A composite catalyst RuO2-NiO-Mo2C-MgO and its preparation method

Abstract

The application provides a composite catalyst RuO2-NiO-Mo2C-MgO and a preparation method, and relates to the technical field of catalysts. The preparation method comprises the following steps: dissolving a ruthenium source, a nickel source, a molybdenum source and a magnesium source according to a required mass ratio to obtain a first solution; adding a chelating agent into the first solution to dissolve and obtain a second solution; adding a surfactant into the second solution, stirring under the condition of being heated to 60-100 DEG C to prepare a sol-gel-like premix; drying the premix to obtain a precursor; and calcining the precursor to obtain the composite catalyst. The composite catalyst is prepared by the preparation method. The application not only reduces the catalyst cost of the catalytic reaction PTA waste gas, but also improves the catalyst activity and the catalyst service life.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a composite catalyst RuO2-NiO-Mo2C-MgO and its preparation method. Background Technology

[0002] Purified terephthalic acid (PTA) is an important chemical raw material, and its demand has been increasing in recent years with industrial development and progress. However, PTA manufacturing processes easily generate PTA waste gas. This waste gas mainly contains volatile organic compounds such as methyl acetate, toluene, and brominated hydrocarbons. Direct emission of these gases can pollute the environment and even harm human health. Therefore, the treatment of PTA waste gas is essential.

[0003] Currently, the main methods for treating PTA waste gas include direct combustion, catalytic combustion, biodegradation, plasma oxidation, and photocatalytic combustion. Among these, catalytic combustion is considered the preferred method for treating PTA waste gas due to its advantages such as low reaction temperature, no need for fuel, and minimal environmental pollution.

[0004] In catalytic combustion processes, catalysts used for PTA waste gas fall into two main categories: The first category consists of noble metal catalysts, such as Pt, Pd, and Rh. These catalysts offer advantages like high catalytic activity and good selectivity, but also suffer from problems such as easy loss of active components and sintering. The second category comprises non-noble metal oxide catalysts, such as those using non-noble metal oxides like nickel, copper, manganese, and cobalt as the active component. While these catalysts are less expensive, they suffer from insufficient catalytic activity, require high reaction temperatures, and the active components are prone to deactivation due to carbon deposition.

[0005] In summary, in order to reduce the catalyst cost of PTA waste gas catalytic reaction and improve catalyst activity and lifespan, it is necessary to develop a composite catalyst RuO2-NiO-Mo2C-MgO and its preparation method. Summary of the Invention

[0006] The purpose of this invention is to provide a composite catalyst RuO2-NiO-Mo2C-MgO and its preparation method. The specific technical solution is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a composite catalyst RuO2-NiO-Mo2C-MgO, comprising:

[0008] Step S1: Add ruthenium source, nickel source, molybdenum source and magnesium source to distilled water in a mass ratio of 0.5-3.5:3-7:10-20:72.5-86.5 and stir until completely dissolved to obtain the first solution;

[0009] S2: Add the chelating agent to the first solution and stir until completely dissolved to obtain a second solution; the mass ratio of the chelating agent to the solute in the first solution is 1:15-30;

[0010] S3: Add the surfactant to the second solution and stir at 60-100°C to obtain a sol-gel premix; the mass ratio of the surfactant to the solute in the second solution is 1:60-80;

[0011] S4: After drying the premix, a foam-like RuO2-NiO-Mo2C-MgO precursor is obtained;

[0012] S5: The RuO2-NiO-Mo2C-MgO precursor was calcined in air to obtain the composite catalyst RuO2-NiO-Mo2C-MgO.

[0013] Optionally, in the composite catalyst RuO2-NiO-Mo2C-MgO, the loading of NiO is 3wt%-7wt%, and the loading of Mo2C is 10wt%-20wt%.

[0014] Optionally, in step S1, the ruthenium source includes any one of ruthenium chloride and ruthenium acetate; the nickel source includes any one of nickel nitrate and nickel acetate; the molybdenum source includes any one of ammonium molybdate and molybdenum acetate; and the magnesium source includes any one of magnesium nitrate and magnesium acetate.

[0015] Optionally, in step S2, the chelating agent includes at least one of citric acid and ethylene glycol.

[0016] Optionally, in step S3, the surfactant includes at least one of β-cyclodextrin, polyvinylpyrrolidone, and fullerene.

[0017] Optionally, in step S4, the drying process uses a drying temperature of 60-100℃ and a drying time of 12-24h.

[0018] Optionally, in step S5, the calcination treatment uses a calcination temperature of 450-550℃ and a calcination time of 4-6h.

[0019] Optionally, in step S5, the heating rate used in the calcination treatment is 3-5℃ / min.

[0020] Optionally, in step S1, the mass fraction of distilled water in the first solution is 50%-80%.

[0021] In a second aspect, the present invention provides a composite catalyst RuO2-NiO-Mo2C-MgO, which is prepared by the method for preparing the composite catalyst RuO2-NiO-Mo2C-MgO.

[0022] The application of the technical solution of the present invention has at least the following beneficial effects:

[0023] (1) The present invention provides a method for preparing a composite catalyst RuO2-NiO-Mo2C-MgO, which combines steps S1-S5, namely, preparing the composite catalyst RuO2-NiO-Mo2C-MgO under defined process conditions using the required amounts of ruthenium source, nickel source, molybdenum source, magnesium source, chelating agent and surfactant. This preparation method not only reduces the catalyst cost for catalytic reaction of PTA waste gas, but also improves catalyst activity and catalyst life. Specifically, in terms of catalytic principle, the composite catalyst uses RuO2 and NiO as active components, Mo2C as an auxiliary agent and MgO as a support; wherein, NiO is used as the main active component and RuO2 as the auxiliary active component, which not only has catalytic activity, but also can effectively disperse NiO, thereby improving the catalytic efficiency of the composite catalyst and synergistically catalytically oxidizing PTA waste gas into harmless substances such as CO2 and water;

[0024] The additive Mo2C can prevent the main active component NiO from becoming inactive due to carbon deposition. Specifically, the inventors considered that during catalytic oxidation, shell-like carbon and filamentous carbon easily form on the surface of the active component NiO, leading to NiO deactivation, i.e., carbon deposition causes NiO deactivation. Shell-like and filamentous carbon are carbon substances produced by incomplete oxidation reactions during the catalytic reaction. These carbon substances coat the surface of the active component NiO, thus isolating NiO from the PTA waste gas, leading to a decrease in the activity of the composite catalyst or even deactivation. Mo2C, due to the oxygen contained in the air in the PTA waste gas or the oxygen-containing active byproducts produced by the catalytic oxidation of PTA waste gas by RuO2 and NiO, will oxidize Mo2C to MoO2. Under high-temperature conditions, MoO2 can react with the shell-like and filamentous carbon coating the NiO surface to regenerate Mo2C. The carbonization cycle process helps to remove the shell-like and filamentous carbon coatings on the surface of NiO, thereby restoring the catalytic activity of NiO and extending the catalyst life.

[0025] The MgO support has a large specific surface area, providing sufficient attachment sites for active components, increasing the reaction surface and enhancing catalytic activity;

[0026] A sol-gel premix was prepared by combining chelating agents, surfactants, and the sol-gel method. During the drying process of the premix, foaming occurred, which resulted in smaller particles of the active components in the composite catalyst, improved the dispersibility of the active components, and avoided the problem that the catalytic performance of the composite catalyst was limited due to the agglomeration of the active components at high temperatures.

[0027] In addition, the use of surfactants creates multiple and dispersed large cavity structures, which can confine and encapsulate the active component, thereby forming multiple dispersed active component particles and improving the dispersibility of the active component.

[0028] (2) In this invention, the loading of NiO in the composite catalyst needs to be strictly controlled to be 3wt%-7wt%, and the loading of Mo2C to be 10wt%-20wt%. The principle is as follows: Excessive NiO content will lead to a faster catalytic oxidation rate of PTA tail gas than... The carbonization cycle rate leads to deactivation of the composite catalyst due to carbon deposition; if the NiO content is too low, the catalytic oxidation rate of PTA tail gas by the composite catalyst is low, and the activity of the composite catalyst decreases. Therefore, this invention uses an appropriate Ni / Mo content to enhance the activity and stability of the composite catalyst, that is, by adjusting the Ni / Mo content, the catalytic oxidation rate of PTA tail gas by RuO2-NiO is compared with... The carbonization cycle rates are matched.

[0029] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0030] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0031] Figure 1A This is a data graph showing the catalytic conversion of PTA tail gas by the composite catalyst prepared in Example 1 of this invention;

[0032] Figure 1B This is a data graph showing the catalytic conversion of PTA tail gas by the composite catalyst prepared in Example 2 of this invention;

[0033] Figure 1C This is a data graph showing the catalytic conversion of PTA tail gas by the composite catalyst prepared in Example 3 of this invention;

[0034] Figure 1D This is a data graph showing the catalytic conversion of PTA tail gas by the composite catalyst prepared in Example 4 of this invention;

[0035] Figure 1E This is a data graph showing the catalytic conversion of PTA tail gas by the composite catalyst prepared in Example 5 of this invention;

[0036] Figure 1F This is a data graph showing the catalytic conversion of PTA tail gas by the composite catalyst prepared in Example 6 of this invention;

[0037] Figure 2A This is a graph showing the stability data of the composite catalyst prepared in Example 5 of this invention for the catalytic conversion of dibromomethane;

[0038] Figure 2B This is a graph showing the stability data of the composite catalyst prepared in Example 5 of this invention for the catalytic conversion of toluene;

[0039] Figure 2C This is a graph showing the stability data of the composite catalyst prepared in Example 5 of this invention for the catalytic conversion of methyl acetate;

[0040] Figure 3 These are the XRD spectra of the composite catalysts prepared in Examples 1-6 of this invention and the reference material;

[0041] Figure 4 Here is a SEM image of the composite catalyst prepared from Comparative Example 1;

[0042] Figure 5 This is a data graph showing the catalytic conversion of PTA tail gas by the composite catalyst prepared in Comparative Example 2;

[0043] Figure 6A This is a graph showing the stability data of the composite catalyst prepared in Comparative Example 3 of this invention for the catalytic conversion of dibromomethane.

[0044] Figure 6B This is a graph showing the stability data of the composite catalyst prepared in Comparative Example 3 of this invention for the catalytic conversion of toluene.

[0045] Figure 6C This is a graph showing the stability data of the composite catalyst prepared in Comparative Example 3 of this invention for the catalytic conversion of methyl acetate;

[0046] Figure 7 This is a TEM image of the composite catalyst in the catalytic activity decrease section in Figure 6. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0048] Example 1:

[0049] A method for preparing a composite catalyst RuO2-NiO-Mo2C-MgO, comprising:

[0050] Step S1: Add ruthenium source (specifically ruthenium chloride), nickel source (specifically nickel nitrate), molybdenum source (specifically ammonium molybdate), and magnesium source (specifically magnesium nitrate) to distilled water at a mass ratio of 0.5:5:10:84.6 and stir at room temperature and pressure for 1-2 hours until completely dissolved to obtain the first solution; the mass fraction of distilled water in the first solution is 50%.

[0051] S2: Add the chelating agent (specifically citric acid) to the first solution and stir until completely dissolved to obtain the second solution; the mass ratio of the chelating agent to the solute in the first solution is 1:15;

[0052] S3: Add a surfactant (specifically β-cyclodextrin) to the second solution and stir at 80°C and normal pressure for 4-6 hours to obtain a sol-gel premix; the mass ratio of the surfactant to the solute in the second solution is 1:60.

[0053] S4: The premix is ​​dried to obtain a foam-like RuO2-NiO-Mo2C-MgO precursor; the drying temperature is 80℃ and the drying time is 12h.

[0054] S5: The RuO2-NiO-Mo2C-MgO precursor was calcined in air to obtain the composite catalyst RuO2-NiO-Mo2C-MgO; the calcination temperature was 550℃ and the calcination time was 4h; the heating rate was 5℃ / min.

[0055] In the composite catalyst RuO2-NiO-Mo2C-MgO, the loading of NiO is 5 wt% and the loading of Mo2C is 10%.

[0056] Based on Example 1, this invention also includes Examples 2-6. The difference between Examples 2-6 and Example 1 lies in the different mass ratios of the ruthenium source, nickel source, molybdenum source, and magnesium source used in step S1, as detailed in Table 1.

[0057] Table 1 shows the mass ratios of the ruthenium, nickel, molybdenum, and magnesium sources used in Examples 1-6.

[0058] Example 1 0.22g 1.94g 1.81g 54.08g Example 2 0.22g 1.94g 2.72g 50.88g Example 3 0.22g 1.94g 3.62g 47.68g Example 4 0.22g 2.71g 1.81g 52.8g Example 5 0.22g 2.71g 2.72g 49.6g Example 6 0.22g 2.71g 3.62g 46.4g

[0059] The loadings of RuO2, NiO, Mo2C, and MgO in the composite catalysts prepared in Examples 1-6 were determined, and the results are shown in Table 2. The loading methods were as follows: the loadings of NiO, Mo2C, and MgO in Examples 1-6 were tested by XRF, and the content of RuO2 in Examples 1-6 was tested by ICP.

[0060] Table 2 shows the loading amounts of each component in the composite catalysts prepared in Examples 1-6.

[0061]

[0062]

[0063] Multiple samples of equal mass of the composite catalysts prepared in Examples 1-6 were subjected to the same PTA tail gas catalytic conversion experiment in sequence. The catalytic results are shown in [reference]. Figure 1A-1F As shown. The catalytic conversion experimental method is as follows: During the catalytic conversion of PTA tail gas (specifically toluene, methyl acetate, and dibromomethane), 1g of composite catalyst powder was loaded. The evaluation conditions were: concentrations of dibromomethane, toluene, and methyl acetate of 500ppm, 1000ppm, and 1000ppm, respectively; and a space velocity of 150000ml·g⁻¹. -1 ·h -1 The reaction temperature is the temperature at which the evaluation device is heated from room temperature to the conversion equilibrium point at a heating rate of 5℃ / min.

[0064] Depend on Figure 1A-1F It is known that the composite catalysts prepared in Examples 1-6 of the present invention all exhibit good catalytic performance, among which the composite catalyst prepared in Example 5 exhibits the best catalytic performance.

[0065] Multiple samples of equal mass of the composite catalyst prepared in Example 5 were subjected to the same PTA tail gas catalytic conversion stability test in sequence. The experimental results are shown in [reference]. Figure 2A-2C As shown. The experimental method for catalytic conversion stability is as follows: The evaluation apparatus was heated from room temperature to 350℃ at a heating rate of 5℃ / min. Reaction gases dibromomethane, toluene, and methyl acetate were introduced, maintaining the evaluation conditions as follows: the concentrations of dibromomethane, toluene, and methyl acetate were 500ppm, 1000ppm, and 1000ppm, respectively, and the space velocity was 150000 ml·g⁻¹. -1 ·h -1 .

[0066] See Figure 2A-2C The composite catalyst prepared in Example 5 showed stable catalytic activity after 200 hours of continuous use.

[0067] Equal masses of the composite catalysts prepared in Examples 1-6 were subjected to XRD tests. Simultaneously, equal masses of Mo2C and RuO2 were selected as references and XRD tests were performed under the same conditions. The test results are as follows: Figure 3 As shown. The XRD test method is as follows: it is performed on a Ulitma-IV type X-ray diffractometer, the X-ray is Cu Ka X-ray, the light source wavelength λ=0.15406nm, the tube voltage is 40kV; the tube current is 20mA, and the scanning angle is 10°-90°.

[0068] See Figure 3 The composite catalysts prepared in Examples 1-6 all showed Mo2C diffraction peaks, indicating the presence of Mo2C in the composite catalysts. However, due to the preparation method used in Examples 1-6 of this invention and the addition of surfactants, Ru species were well dispersed, and therefore, RuO2 XRD diffraction peaks did not appear.

[0069] Based on Examples 1-6, the present invention also includes the following comparative examples:

[0070] Comparative Example 1:

[0071] Unlike Example 5, the amount of molybdenum source used was zero, and the mass ratio of ruthenium source, nickel source and magnesium source was controlled to be 0.5:7:92.5.

[0072] Comparative Example 2:

[0073] Unlike Example 5, the amount of nickel source used was zero, and the mass ratio of ruthenium source, molybdenum source and magnesium source was controlled to be 0.5:15:84.5.

[0074] Comparative Example 3:

[0075] Unlike Example 5, the amount of ruthenium source used was zero, and the mass ratio of nickel source, molybdenum source and magnesium source was controlled at 7:15:78.

[0076] Comparative Example 4:

[0077] Unlike Example 5, the amount of nickel source used was controlled at 3%.

[0078] Comparative Example 5:

[0079] Unlike Example 5, the amount of nickel source used was controlled at 9%.

[0080] Comparative Example 6:

[0081] Unlike Example 5, the amount of molybdenum source used was controlled at 8%.

[0082] Comparative Example 7:

[0083] Unlike Example 5, the amount of molybdenum source was controlled at 22%.

[0084] The composite catalyst prepared in Comparative Example 1 was sampled and characterized by SEM. The results are as follows: Figure 4 As shown.

[0085] See Figure 4 Compared to Example 5, the composite catalyst prepared by Comparative Example 1 showed obvious carbon nanotubes, indicating that the composite catalyst prepared without the addition of a molybdenum source had a carbon deposition problem.

[0086] Multiple samples of equal mass of the composite catalyst prepared in Comparative Example 2 were subjected to the same PTA tail gas catalytic conversion experiment in sequence. The catalytic results are shown in [reference]. Figure 5 As shown in the figure. The catalytic conversion experimental method is the same as in Example 5.

[0087] Compared to Example 5, the composite catalyst prepared from Comparative Example 2 retains only RuO2 as the active component. See [link to Comparative Example 2]. Figure 5 It was clearly observed that although the composite catalyst prepared in Comparative Example 2 achieved the same conversion equilibrium point for methyl acetate as in Example 5, its reaction temperature was significantly higher than that of Example 5. Furthermore, the conversion rates (T90) of the composite catalyst prepared in Comparative Example 2 for both toluene and dibromomethane were significantly lower than those in Example 5.

[0088] Multiple samples of equal mass of the composite catalyst prepared in Comparative Example 3 were subjected to the same PTA tail gas catalytic conversion stability test in sequence. The experimental results are shown in [reference]. Figures 6A-6C As shown in Example 5. The experimental method for catalytic conversion stability was the same as in Example 5.

[0089] Compared to Example 5, the composite catalyst prepared from Comparative Example 3 retains only NiO as the active component. See [link to Comparative Example 3]. Figures 6A-6C It was clearly observed that the composite catalyst prepared by Comparative Example 3 showed a decreasing trend in catalytic activity after a period of stability evaluation.

[0090] right Figure 6A The composite catalyst in the middle stage of catalytic activity decline was characterized by TEM. See also Figure 7TEM characterization revealed sintering in the composite catalyst during the activity decline phase. Specifically, Ni-based catalysts are prone to sintering or agglomeration at high temperatures, leading to the coverage of active sites. Therefore, during the preparation and use of Ni-based catalysts, a second metal is usually added or limiting sites are created to prevent the active component Ni from agglomerating at high temperatures, thus preventing a decrease in catalyst activity. This invention enhances the dispersibility of Ni by adding a second metal, Ru. Therefore, in the comparative example without Ru, although the catalyst maintained a certain catalytic activity in the early evaluation stage, the active sites of Ni were gradually covered as the temperature and reaction time increased, resulting in a decrease in catalyst activity. TEM characterization of the catalyst with decreased activity revealed sintering of the active component NiO, indicating that the decrease in catalyst activity was caused by the sintering of the active component NiO.

[0091] Equal masses of the composite catalysts prepared in Example 5 and Comparative Examples 4-7 were taken and subjected to the same toluene catalytic conversion experiment. The T90 data were measured, and the specific results are shown in Table 3. The method for the toluene catalytic conversion experiment is as follows: 1 g of composite catalyst powder was loaded, and the evaluation conditions were a toluene concentration of 1000 ppm and a space velocity of 150000 mlg. -1 h -1 .

[0092] Table 3 shows the T90 data of the composite catalysts prepared in Example 5 and Comparative Examples 4-7 under the same toluene catalytic conversion experiments.

[0093] T90 250 320 290 350 440

[0094] As shown in Table 3, the present invention requires controlling the appropriate amount of nickel and molybdenum sources when preparing the composite catalyst in order to help improve catalytic performance and reduce T90.

[0095] The T90 data of the composite catalyst prepared in Example 5, along with commercially available Pd, Pt, and Rh catalysts, were obtained under the same test conditions for catalytic conversion of PTA tail gas (specifically toluene, methyl acetate, and dibromomethane). The test results are shown in Table 4. Specifically, the test conditions for catalytic conversion of PTA tail gas were: 1 g of catalyst powder was loaded, and the evaluation conditions were: concentrations of dibromomethane, toluene, and methyl acetate of 500 ppm, 1000 ppm, and 1000 ppm, respectively; and the space velocity was 150,000 ml / g. -1 h -1 .

[0096] Table 4 shows the T90 data of the composite catalyst prepared in Example 5 compared with commercially available Pd, Pt, and Rh catalysts under the same catalytic conversion of PTA tail gas test conditions.

[0097] T90 310 330 347 352

[0098] As shown in Table 4, compared with commercially available Pd catalysts, Pt catalysts and Rh catalysts, the composite catalyst prepared by this invention has a lower T90 and better catalytic performance.

[0099] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite catalyst RuO2-NiO-Mo2C-MgO, characterized in that, include: Step S1: Add ruthenium source, nickel source, molybdenum source and magnesium source to distilled water in a mass ratio of 0.5-3.5:3-7:10-20:72.5-86.5 and stir until completely dissolved to obtain the first solution; S2: Add the chelating agent to the first solution and stir until completely dissolved to obtain a second solution; the mass ratio of the chelating agent to the solute in the first solution is 1:15-30; the chelating agent is citric acid; S3: Add the surfactant to the second solution and stir at 60-100℃ to obtain a sol-gel premix; the mass ratio of the surfactant to the solute in the second solution is 1:60-80; the surfactant is β-cyclodextrin; S4: After drying the premix, a foam-like RuO2-NiO-Mo2C-MgO precursor is obtained; S5: The RuO2-NiO-Mo2C-MgO precursor was calcined in air to obtain the composite catalyst RuO2-NiO-Mo2C-MgO; In the composite catalyst RuO2-NiO-Mo2C-MgO, the loading of NiO is 5wt%-7wt%, and the loading of Mo2C is 10wt%-20wt%.

2. The preparation method of the composite catalyst RuO2-NiO-Mo2C-MgO according to claim 1, characterized in that, In step S1, the ruthenium source includes any one of ruthenium chloride and ruthenium acetate; the nickel source includes any one of nickel nitrate and nickel acetate; the molybdenum source includes any one of ammonium molybdate and molybdenum acetate; and the magnesium source includes any one of magnesium nitrate and magnesium acetate.

3. The method for preparing the composite catalyst RuO2-NiO-Mo2C-MgO according to claim 1, characterized in that, In step S4, the drying process uses a drying temperature of 60-100℃ and a drying time of 12-24h.

4. The method for preparing the composite catalyst RuO2-NiO-Mo2C-MgO according to claim 1, characterized in that, In step S5, the calcination treatment is carried out at a calcination temperature of 450-550℃ and a calcination time of 4-6h.

5. The method for preparing the composite catalyst RuO2-NiO-Mo2C-MgO according to claim 1, characterized in that, In step S5, the heating rate used in the calcination treatment is 3-5℃ / min.

6. The method for preparing the composite catalyst RuO2-NiO-Mo2C-MgO according to claim 1, characterized in that, In step S1, the mass fraction of distilled water in the first solution is 50%-80%.

7. A composite catalyst RuO2-NiO-Mo2C-MgO, characterized in that, The composite catalyst RuO2-NiO-Mo2C-MgO was prepared using the method described in any one of claims 1-6.

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