阅读说明：本技术 一种富含不饱和配位的二维陶瓷材料催化剂及其制备方法和应用 (Unsaturated coordination-rich two-dimensional ceramic material catalyst and preparation method and application thereof ) 是由 韩文锋 杨虹 刘兵 刘永南 俞威 陆佳勤 李西良 唐浩东 李瑛� 于 2019-09-20 设计创作，主要内容包括：本发明公开了一种富含不饱和配位的二维陶瓷材料催化剂及其制备方法和应用,所述二维陶瓷材料催化剂的制备方法包括以下步骤：在刻蚀剂的作用下,刻蚀剂中的插层物质将MAX相材料插层剥离制得二维MXene材料,即制得所述二维陶瓷材料催化剂,所述MAX相材料为Ti<Sub>3</Sub>AlC<Sub>2</Sub>、Cr<Sub>2</Sub>AlC、V<Sub>2</Sub>AlC、Nb<Sub>2</Sub>AlC中的至少一种；所述刻蚀剂为盐酸与LiF的混合物,或者草酸。本发明所制备的催化剂为具有不饱和配位的二维纳米层状催化剂。本发明方法合成的催化剂含氟烷烃脱HF制备含氟烯烃反应中具有良好的催化活性和稳定性。(The invention discloses a two-dimensional ceramic material catalyst rich in unsaturated coordination, a preparation method and application thereof, wherein the preparation method of the two-dimensional ceramic material catalyst comprises the following steps: under the action of an etching agent, an intercalation substance in the etching agent intercalates and peels MAX phase materials to prepare two-dimensional MXene materials, namely the two-dimensional ceramic material catalyst is prepared, wherein the MAX phase materials are Ti 3 AlC 2 、Cr 2 AlC、V 2 AlC、Nb 2 At least one of AlC; the etching agent is a mixture of hydrochloric acid and LiF, or oxalic acid. The catalyst prepared by the invention is a two-dimensional nano layered catalyst with unsaturated coordination. The catalyst synthesized by the method has good catalytic activity and stability in the reaction of removing HF from the fluorine-containing alkane to prepare the fluorine-containing olefin.)

1. A preparation method of a two-dimensional ceramic material catalyst rich in unsaturated coordination is characterized in that under the action of an etching agent, MAX phase materials are intercalated and stripped by intercalation substances in the etching agent to prepare two-dimensional MXene materials, and the two-dimensional ceramic material catalyst is prepared, wherein the MAX phase materials are Ti₃AlC₂、Cr₂AlC、V₂AlC、Nb₂At least one of AlC; the etching agent is a mixture of hydrochloric acid and LiF, or oxalic acid.

2. The method according to claim 1, wherein the etching agent is a mixture of hydrochloric acid and LiF, and the intercalation material in the etching agent is Li⁺The specific process of intercalating and stripping MAX phase material by intercalation substance in etchant comprises diluting concentrated hydrochloric acid with water to 8 ~ 10mol/L to form solution A, adding LiF into solution A, stirring, adding MAX phase material, heating in water bath at 30-55 deg.C, stirring for 10-24 hr, centrifuging to obtain solidAnd washing the body by deionized water to remove hydrochloric acid on the surface of the body and LiCl generated by reaction, and drying to obtain the two-dimensional ceramic material catalyst.

3. The method for preparing a catalyst rich in unsaturated coordination two-dimensional ceramic material according to claim 2, wherein the concentration of LiF in the solution A is 8 ~ 10mol/L, preferably 9mol/L, and the mass ratio of LiF to MAX phase material is 1: 1.

4. The preparation method of the unsaturated coordination-rich two-dimensional ceramic material catalyst as claimed in claim 1, wherein the etchant is oxalic acid, the intercalation material is oxalic acid, and the intercalation material intercalates and exfoliates the MAX phase material by mixing oxalic acid and MAX phase material and placing the mixture in a ball mill pot for ball milling at a ball milling rotation speed of 200 ~ 400r/min for 1 ~ 4h, and the ball milled mixture is filled in a tube furnace and calcined at high temperature to obtain the two-dimensional ceramic material catalyst.

5. The method for preparing the unsaturated coordination-rich two-dimensional ceramic material catalyst as recited in claim 4, wherein the molar ratio of the oxalic acid to the MAX phase material is 1:1 to 3: 1.

6. The preparation method of the two-dimensional ceramic material catalyst rich in unsaturated coordination as claimed in claim 4, wherein the high-temperature roasting process comprises heating from room temperature to 250-400 ℃ at a rate of 2 ~ 4 ℃/min under nitrogen atmosphere, then carrying out heat preservation roasting for 3 ~ 5h, and then naturally cooling to room temperature.

7. A two-dimensional ceramic material catalyst prepared by the method of any one of claims 1 ~ 6.

8. The use of the two-dimensional ceramic material catalyst according to claim 7 in the reaction of dehydrohf of fluorine-containing alkane to prepare fluorine-containing olefin.

9. The method according to claim 8, wherein the fluorine-containing alkane is 1, 1-difluoroethane or 1,1,1,3, 3-pentafluoropropane, the reaction temperature for removing HF from the fluorine-containing alkane to prepare the fluorine-containing alkene is 300-350 ℃, the reaction pressure is normal pressure, and the prepared fluorine-containing alkene is vinyl fluoride or 1,1,1, 3-tetrafluoropropene.

Technical Field

The invention relates to a two-dimensional ceramic material catalyst rich in unsaturated coordination, and a preparation method and application thereof.

Background

A two-dimensional crystal is a two-dimensional material with a thickness of only a single atom or a few atoms, which has exceptional properties and functions due to its absolute two-dimensional structure. Graphene is the most typical two-dimensional crystal and has excellent properties, but graphene is not the end of a two-dimensional atomic crystal material, and some two-dimensional crystals with special properties and containing other elements become the research focus at present. MXene is a novel two-dimensional crystal with a structure similar to that of graphene. Having the chemical formula M_n+1X_nN is 1, 2 and 3, M is an early transition metal element, and X is carbon or/and nitrogen. MXene, as a brand-new two-dimensional material (a general name of metal carbonitride), has wide application prospects in various fields such as rechargeable batteries, supercapacitors, photo (electro) catalysts, transparent conductive films, electromagnetic interference shields and sensors, crude oil and heavy metal adsorbents, flexible high-strength composite materials and the like due to the intrinsic nano-layered structure, adjustable specific surface area, good hydrophilicity, and excellent electrical conductivity and mechanical properties.

MAX phase as mother material of MXene is of chemical formula M_n+1AX_nThe ternary layered compound of (1), wherein A is a group III or IV element. Research shows that in the crystal structure of MAX, X atoms are filled in octahedral voids formed by M atoms, and A atom layers exist in alternating sheets formed by M and X in a manner similar to intercalation, namely transition metal carbide or nitride layers and pure A atom sheets are in the form of (M) ·/[ M ] M_n+1Xn]/A/[M_n+1X_n]A. is arranged alternately. In the prior art, MXene is obtained by etching away an A atom sheet layer by using hydrofluoric acid, but the operation conditions are harsh, and the high-concentration hydrofluoric acid has high toxicity and extremely strong corrosivity, so that the preparation method has certain danger. And if the etching time is too long, the temperature is too high and the concentration of hydrofluoric acid is too high, MXene can be dissolved to a certain extent, and the application of MXene is adversely affected.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention aims to provide a two-dimensional ceramic material catalyst rich in unsaturated coordination, and a preparation method and application thereof. The catalyst prepared by the invention is a two-dimensional nano layered catalyst with unsaturated coordination. The catalyst synthesized by the method has good catalytic activity and stability in the reaction of removing HF from the fluorine-containing alkane to prepare the fluorine-containing olefin.

The preparation method of the unsaturated coordination-rich two-dimensional ceramic material catalyst is characterized in that under the action of an etching agent, MAX phase materials are intercalated and stripped by intercalation substances in the etching agent to prepare the two-dimensional MXeneThe material is the two-dimensional ceramic material catalyst, and the MAX phase material is Ti₃AlC₂、Cr₂AlC、V₂AlC、Nb₂At least one of AlC; the etching agent is a mixture of hydrochloric acid and LiF, or oxalic acid.

The preparation method of the unsaturated coordination-rich two-dimensional ceramic material catalyst is characterized in that the etching agent is a mixture of hydrochloric acid and LiF, and an intercalation substance in the etching agent is Li⁺The specific process of intercalating and stripping MAX phase material by intercalation material in etchant is as follows: adding water into concentrated hydrochloric acid to dilute the concentrated hydrochloric acid to a concentration of 8-10 mol/L to form a solution A; adding LiF into the solution A, uniformly stirring, adding MAX phase materials, heating in a water bath at 30-55 ℃, stirring for 10-24 h, then performing centrifugal separation, washing the obtained solid with deionized water to remove hydrochloric acid on the surface of the solid and LiCl generated by reaction, and drying to obtain the two-dimensional ceramic material catalyst.

The preparation method of the unsaturated coordination-rich two-dimensional ceramic material catalyst is characterized in that the concentration of LiF in the solution A is 8-10 mol/L, preferably 9 mol/L; the mass ratio of LiF to MAX phase material is 1: 1.

The preparation method of the unsaturated coordination-rich two-dimensional ceramic material catalyst is characterized in that the etching agent is oxalic acid, the intercalation material is oxalic acid, and the specific process of intercalation stripping of the MAX phase material by the intercalation material is as follows: mixing oxalic acid and MAX phase materials, placing the mixture in a ball milling tank for ball milling, wherein the ball milling rotating speed is 200-400 r/min, the ball milling time is 1-4 h, filling the ball milled mixture into a tube furnace, and roasting at high temperature to obtain the two-dimensional ceramic material catalyst.

The preparation method of the unsaturated coordination-rich two-dimensional ceramic material catalyst is characterized in that the molar ratio of oxalic acid to MAX phase material is 1: 1-3: 1.

The preparation method of the unsaturated coordination-rich two-dimensional ceramic material catalyst is characterized in that the high-temperature roasting process comprises the following steps: under the nitrogen atmosphere, heating to 250-400 ℃ from room temperature at the speed of 2-4 ℃/min, then carrying out heat preservation roasting for 3-5 h, and then naturally cooling to room temperature.

A two-dimensional ceramic material catalyst prepared according to the above method.

The two-dimensional ceramic material catalyst is applied to the reaction of preparing fluorine-containing olefin by removing HF from fluorine-containing alkane.

The application of the two-dimensional ceramic material catalyst in the reaction of preparing fluorine-containing olefin by removing HF from fluorine-containing alkane is characterized in that the fluorine-containing alkane is 1, 1-difluoroethane or 1,1,1,3, 3-pentafluoropropane, the reaction temperature for preparing fluorine-containing olefin by removing HF from fluorine-containing alkane is 300-350 ℃, the reaction pressure is normal pressure, and the prepared fluorine-containing olefin is vinyl fluoride or 1,1,1, 3-tetrafluoropropene.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, after A atoms in the MAX phase material are stripped by a solid phase or liquid phase etching method, the structure of the MAX phase material substance is changed into a two-dimensional sheet from a ternary layer, and the distance between sheets is obviously increased. The M element is relatively heavy, so that the specific surface area of unit volume is large; the two-dimensional ceramic material rich in unsaturated coordination finally obtained by the invention can change the gas adsorption performance of MXene by increasing the interlayer spacing of MXene, selecting the type of MXene and regulating the surface structure of MXene, thereby realizing the selective adsorption of MXene to certain gas. Therefore, by selecting different reagents to carry out intercalation or ion exchange on MXene, the size of the gap of the sample can be accurately regulated and controlled.

1) The liquid phase etching intercalation process of the unsaturated coordination-rich two-dimensional ceramic material obtained by the invention controls the ratio of hydrochloric acid to LiF to control Li in the dispersion liquid⁺By controlling the reaction temperature to control the rate of in-situ etching, the reaction time can be different to lead Li⁺M to MAX by in situ intercalation_n+1X_nThe degree of the layers is different, so that the degree of in-situ etching is controlled, an A atomic layer is completely etched away or a defect site is generated on the surface after part of A atoms are etched away, and the rest A atoms which are not etched away are also active sites in the reaction of preparing fluorine-containing olefin by removing HF from fluorine-containing alkane; the preparation method has mild conditions, and the product is preparedThe preparation period is short, and the method is safe and environment-friendly.

2) The solid phase etching intercalation process of the two-dimensional ceramic material rich in unsaturated coordination obtained by the invention has the advantage that oxalic acid can enter M during the process_n+1X_nBetween layers, oxalic acid decomposes at high temperature to release gas, so that the distance between MAX layers is increased, and the amount of the gas released by decomposition of the solid phase etchant can be effectively controlled by controlling the roasting temperature; the roasting time is controlled, so that the degree and the size of gaps among MXene layers can be effectively controlled, selective adsorption of gas is realized, and the preparation method is mild in condition, short in preparation period, safe, green and environment-friendly.

Drawings

FIG. 1a is a view of nanoscale Ti obtained in example 1₃Al_xC₂(x is 0 to 1) one of SEM images of the catalyst;

FIG. 1b is a view of the nanoscale Ti obtained in example 1₃Al_xC₂(x is 0 to 1) SEM image two of the catalyst;

FIG. 2 shows nanoscale Ti obtained in example 2₃Al_xC₂(x is 0 to 1) SEM image of catalyst;

FIG. 3 shows nanoscale Ti obtained in example 2₃Al_xC₂(x is 0 to 1) XRD pattern of the catalyst.

Detailed Description

The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the invention.