A method and device for continuously synthesizing levulinic acid

Abstract

The present invention discloses a method and device for continuously synthesizing levulinic acid, the method comprising: adding a compound aqueous solution having a mass concentration of 0.1% to 50% to a closed container filled with acidic catalyst particles, reacting for 10s-30min under the conditions of 50-200°C and 0-3MPa, and obtaining levulinic acid. The device comprises a raw material tank, a raw material pump, a filling microreactor, and a back pressure valve; the filling microreactor is a closed container filled with acidic catalyst particles, the liquid outlet of the raw material tank is connected to the liquid inlet of the filling microreactor, the raw material tank is provided with a raw material pump on the connecting pipeline of the filling microreactor, and the outlet pipeline of the filling microreactor is provided with a back pressure valve. The device and method of the present invention realize the continuous production of synthetic levulinic acid.

Description

Technical Field

[0001] The invention relates to a method and a device for continuously synthesizing levulinic acid, belonging to the field of biomass catalytic conversion. Background Art

[0002] Levulinic acid is a high value-added biomass-derived platform chemical and has been selected by the U.S. Department of Energy as one of the 12 most valuable platform compounds. Levulinic acid is mainly used to produce γ-valerolactone (GVL), aminolevulinic acid (DALA), diphenolic acid (DPA), methyltetrahydrofuran, various ester chemicals and resins, etc. It can be widely used in medicine, food, energy and chemical industries. Levulinic acid is mainly derived from the acid-catalyzed reaction of monosaccharides (glucose, fructose, xylose, etc.). For glucose and xylose, they are first isomerized through the Lewis acid site of the catalyst, and then based on The acid sites catalyze and undergo dehydration and hydration reactions to produce levulinic acid. Compared with glucose and xylose, the conversion of fructose to levulinic acid is considered to be a more feasible reaction mode because of its short reaction path (fructose → 5-hydroxymethylfurfural → levulinic acid) and high yield.

[0003] Based on the traditional stirred tank reactor, a higher yield of levulinic acid (up to 80%) can be obtained under the action of catalysts such as sulfuric acid, hydrochloric acid, phosphoric acid, and transition metal chlorides. However, the disadvantages of using homogeneous acid catalysts are well known: severe corrosion of equipment, difficulty in separating products caused by the use of a large amount of homogeneous catalysts, and environmental pollution. The use of solid acid catalysts can effectively reduce the corrosion of reaction equipment, and has the characteristics of easy recovery and recycling, and is also conducive to the separation and refining of reactants and products. In addition, the fluid backmixing of intermittent reactors (such as reactors) is large, the fluid diffusion distance in the reactor is long, and the mass transfer and heat transfer rate is slow, resulting in low reactant conversion rate and target product yield, and long reaction time, especially when using green solvent pure water. In addition, the reaction temperature and pressure of fructose conversion to levulinic acid are relatively high (70-220°C, 0-3MPa), and large intermittent stirred tank reactors have safety hazards. In recent years, packed microreactors have received extensive attention. Their solid-supported catalyst particles are small in size, have fast mixing and excellent liquid-solid transfer characteristics, and maintain the original fixed bed plug flow characteristics (backmixing is close to 0), making them easy to produce continuously and scale up. The packed microreactor is used in the conversion of fructose to levulinic acid, which can effectively strengthen the liquid-solid reaction process, significantly shorten the reaction time, and is easy to industrially produce continuously and scale up. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of low reaction efficiency, long reaction time, difficulty in continuous production and low safety in the traditional intermittent levulinic acid synthesis process, and to propose a method and device for continuously synthesizing levulinic acid.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A method for continuously synthesizing levulinic acid of the present invention, the specific synthesis steps are as follows:

[0007] Adding a compound aqueous solution with a mass concentration of 0.1% to 50% to a closed container filled with acidic catalyst particles, reacting for 10s to 30min at 50 to 200°C and 0 to 3MPa to obtain levulinic acid; the addition flow rate of the compound aqueous solution is 0.01ml / min to 20ml / min;

[0008] The compound aqueous solution is a fructose aqueous solution or a 5-hydroxymethylfurfural aqueous solution;

[0009] The acidic catalyst particles are ion exchange resin catalysts; preferably Amberlyst 15 particles, Amberlyst 70 particles, HND-8 particles, HND-12 particles or HND-580 particles;

[0010] The diameter of the acidic catalyst particles is 50 μm-2000 μm, preferably 100 μm-500 μm.

[0011] The mass concentration of the compound aqueous solution is preferably 1%-10wt%.

[0012] The addition rate of the aqueous solution of the compound is preferably 0.05-3 ml / min.

[0013] The reaction temperature and pressure are preferably 100-150°C, 1-2MPa.

[0014] The device for continuously synthesizing levulinic acid of the present invention comprises a raw material tank, a raw material pump, a filling microreactor, and a back pressure valve;

[0015] The filled microreactor is a closed container filled with acidic catalyst particles, and the upper end of the filled microreactor is provided with a liquid inlet, and the lower end is provided with a liquid outlet; the acidic catalyst particles are ion exchange resin catalysts; preferably Amberlyst 15 particles, Amberlyst 70 particles, HND-8 particles, HND-12 particles, HND-580 particles;

[0016] The diameter of the acidic catalyst particles is 50 μm-2000 μm, preferably 100 μm-500 μm;

[0017] The raw material tank is filled with a compound aqueous solution with a mass concentration of 0.1% to 50%, and the compound is a fructose aqueous solution or a 5-hydroxymethylfurfural aqueous solution;

[0018] The liquid outlet of the raw material tank is connected to the liquid inlet of the filled microreactor, a raw material pump is arranged on the connecting pipeline between the raw material tank and the filled microreactor, and a back pressure valve is arranged on the outlet pipeline of the filled microreactor.

[0019] The filled microreactor preferably adopts a vertically placed long cylindrical structure, and the aspect ratio of the filled microreactor is greater than 30.

[0020] The outer wall of the filled microreactor is sleeved with a heating pipeline.

[0021] Beneficial Effects

[0022] The device and method of the present invention improve the reaction efficiency of the levulinic acid synthesis process, shorten the reaction time, realize continuous production, and have high safety. The present invention utilizes the high liquid holding capacity and plug flow characteristics of the filled microreactor, strengthens the interphase transfer rate of the reaction process, effectively reduces the occurrence of intermediate products and side reactions, and the catalyst is easy to fix, separate and reuse. The reaction progress is controlled by accurately controlling the residence time, and the greenness and safety of the continuous synthesis process of levulinic acid are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the synthesis device of the present invention;

[0024] In the figure: 1-raw material tank, 2-raw material pump, 3-filling microreactor, 4-back pressure valve. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0026] Example 1

[0027] A method for continuously synthesizing levulinic acid is achieved by using a dedicated synthesis device, the device comprising: Figure 1 As shown, a raw material tank 1, a raw material pump 2, a filling type microreactor 3, and a back pressure valve 4;

[0028] The filled microreactor 3 is a closed container filled with spherical acidic catalyst particles. The closed container is a long cylindrical structure with an aspect ratio of 36. The upper end of the filled microreactor 3 is provided with a liquid inlet, the outer wall of the filled microreactor 3 is sleeved with a heating pipeline, and the lower end of the filled microreactor 3 is provided with a liquid outlet; the acidic catalyst particles are HND-580 particles; the diameter of the acidic catalyst particles is 500 μm;

[0029] The raw material tank 1 contains a fructose aqueous solution with a mass concentration of 8%. The raw material tank 1 is connected to the liquid inlet of the filled microreactor 3 through a pipeline. A raw material pump 3 is provided on the connecting pipeline between the raw material tank 1 and the filled microreactor 3, and a back pressure valve 4 is provided on the outlet pipeline of the filled microreactor 3.

[0030] The specific steps of continuous synthesis of levulinic acid in a filled microreactor are:

[0031] The raw material pump 2 is used to pump the 8% mass concentration fructose aqueous solution in the raw material tank 1 into the packed bed microreactor 3 at a flow rate of 0.1 ml / min, and the temperature in the packed microreactor 3 is heated to 150° C. The operating pressure of the back pressure valve 4 is adjusted to 1.5 MPa. After reacting for 8 minutes, the packed microreactor 3 discharges levulinic acid from the outlet pipeline. The conversion rate and yield of levulinic acid are calculated to be 99% and 65%, respectively.

[0032] Example 2

[0033] A method for continuously synthesizing levulinic acid is realized by using a special synthesis device, the device comprising: a raw material tank 1, a raw material pump 2, a filling microreactor 3, and a back pressure valve 4;

[0034] The filled microreactor 3 is a closed container filled with spherical acidic catalyst particles. The closed container is a long cylindrical structure with an aspect ratio of 36. The upper end of the filled microreactor 3 is provided with a liquid inlet, the outer wall of the filled microreactor 3 is sleeved with a heating pipeline, and the lower end of the filled microreactor 3 is provided with a liquid outlet; the acidic catalyst particles are HND-580 particles; the diameter of the acidic catalyst particles is 500 μm;

[0035] The raw material tank 1 is filled with a 5-hydroxymethylfurfural aqueous solution with a mass concentration of 10%. The raw material tank 1 is connected to the liquid port of the filled microreactor 3 through a pipeline. A raw material pump 3 is provided on the connecting pipeline between the raw material tank 1 and the filled microreactor 3, and a back pressure valve 4 is provided on the outlet pipeline of the filled microreactor 3.

[0036] The specific steps of continuous synthesis of levulinic acid in a filled microreactor are:

[0037] The raw material pump 2 is used to pump the 10% mass concentration 5-hydroxymethylfurfural aqueous solution in the raw material tank 1 into the packed bed microreactor 3 at a flow rate of 0.1 ml / min, and the temperature in the packed microreactor 3 is heated to 150° C. The operating pressure range of the back pressure valve 4 is adjusted to 2 MPa. After reacting for 8 minutes, the packed microreactor 3 discharges levulinic acid from the outlet pipeline. The conversion rate and yield of levulinic acid are calculated to be 100% and 99%, respectively.

[0038] Example 3

[0039] A method for continuously synthesizing levulinic acid is realized by using a special synthesis device, the device comprising: a raw material tank 1, a raw material pump 2, a filling microreactor 3, and a back pressure valve 4;

[0040] The filled microreactor 3 is a closed container filled with spherical acidic catalyst particles. The closed container is a long cylindrical structure with an aspect ratio of 36. The upper end of the filled microreactor 3 is provided with a liquid inlet, the outer wall of the filled microreactor 3 is sleeved with a heating pipeline, and the lower end of the filled microreactor 3 is provided with a liquid outlet; the acidic catalyst particles are Amberlyst 15 particles; the diameter of the acidic catalyst particles is 500 μm;

[0041] The raw material tank 1 contains a fructose aqueous solution, which is connected to the liquid port of the filled microreactor 3 through a pipeline. A raw material pump 3 is provided on the connecting pipeline between the raw material tank 1 and the filled microreactor 3, and a back pressure valve 4 is provided on the outlet pipeline of the filled microreactor 3.

[0042] The specific steps of continuous synthesis of levulinic acid in a filled microreactor are:

[0043] The raw material pump 2 is used to pump the 2% mass fraction fructose aqueous solution in the raw material tank 1 into the packed bed microreactor 3 at a flow rate of 0.2 ml / min, and the temperature in the packed microreactor 3 is heated to 150° C. The operating pressure range of the back pressure valve 4 is adjusted to 3 MPa. After reacting for 6 minutes, the packed microreactor 3 discharges levulinic acid from the outlet pipeline. The conversion rate and yield of levulinic acid are calculated to be 98% and 74.9%, respectively.

Claims

1. A method for continuously synthesizing levulinic acid, characterized in that The specific synthesis steps are as follows: A 10% mass concentration of 5-hydroxymethylfurfural aqueous solution was added to a packed microreactor filled with acidic catalyst particles, and reacted for 480 seconds at 150° C. and 2 MPa to obtain levulinic acid; the addition flow rate of the compound aqueous solution was 0.1 ml / min; The acidic catalyst particles are HND-580 particles, and the particle size is 500 μm; The filled microreactor adopts a vertically or horizontally placed long cylindrical structure, and the aspect ratio of the filled microreactor is 36; a back pressure valve is arranged on the outlet pipeline of the filled microreactor, and a heating pipeline is sleeved on the outer wall of the filled microreactor.

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