Preparation of natural zeolite catalyst and the method of producing dimethyl ether from methyl alcohol using this catalyst

Abstract

The present invention relates to the preparation of various types of natural zeolite catalysts from natural zeolites such as clinoptilolite and the method of producing dimethyl ether from methyl alcohol using these natural zeolite catalysts.

Claims

1. A preparation method of natural zeolite catalyst for use in production of dimethyl ether by dehydration of methyl alcohol, characterized in that process steps of; a) milling natural zeolite to a particle size range of 500-1500 μm, b) drying the milled natural zeolite for 6 to 8 hours at 110-130° C., c) chemical treatment for removal of natural zeolite cations and to increase the ratio of SiO.sub.2:Al.sub.2O.sub.3 comprising following steps; performing a two-stage cation exchange with a NH.sub.4Cl solution on the dried milled natural zeolite, dealumination of the natural zeolite with a HCl solution, performing two-stage cation exchange to the natural zeolite with NH.sub.4Cl solution, d) obtaining a H-natural zeolite catalyst containing proton as a cation with a first calcination treatment of the natural zeolite of which cations are removed and has increased ratio of SiO.sub.2:Al.sub.2O.sub.3, e) obtaining a cation free D-natural zeolite catalyst by a followed second calcination treatment of a H-natural zeolite catalyst wherein the first calcination treatment in step d) is carried out at 350° C., and the second calcination treatment in step e) is carried out at 550° C.

2. The method according to claim 1 wherein the natural zeolite is washed and dried after each sub-step in subjecting to chemical treatment for removal of natural zeolite cations and raising SiO.sub.2:Al.sub.2O.sub.3 ratio.

3. The method according to claim 1, wherein the natural zeolite is clinoptilolite.

4. A method for the production of dimethyl ether by dehydration of methyl alcohol, wherein it is carried out in an inert gas atmosphere at atmospheric pressure and a temperature range of 250-300° C. using at least one of the natural zeolite catalyst obtained by the method according to the claim 3.

5. The method for the production of dimethyl ether by dehydration of methyl alcohol according to claim 4, wherein it is carried out in an inert gas atmosphere at atmospheric pressure and a temperature range of 250-300° C. by using H-Clinoptilolite catalyst.

6. The method for the production of dimethyl ether by dehydration of methyl alcohol according to claim 4, wherein it is carried out in an inert gas atmosphere at atmospheric pressure and a temperature range of 250-300° C. by using D-Clinoptilolite catalyst.

7. The method for the production of dimethyl ether by dehydration of methyl alcohol according to claim 4, wherein it is carried out in flow rate of 0.125 to 0.50 cm.sup.3/min range with regard to liquid methyl alcohol.

8. A method according to claim 1 to prepare zeolite catalyst from natural clinoptilolite characterized with steps of; a) milling natural clinoptilolite to a particle size range of 500-1500 micron, b) drying the milled natural clinoptilolite at 110-130° C. for 6-8 hours in the air environment, c) chemical treatment for removal of natural clinoptilolite cations and to increase the ratio of SiO.sub.2:Al.sub.2O.sub.3 comprising following steps; performing a two-stage cation exchange with a NH.sub.4Cl solution on the dried milled natural clinoptilolite for 6-8 hours at a temperature range of 80-90° C. in a continuous mixing environment, washing with water and air-drying for 2-4 hours at 110-130° C.; dealumination of the natural zeolite with a HCl solution at 70-90° C. for 4-6 h in a continuous mixing environment, washing with water and air-drying for 2-4 hours at 110-130° C.; performing two-stage cation exchange to the natural zeolite with NH.sub.4Cl solution for 2-4 hours at 80-90° C. in a continuous mixing environment; washing with water and air-drying for 2-4 hours at 120° C.; d) obtaining a H-natural zeolite catalyst containing proton as a cation with a first calcination treatment of the natural zeolite of which cations are removed and has increased ratio of SiO.sub.2:Al.sub.2O.sub.3, e) obtaining a cation free D-natural zeolite catalyst by a followed second calcination treatment of a H-natural zeolite catalyst, wherein the first calcination treatment in step d) is carried out at 350° C. for 2-4 h, and the second calcination treatment in step e) is carried out at 550° C. for 2-4 h.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) An objective of this invention is preparing various types of natural zeolite catalyst such as clinoptilolite comprising the steps of; milling natural zeolite; drying the milled natural zeolite; removal of natural zeolite cations and chemical treatment to increase the ratio of SiO.sub.2:Al.sub.2O.sub.3; and obtaining a H-natural zeolite catalyst, containing proton as a cation, with a first calcination treatment of the natural zeolite of which cations are removed and has increased ratio of SiO.sub.2:Al.sub.2O.sub.3; and then followed by a second calcination treatment obtaining cation free D-natural zeolite catalyst. In the preferred application of the invention, the first calcination treatment is carried out at 350° C. In the preferred application of the invention, the second calcination is carried out at 550° C.

(2) In the preferred application of the invention, chemical processes for removing natural zeolite cations and raising SiO.sub.2:Al.sub.2O.sub.3 ratio includes the steps of performing two-stage cation exchange by treating the milled and dried natural zeolite with NH.sub.4Cl solution, dealumination of the natural zeolite with HCl solution, and two-stage cation exchange of natural zeolite with NH.sub.4Cl solution. After each step mentioned above, the chemical processes for removing the natural zeolite cations and raising the SiO.sub.2:Al.sub.2O.sub.3 ratio, the natural zeolite is washed and dried.

(3) An exemplary application of the invention wherein clinoptilolite is used to prepare the natural zeolite catalyst is as follows. Clinoptilolite is first milled and fractionated with a particle size range of 500-1500 μm and dried. Clinoptilolite is then subjected to three-step chemical treatments to remove cations such as Na, K in crystal structure of clinoptilolite and to increase the ratio of SiO.sub.2:Al.sub.2O.sub.3 in the structure at the same time. In the first step, clinoptilolite is subjected to 2-step cation exchange with NH.sub.4Cl solution, then the dealumination process is applied to clinoptilolite with HCl solution, and finally for removal of Na.sup.+ and K.sup.+ cations from the clinoptilolite structure at maximum level, the clinoptilolite is again subjected to 2-step cation exchange with the NH.sub.4Cl solution. As a result of these processes, NH.sub.4.sup.+-Clinoptilolite containing ammonium cations (NH.sub.4.sup.+) is obtained. After each step of the chemical treatment, the clinoptilolite is washed and dried. The washed and dried NH.sub.4.sup.+-Clinoptilolite is then subjected to two-step calcination and eventually H-Clinoptilolite catalyst containing proton (H.sup.+) as a cation with high catalytic activity and by subjecting H-Clinoptilolite catalyst to calcination D-Clinoptilolite catalyst which is free of cations is obtained. In an alternative application of the invention, catalysts containing different metal cations can be obtained by subjecting the NH.sub.4.sup.+-clinoptilolite to the cation exchange with aqueous solutions of various metal salts.

(4) Table 1, Table 2 and Table 3 below show the element contents of the natural zeolite clinoptilolite and the H-Clinoptilolite catalyst and the D-Clinoptilolite catalyst obtained according to the above-mentioned method, respectively.

(5) TABLE-US-00001 TABLE 1 Elemental content of natural zeolite clinoptilolite Element % Weight % Atomic O 42.48 57.17 Al 9.43 7.52 Si 44.44 34.07 Cu 3.19 1.08 Zn 0.46 0.15

(6) TABLE-US-00002 TABLE 2 The element contents of the H-clinoptilolite catalyst obtained by the process subject of the invention Element % Weight % Atomic O 44.67 59.39 Al 4.08 3.21 Si 47.9 36.28 Cu 3.04 1.02 Zn 0.31 0.1

(7) TABLE-US-00003 TABLE 3 The element contents of the D-clinoptilolite catalyst obtained by the process subject of the invention Element % Weight % Atomic O 35.14 50.04 Al 4.29 3.62 Si 54.4 44.13 Cu 5.53 1.98 Zn 0.65 0.23

(8) As can be seen from the above tables, when the Si:Al ratio of the natural zeolite clinoptilolite is 4.71, this ratio is 11.74 in the H-clinoptilolite catalyst and 12.28 in the D-Clinoptilolite catalyst that are obtained by the method subject of invention. This, in turn, significantly increases the activity of the acidic sites of natural zeolite.

(9) When the H-clinoptilolite catalyst and the D-clinoptilolite catalyst that are obtained by the process subject of the invention are compared with the artificial zeolite catalysts, one of their important advantages is that no binder is required for pelletization and in this way the catalyst particles prepared on the basis of natural zeolite have high mechanical resistance. This advantage is achieved by grinding the natural zeolite at the beginning of the process subject of invention and separating the fraction having the desired particle size.

(10) The process of the present invention for the production of dimethyl ether by dehydration of methyl alcohol is carried out in an inert gas atmosphere at atmospheric pressure and a temperature range of 250-300° C. using the natural zeolite catalyst obtained by the process having the abovementioned steps. The conversion of methyl alcohol in these conditions varies between 68.3-96.5% and the selectivity to dimethyl ether is≈100% (in moles).

(11) A few examples of the method of obtaining dimethyl ether by dehydration of methyl alcohol are described below:

Example 1

(12) H-Clinoptilolite catalyst and D-Clinoptilolite catalyst were prepared according to the method described above for the production of dimethyl ether by dehydration of methyl alcohol. For this purpose; 10 g of clinoptilolite having particle sizes of 500-1000 μm were dried for 6 to 8 hours at 110-130° C. in the air environment. The clinoptilolite was then subjected to 2-step cation exchange with NH.sub.4Cl aqueous solution. Both cation exchange steps were carried out for 6 to 8 hours in a continuous mixing environment at a temperature range of 80-90° C. After the second-stage cation exchange, the clinoptilolite was washed with water and air-dried for 2 to 4 hours at a temperature of 110 to 130° C. Clinoptilolite was then subjected to dealumination treatment in the HCl aqueous solution at a temperature of 70° C. to 90° C. for 4 to 6 hours in a continuous mixing environment. The clinoptilolite was then washed with water and dried in the air at a temperature of 110 to 130° C. for 2 to 4 hours. Later the clinoptilolite was subjected to 2-step cation exchange with NH.sub.4Cl aqueous solution for 2 to 4 hours in a continuous mixing environment at a temperature range of 80-90° C. After that the clinoptilolite was washed with water and dried at 120° C. for 2 to 4 hours in air. Finally, H-clinoptilolite catalyst is obtained by subjecting clinoptilolite to calcination treatment at 350° C. for 2 to 4 hours. And D-clinoptilolite catalyst is obtained by subjecting a certain amount of the H-clinoptilolite catalyst to calcination at 550° C. for 2 to 4 hours in air.

(13) 3 g (˜3 cm.sup.3) of the prepared H-Clinoptilolite catalyst was taken and was used in the dehydration process of methyl alcohol. The said dehydration process was carried out in a continuous laboratory experimental system, having tubular fixed bed steel reactor with a diameter of 10 mm and a length of 200 mm under a nitrogen atmosphere. For this purpose, the H-Clinoptilolite catalyst was activated with N.sub.2 gas for 2 hours at 300° C. in atmospheric pressure.

(14) Dehydration was carried out at atmospheric pressure, at a temperature of 300° C., at a flow rate of 0.25 cm.sup.3/min (5 hours.sup.−1) with respect to liquid methyl alcohol and at a flow rate of approximately 11500 hours.sup.−1 with respect to nitrogen gas. The results are as follows:

(15) CH.sub.3OH conversion: % 94.5

(16) Selectivity according to dimethyl ether: % 99.6 (in moles)

Example 2

(17) The catalyst used for the dehydration process and other conditions were the same as in Example 1 at a temperature of 250° C. and results are as follows:

(18) CH.sub.3OH conversion: % 68.5

(19) Selectivity according to dimethyl ether: % 99.9 (in moles)

Example 3

(20) Dehydration was carried out at 350° C. using the D-Clinoptilolite catalyst with the other conditions being the same as in Examples 1 and 2 and results are as follows:

(21) CH.sub.3OH conversion: % 90.7

(22) Selectivity according to dimethyl ether: % 99.3 (in moles)

Example 4

(23) Dehydration was carried out in the same manner as in Example 2 except that the raw material flow rate was 0.125 cm.sup.3/min (2.5 hours.sup.−1) and results are as follows:

(24) CH.sub.3OH conversion: % 84.7

(25) Selectivity according to dimethyl ether: % 99.4 (in moles)

Example 5

(26) The dehydration process was carried out at 350° C. so that the raw material flow rate was 0.50 cm.sup.3/min (10 hours.sup.−1), the same as in Example 3 and results are as follows:

(27) CH.sub.3OH conversion: % 78.7

(28) Selectivity according to dimethyl ether: % 99.8 (in moles)

(29) Around these basic concepts, it is possible to develop a wide variety of applications relating to the invention “The Preparation Of Natural Zeolite Catalyst And The Method Of Producing Dimethyl Ether From Methyl Alcohol Using This Catalyst” and the invention cannot be limited to the examples mentioned herein, it is exactly as specified in the claims.