CN100999676B - Process of preparing rich acetone alcohol biological oil by biomass microwave catalytic pyrolysis - Google Patents

Abstract

The microwave catalytic biomass cracking process for preparing biological oil with rich acetone alcohol features using sodium carbonate as catalyst, silicon carbide as microwave absorbing medium, microwave source as heat source for cracking biomass, and ice water mixture for cooling volatile component to obtain biological oil with rich acetone alcohol. By means of the unique temperature effect of microwave in biomass particle and the unique catalyzing effect of sodium carbonate in cracking biomass, the present invention realizes the creation of acetone alcohol in high selectivity. The present invention can obtain liquid product with acetone alcohol content of 30-55 % and raise the utilization value of acetone alcohol greatly. The present invention uses cheap and facile material and catalyst and has greatly shortened reaction period.

Description

Method for preparing bio-oil rich in acetol by microwave catalytic cracking of biomass

technical field

The invention relates to a method for preparing organic chemical raw materials, that is, a method for preparing acetol-rich bio-oil from biomass.

Background technique

At present, energy and environmental issues have become the focus of global attention, and fossil fuel resources still play the role of the world's energy pillar and the source of bulk organic chemical products. While benefiting mankind, fossil fuels have also caused serious pollution to the environment on which human beings depend. Moreover, fossil fuels will be exhausted in the near future, and it is imperative to seek alternative resources. Biomass, as the only renewable energy that can be converted into liquid fuel, has become a global consensus to expand and optimize its utilization. The liquid fuel converted from biomass cracking, usually called bio-oil, basically does not contain sulfur, nitrogen and metal components, and has no pollution to the environment. In addition to considerations from the perspective of energy utilization, bio-oil is also rich in organic matter with high utilization value, so it can be used as the primary raw material for many organic chemical products. Through the regulation of different catalysts, the highly selective generation of different organic compounds can be realized.

The composition of liquid products obtained by current rapid biomass pyrolysis technology is complex, and it is difficult to achieve high selectivity of specific organic components. Therefore, there is a problem of separation difficulty in the application of the rapidly cracked liquid product as an organic chemical raw material. In order to expand the application range of pyrolysis oil, it is necessary to improve the process to achieve high selectivity of specific organic components.

Acetol is a very important pharmaceutical and chemical intermediate, which is used to synthesize the intermediate 4-methylimidazole of the _H2 blocker cimetidine in the digestive system, and the intermediate of the quinolone antibacterial drug levofloxacin (s) -(+)-2-aminopropanol, intermediate 4-hydroxymethylimidazole of racemic histidine, also used for biotin (vitamin H) and aspirin acetonate, an antipyretic and analgesic drug without ulcer side effects Synthesis of other drugs and chiral intermediate (1)-(-)-1,2-propanediol. The synthesis or production methods of acetol mainly include: monobromoacetone esterification/alcoholysis method and 1,2-propanediol oxygen or K ₂ Cr ₂ O ₇ /H ₂ SO ₄ oxidation method, etc. The former has mild reaction conditions, but the price of the main raw material monobromoacetone leads to high production costs, which is the biggest disadvantage of this method; the latter has high requirements for reaction conditions and equipment, requires expensive metal catalysts, and the product yield is not high.

Although the bio-oil obtained by the rapid pyrolysis technology of biomass fluidized bed currently contains acetol components, the content is relatively low, usually below 10%, and the utilization value is low.

Contents of the invention

In order to avoid the problems in the above-mentioned prior art, the present invention provides a method for preparing acetol-rich bio-oil by microwave catalytic cracking of biomass, so as to overcome the problems of high raw material cost, expensive catalyst and low content of acetol in the prior art. question.

The technical scheme that the present invention solves technical problem adopts is:

Sodium carbonate is used as catalyst, silicon carbide is used as microwave absorption medium, microwave source is used as heating source to crack biomass, and ice-water mixture is used to cool volatile matter to obtain bio-oil rich in acetol.

The inventive method is also characterized in that:

Biomass raw material sawdust is impregnated with sodium carbonate aqueous solution as a catalyst and then dried to remove free water as a spare material; the spare material and silicon carbide are mixed in a mass ratio of 3:3-4, placed in a 2450KHz microwave field for cracking, and nitrogen The volatile matter is collected by purging, and the cracked product is cooled by an ice-bath U-shaped tube to obtain a liquid product.

Specifically, operate as follows:

The average particle size of biomass raw sawdust is less than 1mm, soaked in 5% (w/w) sodium carbonate aqueous solution for half an hour, and the amount of lye is 9-11% of the amount of alkali contained in biomass sawdust by weight percentage , the impregnated biomass sawdust was first dried naturally for a day and night, and then dried at 105°C for 3 hours to remove free moisture as a spare material; the spare material and silicon carbide were mixed and charged in a mass ratio of 3:3-4, placed in The cracking is carried out in a microwave cracking reactor, the initial microwave power is 1kw, when the temperature reaches 470°C, adjust the microwave power to 0.3kw, maintain the temperature at 450-550°C, and the cracking pressure is normal pressure; the nitrogen flow rate is 0.15-0.25m3/h , the cleavage products are successively passed through the multi-stage ice bath "U"-shaped tubes arranged in series to obtain bio-oil rich in acetol.

The mixed charge of spare material and silicon carbide is laid alternately in the quartz reactor, each layer is 0.5-1mm, and a total of 14-18 layers are laid.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. The present invention utilizes the unique temperature effect formed by microwaves in biomass particles and the unique catalytic effect of sodium carbonate on biomass cracking in a microwave field to achieve highly selective generation of acetol. The content of acetol obtained by this method in the liquid product can reach 30-55%, which is greatly improved compared with the content of acetol in the current fluidized bed rapid cracking bio-oil below 10%, and the utilization of acetol Value is higher.

2. The raw materials and catalyst used in the method of the present invention are cheap and easy to get, and the reaction time is greatly shortened.

Description of drawings

Accompanying drawing is the schematic flow chart of the method of the present invention.

Numbers in the figure: 1 nitrogen cylinder, 2 quartz reactor, 3-stage U-shaped tube, 4 secondary U-shaped tube, 5 tertiary U-shaped tube, 6 ice-water bath, 7 microwave cavity.

Below by specific implementation, in conjunction with accompanying drawing, the present invention will be further described:

Detailed ways

The specific implementation is carried out as follows:

1. Raw material preparation

The average particle size of biomass raw sawdust is less than 1mm, dipped in 5% (w/w) sodium carbonate aqueous solution, the amount of lye should be such that the amount of alkali contained therein is 9-11% of the mass of biomass sawdust. After fully stirring, dry it for a whole day and night, then dry it in an oven at 105°C for 3 hours, remove the free moisture, and place it in a desiccator as a spare material.

2. Loading

Weigh 16.5g of spare material and mix it with 20g of silicon carbide. The specific operation is to alternately lay the spare material and silicon carbide in thin layers in the quartz reactor 2, and lay 14-18 layers in total, each layer is 0.5-1mm. Cover the ground reactor cover, place the quartz reactor 2 in the microwave cavity 7, connect the gas inlet pipe connected with the nitrogen cylinder 1 and the gas outlet pipe connected with the first-stage U-shaped pipe 3.

3. Exhaust air

Open the nitrogen cylinder 1, keep the flow rate at 0.15-0.2m ³ /h, ventilate for at least 10 minutes, and discharge the air in the quartz reactor 2 and the piping system.

4. Microwave cracking

Turn on the microwave (2450KHz), the initial power is about 1kw, and when the temperature of the reaction material reaches 470°C, turn down the power to 0.3kw to maintain the temperature of the material. After the liquid is distilled off, turn off the microwave to stop the cracking. Collect the liquid in the primary U-shaped tube 3, the secondary U-shaped tube 4 and the tertiary U-shaped tube 5 placed in the ice-water bath 6 to obtain a mixed organic liquid rich in acetol, and the yield of the liquid product is 10-25 %, wherein the water content is 20-30%, and the content of acetol in the organic liquid is 30-55%. Generally, the liquid starts to distill out after 3 minutes of turning on the microwave, and there is no obvious liquid distillate after 8 minutes.

Example 1:

Using pine sawdust as raw material, it is crushed to a particle size of less than 1 mm, and the method of the present invention is used for raw material preparation, charging, air exhausting and microwave cracking. The cracking time is 12 minutes, and the liquid product is collected. The yield of the liquid product was 22.0%, the content of acetol was 45.3%, and the water content was 28.2%.

Example 2:

Using cotton stalk sawdust as raw material, the same steps as in Example 1 were used to collect the liquid product. The yield of the liquid product was 15.8%, the acetol content was 49.9%, and the water content was 30.3%.

Example 3:

Using Chinese fir sawdust as raw material, adopt the same steps as in Example 1 to collect the liquid product. The yield of the liquid product was 24.7%, the content of acetol was 45.4%, and the water content was 29.6%.

Claims (2)

1. the method for preparing rich acetone alcohol biological oil by biomass microwave catalytic pyrolysis, be to be catalyzer with yellow soda ash, with silicon carbide is the microwave absorbing medium, is that heating source carries out biomass cracking with the microwave source, adopts frozen water miscellany cooling volatile matter to obtain to be rich in the bio oil of hydroxyacetone; It is characterized in that operating according to the following procedure:

Biomass material sawdust median size is less than 1mm, in the aqueous sodium carbonate of 5% (w/w), flood half an hour, by weight percentage, the alkali lye consumption is the make a living 9-11% of material sawdust of institute's alkalinity, biomass sawdust behind the dipping dries earlier diel naturally, removes free water down in dry 3 hours as standby material at 105 ℃ again; Is 3 with silicon carbide by mass ratio with standby material: 3-4 mixes charging, places the microwave cracking reactor to carry out cracking, microwave initial power 1kw, and adjusting microwave power when temperature reaches 470 ℃ is 0.3kw, and holding temperature is 450-550 ℃, and cracking pressure is normal pressure; Nitrogen flow is 0.15-0.25m ³/ h, split product acquire the bio oil that is rich in hydroxyacetone through multistage ice bath " U " the shape pipe that series connection is provided with successively.

2. the method for preparing rich acetone alcohol biological oil by biomass microwave catalytic pyrolysis according to claim 1 is characterized in that standby material mixes charging with silicon carbide be to replace bedding in quartz reactor, and every layer of shop 0.5-1mm spreads the 14-18 layer altogether.

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