阅读说明：本技术 一种微晶纤维素和草酸共热解制备脱水糖混合物的方法 (Method for preparing dehydrated sugar mixture by co-pyrolysis of microcrystalline cellulose and oxalic acid ) 是由 陆强 胡斌 张冠 王博 达娜·波拉提别克 杨勇平 于 2019-09-24 设计创作，主要内容包括：本发明属于生物质能利用领域,具体涉及一种微晶纤维素和草酸共热解制备脱水糖混合物的方法。本发明是以微晶纤维素和草酸为原料,将两者混合接触,在无氧条件下于200～500℃进行快速共热解,将热解气冷凝至室温即可得到富含脱水糖混合物的液体产物。本发明所述方法中的草酸常见易得,价格低廉,在热解过程中起到催化微晶纤维素分解形成脱水糖产物的作用,同时自身分解,不会残留在固相、液相或气相热解产物中,因而该热解过程绿色、高效、无污染。(The invention belongs to the field of biomass energy utilization, and particularly relates to a method for preparing an anhydrosugar mixture by co-pyrolysis of microcrystalline cellulose and oxalic acid. The method comprises the steps of taking microcrystalline cellulose and oxalic acid as raw materials, mixing and contacting the microcrystalline cellulose and the oxalic acid, carrying out fast co-pyrolysis at 200-500 ℃ under an oxygen-free condition, and condensing pyrolysis gas to room temperature to obtain a liquid product rich in a dehydrated sugar mixture. The oxalic acid in the method is common and easy to obtain, has low price, plays a role in catalyzing the decomposition of the microcrystalline cellulose to form dehydrated sugar products in the pyrolysis process, and simultaneously decomposes by itself without remaining in solid-phase, liquid-phase or gas-phase pyrolysis products, so the pyrolysis process is green, efficient and pollution-free.)

1. A method for preparing dehydrated sugar mixture by co-pyrolysis of microcrystalline cellulose and oxalic acid is characterized in that the microcrystalline cellulose and the oxalic acid are used as raw materials and are mixed and contacted; then carrying out fast co-pyrolysis at 200-500 ℃ under an anaerobic condition, wherein the heating time is not more than 20 minutes; and collecting the pyrolysis gas, and condensing to obtain a liquid product rich in the dehydrated sugar mixture.

2. The method for preparing the dehydrated sugar mixture by co-pyrolyzing microcrystalline cellulose and oxalic acid according to claim 1, wherein the mixing contact is mechanical mixing of microcrystalline cellulose and oxalic acid; and the mass ratio of the two components is 1: 10-10: 1.

3. The method for preparing the dehydrated sugar mixture by co-pyrolysis of microcrystalline cellulose and oxalic acid as claimed in claim 1, wherein the mixing contact is that the microcrystalline cellulose is soaked in oxalic acid solution and then dried, the ratio of the microcrystalline cellulose to the oxalic acid solution is 1g:1 mL-1 g:1L, and the concentration of the oxalic acid is 0.1 mol/L-2 mol/L.

4. The method of claim 1, wherein the dehydrated sugar mixture comprises levoglucosan, levoglucosenone, 1, 4; 3, 6-dianhydro-alpha-D-glucopyranose, 2-formyl-1, 4; 3, 6-dianhydro-alpha-D-glucopyranose, 1, 5-anhydro-4-deoxy-D-glycero-hex-1-en-3-psicose, and 1-hydroxy-3, 6-dioxabicyclo [3.2.1] -2-octanone.

5. The process for co-pyrolyzing microcrystalline cellulose and oxalic acid to produce a mixture of dehydrated sugars of claim 1 wherein said anaerobic conditions are maintaining the reaction system under an inert, oxygen-free protective atmosphere.

6. The method for preparing the dehydrated sugar mixture through co-pyrolysis of the microcrystalline cellulose and the oxalic acid as claimed in claim 1, wherein the pyrolysis reaction is that the raw materials are placed in a constant temperature area of a reactor after the reactor is preheated to a set pyrolysis temperature.

7. The method for preparing the dehydrated sugar mixture through co-pyrolysis of microcrystalline cellulose and oxalic acid as claimed in claim 1, wherein the pyrolysis reaction is that the raw materials are placed in a constant temperature area of a reactor at room temperature, and then the reactor is rapidly heated to the set pyrolysis temperature, and the heating rate is not lower than 100 ℃/s.

Technical Field

The invention belongs to the field of biomass energy utilization, and particularly relates to a method for preparing an anhydrosugar mixture by co-pyrolysis of microcrystalline cellulose and oxalic acid.

Background

The biomass resource is the only carbon renewable resource which can be converted into a liquid product, and solid biomass can be directly converted into liquid bio-oil by using a rapid pyrolysis liquefaction technology. Bio-oil compositions are extremely complex, including a variety of high value-added chemicals, such as anhydrosugar derivatives and the like; but the content is generally very low, and the separation and extraction are difficult. Therefore, in order to directly obtain bio-oil rich in specific high value-added chemicals, it is necessary to directionally regulate the biomass pyrolysis process so as to selectively promote the production of specific target chemicals and suppress the production of other liquid by-products.

Cellulose is one of three major components of biomass, and dehydrated sugar products are important products formed by fast pyrolysis of cellulose, and comprise levoglucosan, levoglucosenone and 1, 4; 3, 6-dianhydro-alpha-D-glucopyranose and the like, and the dehydrated sugar products have unique hand-shaped structures, so the method has huge application potential in chemical synthesis. At present, the dehydrated sugar products are not produced industrially in a large scale, are difficult to prepare and are very expensive. When the pyrolysis process incorporates a suitable acidic catalyst, rapid pyrolysis of cellulose can yield bio-oil rich in dehydrated sugar derivatives. The commonly used catalysts are inorganic acids (such as phosphoric acid and sulfuric acid), solid super acids, composite bimetallic, zeolite molecular sieves and the like. Although the addition of the catalyst can significantly improve the fast pyrolysis process of cellulose, the catalytic process has problems of difficult catalyst recovery, environmental pollution, high price and the like, and the large-scale industrial application of the catalytic process is limited. Therefore, there is a need for development of a method for producing an anhydrosugar derivative which is green, free of contamination, and inexpensive.

Oxalic acid, an organic carboxylic acid with a crystalline structure, has mild acidity. It is widely existed in plants, and the industrial production method is mature, so the price is low. More importantly, the oxalic acid can be completely decomposed under the condition of heating to form CO and CO₂And H₂O, so it is possible to try to use oxalic acid instead of the existing conventional catalysts for the selective preparation of dehydrated sugar mixtures.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide an environment-friendly method for preparing a dehydrated sugar mixture by co-pyrolysis of microcrystalline cellulose and oxalic acid.

The method specifically comprises the following steps:

taking microcrystalline cellulose and oxalic acid as raw materials, and mixing and contacting the microcrystalline cellulose and the oxalic acid; then carrying out fast co-pyrolysis at 200-500 ℃ under an anaerobic condition, wherein the heating time is not more than 20 minutes; and collecting the pyrolysis gas, and condensing to obtain a liquid product rich in the dehydrated sugar mixture.

Preferably, the mixing contact is mechanical mixing of microcrystalline cellulose with oxalic acid; and the mass ratio of the two components is 1: 10-10: 1.

Preferably, the mixing contact is to dip microcrystalline cellulose in an oxalic acid solution and then dry the solution, and the ratio of the two solutions is as follows: 1g, 1 mL-1 g, 1L, and oxalic acid concentration of 0.1 mol/L-2 mol/L.

The dehydrated sugar mixture comprises levoglucosan, levoglucosone, 1, 4; 3, 6-dianhydro-alpha-D-glucopyranose, 2-formyl-1, 4; 3, 6-dianhydro-alpha-D-glucopyranose, 1, 5-anhydro-4-deoxy-D-glycero-hex-1-ene-3-psicose and 1-hydroxy-3, 6-dioxabicyclo [3.2.1] -2-octanone, and is levoglucosone, 1, 4; 3, 6-dianhydro- α -D-glucopyranose and 2-formyl-1, 4; 3, 6-dianhydro-alpha-D-glucopyranose is the main product.

The anaerobic condition is to maintain the reaction system under the inert anaerobic protective gas environment.

The pyrolysis reaction is to place the raw materials into a reactor constant-temperature area after the reactor is preheated to a set pyrolysis temperature; or placing the raw materials into a constant temperature area of a reactor at room temperature, and then rapidly heating the reactor to a set temperature at a heating rate of not less than 100 ℃/s.

The invention has the beneficial effects that:

the invention mixes microcrystalline cellulose and oxalic acid for contact and carries out co-pyrolysis to prepare a liquid product rich in dehydrated sugar mixture. Oxalic acid is common and easy to obtain, and cellulose can be converted into levoglucosenone and 1,4 in a pyrolysis process with extremely high selectivity; anhydrosugars such as 3, 6-dianhydro- α -D-glucopyranose and 2-formyl-1, 4; mixture of anhydrosugars with 3, 6-dianhydro-alpha-D-glucopyranose as main product, with decomposition of oxalic acid to CO in pyrolysis₂CO and H₂O, can not remain in solid phase, liquid phase or gas phase products, and the pyrolysis process is green, efficient and pollution-free.

Detailed Description

The invention provides a method for preparing a green dehydrated sugar mixture, which is further described by combining the specific embodiment. It should be understood that the following detailed description is illustrative of the invention only and is not intended to limit the scope of the invention.

The liquid product yield calculation method in the following examples is as follows:

liquid product yield-mass of collected liquid product-mass sum of mass of cellulose and oxalic acid.

In the following examples, the content of the dehydrated sugar mixture was analyzed by a gas chromatography/mass spectrometer and quantified by an external standard method, and the yield and selectivity of the dehydrated sugar mixture were calculated as follows:

yield of single anhydrosugar product ═ mass of single anhydrosugar product ÷ mass of cellulose;

yield of anhydrosugar mixture-the sum of the yields of all anhydrosugar products;

the selectivity of the single anhydrosugar product ═ mass of single anhydrosugar product ÷ mass of organic liquid product (organics in the liquid product excluding moisture);

selectivity of the anhydrosugar mixture is the sum of the selectivities of all anhydrosugar products.

The percentages in the following examples are by mass unless otherwise specified.

The experimental procedures in the following examples are conventional unless otherwise specified.