Lanthanum oxide carbonate catalyst, method for preparing same, and use thereof

Abstract

The present application relates to the technical field of oxy-lanthanum carbonate, and discloses an oxy-lanthanum carbonate catalyst, a preparation method and application thereof, the oxy-lanthanum carbonate catalyst comprising hexagonal crystal phase oxy-lanthanum carbonate and hexagonal crystal phase oxy-lanthanum carbonate containing a doping element.The method comprises the following steps: (1) adding an alkali solution into a solution of a lanthanum source, then performing aging, solid-liquid separation and drying to obtain lanthanum hydroxide; (2) under a protective atmosphere, contacting a solution of a compound containing a doping element with the lanthanum hydroxide, and then performing drying; (3) performing calcination on the dried product of step (2) under an atmosphere containing CO2 to obtain the oxy-lanthanum carbonate catalyst.The catalyst prepared by the present application has a high carbon dihydrocarbon yield when used in a methane oxidative coupling reaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oxy-lanthanum carbonate, and particularly relates to an oxy-lanthanum carbonate catalyst, a preparation method and application thereof. BACKGROUND

[0002] Oxy-lanthanum carbonate is a new material, which is mainly used in water treatment, photoelectric field, catalysis field and the like. At present, the synthesis methods of oxy-lanthanum carbonate mainly include a precipitation method, a lanthanum carbonate thermal decomposition method and a hydrothermal method. However, the oxy-lanthanum carbonate is usually prepared by a two-step method, that is, first, a La(OH)3 precursor is synthesized, and then, calcination is performed at a low temperature. At present, the improvement of the oxy-lanthanum carbonate material is mainly to change the preparation method in order to obtain oxy-lanthanum carbonate with different morphologies or structures.

[0003] CN113797949A discloses a preparation method of oxy-lanthanum carbonate, which comprises synthesizing rod-shaped nano-structured oxy-lanthanum carbonate under ultrasonic conditions. The prepared oxy-lanthanum carbonate can efficiently perform a methane oxidative coupling reaction at a relatively low temperature, but the yield of carbon dihydride of the oxy-lanthanum carbonate is low.

[0004] In the prior art, there are few element-doped oxy-lanthanum carbonate materials, and only a few documents report that a solution containing a doping element is used to impregnate the oxy-lanthanum carbonate material. However, the element doping is not completed in the preparation process of the oxy-lanthanum carbonate in the prior art. SUMMARY

[0005] The present application provides an oxy-lanthanum carbonate catalyst, a preparation method and application thereof. The catalyst can activate methane oxidative coupling, and has a high carbon dihydride yield at 500-650 DEG C.

[0006] In order to achieve the above-mentioned purpose, the present application provides an oxy-lanthanum carbonate catalyst in the first aspect, which comprises hexagonal phase oxy-lanthanum carbonate and hexagonal phase oxy-lanthanum carbonate containing a doping element.

[0007] The present application provides a method for preparing an oxy-lanthanum carbonate catalyst in the second aspect, which comprises:

[0008] (1) adding an alkali solution into a solution of a lanthanum source, and then, performing aging, solid-liquid separation and drying to obtain lanthanum hydroxide;

[0009] (2) contacting a solution of a compound containing a doping element with the lanthanum hydroxide under a protective atmosphere, and then, performing drying;

[0010] (3) performing calcination of the dried product of step (2) under a CO2-containing atmosphere to obtain the oxy-lanthanum carbonate catalyst.

[0011] The present application provides the oxy-lanthanum carbonate catalyst prepared by the method in the third aspect.

[0012] The fourth aspect of the present application provides the use of the lanthanum oxycarbonate catalyst as described above in the preparation of carbon two and above hydrocarbons by methane oxidative coupling reaction.

[0013] The fifth aspect of the present application provides a method for preparing carbon two and above hydrocarbons from methane, which comprises: contacting methane with the lanthanum oxycarbonate catalyst as described above in the presence of oxygen and under the conditions of methane oxidative coupling reaction.

[0014] Alternatively, the lanthanum oxycarbonate catalyst is prepared according to the method described in the second aspect, and then methane is contacted with the obtained lanthanum oxycarbonate catalyst in the presence of oxygen and under the conditions of methane oxidative coupling reaction.

[0015] The catalyst provided by the present application contains both hexagonal lanthanum oxycarbonate and hexagonal lanthanum oxycarbonate containing doping elements, which can effectively promote the occurrence of methane oxidative coupling reaction and improve the carbon two hydrocarbon yield.

[0016] The present application first prepares lanthanum hydroxide by adding lye into a solution containing lanthanum element, and then contacts a solution containing doping elements with the lanthanum hydroxide to obtain the catalyst. The prepared catalyst contains both hexagonal lanthanum oxycarbonate and hexagonal lanthanum oxycarbonate containing doping elements. When the catalyst prepared by the present application is used in methane oxidative coupling reaction, it has a high carbon two hydrocarbon yield. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the XRD spectrum of the lanthanum oxycarbonate catalyst prepared in Example 1;

[0018] Figure 2 is the transmission scanning electron microscope image of the lanthanum oxycarbonate catalyst prepared in Example 1. DETAILED DESCRIPTION

[0019] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The exact values are understood to be within the range of values. Any numerical value, however, can be expressed as approximately or approximately. For ranges, the endpoints are included within the range unless specified otherwise. For numerical values, the endpoints are included within the range unless specified otherwise.

[0020] The first aspect of the present application provides a lanthanum oxycarbonate catalyst, which contains both hexagonal lanthanum oxycarbonate and hexagonal lanthanum oxycarbonate containing doping elements.

[0021] According to the present application, preferably, the doping element is selected from at least one of the elements of Groups IIA, VIII, IB and IIB, more preferably at least one of the elements of Mg, Ca, Sr, Ba, Fe, Zn and Cd, and further preferably Sr and / or Ba.

[0022] According to the present application, preferably, the molar ratio of lanthanum element to doping element in the lanthanum oxycarbonate catalyst is 1:0.01-1, preferably 1:0.03-0.5, and more preferably 1:0.04-0.2. The molar ratio of lanthanum element to doping element in the lanthanum oxycarbonate catalyst can be calculated according to the feeding amount of lanthanum element and doping element.

[0023] According to the present application, preferably, the lanthanum oxycarbonate catalyst has a fibrous nanostructure, the diameter of the lanthanum oxycarbonate catalyst is 10-30 nm, preferably 10-20 nm, and the aspect ratio is 5-50:1, more preferably 15-40:1.

[0024] In the present application, the "diameter" and "aspect ratio" of the lanthanum oxycarbonate catalyst are average values, and the specific test method for the "average diameter" is to select 5-10 samples in the window using a transmission electron microscope scale, measure the diameter of each sample, and then obtain the average value. The specific test method for the "average aspect ratio" is to select 5-10 samples in the window using a transmission electron microscope scale, measure the diameter and length of each sample, respectively, then calculate the aspect ratio of each sample, and then obtain the average value.

[0025] According to the present application, preferably, the specific surface area of the lanthanum oxycarbonate catalyst is 45m 2 / g-90m 2 / g, preferably 50m 2 / g-60m 2 / g, the pore volume is 0.15cm 3 / g-0.5cm 3 / g, preferably 0.26cm 3 / g-0.4cm 3 / g, and the average pore diameter is 8-15 nm, preferably 10-13.5 nm.

[0026] The second aspect of the present application provides a method for preparing a lanthanum oxycarbonate catalyst, which comprises:

[0027] (1) adding a lye to a solution of a lanthanum source, then performing aging, solid-liquid separation and drying to obtain lanthanum hydroxide;

[0028] (2) contacting a solution containing a doping element with the lanthanum hydroxide under a protective atmosphere, and then drying;

[0029] (3) calcining the dried product of step (2) under a CO2-containing atmosphere to obtain a lanthanum oxide carbonate catalyst.

[0030] According to the present application, in order to make the generated lanthanum hydroxide more tend to be fibrous, preferably, the concentration of the lye is 3wt%-25wt%.

[0031] According to the present application, preferably, the base in the lye is a compound of Group IA metal.

[0032] According to the present application, preferably, the adding speed of the lye is 5mL / min-150mL / min per kilogram of the solution of the lanthanum source.

[0033] According to the present application, preferably, the concentration of the solution of the lanthanum source is 0.01wt%-10wt%.

[0034] According to the present application, preferably, the amount of the lye is such that the final pH value of the mixed system of the lye and the solution of the lanthanum source is 10-12.5.

[0035] According to the present application, the lanthanum source can be any substance capable of providing lanthanum element, preferably, the lanthanum source is a water-soluble salt of lanthanum, more preferably at least one of lanthanum nitrate, lanthanum chloride and lanthanum acetate; further preferably lanthanum nitrate.

[0036] According to the present application, the present application does not have special limitation to the aging device, as long as it can meet the conditions of aging temperature and stirring, but based on the safety and comprehensive catalyst performance of the experiment, the aging is carried out under the condition of condensation reflux. Preferably, the aging conditions include: temperature is 80-100℃, time is 10-50h.

[0037] The present application can also include solid-liquid separation of the aged product, and then washing with deionized water to neutral. Among them, the solid-liquid separation method can be the conventional solid-liquid separation method in the art, for example, using a centrifugal separator to separate.

[0038] According to the present application, preferably, in step (1), the drying includes first drying and second drying.

[0039] According to the present application, preferably, the conditions of the first drying include: temperature is 70-90℃, time is 10-20h.

[0040] According to the present application, preferably, the conditions of the second drying include: relative pressure is 10kPa-91kPa, preferably 20kPa-70kPa, temperature is 120-160℃, time is 2-10h.

[0041] According to the present application, preferably, the protective atmosphere is provided by an inert gas and / or nitrogen.

[0042] In the present application, the protective atmosphere can be provided by Schlenk technique (double tubing line operation) or in a glove box with protective atmosphere.

[0043] According to the present application, preferably, in step (1), the process of determining the saturated water absorption of lanthanum hydroxide is further included. Then, the solution of the compound containing the doping element is prepared according to the determined saturated water absorption of lanthanum hydroxide and the amount of the doping element.

[0044] According to the present application, preferably, the concentration of the solution of the compound containing the doping element is 0.01-0.2 g / mL.

[0045] According to the present application, preferably, the molar ratio of lanthanum element to the doping element in the lanthanum hydroxide is 1:0.01-1, preferably 1:0.03-0.5, and more preferably 1:0.04-0.2.

[0046] According to the present application, preferably, the compound containing the doping element is selected from the compounds of at least one element from Group IIA, VIII, IB and IIB, more preferably at least one element from Mg, Ca, Sr, Ba, Fe, Zn and Cd, and further preferably the compound of Sr and / or Ba. The compound containing the doping element can be at least one of the nitrates (such as magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate, iron nitrate, zinc nitrate, cadmium nitrate), chlorides (such as magnesium chloride, calcium chloride, strontium chloride, barium chloride, iron chloride, zinc chloride, cadmium chloride) and acetates (such as magnesium acetate, calcium acetate, strontium acetate, barium acetate, iron acetate, zinc acetate, cadmium acetate) of the doping element, and preferably the nitrate.

[0047] According to the present application, preferably, in step (2), the contacting is performed by adding the solution of the compound containing the doping element into the lanthanum hydroxide under stirring, and continuing the stirring after the addition is completed. More preferably, the adding speed of the solution of the compound containing the doping element is 0.1 mL / min-10 mL / min, preferably 0.1 mL / min-8 mL / min, per gram of the lanthanum hydroxide.

[0048] According to the present application, preferably, the contacting is performed at a temperature of 15-50℃ for 2-5 h.

[0049] According to the present application, in order to make the solution of the compound containing the doping element contact with the lanthanum hydroxide sufficiently, the contacting is performed in a vortex mixer.

[0050] According to the present application, preferably, in step (2), the drying condition comprises: temperature of 60-100℃, time of 10-24h.

[0051] According to the present application, preferably, in step (3), the calcination condition comprises: temperature of 450-550℃, time of 2-8h. Preferably, the CO2-containing atmosphere can be air atmosphere. The carbon element in the lanthanum oxycarbonate catalyst is derived from carbon dioxide in the CO2-containing atmosphere.

[0052] The third aspect of the present application provides the lanthanum oxycarbonate catalyst prepared by the method described above.

[0053] The fourth aspect of the present application provides the use of the lanthanum oxycarbonate catalyst described above in the preparation of carbon two and above hydrocarbons by methane oxidative coupling reaction.

[0054] The fifth aspect of the present application provides a method for preparing carbon two and above hydrocarbons from methane, which comprises: contacting methane with the lanthanum oxycarbonate catalyst described above in the presence of oxygen and under the condition of methane oxidative coupling reaction;

[0055] Alternatively, the lanthanum oxycarbonate catalyst is prepared by the method described in the second aspect, and then methane is contacted with the obtained lanthanum oxycarbonate catalyst in the presence of oxygen and under the condition of methane oxidative coupling reaction.

[0056] According to the present application, preferably, the molar ratio of the methane to the oxygen is 2-9:1.

[0057] According to the present application, preferably, the temperature of the contacting reaction is 500-650℃.

[0058] According to the present application, preferably, the space velocity of the methane is 5000mL / (g·h)-200000mL / (g·h).

[0059] The present application will be described in detail by way of examples below. In the following examples,

[0060] TEM imaging was performed using a JEOL 2100F FEG TEM with a Schottky field emission source. The acceleration voltage was 200kv. The images obtained were selected as representative from imaging of at least six different grid areas.

[0061] The length and diameter of the fibrous catalyst were measured by the scale in the software of the transmission scanning electron microscope image.

[0062] The analysis of the reaction product composition was performed on a gas chromatograph purchased from Agilent, model 7890A.

[0063] XRD diffractogram was measured by X-ray diffractometer (XRD) manufactured by Panalytical, model Empyrean, Cu target generator, working tube pressure 40 KV, working tube flow 40 mA, PixCel 3D Detector, divergence slit 1 / 4°, anti-scatter slit 1 / 2°, optical barrier 10 mm, soller slit 0.04 rad, receiving slit 7.5 mm, scan speed 0.013° / step, scan time 30 s / step, scan range: 5°-90°, measured in reflection mode.

[0064] The content of lanthanum and doping elements in the catalyst was measured by iCAP TQ ICP-MS purchased from Thermo Scientific.

[0065] The pore structure of the catalyst was characterized by BET analysis by a full-automatic adsorption instrument ASAP2420M purchased from MICROMERITICS (Mccrone Instruments) of the United States.

[0066] The calculation method of methane conversion rate is as follows:

[0067] Methane conversion rate = the amount of methane consumed by reaction / the initial amount of methane x 100%.

[0068] The calculation method of ethylene selectivity is as follows:

[0069] Ethylene selectivity = the amount of methane consumed by generated ethylene / the total consumption amount of methane x 100%.

[0070] The calculation method of ethane selectivity is as follows:

[0071] Ethane selectivity = the amount of methane consumed by generated ethane / the total consumption amount of methane x 100%.

[0072] The calculation method of carbon dihydrocarbon yield is as follows:

[0073] Carbon dihydrocarbon yield = methane conversion rate x (ethane selectivity + ethylene selectivity).

[0074] Example 1

[0075] (1) 5 g of lanthanum nitrate hexahydrate was dissolved in 210 g of deionized water, and stirred at 25°C and 9000 rpm for 30 min. Then, sodium hydroxide solution (10 wt% of sodium hydroxide solution, 7 mL / min of the addition rate of the lye with respect to the solution of the lanthanum source per kilogram, and the amount of the lye was such that the final pH of the mixed system of the lye and the solution of the lanthanum source was 11.6) was added dropwise to the aqueous solution of lanthanum nitrate, and stirring was continued at 25°C and 9000 rpm for 10 min after the completion of the dropwise addition. Then, the temperature was raised to 90°C, and the solution was kept under condensation reflux for 12 h. After the solution was cooled to room temperature, the solid material was separated by centrifugation at 10000 rpm, and washed with deionized water until the pH of the washing liquid was neutral. The obtained solid was subjected to first drying and second drying in this order, the first drying was performed at 80°C for 12 h, and the second drying was performed at 140°C for 5 h under a relative pressure of 60 kPa.

[0076] The saturated water absorption of the lanthanum hydroxide after the second drying was measured as follows. Under nitrogen atmosphere, 1 g of the lanthanum hydroxide after the second drying was placed in a round-bottom flask, deionized water was added dropwise to the round-bottom flask using a syringe, and the lanthanum hydroxide was mixed using a vortex mixer until the lanthanum hydroxide did not show a significant further water absorption, and the amount of the deionized water added at this time was recorded. The saturated water absorption of the lanthanum hydroxide was 2 mL / g.

[0077] (2) 0.08 g of strontium nitrate was dissolved in 1.6 mL of deionized water to obtain an aqueous solution of strontium nitrate. Under nitrogen atmosphere, 0.8 g of the lanthanum hydroxide after the second drying was placed in a round-bottom flask, and then the aqueous solution of strontium nitrate was added dropwise to the round-bottom flask using a syringe at 25°C (1 mL / min of the addition rate of the solution containing the doping element with respect to 1 g of the lanthanum hydroxide), and the mixture was sufficiently mixed using a vortex mixer for 5 h. Then, the obtained mixture was dried at 80°C for 12 h.

[0078] (3) The lanthanum oxide carbonate catalyst was prepared by calcination at 500°C for 2 h in an air atmosphere.

[0079] The molar ratio of the lanthanum element to the strontium element of the catalyst was 1:0.091.

[0080] The specific surface area of the lanthanum oxide carbonate catalyst was 52 m 2 / g, the pore volume was 0.31 cm 3 / g, and the average pore diameter was 10.1 nm.

[0081] Figure 1is the XRD spectrum of the lanthanum oxycarbonate catalyst prepared in Example 1, wherein the abscissa is 2Θ and the ordinate is intensity, and compared with the PXRD database (Bruker Diffrac.Eva, version 4.2.1), it can be seen that the catalyst prepared by the method has characteristic peaks of a hexagonal crystal phase, and due to its nanoscale, the crystallinity is low.

[0082] Figure 2 is the transmission scanning electron micrograph of the lanthanum oxycarbonate catalyst prepared in Example 1, wherein the abscissa is the length of the fiber and the ordinate is the number of fibers per unit length. Figure 2 It can be seen that the lanthanum oxycarbonate catalyst has a fibrous nanostructure, and the average diameter is calculated to be 13 nm and the average aspect ratio is calculated to be 40:1.

[0083] Example 2

[0084] (1) 5.15 g of lanthanum nitrate hexahydrate was dissolved in 155 g of deionized water, stirred at 25°C and a rotation speed of 9000 rpm for 30 min, then sodium hydroxide solution (the concentration of the sodium hydroxide solution was 10 wt%, the addition rate of the lye was 5 mL / min per kilogram of solution of the lanthanum source, and the amount of lye was such that the final pH of the lye and lanthanum source solution mixture was 12.2), after the addition was complete, the stirring was continued at 25°C and a rotation speed of 9000 rpm for 10 min. Then the temperature was raised to 100°C and the condensation reflux was maintained for 15 h of continuous stirring, after the solution was cooled to room temperature, the solid material was separated by centrifugation at 9000 rpm, and washed with deionized water until the pH of the washing liquid was neutral, the obtained solid was sequentially subjected to first drying and second drying, the conditions of the first drying included a temperature of 80°C and a time of 15 h, and the conditions of the second drying included a relative pressure of 50 kPa, a temperature of 150°C and a time of 5 h.

[0085] The saturated water absorption of the lanthanum hydroxide after the second drying was measured: 1 g of the lanthanum hydroxide after the second drying was placed in a round-bottom flask under nitrogen protection, deionized water was added dropwise to the round-bottom flask using a syringe, and the lanthanum hydroxide was mixed using a vortex mixer until the lanthanum hydroxide did not have obvious further water absorption, and the amount of deionized water added at this time was recorded. The saturated water absorption of the lanthanum hydroxide was 2.1 mL / g.

[0086] (2) 0.04 g of strontium nitrate was dissolved in 1.68 mL of deionized water to obtain an aqueous solution of strontium nitrate. Under nitrogen protection, 0.8 g of the second dried lanthanum hydroxide was weighed and placed in a round-bottom flask. Then, the aqueous solution of strontium nitrate was added dropwise to the round-bottom flask using a syringe at 30 °C (the addition rate of the solution containing the dopant element was 4 mL / min relative to each gram of lanthanum hydroxide), and the mixture was thoroughly mixed using a vortex mixer for 2 h. The resulting mixture was then dried at 80 °C for 13 h.

[0087] (3) Lanthanum oxycarbonate catalyst was prepared by calcination at 500°C for 2 hours in air atmosphere.

[0088] The molar ratio of lanthanum to strontium in the catalyst is 1:0.046.

[0089] BET analysis showed that the specific surface area of ​​the lanthanum oxycarbonate catalyst was 56 m². 2 / g, pore volume 0.4cm 3 / g, with an average pore size of 13.4nm.

[0090] As can be seen from the transmission scanning electron microscope images (similar to Example 1, not shown again), the lanthanum oxycarbonate catalyst has a fibrous nanostructure, and the calculated average diameter is 14 nm and the average aspect ratio is 35:1.

[0091] Example 3

[0092] (1) Dissolve 10g of lanthanum nitrate hexahydrate in 155g of deionized water and stir at 25℃ and 9000rpm for 30min. Then, add sodium hydroxide solution dropwise to the lanthanum nitrate aqueous solution (the concentration of sodium hydroxide solution is 10wt%, and the addition rate of the alkali solution is 7mL / min relative to each kilogram of the lanthanum source solution, and the amount of alkali solution used is such that the final pH value of the mixture of alkali solution and lanthanum source solution is 12). After the addition is completed, continue stirring at 25℃ and 9000rpm for 10min. Then, raise the temperature to 100℃ and keep stirring under reflux for 15h. After the solution cools to room temperature, centrifuge the solid material at 9000rpm and wash it with deionized water until the pH value of the washing liquid is neutral. The obtained solid is subjected to a first drying and a second drying in sequence. The conditions for the first drying are: temperature of 90℃ and time of 20h; the conditions for the second drying are: relative pressure of 50kPa, temperature of 160℃ and time of 3h.

[0093] The saturated water absorption amount of the second dried lanthanum hydroxide was measured as follows: 1 g of the second dried lanthanum hydroxide was placed in a round bottom flask under nitrogen atmosphere, and deionized water was added dropwise to the round bottom flask using a syringe, and mixed with the lanthanum hydroxide using a vortex mixer until the lanthanum hydroxide did not show a significant further water absorption, and the amount of deionized water added at this time was recorded. The saturated water absorption amount of the lanthanum hydroxide was 2.4 mL / g.

[0094] (2) 0.13 g of strontium nitrate was dissolved in 1.92 mL of deionized water to obtain a strontium nitrate aqueous solution. Under nitrogen atmosphere, 0.8 g of the second dried lanthanum hydroxide was placed in a round bottom flask, and then the strontium nitrate aqueous solution was added dropwise to the round bottom flask at 40°C using a syringe (the addition rate of the solution of the compound containing the doping element was 3 mL / min per gram of the lanthanum hydroxide), and mixed sufficiently using a vortex mixer, and the mixing time was 2 h. Then the obtained mixture was dried at 80°C for 10 h.

[0095] (3) The lanthanum oxycarbonate catalyst was prepared by calcining at 500°C for 2 h in an air atmosphere.

[0096] The molar ratio of the lanthanum element to the strontium element of the catalyst was 1:0.148.

[0097] The specific surface area of the lanthanum oxycarbonate catalyst was 51 m 2 / g by BET analysis, the pore volume was 0.3 cm 3 / g, and the average pore diameter was 10.5 nm.

[0098] It can be seen from the transmission scanning electron microscope image (similar to that of Example 1, not shown again) that the lanthanum oxycarbonate catalyst has a fibrous nanostructure, and the average diameter was calculated to be 18 nm, and the average aspect ratio was calculated to be 20:1.

[0099] Example 4

[0100] (1) 15 g of lanthanum nitrate hexahydrate was dissolved in 155 g of deionized water, and stirred at 25°C and 9000 rpm for 30 min. Then, sodium hydroxide solution (10 wt% of sodium hydroxide solution, 10 mL / min of the addition rate of the base solution with respect to 1 kg of the lanthanum source, and the amount of the base solution was such that the final pH of the mixed system of the base solution and the lanthanum source was 10) was added dropwise to the lanthanum nitrate aqueous solution, and the stirring was continued at 25°C and 9000 rpm for 10 min after the completion of the dropwise addition. Then, the temperature was raised to 100°C, and the solution was stirred for 15 h under the condensation reflux. After the solution was cooled to room temperature, the solid material was separated by centrifugation at 9000 rpm, and washed with deionized water until the pH of the washing liquid became neutral. The obtained solid was subjected to first drying and second drying in this order, the first drying was performed at 80°C for 15 h, and the second drying was performed at 140°C for 5 h under a relative pressure of 40 kPa.

[0101] The saturated water absorption amount of the lanthanum hydroxide after the second drying was measured as follows. Under nitrogen atmosphere, 1 g of the lanthanum hydroxide after the second drying was placed in a round-bottom flask, deionized water was added dropwise to the round-bottom flask using a syringe, and the lanthanum hydroxide was mixed using a vortex mixer until the lanthanum hydroxide did not further absorb water, and the amount of the deionized water added at this time was recorded. The saturated water absorption amount of the lanthanum hydroxide was 1.9 mL / g.

[0102] (2) 0.24 g of strontium nitrate was dissolved in 1.52 mL of deionized water to obtain a strontium nitrate aqueous solution. Under nitrogen atmosphere, 0.8 g of the lanthanum hydroxide after the second drying was placed in a round-bottom flask, and then the strontium nitrate aqueous solution was added dropwise to the round-bottom flask using a syringe at 35°C (1.5 mL / min of the addition rate of the solution containing the doping element with respect to 1 g of the lanthanum hydroxide), and the mixture was sufficiently mixed using a vortex mixer for 3 h. Then, the obtained mixture was dried at 80°C for 15 h.

[0103] (3) The lanthanum strontium carbonate catalyst was prepared by calcination at 500°C for 2 h in an air atmosphere.

[0104] The molar ratio of the lanthanum element to the strontium element of the catalyst was 1:0.146.

[0105] The specific surface area of the lanthanum strontium carbonate catalyst was 50 m 2 / g, the pore volume was 0.26 cm 3 / g, and the average pore diameter was 11.6 nm.

[0106] The lanthanum oxycarbonate catalyst was observed to have a fibrous nanostructure by transmission scanning electron microscopy (similar to that of Example 1, not shown again), and was calculated to have an average diameter of 16 nm and an average aspect ratio of 15:1.

[0107] Example 5

[0108] The preparation of lanthanum oxycarbonate was carried out according to the method of Example 1, except that strontium nitrate was replaced by an equivalent amount of barium nitrate.

[0109] The specific surface area of the lanthanum oxycarbonate catalyst was 49 m 2 / g, the pore volume was 0.29 cm 3 / g, and the average pore diameter was 12.6 nm.

[0110] The lanthanum oxycarbonate catalyst was observed to have a fibrous nanostructure by transmission scanning electron microscopy (similar to that of Example 1, not shown again), and was calculated to have an average diameter of 22 nm and an average aspect ratio of 19:1.

[0111] Example 6

[0112] The preparation of lanthanum oxycarbonate was carried out according to the method of Example 1, except that in step (1), the second drying process was not included.

[0113] The specific surface area of the lanthanum oxycarbonate catalyst was 68 m 2 / g, the pore volume was 0.39 cm 3 / g, and the average pore diameter was 8.5 nm.

[0114] The lanthanum oxycarbonate catalyst was observed to have a fibrous nanostructure by transmission scanning electron microscopy (similar to that of Example 1, not shown again), and was calculated to have an average diameter of 21 nm and an average aspect ratio of 16:1.

[0115] Example 7

[0116] The preparation of lanthanum oxycarbonate was carried out according to the method of Example 1, except that strontium nitrate was replaced by an equivalent amount of zinc nitrate.

[0117] The specific surface area of the lanthanum oxycarbonate catalyst was 42 m 2 / g, the pore volume was 0.21 cm 3 / g, and the average pore diameter was 9.8 nm.

[0118] The lanthanum oxycarbonate catalyst was observed to have a fibrous nanostructure by transmission scanning electron microscopy (similar to that of Example 1, not shown again), and was calculated to have an average diameter of 23 nm and an average aspect ratio of 18:1.

[0119] Example 8

[0120] The preparation of lanthanum oxycarbonate was carried out according to the method of Example 1, except that strontium nitrate was replaced by an equivalent amount of magnesium nitrate.

[0121] The specific surface area of the lanthanum oxycarbonate catalyst was 39 m2 / g, the pore volume was 0.46 cm3 / g, and the average pore diameter was 15.2 nm, as determined by BET analysis. 2 3 The specific surface area of the lanthanum oxycarbonate catalyst was 39 m2 / g, the pore volume was 0.46 cm3 / g, and the average pore diameter was 15.2 nm, as determined by BET analysis.

[0122] As can be seen from observation of the transmission scanning electron micrograph (similar to that of Example 1, not shown), the lanthanum oxycarbonate catalyst had a fibrous nanostructure, and the average diameter was calculated to be 20 nm and the average aspect ratio was 16:1.

[0123] Example 9

[0124] The preparation of lanthanum oxycarbonate was carried out according to the method of Example 1, except that in step (2), the second dried lanthanum hydroxide was added to the aqueous strontium nitrate solution, and the mixture was stirred for 5 h, and then the resulting mixture was dried at 80°C for 12 h.

[0125] The specific surface area of the lanthanum oxycarbonate catalyst was 39 m2 / g, the pore volume was 0.46 cm3 / g, and the average pore diameter was 15.2 nm, as determined by BET analysis. 2 3 The specific surface area of the lanthanum oxycarbonate catalyst was 39 m2 / g, the pore volume was 0.46 cm3 / g, and the average pore diameter was 15.2 nm, as determined by BET analysis.

[0126] As can be seen from observation of the transmission scanning electron micrograph (similar to that of Example 1, not shown), the lanthanum oxycarbonate catalyst had a fibrous nanostructure, and the average diameter was calculated to be 20 nm and the average aspect ratio was 16:1.

[0127] Example 10

[0128] The preparation of lanthanum oxycarbonate was carried out according to the method of Example 1, except that the rate of addition of the solution of the compound containing the doping element was 20 mL / min per gram of the lanthanum hydroxide.

[0129] The specific surface area of the lanthanum oxycarbonate catalyst was 39 m2 / g, the pore volume was 0.46 cm3 / g, and the average pore diameter was 15.2 nm, as determined by BET analysis. 2 3 The specific surface area of the lanthanum oxycarbonate catalyst was 39 m2 / g, the pore volume was 0.46 cm3 / g, and the average pore diameter was 15.2 nm, as determined by BET analysis.

[0130] As can be seen from observation of the transmission scanning electron micrograph (similar to that of Example 1, not shown), the lanthanum oxycarbonate catalyst had a fibrous nanostructure, and the average diameter was calculated to be 20 nm and the average aspect ratio was 16:1.

[0131] Example 11

[0132] ​​​The lanthanum oxycarbonate was prepared according to the method of Example 1, except that in step (2), the amount of deionized water was 5 mL.

[0133] The specific surface area of the lanthanum oxycarbonate catalyst was 38 m 2 / g, the pore volume was 0.2 cm 3 / g, and the average pore diameter was 13.3 nm.

[0134] From the transmission scanning electron micrograph (similar to that of Example 1, not shown), it can be seen that the lanthanum oxycarbonate catalyst had a fibrous nanostructure, and the average diameter was calculated to be 21 nm and the average aspect ratio was 17:1.

[0135] Comparative Example 1

[0136] The lanthanum oxycarbonate was prepared according to the method of Example 1, except that step (2) was not performed.

[0137] The specific surface area of the lanthanum oxycarbonate catalyst was 68 m 2 / g, the pore volume was 6 cm 3 / g, and the average pore diameter was 42 nm.

[0138] From the transmission scanning electron micrograph (similar to that of Example 1, not shown), it can be seen that the lanthanum oxycarbonate catalyst had a fibrous nanostructure, and the average diameter was calculated to be 12 nm and the average aspect ratio was 15:1.

[0139] Comparative Example 2

[0140] (1) The lanthanum hydroxide was prepared according to the method of step (1) of Example 1.

[0141] (2) 0.08 g of strontium nitrate was calcined in an air atmosphere at 500°C for 2 h.

[0142] (3) 0.8 g of lanthanum hydroxide was calcined in an air atmosphere at 500°C for 2 h.

[0143] (4) The product obtained in step (2) and the product obtained in step (3) were then mixed uniformly to obtain the catalyst.

[0144] The specific surface area of the lanthanum oxycarbonate catalyst was 40 m 2 / g, the pore volume was 2.3 cm 3 / g, and the average pore diameter was 14.2 nm.

[0145] Test Example 1

[0146] The catalysts prepared in the above examples and comparative examples were tabletted, sieved to 40-60 mesh, and then 0.1 g was charged into an Inconel fixed bed reactor, and under normal pressure, methane and oxygen (molar ratio of methane to oxygen was 3:1) were introduced to carry out the reaction, and other reaction conditions and results are shown in Table 1.

[0147] Table 1

[0148]

[0149] From the results in Table 1, it can be seen that the carbon dioxide-containing lanthanum oxide catalyst containing a doping element according to the present application has a higher carbon dihydrocarbon yield at 500-650°C compared to Comparative Example 1, and particularly preferably, the catalyst according to Examples 1-5 has a carbon dihydrocarbon yield of higher than 15% at 550-650°C.

[0150] The carbon dihydrocarbon yield of the catalyst obtained by directly mixing lanthanum oxide with strontium oxide according to Comparative Example 2 is lower than 10%, while the carbon dihydrocarbon yield of the catalyst prepared according to the method of Example 1 of the present application is 16.8%, and thus the element doping method according to the present application can improve the carbon dihydrocarbon yield relative to the direct mixing method of Comparative Example 2.

[0151] The above describes preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including combining various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. An oxyprase catalyst, characterized by, The lanthanum oxycarbonate catalyst is composed of hexagonal lanthanum oxycarbonate and hexagonal lanthanum oxycarbonate containing doping elements; The doping elements are selected from at least one of elements of Groups IIA, VIII, IB and IIB; The molar ratio of lanthanum elements to doping elements in the lanthanum oxycarbonate catalyst is 1:0.01-1.

2. The oxyprase catalyst according to claim 1, wherein, The doping elements are selected from at least one of elements of Mg, Ca, Sr, Ba, Fe, Zn and Cd.

3. The lanthanum oxide carbonate catalyst of claim 1 or 2, wherein, The doping elements are Sr and / or Ba.

4. The lanthanum oxycarbonate catalyst of claim 1, wherein, The molar ratio of lanthanum elements to doping elements in the lanthanum oxycarbonate catalyst is 1:0.03-0.

5.

5. The lanthanum oxycarbonate catalyst of claim 4, wherein, The molar ratio of lanthanum elements to doping elements in the lanthanum oxycarbonate catalyst is 1:0.04-0.

2.

6. The oxyprase catalyst according to claim 1 or 2, wherein, The lanthanum oxycarbonate catalyst has a fibrous nanostructure, the diameter of the lanthanum oxycarbonate catalyst is 10-30 nm, and the aspect ratio is 5-50:

1. and / or the specific surface area of the lanthanum oxycarbonate catalyst is 45 m 2 / g-90 m 2 / g, the pore volume is 0.15 cm 3 / g-0.5 cm 3 / g, the average pore diameter is 8 nm-15 nm.

7. The lanthanum oxycarbonate catalyst of claim 6, wherein, The lanthanum oxycarbonate catalyst has a fibrous nanostructure, the diameter of the lanthanum oxycarbonate catalyst is 10-20 nm, and the aspect ratio is 15-40:

1. and / or the specific surface area of the lanthanum oxycarbonate catalyst is 50 m 2 / g-60 m 2 / g, the pore volume is 0.26 cm 3 / g-0.4 cm 3 / g, the average pore diameter is 10 nm-13.5 nm.

8. A method for preparing the lanthanum oxide carbonate catalyst according to any one of claims 1 to 7, characterized in that, The method comprises: (1) adding an alkali solution to a solution of a lanthanum source, then performing aging, solid-liquid separation and drying to obtain lanthanum hydroxide; (2) under a protective atmosphere, contacting a solution of a compound containing doping elements with the lanthanum hydroxide, and then performing drying; (3) performing calcination of the dried product of step (2) under an atmosphere containing CO2 to obtain a lanthanum oxycarbonate catalyst; The molar ratio of lanthanum elements to doping elements in the lanthanum hydroxide is 1:0.01-1. The compound containing doping elements is selected from at least one of compounds of elements of Groups IIA, VIII, IB and IIB.

9. The method of claim 8, wherein, The concentration of the alkali solution is 3wt%-25wt%; And / or, the alkali in the alkali solution is a compound of a Group IA metal; And / or, the amount of the alkali solution is such that the final pH value of the mixed system of the alkali solution and the solution of the lanthanum source is 10-12.5; And / or, the concentration of the solution of the lanthanum source is 0.01wt%-10wt%; And / or, the lanthanum source is a water-soluble salt of lanthanum.

10. The method of claim 8 or 9, wherein, The lanthanum source is at least one of lanthanum nitrate, lanthanum chloride and lanthanum acetate.

11. The method of claim 8, wherein, The conditions of the aging include: the temperature is 80-100℃, and the time is 10-50h; And / or, in step (1), the drying comprises first drying and second drying.

12. The method of claim 11, wherein, The conditions of the first drying include: the temperature is 70-90℃, and the time is 10-20h; And / or, the conditions of the second drying include: the relative pressure is 10kPa-91kPa, the temperature is 120-160℃, and the time is 2-10h.

13. The method of claim 12, wherein, The conditions of the second drying include: the relative pressure is 20kPa-70kPa.

14. The method of claim 8, wherein, The protective atmosphere is provided by an inert gas; And / or, the concentration of the solution of the compound containing doping elements is 0.01-0.2g / mL; And / or, the compound containing doping elements is selected from at least one of compounds of elements of Mg, Ca, Sr, Ba, Fe, Zn and Cd; And / or, the conditions of the contacting include: the temperature is 15-50℃, and the time is 2-5h.

15. The method of claim 14, wherein, The compound containing doping elements is a compound of Sr and / or Ba; And / or, the inert gas is nitrogen.

16. The method of claim 8, wherein, In step (2), the drying condition includes: temperature of 60-100℃, time of 10-24h; and / or, in step (3), the calcination condition includes: temperature of 450-550℃, time of 2-8h.

17. The lanthanum oxycarbonate catalyst prepared by the method of any one of claims 8-16.

18. The use of the lanthanum oxycarbonate catalyst of any one of claims 1-7 and 17 in the oxidative coupling reaction of methane to produce C2+ hydrocarbons.

19. A process for the production of carbon two and higher hydrocarbons from methane, characterized by, The method comprises: contacting methane with the lanthanum oxycarbonate catalyst of any one of claims 1-7 and 17 to react in the presence of oxygen and under the condition of the oxidative coupling reaction of methane.

20. The method of claim 19, wherein, The molar ratio of the methane to the oxygen is 2-9:1; and / or, the temperature of the contacting reaction is 500-650℃; and / or, the space velocity of the methane is 5000 mL / (g·h)-200000 mL / (g·h).

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