Nano Ni—Zr oxide catalyst for activation of methane by tri-reforming and a process for the preparation thereof

Abstract

The present invention provides a NiZr oxide catalyst and a process for the preparation of the catalyst. The invention further provides use of the catalyst for the production of synthesis gas (a mixture of CO and H.sub.2) by Tri-reforming of methane. The process provides a direct single step selective vapor phase partial oxidation of methane to synthesis gas over NiZrO.sub.2 catalyst between temperature range of 600 C. to 800 C. at atmospheric pressure. The process provides a methane conversion of 1-99% with H.sub.2 to CO mole ratio of 1.6 to 2.2.

Claims

1. A nano NiZr oxide catalyst having the formula NiOZrO.sub.2 consisting essentially of NiO in the range of 1-10 wt % and ZrO.sub.2 in the range 90-99 wt %, wherein the NiOZrO.sub.2 catalyst is a co-precipitated catalyst, and wherein the co-precipitated catalyst has a particle size in the range of 20 nm to 100 nm.

2. A process for the preparation of nano NiZr oxide catalyst of claim 1, comprising: (a) stirring a solution of Zr salt, Ni-salt, a surfactant and H.sub.2O for a period ranging between 2-3 hours at a temperature ranging between 25-350 C. followed by adding hydrazine hydrate subsequently followed by a Na.sub.2CO.sub.3 solution to adjust the pH in the range of 11-12; (b) stirring a reaction mixture obtained in step (a) for a period ranging between 1-3 hours at temperature ranging between 25-350 C. followed by heating the mixture in an autoclave at temperature ranging between 170 C. to 180 C. for the time period ranging between 18-24 hours to obtain precipitate; and (c) filtering the precipitate as obtained in step (b) with water and ethanol then dried at temperature ranging between 60 C.-110 C. for a time period ranging between 15-20 hours followed by calcinating the dried product at a temperature in the range of 400-750 C. for a time period in the of 4-10 hours to obtain NiOZrO.sub.2 oxide.

3. The process of claim 2, wherein Zr salt used in step (a) is zirconium propoxide.

4. The process of claim 2, wherein Ni salt used in step (a) is Nickel nitrate hexahydrate.

5. The process of claim 2, wherein surfactant used in step (a) is Cetyltrimethyl ammonium bromide (CTAB).

6. The process of claim 2, wherein wt % ratio of Ni and Zr is in the range of 1:99 to 10:90.

7. A process for activation of methane using the catalyst of claim 1 to obtain syngas comprising passing O.sub.2:CO.sub.2:H.sub.2O:CH.sub.4:He in the molar ratio ranging between 1:1:1.7:5:18 to 1:1:2.4:5:18 ratio in a reactor at atmospheric pressure in the presence of the co-precipitated NiOZrO.sub.2 catalyst at a temperature ranging between 600-800 C. for a period ranging between 1-70 hours at a gas hourly space velocity (GSHV) ranging between 20000-400000 mlg.sup.1 h.sup.1 to obtain syngas.

8. The process of claim 7, wherein conversion percentage of methane is in the range of 1-97%.

9. The process of claim 7, wherein conversion percentage of CO.sub.2 is in the range of 1-98%.

10. The process of claim 7, wherein conversion percentage of H.sub.2O is in the range of 1-98%.

11. The process of claim 7, wherein H.sub.2/CO ratio of syngas obtained is in the range of 1.8-2.2.

Description

BRIEF DESCRIPTION OF DRAWING

(1) FIG. 1 X-ray Diffraction (XRD) of 2.5% NiZrO.sub.2.

(2) FIG. 2 Scanning Electron Microscope (SEM) image of 2.5% NiZrO.sub.2.

(3) FIG. 3 Low magnification Transmission Electron Microscope (TEM) image of 2.5% NiZrO.sub.2.

(4) FIG. 4 High magnification TEM image of 2.5% NiZrO.sub.2.

(5) FIG. 5 Mapping of Zr in 2.5% NiZrO.sub.2.

(6) FIG. 6 Mapping of Ni in 2.5% NiZrO.sub.2.

(7) FIG. 7 X-ray Diffraction (XRD) of 5% NiZrO.sub.2.

(8) FIG. 8 SEM image of 5% NiZrO.sub.2.

(9) FIG. 9 Low magnification TEM image of 5% NiZrO.sub.2.

(10) FIG. 10 High magnification TEM image of 5% NiZrO.sub.2.

(11) FIG. 11 Mapping of Zr in 5% NiZrO.sub.2.

(12) FIG. 12 Mapping of Ni in 5% NiZrO.sub.2.

DETAILED DESCRIPTION OF THE INVENTION

(13) Present invention provides a nano NiZr oxide catalyst having formula NiOZrO.sub.2 comprises NiO in the range of 1-10 wt % and ZrO.sub.2 in the range 90-99 wt %.

(14) The present invention also provides a process for the preparation of Nano NiZr oxide catalyst.

(15) Synthesis of NiZr oxide was carried out using gel composition of Zirconium propoxide, Nickel nitrate hexahydrate, Cetyltrimethylammonium bromide (CTAB), 1(M) Na.sub.2CO.sub.3 solution where Zirconium propoxide was used as the precursor of Zr.

(16) The molar ratio of Ni to CTAB varied in the range of 1:0.75-1.0.

(17) The pH of the gel was adjusted between 11-12.

(18) The molar ratio of H.sub.2O to Zr varied in the range of 100-150.

(19) The mixing gel was stirred for 1-3 h at room temperature.

(20) Heating of the resultant solution was carried out in a closed autoclave at 180 C. for 18-24 hours.

(21) The product was filtered with excess water and ethanol then dried in an oven with temperature range of 60-110 C. for 15-20 h. The dried product was calcined in a furnace in the temperature range of 400-750 C. for 4-10 h.

(22) General Procedure for the Tri-Reforming of Methane to Synthesis Gas

(23) The Tri-reforming of methane was carried out in a fixed-bed down flow reactor at atmospheric pressure. Typically 10 to 500 mg of catalyst was placed in between two quartz wool plugged in the center of the 6 mm quartz reactor. The reaction was carried out with the freshly prepared catalyst at different temperatures ranging 600-800 C. The gas hourly space velocity (GHSV) was varied between 20000 to 400000 ml g.sup.1 h.sup.1 with a molar ratio of O.sub.2:CO.sub.2:H.sub.2O:CH.sub.4:He of 1:1:1.7:5:18 to 1:1:2.4:5:18. The reaction products were analyzed using an online gas chromatography (Agilent 7890A) fitted with a TCD detector using two different columns Molecular sieves (for analyzing H.sub.2) and PoraPack-Q (for analyzing CH.sub.4, CO.sub.2 and CO).

EXAMPLES

(24) The following examples are given by way of illustration and therefore should not be constructed to limit the scope of the present invention.

Example 1

Preparation of 2.5% NiZrO2

(25) 5.4 gm of Zirconium propoxide was taken in a beaker. 20 ml of water was added into it further stirred the solution for 30 min at temperature 30 C. 0.11 gm of nickel nitrate hexahydrate solution in 10 ml water was added in to it followed by continued stirring for 15 min. Added 0.15 gm CTAB solution in 10 ml ethanol to the previous mixture followed by pH of the solution was maintained to 12 using 1(M)Na.sub.2CO.sub.3 solution. The whole mixture was continued stirring for 2 hours at temperature 30 C. After that the total mixture was kept into an autoclave for 24 hours. at 180 C. After 24 hours. the precipitate was washed with water and then ethanol. The precipitate was dried at 110 C. overnight for 15 hours. Then the material was calcined at 550 C. for 6 hours.

(26) The material was characterized by XRD, SEM, elemental mapping and TEM. The XRD pattern of the 2.5% NiZrO.sub.2 is shown in FIG. 1. XRD depicts the presence of NiO and ZrO.sub.2 in the sample. The morphology of the material (2.5% NiZrO.sub.2) was characterized by SEM. The typical image of the 2.5% NiZrO.sub.2 is shown in FIG. 2. From the SEM image it is clear that the particles are almost spherical in shape. The typical TEM images of the 2.5% NiZrO.sub.2 are shown in FIG. 3-4. FIG. 3 is the TEM images at low magnification and FIG. 4 is the image of the 2.5% NiZrO.sub.2 at very high magnification. The dispersion of the Ni particles on ZrO.sub.2 support was analyzed by taking the elemental mapping of Ni and Zr using SEM as shown in FIG. 5 and FIG. 6. The mapping confirms that Ni is highly dispersed on ZrO.sub.2.

Example 2

Preparation of 5% NiZrO2

(27) 5.4 gm of Zirconium propoxide was taken in a beaker. 20 ml of water was added into it further stirred the solution for 30 min at temperature 30 C. 0.23 gm of nickel nitrate hexahydrate solution in 10 ml water was added in to it followed by continued stirring for 15 min. Added 0.30 gm CTAB solution in 10 ml ethanol to the previous mixture followed by pH of the solution was maintained to 12 using 1(M)Na.sub.2CO.sub.3 solution. The whole mixture was continued stirring for 2 hours at temperature 30 C. After that the total mixture was kept into an autoclave for 24 hours. at 180 C. After 24 hours, the precipitate was washed with water and then ethanol. The precipitate was dried at 110 C. overnight for 15 hours. Then the material was calcined at 550 C. for 6 hours.

(28) The material was characterized by XRD, SEM, elemental mapping and TEM. The XRD pattern of the 5% NiZrO.sub.2 is shown in FIG. 7. XRD depicts the presence of NiO and ZrO.sub.2 in the sample. The morphology of the 5% NiZrO.sub.2 catalyst was characterized by SEM. The typical image of the 5% NiZrO.sub.2 is shown in FIG. 8. From the SEM image it is clear that the particles are almost spherical in shape. The typical TEM images of the 5% NiZrO.sub.2 are shown in FIG. 9-10. FIG. 9 is the TEM images at low magnification and FIG. 10 is the image of the 5% NiZrO.sub.2 at very high magnification. The dispersion of the Ni particles on ZrO.sub.2 support was analyzed by taking the elemental mapping of Ni and Zr using SEM as shown in FIG. 11 and FIG. 12. The mapping confirms that Ni is highly dispersed on ZrO.sub.2.

Example 3

(29) The example describes the effect of temperature on conversion and H.sub.2/CO ratio of Tri-reforming of methane. The product analysis presented in Table-1.

(30) Process Conditions

(31) Catalyst: 0.06 g

(32) Ni:ZrO.sub.2 weight ratio in the catalyst=2.5:97.5.

(33) Process pressure: 1 atm.

(34) Gas hourly space velocity (GHSV): 80000 ml g.sup.1 h.sup.1

(35) Reaction time: 4 h

(36) O.sub.2:CO.sub.2:H.sub.2O:CH.sub.4:He=1:1:2.1:5:18 (mol %)

(37) TABLE-US-00001 TABLE 1 Effect of temperature on conversion Methane CO.sub.2 H.sub.2O Temperature Conversion Conversion Conversion ( C.) (%) (%) (%) H.sub.2/CO ratio 600 0 0 0 700 81.4 79.5 76.4 1.9 800 95.3 94.3 98.8 1.9

Example 4

(38) The example describes the effect of temperature on conversion and H.sub.2/CO ratio of Tri-reforming of methane. The product analysis presented in Table-1.

(39) Process Conditions

(40) Catalyst: 0.06 g

(41) Ni:ZrO.sub.2 weight ratio in the catalyst=5:95.

(42) Process pressure: 1 atm.

(43) Gas hourly space velocity (GHSV): 80000 ml g.sup.1 h.sup.1

(44) Reaction time: 4 h

(45) O.sub.2:CO.sub.2:H.sub.2O:CH.sub.4:He=1:1:2.1:5:18 (mol %)

(46) TABLE-US-00002 TABLE 2 Effect of temperature on conversion Methane CO.sub.2 H.sub.2O Temperature Conversion Conversion Conversion ( C.) (%) (%) (%) H.sub.2/CO ratio 600 2 0 0 700 85.3 87.7 87.5 1.9 800 98.2 99.4 99.3 1.9

Example 5

(47) The example describes the effect of temperature on conversion and H.sub.2/CO ratio of Tri-reforming of methane. The product analysis presented in Table-1.

(48) Process Conditions

(49) Catalyst: 0.06 g

(50) Ni:ZrO.sub.2 weight ratio in the catalyst=10:90.

(51) Process pressure: 1 atm.

(52) Gas hourly space velocity (GHSV): 80000 ml g.sup.1 h.sup.1

(53) Reaction time: 4 h

(54) O.sub.2:CO.sub.2:H.sub.2O:CH.sub.4:He=1:1:2.1:5:18 (mol %)

(55) TABLE-US-00003 TABLE 3 Effect of temperature on conversion Methane CO.sub.2 H.sub.2O Temperature Conversion Conversion Conversion ( C.) (%) (%) (%) H.sub.2/CO ratio 600 0.8 0.8 0.9 700 74 78 76 1.9 800 87 89 89 1.9

Example 6

(56) The example describes the effect of gas hourly space velocity on the conversion of methane and H.sub.2/CO ratio of Tri-reforming of methane. The product analysis presented in Table-3.

(57) Process Conditions

(58) Catalyst: 0.030 g

(59) Ni:ZrO2 weight ratio in the catalyst=5:95.

(60) Process pressure: 1 atm.

(61) Gas hourly space velocity (GHSV): 160000 ml g1 h1

(62) Reaction time: 4 h

(63) O.sub.2:CO.sub.2:H.sub.2O:CH.sub.4:He=1:1:2.1:5:18 (mol %)

(64) TABLE-US-00004 TABLE 3 Effect of temperature on conversion Methane CO.sub.2 H.sub.2O Temperature Conversion Conversion Conversion Syngas ( C.) (%) (%) (%) H.sub.2/CO ratio 600 2 0 0 700 85.56 85.89 85.48 1.9 800 97.32 98.56 98.23 1.9

Example 7

(65) The example describes the effect of gas hourly space velocity on the conversion of methane and H.sub.2/CO ratio of Tri-reforming of methane. The product analysis presented in Table-4.

(66) Process Conditions:

(67) Catalyst: 0.030 g

(68) Ni:ZrO2 weight ratio in the catalyst=5:95.

(69) Process pressure: 1 atm.

(70) Temperature: 800 C.

(71) Reaction time: 4 h

(72) O.sub.2:CO.sub.2:H.sub.2O:CH.sub.4:He=1:1:2.1:5:18 (mol %)

(73) TABLE-US-00005 TABLE 4 Effect of temperature on conversion CO.sub.2 H.sub.2O GHSV Methane Conversion Conversion Syngas (ml)/h/gcat) Conversion (%) (%) (%) H.sub.2/CO ratio 20000 99.35 98.76 98.73 1.9 40000 98.48 98.69 98.05 1.9 80000 97.57 98.67 97.98 1.9 160000 97.32 98.56 98.23 1.9 320000 94.95 95.53 95.69 1.9 400000 94.46 94.86 93.78 1.9

Example 8

(74) The example describes the effect of gas hourly space velocity on the conversion of methane and H.sub.2/CO ratio of Tri-reforming of methane. The product analysis presented in Table-5.

(75) Process Conditions

(76) Catalyst: 0.06 g

(77) Ni:ZrO2 weight ratio in the catalyst=5:95.

(78) Process pressure: 1 atm.

(79) Temperature: 800 C.

(80) Gas hourly space velocity (GHSV): 80000 ml g.sup.1 h.sup.1

(81) O.sub.2:CO.sub.2:H.sub.2O:CH.sub.4:He=1:1:2.1:5:18 (mol %)

(82) TABLE-US-00006 TABLE 5 Effect of Time on Stream (TOS) on the conversion of methane Time Methane CO2 H2O H2/CO (h) Conv. (%) Conv. (%) Conv. (%) ratio 0 97.32 98.56 98.23 1.9 1 96.78 98.03 98.33 1.9 2 96.69 97.78 98.12 1.9 4 97.89 97.56 97.63 1.9 5 97.54 97.23 97.73 1.9 6 97.23 97.17 97.73 1.9 7 97.33 97.67 97.52 1.9 8 97.29 97.57 96.89 1.9 10 96.87 97.45 96.75 1.9 15 96.67 97.56 97.64 1.9 20 96.89 97.46 96.53 1.9 25 96.45 96.88 96.65 1.9 30 96.78 96.53 97.55 1.9 35 96.79 96.56 96.63 1.9 40 96.64 96.54 96.23 1.9 50 96.84 96.56 96.64 1.9 60 95.78 95.92 95.32 1.9 70 95.32 95.23 95.04 1.9

ADVANTAGES OF THE INVENTION

(83) The main advantages of the present invention are: The process of the present invention is to utilize methane by converting methane to syngas through Tri-reforming of methane in a single step with a single catalyst. The process of the present invention is to utilize carbon dioxide to produce syngas through Tri-reforming of methane in a single step with a single catalyst. The process of the present invention is to utilize steam by to produce syngas through Tri-reforming of methane in a single step with a single catalyst. The process provides not only good conversion but also good H.sub.2/CO ratio of syngas. The process utilizes a major component of abandoned natural gas to produce syngas with H.sub.2/CO ratio almost equal to two, which become the major advantages of this process and which can be directly use for the production of methanol and Fischer-Tropsch synthesis. The process utilizes three greenhouse gasses to produce synthesis gas. The process does not produce any major by-products which is also a major advantage of this process. The catalyst shows no deactivation up to 70 h time on stream at 800 C.; The catalyst is used in very low amounts.