阅读说明：本技术 一种在微反应器中连续合成硝酸异辛酯并萃取其中残余酸的方法 (Method for continuously synthesizing isooctyl nitrate and extracting residual acid in isooctyl nitrate in microreactor ) 是由 陈光文 张奇 焦凤军 尧超群 于 2019-05-15 设计创作，主要内容包括：一种在微反应器中连续合成硝酸异辛酯并萃取其中残余酸的方法,以异辛醇和硫/硝摩尔比为1.5～2.5的混酸为原料在第一微反应器通过硝化反应,生成硝酸异辛酯和废酸,经液-液自动分离器分离出含酸的硝酸异辛酯粗品；该粗品与NaOH水溶液在第二微反应器内混合,进而反应萃取其中的残余酸,水油分离后得到酸含量极低的硝酸异辛酯。萃取效率高于96％。本发明实现了硝酸异辛酯合成与除酸的连续化操作,降低了危险等级且减少了除酸耗时、提高了生产效率。(A method for continuously synthesizing isooctyl nitrate and extracting residual acid in the isooctyl nitrate in a microreactor comprises the steps of carrying out nitration reaction on isooctyl nitrate and mixed acid with a sulfur/nitrate molar ratio of 1.5-2.5 serving as raw materials in a first microreactor to generate isooctyl nitrate and waste acid, and separating out a crude product of the isooctyl nitrate containing acid by a liquid-liquid automatic separator; and mixing the crude product with a NaOH aqueous solution in a second microreactor, further reacting and extracting residual acid in the crude product, and separating water from oil to obtain isooctyl nitrate with extremely low acid content. The extraction efficiency is higher than 96%. The method realizes continuous operation of isooctyl nitrate synthesis and deacidification, reduces the danger level, reduces the time consumption of deacidification and improves the production efficiency.)

1. A method for continuously synthesizing isooctyl nitrate is characterized by comprising two steps of isooctyl nitrate synthesis and extraction deacidification, and comprises the following specific steps:

(1) synthesis of isooctyl nitrate: introducing nitric-sulfur mixed acid and isooctyl alcohol into a first microreactor according to a proportion to perform a synthesis reaction to generate isooctyl nitrate and a waste acid mixture, and separating an acid-containing isooctyl nitrate crude product and waste acid from the isooctyl nitrate and waste acid mixture by a liquid-liquid automatic separator I; the mixed acid of nitric acid and sulfuric acid is a mixed solution of nitric acid and sulfuric acid;

(2) and (3) extraction and deacidification: and (2) introducing alkali liquor and the isooctyl nitrate crude product obtained in the step (1) into a second microreactor, mixing and reacting to extract residual acid, and separating by using a liquid-liquid automatic separator II to obtain the isooctyl nitrate product.

2. The method according to claim 1, wherein the reaction temperature of the synthesis reaction in the step (1) is 30-60 ℃, and the reaction residence time is 20-40 seconds; in the nitric-sulfuric mixed acid, the molar ratio of sulfuric acid to nitric acid is 1.5-2.5: 1; the molar ratio of the nitric acid to the isooctyl alcohol is 1.0-1.5: 1.

3. The method according to claim 1, wherein the reaction temperature for extracting the residual acid in the step (2) is 15-25 ℃, and the reaction residence time is 10-20 seconds; the molar concentration of the alkali liquor is 0.2-1.5 mol/L; the volume flow ratio of the alkali liquor to the isooctyl nitrate crude product is 1-3: 1.

4. The method according to claim 4, wherein the flow rate of the isooctyl nitrate crude product in the step (2) into the second microreactor is the same as the flow rate of the isooctyl alcohol into the first reactor in the step (1).

5. The method according to claim 3 or 5, wherein the hydraulic diameter of the single and/or multiple channels in the first and/or second microreactor is 100-1500 μm.

6. The method according to claim 1 or 4, characterized in that the lye is a NaOH solution or a KOH solution.

Technical Field

The invention relates to a method for synthesizing and refining isooctyl nitrate, in particular to a method for continuously synthesizing isooctyl nitrate and removing residual acid in isooctyl nitrate by utilizing a micro-reaction technology.

Background

Isooctyl nitrate (EHN for short) has the molecular formula: (C)₈H₁₇O)NO₂The 2-ethylhexyl nitrate is an important liquid energetic material in nitrate compounds, is a diesel cetane number improver which is widely applied and has high cost performance, can participate in a degradation branch reaction before fuel ignition, shortens the chemical stagnation period of the fuel, and has important significance for improving the fuel performance.

In the existing production technology of isooctyl nitrate, a nitric-sulfuric acid-mixed method is generally adopted in a tank reactor, isooctyl alcohol is dripped into nitric-sulfuric acid-mixed acid in a slow dripping mode at normal temperature or below (10-25 ℃) so as to directly mix and stir a separated isooctyl nitrate crude product and alkali liquor/water, and the required product requirements are met through multiple alkali washing and water washing, then settlement separation and drying for dewatering. The production technology has a series of problems and hidden dangers: firstly, the slow dripping mode consumes long time, the long production period limits the industrial application of the EHN, and the synthesis of the EHN is difficult to realize quickly and efficiently; secondly, because the initial decomposition temperature of isooctyl nitrate can be reduced and the thermal sensitivity can be improved under the condition of existence of concentrated sulfuric acid or mixed acid, the danger of explosion can be caused when the temperature is higher than 30 ℃, even if kettle-type dripping is adopted, the local overheating phenomenon caused by incomplete mixing, incapability of timely removing reaction heat and the like can not be completely avoided, so that the side reaction and the reaction runaway phenomenon can be caused, and the accidents occur in China; thirdly, after dropwise synthesis and separation, repeated alkali washing and water washing, and drying and dewatering, the whole process is intermittent and tedious, consumes a large amount of manpower and material resources, and has high production cost, low efficiency and high danger.

The invention patent application document CN 109280007A discloses a method for continuously synthesizing isooctyl nitrate by utilizing a microreactor, wherein the reaction temperature needs to be kept low, excessive waste acid is generated due to overhigh sulfur/nitrate of nitric-sulfuric mixed acid, and the problems of high energy consumption and high pollution exist in the whole nitration and extraction deacidification process.

Therefore, the integrated process of continuous and safe synthesis and refining of EHN is beneficial to process safety and product quality improvement, and the micro-reaction nitration technology and the micro-extraction technology are the most effective ways for solving the problem.

Disclosure of Invention

Aiming at the defects of long reaction time, high danger level, untimely deacidification and the like existing in the synthesis and the refining of EHN in a tank reactor, the invention provides a method for continuously synthesizing isooctyl nitrate and extracting residual acid in the isooctyl nitrate by utilizing a micro-reaction technology, which can quickly and efficiently synthesize EHN and extract the residual acid in the EHN. The adopted technical scheme mainly comprises two steps of isooctyl nitrate synthesis and extraction deacidification, and comprises a process of separating oil-water two phases formed in the two steps by a liquid-liquid automatic separator, wherein the synthesis step is used for synthesizing an isooctyl nitrate crude product containing acid, and the extraction deacidification step is used for reducing the acid content in the isooctyl nitrate crude product, and specifically comprises the following steps:

1) preparing mixed raw materials: mixing concentrated sulfuric acid with the concentration of 98% and fuming nitric acid with the concentration of 98% into nitric-sulfuric mixed acid according to the molar ratio of 1.5-2.5 for later use;

2) preparing an alkali solution: preparing an alkali solution with the concentration of 0.2-1.5 mol/L for later use; the alkali is sodium hydroxide or potassium hydroxide;

and (3) synthesis of isooctyl nitrate:

3) and (3) introducing the nitric-sulfuric mixed acid and isooctanol into a first microreactor, reacting nitric acid in the nitric-sulfuric mixed acid with isooctanol to generate isooctyl nitrate, and using sulfuric acid as a catalyst to be not reacted. The molar ratio of nitric acid to isooctanol of the reactant at the inlet of the microchannel is 1.0-1.5, preferably 1.1-1.3; the constant temperature reaction at 30-60 ℃ in the first microreactor is realized through water bath, and the preferable temperature is 40-60 ℃; the residence time of the reaction mixture in the microreactor is 20-40 s, preferably 25-35 s.

4) In the scheme, the sulfur/nitrate molar ratio of the mixed nitric acid and sulfuric acid is 1.5-2.5, preferably 1.8-2.2; the microreactor may be in the form of a single channel or a multi-channel.

5) Because the automatic separator has a certain volume space, before the separator can stably separate two phases of waste acid and isooctyl nitrate, the synthesis stage in the step 3) needs to be operated for a period of time, preferably 20-30min, till the two phases can be stably separated, and then the next extraction deacidification step is started.

Extraction deacidification of isooctyl nitrate

6) Mixing the isooctyl nitrate crude product obtained by the separation in the step 5) with the alkali solution prepared in the step 2) in a second microreactor, performing reactive extraction on residual acid, and obtaining EHN with low acid content by a liquid-liquid automatic separator, thereby further refining. The reaction is carried out at room temperature, and the volume flow ratio of the alkali solution to the isooctyl nitrate crude product is 1-3, preferably 2-3; the residence time of the reaction mixture in the microreactor is 10-20 seconds(s), and preferably 15-20 s.

7) The molar concentration of the alkali solution in the step 6) is 0.2-1.5 mol/L, preferably 0.2-1.0 mol/L; the flow rate of the crude isooctyl nitrate in the oil phase is kept consistent with the feeding flow rate of isooctyl alcohol in the step 3).

8) The second micro-reactor may be a single-channel or multi-channel type, the hydraulic diameter of the single-channel and/or multi-channel is 100-1500 μm, preferably 500-1000 μm, and the most preferred hydraulic diameter is 600-800 μm.

The alkaline solution of the invention is replaced by NaOH solution, KOH solution or other reagents with alkaline property.

The automatic separator is a column type double-liquid phase (such as oil phase and acid/water phase) separation device, the lower layer is a heavy phase layer H2, the upper layer is a light phase layer H1, and the positions of light phase and heavy phase outlets meet the following relations:

H₁*ρ₁+H₂*ρ₂＝H*ρ₂

H＝H₁+H₂-d

where ρ is₁、ρ₂The density of the light phase and the density of the heavy phase are respectively, and d is the height difference of two outlets of the light phase and the heavy phase.

The microreactor comprises parallel microchannels for fluid mixing and reaction, each microchannel has the same size, length and structure, and the characteristic dimension is sub-millimeter level, namely the inner diameter dimension of 0.1-1.5 mm, and particularly the workable dimension of 0.6-0.8 mm. The micro-scale characteristic of the microreactor enables the reaction of isooctanol and nitric acid and the reaction of sodium hydroxide and residual acid to obtain higher product yield and extraction efficiency under the process parameters, and the micro-scale of the reactor enables the specific surface area of the reactor to be large and the heat and mass transfer to be fast.

Advantageous effects

The invention provides a high-efficiency, low-energy-consumption and low-pollution synthesis method for the synthesis process of isooctyl nitrate, the purity of isooctyl nitrate is higher than 99.3 percent, and the yield is higher than 97.3 percent; meanwhile, the method for quickly extracting and removing the residual acid in the synthetic product is provided, and by adopting the method, the extraction efficiency of the residual acid in the EHN crude product can reach 96 percent, so that the problem of deacidification difficulty caused by long retention time of the crude product is avoided. After the acid is removed by the extraction of the microreactor, the acid removal rate of the product can further reach 100 percent, the acid content in the product is reduced to 0, and the product meets the indexes of superior products of SH/T0597-94 as a diesel cetane number improver.

Drawings

FIG. 1 is a process flow diagram for EHN synthesis and extraction deacidification: 1. the method comprises the following steps of (1) an isooctanol storage tank, (2) an acid mixing storage tank, (3) a metering pump, (4) a metering pump, (5) a first microreactor, (6) a constant-temperature water bath, (7) a waste acid storage tank, (8) a liquid-liquid separator, (9) a sodium hydroxide aqueous solution, (12) a first microreactor, (13) a waste alkali solution and (15) an isooctyl nitrate product.

Fig. 2 is a schematic structural diagram of the liquid-liquid automatic separator, wherein a is a heavy phase outlet, and b is a light phase outlet.

Detailed Description

The present invention will be described in further detail with reference to specific examples.