Calcium oxide as a solid base catalyst for transesterification of soybean oil and its application to biodiesel production

In order to study solid base catalyst for biodiesel production with environmental benignity, transesterification of edible soybean oil with refluxing methanol was carried out in the presence of calcium oxide (CaO), -hydroxide (Ca(OH)₂), or -carbonate (CaCO₃). At 1 h of reaction time, yield of FAME was 93% for CaO, 12% for Ca(OH)₂, and 0% for CaCO₃. Under the same reacting condition, sodium hydroxide with the homogeneous catalysis brought about the complete conversion into FAME. Also, CaO was used for the further tests transesterifying waste cooking oil (WCO) with acid value of 5.1 mg-KOH/g. The yield of FAME was above 99% at 2 h of reaction time, but a portion of catalyst changed into calcium soap by reacting with free fatty acids included in WCO at initial stage of the transesterification. Owing to the neutralizing reaction of the catalyst, concentration of calcium in FAME increased from 187 ppm to 3065 ppm. By processing WCO at reflux of methanol in the presence of cation-exchange resin, only the free fatty acids could be converted into FAME. The transesterification of the processed WCO with acid value of 0.3 mg-KOH/g resulted in the production of FAME including calcium of 565 ppm.     

Long term activity of modified ZnO nanoparticles for transesterification

Biodiesel can be produced by the transesterification of natural oils with methanol using modified ZnO nanoparticles as catalyst. Crude algae oil, corn oil from DDGs, crude palm oil, crude soybean oil, crude coconut oil, waste cooking oil, food-grade soybean oil and food-grade soybean oil with 3% water and 5% FFA addition were converted into FAME within 3 h using this new catalyst. The ZnO nanoparticles were reused 17 times without any activity loss in a batch stirred reactor and the average yield of FAME was around 93.7%. ZnO nanoparticles were used continuously for 70 days in a fix bed continuous reactor and the average yield of FAME was around 92.3%. XRD, ICP, TEM and HRTEM were used to characterize the long term used catalyst structure. Results show that this catalyst is a mixture of wurtzite ZnO nanoparticles and some amorphous materials and that the used catalysts have similar crystal structure to fresh catalyst. ICP results show that this catalyst does not dissolve in biodiesel, methanol, oil and glycerine-methanol solutions. It has a stable crystal structure under the reaction conditions. The high catalytic activity, long catalyst life and low leaching properties demonstrate these modified ZnO nanoparticles have potential in a commercial biodiesel production process.     

乙醇与餐饮废油制备生物柴油的工艺研究

以餐饮废油和乙醇为原料,以氢氧化钾为催化剂,采用酯交换法制备生物柴油。考查了醇油摩尔比、催化剂用量、反应时间和温度对原料转化率的影响。正交试验结果表明,餐饮废油与乙醇酯交换反应的最佳反应条件为：醇油摩尔比12∶1,催化剂用量1.25%,反应温度78℃,反应时间1.5h。在此反应条件下,餐饮废油转化率达65.12%;在此基础上引入四氢呋喃作助溶剂,转化率可提高至86%~90%。     

Alum as a heterogeneous catalyst for the transesterification of palm oil

Alum has been taken beyond its traditional roles as a water treatment chemical and a confectionary additive to a new role as a catalytic precursor in biodiesel production. Its catalytic potentials were empirically proved via palm oil transesterification with methanol and application of solid state instrumental characterization techniques. The catalyst was very clean, efficient, simple and cheap to produce, and could be clearly separated from the reaction products. When the reaction was carried out under the conditions of catalyst to oil ratio of 7.09 wt%, reaction time of 12 h and temperature of 170 °C, methanol to oil molar ratio of 18:1 and catalyst preconditioned at 550 °C, the yield of fatty acid methyl ester (FAME) obtained was 92.5 wt%.     

Production of fatty acid methyl esters over a limestone-derived heterogeneous catalyst in a fixed-bed reactor

Production of fatty acid methyl esters (FAME) via the transesterification of different vegetable oils and methanol with a limestone-derived heterogeneous catalyst was investigated in a fixed-bed reactor at 65 °C and ambient pressure. This heterogeneous catalyst, as a 1 or 2 mm cross-sectional diameter extrudate, was prepared via a wet mixing of thermally treated limestone with Mg and Al compounds as binders and with or without hydroxyethyl cellulose (HEC) as a plasticizer, followed by calcination at 800 °C. The physicochemical properties of the prepared catalysts were characterized by various techniques. Palm kernel oil, palm oil, palm olein oil and waste cooking oil could be used as the feedstocks but the FFA and water content must be limited. The extrudate catalyst prepared with the HEC addition exhibited an enhanced formation of FAME due to an increased porosity and basicity of the catalyst. The FAME yield was increased with the methanol/oil molar ratio. The effect of addition of methyl esters as co-solvents on the FAME production was investigated. The structural and compositional change of the catalysts spent in different reaction conditions indicated that deactivation was mainly due to a deposition of glycerol and FFA (if present). The FAME yield of 94.1 wt.% was stably achieved over 1500 min by using the present fixed-bed system.     

Transesterification of sunflower oil in a countercurrent trickle-bed reactor packed with a CaO catalyst

Transesterification of sunflower oil with methanol to form biodiesel was performed in a countercurrent trickle-bed reactor, using calcium oxide particles 1-2 mm in diameter as a packed, solid base catalyst. Although biodiesel production generally requires a reaction temperature below the boiling point of methanol to maintain a heterogeneous, liquid-liquid reaction, in the present study the reaction temperature was varied from 80 to 140 °C to confirm the progress of transesterification in a gas-liquid-solid phase reaction system. Oil droplets released from a thin tube flowed downward, while vaporized methanol flowed upward in the bed. The effects of the reaction temperature, methanol and oil flow rates, and the bed height on the FAME yield were investigated. The oil residence time in the reactor, which was controlled by changing both the oil flow rate and the bed height, had a significant effect on the FAME yield. In addition, the FAME yield increased with reaction temperature and was maximal at 373 K due to the change in residence time associated with reduced oil viscosity at higher temperatures. The FAME yield was 98% at a reaction temperature of 373 K when the methanol and oil flow rates were 3.8 and 4.1 mL/h, respectively.     

Conversion of waste cooking oil to biodiesel using ferric sulfate and supercritical methanol processes

In this comparative study, conversion of waste cooking oil to methyl esters was carried out using the ferric sulfate and the supercritical methanol processes. A two-step transesterification process was used to remove the high free fatty acid contents in the waste cooking oil (WCO). This process resulted in a feedstock to biodiesel conversion yield of about 85-96% using a ferric sulfate catalyst. In the supercritical methanol transesterification method, the yield of biodiesel was about 50-65% in only 15 min of reaction time. The test results revealed that supercritical process method is probably a promising alternative method to the traditional two-step transesterification process using a ferric sulfate catalyst for waste cooking oil conversion. The important variables affecting the methyl ester yield during the transesterification reaction are the molar ratio of alcohol to oil, the catalyst amount and the reaction temperature. The analysis of oil properties, fuel properties and process parameter optimization for the waste cooking oil conversion are also presented.     

BIODIESEL PRODUCTION FROM PALM OIL VIA HETEROGENEOUS TRANSESTERIFICATION: OPTIMIZATION STUDY

Fatty acid methyl ester (FAME) prepared by transesterification process using a heterogeneous catalyst has received a lot of interest lately as it could overcome the limitations of the current commercial homogeneous catalytic process. Apart from that, palm oil, being the cheapest edible oil in the world, will always remain the most economical source of FAME. Therefore, in this study, the use of sulfated zirconia alumina as a heterogeneous catalyst to catalyze the transesterification of palm oil with methanol to FAME was carried out using design of experiment (DOE), specifically response surface methodology (RSM) based on four-variable central composite design (CCD) with α = 2. The transesterification process variables are reaction temperature (60–180°C), reaction period (1–5 h), methanol-to-oil ratio (4–12 mol mol^?1), and amount of catalyst (2–10 wt.%). In this study involving many multiple process variables, the design of experiment approach was found to be superior to the conventional one-variable-at-one-time approach. Interactions between variables were found to have significant effect on the yield of FAME. At the conditions of 3 h of reaction period, 127°C reaction temperature, methanol-to-palm oil ratio of 8, and 6 wt.% of catalyst, an optimum FAME yield of 83.3% can be obtained, indicating that sulfated zirconia alumina has potential as a heterogeneous catalyst for the production of FAME from palm oil.     

Transesterification of waste cooking palm oil by MnZr with supported alumina as a potential heterogeneous catalyst

The transesterification of waste cooking palm oil (WCPO) with methanol into fatty acid methyl esters (FAMEs) was investigated using solid acidic mixed oxide catalysts Mn_3.5xZr_0.5yAl_xO₃ prepared via coprecipitation. The effects of reaction temperature, time, molar methanol-to-oil ratio, and catalyst loading were investigated. The stability of the catalytic activity was examined via leaching and reusability tests through five consecutive batch runs. The catalyst achieved a FAME content of more than 93%, and the optimal reaction conditions are as follows: reaction temperature of 150 °C, reaction time of 5 h, molar methanol-to-WCPO ratio of 14:1, and catalyst loading of 2.5 wt.%.     

Process optimization for methyl ester production from waste cooking oil using activated carbon supported potassium fluoride

This paper presents the transesterification of waste cooking palm oil (WCO) using activated carbon supported potassium fluoride catalyst. A central composite rotatable design was used to optimize the effect of molar ratio of methanol to oil, reaction period, catalyst loading and reaction temperature on the transesterification process. The reactor was pressurized up to 10 bar using nitrogen gas. All the variables were found to affect significantly the methyl ester yield where the most effective factors being the amount of catalyst and reaction temperature, followed by methanol to oil ratio. A quadratic polynomial equation was obtained for methyl ester yield by multiple regression analysis using response surface methodology (RSM). The optimum condition for transesterification of WCO to methyl ester was obtained at 3 wt.% amount of catalyst, 175 °C temperature, 8.85 methanol to oil molar ratio and 1 h reaction time. At the optimum condition, the predicted methyl ester yield was 83.00 wt.%. The experimental value was well within the estimated value of the model. The catalyst showed good performance with a high yield of methyl ester and the separation of the catalyst from the liquid mixture is easy.     

A process to transesterify vegetable oil with methanol in the presence of quick lime bit functioning as solid base catalyst

As a precursor of the practical catalyst to utilize solid base catalysis of calcium oxide for biodiesel production, crushed lime stone whose size ranged from 1.0 to 1.7 mm was used in this study. The precursor was turned into the practical catalyst by only calcination at 1173 K. At 333 K under atmospheric pressure, rapeseed oil was transesterified with methanol in the presence of the practical catalyst, on a laboratory scale pilot plant characterized by batch unit consisting of a circulating stream passing through the column reactor. In the early trial, the yield of fatty acid methyl esters (FAME) produced after 2 h was around 60%. Moreover, the column reactor was blocked up due to serious agglomeration of the practical catalyst when the reaction time was extended by an extra hour. These drawbacks were hurdled by improving the reacting condition. As a result, the yield of FAME reached 96.5% at 2 h of the reaction time, and the good reaction efficiency went on for the successive 10 operations, without exchanging the catalyst. However, on and after the 11th operation, the reaction efficiency was gradually deteriorated. After the transesterifying operation was successively repeated 17 times, the practical catalyst was withdrawn from the column reactor in order to investigate its deactivation. Additionally, the transesterification of waste cooking oil was performed on the laboratory scale pilot plant in the same manner.     

Synthesis of biodiesel fuel using an electrolysis method

The paper details the first use of a simple electrolysis method to produce biodiesel fuel (BDF) from corn oil and waste cooking oil at room temperature. This novel process exhibited a high fatty acid methyl ester (FAME) yield (>97%) even in the presence of a relatively high water content (as high as 2 wt.% of the total reaction mixture) when using a low concentration of sodium chloride (<1.2 wt.% based on oil weight). FAME yield was influenced by methanol/oil molar ratio, the amount of cosolvent addition, water content, NaCl concentration and electrolysis voltage. With the proceeding of electrolysis, the pH value of the electrolyte rapidly increased from 7 to 12, but the conductivity of the reaction mixture decreased. When the electrolysis was stopped on the way, the transesterification reaction was still continued, but the reaction rate became lower than that when continuing the electrolysis in the case of high water content. During the electrolysis process, no chlorine molecule in the evolved gas was detected (<0.5 ppm).     

Two‐phase flow behavior in microtube reactors during biodiesel production from waste cooking oil

Flow patterns in the course of transesterification of waste cooking oil (WCO), sunflower oil (SFO) with water and/or oleic acid as a model of WCO, and pure SFO in the presence of a KOH catalyst in microtubes were investigated. FAME yield for the transesterification of WCO reached more than 89% in the microtube reactors with a residence time of 252 s at 333 K. The flow patterns when using WCO were changed from a liquid–liquid slug flow at the inlet region to a parallel flow at the middle region, and then to a homogeneous liquid flow at the outlet region as the reaction proceeded at 333 K. Fine droplets containing glycerol and methanol generally formed in oil slugs when using pure SFO, but were almost unobservable when using WCO. The soap produced from free fatty acids was considered to be the main factor affecting the flow patterns of WCO and SFO. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Magnetic Solid Base Catalysts for the Production of Biodiesel

Magnetic solid base catalysts were prepared by loading Na₂SiO₃ on Fe₃O₄ nano-particles with Na₂O·3SiO₂ and NaOH as precipitator. The catalysts were used to catalyze the transesterification reactions for the production of fatty acid methyl esters (FAME, namely biodiesel) from cottonseed oil. The optimum conditions of the catalysts' preparation and transesterification reactions were investigated by orthogonal experiments. The catalyst with the highest catalytic activity was obtained when Si/Fe molar ratio of 2.5, aging time of 2 h, calcination temperature of 350 °C, calcination time of 2.5 h. Magnetic of the catalyst was characterized with Vibrating Sample Magnetometer (VSM) and transmission electron microscopy photograph (TEM), and the results showed the catalyst Na₂SiO₃/Fe₃O₄ had good specific saturation magnetization and paramagnetism, and its water resistance was better than the traditional homogeneous base catalysts; under the transesterification conditions of methanol/oil molar ratio of 7:1, catalyst dosage of 5%, reaction temperature of 60 °C, reaction time of 100 min and stirring speed of 400 rpm, yield of biodiesel was 99.6%. The lifetime and recovery rate of the magnetic solid base catalyst were much better than those of Na₂SiO₃.     

Biodiesel production from waste cooking palm oil using calcium oxide supported on activated carbon as catalyst in a fixed bed reactor

A reactor has been developed to produce high quality fatty acid methyl esters (FAME) from waste cooking palm oil (WCO). Continuous transesterification of free fatty acids (FFA) from acidified oil with methanol was carried out using a calcium oxide supported on activated carbon (CaO/AC) as a heterogeneous solid-base catalyst. CaO/AC was prepared according to the conventional incipient-wetness impregnation of aqueous solutions of calcium nitrate (Ca(NO₃)₂·4H₂O) precursors on an activated carbon support from palm shell in a fixed bed reactor with an external diameter of 60 mm and a height of 345 mm. Methanol/oil molar ratio, feed flow rate, catalyst bed height and reaction temperature were evaluated to obtain optimum reaction conditions. The results showed that the FFA conversion increased with increases in alcohol/oil molar ratio, catalyst bed height and temperature, whereas decreased with flow rate and initial water content in feedstock increase. The yield of FAME achieved 94% at the reaction temperature 60 °C, methanol/oil molar ratio of 25: 1 and residence time of 8 h. The physical and chemical properties of the produced methyl ester were determined and compared with the standard specifications. The characteristics of the product under the optimum condition were within the ASTM standard. High quality waste cooking palm oil methyl ester was produced by combination of heterogeneous alkali transesterification and separation processes in a fixed bed reactor. In sum, activated carbon shows potential for transesterification of FFA.     

Oil transesterification over calcium oxides modified with lanthanum

Investigations were conducted on a series of calcium and lanthanum oxides catalyst for biodiesel production. Mixed oxides catalyst showed a superior transesterification activity over pure calcium or pure lanthanum oxide catalysts. The catalyst activity was correlated with surface basicity and specific surface areas. The effects of water and free fatty acids (FFA) levels in oil feedstock, water and CO₂ in air, mass ratio of catalyst, molar ratio of oil to methanol, and reaction temperature on fatty acid methyl ester (FAME) yield were investigated. Under optimal conditions, FAME yields reached 94.3% within 60 min at 58 °C. Mixed CaO-La₂O₃ catalyst showed a high tolerance to water and FFA, and could be used for converting pure or diluted unrefined/waste oils to biodiesel.     

Response surface modeling and optimization of biodiesel production from Cynara cardunculus oil

Cardoon (Cynara cardunculus L.) is a perennial spontaneous thistle grown in Mediterranean countries and well adapted to marginal lands, recently considered as a non‐food energy crop. Their seeds contain 24% of oil (dry basis). In this study, modeling and optimization of the production of fatty acid methyl esters (FAME) from cardoon oil for biodiesel uses was performed at laboratory scale, via response surface methodology, following a central composite rotatable design. FAME were obtained by transesterification of crude cardoon oil with methanol in the presence of a catalyst (sodium methoxide) for 120 min. The temperature ranged from 26 to 94 °C, the amount of sodium methoxide varied between 0.12 and 2.5 wt‐% and the molar ratio methanol/oil from 0.95 : 1 to 11 : 1. The estimated yield of FAME (97%) was obtained after 30 min, at 52 °C, for a molar ratio of 6.4 : 1 and 1.4 wt‐% of catalyst. In laboratory‐scale model validation experiments, 94% of FAME yield was obtained after 30 min of reaction. Transesterification was performed in a 30‐L reactor, under previously optimized conditions: A yield of 88% FAME was obtained after 90 min of reaction time, due to mass transfer limitations. After purification, the biodiesel showed high quality according to DIN EN 14214 standard specifications.     

Heterogeneous transesterification processes by using CaO supported on zinc oxide as basic catalysts

Zinc oxide, obtained by thermal decomposition of zinc oxalate, has been impregnated with different amounts of calcium oxide, and used as solid catalyst for transesterification processes. Catalysts have been characterized by chemical analysis, XRD, XPS, FT-IR, SEM, N₂ adsorption–desorption at 77 K and CO₂-TPD. The catalytic behaviour has been evaluated by choosing two transesterification processes: a simple model such as the reaction between ethyl butyrate and methanol and the production of biodiesel from sunflower oil and methanol. Calcium oxide is stabilized by filling the mesoporous network of ZnO, as reveal the corresponding pore size distributions, thus avoiding the lixiviation of the active phase in the reaction medium. These supported CaO catalysts, thermally activated at 1073 K, can give rise to FAME (fatty acid methyl esters) yield higher than 90%, after 2 h of reaction, when a methanol:oil molar ratio of 12 and 1.3 wt% of the catalyst with a 16 wt% CaO were employed.     

Dolomite as a heterogeneous catalyst for transesterification of canola oil

In this study, the catalytic activity of dolomite was evaluated for the transesterification of canola oil with methanol to biodiesel in a heterogeneous system. The influence of the calcination temperature of the catalyst and the reaction variables such as the temperature, catalyst amount, methanol/canola oil molar ratio, and time in biodiesel production were investigated. The maximum activity was obtained with the catalyst calcined at 850 °C. When the reaction was carried out at reflux of methanol, with a 6:1 molar ratio of methanol to canola oil and a catalyst amount of 3 wt.% the highest FAME yield of 91.78% was obtained after 3 h of reaction time.     

Fatty Acid Methyl Ester Synthesis over Fe3+-Vanadyl Phosphate Catalysts

A heterogeneous acid catalyst, Fe³⁺-vanadyl phosphate, prepared by the isomorphous substitution of some VO³⁺ groups in vanadyl phosphate with trivalent metal Fe³⁺, was found to be active for the transesterification of soybean oil with methanol. When the transesterification reaction was carried out with a molar ratio of methanol to oil of 30:1, a reaction temperature of 473 K, a reaction time of 3 h and a catalyst amount of 5 wt%, the maximum conversion of soybean oil was 61.3%. Moreover, the catalytic activity of this catalyst was not significantly affected by the presence of free fatty acids and water in the reactants, and it also exhibits catalytic activity towards the esterification of free fatty acids with methanol. Further, it was shown that the spent catalyst could be easily reactivated by calcination at 773 K in air. There was very little change in the catalytic activity of the regenerated catalyst, even after five cycles.