| Sulfonate surfactant is one of the most common and largest anionic surfactant, which is widely used in cosmetics, textile, detergent, paint, pharmaceutical, food, mining, oil, etc. Sulfonate surfactant is synthesized via sulfonation by the alkylbenzene and SO3.The sulfonation process was mainly carried out in a fall ing-film reactor (FFR) by gaseous SO3 in industry. In FFR, the organic liquid reactant flows as films along the tube wall. When the conversion rate in a high level, the system viscosity increases sharply, and the film thickness increases more than 2-4 times, which led to increase of heat and mass transfer resistance, resulting in the local non-homogeneous concentration and temperature distributions, and then causing the generation of the by-products. It is effective to solve the above problems by liquid-liquid sulfonation which is adopting the SO3 organic solvent as sulfonating agent. But the liquid-liquid sulfonation process has higher requirement of fast micro-mixing in the reactor.The traditional liquid-liquid sulfonation reactor, such as stirred tank reactor and continuous stirred-tank reactor, usually with low micromixing and mass transfer efficiency did not be suitable for the fast reaction. Therefore, it is a challenge for liquid-liquid sulfonation to design a reactor with the intensified micro-mixing performance.High gravity (Higee) technology is one of the typical chemical process intensification methods. As the main device of the Higee technology, rotating packed bed (RPB, also called higee reactor) can significantly intensify the mass transfer and micromixing. In the RPB, the liquid is crushed by the high speed packing packed. The liquid can be coalesced and broken many times within the rotating packing, resulting in a significant intensification of the phase interface renewal and micro-mixing. This technology has been applied in the fields of gas-liquid absorption, nanomaterials production, mixing-reaction process, etc.On the basis of the previous study, we have analysized the main problems in sulfonation reaction, and then proposed RPB as a novel sulfonation reactor to synthesize sulfonate surfactants via liquid-liquid route. The main innovative points in this work are as follows:1. A simple and pure component, toluene, was employed to investigate the sulfonation process. The high-purity p-toluene sulfonic acid products were prepared by the mother liquor circulation method with RPB reactor. It was found that the sulfonating agent concentration and reaction temperature have the important effects on the product selectivity. A low sulfonating concentration was in favor of improving the p-isomer selectivity, and a high temperature will promote the o-isomer transfer to m-isomer. The rotation speed has little effect on isomer selectivity, but it could remarkablely decrease the generation of by-product sulfone. The mother liquor circulation method could significantly reduce the selectivity of o- and m- isomer, and improve the p-isomer selectivity. Also, it can inhibit the generation of sulfone. When the mother liquor cycled over three times, the selectivity of p-isomer was increased 15.38%, and the selectivities of o- and m-isomer reduced 71.83% and 56.12% respectively. In addition, the generation of sulfone reduced over 94%.2. The alkyl benzene homologue mixture was employed as a mixed system to research sulfonation process in the RPB. The semi-continuous operation and continuous operation were carried out in the experiments. It was found that the product content reached to 96.58%, free oil content less than 2.0%, and the products met the requirements of qualified products in the semi-continuous operation mode under the operation conditions of a high gravity level of 40-60, a temperature of 40-50℃, a sulfonating agent concetration of 10%-30%, an SO3 dosage of 1.1 and an aging time of 10-20 min. Under the continuous operation mode, RPB reactor combined with STR was used to prolong the reaction time. The active matter content reached 85%-88% under the optimal sulfonation conditions of the high gravity level of 59-85, a liquid flow rate of 40-73 L·h-1, a sulfonating agent concetration of 20-30%, an SO3 dosage of 1.1-1.2, and a temperature of 40-45℃. The results indicated that that the RPB plays as an efficient mixer but also as main reaction vessel in the sulfonation process.3. A mathematical model combined with the micro-mixing model (coalescence-redispersion model) and a simplified kinetics model was established to predict the sulfonation degree in RPB. The effects of operating parameters including rotation speed, liquid flow rate, reaction temperature and sulfonating agent on the yield of active matter content were simulated. The calculated results were in a good agreement with the experimental results with a deviation within ±12%.4. The oil with a wide fraction was selected as the main raw material to synthesize alkali-free and ultra-low oil-water interfacial tension petroleum sulfonate surfactants in the RPB by liquid-liquid sulfonation process. The effects of operating conditions including temperature, solvent amount, sulfonating agent dosage, rotation speed, reaction time, on the petroleum sulfonate content and the oil-water inrerfacial tension were investigated. The results showed that the RPB has a remarkable intensification effect on sulfonation of petroleum fractions and can effectively avoid coking, oxidation and other side reactions. Compared between in STR and RPB, the active mater in the RPB was 11% higher than that in the STR.5. The dynamic interfacial tension (DIT) of alkali-free petroleum sulfonates surfactant was studied by spinning drop method. The CMC of the petroleum sulfonated surfactant is 0.0092% and the yCMC is 0.00205 mN·m-1. The petroleum sulfonated surfactant showed a good performance on saltresistance and stablility and can maintain its ultra-low interfacial tension with the concentration of petroleum sulfonated surfactant in the range of 0.005% to 1.0%. The uneven change of the test oil droplet during the IFT measurement was also discussed. The increase of aqueous phase viscosity can only ease the rebound phenomenon. While the increase of heavy components of petroleum sulfonates can both eliminate the non-uniform changes of the oil droplet and reduce the balance value of the IFT. It can provide the theoretical guidance and basic data for the formation mechanism of IFT and the industrial application of this process. |
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