110 C. for 3 h to obtain a catalyst C-1. The characterization data of the catalyst are shown in Table 1.

(10) Preparation of Isobutene by Dissociation of MTBE

(11) The study of corresponding dissociation reactions is carried out in a microreactor. The reaction conditions comprise an LHSV of MTBE being 2.5 h.sup.1, an LHSV of water being 0.5 h.sup.1, a temperature of 225 C., and a pressure of 0.2 MPa. The test results are shown in Table 2.

Example 2

(12) The method of Example 1 is repeated except that the amorphous silica-alumina SA and the silicalite-1 molecular sieve are mixed in a weight ratio of 4 to 1 to obtain a catalyst C-2, the data of which are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Example 3

(13) The method of Example 1 is repeated except that the amorphous silica-alumina SA and the silicalite-1 molecular sieve are mixed in a weight ratio of 1 to 1, and that the amorphous silica-alumina SA has a SiO.sub.2 content of 83.0 wt %, an Al.sub.2O.sub.3 content of 17.0 wt %, a specific surface area of 320 m.sup.2/g, and a pore volume of 0.61 mL/g. The data of an obtained catalyst C-3 are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Example 4

(14) The method of Example 3 is repeated except that the amorphous silica-alumina SA and the silicalite-1 molecular sieve are mixed in a weight ratio of 5 to 1. The data of an obtained catalyst C-4 are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Example 5

(15) The method of Example 1 is repeated except that the saturated impregnation method is adopted, in which the materials after being treated with steam and dried are immerged into an aqueous solution of nickel chloride and magnesium chloride, and then dried at 110 C. for 3 h to obtain a catalyst C-5, the data of which are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Example 6

(16) The method of Example 2 is repeated except that the saturated impregnation method is adopted, in which the materials after being treated with steam and dried are immerged into an aqueous solution of palladium nitrate and calcium chloride, and then dried at 110 C. for 3 h to obtain a catalyst C-6, the data of which are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Example 7

(17) The method of Example 2 is repeated except that the amorphous silica-alumina SA and the silicalite-1 molecular sieve are mixed with beryllium oxide, wherein the dosage of beryllium oxide base on beryllium is 1.8 wt %. The data of an obtained catalyst C-7 are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Example 8

(18) Silica sol, alumina sol, and a crystalization solution Si-1-A of the silicalite-1 molecular sieve are mixed in a weight ratio of 10:1:5 on a dry basis, ball-rolled for molding, dried at 110 C. for 3 h, and then calcined at 500 C. for 4 h. Next, the obtained materials are treated with saturated steam at 300 C. for 4 h, and then dried at 110 C. for 3 h to obtain a catalyst C-8. The data representing the catalyst are shown in Table 1. The molecular sieve crystalization solution Si-1-A is prepared by the following method. At room temperature, the TPAOH solution with a concentration of 30 wt % is added to TEOS. The resulting mixed slurry is stirred at 80 C. for 3 h and then taken out after being crystallized for 48 h at 150 C. to obtain the crystallization solution Si-1-A of the silicalite-1 molecular sieve.

(19) The study of dissociation reactions is carried out on a microreactor. The reaction conditions comprise a liquid hourly space velocity of MTBE being 2.0 h.sup.1, a liquid hourly space velocity of water being 0.5 h.sup.1, a temperature of 200 C., and a pressure of the atmospheric pressure. The result data of the dissociation reactions are shown in Table 2.

Example 9

(20) The method of Example 8 is repeated except that the silica sol and alumina sol are mixed with the crystalization solution Si-1-A of the silicalite-1 molecular sieve in a weight ratio of 15:2:4 on a dry basis. The data of an obtained catalyst C-9 are shown in Table 1.

Example 10

(21) The method of Example 8 is repeated except that the silica sol and alumina sol are mixed with the crystalization solution Si-1-A of the silicalite-1 molecular sieve in a weight ratio of 10:1:2 on a dry basis. The data of an obtained catalyst C-10 are shown in Table 1. The result data of the dissociation reactions are shown in Table 2.

Example 11

(22) The method of Example 8 is repeated except that the silica sol and alumina sol are mixed with the crystalization solution Si-1-A of the silicalite-1 molecular sieve in a weight ratio of 40:3:10 on a dry basis. The data of an obtained catalyst C-11 are shown in Table 1.

Example 12

(23) The method of Example 9 is repeated except that the saturated impregnation method is adopted, in which the materials after being treated with steam and dried are immerged into an aqueous solution of nickel chloride and magnesium chloride, and then dried at 110 C. for 3 h to obtain a catalyst C-12, the data of which are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Example 13

(24) The method of Example 9 is repeated except that the saturated impregnation method is adopted, in which the materials after being treated with steam and dried are immerged into an aqueous solution of palladium nitrate and calcium chloride, and then dried at 110 C. for 3 h to obtain a catalyst C-13, the data of which are shown in Table 1.

Example 14

(25) The method of Example 10 is repeated except that the saturated impregnation method is adopted, in which the materials after being treated with steam and dried are immerged into an aqueous solution of palladium nitrate, and then dried at 110 C. for 3 h to obtain a catalyst C-14, the data of which are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Example 15

(26) The method of Example 11 is repeated except that the saturated impregnation method is adopted, in which the materials after being treated with steam and dried are immerged into an aqueous solution of beryllium nitrate, and then dried at 110 C. for 3 h to obtain a catalyst C-15, the data of which are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Example 16

(27) The method of Example 8 is repeated except that the silica sol and alumina sol are mixed with the crystalization solution Si-1-A of the silicalite-1 molecular sieve, and magnesium oxide, wherein the dosage of magnesium oxide based on magnesium is 1.8 wt %, and the weight ratio of silica sol to alumina sol to the crystalization solution Si-1-A of the silicalite-1 molecular sieve is, on a dry basis, 20:2:3. A catalyst C-16 is obtained, the data of which are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Comparative Example 1

(28) The method of Example 1 is repeated except that the steam treatment is not performed, and the data of an obtained catalyst H-1 are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Comparative Example 2

(29) The method of Example 9 is repeated except that the steam treatment is not performed, and the data of an obtained catalyst H-2 are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Comparative Example 3

(30) The method of Example 5 is repeated except that the catalyst is free of the silicalite-1-A molecular sieve. The data of an obtained catalyst H-3 are shown in Table 1. The result data of corresponding dissociation reactions are shown in Table 2.

Comparative Example 4

(31) The method of Example 9 is repeated except that the raw materials free of the crystalization solution of the silicalite-1-A molecular sieve comprise the silicon sol and the alumina sol, and that the saturated impregnation method is adopted, in which the materials after being treated with steam and dried are immerged into a solution of nickel chloride and magnesium chloride, and then dried at 110 C. for 3 h to obtain a catalyst H-4. The data are shown in Table 1.

(32) The study of corresponding dissociation reactions is carried out in a microreactor. The reaction conditions are the same as those of Example 9. The data of the dissociation reactions are shown in Table 2.

(33) TABLE-US-00001 TABLE 1 Catalyst Silica-alumina Total acid B Specific Pore Active metal, Cata- to molecular content * acid/L surface volume based on lyst sieve wt:wt mmol/g acid * area m.sup.2/g mL/g metals wt % Example 1 C-1 9:1 0.058 3.14 280 0.56 0 Example 2 C-2 4:1 0.055 2.76 292 0.53 0 Example 3 C-3 1:1 0.049 2.75 313 0.54 0 Example 4 C-4 5:1 0.054 2.77 306 0.59 0 Example 5 C-5 9:1 0.061 3.15 265 0.53 Ni 1.2, Mg 0.5 Example 6 C-6 4:1 0.058 2.78 290 0.55 Pd 0.2, Ca 0.5 Example 7 C-7 4:1 0.057 3.16 272 0.50 Be 1.8 Example 8 C-8 11:5 0.060 2.93 290 0.49 0 Example 9 C-9 17:4 0.059 2.96 301 0.51 0 Example 10 C-10 11:2 0.053 2.87 320 0.57 0 Example 11 C-11 43:10 0.054 3.11 293 0.55 0 Example 12 C-12 17:4 0.057 2.98 286 0.48 Ni 1.2, Mg 0.5 Example 13 C-13 17:4 0.054 2.97 288 0.50 Pd 0.2, Ca 0.5 Example 14 C-14 11:2 0.054 2.89 310 0.55 Pt 0.25 Example 15 C-15 43:10 0.055 3.11 274 0.55 Be 1.8 Example 16 C-16 22:3 0.052 2.79 307 0.52 Mg 1.8 Comparative H-1 9:1 0.091 0.28 289 0.54 0 Example 1 Comparative H-2 17:4 0.051 0.29 298 0.50 0 Example 2 Comparative H-3 0.071 2.16 260 0.65 Ni 1.2, Example 3 Mg 0.5 Comparative H-4 0.039 1.83 256 0.63 Ni 1.2, Example 4 Mg 0.5 * Note: The total acid content described in Table 1 refers to the total IR acid content of weak acids, and the B acid/L acid described in Table 1 refers to the ratio of B acid/L acid of weak acids.

Comparative Example 5

(34) Amorphous silica-alumina SA is mixed with a molecular sieve ZSM-5 (the molar ratio of silica to alumina is 95 to 5) in a weight ratio of 9 to 1, ball-rolled for molding, dried at 110 C. for 3 h, and then calcined at 500 C. for 4 h, to obtain a catalyst H-5. The result data of corresponding dissociation reactions are shown in Table 2.

Comparative Example 6

(35) The catalyst H-5 obtained in Comparative Example 5 is treated with saturated steam at 200 C. for 5 h and then dried at 110 C. for 3 h to obtain a catalyst H-6. The result data of corresponding dissociation reactions are shown in Table 2.

(36) TABLE-US-00002 TABLE 2 Data of dissociation of MTBE for preparing isobutene Content of dimethyl Conversion of Selectivity of ether in MTBE, isobutene, the products, catalysts wt. % wt. % wt. % Example 1 C-1 99.9 99.9 0.27 Example 2 C-2 99.9 99.9 0.27 Example 3 C-3 99.9 99.9 0.29 Example 4 C-4 99.9 99.9 0.25 Example 5 C-5 99.9 99.9 0.20 Example 6 C-6 99.9 99.9 0.19 Example 7 C-7 99.9 99.9 0.21 Example 8 C-8 99.9 99.9 0.28 Example 10 C-10 99.9 99.9 0.24 Example 12 C-12 99.9 99.9 0.21 Example 14 C-14 99.9 99.9 0.19 Example 15 C-15 99.9 99.9 0.23 Example 16 C-16 99.9 99.9 0.27 Comparative H-1 87.2 99.9 0.40 Example 1 Comparative H-2 89.0 99.9 0.37 Example 2 Comparative H-3 99.6 99.8 0.39 Example 3 Comparative H-4 99.7 99.8 0.36 Example 4 Comparative H-5 80.2 96.5 0.44 Example 5 Comparative H-6 85.1 97.8 0.41 Example 6

(37) It can be seen from Table 2 that using the catalyst of the present disclosure comprising amorphous silica-alumina and the silicalite-1 molecular sieve for preparing isobutene by dissociation of MTBE, not only can improve conversion of MTBE and selectivity of isobutene, but also can make an obvious effect on decreasing the by-product dimethyl ether compared with the prior art. This illustrates that the catalyst of the present disclosure has a higher level of activity and selectivity. At the same time, addition of active metal components can effectively control side reactions and thus further reduce the content of the by-product dimethyl ether.