Application of Sulfated Zirconia Solid Superacid and Nickel Carbon Catalyst in Synergistic Catalytic Hydrodeoxygenation of Lignite Model Compounds

Abstract

The present invention discloses the application of sulfuric acid zirconium oxide solid superacid and nickel-carbon catalyst in the synergistic catalysis of hydrodeoxygenation of lignite model compounds. Under mild conditions of 140-180 °C, 1 MPa H2 and 2-4 h, using SO4 2‑ / ZrO2 and 10% Ni / AC as catalysts, 100% conversion of lignite model compounds such as diphenyl ether and 100% high selectivity for cyclohexane are achieved. The solid superacid catalyst of the present invention and the metal catalyst are physically mixed to synergistically catalyze the hydrodeoxygenation of lignite model compounds, providing a new idea for the clean and efficient utilization of coal.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and particularly to the application of zirconium sulfate solid superacid and nickel-carbon catalyst in the synergistic catalysis of hydrodeoxygenation of lignite model compounds. Background Art

[0002] The organic matter in lignite is mainly composed of aromatic structural units connected by bridge bonds. Among the bridge bonds connecting aromatic structural units, the C-O bridge bond is the main connection mode, especially the C-O ether bond. Due to the high oxygen content of lignite, the direct use of hydrocracked oil is restricted by some disadvantages such as low energy density, corrosiveness, and high viscosity. Therefore, an oxygen removal and upgrading process, namely the so-called hydrodeoxygenation (HDO), is required. The conversion of coal and model compounds generally requires high-temperature and high-pressure reaction conditions. Selecting a catalyst that can achieve its efficient conversion under mild conditions is crucial.

[0003] Solid superacid catalysts are environmentally friendly catalysts with advantages such as super strong acidity, stability, reusability, non-corrosion of equipment, and no pollution to the environment. Among them, metal oxide solid superacids have stronger acid sites, which can enhance the efficient adsorption and dissociation of hydrogen molecules under mild conditions in hydrogenation catalytic reactions, can enhance the adsorption of coal macromolecules on the catalyst, and ultimately promote the directional cleavage of C-O bridge bonds connecting aromatic rings in coal organic matter. In conventional bifunctional catalysts, the interaction between the active metal and the carrier restricts the conversion rate of the reaction. The physical mixing of two different functional catalysts is a promising simple solution, which can avoid the problems caused by the interaction between the two catalysts while maintaining their respective functions. Summary of the Invention

[0004] The purpose of the present invention is to provide the application of zirconium sulfate solid superacid and nickel-carbon catalyst in the synergistic catalysis of hydrodeoxygenation of lignite model compounds, to avoid the problems caused by the interaction between the two catalysts, and to improve the conversion rate of the reaction.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: The application of zirconium sulfate solid superacid and nickel-carbon catalyst in the synergistic catalysis of hydrodeoxygenation of lignite model compounds, and the specific steps include:

[0006] Put the substrate lignite model compound, catalyst and n-hexane into a reactor. The catalyst is composed of a sulfuric acid zirconia solid superacid catalyst and a nickel-carbon catalyst compounded according to a mass ratio of 1-5:5. After sealing, residual air is removed by introducing hydrogen. Subsequently, the reactor is pressurized to the desired pressure (0.1-2 MPa) with hydrogen at room temperature, then the temperature is raised to the required reaction temperature of 140-180 °C, and the reaction is stirred for 2-4 h. After the experiment, the reaction system is naturally cooled to room temperature and the pressure is released. The reaction mixture is filtered to remove the catalyst, and the organic phase obtained is analyzed by gas chromatography-mass spectrometry and gas chromatography.

[0007] As a preferred embodiment of the present invention, the sulfuric acid zirconia solid superacid catalyst is prepared by a precipitation method. The specific steps include: preparing an aqueous zirconyl dichloride solution, adjusting the pH value of the solution to 9-10 under stirring conditions, centrifuging after stirring and reacting for 24 h, washing with water until neutral, and drying overnight under vacuum. After grinding, 0.5 mol / L sulfuric acid is added, and the reaction is stirred for 6 h, then filtered and dried. The dried solid is ground into powder and transferred to a tubular furnace, and calcined at 500-600 °C under an inert atmosphere for 3 h to obtain the solid superacid 0.5-SO 4 2- / ZrO 2 .

[0008] As a preferred embodiment of the present invention, the active ingredient in the nickel-carbon catalyst is metallic nickel, the carrier is activated carbon, and the nickel loading is 10%.

[0009] As a more preferred embodiment of the present invention, the nickel-carbon catalyst is prepared by an impregnation method. The specific steps include: adding an activated carbon carrier to an aqueous nickel nitrate solution, ultrasonicating for 15-30 min, then vacuum impregnating the mixture at room temperature for 24 h, and drying after impregnation. Then, the solid sample is first calcined at 450 °C for 2 h in an inert atmosphere, and then reduced at 450 °C for 2 h in an H 2 atmosphere to obtain the catalyst 10% Ni / AC.

[0010] As a preferred embodiment of the present invention, the lignite model compound is one of diphenyl ether, benzyl phenyl ether, phenoxyethylbenzene, p-xylene ether, 4-phenoxyphenol and dibenzyl ether.

[0011] As a preferred embodiment of the present invention, the stirring speed is 800-900 rpm.

[0012] As a preferred embodiment of the present invention, the mass ratio of the amount of the catalyst used to the mass of the substrate is 1:1.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The present invention uses SO 4 2- / ZrO 2 and 10% Ni / AC as catalysts. Under mild conditions of 140 °C, 1 MPa H 2 and 2 h, 100% conversion of the lignite model compound diphenyl ether and 100% high selectivity for cyclohexane are achieved. The catalyst preparation method is simple and only requires physical mixing for use to obtain high hydrodeoxygenation activity.

[0015] 2. The present invention uses SO 4 2- / ZrO 2 and 10% Ni / AC as catalysts. Under the reaction conditions of 140 - 180 °C, 2 - 4 h and 1 MPa H 2 , cleavage of the C - O ether bond of different lignite model compounds including diphenyl ether, benzyl phenyl ether, phenoxyethylbenzene, p - xylene ether, 4 - phenoxyphenol and dibenzyl ether, etc. can be achieved, and most of the products are oxygen - free compounds. The present invention is of great significance for realizing the deoxygenation and upgrading of coal pyrolysis oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 are the XRD spectra of different catalysts.

[0017] Figure 2 are the NH 3 -TPD diagrams of different solid superacids.

[0018] Figure 3 are the XPS diagrams of different catalysts.

[0019] Figure 4 are the TEM and particle size distribution diagrams of different catalysts.

[0020] Figure 5 are the SEM diagrams of different catalysts.

[0021] Figure 6 is the influence of the concentration of sulfuric acid used for synthesizing the solid superacid on the conversion of diphenyl ether.

[0022] Figure 7 is the influence of the reaction temperature on the conversion of diphenyl ether.

[0023] Figure 8 is the influence of the reaction pressure on the conversion of diphenyl ether. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be further described in detail below with reference to the drawings and specific examples.

[0025] Example 1:

[0026] (1) Preparation of SO 4 2- / ZrO 2 :

[0027] All solid superacid catalysts were prepared by the precipitation method. In a typical process, 2 g of ZrOCl 2 ·8H 2 O was weighed and dissolved in deionized water, and ultrasonicated for 5 min at room temperature. Under stirring conditions, ammonia water was slowly added dropwise to adjust the pH value of the solution to 9 - 10. After stirring and reacting for 24 h, it was centrifuged and washed with deionized water until neutral. The obtained solid was dried under vacuum at 70 °C overnight, ground, and then 15 mL of sulfuric acid was added, stirred and reacted for 6 h, and then filtered and dried. The dried solid was ground into powder, and then calcined in a tubular furnace at 550 °C under an argon atmosphere for 3 h to obtain the solid superacid n-SO 4 2- / ZrO 2 , abbreviated as n-SZ (n = 0, 0.25, 0.5, 0.75, and 1, representing the sulfuric acid concentration, unit is mol / L).

[0028] (2) Preparation of 10% Ni / AC by impregnation method:

[0029] The 10% Ni / AC catalyst was prepared by the impregnation method. 5 mL of deionized water was added to 0.5505 g of Ni(NO 3 ) 2 ·6H 2 O, and stirred for 5 min at room temperature. Then 1 g of activated carbon support was added and ultrasonicated for 15 min. The mixture was impregnated in vacuum at room temperature for 24 h. Then it was dried at 110 °C for 12 h. After that, the solid sample was first calcined in a nitrogen atmosphere at 450 °C for 2 h, and then reduced in an H 2 atmosphere at 450 °C for 2 h. The catalyst 10% Ni / AC was obtained.

[0030] Using 0.5-SZ and 0.5-SZ / AC as carriers, 10% Ni / 0.5-SZ and 10% Ni - 0.5-SZ / AC catalysts were prepared by the same method for comparative experiments.

[0031] (3) Characterization of the catalysts:

[0032] From Figure 1It can be seen from the XRD patterns that diffraction peaks of Ni(111) and Ni(200) crystal planes were observed at 44.5° and 51.8° for both the activated carbon-supported nickel-based catalyst and the solid superacid-supported nickel-based catalyst. For the solid superacid-supported nickel catalyst and the n-SZ samples treated with sulfuric acid at different concentrations, obvious diffraction peaks were observed near 2θ = 30.3°, 35.3°, 50.4° and 60.2°, corresponding to the (011), (110), (112) and (121) crystal planes of tetragonal zirconia, respectively. Among them, the characteristic peaks of tetragonal zirconia in 0.5-SZ were particularly prominent. In addition to the above characteristic peaks, obvious diffraction peaks of monoclinic phase were also shown at 2θ = 24.4°, 28.2°, 31.5° and 34.2° for 0-SZ without sulfuric acid treatment. The n-SZ catalysts treated with sulfuric acid all presented a crystal structure of tetragonal zirconia phase, which might be the reason for the excellent catalytic performance of this solid superacid catalyst.

[0033] Using NH 3 -TPD characterization method, the acidity of different solid superacids treated with sulfuric acid was measured. Generally speaking, the acidity distribution in the NH 3 -TPD curve can be divided into four different regions, and the peaks at these four different temperatures represent weak acid sites (T < 300 °C), medium strong acid sites (300 °C < T < 450 °C), strong acid sites (450 °C < T < 600 °C) and super strong acid sites (T > 600 °C), respectively. As Figure 2 shown, 0-SZ without sulfuric acid treatment had almost no acidity, while desorption peaks appeared above 600 °C for n-SZ prepared by different sulfuric acid treatments, indicating that the prepared catalysts had solid superacidic properties. It can be seen that the desorption temperature of the solid superacid gradually increased with the increase of sulfuric acid concentration, indicating that the higher the sulfuric acid concentration, the stronger the acidity of the obtained solid superacid. However, the peak area of 0.5-SZ was the largest, that is, the acid amount was the largest. Appropriate acidity and higher acid amount might be one of the reasons for the best activity of this catalyst.

[0034] XPS detection was carried out on the catalyst to observe the actual chemical valence state of the active metal Ni in the prepared catalyst. As Figure 3 shown, for the 10% Ni / AC catalyst, the content of metal Ni dispersed on the surface of AC 0 was the highest, reaching 30.8%; for the 10% Ni / 0.5-SZ catalyst, the content of metal Ni on the surface of 0.5-SZ 0 was 9.8%; for the 10% Ni-0.5-SZ / AC catalyst, the content of metal Ni on the surface of 0.5-SZ / AC 0 was the lowest, only 8.4%. Generally speaking, the metal Ni in the catalyst 0The higher the content, the more favorable the catalyst is for hydroconversion, which helps the activation and dissociation of hydrogen to generate active hydrogen. Therefore, the 10% Ni / AC catalyst has relatively higher activity.

[0035] The particle size of metal nanoparticles is an important factor affecting the hydrogenation reaction of hydrogenation catalysts. The smaller the particle size of the metal particles in the catalyst, the better its dispersion, so there are relatively more active sites, which plays a key role in the adsorption, activation and dissociation of H 2 and the adsorption and reaction of reactants. As Figure 4 shown, for the 10% Ni / AC catalyst, the average particle size of the metal Ni dispersed on the AC surface is about 7.85 nm; for the 10% Ni / 0.5-SZ catalyst, the metal Ni on the 0.5-SZ surface agglomerates severely, and the average particle size is as high as 21.57 nm. The high agglomeration of the metal may be an important reason for its extremely low catalytic activity; however, for the 10% Ni-0.5-SZ / AC catalyst, although the average particle size of the metal Ni on the 0.5-SZ / AC surface is small, only 6.44 nm, the loading of the metal will cause serious coverage of the active sites and acidic sites of the catalyst, and the content of the active metal Ni 0 in the catalyst is the lowest. Therefore, the activity of the catalyst does not increase, but decreases instead.

[0036] As shown in Table 1, the prepared 10% Ni / AC catalyst has a rich microporous and mesoporous structure, a large specific surface area, which is conducive to the dispersion of the active metal, and a small pore size. For the prepared n-SZ catalysts, they all have a small specific surface area, and the specific surface area is mainly mesoporous structure with a large pore size. The treatment with sulfuric acid will help to form more mesoporous structures and reduce the pore size.

[0037] Table 1 Pore structure information of different catalysts

[0038]

[0039] S BET : Total pore specific surface area; S micro : Micropore specific surface area; S meso : Mesopore specific surface area; V total : Total pore volume; V micro : Micropore volume; V meso : Mesopore volume; D ave : Average pore diameter.

[0040] a : Measured by the multi-point BET method; b : Measured by the t-plot method; c : Calculated according to the nitrogen adsorption amount at a relative pressure P / P 0 of 0.99; d: Use the subtraction method.

[0041] SEM characterization was used to observe the morphological features of the AC, 10% Ni / AC, and 0.5-SZ samples. As Figure 5 shown, there are abundant pore structures on the surfaces of AC and 10% Ni / AC, and metallic Ni is evenly dispersed on the surface of AC. The surface of the 0.5-SZ sample is relatively rough and there are also certain pore structures.

[0042] Example 2: Hydrogenation application of the synthesized catalyst to diphenyl ether

[0043] Take the hydrodeoxygenation reaction of diphenyl ether as an example:

[0044] All hydrodeoxygenation reactions were carried out in a 100 mL stainless steel autoclave. In a typical experiment, the substrate diphenyl ether (100 mg), the catalyst, and n-hexane (20 mL) were placed into the reactor. After sealing, the residual air was removed by purging with hydrogen three times. Subsequently, the reactor was pressurized with hydrogen to the desired pressure (1 MPa) at room temperature. Then the temperature was raised to the required reaction temperature (140 °C), and it was maintained for a certain time (60 min) at a vigorous stirring speed of 800 rpm. After the experiment, the reaction system was naturally cooled to room temperature and the pressure was released. The reaction mixture was filtered to remove the catalyst, and the obtained organic phase was analyzed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC). The main products of diphenyl ether cracking are benzene, cyclohexane, cyclohexanol, oxygenated dicyclohexane (OCE), and cyclohexyl phenyl ether (CPE).

[0045] Table 2 Comparison of different catalysts for the hydrodeoxygenation reaction of diphenyl ether

[0046]

[0047] Reaction conditions: 100 mg diphenyl ether, 20 mL n-hexane, 140 °C, 1 h, 1 MPa H 2 , M = AC, n-SZ (n = 0, 0.25, 0.5, 0.75, and 1); a 50 mg catalyst; b 100 mg catalyst; c 50 mg 10% Ni / AC and 50 mg solid superacid.

[0048] By carrying out the reaction under mild conditions (140 °C, 1 MPa H 2)The catalytic hydrogenation and deoxygenation reaction of diphenyl ether was carried out to evaluate the catalytic activity of the catalysts. As can be seen from Table 2, diphenyl ether could not be converted in the absence of a catalyst and when only AC and n-SZ were used. Under the same reaction conditions, the conversion rate of diphenyl ether on 10% Ni / AC was higher than that on 10% Ni / 0.5-SZ and 10% Ni-0.5-SZ / AC. The main reason for the almost no catalytic activity of 10% Ni / 0.5-SZ was the severe agglomeration of metallic nickel on the 0.5-SZ support and the low Ni 0 content. When a solid acid was added to the reaction system to co-catalyze the diphenyl ether reaction with 10% Ni / AC, the conversion rate of diphenyl ether increased significantly. It should be noted that after adding HZSM-5 and 0.5-SZ, the selectivity of cyclohexane in the products increased significantly. Compared with HZSM-5, the catalytic activity of 0.5-SZ was more excellent. Similarly, when 10% Ni / AC and 0.5-SZ co-catalyzed the hydrogenation and deoxygenation of diphenyl ether, the conversion rate of diphenyl ether was significantly higher than that of the single 10% Ni / AC catalyst. Even when the dosage of 10% Ni / AC was increased to 100 mg, the conversion rate of diphenyl ether was significantly lower than that in the presence of a solid superacid. It can be seen that adding a solid superacid can promote the hydrogenation conversion of diphenyl ether and make it generate more cyclohexane through hydrodeoxygenation reaction.

[0049] 10% Ni / AC and 0.5-SZ showed the best activity when co-catalyzing the hydrogenation and deoxygenation of diphenyl ether. Figure 6 The effect of adding solid superacids treated with sulfuric acid at different concentrations to the catalytic system on the conversion rate of diphenyl ether was shown. When 0-SZ without sulfuric acid treatment was added, the conversion rate of diphenyl ether and the product distribution were similar to those when only 10% Ni / AC was added. When 0.25-SZ was added, the conversion rate of diphenyl ether and the selectivity of cyclohexane increased significantly and reached the maximum value when the sulfuric acid concentration was 0.5 mol / L, and 0.5 mol / L was the optimal sulfuric acid concentration. When the sulfuric acid concentration was too high, the conversion rate of diphenyl ether and the selectivity of cyclohexane decreased slightly. Therefore, in subsequent experiments, 0.5-SZ and 10% Ni / AC in n-hexane were used as catalysts.

[0050] As Figure 7 shown, under the condition of 1 MPa H 2 using n-hexane as the solvent, as the reaction temperature increased from 100 °C to 140 °C, the conversion rate of diphenyl ether and the selectivity of cyclohexane gradually increased and both reached 100% at 140 °C, while the selectivity of benzene gradually decreased to 0 with the increase of temperature. Throughout the process, the selectivity of dioxycyclohexane was very low, and dioxycyclohexane was not detected in the products at 140 °C.

[0051] As Figure 8As shown, the effects of hydrogen pressure on the conversion of diphenyl ether and the selectivity of cyclohexane were investigated. A low hydrogen pressure (0.1 MPa) led to low conversion of diphenyl ether and selectivity of cyclohexane. With the increase of hydrogen pressure, the conversion of diphenyl ether and the selectivity of cyclohexane increased rapidly, reaching a maximum value of 100% at 1 MPa, and then remained unchanged. It can be seen that with the increase of H 2 pressure, the selectivity of benzene gradually decreased. Therefore, the optimal H 2 pressure determined in this study was 1 MPa. Under this pressure, diphenyl ether could be completely converted into cyclohexane.

[0052] Example 3: Hydrogenation application of the synthesized catalyst to different lignite model compounds

[0053] Using 10% Ni / AC and 0.5-SZ as catalysts, the hydrogenation conversion of different lignite model compounds was investigated. As shown in Table 3, diphenyl ether, benzyl phenyl ether, phenoxyethylbenzene, p-xylene ether, 4-phenoxyphenol, and dibenzyl ether all had catalytic effects. Under relatively mild conditions (<180 °C and 1 MPa H 2 ), the C-O bond could be effectively cleaved, and the conversion rate was 100%. The yield of oxygen-containing products was low, and the catalyst could effectively catalyze the hydrogenation and deoxygenation reaction of lignite model compounds to produce oxygen-free compounds.

[0054] Table 3 Hydrogenation conversion results of different lignite model compounds on 10% Ni / AC and 0.5-SZ

[0055]

[0056] a Reaction conditions: 100 mg of reactant, 50 mg of 10% Ni / AC and 50 mg of 0.5-SZ, 20 mL of n-hexane, 1 MPa H 2 .

[0057] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention shall be covered by the protection scope of the present invention.

Claims

1. Application of sulfated zirconium oxide solid superacid and nickel-carbon catalyst to synergistically catalyze the hydrodeoxygenation of lignite model compounds, characterized in that: The specific steps include: A substrate lignite model compound, a catalyst and n-hexane are placed in a reactor, wherein the lignite model compound is one of diphenyl ether, benzyl phenyl ether, phenoxyethylbenzene, p-xylyl ether, 4-phenoxyphenol and dibenzyl ether, and the catalyst is composed of a sulfated zirconium oxide solid superacid catalyst and a nickel-carbon catalyst in a mass ratio of 1-5:5; after sealing, the residual air is removed by passing hydrogen; then, the reactor is pressurized to 0.1-2MPa with hydrogen at room temperature, and then the temperature is raised to the required reaction temperature of 140-180°C, and the reaction is stirred for 2-4h; after the experiment, the reaction system is naturally cooled to room temperature and the pressure is released; the reaction mixture is filtered to remove the catalyst, and the organic phase obtained is analyzed by gas chromatography-mass spectrometry and gas chromatography.

2. The use according to claim 1, characterized in that: The catalyst is composed of a sulfated zirconium oxide solid superacid catalyst and a nickel-carbon catalyst in a mass ratio of 1:

1.

3. The use according to claim 1 or 2, characterized in that: The sulfated zirconium oxide solid superacid catalyst is prepared by a precipitation method, and the specific steps include: preparing a zirconium oxychloride aqueous solution, adjusting the pH value of the solution to 9-10 under stirring conditions, stirring and reacting for 24 hours, centrifuging and washing with water to neutrality, and vacuum drying overnight, grinding and adding 0.5 mol / L sulfuric acid, stirring and reacting for 6 hours, and then filtering and drying; grinding the dried solid into powder and transferring it to a tube furnace, calcining it at 500-600° C. and in an inert atmosphere for 3 hours to obtain a solid superacid 0.5-SO4 2- / ZrO2.

4. The use according to claim 1 or 2, characterized in that: The active component of the nickel-carbon catalyst is metallic nickel, the carrier is activated carbon, and the nickel loading is 10%.

5. The use according to claim 4, characterized in that: The nickel-carbon catalyst is prepared by an impregnation method, and the specific steps include: adding an activated carbon carrier to a nickel nitrate aqueous solution, ultrasonicating for 15 to 30 minutes, and then vacuum impregnating the mixture at room temperature for 24 hours, and drying after the impregnation is completed; thereafter, the solid sample is first calcined at 450°C for 2 hours in an inert atmosphere, and then reduced at 450°C for 2 hours in a H2 atmosphere to obtain a catalyst 10% Ni / AC.

6. The use according to claim 1 or 2, characterized in that: The stirring speed is 800-900 rpm.

7. The use according to claim 1 or 2, characterized in that: The mass ratio of the amount of the catalyst to the substrate is 1:1.

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