AU2012258290B2 - Nickel based catalysts for hydrocarbon reforming - Google Patents

Abstract

A method of preparing a catalyst for use in steam reforming of low molecular weight hydrocarbon and/or carbon dioxide reforming of low molecular weight hydrocarbon or mixing the two reforming comprising the steps of: (A) preparing an aqueous solution comprising:(i) an active component comprising nickel (Ni); (ii) a support component comprising magnesium (Mg) and aluminum (Al); and (iii) a promoter component comprising at least one lanthanide metals; (B) adjusting the pH of the solution to at least 8 to thereby form a slurry comprising a co-precipitate of (i), (ii) and (iii); and (C) separating said co-precipitate from the aqueous solution to form said catalyst. Figure 1

Description

2012258290 20 Nov 2012 AUSTRALIA Patents Act 1990

ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT P/00/011 Regulation 3.2

Invention Title: NICKEL BASED CATALYSTS FOR HYDROCARBON REFORMING

Applicant: Commonwealth Scientific and Industrial

Research Organisation

The following statement is a full description of this invention, including the best method of performing it known to me: 1

6007JCL 2012258290 20 Nov 2012 2

Nickel based catalysts for hydrocarbon reforming Field of the Invention [0001] The present invention relates to multiple metal oxide-based nickel catalysts prepared by co-precipitation. In particular, the present invention relates to catalyst formulations, a process for preparation of the said catalysts, and processes employing the catalysts for production of syngas or hydrogen via (1) the steam reforming of low molecular weight hydrocarbons at low steam to carbon ratios, (2) the mixed steam and carbon reforming of low weight molecular hydrocarbons, and (3) pure carbon dioxide reforming of low molecular weight hydrocarbons.

Background of the Invention [0002] The following discussion of the background to the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.

[0003] Hydrogen is an important feedstock for use in ammonia synthesis and hydrocarbon processing. Recently, there has been an increasing interest in using hydrogen as a future fuel for use in gas turbines and fuel-cells for power generation in both stationary and transport applications. Hydrogen is mainly produced through steam reforming of hydrocarbons such as natural gas. Recently, solar energy has been used to drive steam reforming of methane (SRM) for production of solar-rich syngas which can store solar energy into chemical bonds and reduce C02 emissions by up to 30%. The SRM is highly endothermic reaction and so it is suitable for storing solar energy. The SRM reaction can be described by the following equation: CH4 + H2O (g) ++CO + 3H2 A//2°joc = +206 kJ/mol (1) 2012258290 20 Nov 2012 3 [0004] Moreover, carbon dioxide reforming of methane (CDRM) has a higher enthalpy than SRM as below: CH4 + C02 +-»2CO + 2H2 AH0250c = +247 kJ/mol (2) [0005] Hence, it can store more solar energy than SRM. However, there is no commercial catalyst available for the CDRM because of serious problems with carbon formation on catalyst surface leading to catalyst deactivation.

[0006] Traditional steam reforming has been performed over both AI2O3- and MgAI204-based commercial reforming Ni catalysts operating at about 800 °C and high steam to carbon ratios (S/C: 2.8-3.5). In this process, the high temperature is required to achieve high methane conversion rates and the high steam to carbon ratios are required to suppress carbon deposition on the catalysts that leads to catalyst deactivation even though the stoichiometric ratio for this reaction is 1.0. From the perspective of energy efficiency and reducing capital and operating costs, SRM with low S/C ratios, mixed SRM and CDRM, as well as pure CDRM have many attractions as a means for the production of hydrogen and syngas or storing solar energy. These include • higher energy efficiency due to less demand for evaporating and condensing large quantities of water in the reactant and product; • the potential to achieve higher levels of solar energy storage than conventional SRM; • less water consumption; • production of synthesis gas with any desired H2/CO ratio that might be required for applications such as Fischer-Tropsch or methanol synthesis; and • allowing use of both natural gas and coal seam gases, containing variable concentrations of C02. 2012258290 20 Nov 2012 4 [0007] However, there is no commercial catalyst available for these reforming processes due to severe carbon formation on catalyst surface leading to catalyst deactivation.

[0008] Noble metal-based catalysts are found to have a better performance in terms of conversion, selectivity and susceptibility to coking [1] for SRM at low S/C ratios and for CDRM. Nevertheless, such catalysts are expensive due to high price and limited availability of noble metals, so there is a need to develop inexpensive Ni-based catalysts for SRM at low S/C ratios, the mixed SRM and CDRM, and pure CDRM for use in highly efficient and cost-effective production of syngas and hydrogen as well as storing solar energy.

[0009] International Patent Publication W02007046591 discloses a NixMgyAI catalyst for the steam reforming of liquefied petroleum gas (LPG). The catalyst was prepared by using hydrotalcite-like precursor which is characterized by the active nickel metal being uniformly dispersed onto the surface and the inner part of the catalyst to reduce carbon formation and Ni sintering. Hence, the catalyst has shown high activity and stability for steam reforming of LPG at S/C ratios and a temperature of 800 °C for 200 hours. However, at higher temperatures and a S/C ratio of 3 are required for SRM over the catalyst in order to achieve high catalyst activity and stability because methane is the most stable compound among all the hydrocarbons.

[0010] United States patent publication No. US20080032887 discloses a Ni/Ca-AI-Sr catalyst for production of low H2/CO ratio syngas from the SRM at a H2O/CH4 ratio of 3, a gas hourly space velocity (GHSV) of about 25,000 /h and 427 °C. Although it was claimed that the catalyst could also be used in the mixed SRM/CDRM mode, the results on catalyst activity for the mixed reforming was not reported. In addition, a conventional impregnation method was used to load Ni on the catalyst, which limits a large fraction of the Ni to being loaded on the catalyst surface. In this case, when the Ni loading 5 2012258290 12 Jan 2017 exceeds a certain value, the supported Ni tends to aggregate to form large Ni particles which favour carbon formation.

[0011] There is therefore a need to provide a catalyst which overcomes at least some of the above-mentioned deficiencies and thereby furthers the development of a reduced carbon emission fuel source.

Summary of the invention [0011a] According to an aspect, the invention provides a process for the reforming of low molecular weight hydrocarbon, the process comprising: preparing a catalyst by a method comprising the steps of: (A) preparing an aqueous solution comprising: (i) an active component comprising nickel (Ni); (ii) a support component comprising magnesium (Mg) and aluminum (Al); and (iii) a promoter component comprising at least one lanthanide metals; (B) adjusting the pH of the solution to at least 8 to thereby form a slurry comprising a co-precipitate of (i), (ii) and (iii); and (C) separating said co-precipitate from the aqueous solution to form said catalyst, wherein the catalyst comprises Ni in the range of 10 to 40 molar % relative to the total metallic content; and exposing a stream comprising carbon dioxide and low molecular weight hydrocarbon to the catalyst.

[0011b] According to a further aspect, the invention provides a catalyst for use in reforming of low molecular weight hydrocarbon with carbon dioxide or with a mixture of carbon dioxide and steam, the catalyst having the formula NiaMgbAlcMciOx, wherein M is one of more lanthanide metals, a, b, c, d and x are numerals corresponding to the molar proportion of the catalyst components and wherein the molar ratio of the active component (a) to the support component (b + c) is in the range 1:2 to 1:6 and the ratio of the active component (a) to the promoter component (d) is in the ratio of 20:1 to 2:1. 2012258290 12 Jan 2017 5a [0011c] According to a further aspect, the invention provides use of the catalyst according to any one of the embodiments described herein for the reforming of low molecular weight hydrocarbon, wherein a stream comprising carbon dioxide and low molecular weight hydrocarbon is exposed to the catalyst.

[0012] The abovementioned problems are at least partially addressed through providing, in a first aspect of the present invention, a method of preparing a catalyst for use in steam reforming of low molecular weight hydrocarbon and/or carbon dioxide reforming of low molecular weight hydrocarbon. The method comprises the steps of: (A) preparing an aqueous solution comprising: (i) an active component comprising nickel (Ni) (ii) a support component comprising magnesium (Mg) and aluminum (Al); and (iii) a promoter component comprising at least one lanthanide metals; (B) adjusting the pH of the solution to at least 8 to thereby form a slurry comprising a co-precipitate of (i), (ii) and (iii); and separating said co-precipitate from the aqueous solution to form said catalyst.

[0013] The present invention relates to a catalyst for use in steam reforming of low molecular weight hydrocarbon, carbon dioxide reforming of low molecular weight hydrocarbon, or the mixed steam reforming of low molecular weight hydrocarbon with carbon dioxide reforming of low molecular weight hydrocarbon. The present invention aims to provide a Ni-based catalyst with excellent activity and stability for three reforming modes at low reaction temperatures as well as high space velocity, where the catalyst comprises Ni, Mg, Al, and one or more lanthanide metals. The catalyst is suitable for use in the three reforming processes typically use in the chemical industry and particularly for use in the reforming processes driven by solar 6 2012258290 20 Nov 2012 energy or in “on-board” reformers for fuel cells in automobiles or in a membrane reformer/reactor.

[0014] The present invention has found that a combination of Ni, Mg, Al and lanthanide metals, such as Y or Gd, prepared by the co-precipitation method enables multiple metal oxide-based Ni catalysts to exhibit very high catalyst activity and stability for SRM at low S/C ratios, mixed SRM and CDRM as well as pure CDRM in terms of three reforming modes. The presence of Mg increases the capability of adsorbing CO2, which curbs carbon formation, stabilizing Ni to prevent it from sintering and inhibits incorporation of nickel to AI2O3 which are inactive for reforming reactions. In addition, the presence of Al helps to maintain large BET surface area, high thermal stability and mechanic strength of the catalysts. Furthermore, the addition of small amounts of transition metal as a promoter, could disperse Ni, participate in reforming reaction, and suppressing carbon formation on the catalyst surface.

[0015] The catalyst of the present invention can be used for steam reforming of low molecular weight hydrocarbon and/or carbon dioxide reforming of low molecular weight hydrocarbon. In some embodiments, the low molecular weight hydrocarbon comprises low molecular weight hydrocarbons having the formula CnHn+2, wherein n is an integer in the range of 1 to 4. The low molecular weight hydrocarbon preferably includes no more than 3 carbon atoms, more preferably no more than 2 carbon atoms. Most preferably, the low molecular weight hydrocarbon comprises methane.

[0016] The lanthanide metals consist of Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium and Lutetium. The promoter component of the invention is preferably selected from a group comprising of Lanthanum (La), gadolinium (Gd) and yttrium (Y), cerium (Ce). More preferably, the lanthanide metal M is selected from the group consisting of Gd, Y and Ce. Even more preferably, the lanthanide metal is Gd and/or Y. 7 2012258290 20 Nov 2012 [0017] In some embodiments, the promoter component comprises at least two lanthanide metals. In one embodiment, the promoter component comprises Gd and Y.

[0018] In some embodiments, the catalyst has the formula NiaMgbAlcMdOx, wherein M is one of more lanthanide metals, a, b, c, d and x are numerals corresponding to the molar proportion of the catalyst components and wherein the molar ratio of the active component (a) to the support component (b + c) is in the range 1:2 to 1:6 and the ratio of the active component (a) to the promoter component (d) is in the ratio of 20:1 to 2:1. Preferably, the molar proportion of the active component (a) is in the range 15 to 40, (b) is in the range 40 to 80, (c) is in the range 10 to 40 and M is in the range 1 to 8, wherein (a)+(b)+(c)+(d) = 100.

[0019] The co-precipitate is formed at pH of at least 8. In some embodiments, the pH is between 8 and 12, preferably between 9 and 11.5 and more preferably between 10 and 11.

[0020] In one embodiment of the first aspect of the present invention, the method for preparing the catalyst comprises the steps of (a) dissolving nitrate salts of Ni, Mg, Al and lanthanide metals in water (preferably distilled and/or deionized water) to form an aqueous solution; (b) adding the aqueous solution to a pre-heated base solution at pH of 10 to 11 at 60 to 80 °C; (c) agitating the resulting slurry, preferably for at least 1 hour at 60 to 80 °C and then preferably aging the slurry for about 18 to 24 hours at the same temperature, followed by filtering and washing; (d) drying the resulting precipitates at 60 to 70 °C for 18 to 24 hours; and (e) calcinating the resulting precipitates at 500 to 700 °C for a suitable time, for example, about 16 to 24 hours.

[0021] The aqueous solution may be formed through any suitable precursors, such as nitrate salts. 8 2012258290 20 Nov 2012 [0022] The method preferably includes the further steps of drying washing and calcinating the co-precipitate.

[0023] In a second aspect of the present invention, there is provided a catalyst produced according to the method described in the first aspect of the present invention.

[0024] In a third aspect of the present invention, there is provided a catalyst for use in steam reforming of low molecular weight hydrocarbon and/or carbon dioxide reforming of low molecular weight hydrocarbon having the formula NiaMgbAlcMdOx, wherein M is one or more lanthanide metals, a, b, c, d and x are numerals corresponding to the molar proportion of the catalyst components and wherein the molar ratio of the active component (a) to the support component (b + c) is in the range 1:2 to 1:6 and the ratio of the active component (a) to the promoter component is in the ratio of 20:1 to 2:1, preferably in the ratio of 18:1 to 2.5:1 and even more preferably in the range of 10:1 to 3:1.

[0025] Preferably, the above formula accounts for at least 50 wt%, more preferably at least 70 wt% and even more preferably at least 90 wt% and yet even more preferably at least 95 wt% of the total weight of the catalyst.

[0026] On a molar basis, relative to the total metallic content, catalysts preferably comprise Ni in the range of 10 to 40 molar % (e.g. Ni = 100*Ni/(Ni+AI+Mg+M)), more preferably in the range 15 to 30 molar and even more preferably in the range 18 to 25 molar %. When the nickel content is less than 10 molar % the resultant catalyst activity is very low in terms of percentage low molecular weight hydrocarbon conversion. When the nickel content is more than 40 molar %, the resulting catalyst activity generally remains constant, independent of nickel content.

[0027] Mg is preferably present in the catalyst in the range of 40 to 70 molar % and more preferably in range of 45 to 60 molar %. Al is preferably 9 2012258290 20 Nov 2012 present in the catalyst in the range of 10 to 40 molar % and more preferably in the range of 15 to 30 molar %. The catalyst also comprises lanthanide metals, as promoters, preferably in the range of 1.0 to 8.0 molar % and more preferably between 2.0 and 6.0 molar %. When the molar % is less than 1.0%, the resulting catalyst tends to be less resistant to carbon deposition. When the ratio is more than 8 molar %, the stability of the resulting catalyst tends to deteriorate.

[0028] Preferably, the molar % lanthanide metal, relative to the sum of lanthanide metal, nickel, magnesium and aluminium, is in the range 1.9 to 7.4%, and more preferably in the range 2.5 to 4.0%. When the molar % is less than 1.9%, the resulting catalyst tends to be less resistant to carbon deposition. When the ratio is more than 7.4 molar %, the thermal stability of the resulting catalyst tends to deteriorate.

[0029] Preferably, the molar ratio of nickel to magnesium is in the range of 1:1.5 to 1:6 and more preferably in the range 1:2 to 1:4 and most preferably about 1.3. Within this range a good balance is achieved between catalyst stability and low carbon formation, thereby enabling the catalyst to maintain good activity over time. When the ratio is less than 1:1.5 or more than 1:5, the resulting catalyst activity and stability decreases with time.

[0030] In an embodiment of the present invention, the total content of magnesium and aluminium is 60 to 85 molar % relative to the total metallic content of the catalyst. Preferably, the molar ratio of magnesium to aluminium is in the range 1.5:1 to 4:1, more preferably 1.5:1 to 3:1, yet more preferably in the range 1.7:1 to 3.2:1 and even more preferably in the range 2.0:1 to 3.0:1. When the ratio is less than 1.5:1 or more than 4.1 the resulting catalyst activity decreases with time. It has been found that the use of a coprecipitation technique, rather than other techniques such as conventional coimpregnation methods, has resulted in a more uniform distribution of the active component, resulting in the ability of the catalyst to comprise less AI2O3, thereby reducing the formation of the catalytically inactive Ni-Al203 compound. 10 2012258290 20 Nov 2012 [0031] In selected embodiments, the catalyst has the molar formula selected from the group consisting of: NiMgijAIYo.iOx, NiMg3AIYo.2Ox, NiMg3AIYo.30X) NiMg3AIYo.40x, NiMg3AIGdo.iOx, NiMg3AIGdo.20x, NiMg3AIGdo.30x, NiMg3AIGdo.40x, NiMg3AICeo.iOXl NiMg3AICeo.20xi NiMg3AICeo.30x, and NiMg3AICeo.40x, where x is a numeral corresponding to the oxide content of the catalyst.

[0032] The invention further comprises the process for producing hydrogen or low H2/CO ratio syngas preferably using steam and/or carbon dioxide reforming of methane or other low molecular weight hydrocarbon.

[0033] In a fourth aspect of the present invention, there is provided a process for the steam (H2O) reforming of low molecular weight hydrocarbon comprising the step of exposing a stream of low molecular weight hydrocarbon and steam to the catalyst as previously described in the second and third aspects of the invention. Preferably, the molar ratio of steam to low molecular weight hydrocarbon is less than 2.5, more preferably less than 2.0 and even more preferably less than 1.5. This is in contrast to steam reforming of low molecular weight hydrocarbon being carried out by higher steam to low molecular weight hydrocarbon ratio to suppress carbon formation and consequently a loss in catalyst performance.

[0034] In a fifth aspect of the present invention, there is provided a process for the carbon dioxide (CO2) reforming of CH4 comprising the step of exposing a stream of CO2 and CH4 to the catalyst as previously described in the second and third aspects of the invention. The molar ratio of CH4/CO2 is preferably in the range of 1:1 to 1:1.5 and more preferably in the range of 1.1: 1.3:1.

[0035] In a sixth aspect of the present invention, there is provided a process for the carbon dioxide and steam reforming of methane comprising the step of exposing a stream of carbon dioxide, steam and methane to the catalyst as previously described in the second and third aspects of the invention. The molar ratio of H2O/CO2/CH4 is preferably 0.8:1.0:0.43 with a 11 2012258290 20 Nov 2012 10% absolute variance (e.g. H20 0.72 to 0.88) and more preferably a 20% absolute variance between components.

[0036] The fourth, fifth and sixth aspects of the present invention are preferably conducted at a reaction temperature in the range of 550 to 950 °C, more preferably in the range of 550 to 850 °C and yet more preferably in the range of 650 to 850 °C. The reactions are also preferably conducted at a gas hour space velocities in the range 500,000 to 3,000,000 ml/g./h and more preferably in the range 947,000 to 1,670,000 ml/g./h.

[0037] Unless otherwise indicated, reference to the molar % is relative to the total molar amount of metal (e.g. Al, Ni, Mg and M).

Brief Description of the Drawings [0038] The present invention will now be described with reference to the figures of the accompanying drawings, which illustrate particular preferred embodiments of the present invention, wherein: [0039] Figure 1 provides a graphical plot of Temperature Programmed Reduction (TPR) profiles of LSR-18 (NiMg3AIOx) and LSR-23 (NiCa;jAIOx) [0040] Figure 2 provides a graphical plot of H2-TPR profiles of LSR-16 (NiMg2AIOx), LSR-17 (NiMgAI2Ox), LSR 18 (NiMgsAlOx) and LSR-21 (NiMg3Ox) [0041] Figure 3 provides a graphical plot of TPR profiles of LSR-18 (NiMgaAlOx), LSR-22 (NiMgaAICeoA), LSR-24 (NiMg3AIY0.2Ox), LSR-25 (NiMg3AILa0 2Ox) and LSR-27 (NiMgsAIGdo^Ox) [0042] Figure 4 provides a graphical plot of C02-Temperature Programmed Desorption (TPD) profiles of LSR-18 (NiMg3AIOx) and LSR-23 (NiCasAlOx) 12 2012258290 20 Nov 2012 [0043] Figure 5 provides a graphical plot of CO2-TPD profiles of LSR-16 (NiMg2AIOx), LSR-17 (NiMgAI2Ox), LSR-18 (NiMgsAIO,) and LSR-21 (NiMg3Ox) [0044] Figure 6 provides a graphical plot of CO2-TPD profiles of LSR-18 (NiMgsAIO,), LSR-22 (NiMgaAICeoA), LSR-24 (NiMg3AIY0.2Ox), LSR-25 (NiMg3AILa0.2Ox) and LSR-27 (NiMg3AIGd0 2Ox)

[0045] Figure 7 provides a graph illustrating the effect of the Mg/AI ratio of catalysts NiaMgbAlcMdOx on catalysts activity and commercial reforming catalyst (NiMgAI204)) with time on stream at 750°C and GHSV of 1,454,000 ml/g/h. Variation of CH4 conversion of overtime on stream at 750 °C

[0046] Figure 8 provides a graph illustrating the effect of replacing of Mg by Ca on catalyst activity (LSR-18 (NiMg3AIOx) and LSR-23 (NiCa3AIOx) with time on stream at 750°C and GHSV of 1,454,000 ml/g/h.

[0047] Figure 9 provides a graph illustrating the effect of Ni loading (the symbol “a” denotes) of catalysts NiaMg3AIOx on catalyst activity with time on stream at 750°C and GHSV of 1,454,000 ml/g/h.

[0048] Figure 10 provides a graph illustrating the effect of promoters (Ce, La, Y, La) of catalysts NiMg3AIMo2Ox on catalyst activity with time on stream at 750°C and GHSV of 1,454,000 ml/g/h.

Detailed Description of the Invention [0049] The present invention relates to multiple metal oxide-based Ni catalysts that display high activity and stability for production of hydrogen or low H2/CO ratio syngas using a range of reforming modes with low molecular weight hydrocarbons such as CH4, including steam reforming of methane (SRM), pure carbon dioxide of reforming methane (CDRM), as well as mixed SRM and CDRM. 13 2012258290 20 Nov 2012 [0050] The Ni catalysts of the present invention have the general formula NiaMgbAlcMdOx, wherein Ni is nickel metal, Mg is magnesium, Al is aluminium and M is a lanthanide metal and a, b, c, d and x are numerals corresponding to the molar proportion of the catalyst components [0051] The lanthanide metal M in the catalyst of the invention is preferably selected from a group comprising of lanthanum (La), gadolinium (Gd) and yttrium (Y), cerium (Ce). More preferably, the lanthanide metal M is selected from the group consisting of Gd, Y and Ce. Even more preferably, the lanthanide metal is Gd and/or Y.

[0052] In some embodiments of the present invention, the Ni catalysts may be formed into any size or shape depending on the specific applications of the catalysts. The said Ni catalysts are typically in a form incorporated into a tablet, cylinder or powder, or as a washcoat deposited on a monolithic substrate having high mechanical strength and high thermal stability.

[0053] The co-precipitation method has been used to prepare the Ni catalysts of the present invention. The co-precipitation method allows Ni to be dispersed throughout the catalyst structure and so that high concentrations of Ni can be loaded on the catalysts with a minimum risk of Ni agglomerating to form large particles. This overcomes the limits of the conventional impregnation method in which Ni is deposited on the surface of catalyst and high localised Ni loadings tend to aggregate to form large metal particles, which favour carbon formation and Ni sintering at high temperatures. Furthermore, the co-precipitation method benefits the interaction between Ni and catalyst support to disperse and stabilize Ni to prevent it from aggregation and sintering.

[0054] In an embodiment of the present invention, the co-operation method comprises: (i) dissolving all relevant nitrate salts in distilled and deionized water, (ii) adding the mixed nitrate salt solution to a base solution under stirring at the pH range of 10 to 11 to produce a slurry at elevated temperatures, (iii) keeping the resulting slurry stirred at 60 to 80 °C for 1 h, 14 2012258290 20 Nov 2012 and then standing without agitation at the same temperature for 18 to 24 hours, (iv) separating the precipitate from the slurry by using typical techniques such as filtration or centrifugation, and then washing it with hot distilled and deionized water until it is hydroxide ion free, and (v) drying the resulting precipitate at 60 to 70 °C for 18 to 24 hours and then calcining at 500 to 700 °C for 16 to 24 hours in flowing air.

[0055] In an embodiment of the present invention, all nitrate salts are mixed at ambient temperatures. Preferably, the mixed solution is stirred for 10 to 40 minutes. Ideally, the mixed solution is stirred for 20 to 30 minutes.

[0056] In an embodiment of the present invention, bases used for basic aqueous solutions include ammonia, ammonium hydroxide or carbonate, or alkali metal or alkaline earth metal hydroxides or carbonates.

[0057] In an embodiment of the present invention, the pH of the slurry is controlled in the range of 10 to 11, preferably 10.3 to 10.7 for co-precipitation.

[0058] In an embodiment of the present invention, the pH of the slurry is maintained by adding a 2M NaOH aqueous solution by dropwise.

[0059] In an embodiment of the present invention, the slurry is heated up to the temperatures from 60 to 80 °C, preferably 60 to 70 °C for co-precipitation.

[0060] In an embodiment of the present invention, after addition of all the components has been completed, the resulting slurry is kept at 60 to 80°C, preferably 60 to 70 °C for 1 h under stirring and then standing without agitation for 18 to 24 hours at the same temperature.

[0061] In an embodiment of the present invention, the co-precipitate is separated from the slurry by using filtration and then washing it by using 60 to 15 2012258290 20 Nov 2012 70°C distilled and deionized water twice, with about 100 ml water per 1 g of wet precipitate.

[0062] In an embodiment of the present invention, the resulting coprecipitate is dried at 60 to 70 °C for 18 to 24 hours, preferably at 60 to 65 °C.

[0063] In an embodiment of the present invention, catalyst precursors are calcined at 500 to 700 °C for 16 to 24 hours in flowing air, preferably 500 to 600 °C for 16 hours.

[0064] In a further embodiment of the present invention there is provided a process for the production of hydrogen or low H2/CO ratio syngas from low steam reforming of low molecular weight hydrocarbons such as CH4 or mixed SRM and CDRM, or pure CDRM over the multiple metal oxide-based Ni catalysts at the reaction temperatures of 550 to 850 °C with a gas hour space velocity of 947,000 to 1,670,000 ml/g/h.

[0065] In one embodiment, the reaction temperature is 750 °C or less, and the pressure is about 1 bar.

EXAMPLES

[0066] The present invention is described in more details by the following examples. Examples only illustrate the present invention, and are not intended to limit the scope of the present invention.

Examplel

Preparation of catalyst sample LSR-24 [0067] 7.3783g of AI(N03)2.9H20, 19.2308g of Mg(N03)2.6H20, 7.2703 of Ni(N03)2.6H20 and 1.9151g of Y(N03)3.6H20 were dissolved in 250 ml of distilled and deionized water and then the mixed solution was stirred for 20 minutes at ambient temperature to give Solution 1. 7.9493 g of Na2C03was dissolved in 250 ml of distilled and deionized water; the solution was then stirred for 20 minutes at 65 °C to give Solution 2. Solution 1 was then added 16 2012258290 20 Nov 2012 to the Solution 2 by dropwise at 60 to 70 °C under vigorous stirring, maintaining the pH of the mixed solution at 10.3 to 10.7 by adding 2M NaOH aqueous solution. After completion of this step, the resulting solution was stirred for 1 hour at 60 to 70 °C and then placed into an oven at 60 °C for 18 to 24h. The product was filtered and washed by hot distilled and deionized water (60 to 70 °C) until hydroxide ion free. The resulting precipitate was dried in a drying oven at 60°C for 24 h and then calcined at 500 °C for 16 hour in air.

Example 2

Preparation of catalyst sample LSR-30 [0068] A catalyst was prepared by following the same procedure as for Example 1, except that 0.9575g of Y(N03)3-6H20 was used.

Example 3

Preparation of catalyst sample LSR-27 [0069] A catalyst was prepared by following the same procedure as for

Example 1, except that 2.2568g of Gd(N03)3-6H20 was used instead of 1.9151 g of Y(N03)3.6H20 used.

Example 4

Preparation of catalyst sample LSR-28 [0070] A catalyst was prepared by following the same procedure as for Example 3, except that 1.1284g of Gd(N03)3.6H20 was used.

Example 5

Preparation of catalyst sample LSR-22 [0071] A catalyst was prepared by following the same procedure as for

Example 1, except that 2.1712g of Ce(N03)3-6H20 was used instead of 1.9151g of Y(N03)3.6H20 used.

Comparative example 1 Preparation of catalyst sample LSR-18 2012258290 20 Nov 2012 17 [0072] 7.3783g of AI(N03)2.9H20, 19.2308 g of Mg(N03)2.6H20 and 7.2703 of Ni(N03)2.6H20 were dissolved in 250 ml of distilled and deionized water and then the mixed solution was stirred for 20 minutes at ambient temperature to give Solution 1. 7.9493 g of Na2C03was dissolved in 250 ml of distilled water; the solution was then stirred for 20 minutes at 65 °C to give Solution 2. Solution 1 was then added to the Solution 2 by dropwise at 60 to 70 °C under vigorous stirring, maintaining the pH of the mixed solution at 10.3 to 10.7 by adding 2M NaOH aqueous solution. After completion of this step, the resulting solution was stirred for 1 hour at 60 to 70 °C and then placed into an oven at 60 °C for 18 to 24h. The product was filtered and washed by hot distilled and deionized water (60 to 70°C) until hydroxide ion free. The resulting precipitate was dried in a drying oven at 60 °C for 24 h and then calcined at 500 °C for 16 hour in air.

Catalyst characterization Brauner-Emmett-Teller (BET) surface area [0073] Table 1 summarizes the catalyst formula for the multiple metal oxide-based Ni catalysts, their BET surface areas, pore volumes and pore sizes as produced via the co-precipitation method. All the samples were calcined in air at 500 °C for 16 h before measurement. Table 1 shows that introduction of Al to the multiple metal oxide-based Ni catalysts increase their BET surface areas. Furthermore, the BET surface area values as a function of the Al content, increasing with increasing Al contents. In addition, these catalysts obtained by co-precipitation can obtain larger Ni-loading without significantly affecting the BET surface area. It is well known that the large BET surface areas are of benefit to the dispersion of active metal Ni on the catalyst surface to reduce its agglomeration and sintering at high temperatures. 18 2012258290 20 Nov 2012 [0074] Table 1 Physical properties of NiaMgbAlcMdOx reforming catalysts Catalyst codes Catalyst compositions (at%) BET (mz/g) ±1.0 Pore dia. (nm) ±0.3 Pore ave.vol. (cm3/g) ±0.05 LSR-16 NiMg2AIOx 206 7.8 0.40 LSR-17 NiMgAI2Ox 213 5.9 0.31 LSR-18 NiMgsAIO, 194 6.4 0.31 LSR-21 NiMg3Ox 112 15.3 0.43 LSR-19 Nio75Mg3AIOx 194 6.0 0.29 LSR-20 Ni05Mg3AIOx 198 9.2 0.46 LSR-23 NiCa;jAIOx 58 5.7 0.08 LSR-22 NiMg3AICe0.2Ox 153 5.8 0.22 LSR-24 NiMgjAIYozO, 152 7.5 0.28 LSR-25 NiMg3AILa0 2Ox 136 8.3 0.28 LSR-27 NiMg3AIGd0 20x 156 10.8 0.42 LSR-28 NiMg3AIGd0iOx 169 8.4 0.36 LSR-29 NiMg3AIGd0.4Ox 136 10.4 0.36 LSR-30 NiMg3AIY01Ox 166 7.8 0.32 LSR-31 NiMg3AIY04Ox 147 9.5 0.34 h2-tpr [0075] The purpose of H2-TPR experiments was to determine the reducibility as well as the optimum reduction temperature of multiple metal oxide-based Ni catalysts. Figure 1 shows that LSR-18 and LSR-23 have one reduction peak at about 893 °C. Kumar, P., Y. Sun, and R. Idem [2] report that the reduction peak of NiO appears at 415 °C. It is possible that one reduction peak is contributed to the reduction of the Ni-Mg solid solution in LSR-18 and the reduction of the Ni-AI solid solution in LSR-23, but their reduction temperature is much higher than these in pure NiO. This means 19 2012258290 20 Nov 2012 that Ni2+ species in LSR-18 and LSR-23 have a strong interaction with catalyst support.

[0076] Figure 2 shows that the reduction temperature of catalysts NiMg3AIOx increases from 789 °C to 858 °C to 894 °C with increasing the atomic ratio of Mg to Al from 1:2 to 2:1 to 3:1 whereas the reduction temperature of LSR-21 (NiMg30x) in the absence of Al, is the same as that of LSR-17 (NiMgAI2Ox). This indicates that changing the ratio of Mg to Al has an impact on the reduction temperature of Ni-support solid solution.

[0077] Figure 3 shows that the addition of a small amount of transitional metal such as Ce, Y, Gd to NiMg3AIOx (LSR-18) has a slight impact on the reduction temperature of these catalysts. The presence of La splits the reduction peak of Ni2+ species into one shoulder peak and a large peak located at 748 °C and 921 °C respectively, which means that the presence of La could improve the reducibility of Ni2+ species.

C02-TPD

[0078] CO2-TPD analysis was used to indicate the distribution of a variety of basic sites on catalyst surface. The low temperature desorption peaks reflect the presence of weak basic sites while the high temperature peaks indicate the existence of strong basic sites. Figure 4 shows that three types of CO2 adsorption sites can be observed over LSR-18. Two low temperature C02 desorption peaks are located at about 120 °C and 289 °C while a high temperature C02 desorption peak is observed at 768 °C.

[0079] Based on the reported literature [3, 4], the desorption peak at 100 to 200 °C is assigned to CO2 species adsorbed on OH groups while the higher temperature desorption peak at 200 to 450 °C is attributed to combined CO2 species adsorbed on Mg-0 pairs with access cations, and basic surface O2' anions on surface site. The highest temperature C02 desorption peak at about 768 °C might be contributed to the adsorption of CO2 species on strong basic sites over LSR-18. The peak temperature is 2012258290 20 Nov 2012 20 higher than our operating temperature (750 °C) and so the analysis of CO2 adsorption on the strong basic sites would not be carried in this work. The CO2-TPD profile of LSR-23 reveals that three major basic sites are detected at 143 °C, 318 °C, 579 °C respectively. The intensity of their basic sites increases with increasing temperature, indicating that there more strong basic sites than weak basic sites. In addition, two small shoulders and one flat desorption peaks are located at 437 °C, 492 °C and 861 °C in the CO2-TPD profile of LSR-23, suggesting that non-uniform distribution of basic sites over LSR-23.

[0080] Figure 5 shows that changing an atomic ratio of Mg to Al of NiMgyAIOx has an effect on the location and intensity of three temperature C02 desorption peaks. Moreover, the temperature peak shifts to higher temperature with the increasing ratio. In addition, a new desorption peak appears at 504 °C in the CO2-TPD pattern of LSR-21 as compared to the profiles of the other NiMgyAIOx catalysts.

[0081] Figure 6 demonstrates that adding a small amount of a prompter (Ce, Y, La, Gd) to NiMg3AIOx (LSR-18) impacts the intensity of three temperature desorption peaks. Table 2 surmises the quantitative analysis of CO2-TPD results of catalysts. The following findings can be obtained from Table 2: 21 2012258290 20 Nov 2012 [0082] Table 2 C02-TPD results of catalysts NiaMgbAlcOx Catalyst code Temperature Peak 1 Temperature Peak 2 Temperature Peak 3 Temperature Peak 4 Desorbed C02 (mmol/g) Desorbed C02 (mmol/g) Desorbed C02 (mmol/g) Desorbed C02 (mmol/g) LSR-16 3.76(156 °C) 18.92 (228 °C) 9.91 (759 °C) - LSR-17 32.71 (157 °C) 9.45 (880 °C) - - LSR-18 3.99(120 °C) 13.31 (289 °C) 11.21 (768 °C) - LSR-21 10.29 (180 °C) 13.90 (271 °C) 2.91 (457 °C) 11.64 (769 °C) LSR-23 1.97 (143 °C) 5.52 (318 °C) 21.18 (579 °C) 7.08 (861 °C) LSR-22 3.24 (145 °C) 14.93 (234 °C) 8.34 (770°C) - LSR-24 6.97 (169 °C) 13.85 (279 °C) 9.53 (759 °C) - LSR-25 1.32(115 °C) 17.28 (251 °C) 10.04 (768 °C) - LSR-27 6.04 (159 °C) 14.51 (277 °C) 13.11 (782 °C) -

[0083] Replacing of Mg by Ca obviously decreases the strength of weak and intermediate basic sites in the temperature ranges of 100 to 200 °C and of 200 to 320 °C respectively, but increasing the strength of strong basic sites at 579 °C and 861 °C

[0084] Increasing the atomic ratio of Mg/AI has an effect on the strength of weak and intermediate and strong basic sites. Furthermore, the strength of strong basic sites increases with the increasing Mg/AI ratio.

[0085] Addition of transitional metals (Ce, La, Y, Gd) to NiMg3AIMdOx has an effect on the intensity of three basic sites. Some have a positive impact on each site whereas the others have a negative one. There is a clear rule to be followed.

Catalyst Performance Test [0086] The catalyst activity was tested in a quartz reactor contained within a stainless steel tube to avoid any catalytic effect from the inside metal 2012258290 20 Nov 2012 22 surface. In a typical run, 0.010 g of calcined catalyst (0.15 - 0.21 mm particle size) was mixed with 0.827 g of quartz sand having the same size as the catalyst and then loaded onto a quartz frit located at the centre of the quartz reactor. Novel reforming catalysts were activated with 100% H2 at a temperature of 750 °C for 2 hours prior to introduction of a reformer feed gas. Then, the catalysts were operated at 750 °C and 1 bar in CDRM, or the SRM with the molar ratio of H2O/CH4 = 1.2 or the mixed SRM and CDRM with the molar ratio of H20:CH4:C02 = 0.8:1.0:0.43. The dried product gas was analysed by an online micro-gas chromatograph (GC) (Varian CP4900). Conversion, yield and the H2/CO ratio are defined as follows: [0087] [0088] [0089] CH4 conversion (%) = H2 yield (%) = H2/CO ratio = (moles of CH 4 converted) -x 100% (molesof CH4in the feed) _(molesof H2 formed)_χ jQQ% (2 x moles of CH4 + moles of H20 in the feed) (molesof H2 formed) (molesof CO formed)

The effect of the Mg/AI atomic ratio on catalyst activity for CDRM variety [0090] In order to assess the Mg/AI atomic ratio on the activity of NiaMgbAlcOx, a is fixed as 1.0 (molar units), b is varied from 1 to 3 (molar units) while c is from 0 to 2 (molar units). A variation of these catalyst performances with time on stream is plotted in Figure 7. It is obvious that the Mg/AI molar ratio affects catalyst activity and stability, where catalyst stability increases with increasing the Mg/AI molar ratio from 1:2 to 3:1 with NiMg3AIOx having the highest activity. NiMg30x shows reasonable stability, but its activity is lower than NiMg3AIOx. That means that the presence of a certain amount of Al can improve catalyst activity because the presence of Al can increase the BET surface area of catalyst shown in Table 1, which could disperse Ni on the catalyst surface and result in enhanced catalyst activity. In addition, increasing Mg concentrations can reduce carbon formation because the strong ability of MgO to adsorb CO2 can suppress carbon deposition on the active Ni sites. 2012258290 20 Nov 2012 i 23

The effect of replacing Mg by Ca on catalyst activity for CDRM

[0091] Replacement of Mg by Ca in NiMg^lOx produced NiCaijAIOx. Figure 8 shows that this replacement has a significant influence on catalyst activity for CDRM in terms of CH4 conversion, where NiMg3AIOx exhibits much higher activity and stability than NiCa^lOx. The obvious difference in the catalyst activity of the two catalysts may stem from the difference in an interaction between Ni and alkaline-earth metals.

The effect of Ni loading on the activity of NiaMg3AIOx for CDRM

[0092] Figure 9 shows that catalyst activity and stability increases with increasing Ni loading from 0.5 to 1.0 (molar units), but the degree of the increase in catalyst activity in terms of CH4 conversion (%) is much smaller from 0.75 to 1.0 (molar units) than from 0.5 to 0.75 (molar units). The optimal Ni loading depends on the chemical and physical properties of actual support.

The effect of promoter on catalyst activity for CDRM

[0093] Figure 10 shows that addition of small amount of transition metals such as Y, Gd and Ce to NiMg3AIOx, enhances catalyst activity by about 10% in terms of CH4 conversion. The promotable effect is not as obvious for adding the same amount of La. The possible explanation for the positive effect is that the addition could help inhibit the growth of Ni crystallites and the reoxidation of metallic Ni sites as well as prevent the carbon formation.

[0094] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope of the present invention.

[0095] Where the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps 2012258290 20 Nov 2012 24 or components, but not precluding the presence of one or more other feature, integer, step, component or group thereof.

References 1. S. Wang and G.Q. Lu, Energy Fuels, 1996.10: p. 896. 2. Kumar, P., Y. Sun, and R. Idem, Comparative Study of Ni-based Mixed Oxide Catalyst for Carbon Dioxide Reforming of Methane. Energy & Fuels 2008. 22: p. 3575-3582. 3. de Morais, A.H., et al., Mesoporous MAI204 (M=Cu, Ni or Mg) spinels: Characterisation and application in the catalytic dehydrongenation of ethylbenzene in the presence of C02. Appl Catal A, 2010. 382: p. 148-157. 4. Cosimo, J.I., et al., Structural requirements and reaction pathways in condensation reactions of alcohols on MgyAlOx catalysts. J Catal., 2000. 190: p. 261-275.

Claims (20)

1. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

   1. A process for the reforming of low molecular weight hydrocarbon, the process comprising: preparing a catalyst by a method comprising the steps of: (A) preparing an aqueous solution comprising: (i) an active component comprising nickel (Ni); (ii) a support component comprising magnesium (Mg) and aluminum (Al); and (iii) a promoter component comprising at least one lanthanide metals; (B) adjusting the pH of the solution to at least 8 to thereby form a slurry comprising a co-precipitate of (i), (ii) and (iii); and (C) separating said co-precipitate from the aqueous solution to form said catalyst, wherein the catalyst comprises Ni in the range of 10 to 40 molar % relative to the total metallic content; and exposing a stream comprising carbon dioxide and low molecular weight hydrocarbon to the catalyst.
2. 2. The process according to claim 1, wherein the stream further comprises steam.
3. 3. The process according to claim 1 or claim 2, wherein the reaction temperature is in the range of 550 °C to 950 °C.
4. 4. The process according to claim 3, wherein the reaction temperature is in the range of 650 °C to 850 °C.
5. 5. The process according to any one of claims 1 to 4, wherein the promoter component comprises at least two lanthanide metals.
6. 6. The process according to any one of claims 1 to 5, wherein the lanthanide metals are selected from the group consisting of Ce, Y, and Gd.
7. 7. The process according to claim 6, wherein the lanthanide metals comprise Y and/or Gd.
8. 8. The process according to any one of claims 1 to 7 wherein said catalyst has the formula NiaMgbAlcMdOx, wherein M is one of more lanthanide metals, a, b, c, d and x are numerals corresponding to the molar proportion of the catalyst components and wherein the molar ratio of the active component (a) to the support component (b + c) is in the range 1:2 to 1:6 and the ratio of the active component (a) to the promoter component (d) is in the ratio of 20:1 to 2:1.
9. 9. The process according to claim 8, wherein the molar proportion of the active component (a) is in the range 15 to 40, (b) is in the range 40 to 80, (c) is in the range 10 to 40 and (d) is in the range 1 to 8, wherein (a)+(b)+(c)+(d) = 100.
10. 10. The process according to any one of claims 1 to 9, wherein the co-precipitate is formed at a pH of between 10 and 11.
11. 11. A catalyst for use in reforming of low molecular weight hydrocarbon with carbon dioxide or with a mixture of carbon dioxide and steam, the catalyst having the formula NiaMgbAlcMdOx, wherein M is one of more lanthanide metals, a, b, c, d and x are numerals corresponding to the molar proportion of the catalyst components and wherein the molar ratio of the active component (a) to the support component (b + c) is in the range 1:2 to 1:6 and the ratio of the active component (a) to the promoter component (d) is in the ratio of 20:1 to 2:1.
12. 12. The catalyst according to claim 11, wherein the molar ratio of nickel to magnesium is in the range of 1:1.5 to 1:6.
13. 13. The catalyst according to claims 11 or claim 12, wherein the molar ratio of magnesium to aluminium is in the range 1.5:1 to 3:1.
14. 14. The catalyst according to any one of claims 11 to 13, wherein the molar % lanthanide metal relative to the sum of lanthanide metal, nickel, magnesium and aluminium is in the range 1.9 to 7.4%.
15. 15. The catalyst according to any one of claims 11 to 14, wherein Ni is present in the range of 10 to 40 molar % relative to the total metallic content.
16. 16. The catalyst according to any one of claims 11 to 15, wherein the catalyst has the molar formula selected from the group consisting of: NiMg3AIYo.iOx NiMg3AIYo.20x NiMg3AIY0.3Ox NiMg3AIYo.40x NiMg3AIGdo.iOx NiMg3AIGdo.20x NiMg3AIGd03Ox NiMg3AIGd0.4Ox NiMg3AICeo.iOx NiMg3AICeo.20x NiMg3AICe03Ox NiMg3AICe0.4Ox where x is a numeral corresponding to the oxide content of the catalyst.
17. 17. Use of the catalyst according to any one of claims 11 to 16 for the reforming of low molecular weight hydrocarbon, wherein a stream comprising carbon dioxide and low molecular weight hydrocarbon is exposed to the catalyst.
18. 18. The use according to claim 17, wherein the stream further comprises steam.
19. 19. The use according to claim 17 or claim 18, wherein the reaction temperature is in the range of 550 °C to 950 °C.
20. 20. The use according to claim 19, wherein the reaction temperature is in the range of 650 °C to 850 °C.