Ni—Pt—ZrO2 nanocrystalline oxide catalyst and process thereof useful for the production of syngas by combining oxy-dry reforming of natural gas

Abstract

The present invention provides a process and catalyst for the autothermal and dry reforming of methane to produce syngas. The process provides a direct single step gas phase reforming of methane or natural gas to syngas over NiPt supported nanocrystalline ZrO.sub.2. The process provides methane conversion of 54-99% with H.sub.2/CO ratio of 1.14 to 1.42 (mol %) in the temperature range of 250 to 750 800 C. at atmospheric pressure.

Claims

1. A process for the preparation of NiPtZrO.sub.2 nanocrystalline oxide catalyst, wherein said process comprises the steps of: i. dissolving 0.025 to 0.0372 mol of ZrOCl.sub.2 in 2.78 to 5.56 mol of water, wherein the mole ratio of ZrOCl.sub.2: H.sub.2O ranges from 180 to 400 in the solution with the pH adjusted in the range of 3-10 using NH.sub.4OH solution; ii. transferring the mixture of step i) to a stainless steel autoclave and heating at a temperature in the range of 50 to 70 C. for a period in the range of 1 to 2 hrs to obtain a white precipitate; iii. filtering, washing and drying the white precipitate as obtained in step ii) at a temperature in the range of 100 to 130 C. for a period in the range of 10 to 18 hrs; iv. calcining the materials as obtained in step iii) at a temperature in the range of 300 to 800 C. for a period in the range of 4 to 6 hrs in air to get solid ZrO.sub.2; v. mixing 0.1-0.3 mmol of H.sub.2PtCl.sub.6.6H.sub.2O and 0.2-0.4 mmol of Ni(NO.sub.3).sub.2.6H.sub.2O in 70 to 95 vol % of liquid octadecylamine (ODA), heating the mixture at a temperature in the range of 100-140 C., further heating the content up to 220 C. after transferring the mixture to a lined stainless steel autoclave and stirring for 10 minutes followed by adding 0.008 to 0.016 mol of ZrO.sub.2, a support material as obtained in step iv) with the weight of ZrO.sub.2 maintained in the range of 86-97.5% of the combined weight of Ni, Pt and ZrO.sub.2; vi. stirring the mixture as obtained in step v) for a period in the range of 1 to 2 h, and subjecting the reaction mixture for ultrasonic treatment for a period in the range of 40-60 minutes at room temperature in the range of 25-35 C. after adding concentrated nitric acid in the range of 2.0-5.0 ml to obtain a precipitate; vii. cooling the precipitate of step vi) to room temperature in the range of 25-35 C., collecting and washing the cooled precipitate with ethanol for 2-3 times followed by drying the materials in an oven at a temperature ranging from 100 to 130 C. for a period in the range of 10 to 18 h; and viii. calcining the material of step vii) at a temperature in the range of 300 to 800 C. for a period in the range of 4 to 6 h in air to obtain nanocrystalline oxide NiPtZrO.sub.2 catalyst: wherein the NiPtZrO.sub.2 nanocrystalline oxide catalyst has 2-10 wt % of Ni, 0.5 to 4 wt % of Pt, 86 to 97.5 wt % of ZrO.sub.2, and a particle size in the range of 30-80 nm.

Description

BRIEF DESCRIPTION OF THE INVENTION

(1) Nanocrystalline NiPtZr oxide catalyst is prepared by hydrothermal method with particle size in the 30-80 nm range. This catalyst is highly active for the production of synthesis gas from the mixture of two green house gases (CH.sub.4 and CO.sub.2), oxygen and helium, CH.sub.4+O.sub.2+CO.sub.2+He (combining dry and oxy reforming) at a temperature range between C. The typical mole ratio of the feed mixture was CH.sub.4:CO.sub.2:O.sub.2+He:1:1:0.5:7.5. The catalyst does not deactivate till 100 h at atmospheric pressure.

(2) Preparation of nanostructurd NiPtZrO.sub.2 catalyst was carried out by using colloidial and hydrothermal route. Ni(NO.sub.3).sub.2.6H2O, H.sub.2PtCl.sub.6.6H.sub.2O and ZrOCl.sub.2 was taken as Ni, Pt and Zr source respectively. Initially, ZrO.sub.2 support was prepared by hydrothermal method at 60 C. for 2 h using Zr source, ammonium hydroxide at a pH of 10. Finally the material was calcined at 7500 C. for 5 h. The NiPt was incorporated by using colloidial method first then hydrothermal method. In the colloidial method Ni and Pt salt was dissolved in octadecylamine and heated at 120 C. The it was hydrothermally treated at 220 C. for 10 min and ZrO.sub.2 was added and heated for another 30 min 220 C. Finally the calcination of the C for 6 h in air to get nanocrystallinematerial was carried out at 750 NiPtZr oxide.

(3) FIG. 1 represents the conversion of methane over time on stream for the NiPtZrO.sub.2 catalyst.

(4) FIG. 2 represents X-ray Diffraction (XRD) pattern of the prepared catalyst.

(5) FIG. 3 represents Scanning Electron Microscope (SEM) images of the as prepared ZrO.sub.2.

(6) FIG. 4 represents Transmission Electron Microscope (TEM) images of the prepared catalyst.

DETAILED DESCRIPTION OF THE INVENTION

(7) The present invention provides a catalyst consisting of NiPtZrO.sub.2 prepared by colloidal as well as hydrothermal route and process to produce syngas from methane by gas phase combining the oxy- and dry reforming over NiPtZrO.sub.2 catalyst at atmospheric pressure, at a temperature range of 250 to 750 C. with a gas hourly space velocity (GHSV) in the range of 12000-42000 ml g.sup.1 h.sup.1 in the presence of NiPt supported ZrO.sub.2 catalyst with NiPt to ZrO.sub.2 weight ratio varied between 3 to 6% to obtain desired product syngas for a period of 1-100 hours.

(8) The present invention related to process for oxy-dry reforming of natural gas for the production of syngas (a mixture of CO and H.sub.2) over NiPtZrO.sub.2 catalyst which involves the following steps:

(9) Synthesis of ZrO.sub.2 oxide using of ZrOCl.sub.2, ammonium hydroxide to adjust the pH between 3-10;

(10) Heated at 60 C. after transferring the mixture to a stainless steel autoclave and maintained for 1-2 h;

(11) Filtered the material by washing with excess water (2 liter) and checked by AgNO.sub.3 solution followed by drying the materials in oven at a temperature between 100130 C. for 10-18 h;

(12) Calcination of the materials at 300-800 C. for 4-6 h in air to get solid ZrO.sub.2;

(13) Synthesis of NiPtZrO.sub.2 catalyst was prepared using H.sub.2PtCl.sub.6.6H.sub.2O (Sigma-Aldrich, 99%) and Ni(NO.sub.3).sub.2.6H.sub.2O (Sigma-Aldrich, 99%) as source of Pt and Ni dissolved in liquid octadecylamine (ODA) heated at 120 C.;

(14) The weight ratio of Pt to ZrO.sub.2 varied in the range of 0.5 to 4.0%;

(15) The weight ratio of Ni to ZrO.sub.2 varied in the range of 2 to 10.0%;

(16) After homogenization the mixture was heated up to 220 C. after transferring the mixture to a stainless steel autoclave and stirred for 10 min. A measured amount nanoporous ZrO.sub.2 was successively added and kept at starring for h at same temperature. After the reaction, asprepared NiPt nanoparticles subjected for ultrasonic treatment for 1 min at room temperature after adding excess amount of concentrated nitric acid into it. The precipitate was cooled down to room temperature naturally, collected and washed with ethanol several times;

(17) Calcination of the materials at 300-800 C. for 4-6 h in air to get NiPtZrO.sub.2;

(18) Autothermal and dry reforming of methane was carried out in a fixed bed down-flow reactor using CH.sub.4:CO.sub.2:O.sub.2:He in 1:1:0.5:7.5 ratio for 1-100 h to get methane;

(19) The process pressure was kept at 1 atmosphere;

(20) The reaction temperature is preferably in the range 250 to 750 C.;

(21) The gas hourly space velocity (GHSV in ml g.sup.1 h.sup.1) is preferably in the range 12000 ml to 42000 ml g.sup.1 h.sup.1;

(22) The methane conversion (mol %) of 54-99% with H.sub.2/CO ratio of 1.14 to 1.42 (mol %).

(23) The detailed steps of the process are:

(24) The autothermal and dry reforming of methane was carried out in a fixed-bed down flow reactor at atmospheric pressure. Typically 200 mg of catalyst was placed in between two quartz wool plugged in the centre of the 6 mm quartz reactor and ATR was carried out in a temperature range of 250-750 C. The catalyst was reduced using 5% H.sub.2 balance He at 700 C. for 1 h before the reaction. The gas hourly space velocity (GHSV) was varied between 12000 ml g.sup.1 h.sup.1 to 42000 ml g.sup.1 h.sup.1 with a molar ratio of CH.sub.4:CO.sub.2:O.sub.2:He of 1:1:0.5:7.5. The reaction products were analyzed using an online gas chromatography (Agilent 7890A) fitted with a TCD detector using PoraPack-Q column.

(25) An improved process for the preparation of NiPtZrO.sub.2 catalyst, wherein the said process comprising the steps of:

(26) ZrOCl.sub.2 was dissolved in water and 1N NH.sub.4OH solution was added to adjust the pH between 3-10.

(27) Heating the solution after transferring the mixture to a stainless steel autoclave at 60 C. and maintained for 1-2 h.

(28) Filtered the material by washing with excess water (2 liter) followed by drying the materials in oven at a temperature between 100-130 C. for 10-18 h.

(29) Calcination of the materials at 300-800 C. for 4-6 h in air to get solid ZrO.sub.2.

(30) Synthesis of NiPtZrO.sub.2 catalyst using H.sub.2PtCl.sub.6.6H.sub.2O and Ni(NO.sub.3).sub.2.6H.sub.2O dissolved in liquid octadecylamine (ODA). After homogenization the mixture was heated up after transferring the mixture to a stainless steel autoclave to 220 C. and stirred for 10 min. A measured amount nanoporous ZrO.sub.2 was successively added and continued starring for h at same temperature. After the reaction, as-prepared NiPt nanoparticles subjected for ultrasonic treatment for 1 min at room temperature after adding excess amount of concentrated nitric acid into it. The precipitate was cooled down to room temperature, collected and washed with ethanol several times.

(31) The weight ratio of Pt to ZrO.sub.2 is varied in the range of 0.5 to 4.0%.

(32) The weight ratio of Ni to ZrO.sub.2 is varied in the range of 2 to 10.0%.

(33) Calcination of the materials at 300-800 C. for 4-6 h in air to get NiPtZrO.sub.2.

(34) A process for autothermal and dry reforming of methane to produce syngas with NiPtZrO.sub.2 catalyst comprising the steps of:

(35) Passing methane, CO.sub.2 and O.sub.2 at atmospheric pressure, at a temperature range of 250 750 C. with a gas hourly space velocity (GHSV) in the range of 12000-42000 ml g.sup.1 h.sup.1 in the presence of NiPt supported ZrO.sub.2 catalyst; to obtain syngas for a period of 1-100 hours.

(36) Weight ratio of Ni to ZrO.sub.2 was varied between 2 to 10% and Pt to ZrO.sub.2 weight ratio varied between 0.5 to 4.0%.

(37) Reactor pressure is preferably in the range of 1 atmosphere.

(38) Reaction temperature is preferably in the range 250 to 750 C.

(39) Gas hourly space velocity (GHSV) is preferably in the range of 12000 g ml 1.sup.1 h.sup.1 to 42000 g ml.sup.1 h.sup.1.

(40) Reaction time used is preferably in the range 1-100 h. Conversion (mol %) of methane is in the range of 54-99% with H.sub.2/CO ratio of 1.14 to 1.42 (mol %).

EXAMPLES

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

Example1

Synthesis of ZrO2

(42) 10 g (0.031 mol, 0.7 mol %) zirconium oxychloride was taken in 75 ml (4.17 mol, 99.3 mol %) distilled water to form a homogeneous solution, the pH of the solution was adjusted by ammonium hydroxide solution and pH of the mixed solution was fixed at 10. Finally, the mixed solution was heated at 60 C. after transferring the mixture to a stainless steel autoclave and maintained for 2 h. The resultant solid was collected by filtration, washed thoroughly with distilled water and ethanol and dried at 100 C. for 12 h. The as-synthesized material was calcined to 750 C. with a temperature ramp of 1.5 C./min under static air and kept at the same temperature for 5 h. This was used as a ZrO.sub.2 support material.

Synthesis of NiPtZrO2

(43) Synthesis of NiPtZrO.sub.2 catalyst was carried out taking 0.1 mmol (1.2 mmol %) H.sub.2PtCl.sub.6.6H.sub.2O (Sigma-Aldrich, 99%) and 0.2 mmol (3.6 mmol %) of Ni(NO.sub.3).sub.2.6H.sub.2O (Sigma-Aldrich, 99%) dissolved in 10 ml (95 vol %) liquid octadecylamine (ODA) heated at 120 C. After the homogenization, the content was heated up to 220 C. after transferring the mixture to a stainless steel autoclave and stirred for 10 min. A measured amount, 1-2 grams (0.008-0.016 mol) of nanoporous ZrO.sub.2 was successively added and kept at starring for h at same temperature. After the reaction, as-prepared PtNi nanoparticles subjected for ultrasonic treatment for 1 min at room temperature after adding excess amount of concentrated nitric acid into it. The precipitate was cooled down to room temperature naturally, collected and washed with ethanol several times. Finally the calcination of the material was carried out at 750 C. for 6 h in air.

(44) The X-ray diffraction pattern, Scanning Electron Microscope (SEM) images and Transmission Electron Microscope (TEM) images of this material are given below.

Example2

Synthesis of ZrO2

(45) 10 g(0.031 mol, 0.7 mol %) zirconium oxychloride was taken in 75 ml (4.17 mol, 99.3 mol %) distilled water to form a homogeneous solution, the pH of the solution was adjusted by ammonium hydroxide solution and pH of the mixed solution was fixed at 10. Finally, the mixed solution was heated at 60 C. after transferring the mixture to a stainless steel autoclave and maintained for 2 h. The resultant solid was collected by filtration, washed thoroughly with distilled water and ethanol, dried at 100 C. for 12 h followed by calcination at 750 C. This was used as a ZrO.sub.2 support material.

Synthesis of NiPtZrO2

(46) Synthesis of NiPtZrO.sub.2 catalyst was carried out taking 0.1 mmol (1.2 mmol %) H.sub.2PtCl.sub.6.6H.sub.2O (Sigma-Aldrich, 99%) and 0.4 mmol (7.2 mmol %) of Ni(NO.sub.3).sub.2.6H.sub.2O (Sigma-Aldrich, 99%) dissolved in 10 ml (95 vol %) liquid octadecylamine (ODA) heated at 120 C. After the homogenization, the content was heated up to 220 C. after transferring the mixture to a lined stainless steel autoclave and stirred for 10 min. A measured amount 1-2 grams (0.008-0.016 mol) of nanoporous ZrO.sub.2 was successively added and kept at stirring for h at same temperature. After the reaction, as-prepared PtNi nanoparticles subjected for ultrasonic treatment for 1 min at room temperature after adding excess amount of concentrated nitric acid into it. The precipitate was cooled down to room temperature naturally, collected and washed with ethanol several times. Finally the calcination of the material was carried out at 750 C. for 6 h in air.

(47) The Transmission Electron Microscope (TEM) images of this material are given below.

Example 3

(48) This example describes the autothermal and dry reforming of methane by gas phase reaction with CH.sub.4:CO.sub.2:O.sub.2::He mole ratio 1:1:0.5: 7.5 using NiPtZrO.sub.2 nanocrystalline oxide as the catalyst. (Table1)

(49) The autothermal and dry reforming of methane ware carried out in a fixed-bed down flow quartz reactor at atmospheric pressure. Typically 200 mg of catalyst was placed in between two quartz wool plugged in the center of the 6 mm quartz reactor and reforming of methane was carried out in a temperature range of 250-750 C. The gas hourly space velocity (GHSV) was varied between 12000 ml g.sup.1 h.sup.1 to 42000 ml g.sup.1 h.sup.1 with a molar ratio of CH.sub.4:CO.sub.2:O.sub.2:He is 1:1:0.5: 7.5

(50) Process Conditions

(51) Catalyst: 0.2 g Ni:ZrO.sub.2 wt % in the catalyst=4% Pt:ZrO.sub.2 wt % in the catalyst=2% Pressure: 1 atmosphere CH.sub.4:CO.sub.2:O.sub.2: He mole ratio=1:1:0.5: 7.5 Total flow=40 ml/min (GHSV=12000), Reaction time: 1 h

(52) TABLE-US-00001 TABLE 1 Methane Catalyst Temperature Conversion H.sub.2/CO (mol (NiPtZrO.sub.2) ( C.) (mol %) %) Combining Oxy- and dry 750 99.6 1.4 reforming

Example4

(53) The example describes the effect of temperature on methane conversion and H.sub.2/CO ratio. The product analysis presented in Table2.

(54) Process Conditions:

(55) Catalyst: 0.2 g Ni: ZrO.sub.2 wt % in the catalyst=4% Pt: ZrO.sub.2 wt % in the catalyst=2% Pressure: 1 atmosphere CH.sub.4:CO.sub.2:O.sub.2:He mole ratio=1:1:0.5: 7.5 Total flow=40 ml/min (GHSV=12000) Reaction time: 1 h

(56) TABLE-US-00002 TABLE 2 Effect of temperature on methane conversion and H.sub.2/CO ratio Methane Temperature Conversion H.sub.2/CO ratio ( C.) (mol %) (mol %) Combining 250 54.4 1.9 Oxy- and 350 46.3 1.7 dry 450 39.9 1.6 reforming 550 67.3 1.3 650 93.6 1.4 750 99.6 1.4

Example 5

(57) The example describes the effect of time on stream on methane conversion and CO/H.sub.2 ratio. The product analysis presented in Table 3

(58) Process Conditions:

(59) Catalyst: 0.2 g, Ni: ZrO.sub.2 wt % in the catalyst=4% Pt: ZrO.sub.2 wt % in the catalyst=2% Pressure: 1 atmosphere CH.sub.4:CO.sub.2:O.sub.2:he mole ratio=1:1:0.5: 7.5 Total flow=40 ml/min (GHSV=12000), Reaction temperature: 750 C.

(60) TABLE-US-00003 TABLE 3 Effect of time-on-stream on oxy-dry reforming of methane Methane Time (h) Conversion (mol %) oxy-dry 0 99.6 reforming 1 99.1 of methane 4 99.4 8 99.8 12 99.5 16 99.2 20 99.7 25 99.1 30 99.6 35 99.2 40 99.8 45 99.4 50 99.6 55 99.6 60 99.9 65 99.3 70 99.5

Example6

(61) The example describes the effect of gas hourly space velocity (GHSV) on methane conversion and H.sub.2/CO ratio. The product analysis presented in Table3.

(62) Process Conditions:

(63) Catalyst: 0.2 g Ni: ZrO.sub.2 wt % in the catalyst=4% Pt: ZrO.sub.2 wt % in the catalyst=2% Pressure: 1 atmosphere CH.sub.4:CO.sub.2:O.sub.2:He mole ratio=1:1:0.5: 7.5 Reaction temperature: 750 C. Reaction time: 1 h

(64) TABLE-US-00004 TABLE 4 Effect of gas hourly space velocity (GHSV) on methane conversion and H.sub.2/CO ratio Methane GHSV Conversion (mol H.sub.2/CO (ml g.sup.1 h.sup.1) %) (mol %) Combining 12000 99.6 1.42 Oxy- and 18000 99.1 1.44 dry 24000 97.9 1.45 reforming 30000 95.6 1.46 36000 95.3 1.47 42000 84.9 1.49

ADVANTAGES OF THE INVENTION

(65) The main advantages of the present invention are:

(66) The process of the present invention converts methane to synthesis gas along with carbon dioxide and oxygen in a single step with a single catalyst.

(67) The process provides not only good conversion but also good H.sub.2/CO ratio in the synthesis gas.

(68) The process runs at atmospheric pressure in a continuous process to achieve 99.6% methane conversion, which is also a major advantage of this process.

(69) The exothermic oxy-reforming is coupled with endothermic dry-reforming to produce H.sub.2/CO which is the major advantage of the process.

(70) The catalyst is used in very low amounts.

(71) The catalyst does not deactivate till 1000 h with the reaction stream.