Study On The Process Of C4 Alkylation Catalyzed By Sulfuric Acid And The Law Of Liquid-Liquid Mass Transfer In High Gravity Intensification Process

In recent years,environmental protection standards are becoming increasingly stringent due to the atmospheric issues such as haze,and the demand for eco-friendly gasoline is climbing.Alkylate oil is considered to be the unique blending component of gasoline which can concurrently meet the requirements of clean and high-octane,and it is manufactured from isobutane and butene(C4)catalyzed by strong acid.Alkylation process is usually catalyzed by sulfuric acid(H₂SO₄),which is a process of rapid and liquid-liquid two-phase reaction with complex product distribution.Hence,the micro-mixing and mass transfer between the two-phase of acid and hydrocarbon play a decisive role in the alkylation process to promote the quality of alkylate oil and reduce the energy consumption.There are two strategies that can be adopted to explore a novel C4 alkylation technology.Firstly,promoting the heterogeneous mixing between the acid and hydrocarbon phases by process intensification technique such as high gravity technique,which is regarded as an effective way to increase the mass transfer of isobutene to the liquid-liquid interface.Secondly,regulating the interfacial characteristic between acid and hydrocarbon by additives,improving the solubility of isobutane,which also elevates the mass transfer driving force of isobutane to the interface.In this work,the rotating packed bed(RPB)was employed to enhance H₂SO₄-C4 alkylation process,and the process conditions were discussed.The artificial neural network(ANN)was first applied to build a model for predicting the product distribution and research octane number(RON)of H₂SO₄-C4 alkylation process in the stirred tank reactor(STR)and RPB.The effects of different additives on alkylation performances were investigated in a STR,and the high-octane alkylate oil was obtained by the intensified process in the RPB.The synergistic effect of the Hammett acidity and solubility of isobutane in acid solution on alkylation performance was revealed.The sulphur content in product and catalyst life were referred to the additive selection.The liquid-liquid mass transfer was developed in the RPB,which provided the elementary data for reactor scale-up and process development.The main research results were as follows:(1)The RPB was adopted to intensify H₂SO₄-C4 alkylation process for obtaining the high-RON alkylate oil(RON>97).ANN model was successfully developed for the prediction and estimation on the products distribution and RON synchronously in the RPB and STR,which made a breakthrough on the high dimensional nonlinearity of alkylation process prediction.An optimal ANN model was obtained,a network topology of10-20-30-5 with Bayesian regularization backpropagation algorithm.The ANN model was examined to obtain a training mean square error(MSE)of5.8×10^-4,a testing MSE of 8.66×10^-3 and a global deviation of±22%.Besides,the correlation coefficient value was 0.9997,and the standard deviation of error were acquired was 0.5592.(2)Three homologs of polymer sulfates and two high hydrophilic surfactants were employed in H₂SO₄-C4 alkylation process in a STR.The results establish that quality of the alkylate oil was kept with the addition of tetramethylene sulfone and 2-naphthalenesulfonic acid.di-n-butyl sulphate,dodecylbenzene sulfonic acid and Tween-20 were positively proved to be beneficial to improve the distribution of alkylation products and RON.(3)The alkylation performances were investigated by a conjunction of additives and RPB.The relationships of Hammett acidity and isobutane solubility in acid solution with additives on alkylation performances were explored in the RPB.The sulphur content and catalyst life were tested for the reference of additive selection.Tetramethylene sulfone and2-naphthalenesulfonic acid did not have the obvious increment on the solubility of isobutane,but the acidity and the RON of product decreased.The acidity and isobutane solubility increased clearly when di-n-butyl sulphate was added into H₂SO₄,and the alkylation performances of that was improved.Besides,surfactant increased the solubility of isobutane in sulfuric acid,reduced the acidity,and raised the RON of alkylate oil.The synergistic effects of acidity and solubility of isobutane in acid solution on the alkylation performances were revealed.In consideration of the sulfur content of the product and catalyst life,Tween-20 was an excellent additive with trace amount addition,which contributed to an alkylate oil with a RON of 98.92 with 8°C and I/O=30:1.Additive and RPB promoted the quality of the alkylate oil and raised the temperature to reduce the energy consumption.The results prove that a combination of additive and RPB has an excellent applicant prospect for the alkylation process.(4)The liquid-liquid mass transfer coefficient in the RPB was studied by water-acetic acid-kerosene system,and the effects of high gravity level,liquid flow rate,the volumetric ratio of oil to water,initial liquid distribution and viscosity on the total oil mass transfer coefficient(K_oa)were investigated in the RPB.Results show that the increment of the high-gravity level,the liquid flow rate,and the decrement of the ratio of oil to water can effectively raise K_oa.A correlation was built for predicting the K_oa in the RPB(R²=0.979).Besides,the K_oa of homo-disperse or premixed feed was better at low rotating speeds.The effect of two-phase mass transfer was affected significantly by viscosity,which the K_oa plummeted as the oil-phase viscosity increased.The study of liquid-liquid mass transfer provided a fundamental data for the scale-up of the liquid-liquid RPB.