阅读说明：本技术 一种成型层状双金属氢氧化物及其衍生物的制备方法和应用 (Preparation method and application of formed layered double hydroxide and derivatives thereof ) 是由 王光辉 李德昌 张潜 于 2021-08-19 设计创作，主要内容包括：本公开涉及生物质功能材料技术领域,具体为一种成型层状双金属氢氧化物及其衍生物的制备方法和应用。选用具有蜂窝状有序大孔的玉米秸秆作为载体或模板,通过浸渍-水热工艺在秸秆细胞表面均匀生长LDHs,得到玉米秸秆负载的LDHs。将其进一步进行有氧煅烧、碳掺杂、硫化或磷化等工艺,可分别获得保持有秸秆生物结构和LDHs纳米片形貌的金属氧化物、碳化物、硫化物或磷化物。玉米秸秆的生物结构和LDHs纳米片形貌的保持有助于传质和活性位点的暴露,该方法制备成本低、工艺简单、普适性广、绿色可持续,具有较好的规模化应用前景。(The disclosure relates to the technical field of biomass functional materials, in particular to a preparation method and application of a formed layered double hydroxide and a derivative thereof. The corn straw with honeycomb-shaped ordered macropores is selected as a carrier or a template, and the LDHs uniformly grow on the surfaces of straw cells through a dipping-hydrothermal process to obtain the LDHs loaded by the corn straw. The straw nano-sheet is further subjected to processes such as aerobic calcination, carbon doping, vulcanization or phosphorization, and the like, so that metal oxides, carbides, sulfides or phosphorides which keep the straw biological structure and the LDHs nano-sheet morphology can be obtained respectively. The retention of the biological structure of the corn straw and the appearance of the LDHs nanosheet is beneficial to mass transfer and active site exposure, and the method has the advantages of low preparation cost, simple process, wide universality, greenness, sustainability and good large-scale application prospect.)

1. A method for preparing a shaped layered double hydroxide, comprising:

(1): soaking corn stalks in a solution containing metal salts and alkali precursors required for synthesizing LDHs;

(2): and transferring the corn straws soaked with the solution into a reactor, heating, reacting, and carrying out nucleation and growth of the LDHs to obtain the LDHs loaded by the corn straws.

2. The process for preparing a shaped layered double hydroxide according to claim 1, wherein the corn stover is pretreated before being impregnated; the corn stalk pretreatment comprises the following steps: peeling corn stalks, cutting into sections, washing with acid, then washing with water to be neutral, and drying; or, the acid is selected from one or more of hydrochloric acid, sulfuric acid and nitric acid, and hydrochloric acid is preferred.

3. The process according to claim 1, wherein in the step (1), the solvent of the solution is selected from one or more of water, ethanol and methanol, preferably water; or, in the step (1), the metal is selected from one or more of Mg, Ni, Co, Zn, Cu, Ni, Ca, Al, Fe, Cr and Mn; or, in the step (1), the metal salt is selected from one or more of nitrate, sulfate, acetylacetone salt, halide salt, acetate and metal acid salt; preferred are nickel nitrate and aluminum nitrate, wherein the molar ratio of Ni to Al is between 5:1 and 1:5, preferably between 4:1 and 2: 1.

4. The process according to claim 1, wherein in step (1), the concentration of the metal salt is between 0.01 and 5mol/L, preferably between 0.05 and 0.15 mon/L; or, in the step (1), the alkali precursor is selected from one or more of urea, hexamethylene tetramine, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, sodium hydroxide and potassium hydroxide, and is preferably urea; the molar ratio of urea to the total amount of metals is between 50:1 and 1:1, preferably between 4:1 and 2: 1.

5. The process according to claim 1, wherein in step (2), the reaction temperature is between 80 ℃ and 150 ℃, preferably between 90 ℃ and 110 ℃; the reaction time is between 1 and 48 hours, preferably between 12 and 24 hours.

6. The method for preparing the formed layered double hydroxide as claimed in claim 1, wherein the LDHs loaded on the corn stalks can be changed in metal composition in the LDHs by ion exchange to obtain a wider variety of LDHs/stalk composite systems; further, the ion exchange means that metal ions in the LDHs are exchanged with other metal ions in a solution; the time of ion exchange is between 1 and 48 h.

7. A method for preparing a shaped layered double hydroxide derivative, which is characterized by comprising the following steps:

(1) carrying out aerobic calcination on layered double hydroxide loaded by corn straws prepared by the preparation method of any one of claims 1 to 7 to remove the straws, thus obtaining metal oxide maintaining the biological structure of the corn straws and the morphology of LDHs nanosheets;

(2) further carrying out carbon doping, vulcanization or phosphorization on the metal oxide to obtain metal carbide, sulfide or phosphide maintaining the biological structure of the corn straws and the morphology of the LDHs nanosheets;

furthermore, the carbon doping process can be a temperature programming reduction method, a chemical vapor deposition method or a thermal decomposition method; alternatively, the sulfidation process may be a solvothermal process, a high pressure reaction process, or a chemical vapor deposition process; or, the phosphorization process can be a solvothermal method, a temperature programmed reduction method or a gas-solid reaction method.

8. The method as claimed in claim 7, wherein the temperature of the aerobic calcination is between 350-2000 ℃, preferably between 600-800 ℃; the calcination time is 0.1-24h, preferably 0.5-2 h.

9. The layered double hydroxide with the biological structure of the corn straws prepared by the preparation method of any one of claims 1 to 6 and/or the layered double hydroxide derivatives prepared by the preparation method of any one of claims 7 to 8.

10. The use of the layered double hydroxide and/or layered double hydroxide derivative with corn stalk biological structure as claimed in claim 9 in the adsorption and catalysis fields; further, the application includes: the LDHs loaded by the corn straws are used for adsorbing phosphorus in the water body: weighing a LDHs material loaded by corn straws, placing the LDHs material into a centrifugal tube, and adding a potassium dihydrogen phosphate solution for adsorption reaction; furthermore, the LDHs loaded on the corn straws is MgAl-LDHs;

or, the formed layered double hydroxide derivative is used for catalyzing the reaction of preparing undecane/dodecane by hydrodeoxygenation of methyl laurate; furthermore, the derivative is NiAl-LDHs/straw-derived nickel aluminum phosphide with a straw biological structure.

Technical Field

The disclosure relates to the technical field of biomass functional materials, in particular to a preparation method and application of a formed layered double hydroxide and a derivative thereof.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

Layered double hydroxides (LDHs for short, comprising hydrotalcite and hydrotalcite-like compounds) are layered composite metal hydroxides composed of divalent metal and polyvalent metal sharing oxygen octahedral edges, and the structural general formula is [ M²⁺ _1-xM³⁺ _x(OH)₂]^x+[(A^n-)_x/n·mH₂O]^x-Wherein M is²⁺(M³⁺)、A^n-X and M are respectively divalent (trivalent) metal cation, interlayer anion and M³⁺/(M²⁺+M³⁺) Molar ratio and amount of crystal water. Due to the repulsion between high-valence metal ions, the metals are generally doped in a highly dispersed manner, and the composition of the material can be regulated and controlled on an atomic level by controlling the types and the proportion of the metals. In addition, the LDHs can be converted into other functional materials through processes of ion exchange, high-temperature calcination, C/P/S doping and the like, and the porosity and the regular morphology of the LDHs are kept. Therefore, the LDHs and the derivative materials thereof have wide application in the fields of catalysis, adsorption, medicine and the like.

However, in the practical application process, in order to improve the convenience in the processes of transportation, application, separation and the like, the powder-state LDHs generally need to be molded by means of an adhesive or high pressure, and the process can inhibit mass transfer and exposure of reaction sites, and seriously affect the exertion of the intrinsic performance. In recent years, researchers have developed a variety of supported LDHs materials, and the porous carriers selected for use mainly include: nickel foam, carbon cloth, aerogel, and the like. These discoveries provide solutions for improving the mass transfer performance of three-dimensional formed LDHs. However, these carriers have high preparation cost, complex process and poor sustainability, which limits their large-scale application.

Disclosure of Invention

In order to solve the problems, the disclosure provides a preparation method and application of a formed layered double hydroxide and derivatives thereof, corn straws are used as carriers or templates, the biological structure of the corn straws is beneficial to mass transfer and exposure of active sites, and the formed layered double hydroxide and derivatives thereof have the advantages of low preparation cost, simple process, wide universality, greenness, sustainability and good large-scale application prospect.

Specifically, the technical scheme of the present disclosure is as follows:

in a first aspect of the present disclosure, a method of preparing a shaped layered double hydroxide comprises:

(1): soaking corn stalks in a solution containing metal salts and alkali precursors required for synthesizing LDHs;

(2): and transferring the corn straws soaked with the solution into a reactor, heating, reacting, and carrying out nucleation and growth of the LDHs to obtain the LDHs loaded by the corn straws.

In a second aspect of the disclosure, a preparation method of a formed layered double hydroxide derivative is provided, wherein the LDHs loaded on corn straws prepared by the preparation method is aerobically calcined to remove straws, so as to obtain a metal oxide maintaining a straw biological structure and LDHs nanosheet morphology; and further carrying out carbon doping, vulcanization or phosphorization on the metal oxide to obtain the metal carbide, sulfide or phosphide maintaining the biological structure of the corn straw and the morphology of the LDHs nanosheet.

In a third aspect of the disclosure, the layered double hydroxide with corn stalk biological structure prepared by the preparation method and/or the layered double hydroxide derivative prepared by the preparation method.

In a fourth aspect of the disclosure, the layered double hydroxide and/or layered double hydroxide derivative with corn stalk biological structure is applied in the fields of adsorption, catalysis and the like.

One or more technical schemes in the disclosure have the following beneficial effects:

(1) the corn straw is a traditional agricultural waste, the yield is high, the green sustainability is realized, and the value-added utilization of the corn straw not only has economic benefits, but also can generate environmental benefits; the corn straw is used as a mass transfer channel and a supporting framework for corn growth, has rich porosity and oxygen-containing groups and good structural stability, and is an ideal three-dimensional carrier material; therefore, the method can solve the problems that the traditional formed LDHs are expensive in preparation cost, can not be sustained and the like.

(2) The method comprises the following steps of selecting corn straws as a carrier or a template, soaking an LDHs precursor solution, heating to realize uniform and dense growth of LDHs on the surfaces of the corn straws to obtain LDHs/straws with a corn straw biological structure, and performing three-dimensional assembly on micron-sized macroporous channels of the corn straws and LDHs nanosheets to facilitate mass transfer and exposure of active sites; moreover, the method has the advantages of low cost, simple process, easy scale-up production and the like, and has better scale application prospect.

(3) The prepared hydrotalcite with the corn straw biological structure and the derivative material thereof belong to a formed block material and have good mechanical strength; the LDHs uniformly grow on the cell wall surface of the corn straws and are mutually interpenetrated and connected, so that the biological structure of the corn straws can be completely re-engraved after the straw template is removed, and the advantages of the LDHs in the aspects of porosity, mass transfer, active site exposure and the like are kept; the micron-order macropores formed by repeatedly etching the biological structure are difficult to obtain by a chemical synthesis method.

(4) The LDHs with the corn straw biological structure obtained by the method can be further converted into other functional materials with the corn straw biological structure and the LDHs shape through the processes of ion exchange, aerobic calcination, doping and the like, and the LDHs has wide universality and simple method and is easy to produce in an enlarged mode.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.

FIG. 1: a) pretreated straws; b) NiAl-LDHs/straw prepared in example 1; c) nickel aluminum oxide prepared in example 5; d) nickel phosphide prepared in example 6;

FIG. 2 is SEM pictures of pretreated straws of example 1, wherein the pictures a, b, c and d are respectively a schematic view of shooting angles and SEM pictures at different shooting angles and SEM pictures at high magnification;

FIG. 3 is an SEM photograph of NiAl-LDHs/straw obtained in example 1: a-b) is a low-magnification SEM image showing the biological structure of the straw; c-d) is a high-magnification SEM image showing LDHs nanosheets on the surface of straw cells (example 1);

FIG. 4 is an SEM image of the nickel aluminum oxide prepared from NiAl-LDHs/straw of example 5: a-b) is a low-magnification SEM image showing the biological structure of the straw; c-d) is a high-magnification SEM image, which shows NiAl-LDHs derived nanosheets on the surfaces of the straw cells;

FIG. 5 is an XRD pattern for examples 1, 5, 6;

FIG. 6 is an SEM photograph of comparative example 1;

FIG. 7 is an SEM photograph of comparative example 2;

FIG. 8 is an SEM photograph of comparative example 3;

FIG. 9 is a graph showing the comparison of phosphorus adsorption performance of LDHs having a corn stalk biostructure and LDHs formed by pressing (example 8)

FIG. 10 is a graph showing the comparison of the conversion rate of the hydrodeoxygenation reaction of methyl laurate under the action of the metal phosphide with straw biological structure and the compression-molded metal phosphide (example 9).

Detailed Description

The disclosure is further illustrated with reference to specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The reagents or starting materials used in the present invention can be purchased from conventional sources, and unless otherwise specified, the reagents or starting materials used in the present invention can be used in a conventional manner in the art or in accordance with the product specifications. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention. The preferred embodiments and materials described herein are intended to be exemplary only.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the stated features, steps, operations, and/or combinations thereof, unless the context clearly indicates otherwise.

At present, the traditional forming LDHs have the problems of low mass transfer efficiency, insufficient exposure of reaction sites, high preparation cost, poor application performance and the like, so the disclosure provides a preparation method and application of a forming layered double hydroxide and derivatives thereof.

In one embodiment of the present disclosure, a method of preparing a shaped layered double hydroxide comprises:

(1): soaking corn stalks in a solution containing metal salts and alkali precursors required for synthesizing LDHs;

(2): and transferring the corn straws soaked with the solution into a reactor, heating, reacting, and carrying out nucleation and growth of the LDHs to obtain the LDHs loaded by the corn straws.

Based on the corn straws as carriers or templates, the LDHs with the biological structure of the corn straws can be obtained. The layered double hydroxide of this structure facilitates mass transfer and active site exposure. The preparation method is simple and the preparation cost is low.

Or, before the corn stalks are soaked, pretreating the corn stalks; the corn stalk pretreatment comprises the following steps: peeling corn stalks, cutting into sections, washing with acid, then washing with water to be neutral, and drying; or, the acid is selected from one or more of hydrochloric acid, sulfuric acid and nitric acid, and hydrochloric acid is preferred. Through pretreatment of the corn straws, the influence of background metal in the corn straws on the growth of LDHs can be eliminated, and the porosity and the specific surface area are improved.

Or, in the step (1), the solvent of the solution is selected from one or more of water, ethanol and methanol, and preferably water; or, in the step (1), the metal is selected from one or more of Mg, Ni, Co, Zn, Cu, Ni, Ca, Al, Fe, Cr and Mn; or, in the step (1), the metal salt is selected from one or more of nitrate, sulfate, acetylacetone salt, halide salt, acetate and metal acid salt; preferred are nickel nitrate and aluminum nitrate, wherein the molar ratio of Ni to Al is between 5:1 and 1:5, preferably between 4:1 and 2: 1. By controlling the molar ratio, the loading and dispersion of the active metal in the resulting double hydroxide can be optimized, which facilitates exposure of more active sites.

Or, in the step (1), the concentration of the metal salt is between 0.01 and 5mol/L, preferably between 0.05 and 0.15 mol/L; or, in the step (1), the alkali precursor is selected from one or more of urea, hexamethylene tetramine, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, sodium hydroxide and potassium hydroxide, and is preferably urea; the molar ratio of urea to the total amount of metals (total amount of divalent and polyvalent metals) is between 50:1 and 1:1, preferably between 4:1 and 2: 1. Based on the above-mentioned base precursor, a hydroxide having a uniform structure can be obtained.

Or, in the step (2), the reaction temperature is between 80 and 150 ℃, preferably between 90 and 110 ℃; the reaction time is between 1 and 48 hours, preferably between 12 and 24 hours.

Or, the LDHs loaded by the corn straws can change the metal composition in the LDHs in an ion exchange mode to obtain a wider variety of LDHs/straw composite systems; further, the ion exchange means that metal ions in the LDHs are exchanged with other metal ions in a solution; the time of ion exchange is between 1 and 48 h. The ion exchange method is simpler. Through ion exchange, LDHs with various structural compositions can be obtained.

In one embodiment of the disclosure, a preparation method of a formed layered double hydroxide derivative is provided, wherein the corn straw-loaded LDHs prepared by the preparation method is aerobically calcined to remove straws to obtain a metal oxide maintaining a straw biological structure and LDHs nanosheet morphology; further, the aerobic calcination temperature is between 350 and 2000 ℃, preferably between 600 and 800 ℃; the calcination time is 0.1-24h, preferably 0.5-2 h. Under the calcination temperature, higher porosity and smaller metal particle size can be maintained on the premise of ensuring the removal of the corn straw template, and more active sites can be obtained. Further, the metal oxide is subjected to carbon doping, vulcanization or phosphorization process to obtain metal carbide, sulfide or phosphide maintaining the biological structure of the corn straw and the appearance of the LDHs nanosheet. Further, the carbon doping process can be a temperature programmed reduction method, a chemical vapor deposition method, a thermal decomposition method and the like; alternatively, the sulfidation process may be a solvothermal method, a high pressure reaction method, a chemical vapor deposition method, or the like; or, the phosphorization process can be a solvothermal method, a temperature programmed reduction method, a gas-solid reaction method and the like. Based on the layered double hydroxide with the biological structure of the corn straws, different derivatives can be obtained through simple post-treatment. The method is very simple and efficient. In particular, the straw biological structure is maintained, rich porosity can be provided, and more active sites can be exposed.

In an embodiment of the disclosure, the layered double hydroxide with straw biological structure prepared by the preparation method and/or the layered double hydroxide derivative prepared by the preparation method are/is used as a raw material.

In one embodiment of the disclosure, the layered double hydroxide and/or layered double hydroxide derivative with corn stalk biological structure is applied in the fields of adsorption, catalysis and the like. The layered double hydroxide and the derivative thereof have wide application fields, and compared with the traditional similar forming materials, the layered double hydroxide and the derivative thereof disclosed by the invention have advantages in the aspects of mass transfer and active site exposure, so that the layered double hydroxide and the derivative thereof have potential advantages in many application scenes. In particular, the layered double hydroxides and derivatives with the corn stalk biological structure prepared by the method have more excellent performance in phosphorus adsorption in water and hydrodeoxygenation of fatty acid methyl ester.

Further, the application includes: the LDHs loaded by the corn straws are used for adsorbing phosphorus in the water body: weighing a LDHs material loaded by corn straws, placing the LDHs material into a centrifugal tube, and adding a potassium dihydrogen phosphate solution for adsorption reaction; furthermore, the LDHs loaded on the corn straws is MgAl-LDHs.

Or, the formed layered double hydroxide derivative is used for catalyzing the reaction of preparing undecane/dodecane by hydrodeoxygenation of methyl laurate; furthermore, the derivative is NiAl-LDHs/straw-derived nickel aluminum phosphide with a straw biological structure.

In order to make the technical solutions of the present disclosure more clearly understood by those skilled in the art, the technical solutions of the present disclosure will be described in detail below with reference to specific embodiments.

Example 1

A method for preparing NiAl-LDHs/straw with a corn straw biological structure comprises the following steps:

a) pretreating corn stalks, peeling the corn stalks, cutting the corn stalks into sections, washing the corn stalks for 3 times by using 1M dilute hydrochloric acid, then washing the corn stalks to be neutral by using water, and drying the corn stalks to obtain the pretreated corn stalks;

b) 4.5mmol of Ni (NO)₃)₂·6H₂O、1.5mmol Al(NO₃)₃·9H₂Dissolving O and 13.5mmol of urea in 90mL of deionized water, and stirring until the solution is clear;

c) soaking the washed and dried straws in the solution to be fully saturated;

d) transferring the straws filled with the LDHs precursor solution into a hydrothermal kettle, and raising the temperature to 100 ℃ for 24 hours; and then washing the obtained product with water for several times, removing the residual reactant, and drying to obtain the NiAl-LDHs/straw with the biological structure of the corn straw.

Example 2

A method for preparing NiAl-LDHs/straw (high load) with corn straw biological structure comprises the following steps:

a) peeling corn stalk, cutting into segments, washing with 1M dilute hydrochloric acid for 3 times, then washing with water to neutrality, and drying;

b) adding 9mmol of Ni (NO)₃)₂·6H₂O、3mmol Al(NO₃)₃·9H₂Dissolving O and 27mmol urea in 90mL deionized water, and stirring until the solution is clear;

c) soaking the washed and dried straws in the solution to be fully saturated;

d) transferring the straws filled with the LDHs precursor solution into a hydrothermal kettle, and raising the temperature to 100 ℃ for 24 hours; and then washing the obtained product with water for several times, removing the residual reactant, and drying to obtain the NiAl-LDHs/straw with high load and maintaining the biological structure of the corn straw.

Example 3

Preparing NiFe-LDHs/straws with a corn straw biological structure:

a) peeling corn stalk, cutting into segments, washing with 1M dilute hydrochloric acid for 3 times, then washing with water to neutrality, and drying;

b) adding 9mmol of Ni (NO)₃)₂·6H₂O、3mmol Fe(NO₃)₃·9H₂Dissolving O and 27mmol urea in 90mL deionized water, and stirring until the solution is clear;

c) soaking the washed and dried straws in the solution to be fully saturated;

d) transferring the straws filled with the LDHs precursor solution into a hydrothermal kettle, and raising the temperature to 100 ℃ for 24 hours; and then washing the obtained product with water for several times, removing the residual reactant, and drying to obtain the NiFe-LDHs/straw with the straw biological structure.

Example 4

Preparing NiCoFe-LDHs/straw with a corn straw biological structure by ion exchange:

a) peeling corn stalk, cutting into segments, washing with 1M dilute hydrochloric acid for 3 times, then washing with water to neutrality, and drying;

b) adding 9mmol of Ni (NO)₃)₂·6H₂O、3mmol Fe(NO₃)₃·9H₂Dissolving O and 27mmol urea in 90mL deionized water, and stirring until the solution is clear;

c) soaking the washed and dried straws in the solution to be fully saturated;

d) transferring the straws filled with the LDHs precursor solution into a hydrothermal kettle, and raising the temperature to 100 ℃ for 24 hours; then washing the obtained product with water for several times, removing the residual reactant, and drying to obtain NiFe-LDHs/straws with the straw biological structure;

e) will be provided withSoaking NiFe-LDHs/straw in 50mmol/L Co (NO)₃)₂Slowly stirring and soaking the mixture in the solution for 24 hours, washing the obtained product with water for several times, and drying to obtain NiCoFe-LDHs/straws with the straw biological structure; example 5

Preparing Ni-Al oxide which is derived from NiAl-LDHs and has a corn straw biological structure:

putting the NiAl-LDHs/straws prepared in the example 1 into a muffle furnace, heating to 700 ℃ at the heating rate of 10 ℃/min, calcining for 1h, and cooling to obtain the Ni-Al oxide which is derived from the NiAl-LDHs and has the corn straw biological structure.

Example 6

Preparing phosphide with a corn straw biological structure derived from NiAl-LDHs:

placing the NiAl-LDHs/straws prepared in the example 1 in a muffle furnace, heating to 500 ℃ at a heating rate of 10 ℃/min, calcining for 1h, and cooling to obtain an oxide which is derived from the NiAl-LDHs and has a corn straw biological structure; then the oxide is mixed with NaH with 10 times of mass₂PO₂Placing in a tube furnace, vacuumizing, heating to 450 deg.C at a rate of 5 deg.C/min for 2h, and cooling to obtain NiAl-LDHs derived Ni with corn stalk biological structure₂P。

Example 7

Preparing MgAl-LDHs/straws with a corn straw biological structure:

peeling corn stalk, cutting into segments, washing with 1M dilute hydrochloric acid for 3 times, then washing with water to neutrality, and drying; 4.5mmol of Mg (NO)₃)₂·6H₂O、1.5mmol Al(NO₃)₃·9H₂Dissolving O and 13.5mmol of urea in a mixed solution of 45mL of deionized water and 45mL of ethanol, and stirring until the solution is clear; soaking the washed and dried straws in the solution to be fully saturated; transferring the straws filled with the LDHs precursor solution into a hydrothermal kettle, and raising the temperature to 100 ℃ for 24 hours; and then washing the obtained product with water for several times, removing the residual reactant, and drying to obtain the MgAl-LDHs/straw with the straw biological structure.

Example 8

The MgAl-LDHs/straw which is prepared in example 7 and keeps the biological structure of the straw is used for adsorbing phosphorus in water:

80mg of the MgAl-LDHs/straw material prepared in example 7 is weighed and placed in a 50mL centrifuge tube, 40mL of potassium dihydrogen phosphate solution with initial P concentration of 30ppm is added, the initial pH is adjusted to 5.0, rotary adsorption reaction is carried out on a rotary bed, and sampling test is carried out at certain intervals. The same mass of MgAl-LDHs granules (comparative example 4) which were press-molded under high pressure were used as a control group, and the performance test was conducted under the same conditions.

The result is shown in figure 9, the adsorption rate of the MgAl-LDHs/straw with straw biological structure to P is obviously superior to that of MgAl-LDHs particles formed by high-pressure pressing, and the expectation that the biological structure promotes mass transfer and active site exposure is supported.

Example 9

The nickel aluminum phosphide with the straw biological structure derived from NiAl-LDHs/straws is used for catalyzing the reaction of preparing undecane/dodecane by hydrodeoxygenation of methyl laurate:

firstly, 100mg of the nickel aluminum phosphide catalyst prepared in the example 6 is weighed and filled in a fixed bed reactor, hydrogen is charged into the reactor to 3Mpa, the reaction temperature is 350 ℃, the flow rate of the hydrogen is 110mL/min, and methyl laurate is introduced into the reactor according to the flow rate of 0.055 mL/min. Sampling and testing at certain time intervals, wherein the internal standard substance is tetrahydronaphthalene, and detecting the reaction product by using gas chromatography and a gas chromatography-mass spectrometer. Taking high-pressure compression molding nickel aluminum phosphide particles with the same mass as a control group, and carrying out performance test under the same condition.

The result is shown in fig. 10, under the catalysis of the nickel aluminum phosphide with the straw biological structure, the conversion rate of the methyl laurate is about 90%, which is obviously superior to that of the high-pressure compression-molded nickel aluminum phosphide particles (54%), and the expectation that the biological structure promotes mass transfer and active site exposure is supported.

Comparative example 1

Preparing NiAl-LDHs powder without straws:

adding 9mmol of Ni (NO)₃)₂·6H₂O、3mmol Al(NO₃)₃·9H₂O, 27mmol of urea are dissolved in 90mLStirring the mixture in deionized water until the mixture is clear, putting the mixture into a polytetrafluoroethylene hydrothermal kettle, and putting the kettle in a drying oven at 100 ℃ for reaction for 24 hours. After the hydrothermal reaction is finished, the precipitate is separated by suction filtration, washed with water for 3-5 times and dried to obtain the common NiAl-LDHs powder.

Comparative example 2

Preparing straw-free Ni-Al oxide powder:

placing the NiAl-LDHs powder obtained in the comparative example 1 in a muffle furnace for aerobic roasting at the temperature rising rate of 10 ℃/min and the roasting temperature of 800 ℃ for 1 h; and cooling to obtain Ni-Al oxide derived from NiAl-LDHs.

Comparative example 3

Preparing NiO with a corn straw structure but without LDHs morphology:

a) peeling corn stalk, cutting into segments, washing with 1M dilute hydrochloric acid for 3 times, then washing with water to neutrality, and drying;

b) adding 9mmol of Ni (NO)₃)₂·6H₂Dissolving O and 27mmol urea in 90mL deionized water, and stirring until the solution is clear;

c) soaking the washed and dried straws in the solution to be fully saturated;

d) transferring the straws filled with the LDHs precursor solution into a hydrothermal kettle, and raising the temperature to 100 ℃ for 24 hours; then washing the obtained product with water for several times, removing the residual reactant, and drying;

e) placing the sample in a muffle furnace for aerobic roasting, wherein the heating rate is 10 ℃/min, the roasting temperature is 800 ℃, and keeping for 1 h; and cooling to obtain NiO with a straw structure but without LDHs morphology.

Comparative example 4

Preparing MgAl-LDHs formed particles without biological structures:

adding 9mmol of Mg (NO)₃)₂·6H₂O、3mmol Al(NO₃)₃·9H₂Dissolving O and 27mmol urea in 90mL deionized water, stirring to clarify, placing in a polytetrafluoroethylene hydrothermal kettle, and placing in an oven at 100 ℃ for reaction for 24 h. After the hydrothermal reaction is finished, the precipitate is separated by suction filtration, washed for 3 to 5 times and dried to obtain MgAl-LDHs powder. And putting the obtained common MgAl-LDHs powder into a tablet machine, and pressing and forming under the pressure of 5MPa to obtain MgAl-LDHs granules.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.