Producing Fatty Acid Methyl Esters from Free Fatty Acids with Ionic Liquids as Catalyst

Three Brønsted acidic imidazole dicationic ionic liquids (ILs) with different length of alkyl chains, [C_n(Mim)₂][HSO₄]₂ (n = 3, 6, 12), were prepared and used as catalyst for the esterification reaction of free fatty acids and methanol. Taking oleic acid as model acid, the catalytic performances of the synthesized ILs for the esterification were evaluated. The main physicochemical properties of the ILs, thermal stability, acidity, solubility in common solvents, and causticity on Austenitic stainless steel 316, were examined. [C₃(Mim)₂][HSO₄]₂ demonstrated the highest catalytic activity and enabled to assess the preliminary optimum esterification condition of oleic acid and methanol. Under optimized reaction conditions, the yield of oleic acid methyl ester was up to 95 %. The ILs have great potential as catalysts for producing fatty acid methyl esters from long‐chain free fatty acids.     

Enantioselective esterification of (R,S)-2-(4-methylphenyl) propionic acid via Novozym 435: Optimization and application

This paper reports on the resolution of(R,S)-2-(4-methylphenyl) propionic acid(MPPA) enantiomers by enzymatic esterification in organic solvent. Novozym 435(CALB) has the best catalytic performance compared with other lipases. Of the alcohols screened, n-hexanol is the best acyl acceptor and gives the highest enzyme activity and enantioselectivity in n-hexane. Response surface methodology(RSM) was used to evaluate the influence of the factors, such as temperature, enzyme amount, substrate concentration and reaction time on the substrate conversion(c) and enantiomeric excess(ee). The correlation coefficient R~2 for enantiomeric excess and the conversion are 0.9827 and 0.9910, respectively, indicating that can accurately predict the experimental results. By simulation and optimization, the optimal conditions were obtained, involving 600 mmol·L~(-1) MPPA concentration(0.60 mmol), 850 mmol·L~(-1) hexanol concentration(0.85 mmol), 58 mg enzyme amount, 75 ℃ temperature and 4.5 h reaction time, respectively. Under the optimized conditions, the experimental values of conversion and enantiomeric excess were 89.34% and 97.84%, respectively, which are in good agreement with the model predictions.     

增稠剂PGE的研制

将脂肪酸和聚乙二醇经酯化反应再经复配而成新型非离子表面后性剂ＰＧＥ。ＰＧＥ是洗发香波、各类液体洗涤剂的特效增稠剂，也是纺织业的高效印染助剂￣［１］。本文采用正交试验法确定了脂肪酸与聚乙二醇酯化反应的最佳条件。     

Monitoring of a biodiesel production process via reset observer

This paper is concerned with the monitoring of a biodiesel production process, more specifically with the monitoring of the esterification of grease trap wastes, a low quality feedstock for biodiesel production typically characterized by its high content of Free Fatty Acids (FFAs). The esterification takes place in a jacketed Continuous Stirred Tank Reactor (CSTR). A reset observer is designed and applied in order to provide on-line estimation of the concentration of FFAs from temperature measurements within the CSTR. In addition, the proposed reset observer is compared to two other observers (classical fuzzy observer and extended Kalman filter). According to a multiple range test conducted for analyzing the estimation error, the monitoring task for the process under study has been better fulfilled by the reset observer which is able to update the estimation results every instant when the measurements were available.     

Production of Methyl Oleate in Reactive‐Separation Systems

The esterification of oleic acid and methanol using sulfuric acid as a homogeneous catalyst is studied in reactive‐separation systems. The conversion of the free fatty acid was investigated in two different experiments with the molar ratio of methanol/oleic acid, amount of catalyst, temperature, and reaction time as variables. The conversion of the free fatty acid was found to depend strongly on the molar ratio of methanol/oleic acid. The reaction time had a direct effect on the conversion of the free fatty acid, and this conversion decreased with higher temperature. These results were valuable for a preliminary study on biodiesel production, using an acid homogeneous catalyst in a reactive dividing‐wall distillation column.     

Theoretical Study on Free Fatty Acid Elimination Mechanism for Waste Cooking Oils to Biodiesel over Acid Catalyst

A theoretical investigation on the esterification mechanism of free fatty acid (FFA) in waste cooking oils (WCOs) has been carried out using DMol³ module based on the density functional theory (DFT). Three potential pathways of FFA esterification reaction are designed to achieve the formation of fatty acid methyl ester (FAME), and calculated results show that the energy barrier can be efficiently reduced from 88.597 kcal/mol to 15.318 kcal/mol by acid catalyst. The molar enthalpy changes (Δ_rH_m°) of designed pathways are negative, indicating that FFA esterification reaction is an exothermic process. The obtained favorable energy pathway is: H⁺ firstly activates FFA, then the intermediate combines with methanol to form a tetrahedral structure, and finally, producing FAME after removing a water molecule. The rate-determining step is the combination of the activated FFA with methanol, and the activation energy is about 11.513 kcal/mol at 298.15 K. Our results should provide basic and reliable theoretical data for further understanding the elimination mechanism of FFA over acid catalyst in the conversion of WCOs to biodiesel products.     

Kinetics of biofuel generation from deodorizer distillates derived from the physical refining of olive oil and squalene recovery

The recovery of squalene from deodorizer distillate derived from the physical refining of olive oil was evaluated by combining pressurized acidic esterification in a closed system with vacuum distillation. Esterification was carried out at 341, 359, 366, 391 and 395 K. The reaction at 395 K was found to be satisfactory as it decreased the acid value by 99.21% and generated a FAME concentration of 67.53% within 1 h. In order to demonstrate that the generation of FAME from deodorizer distillate was mainly due to the transformation of FFA, the reaction extent, which characterizes the reaction and simplifies calculations, was evaluated for FFA removal and the generation of FAME. Subsequent vacuum distillation allowed the separation of one fraction rich in FAME (94%), which can be used as a biofuel and accounted for 85% of the initial mass, and another fraction that was rich in squalene (78%) and may be used for manufacturing pharmaceutical products. The global squalene yield was 117 g kg⁻¹ initial deodorizer distillate.     

A green sulfonated carbon-based catalyst derived from coffee residue for esterification

A green sulfonated carbon-based catalyst was successfully synthesized through sulfonation of incompletely carbonized coffee residue (SCAC catalyst). The sulfonation temperature was investigated and the catalytic activity was tested via esterification of caprylic acid. SCAC-200, the highest caprylic acid conversion at 4 h (71.5%) and initial TOF based on SO₃H acid sites, was synthesized under a carbonization temperature of 600 °C for 4 h and sulfonation temperature of 200 °C for 18 h. Sulfonation temperature plays a dominant role in determining the SO₃H site density of SCAC catalysts because side reactions (condensation/oxidation/dehydrogenation) take place at high sulfonation temperature as indicated by oxygen-to-carbon surface ratio. The activities of the SCAC catalysts were also substantially greater than that of Amberlyst-15. A high catalytic activity and catalyst stability for esterification of HCp were achieved in the SCAC catalysts with high surface area and by balancing strong (SO₃H) and weak (carboxylic and phenolic) acid site densities. Additionally, this catalyst could be regenerated to obtain essentially its initial catalytic activity by MeOH washing. Therefore, the sulfonated coffee residue derived catalyst is promising, economic eco-friendly and potentially substituted for homogeneous H₂SO₄ catalyst for esterification in industries in the near future.     

Metal-organic framework MIL-101(Cr) based mixed matrix membranes for esterification of ethanol and acetic acid in a membrane reactor

Mixed matrix membranes (MMMs) based on the polyimide Matrimid^® (PI) with metal-organic framework (MOF) MIL-101(Cr) as porous nanostructured filler were synthesized and applied as separation element in a membrane reactor to carry out the esterification of acetic acid with ethanol. The MMMs were characterized by techniques including X-ray diffraction, IR spectroscopy and scanning electron microscopy. In order to compare the performance of MIL-101(Cr)-PI MMMs in the membrane reactor, pure PI and HKUST-1-PI membranes were also used. MMMs provided a better reactor performance than the bare PI membrane because of the increase in permeability associated to the presence of MOF as filler. The PI membrane reactor barely achieved the same conversion as a fixed bed reactor, while the MIL-101(Cr)-PI membrane showed a reactor performance similar to that of the HKUST-1-PI membrane with higher stability, as confirmed by membrane characterization after the reaction experiments.