Method for continuously preparing secondary alkyl sulfonate through photocatalytic sulfonation reaction

Abstract

The invention relates to a method for continuously preparing secondary alkane sulfonate through photocatalytic sulfonation reaction, which comprises the step of enabling dry mixed gas containing SO2 and oxygen and liquid hydrocarbon raw materials containing one or more of C5-C30 n-alkanes to be subjected to sulfonation reaction in a micro reaction tube of a micro-tube reactor under the irradiation of optical radiation. The method provided by the invention can shorten the reaction time for preparing the secondary alkyl sulfonate through photocatalytic sulfonation reaction, reduce the generation of by-products sulfuric acid and secondary alkyl disulfonic acid products, improve the raw material conversion rate, product selectivity and product quality, basically have no amplification effect, have low equipment loss and are simple to operate.

Description

Technical Field

[0001] The present application belongs to the field of fine chemical synthesis, and specifically relates to a method for continuously preparing secondary alkyl sulfonate by photocatalytic sulfoxidation reaction. Prior art

[0002] Sodium secondary alkyl sulfonate (SAS) not only maintains excellent cleaning ability under high temperature and strong alkaline conditions, but also has high solubility in water, which enables it to quickly penetrate clothing and reach the surface of the material. It also has relatively stable emulsification, and can dissolve in water after absorbing dirt, stably taking the dirt away from the clothes, making the clothes cleaner.

[0003] There are two main industrial processes for producing SAS, namely, chlorosulfonylation and sulfoxidation. The chlorosulfonylation process uses petroleum, liquid chlorine and sulfur dioxide as raw materials to produce alkyl sulfonyl chloride (its reaction formula is shown in the following formula (1)), and then neutralizes with sodium hydroxide to obtain sodium secondary alkyl sulfonate.

[0004] RH+SO2+Cl2→RSO2Cl+HCl (1)

[0005] The sulfoxidation method, also known as water-light sulfoxidation, uses paraffin as a raw material, which reacts with sulfur dioxide, oxygen and water under ultraviolet light to produce alkyl sulfonic acid (the reaction formula is shown in the following formula (2)), and then the product is purified and treated to obtain sodium secondary alkyl sulfonate.

[0006] RH+2 SO2+O2+H2O → RSO3H+H2SO4 (2)

[0007] However, in the chlorosulfonylation method, not only the main product benzenesulfonyl chloride is generated during the reaction, but also a certain amount of chlorine-containing byproducts such as polysulfonyl chloride is generated, and the more these byproducts are generated, the more the chlorosulfonylation reaction progresses. The traditional sulfonation method uses an intermittent reaction, which has the disadvantages of uneven material mixing and compression of a large amount of oxygen and sulfur dioxide during production. The heat generated is not easy to transfer, and high pressure is generated, resulting in over-sulfonation, darkening of the product color, and even explosion.

[0008] In addition, since the traditional batch reaction is an intermittent reaction and is discontinuous, it has problems such as large space occupation, high energy consumption, poor mixing effect, low efficiency, and low yield selectivity. The photocatalytic sulfonation reaction is a rapid reaction process, and too long a residence time will lead to the formation of by-products. The traditional batch reactor takes a long time to complete the reaction, resulting in serious over-sulfonation.

[0009] Therefore, there is still a need for a continuous method for preparing sodium secondary alkyl sulfonate quickly and efficiently with high yield. Summary of the invention

[0010] The purpose of the present application is to provide a method for preparing secondary alkyl sulfonates by photocatalytic sulfonation reaction, which utilizes microchannel reaction technology to carry out the photocatalytic sulfonation reaction and hydrolysis reaction, shortens the reaction time, reduces the production of by-products sulfuric acid and secondary alkyl disulfonic acid products, and improves product quality.

[0011] In order to achieve the above object, the present application provides a method for continuously preparing secondary alkyl sulfonate by photocatalytic sulfoxidation reaction, comprising the following steps:

[0012] 1) Providing a dry mixed gas containing SO2 and oxygen;

[0013] 2) making the mixed gas and the 30 Normal alkanes, preferably C7-C 30 One or more liquid hydrocarbon raw materials of normal alkanes are subjected to sulfoxidation reaction in a micro-reaction tube of a micro-tube reactor under light radiation to obtain a reaction liquid;

[0014] 3) contacting the reaction solution obtained in step 2) with water in a microchannel hydrolysis device including a mixer and a microchannel reactor to carry out a hydrolysis reaction to obtain a crude sulfonic acid product;

[0015] 4) separating the crude sulfonic acid product obtained in step 3) to obtain an unreacted liquid hydrocarbon feedstock and a sulfonic acid product solution; and

[0016] 5) neutralizing the sulfonic acid product solution obtained in step 4) with an alkaline compound, optionally performing degassing and / or decolorization treatment before neutralization, to obtain secondary alkyl sulfonate.

[0017] The method of the present application utilizes microchannel reaction technology to realize the separation of the photocatalytic sulfonation reaction process and the hydrolysis reaction process for preparing secondary alkyl sulfonates in different reaction equipment, and uses a microtube reactor as a sulfonation reaction unit and a microchannel hydrolysis device as a hydrolysis reaction unit, thereby overcoming the problems of long reaction time, large number of by-products and low selectivity in the traditional method of preparing secondary alkyl sulfonates by photocatalytic sulfonation reaction.

[0018] The method of the present application can realize the continuous production of secondary alkyl sulfonate, which can not only effectively control the reaction rate and ensure the safety of production, but also shorten the reaction time, reduce the production of byproduct sulfuric acid and secondary alkyl disulfonic acid products, and improve the raw material conversion rate, product selectivity and product quality. In addition, the method of the present application has basically no amplification effect, low equipment loss, simple operation, and is conducive to industrial amplification, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present application but do not constitute a limitation to the present application. In the accompanying drawings:

[0020] Figure 1 A schematic diagram of a micro-tube reactor used in a preferred embodiment of the method of the present application is shown. DETAILED DESCRIPTION

[0021] The specific implementation methods of the present application are described in detail below, but it should be noted that the protection scope of the present application is not limited by these specific implementation methods, but is determined by the claims in the appendix.

[0022] Any specific numerical value disclosed herein (including the endpoint of the numerical range) is not limited to the exact value of the numerical value, but should be understood to also cover values ​​close to the exact value, such as all possible numerical values ​​within the range of ±5% of the exact value. In addition, for the disclosed numerical range, the endpoint values ​​of the range, the endpoint values ​​and the specific point values ​​in the range, and the specific point values ​​can be arbitrarily combined to obtain one or more new numerical ranges, and these new numerical ranges should also be regarded as specifically disclosed herein.

[0023] Unless otherwise specified, the terms used herein have the same meaning as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition herein shall prevail.

[0024] In the context of the present application, "mainly composed of..." or "mainly contains" means that more than 80%, preferably more than 90%, more preferably more than 95%, and particularly preferably more than 98% of the material are composed of the defined components, and most preferably consist of the defined components excluding unavoidable impurities.

[0025] In this application, except for the contents clearly stated, any matters or items not mentioned are directly applicable to the aspects known in the art without any changes. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of this application, and should not be regarded as new contents not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0026] All patent and non-patent literature, including but not limited to textbooks and journal articles, mentioned herein are incorporated herein by reference in their entirety.

[0027] As described above, the present application provides a method for continuously preparing secondary alkyl sulfonate by photocatalytic sulfoxidation reaction, comprising the following steps:

[0028] 1) Providing a dry mixed gas containing SO2 and oxygen;

[0029] 2) making the mixed gas and the 30 Normal alkanes, preferably C7-C 30 One or more liquid hydrocarbon raw materials of normal alkanes are subjected to sulfoxidation reaction in a micro-reaction tube of a micro-tube reactor under light radiation to obtain a reaction liquid;

[0030] 3) contacting the reaction solution obtained in step 2) with water in a microchannel hydrolysis device including a mixer and a microchannel reactor to carry out a hydrolysis reaction to obtain a crude sulfonic acid product;

[0031] 4) separating the crude sulfonic acid product obtained in step 3) to obtain an unreacted liquid hydrocarbon feedstock and a sulfonic acid product solution; and

[0032] 5) neutralizing the sulfonic acid product solution obtained in step 4) with an alkaline compound, optionally performing degassing and / or decolorization treatment before neutralization, to obtain secondary alkyl sulfonate.

[0033] According to the present application, the mixed gas in step 1) may contain SO2 and O2, and optionally a gas that is substantially inert to subsequent reactions, such as nitrogen and carbon dioxide. Usually, the volume percentage of SO2 in the mixed gas is 20-40%, the volume percentage of O2 is 10-20%, and the remainder is a gas that is inert to subsequent reactions, such as nitrogen and carbon dioxide. In certain preferred embodiments, the mixed gas is a mixed gas of SO2 and dry air, wherein the volume percentage of SO2 is 20-40%. Preferably, the water content in the mixed gas is 0.01 g / m 3 the following.

[0034] According to the present application, in step 2), the liquid hydrocarbon feedstock is reacted with sulfur dioxide and oxygen under light radiation in a substantially anhydrous condition to obtain persulfonic acid, and the specific reaction formula is as follows:

[0035] RH+SO2+O2→RSO2O2H.

[0036] According to the present application, the liquid hydrocarbon feedstock used in step 2) is a hydrocarbon containing C5-C 30 Normal alkanes, preferably C7-C 30 Normal alkanes (such as C7-C 26 Normal alkanes, C7-C 24 Normal alkanes, C 10 -C 24 Normal alkanes, C10 -C 22 Normal alkanes or C7-C 20 n-alkanes), more preferably C 10 -C 20 The liquid hydrocarbon feedstock of one or more normal alkanes is preferably mainly composed of the C5-C 30 Normal alkanes, especially C7-C 30 Normal alkanes (such as C7-C 26 Normal alkanes, C7-C 24 Normal alkanes, C 10 -C 24 Normal alkanes, C 10 -C 22 Normal alkanes or C7-C 20 It is preferably mainly composed of one or more of C 10 -C 20 One or more components of normal alkanes, for example, may be mainly composed of C 10 -C 17 Normal alkanes (such as C 14 -C 17 normal alkanes), such as C 10 -C 17 Normal alkanes (such as C 14 -C 17 Liquid paraffin oil having a normal alkane) content of 80% by mass or more.

[0037] According to the present application, in step 2), the mixed gas and liquid hydrocarbon feedstock can be fed into the micro-reaction tube of the micro-tube reactor separately, or fed into the micro-reaction tube together after mixing, preferably fed into the micro-reaction tube after pre-mixing. The mixing can be carried out by any conventional gas-liquid mixing method, such as using a tee, a microchannel mixer (also called a micro mixer) or a bus, preferably by a bus.

[0038] According to the present application, the sulfoxidation reaction of step 2) is carried out in a microtubular reactor, and the microtubular reactor can be various microtubular reactors including microreaction tubes. Preferably, the inner diameter of the microreaction tube is 0.5-10.0 mm, preferably 1.0-4.5 mm, more preferably 1.0-3.0 mm; the outer diameter is 1.5-14.0 mm, preferably 1.5-7.5 mm, more preferably 1.5-5.0 mm; the length is 5.0-50.0 m, preferably 10.0-40.0 m, more preferably 10.0-30.0 m. According to the present application, in order to increase the reaction flux, the sulfoxidation reaction of step 2) can be carried out in two or more microreaction tubes or microtubular reactors connected in parallel, for example, in a microtubular reactor in which one, two or more microreaction tubes each include 2-100, such as 10-16 microreaction tubes connected in parallel.

[0039] According to the present application, in order to meet the needs of the photocatalytic reaction, the micro-reaction tube is preferably composed of a light-transmitting material so that the light radiation can penetrate the wall of the reaction tube and irradiate the reactants. The transmittance of the light-transmitting material to the light radiation is preferably greater than or equal to 50%, more preferably greater than or equal to 80%. Further preferably, the light-transmitting material is selected from light-transmitting glass, organic glass, plastic, biomass and oxide materials, and is particularly preferably selected from light-transmitting glass, organic glass and plastic materials.

[0040] In a preferred embodiment, the micro-reaction tube is made of a highly light-transmitting material selected from polytetrafluoroethylene, quartz glass and borosilicate glass, and is particularly preferably selected from quartz glass tube and polytetrafluoroethylene tube.

[0041] According to the present application, the micro-reaction tube can be in the form of tubes of various shapes, such as straight tubes, curved tubes, U-shaped tubes, ring tubes, spiral tubes, etc. Preferably, in order to save space, the micro-reaction tube is a micro-tube spiral reaction tube.

[0042] According to the present application, the light radiation can be any light radiation suitable for catalyzing the sulfoxidation reaction, such as X-rays, gamma rays, ultraviolet light, preferably ultraviolet light, more preferably ultraviolet light with a wavelength in the range of 252-365nm, such as in the range of 252-275nm. Further preferably, the power of the ultraviolet light is 10-100W, such as 10-40W.

[0043] According to the present application, the optical radiation source can be any device capable of generating the optical radiation, preferably an ultraviolet lamp. The present application does not have strict restrictions on the specific form of the optical radiation source, which can be selected from a point light source, a line light source, a plane light source and a curved light source, preferably selected from a line light source, a plane light source and a curved light source.

[0044] In the present application, there is no strict restriction on the specific arrangement of the micro-reaction tubes and the light radiation source of the micro-tube reactor, as long as the light radiation emitted by the light radiation source can effectively irradiate the micro-reaction tubes.

[0045] In certain preferred embodiments, the reaction temperature is controlled by immersing the micro-reaction tube in a water bath.

[0046] Figure 1 A schematic diagram of a preferred embodiment of the microtube reactor used in step 2) of the present application is shown, wherein the microtube reactor comprises 16 microtube spiral reaction tubes connected in parallel, and the light radiation source is a linear light source and is arranged between two adjacent microtube spiral reaction tubes. The microtube spiral reaction tubes are immersed in a water bath for temperature control.

[0047] According to the present application, in a preferred embodiment, the conditions of the sulfoxidation reaction in step 2) include: the reaction temperature is 10-70°C, preferably 10-60°C, the flow rate of SO2 gas in each microreaction tube is 0.1-1.5L / min, preferably 0.1-1.0L / min; the flow rate of dry air is 0.2-5.0L / min, preferably 0.2-2.0L / min, and / or the flow rate of liquid hydrocarbon feedstock in each microreaction tube is 3.0-32.0mL / min, preferably 4.0-15.0mL / min.

[0048] According to the present application, after the reaction in step 2), gas-liquid separation is usually performed to obtain a reaction solution containing unreacted normal alkanes and persulfonic acid. The reaction solution will spontaneously separate into two liquid phases, the upper reaction liquid mainly containing unreacted normal alkanes and persulfonic acid, and the lower reaction liquid mainly containing pyrosulfonic acid.

[0049] According to the present application, in certain preferred embodiments, after the reaction in step 2) and before the hydrolysis reaction in step 3), the reaction liquid obtained in step 2) is phase-separated to obtain an upper layer reaction liquid and a lower layer reaction liquid, and the upper layer reaction liquid is used as a liquid raw material to repeat the sulfonation reaction in step 2), and the process is performed once or multiple times, for example, 1-5 times, preferably 1-3 times, to obtain a multi-stage reaction liquid, and the lower layer reaction liquid obtained by each separation is combined with the multi-stage reaction liquid to obtain a mixed reaction liquid; then the obtained mixed reaction liquid is hydrolyzed in step 3) to obtain a crude sulfonic acid product. Specifically, after the reaction in step 2), the reaction liquid obtained in step 2) (also called the primary reaction liquid) is phase-separated, and the obtained upper layer reaction liquid and the fresh mixed gas are separately or mixed and sent to the micro-reaction tube of the second-stage micro-tube reactor, and the second-stage sulfonation reaction is carried out under light radiation to obtain a secondary reaction liquid. As needed, the obtained secondary reaction liquid can be phase-separated in the same manner and then subjected to a third-stage sulfonation reaction, which is repeated until the desired goal is achieved. By adopting the staged reaction method, a relatively short reaction tube can be used in each stage of the reaction, avoiding the use of a long reaction tube for a long sulfonation reaction, thereby reducing the production of disulfonation and polysulfonation by-products; at the same time, the viscous products that have been sulfonated can be collected in advance between each stage of the reaction, thereby solving the problem of over-sulfonation products adhering to the wall of the micro-reaction tube, reducing the light radiation transmittance and clogging the channel; and the reactant flow that is not fully sulfonated continues to enter the next stage reactor for reaction, thereby improving the overall conversion rate and selectivity of the reaction.

[0050] In a further preferred embodiment, the phase separation can be performed by a conventional method in the art, and the present application has no strict limitation thereto. Preferably, the phase separation can be performed by static separation.

[0051] According to the present application, in step 3), the reaction solution obtained in step 2) is hydrolyzed, and in the preferred embodiment described above, the mixed reaction solution obtained by the multi-stage reaction is mainly reacted with water to obtain a crude sulfonic acid product containing alkyl sulfonic acid. The specific reaction formula is as follows:

[0052] RSO2O2+H2O+SO2→RSO3H+H2SO4.

[0053] According to the present application, the hydrolysis reaction in step 3) is carried out in a microchannel hydrolysis device including a mixer and a microchannel reactor, thereby greatly increasing the mixing area of ​​the two phases and greatly shortening the reaction time of the hydrolysis part. Preferably, the flow rate of water is 2-20% of the flow rate of the reaction solution in terms of mass flow rate, and the hydrolysis temperature is preferably 10-80°C, more preferably 20-40°C.

[0054] In a preferred embodiment, the mixer can be a micro mixer or a mixer containing fillers. Further preferably, the channel size of the micro mixer is 0.1-1.0 mm.

[0055] In a preferred embodiment, the reaction channel of the micro channel reactor can be straight tube type, heart type, spherical, diamond-shaped, rectangular, serpentine or wavy, and the present application has no strict restrictions on this. Usually, the micro channel reactor is made of acid-resistant material. The internal diameter of the micro channel reactor is 0.1-1.5mm, and the liquid holdup of the micro channel reactor is 1-200mL, preferably 3-50mL.

[0056] In certain preferred embodiments, the hydrolyzate is aged after the hydrolysis reaction in step 3) and before step 4), so that the pyrosulfonic acid byproduct generated in the sulfoxidation reaction continues to react with the unreacted normal alkanes to be converted into alkyl sulfonic acid. The aging can be carried out in a conventional reactor, such as in a stirred tank. Preferably, the aging conditions include: temperature 0-80°C, such as 10-50°C, preferably 10-30°C, preferably 20-30°C, time 5-120min, preferably 10-30min. The stirred tank can be a stirred tank commonly used in the art, and its capacity can be 1-2000L, and the rotation speed of the stirred tank can be 50-1000r / min. In such preferred embodiments, by adopting the combined technology of microchannel reaction and kettle reaction, a certain aging time can be provided while ensuring continuous production, thereby improving the overall yield of the reaction.

[0057] According to the present application, in step 4), the crude sulfonic acid product obtained in step 3) is separated to obtain unreacted liquid hydrocarbon feedstock and sulfonic acid product solution. The separation is preferably performed by centrifugation. For example, the centrifugation can be performed using a centrifuge, such as a tubular centrifugal separator, with a centrifugal speed of 6000-20000 r / min, preferably 10000-14000 r / min.

[0058] According to the present application, preferably, the unreacted liquid hydrocarbon feedstock separated in step 4) can be returned to step 2) for further reaction, for example, it can be mixed with fresh feedstock as a recycled material and used as a raw material for step 2). Further preferably, the mixing ratio of the recycled material to the fresh feedstock is 0.01-1:1.

[0059] According to the present application, in step 5), the sulfonic acid product solution obtained in step 4) is neutralized with an alkaline compound to obtain the target secondary alkyl sulfonate product. The alkaline compound used can be any alkaline compound that can react with the obtained alkyl sulfonic acid to neutralize it to obtain secondary alkyl sulfonate, such as ammonia, alkaline metal oxide, alkaline metal salt or hydroxide, preferably sodium carbonate or sodium hydroxide, more preferably sodium hydroxide. In particular, the neutralization can be carried out with a sodium hydroxide solution with a mass concentration of 30-50%.

[0060] According to the present application, optionally and preferably, before the neutralization in step 5), the sulfonic acid product solution obtained in step 4) is degassed to reduce the sulfur dioxide content and acid value in the liquid phase product, reduce the amount of alkaline solution used in the neutralization reaction, reduce the generation of by-products, and recover sulfur dioxide, thereby reducing energy consumption and material consumption. The degassing can be carried out in a conventional manner in the art, such as heating reflux degassing, vacuum degassing, thin film ultrasonic degassing, and air ultrasonic degassing. In a preferred embodiment, the degassing is carried out by air ultrasonic degassing, that is, air is introduced while the reaction solution is subjected to ultrasonic treatment to carry out the SO2 contained therein, thereby conveniently achieving the removal of SO2 gas at normal temperature and pressure.

[0061] According to the present application, optionally and preferably, in step 5), the sulfonic acid product solution after optional degassing is subjected to decolorization treatment before the neutralization, preferably using a bleaching agent to treat the residual oversulfonated product therein and destroy its chromogenic functional group, thereby achieving the purpose of decolorization. Further preferably, the bleaching agent is a hydrogen peroxide solution with a concentration of 10-30%.

[0062] Compared with the prior art, the technology of this application has the following advantages:

[0063] 1. The use of microchannel reaction technology can increase the mass transfer effect of the gas-liquid mixture, making the gas-liquid two phases more fully mixed, thereby increasing the reaction rate and improving the reaction efficiency.

[0064] 2. The use of microchannel reaction technology for photocatalytic sulfonation reaction can shorten the light transmission path and improve light utilization and reaction efficiency.

[0065] 3. In the sulfoxidation reaction, the reaction time has a significant effect on the production of oversulfonation by-products. The use of microchannel reaction technology can achieve fine control of the reaction time, reduce oversulfonation, and improve raw material conversion rate, product selectivity and product quality.

[0066] 4. The use of a microchannel hydrolysis device for hydrolysis reaction can greatly increase the mixing area of ​​the two phases and greatly shorten the reaction time of the hydrolysis part. At the same time, combined with aging the hydrolysis product in the reactor, the residual pyrosulfonic acid by-product in the hydrolysis product can be further converted into alkyl sulfonic acid, providing a certain aging time while ensuring continuous production, thereby improving the overall yield of the reaction.

[0067] 5. The use of microchannel reaction technology has low equipment loss, and the microchannel technology equipment is small in size, simple to operate, and has no amplification effect. It can ensure production safety and is conducive to large-scale production.

[0068] 6. The use of multi-channel parallel reaction technology solves the problem of small liquid holding capacity and low output of single-channel micro-tube reactor, which is conducive to expanding production.

[0069] 7. The air ultrasonic degassing method can conveniently reduce the sulfur dioxide content and acid value in the sulfonic acid product solution, reduce the amount of alkaline solution required for the neutralization reaction, and at the same time recycle sulfur dioxide, reduce the generation of by-products, and reduce energy consumption and material consumption.

[0070] Example

[0071] The embodiments of the present application will be described in detail below in conjunction with examples, but those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be construed as limiting the scope of the present application.

[0072] In the following examples and comparative examples, the composition of the liquid paraffin oil raw material used is as follows:

[0073]

[0074] The sodium sulfonate yields (by mass) given in the following examples and comparative examples are calculated by the following formula:

[0075] Sodium sulfonate yield = (mass of sodium sulfonate product × content of sodium alkyl monosulfonate) / (mass of paraffin oil feed / average molecular weight of paraffin oil × (average molecular weight of paraffin oil + 102)) × 100%;

[0076] The content of sodium alkyl monosulfonate is obtained by detecting the obtained sodium sulfonate product according to the method of GB / T 20199-2006, and the average molecular weight of the paraffin oil used in the embodiments and comparative examples is 205 and the density is 0.760 for calculation.

[0077] In the following examples and comparative examples, unless otherwise specified, all reagents and raw materials used are commercially available products.

[0078] The operating steps and methods without specifying specific conditions in the following examples and comparative examples are carried out in conventional manners and conditions, or according to the product instructions of the relevant equipment.

[0079] Example 1

[0080] Open the gas valve of the sulfur dioxide storage tank and the valve of the dry air storage tank, adjust the pressure reducing valve and the flow meter to make them flow out at a flow rate of 2.6L / min and 6L / min respectively, mix them through the gas mixer to obtain a mixed gas, and at the same time, pump liquid paraffin oil through the liquid feed pump at a flow rate of 64mL / min. The paraffin oil and the mixed gas are preheated to 30°C through the liquid preheater and the gas preheater respectively, and after mixing through the gas-liquid mixer, enter the primary microtubule reactor (such as Figure 1 The light source used is an ultraviolet lamp with a wavelength of 254nm and a power of 30W. The micro-tube spiral reaction tube is made of a polytetrafluoroethylene tube. Each micro-tube spiral reaction tube has an inner diameter of 1.5mm, an outer diameter of 2mm, and a length of 20m. The reaction temperature is controlled at 30°C. The reaction effluent is separated into gas and liquid in a separation box to obtain a primary reaction liquid and tail gas.

[0081] The obtained primary reaction liquid and water with a flow rate of 3mL / min are fed into a microchannel hydrolysis device including a micromixer and a microchannel reactor for hydrolysis reaction to obtain a crude sulfonic acid product, wherein the channel size of the micromixer is 0.15mm, and the reaction channel of the microchannel reactor is a straight tube type with an inner diameter of 1.5mm and a liquid holding capacity of 5mL. The crude sulfonic acid product is then pumped into a tubular centrifugal separator and separated at a speed of 14000rpm to obtain unreacted paraffin oil and a sulfonic acid product solution. The obtained sulfonic acid product solution is neutralized with a sodium hydroxide solution with a mass concentration of 40%, and then deoiled, desalted and dehydrated to obtain a secondary alkyl sodium sulfonate product, and the sodium sulfonate yield is 21.33%.

[0082] Example 2

[0083] The first stage sulfonation reaction was carried out with reference to Example 1, and the obtained first stage reaction liquid was phase-separated to obtain a first stage upper layer reaction liquid and a first stage lower layer reaction liquid. The first stage upper layer reaction liquid was continuously mixed with the fresh mixed gas of the same flow rate in the first stage sulfonation reaction and entered into a second stage micro-tube reactor including 16 parallel micro-tube spiral reaction tubes, and the second stage sulfonation reaction was carried out under the same conditions as described in Example 1, and the reaction effluent was separated into gas and liquid by a separation box to obtain a second stage reaction liquid and tail gas. The first stage lower layer reaction liquid was combined with the second stage reaction liquid, and a hydrolysis reaction and centrifugal separation were carried out with reference to Example 1, and the flow rate of water was 5 mL / min. Then, the subsequent treatment was carried out with reference to Example 1 to obtain a secondary alkyl sodium sulfonate product, and the sodium sulfonate yield was 38.48%.

[0084] Example 3

[0085] The first and second stage sulfonation reactions were carried out with reference to Example 2, and the obtained second stage reaction liquid was phase separated to obtain the second stage upper layer reaction liquid and the second stage lower layer reaction liquid. The second stage upper layer reaction liquid was further mixed with the fresh mixed gas of the same flow rate in the first stage sulfonation reaction and entered into the third stage micro-tube reactor including 16 parallel micro-tube spiral reaction tubes, and the third stage sulfonation reaction was carried out under the same conditions as described in Example 1, and the reaction effluent was separated by gas-liquid separation in the separation box to obtain the third stage reaction liquid and tail gas. The first stage lower layer reaction liquid, the second stage lower layer reaction liquid and the third stage reaction liquid were combined, and the hydrolysis reaction and centrifugal separation were carried out with reference to Example 1, and the flow rate of water was 7.5 mL / min. Then, the subsequent treatment was carried out with reference to Example 1 to obtain the secondary alkyl sodium sulfonate product, and the sodium sulfonate yield was 49.17%.

[0086] Example 4

[0087] The first, second and third stage sulfoxidation reactions were carried out with reference to Example 3, and the obtained third stage reaction liquid was phase separated to obtain a third stage upper layer reaction liquid and a third stage lower layer reaction liquid. The third stage upper layer reaction liquid was continued to be mixed with the fresh mixed gas of the same flow rate in the first stage sulfoxidation reaction and entered into a fourth stage micro-tube reactor including 16 parallel micro-tube spiral reaction tubes, and the fourth stage sulfoxidation reaction was carried out under the same conditions as described in Example 1, and the reaction effluent was separated by gas-liquid separation in a separation box to obtain a fourth stage reaction liquid and tail gas. The first stage lower layer reaction liquid, the second stage lower layer reaction liquid, the third stage lower layer reaction liquid and the fourth stage reaction liquid were combined, and the hydrolysis reaction and centrifugal separation were carried out with reference to Example 1, and the flow rate of water was 9 mL / min. Then, the subsequent treatment was carried out with reference to Example 1 to obtain a secondary alkyl sodium sulfonate product, and the sodium sulfonate yield was 57.17%.

[0088] Example 5

[0089] The experiment was carried out with reference to Example 1, except that the flow rate of the liquid paraffin oil was 400 mL / min, and the flow rate of the water for the hydrolysis reaction was 9 mL / min. The yield of the obtained sodium sulfonate was 13.86%.

[0090] Example 6

[0091] The experiment was carried out with reference to Example 1, except that the flow rate of sulfur dioxide was 5 L / min, the flow rate of dry air was 10 L / min, and the flow rate of water was 4 mL / min. The yield of sodium sulfonate obtained was 26.74%.

[0092] Example 7

[0093] The experiment was carried out in accordance with Example 1, except that the preheating and reaction temperature was 20°C, and the water flow rate was 2 mL / min. The yield of sodium sulfonate obtained was 17.26%.

[0094] Example 8

[0095] The experiment was carried out in accordance with Example 1, except that the flow rate of sulfur dioxide was 2 L / min, the flow rate of dry air was 8 L / min, and the flow rate of water was 2.5 mL / min. The yield of sodium sulfonate obtained was 20.33%.

[0096] Example 9

[0097] The experiment was carried out with reference to Example 1, except that the inner diameter of the micro-tube spiral reaction tube was 2 mm, the outer diameter was 3 mm, and the flow rate of water was 1.5 mL / min. The yield of sodium sulfonate obtained was 9.44%.

[0098] Example 10

[0099] The experiment was carried out in accordance with Example 1, except that the hydrolysis reaction effluent was further aged for 20 min in multiple 2L stirred tanks in switching operation at a rotation speed of 200 rpm and a temperature of 20° C. to obtain a crude sulfonic acid product. The yield of the obtained sodium sulfonate was 24.40%.

[0100] Embodiment 11

[0101] The experiment was carried out with reference to Example 1, except that the inner diameter of the micro-tube spiral reaction tube was 1 mm, the outer diameter was 2 mm, and the flow rate of water was 4 mL / min. The yield of sodium sulfonate obtained was 25.51%.

[0102] Example 12

[0103] The experiment was carried out in accordance with Example 1, except that the preheating and reaction temperature was 60° C., and the water flow rate was 1.5 mL / min. The yield of sodium sulfonate obtained was 15.53%.

[0104] Example 13

[0105] The experiment was carried out in accordance with Example 1, except that the length of the micro-tube spiral reaction tube was 40 m, the flow rate of water was 4.5 mL / min, and the yield of sodium sulfonate obtained was 32.61%.

[0106] Embodiment 14

[0107] The experiment was carried out with reference to Example 1, except that the flow rate of the hydrolysis reaction water was 12 mL / min. The yield of the obtained sodium sulfonate was 15.15%.

[0108] Embodiment 15

[0109] The experiment was carried out with reference to Example 1, except that the sulfonic acid product solution was subjected to air ultrasonic degassing for 5 minutes before being neutralized with sodium hydroxide solution. The amount of sodium hydroxide solution used for neutralization was reduced by 10%, and the recovered SO2 was recycled.

[0110] Comparative Example 1

[0111] The reaction is carried out by adopting the existing kettle reaction technology, the raw material liquid paraffin oil is introduced into a 10L (Φ150×600) internal illumination reactor at 0.18L / min, then the gas valve of the sulfur dioxide storage tank and the valve of the dry air storage tank are opened, the pressure reducing valve and the flow meter are adjusted to make them flow out at a flow rate of 4L / min and 10L / min respectively, and mixed through a gas mixer to obtain a mixed gas. Then the mixed gas is introduced into the reactor through a gas distributor to carry out ultraviolet light catalytic sulfoxidation reaction with the raw material paraffin oil, the power of the ultraviolet lamp is 375W, and water is added into the reactor at a flow rate of 4mL / min, the reaction temperature is 30°C, the reaction pressure is 0.2Mpa, and the reaction residence time is 50min.

[0112] The obtained crude sulfonic acid product was centrifuged and subsequently treated as described in Example 1 to obtain a secondary alkyl sodium sulfonate product with a sodium sulfonate yield of 4.41%.

[0113] Comparative Example 2

[0114] The reaction is carried out by using the existing kettle reaction technology, 7L of raw material liquid paraffin oil is put into a 10L (Φ150×600) internally illuminated stirring reactor at one time, then the gas valve of the sulfur dioxide storage tank and the valve of the dry air storage tank are opened, the pressure reducing valve and the flow meter are adjusted to make them flow out at a flow rate of 2L / min and 5L / min respectively, and mixed through a gas mixer to obtain a mixed gas. Then the mixed gas is introduced into the reactor through a gas distributor to carry out ultraviolet light catalytic sulfoxidation reaction with the raw material paraffin oil, the power of the ultraviolet lamp is 375W, and water is added to the reactor at a flow rate of 2mL / min, the reaction temperature is 30°C, the reaction pressure is 0.2Mpa, and the reaction time is 120min.

[0115] The obtained crude sulfonic acid product was centrifuged and subsequently treated as described in Example 1 to obtain a secondary alkyl sodium sulfonate product with a sodium sulfonate yield of 3.31%.

[0116] Comparative Example 3

[0117] The experiment was carried out with reference to Example 1, except that the inner diameter of the micro-tube spiral reaction tube was 0.5 mm and the length was 60 m. After 10 hours of reaction, the micro-reaction tube was blocked, making it impossible to achieve continuous reaction.

[0118] Comparative Example 4

[0119] The experiment was carried out with reference to Example 1, except that the hydrolysis reaction was carried out in multiple 20 L stirring tanks in switching operation, the stirring tank speed was 150 r / min, the reaction time was 120 min, and the amount of water was 1.5 L. The yield of sodium sulfonate obtained was 18.58%.

[0120] Although the specific implementations of the present application have been described in detail above in conjunction with the embodiments, it should be pointed out that the protection scope of the present application is not limited by these specific implementations, but is determined by the appended claims. Those skilled in the art may make appropriate changes to these implementations without departing from the technical ideas and purposes of the present application, and these changed implementations are obviously also included in the protection scope of the present application.

Claims

1. A method for continuously preparing secondary alkyl sulfonate by photocatalytic sulfoxidation reaction, comprising the following steps: 1) Providing a dry mixed gas containing SO2 and oxygen; 2) making the mixed gas and the 30 Normal alkanes, preferably C7-C 30 One or more liquid hydrocarbon raw materials of normal alkanes are subjected to sulfoxidation reaction in a micro-reaction tube of a micro-tube reactor under light radiation to obtain a reaction liquid; 3) contacting the reaction solution obtained in step 2) with water in a microchannel hydrolysis device including a mixer and a microchannel reactor to carry out a hydrolysis reaction to obtain a crude sulfonic acid product; 4) separating the crude sulfonic acid product obtained in step 3) to obtain an unreacted liquid hydrocarbon feedstock and a sulfonic acid product solution; and 5) neutralizing the sulfonic acid product solution obtained in step 4) with an alkaline compound, optionally performing degassing and / or decolorization treatment before neutralization, to obtain secondary alkyl sulfonate.

2. The method according to claim 1, wherein after the hydrolysis reaction in step 3) and before step 4), the hydrolyzate is aged in a reactor, such as a stirred tank, Preferably, the aging conditions include: The temperature is 0-80°C, preferably 10-30°C, more preferably 20-30°C, and the time is 5-120 minutes, preferably 10-30 minutes.

3. The method according to claim 1 or 2, wherein the micro-reaction tube has an inner diameter of 0.5-10.0 mm, preferably 1.0-4.5 mm, more preferably 1.0-3.0 mm, an outer diameter of 1.5-14.0 mm, preferably 1.5-7.5 mm, more preferably 1.5-5.0 mm, and a length of 5.0-50.0 m, preferably 10.0-40.0 m, more preferably 10.0-30.0 m.

4. The method according to any one of claims 1 to 3, wherein the micro-reaction tube is in a form selected from a straight tube, a curved tube, a U-shaped tube, a ring tube and a spiral tube, preferably a micro-tube spiral reaction tube.

5. The method according to any one of claims 1 to 4, wherein the light radiation is ultraviolet light, preferably ultraviolet light with a wavelength in the range of 252-365 nm, more preferably ultraviolet light with a wavelength in the range of 252-275 nm, Preferably, the power of the ultraviolet light is 10-100W, preferably 10-40W. Further preferably, the optical radiation source is an ultraviolet lamp.

6. The method according to any one of claims 1 to 5, wherein: The mixed gas in step 1) is a mixed gas of SO2 and dry air, wherein the volume percentage of SO2 is preferably 20-40%; and / or The liquid hydrocarbon feedstock in step 2) is a C7-C 20 The liquid hydrocarbon feedstock is one or more of the normal alkanes, preferably mainly comprising C 10 -C 17 Liquid paraffin oil containing normal alkanes.

7. The method according to any one of claims 1 to 6, wherein the conditions of the sulfoxidation reaction in step 2) include: The reaction temperature is 10-70°C, the flow rate of SO2 gas in each micro-reaction tube is 0.1-1.5L / min, preferably 0.1-1.0L / min; the flow rate of dry air is 0.2-5.0L / min, preferably 0.2-2.0L / min, and / or the flow rate of liquid hydrocarbon feedstock in each micro-reaction tube is 3.0-32.0mL / min, preferably 4.0-15.0mL / min; Preferably, the sulfoxidation reaction in step 2) is carried out in multiple (eg, 2-100) parallel micro-reaction tubes or micro-tube reactors.

8. The method according to any one of claims 1 to 7, wherein in the hydrolysis reaction of step 3), the flow rate of water is 2-20% of the flow rate of the reaction solution by mass flow meter, and the hydrolysis temperature is preferably 10-80° C., more preferably 20-40° C.; Preferably, the mixer is a micro mixer or a mixer containing fillers, and further preferably, the channel size of the micro mixer is 0.1-1.0 mm; Further preferably, the inner diameter of the microchannel reactor is 0.1-1.5 mm, and the liquid holding capacity of the microchannel reactor is 1-200 mL, preferably 3-50 mL.

9. The method according to any one of claims 1 to 8, wherein in step 5): The alkaline compound used is ammonia, alkaline metal oxide, alkaline metal salt or hydroxide, preferably sodium carbonate or sodium hydroxide, and more preferably the neutralization is carried out with a sodium hydroxide solution having a mass concentration of 30-50%; The degassing treatment is carried out by heating reflux degassing, vacuum degassing, thin film ultrasonic degassing or air ultrasonic degassing, preferably by air ultrasonic degassing; and / or The decolorization treatment is performed by bleaching, and the bleaching agent is preferably a hydrogen peroxide solution with a concentration of 10-30%.

10. The method according to any one of claims 1 to 9, wherein the separation in step 4) is centrifugal separation, and the centrifugation is preferably carried out using a centrifuge, such as a tubular centrifugal separator, and the centrifugal speed is 6000-20000 r / min, preferably 10000-14000 r / min.

11. The method according to any one of claims 1 to 10, wherein the micro-reaction tube is made of a light-transmitting material, and the transmittance of the light-transmitting material to the light radiation is preferably greater than or equal to 50%, more preferably greater than or equal to 80%, Preferably, the light-transmitting material is selected from light-transmitting glass, organic glass, plastic, biomass and oxide materials, preferably selected from light-transmitting glass, organic glass and plastic materials, more preferably selected from quartz glass and polytetrafluoroethylene.

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