Alumina/silica supported K2CO3 as a catalyst for biodiesel synthesis from sunflower oil

The new type of catalyst for fatty acid methyl esters (FAME or biodiesel) synthesis with K₂CO₃ as active component on alumina/silica support was synthesized using sol–gel method. Corresponding catalyst (xerogel) was prepared by 12 h drying the wet gel in air at 300 °C, 600 °C or 1000 °C at atmospheric pressure. The catalysts activity in the methanolysis of sunflower oil was compared to the activity of the pure K₂CO₃. The effects of various reaction variables on the yield of FAME were investigated. It was found that the temperature of 120 °C and methanol to oil molar ratio of 15:1, are optimal conditions for FAME synthesis with synthesized catalyst. Repeated use of same amount of catalyst indicated that effect of potassium leaching obviously existed leading to decrease of catalyst activity.     

Enzymatic conversion of sunflower oil to biodiesel in a solvent-free system: Process optimization and the immobilized system stability

The feasibility of using the commercial immobilized lipase from Candida antarctica (Novozyme 435) to synthesize biodiesel from sunflower oil in a solvent-free system has been proved. Using methanol as an acyl acceptor and the response surface methodology as an optimization technique, the optimal conditions for the transesterification has been found to be: 45 ^oC, 3% of enzyme based on oil weight, 3:1 methanol to oil molar ratio and with no added water in the system. Under these conditions, >99% of oil conversion to fatty acid methyl ester (FAME) has been achieved after 50 h of reaction, but the activity of the immobilized lipase decreased markedly over the course of repeated runs. In order to improve the enzyme stability, several alternative acyl acceptors have been tested for biodiesel production under solvent-free conditions. The use of methyl acetate seems to be of great interest, resulting in high FAME yield (95.65%) and increasing the half-life of the immobilized lipase by about 20.1 times as compared to methanol. The reaction has also been verified in the industrially feasible reaction system including both a batch stirred tank reactor and a packed bed reactor. Although satisfactory performance in the batch stirred tank reactor has been achieved, the kinetics in a packed bed reactor system seems to have a slightly better profile (93.6 ± 3.75% FAME yield after 8–10 h), corresponding to the volumetric productivity of 48.5 g/(dm³ h). The packed bed reactor has operated for up to 72 h with almost no loss in productivity, implying that the proposed process and the immobilized system could provide a promising solution for the biodiesel synthesis at the industrial scale.     

Performance of heterogeneous ZrO2 supported metaloxide catalysts for brown grease esterification and sulfur removal

In order to achieve a viable biodiesel industry, new catalyst technology is needed which can process a variety of less expensive waste oils, such as yellow grease and brown grease. However, for these catalysts to be effective for biodiesel production using these feedstocks, they must be able to tolerate higher concentrations of free fatty acids (FFA), water, and sulfur. We have developed a class of zirconia supported metaloxide catalysts that achieve high FAME yields through esterification of FFAs while simultaneously performing desulfurization and de-metallization functions. In fact, methanolysis, with the zirconia supported catalysts, was more effective for desulfurization than an acid washing process. In addition, using zirconia supported catalysts to convert waste grease, high in sulfur content, resulted in a FAME product that could meet the in-use ASTM diesel fuel sulfur specification (<500 ppm). Possible mechanisms of desulfurization and de-metallization by methanolysis were proposed to explain this activity.     

Transesterification of Nannochloropsis oculata microalga’s lipid to biodiesel on Al2O3 supported CaO and MgO catalysts

In this study, we present the activities of Al₂O₃ supported CaO and MgO catalysts in the transesterification of lipid of yellow green microalgae, Nannochloropsis oculata, as a function of methanol amount and the CaO and MgO loadings at 50 °C. We found that pure CaO and MgO were not active and CaO/Al₂O₃ catalyst among all the mixed oxide catalysts showed the highest activity. Not only the basic site density but also the basic strength is important to achieve the high biodiesel yield. Biodiesel yield over 80 wt.% CaO/Al₂O₃ catalyst increased to 97.5% from 23% when methanol/lipid molar ratio was 30.     

A packed bed membrane reactor for production of biodiesel using activated carbon supported catalyst

In this study, a novel continuous reactor has been developed to produce high quality methyl esters (biodiesel) from palm oil. A microporous TiO₂/Al₂O₃ membrane was packed with potassium hydroxide catalyst supported on palm shell activated carbon. The central composite design (CCD) of response surface methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst amount and cross flow circulation velocity on the production of biodiesel in the packed bed membrane reactor. The highest conversion of palm oil to biodiesel in the reactor was obtained at 70 °C employing 157.04 g catalyst per unit volume of the reactor and 0.21 cm/s cross flow circulation velocity. The physical and chemical properties of the produced biodiesel were determined and compared with the standard specifications. High quality palm oil biodiesel was produced by combination of heterogeneous alkali transesterification and separation processes in the packed bed membrane reactor.     

Microwave assisted alkali-catalyzed transesterification of Pongamia pinnata seed oil for biodiesel production

In this study, microwave assisted transesterification of Pongamia pinnata seed oil was carried out for the production of biodiesel. The experiments were carried out using methanol and two alkali catalysts i.e., sodium hydroxide (NaOH) and potassium hydroxide (KOH). The experiments were carried out at 6:1 alcohol/oil molar ratio and 60 °C reaction temperature. The effect of catalyst concentration and reaction time on the yield and quality of biodiesel was studied. The result of the study suggested that 0.5% sodium hydroxide and 1.0% potassium hydroxide catalyst concentration were optimum for biodiesel production from P. pinnata oil under microwave heating. There was a significant reduction in reaction time for microwave induced transesterification as compared to conventional heating.     

Esterification of acidified oil with methanol by SPES/PES catalytic membrane

A sulfonated polyethersulfone (SPES)/polyethersulfone (PES) blend catalytic membrane was prepared and used as a heterogeneous catalyst in the esterification of the acidified oil (acid value 153 mg KOH/g) with methanol for producing biodiesel. The results showed that the free fatty acids conversion reached 97.6% using SPES/PES catalytic membrane under the optimal esterification conditions. Meanwhile, the SPES/PES membrane with 20.3% degree of sulfonation showed a good catalytic stability. A pseudo-homogeneous kinetic model was established. The results indicated that the reaction rate constant increased with increasing methanol/acidified oil molar ratio, the loading of catalytic membrane and reaction temperature. The reaction order was 2 and the activation energy decreased from 74.65 to 21.07 kJ/mol with increasing catalytic membrane loading from 0 to 0.135 meq/g(oil). It implies that the esterification is not diffusively controlled but kinetically controlled. The predicted results were in good agreement with the experimental data.     

Technoeconomic analysis of five microalgae-to-biofuels processes of varying complexity

The economics surrounding five algae-to-fuels process scenarios were examined. The different processes modeled were as follows: an open pond producing either triacylglycerides (TAG) or free fatty acid methyl ester (FAME), a solar-lit photobioreactor producing either FAME or free fatty acids (FFA), and a light emitting diode irradiated (LED-lighted) photobioreactor producing TAG. These processes were chosen to represent both classical and esoteric approaches presented in the open literature. Viable (or suggested) processing techniques to liberate and purify (and convert) the microalgal triacylglycerides were then modeled to accompany each growth option. The investment and cost per kg of fuel or fuel precursor for each process was determined. The open pond produced TAG at ～$7.50/kg, while the process using the LED-lit photobioreactor produced TAG at ～$33/kg. The scenario containing the solar-lit photobioreactor produced FAME at ～$25/kg, while the open pond produced FAME at ～$4/kg. The scenario containing the solar-lit photobioreactor produced FFA at ～$29/kg. The open pond scenarios appear to be closest to the $1/kg pricepoint at this time, and thus are the most viable economic options. Future technological advancements that reduce the cost of bioreactor vessels, LED lighting, and solvent recovery, may reduce the oil production costs of these scenarios to a more attractive level.     

Determination of 2-hydroxyflutamide in human plasma by liquid chromatography–tandem mass spectrometry (LC–MS/MS): Application to a bioequivalence study on Chinese volunteers

A sensitive, simple and rapid ultra fast liquid chromatography (UFLC)–ESI-MS/MS method was developed for the determination of 2-hydroxyflutamide in human plasma using tegafur as the internal standard. The plasma sample was pretreated with methanol for protein precipitation and the analytes were separated on an Ultimate C18 column (5 μm, 2.1 mm × 50 mm, MD, USA) with the mobile phase consisted of acetonitrile and water (2:1, v/v). Detection was performed on a triple-quadrupole tandem mass spectrometer under a negative multiple reaction-monitoring mode (MRM). The mass transition ion-pair was followed as m/z 290.90–204.8 for 2-hydroxyflutamide and 198.9–128.8 for tegafur. Linear calibration curves were obtained in the concentration range of 1.742–1452 ng/ml with a lower limit of quantification of 1.742 ng/ml. The intra- and inter-batch precision values were less than 8.1% and 5.6%, respectively. The established method was successfully applied to a bioequivalence study of two flutamide preparations (250 mg) in 20 healthy male volunteers.     

Transesterification of palm oil to methyl ester on activated carbon supported calcium oxide catalyst

In this study, methyl ester (ME) was produced by transesterification of palm oil (CPO) (cooking grade) using activated carbon supported calcium oxide as a solid base catalyst (CaO/AC). Response surface methodology (RSM) based on central composite design (CCD) was used to optimize the effect of reaction time, molar ratio of methanol to oil, reaction temperature and catalyst amount on the transesterification process. The optimum condition for CPO transesterification to methyl ester was obtained at 5.5 wt.% catalyst amount, 190 °C temperature, 15:1 methanol to oil molar ratio and 1 h 21 min reaction time. At the optimum condition, the ME content was 80.98%, which is well within the predicted value of the model. Catalyst regeneration studies indicate that the catalyst performance is sustained after two cycles.     

Optimization Studies and Chemical Kinetics of Silica Sulfuric Acid-Catalyzed Biodiesel Synthesis from Waste Cooking Oil

In the present study conversion of waste cooking oil to biodiesel has been carried out via simultaneous esterification and transesterification reaction over silica sulfuric acid as a solid acid catalyst. The process variables that influence the fatty acid methyl ester (FAME) conversion, such as reaction temperature, reaction time, catalyst concentration and methanol to oil molar ratio were investigated and optimized using Taguchi method. Highest FAME production obtained under the optimized condition was 98.66 %. Analysis of variance revealed that temperature was the most significant factor effecting the FAME production among four factors studied. From the kinetic study, the reaction was found to follow pseudo first-order kinetics and rate constant of the reaction under optimum condition was 0.00852 min^?1.     

Ultrasonic monitoring of glycerol settling during transesterification of soybean oil

A low-intensity ultrasonic measurement system was used to monitor the products of transesterification of soybean oil in methanol to FAME (biodiesel). The byproducts of the transesterification reaction are methyl esters, glycerol and other products. During the transesterification reaction, the glycerol, having a higher density than the methyl ester, settles at the bottom of the reaction vessel. The aim of this study was to measure the glycerol deposition rate during transesterification and to assess the reaction rate and end time. Soybean oil was converted into biodiesel at four temperature levels. The amount of catalyst (KOH) used in the transesterification reactions was determined by titration. The ultrasonic waveforms captured during the reaction were recorded and analyzed automatically. The ultrasonic system monitored the effects of reaction temperatures on the glycerol settling rate and the reaction end times. The ultrasonic measurement of glycerol settling would be a useful non-destructive method for evaluating the effects of parameters such as catalyst amount, mixing time and temperature on transesterification reactions.     

A glycerol-free process to produce biodiesel by supercritical methyl acetate technology: An optimization study via Response Surface Methodology

In this study, fatty acid methyl esters (FAME) have been successfully produced from transesterification reaction between triglycerides and methyl acetate, instead of alcohol. In this non-catalytic supercritical methyl acetate (SCMA) technology, triacetin which is a valuable biodiesel additive is produced as side product rather than glycerol, which has lower commercial value. Besides, the properties of the biodiesel (FAME and triacetin) were found to be superior compared to those produced from conventional catalytic reactions (FAME only). In this study, the effects of various important parameters on the yield of biodiesel were optimized by utilizing Response Surface Methodology (RSM) analysis. The mathematical model developed was found to be adequate and statistically accurate to predict the optimum yield of biodiesel. The optimum conditions were found to be 399 °C for reaction temperature, 30 mol/mol of methyl acetate to oil molar ratio and reaction time of 59 min to achieve 97.6% biodiesel yield.     

Characterization of a microalga Chlorella sp. well adapted to highly concentrated municipal wastewater for nutrient removal and biodiesel production

The feasibility of growing Chlorella sp. in the centrate, a highly concentrated municipal wastewater stream generated from activated sludge thickening process, for simultaneous wastewater treatment and energy production was tested. The characteristics of algal growth, biodiesel production, wastewater nutrient removal and the viability of scale-up and the stability of continuous operation were examined. Two culture media, namely autoclaved centrate (AC) and raw centrate (RC) were used for comparison. The results showed that by the end of a 14-day batch culture, algae could remove ammonia, total nitrogen, total phosphorus, and chemical oxygen demand (COD) by 93.9%, 89.1%, 80.9%, and 90.8%, respectively from raw centrate, and the fatty acid methyl ester (FAME) content was 11.04% of dry biomass providing a biodiesel yield of 0.12 g-biodiesel/L-algae culture solution. The system could be successfully scaled up, and continuously operated at 50% daily harvesting rate, providing a net biomass productivity of 0.92 g-algae/(L day).     

Synthesis of fatty acid methyl ester from palm oil (Elaeis guineensis) with Ky(MgCa)2xO3 as heterogeneous catalyst

Fatty acid methyl esters (FAME) were produced from palm oil using eggshell modified with magnesium and potassium nitrates to form a composite, low-cost heterogeneous catalyst for transesterification. The catalyst, prepared by the combination of impregnation/co-precipitation was calcined at 830 °C for 4 h. Transesterification was conducted at a constant temperature of 65 °C in a batch reactor. Design of experiment (DOE) was used to optimize the reaction parameters, and the conditions that gave highest yield of FAME (85.8%) was 5.35 wt.% catalyst loading at 4.5 h with 16:1 methanol/oil molar ratio. The results revealed that eggshell, a solid waste, can be utilized as low-cost catalyst after modification with magnesium and potassium nitrates for biodiesel production.     

Use of experimental design to investigate biodiesel production by multiple-stage Ultra-Shear reactor

This work presents biodiesel production from soybean oil and bioethanol by multiple-stage Ultra-Shear reactor (USR). The experiments were carried out in the following conditions: reaction time from 6 to 12 min; catalyst concentration from 0.5% to 1.5% by weight of soybean oil; ethanol: soybean oil molar ratio from 6:1 to 10:1. The experimental design was used to investigate the influence of process variables on the conversion in biodiesel. The best ethyl ester conversion obtained was 99.26 wt.%, with ethanol:soybean oil molar ratio of 6:1, catalyst concentration of 1.35% and with 12 min of reaction time.     

Biodiesel synthesis at high pressure and temperature: Analysis of energy consumption on industrial scale

Analysis of several different schemes for industrial FAME production at higher pressure and temperature (catalytic or non-catalytic synthesis) was realized with the aim to find the best route to reduce the energy consumption (EC) and to improve the life cycle energy efficiency. Obtained results indicated that the EC (MJ/kg FAME) mainly depends on degree of conversion of triglycerides being almost 25% smaller if degree of conversion increase from 97 mass% to complete conversion. Further significant decrease of EC might be obtained at subcritical conditions but only after substantial decrease of methanol to oil molar ratio (from 42 to 15) which requires use of appropriate catalyst. On account of that, the kinetics of heterogeneous catalyzed methanolysis of triglycerides was analyzed using data published in literature (CaO) as well as own experimental data (K₂CO₃/Al–O–Si) with a goal to obtain reliable kinetic rate constant which might be used for process simulation.This study shows that if heterogeneous process of biodiesel synthesis is realized at subcritical conditions then further decrease of EC is possible.     

Microwave-assisted preparation and adsorption performance of activated carbon from biodiesel industry solid reside: influence of operational parameters

Preparation of activated carbon has been attempted using KOH as activating agent by microwave heating from biodiesel industry solid residue, oil palm empty fruit bunch (EFBAC). The significance of chemical impregnation ratio (IR), microwave power and activation time on the properties of activated carbon were investigated. The optimum condition has been identified at the IR of 1.0, microwave power of 600 W and activation time of 7 min. EFBAC was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption isotherm. The surface chemistry was examined by zeta potential measurement, determination of surface acidity/basicity, while the adsorptive property was quantified using methylene blue as dye model compound. The optimum conditions resulted in activated carbon with a monolayer adsorption capacity of 395.30 mg/g and carbon yield of 73.78%, while the BET surface area and total pore volume were corresponding to 1372 m²/g and 0.76 cm³/g, respectively.     

Biodiesel surrogates: Achieving performance demands

Synthesis of surrogate molecules is particularly useful for generating in sight of structural-activity relationships, understanding processes and improving the performance. In order to improve upon the physico-chemical properties of biodiesel, methyl, ethyl, isopropyl and n-butyl esters of β-branched fatty acid have been synthesized, initiating from β-branched alcohols. β-Branched alcohols upon oxidation gave corresponding acids, which were converted to their esters. The synthesized esters have substantially better oxidative stability, exhibited by Rancimat oxidation induction period of more than 24 h. The cloud point of synthesized esters is <−36 °C, pour point is <−42 °C and CFPP is <−21 °C, which is substantially better than fatty acid methyl esters. Besides achieving the objective of better oxidative stability and improved low temperature properties, the synthesized surrogate esters have viscosity in the range of 4.2–4.6 cSt at 40 °C, meeting the international diesel and biodiesel standards. The cetane number of synthesized esters is 62–69, which is much better than diesel and biodiesel. The blends of the synthesized esters in diesel at 5% and 10% meet Indian standards of diesel.     

Biodiesel production using a membrane reactor

The immiscibility of canola oil in methanol provides a mass-transfer challenge in the early stages of the transesterification of canola oil in the production of fatty acid methyl esters (FAME or biodiesel). To overcome or rather, exploit this situation, a two-phase membrane reactor was developed to produce FAME from canola oil and methanol. The transesterification of canola oil was performed via both acid- or base-catalysis. Runs were performed in the membrane reactor in semi-batch mode at 60, 65 and 70 degrees C and at different catalyst concentrations and feed flow rates. Increases in temperature, catalyst concentration and feedstock (methanol/oil) flow rate significantly increased the conversion of oil to biodiesel. The novel reactor enabled the separation of reaction products (FAME/glycerol in methanol) from the original canola oil feed. The two-phase membrane reactor was particularly useful in removing unreacted canola oil from the FAME product yielding high purity biodiesel and shifting the reaction equilibrium to the product side.