CN105802678B - A kind of liquefied using stalk catalytic hydrogenation prepares the method for bio oil - Google Patents

Abstract

The invention provides a method for preparing bio-oil by catalytic hydrogenation liquefaction of straw, the process steps are: (1) crushing the rice straw, and mixing the crushed rice straw with a certain proportion of ethanol; (2) adding A certain amount of catalyst, the mass ratio of the catalyst to the stalk is 1:40～4:40; (3) the mixed solution is placed in a high-pressure reactor, and a certain amount of hydrogen is introduced, and the hydrogen pressure is 0.5～2.0MPa, and the temperature is raised to 230-290°C, keep for 30-120min, cool naturally to room temperature, and collect the resulting mixture; (4) Separate the solid-liquid mixture obtained from the reaction, and separate the solid and liquid by suction filtration, and then use ethanol to decontaminate the obtained mixture. The obtained solid was washed, and then the ethanol solvent was removed by rotary evaporation to obtain bio-oil. The invention improves the problems of low oil production rate and poor bio-oil performance of straw hydrogenation liquefaction and the like.

Description

A method for preparing bio-oil by catalytic hydrogenation liquefaction of straw

technical field

The invention belongs to the technical field of catalysis and comprehensive utilization of biomass, and in particular relates to a method for hydrogenating and liquefying rice straw as a raw material to produce bio-oil.

Background technique

In today's society where energy is relatively scarce, human beings are faced with the challenge of coal and oil. As the mining of fossil energy is gradually decreasing and the combustion of fossil fuels produces a large amount of carbon dioxide gas, causing the greenhouse effect, and the combustion of fossil fuels will also produce harmful gases, such as SO ₂ , NO _X , etc., causing air pollution, another important The reason is that fossil energy is an impossible renewable energy source, and it is an important task to find renewable energy sources that are less polluting to the environment as soon as possible to replace this energy source.

At present, humans mainly use renewable energy such as solar energy, wind energy, and tidal energy to assist fossil energy to reduce the exploitation and use of oil, but these energy sources are limited by factors such as geographical environment, and it is difficult to promote them on a large scale and cannot successfully replace fossil energy. energy. Studies have shown that biomass energy is the renewable energy that is most likely to completely replace fossil energy. It is cheap, renewable, and has a wide range of sources. The CO ₂ produced by biomass energy combustion will be completely absorbed by plants through photosynthesis, and almost no harmful gases such as SO ₂ and NO _X will be produced.

Straw is the most abundant and cheapest biomass energy in the world, but it has not been fully utilized. A large amount of straw is burned on the spot or discarded everywhere, which not only wastes precious resources and pollutes the environment, but also brings many hazards, such as causing Fires, causing air pollution, destroying the soil environment, etc., have seriously affected the ecological environment on which human beings depend. The main reasons why straw is discarded and incinerated are: the material volume per unit mass is relatively large, and the transportation cost is too high; with the improvement of living standards, the power and efficiency of burning straw as fuel cannot meet the level of people's needs; The use of rural straw is mainly direct combustion, and the utilization rate of combustion is very low. If straw can be converted into liquid fuel, it can not only eliminate the problems of transportation, but also improve the combustion efficiency and other conditions; but there is still a fatal disadvantage of converting straw into bio-oil: high oxygen content and low calorific value.

In order to solve the above problems, it is necessary to synthesize a highly efficient, pollution-free, and cheap hydrogenation catalyst.

Contents of the invention

Technical problem: The purpose of the present invention is to provide a method for preparing bio-oil by catalytic hydrogenation liquefaction of rice straw, which uses rich sources of raw materials, low price, simple production process, mild conditions, and effectively improves the transformation of straw into bio-oil. Low oil yield and increasing the calorific value of bio-oil.

Technical solution: A method of using straw catalytic hydrogenation liquefaction to prepare bio-oil of the present invention includes the following steps:

1). The straw is crushed, and the crushed straw is mixed with a solvent;

2). A certain amount of catalyst is added, and the mass ratio of catalyst to straw is 1:40 to 4:40 to obtain a solid-liquid mixture;

3). Put the above solid-liquid mixture in a high-pressure reactor, pass in hydrogen, the hydrogen pressure is 0.5-2.0MPa, stir and heat up to 230-290°C, keep it for 30-120min, cool naturally to room temperature, and collect the obtained solid liquid mixture;

4). Separating the solid-liquid mixture obtained from the reaction in step 3), the separation adopts suction filtration to separate the solid and liquid, and then washes the obtained solid with an ethanol solvent, and removes the ethanol solvent by rotary evaporation. to obtain bio-oil.

in:

The solvent used in the preparation step 1) is ethanol, which can react with the generated acid during the reaction to reduce the acidity of the generated bio-oil, thereby avoiding the corrosion of the container by the bio-oil.

The catalyst described in the preparation step 2) adopts a high-efficiency hydrogenation catalyst MoS ₂ or CoS ₂ /MoS ₂ , which can increase the hydrogenation rate and change the quality of the oil during the reaction process.

Beneficial effect: compared with the prior art, the present invention has the following advantages:

1. The method of the present invention has cheap raw materials, low production cost, mild reaction conditions, is suitable for large-scale production, and can effectively alleviate the energy crisis;

2. The present invention selects ethanol as a solvent, which can react with the acid produced in the reaction process to reduce the acidity of the bio-oil produced, thereby avoiding the corrosion of the container by the bio-oil.

3. The catalyst prepared by the present invention has high activity and long life, which can effectively replace precious metals;

4. The hydrogenation catalyst CoS ₂ /MoS ₂ prepared by the present invention belongs to the category of heterojunction, which can accelerate the electron transfer in MoS ₂ and generate more vacant potentials, thereby increasing the hydrogenation rate and changing the quality of oil.

Description of drawings

Figure 1 is a schematic diagram of the change of reaction temperature and oil production rate of rice straw.

Fig. 2 is a schematic diagram of changes in reaction time and oil production rate of rice straw.

Fig. 3 is a schematic diagram of the change of hydrogen pressure and oil yield of straw.

Fig. 4 is a schematic diagram of the change of catalyst addition amount and oil production rate of straw.

Detailed ways

The technical solutions of the present invention will be further described in detail below through examples.

Example 1:

The catalyst in this embodiment is MoS ₂ , and the mass ratio of the added catalyst to the straw is 1:20.

The preparation method of catalyst: join 1.44g sodium molybdate and 2.27g thiourea into the deionized water of 50mL, stir and mix evenly, then add 1.20g hydroxylamine hydrochloride in the solution, slowly add the templating agent of 0.18g after half an hour (CTAB ), after continuing stirring for 1 h, the solution was placed in a hydrothermal kettle, heated at 200°C for 48 h, and after natural cooling, the product was washed with deionized and ethanol three times respectively, and the MoS ₂ catalyst was obtained after vacuum drying.

The raw material is rice straw, which is crushed into 60-mesh powder, weighs 4g of straw powder and moves it to a 100mL autoclave, adds 40mL of ethanol and 0.2g of catalyst, and injects hydrogen at a pressure of 1MPa. Magnetic stirring conditions Raise the temperature to 230-290°C, adjust the rotation speed to 700 after reaching the set temperature, keep this temperature for 1 hour, and perform suction filtration after the temperature of the reaction kettle drops to room temperature, separate the solution from the solid residue, and transfer the solution to a round bottom flask Rotary evaporation is carried out, and the obtained bio-oil is obtained after the ethanol solvent is evaporated. It can be concluded from Figure 1 that at a lower temperature of 230 °C, rice straw was hydrolyzed due to catalytic hydrogenation, and when the temperature increased, the conversion rate and oil production rate of rice straw also increased correspondingly, at 290 Under the condition of ℃, the conversion rate can reach 74.5%, and the oil yield rate is 50.23%.

Example 2:

The preparation method of the catalyst is the same as in Example 1. The raw material is rice straw, which is crushed into a 60-mesh powder, and 4g of straw powder is weighed and transferred to a 100mL autoclave, and 40mL of ethanol and 0.2g of _MoS2 catalyst are added. , the pressure of introducing hydrogen gas is 1MPa, and the temperature is raised to 290°C under the condition of magnetic stirring. After reaching the set temperature, the speed is adjusted to 700, and the temperature is maintained for 0.5-2h. The residue was separated, and the solution was transferred to a round bottom flask for rotary evaporation, and the obtained bio-oil was obtained after the ethanol solvent was evaporated. It can be concluded from Fig. 2 that when the reaction time is 0.5h, the conversion rate and oil production rate of straw are 65.87% and 45.29% respectively. As the reaction time increases, the conversion rate and oil production rate both increase. After the time was extended to 1 hour, with the prolongation of the reaction time, the conversion rate and oil production rate increased slowly, mainly because prolonging the reaction time can make the straw liquefy, but it will also lead to secondary cracking or secondary cracking of the bio-oil produced. The interaction between bio-oils becomes macromolecular solids, which leads to a slow increase in conversion rate and oil production rate. In consideration of factors such as economy and environmental protection, it is an unreasonable choice to extend the reaction time too long.

Example 3:

The preparation method of the catalyst is the same as in Example 1. The raw material is rice straw, which is crushed into a 60-mesh powder, and 4g of straw powder is weighed and transferred to a 100mL autoclave, and 40mL of ethanol and 0.2g of _MoS2 catalyst are added. , the pressure of introducing hydrogen gas is 0.5-2MPa, and the temperature is raised to 290°C under the condition of magnetic stirring. After reaching the set temperature, the speed is adjusted to 700, and the temperature is maintained for 1h. The residue was separated, and the solution was transferred to a round bottom flask for rotary evaporation, and the obtained bio-oil was obtained after the ethanol solvent was evaporated. It can be concluded from Figure 3 that with the increase of the hydrogen pressure, more hydrogen molecules react with the straw during the reaction process, thus increasing the oil yield and conversion rate of the straw.

Example 4:

The preparation method of the catalyst is the same as in Example 1. The raw material is rice straw, which is crushed into a 60-mesh powder. Weigh 4g of the straw powder and move it to a 100mL autoclave, add 40mL of ethanol and 0.1-0.4g of MoS ₂ Catalyst, the pressure of introducing hydrogen gas is 2MPa, the temperature is raised to 290°C under the condition of magnetic stirring, and the speed is adjusted to 700 after reaching the set temperature, and the temperature is maintained for 1 hour. The residue was separated, and the solution was transferred to a round bottom flask for rotary evaporation, and the obtained bio-oil was obtained after the ethanol solvent was evaporated. It can be concluded from Figure 4 that the conversion rate and oil production rate of rice straw increase with the increase of the amount of catalyst added, but after the amount of catalyst is increased to a certain amount, the conversion rate does not increase very obviously, because Economic considerations are unreasonable.

Example 5:

The preparation method of the catalyst: add 1.44g of sodium molybdate and 0.29g of cobalt nitrate into 50mL of deionized water containing 2.27g, stir and mix evenly, then add 1.20g of hydroxylamine hydrochloride to the solution, and slowly add 0.18g of Template agent (CTAB), continue to stir for 1 hour, put the solution in a hydrothermal kettle, heat it at 200°C for 48 hours, wash the product with deionization and ethanol three times after natural cooling, and obtain CoS after vacuum drying ₂ / _MoS2 catalyst.

The raw material is rice straw, which is crushed into a 60-mesh powder, weighs 5g of the straw powder, and moves it into a 100mL high-pressure reactor filled with 45mL of ethanol, respectively adds 0.25g of CoS ₂ /MoS ₂ catalyst, and passes in hydrogen The pressure is 2MPa, and the temperature is raised to 290°C under the condition of magnetic stirring. After reaching the set temperature, adjust the speed to 700, and keep this temperature for 1h. Rotary evaporation was carried out in a round bottom flask, and the obtained bio-oil was obtained after the ethanol solvent was evaporated. The conversion rate of this reaction was only 59.71% and the oil production rate was 35.50% without adding catalyst, while the conversion rate increased by 14.07% and the oil production rate increased by 18.40% when _MoS2 catalyst was added. ₂ /MoS ₂ catalyst, the conversion rate can reach 83.56%, and the oil production rate can reach 63.00%. It can be concluded that the addition of catalyst can increase the yield of oil and the conversion rate of rice straw.

Embodiment 6:

The bio-oil obtained in Example 5 is tested for calorific value: the operation steps are as follows: cut off a 15cm nickel wire and accurately weigh it on an electronic balance, wrap the middle part of the nickel wire on a thin metal rod for 4-5 circles, pull out the metal rod, Wrap the two sections of nickel wire tightly around the lower end of the electrode respectively. Accurately weigh about 1g of bio-oil in a combustion vessel, immerse the middle helix of the nickel wire in the oil, and tighten the device. Fill the device with 1.2MPa oxygen, then open the oxygen ejection hole, release the air in the oxygen bomb, and then inject 1.2MPa. Add 2000mL of temperature-adjusted water into the inner cylinder (control the water temperature in the inner cylinder to be 1.5°C lower than the jacket water temperature). Install the stirring motor, connect the two poles of the oxygen bomb to the ignition transformer with wires, insert the probe of the temperature difference measuring instrument into the jacket, connect the precise temperature and temperature difference measuring instrument, and determine the base temperature. Heat for 5 minutes, start the experiment, and read the data every 1 minute. After ten minutes, press the ignition button, and change the timing interval to 15s; know that the temperature rise is less than 0.005°C at each reading, and end the experiment. The experimental results show that the calorific value of bio-oil without catalyst is 25.173kJ/g, the calorific value of bio-oil with catalyst is 27.096kJ/g, and the calorific value of bio-oil with catalyst is 29.829kJ/g. It can be concluded that, The addition of catalyst can increase the calorific value of oil.

From the experimental results, it can be concluded that the addition of the catalyst can not only increase the conversion rate and oil production rate of rice straw, but also effectively improve the properties of bio-oil.

Claims (2)

1. a kind of liquefied using stalk catalytic hydrogenation prepares the method for bio oil, it is characterised in that includes the following steps：

1) will be mixed after stalk pulverization process with solvent；

2) adds MoS₂Or CoS₂/MoS₂The mass ratio of catalyst, the catalyst and stalk is 0.025~0.1:1, obtain solid-liquid Mixture；

3) solid-liquid mixture is placed in high-pressure reactor by, is passed through hydrogen, and Hydrogen Vapor Pressure is 0.5~2.0MPa, and stirring is warming up to 230~290 DEG C, keep 30~120min, cooled to room temperature, collect gained solidliquid mixture；

4) solidliquid mixture is carried out separation of solid and liquid by, and isolated solid is washed with alcohol solvent, then to remove ethanol molten Agent obtains bio oil.

2. according to claim 1 liquefied using stalk catalytic hydrogenation prepares the method for bio oil, it is characterised in that step 1) in, the solvent is ethanol.