System, process and matched catalyst for producing C6-C9 carboxylic acid by dehydrogenation of C6-C9 mixed alcohol

Abstract

The invention discloses a system, a process and a matched catalyst for producing C6-C9 carboxylic acid by dehydrogenation of C6-C9 mixed alcohol. The system comprises a feeding unit, a dehydrogenation reaction unit, an acidification unit, a standing separation unit, a washing unit, a graded rectification unit and a byproduct collection unit. A discharge port of the feeding unit is communicated with a feed port of the dehydrogenation reaction unit, a discharge port of the dehydrogenation reaction unit is communicated with a feed port of the acidification unit, an upper-layer oil phase outlet of the standing separation unit is communicated with a feed port of the water washing unit, a lower-layer water phase outlet of the standing separation unit is communicated with the byproduct collecting unit, and the byproduct collecting unit is communicated with the water washing unit. An oil phase outlet of the washing unit is communicated with a feed port of the graded rectification unit, the graded rectification unit comprises at least five rectification towers, and C6, C7, C8 and C9 carboxylic acid products are respectively obtained after graded purification by the multiple rectification towers of the graded rectification unit. According to the method, the C6-C9 carboxylic acid can be continuously prepared from the C6-C9 mixed alcohol, and the separation of the C6-C9 carboxylic acid is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical catalysis, and particularly to a system, a process and a supporting catalyst for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids. Background Art

[0002] C6-C9 carboxylic acids are a class of carboxylic acid compounds with important uses. They are usually colorless to light yellow liquids, have a specific odor at room temperature, can react with bases to form salts, react with alcohols to form esters, etc. C6-C9 carboxylic acids are sparingly soluble in water but usually have good solubility in organic solvents, which makes them have good solubility and reactivity in some organic synthesis reactions. They have a very wide market application and a very large demand. Among them, C6 carboxylic acids (such as n-hexanoic acid) have a wide range of uses. In the food industry, they can be used to produce products such as edible flavors and seasonings; in the pharmaceutical industry, n-hexanoic acid can be used as a raw material to produce drugs such as anti-cancer drugs; in the daily chemical industry, n-hexanoic acid can be used to produce fragrances, perfumes, etc.; in the chemical industry, n-hexanoic acid can be used as a surfactant additive, a lubricating oil thickener, a synthetic resin and rubber auxiliary, a metal working fluid, etc.; C7-C9 carboxylic acids are also widely used in the fields of drug synthesis, fragrances and food additives, organic synthesis, etc.

[0003] Currently, C6-C9 carboxylic acids are usually prepared by catalytic dehydrogenation of alcohols. And due to the different catalytic dehydrogenation effects of catalysts on different alcohols, usually only one alcohol is used to prepare the corresponding carboxylic acid during the preparation of C6-C9 carboxylic acids. For example, Chinese Patent Application CN118047672A discloses a new process and a supporting catalyst for producing isooctanoic acid, which uses a Sn / ZnO-Al 2 O 3 catalyst to achieve the dehydrogenation of isooctanol to produce isooctanoic acid. The conversion rate of isooctanol and the selectivity of isooctanoic acid are both very high, and the continuous production of isooctanoic acid is realized. However, for other alcohols, such as the dehydrogenation of isononanol to produce isononanoic acid, the conversion rate of isononanol and the selectivity of isononanoic acid are relatively low. C6-C9 mixed alcohols are common petrochemical products and often exist in the form of mixtures. Compared with the traditional method of first separating into single alcohol substances, respectively preparing the corresponding carboxylic acids and then separating the carboxylic acid products and the unreacted alcohols for the second time, directly reacting the C6-C9 mixture and then separating is more resource-saving. Therefore, if the C6-C9 mixed alcohols can be catalytically dehydrogenated to form the corresponding C6-C9 carboxylic acids and separated, the effective utilization of C6-C9 mixed alcohols can be realized. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a system, a process and a supporting catalyst for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids, which can realize the continuous preparation of C6-C9 carboxylic acids from C6-C9 mixed alcohols.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a system for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids, comprising a feeding unit, a dehydrogenation reaction unit, an acidification unit, a static separation unit, a water washing unit, a fractional distillation unit, and a by-product collection unit; the discharge port of the feeding unit is communicated with the feed port of the dehydrogenation reaction unit, the discharge port of the dehydrogenation reaction unit is communicated with the feed port of the acidification unit, the upper oil phase outlet of the static separation unit is communicated with the feed port of the water washing unit, the lower water phase outlet of the static separation unit is communicated with the by-product collection unit, the oil phase outlet of the water washing unit is communicated with the feed port of the fractional distillation unit, the fractional distillation unit comprises at least 5 distillation columns, and C6, C7, C8, and C9 carboxylic acid products are respectively obtained after being fractionally purified by the multiple distillation columns of the fractional distillation unit.

[0007] Further, the dehydrogenation reaction unit is a fixed bed reactor and / or a multi-stage series dehydrogenation reaction kettle. When the dehydrogenation reaction unit is a fixed bed reactor and a multi-stage series dehydrogenation reaction kettle, the fixed bed reactor is in parallel with the multi-stage series dehydrogenation reaction kettle.

[0008] Further, when the dehydrogenation reaction unit comprises a multi-stage series dehydrogenation reaction kettle, the discharge port of the last-stage dehydrogenation reaction kettle is sequentially connected with a buffer unit and a dissolution and filtration unit, and the water phase outlet of the water washing unit is connected to the water inlet of the dissolution and filtration unit. The liquid phase discharge port of the dissolution and filtration unit is communicated with the feed port of the acidification unit, and the solid catalyst collected at the solid phase discharge port of the dissolution and filtration unit is added to the feeding unit.

[0009] Further, when the dehydrogenation reaction unit is a parallel connection of a fixed bed reactor and a multi-stage series dehydrogenation reaction kettle, 2 feeding units are provided, and the discharge ports of the 2 feeding units are respectively communicated with the fixed bed reactor and the first-stage dehydrogenation reaction kettle in the multi-stage series dehydrogenation reaction kettle.

[0010] Further, the fractional distillation unit comprises a first to a seventh distillation column connected in series in sequence. The feed port of the first distillation column is communicated with the oil phase outlet of the water washing unit. When the dehydrogenation reaction unit comprises a multi-stage series dehydrogenation reaction kettle, the overhead discharge port of the first distillation column is connected to the dissolution and filtration unit. The overhead discharge ports of the second and fourth distillation columns are respectively connected to the feeding unit. The overhead discharge ports of the third distillation column and the fifth to seventh distillation columns are respectively connected to a C6 carboxylic acid storage tank, a C7 carboxylic acid storage tank, a C8 carboxylic acid storage tank, and a C9 carboxylic acid storage tank. The bottom discharge ports of the first to sixth distillation columns are respectively connected to the feed ports of the next-stage distillation column in sequence. The bottom discharge port of the seventh distillation column is connected to the waste treatment unit.

[0011] In a second aspect, the present invention provides a process for producing C6-C9 carboxylic acid by dehydrogenation of C6-C9 mixed alcohol, comprising the steps of:

[0012] The raw materials C6-C9 mixed alcohol and NaOH are added to the feeding unit and fully stirred to dissolve, and then transported to the dehydrogenation reaction unit, and a catalyst is added to the feeding unit or the dehydrogenation reaction unit. The reaction temperature in the dehydrogenation reaction unit is set to 200-300°C, and the total reaction time is 90-150min; after the reaction is completed, the reaction product C6-C9 sodium carboxylate of the dehydrogenation reaction unit is transported to the acidification unit, and dilute sulfuric acid is added to adjust the pH to 2-3, and acidification treatment is performed to obtain C6-C9 carboxylic acid crude product; the C6-C9 carboxylic acid crude product is transported to the static separation unit for stratification, and the oil phase after stratification is transported to the water washing unit for water washing to remove residual sulfuric acid, and the washed C6-C9 carboxylic acid crude product is transported to the graded distillation unit, and is separated by vacuum distillation in multiple distillation towers to obtain C6, C7, C8, C9 carboxylic acid products.

[0013] Furthermore, the molar ratio of C6-C9 mixed alcohol to NaOH in the feeding unit is 1:0.7-1.8, and the mass of the catalyst is 0.5%-2.0% of the mass of the C6-C9 mixed alcohol.

[0014] Further, the distillation temperature of the first distillation tower is 70°C;

[0015] The distillation temperature of the second distillation tower is 150°C;

[0016] The distillation temperature of the third distillation tower is 180°C;

[0017] The distillation temperature of the fourth distillation tower is 210°C;

[0018] The distillation temperature of the fifth distillation tower is 220°C;

[0019] The distillation temperature of the sixth distillation tower is 235°C;

[0020] The distillation temperature of the seventh distillation tower is 250°C.

[0021] In a third aspect, the present invention provides a catalyst for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids, wherein the catalyst is Ge-ZnO-MgO / Al 2 O 3 Catalyst, the mass of Ge is Al 2 O 3 0.3~6% of mass,Al 2 O 3 The mass of ZnO is 5-35% of the total mass of the catalyst, and the mass ratio of ZnO to MgO is 1-10:1.

[0022] Fourthly, the present invention provides a method for preparing a catalyst for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids, comprising the steps of:

[0023] (1) Adding ZnO and MgO powders to a Ge salt solution, stirring until a colloidal substance is formed, and aging in a closed environment for 4 to 8 h to obtain Ge-ZnO-MgO;

[0024] (2) Mixing Ge-ZnO-MgO with a polyvinylpyrrolidone solution and stirring evenly, then adding Al 2 O 3 powder, stirring until evenly mixed, filtering, drying the filtered solid, and then calcining at 400 to 600 °C to obtain a Ge-ZnO-MgO / Al 2 O 3 catalyst.

[0025] The beneficial effects of the present invention are as follows:

[0026] The Ge-ZnO-MgO / Al 2 O 3 catalyst provided by the present invention has high catalytic activity for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids, can make the conversion rate of C6-C9 mixed alcohols reach more than 98%, the selectivity of C6-C9 reach more than 98%, and continuous production of C6-C9 carboxylic acids can be realized by using this Ge-ZnO-MgO / Al 2 O 3 catalyst; in addition, separation of C6-C9 carboxylic acids can also be realized by using the system and process of the present invention. Description of the Drawings

[0027] Figure 1 System connection diagram of Example 3 of the present invention. Detailed Embodiments

[0028] The present invention provides a system, a process and a supporting catalyst for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids. To make the purpose, technical solutions and effects of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] Among them, the present invention does not have special restrictions on the sources of all raw materials, and they can be commercially available.

[0030] In a first aspect, the present invention provides a system for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids, comprising a feeding unit, a dehydrogenation reaction unit, an acidification unit, a static separation unit, a water washing unit, a fractional distillation unit, and a by-product collection unit; the discharge port of the feeding unit is communicated with the feed port of the dehydrogenation reaction unit, the discharge port of the dehydrogenation reaction unit is communicated with the feed port of the acidification unit, the upper oil phase outlet of the static separation unit is communicated with the feed port of the water washing unit, the lower water phase outlet of the static separation unit is communicated with the by-product collection unit, the oil phase outlet of the water washing unit is communicated with the feed port of the fractional distillation unit, the fractional distillation unit includes at least 5 distillation columns, and C6, C7, C8, and C9 carboxylic acid products are respectively obtained after fractional purification by the multiple distillation columns of the fractional distillation unit.

[0031] In a preferred embodiment of the present invention, a storage tank is provided between the water washing unit and the fractional distillation unit for temporarily storing the crude C6-C9 carboxylic acids after water washing.

[0032] Specifically, the feeding unit is used to stir the raw material C6-C9 mixed alcohols and NaOH to make the raw materials evenly mixed.

[0033] In a preferred embodiment of the present invention, the feeding unit may specifically adopt a feeding kettle, and a stirring device is arranged inside the feeding kettle, and a heat exchange jacket capable of introducing a heat exchange medium is arranged outside the feeding kettle.

[0034] Specifically, the dehydrogenation reaction unit is used for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 sodium carboxylates.

[0035] In a preferred embodiment of the present invention, the dehydrogenation reaction unit may specifically adopt a fixed-bed reactor, and continuous feeding of the fixed-bed reactor can be achieved by controlling the space velocity; a catalyst fixed bed is arranged inside the fixed-bed reactor, and the catalyst and an inert carrier are jointly loaded into the catalyst fixed bed. The inert carrier can be selected from quartz sand, silicon carbide, ceramic balls, and inert alumina, and the loading mass of the inert carrier accounts for 15-55% of the total mass of the catalyst and the inert carrier, and preferably 35 wt% of quartz sand is adopted.

[0036] In another preferred embodiment of the present invention, the dehydrogenation reaction unit specifically adopts a multi-stage series dehydrogenation reaction kettle, and the dehydrogenation reaction kettle is provided with 3-10 stages. When the dehydrogenation reaction unit specifically adopts a multi-stage series dehydrogenation reaction kettle, a catalyst needs to be added simultaneously in the feeding unit, that is, C6-C9 mixed alcohols, NaOH, and a catalyst are added simultaneously in the feeding unit and stirred until evenly mixed.

[0037] In another preferred embodiment of the present invention, the dehydrogenation reaction unit may also simultaneously adopt a fixed-bed reactor and a dehydrogenation reaction kettle in multiple stages connected in series, and the two are arranged in parallel; and when the dehydrogenation reaction unit is a parallel connection of a fixed-bed reactor and a dehydrogenation reaction kettle in multiple stages connected in series, two feeding units are provided, and the discharge ports of the two feeding units are respectively communicated with the fixed-bed reactor and the first-stage dehydrogenation reaction kettle in the dehydrogenation reaction kettle in multiple stages connected in series.

[0038] In addition, in the above preferred embodiment of the present invention, when the dehydrogenation reaction unit includes a dehydrogenation reaction kettle in multiple stages connected in series, the discharge port of the last-stage dehydrogenation reaction kettle is sequentially connected with a buffer unit and a dissolution and filtration unit, and the aqueous phase outlet of the water washing unit is connected to the water inlet of the dissolution and filtration unit, the liquid phase discharge port of the dissolution and filtration unit is communicated with the feed port of the acidification unit, and the catalyst solid collected at the solid phase discharge port of the dissolution and filtration unit is added to the feeding unit.

[0039] Specifically, the above acidification unit is used to acidify the C6-C9 carboxylate sodium product of the dehydrogenation reaction unit to obtain a crude C6-C9 carboxylic acid product.

[0040] In the preferred embodiment of the present invention, the above acidification unit may specifically adopt an acidification kettle, and a stirring device is arranged inside the acidification kettle for continuously stirring the C6-C9 carboxylate sodium with an acid to acidify the C6-C9 carboxylate sodium to obtain a crude C6-C9 carboxylic acid product.

[0041] Specifically, the above static separation unit is used to statically separate the crude C6-C9 carboxylic acid product obtained by the acidification treatment of the acidification unit to separate the aqueous phase from the oil phase (i.e., C6-C9 carboxylic acid), which is convenient for further treatment of the oil phase subsequently.

[0042] In the preferred embodiment of the present invention, the above static separation unit is specifically a static separation tank, and the static separation tank is provided with an oil phase outlet and an aqueous phase outlet.

[0043] Specifically, the above water washing unit is used to wash the C6-C9 carboxylic acid after static separation to remove residual sulfuric acid and metal impurities.

[0044] In the preferred embodiment of the present invention, the above water washing unit is provided with at least two stages to facilitate cleaning the sulfuric acid and metal impurities, and the above water washing unit specifically adopts a water washing tower.

[0045] Specifically, the above buffer unit is used to temporarily store and cool the C6-C9 carboxylate sodium product produced by the reaction kettle in multiple stages connected in series, and the above dissolution and filtration unit is used to dissolve the cooled C6-C9 carboxylate sodium product and filter out the catalyst solid, and the filtered catalyst solid is recovered and continuously added to the feeding unit to improve the utilization rate of the catalyst.

[0046] In a preferred embodiment of the present invention, the above-mentioned buffer unit is specifically a buffer kettle, and a heat exchange jacket for introducing a heat exchange medium is arranged outside the buffer kettle to facilitate the cooling of the C6-C9 sodium carboxylate product in the buffer kettle; the above-mentioned dissolution and filtration unit is specifically a filtration kettle provided with a filtration device.

[0047] Specifically, the above-mentioned fractional distillation unit is used to separate the C6-C9 carboxylic acid mixture by vacuum distillation to obtain C6, C7, C8, and C9 carboxylic acids respectively.

[0048] In a preferred embodiment of the present invention, the above-mentioned fractional distillation unit includes the first to seventh distillation towers connected in series in sequence. The feed inlet of the first distillation tower is communicated with the outlet of the water washing unit or the temporary storage tank. And when the dehydrogenation reaction unit includes multiple dehydrogenation reaction kettles connected in series, the top outlet of the first distillation tower is connected to the dissolution and filtration unit. The top outlets of the second distillation tower and the fourth distillation tower are respectively connected to the feeding unit. The top outlets of the third distillation tower and the fifth to seventh distillation towers are respectively connected to the C6 carboxylic acid storage tank, the C7 carboxylic acid storage tank, the C8 carboxylic acid storage tank, and the C9 carboxylic acid storage tank. The bottom outlets of the first to sixth distillation towers are respectively connected to the feed inlets of the next-stage distillation towers in sequence. The bottom outlet of the seventh distillation tower is connected to the waste treatment unit.

[0049] Specifically, the above-mentioned by-product collection unit is used to treat the aqueous phase of the static separation unit to obtain C6-C9 sodium carboxylate by-products.

[0050] In a preferred embodiment of the present invention, the above-mentioned by-product collection unit includes a neutralization reaction kettle, a purification device, and a by-product collection tank connected in sequence; the above-mentioned neutralization reaction kettle is used to add dilute sulfuric acid to neutralize the excessive NaOH, and the above-mentioned purification device can specifically adopt a triple-effect evaporation device.

[0051] In a second aspect, the present invention provides a process for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids, which is realized by using the above-mentioned system for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids, and the following three processes can be realized.

[0052] Specifically, the first process is implemented using a system with a dehydrogenation reaction unit as a fixed-bed reactor. Its process flow is as follows: The raw material C6-C9 mixed alcohol and NaOH are added to the feeding unit in proportion and stirred thoroughly to dissolve, and then transported to the dehydrogenation reaction unit (i.e., the fixed-bed reactor). A catalyst fixed bed filled with a catalyst and an inert carrier is provided in the fixed-bed reactor. The C6-C9 mixed alcohol dehydrogenation reaction occurs under an inert gas atmosphere and the catalysis of the catalyst to generate C6-C9 sodium carboxylate. After the reaction is completed, the reaction product C6-C9 sodium carboxylate from the dehydrogenation reaction unit is transported to the acidification unit, and dilute sulfuric acid is added to adjust the pH to 2-3 for acidification treatment to obtain a crude C6-C9 carboxylic acid product. The crude C6-C9 carboxylic acid product is transported to the static separation unit for layering, and the oil phase after layering is transported to the water washing unit for water washing to remove residual sulfuric acid and metal impurities. The crude C6-C9 carboxylic acid product after water washing is temporarily stored in a temporary storage tank and then transported to the fractional distillation unit, and C6, C7, C8, and C9 carboxylic acid products are separated by vacuum distillation in multiple distillation columns. The aqueous phase after layering in the static separation unit is transported to the by-product collection unit for neutralization and purification to obtain a C6-C9 sodium carboxylate by-product.

[0053] In a preferred embodiment of the present invention, the heating temperature of the above-mentioned feeding unit is set to 110-150 °C to enable the raw materials to be quickly and evenly mixed. Preferably, the heating temperature is 120-130 °C.

[0054] In a preferred embodiment of the present invention, the molar ratio of C6-C9 mixed alcohol to NaOH in the above-mentioned feeding unit is 1:0.7-1.8, preferably 1:1.1-1.3.

[0055] In a preferred embodiment of the present invention, the mixture of C6-C9 mixed alcohol and NaOH enters the fixed-bed reactor at a mass space velocity of 0.3-15 h -1 Preferably, the space velocity is 7-10 h -1 , and feeding at this space velocity makes the dosage of the catalyst filled in the fixed-bed reactor 0.5-2.0% of the mass of the C6-C9 mixed alcohol, preferably 1-1.5%.

[0056] In a preferred embodiment of the present invention, the reaction temperature in the fixed-bed reactor is set to 200-300 °C, and the total reaction time is 90-120 min. Preferably, the reaction temperature is 260 °C.

[0057] In a preferred embodiment of the present invention, the initial gauge pressure after introducing an inert gas into the fixed-bed reactor is 0.1-0.6 MPa, preferably 0.3-0.5 MPa. As the reaction proceeds, hydrogen is generated to increase the pressure. When the pressure rises to a certain level and then basically remains unchanged, it indicates that the reaction is basically completed. This process takes 90-150 min.

[0058] In a preferred embodiment of the present invention, the fractional distillation unit performs vacuum distillation separation in ascending order of boiling points, specifically as follows:

[0059] The distillation temperature of the first distillation column is 70 °C;

[0060] The distillation temperature of the second distillation column is 150 °C;

[0061] The distillation temperature of the third distillation column is 180 °C;

[0062] The distillation temperature of the fourth distillation column is 210 °C;

[0063] The distillation temperature of the fifth distillation column is 220 °C;

[0064] The distillation temperature of the sixth distillation column is 235 °C;

[0065] The distillation temperature of the seventh distillation column is 250 °C.

[0066] Specifically, the second process is realized by a system of multiple series-connected dehydrogenation reaction kettles in the dehydrogenation reaction unit. Its process flow is as follows: The raw material C6-C9 mixed alcohol, NaOH, and catalyst are added to the feeding unit in proportion and stirred thoroughly to dissolve, and then transported to the first-stage multi-stage dehydrogenation reactor and reacted for the first set time under an inert gas atmosphere. Then the reaction mixture is transported to the second-stage dehydrogenation reaction kettle and reacted for the second set time under an inert gas atmosphere, and then successively transported to the third-stage dehydrogenation reaction kettle to the nth-stage dehydrogenation reaction kettle for reaction; after the reaction is completed, the reaction product C6-C9 sodium carboxylate in the nth-stage dehydrogenation reaction kettle of the dehydrogenation reaction unit is transported to the buffer unit for temporary storage and cooling, and then transported to the dissolution and filtration unit, diluted with water and filtered to remove the solid catalyst. The filtered liquid phase is transported to the acidification unit, and dilute sulfuric acid is added to adjust the pH to 2-3 for acidification treatment to obtain the crude C6-C9 carboxylic acid; the crude C6-C9 carboxylic acid is transported to the static separation unit for stratification, and the oil phase after stratification is transported to the water washing unit for water washing to remove residual sulfuric acid and metal impurities. The crude C6-C9 carboxylic acid after water washing is temporarily stored in the temporary storage tank, and then transported to the fractional distillation unit, and the C6, C7, C8, and C9 carboxylic acid products are obtained by vacuum distillation separation in multiple distillation columns; the aqueous phase after stratification in the static separation unit is transported to the by-product collection unit for neutralization and purification to obtain the C6-C9 sodium carboxylate by-product.

[0067] In a preferred embodiment of the present invention, the heating temperature of the above-mentioned feeding unit is set to 110-150 °C to enable the raw materials to be quickly mixed evenly. Preferably, the heating temperature is 120-130 °C.

[0068] In a preferred embodiment of the present invention, the molar ratio of C6-C9 mixed alcohols to NaOH in the above feeding unit is 1:0.7 to 1.8, preferably 1:1.1 to 1.3, and the dosage of the catalyst is 0.5 to 2.0% of the mass of C6-C9 mixed alcohols, preferably 1 to 1.5%.

[0069] In a preferred embodiment of the present invention, the reaction temperature in the dehydrogenation reactor is set to 200 - 300 °C, preferably, the reaction temperature is 260 °C; the reaction time for each stage of the dehydrogenation reactor is 10 - 40 min, and the total reaction time for multiple stages of dehydrogenation reactors is 90 - 150 min.

[0070] In a preferred embodiment of the present invention, the initial gauge pressure after introducing an inert gas into the dehydrogenation reactor is 0.1 - 0.6 MPa, preferably 0.3 - 0.5 MPa. As the reaction proceeds, hydrogen is generated, causing the pressure to increase. When the pressure in the nth stage dehydrogenation reactor rises to a certain level and then basically remains unchanged, it indicates that the reaction is basically completed. The total time for this process is 90 - 150 min, that is, the total reaction time from the first stage to the nth stage dehydrogenation reactor is 90 - 150 min.

[0071] Specifically, the third process is realized by a system using a dehydrogenation reaction unit of a fixed bed reactor and multiple stages of serially connected dehydrogenation reactors. This system can actually operate with the fixed bed reactor alone, multiple stages of serially connected dehydrogenation reactors alone, or the fixed bed reactor alone and multiple stages of serially connected dehydrogenation reactors together. When the fixed bed reactor operates alone or multiple stages of serially connected dehydrogenation reactors operate alone, their process flows are respectively the same as the above first process flow and second process flow; when the fixed bed reactor operates alone and multiple stages of serially connected dehydrogenation reactors operate together, only during feeding, it is necessary to set up 2 feeding units to be connected to the fixed bed reactor and the first stage dehydrogenation reactor of multiple stages of serially connected dehydrogenation reactors respectively. And the feeding unit connected to the fixed bed reactor only needs to proportionally configure C6-C9 mixed alcohols and NaOH, and load the catalyst into the fixed bed reactor. The feeding unit connected to the first dehydrogenation reactor needs to proportionally configure C6-C9 mixed alcohols, NaOH, and the catalyst. Other process flows and parameter settings are the same as the above first process flow and second process flow.

[0072] In a third aspect, the present invention provides a catalyst for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids. This catalyst has a high conversion rate for all C6-C9 mixed alcohols, a high selectivity for all C6-C9 carboxylic acids, and high catalytic efficiency and short reaction time, thus enabling the continuous operation of the above process. The catalyst of the present invention is Ge-ZnO-MgO / Al 2 O 3 catalyst, the mass of Ge is Al 2 O 30.3 to 6% by mass, preferably, the mass of Ge is that of Al 2 O 3 1.5 to 3% by mass; the mass of Al 2 O 3 is 5 to 35% of the total mass of the catalyst, preferably, the mass of Al 2 O 3 is 15 to 25% of the total mass of the catalyst; the mass ratio of ZnO to MgO is 1 to 10:1, preferably, the mass ratio of ZnO to MgO is 5:1.

[0073] Fourthly, the present invention also provides a preparation method of the above Ge-ZnO-MgO / Al 2 O 3 catalyst, comprising the steps of:

[0074] (1) Adding ZnO and MgO powders to a Ge salt solution, stirring until a colloidal substance is formed, and aging in a closed environment for 4 to 8 h, drying the aged colloid to obtain Ge-ZnO-MgO;

[0075] (2) Mixing Ge-ZnO-MgO with a polyvinylpyrrolidone solution and stirring evenly, then adding Al 2 O 3 powder, stirring until evenly mixed, filtering, drying the filtered solid, and then calcining in an air atmosphere to obtain Ge-ZnO-MgO / Al 2 O 3 catalyst.

[0076] In a preferred embodiment of the present invention, the drying temperature in the above steps (1) and (2) is 110 to 140 °C, and the drying time is 9 to 15 h.

[0077] In a preferred embodiment of the present invention, the aging time in the above step (1) is preferably 6 to 7 h, and aging is carried out statically for a certain time to make the interaction between Ge and ZnO and MgO more sufficient.

[0078] In a preferred embodiment of the present invention, the mass of the polyvinylpyrrolidine solution in the above step (2) is 4 to 6% of the mass of ZnO. The addition of an appropriate amount of PVP can better combine Ge-ZnO-MgO with Al 2 O 3 to facilitate subsequent co-calcination.

[0079] In a preferred embodiment of the present invention, the calcination temperature in the above step (2) is 400 to 600 °C, and the calcination time is 4 to 8 h.

[0080] Example 1

[0081] Example 1 prepares a Ge-ZnO-MgO / Al 2 O 3 catalyst, and the steps are as follows:

[0082] (1) First, dissolve 0.250 g of germanium chloride in 8 mL of deionized water, stir well and set aside. While stirring, add 5.5 g of industrial-grade ZnO and 6 g of MgO to the container, stir until a uniform colloidal substance is formed, then seal the container and let it stand and age for 8 h. Dry the aged colloidal substance at 110 °C for 13 h, and obtain Ge-ZnO-MgO after drying is completed;

[0083] (2) Take 0.30 g of PVP (relative viscosity is 90), dissolve it in 15 mL of deionized water, stir well, then grind the Ge-ZnO-MgO in the above step (1) into powder, add 30 mL of deionized water, dropwise add the PVP solution, and then add 2.0 g of Al 2 O 3 and continuously stir for 40 minutes. Dry the solid obtained by suction filtration at 130 °C for 10 h, then heat it to 550 °C at a rate of 4 °C / minute in an air atmosphere and calcine for 6 h. Grind the solid into powder after calcination to obtain Ge-ZnO-MgO / Al 2 O 3 catalyst.

[0084] In the Ge-ZnO-MgO / Al 2 O 3 catalyst prepared in this example,

[0085] wherein, the loading amount of Ge is 2.5 wt% of the mass of Al 2 O 3 , the mass of Al 2 O 3 is 18 wt% of the total mass of the catalyst, and the mass ratio of ZnO to MgO is 5:1.

[0086] Example 2

[0087] Compare the Ge-ZnO-MgO / Al 2 O 3 catalyst prepared in the above Example 1 with a germanium compound catalyst having similar catalytic performance. This reaction is carried out in a single batch reactor, with the molar ratio of C6-C9 mixed alcohol to sodium hydroxide being 1.2:1, the catalyst dosage being 1% of the mass of C6-C9 mixed alcohol, and dehydrogenation reaction being carried out for 100 minutes under the conditions of 240 °C and 0.6 MPa nitrogen, and then acidification is carried out. The results are shown in Table 1 below:

[0088] Table 1 Ge-ZnO-MgO / Al2 O 3 Comparison Results of Catalytic Performance between Catalyst and Germanium Compound Catalyst

[0089]

[0090] As can be seen from the above table, Ge-ZnO-MgO / Al 2 O 3 The catalyst has higher catalytic performance than the germanium compound catalyst, and its conversion rate of C6-C9 mixed alcohol reaches more than 98%, and the selectivity of C6-C9 carboxylic acid reaches more than 99%, which can meet the requirements of continuous and efficient production of C6-C9 carboxylic acid.

[0091] Example 3

[0092] Refer to Figure 1 , this example provides a system for dehydrogenating C6-C9 mixed alcohol to produce C6-C9 carboxylic acid, including a feeding unit, a dehydrogenation reaction unit, an acidification unit, a static separation unit, a water washing unit, a temporary storage tank, a fractional distillation unit, and a by-product collection unit. The discharge port of the feeding unit is connected to the feed port of the dehydrogenation reaction unit, the discharge port of the dehydrogenation reaction unit is connected to the feed port of the acidification unit, the upper oil phase outlet of the static separation unit is connected to the feed port of the water washing unit, the lower water phase outlet of the static separation unit is connected to the by-product collection unit, the oil phase outlet of the water washing unit is connected to the feed port of the temporary storage tank, the discharge port of the temporary storage tank is connected to the feed port of the fractional distillation unit. The fractional distillation unit includes at least 5 distillation towers, and C6, C7, C8, and C9 carboxylic acid products are obtained respectively after being purified by multiple distillation towers of the fractional distillation unit.

[0093] In this example, the above feeding unit uses a feeding kettle, and a stirring device is arranged inside the feeding kettle, and a heat exchange jacket capable of introducing a heat exchange medium is arranged outside the feeding kettle; the above feeding unit is used to stir the raw material C6-C9 mixed alcohol and NaOH to make the raw materials evenly mixed. In this example, 2 above feeding units are arranged.

[0094] In this example, the above dehydrogenation reaction unit is a fixed bed reactor arranged in parallel and a dehydrogenation reaction kettle in series with multiple stages. The feed ports of the fixed bed reactor and the first-stage dehydrogenation reaction kettle in the series of multiple-stage dehydrogenation reaction kettles are respectively connected to the discharge ports of the above 2 feeding units; the above dehydrogenation reaction unit is used for dehydrogenating C6-C9 mixed alcohol to generate C6-C9 sodium carboxylate.

[0095] Specifically, a catalyst fixed bed for loading the catalyst is further arranged inside the above fixed bed reactor. The above series of multiple-stage dehydrogenation reaction kettles are connected in series from the first stage to the nth stage, and specifically, 3 to 10 stages can be set. And a stirring device is arranged inside the above dehydrogenation reaction kettle, and a heat exchange jacket capable of introducing a heat exchange medium is arranged outside the dehydrogenation reaction kettle.

[0096] In this embodiment, the discharge port of the nth-stage dehydrogenation reactor is successively connected with a buffer unit and a dissolution and filtration unit, and the aqueous phase outlet of the water washing unit is connected to the water inlet of the dissolution and filtration unit. The liquid phase discharge port of the dissolution and filtration unit is communicated with the feed port of the acidification unit, and the solid catalyst collected at the solid phase discharge port of the dissolution and filtration unit is added into the feeding unit.

[0097] Specifically, the above-mentioned buffer unit is a buffer kettle, and an external heat exchange jacket for introducing a heat exchange medium is arranged outside the buffer kettle, which is used for temporarily storing and cooling the C6-C9 sodium carboxylate product produced by the multi-stage series reactors; the above-mentioned dissolution and filtration unit can adopt a filtration kettle provided with a filtration device, which is used for dissolving the cooled C6-C9 sodium carboxylate product and filtering out the solid catalyst, and the filtered solid catalyst is recycled and added into the feeding unit to improve the utilization rate of the catalyst.

[0098] In this embodiment, the above-mentioned acidification unit can specifically adopt an acidification kettle, and a stirring device is arranged inside the acidification kettle for continuously stirring the C6-C9 sodium carboxylate and an acid to acidify the C6-C9 sodium carboxylate to obtain a crude C6-C9 carboxylic acid product.

[0099] In this embodiment, the above-mentioned static separation unit is specifically a static separation tank, and the static separation tank is provided with an oil phase outlet and an aqueous phase outlet; the above-mentioned static separation unit is used for statically separating the crude C6-C9 carboxylic acid product obtained by the acidification treatment of the acidification unit to separate the aqueous phase from the oil phase (i.e., C6-C9 carboxylic acid), which is convenient for further processing of the oil phase.

[0100] In this embodiment, the above-mentioned water washing unit is provided with at least two stages and specifically adopts a water washing tower for cleaning sulfuric acid and metal impurities.

[0101] In this embodiment, the above-mentioned fractional distillation unit includes the first to seventh distillation towers connected in series. The feed port of the first distillation tower is communicated with the discharge port of the storage tank. The top discharge port of the first distillation tower is connected to the dissolution and filtration unit. The top discharge ports of the second and fourth distillation towers are respectively connected to the feeding unit. The top discharge ports of the third distillation tower and the fifth to seventh distillation towers are respectively connected to the C6 carboxylic acid storage tank, the C7 carboxylic acid storage tank, the C8 carboxylic acid storage tank, and the C9 carboxylic acid storage tank. The bottom discharge ports of the first to sixth distillation towers are respectively connected to the feed ports of the next-stage distillation tower in sequence. The bottom discharge port of the seventh distillation tower is connected to the waste treatment unit. Through the above-mentioned fractional distillation unit, the C6-C9 carboxylic acid mixture is separated by vacuum distillation to obtain C6, C7, C8, and C9 carboxylic acids respectively.

[0102] In this embodiment, the by-product collection unit includes a neutralization reactor, a purification device, and a by-product collection tank that are connected in sequence. The neutralization reactor is used to add dilute sulfuric acid to neutralize the excessive NaOH. The purification device can specifically adopt a triple-effect evaporation device. The by-product collection unit is used to process the aqueous phase of the static separation unit to obtain a by-product of C6-C9 carboxylate sodium.

[0103] Example 4

[0104] This embodiment provides a system for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids. The difference from Example 3 is that in this embodiment, the dehydrogenation reaction unit only includes a fixed-bed reactor.

[0105] Example 5

[0106] This embodiment provides a system for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids. The difference from Example 3 is that in this embodiment, the dehydrogenation reaction unit only includes a series of dehydrogenation reactors connected in series.

[0107] Example 6

[0108] This embodiment uses the system of Example 4 to dehydrogenate C6-C9 mixed alcohols to produce C6-C9 carboxylic acids. The process is as follows:

[0109] The raw material C6-C9 mixed alcohol and NaOH are added to the feeding unit according to a molar ratio of 1.1:1 and stirred and dissolved at 140°C. Then, they are transported to the dehydrogenation reaction unit (i.e., the fixed-bed reactor) through a pipeline and a transfer pump. A catalyst fixed bed filled with a catalyst and (35 wt% quartz sand) is provided in the fixed-bed reactor, and nitrogen is introduced into it. In the fixed-bed reactor, the reaction temperature of the fixed-bed reactor is adjusted to 240°C, and the back pressure is adjusted through a back pressure valve so that the back pressure in the fixed-bed reactor is maintained at 0.3 MPa. After the temperature and pressure reach the set values, start the transfer pump with a metering function to start feeding. Control the mass ratio of the hourly C6-C9 mixed alcohol feed and the filled Ge-ZnO-MgO / Al 2 O 3 catalyst to be 10:1;

[0110] After reacting for 100 minutes, the reaction product C6-C9 sodium carboxylate in the dehydrogenation reaction unit is transported to the acidification unit by a transfer pump. After the temperature is reduced to 80°C, the reaction solution is diluted with deionized water with a mass fraction of 10% of the mixed alcohol. Subsequently, the pH is adjusted to 2.0 with 30% dilute sulfuric acid for acidification treatment to obtain crude C6-C9 carboxylic acid; then the crude C6-C9 carboxylic acid is transported to the static separation unit by a transfer pump for layering, and the oil phase after layering is transported to the water washing unit by a transfer pump for water washing to remove residual sulfuric acid and metal impurities. The crude C6-C9 carboxylic acid after water washing is temporarily stored in a temporary storage tank and then transported to the fractional distillation unit. The C6, C7, C8, and C9 carboxylic acid products are separated by vacuum fractional distillation in seven distillation columns; the aqueous phase after layering in the static separation unit is transported to the by-product collection unit for neutralization and purification to obtain C6-C9 sodium carboxylate by-products.

[0111] In addition, in this embodiment, the temperatures or parameter settings of different distillation columns in the fractional distillation unit are as follows:

[0112] The distillation temperature of the first distillation column is 70°C;

[0113] The distillation temperature of the second distillation column is 150°C;

[0114] The distillation temperature of the third distillation column is 180°C;

[0115] The distillation temperature of the fourth distillation column is 210°C;

[0116] The distillation temperature of the fifth distillation column is 220°C;

[0117] The distillation temperature of the sixth distillation column is 235°C;

[0118] The distillation temperature of the seventh distillation column is 250°C.

[0119] After vacuum fractional distillation in the above-mentioned fractional distillation unit, the products of the first to seventh distillation columns are respectively:

[0120] The top product of the first distillation column is water, the top product of the second distillation column is the unreacted C6-C8 alcohol, the top product of the third distillation column is C6 carboxylic acid, the top product of the fourth distillation column is the unreacted C9 alcohol raw material, and the top products of the fifth to seventh distillation columns are C7 carboxylic acid - C9 carboxylic acid respectively; in addition, the bottom of the seventh distillation column is the still residue. The still residue is treated with sulfuric acid, and the recovered upper oil phase is recycled, and the lower layer is treated as hazardous waste.

[0121] In this embodiment, the upper oil phase sample after layering in the static separation unit is taken for gas chromatography analysis, and the conversion rate of C6-C9 mixed alcohol is 96.32%, and the molar selectivity of C6-C9 carboxylic acid is 99.79%.

[0122] Example 7

[0123] In this example, the system of Example 5 is used for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids. The process is as follows: The raw materials C6-C9 mixed alcohols, NaOH, and the catalyst are added to the feeding unit at a molar ratio of 1.1:1, and Ge-ZnO-MgO / Al 2 O 3 catalyst with a mass of 1wt% of the C6-C9 mixed alcohols is added, and they are fully stirred and dissolved at 140°C; then they are transported to the first-stage multi-stage dehydrogenation reactor by a transfer pump and react in an inert gas atmosphere, and then the reaction mixture is successively transported to the second-stage to the third-stage dehydrogenation reaction kettle to the fifth-stage dehydrogenation reaction kettle for reaction. The reaction temperature in each reaction kettle is 240°C, and the reaction time is 30 min;

[0124] After the reaction is completed, the reaction product C6-C9 sodium carboxylate in the fifth-stage dehydrogenation reaction kettle is transported to the buffer unit for temporary storage and cooling, and then transported to the dissolution and filtration unit. After adding 20% water by mass of the C6-C9 mixed alcohols to dilute and filter the solid catalyst, the filtered solid catalyst can be dried and then added to the feeding unit for reuse. The filtered liquid phase is transported to the acidification unit, and dilute sulfuric acid with a mass fraction of 30% is added to adjust the pH to 2 for acidification treatment to obtain the crude C6-C9 carboxylic acids; the crude C6-C9 carboxylic acids are transported to the static separation unit for stratification, and the oil phase after stratification is transported to the water washing unit for water washing to remove residual sulfuric acid and metal impurities. The crude C6-C9 carboxylic acids after water washing are temporarily stored in a temporary storage tank, and then transported to the fractional distillation unit. The C6, C7, C8, and C9 carboxylic acid products are separated by vacuum fractional distillation through seven distillation columns; the aqueous phase after stratification in the static separation unit is transported to the by-product collection unit for neutralization and purification to obtain the C6-C9 sodium carboxylate by-product.

[0125] In this example, the upper oil phase sample after stratification in the static separation unit is taken for gas chromatography analysis, and the conversion rate of C6-C9 mixed alcohols is 97.92%, and the molar selectivity of C6-C9 carboxylic acids is 99.83%.

[0126] Example 8

[0127] In this example, the same scheme as in Example 7 is used for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids. The difference from Example 7 is that the reaction duration and the number of dehydrogenation reaction kettles of different levels are adjusted. Samples are taken for acidification at the end of the reaction in each dehydrogenation reaction kettle, and their conversion rates and selectivities are recorded. The results are shown in Table 2 below.

[0128] Table 2 Detection results of dehydrogenation reaction kettles of different levels at different reaction durations

[0129]

[0130]

[0131] As can be seen from Table 2 above: When using a dehydrogenation reactor with 3 to 9 stages for reaction at different reaction durations, the total reaction time is 90 to 120 min, the conversion rate of C6-C9 mixed alcohols reaches over 98%, and the selectivity of C6-C9 carboxylic acids reaches over 99%, enabling the continuous production of C6-C9 carboxylic acids.

[0132] It should be noted that in the above-mentioned Example 2 and Examples 6-8, during the calculation of the conversion rate of C6-C9 mixed alcohols and the selectivity of C6-C9 carboxylic acids, the average value of the conversion rates of C6, C7, C8, and C9 alcohols is taken to obtain the conversion rate of C6-C9 mixed alcohols, and the average value of the selectivities of C6, C7, C8, and C9 carboxylic acids is taken to obtain the selectivity of C6-C9 carboxylic acids.

[0133] It should also be noted that to ensure the continuous production of the system, according to the conveying requirements between various devices, pumping devices such as ordinary transfer pumps or metering pumps with metering functions are provided on the connecting pipelines between various devices; valve fittings are also provided on the connecting pipelines between various devices to facilitate controlling the corresponding devices to close in case of emergencies or for maintenance and repair.

[0134] In the present invention, the parts not described can be realized by adopting or referring to the existing technologies.

[0135] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions, or substitutions made by those skilled in the art within the substantial scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A system for producing C6-C9 carboxylic acid by dehydrogenation of C6-C9 mixed alcohols, characterized in that: The invention comprises a feeding unit, a dehydrogenation reaction unit, an acidification unit, a standing separation unit, a water washing unit, a graded distillation unit and a by-product collection unit; the discharge port of the feeding unit is connected with the feed port of the dehydrogenation reaction unit, the discharge port of the dehydrogenation reaction unit is connected with the feed port of the acidification unit, the upper oil phase outlet of the standing separation unit is connected with the feed port of the water washing unit, the lower water phase outlet of the standing separation unit is connected with the by-product collection unit, the oil phase outlet of the water washing unit is connected with the feed port of the graded distillation unit, the graded distillation unit comprises at least 5 distillation towers, and C6, C7, C8 and C9 carboxylic acid products are obtained after graded purification by the multiple distillation towers of the graded distillation unit.

2. The system for producing C6-C9 carboxylic acid by dehydrogenation of C6-C9 mixed alcohol according to claim 1, characterized in that: The dehydrogenation reaction unit is a fixed bed reactor and / or a multi-stage series dehydrogenation reactor. When the dehydrogenation reaction unit is a fixed bed reactor and a multi-stage series dehydrogenation reactor, the fixed bed reactor and the multi-stage series dehydrogenation reactor are connected in parallel.

3. The system for producing C6-C9 carboxylic acid by dehydrogenation of C6-C9 mixed alcohol according to claim 2, characterized in that: When the dehydrogenation reaction unit comprises multiple stages of dehydrogenation reactors connected in series, the discharge port of the last stage of the dehydrogenation reactor is connected to the buffer unit and the dissolution and filtration unit in sequence, and the water phase outlet of the water washing unit is connected to the water inlet of the dissolution and filtration unit, the liquid phase discharge port of the dissolution and filtration unit is connected to the feed port of the acidification unit, and the catalyst solid phase collected by the solid phase discharge port of the dissolution and filtration unit is added to the feeding unit.

4. The system for producing C6-C9 carboxylic acid by dehydrogenation of C6-C9 mixed alcohol according to claim 2, characterized in that: When the dehydrogenation reaction unit is a fixed bed reactor and a multi-stage series dehydrogenation reactor in parallel, two feeding units are provided, and the discharge ports of the two feeding units are respectively connected to the fixed bed reactor and the first stage dehydrogenation reactor in the multi-stage series dehydrogenation reactor.

5. The system for producing C6-C9 carboxylic acid by dehydrogenation of C6-C9 mixed alcohol according to claim 3, characterized in that: The graded distillation unit includes first to seventh distillation towers connected in series in sequence, the feed port of the first distillation tower is connected to the oil phase outlet of the water washing unit, and when the dehydrogenation reaction unit includes multiple stages of dehydrogenation reactors connected in series, the top discharge port of the first distillation tower is connected to the dissolution and filtration unit; the top discharge ports of the second distillation tower and the fourth distillation tower are respectively connected to the feeding unit, the top discharge ports of the third distillation tower and the fifth to seventh distillation towers are respectively connected to the C6 carboxylic acid storage tank, the C7 carboxylic acid storage tank, the C8 carboxylic acid storage tank, and the C9 carboxylic acid storage tank, the bottom discharge ports of the first to sixth distillation towers are respectively connected to the feed port of the next distillation tower in sequence, and the bottom discharge port of the seventh distillation tower is connected to the waste treatment unit.

6. A process for producing C6-C9 carboxylic acid by dehydrogenation of C6-C9 mixed alcohol, using the system according to any one of claims 1 to 6, characterized in that: Includes steps: The raw materials C6-C9 mixed alcohol and NaOH are added to the feeding unit and fully stirred to dissolve, and then transported to the dehydrogenation reaction unit, and a catalyst is added to the feeding unit or the dehydrogenation reaction unit. The reaction temperature in the dehydrogenation reaction unit is set to 200-300°C, and the total reaction time is 90-150min; after the reaction is completed, the reaction product C6-C9 sodium carboxylate of the dehydrogenation reaction unit is transported to the acidification unit, and dilute sulfuric acid is added to adjust the pH to 2-3, and acidification treatment is performed to obtain C6-C9 carboxylic acid crude product; the C6-C9 carboxylic acid crude product is transported to the static separation unit for stratification, and the oil phase after stratification is transported to the water washing unit for water washing to remove residual sulfuric acid, and the washed C6-C9 carboxylic acid crude product is transported to the graded distillation unit, and is separated by vacuum distillation in multiple distillation towers to obtain C6, C7, C8, C9 carboxylic acid products.

7. The process for producing C6-C9 carboxylic acid by dehydrogenation of C6-C9 mixed alcohol according to claim 6, characterized in that: The molar ratio of C6-C9 mixed alcohol to NaOH in the feeding unit is 1:0.7-1.8, and the mass of the catalyst is 0.5%-2.0% of the mass of the C6-C9 mixed alcohol.

8. The process for producing C6-C9 carboxylic acid by dehydrogenation of C6-C9 mixed alcohol according to claim 6, characterized in that: The distillation temperature of the first distillation tower is 70°C; The distillation temperature of the second distillation tower is 150°C; The distillation temperature of the third distillation tower is 180°C; The distillation temperature of the fourth distillation tower is 210°C; The distillation temperature of the fifth distillation tower is 220°C; The distillation temperature of the sixth distillation tower is 235°C; The distillation temperature of the seventh distillation tower is 250°C.

9. A catalyst for dehydrogenating C6-C9 mixed alcohols to produce C6-C9 carboxylic acids, characterized in that: The catalyst is a Ge-ZnO-MgO / Al2O3 catalyst, the mass of Ge is 0.3-6% of the mass of Al2O3, the mass of Al2O3 is 5-35% of the total mass of the catalyst, and the mass ratio of ZnO to MgO is 1-10:

1.

10. A method for preparing the catalyst according to claim 9, characterized in that: Includes steps: (1) adding ZnO and MgO powders to a Ge salt solution, stirring until a colloidal substance is formed, and placing the solution in a sealed environment for aging for 4 to 8 hours to obtain Ge-ZnO-MgO; (2) Ge-ZnO-MgO and polyvinyl pyrrolidone solution are mixed and stirred evenly, and then Al2O3 powder is added, stirred until the mixture is evenly mixed, filtered, and the filtered solid is dried and then calcined at 400-600°C to obtain a Ge-ZnO-MgO / Al2O3 catalyst.

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