CN118698595A - A Cu/HZSM-5 catalyst and its application in glycerol conversion - Google Patents

Abstract

The invention provides a Cu/HZSM-5 catalyst and application thereof in glycerin conversion, belonging to the technical field of biomass conversion, the invention takes Cu/HZSM-5 as the catalyst, A method for preparing monohydric alcohol (including ethanol, n-propanol and isopropanol) with high conversion rate and high selectivity by catalyzing hydrogenolysis of glycerol, namely, the glycerol is subjected to selective hydrogenation reaction on a Cu/HZSM-5 catalyst to generate ethanol, n-propanol and isopropanol. According to the invention, 0.45g of Cu/HZSM-5 catalyst, 1g of glycerol and 9g of water are put into a reaction kettle to react for 18 hours under the conditions of 250 ℃ and 5MPa H ₂, the conversion rate of the glycerol can reach 100%, and the selectivity of monohydric alcohol can reach more than 80%.

Description

A Cu/HZSM-5 catalyst and its application in glycerol conversion

Technical Field

The invention belongs to the technical field of biomass conversion, and in particular relates to a Cu/HZSM-5 catalyst and application thereof in glycerol conversion.

Background Art

At present, the world is facing the problem of limited fossil fuels and increasingly serious environmental pollution. The sustainable development of economy and society is facing severe challenges. Therefore, the development of clean and sustainable new energy is a major problem. As a substitute for fossil fuels, biodiesel has the advantages of biodegradability, complete combustion, non-volatile, safer transportation and storage than petrochemical diesel. It is a green energy that can be developed. In the past decade, the vigorous development of biodiesel has led to a large surplus of by-product glycerol. According to statistics, about 100 kg of glycerol is produced for every ton of biodiesel produced. Although glycerol has a wide range of uses, the current market still cannot consume a large amount of glycerol. The oversupply of the glycerol market and the decline in glycerol prices have given rise to industrial production using glycerol as raw material. Glycerol as a raw material can be converted into a series of high-value-added chemicals such as ethanol (EtOH), 1,2-propylene glycol (1,2-PDO), 1,3-propylene glycol (1,3-PDO), n-propanol (1-PO), isopropanol (2-PO), etc. through catalysis. The products of glycerol hydrogenation are highly dependent on the catalyst and reaction conditions.

The monohydric alcohols produced by the hydrogenolysis of glycerol include ethanol, n-propanol and isopropanol. Ethanol is widely used in medicine, fuel additives, clean fuels, engine fuels, solvents, raw materials, beverages, food additives and other fields. All laboratory processes for the production of ethanol require the use of _H2 . Therefore, direct catalytic conversion of glycerol into ethanol in the gas phase without an external hydrogen donor is a promising alternative. n-Propanol is often used in organic synthesis and can also be used in the synthesis of cosmetics, dental detergents, insecticides and sterilizations, inks, and plastics. For example, it can be used to synthesize propyl acetate, which is used as a coating solvent and ink printing. Isopropanol is also an important chemical raw material, mainly used in pharmaceuticals and plastics, and is involved in the research and development of products such as disinfectants, hand sanitizers, and fragrances.

In the catalytic reaction of preparing monohydric alcohol by hydrogenolysis of glycerol, the catalysts are mostly heteropolyacid catalysts which are complicated to prepare or precious metal catalysts which are expensive. Therefore, it is necessary to provide a catalyst which is simple to prepare and inexpensive.

Summary of the invention

In order to solve the above technical problems, the present invention proposes a Cu/HZSM-5 catalyst and its application in glycerol conversion.

To achieve the above object, the present invention provides the following technical solutions:

The invention provides a Cu/HZSM-5 catalyst, wherein the Cu loading amount in the Cu/HZSM-5 catalyst is 10wt%-25wt%; and the silicon-aluminum ratio of HZSM-5 is 70, 120 or 200.

Furthermore, the Cu loading in the Cu/HZSM-5 catalyst is 20wt%; and the silicon-aluminum ratio of HZSM-5 is 120.

The appropriate Cu loading and silicon-aluminum ratio of HZSM-5 will improve the selectivity of glycerol hydrogenation to produce monohydric alcohol. If the loading is too low, the metal sites that can be provided will be reduced, which is not conducive to the hydrogenation reaction; if the loading is too high, it will cause Cu particles to accumulate, affecting the uniform dispersion of Cu, and secondly, it may cover the original acid sites of HZSM-5, which is not conducive to the reaction. The high or low silicon-aluminum ratio represents the high or low Al content, which directly affects the acid properties of HZSM-5. The appropriate distribution of acid sites helps to remove hydroxyl groups during glycerol hydrogenation.

The present invention also provides a method for preparing the Cu/HZSM-5 catalyst, comprising the following steps:

The copper salt is dissolved in water to obtain a copper salt solution, HZSM-5 is immersed in the copper salt solution, an alkali solution is added dropwise until the metal ions are completely precipitated, and the catalyst is washed, filtered, dried, calcined, and reduced to obtain a Cu/HZSM-5 catalyst.

Furthermore, in the preparation method of the Cu/HZSM-5 catalyst, the copper salt is Cu(NO ₃ ) ₂ ; the alkali solution is a NaOH solution, and the concentration of the NaOH solution is 2 mol/L.

Furthermore, in the preparation method of the Cu/HZSM-5 catalyst, the calcination temperature is 400-600°C.

Furthermore, in the preparation method of the Cu/HZSM-5 catalyst, the reduction temperature is 300-500°C. When the reduction temperature is low, the diffusion of hydrogen on the catalyst surface will not be affected; however, if the reduction temperature is too high, the catalyst may be sintered prematurely, resulting in insufficient contact with hydrogen and reduced monohydric alcohol selectivity. The appropriate reduction temperature allows hydrogen to fully react with the catalyst, exposing more Cu sites, improving the hydrogenation effect of the catalyst, and increasing the selectivity of monohydric alcohols (including ethanol, n-propanol and isopropanol).

Furthermore, in the preparation method of the Cu/HZSM-5 catalyst, the reduction is performed in a 10% H ₂ /N ₂ atmosphere.

Furthermore, the preparation method of the Cu/HZSM-5 catalyst is as follows:

(1) Preparing a precursor solution: Place Cu(NO ₃ ) ₂ in a beaker and dissolve it in ultrapure water to prepare a copper salt solution. In order to better dissolve Cu(NO ₃ ) ₂ , the copper salt solution is prepared under stirring. The stirring rate is preferably 600 r/min, and the stirring time is preferably 10 min.

(2) Impregnation: adding HZSM-5 to the copper salt solution, stirring at 40° C. for 30 min with a magnetic stirring rate of 600 r/min, so that the copper salt solution is absorbed by HZSM-5, and the Cu loading in the Cu/HZSM-5 catalyst is 10 wt% to 25 wt%;

(3) Precipitation: After the immersion is completed, add 2 mol/L NaOH solution to the solution until the pH is 9, and let it stand to ensure that the metal ions are completely precipitated;

(4) Washing: The sample after standing in step (3) is repeatedly washed with pure water for 5-6 times until the pH of the supernatant is 7, and then the solid sample is retained by suction filtration;

(5) Drying: The solid sample in step (4) was transferred to an oven at 105° C. and dried for 12 h. After drying, it was taken out and fully ground into powder using an agate mortar;

(6) Calcination: The powder sample in step (5) is placed in a crucible and calcined in a muffle furnace in an air atmosphere at a temperature of 400-600° C., preferably 550° C., for 6 h, and at a muffle furnace heating rate of 5° C./min;

(7) Reduction: The powder sample in step (6) was placed in a quartz boat and reduced in a tube furnace in a 10% H ₂ /N ₂ atmosphere at a reduction temperature of 300-500° C. to obtain a Cu/HZSM-5 catalyst.

Furthermore, in the preparation method of the Cu/HZSM-5 catalyst, the reduction temperature in step (7) is preferably 400° C., the reduction time is 2 h, and the heating rate of the tubular furnace is 10° C./min.

The present invention also provides application of the Cu/HZSM-5 catalyst in catalyzing glycerol hydrogenolysis to prepare monohydric alcohol.

The present invention also provides a method for preparing monohydric alcohol by catalytic hydrogenolysis of glycerol, using the above-mentioned Cu/HZSM-5 catalyst as a catalyst, comprising the following steps:

Glycerol, the Cu/HZSM-5 catalyst and water are added into a reaction kettle, and the reaction kettle is sealed and filled with hydrogen to react at 230-260°C.

Furthermore, in the method for preparing monohydric alcohol by catalytic hydrogenolysis of glycerol, the hydrogen pressure is 1-6 MPa.

Furthermore, in the method for preparing monohydric alcohol by catalytic hydrogenolysis of glycerol, the reaction time is 1-24h.

The present invention uses glycerol as a raw material and water as a solvent, and catalytically converts the monohydric alcohol with high selectivity under the action of a Cu/HZSM-5 catalyst. The reaction temperature is 230-260° C., preferably 230-250° C., the reaction time is 1-24 h, preferably 2-20 h, and the hydrogen pressure in the reaction system is 1-6 MPa, preferably 3-6 MPa.

In the process of glycerol conversion catalyzed by Cu/HZSM-5 catalyst, higher temperature is conducive to the breaking of chemical bonds. From a thermodynamic point of view, higher temperature can accelerate the reaction rate, but the temperature higher than the optimal temperature may accelerate the rate of carbon accumulation on the catalyst surface and reduce the selectivity of the target product. The glycerol hydrogenation reaction usually requires a long reaction time, which can ensure the smooth dehydration and hydrogenation of glycerol, but too long a time will cause the target product to continue to be hydrogenated, reducing the selectivity of the target product. Hydrogen is filled into the reaction system to increase the reaction pressure, which is beneficial to the thermodynamic equilibrium of hydrogenation, and to supply hydrogen to the reaction system, but too high a hydrogen pressure will cause local overheating in the reactor, deactivate the active species of the catalyst, and reduce the degree of hydrogenation of the double bond.

The invention discloses a method for preparing monohydric alcohol (including ethanol, n-propanol and isopropanol) with high conversion rate and high selectivity by catalyzing glycerol hydrogenolysis with Cu/HZSM-5 as a catalyst, that is, glycerol undergoes a selective hydrogenation reaction on the Cu/HZSM-5 catalyst to generate ethanol, n-propanol and isopropanol. The invention discloses a method for preparing monohydric alcohol (including ethanol, n-propanol and isopropanol) with high conversion rate and high selectivity by adding 0.45g of Cu/HZSM-5 catalyst, 1g of glycerol and 9g of water into a reactor, reacting for 18h at 250°C and 5MPa _H2 , the conversion rate of glycerol can reach 100%, and the selectivity of monohydric alcohol can reach 80%.

Compared with the prior art, the present invention has the following advantages and technical effects:

1. The present invention provides a Cu/HZSM-5 catalyst and its application in glycerol conversion. The Cu/HZSM-5 catalyst of the present invention achieves the purpose of catalytic conversion of glycerol to monohydric alcohol with high conversion rate and high selectivity through hydrogenation of metal sites and dehydration of acid sites.

2. The catalyst of the present invention uses non-precious metal raw materials, the raw materials are easy and cheap to obtain, the process is simple, and it has good application prospects.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

FIG1 is a GC spectrum of the catalytic conversion of glycerol into monohydric alcohol in Example 1;

FIG2 is an XRD diagram of the catalysts prepared in Example 1, Example 4, Example 5 and Example 6;

FIG3 is an NH ₃ -TPD graph of the catalysts prepared in Example 1, Example 4, Example 5 and Example 6;

FIG. 4 is a pyridine infrared image of the catalyst of Example 1.

DETAILED DESCRIPTION

Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

Unless otherwise specified, the room temperature in the embodiments of the present invention is 25±2°C.

In the embodiment of the present invention, the calculation method of the Cu loading in the Cu/HZSM-5 catalyst is: Where mCu is the mass of Cu salt converted into Cu under ideal conditions, and mHZSM-5 is the actual amount of HZSM-5 input.

All raw materials used in the embodiments of the present invention are purchased from commercial sources. As an example, HZSM-5 is purchased from Zhuoran Environmental Protection Technology Co., Ltd.

The technical solution of the present invention is further illustrated by the following embodiments.

Example 1

Catalyst preparation:

(1) According to the loading amount of 20 wt% Cu in the Cu/HZSM-5 catalyst (hereinafter referred to as "according to the loading amount of 20 wt% Cu"), Cu( _NO3 ) ₂ was placed in a beaker, 30 mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600 r/min for 10 min to prepare a copper salt solution with a concentration of 0.3125 mol/L;

(2) adding HZSM-5 with a silicon-aluminum ratio of 120 to the copper salt solution, and impregnating the solution at 40° C. and 600 r/min for 30 min with magnetic stirring;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C and dried for 12 hours. After drying, it was taken out and ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined in a muffle furnace at 550°C in an air atmosphere for 6 hours. The calcined powder sample was placed in a quartz boat and reduced in a tube furnace at 400°C in a 10% _H2 / _N2 ( _H2 volume content 10%, the same below) atmosphere for 2 hours. The catalyst finally obtained was recorded as 20wt%Cu/HZSM-5.

Reaction evaluation: The Cu/HZSM-5 catalyst prepared by the above method was added to a high-pressure reactor, glycerol and water were added, mixed evenly, and the reactor was sealed; wherein the mass of glycerol was 1 g, the mass of water was 9 g, and the mass of the catalyst was 0.45 g; then the air in the autoclave was replaced with hydrogen 5 times, and then 5 MPa of hydrogen was filled, and the reaction was carried out at 250°C for 18 h, with a heating rate of 5°C/min. After the reaction, the reaction was cooled to room temperature, and the product was analyzed by gas chromatography and GC-MS. The glycerol conversion rate was 100%, and the monohydric alcohol selectivity was 80.74%. The reaction evaluation conditions and results are shown in Table 1.

Example 2 (Preparation of Ni/HZSM-5 catalyst as a comparison)

Catalyst preparation:

(1) According to the loading amount of 20wt% Ni, Ni(NO ₃ ) ₂ ·6H ₂ O was placed in a beaker, 30mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600r/min for 10min to prepare a nickel salt solution with a concentration of 0.3408mol/L;

(2) adding HZSM-5 with a silicon-aluminum ratio of 120 to the above nickel salt solution, and impregnating the solution at 40° C. with magnetic stirring at a speed of 600 r/min for 30 min;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C and dried for 12 hours. After drying, it was taken out and ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined in a muffle furnace at 550°C in an air atmosphere for 6 hours. The calcined powder sample was placed in a quartz boat and reduced in a tube furnace at 400°C in a 10% _H2 / _N2 atmosphere for 2 hours. The catalyst finally obtained was recorded as 20wt% Ni/HZSM-5.

Reaction evaluation: The operating procedure of the reaction evaluation is consistent with that of Example 1, but the reaction conditions and results are shown in Table 1.

Example 3 (Preparation of Co/HZSM-5 catalyst as a comparison)

Catalyst preparation:

(1) According to the loading amount of 20wt% Co, Co(NO ₃ ) ₂ ·6H ₂ O was placed in a beaker, 30mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600r/min for 10min to prepare a cobalt salt solution with a concentration of 0.3394mol/L;

(2) adding HZSM-5 with a silicon-aluminum ratio of 120 to the above cobalt salt solution, and impregnating the solution at 40° C. and 600 r/min for 30 min with magnetic stirring;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C and dried for 12 hours. After drying, it was taken out and ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined in a muffle furnace at 550°C in an air atmosphere for 6 hours. The calcined powder sample was placed in a quartz boat and reduced in a tube furnace at 400°C in a 10% _H2 / _N2 atmosphere for 2 hours. The catalyst finally obtained was recorded as 20wt% Co/HZSM-5.

Reaction evaluation: The operating procedure of the reaction evaluation is consistent with that of Example 1, but the reaction conditions and results are shown in Table 1.

Example 4 (for comparison, the carrier for loading Cu is SiO ₂ )

Catalyst preparation:

(1) According to the loading amount of 20wt% Cu, Cu(NO ₃ ) ₂ was placed in a beaker, 30mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600r/min for 10min to prepare a copper salt solution with a concentration of 0.3125mol/L;

(2) Weigh 2.4 g of SiO ₂ and add it to the copper salt solution. Perform impregnation at 40°C and 600 r/min for 30 min with magnetic stirring;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C and dried for 12 hours. After drying, it was taken out and fully ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined in a muffle furnace at 550°C in an air atmosphere for 6 hours. The calcined powder sample was placed in a quartz boat and reduced in a tube furnace at 400°C in a 10% _H2 / _N2 atmosphere for 2 hours. The catalyst finally obtained was recorded as 20wt% Cu/ _SiO2 .

Reaction evaluation: The operating procedure of the reaction evaluation is consistent with that of Example 1, but the reaction conditions and results are shown in Table 1.

Example 5 (for comparison, the carrier for loading Cu is Al ₂ O ₃ )

Catalyst preparation:

(1) According to the loading amount of 20wt% Cu, Cu(NO ₃ ) ₂ was placed in a beaker, 30mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600r/min for 10min to prepare a copper salt solution with a concentration of 0.3125mol/L;

(2) Weigh 2.4 g of Al ₂ O ₃ and add it to the copper salt solution. Perform impregnation at 40°C and 600 r/min for 30 min with magnetic stirring;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C and dried for 12 hours. After drying, it was taken out and fully ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined in a muffle furnace at 550°C in an air atmosphere for 6 hours. The calcined powder sample was placed in a quartz boat and reduced in a tube furnace at 400° _C in a 10% _H2 / _N2 atmosphere for 2 hours. The catalyst finally obtained was recorded as 20wt% Cu/ _Al2O3 .

Reaction evaluation: The operating procedure of the reaction evaluation is consistent with that of Example 1, but the reaction conditions and results are shown in Table 1.

Example 6 (for comparison, the carrier for loading Cu is MgO)

Catalyst preparation:

(1) According to the loading amount of 20wt% Cu, Cu(NO ₃ ) ₂ was placed in a beaker, 30mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600r/min for 10min to prepare a copper salt solution with a concentration of 0.3125mol/L;

(2) Weigh 2.4 g of MgO, add it to the copper salt solution, and impregnate it at 40° C. with magnetic stirring at a speed of 600 r/min for 30 min;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C and dried for 12 hours. After drying, it was taken out and ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined in a muffle furnace at 550°C for 6 hours in an air atmosphere. The calcined powder sample was placed in a quartz boat and reduced in a tube furnace at 400°C for 2 hours in a 10% _H2 / _N2 atmosphere. The catalyst finally obtained was recorded as 20wt% Cu/MgO.

Reaction evaluation: The operating procedure of the reaction evaluation is consistent with that of Example 1, but the reaction conditions and results are shown in Table 1.

Example 7

Catalyst preparation:

(1) According to the loading amount of 20wt% Cu, Cu(NO ₃ ) ₂ was placed in a beaker, 30mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600r/min for 10min to prepare a copper salt solution with a concentration of 0.3125mol/L;

(2) Weighing the corresponding HZSM-5 with a silicon-aluminum ratio of 70, adding it to the above copper salt solution, and impregnating it at 40° C. and 600 r/min for 30 min with magnetic stirring;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C for 12 hours and then taken out after drying. The sample was fully ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined in a muffle furnace at 550°C for 6 hours in an air atmosphere. The calcined powder sample was placed in a quartz boat and reduced in a tube furnace at 400°C for 2 hours in a 10% _H2 / _N2 atmosphere. The catalyst finally obtained was recorded as 20wt%Cu/HZSM-5.

Reaction evaluation: The operating procedure of the reaction evaluation is consistent with that of Example 1, but the reaction conditions and results are shown in Table 1.

Example 8

Catalyst preparation:

(1) According to the loading amount of 20wt% Cu, Cu(NO ₃ ) ₂ was placed in a beaker, 30mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600r/min for 10min to prepare a copper salt solution with a concentration of 0.3125mol/L;

(2) Weighing HZSM-5 with a corresponding silicon-aluminum ratio of 200, adding it to the above copper salt solution, and impregnating it at 40° C. and 600 r/min with magnetic stirring for 30 min;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C for 12 hours and then taken out after drying. The sample was fully ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined in a muffle furnace at 550°C for 6 hours in an air atmosphere. The calcined powder sample was placed in a quartz boat and reduced in a tube furnace at 400°C for 2 hours in a 10% _H2 / _N2 atmosphere. The catalyst finally obtained was recorded as 20wt%Cu/HZSM-5.

Reaction evaluation: The operating procedure of the reaction evaluation is consistent with that of Example 1, but the reaction conditions and results are shown in Table 1.

Embodiment 9

Catalyst preparation:

(1) According to the loading amount of 15wt% Cu, Cu(NO ₃ ) ₂ was placed in a beaker, 30mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600r/min for 10min to prepare a copper salt solution with a concentration of 0.3125mol/L;

(2) Weighing the corresponding HZSM-5 with a silicon-aluminum ratio of 120, adding it to the above copper salt solution, and impregnating it at 40° C. and 600 r/min for 30 min with magnetic stirring;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C for 12 hours and then taken out after drying. The sample was fully ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined in a muffle furnace at 550°C for 6 hours in an air atmosphere. The calcined powder sample was placed in a quartz boat and reduced in a tube furnace at 400°C for 2 hours in a 10% _H2 / _N2 atmosphere. The catalyst finally obtained was recorded as 15wt%Cu/HZSM-5.

Reaction evaluation: The operating procedure of the reaction evaluation is consistent with that of Example 1, but the reaction conditions and results are shown in Table 1.

Example 10

Catalyst preparation:

(1) According to the loading amount of 25wt% Cu, Cu(NO ₃ ) ₂ was placed in a beaker, 30mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600r/min for 10min to prepare a copper salt solution with a concentration of 0.3125mol/L;

(2) Weighing the corresponding HZSM-5 with a silicon-aluminum ratio of 120, adding it to the above copper salt solution, and impregnating it at 40° C. and 600 r/min for 30 min with magnetic stirring;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C for 12 hours and then taken out after drying. The sample was fully ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined in a muffle furnace at 550°C for 6 hours in an air atmosphere. The calcined powder sample was placed in a quartz boat and reduced in a tube furnace at 400°C for 2 hours in a 10% _H2 / _N2 atmosphere. The catalyst finally obtained was recorded as 25wt%Cu/HZSM-5.

Reaction evaluation: The operating procedure of the reaction evaluation is consistent with that of Example 1, but the reaction conditions and results are shown in Table 1.

In addition to studying the effects of the types of metal ions loaded on HZSM-5, the types of carriers loaded with Cu, and the silicon-aluminum ratio of HZSM-5 on the catalyst performance, the present invention also studies the effects of the reduction temperature during the catalyst preparation process (referred to as "catalyst reduction temperature"), the reaction temperature, reaction time, and hydrogen pressure during the reaction (referred to as "reaction hydrogen pressure") on the glycerol conversion rate and monohydric alcohol selectivity:

Embodiment 11

The preparation method of the catalyst is the same as that of Example 1.

Reaction evaluation: The Cu/HZSM-5 catalyst prepared by the above method was added to a high-pressure reactor, glycerol and water were added, mixed evenly, and the reactor was sealed; wherein the mass of glycerol was 1 g, the mass of water was 9 g, and the mass of the catalyst was 0.45 g; then the air in the autoclave was replaced with hydrogen 5 times, and then 5 MPa of hydrogen was filled, and the reaction was carried out at 250°C for 8 h, with a heating rate of 5°C/min. After the reaction, the reaction was cooled to room temperature, and the product was analyzed by gas chromatography and GC-MS. The glycerol conversion rate was 94.67%, and the monohydric alcohol selectivity was 34.03%. The reaction evaluation conditions and results are shown in Table 1.

Example 12

The preparation method of the catalyst is the same as that of Example 1.

Reaction evaluation: The Cu/HZSM-5 catalyst prepared by the above method was added to a high-pressure reactor, glycerol and water were added, mixed evenly, and the reactor was sealed; wherein the mass of glycerol was 1 g, the mass of water was 9 g, and the mass of the catalyst was 0.45 g; then the air in the autoclave was replaced with hydrogen 5 times, and then 5 MPa of hydrogen was filled, and the reaction was carried out at 250°C for 15 h, with a heating rate of 5°C/min. After the reaction, the reaction was cooled to room temperature, and the product was analyzed by gas chromatography and GC-MS. The glycerol conversion rate was 100%, and the monohydric alcohol selectivity was 48.03%. The reaction evaluation conditions and results are shown in Table 1.

Embodiment 13

The preparation method of the catalyst is the same as that of Example 1.

Reaction evaluation: The Cu/HZSM-5 catalyst prepared by the above method was added to a high-pressure reactor, glycerol and water were added, mixed evenly, and the reactor was sealed; wherein the mass of glycerol was 1 g, the mass of water was 9 g, and the mass of the catalyst was 0.45 g; then the air in the autoclave was replaced with hydrogen 5 times, and then 5 MPa of hydrogen was filled, and the reaction was carried out at 250°C for 20 h, with a heating rate of 5°C/min. After the reaction, the reaction was cooled to room temperature, and the product was analyzed by gas chromatography and GC-MS. The glycerol conversion rate was 100%, and the monohydric alcohol selectivity was 51.53%. The reaction evaluation conditions and results are shown in Table 1.

Embodiment 14

The preparation method of the catalyst is the same as that of Example 1.

Reaction evaluation: The Cu/HZSM-5 catalyst prepared by the above method was added to a high-pressure reactor, glycerol and water were added, mixed evenly, and the reactor was sealed; wherein the mass of glycerol was 1g, the mass of water was 9g, and the mass of the catalyst was 0.45g; then the air in the autoclave was replaced with hydrogen 5 times, and then 5MPa of hydrogen was filled, and the reaction was carried out at 230°C for 20h, with a heating rate of 5°C/min. After the reaction, the reaction was cooled to room temperature, and the product was analyzed by gas chromatography and GC-MS. The glycerol conversion rate was 94.29%, and the monohydric alcohol selectivity was 13.79%. The reaction evaluation conditions and results are shown in Table 1.

Embodiment 15

The preparation method of the catalyst is the same as that of Example 1.

Reaction evaluation: The Cu/HZSM-5 catalyst prepared by the above method was added to a high-pressure reactor, glycerol and water were added, mixed evenly, and the reactor was sealed; wherein the mass of glycerol was 1 g, the mass of water was 9 g, and the mass of the catalyst was 0.45 g; then the air in the autoclave was replaced with hydrogen 5 times, and then 5 MPa of hydrogen was filled, and the reaction was carried out at 240°C for 20 h, with a heating rate of 5°C/min. After the reaction, the reaction was cooled to room temperature, and the product was analyzed by gas chromatography and GC-MS. The glycerol conversion rate was 95.17%, and the monohydric alcohol selectivity was 31.78%. The reaction evaluation conditions and results are shown in Table 1.

Example 16

The preparation method of the catalyst is the same as that of Example 1.

Reaction evaluation: The Cu/HZSM-5 catalyst prepared by the above method was added to a high-pressure reactor, glycerol and water were added, mixed evenly, and the reactor was sealed; wherein the mass of glycerol was 1 g, the mass of water was 9 g, and the mass of the catalyst was 0.45 g; then the air in the autoclave was replaced with hydrogen 5 times, and then 5 MPa of hydrogen was filled, and the reaction was carried out at 260°C for 20 h, with a heating rate of 5°C/min. After the reaction, the reaction was cooled to room temperature, and the product was analyzed by gas chromatography and GC-MS. The glycerol conversion rate was 93.55%, and the monohydric alcohol selectivity was 41.19%. The reaction evaluation conditions and results are shown in Table 1.

Embodiment 17

The preparation method of the catalyst is the same as that of Example 1.

Reaction evaluation: The Cu/HZSM-5 catalyst prepared by the above method was added to a high-pressure reactor, glycerol and water were added, mixed evenly, and the reactor was sealed; wherein the mass of glycerol was 1 g, the mass of water was 9 g, and the mass of the catalyst was 0.45 g; then the air in the autoclave was replaced with hydrogen 5 times, and then 4 MPa of hydrogen was filled, and the reaction was carried out at 250°C for 20 h, with a heating rate of 5°C/min. After the reaction, the reaction was cooled to room temperature, and the product was analyzed by gas chromatography and GC-MS. The glycerol conversion rate was 66.11%, and the monohydric alcohol selectivity was 12.40%. The reaction evaluation conditions and results are shown in Table 1.

Embodiment 18

The preparation method of the catalyst is the same as that of Example 1.

Reaction evaluation: The Cu/HZSM-5 catalyst prepared by the above method was added to a high-pressure reactor, glycerol and water were added, mixed evenly, and the reactor was sealed; wherein the mass of glycerol was 1 g, the mass of water was 9 g, and the mass of the catalyst was 0.45 g; then the air in the autoclave was replaced with hydrogen 5 times, and then 6 MPa of hydrogen was filled, and the reaction was carried out at 250°C for 20 h, with a heating rate of 5°C/min. After the reaction, the reaction was cooled to room temperature, and the product was analyzed by gas chromatography and GC-MS. The glycerol conversion rate was 76.48%, and the monohydric alcohol selectivity was 18.40%. The reaction evaluation conditions and results are shown in Table 1.

Embodiment 19

Catalyst preparation:

(1) According to the loading amount of 20wt% Cu, Cu(NO ₃ ) ₂ was placed in a beaker, 30mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600r/min for 10min to prepare a copper salt solution with a concentration of 0.3125mol/L;

(2) Weigh 2.4 g of HZSM-5 with a silicon-aluminum ratio of 120, add it to the above salt solution, and impregnate it at 40° C. and 600 r/min for 30 min with magnetic stirring;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C and dried for 12 hours. After drying, it was taken out and ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined in a muffle furnace at 550°C in an air atmosphere for 6 hours. The calcined powder sample was placed in a quartz boat and reduced in a tube furnace at 300°C in a 10% _H2 / _N2 atmosphere for 2 hours. The catalyst finally obtained was recorded as 20wt%Cu/HZSM-5.

Reaction evaluation: The operating procedure of the reaction evaluation is consistent with that of Example 1, but the reaction conditions and results are shown in Table 1.

Embodiment 20

Catalyst preparation:

(1) According to the loading amount of 20wt% Cu, Cu(NO ₃ ) ₂ was placed in a beaker, 30mL of ultrapure water was added to dissolve it, and the solution was stirred at a speed of 600r/min for 10min to prepare a copper salt solution with a concentration of 0.3125mol/L;

(2) Weighing the corresponding HZSM-5 with a silicon-aluminum ratio of 120, adding it to the above salt solution, and impregnating it at 40° C. and 600 r/min for 30 min with magnetic stirring;

(3) After the impregnation is completed, 2 mol/L NaOH solution is added dropwise to the solution until the pH is 9, and the solution is allowed to stand to ensure complete precipitation of metal ions;

(4) After standing, the sample was repeatedly washed with pure water for 5-6 times until the pH of the supernatant was 7, and then the solid sample was retained by suction filtration;

(5) The solid sample was placed in an oven at 105°C and dried for 12 hours. After drying, it was taken out and ground into powder using an agate mortar. The powder sample was then placed in a crucible and calcined at 550°C for 6 hours in a muffle furnace in an air atmosphere. The calcined powder sample was placed in a quartz boat and reduced at 500°C for 2 hours in a tube furnace in a 10% _H2 / _N2 atmosphere. The catalyst finally obtained was recorded as 20wt%Cu/HZSM-5.

Reaction evaluation: The operating procedure of the reaction evaluation is consistent with that of Example 1, but the reaction conditions and results are shown in Table 1.

Table 1

The GC spectrum of glycerol catalytically converted into monohydric alcohol in Example 1 is shown in FIG1 , which shows that Cu20/HZSM-5 can be used for glycerol hydrogenation reaction to obtain highly selective monohydric alcohol under complete conversion of raw materials;

The XRD patterns of the catalysts prepared in Example 1, Example 4, Example 5 and Example 6 are shown in Figure 2. It can be seen that Cu20/HZSM-5 still has the diffraction peaks of the ZSM-5 sample, indicating that the introduction of Cu species still maintains the unique crystal structure of ZSM-5. In addition, Cu20/HZSM-5, Cu20/Al ₂ O ₃ , Cu20/SiO ₂ and Cu20/MgO all show weaker diffraction peaks of Cu species, indicating that the Cu species is evenly distributed on the carrier surface. Cu presents three crystal planes on the surface of HZSM-5, namely Cu(111), Cu(200) and Cu(220).

The NH ₃ -TPD diagrams of the catalysts prepared in Example 1, Example 4, Example 5 and Example 6 are shown in Figure 3. It can be seen that Cu20/HZSM-5, Cu20/Al ₂ O ₃ and Cu20/SiO ₂ all have NH 3 desorption peaks in the low temperature section of 100°C, corresponding to the weak acid sites of the catalyst, which are attributed to the physically adsorbed NH _3. Cu20/HZSM-5 and Cu20/Al ₂ O ₃ have NH ₃ desorption peaks at 350°C and 400°C, respectively, which are attributed to the desorption of strong acid sites. According to reports, the peaks at higher temperatures (such as 300-600°C) correspond to the desorption of NH ₃ from the catalytic active acid sites, indicating that Cu20/HZSM-5 and Cu20/Al ₂ O ₃ both have active acid sites.

Cu20/MgO shows a weak NH ₃ desorption peak, indicating that Cu20/MgO has relatively less acid content.

The pyridine infrared images of the catalysts prepared in Example 1 are shown in Figure 4. It can be seen that Cu20/HZSM-5, Cu20/Al ₂ O ₃ , Cu20/SiO ₂ and Cu/MgO all have a peak of pyridine adsorption at Lewis acid sites near 1450 cm-1, but Cu20/HZSM-5 obviously has more Lewis acid sites. At around 1490 cm-1, each catalyst has a peak of pyridine adsorption at Lewis acid sites. The acid sites and Lewis acid sites jointly adsorbed pyridine, and each catalyst showed a hydrogen bond-pyridine desorption peak near 1594 cm-1. In addition, Cu20/HZSM-5 showed a strong Lewis acid site desorption peak of pyridine at 1610 cm-1, indicating that Cu20/HZSM-5 exposed a strong Lewis acid site compared with other catalysts.

Comparing Example 1 with Examples 2-3, it can be seen that Cu, compared with Ni and Co, synergistically catalyzes glycerol hydrogenation with HZSM-5, and has a higher selectivity for monohydric alcohols. This may be because the strong metal-support interaction between Cu and HZSM-5 is more conducive to the formation of monohydric alcohols, and Ni and Co have stronger C-C bond breaking and hydrogenation capabilities, but have lower selectivity for monohydric alcohols.

Comparing Example 1 with Examples 4-6, it can be seen that the synergistic effect of HZSM-5 with Cu is more conducive to the generation path of glycerol to monohydric alcohol. Compared with the reference carrier, HZSM-5 has greater catalytic advantages due to its rich pore structure and surface acid properties. According to Figures 2, 3, and 4, HZSM-5 can promote better reduction of Cu to Cu ⁰ and provide more Lewis acid sites, which is conducive to the route of glycerol hydrogenation to generate monohydric alcohol.

By comparing Example 1 with Examples 7-8, it can be seen that 120 is a suitable silicon-aluminum ratio for HZSM-5, which enables better synergy between the acid sites on the carrier surface and the dispersion of Cu particles. The hydrogenation effect of Cu will not be reduced due to too many acid sites, nor will the catalyst performance be reduced due to Cu covering the acid sites due to too few acid sites.

In conclusion, Cu/HZSM-5 has the best catalytic effect on the conversion of glycerol to monohydric alcohol. The combined effect of Cu metal and HZSM-5 with a Si/Al ratio of 120 promotes the highly selective conversion of glycerol to monohydric alcohol.

Comparison between Example 1 and Examples 9 and 10 shows that the appropriate Cu loading improves the selectivity of glycerol conversion to monohydric alcohol by improving the dispersion of Cu on the surface of HZSM-5.

Comparison of Example 1 with Examples 11-13 shows that the time is appropriately extended to allow both glycerol and the intermediate product to fully contact and react with the catalyst, thereby obtaining highly selective monohydric alcohol.

Comparison of Example 1 with Examples 14-18 shows that appropriate temperature and hydrogen pressure improve the reaction efficiency of catalytic hydrogenolysis of glycerol to generate monohydric alcohol.

By comparing Example 1 with Examples 19 and 20, it can be seen that when preparing the Cu/HZSM-5 catalyst, the reduction temperature is too low, which does not affect the diffusion of hydrogen on the catalyst surface, while too high a temperature may cause the catalyst to sinter prematurely, resulting in insufficient contact with hydrogen. The appropriate reduction temperature allows hydrogen to fully react with the catalyst, exposing more Cu sites, improving the hydrogenation effect of the catalyst and increasing the selectivity for monohydric alcohols.

The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (10)

1. A Cu/HZSM-5 catalyst, characterized in that the Cu loading in the Cu/HZSM-5 catalyst is 10wt%-25wt%; the silicon-aluminum ratio of HZSM-5 is 70, 120 or 200. 2. The Cu/HZSM-5 catalyst according to claim 1 is characterized in that the Cu loading in the Cu/HZSM-5 catalyst is 20wt%; and the silicon-aluminum ratio of HZSM-5 is 120. 3. A method for preparing the Cu/HZSM-5 catalyst according to claim 1, characterized in that it comprises the following steps: The copper salt is dissolved in water to obtain a copper salt solution, HZSM-5 is immersed in the copper salt solution, an alkali solution is added dropwise until the metal ions are completely precipitated, and the catalyst is washed, filtered, dried, calcined, and reduced to obtain a Cu/HZSM-5 catalyst. 4 . The method for preparing the Cu/HZSM-5 catalyst according to claim 3 , wherein the copper salt is Cu(NO ₃ ) ₂ ; and the alkali solution is NaOH solution. 5. The method for preparing the Cu/HZSM-5 catalyst according to claim 3, characterized in that the calcination temperature is 400-600°C. 6. The method for preparing the Cu/HZSM-5 catalyst according to claim 3, characterized in that the reduction temperature is 300-500°C. 7. Use of the Cu/HZSM-5 catalyst according to any one of claims 1 to 2 in catalyzing the hydrogenolysis of glycerol to prepare monohydric alcohol. 8. A method for preparing monohydric alcohol by catalytic hydrogenolysis of glycerol, characterized in that the Cu/HZSM-5 catalyst according to any one of claims 1 to 2 is used as a catalyst, comprising the following steps: Glycerol, the Cu/HZSM-5 catalyst according to any one of claims 1 to 2 and water are added into a reaction kettle, the reaction kettle is sealed and filled with hydrogen, and the reaction is carried out at 230-260°C. 9. The method for preparing monohydric alcohol by catalytic hydrogenolysis of glycerol according to claim 8, characterized in that the hydrogen pressure is 1-6 MPa. 10. The method for preparing monohydric alcohol by catalytic hydrogenolysis of glycerol according to claim 8, characterized in that the reaction time is 1-24 hours.