Alkali-catalyzed Transesterification Reaction Research Articles

Mathematical Modeling of Reversible Bimolecular Catalyzed Transesterification Reaction Kinetics for PKO and Methanol synthesis

Continuous appraisal for alternative renewable energy sources particularly for bio-diesel production is a great concern to engineers and scientist globally. Actually, vegetable oils and C1 to C3 alcohol group alkali catalyzed transesterification reaction leads to bio-diesel production. The aspect of developing reaction time and disappearance rate (-RA) mathematical models for effective various reactor types design seems impassive. Hence, in this work the authors developed a unified reaction time and disappearance rate (-RA) predictive models as a function of reactants and product reaction rate constants (K1 K2), molar masses (MW), conversion (XA), fractional volume change (ɛ) and density (ρ) dimensions using partial fraction and by parts integration methods. The developed models were simulated with Matlab codes programming approach exploiting the kinetics parameters of PKO , Methanol and biodiesel. The results of the reaction time (t) at equilibrium, none equilibrium and disappearance rate (-RɛA) show dependable relationship with the stipulated dimensions and were quite compatible with those of inferential laboratory physicochemical data reported. Thus;

Simplified Rate Expression for Palm Kernel Oil (PKO) and Methanol Alkali Catalyzed Transesterification Reaction

The need for the development of simplified kinetics rates expression (-RA) for Vegetable Oils Alkali catalyzed Transesterification processes to enhance biodiesel production motivated this study. The study, therefore aimed at proposing unified simple rate expression that may be a useful prelude to design various reactor types for Alkali Catalyzed Transesterification of palm kernel oil (PKO) and Methanol reactions. The kinetics rate expression is proposed using simple explicit algebraic technique with the consideration that alkali catalyzed transesterification reaction of palm kernel oil and methanol is a reversible bimolecular reaction. The proposed kinetic reaction rate expression is developed as a function of conversion (XA), reactants and products concentration and reaction rate constants (k1 and k2). The kinetics reaction rate expression obtained is further evaluated on the basis of reactants and product molar masses and densities. The developed models were simulated using Matlab codes programming techniques. The results for kinetic reaction rates (-RA & -ReA) decreases with decrease in fractional volume change (e) and increase in fractional conversion at constant reaction time. The results were quite compatible with those of inferential laboratory physicochemical characterization reported.

Simplified Rate Expression for Palm Kernel Oil (PKO) and Methanol Alkali Catalyzed Transesterification Reaction

The need for the development of simplified kinetics rates expression (-RA) for Vegetable Oils Alkali catalyzed Transesterification processes to enhance biodiesel production motivated this study. The study, therefore aimed at proposing unified simple rate expression that may be a useful prelude to design various reactor types for Alkali Catalyzed Transesterification of palm kernel oil (PKO) and Methanol reactions. The kinetics rate expression is proposed using simple explicit algebraic technique with the consideration that alkali catalyzed transesterification reaction of palm kernel oil and methanol is a reversible bimolecular reaction. The proposed kinetic reaction rate expression is developed as a function of conversion (XA), reactants and products concentration and reaction rate constants (k1 and k2). The kinetics reaction rate expression obtained is further evaluated on the basis of reactants and product molar masses and densities. The developed models were simulated using Matlab codes programming techniques. The results for kinetic reaction rates (-RA & -ReA) decreases with decrease in fractional volume change (e) and increase in fractional conversion at constant reaction time. The results were quite compatible with those of inferential laboratory physicochemical characterization reported.

Experimental investigation of the effect of fatty acids configuration, chain length, branching and degree of unsaturation on biodiesel fuel properties obtained from lauric oils, high-oleic and high-linoleic vegetable oil biomass

A very good understanding of the structure, level, type and physical property relationships of fatty acids in plants oils and their methyl esters (FAMEs) is of utmost importance when selecting vegetable oils for a particular desired biodiesel quality that meets the operating condition requirements of the compression-ignition diesel engine and the climatic dictate of the environment under which the engine is operated. It is on this premise that the degree of influence of fatty acid configuration, chain length, branching and unsaturation on cold flow and critical properties of biodiesel was investigated. The critical properties studied include: saponification and cetane number, iodine value, higher heating values, density, flash point and kinematic viscosity. The feed stock consists of three groups of vegetable oil biomass. The group one is made up of highly saturated, lauric coconut and palm kernel oils while group two consists of high linoleic, soyabean and corn oil biomass with low percentage of mono-unsaturated and high percentage of poly-unsaturated fatty acid. High oleic olive and canola oil constituted the third group of biomass. The triglycerides in these oils were converted to methyl esters by alkali-catalyzed transesterification reaction under standard conditions. The fatty acid methyl esters (FAMEs) compositional analyses of these feed stocks was done by using Agilent, HP 6890 Gas Chromatograph equipped with Flame ionization detector and 6890 Auto Sampler that connects with a controller box (GC-FID). The various biodiesel cold flow behaviour and critical properties under investigation were evaluated by the American society for testing materials (ASTM D6751-07b) and the European union (EN 14214) standard procedures and techniques.Better cold flow behaviour was exhibited by biomass with higher degree of unsaturation, longer chain length, higher degree of branching and with cis configuration. While critical properties showed a lot of variations based on fatty acid profile.

Biodiesel Synthesis Monitoring using Near Infrared Spectroscopy

Objective: Biodiesel is a renewable fuel considered as the main substitute for fossil fuels. Its industrial production is mainly made by the transesterification reaction. In most processes, information on the production of biodiesel is essentially done by off-line measurements. Methods: However, for the purpose of control, where online monitoring of biodiesel conversion is required, this is not a satisfactory approach. An alternative technique to the online quantification of conversion is the near infrared (NIR) spectroscopy, which is fast and accurate. In this work, models for biodiesel reactions monitoring using NIR spectroscopy were developed based on the ester content during alkali-catalyzed transesterification reaction between soybean oil and ethanol. Gas chromatography with flame ionization detection was employed as the reference method for quantification. FT-NIR spectra were acquired with a transflectance probe. The models were developed using Partial Least Squares (PLS) regression with synthetic samples at room temperature simulating reaction composition for different ethanol to oil molar ratios and conversions. Model predictions were then validated online for reactions performed with ethanol to oil molar ratios of 6 and 9 at 55ºC. Standard errors of prediction of external data were equal to 3.12%, hence close to the experimental error of the reference technique (2.78%), showing that even without using data from a monitored reaction to perform calibration, proper on-line predictions were provided during transesterification runs. Results: Additionally, it is shown that PLS models and NIR spectra of few samples can be combined to accurately predict the glycerol contents of the medium, making the NIR spectroscopy a powerful tool for biodiesel production monitoring.

Biodiesel separation using ultrafiltration poly(ether sulfone) hollow fiber membranes: Improving biodiesel and glycerol rich phases settling

After alkali-catalyzed transesterification reaction for biodiesel production, the glycerol-rich phases have to be separated. These phases are traditionally separated by settling, requiring long residence time, especially when soaps and gels are formed. In this work, biodiesel, and glycerol rich phases separation was experimentally assessed using poly(ether sulfone) hollow fiber membranes (PES-HFM). Experimental data were obtained in a continuous bench scale system. The effect of pressure difference through the membrane (0–0.6bar), feed composition and biodiesel-rich phase mass fraction (0–0.8) on permeability and permeate composition were studied. In addition, a mathematical model adopting the Hagen–Poiseuille transport equation for membrane ultrafiltration, where permeate fluxes and compositions depend on the Liquid–Liquid Equilibrium (LLE), was proposed, correlated and experimentally validated. Experimental results demonstrated only glycerol-rich phase permeated through the membrane following the LLE. Glycerol-rich phase flux increased when pressure difference through the membrane augmented, and decreased when permeate viscosity increased. The highest experimental permeability (33.2kgbar−1h−1m−2) was obtained at the highest methanol content in the feed stream, 66%wt., equivalent to a molar ratio methanol to oil 18:1 fed to the reactor. The mathematical model predicts an increase in the glycerol-rich phase flux when temperature and methanol content augment. The transport mechanism coupled to the mathematical model explained accurately the membrane role in the separation of the compounds involved in transesterification of vegetable oils, as well as the membrane selectivity.

Intensification of esterification of karanja oil for production of biodiesel using ultrasound assisted approach with optimization using response surface methodology

Intensification of acid catalyzed esterification of karanja oil using an ultrasound assisted approach was investigated with the use of sulphuric acid as catalyst in the esterification. Pretreated oil was also utilized further for biodiesel production via alkali catalyzed transesterification reaction. Response Surface Methodology (RSM) was employed to optimize the operating parameters in the case of ultrasonic (US) horn and US flow cell. The optimum conditions established for US horn were molar ratio of 1:6, catalyst loading of 1.5 wt% with duty cycle of 70% in addition to reaction time of 90 min. In the case of US flow cell, optimized parameters were molar ratio of 1:6, catalyst loading of 1.5 wt% with an amplitude of 70% and flow rate as 0.33 Lpm for a total reaction time of 45 min. Highest conversion obtained for esterification using optimum conditions for US horn and US flow cell was 77% and 74% respectively. Biodiesel yield of 83% and 80% was obtained in the transesterification of from one step esterified oil using US horn and US flow cell respectively. Enhanced yield of biodiesel as 92% and 88% was observed when esterification reaction was performed in two steps followed by transesterification, confirming the degree of improvement due to the use of two stages. The present work has clearly demonstrated an effective way for utilization of non-edible oil for biodiesel production with process intensification benefits at different stages of processing based on the use of ultrasound and optimization of operating conditions.

Chemical Composition and Cold Flow Property of Cottonseed Oil Biodiesel Fuel

The Cottonseed oil methyl ester (COME) was prepared using an alkali catalyzed trans esterification reaction, and its chemical composition and cold flow properties (CFP) were studied. Two approaches, viz. blending with petrodiesel and treating with cold flow improver (CFI) were used to improve the CFP of COME. The results showed that COME was mainly composed of fatty acid methyl esters (FAMEs): C14:0–C22:0, C16:1–C20:1, C18:2 and C18:3–C20:3. The mass fractions of saturated and unsaturated FAMEs were 27.69% and 71.65%, respectively. The cold filter plugging point (CFPP) and kinematic viscosity (KV) at 40 °C of COME are -1 °C and 4.63 mm2/s respectively. Blending with -10 petrodiesel (-10PD) and 0 petrodiesel (0PD) can decrease the CFPP of COME/-10PD (B30-B40) and COME/0PD (B40-B50) -12 and -8 °C respectively. With the increase in petrodiesel content, the KV at 40 °C of blending oil decreased, and viscosity-temperature characteristics of blending oil were improved. When used Flow Fit (≤3vol.%), the CFPPs were reduce from COME/-10PD B5, B7, B10, B20, B50 and COME -8, -8, -9, -11, -11 and -1 °C to -28, -27, -26, -25, -16 and -5 °C respectively; COME/0PD -3, -3, -4, -5, -8 and -1 °C to -26, -25, -24, -24, -16 and -5 °C respectively.

Study of reversible kinetic models for alkali-catalyzed Jatropha curcas transesterification

Biodiesel is a promising alternative to diesel fuel because of its renewable feedstocks and potential environmental benefits. Chemically, biodiesel is monoalkyl esters of long-chain fatty acids, which fall in the carbon range of C12–C22. It has similar properties as mineral diesel. Transesterification process is a chemical transformation of triglycerides to biodiesel. Experimental studies of alkali-catalyzed transesterification of nonedible feedstock, Jatropha curcas, to produce Jatropha methyl esters (biodiesel) in a batch reactor are reported. The effects of operating conditions, temperatures (30–60 °C), and stirring rates (750 and 300 rpm), at constant concentration of catalyst (0.5 % w/w of oil) and constant molar ratio of methanol to oil (6:1), on product yields were investigated. The equilibrium conversions of triglycerides to biodiesel were achieved in approximately 40 min for all the experiments conducted and were observed in the range of 43–80 %. The conversion values were observed to increase with the increase in temperature and stirring rate. The main thrust of the present work was to model the kinetics and to simulate alkali-catalyzed transesterification process. Reversible kinetic models for overall transesterification reaction were applied on experimentally obtained conversion data. The model parameters were optimized. The optimal equilibrium rate constant obtained from systematic approaches was found to increase with the increase in temperature and stirring rate. It was concluded that the overall alkali-catalyzed transesterification reaction of Jatropha curcas is a reversible endothermic reaction. Characterization of feedstock oil and biodiesel produced had revealed significant changes in the physical properties during transesterification.

Single and Two-Step Homogeneous Catalyzed Transesterification of Waste Cooking Oil: Optimization by Response Surface Methodology

Large number of studies related to alkali and acid catalyzed transesterification of waste cooking oil are widely available, but references for optimization and modeling comparison between single and two-step transesterification are scarce. Therefore, response surface methodology (RSM) has been employed to study the relationship between process variables and predict the optimal conditions. Sulfuric acid and sodium hydroxide were utilized in the pretreatment step and alkali catalyzed transesterification reaction, respectively. The highest free fatty acid (FFA) conversion in the two- and single-step reactions was 93.8% and 82.7%, respectively at the optimal reaction conditions being 1.1 wt% catalyst loading, 6.5:1 methanol to oil ratio, 60°C reaction temperature, and 65 min reaction time. .RSM could accurately predict the optimal FFA conversion in both two- and single-step processes by only 0.3% and 1.01% error, respectively. In addition, the two-step method produced higher fatty acid methyl ester (FAME) yield (86.7%) and also improved the final product quality compared to single-step method with only 73.7% biodiesel yield.

Improving the low temperature flow properties of palm oil biodiesel: Addition of cold flow improver

Palm methyl ester (PME) was prepared using an alkali-catalyzed transesterification reaction, and its cold flow properties (CFP) were studied. Commercial DEP (trade name) and polyglycerol ester (PGE), and self-made PA (given name by our laboratory researchers), were used as cold flow improvers (CFIs) to improve the CFP of the biodiesel, and the effects of these CFIs on the CFP of PME were investigated. The results showed that the peak crystallization temperature of PME was very close to the cold filter plug point (CFPP). There was no unique linear relationship between the CFPP and the content of saturated fatty acid methyl esters. When used individually as CFIs, DEP, PGE and PA exerted only moderate pour point depression effects on the biodiesel, and effects to decrease the CFPP of PME were only observed when the CFI concentration was 1% or higher. Compared with single-compound CFIs and CFIs formulated from two components, at a specified complex formulation ratio, CFIs formulated from three components exhibited the best performance. When the ratio of DEP:PGE:PA was 3:1:1 or 2:2:1, the CFPP of PME was decreased by 7°C.

Eutectic solvents for the removal of residual palm oil-based biodiesel catalyst

The production of biodiesel through transesterification requires numerous purification steps to remove the unreacted components and unwanted products for the biodiesel grade to satisfy the international standard specifications EN 14214 and ASTM D6751. The residual catalyst (KOH) is one of those impurities which must be removed at the end of alkali-catalyzed transesterification reaction. In this work, nine Deep eutectic solvents (DESs) based on choline chloride (ChCl) as well as another nine DESs based on methyltriphenylphosphonium bromide (MTPB) salts with different compositions were synthesized and utilized as solvents for the removal of residual KOH content from palm oil-based biodiesel. The results revealed that the removal efficiency of KOH by all used DESs increased with increase in DES:biodiesel molar ratio and the mole fraction of hydrogen bond donors (HBD) in mixture of salt:HBD apart from 2,2,2-trifluoroacetamide as HBD. The ChCl:glycerol DESs and MTPB:glycerol DESs proved their superiority in removing the KOH from palm oil-based biodiesel with an average removal efficiency of 98.59% and 97.57% respectively. These DESs fulfilled both international standards specification for KOH content at all DES:biodiesel molar ratios except for the 0.75:1 (DES1:biodiesel) ratio. The optimum molar ratio of DES to biodiesel for each DES was calculated and the decontamination factors for KOH removal at the optimum molar ratios for all tested DESs were determined. The reusability of these DESs for removing KOH from palm oil-based biodiesel was also investigated. Furthermore, it was found that the tested DESs were able to decrease the biodiesel water content to a value below that stated by the international standards.

Design and analysis of biodiesel production from algae grown through carbon sequestration

This paper addresses the design and techno-economic analysis of an integrated system for the production of biodiesel from algal oil produced via the sequestration of carbon dioxide from the flue gas of a power plant. The proposed system provides an efficient way to the reduction in greenhouse gas emissions and yields algae as a potential alternative to edible oils currently used for biodiesel production. Algae can be processed into algal oil by various pathways. The algal oil can then be used to produce biodiesel. A flowsheet of the integrated system is synthesized. Then, process simulation using ASPEN Plus is carried out to model a two-stage alkali catalyzed transesterification reaction for converting microalgal oil of Chlorella species to biodiesel. Cost estimation is carried out with the aid of ICARUS software. Further economic analysis is performed to determine profitability of the algal oil to biodiesel process. The results suggest that, for the algal oil to biodiesel process analyzed in this study, factors such as choosing the right algal species, using the appropriate pathway for converting algae to algal oil, selling the resulting biodiesel and glycerol at a favorable market selling prices, and attaining high levels of process integration can collectively render algal oil to be a competitive alternative to food-based plant oils.