CN116237058A - Catalyst applicable to preparation of ethanol from lignocellulose, preparation and catalysis method - Google Patents

Abstract

The invention discloses a catalyst suitable for preparing ethanol from lignocellulose, a preparation method and a catalytic method. Compared with the existing bimetallic catalysts, two kinds of metal salts are simultaneously added during the preparation of the precursor and calcined at high temperature. During the preparation of the catalyst, Ni particles can be used as a hard template at a lower calcination temperature. After the calcination is completed, most of the Ni particles can be removed by pickling, leaving a graphene shell; and then further introduced by impregnation. Noble metal particles; as the reaction center, the noble metal particles exist in nanoreactors composed of carbon shells, which avoids the aggregation and agglomeration of metal particles. The biomass raw material used has a wide range of sources and can be used only after simple crushing, which makes the industrial preparation of ethanol by the biomass catalytic method possible. Compared with the Ni content in the existing catalyst as high as 70%, the Ni content in the catalyst is only 5%.

Description

Catalyst, preparation and catalytic method suitable for preparing ethanol from lignocellulose

technical field

The invention belongs to the field of ethanol preparation from biomass, and in particular relates to a catalyst, preparation and catalytic method suitable for ethanol preparation from lignocellulose.

Background technique

Biomass is the only renewable organic carbon resource on Earth. The global annual biomass production is about 200 billion tons. As a large agricultural country, my country has abundant biomass resources, with a potential of up to 1 billion tons of standard coal. The total amount of biomass resources that can be sourced and utilized every year is about 460 million tons of standard coal, mainly agricultural and forestry waste (lignocellulose). Except for 40% used as feed, fertilizer and industrial raw materials, about 60% has not been effectively utilized. Among the three major constituent units of lignocellulosic biomass (cellulose, hemicellulose and lignin), cellulose has the largest content, accounting for 30-50% of the weight of lignocellulose, and is the most abundant biomass in the world. The key to the utilization of biomass is to transform it into high-value resources.

Ethanol is an important popular chemical product, which is widely used in the fields of biofuel, chemical industry, biomedicine and organic synthesis. In the field of biofuels, ethanol is a high-quality fuel additive, containing oxygen atoms, which can promote the combustion of hydrocarbon gasoline, reduce the emission of harmful exhaust gases, and is more friendly to the environment; on the other hand, ethanol has a high octane number, and its explosion-proof , Excellent anti-seismic performance, blended with gasoline can replace the more toxic tetraethyl lead and the controversial methyl tert-butyl ether [4]. Due to my country's mandatory promotion and use of E10 gasoline (10% ethanol mixed with existing gasoline), it is expected that the consumption of ethanol will increase significantly in the future. Therefore, the development of ethanol fuel has become a national strategy, and the green and directional preparation of ethanol has become an international research frontier and focus.

One of the sources of ethanol is to use fossil resources as raw materials (coal, petroleum, natural gas) through the conversion of the following routes: ethylene hydration, synthesis gas Fischer-Tropsch direct synthesis and dimethyl ether carbonylation-hydrogenolysis, but these The path has problems such as non-renewable raw materials, low yield of one-way reaction (the unreacted raw materials need to be forced to circulate to improve the utilization rate of reactants), long reaction route and low efficiency. Ethanol can also be produced from lignocellulosic biomass through biochemical pathways.

Traditionally, the production of ethanol from biomass uses enzyme/acid hydrolysis to first convert the cellulose component to glucose, which is then fermented to ethanol (two-step process), or saccharification and fermentation to ethanol in the same reactor ( one-step method). The advantages of the biochemical pathway reaction are mild reaction conditions (≤50oC) and high ethanol selectivity. However, whether it is a two-step method or a one-step method, the conversion path has problems such as long production cycle, expensive enzymes, and easy poisoning and inactivation.

Existing chemical preparation methods, such as patent CN110092708B, developed a Ni-based catalyst wrapped in a graphene-like shell to catalyze lignocellulose to produce ethanol under the synergistic effect of phosphoric acid, using liquid acid phosphoric acid as an auxiliary agent. However, the use of liquid acid brings a series of problems, such as the material of the reactor, the recovery and treatment of the liquid acid, and environmental pollution. Secondly, in the preparation of existing catalysts, the amount of metal used is high, and the Ni content in the Ni@C catalyst is as high as 70%, and the reaction efficiency is low; secondly, in the prior art, the catalyst using noble metals generally has a higher loading of noble metals by about 5% , and the catalyst is stable.

Contents of the invention

The purpose of the present invention is to address the above problems, to provide a catalyst, preparation and catalytic method suitable for ethanol preparation from lignocellulose, which has high reaction efficiency, low metal load and stable catalytic efficiency.

Technical scheme of the present invention: the present invention discloses a catalyst preparation method suitable for preparing ethanol from lignocellulose, comprising the following steps:

S1. Select nickel nitrate, organic matter and deionized water, and stir at 60-110°C for 12 hours at a stirring rate of 600rpm; heat up to 120-160°C and keep for 12 hours to obtain a powder sample at 400°C; The sample was roasted under the protection of N2 atmosphere for 3 hours to obtain a black powder;

S2. Quickly transfer the black powder into a 1M sulfuric acid solution, reflux for 6 hours, wash with deionized water until neutral, and freeze-dry to obtain a Ni-based catalyst;

S3. Add Co, Pt, Pd, Ru metal salts and a certain proportion of organic matter to the Ni-based catalyst obtained by the freeze-drying according to a certain proportion, add a certain amount of water, stir and dry, and heat the obtained solid at 500-700° C. , treated in 10% H2/N2 mixed gas for 1-4 hours to obtain target catalysts Co-Ni@C, x ₁ Pt-Ni@C, x ₂ Pd-Ni@C, x ₃ Ru-Ni@C.

The invention also discloses a catalyst suitable for producing ethanol from lignocellulose, the catalyst is a nano-metal reactor catalyst, including Co-Ni@C, x ₁ Pt-Ni@C, x ₂ Pd-Ni@C, x ₃ Ru-Ni@C;

The shell of the catalyst is a graphene-like shell with a hollow interior, the graphene-like shell contains Pt, Pd and Ru metal nanoparticles, and the graphene-like shell is wrapped with magnetic Ni.

Further, said x ₁ , x ₂ , and x ₃ are metal contents, said x ₁ is 0.05, x ₂ is 0.10, and X ₃ is 0.25.

Further, the catalyst suitable for producing ethanol from lignocellulose is prepared by the above catalyst preparation method suitable for producing ethanol from lignocellulose.

The invention also discloses a catalyst catalytic method suitable for preparing ethanol from lignocellulose, using biomass, cellulose and its derivatives C5 and C6 sugars as raw materials, and reacting the reactants under the use of acid and nano-metal reactor catalysts Obtain ethanol through selective hydrodeoxygenation reaction, the reaction temperature is 180-260°C, the reaction time is 0.1-6h, and the hydrogen pressure in the reaction system is 1-5.0MPa;

Described acid is phosphoric acid, sulfuric acid, hydrochloric acid and MCM-41, Hβ, HY, USY molecular sieve;

The nano-metal reactor catalyst is the above-mentioned catalyst suitable for producing ethanol from lignocellulose.

Further, the acid includes any one of phosphoric acid, sulfuric acid and hydrochloric acid.

Further, the biomass raw material includes one of eucalyptus wood powder, pine wood powder, birch wood powder, corn straw, wheat straw, rice stalk, sorghum stalk, foxtail grass, cellulose, glucose, fructose, and xylose.

The beneficial effects of the present disclosure are:

1. Compared with the existing bimetallic catalysts, two kinds of metal salts are added at the same time during the preparation of the precursor and roasted at high temperature. During the preparation of the catalyst, Ni particles can be used as a hard template at a lower calcination temperature. After the calcination is completed, most of the Ni particles can be removed by pickling, leaving a graphene shell; and then further introduced by impregnation. Noble metal particles; as the reaction center, the noble metal particles exist in nanoreactors composed of carbon shells, which avoids the aggregation and agglomeration of metal particles. The biomass raw material used has a wide range of sources and can be used only after simple crushing, which makes the industrial preparation of ethanol by the biomass catalytic method possible.

2. Compared with the Ni content in the existing catalyst as high as 70%, the Ni content in the catalyst is only 5%; compared with the existing noble metal catalyst, the Ni particles partially wrapped by carbon can be used as the magnetic center, and after the reaction , Solid-liquid separation can be achieved by magnetic adsorption. Because of being wrapped by carbon, the Ni particles as the magnetic center can be stored for a long time without further reduction before use, no environmental pollution, and the preparation is simple and convenient.

Description of drawings

Fig. 1 is the TEM figure of 0.1Pt-Ni@C catalyst in the embodiment 1 of the present invention;

Fig. 2 is the NH ₃ -TPD diagram of different molecular sieves in Examples 18-17 of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. the embodiment. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1: Preparation of 0.1Pt-Ni@C catalyst

Add 10 mL of deionized water, 0.03 mol of metal salt, and 0.03 mol of organic matter into the beaker and stir at 600 rpm, keep at 90°C for 12 hours, then raise the temperature to 100-140°C until the sample is completely dry. The resulting green powder was heated to 400 °C in _N2 atmosphere and kept for 3 hours. The obtained black powder was transferred into 1M sulfuric acid solution and refluxed for 6 hours. The solid remaining after reflux was filtered, washed and lyophilized. Subsequently, a certain amount of Ni-based catalyst precursor, organic matter, a certain proportion of metal salt and 5 ml of water were weighed and stirred at 100 degrees until dry. The obtained solid was treated with 10% H ₂ /N ₂ mixed gas at 600° C. for 3 hours to finally obtain a catalyst. As can be seen from the TEM image shown in Figure 1, this method has prepared a nanoreactor catalyst with a Ni particle core.

Example 2:

Add 0.15g of 0.05Pt-Ni@C catalyst, 0.4g of cellulose and 40.0ml of 0.05M phosphoric acid aqueous solution into a 100ml autoclave, seal the autoclave, replace the gas in the autoclave with _H2 for 6 times, and fill with _H2 to increase the temperature. Pressure to 3MPa. Turn on the stirring paddle (800rpm), raise the temperature of the reactor to 180oC at a heating rate of 5°C/min, and start timing the reaction. Using the catalyst, at the reaction temperature of 180oC, the reaction time is 1h, and the ethanol product yield is 95.1%.

Examples 3-17: Refer to Example 2, the difference is that the reaction temperature, pressure and time are different, see Table 1 for details. Through this table, we found that the reaction conditions including temperature, pressure and reaction time have a significant impact on the reaction. Under the optimal reaction conditions of 180oC, 3Mpa hydrogen initial pressure, reaction for 1 hour, the yield of ethanol can reach up to 95.1% .

Table 1:

Examples 18-27:

In order to verify the influence of different acids on the reaction results, it can be concluded from Table 2 that different structures and types of acids have different effects on the yield of ethanol. Phosphoric acid works best when using liquid acids, and HY works best when using molecular sieves.

It can be obtained with reference to Example 2 and Fig. 2, the difference is that the molecular sieves used are different, and the reaction results are shown in Table 2.

Examples 28-37:

Referring to Example 2, the difference is that the metal catalysts used are different, see Table 3 for details.

table 3

From the examples in Table 3, it can be seen that different hydrogenation metals have different effects on the reaction results, and the bimetallic catalyst composed of noble metal and Ni has a better effect; when the loading is different, the catalytic effect is different. When the loading of the noble metal is too high, there is With excessive hydrogenation, the product will tend to generate more meteorological products such as methane.

Examples 38-49:

Referring to Example 2, the difference is that the raw materials used are different, see Table 4 for details.

Table 4

Example catalyst Ethanol yield (%) 38 Eucalyptus powder 37.2 39 Pine powder 36.1 40 birch powder 35.2 41 Corn stalks 31.4 42 sorghum stalks 30.7 43 Pennisetum 28.9 44 wheat stalk 31.7 45 rice stalk 29.6 46 Cellulose 95.1 47 glucose 94.3 48 fructose 67.7 49 Xylose 75.8

From the results of the examples in Table 4, it can be seen that the catalyst and the catalytic system also have a catalytic effect on real biomass.

In the table, the yield of ethanol is the quality of the ethanol obtained and the mass ratio of adding raw material.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (7)

1. A preparation method of a catalyst suitable for preparing ethanol from lignocellulose is characterized by comprising the following steps of: comprises the following steps of

S1, selecting nickel nitrate, organic matters and deionized water, and stirring for 12 hours at 60-110 ℃ at a stirring speed of 600rpm; heating to 120-160 ℃, and keeping for 12 hours to obtain a powder sample at 400 ℃; roasting the powder sample for 3 hours under the protection of N2 atmosphere to obtain black powder;

s2, rapidly transferring the black powder into a 1M sulfuric acid solution, refluxing for 6 hours, washing with deionized water to be neutral, and freeze-drying to obtain a Ni-based catalyst;

s3, adding Co, pt, pd, ru metal salt and a certain proportion of organic matters into the Ni-based catalyst obtained by freeze drying according to a certain proportion, adding a certain amount of water, stirring and drying, and treating the obtained solid in a mixed gas of 10% H2/N2 at 500-700 ℃ for 1-4 hours to obtain a target catalyst Co-Ni@C, x ₁ Pt-Ni@C，x ₂ Pd-Ni@C，x ₃ Ru-Ni@C。

2. A catalyst suitable for use in the production of ethanol from lignocellulose, characterized in that: the catalyst is a nano metal reactor catalyst and comprises Co-Ni@C, x ₁ Pt-Ni@C，x ₂ Pd-Ni@C，x ₃ Ru-Ni@C；

The shell of the catalyst is a graphene-like shell, the interior of the catalyst is hollow, the graphene-like shell contains Pt, pd and Ru metal nano particles, and the graphene-like shell is internally wrapped with magnetic Ni.

3. The catalyst for the production of ethanol from lignocellulose according to claim 2, characterized in that: the x is ₁ 、x ₂ 、x ₃ Is of metal content, x is ₁ 0.05, x ₂ 0.10, X ₃ 0.25.

4. A catalyst suitable for the production of ethanol from lignocellulose according to claim 2 or 3, characterized in that: prepared by the process of claim 1.

5. A catalytic method of a catalyst suitable for preparing ethanol from lignocellulose, which is characterized by comprising the following steps: taking biomass, cellulose and derivatives C5 and C6 sugar thereof as raw materials, and carrying out selective hydrodeoxygenation reaction on reactants under the use of acid and a nano metal reactor catalyst to obtain ethanol, wherein the reaction temperature is 180-260 ℃, the reaction time is 0.1-6h, and the hydrogen pressure in a reaction system is 1-5.0MPa;

the acid is phosphoric acid, sulfuric acid, hydrochloric acid and MCM-41, H beta, HY and USY molecular sieves;

the nano metal reactor catalyst is the catalyst of any one of claims 2-4.

6. The catalytic process for preparing ethanol from lignocellulose according to claim 5, wherein: the acid includes any one of phosphoric acid, sulfuric acid and hydrochloric acid.

7. The catalytic process for preparing ethanol from lignocellulose according to claim 5, wherein: the biomass raw materials comprise eucalyptus powder, pine powder, birch powder, corn straw, wheat straw, rice straw, sorghum stalk, green bristlegrass, cellulose, glucose, fructose and xylose.

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