CN111229202A

CN111229202A - Catalyst for modifying and upgrading bio-oil and preparation method thereof

Info

Publication number: CN111229202A
Application number: CN202010095111.0A
Authority: CN
Inventors: 卜权; 孔祥海; 陈坤; 曹梦杰
Original assignee: Jiangsu University
Current assignee: Jiangsu University
Priority date: 2020-02-14
Filing date: 2020-02-14
Publication date: 2020-06-05

Abstract

The invention belongs to the technical field of biomass conversion and recycling, and particularly relates to a catalyst for modifying and upgrading bio-oil and a preparation method thereof. The invention adds MoO₃To make pure TiO₂Has more weakly acidic and neutral acidic sites, and the synergistic effect can increase the conversion rate of lignin-derived phenols in the HDO process of the lignin-derived phenols and can be carried out under milder conditions (low H)₂Pressure and lower reaction temperature) to selectively cleave C-O bonds in complex oxygenates in the bio-oil, especially lignin derivatives such as phenol and its derivatives, to produce aromatic and aliphatic hydrocarbons.

Description

Catalyst for modifying and upgrading bio-oil and preparation method thereof

Technical Field

The invention belongs to the technical field of biomass conversion and reuse, and particularly relates to a catalyst for modifying and upgrading bio-oil and a preparation method thereof, in particular to a catalyst for catalytic hydrogenation, deoxidation, modification and upgrading of bio-oil and catalytic reforming of lignocellulose biomass and waste plastic pyrolysis gas and a preparation process thereof.

Background

With the large-scale exploitation and gradual exhaustion of fossil energy, renewable resources are receiving more and more attention from people in recent decades, and biomass energy is also gradually becoming one of the objects of people's research. China is rich in biomass resources, including forestry residues, corn, wheat, rice and other crops, straw, rice hull and sugarcane agricultural product processing residues, and the biomass resources can reach hundreds of millions of tons every year. The agricultural and forestry wastes serving as raw materials for biomass catalytic cracking reaction can relieve the problems of energy source and environmental pollution at present. However, many problems still exist in the reaction process such as: the liquid oil obtained by thermal cracking has low yield, and the biological oil contains a large amount of phenols or acids, so that the biological oil has the defects of low heat value, unstable chemical properties and the like. Generally, modification and quality improvement treatment can be realized under the action of high-pressure hydrogen and a noble metal catalyst, which seriously restricts the wide application of biomass and liquefied products thereof. The prior art mainly overcomes the defects of the bio-oil by carrying out hydrodeoxygenation biomass pyrolysis gas catalytic reforming on main components in the bio-oil, such as lignin-derived phenol, and the like, but the existing catalytic modification quality-improving technology is still not ideal.

The thermal cracking technology has the advantages of low energy consumption, short reaction time, easy industrialization and the like, and has attracted wide attention of scientific and technical workers at home and abroad in the research on the conversion of biomass and waste plastics. Waste plastics such as polyolefin polymers generate a large amount of H during thermal cracking₂And H⁺Hydrogen may be provided when co-pyrolyzed with biomass, thereby improving the quality of the liquid product of biomass pyrolysis.

The invention combines the comprehensive development and utilization of renewable wood fiber biomass and waste plastic resources, and designs a catalyst by taking a selective catalytic hydrodeoxygenation regulation mechanism of a lignin-derived phenolic model compound phenol as a starting point aiming at the defects of harsh reaction conditions, high cost and the like of catalytic modification and upgrading of a lignin-derived phenolic component in the traditional bio-oil. Research on a metal oxide carrier and an active precursor shows that the molybdenum modified titanium dioxide catalyst has strong acid strength, has weak acid and moderate acid sites, has the advantage of hydrothermal stability, and can adjust the acidity of the catalyst to adapt to different reaction requirements by controlling the components of the active precursor and the addition proportion thereof. The catalyst is used for carrying out catalytic hydrodeoxygenation on lignin-derived phenol model compound (phenol) in a high-pressure reaction kettle, and has mild reaction conditions (low H)₂Pressure and lower reactionTemperature) of the sample. The catalyst is further used for catalytic reforming reaction of co-pyrolysis gas of wood fiber biomass and waste plastics, and can realize one-step catalytic pyrolysis of wood fiber biomass to improve the quality and yield of bio-oil. Thereby providing theoretical and technical basis for developing biological oil modification and upgrading and application of wood fiber biomass and waste plastic resources, and expanding a new way for efficiently utilizing waste resources such as wood fiber agriculture and forestry biomass resources and organic solid wastes.

Disclosure of Invention

The invention aims to provide a catalyst for modifying and upgrading bio-oil and a preparation method thereof, wherein in the catalytic Hydrodeoxygenation (HDO) process, the regulation of the acidity of a carrier and the surface of the catalyst is particularly important for the catalytic activity, and TiO is used for modifying and upgrading bio-oil₂Has the advantages of stable chemical property, no toxicity, low cost, high catalytic activity and the like, is the most widely used catalytic material, and MoO₃The unique octahedral basic structural units give it good catalytic properties, in particular the ability to promote hydrodeoxygenation reactions by means of an oxygen vacancy driving mechanism on the molybdenum surface. The invention adds MoO₃To make pure TiO₂Has more weakly acidic and neutral acidic sites, and the synergistic effect can increase the conversion rate of lignin-derived phenols in the HDO process of the lignin-derived phenols and can be carried out under milder conditions (low H)₂Pressure and lower reaction temperature) to selectively cleave C-O bonds in complex oxygenates in the bio-oil, especially lignin derivatives such as phenol and its derivatives, to produce aromatic and aliphatic hydrocarbons.

The invention synthesizes the supported metal oxide catalyst by adopting a sol-gel method, reveals the influence of molybdenum metal oxide modification on the prepared catalyst, and adopts XRD, SEM, BET and NH₃Analysis means such as TPD (thermoplastic vulcanizate) and the like analyze the micro-morphological change, the active component, the specific surface area, the combination mode of the pore diameter and the carrier, the distribution state and the acid strength of the prepared supported metal oxide catalyst.

The specific technical scheme of the invention is as follows:

a preparation method of a catalyst for modifying and upgrading bio-oil comprises the following specific steps:

(1) respectively weighing titanium dioxide solids and preparing a metal salt solution with a certain mass fraction, wherein the metal salt solution is an ammonium molybdate solution, other transition metal salt solutions or a mixed solution of the ammonium molybdate solution and other transition metal salt solutions;

(2) mixing according to a certain proportion, and mechanically stirring to form gel;

(3) then drying in a drying oven at 105 ℃ for 4 hours for aging, cooling and grinding into powder;

(4) the catalyst for modifying and upgrading the bio-oil is obtained by utilizing a tubular furnace temperature programming roasting method.

The catalyst can improve the conversion rate of lignin-derived phenols, particularly phenol, in the bio-oil and the selectivity of the lignin-derived phenols, particularly phenol, to hydrocarbon compounds and aromatic hydrocarbons contained in the hydrocarbon compounds, and can improve the yield and quality of liquid products (bio-oil) generated by catalytic pyrolysis reaction of biomass and waste plastics through catalytic reforming reaction of pyrolysis gas of biomass, and is specifically embodied in that the proportion of oxygen in the bio-oil is selectively reduced and C-O bonds of the phenol compounds are selectively cut off so as to reduce saturated hydrogenation of the aromatic hydrocarbons to the hydrocarbon compounds, improve the quality of the bio-oil and reduce the production cost.

In the step (1), deionized water is used for preparing the metal salt solution, and the mass fraction of the metal salt solution is 1 wt% -10 wt%.

In the step (2), the titanium dioxide solid: mixing the metal salt solution solutions in a mass ratio of 1: 1-3: 1;

pouring the formed gel into the inner liner of the reaction kettle in the step (2), sealing, and putting into a 50 ℃ oven for 4-5 hours; the purpose is to make the metal ions better attached to the solid surface.

In the step (3), the gel is placed in a quartz boat, laid flat, set at the temperature of 105 ℃ in an oven, and dried and aged for 4 hours;

in the step (4), the roasting in the high-temperature tube furnace is carried out under the following conditions. Roasting at 400 ℃ for 6h and 550 ℃ for 6h in the atmosphere of air introduction, wherein the heating rate is 37 ℃/min. The purpose is to convert the metal ions on the surface of the titanium dioxide into metal oxides to be loaded on the surface of the titanium dioxide.

In the step (4), the active component in the catalyst for modifying and upgrading the bio-oil is pure MoO₃Other transition metal oxides or MoO₃And other transition metal oxides.

The molybdenum modified titanium dioxide metal oxide catalyst prepared by the method keeps the advantages of stable chemical property, high catalytic activity and the like of titanium dioxide, and is more suitable for modification and quality improvement reaction of oxygen-containing compounds in biological oil, particularly lignin-derived phenolic compounds such as phenol and derivatives thereof by combining regulation and control of molybdenum element on acidity and change of the surface of the catalyst through a sol-gel method. .

Drawings

FIG. 1 shows whether a molybdenum-base molecular sieve catalyst (A: TiO) is negative₂；B:Mo/TiO₂) Scanning Electron Microscopy (SEM)

FIG. 2 shows whether or not a molybdenum-base molecular sieve catalyst (A, C: TiO)₂；B,D:Mo/TiO₂) Transmission electron spectrum (TEM)

FIG. 3 is TiO₂、MoO₃And Mo/TiO₂XRD diffractogram of

FIG. 4 transition metal molybdenum modified TiO₂NH of catalyst₃Results of TPD analysis

FIG. 5 Effect of different catalysts on the chemical Selectivity of phenol hydrodeoxygenation reaction products

FIG. 6 distribution of main chemical group content of bio-oil produced by catalytic reforming of lignocellulosic biomass and waste plastics

Detailed Description

The technical solution of the present invention is further described in detail with reference to the accompanying drawings and specific embodiments.

Example one

Preparing 10 wt% ammonium molybdate solution, and then preparing the titanium dioxide catalyst: mixing ammonium molybdate solution according to the mass ratio of 1.2: 1; stirring for 10min to form gel, sealing at 50 deg.C for 4-5 hr, oven drying in 105 deg.C oven for 4 hr, aging, cooling, grinding into powder, baking at 400 deg.C in a tubular furnace in air atmosphereBurning for 6h, then roasting for 6h at 550 ℃, the temperature rate is 37 ℃/min, and the catalyst is molded and crystallized to obtain Mo/TiO₂A catalyst. Wherein the content of molybdenum is 1 percent of the total mass of the catalyst.

To verify the results of the synthesized catalyst, TEM, XRD, SEM, NH were performed₃-characterization of TPD and the like.

As shown in FIG. 1, TiO not modified with molybdenum was found from the SEM image₂Metal oxides and Mo/TiO₂Compared with the catalyst, the latter is smoother, which shows that the unmodified catalyst has a relatively fragile pore structure, and the modified catalyst has a stronger pore structure and good high hydrothermal stability although the number of surface pores is reduced.

As shown in FIG. 2, Mo/TiO produced was found in a TEM image₂Regular pore channels can be clearly observed in a catalyst sample, which shows that the pore channels of the original carrier can not be damaged by the loading of molybdenum ions, the molybdenum ions are well distributed and dispersed on the surface of the catalyst carrier, and the particles are uniformly distributed. Most areas in the figure are dark under a transmission electron microscope, which shows that Mo/TiO₂The catalyst sample particles have a certain thickness, the surface adsorbs dense granular molybdenum oxide metal oxides, and the sheet structure is compact.

As shown in FIG. 3, TiO modified with metallic molybdenum ions was found from the XRD pattern₂The metal oxide shows distinct characteristic diffraction peaks at diffraction angles 2 theta of 11 degrees, 23.8 degrees, 25.9 degrees, 26.4 degrees, 35.1 degrees, 40 degrees and 52.3 degrees, strong diffraction peaks at 2 theta of 27 degrees, 35.1 degrees and 52.3 degrees, and weak diffraction peaks at 2 theta of 11 degrees, 23.8 degrees, 25.9 degrees and 40 degrees. And MoO₃The metal oxide shows a strong diffraction peak at all the above diffraction angles, and TiO₂No obvious characteristic peak appears in the metal oxide at relevant angles, so that the synthesized catalyst can be judged to be Mo/TiO₂And (3) compounding a catalyst. Mo/TiO₂The composite catalyst has original TiO₂Metal oxide and MoO₃Characteristic diffraction peaks of the metal oxide, indicating that the sample contains native TiO₂Metal oxide and MoO₃Both structures of metal oxides.

As shown in FIG. 4, it was found from the TPD plot that both the modified and unmodified catalysts had two peaks, the first peak appearing in the range of 100-130 ℃ and the second peak at 400-450 ℃; the presence of molybdenum is bimodal indicating that there are two acids of different strengths. From Table 1, it can be seen that the unmodified TiO₂The weak acid amount of the catalyst is 0.426mmol/g, and the strong acid amount is 0.130 mmol/g. TiO modified by molybdenum₂More weak and medium acid sites are formed on the catalyst surface by addition of MoO₃，TiO₂Has more weakly and moderately acidic sites, and the weakly and moderately acidic sites are doubled, which indicates that MoO₃With TiO₂The surfaces have both stronger and weaker interactions.

Example two

In order to verify the effect of the molybdenum/titanium dioxide metal oxide catalyst on the hydrodeoxygenation of biomass pyrolysis oil, particularly lignin-derived phenolic compounds therein, a catalytic hydrodeoxygenation experiment was conducted using a reaction kettle. The starting material used in the experiments was a model compound of lignin-derived phenols such as phenol. Respectively weighing 1g of phenol, 0.1g (10% of the weight of the light component) of catalyst (one group is not added with the catalyst, one group is added with the molybdenum trioxide catalyst and one group is added with the molybdenum/titanium dioxide catalyst) and 20ml of decahydronaphthalene, adding the mixture into a high-pressure reaction kettle, purging the kettle with nitrogen for 3 times to discharge air in the kettle, and introducing hydrogen till P_H220Bar (2 standard atmospheres). The reactor was heated (at a rate of 10 ℃/min) to the specified temperature (330 ℃) and the time was counted for 4 hours in total. After the reaction is completed, the reaction kettle is quickly cooled to room temperature by water, the gas in the kettle is discharged, and the product is taken out and filtered to obtain liquid. The liquid phase product is obviously divided into an oil phase and a water phase. Extracting, rotary evaporating to obtain modified and upgraded liquid phase product, and analyzing chemical component selectivity by gas chromatography-mass spectrometer (GC/MS) (as shown in FIG. 5).

The results show that the control group is added with MoO₃And Mo/TiO₂The phenol conversion of the catalyst was 45.3%, 54.5% and 86.6%, respectively, which may be due primarily to MoO₃In TiO₂Better dispersion on the carrier, catalystMore weak acid sites and medium acid sites, crystal MoO, are formed on the surface₃With TiO₂The vector's synergy, which may increase the conversion of lignin-derived phenols. And the chemical composition selectivity analysis result of the liquid phase product shows that: adding MoO into the control group₃And Mo/TiO₂The hydrocarbon compound content in the liquid-phase product of the catalyst is respectively 8.9%, 20.58% and 41.07%; the main component of hydrocarbon compounds in the obtained liquid-phase product is aromatic hydrocarbon, and the result shows that MoO is added into a control group₃And Mo/TiO₂The aromatic compound content in the liquid-phase product of the catalyst was 8.6%, 20.01% and 35.41%, respectively. Adding Mo/TiO₂After the catalyst is used, the conversion rate of phenol and the selectivity of hydrocarbon compounds or aromatic hydrocarbon in liquid-phase products are obviously improved. The GC/MS analysis result shows that benzene is the main component of aromatic hydrocarbon, wherein Mo/TiO is used₂The selectivity to benzene reached 99.7% of the results obtained for the catalyst. This may be that in HDO processes, the carrier and surface acidity of the catalyst are of particular importance, MoO being compared to other catalysts₃/TiO₂Has a stronger acidity and has medium and weaker acid sites, which is advantageous for hydrodeoxygenation of phenol to benzene. While titanium materials interact more with hydrogen molecules and can readily decompose hydrogen at the surface.

EXAMPLE III

In order to verify the influence of the molybdenum/titanium dioxide metal oxide catalyst on the production of bio-oil by the pyrolysis of the wood fiber biomass, a catalytic pyrolysis experiment of the wood fiber biomass and waste plastics is carried out by combining a catalytic fixed bed reactor and a microwave pyrolysis device. The raw material used in the test was a mixture of pine and low density polyethylene (LDPE added at 25% of pine): 50g of pine raw material, 10 percent (5g) of molybdenum/titanium dioxide metal oxide catalyst based on biomass raw material, 2.5g of microwave absorbent (active carbon), 550 ℃ of reaction temperature of microwave pyrolysis, 8min of reaction time and 750W of power; after microwave pyrolysis reaction, the pyrolysis gas is subjected to catalytic reforming reaction through a catalytic fixed bed, the temperature of the catalytic reforming reaction is 650 ℃, and then the bio-oil is collected after rapid condensation. The results show that Mo/Ti is addedO₂After the catalyst is used, the yield of the bio-oil is obviously improved (26.53% vs. 18.15%), the organic components of the bio-oil after the reaction are collected and analyzed by GC/MS, and the reaction result is shown in FIG. 6. The GC/MS analysis showed that Mo/TiO was added compared to the reaction without catalyst₂The catalyst has a phenol content reduced to 18% from 62.97% without catalyst, the hydrocarbon content is increased to 42.33% from less than 1% without catalyst, and the selectivity of aromatic hydrocarbon in the hydrocarbon is increased to 11.47% from about 0.1% of the control experiment. The result shows that Mo/TiO is added in the catalytic pyrolysis process of biomass and waste plastics₂The catalyst can obviously improve the yield of the obtained bio-oil and the selectivity of chemical components thereof, and can obviously improve the quality of the obtained bio-oil.

TABLE 1 TiO based on TPD Peak area₂Acidity of the base catalyst

Claims

1. A preparation method of a catalyst for modifying and upgrading bio-oil is used for catalytic hydrogenation, deoxidation, modification and upgrading of bio-oil and catalytic reforming of lignocellulose biomass and waste plastic pyrolysis gas, and is characterized by comprising the following specific steps:

2. The method for preparing the catalyst for modifying and upgrading the bio-oil according to claim 1, wherein in the step (1), the metal salt solution is prepared by deionized water, and the mass fraction of the metal salt solution is 1 wt% to 10 wt%.

3. The method for preparing the catalyst for modifying and upgrading the bio-oil according to claim 1, wherein in the step (2), the titanium dioxide solid: and mixing the metal salt solution solutions in a mass ratio of 1: 1-3: 1.

4. The preparation method of the catalyst for modifying and upgrading the bio-oil according to claim 1, wherein in the step (2), the formed gel is poured into a lining of a reaction kettle, then sealed and placed into a 50 ℃ oven for 4-5 hours; the purpose is to make the metal ions better attached to the solid surface.

5. The method for preparing the catalyst for modifying and upgrading the bio-oil according to claim 1, wherein in the step (3), the gel is placed in a quartz boat, laid flat, set at an oven temperature of 105 ℃, and dried and aged for 4 hours.

6. The method for preparing the catalyst for modifying and upgrading the bio-oil according to the claim 1, wherein in the step (4), the roasting in the high-temperature tube furnace is carried out under the following conditions; roasting at 400 ℃ for 6h and 550 ℃ for 6h in the atmosphere of air introduction, wherein the heating rate is 37 ℃/min, so as to convert metal ions on the surface of the titanium dioxide into metal oxides to be loaded on the surface of the titanium dioxide.

7. The method for preparing the catalyst for modifying and upgrading the bio-oil according to claim 1, wherein in the step (4), the active component in the catalyst for modifying and upgrading the bio-oil is pure MoO₃Other transition metal oxides or MoO₃And other transition metal oxides.

8. A catalyst for modifying and upgrading bio-oil, which is characterized by being prepared by the method of any one of claims 1 to 7.