CLIAMS:STATEMENT OF CLAIMS
What is claimed is:
1. A catalytic composition for gas production, the catalytic composition comprising: a metal oxide, and a catalytic particle supported on the metal oxide, wherein the catalytic particle includes Nickel and Cobalt.
2. The catalytic composition as claimed in claim 1, wherein the metal oxide is an inorganic metal oxide.
3. The catalytic composition as claimed in claim 2, wherein the inorganic metal oxide is at least one selected from a group comprising of TiO2, Al2O3, ZrO2, LaAlO3, MgO, and BaO.
4. The catalytic composition as claimed in claim 1, wherein the nickel is present in an amount ranging from 10 – 20% by weight of the metal oxide.
5. The catalytic composition as claimed in claim 1, wherein the cobalt is present in an amount ranging from 1-3 % by weight of the metal oxide.
6. The catalytic composition as claimed in claim 1, wherein the metal oxide, Nickel, and Cobalt are in a weight ratio of 1: 0.15: 0.02.
7. The catalytic composition as claimed in claim 1, is configured to produce the gas with a conversion efficiency of at least 96% at a temperature range of 640- 700 oC at least for up to 420 hours.
8. A process for manufacturing a catalytic composition for gas production, the process comprising the steps of:
dissolving a water soluble salt of Nickel (Ni) to a solution of a metal salt to obtain a slurry;
sonicating the slurry obtained in the step (a) to obtain a Ni/metal oxide composite; and
impregnating the Ni/metal oxide composite with a water soluble salt of Cobalt (Co) to obtain a Co - Ni/metal oxide composite.
9. The process as claimed in claim 10, further comprises purifying of the cobalt - Ni/metal oxide composite to obtain the catalytic composition, wherein the purifying comprises the steps of:
washing the Co - Ni/metal oxide composite with an aqueous solvent; and
drying the Co - Ni/metal oxide composite to obtain the catalytic composition.
10. The process as claimed in 8, wherein the water soluble salt of Nickel includes at least one selected from the group comprising of chloride, nitrate, and hydrate.
11. The process as claimed in claim 10, wherein the water soluble salt of Nickel is Nickel Nitrate.
12. The process as claimed in claim 8, wherein the metal salt is obtained by addition of a mineral acid to a metal oxide
13. The process as claimed in claim 12, wherein the mineral acid is one of a nitric acid, hydrochloric acid, and sulphuric acid.
14. The process as claimed in claim 12, wherein the metal oxide is an inorganic metal oxide, and wherein the inorganic metal oxide is one of a group consisting of TiO2, Al2O3, ZrO2, LaAlO3, MgO, and BaO.
15. The process as claimed in claim 8, wherein the Ni/metal oxide composite is Ni/TiO2.
16. The process as claimed in 8, wherein the water soluble salt of Cobalt includes at least one selected from the group comprising of chloride, nitrate, and hydrate.
17. The process as claimed in claim 16, wherein the water soluble salt of Cobalt is Cobalt Nitrate Hexahydrate.
18. The process as claimed in claim 8, wherein the Co - Ni/metal oxide composite is Co – Ni/TiO2.

Dated: 22nd Day of July, 2015 Signature:
Arun Kishore Narasani Patent Agent

,TagSPECI:FIELD OF THE INVENTION
[0001] The present invention is generally related to a catalytic composition for gas production, and more particularly, related to a catalytic composition for syngas production.
BACKGROUND OF INVENTION
[0002] Hydrocarbons, such as natural gas and petroleum gas, may be reformed in the presence of a reforming material and a catalyst. The reforming material includes carbon dioxide, water vapor, and oxygen. Carbon dioxide reforming also known as dry reforming, which is one way of producing syngas; and is one of the method to utilize the major greenhouse contributors. For example, methane in natural gas may produce gases such as syngas (hydrogen and carbon monoxide) in the presence of carbon dioxide; and is represented by the following reaction scheme.
CH4+CO2?2CO+2H2 [?Ho=247.3 kJ/mol] (1)
[0003] However, this reaction is highly endothermic, and requires a high temperature for a forward reaction to proceed.
[0004] In the past, Nickel based catalysts were widely used for dry/steam reformation of methane. However, the problem associated with Nickel based catalysts in CO2 reformation causes deposition of coke on the catalyst and may lead to reactor plugging. Coke deposition on the catalyst is one major drawback associated with dry reforming, because the coke deposition leads to catalyst deactivation, and consequently reduced activity.
[0005] Direct partial oxidation of methane, another conventional method, is widely used for syngas production. While this is a more energy-efficient method, as compared to reformation, one major problem associated with catalytic partial oxidation is the overheating or hot spot formation caused by the exothermic nature of the partial oxidation reaction. The nature of the reaction is exothermic, and heat removal is an issue. Hot spot formation is a common problem found in catalytic partial oxidation and it can cause deactivation of catalyst.
[0006] Some of the conventional catalytic compositions used for partial oxidation include Ruthenium supported lanthanide oxide catalyst, Rhodium, Platinum based catalysts, or the like. These catalytic compositions have demonstrated excellent catalytic activity with no carbon formation. However, the problem associated with the use of these catalytic compositions, in addition to hot spot formation caused by the exothermic nature, is their limited availability and high cost.
[0007] One way to overcome the problem associated with dry (CO2) reforming and partial oxidation is by integrating partial oxidation with CO2 reforming. The idea to combine the partial oxidation and CO2 reforming processes is to solve the high energy requirement problem of CO2 reforming. Heat produced from the partial oxidation process is supplied to CO2 reforming process. Therefore, the combined process is a thermally self-sustaining and may not need to consume external thermal energy.
[0008] Magnesium and Aluminum based catalysts have been reportedly used for the combined partial oxidation with CO2 reforming process. However, the disadvantage associated with these catalytic compositions is that the conversion efficiency of these catalysts is rather limited and the catalyst loses its performance activity after a short period of time.
[0009] The above information is presented as background information only to help the reader to understand the present invention. Applicants have made no determination and make no assertion as to whether any of the above might be applicable as Prior Art with regard to the present application.

OBJECT OF INVENTION
[0010] The principal object of the embodiments herein is to provide a catalytic composition for dry reforming, partial oxidation, and combined partial oxidation with CO2 reforming process.
[0011] Another object of the embodiments herein is to provide a catalytic composition for gas production.
[0012] Another object of the embodiments herein is to provide the catalytic composition for syngas production.
[0013] Another object of the embodiments herein is to provide a process for synthesizing the catalytic composition for gas production.
[0014] Yet another object of the embodiments herein is to provide a process for synthesizing the catalytic composition for gas production.
SUMMARY
[0015] Accordingly the embodiments herein provide a catalytic composition for gas production. The catalytic composition includes a metal oxide and a catalytic particle, where the catalytic particle is supported on the metal oxide. The catalytic particle includes Nickel and Cobalt.
[0016] In an embodiment, the metal oxide includes an inorganic metal oxide. The inorganic metal oxide is at least one selected from a group comprising of TiO2, Al2O3, ZrO2, LaAlO3, MgO, and BaO.
[0017] In an embodiment, the nickel is present in an amount ranging from 10 – 20% by weight of the metal oxide.
[0018] In an embodiment, the cobalt is present in an amount ranging from 1-3 % by weight of the metal oxide.
[0019] In an embodiment, the metal oxide, nickel, and cobalt are in a weight ratio of 1: 0.15: 0.02.
[0020] In an embodiment, the catalytic composition is configured to produce the gas with a conversion efficiency of at least 96% at a temperature range of 640- 700oC at least for up to 420 hours.
[0021] Accordingly the embodiments herein provide a process for manufacturing a catalytic composition for gas production. The process includes the steps of adding a metal oxide to a mineral acid to produce a metal salt. Further, the process comprises dissolving a water soluble salt of Nickel (Ni) to a solution of a metal salt to obtain slurry. In an embodiment, the water soluble salt of Nickel includes at one of a chloride, nitrate, and hydrate. In another embodiment, the water soluble salt of Nickel is Nickel Nitrate.
[0022] Further, the method includes sonicating the slurry for a time period of 2-4 hours, preferably 3 hours, to obtain a Ni/metal oxide composite. Furthermore, the Ni/metal oxide composite is impregnated with a water soluble salt of Cobalt (Co). In an example, the Co - Ni/metal oxide composite is Co – Ni/TiO2. In an embodiment, the water soluble salt of Cobalt includes at one of a chloride, nitrate, and hydrate. In another embodiment, the water soluble salt of Cobalt is Cobalt nitrate hexahydrate,
[0023] The method further comprises purifying the Cobalt - Ni/metal oxide composite to obtain the catalytic composition. In an embodiment, the purification comprises washing the Co - Ni/metal oxide composite with an aqueous solvent. The method further comprises drying the Co - Ni/metal oxide composite to obtain the catalytic composition.
[0024] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF FIGURES
[0025] This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0026] FIG. 1 illustrates a process to synthesize a catalytic composition for production of a gas, according to embodiments as described herein;
[0027] FIG. 2 illustrates X- Ray Diffraction (XRD) patterns of (a) 15% Ni/TiO2 (imp) before reaction (b) 15% Ni/TiO2 (imp) after reaction, (c) 15% Ni/TiO2 (sonic) before reaction and (d) 15% Ni/TiO2 (sonic) after reaction, according to embodiments as described herein; and
[0028] Fig. 3(a) shows H2/CO ratio as a function of temperature for 2% Co- 15% Ni/TiO2 (sonic) catalyst, according to embodiments as described herein.
[0029] FIG. 3(b) shows a H2/CO molar ratio for 2% Co- 15% Ni/TiO2 (sonic) at various reaction temperatures, according to embodiments as described herein.

DETAILED DESCRIPTION OF INVENTION
[0030] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. The term “or” as used herein, refers to a non-exclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embo6diments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0031] Accordingly the embodiments herein achieve a catalytic composition for gas production. The catalytic composition includes a metal oxide and a catalytic particle, where the catalytic particle is supported on the metal oxide. The catalytic particle includes Nickel and Cobalt.
[0032] In an embodiments, a process for manufacturing the catalytic composition for gas production is described. The process includes the steps of adding a metal oxide to a mineral acid to produce a metal salt. Further, the process includes dissolving a water soluble salt of Nickel (Ni) to a solution of a metal salt to obtain slurry. The slurry is sonicated for a time period of 2-4 hours, preferably 3 hours, to obtain a Ni/metal oxide composite. Further, a water soluble salt of Cobalt (Co) on the Ni/metal oxide composite. In an example, the Co - Ni/metal oxide composite is Co – Ni/TiO2. The process further comprises purifying the Co - Ni/metal oxide composite to obtain the catalytic composition. In an embodiment, the purification of the catalytic composition includes washing the Co - Ni/metal oxide composite with an aqueous solvent. Further, the Co - Ni/metal oxide composite is dried to obtain the catalytic composition.
[0033] Unlike the conventional composition and process, the proposed composition and process can be used to achieve reduced coke deposition on the catalytic composition. The use of Cobalt in the catalytic composition enhances the efficiency of the reforming reaction, and also the deposited amount of carbon may decrease and the disassociation rate of the reforming reaction product may increase. Also, the inclusion of Cobalt causes the catalytic composition to exhibit a high level of thermal stability and the durability of the catalyst may be enhanced. The proposed composition and process can be used develop catalytic compositions with better catalytic conversion efficiency. The stability of the catalyst composition can be observed for a long time. Further, the proposed composition and process can be used for effective dry reforming, partial oxidation, and combined partial oxidation with CO2 reforming process.
[0034] Referring now to the drawings, and more particularly to FIGS. 1 through 3, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.
[0035] The embodiments herein described provide a catalytic composition for reformation of hydrocarbons. The hydrocarbons include, but are not particularly limited to, fossil fuels such as natural gas, petroleum gas, naphtha, heavy oil, crude oil, coal, or the like. The sources of hydrocarbon may also include a non-fossil fuel such as one or more of a mixed biomass including crude ethanol, wood waste, agricultural waste residue, municipal solid waste, pulp sludge, or grass straw. The hydrocarbons may be converted to syngas by dry reforming, partial oxidation, or a combination of partial oxidation with dry reforming. Such a conversion is carried out in the presence of catalytic composition.
[0036] The embodiments herein described relate to catalytic compositions for conversion of hydrocarbons, such as methane or carbon dioxide to a gas. In an example, the gas is syngas.
[0037] In an embodiment, the catalytic composition comprises of a metal oxide and a catalytic particle supported on the metal oxide, wherein the catalytic particle includes Nickel and Cobalt. The metal oxide may be an inorganic metal oxide. The inorganic metal oxide may be at least one selected from a group comprising of TiO2, Al2O3, ZrO2, LaAlO3, MgO, and BaO. The use of Cobalt in the catalytic composition enhances the efficiency of the reforming reaction, and also the deposited amount of carbon may decrease and the disassociation rate of the reforming reaction product may increase. Also, the inclusion of Cobalt causes the catalytic composition to exhibit a high level of thermal stability and the durability of the catalyst may be enhanced.
[0038] In an embodiment, the catalytic composition may include nickel in an amount ranging from 10 – 20%, preferably 15% by weight of the metal oxide. In other words, the amount of Nickel being about 0.1 g to about 0.2 g per 1 g of nickel. In an embodiment, the catalytic composition may include cobalt in an amount ranging from 1-3%, preferably 2%, by weight of the metal oxide. In other words, the amount of Cobalt being about 0.01 g to about 0.03 g per 1 g of cobalt.
[0039] In an embodiment, a weight ratio among the metal oxide, Nickel, and Cobalt in the catalytic composition may be the range of 1: 0.15: 0.02. The catalytic composition of the present invention shows reduced coke deposition and enhanced stability for a long period of time. The enhancement in catalytic activity of the catalytic composition may be due to intimate contact between Ni and TiO2 support.
[0040] FIG. 1 illustrates a process to synthesize a catalytic composition for production of a gas, according to embodiments as described herein. The gas is a syngas. In an embodiment, a process for manufacturing a catalytic composition is herein disclosed.
[0041] According to an embodiment, at step 102, the process includes adding a mineral acid to a metal oxide to produce a metal salt. The metal oxide described herein may be an inorganic metal oxide. The inorganic metal oxide may include at least one selected from a group comprising of TiO2, Al2O3, ZrO2, LaAlO3, MgO, and BaO. In an example, the metal oxide is preferably TiO2. In an embodiment, the mineral acid may be added to one or more of these metal oxides to produce the metal salt. In an embodiment, the mineral acids may include one of a nitric acid, hydrochloric acid, and sulphuric acid.
[0042] At step 104, the process includes dissolving a water soluble salt of Nickel (Ni) to the metal salt to obtain slurry. The water soluble salt of Nickel includes at least one of chloride, nitrate, and hydrate. In an embodiment, the water soluble salt of Nickel may be Nickel Nitrate.
[0043] At step 106, the process includes sonicating the slurry to obtain a Ni/metal oxide composite. The sonication may be carried out for a time period of 2- 4 hours, preferably 3 hours, using a high intensity Ti-horn probe of 25 mm diameter (50 KHz, and 125 W/cm2 at 60% efficiency), to obtain a Ni/metal oxide composite. In an embodiment, the Ni/metal oxide composite is Ni/TiO2.
[0044] At step 108, the process includes impregnating a water soluble salt of Cobalt (Co) on the Ni/metal oxide composite. The water soluble salt of Cobalt includes at least one of chloride, nitrate, and hydrate. In an embodiment, the water soluble salt of Cobalt is Cobalt Nitrate Hexahydrate. This impregnation is done so as to obtain a Co - Ni/metal oxide composite. In an example, the Co - Ni/metal oxide composite is Co – Ni/TiO2. .The inclusion of Cobalt causes the catalytic composition to exhibit a high level of thermal stability and the durability of the catalyst may be enhanced.
[0045] At step 110, the process includes purifying the cobalt - Ni/metal oxide composite to obtain the catalytic composition. The purification includes washing the Co - Ni/metal oxide composite with an aqueous solvent followed by drying the Co - Ni/metal oxide composite at a sufficient temperature to obtain the catalytic composition. The use of Cobalt in the catalytic composition enhances the efficiency of the reforming reaction, and also the deposited amount of carbon may decrease and the disassociation rate of the reforming reaction product may increase.
[0046] In an embodiment, the aqueous solvent is water – ethanol mixture. In an embodiment, the water to ethanol weight ratio in the water –ethanol mixture may be in the range of 0.1:1 to 1:0.1 (v/v). In an embodiment, the sufficient temperature to obtain the catalytic composition may be in the range of about 100 – 150 C, preferably 120 C.
[0047] Although most of the embodiments in the description herein included are with reference to TiO2, it may be understood by a person skilled in the art that the metal oxide can be any other metal oxide as well. In an embodiment, the catalyst composition is Co – Ni/TiO2. The nickel in the catalytic composition including Co – Ni/TiO2 may be present in an amount ranging from 10 – 20% by weight of the metal oxide. In another embodiment, the cobalt in the catalytic composition including Co – Ni/TiO2 may be present in an amount ranging from 1-3 % by weight of the metal oxide. In an embodiment, a weight ratio the metal oxide, Nickel, and Cobalt in the catalytic composition is the range of 1: 0.15: 0.02.
[0048] Hereinafter, the embodiments are illustrated in more detail with reference to examples. However, the following example embodiments are not construed to be limiting the scope of the present invention.
EXAMPLE 1: Preparation of a Catalyst Including Ni – Co particles supported onto TiO2
[0049] Titanyl nitrate (TiO(NO3)2) solution and nickel nitrate (S.D Fine, India) was used for synthesis of 15% TiO2. For this purpose, titanyl nitrate may be obtained by performing controlled hydrolysis of 5 ml of titanium isopropoxide under ice cold conditions to obtain a white colored precipitate of TiO(OH)2. Further, 10 ml of HNO3 was added to the precipitate to obtain a clear solution of TiO(NO3)2 (titanyl nitrate). In parallel, 0.99 g of nickel nitrate was dissolved in 20 ml of distilled water to obtain a solution of nickel nitrate. Further, both the solutions, i.e., the solution containing nickel nitrate and the solution containing titanyl nitrate were mixed together to obtain a slurry. Furthermore, the slurry was sonicated for 3 h using a high intensity Ti-horn probe of 25 mm diameter (50 KHz, and 125 W/cm2 at 60% efficiency) to obtain a powder. The powder thus obtained was separated, washed with water-ethanol mixture, and dried in hot air oven at 120°C. The catalytic activity of 15% Ni/TiO2 catalyst, synthesized by conventional wet impregnation method was compared to the catalyst synthesized via sonication method of the present invention.
[0050] The process to synthesize the15% Ni/TiO2 catalyst by the conventional methods is as outlines further. Pure known weight of TiO2 (prepared by sonication method) was dispersed in water. Further, 15 wt % of nickel nitrate was added to the water. Ni2+ ions to the water and nickel nitrate equivalent were reduced to Ni metals by hydrazine hydrate (S.D Fine, India) solution at room temperature. A solid was obtained which was separated and dried at 120° C, and further calcined at 700° C for 1 h. The catalyst synthesized via sonochemical method is designated as 15% Ni/TiO2 (sonic) while the catalyst synthesized via the impregnation method is designated as 15% Ni/TiO2 (imp). Further, the Cobalt was impregnated on the sonicated catalyst by using cobalt nitrate hexahydrate (Co(NO3)2. 6H2O, SD Fine – India). The catalytic composition so obtained was designated as 2% Co- 15% Ni/TiO2 (sonic).
[0051] The formation of the catalytic composition, i.e., the presence of the catalytic particle on the metal oxide can be confirmed by characterization tools/analytical techniques. The analytical characterization tools/analytical techniques include XRD (X Ray Diffraction), TEM (Transmission Electron Microscope), XPS (X ray photoelectron spectroscopy), BET analyzer and TGA/DTA (Thermo Gravimetric Analysis).
[0052] FIG. 2 illustrates X Ray Diffraction patterns of the catalytic composition (both the sonicated catalyst and the catalyst synthesized by impregnation method), according to embodiments as described herein. The X-ray diffraction (XRD) patterns were recorded on a Philips X’Pertdiffractometer with Cu-Ka radiation (?=1.54178 Å) in the 2? range of 20-80° C.
[0053] From the FIG. 2, it may be understood that the catalytic composition, i.e., 2% Co- 15% Ni/TiO2 (sonic) shows well resolved peaks characteristic of a rutile structure of TiO2. The peaks observed at 2? = 76.4, 51.8 and 44.5° can be assigned to the (220), (200), (111) planes of Nickel metal. However, the peaks corresponding to 15% Ni/TiO2 (imp) catalyst shows peaks along with anatase phases of TiO2. The small peak at 27.4° indicates that the small amount of rutile phase is also present in 15% Ni/TiO2 (imp) catalyst. Further, the average crystallite size of Ni was determined by the peak broadening of the (111) reflection in the XRD patterns, using the Scherrer formula; and was found to be 13 nm and 19 nm respectively, for 2% Co- 15% Ni/TiO2 (sonic) and 15% Ni/TiO2 (imp) catalyst. Further, the close observation of XRD patterns of 15% Ni/TiO2 (sonic) catalyst shows that the peak of rutile TiO2 phase observed at 27.6° is shifted to higher values by 0.4° due to decrease in d-spacing. This shows partial substitution of Ni into TiO2 lattice during synthesis. In contrast, no shift in XRD pattern of 15% Ni/TiO2 (imp) catalyst was observed. Therefore, partial incorporation of Ni into TiO2 lattice is possible during synthesis, as can be confirmed from the FIG. 2.
[0054] The activity of the catalytic composition as cited in the example 1 was studied at various temperatures for dry reforming/ steam reforming or partial oxidation, and a combination process. The following example illustrates methods and catalytic conditions used to carry out dry reforming of methane with the catalytic compositions of the present invention.
EXAMPLE 2: Dry reforming of methane with the catalytic composition
[0055] Dry reforming of CH4 was studied in a fixed bed reactor under atmospheric pressure. For this purpose, a quartz reactor (4 mm ID and length of 30 cm) was heated in an electric furnace and the temperature of bed was controlled by a K-type thermocouple positioned in the center of the fixed bed reactor. Further, 75 mg of catalyst was packed between two glass wool plugs in the center of the fixed bed reactor.
[0056] The feed mixture consisting of CH4, CO2, and balance of N2 may be contacted with the catalytic composition to produce the syngas. Further, the feed mixture may be adjusted in light of, for example, but not limited to, a H2/CO ratio, a CH4 conversion rate, a CO2 conversion rate, a yield, or the like. In an embodiment, contact of the catalyst with the feed mixture under the conditions of operation of the reactor, herein referred to as contact conditions, are not particularly limited as long as a gas, including hydrogen, is produced by the reforming reaction triggered by the contact.
[0057] In an embodiment, the contact may be performed by keeping the total flow rate at 100 ml/min (GHSV of 95500 h-1 is based on the catalyst bed volume of 0.0628 cm3).
[0058] Further, the oxidized catalyst in air showed the formation of inactive NiTiO3 phase and no activity for both the reactions. Therefore, the catalyst was reduced at 650°C for 2 h with pure H2 at a flow of 20 ml/min before the reaction. The product was analyzed using an on-line gas chromatograph (Mayura Analytical Bangalore, India) equipped with a TCD and FID (incorporating a methanator).
[0059] The conversions (X) and the H2/CO ratio were calculated as follows:
-------------------------------- (1)
--------------------------------- (2)
------------------------------------ (3)
[0060] In the above equations, the bracketed quantity represents the concentration of the component in the product stream. Further, the activity of the catalyst was measured under steady state at various temperatures. In order to ensure steady state, the temperature of the reactor was set at desired value and the gases were allowed to flow over the catalyst continuously. After 15 min, four readings at the same temperature were averaged. The temperature of the fixed bed reactor was further set to the next high temperature and the same procedure was repeated. The average of the four readings was taken for the calculation and standard deviation of reported conversion was less than 3%. The experimental data was collected under the absence of any external and internal diffusion limitation.
[0061] The following example illustrates methods and catalytic conditions used to carry out steam reforming of methane with the catalytic compositions of the present invention.
Example 3: Steam reforming of methane with the catalytic composition
[0062] The steam reforming reaction was carried over 150 mg of catalyst diluted by required amount of glass beads. The feed mixture consisting of CH4 and N2 may be adjusted in light of a H2/CO ratio, a CH4 conversion rate, a yield, or the like, but it is not particularly limited. The contact conditions between the feed mixture and the catalyst for reforming hydrocarbons are not particularly limited as long as a gas including hydrogen is produced by the reforming reaction triggered by the contact.
[0063] In an embodiment, the feed mixture consists of 3 volume % of CH4 and balance of N2 was passed at rate of 100 ml/min. In yet another embodiment, the gas hourly space velocity is 48000 h-1 (based on the catalyst bed volume of 0.125 cm3). Further, water was fed to the steam generator using a HPLC pump (Waters 515) at flow rate of 0.1 ml/min. Further, the generated vapor (3.6 ml/min) was mixed with feed mixture before entering the reactor. A moisture trap was kept at the outlet of the reactor to condense any water from the product gas stream. Prior to reaction, the catalyst was reduced in pure H2 with a flow rate of 20 ml/min for 2 h at 650°C.
[0064] The CH4 conversion (X) and CO selectivity were calculated as follows:
----------------------- (4)
CO selectivity (%) = ------------------- (5)
[0065] The rate of formation of (CO + CO2) was nearly same to the rate of disappearance of CH4 which indicates that the rate of carbon formation was negligible over the catalyst. Unlike conventional catalytic compositions, the catalytic compositions of the present invention show negligible/ reduced coke deposition on the catalytic composition. As a result, the catalytic composition shows enhanced activity for a long period of time.
[0066] The catalytic composition was thus tested for dry, steam and combined reforming (dry and partial oxidation of methane). The activity of the catalytic composition was evaluated in terms of conversion of reactants.
[0067] FIG. 3a shows H2/CO ratio as a function of temperature for 2% Co- 15% Ni/TiO2 (sonic) catalyst, according to embodiments as described herein. From the figure, it can be understood that the variation of CH4 and CO2 conversions over 2% Co- 15% Ni/TiO2 (sonic) catalyst increased with increase in temperature. Further it was also observed that the CO2 conversion was similar to CH4 conversion, indicating that the contribution of reverse water gas shift reaction (CO2 + H2 ? CO + H2O) is negligible. From the FIG 3(a), it can also be observed that nearly 96% CH4 conversion and 96% CO2 conversion was observed at 700°C. Although not depicted in the figure, the catalytic compositions with the low Ni loading namely, 5% and 10% over TiO2 were also synthesized and tested for dry reforming reaction. Both CH4 and CO2 conversions were found to be lower than 15% Ni/TiO2 catalyst. At 700°C, 31% CH4 and 34% CO2 conversion was obtained over 5% Ni/TiO2 catalyst while only 59% CH4 and 56% CO2 conversion was obtained over 10% Ni/TiO2 catalyst, unlike the catalytic composition of the present invention. From this it may be inferred that the, catalytic compositions of the present invention shows enhanced conversion efficiency, and also enhanced stability at high temperatures. This enhanced conversion efficiency may be attributed to reduced coke deposition, thereby, showing better catalytic activity for conversion of the reactants.
[0068] At high temperature, the rate of reaction is controlled by diffusion of reactant. Further, the performance of both the catalysts was then compared to its activity at low temperature. It was found that the reaction rates were higher for 2% Co- 15% Ni/TiO2 (sonic) catalyst. Therefore, the catalyst synthesized by sonication method exhibits higher activity than the catalyst synthesized via conventional wet impregnation. The enhancement in reforming activities of 2% Co- 15% Ni/TiO2 (sonic) catalyst is due to intimate contact between Ni and TiO2 support, as evidenced from TEM, XRD and XPS Studies.
[0069] Transmission electron microscopy (TEM; FEI Technai 20) was used to study morphology and microstructures of the catalyst. The TEM specimen was prepared by dropping a trace amount of sample dispersed in ethanol on a carbon coated grid (300 mesh).
[0070] The X-ray diffraction (XRD) patterns were recorded on a Philips X’Pertdiffractometer with Cu-Ka radiation (?=1.54178 Å) in the 2? range of 20-80° C.
[0071] XPS spectra were recorded on a Thermo Scientific Multilab 2000 instrument with monochromatized Al-Ka X-rays (1486.6 eV). The binding energies were charge corrected using the C 1s peak observed at 285 eV.
[0072] Further, it must be noted that XRD and TEM studies showed that Ni in the catalyst synthesized by sonication method had smaller crystallites size and high metal dispersion. Therefore, the enhancement in the activity of the catalyst is related to the intimate contact of Ni and TiO2 support and fine dispersion of the active species. Further, despite an equimolar amount of CH4 and CO2 in the feed mixture, CO2 conversion was higher compared to conversion of CH4 for the temperature range over 15% Ni/TiO2 (imp) catalyst. This indicates that the extent of occurrence of the reverse water gas shift reaction is higher over the catalyst.
[0073] Further, FIG. 3a, also illustrates that the CH4 conversion increases gradually with increase in temperature. This is particularly observed in combined reforming as the exothermic reactions of combustion and partial oxidation of methane are more dominant at low and medium temperatures. However, at high temperatures the dominant reactions are CO2 reforming reaction, and hence the CH4 conversion remained high.
[0074] FIG. 3b shows a H2/CO molar ratio for 2% Co- 15% Ni/TiO2 (sonic) at various reaction temperatures, according to embodiments as described herein. From the figure, it can be understood that the H2/CO ratio increased with an increase in temperature for both the catalysts (sonicated catalyst and the impregnated catalyst). Further, the H2/CO ratio particularly for the 2% Co- 15% Ni/TiO2 (sonic) catalyst reached close to 1 above 650°C.
[0075] Although, not illustrated in any figure, the dependence of catalytic activity on time on stream over 2% Co- 15% Ni/TiO2 catalyst was studied at 650° C for 420 h for both dry and steam reforming reactions. A small drop (about 2-3%) in both the conversions was observed for the initial few hours, which might be due to some modification of the catalyst surface causing instability in the carbon deposition. However, the H2/CO ratio (~0.96) was nearly stable over 240 h reaction period.
[0076] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.