Method for directly preparing dimethyl ether by synthesis gas

Abstract

Provided is a method for directly preparing dimethyl ether by synthesis gas, the method comprises: the synthesis gas is passed through a reaction zone carrying a catalyst, and reacted under the reaction conditions sufficient to convert at least a portion of the raw materials to obtain the reaction effluent comprising dimethyl ether; and the dimethyl ether is separated from the reaction effluent, wherein the catalyst is zinc aluminum spinel oxide. In the present invention, only one zinc aluminum spinel oxide catalyst is used, which can make the synthesis gas to highly selectively form dimethyl ether, the catalyst has good stability and can be regenerated. The method of the present invention realizes the production of dimethyl ether in one step by the synthesis gas, and reduces the large energy consumption problem caused by step-by-step production.

Claims

1. A method for directly preparing dimethyl ether from syngas comprising: a) passing syngas through a reaction zone loaded with catalyst, and reacting under a reaction condition sufficient to convert at least part of the syngas as raw materials to obtain a reaction effluent containing dimethyl ether; and b) separating dimethyl ether from the reaction effluent; wherein, the catalyst is only zinc-aluminum spinel oxide; wherein the Zn/Al molar ratio in the zinc-aluminum spinel oxide is Zn/Al=1:9 to 1:1.

2. The method as claimed in claim 1, wherein, the zinc-aluminum spinel oxide is prepared by following steps: formulating a zinc salt and an aluminum salt into a mixed metal salt aqueous solution; contacting the mixed metal salt aqueous solution with a precipitant aqueous solution so as to make the metal ions in the mixed metal salt aqueous solution be co-precipitated followed by aging; washing the obtained precipitate followed by drying and then calcining to obtain the zinc-aluminum spinel oxide.

3. The method as claimed in claim 2, wherein, the method has at least one of the following characteristics: the zinc salt and aluminum salt are selected from hydrochloride, sulfate and nitrate; the precipitant is selected from sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, aqueous ammonia, sodium hydroxide, potassium hydroxide, and mixtures thereof; co-precipitation is carried out at a temperature ranging from 20° C. to 95° C.; pH during the co-precipitation ranges from 7.0 to 9.0; an aging time is not less than one hour; and calcination is carried out at a temperature ranging from 450° C. to 800° C.

4. The method as claimed in claim 1, wherein, the zinc-aluminum spinel oxide comprises at least one other element selected from chromium, zirconium, copper, manganese, indium, gallium, and silicon, and a mass fraction of the at least one other element in the zinc-aluminum spinel oxide is less than or equal to 10%.

5. The method as claimed in claim 4, wherein, the at least one other element is added to the zinc-aluminum spinel oxide by impregnating and/or co-precipitating a salt solution of the at least one other element.

6. The method as claimed in claim 5, wherein, the salt of the at least one other element is selected from hydrochloride, sulfate and nitrate.

7. The method as claimed in claim 1, wherein, the reaction zone contains one fixed bed reactor, or multiple fixed bed reactors connected in series and/or in parallel.

8. The method as claimed in claim 1, wherein, the reaction condition comprises: a reaction temperature ranging from 300 to 450° C., a reaction pressure ranging from 0.5 to 10.0 MPa, a molar ratio of hydrogen to carbon monoxide in the syngas ranging from 1:9 to 9:1, and the volume hourly space velocity of syngas under standard conditions ranging from 1,000 to 20,000 h.sup.−1.

9. The method as claimed in claim 8, wherein, the reaction condition comprises: a reaction temperature ranging from 310 to 360° C., a reaction pressure ranging from 1.0 to 4.0 MPa, a molar ratio of hydrogen to carbon monoxide in the syngas ranging from 3:1 to 6:1, and the volume hourly space velocity of syngas under standard conditions ranging from 3000 to 8000 h.sup.−1.

10. The method as claimed in claim 1, wherein, the syngas comprises carbon dioxide, and the molar concentration of carbon dioxide in the syngas ranges from 1.0% to 20.0%.

Description

BRIEF DESCRIPTION OF FIGURES

(1) FIG. 1 shows a XRD pattern of material A according to Example 1 of the present application.

(2) FIG. 2 shows a TEM image of material A according to Example 1 of the present application.

DETAILED DESCRIPTION

(3) The present invention is described in detail by the following examples, but the invention is not limited to these examples.

(4) Unless otherwise indicated, raw materials employed in the examples of the present application are commercially purchased.

(5) In the examples, automatic analysis is performed by an Agilent 7890 Gas Chromatograph with a gas autosampler, a TCD detector connected to a TDX-1 packed column, and an FID detector connected to a PLOT-Q capillary column.

(6) In the examples, conversion efficiency and selectivity are calculated based on the molar number of carbon:
Conversion efficiency of carbon monoxide=[(the molar number of carbon monoxide in the feeding raw materials)−(the molar number of carbon monoxide in the product)]÷(the molar number of carbon monoxide in the feeding raw materials)×100%
Dimethyl ether selectivity=(the molar number of carbon of dimethyl ether in the product)÷(the sum of the molar number of carbon in all hydrocarbons, methanol, and dimethyl ether in the product)×100%
Methanol ether selectivity=(the molar number of carbon of methanol in the product)÷(the sum of the molar number of carbon in all hydrocarbons, methanol, and dimethyl ether in the product)×100%
Hydrocarbons selectivity=(the molar number of carbon of hydrocarbons in the product)÷(the sum of the molar number of carbon in all hydrocarbons, methanol, and dimethyl ether in the product)×100%
Carbon dioxide selectivity=(the molar number of carbon dioxide produced in the reaction)÷(the molar number of carbon monoxide converted)×100%.
Preparation of Zinc-Aluminum Spinel Oxide

Example 1

(7) 95 g Zn(NO.sub.3).sub.2.6H.sub.2O and 80 g Al(NO.sub.3).sub.3.9H.sub.2O were dissolved in 200 ml deionized water to form a salt solution. 25 g ammonium carbonate was dissolved in 200 ml deionized water to form an alkaline solution. The salt solution and the alkaline solution were mixed in co-current manner by two peristaltic pumps respectively and co-precipitated, wherein the precipitation reaction temperature was controlled at 60° C. and the pH was 7.2. Aging step was then performed at 60° C. for 4 hours, followed by filtering, washing, drying at 100° C. for 24 hours, and then calcining at 500° C. for 4 hours to obtain the zinc-aluminum spinel oxide, which was denoted as A. X-ray fluorescence spectroscopy (XRF) shows that Zn/Al (molar ratio) in the A is 1:1, the XRD pattern of the A is shown in FIG. 1, and the TEM image thereof is shown in FIG. 2.

Example 2

(8) 48 g Zn(NO.sub.3).sub.2.6H.sub.2O and 80 g Al(NO.sub.3).sub.3.9H.sub.2O were dissolved in 200 ml deionized water to form a salt solution. 25 g aqueous ammonia (comprising 25% NH.sub.3) was dissolved in 200 ml deionized water to form an alkaline solution. The salt solution and the alkaline solution were mixed in co-current manner by two peristaltic pumps respectively and co-precipitated, wherein the precipitation reaction temperature was controlled at 70° C. and the pH was 7.5. Aging step was then performed at 70° C. for 6 hours, followed by filtering, washing, drying at 100° C. for 24 hours, and then calcining at 500° C. for 4 hours to obtain the zinc-aluminum spinel oxide, which was denoted as B. XRF shows that Zn/Al (molar ratio) in the B is 1:2.

Example 3

(9) 10.6 g Zn(NO.sub.3).sub.2.6H.sub.2O and 80 g Al(NO.sub.3).sub.3.9H.sub.2O were dissolved in 200 ml deionized water to form a salt solution. 25 g sodium carbonate was dissolved in 200 ml deionized water to form an alkaline solution. The salt solution and the alkaline solution were mixed in co-current manner by two peristaltic pumps respectively and co-precipitated, wherein the precipitation reaction temperature was controlled at 80° C. and the pH was 7.8. Aging step was then performed at 80° C. for 6 hours, followed by filtering, washing, drying at 100° C. for 24 hours, and then calcining at 500° C. for 6 hours to obtain the zinc-aluminum spinel oxide, which was denoted as C. XRF shows that Zn/Al (molar ratio) in the C is 1:9.

Example 4

(10) 10.6 g Zn(NO.sub.3).sub.2.6H.sub.2O and 40 g Al(NO.sub.3).sub.3.9H.sub.2O were dissolved in 200 ml deionized water to form a salt solution. 15 g potassium carbonate was dissolved in 200 ml deionized water to form an alkaline solution. The salt solution and the alkaline solution were mixed in co-current manner by two peristaltic pumps respectively and co-precipitated, wherein the precipitation reaction temperature was controlled at 70° C. and the pH was 7.1. Aging step was then performed at 70° C. for 6 hours, followed by filtering, washing, drying at 100° C. for 24 hours, and then calcining at 500° C. for 4 hours to obtain the zinc-aluminum spinel oxide, which was denoted as D. XRF shows that Zn/Al (molar ratio) in the D is 1:4.5.

Example 5

(11) 7.7 g Cr(NO.sub.3).sub.3.9H.sub.2O was dissolved in 15 ml deionized water, and then was impregnated with 20 g catalyst B at room temperature for 24 hours, followed by drying at 100° C. for 24 hours, and calcining at 500° C. for 4 hours to obtain 5% (mass fraction) chromium-modified zinc-aluminum spinel oxide, which was denoted as E.

Example 6

(12) 4.7 g Zr(NO.sub.3).sub.3.5H.sub.2O was dissolved in 15 ml deionized water, and then was impregnated with 20 g catalyst B at room temperature for 24 hours, followed by drying at 100° C. for 24 hours, and calcining at 500° C. for 4 hours to obtain 5% (mass fraction) zirconium-modified zinc-aluminum spinel oxide, which was denoted as F.

(13) Performance Evaluation of Catalyst

Example 7

(14) The catalyst A was crushed and sieved into particles ranging from 0.4 to 0.8 mm. 2 g obtained particles was loaded into a stainless-steel reaction tube with an inner diameter of 8 mm, and activated with 50 ml/min hydrogen at 300° C. for 1 hour. The reaction was carried out under the following conditions: reaction temperature (T)=320° C., reaction pressure (P)=4.0 MPa, the molar ratio of hydrogen to carbon monoxide in syngas (H.sub.2:CO)=3:1, the volume hourly space velocity (GHSV) of the syngas under standard conditions=6000 h.sup.−1. After reaction for 500 hours, the product was analyzed by gas chromatography. The reaction results are shown in Table 1.

Examples 8 to 12

(15) The reaction conditions and reaction results are shown in Table 1. Other procedures are the same as those in Example 7.

Example 13

(16) The catalyst G was crushed and sieved into particles ranging from 0.4 to 0.8 mm. 2 g obtained particles was loaded into a stainless-steel reaction tube with an inner diameter of 8 mm, and activated with 50 ml/min hydrogen at 300° C. for 1 hour. The reaction was carried out under the following conditions: reaction temperature (T)=320° C., reaction pressure (P)=4.0 MPa, the molar ratio of hydrogen, carbon monoxide and carbon dioxide in syngas (H.sub.2:CO:CO.sub.2)=3:1:0.04 (that is, the content of CO.sub.2 in the syngas is 1%), the volume hourly space velocity (GHSV) of the syngas under standard conditions=6000 h.sup.−1. After reaction for 500 hours, the product was analyzed by gas chromatography. The reaction results are shown in Table 1.

Example 14

(17) The catalyst G was crushed and sieved into particles ranging from 0.4 to 0.8 mm. 2 g obtained particles was loaded into a stainless-steel reaction tube with an inner diameter of 8 mm, and activated with 50 ml/min hydrogen at 300° C. for 1 hour. The reaction was carried out under the following conditions: the reaction temperature (T)=320° C., the reaction pressure (P)=4.0 MPa, the molar ratio of hydrogen, carbon monoxide and carbon dioxide in syngas (H.sub.2:CO:CO.sub.2)=3:1:0.2 (that is, the content of CO.sub.2 in the syngas is 4.8%), the volume hourly space velocity (GHSV) of the syngas under standard conditions=6000 h.sup.−1. After reaction for 500 hours, the product was analyzed by gas chromatography. The reaction results are shown in Table 1.

Example 15

(18) The catalyst G was crushed and sieved into particles ranging from 0.4 to 0.8 mm. 2 g obtained particles was loaded into a stainless-steel reaction tube with an inner diameter of 8 mm, and activated with 50 ml/min hydrogen at 300° C. for 1 hour. The reaction was carried out under the following conditions: the reaction temperature (T)=320° C., the reaction pressure (P)=4.0 MPa, the molar ratio of hydrogen, carbon monoxide and carbon dioxide in syngas (H.sub.2:CO:CO.sub.2)=3:1:1 (that is, the content of CO.sub.2 in the syngas is 20%), the volume hourly space velocity (GHSV) of the syngas under standard conditions=6000 h.sup.−1. After reaction for 500 hours, the product was analyzed by gas chromatography. The reaction results are shown in Table 1.

(19) TABLE-US-00001 TABLE 1 Catalytic Reaction results in Examples 7 to 15 CO Conversion Dimethyl ether Methanol Hydrocarbons CO.sub.2 efficiency Selectivity Selectivity selectivity selectivity Example Catalyst Reaction condition (%) (%) (%) (%) (%) 7 A T = 320° C.; 18.2 87.6 12.3 0.1 31.4 P = 4.0 MPa; GHSV = 6000 h.sup.−1; H.sub.2:CO = 3:1 8 B T = 360° C.; 25.7 90.3 9.5 0.2 28.7 P = 6.0 MPa; GHSV = 10,000 h.sup.−1; H.sub.2:CO = 5:1 9 C T = 370° C.; 28.9 88.5 11.2 0.3 29.0 P = 2.0 MPa; GHSV = 3000 h.sup.−1; H.sub.2:CO = 6:1 10 D T = 400° C.; 17.5 82.4 17.2 0.4 35.7 P = 8.0 MPa; GHSV = 15000 h.sup.−1; H.sub.2:CO = 2:1 11 E T = 300° C.; 16.8 80.6 19.3 0.1 22.9 P = 0.5 MPa; GHSV = 1000 h.sup.−1; H.sub.2:CO = 9:1 12 F T = 450° C.; 2.1 82.4 17.3 0.3 20.0 P = 10.0 MPa; GHSV = 20,000 h.sup.−1; H.sub.2:CO = 1:9 13 A T = 320° C.; 17.2 86.5 13.4 0.1 23.1 P = 4.0 MPa; GHSV = 6000 h.sup.−1; H.sub.2:CO:CO.sub.2 = 3:1:0.04 14 A T = 320° C.; 10.3 84.4 15.5 0.1 14.2 P = 4.0 MPa; GHSV = 6000 h.sup.−1 ; H.sub.2:CO:CO.sub.2 = 3:1:0.2 15 A T = 320° C.; 8.8 83.5 16.4 0.1 3.2 P = 4.0 MPa; GHSV = 6000 h.sup.−1; H.sub.2:CO:CO.sub.2 = 3:1:1
Performance Evaluation of Regenerated Catalyst

Example 16

(20) The deactivated catalyst in Example 7 was treated with a mixture of 2% oxygen and 98% nitrogen in volume fraction at 550° C. for 10 hours to make the catalyst regenerate one round and catalyze reaction under the reaction conditions of Example 7. Five rounds of regeneration were performed in the same way, and the catalytic activity data after reaction for 500 hours in each round were selected for comparison. The results are shown in Table 2.

(21) TABLE-US-00002 TABLE 2 Catalytic Reaction results in Example 16 CO CO.sub.2 Regeneration Conversion Dimethyl ether Methanol Hydrocarbons selectivity Life per round number efficiency (%) Selectivity (%) Selectivity (%) selectivity (%) (%) round (h) 1 17.9 88.6 11.3 0.1 31.0 8500 2 17.6 88.0 11.9 0.1 30.9 8700 3 17.7 87.3 12.6 0.1 30.0 8400 4 17.3 84.5 15.4 0.1 29.8 8500 5 16.9 83.8 16.1 0.1 29.7 8600

(22) The aforesaid only show several examples of the present invention, and do not intend to limit the present invention in any manner. Though relatively preferred examples above disclose the present invention, they do not intend to limit the present invention. Without departing the scope of the technical solutions of the present invention, some variations or modifications made by the skilled in the art, who is familiar with this field by use of the above disclosed technical solutions, are all equal to the equivalent embodiments of the present invention, and fall within the scope of the technical solutions of the present invention.