Process for the continuous flow preparation of nonylcyclohexanol ethoxylated by acid-base catalysis and the product

Abstract

The application discloses a continuous flow preparation method of nonylcyclohexanol ethoxylated by acid-base catalysis and a product, the method injects nonylcyclohexanol and ethylene oxide into a micro-channel reactor with a pulse variable-diameter structure through a precision metering pump for continuous flow reaction; the physical reinforced mass transfer and heat transfer characteristics of the micro-channel reactor are utilized, a cascade directional regulation mechanism of an acid or base catalytic system is coupled, and the accurate control of the number of ethoxy addition in the target product is realized by switching the catalytic system. The process not only effectively overcomes the defects such as low selectivity, safety risks caused by local hot spots and many by-products in the traditional kettle process, but also realizes the high-selectivity synthesis of mono-ethoxylated product (NCH-EO1) and di-ethoxylated product (NCH-EO2) by accurately regulating the EO consumption through the'starvation stop' mechanism. The prepared product has a free nonylcyclohexanol content of ≤2.5%, a colority (Pt-Co) of ≤50 and a main content of ≥99.0%, and the quality is excellent, and the flexibility and safety of continuous production of fine chemicals are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of organic chemical synthesis and fine chemical technology, specifically relating to an acid-base catalytic continuous flow preparation method and product of nonylcyclohexanol ethoxylation. Background Technology

[0002] Nonylcyclohexanol polyoxyethylene ether (NCEO) has become one of the key nonionic surfactants to replace nonylphenol polyoxyethylene ether (NPEO) due to its excellent surface activity and significantly improved environmental friendliness. Its application performance is highly dependent on the number of ethoxy (EO) chains in the molecule. Therefore, products with highly selective and controllable preparation of specific EO chain numbers (especially monosubstituted and disubstituted) have important industrial value.

[0003] Traditional batch reactor processes have significant drawbacks when synthesizing NCEOs with low EO numbers (e.g., EO=1-2):

[0004] (1) The reaction selectivity is difficult to control: secondary alcohols have low reactivity, ethylene oxide is prone to multi-molecule continuous addition, resulting in a wide product distribution and low selectivity of target mono / diethoxy compounds.

[0005] (2) Heat and mass transfer bottleneck: The reaction is highly exothermic, and local hot spots are easily formed in the reactor, which can trigger side reactions such as ethylene oxide self-polymerization, affecting the color and quality of the product, and posing a risk of overheating.

[0006] (3) Difficulty in catalyst separation: Homogeneous catalysts are complicated to process and are prone to product residue.

[0007] (4) Lack of control logic: Existing processes mostly rely on a single catalytic mode, making it difficult to accurately switch between mono-addition and di-addition products through process parameters.

[0008] To overcome these shortcomings, the industry has explored various improvement routes. For example, continuous hydrogenation processes are used to prepare the feedstock nonylcyclohexanol, or a two-step "etherification-hydrogenation" method is used to prepare NCEO. While these methods achieve continuous processing and improve environmental friendliness, their core reaction step (ethoxylation) either still uses a batch process or has not been specifically optimized for the high-selectivity synthesis of low EO number products, failing to fundamentally solve the bottlenecks in heat and mass transfer and the problem of precise selectivity. Other methods use specific catalyst suspensions to synthesize products with higher EO numbers, but their process focus is on suppressing PEG formation, with insufficient attention paid to the precise control of the selectivity for monoether or diether formation through catalyst type, and they also fail to fully utilize the advantages of continuous flow microreactors.

[0009] Therefore, how to develop a continuous preparation method that can precisely control the reaction path and improve process safety and product quality has become a key problem that urgently needs to be solved in this field. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides an acid-base catalytic continuous flow preparation method and product of nonylcyclohexanol ethoxylation. By constructing an acid-base catalytic pathway switching mechanism, the structure of the nonylcyclohexanol ethoxylation product is directionally controlled. Furthermore, by combining microchannel continuous flow reaction technology, the traditional heterogeneous stirring mass transfer process is transformed into a highly efficient homogeneous microfluidic reaction process, effectively solving the problems of low selectivity, deep color, and high risk of thermal runaway in existing technologies. This achieves high-quality, high-selectivity, and highly flexible industrial continuous production. The specific technical solution is as follows:

[0011] A continuous flow method for the acid-base catalytic preparation of nonylcyclohexanol by ethoxylation, characterized by the following steps:

[0012] Step 1: Nonylcyclohexanol (NCH) is mixed with a multi-component catalyst to form a catalytic reaction solution, which is material 1. Ethylene oxide (EO) is cooled to 0-8°C in liquid form and precisely metered, then mixed with an inert diluent and a co-solvent to form material 2. Material 2 is continuously injected into a microchannel reactor with a pulse-diameter variable structure through a precision feed pump. The reaction temperature is precisely controlled by an external heat exchanger.

[0013] Step 2: Materials 1 and 2 from Step 1 are thoroughly mixed and reacted in a continuous flow reactor. The system temperature, pressure and residence time are controlled. The reaction products flow out of the reactor outlet and enter the product collection system after being depressurized by the back pressure valve. The collected crude products are washed to remove impurities, remove catalyst and dehydrate to obtain the target monoethoxylated product NCH-EO1 and / or diethoxylated product NCH-EO2.

[0014] The multi-component catalyst system includes an acidic catalyst system, an alkaline catalyst system, and a solvent A for dissolving or dispersing the catalyst; by switching between the acidic and alkaline catalyst systems, the directional control of the number of ethoxy groups in the target product can be achieved.

[0015] When an acidic catalytic system is used, the reaction mainly produces the monoethoxylated product NCH-EO1; when an alkaline catalytic system is used, the reaction mainly produces the diethoxylated product NCH-EO2.

[0016] Preferably, when an acidic catalytic system is used, the molar ratio of nonylcyclohexanol to ethylene oxide is controlled at 1:1.0~1.5; when an alkaline catalytic system is used, the molar ratio of nonylcyclohexanol to ethylene oxide is controlled at 1:1.8~2.2.

[0017] Preferably, the acidic catalytic system comprises a main acidic catalyst and an acidic co-catalyst;

[0018] The primary acidic catalyst is at least one of trifluoromethanesulfonic acid, supported heteropoly acid, acidic ion exchange resin, and perfluorosulfonic acid resin; the acidic co-catalyst is at least one of tert-butyl chloride, trimethylchlorosilane, and organic sulfonate ester.

[0019] Preferably, the alkaline catalytic system comprises a main alkaline catalyst and a phase transfer co-catalyst;

[0020] The primary alkaline catalyst is at least one of potassium tert-butoxide (t-BuOK), KOH / γ-Al2O3, and Cs2CO3; the alkaline co-catalyst is at least one of tetrabutylammonium chloride and benzyltriethylammonium chloride.

[0021] Preferably, the internal structure of the microchannel reactor is a microchannel module with a pulsed variable diameter structure, the internal channel diameter is 1-5 mm, the reaction temperature is controlled at 90-120℃, the residence time is 12-22 min, and the system pressure is 0.5-2.0 MPa.

[0022] Preferably, solvent A is at least one of nitromethane, sulfolane, and dimethyl sulfoxide (DMSO).

[0023] Preferably, the co-solvent is selected from at least one of trifluoroacetic anhydride, 3-dimethyl-2-imidazolinone, and N-methylpyrrolidone (NMP).

[0024] Preferably, in the catalytic reaction solution in step 1, the total amount of catalyst is 0.05 to 0.1 times the amount of nonylcyclohexanol, wherein the co-catalyst accounts for 10% to 25% of the total catalyst mass; solvent A is 20% to 50% of the amount of nonylcyclohexanol; the total amount of inert diluent and co-solvent accounts for 10% to 30% of the total mass of ethylene oxide, and the co-solvent accounts for no more than 10%.

[0025] Preferably, the microchannel reactor is an enhanced mass transfer microchannel reactor, which is composed of multiple modules and is made of stainless steel or alloy metal coated with a corrosion-resistant coating.

[0026] The present invention also provides a nonylcyclohexanol ethoxylated product, which is prepared by the method described in any one of the above methods, and the nonylcyclohexanol ethoxylated product meets the following quality indicators: free nonylcyclohexanol content ≤2.5%; color (Pt-Co) ≤50; nonylphenol polyoxyethylene ether content <10 ppm; main content ≥99.0%.

[0027] The above technical solution has the following advantages or beneficial effects:

[0028] (1) The present invention achieves instantaneous and efficient mixing through microchannel pulse diameter structure, combined with the directional regulation of acid / base catalytic pathway, which effectively suppresses the continuous over-addition of EO. The selectivity of monoethoxylation (NCH-EO1) and dieethoxylation (NCH-EO2) can reach more than 94%, significantly improving the selectivity of the target product.

[0029] (2) This invention utilizes the excellent heat transfer capability of the microchannel reactor to eliminate local hot spots, control the product color (Pt-Co) below 50, and the main content ≥99.0%. Furthermore, the by-product content is significantly reduced through the "starvation stop" mechanism, resulting in higher product purity and achieving excellent product quality control.

[0030] (3) This invention can efficiently and flexibly produce single or diethers on the same microchannel device by simply switching the catalyst system, realizing the homogeneous continuous reaction of EO under low pressure, which not only reduces the equipment switching cost, but also significantly improves the flexibility and safety of the process. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention, wherein:

[0032] Figure 1 This is a schematic diagram of the parallel reaction pathways of monoaddition and multiple addition in the ethoxylation reaction of nonylcyclohexanol in this invention;

[0033] Figure 2 This is the internal structure of the microchannel reactor used in this invention;

[0034] Figure 3 This is the heat exchange structure of the membrane in the microchannel reactor of the present invention;

[0035] Figure 4 The following is a flow chart of the continuous flow reaction apparatus of the present invention: Wherein, 1 and 2 are raw material tanks, 3 and 4 are raw material metering pumps, 5 and 6 are preheating zones, 7 and 8 are reaction zones, and 9 is a product collection zone. Detailed Implementation

[0036] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0037] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0038] Please refer to Figure 4 The flow chart of the continuous flow reactor shows the specific reaction steps as follows:

[0039] Nonylcyclohexanol (NCH) and a multi-component catalyst mixture, ethylene oxide (EO) and an inert diluent and optional co-solvent mixture from the raw material storage tanks 1 and 2 are pumped into a microchannel reactor in a certain proportion through metering pumps 3 and 4. The mixture is thoroughly mixed and reacted in the microchannel reactor. The product is collected at the outlet and, after washing to remove impurities, removing the catalyst, and dehydrating, the target monoethoxylated product (NCH-EO1) and / or diethoxylated product (NCH-EO2) are obtained.

[0040] The microchannel reactor in this embodiment is an enhanced mass transfer microchannel reactor, and it consists of multiple modules. The material is stainless steel or alloy metal coated with a corrosion-resistant coating, such as silicon carbide (SiC) or Hastelloy.

[0041] In this embodiment of the invention, the mixing process of ethylene oxide (EO) with an inert diluent should be carried out in a closed pressure pipeline to prevent EO flash evaporation from causing inaccurate measurement.

[0042] Although the cosolvent (such as trifluoroacetic anhydride) in the embodiments of the present invention has acylation activity, the nucleophilic addition rate of ethylene oxide in the reaction system is much faster than the esterification rate of hydroxyl groups. Furthermore, by controlling the reaction temperature, the cosolvent mainly plays the role of improving the homogenization of the reaction system and reducing the mass transfer resistance at the interface in the microchannel, and will not produce obvious acylation byproducts.

[0043] Example 1

[0044] This embodiment provides a specific technical solution for preparing nonylcyclohexanol monoethoxy ether (NCH-EO1) using an acidic catalytic system.

[0045] This embodiment uses a microchannel reactor with an internal channel diameter of 3 mm and a pulsed diameter variable structure to conduct a continuous flow reaction. The specific reaction process is as follows:

[0046] (1) Mix 150g nonylcyclohexanol (NCH), 12.0g trifluoromethanesulfonic acid, 1.5g tert-butyl chloride, and 45.0g nitromethane evenly to form material 1.

[0047] (2) Cool 37.0 g of ethylene oxide EO to 5°C and mix it with 10.0 g of n-hexane and 2.0 g of trifluoroacetic anhydride to form material 2.

[0048] (3) Material 1 and material 2 are continuously injected into the microchannel reactor by a precision metering pump, and the feed ratio ensures that the molar ratio of NCH to EO is 1:1.3. The material temperature in the reactor is precisely controlled at 100℃ by external heat transfer oil, the total flow rate is controlled at 15ml / min, the pressure is controlled at 1.0MPa, and the residence time is controlled at 20 minutes. The reaction is fully mixed in the microchannel reactor, and the product is collected at the outlet to obtain the crude product.

[0049] (4) Transfer the collected crude product into a separatory funnel, add an appropriate amount of deionized water (or saturated saline) for multi-stage extraction and washing to remove acidic catalysts and residual co-catalysts in the system; add an equal amount of distilled water to the crude product, and discard the lower aqueous solution (containing inorganic salts) after separation; wash the upper organic layer with distilled water 3 to 5 times until the pH of the washing solution is 6.5 to 7.5; transfer the organic layer to a drying bottle, add anhydrous calcium chloride or molecular sieve, let stand for 2 to 4 h, and then filter; finally, heat at 60℃ and vacuum conditions (<1 kPa) to remove residual water and low-boiling-point solvents to obtain the final product.

[0050] (5) The composition of the crude and final products was analyzed by gas chromatography-FID. The results are as follows: NCH conversion rate was 99.5%, NCH-EO1 was 94.2%, NCH-EO2 was 4.5%, free nonylcyclohexanol content was 0.4%, color (Pt-Co) was 22, nonylphenol polyoxyethylene ether content was undetectable, moisture content was 0.2%, pH value was 7.2, and the main content (NCH-EO1 + NCH-EO2) was 99.1%. This embodiment successfully achieved highly selective monoethoxylation of nonylcyclohexanol in a microchannel reactor using an acidic catalytic system, and the final product met all quality standards for high-quality surfactants. In particular, the characteristics of light color, high main content, and few impurities fully demonstrate the advantages of microchannel reactors in heat and mass transfer control.

[0051] Different acidic catalytic systems and solvents were explored, while the other reaction conditions and amounts were the same as in Example 1. The results are shown in Table 1 below.

[0052] Table 1

[0053] To further explore the importance of microchannels and acid catalysis systems in improving selectivity, the technical effects of Example 1 were compared with typical process schemes reported in existing literature. The results are shown in Table 2 below:

[0054] Table 2

[0055]

[0056] The comparative analysis in Table 2 shows that: (1) Under the same catalytic system, the NCH-EO1 selectivity of the traditional batch process is much lower than that of the microchannel process, and the color is also darker, which fully demonstrates that the advantages of microchannels in temperature control and mixing effect are necessary conditions for improving selectivity. (2) Even if microchannels are used, the selectivity will decrease if the pulse-variable diameter structure (straight channel) is not used, indicating that the enhanced mixing effect of the pulse-variable diameter design is an important factor for further optimization. (3) Even under the same microchannel pulse-variable diameter process, the choice of catalyst type will significantly affect the selectivity, demonstrating the importance of the acid strength and chemical properties of the catalyst for EO activation and nucleophilic regulation.

[0057] Example 2

[0058] This Example 2 provides a specific technical solution for preparing nonylcyclohexanol diethoxy ether (NCH-EO2) using an alkaline catalytic system.

[0059] In this embodiment 2, a continuous flow reaction is carried out in a microchannel reactor with an internal channel diameter of 3 mm and a pulsed diameter variable structure. The specific reaction is as follows:

[0060] (1) Mix 150g nonylcyclohexanol, 9.5g potassium tert-butoxide, 1.5g tetrabutylammonium chloride and 45.0g dimethyl sulfoxide evenly to form material 1.

[0061] (2) Cool 70.0 g of ethylene oxide to 5°C and mix it with 10.5 g of cyclohexane and 3.5 g of N-methylpyrrolidone to form material 2.

[0062] (3) Material 1 and material 2 are continuously injected into the microchannel reactor by a precision metering pump. The feed ratio ensures that the molar ratio of NCH to EO is 1:2.0. The material temperature in the reactor is precisely controlled to 100℃ by external heat transfer oil. The total flow rate is controlled to 15ml / min, the pressure is 1.0MPa, and the residence time is 20 minutes. The materials are fully mixed and reacted in the microchannel reactor. The product is collected at the outlet to obtain the crude product.

[0063] (4) The crude product processing method is the same as in Example 1.

[0064] Gas chromatography analysis showed that the NCH conversion rate was 99.6%, NCH-EO1 was 2.7%, NCH-EO2 was 96.8%, free nonylcyclohexanol content was 0.2%, color (Pt-Co) was 35, nonylphenol polyoxyethylene ether content was undetectable, moisture content was 0.25%, pH value was 6.9, and the main content (NCH-EO1 + NCH-EO2) was 99.5%.

[0065] This embodiment successfully achieved highly selective diethoxylation of nonylcyclohexanol using an alkaline catalytic system under the same microchannel reaction process, with an NCH-EO2 selectivity as high as 96.8%, a stark contrast to the results of monoethoxylation under acidic conditions. This fully demonstrates the core concept of this invention—that by switching the catalyst system, the reaction pathway can be actively controlled to achieve the precise synthesis of different target products.

[0066] Different alkaline catalytic systems and solvents were explored, while the other reaction conditions and amounts were the same as in Example 2. The results are shown in Table 3 below.

[0067] Table 3

[0068]

[0069] The data in Table 3 show that: ① The main product content of all the above alkaline catalytic systems is >98%, proving that the alkaline catalytic system claimed in this invention also has wide applicability; ② The main product content of the Cs2CO3 system (98.3%) is slightly lower than that of other systems, possibly because the alkalinity and solubility characteristics of cesium carbonate are not as ideal as t-BuOK or KOH / γ-Al2O3 under these conditions, but it is still higher than the level of existing batch process; ③ KOH / γ-Al2O3, as a solid alkaline catalyst, has the advantage of easy catalyst recovery while ensuring high selectivity, and is particularly suitable for packed bed or fluidized bed microreactor configuration in industrial continuous production.

[0070] Example 3

[0071] In this embodiment 3, a microchannel reactor with an internal channel diameter of 3 mm and a pulsed diameter variable structure is used to carry out a continuous flow reaction.

[0072] Example 3 was conducted to investigate the effects of different catalyst and solvent dosages; all other conditions were the same as in Example 1. The results are shown in Table 4.

[0073] Table 4

[0074] Table 4 shows that: ① The optimal amount of catalyst is 0.05 to 0.1 times the amount of NCH (usually 0.08 to 0.1 times is optimal). Exceeding 0.1 times will lead to a decrease in the content of the main catalyst because the catalyst concentration is too high and impurities will be generated. ② The effect of solvent A: 0.3 to 0.5 times the amount of NCH has the best effect. Too little will affect mixing, and too much may dilute the concentration of reactants. ③ The ratio of diluent and cosolvent: The total amount is 10 to 30% of EO, and the cosolvent should not exceed 10% of the total diluent.

[0075] Example 4

[0076] In this embodiment 4, a microchannel reactor with an internal channel diameter of 3 mm and a pulsed diameter variable structure is used to carry out a continuous flow reaction.

[0077] Example 4 was conducted to investigate the effect of the molar ratio of NCH to EO in the range of 1:0.6–2.5. An acidic catalytic system was used, and the other conditions were the same as in Example 1. The results are shown in Table 5.

[0078] Table 5

[0079]

[0080] From the data in Table 5, we can conclude the following: Too little (1:0.6~0.8): NCH fails to fully utilize EO, resulting in low conversion. Although the selectivity of NCH-EO1 is extremely high (due to insufficient EO for diaddition), the overall yield is low and uneconomical. Appropriate (1:1.0~1.5): Within this range, by precisely controlling the amount of EO and the mild reaction rate catalyzed by acid, most of the NCH can complete monoaddition and remain at this stage. When the molar ratio is 1.3, on the one hand, EO is sufficient to achieve a NCH conversion >99%, and on the other hand, most of the EO is consumed in monoaddition, leaving insufficient EO to drive significant diaddition, thus resulting in the highest selectivity (94.2%). Too much (1:2.0~3.0): Although the NCH conversion is still high, excessive EO drives the monoaddition product (NCH-EO1) to continue diaddition, leading to an increase in the proportion of NCH-EO2 and higher-order products. Even under acid catalysis (theoretically, multiple additions should be suppressed), excessive EO will still disrupt this suppression effect. Therefore, when selective synthesis of monoethers is required, the molar ratio should not exceed 1:1.5.

[0081] For the preparation of diethers in an alkaline system (see Example 2), the deprotonation effect of the alkaline catalyst increases the nucleophilicity of the products at each stage, naturally leading to a tendency for continuous multiple additions, which is completely opposite to the processing logic of acid-catalyzed systems. To achieve precise control over the diaddition stage, this invention uses a relatively sufficient amount of ethylene oxide, precisely controlling the molar ratio within the range of 1:1.8~2.2. A 1.8 equivalent ensures that after all nonylcyclohexanol undergoes monoaddition, there is still enough ethylene oxide to drive the diaddition reaction to proceed fully, while the upper limit of 2.2 equivalents ensures that excess ethylene oxide is essentially depleted after the diaddition reaction, naturally stopping due to ethylene oxide shortage. This "starvation-type shutdown" mechanism effectively prevents the teraddition reaction from occurring.

[0082] Example 5

[0083] In this embodiment 5, a microchannel reactor with an internal channel diameter of 3 mm and a pulsed diameter variable structure is used to carry out a continuous flow reaction.

[0084] The purpose of this Example 5 is to investigate the effect of different reaction temperatures. An alkaline catalytic system was used, and the other conditions were the same as in Example 2. The results are shown in Table 6 below.

[0085] Table 6

[0086]

[0087] From the data in Table 6, we can conclude that: Low temperature (<90℃): Although the selectivity is still good, the reaction rate is relatively slow, and the conversion rate decreases under the same residence time; and low temperature may cause the fluidity of some solvents (such as DMSO) to deteriorate, which is not conducive to the mixing effect of microchannels. Optimal temperature (90~120℃): Within this range, the base-catalyzed reaction rate is moderate, with 100~110℃ being the most ideal, at which point the conversion rate is >99.5%, the diether selectivity is >95%, and the main product content is >99%. This temperature range reflects a kinetic and thermodynamic balance: a sufficiently high temperature ensures the reaction rate and complete conversion, but is not so high as to cause side reactions (such as the thermal decomposition or polymerization of ethylene oxide). High temperature (>120℃): Although the conversion rate remains close to quantification, the main content begins to decrease at 130℃ (from 99.5% to 98.8%), and the color may also deepen due to increased side reactions. Excessive temperature can trigger the following side reactions: (a) thermal polymerization of ethylene oxide itself, producing polyethylene glycol (PEG); (b) thermal decomposition or rearrangement of the ether bonds in the product; (c) accelerated multiple addition reactions, leading to further reactions of NCH-EO2 to NCH-EO3, etc. Therefore, 120℃ is the recommended upper limit. Thus, for the preparation of diethoxy ethers in an alkaline system, the optimal reaction temperature is 100~110℃; for the preparation of monoethoxy ethers in an acidic system, the optimal reaction temperature is 95~105℃ (corresponding to the optimal conditions for the acidic system in Example 4).

[0088] Example 6

[0089] In this embodiment 6, a microchannel reactor with an internal channel diameter of 3 mm and a pulsed diameter variable structure is used to carry out a continuous flow reaction.

[0090] The purpose of Example 6 is to investigate the effect of different system pressures. An acidic catalytic system was used, and the other conditions were the same as in Example 1. The results are shown in Table 7.

[0091] Table 7

[0092]

[0093] Ethylene oxide (EO) has a normal boiling point of 10.7℃ and requires pressure to maintain its liquid state at reaction temperatures (90~120℃). As shown in Table 7: ① At 0.3 MPa, EO partially vaporizes, resulting in uneven mixing and localized concentration differences due to the coexistence of gas and liquid phases, leading to a conversion rate of only 96.5% and a main content of 96.0%. ② When the pressure increases to 0.5~2.0 MPa, EO completely liquefies, the reaction becomes homogeneous, and the conversion rate is >98%, with stable selectivity and a main content >98%. The 1.0~1.5 MPa range shows the best performance in all indicators and has a wide operating window. ③ When the pressure increases to 2.5 MPa, the selectivity of NCH-EO1 drops sharply from 95.1% to 82.9%, while that of NCH-EO2 increases from 4.2% to 14.1%, and the main content decreases to 97.0%. This abnormal change may be related to the dissociation equilibrium of the acid catalyst or a change in the solvent dielectric constant under high pressure.

[0094] For alkaline systems (under the conditions of Example 2), due to the higher EO content, a pressure of 1.0~1.5 MPa is recommended to ensure complete EO liquefaction and maintain selective stability.

[0095] In summary, the optimal operating pressure is 0.8~2.0 MPa, and 1.0~1.5 MPa is recommended for both monoether and diether synthesis. The system pressure rating is recommended to be ≥2.5 MPa.

[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A continuous flow method for the acid-base catalytic preparation of nonylcyclohexanol by ethoxylation, characterized in that, Follow these steps: Step 1: Nonylcyclohexanol (NCH) is mixed with a multi-component catalyst to form a catalytic reaction solution, which is material 1. Ethylene oxide (EO) is cooled to 0-8°C in liquid form and precisely metered, then mixed with an inert diluent and a co-solvent to form material 2. Material 2 is continuously injected into a microchannel reactor with a pulse-diameter variable structure through a precision feed pump. The reaction temperature is precisely controlled by an external heat exchanger. Step 2: Materials 1 and 2 from Step 1 are thoroughly mixed and reacted in a continuous flow reactor. The system temperature, pressure and residence time are controlled. The reaction products flow out of the reactor outlet and enter the product collection system after being depressurized by the back pressure valve. The collected crude products are washed to remove impurities, remove catalyst and dehydrate to obtain the target monoethoxylated product NCH-EO1 and / or diethoxylated product NCH-EO2. The multi-component catalyst system includes an acidic catalyst system, an alkaline catalyst system, and a solvent A for dissolving or dispersing the catalyst; by switching between the acidic and alkaline catalyst systems, the directional control of the number of ethoxy groups in the target product can be achieved. When an acidic catalytic system is used, the reaction mainly produces the monoethoxylated product NCH-EO1; when an alkaline catalytic system is used, the reaction mainly produces the diethoxylated product NCH-EO2.

2. The acid-base catalytic continuous flow preparation method according to claim 1, characterized in that, When using an acidic catalytic system, the molar ratio of nonylcyclohexanol to ethylene oxide should be controlled at 1:1.0~1.5; when using an alkaline catalytic system, the molar ratio of nonylcyclohexanol to ethylene oxide should be controlled at 1:1.8~2.

2.

3. The acid-base catalytic continuous flow preparation method according to claim 1, characterized in that, The acidic catalytic system comprises a main acidic catalyst and an acidic co-catalyst; The primary acidic catalyst is at least one of trifluoromethanesulfonic acid, supported heteropoly acid, acidic ion exchange resin, and perfluorosulfonic acid resin; the acidic co-catalyst is at least one of tert-butyl chloride, trimethylchlorosilane, and organic sulfonate ester.

4. The acid-base catalytic continuous flow preparation method according to claim 1, characterized in that, The alkaline catalytic system comprises a main alkaline catalyst and a phase transfer co-catalyst; The primary alkaline catalyst is at least one of potassium tert-butoxide (t-BuOK), KOH / γ-Al2O3, and Cs2CO3; the alkaline co-catalyst is at least one of tetrabutylammonium chloride and benzyltriethylammonium chloride.

5. The acid-base catalytic continuous flow preparation method according to claim 1, characterized in that, The internal structure of the microchannel reactor is a pulse-diameter variable-diameter microchannel module with an internal channel diameter of 1-5 mm. The reaction temperature is controlled at 90-120℃, the residence time is 12-22 min, and the system pressure is 0.5-2.0 MPa.

6. The acid-base catalytic continuous flow preparation method according to claim 1, characterized in that, Solvent A is at least one of nitromethane, sulfolane, and dimethyl sulfoxide (DMSO).

7. The acid-base catalytic continuous flow preparation method according to claim 1, characterized in that, The co-solvent is selected from at least one of trifluoroacetic anhydride, 3-dimethyl-2-imidazolinone, and N-methylpyrrolidone (NMP).

8. The acid-base catalytic continuous flow preparation method according to claim 1, characterized in that, In the catalytic reaction solution in step 1, the total amount of catalyst is 0.05 to 0.1 times the amount of nonylcyclohexanol, wherein the co-catalyst accounts for 10% to 25% of the total catalyst mass; solvent A is 20% to 50% of the amount of nonylcyclohexanol; the total amount of inert diluent and co-solvent accounts for 10% to 30% of the total mass of ethylene oxide, and the co-solvent accounts for no more than 10%.

9. The acid-base catalytic continuous flow preparation method according to claim 1, characterized in that, The microchannel reactor is an enhanced mass transfer type microchannel reactor, which is composed of multiple modules and is made of stainless steel or alloy metal coated with a corrosion-resistant coating.

10. A nonylcyclohexanol ethoxylated product, characterized in that, The nonylcyclohexanol ethoxylated product prepared by any one of claims 1 to 8 meets the following quality indicators: free nonylcyclohexanol content ≤ 2.5%; color (Pt-Co) ≤ 50; nonylphenol polyoxyethylene ether content < 10 ppm; main content ≥ 99.0%.

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