Method for preparing acid by catalyzing alkali oxidation through primary alcohol

Abstract

The invention relates to the technical field of fine chemical engineering, in particular to a method for preparing acid through primary alcohol catalytic alkali oxidation. The method comprises the following steps: carrying out oxidation reaction by utilizing primary alcohol, a catalyst and strong alkali, and sequentially carrying out acidification treatment, extraction, brine treatment and rectification on a reaction product to prepare the organic acid, reaction devices used in the method are as follows: the reaction devices comprise a reaction kettle used for oxidation reaction, a condenser, an acidification kettle used for acidification treatment, an extraction kettle used for extracting acidification products, a salt forming kettle used for carrying out salt water treatment on extracted substances, and an extraction agent recovery kettle used for recovering the organic acid, and the rectifying still is used for purifying the organic acid. The method for preparing the organic acid has the advantages of high conversion rate, high selectivity and high product yield. Meanwhile, the reaction is a replacement reaction, the by-product is hydrogen, the danger coefficient is low, the by-product is easy to treat, and the influence on the environment is low.

Description

Technical Field

[0001] The present application relates to the technical field of fine chemicals, and in particular to a method for producing acid by catalytic alkaline oxidation of primary alcohols. Background Art

[0002] At present, the alcohol oxidation acid production methods commonly used by enterprises mainly include potassium permanganate oxidation, potassium dichromate oxidation and nitric acid high-temperature oxidation. Among them, potassium permanganate oxidation and potassium dichromate oxidation react violently during the reaction process, and the temperature is difficult to control. In addition, since they are strong oxidants and the oxidation temperature is high, many by-products will be produced, which will affect the purification and yield of the product, and the oxidation waste liquid cannot be treated. Nitric acid high-temperature oxidation is unstable, which can easily lead to unstable product quality, produce low-molecular acids, and have many product by-products, affecting purity and yield.

[0003] Therefore, it is urgent to develop a method for producing acid by alcohol oxidation, which has a low risk factor in the preparation process, high conversion rate and selectivity, high product yield, easy treatment of by-products, and low impact on the environment. Summary of the invention

[0004] The present application provides a method for preparing acid by catalytic alkali oxidation of primary alcohol. The method of the present application is used to prepare organic acid with high conversion rate and selectivity and high product yield. At the same time, the reaction of the present application is a displacement reaction, the byproduct is hydrogen, the risk factor is low, and the byproduct is easy to handle, with low impact on the environment.

[0005] The present application utilizes a small-scale oxidation reactor, into which primary alcohol, catalyst, and strong base are put in proportion to carry out a replacement reaction, and a replacement reaction product is obtained under a certain temperature and pressure, and then subjected to acidification treatment, extraction, brine treatment, and distillation to obtain an organic acid.

[0006] Taking propionic acid as an example, the preparation of propionic acid requires propanol at a low moisture content, with metal oxides (such as zinc oxide, copper oxide, magnesium oxide, barium oxide, etc.) as catalysts, and the reaction kettle temperature is heated to 200-260°C (preferably 210-245°C) and the pressure reaches 1.5-3.2MPa (preferably 2-3.2MPa) under the action of a strong base (such as sodium hydroxide) through heat transfer oil. The reaction is stabilized for 2 hours, and the hydrogen produced by the reaction is continuously discharged during the period to stabilize the pressure in the kettle to generate sodium propionate. Sodium propionate is dissolved and discharged by adding water, and sulfuric acid is added to the sodium salt solution to acidify and control the pH at about 2-3 to obtain a mixed solution of organic acid and sodium sulfate. The above mixed solution is extracted to separate the organic acid and the sodium sulfate aqueous solution, and the extractant containing the organic acid is recovered to complete the extraction, and the organic acid product is obtained by further distillation. Taking n-propanol as an example, the reaction equation is as follows: CH3CH2OH+NaOH→CH3CO2Na+2H2; 2CH3CO2Na+H2SO4→2CH3CO2H+Na2SO4.

[0007] Taking a 500mL small-scale oxidation reactor as an example, 50-65g of sodium hydroxide, 1.5-2.5g of metal oxide, and 180-250g of primary alcohol are added into the reactor. After heating for 3h and reacting for 2h, 78.5-180g of organic acid can be obtained after acidification treatment. About 65-139g of primary alcohol is discharged with the hydrogen and condensed and collected for reuse. The conversion rate is above 98%.

[0008] The present application provides a method for producing acid by catalytic alkali oxidation of primary alcohols, which adopts the following technical scheme: A method for preparing acid by catalytic alkali oxidation of primary alcohol, the method comprising: performing oxidation reaction using primary alcohol, catalyst and strong base, and then sequentially performing acidification treatment, extraction, brine treatment and distillation on the reaction product to prepare organic acid; The reaction device used in the method is as follows: The reaction device comprises a reaction kettle for performing oxidation reaction, a condenser, an acidification kettle for performing acidification treatment, an extraction kettle for extracting the acidification product, a salting kettle for treating the extracted substance with brine, an extractant recovery kettle for recovering the organic acid, and a rectification kettle for purifying the organic acid; The top of the reactor is connected to the condenser through a pipeline, and the bottom is connected to the acidification kettle and the extraction kettle in sequence through pipelines; the extraction kettle is connected to the salt-forming kettle, the extractant recovery kettle, and the distillation kettle in sequence through pipelines; the distillation kettle is connected to a vacuum component through the condenser.

[0009] Optionally, the reactor is provided with a jacket on the outside and a coil on the inside; the material in the reactor is heated by adding a heat source to the jacket and / or the coil.

[0010] Optionally, the temperature of the material in the reactor is controlled to be 200-260° C. by adding a heat source to the jacket and the coil; and the pressure in the reactor is 1.5-3.2 MPa.

[0011] Optionally, the heat source is thermal oil.

[0012] Optionally, the temperature of the heat transfer oil is 270-280°C.

[0013] Optionally, the condenser is a shell-and-tube condenser; optionally, the shell-and-tube condenser is divided into two stages, 25°C normal temperature water is introduced into the first stage refrigerant, and 0°C chilled brine is introduced into the second stage refrigerant.

[0014] Optionally, the acidification kettle is provided with an external jacket, and cooling water is passed into the jacket of the acidification kettle.

[0015] Optionally, the acidification reaction is completed by adding concentrated sulfuric acid dropwise into the acidification kettle until the pH value of the solution reaches 2-3.

[0016] Optionally, the weight ratio of the solution to be extracted and the extractant added to the extraction kettle is 1:(1-1.5).

[0017] Optionally, the reflux ratio of the extractant recovery kettle is controlled to be (1-3):1.

[0018] Optionally, the reflux ratio of the distillation kettle is controlled to be (1-4):1, and the pressure is controlled to be (-95)~(-99) KPa.

[0019] Optionally, the primary alcohol is any one of n-propanol, isobutanol, isopentanol, n-heptanol and isooctyl alcohol.

[0020] Optionally, the strong base is any one or more of sodium hydroxide and potassium hydroxide.

[0021] Optionally, the catalyst is selected from any one or more of zinc oxide, copper oxide, magnesium oxide and barium oxide.

[0022] In summary, the present application includes at least one of the following beneficial technical effects: The method of the present invention is used to prepare organic acids with high conversion rate, selectivity and product yield. At the same time, the reaction of the present invention is a replacement reaction, the byproduct is hydrogen, the risk factor is low, and the byproduct is easy to handle and has low impact on the environment.

[0023] The present application utilizes a small-scale oxidation reactor, into which primary alcohol, catalyst, and strong base are put in proportion to carry out a replacement reaction, and a replacement reaction product is obtained under a certain temperature and pressure, and then subjected to acidification treatment, extraction, brine treatment, and distillation to obtain an organic acid. DETAILED DESCRIPTION

[0024] Before describing the embodiments of the present application in detail, it should be understood that the terms used herein are only used for the purpose of describing specific embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by ordinary technicians in the field to which the terms belong.

[0025] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0026] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0027] In the present application, the terms "comprise" or "include" are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0028] The present application provides a method for preparing acid by catalytic alkali oxidation of primary alcohols, the method comprising: performing oxidation reaction using primary alcohols, catalysts and strong bases, and then sequentially performing acidification treatment, extraction, brine treatment and distillation on the reaction products to prepare organic acids; The reaction device used in the method is as follows: The reaction device comprises a reaction kettle for performing oxidation reaction, a condenser, an acidification kettle for performing acidification treatment, an extraction kettle for extracting the acidification product, a salting kettle for treating the extracted substance with brine, an extractant recovery kettle for recovering the organic acid, and a rectification kettle for purifying the organic acid; The top of the reactor is connected to the condenser through a pipeline, and the bottom is connected to the acidification kettle and the extraction kettle in sequence through pipelines; the extraction kettle is connected to the salt-forming kettle, the extractant recovery kettle, and the distillation kettle in sequence through pipelines; the distillation kettle is connected to a vacuum component through the condenser.

[0029] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiment of the present application will be clearly and completely described below. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. The embodiments described below are exemplary and are only used to explain the present application to illustrate catalyst components and preparation process, and cannot be interpreted as limiting the present application.

[0030] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0031] The present application is further described in detail below in conjunction with the embodiments and test results. Example Example 1

[0032] This embodiment provides a method for producing acid by catalytic alkali oxidation of a primary alcohol. In this embodiment, the primary alcohol is n-propanol.

[0033] The specific steps include: (1) The alkaline oxidation reactor is a 500 mL stainless steel jacketed reactor with a coil inside. 270°C heat transfer oil is passed through the jacket and the coil as a heat source. A stirring device is installed in the reactor. The hydrogen discharge pipe on the top of the reactor is connected to the condenser. The condenser condenses the n-propanol discharged with the hydrogen into the receiving tank.

[0034] 55 g of sodium hydroxide, 2.5 g of a metal oxide catalyst (zinc oxide in this embodiment) and 200 g of n-propanol were added into an alkaline oxidation reactor.

[0035] (2) Check the air tightness of the alkali oxidation reactor, replace the alkali oxidation reactor with nitrogen several times until the oxygen content is lower than 1%, close all valves on the alkali oxidation reactor, and continue to heat the alkali oxidation reactor.

[0036] When the temperature in the kettle reaches 180°C, stirring is started, and the pressure in the kettle reaches 2.7Mpa and hydrogen is discharged to generate sodium propionate and hydrogen. After the reaction stabilizes, the temperature in the kettle is maintained at 220-240°C and the pressure in the kettle is maintained at 3.0-3.2Mpa.

[0037] (3) After 2 hours of hydrogen discharge, the pressure in the kettle could not be maintained. The pressure was slowly released, the stirring device was turned off, and the unreacted n-propanol in the kettle was evaporated.

[0038] (4) Add a certain amount of soft water into the alkaline oxidation reactor and start stirring for about 30 minutes until the sodium propionate is completely dissolved to obtain a sodium propionate salt solution. Transfer the solution to temporary storage and cool it.

[0039] (5) The cooled sodium propionic acid salt solution is acidified with 98% sulfuric acid. When the pH value of the solution reaches about 2-3, the acidification is completed to obtain a mixed solution of sodium sulfate water and crude propionic acid.

[0040] (6) Extracting the mixed solution, the weight ratio of the added solution to be extracted to the added methyl tert-butyl ether is 1:(1-1.5). The sodium sulfate aqueous solution after extraction is treated with brine to obtain solid sodium sulfate. The crude propionic acid and methyl tert-butyl ether in the extractant solution are distilled and recovered.

[0041] (7) The crude propionic acid is distilled, and the light component material in the head section is extracted by controlling the reflux ratio. When the propionic acid content in the reflux reaches 99.5%, the extraction is switched to the qualified product receiving bottle. After the distillation is completed, about 56g of propionic acid with a content of more than 99.5% is obtained by weighing.

[0042] By content calculation, there are about 16g of propionic acid in the light component material in the first stage, and about 6g of propionic acid is not produced in the kettle, totaling about 78g. Example 2

[0043] This embodiment provides a method for producing acid by catalytic alkali oxidation of a primary alcohol. In this embodiment, the primary alcohol is isobutanol.

[0044] The difference between the above embodiment and embodiment 1 is that the parameters of the reactants and the reaction process are controlled as follows, which are consistent with those of embodiment 1.

[0045] The differences are as follows: In step (1), 52.5 g of sodium hydroxide, 2.2 g of a metal oxide catalyst (zinc oxide in this embodiment) and 220 g of isobutanol are added into an alkaline oxidation reactor.

[0046] In step (2), when the pressure in the autoclave reaches 2.5 MPa, hydrogen is discharged and sodium isobutyrate and hydrogen are generated by reaction. After the reaction is stable, the temperature in the autoclave is maintained at 225-240°C and the pressure in the autoclave is maintained at 2.5-2.8 MPa.

[0047] In step (3), after 2 hours of hydrogen discharge, the pressure in the kettle could not be maintained, and the pressure was slowly released, the stirring device was turned off, and the unreacted isobutanol in the kettle was evaporated.

[0048] In step (4), a certain amount of soft water is added to the alkaline oxidation reactor, and stirring is started for about 30 minutes until the sodium isobutyrate is completely dissolved to obtain a sodium isobutyrate salt solution, which is then transferred to temporary storage and cooled.

[0049] In step (5), the cooled sodium isobutyrate salt solution is acidified with 98% sulfuric acid. When the pH value of the solution reaches about 2-3, the acidification is completed to obtain a mixed solution of sodium sulfate water and crude isobutyric acid.

[0050] In step (6), the mixed solution is extracted, and the weight ratio of the added solution to be extracted to the added methyl tert-butyl ether is 1:(1-1.5). The sodium sulfate aqueous solution after extraction is treated with brine to obtain solid sodium sulfate. The extractant in the crude isobutyric acid and methyl tert-butyl ether solution is distilled and recovered.

[0051] In step (7), the obtained crude isobutyric acid is distilled, and the light component material of the head section is extracted by controlling the reflux ratio. When the isobutyric acid content in the reflux reaches 99.5%, the extraction is switched to the qualified product receiving bottle. After the distillation is completed, about 88g of isobutyric acid with a content of more than 99.5% is obtained by weighing.

[0052] By content calculation, there are about 12.6g of isobutyric acid in the light component material in the first stage, and about 6.1g of isobutyric acid is not produced in the kettle, totaling about 106.7g. Example 3

[0053] This embodiment provides a method for producing acid by catalytic alkali oxidation of a primary alcohol. In this embodiment, the primary alcohol is isopentanol.

[0054] The difference between the above embodiment and embodiment 1 is that the parameters of the reactants and the reaction process are controlled as follows, which are consistent with those of embodiment 1.

[0055] The differences are as follows: In step (1), 55 g of sodium hydroxide, 2 g of a metal oxide catalyst (zinc oxide in this embodiment) and 200 g of isoamyl alcohol are added into an alkaline oxidation reaction kettle.

[0056] In step (2), when the pressure in the autoclave reaches 1.8 MPa, hydrogen is discharged to generate sodium isovalerate and hydrogen. After the reaction stabilizes, the temperature in the autoclave is maintained at 210-245°C and the pressure in the autoclave is maintained at 2.0-2.5 MPa.

[0057] In step (3), after 2 hours of hydrogen discharge, the pressure in the kettle could not be maintained, so the pressure was slowly released, the stirring device was turned off, and the unreacted isoamyl alcohol in the kettle was evaporated.

[0058] In step (4), a certain amount of soft water is added to the alkaline oxidation reaction kettle, and stirring is started for about 30 minutes until the sodium isovalerate is completely dissolved to obtain a sodium isovalerate salt solution, which is then transferred to temporary storage and cooled.

[0059] In step (5), the cooled sodium isovaleric acid salt solution is acidified with 98% sulfuric acid. When the pH value of the solution reaches about 2-3, the acidification is completed to obtain a mixed solution of sodium sulfate water and crude isovaleric acid.

[0060] In step (6), the mixed solution is extracted, and the weight ratio of the added solution to be extracted to the added methyl tert-butyl ether is 1:(1-1.5). The sodium sulfate aqueous solution after extraction is treated with brine to obtain solid sodium sulfate. The crude isovaleric acid and methyl tert-butyl ether in the extractant solution are distilled and recovered.

[0061] In step (7), the obtained crude isovaleric acid is distilled, and the light component material of the head section is extracted by controlling the reflux ratio. When the isovaleric acid content in the reflux reaches 99.5%, the extraction is switched to the qualified product receiving bottle. After the distillation is completed, about 102.3 g of isovaleric acid with a content of more than 99.5% is obtained by weighing.

[0062] By content calculation, there are about 13.1g of isovaleric acid in the light component material in the head stage, and about 4.8g of isovaleric acid is not produced in the kettle, totaling about 120.2g. Example 4

[0063] This embodiment provides a method for producing acid by catalytic alkali oxidation of a primary alcohol. In this embodiment, the primary alcohol is isooctyl alcohol.

[0064] The difference between the above embodiment and embodiment 1 is that the parameters of the reactants and the reaction process are controlled as follows, which are consistent with those of embodiment 1.

[0065] The differences are as follows: In step (1), 57.5 g of sodium hydroxide, 1.5 g of a metal oxide catalyst (zinc oxide in this embodiment) and 225 g of isooctyl alcohol are added into an alkaline oxidation reaction kettle.

[0066] In step (2), when the pressure in the autoclave reaches 2.3 MPa, hydrogen is discharged and sodium isooctanoate and hydrogen are generated by reaction. After the reaction is stable, the temperature in the autoclave is maintained at 240-255°C and the pressure in the autoclave is maintained at 2.4-2.7 MPa.

[0067] In step (3), after 2 hours of hydrogen discharge, the pressure in the kettle could not be maintained, and the pressure was slowly released, the stirring device was turned off, and the unreacted isooctyl alcohol in the kettle was evaporated.

[0068] In step (4), a certain amount of soft water is added to the alkaline oxidation reactor, and stirring is started for about 30 minutes until the sodium isooctanoate is completely dissolved to obtain a sodium isooctanoate salt solution, and the solution is transferred to temporary storage and cooled.

[0069] In step (5), the cooled sodium isooctanoic acid salt solution is acidified with 98% sulfuric acid. When the pH value of the solution reaches about 2-3, the acidification is completed to obtain a mixed solution of sodium sulfate water and crude isooctanoic acid. The mixture is allowed to stand for stratification, wherein the upper layer is the crude isooctanoic acid solution and the lower layer is the mixed solution of sodium sulfate water and a very small amount of isooctanoic acid.

[0070] In step (6), the above-mentioned layered solutions are separated, and the lower layer of sodium sulfate aqueous solution after separation is treated with brine to obtain solid sodium sulfate.

[0071] In step (7), the crude isooctanoic acid in the upper layer is distilled, and the light component material in the head section is extracted by controlling the reflux ratio. When the isooctanoic acid content in the reflux reaches 99.5%, the extraction is switched to the qualified product receiving bottle. After the distillation is completed, about 158.4 g of isooctanoic acid with a content of more than 99.5% is obtained by weighing.

[0072] By content calculation, there are about 9.8g of isooctanoic acid in the light component material in the first stage, and about 6.6g of isooctanoic acid is not produced in the kettle, totaling about 174.8g.

[0073] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing acid by catalytic alkali oxidation of primary alcohols, characterized in that: The method comprises: using primary alcohol, catalyst and strong base to carry out oxidation reaction, and then subjecting the reaction product to acidification treatment, extraction, brine treatment and rectification in sequence to obtain organic acid; The reaction device used in the method is as follows: The reaction device comprises a reaction kettle for performing oxidation reaction, a condenser, an acidification kettle for performing acidification treatment, an extraction kettle for extracting the acidification product, a salting kettle for treating the extracted substance with brine, an extractant recovery kettle for recovering the organic acid, and a rectification kettle for purifying the organic acid; The top of the reactor is connected to the condenser through a pipeline, and the bottom is connected to the acidification kettle and the extraction kettle in sequence through pipelines; the extraction kettle is connected to the salt-forming kettle, the extractant recovery kettle, and the distillation kettle in sequence through pipelines; the distillation kettle is connected to a vacuum component through the condenser.

2. The method according to claim 1, characterized in that: The reactor is provided with a jacket outside and a coil inside; the material in the reactor is heated by adding a heat source to the jacket and / or the coil; Optionally, the temperature of the material in the reactor is controlled to be 200-260° C. by adding a heat source to the jacket and the coil; the pressure in the reactor is 1.5-3.2 MPa; Optionally, the heat source is thermal oil; Optionally, the temperature of the heat transfer oil is 270-280°C.

3. The method according to claim 1, characterized in that: The condenser is a shell-and-tube condenser; optionally, the shell-and-tube condenser is divided into two stages, the first stage refrigerant is fed with 25°C normal temperature water, and the second stage refrigerant is fed with 0°C chilled brine.

4. The method according to claim 1, characterized in that: The acidification kettle is provided with an external jacket, and cooling water is introduced into the jacket of the acidification kettle; Optionally, the acidification reaction is completed by adding concentrated sulfuric acid dropwise into the acidification kettle until the pH value of the solution reaches 2-3.

5. The method according to claim 1, characterized in that The weight ratio of the solution to be extracted and the extractant added to the extraction kettle is 1:(1-1.5).

6. The method according to claim 1, characterized in that The reflux ratio of the extractant recovery kettle is controlled to be (1-3):

1.

7. The method according to claim 1, characterized in that The reflux ratio of the distillation kettle is controlled to be (1-4):1, and the pressure is (-95)~(-99) KPa.

8. The method according to claim 1, characterized in that: The primary alcohol is any one of n-propanol, isobutanol, isopentanol, n-heptanol and isooctyl alcohol.

9. The method according to claim 1, characterized in that: The strong base is any one or more of sodium hydroxide and potassium hydroxide.

10. The method according to claim 1, characterized in that The catalyst is selected from any one or more of zinc oxide, copper oxide, magnesium oxide and barium oxide.