PROCESS AND CATALYST FOR LOW TEMPERATURE NON-OXIDATIVE DEHYDROGENATION OF PROPANE TO PROPYLENE

Abstract

A process and catalyst are provided for the non-oxidative dehydrogenation of propane for the production of propylene as petrochemical building blocks. The process provides a direct single-step gas-phase dehydration of propane mixed with nitrogen in the presence and absence of steam/hydrogen over supported bimetallic alumina-silicates zeolites. The catalyst contains no precious metal entities and may contain one metal from group VIB in combination with another metal from group IIIA or IVA supported on FAU, MFI, KFI, BEA type alumina-silicates zeolites. The process provides a propane conversion of 18% to 52% with a propylene yield of 10% to 25%.

Claims

1. A catalyst composition comprising: (a) a porous alumina-silicates zeolite Faujasite (FAU), Zeolite Mobil type Five (MFI), Zeolite Kerr Five (KFI) and Zeolite Beta polymorph A (BEA) as catalyst support; (b) a first metal selected from transition metals of group VIB, wherein the amount of the first metal is from 1 wt % to 10 wt % based on the porous zeolite catalyst support; (c) a second metal selected from a metals of group IIIA or IVA, wherein the amount of the second metal is from 1 wt % to 8 wt % based on the porous zeolite catalyst support; and (d) an alkaline metal, wherein the amount of alkaline metal from 0.5 wt % to 2 wt % based on the porous zeolite catalyst support.

2. The catalyst of claim 1, wherein the transition metal is selected from the group consisting of molybdenum, chromium, and tungsten.

3. The catalyst of claim 1, wherein the second metal is selected from the group consisting of tin, gallium, and indium.

4. The catalyst of claim 1, wherein the alkaline metal is selected from the group consisting of sodium, potassium, and cesium.

5. A process for preparing the catalyst composition according to claim 1, the process comprising: (a) depositing on a porous alumina-silicates zeolite support a first metal selected from transition metals of group VIB, a second metal selected from a metals of group IIIA or IVA, and an alkaline metal, to obtain a catalyst precursor; and (b) exposing the catalyst precursor of (a) for calcination in an environment comprising air or nitrogen to obtain the catalyst composition, wherein the porous alumina-silicates zeolite support is selected from the group consisting of FAU, MFI, KFI, and BEA.

6. The process of claim 5, wherein the first metal is selected from the group consisting of molybdenum, chromium, and tungsten.

7. The process of claim 5, wherein the second metal is selected from the group consisting of tin, gallium, and indium.

8. The process of claim 5, wherein the alkaline metal is selected from the group consisting of sodium, potassium, and cesium.

9. The process of claim 5, wherein (a) further comprises: (i) dissolving in water an ammonium salt, a nitrate salt, and a chloride salt of either one of the first metal selected from transition metal of group VIB to obtain a first solution, wherein the transition metal is selected from the group consisting of molybdenum, chromium, and tungsten; (ii) dissolving in water a nitrate salt and a chloride salt of either one of the second metal selected from group IIIA or IVA to obtain a second solution, wherein the second metal is selected from the group consisting of tin, gallium, and indium; (iii) mixing the first solution and the second solution, then adding addition cetyl trimethylammonium bromide in an amount of ratio of first and/or second metal(s) to CTAB of 1:0.1 to 1:10, then aging for a time period from 1 hour to 2 hours; (iv) adding the porous alumina-silicates zeolite in the form of powder during the aging of (iii) to obtain a white slurry, wherein a temperature of the white slurry containing CTAB, zeolite, metal(s), and alkaline metal is from 40° C. to 90° C.; (v) homogenizing the white slurry of (iv), then drying in an oven at a temperature from 100° C. to 150° C. for a time period from 10 hours to 18 hours to obtain a material; and (vi) calcining in air the material obtained in (v) at a temperature from 300° C. to 800° C. for a time period from 4 hours to 6 hours to obtain the catalyst precursor.

10. A continuous process for low temperature non-oxidative dehydrogenation of propane to propylene using the catalyst composition according to claim 1, the process comprising: (a) passing a mixture of propane and helium in the absence or presence of hydrogen (1%-5%) or steam (1%-5%) in a ratio of 4:20 in a reactor, wherein the reactor is kept at a pressure from 0.9 bar to 5 bar, a temperature from 350° C. to 700° C. with a gas hourly space velocity (GHSV) from 5000 h.sup.−1 to 9000 h.sup.−1 over the catalyst composition, for a time period from 1 hour to 24 hours to obtain a reaction product predominated with the propylene.

11. The continuous process of claim 10, wherein the reaction product contains side products selected from methane, ethane, ethylene, or combination thereof.

12. The continuous process of claim 10, wherein the propane to propylene conversion is from 18% to 52% at a temperature of 450° C.

13. The continuous process of claim 10, wherein a yield of the propylene is from 10% to 25%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] FIG. 1 represents the X-ray Diffraction (XRD) pattern of the prepared catalyst.

[0059] FIG. 2 represents the Transmission Electron Microscope (TEM) images of the prepared catalyst.

[0060] FIG. 3 represents the carbon elemental mapping of the prepared catalyst.

DETAILED DESCRIPTION

[0061] The present disclosure provides a catalyst consisting of a transition metal selected from group VIB, comprising one of Molybdenum (Mo), chromium (Cr), and tungsten (W), and a second metal from group IIIA or IVA, comprising one of tin (Sn), gallium (Ga), and Indium (In) on porous alumina-silicates zeolite like FAU, MFI, KFI, BEA, etc. The amount of transition metal selected from group VIB is kept between 1 to 10 wt % based on the porous zeolite support and the amount of second metal selected from group IIIA or IVA was kept between 1% to 8%. The catalyst was prepared by wetness impregnation as well as template-assisted (CTAB) wetness impregnation method for temperature non-oxidative dehydrogenation of propane. The process pressure was kept between 0.9-5 bar, at a temperature range of 350 to 700° C. with a gas hourly space velocity (GHSV) in the range of 5000-9000 If′. The catalyst was found stable for a period of 12-24 h time-on-steam.

[0062] The present disclosure relates to the synthesis of Mo—Sn-FAU catalyst as described above for the non-oxidative dehydrogenation of propane for the production of propylene which involves the following steps: [0063] i. Synthesizing molybdenum impregnated faujasite using molybdenum precursor and CTAB; [0064] ii. heating the Molybdenum impregnated faujasite at 50° C. and maintained for 1-2 h; [0065] iii. filtering the material obtained in step ii by washing with excess water and ethanol (1 liter) followed by drying the material in the oven at a temperature between 100-130° C. for 10-18 h; [0066] iv. Calcining the material of step ii at a temperature of 500° C. for time period of 4-6 h in the air to get solid Mo-FAU; [0067] v. Synthesizing Mo—Sn-FAU catalyst using tin chloride (Sigma-Aldrich, ≥99%) as a source of Sn, which is dissolved in water and heated at a temperature of 50° C.; [0068] vi. The weight ratio of Mo to faujasite was kept in the range of 2 to 8%; The weight ratio of Sn to faujasite was kept in the range of 3 to 5%; after homogenizing, the mixture of step v was heated further at a temperature of 60° C. and stirred for 1 h. [0069] vii. Adding 5-10 g of previously prepared nanoporous Mo-FAU zeolite in step vi material and kept at stirring for 1-2 h at the same temperature to obtain precipitate. [0070] viii. The precipitate of step vii was cooled down to room temperature naturally, collected and washed with ethanol and water several times; [0071] ix. Calcining the material of step viii at a temperature of 500° C. for time period of 4-6 h in the air to get Mo—Sn-FAU catalyst; [0072] x. Thereafter, a Non-oxidative dehydrogenation of propane was carried out in a fixed bed down-flow reactor using C.sub.3H.sub.8:N.sub.2 in 1:5 ratio in presence of Mo—Sn-FAU catalyst for 1-24 h to get propylene; [0073] xi. The reaction parameters of step x like pressure was kept at 1 atmosphere; temperature is preferably in the range 250 to 550° C.; The gas hourly space velocity (GHSV in ml g.sup.−1 h.sup.−1) is preferably in the range 5000 ml g.sup.−1 h.sup.−1 to 9000 ml g.sup.−1 h.sup.−1;

[0074] The propane conversion (mol %) of 30-50% and propylene selectivity of 40-50% with ratio of C.sub.3H.sub.8:N.sub.2 in 1:5 (mol %).

[0075] The present disclosure is also related to the synthesis of Mo—Ga-MFI catalyst as described above for the non-oxidative dehydrogenation of propane for the production of propylene which involves the following steps: [0076] i. Synthesizing of Molybdenum impregnated MFI using of molybdenum precursor, and CTAB; [0077] ii. heating the Molybdenum impregnated MFI at 50° C. and maintained for 1 hour to 2 hours; [0078] iii. filtering the material obtained in step ii by washing with excess water and ethanol (1 liter) followed by drying the materials in the oven at a temperature from 100° C. to 130° C. for 10 hours to 18 hours; [0079] iv. Calcining the materials of step iii at a temperature of 500° C. for the time period of 4-6 h in the air to get solid Mo-MFI; [0080] v. Synthesizing of Mo—Ga-MFI catalyst using gallium nitrate (Sigma-Aldrich, ≥99%) as a source of Ga, which is dissolved in water heated at a temperature of 50° C.; [0081] vi. The weight ratio of Mo to MFI was kept in the range of 2 to 8%; [0082] vii. The weight ratio of Ga to MFI was kept in the range of 3 to 5%; [0083] viii. After homogenization, the mixture was heated further to a temperature of 60° C. and stirred for 1 h. [0084] ix. Adding 5-10 g of previously prepared nanoporous Mo-MFI zeolite in step viii materials and kept at starring for 1-2 h at the same temperature to obtain precipitate. [0085] x. The precipitate of step ix was cooled down to room temperature naturally, collected and washed with ethanol and water several times; [0086] xi. Calcining of the materials of step x at a temperature of 500° C. for a time period of 4-6 h in the air to get catalyst Mo—Ga-MFI; [0087] xii. Thereafter a dehydrogenation of propane was carried out in a fixed bed down-flow reactor using C.sub.3H.sub.8:N.sub.2 in 1:5 ratio in presence of Mo—Ga-MFI catalyst for 1-24 h to get propylene; [0088] xiii. The reaction parameters like pressure was kept at 1 atmosphere; the reaction temperature is preferably in the range 250 to 550° C.; the gas hourly space velocity (GHSV in ml g.sup.−1 h.sup.−1) is preferably in the range 5000 ml g.sup.−1 h.sup.−1 to 9000 ml g.sup.−1 h.sup.−1;

[0089] The propane conversion (mol %) of 25-45% and propylene selectivity of 45-60% with ratio of C.sub.3H.sub.8:N.sub.2 in 1:5 (mol %).

[0090] The present invention is also related to the synthesis of K—Mo—Sn-MFI catalyst as described above for the non-oxidative dehydrogenation of propane for the production of propylene which involves the following steps: [0091] i. Synthesizing potassium loaded MFI zeolite using potassium precursor; [0092] ii. Mixing the potassium loaded MFI zeolite homogeneously and maintained for 2-3 h; [0093] iii. Filtering the materials obtained in step ii with excess water and ethanol and dried the material in the oven at a temperature of 100-150° C. for overnight; [0094] iv. Calcining the synthesized materials of step iii at a temperature of 450° C. for a time period of 4-6 h in the air to get K-MFI; [0095] v. Synthesizing Molybdenum impregnated K-MFI catalyst using of potassium precursor, and CTAB; [0096] vi. Heating the materials obtained in step v at a temperature of 50° C. and maintained for a time period of 1-2 h; [0097] vii. filtering the materials obtained in step vi by washing with excess water and ethanol (1 liter) followed by drying the materials in the oven at a temperature between 100-130° C. for a time period of 10-18 h; [0098] viii. Calcining the materials obtained in step vii at a temperature of at 500° C. for a time period of 4-6 h in the air to get solid K—Mo-MFI; [0099] ix. Synthesizing K—Mo—Sn-MFI catalyst using ammonium molybdate (Sigma-Aldrich, ≥99%) and tin chloride (Sigma-Aldrich, ≥99%) as a source of Mo and Sn, which is dissolved in water heated at a temperature of 50° C.; [0100] x. The weight ratio of Kto MFI was kept in the range of 0.5 to 2%; [0101] xi. The weight ratio of Mo to MFI was kept in the range of 2 to 8%; [0102] xii. The weight ratio of Sn to MFI was kept in the range of 3 to 5%; [0103] xiii. After homogenization, the mixture was heated further to a temperature of 60° C. and stirred for 1 hour. [0104] xiv. Adding a 5-10 g of previously prepared nanoporous K-MFI zeolite of step xiii materials and kept at starring for 1-2 h at the same temperature to obtain a precipitate. [0105] xv. The precipitate obtained in step xiv was cooled down to room temperature naturally, collected and washed with ethanol and water several times; [0106] xvi. Calcining the materials as obtained in step xv at heated a temperature of 500° C. for a time period of 4-6 h in the air to get K—Mo—Sn-MFI catalyst; [0107] xvii. Thereafter, a dehydrogenation of propane was carried out in a fixed bed down-flow reactor using C.sub.3H.sub.8:N.sub.2 in 1:5 ratio in presence of K—Mo—Sn-MFI for 1-24 h to get propylene; [0108] xviii. The reaction parameters like pressure was kept at 1 atmosphere; the reaction temperature is preferably in the range 250 to 550° C.; the gas hourly space velocity (GHSV in ml g.sup.−1 h.sup.−1) is preferably in the range 5000 mL g.sup.−1 h.sup.−1 to 9000 mL g.sup.−1 h.sup.−1;

[0109] The propane conversion (mol %) of 35-45% and propylene selectivity of 50-55% with ratio of C.sub.3H.sub.8:N.sub.2 in 1:5 (mol %).

EXAMPLES

[0110] The following examples are given by way of illustration, therefore, should not be construed to limit the scope of this disclosure or the appended claims.

Example 1

Synthesis of Metal-Doped Alumina-Silicates

[0111] All the catalysts were synthesized by the incipient wet-impregnation method. The support alumina-silicates were selected from FAU, MFI, KFI, BEA; as they offer different pore networks, surface area, etc. Metals were impregnated on the above-mentioned support in a predefined manner. The concentration of metals was decided based on the already available industrial catalysts.

Synthesis of Molybdenum Impregnated Alumina-Silicate Zeolites

[0112] The synthesis of Mo-FAU was carried out by a template-assisted wetness impregnation method. The amount of molybdenum was doped on the surface was kept 6%. It was synthesized by taking a calculated amount of molybdenum salt and it was dissolved in a sufficient amount of water. During stirring 10 g of each faujasite and MFI zeolite were added slowly into the different vessels. The whole solution was allowed to stir for 1-3 h to ensure the homogeneity of the mixture. Then, the solution was kept in the oven overnight at 50° C. Then the solution was filtered using grade 1, 2.5 μm Whatman filter paper and washed with water and ethanol. Finally, the calcination of the material was carried out at 500° C. for 4 h in air with a slow ramp rate.

[0113] The X-ray powder diffraction pattern and Transmission Electron Microscope (TEM) images of this material are given below.

Example 2

Synthesis of Sn Impregnated Mo-FAU Zeolites

[0114] Synthesis of Mo—Sn-FAU was carried out by a template-assisted wetness impregnation method. The amount of Tin was doped on the surface was kept at 4%. The above-mentioned zeolite was synthesized by taking the known amount of tin salt and it was dissolved in a sufficient amount of water. During stirring 2 g previously prepared Mo-FAU zeolite was added slowly. The whole solution was allowed to stir for 1-3 h to ensure the homogeneity of the mixture. Then the solution was kept in the oven overnight at 50° C. Then the solution was filtered using grade 1, 2.5 μm Whatman filter paper and washed with water and ethanol. Finally, the calcination of the material was carried out at 500° C. for 4 h in air with a slow ramp rate.

Example 3

Synthesis of Ga Impregnated Mo-MFI Zeolites

[0115] Synthesis of Mo—Ga-MFI was carried out by a template-assisted wetness impregnation method. The amount of Ga was doped on the surface was kept in between 4%. The above-mentioned zeolite was synthesized by taking the known amount of gallium salt and it was dissolved in a sufficient amount of water. During stirring 2 g previously prepared Mo-MFI zeolite was added slowly. The whole solution was allowed to stir for some more time to ensure the homogeneity of the mixture. Then The solution was kept in the oven overnight at 50° C. Then the solution was filtered using grade 1, 2.5 μm Whatman filter paper and washed with water and ethanol. Finally, the calcination of the material was carried out at 500° C. for 4 h in air with a slow ramp rate.

TABLE-US-00001 TABLE 1 Weight of Pt- Weight of Sn/ Weight of CTAB Catalyst salt (mg) Ga-salt (mg) (mg) Sn—Mo-FAU — 300-500 500 Ga—Mo-MFI — 500-600 500

Example 4

[0116] This example describes the propane dehydrogenation by gas phase reaction with C.sub.3H.sub.8:N.sub.2 mole ratio 1:5 using all the synthesised nanocrystalline zeolites as the catalysts. (Table 2)

[0117] The dehydrogenation of propane was carried out in a fixed-bed, down flow quartz reactor at atmospheric pressure. Typically, 200 mg of said synthesized catalyst (as provided in Examples 2 and 3 of this disclosure) was placed in between Silicon carbide with one quartz wool plugged at the bottom of the 8 mm quartz reactor and dehydrogenation of methane was carried out in a temperature range of 250-550° C. The gas hourly space velocity (GHSV) was varied between 3000 mL g.sup.−1 h.sup.−1 to 10000 mL g.sup.−1 h.sup.−1 with a molar ratio of C.sub.3H.sub.8:N.sub.2 of 1:5.

Process Conditions

[0118] Catalyst: 0.2 g

[0119] Mo—Sn-FAU wt % in the catalyst=6% of Mo and 4% of Sn

[0120] Pressure: 1 atmosphere

[0121] Total flow=25 mL/min (GHSV=7200)

[0122] Reaction time: 3 h

[0123] Molar ratio of C.sub.3H.sub.8/N.sub.2:1:5.

TABLE-US-00002 TABLE 2 Propane Propylene Temperature Conversion Selectivity C.sub.3H.sub.8/N.sub.2 Catalyst (° C.) (mol %) * (mol %) .sup.† (mol %) Mo—Sn-FAU 450 45 50 1:5 * X, .sup.† Y: The conversion and selectivity were taken as the base in subsequent tables.

Example 5

[0124] The present example describes the effect of different temperature values on propane conversion. The product analysis is presented in Table 3.

Process Conditions:

[0125] Catalyst: 0.2 g

[0126] Mo—Ga-MFI wt % in the catalyst=6% of Mo and 4% of Ga

[0127] Pressure: 1 atmosphere

[0128] Total flow=25 mL/min (GHSV=7200)

[0129] Reaction time: 3 h

[0130] Molar ratio of C.sub.3H.sub.8/N.sub.2:1:5

TABLE-US-00003 TABLE 3 Effect of temperature on propane conversion Propane Propylene Temperature Conversion Selectivity C.sub.3H.sub.8/N.sub.2 (° C.) (mol %) (mol %) (mol %) Dehydrogenation 300 X − 20 Y − 20 1:5 of propane 400 X − 12 Y − 10 1:5 to propylene 450 X − 5  Y − 5  1:5 500 X + 2  Y + 10 1:5 550 X + 10 Y + 15 1:5 X = 45% and Y = 50%

[0131] Here, X is % conversion of propane dehydrogenation to propylene using Mo—Sn/FAU catalyst and Y is % selectivity of propane dehydrogenation to propylene using Mo—Sn/FAU catalyst.

Example 6

[0132] The example describes the effect of time on stream on propane conversion. The product analysis presented in Table 4.

Process Conditions:

[0133] Catalyst: 0.2 g

[0134] Mo—Sn-FAU wt % in the catalyst=6% of Mo and 4% of Sn

[0135] Pressure: 1 atmosphere

[0136] Total flow=25 ml/min (GHSV=7200)

[0137] Reaction time: 22 h

[0138] Molar ratio of C.sub.3H.sub.8/N.sub.2:1:5.

TABLE-US-00004 TABLE 4 Effect of time-on-stream on propane conversion Propane Propylene Time Conversion Selectivity C.sub.3H.sub.8/N.sub.2 (mins) (mol %) (mol %) (mol %) Dehydrogenation 240 X − 25 Y + 2 1:5 of propane to 480 X − 27 Y + 5 1:5 propylene 720 X − 32 Y + 3 1:5 960 X − 35 Y + 2 1:5 1200 X − 33 Y + 6 1:5 X = 45% and Y = 50%

[0139] Here, X is % conversion of propane dehydrogenation to propylene using Mo—Sn/FAU catalyst and Y is % selectivity of propane dehydrogenation to propylene using Mo—Sn/FAU catalyst.

[0140] The main advantages of embodiments herein are: [0141] 1. The processes convert propane to propylene at a low temperature in a single step with a single bi-metallic catalyst. [0142] 2. The processes provide not only a good conversion but also an excellent yield of propylene in continuous process. [0143] 3. The processes run at atmospheric pressure to achieve 18-25% propylene yield at a temperature of 450° C., which is the major advantage of this process. [0144] 4. The employed catalyst does not contain any noble metal and comprises one metal from group VI B in combination with another metal from group III A or IV A which is the major advantage of the process. [0145] 5. The catalyst can be prepared easily and used in very low amounts (GHSV range of 5000-9000 h.sup.−1); therefore, very economical to produce propylene. [0146] 6. The catalyst does not show major deactivation until 24 h of time-on-stream in a continuous process.