Method for coarse refining of lignin in straws by catalyzing ethanol with oxygen and application of method

Abstract

The invention belongs to the technical field of resource recycling, and particularly relates to a method for coarsely smelting lignin in straws by catalyzing ethanol with oxygen and application of themethod. According to the method, under the conditions of low temperature and low pressure, ethanol is catalyzed by oxygen to extract lignin. Compared with an existing catalytic ethanol pulping technology, the method has the advantages that the pulping process is safer, and the yield of lignin is higher. The method comprises the following steps: 1) adding crushed straws into a reaction kettle, andadding an ethanol water solution; 2) introducing oxygen into the reaction kettle, and sealing the reaction kettle after the air above the material is completely replaced by the oxygen; 3) heating andkeeping the temperature of the reaction kettle for reaction; 4) opening a valve of the reaction kettle to release pressure after the reaction is finished; 5) immediately filtering the mixture to separate the straws from the liquid after the pressure release is finished; 6) distilling the liquid to remove the ethanol and obtain a lignin mixture; and 7) hydrolyzing the lignin mixture to flocculateand precipitate the lignin, carrying out centrifugal operation, and performing freeze drying on the precipitate at the lower layer to obtain the lignin.

Description

technical field [0001] The invention belongs to the technical field of resource regeneration and utilization, and in particular relates to a method for using oxygen to catalyze ethanol to crudely refine lignin in straw and its application. Background technique [0002] There are about 1 billion tons of agricultural waste in my country every year, mainly wheat straw and rice straw, etc. Most of the wheat straw and rice straw are still at the level of rough processing or unprocessed. Straws such as wheat straw contain about 60% to 80% of cellulose and about 15% to 25% of lignin. If wheat straw or rice straw is burned directly, it will not only aggravate the severity of smog, but also cause agricultural waste. massive waste of biomass resources. [0003] At present, the effective utilization of agricultural waste is mainly to use wheat straw to make paper, and the more mature method is alkaline pulping. However, the high silicon content in non-wood biomass raw materials such ...

AI Technical Summary

Problems solved by technology

Since the acetyl group content in the hemicellulose of softwood raw materials is very small, it cannot produce autocatalytic effect

[0006] 2) The cooking temperature is too high and the operating pressure is too high

The pressure of 65% ethanol aqueous solution at 195°C can reach 2.3MPa, which obviously brings great operational risks

[0008] The acid-catalyzed ethanol pulping for the purpose of pulping is still kept at a relatively high temperature, and the acid in the solution system will not only cause corrosion of equipment, but also easily cause condensation of lignin and excessive degradation of carbohydrates, thereby reducing lignin Removal rate

In addition, the presence of inorganic acids adds to the difficulty in the chemical recovery process

In the base-catalyzed process, the delignification rate increases, but the degree of cellulose degradation is bound to increase, and there is also a bottleneck for chemical recovery

Salt catalysis can greatly reduce the cooking temperature and pressure under the premise of ensuring that the yield of fine pulp is similar to the Kappa value, but the holding time is prolonged by 1 hour, and the ethanol concentration is increased by 5%, which will inevitably affect the work efficiency and cost. There are defects such as difficulty in chemical recycling

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