Rectification process of dipropylene glycol

Abstract

The invention belongs to the technical field of rectification of dipropylene glycol, and relates to a rectification process of dipropylene glycol. The process comprises the following steps: preheating a crude product raw material containing dipropylene glycol, then feeding the crude product raw material into a pre-separation tower for pre-rectification, then feeding tower bottoms of the pre-separation tower into a packed tower for rectification, and extracting from the tower top of the packed tower to obtain a dipropylene glycol product; the interior of the packed tower is sequentially filled with modified ceramic corrugated packing, a stainless steel wire net and modified molecular sieve packing from bottom to top; the modified ceramic corrugated filler is obtained by sequentially acidizing a ceramic corrugated filler and loading SiO2 / CeO2; the modified molecular sieve filler is obtained by alkalization, calcination and SiO2 / Al2O3 loading of molecular sieve honeycomb ceramics in sequence. Through the modified ceramic corrugated filler, the stainless steel wire mesh and the modified molecular sieve filler which are sequentially arranged from bottom to top, the material transfer efficiency, the component separation precision and the operation stability of the device in the crude product raw material rectification process are optimized, and the overall process efficiency is effectively improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of dipropylene glycol rectification, and relates to a dipropylene glycol rectification process. BACKGROUND

[0002] In the production process of dipropylene glycol, the crude raw material usually contains various impurity components with similar boiling points, including unreacted monopropylene glycol, polyether by-products and trace moisture. The traditional rectification process often adopts a double-tower series rectification mode, that is, the light components are removed through a pre-separation tower, and then the target product is obtained by purification through a main tower. However, this process has significant defects in actual operation: on the one hand, the pressure drop switching between the pre-separation tower and the main tower easily causes material phase disturbance, resulting in entrainment of light components or backmixing of heavy components; on the other hand, the mass transfer efficiency of the conventional packing in the main tower is limited, and the selectivity for impurities with similar molecular structures is insufficient, so that the product purity is difficult to break through the technical threshold of 99.3%.

[0003] Especially under high vacuum operating conditions, the pressure drop control of the tower packing becomes a core contradiction. Although traditional high-density packings such as metal wire mesh have excellent mechanical strength, the excessive gas resistance will cause a sharp increase in energy consumption of the vacuum system, and the uneven liquid holdup distribution will cause local channeling. Although adsorbent materials such as molecular sieves can improve the separation precision, the particle accumulation structure is easy to collapse in continuous operation, not only blocking the tray, but also forcing the device to frequently shut down and replace the packing. In addition, the azeotropic effect of light and heavy components will intensify as the pressure decreases, and if the gas-liquid distribution and adsorption retention mechanism are not optimized simultaneously in the rectification process, the yield of dipropylene glycol will decrease, and the residual heavy components will exceed the standard.

[0004] The current industry urgently needs a rectification process that takes into account separation precision, energy consumption economy and device stability, ensures product purity > 99.5%, and realizes the coordinated optimization of packing life and vacuum system. This requires fundamentally reconstructing the mass transfer-adsorption balance inside the rectification tower, and breaking through the dilemma of traditional packing between pressure drop and separation efficiency. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a dipropylene glycol rectification process, which optimizes the mass transfer efficiency, component separation precision and device operation stability in the crude raw material rectification process by sequentially arranging modified ceramic corrugated packing, stainless steel wire mesh and modified molecular sieve packing from bottom to top, and effectively improves the overall process efficiency.

[0006] To achieve this purpose, the technical scheme adopted by the present application is as follows:

[0007] The present application provides a dipropylene glycol rectification process, which comprises:

[0008] The crude raw material containing dipropylene glycol is preheated and then sent into a pre-separation tower for pre-distillation, and then the tower bottom liquid of the pre-separation tower is sent into a packed tower for distillation, and a dipropylene glycol product is obtained from the top of the packed tower;

[0009] The interior of the packed tower is sequentially filled from bottom to top with modified ceramic corrugated packing, stainless steel wire mesh and modified molecular sieve packing;

[0010] The modified ceramic corrugated packing is obtained by sequentially subjecting ceramic corrugated packing to acidification and SiO2 / CeO2 loading;

[0011] The modified molecular sieve packing is obtained by sequentially subjecting molecular sieve honeycomb ceramic to alkalization, calcination and SiO2 / Al2O3 loading.

[0012] The rectification process provided by the application optimizes the material transfer efficiency, component separation precision and stability of device operation in the distillation process of the crude raw material, and effectively improves the overall process efficiency.

[0013] The concentration of heavy components in the bottom region is high, and the ceramic corrugated packing subjected to acidification and SiO2 / CeO2 loading is placed in the tower bottom, which has the following effects: acidification treatment increases the roughness and effective contact area of the ceramic surface, which is beneficial to the contact of gas and liquid phases; the loaded SiO2 / CeO2 composite makes the surface of the modified ceramic corrugated packing have a certain hydrophilicity, which helps to wet the liquid phase and form a uniform liquid film, in addition, the CeO2 component has a moderate catalytic conversion and adsorption effect on some trace high-boiling heavy component impurities, which helps to reduce the migration of heavy component impurities to the upper tower section.

[0014] The stainless steel wire mesh in the middle layer undertakes the key functions of gas-liquid distribution adjustment and pressure buffering, and the fine structure with a mesh size of 300-400 can effectively divide large bubbles in the rising gas stream, promote the formation of fine and dispersed gas-liquid contact interfaces, and significantly reduce the "channeling" problem caused by uneven fluid distribution. At the same time, its open hole characteristics make the resistance of gas passing through relatively low, which helps to reduce the pressure drop of the entire packed tower under the condition of maintaining high vacuum (1-1.2 kPa) operating pressure, effectively alleviating the energy consumption problem caused by excessive resistance of the packed tower in high vacuum rectification while ensuring separation precision.

[0015] The modified molecular sieve filler is filled at the top of the tower, the molecular sieve honeycomb ceramic is pretreated by alkalization and calcination to enhance the firmness of its skeleton, and after being loaded with SiO2 / Al2O3, a composite layer with specific pore structure and surface chemical properties is formed on the surface. The loading of SiO2 / Al2O3 can adjust the properties of the molecular sieve surface, provide more suitable adsorption sites and selectivity for target impurities (such as residual monopropylene glycol, trace water, and small molecule ethers), and significantly enhance the mechanical strength and heat resistance of the filler. This filler is located in the light component enrichment area at the top of the tower, which can accurately capture and intercept trace light impurities with similar structure and boiling point to dipropylene glycol, thereby ensuring the purity of the tower top product. Through structure strengthening, the problem of powdering and collapse of traditional molecular sieve filler in long-term continuous operation is avoided, and the service life of the filler and the operation reliability of the device are improved.

[0016] The synergistic effect of the three-layer filler constitutes an efficient integrated rectification system. The modified ceramic corrugated filler filled at the bottom of the tower is used to treat heavy component impurities and improve the initial separation effect; the stainless steel wire mesh filled in the middle is used to optimize fluid distribution and control pressure drop; and the modified molecular sieve filler filled at the top is used to remove light impurities in depth. Through the functional modification and spatial arrangement of different fillers, the performance of the traditional two-tower series rectification process in the purification of dipropylene glycol can be significantly improved without changing the basic structure of the tower body, which improves the separation efficiency, reduces the process energy consumption, enhances the stability and continuity of the device operation, and has good industrial application prospect.

[0017] As a preferred technical solution of the present application, the crude raw material is preheated to 100-110℃, for example, it can be 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, 106℃, 107℃, 108℃, 109℃ or 110℃, but not limited to the listed values, other values not listed in this range are also applicable.

[0018] In some optional examples, the pre-separation tower has a bottom temperature of 150-160℃, for example, it can be 150℃, 151℃, 152℃, 153℃, 154℃, 155℃, 156℃, 157℃, 158℃, 159℃ or 160℃, but not limited to the listed values, other values not listed in this range are also applicable.

[0019] In some optional examples, the pre-separation tower has a top temperature of 100-110℃, for example, it can be 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, 106℃, 107℃, 108℃, 109℃ or 110℃, but not limited to the listed values, other values not listed in this range are also applicable.

[0020] In some optional examples, the pre-separation column has a reflux ratio of (6-8): 1, such as 6.0:1, 6.2:1, 6.4:1, 6.6:1, 6.8:1, 7.0:1, 7.2:1, 7.4:1, 7.6:1, 7.8:1, or 8.0:1, but not limited to the recited values, other unrecited values within the range are also applicable.

[0021] In some optional examples, the pre-separation column has an operating pressure of 2-3 kPa, such as 2.0 kPa, 2.1 kPa, 2.2 kPa, 2.3 kPa, 2.4 kPa, 2.5 kPa, 2.6 kPa, 2.7 kPa, 2.8 kPa, 2.9 kPa, or 3.0 kPa, but not limited to the recited values, other unrecited values within the range are also applicable.

[0022] In some optional examples, the pre-separation column has a number of trays of 18-24, such as 18, 19, 20, 21, 22, 23, or 24, but not limited to the recited values, other unrecited values within the range are also applicable.

[0023] In some optional examples, the column bottom liquid is fed to the middle of the packed column, corresponding to the location of the modified ceramic corrugated packing.

[0024] In some optional examples, the packed column has a column bottom temperature of 160-170 °C, such as 160 °C, 161 °C, 162 °C, 163 °C, 164 °C, 165 °C, 166 °C, 167 °C, 168 °C, 169 °C, or 170 °C, but not limited to the recited values, other unrecited values within the range are also applicable.

[0025] In some optional examples, the packed column has a column top temperature of 105-108 °C, such as 105 °C, 105.5 °C, 106 °C, 106.5 °C, 107 °C, 107.5 °C, or 108 °C, but not limited to the recited values, other unrecited values within the range are also applicable.

[0026] In some optional examples, the packed column has a reflux ratio of (8-10): 1, such as 8.0:1, 8.2:1, 8.4:1, 8.6:1, 8.8:1, 9.0:1, 9.2:1, 9.4:1, 9.6:1, 9.8:1, or 10.0:1, but not limited to the recited values, other unrecited values within the range are also applicable.

[0027] In some optional examples, the operating pressure of the packing tower is 1-1.2 kPa, for example, can be 1.0 kPa, 1.02 kPa, 10.4 kPa, 1.06 kPa, 1.08 kPa, 1.1 kPa, 1.12 kPa, 1.14 kPa, 1.16 kPa, 1.18 kPa or 1.2 kPa, but not only limited to the listed values, other values not listed in the range are also applicable.

[0028] In some optional examples, the bulk density of the modified ceramic corrugated packing is 480-500 kg / m 3 , for example, can be 480 kg / m 3 , 482 kg / m 3 , 484 kg / m 3 , 486 kg / m 3 , 488 kg / m 3 , 490 kg / m 3 , 492 kg / m 3 , 494 kg / m 3 , 496 kg / m 3 , 498 kg / m 3 or 500 kg / m 3 , but not only limited to the listed values, other values not listed in the range are also applicable.

[0029] The present application particularly limits the bulk density of the modified ceramic corrugated packing to be 480-500 kg / m 3 . When in this range, the modified ceramic corrugated packing layer has sufficient mechanical strength to ensure that the packing can withstand the high temperature environment of 160-170℃ at the bottom of the tower and the static pressure and scouring of the heavy component liquid, preventing structural deformation or fragmentation, and protecting the integrity of the SiO2 / CeO2 functional layer; in addition, the moderate porosity provides sufficient gas-liquid channels and effective specific surface area, promoting the uniform spreading of the liquid phase on the packing surface to form an efficient mass transfer interface, realizing the initial effective separation of the heavy components.

[0030] When the bulk density of the modified ceramic corrugated packing is less than 480 kg / m 3 , the packing structure is too loose and fragile, and the mechanical strength is significantly insufficient, which is easily crushed or broken under the harsh conditions at the bottom of the tower, not only destroying the uniformity of the packing bed and reducing the effective mass transfer area of the packing bed, but also the generated fragments can block the tower kettle or wear the upper layer of packing with the gas flow. At the same time, the excessively low bulk density will produce larger pores, weaken the liquid retention capacity, and lead to uneven liquid film distribution or even local dryness, thereby reducing the mass transfer efficiency.

[0031] When the bulk density of the modified ceramic corrugated packing is higher than 500 kg / m 3When the packing bed is too dense, the specific surface area is greatly reduced, which significantly weakens the gas-liquid contact efficiency and reduces the initial interception ability of high-boiling-point impurities. In addition, high-density stacking leads to a sharp increase in gas flow resistance, and the pressure drop at the bottom of the tower is significantly increased. Under the condition of maintaining a high vacuum of 1-1.2 kPa at the top of the tower, a large amount of energy will be consumed by the vacuum system, greatly increasing the operating cost. At the same time, the excessive liquid holdup will prolong the residence time of heavy components in the high-temperature zone, and intensify the tendency of side reactions or polymerization coking.

[0032] In some optional examples, the modified ceramic corrugated packing has a packing height of 1.5-1.8 m, for example, it can be 1.5 m, 1.52 m, 1.54 m, 1.56 m, 1.58 m, 1.6 m, 1.62 m, 1.64 m, 1.66 m, 1.68 m, 1.7 m, 1.72 m, 1.74 m, 1.76 m, 1.78 m, or 1.8 m, but not limited to the listed values, and other values not listed in the range are also applicable.

[0033] In some optional examples, the stainless steel wire mesh has a mesh number of 300-400 meshes, for example, it can be 300 meshes, 310 meshes, 320 meshes, 330 meshes, 340 meshes, 350 meshes, 360 meshes, 370 meshes, 380 meshes, 390 meshes, or 400 meshes, but not limited to the listed values, and other values not listed in the range are also applicable.

[0034] In some optional examples, the stainless steel wire mesh has a bulk density of 300-350 kg / m 3 , for example, it can be 300 kg / m 3 , 305 kg / m 3 , 310 kg / m 3 , 315 kg / m 3 , 320 kg / m 3 , 325 kg / m 3 , 330 kg / m 3 , 335 kg / m 3 , 340 kg / m 3 , 345 kg / m 3 , or 350 kg / m 3 , but not limited to the listed values, and other values not listed in the range are also applicable.

[0035] In some optional examples, the packing height of the stainless steel wire mesh is 1.2-1.5 m, for example, can be 1.2 m, 1.22 m, 1.24 m, 1.26 m, 1.28 m, 1.3 m, 1.32 m, 1.34 m, 1.36 m, 1.38 m, 1.4 m, 1.42 m, 1.44 m, 1.46 m, 1.48 m or 1.5 m, but not only limited to the listed values, other unlisted values within the range are also applicable.

[0036] In some optional examples, the bulk density of the modified molecular sieve filler is 560-580 kg / m 3 , for example, can be 560 kg / m 3 , 562 kg / m 3 , 564 kg / m 3 , 566 kg / m 3 , 568 kg / m 3 , 570 kg / m 3 , 572 kg / m 3 , 574 kg / m 3 , 576 kg / m 3 , 578 kg / m 3 or 580 kg / m 3 , but not only limited to the listed values, other unlisted values within the range are also applicable.

[0037] The present application particularly limits the bulk density of the modified molecular sieve filler to be 560-580 kg / m 3 , when within this range, the filler bed has sufficient structural strength to ensure that it can withstand the top negative pressure environment and the continuous scouring of gas-liquid flow, effectively preventing the pulverization or collapse of the molecular sieve skeleton due to insufficient mechanical strength, and providing reliable support for the firmly loaded SiO2 / Al2O3 composite functional layer; in addition, the appropriate density and pore structure not only ensure a sufficient number of micropore channels for target light impurity molecules (such as monopropylene glycol and water molecules) to diffuse into and be captured by the selective adsorption sites, but also avoid the instability of the filler bed structure caused by excessive looseness; at the same time, this bulk density range is conducive to maintaining a lower pressure drop, avoiding the influence of excessive tower top resistance on the stability of the overall tower vacuum.

[0038] When the bulk density of the modified molecular sieve filler is less than 560 kg / m 3When the packed bed structure is too loose and fragile, with significantly insufficient mechanical strength, it is prone to structural loosening, breakage, or even pulverization under the continuous impact of gas-liquid flow during high vacuum operation. The resulting fine particles can rise with the gas flow, clogging the top pipeline or contaminating the product, severely impairing the continuity of the distillation process and product purity. Simultaneously, the effective adsorption channels of the loose packed bed structure will decrease or become blocked due to structural deformation or collapse, weakening its adsorption capacity for light impurities. Furthermore, the structural instability of the packed bed accelerates the peeling failure of the SiO2 / Al2O3 composite layer, leading to a rapid decline in adsorption performance.

[0039] When the bulk density of the modified molecular sieve packing is higher than 580 kg / m³ 3 When the packed bed structure is too dense, the porosity is significantly reduced, resulting in a substantial decrease in the effective specific surface area and the number of active sites available for the adsorption of light impurity molecules (such as monopropylene glycol and trace amounts of water), severely weakening the adsorption capacity of the packed bed. Furthermore, although the packed bed structure has high strength, an excessively dense bed structure significantly increases gas flow resistance, leading to an abnormally high pressure drop at the top of the column. This not only increases the energy consumption of the vacuum system but also disrupts the vacuum balance of the entire column, affecting the efficiency of gas-phase removal of light impurities. Simultaneously, an excessively high liquid holdup prolongs the residence time of the material at the top of the column, hindering timely product collection.

[0040] In some alternative examples, the filling height of the modified molecular sieve packing is 1 to 1.2 m, for example, it can be 1.0 m, 1.02 m, 1.04 m, 1.06 m, 1.08 m, 1.1 m, 1.12 m, 1.14 m, 1.16 m, 1.18 m or 1.2 m, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0041] In the dipropylene glycol distillation process, modified ceramic corrugated packing, stainless steel wire mesh and modified molecular sieve packing are arranged from bottom to top and complement each other in function to form a highly efficient and synergistic distillation system, which significantly improves separation efficiency, reduces energy consumption and ensures long-term stable operation of the unit.

[0042] The modified ceramic corrugated packing at the bottom of the tower is mainly responsible for initial separation and heavy component treatment. The ceramic surface with acidification and SiO2 / CeO2 loading has a certain roughness and hydrophilicity, effectively promoting the wetting and spreading of the feed liquid on the packing surface, providing sufficient contact area for gas-liquid two phases, and improving the mass transfer efficiency of the bottom area. More importantly, the SiO2 / CeO2 composite coating endows the surface with chemical function: the hydrophilic SiO2 layer is beneficial to the liquid phase distribution, and the dispersed CeO2 nanoparticles have weak catalytic and adsorption properties, which can inhibit and convert the trace high-boiling impurities in the crude raw material that are prone to accumulate or coking in the tower kettle, effectively avoiding the accumulation and coking of heavy component impurities on the packing surface and in the tower kettle, reducing the burden on the subsequent packing. At the same time, its stable mechanical structure provides reliable support for bearing the high temperature and heavy component load at the bottom of the tower.

[0043] The stainless steel wire mesh in the middle section of the tower is used to regulate the balance of flow field and pressure drop. The fine mesh structure of 300-400 mesh has high efficiency in breaking large bubbles in the rising gas flow, promoting the formation of small and uniform dispersed bubble groups or gas-liquid mixed phases, greatly reducing the "channeling" or "wall flow" phenomenon caused by uneven gas-liquid distribution, and ensuring uniform contact of gas-liquid phases in the packing bed. At the same time, the relatively open structure of the stainless steel wire mesh provides low flow resistance, effectively controls the total tower pressure drop under the premise of maintaining the high vacuum operating pressure of the rectifying tower, and significantly reduces the energy consumption burden of the vacuum system. Its stable and low-resistance flow field distribution creates an ideal feed environment for the modified molecular sieve packing, with uniform gas-liquid phase distribution and stable flow rate, avoiding local overload or short circuit. The flow field optimization by the stainless steel wire mesh enables the efficiency of the bottom packing to be transmitted upwards, and at the same time, the top packing can perform precise separation function.

[0044] The modified molecular sieve packing at the top of the tower achieves further rectification and purification of the crude dipropylene glycol through specific adsorption selectivity, finally obtaining high-purity product. The activation process of alkali treatment and high-temperature calcination optimizes the pore structure of the molecular sieve carrier and increases the active sites. The loaded SiO2 as a reinforcing phase significantly improves the overall mechanical strength and structural stability of the molecular sieve carrier, solving the problem of easy pulverization and collapse of traditional molecular sieve packing, and ensuring the structural integrity in long-term operation. The acidic sites provided by Al2O3 have stronger affinity and specific adsorption capacity for light impurities with slightly stronger polarity than dipropylene glycol, such as residual monopropylene glycol, trace water, small molecule ethers, and some oxygen-containing heterocyclic compounds. Benefiting from the stable and uniform feed state provided by the middle layer of stainless steel wire mesh, the top layer of modified molecular sieve packing can fully exert its selective adsorption capacity based on pore size screening and surface chemical differences, accurately capture and remove these trace light impurities that are extremely difficult to separate, thereby obtaining high-quality dipropylene glycol products with purity >99.5% at the top of the tower.

[0045] The synergistic effect of the three-layer packing is as follows: the modified ceramic corrugated packing for bottom filling can realize efficient treatment of heavy components, improve initial separation and inhibit coking by optimizing physical structure and surface chemical modification, thereby providing a stable foundation for the whole tower; the stainless steel wire mesh for middle filling is used for flow field regulation to realize uniform gas-liquid distribution and low pressure drop operation, thereby creating conditions for efficient mass transfer and precise separation at the top; the modified molecular sieve packing for top filling realizes deep removal of light impurities which are most difficult to separate by using its reinforced structure and selective adsorption sites, thereby outputting high-purity dipropylene glycol product. Through the synergistic cooperation between different packings, the packing combination can realize high separation precision at lower energy consumption and has excellent anti-interference ability and long-term operation stability.

[0046] As a preferred technical solution of the present application, the modified ceramic corrugated packing is prepared by the following method:

[0047] (I) The ceramic corrugated packing is soaked in a mixed acid solution, ultrasonic oscillation is performed under heating conditions, then it is taken out and washed to neutral, and after drying, an acidified ceramic corrugated packing is obtained;

[0048] (II) Tetraethyl orthosilicate is dropped into an aqueous ethanol solution, then a hydrochloric acid solution is added, a precursor solution is obtained after mixing, cerium dioxide nanoparticles are added to the precursor solution, and a modified solution is obtained after high-speed stirring;

[0049] (III) The acidified ceramic corrugated packing is soaked in the modified solution, and after soaking, it is taken out and calcined at high temperature to obtain the modified ceramic corrugated packing.

[0050] The modified ceramic corrugated packing provided by the present application significantly improves the surface properties and functions of the packing while ensuring the basic mechanical properties of the packing. First, the ceramic corrugated packing is soaked in a mixed acid solution under heating and ultrasonic oscillation conditions for controllable etching and activation of the surface of the ceramic corrugated packing. This not only effectively removes impurities and weakly bound particles on the surface of the ceramic, but also increases the micro-roughness and active site density of the ceramic surface by moderate corrosion, thereby forming a larger specific surface area and more abundant surface hydroxyl (-OH) groups. This greatly enhances the adhesion ability of the subsequent modified coating and provides a more sufficient contact interface for gas-liquid two phases, which helps to improve the initial mass transfer efficiency.

[0051] Subsequently, tetraethyl orthosilicate is added into the acidic aqueous ethanol solution for hydrolysis, a silica sol network is constructed, cerium dioxide nanoparticles are introduced and dispersed by high-speed stirring, so that the cerium dioxide nanoparticles are uniformly embedded or attached in the sol network, and finally the modified solution is soaked into the acidized ceramic filler, so that the SiO2 / CeO2 composite precursor can fully penetrate and adhere to the microporous structure of the ceramic surface expanded by acid etching, wherein SiO2 provides good chemical stability and certain hydrophilicity, which is beneficial to liquid wetting and spreading; dispersed CeO2 nanoparticles can realize adsorption or catalytic conversion of some trace impurities with specific structure, which helps to reduce their accumulation on the surface of the filler.

[0052] Finally, the physical adsorption precursor is converted into stable chemical combination by high-temperature calcination. During the high-temperature calcination process, the precursor undergoes dehydration condensation reaction to form a stable Si-O-Si and Si-O-Ce network structure. This process forms a firm chemical bond or strong physical anchoring between the SiO2 / CeO2 composite coating and the ceramic matrix, greatly enhancing the mechanical strength, wear resistance and thermal stability of the SiO2 / CeO2 coating. The SiO2 / CeO2 coating solidified by calcination can withstand the higher operating temperature at the bottom of the rectifying column and the physical erosion of gas-liquid flow during long-term operation, effectively preventing the peeling, pulverization or structural failure of the SiO2 / CeO2 coating during use, ensuring the durability and reliability of the filler performance.

[0053] The continuous coating of silicon dioxide formed on the surface of the ceramic filler mainly provides stable hydrophilicity and physical protection function. Its hydrophilic property significantly improves the wettability and spreading performance of the crude material on the surface of the filler, which helps to form a uniform and continuous thin liquid film, effectively increases the gas-liquid two-phase contact area, and improves the initial mass transfer efficiency of the tower bottom area. At the same time, SiO2 itself has excellent chemical inertness and heat resistance, which can withstand the operating temperature of 160~170℃ and chemical environment at the tower bottom, providing a strong protective barrier for the ceramic matrix, significantly enhancing the mechanical stability and service life of the filler.

[0054] CeO2 nanoparticles can realize adsorption or catalytic conversion of some trace impurities with specific structure, which helps to reduce their accumulation on the surface of the filler. 3+ / Ce 4+) and surface oxygen vacancy properties, under high-temperature rectification environment, produce certain physical adsorption or weak chemical action on trace but higher boiling point, easily enriched or reactive polar impurities (such as residual aldehydes, by-products containing unsaturated bonds or trace peroxides), which can slow down the accumulation rate of such impurities on the packing surface. At the same time, the redox properties of CeO2 can also intervene in some side reactions that can lead to coking (such as dehydration or oxidative polymerization of trace impurities), by capturing free radicals or promoting electron transfer, reducing the polymerization or coking phenomenon of heavy components on the packing surface at high temperature, which helps to maintain the cleanliness and flux of the packing surface.

[0055] SiO2 and CeO2 do not function independently, but through a composite structure to achieve a synergistic effect of function. CeO2 nanoparticles are uniformly dispersed and embedded in a continuous SiO2 network matrix. The advantage of this structural design is that the SiO2 matrix provides a stable dispersion carrier and physical anchor point for CeO2 particles, effectively preventing their agglomeration or loss during use, ensuring that the active surface of CeO2 can be exposed to the environment for a long time and stably.

[0056] As a preferred technical solution of the present application, in step (I), the pore size of the ceramic corrugated packing is 0.8-1.2 mm, for example, it can be 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1.0 mm, 1.05 mm, 1.1 mm, 1.15 mm or 1.2 mm, but not limited to the listed values, other values not listed in this range are also applicable.

[0057] In some optional examples, the mixed acid solution is composed of hydrofluoric acid, nitric acid and deionized water.

[0058] In some optional examples, the mass fraction of hydrofluoric acid in the mixed acid solution is 8-10%, for example, it can be 8.0%, 8.2%, 8.4%, 8.6%, 8.8%, 9.0%, 9.2%, 9.4%, 9.6%, 9.8% or 10.0%, but not limited to the listed values, other values not listed in this range are also applicable.

[0059] In some optional examples, the mass fraction of nitric acid in the mixed acid solution is 4-6%, for example, it can be 4.0%, 4.2%, 4.4%, 4.6%, 4.8%, 5.0%, 5.2%, 5.4%, 5.6%, 5.8% or 6.0%, but not limited to the listed values, other values not listed in this range are also applicable.

[0060] In some alternative examples, the solid-liquid ratio of the ceramic corrugated filler to the mixed acid solution is 1 g:(10~20) mL, for example, it can be 1 g:10 mL, 1 g:11 mL, 1 g:12 mL, 1 g:13 mL, 1 g:14 mL, 1 g:15 mL, 1 g:16 mL, 1 g:17 mL, 1 g:18 mL, 1 g:19 mL or 1 g:20 mL, but not limited to the listed values, other values not listed in the range are also applicable.

[0061] In some alternative examples, the heating temperature of the ceramic corrugated filler when immersed in the mixed acid solution is 45~55℃, for example, it can be 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃ or 55℃, but not limited to the listed values, other values not listed in the range are also applicable.

[0062] In some alternative examples, the ultrasonic power of the ultrasonic oscillation of the ceramic corrugated filler when immersed in the mixed acid solution is 300~400 W, for example, it can be 300 W, 310 W, 320 W, 330 W, 340 W, 350 W, 360 W, 370 W, 380 W, 390 W or 400 W, but not limited to the listed values, other values not listed in the range are also applicable.

[0063] In some alternative examples, the immersion time of the ceramic corrugated filler in the mixed acid solution is 15~25 min, for example, it can be 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min or 25 min, but not limited to the listed values, other values not listed in the range are also applicable.

[0064] As a preferred technical solution of the present application, in step (II), the volume ratio of ethanol to deionized water in the aqueous ethanol solution is (8~10):1, for example, it can be 8.0:1, 8.2:1, 8.4:1, 8.6:1, 8.8:1, 9.0:1, 9.2:1, 9.4:1, 9.6:1, 9.8:1 or 10.0:1, but not limited to the listed values, other values not listed in the range are also applicable.

[0065] In some embodiments, the tetraethyl orthosilicate is added dropwise into the aqueous ethanol solution under stirring at 200-300 rpm, for example, 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm, or 300 rpm, but not limited to the listed values, and other values not listed in the range are also applicable.

[0066] In some embodiments, the molar ratio of the tetraethyl orthosilicate to ethanol in the aqueous ethanol solution is 1:8-10, for example, 1:8.0, 1:8.2, 1:8.4, 1:8.6, 1:8.8, 1:9.0, 1:9.2, 1:9.4, 1:9.6, 1:9.8, or 1:10.0, but not limited to the listed values, and other values not listed in the range are also applicable.

[0067] In some embodiments, the mass of the hydrochloric acid solution is 0.8-1.2 wt% of the mass of the tetraethyl orthosilicate, for example, 0.8 wt%, 0.85 wt%, 0.9 wt%, 0.95 wt%, 1.0 wt%, 1.05 wt%, 1.1 wt%, 1.15 wt%, or 1.2 wt%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0068] In some embodiments, the ceria nanoparticles have a particle size of 30-50 nm, for example, 30 nm, 32 nm, 34 nm, 36 nm, 38 nm, 40 nm, 42 nm, 44 nm, 46 nm, 48 nm, or 50 nm, but not limited to the listed values, and other values not listed in the range are also applicable.

[0069] In some embodiments, the mass of the ceria nanoparticles is 3-5 wt% of the mass of the tetraethyl orthosilicate, for example, 3.0 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt%, 4.0 wt%, 4.2 wt%, 4.4 wt%, 4.6 wt%, 4.8 wt%, or 5.0 wt%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0070] The application particularly limits the mass of the cerium dioxide nanoparticles to be 3-5wt% of the mass of the tetraethyl orthosilicate. When the range is reached, the necessary dispersion concentration of CeO2 in the formed SiO2 matrix can be ensured, so that the surface active sites (such as oxygen vacancies, variable valence) on the filler surface are effectively covered, thereby producing weak adsorption or weak catalytic inhibition effect on trace heavy component impurities prone to coking in the tower bottom high temperature environment, and reducing the risk of accumulation and coking. In addition, the addition amount range also effectively avoids the agglomeration tendency caused by excessive CeO2. In the high-speed stirring and subsequent calcination process, CeO2 can be well wrapped and dispersed by the SiO2 network, maintaining the uniformity and structural integrity of the coating.

[0071] When the addition amount of CeO2 is less than 3wt%, the CeO2 nanoparticles are too sparse in the finally formed SiO2 / CeO2 composite coating, and the number of effective active sites is insufficient, which makes it difficult to effectively slow down the accumulation or coking of tower bottom heavy component impurities on the filler surface.

[0072] When the addition amount of CeO2 is higher than 5wt%, the excess CeO2 nanoparticles are prone to agglomeration in the high-speed stirring and sol environment, forming larger agglomerates. These agglomerates are difficult to be completely wrapped and dispersed by the SiO2 matrix in the subsequent calcination process, which destroys the uniformity and density of the coating. The uneven coating structure will weaken the mechanical strength and bonding force of the filler, and is prone to local peeling or cracking in the tower bottom high temperature and scouring environment. In addition, the agglomerated CeO2 particles exposed on the coating surface or interface become the nucleation point for impurity adhesion or coking, which increases the risk of coking. At the same time, the excess CeO2 also partially blocks the micropores on the surface of the ceramic filler, reducing the effective specific surface area and being not conducive to mass transfer.

[0073] In some optional examples, the rotation speed of the high-speed stirring is 12000-15000rpm, for example, it can be 12000rpm, 12500rpm, 13000rpm, 13500rpm, 14000rpm, 14500rpm or 15000rpm, but not limited to the listed values, and other values not listed in the range are also applicable.

[0074] In some optional examples, the high-speed stirring time is 25-35min, for example, it can be 25min, 26min, 27min, 28min, 29min, 30min, 31min, 32min, 33min, 34min or 35min, but not limited to the listed values, and other values not listed in the range are also applicable.

[0075] As a preferred technical solution of the present application, in step (III), the solid-liquid ratio of the acidified ceramic corrugated filler to the modified solution is 1g:(8~10)mL, for example, it can be 1g:8.0mL, 1g:8.2mL, 1g:8.4mL, 1g:8.6mL, 1g:8.8mL, 1g:9.0mL, 1g:9.2mL, 1g:9.4mL, 1g:9.6mL, 1g:9.8mL or 1g:10.0mL, but not limited to the listed values, other values not listed in this range are also applicable.

[0076] In some optional examples, the soaking time of the acidified ceramic corrugated filler in the modified solution is 30~40min, for example, it can be 30min, 31min, 32min, 33min, 34min, 35min, 36min, 37min, 38min, 39min or 40min, but not limited to the listed values, other values not listed in this range are also applicable.

[0077] The present application particularly limits the soaking time of the acidified ceramic corrugated filler in the modified solution to 30~40min, within this range, the modified solution can fully penetrate into the micropores and rough surface formed by acid treatment, and achieve moderate adsorption, and in subsequent calcination, a composite layer with moderate thickness, firm bonding and dense structure can be formed, providing effective surface modification and protection for the filler.

[0078] When the soaking time is less than 30min, the modified solution cannot fully infiltrate and penetrate into the deep pores and concave-convex structure of the acidified ceramic, resulting in low coating load and uneven distribution, and it is difficult to form a continuous and complete composite layer after subsequent calcination, and the area where the coating is not fully covered is more easily eroded in the high temperature and high pressure environment at the tower bottom, leading to exposure of the ceramic matrix or local peeling of the coating, and loss of surface function. In addition, short soaking time cannot fully utilize the active sites generated by acid etching for effective bonding, which weakens the bonding strength of the coating and the matrix, and reduces the service life and reliability of the filler.

[0079] When the soaking time exceeds 40min, long soaking time will cause the ceramic matrix to continuously adsorb the modified solution, leading to excessive enrichment of solutes in local areas and even blocking the micropores of the ceramic matrix, not only destroying the uniformity of the coating, but also producing microcracks due to uneven internal stress during subsequent calcination.

[0080] In some alternative examples, the high-temperature calcination has a heating rate of 1-2℃ / min, for example, 1.0℃ / min, 1.1℃ / min, 1.2℃ / min, 1.3℃ / min, 1.4℃ / min, 1.5℃ / min, 1.6℃ / min, 1.7℃ / min, 1.8℃ / min, 1.9℃ / min or 2.0℃ / min, but not limited to the listed values, and other values not listed in the range are also applicable.

[0081] In some alternative examples, the high-temperature calcination has a calcination temperature of 600-620℃, for example, 600℃, 602℃, 604℃, 606℃, 608℃, 610℃, 612℃, 614℃, 616℃, 618℃ or 620℃, but not limited to the listed values, and other values not listed in the range are also applicable.

[0082] In some alternative examples, the high-temperature calcination has a holding time of 1-3h, for example, 1.0h, 1.2h, 1.4h, 1.6h, 1.8h, 2.0h, 2.2h, 2.4h, 2.6h, 2.8h or 3.0h, but not limited to the listed values, and other values not listed in the range are also applicable.

[0083] As a preferred technical solution of the present application, the modified molecular sieve filler is prepared by the following method:

[0084] (1) Soaking the molecular sieve honeycomb ceramic in a potassium hydroxide solution, ultrasonic oscillation under heating conditions, then washing to neutral and high-temperature calcination to obtain an activated carrier;

[0085] (2) Mixing and stirring aluminum chloride hexahydrate with ethanol and heating to obtain an aluminum chloride solution, dropping an ammonia solution into the aluminum chloride solution to generate a precipitate, then adding a dispersing agent and high-pressure homogenization to obtain an aluminum hydroxide sol;

[0086] (3) Mixing the silica sol with the aluminum hydroxide sol to obtain a composite sol, soaking the activated carrier in the composite sol, taking it out and performing gelation and high-temperature calcination to obtain the modified molecular sieve filler.

[0087] In the preparation method of the modified molecular sieve filler provided by the present application, first, the molecular sieve honeycomb ceramic is subjected to alkali treatment and high-temperature calcination activation, which not only can clean the surface of the molecular sieve and expand the hole, but also can dissolve part of the silicon and aluminum components through the alkali solution, form more abundant active sites (such as silicon hydroxyl and aluminum hydroxyl) on the molecular sieve framework and optimize the pore structure, and provide a high-reactivity substrate for the subsequent firm loading of the composite sol through the activation treatment.

[0088] Silica is introduced by silica sol and alumina is introduced by aluminum hydroxide sol. By gelation through standing and control of the calcination process, the uniform distribution, full penetration and firm bonding of the composite coating on the surface of the molecular sieve carrier are ensured, forming a strong and firm functional layer.

[0089] The role of silica is to enhance structural stability and regulate surface properties. The silica sol forms a continuous silica network in the composite sol. When it covers the surface of the activated molecular sieve carrier and is solidified by high-temperature calcination, a firm protective layer is constructed outside the original molecular sieve framework, significantly enhancing the mechanical strength and compressive strength of the filler, effectively solving the problem of powdering and collapse of traditional molecular sieve fillers under long-term scouring of gas-liquid flow and the weight of their own liquid holdup, and ensuring the long-term structural stability of the filler bed. At the same time, silica gives the filler surface a certain degree of hydrophobicity, which helps to reduce the excessive adsorption and retention of strong polar small molecules such as water molecules on the surface of the filler, optimizes the surface properties, and makes it easier to adsorb target impurities.

[0090] The role of alumina is to provide acidic sites and enhance the adsorption selectivity of specific impurities. After high-temperature calcination, the aluminum hydroxide sol is converted into active γ-Al2O3. The alumina surface has Lewis acid sites and a certain number of Bronsted acid sites. In the overhead area of the filler column, these acid sites show stronger affinity and adsorption capacity for trace impurities with similar boiling points to dipropylene glycol but with stronger polarity (such as residual monopropylene glycol, trace water molecules, and certain oxygen-containing heterocyclic by-products). The presence of Al2O3 can effectively adsorb and retain these polar and protonatable light impurities, thereby improving the purity of the product dipropylene glycol.

[0091] The synergistic effect of SiO2 and Al2O3 is as follows: on the one hand, in the composite coating, SiO2 mainly serves as a structural support, providing mechanical strength and overall thermal stability; Al2O3 dispersed in the SiO2 matrix serves as a functional phase, providing adsorption sites and selectivity. The skeletal role of SiO2 ensures the firm anchoring and uniform dispersion of the Al2O3 active component, preventing its aggregation and loss due to erosion. On the other hand, the combination of the two forms a specific surface acid and pore property interface region of silicon-aluminum mixed oxide, which has better adsorption capacity than single SiO2 and single Al2O3, and can more accurately adsorb complex light impurities in the crude dipropylene glycol (such as monopropylene glycol and small molecule alcohol ethers).

[0092] As a preferred technical solution of the present application, in step (1), the pore size of the molecular sieve honeycomb ceramic is 0.5-0.8 mm, for example, it can be 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm or 0.8 mm, but it is not limited to the listed values, other values not listed in this range are also applicable.

[0093] In some optional examples, the mass fraction of the potassium hydroxide solution is 8-10wt%, for example, it can be 8.0wt%, 8.2wt%, 8.4wt%, 8.6wt%, 8.8wt%, 9.0wt%, 9.2wt%, 9.4wt%, 9.6wt%, 9.8wt% or 10.0wt%, but not limited to the listed values, other values not listed in the range are also applicable.

[0094] In some optional examples, the solid-liquid ratio of the molecular sieve honeycomb ceramic to the potassium hydroxide solution is 1g:(10-15)mL, for example, it can be 1g:10mL, 1g:10.5mL, 1g:11mL, 1g:11.5mL, 1g:12mL, 1g:12.5mL, 1g:13mL, 1g:13.5mL, 1g:14mL, 1g:14.5mL or 1g:15mL, but not limited to the listed values, other values not listed in the range are also applicable.

[0095] In some optional examples, the heating temperature of the molecular sieve honeycomb ceramic when immersed in the potassium hydroxide solution is 40-50℃, for example, it can be 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃ or 50℃, but not limited to the listed values, other values not listed in the range are also applicable.

[0096] In some optional examples, the ultrasonic power of the ultrasonic oscillation when the molecular sieve honeycomb ceramic is immersed in the potassium hydroxide solution is 200-300W, for example, it can be 200W, 210W, 220W, 230W, 240W, 250W, 260W, 270W, 280W, 290W or 300W, but not limited to the listed values, other values not listed in the range are also applicable.

[0097] In some optional examples, the immersion time of the molecular sieve honeycomb ceramic in the potassium hydroxide solution is 30-40min, for example, it can be 30min, 31min, 32min, 33min, 34min, 35min, 36min, 37min, 38min, 39min or 40min, but not limited to the listed values, other values not listed in the range are also applicable.

[0098] In some optional examples, the high-temperature calcination has a heating rate of 3-5°C / min, for example, 3.0°C / min, 3.2°C / min, 3.4°C / min, 3.6°C / min, 3.8°C / min, 4.0°C / min, 4.2°C / min, 4.4°C / min, 4.6°C / min, 4.8°C / min, or 5.0°C / min, but not only limited to the listed values, other values not listed in the range are also applicable.

[0099] In some optional examples, the high-temperature calcination has a calcination temperature of 500-520°C, for example, 500°C, 502°C, 504°C, 506°C, 508°C, 510°C, 512°C, 514°C, 516°C, 518°C, or 520°C, but not only limited to the listed values, other values not listed in the range are also applicable.

[0100] In some optional examples, the high-temperature calcination has a holding time of 2-3h, for example, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, or 3.0h, but not only limited to the listed values, other values not listed in the range are also applicable.

[0101] As a preferred technical solution of the present application, in step (2), the mass ratio of aluminum chloride hexahydrate to ethanol is 1:(4.5-5.5), for example, 1:4.5, 1:4.6, 1:4.7, 1:4.8, 1:4.9, 1:5.0, 1:5.1, 1:5.2, 1:5.3, 1:5.4, or 1:5.5, but not only limited to the listed values, other values not listed in the range are also applicable.

[0102] In some optional examples, the mixing and stirring of aluminum chloride hexahydrate and ethanol is heated to a temperature of 65-75°C, for example, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, or 75°C, but not only limited to the listed values, other values not listed in the range are also applicable.

[0103] In some optional examples, the mixing and stirring of aluminum chloride hexahydrate and ethanol is performed for a time of 30-40min, for example, 30min, 31min, 32min, 33min, 34min, 35min, 36min, 37min, 38min, 39min, or 40min, but not only limited to the listed values, other values not listed in the range are also applicable.

[0104] In some optional examples, the mass fraction of the ammonia solution is 10-12 wt%, for example, it can be 10 wt%, 10.2 wt%, 10.4 wt%, 10.6 wt%, 10.8 wt%, 11 wt%, 11.2 wt%, 11.4 wt%, 11.6 wt%, 11.8 wt% or 12 wt%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0105] In some optional examples, the ammonia solution is added dropwise to the aluminum chloride solution to adjust the pH value to 9.0-9.5, for example, it can be 9.0, 9.05, 9.1, 9.15, 9.2, 9.25, 9.3, 9.35, 9.4, 9.45 or 9.5, but not limited to the listed values, and other values not listed in the range are also applicable.

[0106] In some optional examples, the mass of the dispersant is 0.2-0.3 wt% of the mass of the generated precipitate, for example, it can be 0.2 wt%, 0.21 wt%, 0.22 wt%, 0.23 wt%, 0.24 wt%, 0.25 wt%, 0.26 wt%, 0.27 wt%, 0.28 wt%, 0.29 wt% or 0.3 wt%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0107] In some optional examples, the pressure of the high-pressure homogenization is 120-150 MPa, for example, it can be 120 MPa, 125 MPa, 130 MPa, 135 MPa, 140 MPa, 145 MPa or 150 MPa, but not limited to the listed values, and other values not listed in the range are also applicable.

[0108] In some optional examples, the number of times of high-pressure homogenization is 5-8 times, for example, it can be 5 times, 6 times, 7 times or 8 times, but not limited to the listed values, and other values not listed in the range are also applicable.

[0109] As a preferred technical solution of the present application, in step (3), the mass fraction of the silica sol is 30-40 wt%, for example, it can be 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt% or 40 wt%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0110] In some optional examples, the mass ratio of the silica sol to the aluminum hydroxide sol is 1: (0.8-1.2), which can be 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1.0, 1:1.05, 1:1.1, 1:1.15 or 1:1.2, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0111] The present application particularly limits the mass ratio of the silica sol to the aluminum hydroxide sol to be 1: (0.8-1.2), and when in this range, the silicon aluminum species can form a uniform and stable composite sol system through Si-O-Al bonding, and after subsequent gelation and high-temperature calcination, SiO2 provides a strong skeleton structure and thermal stability, effectively enhancing the overall mechanical strength of the molecular sieve carrier, preventing it from collapsing and powdering in a high-vacuum environment at the top of the tower; at the same time, uniformly dispersed Al2O3 provides a rich surface acidic site for the coating, giving the filler specific adsorption capacity for polar light impurities (such as monopropylene glycol, trace water, and small molecule ethers).

[0112] When the addition amount of the aluminum hydroxide sol is lower than the lower limit of the range defined by the present application, the Al2O3 precursor content in the composite sol is insufficient, resulting in too few active Al2O3 components in the final coating, and too few acidic adsorption sites on the surface of the coating, significantly reducing the adsorption capacity and selectivity of the coating for light impurities with close boiling points but stronger polarity (especially monopropylene glycol), making it difficult to achieve high purity of the product.

[0113] When the addition amount of the aluminum hydroxide sol is higher than the upper limit of the range defined by the present application, excess aluminum hydroxide sol in the mixed system is prone to cause aggregation and flocculation of the sol particles, destroying the colloidal stability of the system, and making it difficult to form a uniform and stable composite sol. In the subsequent dipping and gelation processes, the uniformity of the coating will be poor, and local Al2O3-rich areas or defects are likely to form. In addition, when the Al2O3 content is too high, the Al2O3-rich areas in the coating formed after calcination will exhibit stronger hydrophilicity, which will cause local swelling in the presence of trace amounts of water vapor at the top of the tower. At the same time, excess Al2O3 cannot be completely embedded in the SiO2 network, forming some weak Al-O-Al structures, which weakens the overall mechanical strength and bonding force of the coating, leading to peeling of the coating under long-term airflow scouring.

[0114] In some optional examples, the silica sol and the aluminum hydroxide sol are mixed and then an acetic acid solution is added to adjust the pH value to 4.5-5, followed by simultaneous mechanical stirring and ultrasonic oscillation to obtain the composite sol, which can be 4.5, 4.55, 4.6, 4.65, 4.7, 4.75, 4.8, 4.85, 4.9, 4.95 or 5, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0115] In some optional examples, the rotation speed of mechanical stirring of the silica sol and the aluminum hydroxide sol is 400-500 rpm, for example, it can be 400 rpm, 410 rpm, 420 rpm, 430 rpm, 440 rpm, 450 rpm, 460 rpm, 470 rpm, 480 rpm, 490 rpm or 500 rpm, but not only limited to the listed values, other values not listed in the range are also applicable.

[0116] In some optional examples, the ultrasonic power of ultrasonic oscillation of the silica sol and the aluminum hydroxide sol is 200-300 W, for example, it can be 200 W, 210 W, 220 W, 230 W, 240 W, 250 W, 260 W, 270 W, 280 W, 290 W or 300 W, but not only limited to the listed values, other values not listed in the range are also applicable.

[0117] In some optional examples, the time of ultrasonic oscillation of the silica sol and the aluminum hydroxide sol is 30-40 min, for example, it can be 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min or 40 min, but not only limited to the listed values, other values not listed in the range are also applicable.

[0118] In some optional examples, the activated carrier is soaked in the composite sol under a negative pressure environment of 0.015-0.025 MPa, for example, it can be 0.015 MPa, 0.016 MPa, 0.017 MPa, 0.018 MPa, 0.019 MPa, 0.02 MPa, 0.021 MPa, 0.022 MPa, 0.023 MPa, 0.024 MPa or 0.025 MPa, but not only limited to the listed values, other values not listed in the range are also applicable.

[0119] In some optional examples, the solid-liquid ratio of the activated carrier and the composite sol is 1 g:(4-6) mL, for example, it can be 1 g:4.0 mL, 1 g:4.2 mL, 1 g:4.4 mL, 1 g:4.6 mL, 1 g:4.8 mL, 1 g:5.0 mL, 1 g:5.2 mL, 1 g:5.4 mL, 1 g:5.6 mL, 1 g:5.8 mL or 1 g:6.0 mL, but not only limited to the listed values, other values not listed in the range are also applicable.

[0120] In some optional examples, the soaking time of the activated carrier in the composite sol is 60-90 min, for example, it can be 60 min, 65 min, 70 min, 75 min, 80 min, 85 min or 90 min, but not limited to the listed values, and other values not listed in this range are also applicable.

[0121] The present application particularly limits the soaking time of the activated carrier in the composite sol to 60-90 min. Within this range, the composite sol can fully penetrate into the porous structure and surface active sites of the activated molecular sieve carrier, and achieve moderate adsorption, which helps to form a composite gel layer with moderate thickness, uniform distribution and tight combination during the subsequent gelation process, and finally obtain a functional coating with complete structure and stable performance after high-temperature calcination.

[0122] When the soaking time is less than 60 min, the composite sol cannot fully infiltrate and penetrate into the porous structure of the molecular sieve carrier, especially the deeper or finer pores in the interior, which are difficult to be effectively filled, resulting in low loading and uneven distribution of the coating on the surface of the molecular sieve carrier. After subsequent gelation and high-temperature calcination, the functional layer formed is too thin and discontinuous, and the improvement effect on the mechanical strength of the molecular sieve carrier is limited, which makes it difficult to effectively prevent the risk of pulverization of the molecular sieve carrier during long-term operation at the top of the tower. In addition, insufficient modification of the internal pores of the molecular sieve carrier leads to the adsorption capacity and selectivity of light impurities not reaching the ideal effect, which seriously affects the product purity. At the same time, the combination interface between the thin coating and the substrate is relatively weak, which is easy to peel off during operation.

[0123] When the soaking time exceeds 90 min, long-term soaking will cause the molecular sieve carrier to continuously adsorb the composite sol, resulting in excessive enrichment of the sol on the surface layer of the molecular sieve carrier, especially in the entrance area of the pores, and even forming local blockage. This uneven loading is prone to induce micro-cracks or coating peeling due to the difference in shrinkage stress in different regions during subsequent gelation and calcination. In addition, long-term soaking can cause erosion or swelling of the molecular sieve carrier, which in turn leads to changes in the pore structure of the molecular sieve carrier, weakening the mechanical strength of the molecular sieve carrier.

[0124] In some optional examples, the gelation is carried out in an environment with a relative humidity of 50-60%, for example, it can be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59% or 60%, but not limited to the listed values, and other values not listed in this range are also applicable.

[0125] In some optional examples, the standing gel time is 8-12 hours, for example, it can be 8.0 hours, 8.5 hours, 9.0 hours, 9.5 hours, 10.0 hours, 10.5 hours, 11.0 hours, 11.5 hours or 12.0 hours, but not limited to the listed values, and other values not listed in the range are also applicable.

[0126] In some optional examples, the high-temperature roasting temperature is 560-580 DEG C, for example, it can be 560 DEG C, 562 DEG C, 564 DEG C, 566 DEG C, 568 DEG C, 570 DEG C, 572 DEG C, 574 DEG C, 576 DEG C, 578 DEG C or 580 DEG C, but not limited to the listed values, and other values not listed in the range are also applicable.

[0127] In some optional examples, the high-temperature roasting temperature is 560-580 DEG C, for example, it can be 560 DEG C, 562 DEG C, 564 DEG C, 566 DEG C, 568 DEG C, 570 DEG C, 572 DEG C, 574 DEG C, 576 DEG C, 578 DEG C or 580 DEG C, but not limited to the listed values, and other values not listed in the range are also applicable.

[0128] In some optional examples, the high-temperature roasting temperature is 560-580 DEG C, for example, it can be 560 DEG C, 562 DEG C, 564 DEG C, 566 DEG C, 568 DEG C, 570 DEG C, 572 DEG C, 574 DEG C, 576 DEG C, 578 DEG C or 580 DEG C, but not limited to the listed values, and other values not listed in the range are also applicable.

[0129] Compared with the prior art, the present application has the following advantages:

[0130] The rectification process provided by the present application optimizes the material transfer efficiency, component separation precision and device running stability in the crude material rectification process by sequentially arranging the modified ceramic corrugated packing, stainless steel wire mesh and modified molecular sieve packing from bottom to top, and effectively improves the overall process performance.

[0131] The three-layer packing synergistic effect constitutes a high-efficiency integrated rectification system, the modified ceramic corrugated packing filled at the bottom of the column is used for treating heavy component impurities and improving the initial separation effect, the stainless steel wire mesh filled in the middle is used for optimizing fluid distribution and controlling pressure drop, and the modified molecular sieve packing filled at the top of the column is used for deep removal of light impurities. Through the functional modification and spatial arrangement of different packings, the performance of the traditional double-tower series rectification process in the purification of dipropylene glycol can be significantly improved without changing the basic structure of the tower body, the separation efficiency is improved, the process energy consumption is reduced, the stability and continuity of device running are enhanced, and the present application has good industrial application prospect. Attached Figure Description

[0132] Figure 1 The process flow diagram is shown for the preparation of the modified ceramic corrugated packing provided in Examples 1-17 of this invention.

[0133] Figure 2 The process flow diagrams are for preparing the modified molecular sieve packings provided in Examples 1-17 of this invention. Detailed Implementation

[0134] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0135] Example 1

[0136] This embodiment provides a distillation process for dipropylene glycol, such as... Figure 1 As shown, the distillation process of dipropylene glycol specifically includes the following steps:

[0137] The crude raw material containing dipropylene glycol is preheated to 100°C and then fed into a pre-separation column for pre-distillation. The bottom temperature of the pre-separation column is 150°C, the top temperature is 100°C, the reflux ratio is 6:1, the operating pressure is 2 kPa, and the number of trays is 24.

[0138] Subsequently, the bottom liquid of the pre-separation tower is fed into a packed tower. The interior of the packed tower is filled from bottom to top with modified ceramic corrugated packing, stainless steel wire mesh, and modified molecular sieve packing. The bulk density of the modified ceramic corrugated packing is 480 kg / m³. 3 The filling height is 1.8m; the stainless steel wire mesh has a mesh count of 300 and a bulk density of 300kg / m³. 3 The filling height is 1.5m; the bulk density of the modified molecular sieve packing is 560kg / m³. 3 The packing height is 1.2m. The bottom liquid is fed from the middle of the packed tower, corresponding to the position of the modified ceramic corrugated packing. The bottom temperature of the packed tower is 160℃, the top temperature is 105℃, the reflux ratio is 8:1, the operating pressure is 1kPa, and the dipropylene glycol product is collected from the top of the packed tower.

[0139] like Figure 1 As shown, the modified ceramic corrugated packing was prepared using the following method:

[0140] (I) ceramic corrugated filler with a pore size of 0.8 mm is soaked in a mixed acid solution according to a solid-liquid ratio of 1 g:10 mL, the mixed acid solution is composed of hydrofluoric acid (concentration 22.5 mol / L), nitric acid and deionized water, the mass fraction of hydrofluoric acid in the mixed acid solution is 10%, and the mass fraction of nitric acid is 6%; ultrasonic oscillation is carried out at a heating condition of 45℃ and an ultrasonic power of 300 W for 25 min, then it is taken out and washed to neutral, and after drying, acidified ceramic corrugated filler is obtained;

[0141] (II) under the condition of stirring at 200 rpm, tetraethyl orthosilicate is dropped into an ethanol aqueous solution (the ethanol aqueous solution is composed of ethanol and deionized water with a volume ratio of 8:1), the molar ratio of tetraethyl orthosilicate to ethanol in the ethanol aqueous solution is 1:8, then 0.1 mol / L hydrochloric acid solution is added, the mass of the hydrochloric acid solution is 0.8wt% of the mass of tetraethyl orthosilicate, after mixing uniformly, a precursor solution is obtained; cerium dioxide nanoparticles with an average particle size of 30 nm are added to the precursor solution, the mass of the cerium dioxide nanoparticles is 3wt% of the mass of tetraethyl orthosilicate, high-speed stirring is carried out at a rotating speed of 12000 rpm for 35 min, and a modified solution is obtained;

[0142] (III) the acidified ceramic corrugated filler obtained in step (I) is soaked in the modified solution obtained in step (II) according to a solid-liquid ratio of 1 g:8 mL, it is taken out after soaking for 40 min, heated to 600℃ at a heating rate of 1℃ / min and kept for 3 h to complete high-temperature calcination, and modified ceramic corrugated filler is obtained.

[0143] As shown in Figure 2 , the modified molecular sieve filler is prepared by the following method:

[0144] (1) molecular sieve honeycomb ceramic with a pore size of 0.5 mm is soaked in a potassium hydroxide solution with a mass fraction of 8wt%, the solid-liquid ratio of the molecular sieve honeycomb ceramic to the potassium hydroxide solution is 1 g:10 mL, ultrasonic oscillation is carried out at a heating condition of 40℃ and an ultrasonic power of 200 W for 40 min, then it is taken out and washed to neutral, heated to 500℃ at a heating rate of 3℃ / min and kept for 3 h to complete high-temperature calcination, and an activated carrier is obtained;

[0145] (2) aluminum chloride hexahydrate is mixed with ethanol according to a mass ratio of 1:4.5, stirred at a heating condition of 65℃ for 40 min, and an aluminum chloride solution is obtained, ammonia water solution with a mass fraction of 10wt% is dropped into the aluminum chloride solution to adjust the pH value to 9.0 and generate a precipitate, then a dispersant polyethylene glycol 6000 is added, the mass of the polyethylene glycol 6000 is 0.2wt% of the mass of the generated precipitate, and finally high-pressure homogenization is carried out 8 times under a pressure of 120 MPa, and an aluminum hydroxide sol is obtained;

[0146] (3) mixing the silica sol with a mass fraction of 30wt% with the aluminum hydroxide sol obtained in step (2) according to a mass ratio of 1:0.8, adding acetic acid solution after mixing to adjust the pH value to 4.5, then performing mechanical stirring at a rotating speed of 400 rpm, and performing ultrasonic oscillation at an ultrasonic power of 200 W for 40 min to obtain a composite sol;

[0147] (4) immersing the activated carrier obtained in step (1) in the composite sol obtained in step (3) under a negative pressure of 0.015 MPa, the solid-liquid ratio of the activated carrier to the composite sol being 1g:4mL, taking out after immersion for 90 min, and completing gelation in an environment with a relative humidity of 50% for 12h, then heating to 560℃ at a heating rate of 3℃ / min and keeping for 3h to complete high-temperature calcination, to obtain a modified molecular sieve filler.

[0148] Example 2

[0149] The present embodiment provides a rectification process of dipropylene glycol, as shown in the following scheme: Figure 1 The rectification process of dipropylene glycol specifically comprises the following steps:

[0150] The crude dipropylene glycol raw material is preheated to 102℃ and then sent into the pre-separation tower for pre-distillation, the tower bottom temperature of the pre-separation tower is 152℃, the tower top temperature is 102℃, the reflux ratio is 6.5:1, the operating pressure is 2.2kPa, and the number of tower plates is 22;

[0151] Subsequently, the tower bottom liquid of the pre-separation tower is sent into the packing tower, the inside of the packing tower is sequentially filled from bottom to top with modified ceramic corrugated packing, stainless steel wire mesh and modified molecular sieve filler, wherein the packing density of the modified ceramic corrugated packing is 485kg / m 3 , the filling height is 1.7m; the mesh number of the stainless steel wire mesh is 320mesh, the packing density is 320kg / m 3 , the filling height is 1.4m; the packing density of the modified molecular sieve filler is 565kg / m 3 , and the filling height is 1.15m. The tower bottom liquid is fed from the middle part of the packing tower, corresponding to the position of the modified ceramic corrugated packing, the tower bottom temperature of the packing tower is 162℃, the tower top temperature is 106℃, the reflux ratio is 8.5:1, the operating pressure is 1.05kPa, and the dipropylene glycol product is collected from the tower top of the packing tower.

[0152] As shown in the following scheme: Figure 1 The modified ceramic corrugated packing is prepared by the following method:

[0153] (I) ceramic corrugated fillers with a pore size of 0.9 mm are immersed in a mixed acid solution according to a solid-liquid ratio of 1 g:12 mL, the mixed acid solution is composed of hydrofluoric acid (concentration 22.5 mol / L), nitric acid and deionized water, the mass fraction of hydrofluoric acid in the mixed acid solution is 9.5%, and the mass fraction of nitric acid in the mixed acid solution is 5.5%; ultrasonic oscillation is performed at a heating condition of 48℃ and an ultrasonic power of 320 W for 22 min, then the ceramic corrugated fillers are taken out and washed to neutral, and after drying, acidified ceramic corrugated fillers are obtained;

[0154] (II) under the stirring condition of 220 rpm, tetraethyl orthosilicate is dropped into an ethanol aqueous solution (the volume ratio of ethanol to deionized water is 8.5:1), the molar ratio of tetraethyl orthosilicate to ethanol in the ethanol aqueous solution is 1:8.5, then 0.1 mol / L hydrochloric acid solution is added, the mass of the hydrochloric acid solution is 0.9 wt% of the mass of the tetraethyl orthosilicate, after being uniformly mixed, a precursor solution is obtained; cerium dioxide nanoparticles with an average particle size of 35 nm are added to the precursor solution, the mass of the cerium dioxide nanoparticles is 3.5 wt% of the mass of the tetraethyl orthosilicate, high-speed stirring is performed at a rotating speed of 13000 rpm for 32 min, and a modified solution is obtained;

[0155] (III) the acidified ceramic corrugated fillers obtained in step (I) are immersed in the modified solution obtained in step (II) according to a solid-liquid ratio of 1 g:8.5 mL, the ceramic corrugated fillers are taken out after being immersed for 38 min, heated to 605℃ at a heating rate of 1.2℃ / min and kept for 2.5 h to complete high-temperature calcination, and modified ceramic corrugated fillers are obtained.

[0156] As shown in FIG. 1, the modified molecular sieve filler is prepared by the following method: Figure 2

[0157] (1) molecular sieve honeycomb ceramics with a pore size of 0.6 mm are immersed in a potassium hydroxide solution with a mass fraction of 8.5 wt%, the solid-liquid ratio of the molecular sieve honeycomb ceramics to the potassium hydroxide solution is 1 g:11 mL, ultrasonic oscillation is performed at a heating condition of 42℃ and an ultrasonic power of 220 W for 38 min, then the molecular sieve honeycomb ceramics are taken out and washed to neutral, heated to 505℃ at a heating rate of 3.5℃ / min and kept for 2.8 h to complete high-temperature calcination, and an activated carrier is obtained;

[0158] (2) aluminum chloride hexahydrate is mixed with ethanol according to a mass ratio of 1:4.8, and stirred at a heating condition of 68℃ for 38 min to obtain an aluminum chloride solution, ammonia water solution with a mass fraction of 10.5 wt% is dropped into the aluminum chloride solution to adjust the pH value to 9.1 and generate a precipitate, then a dispersant polyethylene glycol 6000 is added, the mass of the polyethylene glycol 6000 is 0.22 wt% of the mass of the generated precipitate, and finally the aluminum hydroxide sol is obtained by high-pressure homogenization 7 times at a pressure of 130 MPa;

[0159] ​(3) mixing the silica sol with a mass fraction of 32wt% and the aluminum hydroxide sol obtained in step (2) according to a mass ratio of 1:0.9, adding acetic acid solution after mixing to adjust the pH value to 4.6, and then performing mechanical stirring at a rotating speed of 420 rpm, and performing ultrasonic oscillation at an ultrasonic power of 220 W for 38 min to obtain a composite sol;

[0160] (4) immersing the activated carrier obtained in step (1) in the composite sol obtained in step (3) under a negative pressure of 0.018 MPa, the solid-liquid ratio of the activated carrier to the composite sol being 1g:4.5mL, taking out after immersing for 80 min, and completing gelation in an environment with a relative humidity of 52% for 11h, and then heating to 565℃ at a heating rate of 3.5℃ / min and keeping for 2.8h to complete high-temperature calcination, to obtain a modified molecular sieve filler.

[0161] Example 3

[0162] The present embodiment provides a rectification process of dipropylene glycol, as shown in the following scheme: Figure 1 The rectification process of dipropylene glycol specifically comprises the following steps:

[0163] The crude dipropylene glycol raw material is preheated to 105℃ and then sent into the pre-separation tower for pre-distillation, the tower bottom temperature of the pre-separation tower is 155℃, the tower top temperature is 105℃, the reflux ratio is 7:1, the operating pressure is 2.5kPa, and the number of tower plates is 21;

[0164] Subsequently, the tower bottom liquid of the pre-separation tower is sent into the packing tower, the inside of the packing tower is sequentially filled from bottom to top with modified ceramic corrugated packing, stainless steel wire mesh and modified molecular sieve filler, wherein the packing density of the modified ceramic corrugated packing is 490kg / m 3 , the filling height is 1.6m; the mesh number of the stainless steel wire mesh is 350 meshes, the packing density is 330kg / m 3 , and the filling height is 1.3m; the packing density of the modified molecular sieve filler is 570kg / m 3 , and the filling height is 1.1m. The tower bottom liquid is fed from the middle part of the packing tower, corresponding to the position of the modified ceramic corrugated packing, the tower bottom temperature of the packing tower is 165℃, the tower top temperature is 107℃, the reflux ratio is 9:1, the operating pressure is 1.1kPa, and the dipropylene glycol product is collected from the tower top of the packing tower.

[0165] As shown in the following scheme: Figure 1 The modified ceramic corrugated packing is prepared by the following method:

[0166] (I) Ceramic corrugated packing with a pore size of 1 mm was immersed in a mixed acid solution at a solid-liquid ratio of 1 g: 15 mL. The mixed acid solution consisted of hydrofluoric acid (concentration 22.5 mol / L), nitric acid and deionized water. The mass fraction of hydrofluoric acid in the mixed acid solution was 9% and the mass fraction of nitric acid was 5%. The packing was ultrasonically vibrated at 350 W for 20 min under a heating condition of 50 °C. Then it was taken out, cleaned until neutral, and dried to obtain acidified ceramic corrugated packing.

[0167] (II) Under stirring at 250 rpm, tetraethyl orthosilicate was added dropwise to an aqueous ethanol solution (the volume ratio of ethanol to deionized water was 9:1), and the molar ratio of tetraethyl orthosilicate to ethanol in the aqueous ethanol solution was 1:9. Then, 0.1 mol / L hydrochloric acid solution was added, with the mass of the hydrochloric acid solution being 1 wt% of the mass of tetraethyl orthosilicate. After mixing evenly, a precursor solution was obtained. Cerium dioxide nanoparticles with an average particle size of 40 nm were added to the precursor solution, with the mass of the cerium dioxide nanoparticles being 4 wt% of the mass of tetraethyl orthosilicate. The mixture was stirred at 13000 rpm for 30 min to obtain a modified solution.

[0168] (III) The acidified ceramic corrugated packing obtained in step (I) is immersed in the modified solution obtained in step (II) at a solid-liquid ratio of 1g:9mL. After immersion for 35min, it is taken out and heated to 610℃ at a heating rate of 1.5℃ / min and kept at the temperature for 2h to complete the high-temperature calcination, thereby obtaining the modified ceramic corrugated packing.

[0169] like Figure 2 As shown, the modified molecular sieve packing was prepared using the following method:

[0170] (1) Molecular sieve honeycomb ceramic with a pore size of 0.7 mm was immersed in a potassium hydroxide solution with a mass fraction of 9 wt%. The solid-liquid ratio of molecular sieve honeycomb ceramic to potassium hydroxide solution was 1 g: 12 mL. The mixture was ultrasonically vibrated at 250 W for 35 min under heating conditions of 45 °C. Then it was taken out, cleaned until neutral, heated to 510 °C at a heating rate of 4 °C / min and kept at the temperature for 2.5 h to complete the high-temperature calcination and obtain the activated carrier.

[0171] (2) Aluminum chloride hexahydrate and ethanol were mixed at a mass ratio of 1:5 and stirred at 70°C for 35 min to obtain an aluminum chloride solution. An 11 wt% ammonia solution was added dropwise to the aluminum chloride solution to adjust the pH value to 9.2 and generate a precipitate. Then, polyethylene glycol 6000 was added as a dispersant, with the mass of polyethylene glycol 6000 being 0.25 wt% of the mass of the precipitate generated. Finally, the mixture was homogenized under high pressure for 6 times at a pressure of 140 MPa to obtain aluminum hydroxide sol.

[0172] (3) Mix the silica sol with a mass fraction of 35wt% with the aluminum hydroxide sol obtained in step (2) at a mass ratio of 1:1. After mixing, add acetic acid solution to adjust the pH value to 4.7. Then, mechanically stir at a speed of 450rpm and ultrasonically vibrate at an ultrasonic power of 250W for 35min to obtain the composite sol.

[0173] (4) Under a negative pressure of 0.02 MPa, the activated carrier obtained in step (1) is immersed in the composite sol obtained in step (3). The solid-liquid ratio of the activated carrier to the composite sol is 1 g: 5 mL. After immersion for 80 min, the carrier is taken out and allowed to stand for 10 h in an environment with a relative humidity of 55% to complete gelation. Then, the carrier is heated to 570 °C at a heating rate of 4 °C / min and kept at the temperature for 2.5 h to complete high-temperature calcination and obtain the modified molecular sieve filler.

[0174] Example 4

[0175] This embodiment provides a distillation process for dipropylene glycol, such as... Figure 1 As shown, the distillation process of dipropylene glycol specifically includes the following steps:

[0176] The crude feed containing dipropylene glycol is preheated to 108°C and then fed into a pre-separation column for pre-distillation. The bottom temperature of the pre-separation column is 158°C, the top temperature is 108°C, the reflux ratio is 7.5:1, the operating pressure is 2.8 kPa, and the number of trays is 20.

[0177] Subsequently, the bottom liquid of the pre-separation tower is fed into a packed tower. The interior of the packed tower is filled from bottom to top with modified ceramic corrugated packing, stainless steel wire mesh, and modified molecular sieve packing. The bulk density of the modified ceramic corrugated packing is 495 kg / m³. 3 The filling height is 1.6m; the stainless steel wire mesh has a mesh count of 380 and a bulk density of 340kg / m³. 3 The filling height is 1.3m; the bulk density of the modified molecular sieve packing is 575kg / m³. 3 The packing height is 1.05m. The bottom liquid is fed from the middle of the packed tower, corresponding to the position of the modified ceramic corrugated packing. The bottom temperature of the packed tower is 168℃, the top temperature is 107℃, the reflux ratio is 9.5:1, the operating pressure is 1.15kPa, and dipropylene glycol is collected from the top of the packed tower.

[0178] like Figure 1 As shown, the modified ceramic corrugated packing was prepared using the following method:

[0179] (I) ceramic corrugated fillers with a pore size of 1.1 mm are immersed in a mixed acid solution at a solid-liquid ratio of 1 g:18 mL, the mixed acid solution is composed of hydrofluoric acid (concentration 22.5 mol / L), nitric acid and deionized water, the mass fraction of hydrofluoric acid is 8.5% of the mass fraction of hydrofluoric acid in the mixed acid solution, and the mass fraction of nitric acid is 4.5%; under the condition of heating at 52°C, ultrasonic oscillation is carried out at a power of 380W for 18min, then it is taken out and washed to neutral, and after drying, acidified ceramic corrugated fillers are obtained;

[0180] (II) under the condition of stirring at 280 rpm, tetraethyl orthosilicate is dropped into an ethanol aqueous solution (the volume ratio of ethanol and deionized water is 9.5:1), the molar ratio of tetraethyl orthosilicate to ethanol in the ethanol aqueous solution is 1:9.5, then 0.1 mol / L hydrochloric acid solution is added, the mass of the hydrochloric acid solution is 1.1wt% of the mass of tetraethyl orthosilicate, after mixing uniformly, a precursor solution is obtained; cerium dioxide nanoparticles with an average particle size of 45 nm are added to the precursor solution, the mass of the cerium dioxide nanoparticles is 4.5wt% of the mass of tetraethyl orthosilicate, high-speed stirring is carried out at a speed of 14000 rpm for 28 min, and a modified solution is obtained;

[0181] (III) the acidified ceramic corrugated fillers obtained in step (I) are immersed in the modified solution obtained in step (II) at a solid-liquid ratio of 1 g:9.5 mL, after soaking for 32 min, it is taken out, heated to 615°C at a heating rate of 1.8°C / min and kept for 1.5 h to complete high-temperature calcination, and modified ceramic corrugated fillers are obtained.

[0182] As shown in Figure 2 , the modified molecular sieve filler is prepared by the following method:

[0183] (1) molecular sieve honeycomb ceramic with a pore size of 0.7 mm is immersed in a potassium hydroxide solution with a mass fraction of 9.5wt%, the solid-liquid ratio of the molecular sieve honeycomb ceramic to the potassium hydroxide solution is 1g:13mL, ultrasonic oscillation is carried out at a power of 280W under the condition of heating at 48°C for 32min, then it is taken out and washed to neutral, heated to 515°C at a heating rate of 4.5°C / min and kept for 2.2h to complete high-temperature calcination, and an activated carrier is obtained;

[0184] (2) aluminum chloride hexahydrate is mixed with ethanol at a mass ratio of 1:5.2, stirred at 72°C for 32min to obtain an aluminum chloride solution, an ammonia water solution with a mass fraction of 11.5wt% is dropped into the aluminum chloride solution to adjust the pH value to 9.3 and generate a precipitate, then a dispersant polyethylene glycol 6000 is added, the mass of the polyethylene glycol 6000 is 0.28wt% of the mass of the generated precipitate, and finally high-pressure homogenization is carried out 6 times at a pressure of 140MPa to obtain an aluminum hydroxide sol;

[0185] (3) mixing the silica sol with a mass fraction of 38wt% and the aluminum hydroxide sol obtained in step (2) according to a mass ratio of 1:1.1, adding acetic acid solution after mixing to adjust the pH value to 4.8, and then performing mechanical stirring at a rotating speed of 480 rpm, and ultrasonic oscillation at an ultrasonic power of 280 W for 32 min to obtain a composite sol;

[0186] (4) immersing the activated carrier obtained in step (1) in the composite sol obtained in step (3) under a negative pressure of 0.022 MPa, the solid-liquid ratio of the activated carrier to the composite sol being 1g:5.5mL, taking out after immersion for 70 min, and completing gelation by standing in an environment with a relative humidity of 58% for 9h, and then heating to 575℃ at a heating rate of 4.5℃ / min and keeping for 2.2h to complete high-temperature calcination, to obtain a modified molecular sieve filler.

[0187] Example 5

[0188] The present embodiment provides a rectification process of dipropylene glycol, as shown in the following scheme, which specifically comprises the following steps: Figure 1

[0189] The crude dipropylene glycol raw material is preheated to 110℃ and then sent into the pre-separation tower for pre-distillation, the tower bottom temperature of the pre-separation tower is 160℃, the tower top temperature is 110℃, the reflux ratio is 8:1, the operating pressure is 3kPa, and the number of tower plates is 18;

[0190] Subsequently, the tower bottom liquid of the pre-separation tower is sent into the packed tower, the inside of the packed tower is sequentially filled from bottom to top with modified ceramic corrugated packing, stainless steel wire mesh and modified molecular sieve filler, wherein the packing density of the modified ceramic corrugated packing is 500kg / m 3 , the filling height is 1.5m; the mesh number of the stainless steel wire mesh is 400mesh, the packing density is 350kg / m 3 , the filling height is 1.2m; the packing density of the modified molecular sieve filler is 580kg / m 3 , and the filling height is 1m. The tower bottom liquid is fed from the middle part of the packed tower, corresponding to the position of the modified ceramic corrugated packing, the tower bottom temperature of the packed tower is 170℃, the tower top temperature is 108℃, the reflux ratio is 10:1, the operating pressure is 1.2kPa, and the dipropylene glycol product is collected from the tower top of the packed tower.

[0191] As shown in the following scheme, the modified ceramic corrugated packing is prepared by the following method: Figure 1

[0192] ​​(I) ceramic corrugated fillers with a pore size of 1.2 mm are immersed in a mixed acid solution according to a solid-liquid ratio of 1 g:20 mL, the mixed acid solution is composed of hydrofluoric acid (concentration 22.5 mol / L), nitric acid and deionized water, the mass fraction of hydrofluoric acid in the mixed acid solution is 8%, and the mass fraction of nitric acid in the mixed acid solution is 4%; ultrasonic oscillation is performed at a heating condition of 55℃ and an ultrasonic power of 400 W for 15 min, then the ceramic corrugated fillers are taken out and washed to neutral, and after drying, acidified ceramic corrugated fillers are obtained;

[0193] (II) under the condition of stirring at 300 rpm, tetraethyl orthosilicate is dropped into an ethanol aqueous solution (the volume ratio of ethanol to deionized water is 10:1), the molar ratio of tetraethyl orthosilicate to ethanol in the ethanol aqueous solution is 1:10, then 0.1 mol / L hydrochloric acid solution is added, the mass of the hydrochloric acid solution is 1.2 wt% of the mass of the tetraethyl orthosilicate, after mixing uniformly, a precursor solution is obtained; cerium dioxide nanoparticles with an average particle size of 50 nm are added to the precursor solution, the mass of the cerium dioxide nanoparticles is 5 wt% of the mass of the tetraethyl orthosilicate, high-speed stirring is performed at a rotating speed of 15000 rpm for 25 min, and a modified solution is obtained;

[0194] (III) the acidified ceramic corrugated fillers obtained in step (I) are immersed in the modified solution obtained in step (II) according to a solid-liquid ratio of 1 g:10 mL, the ceramic corrugated fillers are taken out after being immersed for 30 min, heating is performed at a heating rate of 2℃ / min to 620℃ and the ceramic corrugated fillers are kept at 620℃ for 1 h to complete high-temperature calcination, and modified ceramic corrugated fillers are obtained.

[0195] As shown in Figure 2 , the modified molecular sieve filler is prepared by the following method:

[0196] (1) molecular sieve honeycomb ceramic with a pore size of 0.8 mm is immersed in a potassium hydroxide solution with a mass fraction of 10 wt%, the solid-liquid ratio of the molecular sieve honeycomb ceramic to the potassium hydroxide solution is 1 g:15 mL, ultrasonic oscillation is performed at a heating condition of 50℃ and an ultrasonic power of 300 W for 30 min, then the molecular sieve honeycomb ceramic is taken out and washed to neutral, and heating is performed at a heating rate of 5℃ / min to 520℃ and the molecular sieve honeycomb ceramic is kept at 520℃ for 2 h to complete high-temperature calcination, and an activated carrier is obtained;

[0197] (2) aluminum chloride hexahydrate is mixed with ethanol according to a mass ratio of 1:5.5, and stirring is performed at a heating condition of 75℃ for 30 min to obtain an aluminum chloride solution, ammonia water solution with a mass fraction of 12 wt% is dropped into the aluminum chloride solution to adjust the pH value to 9.5 and generate a precipitate, then a dispersant polyethylene glycol 6000 is added, the mass of the polyethylene glycol 6000 is 0.3 wt% of the mass of the generated precipitate, and finally high-pressure homogenization is performed 5 times at a pressure of 150 MPa to obtain an aluminum hydroxide sol;

[0198] (3) mixing the silicon sol with a mass fraction of 40wt% with the aluminum hydroxide sol obtained in step (2) according to a mass ratio of 1:1.2, adding acetic acid solution after mixing to adjust the pH value to 5, then performing mechanical stirring at a rotating speed of 500rpm, and performing ultrasonic oscillation at an ultrasonic power of 300W for 30min, to obtain a composite sol;

[0199] (4) under a negative pressure environment of 0.025MPa, immersing the activated carrier obtained in step (1) in the composite sol obtained in step (3), the solid-liquid ratio of the activated carrier to the composite sol being 1g:6mL, taking out after immersing for 60min, and completing gelation by standing in an environment with a relative humidity of 60% for 8h, then heating to 580℃ at a heating rate of 5℃ / min and keeping for 2h to complete high-temperature calcination, to obtain a modified molecular sieve filler.

[0200] Example 6

[0201] This example provides a rectification process of dipropylene glycol, which is different from example 1 in that the bulk density of the modified ceramic corrugated filler is adjusted to 400kg / m 3 , and other operation steps and process parameters are completely same as example 1.

[0202] Example 7

[0203] This example provides a rectification process of dipropylene glycol, which is different from example 1 in that the bulk density of the modified ceramic corrugated filler is adjusted to 550kg / m 3 , and other operation steps and process parameters are completely same as example 1.

[0204] Example 8

[0205] This example provides a rectification process of dipropylene glycol, which is different from example 1 in that the bulk density of the modified molecular sieve filler is adjusted to 500kg / m 3 , and other operation steps and process parameters are completely same as example 1.

[0206] Example 9

[0207] This example provides a rectification process of dipropylene glycol, which is different from example 1 in that the bulk density of the modified molecular sieve filler is adjusted to 600kg / m 3 , and other operation steps and process parameters are completely same as example 1.

[0208] Example 10

[0209] The embodiment provides a rectification process of dipropylene glycol, and the difference from the embodiment 1 is that the mass of the cerium dioxide nanoparticles is adjusted to be 1wt% of the mass of the tetraethyl orthosilicate, and other operation steps and process parameters are completely same as those of the embodiment 1.

[0210] Embodiment 11

[0211] The embodiment provides a rectification process of dipropylene glycol, and the difference from the embodiment 1 is that the mass of the cerium dioxide nanoparticles is adjusted to be 8wt% of the mass of the tetraethyl orthosilicate, and other operation steps and process parameters are completely same as those of the embodiment 1.

[0212] Embodiment 12

[0213] The embodiment provides a rectification process of dipropylene glycol, and the difference from the embodiment 1 is that the soaking time of the acidified ceramic corrugated filler in the modification solution is adjusted to be 20min, and other operation steps and process parameters are completely same as those of the embodiment 1.

[0214] Embodiment 13

[0215] The embodiment provides a rectification process of dipropylene glycol, and the difference from the embodiment 1 is that the soaking time of the acidified ceramic corrugated filler in the modification solution is adjusted to be 50min, and other operation steps and process parameters are completely same as those of the embodiment 1.

[0216] Embodiment 14

[0217] The embodiment provides a rectification process of dipropylene glycol, and the difference from the embodiment 1 is that the mass ratio of the silica sol and the aluminum hydroxide sol is adjusted to be 1:0.5, and other operation steps and process parameters are completely same as those of the embodiment 1.

[0218] Embodiment 15

[0219] The embodiment provides a rectification process of dipropylene glycol, and the difference from the embodiment 1 is that the mass ratio of the silica sol and the aluminum hydroxide sol is adjusted to be 1:1.5, and other operation steps and process parameters are completely same as those of the embodiment 1.

[0220] Embodiment 16

[0221] The embodiment provides a rectification process of dipropylene glycol, and the difference from the embodiment 1 is that the soaking time of the activated carrier in the composite sol is adjusted to be 50min, and other operation steps and process parameters are completely same as those of the embodiment 1.

[0222] Embodiment 17

[0223] The embodiment provides a rectification process of dipropylene glycol, which is different from the embodiment 1 in that the soaking time of the activated carrier in the composite sol is adjusted to 100 min, and other operation steps and process parameters are completely same as those of the embodiment 1.

[0224] Comparative example 1

[0225] The comparative example provides a rectification process of dipropylene glycol, which is different from the embodiment 1 in that the ceramic corrugated filler is not subjected to the modification treatment, and other operation steps and process parameters are completely same as those of the embodiment 1.

[0226] Comparative example 2

[0227] The comparative example provides a rectification process of dipropylene glycol, which is different from the embodiment 1 in that the molecular sieve honeycomb ceramic is not subjected to the modification treatment, and other operation steps and process parameters are completely same as those of the embodiment 1.

[0228] The product purity and product yield of the dipropylene glycol prepared from the embodiment 1-17 and the comparative example 1-2 are detected, and the detection results are shown in Table 1.

[0229] Table 1 Product purity and yield of the embodiment 1-17 and the comparative example 1-2

[0230]

[0231] As can be seen from the test data of the embodiment 1, the embodiment 6 and the embodiment 7, in the embodiment 6, the bulk density of the modified ceramic corrugated filler is adjusted to 400 kg / m 3 , so that the support force of the filler structure is insufficient, local collapse occurs under the high-temperature heavy component environment, the gas-liquid mass transfer interface is reduced, and the heavy component back mixing is aggravated; in the embodiment 7, the bulk density of the modified ceramic corrugated filler is adjusted to 550 kg / m 3 , so that the porosity of the filler bed layer is reduced, the pressure difference is steeply increased, the energy consumption of the vacuum system is increased, the residence time of the heavy component is prolonged, and the by-products are increased.

[0232] As can be seen from the test data of the embodiment 1, the embodiment 8 and the embodiment 9, in the embodiment 8, the bulk density of the modified molecular sieve filler is adjusted to 500 kg / m 3 , so that the compression strength of the molecular sieve skeleton is reduced, the micro powder is fallen off in the continuous negative pressure environment, the fallen particles not only block the rectification channel, but also greatly reduce the effective adsorption area; in the embodiment 9, the bulk density of the modified molecular sieve filler is adjusted to 600 kg / m 3 , the micro-pore channel cross-sectional area is compressed, the interception efficiency of the monopropylene glycol impurity is reduced, and the vacuum balance is damaged due to the abnormally high tower top pressure drop.

[0233] As can be seen from the test data of Example 1, Example 10 and Example 11, in Example 10, the mass of cerium dioxide nanoparticles is adjusted to 1wt% of the mass of tetraethyl orthosilicate, the insufficient dispersion of the catalyst surface reduces the coverage of active sites, and the catalytic conversion efficiency of high-boiling aldehyde impurities decreases, and the accumulation rate of tower kettle coke increases; in Example 11, the mass of cerium dioxide nanoparticles is adjusted to 8wt% of the mass of tetraethyl orthosilicate, and the excessive loading causes serious agglomeration of cerium dioxide nanoparticles, forming cluster structures, and the specific surface area is greatly reduced. These clusters not only lose catalytic function, but also become the deposition core of tar-like by-products.

[0234] As can be seen from the test data of Example 1, Example 12 and Example 13, in Example 12, the soaking time of the acidified ceramic corrugated filler in the modification solution is adjusted to 20min, which causes the mixed acid solution to only etch the shallow layer of the ceramic surface, and the modification solution cannot be anchored in the deep pores during the subsequent loading process, resulting in insufficient coating coverage; in Example 13, the soaking time of the acidified ceramic corrugated filler in the modification solution is adjusted to 50min, which causes local areas to have excessive solute enrichment and even block the micropores of the ceramic matrix, which not only destroys the uniformity of the coating, but also produces microcracks due to uneven internal stress during the subsequent calcination process.

[0235] As can be seen from the test data of Example 1, Example 14 and Example 15, in Example 14, the mass ratio of silica sol to aluminum hydroxide sol is adjusted to 1:0.5, which causes a serious lack of aluminum oxide component, and the density of Bronsted acid sites in the composite coating decreases, weakening the selective adsorption capacity of polar impurities; in Example 15, the mass ratio of silica sol to aluminum hydroxide sol is adjusted to 1:1.5, which causes a significant difference in sol gelation rate, resulting in uneven shrinkage stress during the calcination stage and causing cracks in the coating.

[0236] As can be seen from the test data of Example 1, Example 16 and Example 17, in Example 16, the soaking time of the activated carrier in the composite sol is adjusted to 50min, and the composite sol only partially penetrates the main channels of the molecular sieve, and the internal micropore modification rate is insufficient; in Example 17, the soaking time of the activated carrier in the composite sol is adjusted to 100min, and the excessive soaking causes the sol to gel and block the micropores of the activated carrier, reducing the effective pore size distribution.

[0237] As can be seen from the test data of Example 1 and Comparative Example 1, in Comparative Example 1, the ceramic corrugated filler is not modified, and the unmodified ceramic filler lacks the surface regulation function of the SiO2 / CeO2 composite coating, forming hydrophobic patches in the tower bottom area. These patches hinder the spread of the liquid phase and cause local overheating, promoting the dehydration and condensation of heavy components at high temperatures, and significantly increasing the amount of polymer residue in the tower kettle.

[0238] From the test data of Example 1 and Comparative Example 2, it can be seen that in Comparative Example 2, the molecular sieve honeycomb ceramic is not modified, and the original molecular sieve filler is not subjected to alkali activation, hole expansion and composite coating strengthening, so that a certain degree of mass loss will occur after long-term operation, the detached molecular sieve fragments will pollute the tower top product along with the rising gas flow, and the low surface acid amount will cause the increase of the light impurity breakthrough rate, resulting in the loss of the deep purification ability of the rectification system.

[0239] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A rectification process of dipropylene glycol, characterized by, The rectification process of the dipropylene glycol comprises: The crude dipropylene glycol raw material is preheated and then sent into a pre-separation tower for pre-distillation, and then the tower bottom liquid of the pre-separation tower is sent into a packed tower for rectification, and the dipropylene glycol product is obtained from the top of the packed tower; The inside of the packed tower is sequentially filled with modified ceramic corrugated packing, stainless steel wire mesh and modified molecular sieve packing from bottom to top; The modified ceramic corrugated packing is obtained by sequentially subjecting ceramic corrugated packing to acidification and SiO2 / CeO2 loading; The modified molecular sieve packing is obtained by sequentially subjecting molecular sieve honeycomb ceramic to alkalization, calcination and SiO2 / Al2O3 loading.

2. The rectification process of dipropylene glycol according to claim 1, characterized in that, The crude raw material is preheated to 100-110℃; The tower bottom temperature of the pre-separation tower is 150-160℃; The tower top temperature of the pre-separation tower is 100-110℃; The reflux ratio of the pre-separation tower is (6-8):1; The operating pressure of the pre-separation tower is 2-3kPa; The number of plates of the pre-separation tower is 18-24; The tower bottom liquid is fed from the middle part of the packed tower, corresponding to the position of the modified ceramic corrugated packing; The tower bottom temperature of the packed tower is 160-170℃; The tower top temperature of the packed tower is 105-108℃; The reflux ratio of the packed tower is (8-10):1; The operating pressure of the packed tower is 1-1.2kPa; The modified ceramic corrugated filler has a bulk density of 480-500 kg / m 3 ; The filling height of the modified ceramic corrugated packing is 1.5-1.8m; The mesh number of the stainless steel wire mesh is 300-400; The stainless steel wire mesh has a bulk density of 300-350 kg / m 3 ; The filling height of the stainless steel wire mesh is 1.2-1.5m; The modified molecular sieve filler has a bulk density of 560-580 kg / m 3 ; The filling height of the modified molecular sieve packing is 1-1.2m.

3. The rectification process of dipropylene glycol according to claim 1, characterized in that, The modified ceramic corrugated packing is prepared by the following method: (I) The ceramic corrugated packing is immersed in a mixed acid solution, ultrasonic oscillation is performed under heating, then it is taken out, washed to neutral, dried to obtain acidified ceramic corrugated packing; (II) Tetraethyl orthosilicate is dropped into an ethanol aqueous solution, then hydrochloric acid solution is added, the mixture is uniformly mixed to obtain a precursor solution, cerium dioxide nanoparticles are added to the precursor solution, and high-speed stirring is performed to obtain a modified solution; (III) The acidified ceramic corrugated packing is immersed in the modified solution, after the immersion is completed, it is taken out and calcined at high temperature to obtain the modified ceramic corrugated packing.

4. The rectification process of dipropylene glycol according to claim 3, characterized in that, In step (I), the pore size of the ceramic corrugated packing is 0.8-1.2mm; The mixed acid solution is composed of hydrofluoric acid, nitric acid and deionized water; The mass fraction of hydrofluoric acid in the mixed acid solution is 8-10%; The mass fraction of nitric acid in the mixed acid solution is 4-6%; The solid-liquid ratio of the ceramic corrugated packing to the mixed acid solution is 1g:(10-20)mL; The heating temperature of the ceramic corrugated packing in the mixed acid solution is 45-55℃; The ultrasonic power of ultrasonic oscillation of the ceramic corrugated packing in the mixed acid solution is 300-400W; The immersion time of the ceramic corrugated packing in the mixed acid solution is 15-25min.

5. The rectification process of dipropylene glycol according to claim 3, characterized in that, In step (II), the volume ratio of ethanol to deionized water in the ethanol aqueous solution is (8-10):1; The tetraethyl orthosilicate is dripped into the aqueous ethanol solution under stirring at 200-300 rpm; The molar ratio of the tetraethyl orthosilicate to ethanol in the aqueous ethanol solution is 1:(8-10); The mass of the hydrochloric acid solution is 0.8-1.2 wt% of the mass of the tetraethyl orthosilicate; The particle size of the cerium dioxide nanoparticles is 30-50 nm; The mass of the cerium dioxide nanoparticles is 3-5 wt% of the mass of the tetraethyl orthosilicate; The rotation speed of the high-speed stirring is 12,000-15,000 rpm; The time of the high-speed stirring is 25-35 min.

6. The rectification process of dipropylene glycol according to claim 3, characterized in that, In step (III), the solid-liquid ratio of the acidified ceramic corrugated filler to the modification solution is 1 g:(8-10) mL; The soaking time of the acidified ceramic corrugated filler in the modification solution is 30-40 min; The heating rate of the high-temperature calcination is 1-2 ℃ / min; The calcination temperature of the high-temperature calcination is 600-620 ℃; The holding time of the high-temperature calcination is 1-3 h.

7. The rectification process of dipropylene glycol according to claim 1, characterized in that, The modified molecular sieve filler is prepared by the following method: (1) The molecular sieve honeycomb ceramic is soaked in a potassium hydroxide solution, ultrasonically oscillated under heating, then washed to neutral, and high-temperature calcined to obtain an activated carrier; (2) Aluminum chloride hexahydrate is mixed with ethanol and heated to obtain an aluminum chloride solution, ammonia water solution is dripped into the aluminum chloride solution to generate a precipitate, then a dispersant is added and high-pressure homogenized to obtain an aluminum hydroxide sol; (3) Silicon sol is mixed with the aluminum hydroxide sol to obtain a composite sol, the activated carrier is soaked in the composite sol, taken out and subjected to static gelation and high-temperature calcination to obtain the modified molecular sieve filler.

8. The rectification process of dipropylene glycol according to claim 7, characterized in that, In step (1), the pore size of the molecular sieve honeycomb ceramic is 0.5-0.8 mm; The mass fraction of the potassium hydroxide solution is 8-10 wt%; The solid-liquid ratio of the molecular sieve honeycomb ceramic to the potassium hydroxide solution is 1 g:(10-15) mL; The heating temperature when the molecular sieve honeycomb ceramic is soaked in the potassium hydroxide solution is 40-50 ℃; The ultrasonic power of the ultrasonic oscillation when the molecular sieve honeycomb ceramic is soaked in the potassium hydroxide solution is 200-300 W; The soaking time of the molecular sieve honeycomb ceramic in the potassium hydroxide solution is 30-40 min; The heating rate of the high-temperature calcination is 3-5 ℃ / min; The calcination temperature of the high-temperature calcination is 500-520 ℃; The holding time of the high-temperature calcination is 2-3 h.

9. The rectification process of dipropylene glycol according to claim 7, characterized in that, In step (2), the mass ratio of the aluminum chloride hexahydrate to ethanol is 1:(4.5-5.5); The heating temperature of the mixing and stirring of the aluminum chloride hexahydrate and ethanol is 65-75 ℃; The time of the mixing and stirring of the aluminum chloride hexahydrate and ethanol is 30-40 min; The mass fraction of the ammonia water solution is 10-12 wt%; The ammonia water solution is dripped into the aluminum chloride solution to adjust the pH value to 9.0-9.5; The mass of the dispersant is 0.2-0.3 wt% of the mass of the generated precipitate; The pressure of the high-pressure homogenization is 120-150 MPa; The number of times of the high-pressure homogenization is 5-8.

10. The rectification process of dipropylene glycol according to claim 7, characterized in that, In step (3), the mass fraction of the silica sol is 30-40 wt%; The mass ratio of the silica sol to the aluminum hydroxide sol is 1:(0.8-1.2); After mixing the silica sol and the aluminum hydroxide sol, acetic acid solution is added to adjust the pH value to 4.5-5, and then mechanical stirring and ultrasonic oscillation are simultaneously performed to obtain the composite sol; The rotating speed of the mechanical stirring of the silica sol and the aluminum hydroxide sol is 400-500 rpm; The ultrasonic power of the ultrasonic oscillation of the silica sol and the aluminum hydroxide sol is 200-300 W; The time of the ultrasonic oscillation of the silica sol and the aluminum hydroxide sol is 30-40 min; The activated carrier is soaked in the composite sol under a negative pressure of 0.015-0.025 MPa; The solid-liquid ratio of the activated carrier to the composite sol is 1 g:(4-6) mL; The soaking time of the activated carrier in the composite sol is 60-90 min; The standing gelation is performed in an environment with a relative humidity of 50-60%; The standing gelation time is 8-12 h; The heating rate of the high-temperature calcination is 3-5 ℃ / min; The calcination temperature of the high-temperature calcination is 560-580 ℃; The holding time of the high-temperature calcination is 2-3 h.

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