Preparation of high-efficiency paraformaldehyde sulfonic acid catalyst and application thereof in catalytic synthesis of C14 secondary alcohol

Abstract

This invention discloses the preparation of a high-efficiency paraformaldehyde sulfonic acid catalyst and its application in the catalytic synthesis of C14 secondary alcohols, relating to the field of olefin catalytic hydration technology. The catalyst is prepared by high-temperature polymerization of p-toluenesulfonic acid and paraformaldehyde under concentrated sulfuric acid catalysis. C14 olefins, the paraformaldehyde sulfonic acid catalyst, isopropanol, and deionized water are added to a reactor, and a catalytic reaction is carried out at a certain temperature. The product conversion rate is 0.46%, and the selectivity is >99%. The catalyst of this invention is simple to prepare, has a well-developed mesoporous structure and sufficient acidic sites, provides mild catalytic hydration reaction conditions, exhibits good olefin conversion and secondary alcohol selectivity, and is easily recoverable and reusable. The process is green and environmentally friendly, with high atom economy, and is beneficial for the industrial conversion and application of high-value utilization of Fischer-Tropsch olefins from coal-to-oil.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology for olefin catalytic hydration, specifically relating to a method for preparing a polyoxymethylene sulfonic acid solid acid catalyst, and a process for catalytically synthesizing C14 secondary alcohols from Fischer-Tropsch C14 olefins using this catalyst. Background Technology

[0002] The Fischer-Tropsch synthesis process can produce a large number of long-chain olefins with a wide carbon number distribution, among which C14 long-chain olefins are an important component of the Fischer-Tropsch synthesis products. Converting these inexpensive long-chain olefins into secondary alcohols via catalytic hydration can significantly increase the added value of oil products. Secondary alcohols possess advantages such as excellent low-temperature fluidity, chemical stability, and wide compatibility, and can be widely used in surfactants, lubricating additives, and fine chemical intermediates. This is an important technology for extending the coal-to-oil industrial chain and improving the comprehensive utilization rate of resources (CN202411706832.5).

[0003] The direct hydration process of olefins has advantages such as high atom utilization, short reaction process, no by-product pollution, and green and environmentally friendly process, and is currently the mainstream research direction for alcohol synthesis (Chemical Industry Progress, 2023, 42 (7): 3489-3500). However, long-chain Fischer-Tropsch olefins have the characteristics of long carbon chains and weak polarity, resulting in extremely low solubility in polar aqueous phases and large mass transfer resistance at the oil-water interface; at the same time, the olefin hydration reaction is strictly limited by thermodynamics, and the single-pass conversion is difficult under conventional catalytic systems; moreover, Fischer-Tropsch olefin feedstocks contain a mixture of α-olefins and internal olefins, which imposes strict requirements on the acidity, selectivity, and spatial structure of the catalyst, greatly increasing the research and development difficulty of the directional preparation of secondary alcohols from long-chain olefins.

[0004] Currently, the commonly used olefin hydration catalysts in the industry mainly include four categories: liquid strong acid, supported solid acid, acidic ion exchange resin, and molecular sieve (Langmuir, 2025, 41(31): 1-9). (1) Liquid strong acid catalytic system: strong acidity, but extremely corrosive, reactor requires special alloy material, and generates a large amount of waste acid and waste liquid, with high post-treatment costs; (2) Supported solid acid catalytic system: good thermal stability, but active components are easily lost and require periodic replenishment of active materials; (3) Polymer-based acidic resin catalytic system: excellent mass transfer performance, but generally suffers from hydrolysis and shedding of sulfonic acid groups, and high-temperature swelling and pulverization problems; (4) Molecular sieve-based catalytic system: acid density is controllable, but the micropore confinement effect is obvious, large molecular long chain olefins are difficult to diffuse, and the carbon deposition rate is fast (Journal of Chemical Industry and Engineering, 2019, 70(5): 1870-1878).

[0005] In summary, existing catalysts are difficult to adapt to the hydration reaction of C14 long-chain olefins. Developing a novel solid acid catalyst with excellent acidity, stable structure, hydrophobic properties, and adaptability to the diffusion and adsorption of long-chain olefins, and establishing an efficient, stable, and low-corrosion hydration process for long-chain olefins, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing a highly efficient paraformaldehyde sulfonic acid catalyst and its application in the catalytic synthesis of C14 secondary alcohols.

[0007] To achieve the above objectives, the present invention provides the following technical solution: preparation of a highly efficient paraformaldehyde sulfonic acid catalyst and its application in the catalytic synthesis of C14 secondary alcohols, obtained by catalyzing the Fischer-Tropsch C14 olefin reaction using a paraformaldehyde sulfonic acid solid acid catalyst; the reaction equation is shown below:

[0008]

[0009] The paraformaldehyde sulfonic acid solid acid catalyst was prepared by a high-temperature reaction of p-toluenesulfonic acid and paraformaldehyde in the presence of concentrated sulfuric acid. The reaction equation is shown below:

[0010]

[0011] The acid catalyst is concentrated sulfuric acid. The mass ratio of p-toluenesulfonic acid to paraformaldehyde is 5:1; the high-temperature reaction temperature is 100-110 °C; and the high-temperature reaction time is 48 h.

[0012] The C14 secondary alcohol is prepared by the following method: deionized water, organic solvent, Fischer-Tropsch C14 olefin, and polyoxymethylene sulfonic acid solid acid catalyst are added sequentially to a reactor, and the reaction is carried out at high temperature and high pressure to obtain the C14 secondary alcohol.

[0013] The organic solvent is isopropanol. The mass ratio of the Fischer-Tropsch C14 olefin to the polyoxymethylene sulfonic acid solid acid catalyst is 1:(0.2-0.6); the volume ratio of the deionized water to the organic solvent is 1:(0.5-2); the high-temperature reaction is carried out at 100-150 °C for 12-36 h; the reaction pressure is 3-7 MPa, and the system is kept stable by nitrogen pressurization.

[0014] The beneficial effects of this invention due to the adoption of the above technical solutions include: This application prepares a novel polyoxymethylene sulfonic acid solid acid catalyst. This catalyst constructs a hydrophobic mesoporous framework through covalent cross-linking, resulting in firmly established sulfonic acid active sites that are not easily detached. It exhibits excellent thermal stability and structural strength, effectively solving problems such as easy swelling and pulverization, activity loss, and strong corrosivity of traditional catalysts. The catalyst is adapted for diffusion adsorption of long-chain olefins, and when combined with an isopropanol co-solvent system, it significantly reduces the mass transfer resistance between the oil and water phases. Under mild conditions, it achieves directional hydration of Fischer-Tropsch C14 olefins with high product selectivity and few byproducts. Simultaneously, the catalyst can be recycled and reused, maintaining stable activity. The process is green and environmentally friendly, simple to operate, and easy to separate. It achieves high-value-added conversion using inexpensive Fischer-Tropsch olefins as raw materials, significantly improving economic benefits. It provides a stable and efficient new technical route for the hydration of long-chain olefins to produce high-carbon secondary alcohols, possessing outstanding industrial application value and market prospects. Attached Figure Description

[0015] Figure 1 The N2 adsorption-desorption curves and pore size distribution diagrams of the paraformaldehyde sulfonic acid catalyst of this invention are shown below.

[0016] Figure 2 This is a scanning electron microscope (SEM) image of the paraformaldehyde sulfonic acid catalyst of this invention. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to preferred embodiments and comparative examples. The embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0018] Example 1: Preparation of paraformaldehyde sulfonic acid catalyst:

[0019] 10 g of p-toluenesulfonic acid and 2 g of paraformaldehyde were accurately weighed and added to a 50 mL three-necked flask. 220 μL of concentrated sulfuric acid was added dropwise to the mixture as a crosslinking initiator. The reaction system was heated to 105 °C and stirred continuously at this temperature for 48 h, producing a black, blocky solid. After the reaction was complete, the solid product was collected by filtration. The solid was repeatedly washed with deionized water at 85 °C, and the washing filtrate was tested with barium chloride solution until no white precipitate formed, indicating complete removal of sulfate ions. The washed and purified solid was then dried overnight in a 100 °C oven to obtain the paraformaldehyde sulfonic acid catalyst.

[0020] The catalyst prepared in this embodiment was characterized by the following tests: BET analysis showed that the N2 adsorption-desorption isotherm of the catalyst was type IV, with an H3 hysteresis loop, and a specific surface area of ​​179 m². 2 / g, with an average pore size of 10 nm, belonging to mesoporous materials; SEM images show that the catalyst has an irregular blocky stacked morphology.

[0021] Example 2: Catalytic hydration of C14 olefins to prepare C14 secondary alcohols:

[0022] A 100 mL high-pressure reactor was selected as the reaction vessel. 3 g of paraformaldehyde sulfonic acid catalyst, 10 mL of deionized water, 10 mL of isopropanol, and 5 mL of Fischer-Tropsch C14 olefin feedstock oil were added sequentially. The reactor was sealed, and high-purity nitrogen was introduced three times to purge the air inside the reactor to eliminate oxygen interference. Nitrogen was then continuously introduced to raise the pressure inside the reactor to 5 MPa. The heating temperature was set at 130 ℃, and the reaction was carried out at a constant stirring rate for 24 h. After the reaction, the reactor was allowed to cool naturally to room temperature. The pressure inside the reactor was slowly released to expel the gas, and the mixture was collected. The solid catalyst was separated by filtration, and the filtrate was qualitatively and quantitatively analyzed using gas chromatography-mass spectrometry.

[0023] Experimental results: The conversion rate of C14 olefins was 0.46%, and the product was identified as a high-purity C14 secondary alcohol. Due to the extremely low aqueous solubility of long-chain olefins, the resistance to mass transfer in macromolecules, and thermodynamic equilibrium limitations, the conversion rate in this example was relatively low. However, it still exhibits significant advantages compared to traditional catalytic systems, and confirms that this catalyst can effectively activate long-chain olefins and directionally generate secondary alcohols without the formation of other byproducts, demonstrating excellent selectivity.

[0024] Example 3: Effect of reaction temperature on hydration reaction:

[0025] This embodiment investigates the effect of temperature on the catalytic reaction by controlling variables. The basic operating procedure is consistent with that of Example 2, with a fixed isopropanol to deionized water volume ratio of 1:1, a reaction time of 24 h, a reaction pressure of 5 MPa, and a catalyst dosage of 1 g. The reaction temperatures were set at 110 ℃, 120 ℃, 130 ℃, and 140 ℃. The experimental results show that when the reaction temperature is below 120 ℃, the activation ability of the catalyst active sites is insufficient, and almost no olefin conversion occurs. When the temperature is increased to 130 ℃, the molecular motion rate increases, the acidic activity of the catalyst is fully released, and the olefin conversion rate reaches the peak value of this group of experiments. As the temperature continues to rise, the system pressure increases, the side reaction tendency increases, and the conversion rate does not improve significantly. Therefore, the optimal reaction temperature of this invention is preferably 130 ℃.

[0026] Example 4: Effect of catalyst dosage on hydration reaction:

[0027] This embodiment investigates the effect of catalyst dosage on the reaction by controlling variables. The basic operating procedure is the same as in Example 2, with a fixed reaction temperature of 130 °C, a reaction pressure of 5 MPa, a reaction time of 24 h, and an isopropanol to water volume ratio of 1:1. The catalyst dosage is set to 1 g, 2 g, and 3 g, respectively. The experimental results show that within the experimental variable range, as the catalyst dosage increases, the number of acidic active sites in the system increases, and the olefin conversion rate shows a slow upward trend; however, due to the inherent solubility bottleneck of long-chain olefins, the increase in catalyst dosage has a limited effect on the conversion rate.

[0028] Example 5: Effect of solvent ratio on hydration reaction:

[0029] This embodiment investigates the effect of the ratio of organic solvent to water on the reaction by controlling variables. The basic operating procedure is the same as in Example 2, with a fixed reaction temperature of 130 °C, a reaction pressure of 5 MPa, a reaction time of 24 h, and a catalyst dosage of 3 g. The volume ratios of isopropanol to deionized water are set to 0.5:1, 1:1, 1.5:1, and 2:1, respectively. The experimental results show that as the proportion of isopropanol increases, the compatibility between the oil and water phases improves, the dispersion uniformity of long-chain olefins increases, the mass transfer resistance decreases, and the olefin conversion rate increases slightly. This confirms that the organic solvent is a key medium to ensure the normal progress of the hydration reaction of long-chain olefins.

[0030] Example 6 Catalyst Cyclic Stability Experiment:

[0031] The solid catalyst separated by filtration after the reaction in Example 2 was rinsed with anhydrous ethanol to remove residual oil phase, and then dried in a vacuum oven at 60 °C for 12 h to obtain the recovered catalyst. The recovered catalyst was reused in the reaction process of Example 2 for five consecutive cycles, and the olefin conversion rate was recorded each time. The experimental results showed that after five cycles, the olefin conversion rate remained above 0.42%, and the catalyst did not pulverize, agglomerate, or dissolve. Characterization tests showed that the sulfonic acid groups of the catalyst did not fall off after cycling, and the mesoporous structure remained intact, proving that the paraformaldehyde sulfonic acid catalyst of the present invention has excellent cyclic stability.

[0032] Table 1. Summary of the effects of different process conditions on the hydration reaction of C14 olefins

[0033] project Catalyst dosage / g Isopropanol:water Reaction temperature / °C Reaction time / h Olefin conversion rate / % Example 2 3 1:01 130 24 0.46 Example 3 1 1:01 110 24 0.12 Example 3 1 1:01 120 24 0.25 Example 4 2 1:01 130 24 0.37 Example 5 3 2:01 130 24 0.44

[0034] Comparative Example 1: Control experiment without catalyst:

[0035] This comparative example omits the catalyst addition step; all other experimental conditions and procedures are completely consistent with Example 2. After the reaction, the products were analyzed, and no C14 secondary alcohols were detected in the system, indicating no conversion of C14 olefins. The experiment demonstrates that olefin hydration cannot proceed spontaneously without a catalyst, and the paraformaldehyde sulfonic acid catalyst prepared in this invention is the core condition driving the hydration reaction.

[0036] Comparative Example 2: Control experiment relative to toluenesulfonic acid catalyst:

[0037] In this comparative example, the self-made catalyst was replaced with an equal mass (3g) of p-toluenesulfonic acid homogeneous catalyst, while other experimental parameters remained unchanged. Post-reaction testing showed that the system was extremely acidic, with obvious equipment corrosion, a C14 olefin conversion rate of less than 0.1%, and the product contained impurities and exhibited poor selectivity for secondary alcohols. Furthermore, the homogeneous catalyst could not be recovered, resulting in a large amount of acidic waste liquid and poor environmental performance.

[0038] Comparative Example 3: Control experiment of commercial sulfonic acid resin catalyst:

[0039] In this comparative example, commercially available Amberlyst-35 sulfonic acid resin was used instead of the self-made catalyst, and the reaction was carried out under the same experimental conditions. The test results showed that the olefin conversion rate was only 0.23%, which was lower than that in Example 2 of this invention; and after the reaction, the resin catalyst showed obvious swelling and pulverization, indicating poor structural stability and difficulty in recycling and reuse.

[0040] Comparative Example 4: Blank solvent control experiment without organic solvent:

[0041] This comparative example removed isopropanol as the organic solvent, using only 10 mL of deionized water as the reaction solvent, with all other conditions consistent with Example 2. No olefin conversion products were detected after the reaction, and the conversion rate was below the instrument detection limit. This demonstrates that a pure water system cannot disperse long-chain olefins; the oil and water phases completely separated, and the reactants could not contact the active sites of the catalyst, further verifying the solubilizing and mass transfer effect of the organic solvent.

[0042] Comparative Example 5: Control experiment with altered monomer structure:

[0043] In this comparative example, p-toluenesulfonic acid was replaced with phenolsulfonic acid in equal molar amounts in the raw materials. The remaining synthesis process and reaction conditions were completely consistent with those in Examples 1 and 2. A modified sulfonic acid catalyst was prepared. Test results showed that the catalyst had a low degree of crosslinking, a loose framework, weak acidity, and a C14 olefin conversion rate of only 0.18%. This indicates that the use of p-toluenesulfonic acid as the polymerization monomer in this invention can construct a dense crosslinked framework and ensure a high acid site density, making it the optimal monomer choice for this invention.

[0044] Comparative Example 6: Control experiment with varying amounts of crosslinking agent.

[0045] In this comparative example, the amount of concentrated sulfuric acid added was reduced to 100 μL, while the other catalyst synthesis conditions remained unchanged. The results showed that insufficient crosslinking agent led to incomplete polymerization, a loose catalyst framework, easy shedding of sulfonic acid groups during the reaction, and poor catalyst stability. Under the same reaction conditions, the olefin conversion rate was only 0.29%, proving that the amount of concentrated sulfuric acid added in this invention is the optimal crosslinking ratio.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, improvements, or optimizations made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. Technical features and processes not described in detail in this invention are all existing mature technologies, and those skilled in the art can implement them by referring to existing technologies.

Claims

1. A process for the preparation of a highly efficient paraformaldehyde sulfonic acid catalyst and its use in the catalytic synthesis of C14 secondary alcohols, characterized by, The reaction of paraformaldehyde with C14 olefins was catalyzed by a paraformaldehyde sulfonic acid catalyst. The paraformaldehyde sulfonic acid catalyst was prepared by high-temperature polymerization of paraformaldehyde with p-toluenesulfonic acid under acid catalysis.

2. The preparation of a high-efficiency paraformaldehyde sulfonic acid catalyst according to claim 1 and its application in the catalytic synthesis of C14 secondary alcohols, characterized in that, The acid catalyst is concentrated sulfuric acid.

3. The preparation of a high-efficiency paraformaldehyde sulfonic acid catalyst according to claim 1 and its application in the catalytic synthesis of C14 secondary alcohols, characterized in that, The mass ratio of p-toluenesulfonic acid to paraformaldehyde is 10:

2.

4. The preparation of a high-efficiency paraformaldehyde sulfonic acid catalyst according to claim 1 and its application in the catalytic synthesis of C14 secondary alcohols, characterized in that, The catalyst was prepared at a temperature of 100~110 ℃.

5. The preparation of a high-efficiency paraformaldehyde sulfonic acid catalyst according to claim 1 and its application in the catalytic synthesis of C14 secondary alcohols, characterized in that, The catalyst was prepared over a period of 48 hours.

6. The preparation of a high-efficiency paraformaldehyde sulfonic acid catalyst according to claim 1 and its application in the catalytic synthesis of C14 secondary alcohols, characterized in that, The method specifically involves adding deionized water, isopropanol, Fischer-Tropsch C14 olefin, and paraformaldehyde sulfonic acid catalyst sequentially into a reactor and heating the reaction to obtain C14 secondary alcohol.

7. The preparation of a high-efficiency paraformaldehyde sulfonic acid catalyst according to claim 1 and its application in the catalytic synthesis of C14 secondary alcohols, characterized in that, The mass ratio of the Fischer-Tropsch C14 olefin to the catalyst is 1:(0.05-0.3); the volume ratio of the deionized water to the organic solvent is 1:(1-2); the reaction temperature is 110-150 °C; and the reaction time is 20-30 h.

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