Preparation Of Green Plasticizer Epoxidized Fatty Acid 2-ethylhexyl Esters From Biodiesel And Its Application

The decline in international crude oil prices has a huge impact on the biodiesel?fatty acid methyl esters,FAME?industry.The issue of how to develop biodiesel industrial chain in a sustainable way is becoming one of the focuses of current scientific research.In addition,the current widely used phthalate plasticizers have been severely restricted by countries due to the generation of xenoestrogen,and the development and application of green plasticizers have great prospects in the future.Thus,it is necessary for the biodiesel industry to extend to the field of bio-based chemicals to gradually form a rich source of energy-derived alternatives.This paper uses FAME as a biomass platform compound to prepare epoxidized fatty acid 2-ethylhexyl esters?Ep-FAEtHE?,which not only achieves high value-added conversion of FAME,but also improves the level and competitiveness of developing green plasticizers in China.Presently,the production of bio-based additives from oils and fats exists some problems such as low degree of continuity,high pollution,high energy consumption and low product quality.Therefore,this work firstly developed a green production process of fatty acid 2-ethylhexyl esters?FAEtHE?from FAME by solid base catalyst.The basic chemical thermodynamic data of FAEtHE was then correlated,and the mass transfer-reaction kinetics of the reaction was also studied.Furthermore,the continuous production of Ep-FAEtHE was explored.Lastly,the plasticization performance of the product was researched in detail.The specific contents and main achievements are as follows:?1?Unsupported K₂CO₃ and supported K₂CO₃/?-Al₂O₃ were used as solid base catalysts to prepare FAEtHE,respectively,both their catalytic activities and reaction conditions were studied.The optimal conditions for the K₂CO₃ catalytic process were:reaction temperature of 180?,catalyst to FAME of 3.0 wt.%,2-ethyl-1-hexanol to FAME of 3:1,reaction time of 1 h.The FAME conversion reached up to 100%under these conditions.And the K₂CO₃/?-Al₂O₃ catalyst with a K₂CO₃ dosage of 30 wt.%had the best catalytic activity.Compared with the unsupported K₂CO₃?about 200 mesh?,the catalytic activity of K₂CO₃/?-Al₂O₃ was much better and the amount of K₂CO₃ was greatly reduced.The catalyst structure was characterized by XRD,FT-IR,BET,XRF and CO₂-TPD.Catalyst reusability results indicated that the activity of the K₂CO₃/?-Al₂O₃catalyst decreased slightly after used for 4 times;potassium leaching from catalyst into the liquid mixture was approximately 258 ppm;and the solubility of potassium ions in 2-ethyl-1-hexanol was only 0.0028 g/100 g.The good catalytic activity and stability of the catalyst made it more attractive for potential application in the transesterification of biodiesel with high alcohols in industry.?2?Accurate and reliable basic chemical thermodynamic data can provide the necessary technical parameters for reaction process research and equipment design.Firstly,palmitic acid 2-ethylhexyl ester,stearic acid 2-ethylhexyl ester and soybean oil 2-ethylhexyl esters with all purity greater than 99%were prepared and purified by high-temperature high-vacuum distillation method.Then,the density and viscosity of the three model compounds were measured in the temperature range of 298.65-368.15 K,and the density and viscosity were correlated by a linear equation and the Vogel-Tamman-Fulcher equation,respectively.The saturated vapor pressures of the three compounds in their respective temperature ranges?476.95⁵00.85 K,477.05⁴98.05 K,477.75⁵00.05 K?were measured,and the data was correlated using the Antoine equation and the Wagner equation,respectively.The correlation coefficients of all correlations were greater than0.999.The reliability of these experimental data was further verified by comparison with literature values and calculated values of the group contribution method.In addition,the average molar vaporization enthalpies were calculated in range of 85.32¹00.75 kJ·mol^-11 according to the Clausius-Clapeyron equation.?3?Based on the K₂CO₃/?-Al₂O₃ catalyzed preparation process of FAEtHE,the chemical equilibrium and intrinsic reaction kinetics of the transesterification reaction were studied under the elimination of internal and external diffusion.Results shown that the equilibrium constant of the reaction was about 1 in the temperature range of 423⁴53K,and the heat of reaction was 3.2 kJ?mol^-1.The kinetic data were correlated by the PH model,and the model values were in good agreement with the experimental values.The rate constant was obtained in the range of 0.0016⁰.0033 mol·g^-1·min^-1.The activation energy of the reaction calculated according to the Arrhenius formula was 36.78 kJ·mol^-1.In addition,the continuous production of FAEtHE was studied in a fixed-bed reactor,and a macroscopic kinetic model of the reactor was further established.The obtained model can describe the mass transfer-reaction behaviors well at different weight hourly space velocities(0.57².28 h^-1).The deviation between the model value and the experimental value was within±15%.Moreover,the catalyst in the fixed bed had good stability,and product with the transesterification conversion greater than 95%can be continuously obtained.The model can provide theoretical guidance for the industrialization of continuous preparation of FAEtHE from FAME catalyzed by solid base.?4?Ep-FAEtHE was prepared through formic acid?FA?-hydrogen peroxide?H₂O₂?autocatalytic method by using FAEtHE as raw material.Both batch and continuous reaction processes were studied.The batch epoxidation reaction was mainly discussed by response surface methodology model.The optimal conditions were:reaction time of 7 h,molar ratio of C=C double bond:H₂O₂:FA was 1.00:2.41:0.35,and reaction temperature of 65.84?.A maximum relative percentage conversion to oxirane?RCO?of 92%was obtained under these conditions.The regression and analysis of variance revealed that the experimental data was in accordance with the predicted values.In order to realize the continuous epoxidation production,a helical tube reactor was designed,in which the inside of the reactor was filled with small spherical fillers for strengthening the local liquid-liquid heterogeneous micro-mixing.The back-mixing performance of the reactor was characterized by determining the residence time distribution.The calculated Pe quasi number was about 100 from the experimental data,indicating that the fluid flow was close to plug flow,and the degree of back-mixing was small.The pressure drop of the reactor was calculated to be less than 0.1 MPa according to Ergun formula.By adding 1%sulfuric acid and reacting at 90?,the double bond conversion of FAEtHE was 93.5%and the RCO was 88.3%at the space time of 48 min in the reactor,which can meet the requirements of industrial products.?5?The chemical structure of Ep-FAEtHE was confirmed by FT-IR,¹H NMR and¹³C NMR.Various plasticized PVC samples were prepared by blending Ep-FAEtHE,DOP,PVC powder and Ca-Zn heat stabilizer in a series of formulations.The mechanical properties,thermal stability,extraction resistance,migration stability and processability were systematically studied by universal testing machine,thermogravimetric analysis,thermal aging oven and dynamic thermomechanical analyzer.The results shown that Ep-FAEtHE proved to be an alternative to DOP,replacing about 40%of the total plasticizer.Compared with DOP,the mechanical and thermal performance of PVC samples plasticized with partial substitutions of Ep-FAEtHE was significantly improved,while the migration resistance was changed slightly.The addition of Ep-FAEtHE can also significantly reduce the glass transition temperature of PVC?T_g=43.54??,which made PVC own better processabilities.Moreover,compared with epoxidized fatty acid methyl esters,Ep-FAEtHE had superior low temperature fluidity,better oxidation stability and a higher thermal decomposition temperature.Therefore,the prepared product of Ep-FAEtHE can be a novel green plasticizer to partial substitute the traditional petroleum-based plasticizer DOP.