Method and system for purifying crude n-butyl alcohol

Abstract

The invention belongs to the technical field of chemical engineering, and particularly provides a crude n-butyl alcohol purification method and system.The purification method comprises the steps that crude n-butyl alcohol to be purified is input into a dehydration device, dehydration is conducted through membrane separation, and a first mixture is obtained; after preheating, carrying out hydrogenation reaction under the action of a catalyst to obtain a second mixture; performing reduced-pressure flash evaporation on the second mixture in a gas-liquid separation tank to obtain a third mixture; and rectifying the third mixture in a rectifying tower to obtain purified n-butyl alcohol. According to the method, unsaturated coloring functional groups in the crude n-butyl alcohol are efficiently removed through the modified low-load Pd-C catalyst, the difficulty of rectification separation is reduced, the purified n-butyl alcohol meets the requirements of GB / T6027-2023 for color number and sulfuric acid color development test key indexes, the method has the advantages of being simple in production process and low in energy consumption, and the method is suitable for industrial production. The method has great industrial application value.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and specifically provides a method and system for purifying crude n-butanol. Background Art

[0002] my country is a major producer of BDO (1,4-Butanediol, BDO for short). The industrial production processes of BDO mainly include the Reppe method and the maleic anhydride method. Both the Reppe and the maleic anhydride BDO processes will produce a certain amount of n-butanol during the production process. The butanol content of the crude n-butanol produced as a byproduct of the Reppe BDO process is 1% to 10%, and the n-butanol content of the crude n-butanol produced as a byproduct of the maleic anhydride BDO process is ≥30%. The above-mentioned crude n-butanol contains a variety of impurities such as water, propanol, methanol and other aldehydes. The crude butanol not only has a butanol-water miscible constant boiling system, but also has other light component impurities such as methanol, propanol, tetrahydrofuran, etc. The physical properties are complex and difficult to separate. The purification of n-butanol has always been a difficulty in producing high-quality butanol. The existing treatment method usually increases the concentration of butanol by distillation and combines it with physical adsorption to eliminate odor and impurities. There are problems such as complex process, high energy consumption, and frequent replacement of adsorption materials. Although the concentration of n-butanol after secondary purification is increased, it is still difficult to remove trace impurities, and it cannot meet the requirements of color number and key indicators of sulfuric acid color development test in GB / T6027-2023, and the added value of the product cannot be improved. Due to the problems of high energy consumption, complex process, large investment, low product quality, and difficulty in meeting the requirements of national standard products in existing purification technologies, it is often only possible to process it with cheap fuel, resulting in a huge waste of resources.

[0003] Butanol (English name: butyl alcohol, CH 3 CH 2 CH 2 CH 2 OH) is widely used in the fields of chemical industry, medicine, food and even energy. Its wide application and consumption also determines its wide attention in industrial production and scientific research. n-Butanol is an important basic organic chemical raw material, a solvent for various coatings and a raw material for making plasticizers. It is mainly used to produce plasticizers such as dibutyl phthalate (DBP) and butyl acetate, butyl acrylate, butyl methacrylate, etc. It is also often used as an organic synthesis intermediate and an extractant for biochemical drugs, and is also used to manufacture surfactants.

[0004] Therefore, with the rapid development of the BDO industry, it is of great significance to improve the quality of by-product n-butanol and reduce production costs. Summary of the invention

[0005] In order to overcome the above-mentioned defects, the present invention proposes a method and system for purifying crude n-butanol. After the purification method of the present invention, the crude n-butanol is purified to obtain an n-butanol product with not only high purity but also better performance in color number and sulfuric acid color development test.

[0006] In a first aspect, the present invention provides a method for purifying crude n-butanol, comprising:

[0007] The crude n-butanol to be purified is fed into a dehydration device and dehydrated by membrane separation to obtain a first mixture;

[0008] After preheating the first mixture in a first preheater, catalytic hydrogenation reaction is performed under the action of a Pd / C catalyst to obtain a second mixture;

[0009] flash evaporating the second mixture under reduced pressure in a gas-liquid separation tank to obtain a third mixture;

[0010] The third mixture is distilled in a distillation tower to obtain purified n-butanol.

[0011] Furthermore, the step of inputting the crude n-butanol to be purified into a dehydration device and dehydrating the mixture by membrane separation to obtain the first mixture comprises:

[0012] The dehydration device comprises n membrane modules with gradient flux connected in sequence, and the crude n-butanol to be purified passes through each of the membrane modules in sequence for dehydration, wherein the feed pressure of the crude n-butanol to be purified in each membrane module is 0.1-5 kPaA;

[0013] After dehydration through the n membrane modules, a first mixture is obtained, wherein the mass fraction of water in the first mixture is ≤10%.

[0014] Furthermore, the membrane fluxes of the n membrane modules decrease in sequence; 1≤n≤5; the membrane module comprises a molecular sieve membrane, wherein the separation factor of the molecular sieve membrane is 20-80, and the permeation flux is 200-2000 g / (m 2 ·hr).

[0015] Furthermore, the Pd / C catalyst is also doped with a metal element M, wherein the M includes at least one of nickel, chromium, molybdenum, silver and copper; the mass ratio of the doping amount of the metal element M to Pd is (0.01-1):1.

[0016] Further, preheating the first mixture in a first preheater comprises:

[0017] heating the first mixture to 100-150° C. in a first preheater;

[0018] The mass fraction of the Pd element in the Pd / C catalyst is 0.1 to 5 wt%; the hydrogenation reactor is a fixed bed reactor;

[0019] The space-time yield (STY) of the catalyst is 20 to 60 mg / g·h -1 The reaction temperature of the catalytic hydrogenation reaction is 100-150° C., the reaction time is 1-3 hours, the reaction pressure is 2-3 MPa, and the molar ratio of the hydrogen to the first mixture is 1:(150-250).

[0020] Furthermore, before the crude n-butanol to be purified is fed into the dehydration device, the method further comprises:

[0021] The crude n-butanol to be purified is heated to 50-80°C in the second preheater.

[0022] Further, the flash evaporation of the second mixture under reduced pressure in a gas-liquid separation tank comprises:

[0023] The second mixture is input into a gas-liquid separation tank for reduced pressure flash evaporation, wherein during reduced pressure flash evaporation, the pressure of the gas-liquid separation tank is controlled to be 0.4-0.6 MPa, and the condensation temperature at the top of the gas-liquid separation tank is set to be ≤40° C.;

[0024] The condensed liquid phase is refluxed into the gas-liquid separation tank, and the uncondensed gas phase is discharged into the tail gas pipe.

[0025] Further, the step of distilling the third mixture in a distillation tower to obtain purified n-butanol comprises:

[0026] After the reduced pressure flash evaporation, the liquid phase in the gas-liquid separation tank is input into a distillation tower for distillation;

[0027] The reflux ratio of the top reflux liquid of the distillation tower is 30-50, the distillation tower kettle is distilled at 101-120 kPa, the temperature of the distillation tower kettle is 140-160°C, and the condensation temperature of the top of the tower is 30-40°C;

[0028] The liquid in the middle and / or upper part of the distillation tower kettle is collected to obtain purified n-butanol.

[0029] Furthermore, the mass fraction of n-butanol in the crude n-butanol to be purified is 1% to 10%; the crude n-butanol to be purified is a by-product of a 1,4-butanediol device.

[0030] In a second aspect, the present invention provides a crude n-butanol purification system, comprising: a dehydration device, a first preheater, a hydrogenation reactor, a gas-liquid separation tank and a distillation tower connected in sequence.

[0031] Further, the dehydration device comprises n gradient flux membrane modules connected in sequence;

[0032] A catalyst filter is also arranged between the hydrogenation reactor and the gas-liquid separation tank.

[0033] The above one or more technical solutions of the present invention have at least one or more of the following beneficial effects:

[0034] 1. High-efficiency decolorization: The present invention can effectively eliminate the unsaturated bonds in crude n-butanol, reduce the color number of butanol, make it meet the requirements of GB / T6027-2023 "Industrial n-butanol" Type I, and improve the appearance quality of the product.

[0035] 2. High-purity output: After the purification process of the present invention, the purity of butanol can reach 99.9wt.%, which is much higher than the level of the prior art, thereby improving the use value of the product.

[0036] 3. Simplified process: The present invention adopts equipment such as a hydrogenation reactor and a butanol refining tower, and through a series of physical and chemical processes, achieves efficient purification of butanol, simplifies the production process, and reduces production costs.

[0037] 4. Environmental protection and safety: During the processing process, the present invention effectively recovers and utilizes hydrogen, avoids environmental pollution, and also ensures the safety of the production process.

[0038] 5. Strong adaptability: The present invention is not only applicable to the purification of crude n-butanol produced as a by-product of the BDO process of the acetylene aldehyde method, but is also applicable to the purification of crude n-butanol from other sources, and has strong adaptability and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In addition, similar numbers in the figures are used to represent similar components, among which:

[0040] Figure 1 1. It is a schematic flow chart of main steps of a method for purifying crude n-butanol according to one embodiment of the present invention;

[0041] Figure 2 2 is a schematic diagram of the main structure of a crude n-butanol purification system according to an embodiment of the present invention;

[0042] Figure 3 2 is a schematic diagram of the main structure of a crude n-butanol purification system according to Comparative Example 1 of the present invention;

[0043] Figure 4Schematic diagram of the main structure of the crude n-butanol purification system according to Comparative Example 2 of the present invention.

[0044] Reference numerals list :

[0045] 1 membrane module, 2 hydrogenation reactor, 2-1 hydrogen delivery pipe, 2-2 reactor input pipe, 2-3 reactor input pipe, 3 distillation tower, 4 permeate collection tank, 5 condensate collection tank, 6 gas-liquid separation tank, 6-1 separation tank delivery pipe, 7 distillation tank, 8 second preheater, 9 evaporator superheater, 10 jet pump condenser, 11 first preheater, 12 first condenser, 13 reboiler, 14 top condenser, 14-1 first liquid outlet, 14-2 second liquid outlet, 15 full condenser, 16 n-butanol cooler, 17 tower bottom liquid cooler, 18 second condenser, 19 filter, 20 steam jet vacuum pump, 21 material delivery pump, 22 tower bottom liquid delivery Pump, 23 distillate delivery pump, 24 n-butanol purified liquid delivery pump; 25-alcohol tower, 26-butanol tower, 27-butanol chromatograph, 28-alcohol tower reflux tank, 29-butanol chromatograph feed tank, 30-butanol tower reflux tank, 31-alcohol tower reboiler, 32-alcohol tower top condenser, 33-alcohol tower mid-production condenser, 34-alcohol tower kettle cooler, 35-butanol cooler, 36-butanol tower reboiler, 37-butanol tower top condenser, 38-butanol tower kettle cooler, 39-alcohol tower reflux pump, 40-alcohol tower kettle liquid delivery pump, 41-chromatograph feed pump, 42-butanol tower reflux pump, 43-butanol tower kettle liquid delivery pump; 44-decolorization column. DETAILED DESCRIPTION

[0046] Some embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0047] The present invention provides a method for purifying crude n-butanol, referring to Figure 1 ,include:

[0048] S1, the crude n-butanol to be purified is input into a dehydration device, and dehydrated by membrane separation to obtain a first mixture. The present invention treats the crude n-butanol to be purified by first dehydrating it.

[0049] S2, after preheating the first mixture in a first preheater, subjecting the first mixture to a catalytic hydrogenation reaction under the action of a Pd / C catalyst to obtain a second mixture. The Pd / C catalyst is prepared in advance.

[0050] S3, flash evaporating the second mixture under reduced pressure in a gas-liquid separation tank to obtain a third mixture.

[0051] S4, distilling the third mixture in a distillation tower to obtain purified n-butanol.

[0052] The treatment object of the present invention is crude n-butanol, which includes n-butanol and impurities, and the impurities are to be removed during the purification process, such as unsaturated substances such as propanol, methanol, aldehydes, and water.

[0053] In one embodiment, the crude n-butanol to be purified has a low n-butanol concentration, for example, the mass fraction of n-butanol in the crude n-butanol is 1% to 10%. The present invention has shown significant advantages and broad application prospects in purifying low-concentration n-butanol. It not only solves the problems of high energy consumption, complex process, and large investment in traditional purification methods, but also realizes a high-efficiency, low-energy consumption, and low-investment purification process through specific purification processes and technical means.

[0054] In one embodiment, the crude n-butanol to be purified is a by-product of preparing 1,4-butanediol, and the n-butanol content in the n-butanol solution produced as a by-product of the acetylene aldehyde BDO process is 1% to 10%.

[0055] In one embodiment, the contents of various components of crude n-butanol, a byproduct of preparing 1,4-butanediol, include:

[0056] n-Butanol 3.07wt.%;

[0057] Methanol 0.28wt.%;

[0058] Propanol 0.05wt.%;

[0059] Water 96.42%.

[0060] Butyraldehyde 0.06%;

[0061] The heavy component is 0.12%.

[0062] The present invention has a good purification effect on crude n-butanol, a byproduct of preparing 1,4-butanediol by the acetylene aldehyde process. The present invention effectively removes various impurities in the crude n-butanol, including unsaturated substances such as propanol, methanol, and aldehydes, under low energy consumption, thereby improving the purity of the butanol. In addition, the color number and odor of the butanol are effectively reduced, thereby improving the use experience and safety of the n-butanol.

[0063] As a major producer of BDO (1,4-butanediol) and the largest producer of acetylene-aldehyde process, my country has a great significance for the effective purification of by-products in the process of preparing BDO by acetylene-aldehyde process. The n-butanol extracted through this process is a widely used basic organic chemical raw material, which is widely used in the manufacture of various chemicals.

[0064] The following is a detailed description of the various steps for purifying crude n-butanol, referring to Figure 2 .

[0065] Explanation of Step S1

[0066] The present invention first dehydrates the crude solution, inputs the crude solution to be purified into a dehydration device, and arranges one or more layers of membranes for dehydration. In the dehydration device, the membrane used for dehydration uses the dehydration membrane to separate the solvent from water and improve the purity of the solvent. These membranes have excellent solvent selective permeability and water barrier properties, and can achieve accurate separation of solvent and water molecules under mild operating conditions. After dehydration in step S1, the mass fraction of water in the first mixture is ≤10%.

[0067] Through membrane separation technology, the crude solution (crude n-butanol) is dehydrated efficiently, and most of the impurities and water in the crude n-butanol are removed, laying a good foundation for the subsequent purification steps. The introduction of this step not only improves the purification efficiency, but also reduces the burden of subsequent processes.

[0068] In one embodiment, before the crude n-butanol to be purified is fed into a dehydration device, the method further comprises:

[0069] The crude n-butanol to be purified is heated to 50-80°C in the second preheater.

[0070] In an application scenario, refer to Figure 2 The crude n-butanol to be purified is pumped by the material delivery pump 21, and is sent to the second preheater 8 and the evaporator superheater 9 at a pressure of 0.8 MPa, and is preheated with saturated steam at a preheating temperature of 150°C. The crude n-butanol is heated to 120°C and then sent to the dehydration device. This preheating method can effectively increase the temperature of butanol and prepare for the subsequent decolorization reaction.

[0071] In order to improve the effect and efficiency of dehydration, dehydration is performed in stages and multiple times according to the different water contents. In one embodiment, the crude n-butanol to be purified is input into a dehydration device and dehydrated by membrane separation to obtain a first mixture, which comprises:

[0072] The dehydration device comprises n membrane modules with gradient flux connected in sequence, and the crude n-butanol to be purified passes through each membrane module in sequence for dehydration, wherein the feed temperature of the crude n-butanol to be purified in each membrane module is 50-80° C. and the pressure is 0.1-5 kPaA;

[0073] After dehydration through the n membrane modules 1, a first mixture is obtained, wherein the mass fraction of water in the first mixture is ≤10%.

[0074] In one embodiment, the membrane fluxes of the n membrane modules decrease in sequence; 1≤n≤5.

[0075] In one embodiment, the dehydration and concentration of the present invention adopts molecular sieve membrane separation. The membrane assembly 1 includes a molecular sieve membrane, which uses the strong adsorption of water molecules by the molecular sieve membrane to achieve the purpose of deep dehydration. The molecular sieve membrane dehydration has many advantages such as high efficiency, energy saving, and no environmental pollution. The separation factor of the molecular sieve membrane is 20-80, and the permeation flux is 200-2000g / (m 2 ·hr).

[0076] In an application scenario, still refer to Figure 2 , taking n=5 as an example, specifically, the crude n-butanol to be purified is preheated and input into the 5-stage membrane assembly 1 to concentrate the n-butanol aqueous solution. Each membrane assembly 1 is a dehydration tank, which is provided with a molecular sieve membrane for dehydration, and the 5-stage membrane assembly 1 is connected in sequence. After the crude n-butanol is dehydrated from the previous membrane assembly 1, the concentrated liquid enters the next membrane assembly 1 to continue to concentrate and remove water until it is dehydrated 5 times, and after being dehydrated by the last membrane assembly 1, it enters the second preheater 8 for heating.

[0077] The bottom of each membrane assembly 1 is connected to a permeate collection tank 4. Water is separated by the membranes of each membrane assembly 1, enters the permeate collection tank 4 from the bottom of the membrane assembly 1, and is discharged outside.

[0078] The permeate collection tank 4 is evacuated by a steam jet vacuum pump 20, and the exhaust gas and steam are mixed and condensed by a jet pump condenser 10, the gas phase is discharged, and the liquid phase is collected in a condensate collection tank 5, discharged outside the boundary, and reused as industrial water.

[0079] Explanation of Step S2

[0080] 1. Preheating

[0081] The concentrated liquid after dehydration by the membrane module 1 of the dehydration device is recorded as the first mixture, which is input into the first preheater 11 for preheating. The first mixture is heated to 100-150° C., preferably 110-130° C. in the first preheater 11. After preheating, the first mixture is input into the hydrogenation reactor 2.

[0082] Still refer to Figure 2 In one application scenario, the concentrated butanol solution is discharged from the other side of the membrane assembly 1, and after condensation by the second preheater 8 and the second condenser 18, the concentrated butanol solution is sent to the first preheater 11 at a pressure of 0.8 MPa, and is preheated to a temperature of 120°C and sent to the hydrogenation reactor 2.

[0083] The crude butanol is heated by a preheater to ensure that the crude butanol is fed into the hydrogenation reactor 2 at the reaction temperature, and that the crude butanol can start to react as soon as it contacts the catalyst, thereby preparing for the subsequent hydrogenation reaction.

[0084] 2. Hydrogenation catalytic reaction

[0085] Dehydrated crude n-butanol (dehydrated crude n-butanol) and hydrogen are fed from the top of the hydrogenation reactor 2.

[0086] The catalyst for the catalytic hydrogenation reaction is a Pd / C catalyst, which is a catalyst made of palladium (Pd) metal supported on a carbon (C) material.

[0087] In one embodiment, the Pd / C catalyst is further doped with a metal element M, wherein the metal element M is one or more selected from transition metal elements (excluding lanthanides and actinides), preferably at least one of nickel, chromium, molybdenum, silver, and copper; the mass ratio of the doping amount of the metal element M to Pd is (0.01-1):1, preferably (0.05-0.5):1, and the doping amount of the metal element M does not exceed the loading amount of Pd.

[0088] In the present embodiment, a catalyst using activated carbon as a carrier is adopted. Specifically, a compound containing palladium metal is loaded on an activated carbon carrier. In order to further optimize the performance of the catalyst, a second metal element, i.e., metal element M, is also introduced on the activated carbon for modification. The purpose of this modification is to reduce the loading amount of palladium metal, thereby forming a novel (Pd-M) / C catalyst, which is a catalyst by loading metal palladium (Pd) and another metal element M on a carbon carrier (C). In this way, not only can the use of precious metals be significantly reduced, thereby effectively reducing the manufacturing cost of the catalyst, but also the overall activity and stability of the catalyst can be significantly improved. There is a certain synergistic effect between metal palladium (Pd) and metal element M, and this synergistic effect can still efficiently complete the goal of hydrogenation reaction under the condition of low loading amount of precious metal palladium. In this way, not only the efficiency of catalytic hydrogenation is improved, but also the effect of catalytic hydrogenation is further improved, making the whole reaction process more economical and efficient.

[0089] In the (Pd-M) / C catalyst, the mass fraction of the Pd element is 0.1-5wt%, more preferably 0.1-2%.

[0090] The space-time yield (STY) of the catalyst is 20 to 60 mg / g·h -1 .

[0091] In one embodiment, the metal element M is Ni.

[0092] The preparation process of the (Pd-M) / C catalyst is preferably carried out by an equal volume impregnation method. First, a commercial activated carbon carrier is purchased and then dried at a temperature of 100-150° C. for 12-24 hours. After drying, the activated carbon carrier is cooled to room temperature for subsequent use.

[0093] Next, the prepared Pd source and the second metal source (metal element M doping source) are impregnated onto the activated carbon carrier by an impregnation method. Specifically, the Pd source and the second metal source (metal element M doping source) are evenly mixed to form a mixed solution, and the activated carbon carrier and the mixed solution are fully stirred into a suspension, and then impregnated. During the impregnation process, it is necessary to stand for 2-4 hours to ensure that Pd and the second metal (metal element M) can fully penetrate into the activated carbon carrier. After standing, the impregnated activated carbon carrier is dried at 120°C.

[0094] After drying, the impregnated activated carbon is placed in a calcining furnace and calcined at 550°C for 24-48 hours. After calcination, the catalyst is cooled to room temperature to obtain a catalyst, which is then loaded into a reactor for use.

[0095] When selecting a Pd source, it is preferred to use a Pd salt solution, such as PdCl 2 As the Pd source. For the metal element M doping source (second metal source), it is preferred to use a salt solution of the metal element M, such as a Ni source, and select Ni(NO3) 2 6H 2 When selecting an activated carbon carrier, its diameter is preferably 0.5-5 mm, and the specific surface area of ​​the carbon carrier is preferably ≥ 200 m 2 / g, and the pore volume of the carrier is preferably 0.30-0.80cm 3 Through the above steps, a (Pd-M) / C catalyst with excellent performance can be prepared.

[0096] Liquid phase hydrogenation reaction under the action of (Pd-M) / C catalyst can effectively eliminate the coloring functional groups.

[0097] In one embodiment, the reactor is a fixed bed reactor, preferably a trickle bed reactor. In one embodiment, the reaction pressure of the catalytic hydrogenation reaction is 2-3 MPa, the reaction temperature is 100-150° C., the reaction time is 1-3 hours, and the feed molar ratio of hydrogen to the first mixture is 1:200.

[0098] In one application scenario, in the hydrogenation reactor 2, crude n-butanol reacts with the catalyst Pd / (NiC), wherein the catalyst particle diameter is 0.5 mm, the two are in full contact, and a hydrogenation reaction occurs on the catalyst surface. The reaction temperature is 120°C, and the reaction time is 2 hours. The unsaturated organic matter contained in the crude n-butanol is hydrogenated to eliminate the influence of the unsaturated organic matter on the color number of butanol.

[0099] This hydrogenation reaction can effectively eliminate the unsaturated bonds in butanol and reduce the color and odor of butanol.

[0100] Explanation of Step S3

[0101] After the catalytic hydrogenation reaction in the hydrogenation reactor 2, a second mixture is obtained, the main components of which are n-butanol, water, propanol and heavy components, and also contain a trace amount of unreacted hydrogen. Hydrogen is continuously discharged below the packing section of the hydrogenation reactor 2, and is flashed under reduced pressure in the gas-liquid separation tank 6 to remove dissolved hydrogen in the liquid phase.

[0102] The process of reduced pressure flash evaporation is: inputting the second mixture into the gas-liquid separation tank 6 for reduced pressure flash evaporation, wherein during the reduced pressure flash evaporation, the pressure of the gas-liquid separation tank 6 is controlled to be 0.4-0.6MPa to perform flash evaporation to separate the dissolved gas.

[0103] The condensation temperature at the top of the gas-liquid separation tank 6 is set to ≤40° C., and the entrained organic matter is removed before discharge.

[0104] Reference Figure 2 The tail gas condenser, i.e., the first condenser 12, at the top of the gas-liquid separation tank 6 is condensed, and the condensate is returned to the gas-liquid separation tank 6, and the uncondensed gas phase is discharged to the tail gas pipeline for treatment to ensure the purity of the hydrogen. The butanol entrained in the gas phase can also be effectively recovered to improve the product yield.

[0105] In one embodiment, the liquid phase at the bottom of the reactor, i.e., the second mixture, is depressurized by a regulating valve, for example, to 0.6 MPa, and then filtered through a filter 19, wherein the pore size of the filter membrane in the filter 19 is 0.2 μm, so as to remove the catalyst powder, and then input into the gas-liquid separation tank 6 for flash evaporation to separate hydrogen. This treatment method can effectively remove the catalyst powder and improve the purity of butanol.

[0106] After the hydrogen dissolved in the second mixture is flash-evaporated and separated in the gas-liquid separation tank 6, the liquid phase obtained is the third mixture, which is transported to the butanol refining tower for further treatment.

[0107] Explanation of Step S4

[0108] In one embodiment, the step of distilling the third mixture in a distillation tower 3 to obtain purified n-butanol comprises:

[0109] After the reduced pressure flash evaporation, the liquid phase in the gas-liquid separation tank 6, i.e., the third mixture, is pressed into the distillation tower 3 by the pressure of the gas-liquid separation tank 6 for distillation;

[0110] The reflux ratio of the top reflux liquid of the distillation tower 3 is 30-50, and the distillation tower kettle is distilled at 101-120 kPa.

[0111] The liquid in the middle and / or upper part of the bottom of the distillation tower 3 is collected to obtain purified n-butanol.

[0112] In an application scenario, refer to Figure 2 The distillation tower 3 is a 5-stage packed tower. The third mixture is finally purified by the butanol refining tower, i.e., the distillation tower 3. The light components are removed from the top of the distillation tower 3, the heavy components are extracted from the bottom of the distillation tower 3, and the n-butanol product is extracted from the distillation tower.

[0113] During distillation, the temperature of the bottom of the distillation tower 3 is 110-150°C, and the heat for heating is provided by the reboiler 13 connected to the bottom of the bottom of the distillation tower 3. The top of the distillation tower 3 mainly consists of butanol, water and a trace of light components of propanol solution, which are condensed by the top condenser 14 at a condensation temperature of 40°C. The condensate is collected in the distillation tank 7, part of which is refluxed into the bottom of the tower by the distillate delivery pump 23, and part of which is sent to the butanol chromatograph of the BDO distillation unit to continue to treat water. The light components at the top of the tower can also be sent to the upstream device for reuse. The bottom liquid mainly contains n-butanol and heavy components. The heavy components are sent out by the bottom liquid delivery pump 22 connected to the bottom of the distillation tower 3, cooled to 60°C by the bottom liquid cooler 17, and the liquid phase containing the heavy components is sent out for external treatment.

[0114] The qualified n-butanol product is extracted from the distillation tower 3 by the n-butanol purified liquid delivery pump 24, cooled to 60°C by the n-butanol cooler 16, and delivered to the storage tank. The middle extraction pump 24 is used to extract the liquid phase from the upper part of the distillation tower 3, specifically the area below the top and above the middle of the distillation tower 3.

[0115] In addition, the top condenser 14 is also connected to a full condenser 15, and the liquid cooled by the full condenser 15 is collected in the distillation tank 7, and the uncondensed gas phase is discharged.

[0116] The present invention adopts a specific purification process, and finally only one distillation tower is used for purification, so that the purity of butanol can be effectively improved. After being processed by the purification process of the present invention, the purity of the n-butanol product reaches 99.9wt.%, and the color number is controlled within 10 (Hazen unit), which is better than the requirements of GB / T6027-2023 "Industrial n-butanol" Type I. It shows better performance in the sulfuric acid color development test, which can reach within 20. The purification method of the present invention can effectively improve the quality of n-butanol and meet the needs of industrial production.

[0117] The present invention provides a method for treating crude n-butanol produced as a byproduct of BDO, wherein the concentration is increased by more than 99.6% by dehydration through membrane separation technology, and the impurities in the crude butanol are hydrogenated at the same time, and the sulfuric acid color test reaches less than No. 20, and finally the fusel alcohol light components and heavy components contained in the butanol are removed by primary distillation in a distillation tower 3, and then the n-butanol product that meets the requirements of the national standard GB / T 6027-2023 Type I is obtained through intermediate mining. The purification method of the present invention has the advantages of low energy consumption, simple process and high product quality. my country is a major producer of BDO. Under the increasingly fierce competition in the BDO industry, the present invention is of great significance in reducing production costs, reducing environmental pressure and improving economic benefits in the BDO industry.

[0118] As an important chemical raw material, n-butanol plays a vital role in the production process of many products. Especially in the cosmetics industry, the color of n-butanol directly affects the quality of the final product. For example, in the production of cosmetics, n-butanol is often used as a solvent, especially in products such as nail polish, where it is used as a co-solvent in combination with main solvents such as ethyl acetate. This combination helps dissolve the colorant and also adjusts the evaporation rate and viscosity of the solvent, thereby ensuring the stability and use effect of the product.

[0119] Through the process proposed by the present invention, high-purity n-butanol can be obtained, and its color number can be significantly reduced through an efficient decolorization process. In this way, when used as a solvent for products such as cosmetics that have extremely high color requirements, the quality of the applied products can be significantly improved. The high purity and low color number of n-butanol not only help to improve the color of the product, but also ensure the safety and stability of the product, thereby meeting consumers' demand for high-quality cosmetics.

[0120] In addition, n-butanol is also widely used in the production of screen printing inks. It can be used as a defoamer in the ink preparation process to help achieve more accurate ink preparation. By using n-butanol that has been efficiently decolorized, the uniformity and stability of the ink can be ensured, thereby ensuring the quality of the final product. In the field of fine printing such as screen printing, the use of n-butanol can significantly improve the printing effect and ensure the clarity of the pattern and the saturation of the color.

[0121] In the spices and flavors industry, n-butanol also plays an important role. It can be used not only as a solvent, but also as a diluent to help adjust the concentration and uniformity of the fragrance. The high-quality n-butanol obtained by the present invention can better play its role in the production process of the fragrance, thereby improving the quality of the fragrance. The excellent performance of n-butanol makes the fragrance more stable during the preparation process, and the fragrance is more lasting and natural, meeting the market demand for high-quality fragrances.

[0122] In summary, the high-efficiency decolorization process involved in the present invention not only improves the quality of n-butanol, but also has wide application value and promotion significance. Through this technology, higher-standard raw materials can be provided for multiple industries such as cosmetics, inks and flavors, thereby promoting the development of related industries and meeting consumers' demand for high-quality products.

[0123] Reference Figure 2 The present invention also provides a crude n-butanol purification system, which includes: a dehydration device, a first preheater 11, a hydrogenation reactor 2, a gas-liquid separation tank 6 and a distillation tower 3 connected in sequence.

[0124] The dehydration device comprises a plurality of membrane modules 1 connected in sequence, wherein the membrane modules 1 are connected end to end in sequence. The number of the membrane modules 1 is n, where n is a natural number and satisfies 2≤n≤5, and the bottom of each membrane module 1 is connected to a permeate collection tank 4. The membrane flux of the membrane modules 1 decreases in sequence.

[0125] The upper part of the hydrogenation reactor 2 is connected to a hydrogen delivery pipe 2-1, the top of the hydrogenation reactor 2 is connected to a reactor input pipe 2-2 for connecting to the first preheater 11, and the bottom of the hydrogenation reactor 2 is connected to a reactor output pipe 2-3 for connecting to a gas-liquid separation tank 6;

[0126] The top of the gas-liquid separation tank 6 is connected to the first condenser 12 , and the bottom of the gas-liquid separation tank 6 is provided with a separation tank delivery pipe 6 - 1 for connecting to the middle of the distillation tower 3 .

[0127] A top condenser 14 is provided at the top of the distillation tower 3 , and a heating device is connected to the bottom of the distillation tower 3 .

[0128] In one embodiment, the system further includes: a material conveying pump 21 and a second preheater 8; wherein the material conveying pump 21 is used to convey the crude n-butanol to be purified, the material conveying pump 21 is connected to one end of the second preheater 8, and the other end of the second preheater 8 is connected to the dehydration device.

[0129] The concentrated butanol solution is discharged from the other side of the membrane assembly 1, and after being preheated by the second preheater 8 and condensed by the second condenser 18, the concentrated butanol solution is sent to the first preheater 11 at a pressure of 0.8 MPa, and is preheated to a temperature of 120°C and sent to the hydrogenation reactor 2.

[0130] The crude butanol to be purified is heated by the first preheater 11 and the second preheater 8 to ensure that the crude butanol is fed into the hydrogenation reactor 2 at the reaction temperature and that the crude butanol can start to react as soon as it contacts the catalyst, thereby preparing for the subsequent hydrogenation reaction.

[0131] In one embodiment, the dehydration device comprises n gradient flux membrane modules 1 connected in sequence.

[0132] In one embodiment, the system further comprises: an evaporator superheater 9 and a second condenser 18; the dehydration device comprises a first membrane assembly 1-1, a second membrane assembly 1-2, a third membrane assembly 1-3, a fourth membrane assembly 1-4 and a fifth membrane assembly 1-5 connected in sequence.

[0133] One end of the evaporator superheater 9 is connected to the second preheater 8, the other end of the evaporator superheater 9 is connected to the liquid inlet of the first membrane assembly 1-1, and the liquid outlet of the fifth membrane assembly 1-5 is connected to the second preheater 8, the second condenser 18 and the first preheater 11 in sequence.

[0134] When in use, the crude n-butanol to be purified is heated by the material delivery pump 21 through the second preheater 8 and the evaporator superheater 9 to 60°C, and then input into the 5-stage membrane assembly 1 to concentrate the crude n-butanol to improve the dehydration effect. The membrane assembly 1 includes a molecular sieve membrane, the separation factor of the molecular sieve membrane is 20-80, and the permeation flux is 200-2000g / (m 2 ·hr). The membrane flux of the five membrane modules decreases in sequence, that is, the dehydration is carried out in sequence from coarse to fine, which can improve the efficiency and accuracy of dehydration.

[0135] In one embodiment, the reactor output pipe 2-3 is further connected with a filter 19. The filter 19 is a catalyst filter, and the catalyst comes from the hydrogenation reactor 2.

[0136] The liquid phase at the bottom of the hydrogenation reactor 2, i.e., the second mixture, is decompressed by a regulating valve, such as to 0.6 MPa, and then filtered by a filter 19, the filter membrane pore size in the filter 19 being 0.2 μm, thereby removing the catalyst powder, and then inputting the gas-liquid separator 6 to separate hydrogen by flash evaporation. This treatment method can effectively remove the catalyst powder and improve the purity of butanol. The first condenser 12 at the top of the gas-liquid separator 6 is the first condenser, and the condensate in the first condenser 12 returns to the gas-liquid separator 6, and the uncondensed gas phase is discharged to the tail gas pipeline for processing to ensure the purity of hydrogen. And the butanol carried entrained in the gas phase can be effectively recovered to improve the product yield.

[0137] After the hydrogen dissolved in the second mixture is flash-evaporated and separated in the gas-liquid separation tank 6, the liquid phase obtained is the third mixture, which is transported to the butanol refining tower, i.e., the distillation tower 3, for further treatment.

[0138] In one embodiment, a reboiler 13 is connected to the bottom of the distillation tower 3. The reboiler 13 is used as a heating device for the distillation tower 3. The heat of the distillation tower 3 is provided by the reboiler 13 using 0.8MPG saturated steam, and the operating pressure is 0.6MPa. The heating temperature of the distillation tower 3 is 150°C. The distillation tower kettle is distilled at 110kPa, and the reflux ratio of the top reflux liquid is 40.

[0139] In one embodiment, the system further includes: a full condenser 15, a distillation tank 7 and a distillate delivery pump 23; wherein the tower top condenser 14 includes a first liquid outlet 14-1 and a second liquid outlet 14-2, the first liquid outlet 14-1 is connected to the distillation tank 7, the second liquid outlet 14-2 is connected to the full condenser 15, the liquid outlet of the full condenser 15 is connected to the liquid inlet of the distillation tank 7, the liquid outlet of the distillation tank 7 is connected to the liquid inlet of the distillate delivery pump 23, and the liquid outlet of the distillate delivery pump 23 is connected to the top of the distillation tower 3.

[0140] The liquid cooled by the total condenser 15 is collected in the distillation tank 7, and the uncondensed gas phase is discharged.

[0141] The distillate delivery pump 23 refluxes the liquid collected in the distillation tank 7 to the top of the distillation tower 3 .

[0142] In one embodiment, the system further includes: a n-butanol purified liquid delivery pump 24 and a n-butanol cooler 35; wherein one end of the n-butanol purified liquid delivery pump 24 is connected to the middle or upper part of the distillation tower 3, and the other end of the n-butanol purified liquid delivery pump 24 is connected to the n-butanol cooler 16.

[0143] The purified n-butanol product is extracted from the distillation tower 3 by the n-butanol purified liquid delivery pump 24, cooled to 60° C. by the n-butanol cooler 35, and delivered to the purified product storage tank.

[0144] In one embodiment, the system of the present invention further includes: a steam jet vacuum pump 20 , a jet pump condenser 10 and a condensate collection tank 5 .

[0145] The permeate collection tank 4, the steam jet vacuum pump 20, the jet pump condenser 10 and the condensate collection tank are connected in sequence.

[0146] The permeate collection tank 4 is evacuated by a steam jet vacuum pump 20, and the exhaust gas and steam are mixed and condensed by a jet pump condenser 10, the gas phase is discharged, and the liquid phase is collected in a condensate collection tank 5, discharged, and reused as industrial water.

[0147] In one embodiment, the system further includes: a bottom liquid delivery pump 22 and a bottom liquid cooler 17; wherein the liquid inlet of the bottom liquid delivery pump 22 is connected to the bottom of the distillation tower 3, and the bottom liquid cooler 17 is connected to the liquid outlet of the bottom liquid delivery pump 22.

[0148] The system of the present invention effectively reduces the color and odor of butanol through dehydration, hydrogenation reaction of the hydrogenation reactor 2, gas-liquid separation and distillation purification process, and improves the use experience and safety of n-butanol. At the same time, under low energy consumption, various impurities in butanol, including unsaturated substances such as propanol, methanol, and aldehydes, are effectively removed, thereby improving the purity of n-butanol.

[0149] The purification effect of the present invention is described below in conjunction with the embodiments and comparative examples.

[0150] Example 1

[0151] Treatment of crude n-butanol produced as a byproduct of a BDO unit using the acetylene aldehyde process. The contents of the various components of the crude n-butanol to be purified are shown in Table 1, and the flow rate is 200 kg / h.

[0152] Table 1 Material composition of the input device of Example 1

[0153] project unit index Appearance Light yellow transparent liquid with pungent odor Color Hazen Unit 30 purity wt.% 3.07％ Water content wt.% 96.42％ Methanol content wt.% 0.28％ Propanol content wt.% 0.05％ Butyraldehyde wt.% 0.06％ Heavy component content wt.% 0.12％

[0154] S1, the crude n-butanol of the content in Table 1 is heated by the material delivery pump 21 through the second preheater 8 and the evaporator superheater 9 to 60°C, and then input into the 5-stage membrane assembly 1 to concentrate the crude n-butanol. The membrane assembly 1 includes a molecular sieve membrane, the separation factor of the molecular sieve membrane is 20-80, and the permeation flux is 200-2000g / (m 2 ·hr). The membrane fluxes of the five membrane modules decrease in sequence. The feed pressure of the crude n-butanol to be purified in each membrane module is 0.1-5 kPaA.

[0155] After concentration, a first mixture is obtained, and the water removed by concentration enters the permeate collection tank 4 from the bottom of the membrane module 1 and is discharged outside.

[0156] S2, the first mixture obtained after concentration is discharged from the output end of the dehydration device, condensed by the preheater 8 and the second condenser 18, and then sent to the first preheater 11 at a pressure of 0.8 MPa, and then preheated to a temperature of 120°C and sent to the hydrogenation reactor 2.

[0157] In the hydrogenation reactor 2, a (Pd-Ni) / C catalyst (Pd content is 0.3 wt%) is prepared in advance. The preparation method of the (Pd-Ni) / C catalyst is as follows:

[0158] Calculate the palladium chloride (PdCl 2) was fully dissolved in concentrated hydrochloric acid, stirred thoroughly, and then Ni(NO 3 ) 2 6H 2 O, prepare the mixed solution.

[0159] The commercially available pre-treated carbon carrier (Japan OGC, C2X granular activated carbon carrier, diameter 3mm, specific surface area 810m 2 / g) weigh 3.43kg for pretreatment, mix with the mixed solution, stir thoroughly to form a suspension, and stir at a constant temperature of 60°C for 6 hours. After adding 0.1mol / L sodium hydroxide to the impregnated catalyst, add formaldehyde dropwise, stir continuously to adjust the pH value, let it stand for 2 hours, and cool to room temperature. Wash with distilled water until the conductivity is less than 10 (us / cm), and dry at 110°C for 8 hours. The impregnated catalyst is placed in a calcination furnace and calcined at 550°C for 24 hours. After calcination, cool to room temperature, and the space-time yield of the obtained catalyst is in the range of 20 to 60mg / g·h -1 , and add the obtained catalyst into hydrogenation reactor 2.

[0160] A catalytic hydrogenation reaction is carried out in a hydrogenation reactor 2 filled with the above-mentioned catalyst, the extract to be extracted output from the first preheater 11 is fully contacted with the catalyst ((Pd-Ni) / C catalyst, the catalyst particle diameter is 3 mm), the molar ratio of the hydrogen to the first mixture is 1:200, a hydrogenation reaction occurs on the catalyst surface, the reaction temperature is 120°C, the reaction pressure of the catalytic hydrogenation reaction is 2.5 MPa, the reaction time is 2 hours, and a second mixture is obtained after the reaction.

[0161] S3, after the liquid phase at the bottom of the hydrogenation reactor 2 is depressurized to 0.6MPa by a regulating valve, the hydrogen dissolved in the liquid is separated, and the liquid, i.e., the second mixture, is passed through a filter 19 to remove the catalyst powder and then fed to the gas-liquid separation tank 6 for reduced pressure flash evaporation, and the condensation temperature at the top of the gas-liquid separation tank 6 is controlled to be set to 40°C, and the pressure of the gas-liquid separation tank is 0.6MPa. The tail gas condenser 12 at the top of the gas-liquid separation tank 6 condenses, and the condensate returns to the gas-liquid separation tank 6, and the uncondensed gas phase is discharged to the tail gas pipeline for treatment.

[0162] After reduced pressure flash evaporation, the third mixture is output from the bottom of the gas-liquid separation tank 6 .

[0163] S4, the third mixture is input into the distillation tower 3, which is a 5-stage packed tower, and condensed by the top condenser 14, the condensation temperature is 40°C, the condensate is collected in the distillation tank 7, and part of it is refluxed into the tower kettle by the distillate delivery pump 23. The heat of the distillation tower 3 is provided by the reboiler 13 using 0.8MPG saturated steam, the operating pressure is 0.6MPa, and the heating temperature of the distillation tower 3 is 150°C. The distillation tower kettle is distilled at 110kPa, and the reflux ratio of the top reflux liquid is 40.

[0164] The purified n-butanol product is extracted from the distillation tower 3 by the intermediate extraction pump 24, cooled to 60° C. by the n-butanol cooler 16, and then sent to the storage tank.

[0165] The n-butanol product in the storage tank described in Example 1 was tested, and the test results are shown in Table 2.

[0166] Table 2 Test results of n-butanol product obtained in Example 1

[0167]

[0168] Example 2

[0169] The difference between this embodiment and embodiment 1 is that in step S2, the Pd element content in the (Pd-Ni) / C catalyst is 1 wt%.

[0170] Example 3

[0171] The difference between this embodiment and embodiment 1 is that:

[0172] 1. In step S1, the crude n-butanol is heated to 50°C.

[0173] 2. In step S2, the preheated mixture is heated to a temperature of 150°C and then fed into a hydrogenation reactor 2. A (Pd-Ni) / C catalyst is prepared in advance, wherein the Pd content is 0.01wt% and the mass ratio of Ni:Pd is 1:1. A catalytic hydrogenation reaction is carried out in the hydrogenation reactor 2, the molar ratio of hydrogen to the first mixture is 1:250, a hydrogenation reaction occurs on the catalyst surface, the reaction temperature is 100°C, the reaction pressure of the catalytic hydrogenation reaction is 3MPa, and the reaction time is 3 hours.

[0174] 3. In step S3, the condensation temperature at the top of the gas-liquid separation tank 6 is controlled to be set to 35° C., and the pressure of the gas-liquid separation tank is 0.4 MPa.

[0175] 4. In step S4, the condensation temperature of the distillation tower 3 is 30° C., and the heating temperature of the distillation tower 3 is 140° C. The distillation tower kettle is distilled at 120 kPa, and the reflux ratio is 30.

[0176] Example 4

[0177] The difference between this embodiment and embodiment 1 is that:

[0178] 1. In step S1, the crude n-butanol is heated to 80°C.

[0179] 2. In step S2, the mixture is preheated to a temperature of 100°C and then fed into a hydrogenation reactor 2. A (Pd-Ni) / C catalyst (with a Pd content of 5 wt% and a mass ratio of Ni:Pd of 0.01:1) is prepared in advance. A catalytic hydrogenation reaction is carried out in the hydrogenation reactor 2, the molar ratio of hydrogen to the first mixture is 1:150, a hydrogenation reaction occurs on the catalyst surface, the reaction temperature is 150°C, the reaction pressure of the catalytic hydrogenation reaction is 2 MPa, and the reaction time is 1 hour.

[0180] 3. In step S3, the condensation temperature at the top of the gas-liquid separation tank 6 is controlled to be set to 30°C, and reduced pressure flash evaporation is performed, and the pressure of the gas-liquid separation tank is 0.5 MPa.

[0181] 4. In step S4, the condensation temperature of the distillation tower 3 is 38° C., and the heating temperature of the distillation tower 3 is 160° C. The distillation tower kettle is distilled at 101 kPa, and the reflux ratio is 50.

[0182] Comparative Example 1

[0183] The Pd / C catalyst was prepared according to the method of Example 1, and crude n-butanol was treated. The process conditions were the same as those of Example 1, except that the second metal element level, i.e., the metal element M, was not introduced into the catalyst. Specifically, Ni(NO 3 ) 2 6H 2 O, only palladium chloride is dissolved and loaded on activated carbon. In the Pd / C catalyst of this comparative example, the mass fraction of Pd is 0.3%.

[0184] Comparative Example 2

[0185] A Pd / C catalyst was prepared according to the method of Example 1, and crude n-butanol was treated. The process conditions were the same as those of Example 1, except that the mass fraction of Pb in the catalyst, specifically, when preparing the (Pd-Ni) / C catalyst, the mass fraction of Pd in ​​the (Pd-Ni) / C catalyst of the comparative example was 0.05%.

[0186] Comparative Example 3

[0187] According to the attached Figure 3 The extraction system processes the crude butanol, and the feeding conditions are the same as those in Example 1. This comparative example uses a distillation method to purify the crude butanol, and the purification process includes:

[0188] Step 1: Crude n-butanol is first fed into the first distillation tower, i.e., the alcohol tower 25, with an operating pressure of 101-103 kpa, an operating temperature of 90-110°C, and a reflux ratio of 11, in which the light components of the fusel alcohol are removed. The fusel alcohols containing methanol, propanol, butanol, water and other light components are condensed to 60°C by the first top condenser, i.e., the alcohol tower top condenser 32, and then collected in the first reflux tank, i.e., the alcohol tower reflux tank 28. Part of the water is refluxed to the top of the tower by the first reflux pump, i.e., the alcohol tower reflux pump 39, and part of the water is extracted to the outside for treatment. The tower bottom liquid process water is extracted by the first tower bottom pump, i.e., the alcohol tower bottom liquid delivery pump 40, and is reused after being cooled to 40°C by the first tower bottom cooler, i.e., the alcohol tower bottom cooler 34. The intermediate extraction is water-containing n-butanol with a water content of ≤10%. After being condensed to 75°C by the intermediate extraction condenser 33 of the alcohol tower, it is collected in the chromatograph feed tank 29.

[0189] Step 2: The water-containing n-butanol in the chromatograph feed tank 29 is further sent to the butanol cooler 35 by the chromatograph feed pump 41, cooled to below 40°C, and input into the butanol chromatograph 27. Water and butanol are immiscible in the butanol chromatograph 27 and separated into layers. The upper layer is butanol and is sent to the second distillation tower 26; the lower layer is water and is returned to the alcohol tower 25 for further dehydration.

[0190] Step 3: The second distillation tower, i.e., the butanol tower 26, has an operating pressure of 105-110 kpa, an operating temperature of 95-120°C, and a reflux ratio of 1. The top of the tower is the butanol with a high water content, which is condensed to 75°C by the second top condenser, i.e., the butanol tower top condenser 37, and then collected in the second reflux tank, i.e., the butanol tower reflux tank 30, and partially refluxed to the top of the tower by the second reflux pump, i.e., the butanol tower reflux pump 42, and partially sent to the chromatograph feed tank 29 to continue separating butanol and water. The bottom of the second distillation tower 26 is the n-butanol product, which is extracted by the second bottom pump, i.e., the butanol tower bottom liquid delivery pump 43, and then cooled to 40°C by the second bottom cooler 38 and sent to the product storage tank.

[0191] Comparative Example 4

[0192] According to the attached Figure 4 The extraction system processes the crude butanol, and the feeding conditions are the same as those in Example 1. This comparative example uses a distillation method to purify the crude butanol. The purification process is different from that in Comparative Example 1 in that:

[0193] After the butanol product in the second distillation tower 2" kettle liquid is cooled, the butanol color problem is treated by adding resin physical adsorption.

[0194] The decolorizing column 44 is specifically a resin decolorizing column, which is equipped with a general macroporous adsorption resin without special restrictions. The butanol product passing through the resin decolorizing column 44 is sent to a storage tank.

[0195] The butanol products in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 were analyzed respectively, and the component contents of butyraldehyde therein were compared. The analysis results are shown in Table 1:

[0196] Table 1 Experimental data of Examples 1-2 and Comparative Examples 1-2

[0197]

[0198] From the results of the above comparative analysis, it can be seen that under the same Pd content, the butyraldehyde content of the catalyst without Ni is relatively high. This shows that the present invention introduces a second metal, and under the synergistic effect of the two metals, the goal of hydrogenation can be achieved under the condition of a low precious metal Pd loading.

[0199] The butanol products in Example 1, Example 2, Comparative Example 3 and Comparative Example 4 were analyzed respectively. The analysis results are shown in Table 3 below.

[0200] Table 2 Test results of n-butanol products obtained in Examples and Comparative Examples

[0201]

[0202] From the above analysis results, it can be concluded from the comparative examples and comparative example 1 that the use of (Pd-Ni) / C catalyst hydrogenation has a significant effect on the removal of trace coloring functional groups in n-butanol, so that the trend of carbonyl number and sulfuric acid color development test is consistent. From the comparison of the embodiment and comparative examples 3 and 4, it can be seen that although the concentration of butanol has exceeded the national standard requirements through rectification means, the chromaticity cannot be effectively reduced by rectification means, and the indicators of sulfuric acid color development test cannot be removed by physical adsorption means such as resin adsorption, and still cannot appear as qualified national standard products.

[0203] The product that has not been subjected to the crude n-butanol purification system of the present invention is inferior to the product that has been subjected to the crude n-butanol purification system of the present invention in terms of n-butanol content, water content, color number and heavy component content; by comparing the embodiment with comparative examples 1-2, it can be concluded that the modified catalyst can reduce the loading amount of the precious metal Pd and reduce the cost of the catalyst without affecting the hydrogenation effect. By comparing the embodiment with comparative examples 3-4, it can be concluded that the color number and sulfuric acid color development test of the n-butanol product subjected to the hydrogenation decolorization reaction of the present invention are significantly better than the color number of the conventional resin decolorization method.

[0204] The purity and detailed composition analysis of n-butanol were measured using an Agilent 7890 chromatograph.

[0205] The color number test is based on GB3143-1982 and measured by Lovibond Tintometer PFX190.

[0206] The sulfuric acid color number test is carried out according to the method in GB / T6027-2023, and the colorimetry is carried out according to the provisions of GB / T3143-1982.

[0207] The carbonyl number is used to analyze the carbonyl functional group content in butanol. It is measured by hydroxylamine hydrochloride titration using a Mettler T90 titrator. The carbonyl compounds in the sample can react with hydroxylamine hydrochloride to generate H+, and the H+ is titrated with a NaOH standard solution. The calculation of the measurement result

[0208]

[0209] Where: SN——the number of carbonyl groups in the sample

[0210] V——NaOH consumed by the sample, ml

[0211] C——Concentration of NaOH standard solution, M

[0212] M——mass of sample, g.

[0213] It can be seen from the above experimental data that compared with the existing technology, the beneficial effects of this technical solution are as follows:

[0214] 1. Efficient decolorization: Decolorization reaction is carried out in a hydrogenation reactor, which can effectively eliminate the unsaturated bonds in butanol, solve the problem that the by-product crude butanol or waste butanol of the existing device is difficult to meet the color number required by the national standard and the two key indicators of sulfuric acid color development test, thereby improving the quality of the product.

[0215] 2. High economic benefits: Through the present invention, the loading amount of precious metal Pd can be effectively reduced, and the cost of the catalyst can be reduced. The treated butanol can not only achieve a purity of 99.9%, but also the color number of the butanol, which is more important, meets the requirements of GB / T6027-2023 "Industrial n-Butanol" Type I in the sulfuric acid color development test, which is much higher than the level of the prior art, thereby increasing the added value of the product.

[0216] 3. Simplified process: The present invention adopts equipment such as a hydrogenation reactor and a butanol refining tower, and through a series of physical and chemical processes, achieves efficient purification of butanol, simplifies the production process, and reduces production costs.

[0217] 4. Environmental protection and safety: During the processing process, the present invention effectively recovers and utilizes hydrogen through equipment such as a gas-liquid separation tank and a tail gas condenser, thereby avoiding environmental pollution and ensuring the safety of the production process.

[0218] 5. Strong adaptability: The present invention is not only applicable to the purification of crude n-butanol produced as a by-product of the BDO process of the acetylene aldehyde method, but is also applicable to the purification of crude n-butanol from other sources, and has strong adaptability and broad application prospects.

[0219] It should be pointed out that although the various steps in the above embodiments are described in a specific order, those skilled in the art can understand that in order to achieve the effects of the present invention, different steps do not have to be performed in such an order. They can be performed simultaneously (in parallel) or in other orders. These changes are within the scope of protection of the present invention.

[0220] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for purifying crude n-butanol, characterized in that: include: The crude n-butanol to be purified is fed into a dehydration device and dehydrated by membrane separation to obtain a first mixture; After preheating the first mixture in a first preheater, catalytic hydrogenation reaction is performed under the action of a Pd / C catalyst to obtain a second mixture; flash evaporating the second mixture under reduced pressure in a gas-liquid separation tank to obtain a third mixture; The third mixture is distilled in a distillation tower to obtain purified n-butanol.

2. The method according to claim 1, characterized in that The step of inputting the crude n-butanol to be purified into a dehydration device and performing dehydration by membrane separation to obtain a first mixture comprises: The dehydration device comprises n gradient flux membrane components connected in sequence, the crude n-butanol to be purified sequentially through each of the membrane components, dehydration, wherein the crude n-butanol to be purified in each membrane component feed pressure is 0.1-5 kPaA; After dehydration through the n membrane modules, a first mixture is obtained, wherein the mass fraction of water in the first mixture is ≤10%.

3. The method according to claim 2, characterized in that The membrane flux of the n membrane components decreases in sequence; 1≤n≤5; the membrane component includes a molecular sieve membrane, wherein the separation factor of the molecular sieve membrane is 20-80, and the permeation flux is 200-2000g / (m 2 •hr).

4. The method according to claim 1, characterized in that: The Pd / C catalyst is further doped with a metal element M, wherein the M comprises at least one of nickel, chromium, molybdenum, silver and copper; the mass ratio of the doping amount of the metal element M to Pd is (0.01-1):

1.

5. The method according to claim 1 or 2, characterized in that: Preheating the first mixture in a first preheater comprises: heating the first mixture to 100-150° C. in a first preheater; In the Pd / C catalyst, the mass fraction of the Pd element is 0.1-5wt%; the hydrogenation reactor is a fixed bed reactor; The catalyst space-time yield ranges from 20 to 60 mg / g•h -1 The reaction temperature of the catalytic hydrogenation reaction is 100-150° C., the reaction time is 1-3 hours, the reaction pressure is 2-3 MPa, and the molar ratio of the hydrogen to the first mixture is 1:(150-250).

6. The method according to claim 1, characterized in that Before the crude n-butanol to be purified is introduced into the dehydration device, the method further comprises: The crude n-butanol to be purified is heated to 50-80°C in the second preheater.

7. The method according to claim 1, characterized in that The flash distillation of the second mixture under reduced pressure in a gas-liquid separation tank comprises: The second mixture is input into a gas-liquid separation tank for reduced pressure flash evaporation, wherein during reduced pressure flash evaporation, the pressure of the gas-liquid separation tank is controlled to be 0.4-0.6 MPa, and the condensation temperature at the top of the gas-liquid separation tank is set to be ≤40° C.; The condensed liquid phase is refluxed into the gas-liquid separation tank, and the uncondensed gas phase is discharged into the tail gas pipe.

8. The method according to claim 1, characterized in that The step of distilling the third mixture in a distillation tower to obtain purified n-butanol comprises: After the reduced pressure flash evaporation, the liquid phase in the gas-liquid separation tank is input into a distillation tower for distillation; The reflux ratio of the top reflux liquid of the distillation tower is 30-50, the distillation tower kettle is distilled at 101-120 kPa, the temperature of the distillation tower kettle is 140-160°C, and the condensation temperature of the top of the tower is 30-40°C; The liquid in the middle and / or upper part of the distillation tower kettle is collected to obtain purified n-butanol.

9. The method according to claim 1, characterized in that: The mass fraction of n-butanol in the crude n-butanol to be purified is 1% to 10%; the crude n-butanol to be purified is a by-product of a 1,4-butanediol device.

10. A crude n-butanol purification system, characterized in that: include: The dehydration device, the first preheater, the hydrogenation reactor, the gas-liquid separation tank and the distillation tower are connected in sequence.

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