CN104177247A - Method for preparation of formic acid by catalytic oxidation of biomass - Google Patents

Abstract

The invention provides a method for preparation of formic acid by catalytic oxidation of biomass, and according to the method, water is used as a medium, a water soluble metavanadate and inorganic acid mixture is used as a catalyst, under the effect of an oxidant, the biomass is converted into the formic acid. The method uses the cheap, abundant, renewable and large-amount natural biomass as a raw material for preparing the formic acid, the reaction condition is mild, the used catalytic system is cheap, high in catalytic activity and good in selectivity, and the yield of the target product formic acid is high.

Description

A method for preparing formic acid by catalytically oxidizing biomass

technical field

The invention relates to a method for preparing formic acid, in particular to a method for preparing formic acid by catalytically oxidizing biomass.

Background technique

At present, about 86% of my country's energy and 96% of organic chemicals are supplied by fossil fuels such as coal, oil and natural gas. On the one hand, the reserves of fossil fuel resources are limited and non-renewable, and the demand of human beings is constantly increasing, so that the supply of fossil fuels cannot meet the needs of human development. On the other hand, the environmental problems caused by the use of fossil fuels (such as excessive emission of CO ₂ and environmental pollution problems such as SO ₂ , NO _x , and heavy metals) have also attracted people's attention. Therefore, the development of clean and renewable energy has become an urgent research topic. Among them, biomass is the most abundant in nature, and the use of biomass resources has many advantages: (1) Biomass energy comes indirectly from solar energy, which is inexhaustible and inexhaustible; (2) Biomass is a renewable substance, The annual output is extremely large; (3) Zero emission of CO ₂ during the biomass combustion process, that is, the CO ₂ generated by combustion can be recycled and absorbed by plants; (4) The content of sulfur and heavy metals in the biomass is extremely low, and no pollution will be caused during the conversion process. environmental pollution. Therefore, the rational use of biomass can solve the energy and environmental problems faced by fossil fuels, so as to achieve the sustainable development of our society.

Formic acid is one of the basic raw materials of organic chemical industry, widely used in textile, printing and dyeing, electroplating, leather, medicine and rubber industries. At present, the main industrial preparation methods of formic acid include sodium formate method and carbon monoxide-methanol carbonylation method, but these two methods are all based on fossil fuel routes, so it is easy to cause serious pollution problems, and the energy consumption is high. With the supply of fossil fuels The economics of this process will become more pronounced with increasing scarcity and rising prices. Therefore, developing a path to efficiently prepare formic acid from biomass can not only meet the rapidly rising market demand for formic acid, but also promote the implementation of carbon emission reduction, reduce the consumption of fossil fuels, reduce environmental pollution, maintain ecological balance, and realize material The recycling of waste will be of great significance to the development of our country.

At present, there are some related reports on the production of formic acid from biomass. For example, Chinese patent application 200910199790.X discloses a method for hydrothermally reducing _CO2 to formic acid from carbohydrate biomass. Chinese patent application 201110099183.3 discloses a method for preparing acetone and calcium formate from biomass waste, which involves converting biomass into formic acid and acetic acid under severe reaction conditions, but the yield of formic acid is low and the energy consumption of the reaction is low High, the product is complex and difficult to separate. Chinese patent application 201080019836.6 discloses a method for producing formic acid from carbohydrate-containing materials. The method prepares formic acid by two-step acid hydrolysis of carbohydrates, but there are also problems such as low yield of formic acid and complex products.

There are many reports on the preparation of formic acid by catalytic oxidation of biomass in journal literature. Mcginnis et al. (GD Mcginnis, SE Prince, CJ Biermann, JT Lowrimore. Wet oxidation of model carbohydrate compounds. Carbohydr. Res., 1984, 128, 51? 60) used iron sulfate or copper sulfate as a catalyst to oxidize Cellulose yielded only 27.6 wt% formic acid yield. Wasserscheid et al. (J. Albert, R. Wolfel, A. Bosmann, P. Wasserscheid. Selective oxidation of complex, water-insoluble biomass to formic acid using additives as reaction accelerators. Energy Environ. Sci. 2012 , 5 , 7956–7962 ) reported the preparation of formic acid by using water-soluble heteropolyacid H ₅ PV ₂ Mo ₁₀ O ₄₀ as catalyst, using cellulose and hemicellulose as raw materials in aqueous medium, and the reaction time was 24 h~66 h. The yields can reach 40 wt% and 70 wt%, respectively. However, this method has defects such as complex operation, by-products, and low purity of formic acid.

Contents of the invention

In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for preparing formic acid by catalytically oxidizing biomass. The method directly uses biomass as a raw material, water as a medium, and oxygen or air as an oxidant. The method is a cheap , Green, renewable formic acid production method, laying the foundation for the industrialization process of biomass to prepare formic acid.

The present invention is achieved through the following technical solutions.

The invention provides a method for preparing formic acid by catalytically oxidizing biomass. The method comprises using water as a medium, using a mixture of water-soluble metavanadate and inorganic acid as a catalyst, and under the action of an oxidizing agent, the raw The step in which the substance is converted to formic acid.

In the above preparation method, the biomass is selected from one of glucose, fructose, xylose, sucrose, cellobiose, cellulose, hemicellulose, lignin, wheat straw, corn cob, bagasse, trees and leaves or more.

In the above preparation method, the metavanadate is sodium metavanadate or potassium metavanadate.

In the above preparation method, the inorganic acid is sulfuric acid, hydrochloric acid or phosphoric acid, preferably sulfuric acid.

In the above preparation method, the oxidizing agent is oxygen, and the initial pressure of oxygen is 1MPa~5MPa, preferably 2MPa~4MPa, more preferably 3MPa.

In the above preparation method, based on the amount of medium water, the amount of biomass added is 0.5 wt% to 20 wt%, preferably 1 wt% to 15 wt%, more preferably 1.7 wt% to 14 wt%.

In the above preparation method, based on the amount of medium water, the concentration of the metavanadate is 0.1 wt% ~ 1.5 wt%, preferably 0.2 wt% ~ 1 wt%.

In the above preparation method, based on the amount of medium water, the concentration of the inorganic acid is 0.1 wt% to 2 wt%, preferably 0.3 wt% to 1.5 wt%.

In the above preparation method, the reaction temperature is controlled at 100 ^oC ~ 200 ^oC , preferably 120 ^oC ~ 180 ^oC , more preferably 160 ^oC .

In the above-mentioned preparation method, the reaction time is 1min ~ 360min, preferably 1min ~ 330min, more preferably 120min.

In a specific embodiment, the present invention prepares the method for formic acid by catalytic oxidation biomass, comprises the steps:

(1) Add biomass (such as wheat straw), catalysts (such as sodium metavanadate and sulfuric acid), and deionized water into a high-temperature and high-pressure reactor (with a magnetic stirring device) with a volume of 25 mL, and fill it with an initial pressure of 3.0 Oxygen in MPa;

(2) Put the reaction kettle filled with the reaction materials in step (1) into the heating furnace, stir at a speed of 500 r/min, control the reaction temperature at 160°C, and stop the reaction immediately after reaching the reaction time, for example, 120 minutes reaction and analyze the product.

Biomass can produce formic acid under the oxidation of oxygen, but because there are many side reactions in the production of formic acid by oxygen oxidation of biomass without the action of a catalyst, the yield of formic acid in the final product is low. The method principle of the method for preparing formic acid by catalytic oxidation of biomass of the present invention is: by adding water-soluble metavanadate and inorganic acid in the water medium, the selectivity and yield of biomass conversion can be greatly improved; Under the action of metavanadate, VO ₂ ⁺ species will be generated after a series of hydrolysis and polymerization reactions. The vanadium-oxygen species with this structure has a strong oxidation ability, and it can quickly oxidize biomass, especially for the reaction of biomass oxidation to formic acid Very selective. This study found that while VO ₂ ⁺ oxidized the biomass, it was reduced to the form of tetravalent vanadium, that is, V ^IV O*, and then V ^IV O* was oxidized to VO ₂ ⁺ by the oxygen dissolved in the water phase to restore its oxidation ability . For polysaccharides such as cellulose and hemicellulose, the role of inorganic acid also includes hydrolyzing cellulose and hemicellulose, breaking its polymeric structure, and the monosaccharides produced can be quickly and highly selectively oxidized to formic acid.

According to one embodiment of the present invention, the technological process and operating method of preparing formic acid by catalytic oxidation of biomass provided by the present invention are as follows:

Add a certain amount of reaction materials, including biomass, metavanadate, inorganic acid, water, and oxygen, into a high-temperature and high-pressure reactor according to a certain ratio, and then put the reactor into a heating furnace with a set temperature for heating. And start stirring, after reaching the target temperature, count the time, control a certain reaction time, take out the reactor and put it in a cold water bath, the temperature of the reactor can quickly drop below 100 ℃ and the reaction is terminated.

In the above method for preparing formic acid by catalytically oxidizing biomass, the yield of formic acid depends on the type and concentration of the catalyst, initial pressure, reaction temperature, reaction time and other factors.

Compared with the method for preparing formic acid in industry at present, the inventive method has the following advantages:

First of all, this method uses cheap and abundant biomass as raw material, which can not only reduce the cost, but also avoid environmental pollution caused by the use of fossil resources. This method is based on renewable biomass resources, making this method feasible. Persistent;

Secondly, the method reaction condition of the present invention is gentle, and process is simple, and catalyst metavanadate and inorganic acid are all chemicals commonly used in industry, cheap and easy to obtain, and it can be predicted that this method has very high application potential;

Again, the present invention selects water-soluble metavanadate and inorganic acid as a catalyst to convert biomass to prepare formic acid, which not only has high catalytic activity and good selectivity, but also has a high yield of product formic acid;

Finally, the method of the present invention has mild operating conditions, a simple catalytic system that does not require synthesis steps, greatly increases the yield of product formic acid, and has no other by-products in the liquid phase, and the purity of formic acid is extremely high.

Claims (10)

1. prepare a method for formic acid by catalytic oxidizing biomass, the method comprises taking water as medium, using the mixture of water-soluble metavanadate and mineral acid as catalyzer, and under the effect of oxygenant, the step that is formic acid by Wood Adhesives from Biomass.

2. preparation method according to claim 1, it is characterized in that, described biomass are selected from glucose, fructose, wood sugar, sucrose, cellobiose, Mierocrystalline cellulose, hemicellulose, xylogen, one or more in wheat stalk, corn cob, bagasse, trees and leaf.

3. preparation method according to claim 1 and 2, is characterized in that, described metavanadate is sodium metavanadate or potassium metavanadate.

4. according to the preparation method described in any one in claims 1 to 3, it is characterized in that, described mineral acid is sulfuric acid, hydrochloric acid or phosphoric acid, is preferably sulfuric acid.

5. according to the preparation method described in any one in claim 1 to 4, it is characterized in that, described oxygenant is oxygen, and the original pressure of oxygen is 1 MPa ~ 5 MPa, is preferably 2 MPa ~ 4 MPa, more preferably 3 MPa.

6. according to the preparation method described in any one in claim 1 to 5, it is characterized in that, taking the consumption of WATER AS FLOW MEDIUM as benchmark, the add-on of described biomass is 0.5 wt% ~ 20 wt%, is preferably 1 wt% ~ 15 wt%, more preferably 1.7wt% ~ 14wt%.

7. according to the preparation method described in any one in claim 1 to 6, it is characterized in that, taking the consumption of WATER AS FLOW MEDIUM as benchmark, the concentration of described metavanadate is 0.1 wt% ~ 1.5 wt%, is preferably 0.2 wt% ~ 1 wt%.

8. according to the preparation method described in any one in claim 1 to 7, it is characterized in that, taking the consumption of WATER AS FLOW MEDIUM as benchmark, the concentration of described mineral acid is 0.1 wt% ~ 2 wt%, is preferably 0.3 wt% ~ 1.5 wt%.

9. according to the preparation method described in any one in claim 1 to 8, it is characterized in that, the temperature of reaction is controlled at 100 ^oC~ 200 ^oc, is preferably 120 ^oc ~ 180 ^oC, more preferably 160 ^oC.

10. according to the preparation method described in any one in claim 1 to 9, it is characterized in that, the reaction times is 1min ~ 360min, is preferably 1min ~ 330min, more preferably 120min.