Transesterification of castor oil assisted by microwave irradiation

Microwave assisted transesterification of castor bean oil was carried out in the presence of methanol or ethanol, using a molar ratio alcohol/castor bean oil of 6:1, and 10% w/w of acidic silica gel or basic alumina (in relation to the oil mass) as catalyst. Under acid catalysis, the reaction occurred with satisfactory yields using H₂SO₄ immobilized in SiO₂, methanol under conventional conditions (60 °C for 3 h) as well as using microwave irradiation for 30 min. The best results were obtained under basic conditions (Al₂O₃/50% KOH) using methanol and conventional (60 °C, stirring, 1 h) or microwave conditions (5 min). In comparison with conventional heating, the catalyzed alcoholysis assisted by microwaves is much faster and leads to higher yields of the desired fatty esters.     

Preparation of dandelion-type silica spheres and their application as catalyst supports

Dandelion-type silica spheres with a dendrimer-like porous structure were prepared by adding pore modifiers into aqueous synthetic mixtures of tetraethylorthosilicate (TEOS), hexadecyltrimethylammonium bromide (CTAB), ammonium hydroxide, and acetone. The formation of silica spheres and their porous characteristics were investigated using various techniques, including electron microscopy, nitrogen adsorption, and thermogravimetric analysis. Benzyl acetate (BENA) was very effective in the formation of a dendrimer-like porous structure. However, the composition of TEOS, CTAB, acetone, and BENA strongly influenced the size and shape of the silica spheres and their porous structure. The synthetic mixture of 1 TEOS: 0.22 CTAB: 1.9 BENA: 0.32 NH₄OH: 36 acetone: 236 H₂O produced dandelion-type silica spheres with diameters of ~300 nm. The phosphazenium hydroxide (PzOH) catalyst supported on the dandelion-type silica spheres prepared by adding BENA showed high catalytic performance in the transesterification of soybean oil with methanol due to its high feasibility for rapid access of large triglyceride molecules into the basic PzOH moieties incorporated in the pores.     

Transesterification of sunflower oil catalyzed by flyash-based solid catalysts

Flyash-based base catalyst was used in the transesterification of sunflower oil with methanol to methyl esters in a heterogeneous manner. Catalyst preparation variables such as, the KNO₃ loading amount and calcination temperature were optimized. The catalysts were characterized by powder XRD. The catalyst prepared by loading of 5 wt.% KNO₃ on flyash followed by its calcination at 773 K has exhibited maximum oil conversion (87.5 wt.%). The influence of various reaction parameters such as % catalyst loading, methanol to oil molar ratio, reaction time, temperature, reusability of the catalyst on the catalytic activity was investigated. K₂O derived from KNO₃ might be an essential component in the catalyst for its efficiency.     

Rape oil transesterification over heterogeneous catalysts

This work studies the application of KNO₃/CaO catalyst in the transesterification reaction of triglycerides with methanol. The objective of the work was characterizing the methyl esters for its use as biodiesel in compression ignition motors. The variables affecting the methyl ester yield during the transesterification reaction, such as, amount of KNO₃ impregnated in CaO, the total catalyst content, reaction temperature, agitation rate, and the methanol/oil molar ratio, were investigated to optimize the reaction conditions.The evolution of the process was followed by gas chromatography, determining the concentration of the methyl esters at different reaction times. The biodiesel was characterized by its density, viscosity, cetane index, saponification value, iodine value, acidity index, CFPP (cold filter plugging point), flash point and combustion point, according to ISO norms. The results showed that calcium oxide, impregnated with KNO₃, have a strong basicity and high catalytic activity as a heterogeneous solid base catalyst.The biodiesel with the best properties was obtained using an amount of KNO₃ of 10% impregnated in CaO, a methanol/oil molar ratio of 6:1, a reaction temperature of 65 °C, a reaction time of 3.0 h, and a catalyst total content of 1.0%. In these conditions, the oil conversion was 98% and the final product obtained had very similar characteristics to a no. 2 diesel, and therefore, these methyl esters might be used as an alternative to fossil fuels.     

Biodiesel production from soybean oil and methanol using hydrotalcites as catalyst

Esters of fatty acids, derived from vegetable oils or animal fats, and known as biodiesel, are a promising alternative diesel fuel regarding the limited resources of fossil fuels and the environmental concerns. In this work, methanolysis of soybean oil was investigated using Mg-Al hydrotalcites as heterogeneous catalyst, evaluating the effect of Mg/Al ratio on the basicity and catalytic activity for biodiesel production. The catalysts were prepared with Al/(Mg + Al) molar ratios of 0.20, 0.25 and 0.33, and characterized by X-ray diffraction (XRD), textural analysis (BET method) and temperature-programmed desorption of CO₂ (CO₂-TPD). When the reaction was carried out at 230 °C with a methanol:soybean oil molar ratio of 13:1, a reaction time of 1 h and a catalyst loading of 5 wt.%, the oil conversion was 90% for the sample with Al/(Mg + Al) ratio of 0.33. This sample was the only one to show basic sites of medium strength. We also investigated the reuse of this catalyst, the effect of calcination temperature and made a comparison between refined and acidic oil.     

Hydrodearomatization of petroleum fuel fractions on silica supported Ni-W sulphide with increased stacking number of the WS2 phase

Ni-W catalysts supported on commercial γ-alumina and silica displayed similar activity in dibenzothiophene hydrodesulfurization (DBT HDS), while the activity of the Ni-W/SiO₂ catalyst in toluene hydrogenation (HYD) was 6 times higher compared with Ni-W/Al₂O₃. The dearomatization performance of Ni-W/SiO₂ catalyst was tested over a wide range of operation conditions with naphtha and middle distillates. 90% saturation of aromatics in FCC naphtha (340 °C, LHSV of 1 h⁻¹) and 50% in Light cyclic oil (LCO) (360 °C, LHSV of 1 h⁻¹) was achieved at 5.4 MPa. In a two stage process with the same Ni-W/SiO₂ and intermediate separation of hydrogen sulphide 90% saturation of aromatics in LCO was achieved at 320 °C and total LHSV of 0.5 h⁻¹. At equal conditions, Ni-W/Al₂O₃ catalyst yielded 1.5-4 times lower total aromatics saturation.     

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.     

Transesterification of triglycerides with methanol over thermally treated Zn5(OH)8(NO3)2×2H2O salt

Methanolysis of natural oil, i.e. castor oil and triacetin, a model compound for the transesterification of triglycerides in biodiesel production was studied under atmospheric pressure at temperature of 50-60 °C. As-received zinc hydroxy nitrate Zn₅(OH)₈(NO₃)₂×2H₂O (Zn-5) and samples obtained by thermal treatment of Zn-5 for 2 h in the temperature range of 105-300 °C were used as the catalysts. The catalysts were characterized by thermogravimetric (TG) analysis, X-ray powder diffraction (XRD), infrared spectroscopy (FTIR), nitrogen sorption (BET) and scanning electron microscopy (SEM). The effect of thermal treatment of Zn-5 salt on the activity and reusability in methanolysis of triglycerides was studied. During thermal treatment of as-received Zn-5 salt a gradual decomposition via various hydroxy nitrates intermediates such as Zn₅(OH)₈(NO₃)₂ and Zn₃(OH)₄(NO₃)₂ to ZnO occurred. This was accompanied by significant morphological and textural changes. Plate-like particles of Zn-5 salt reorganized into spherically shaped particles of ZnO. Moreover, decrease in specific surface area and porosity occurred. In methanolysis of both triglycerides, the activity of Zn-catalysts gradually decreased as the temperature of thermal treatment increased and the activity of ZnO, a final product of thermal decomposition was very low. The most active was as-received Zn-5 salt and its morphological/chemical properties did not change during methanolysis reaction performed at temperature of 50-60 °C. Moreover, the activity of original Zn-5 salt was fully restored after methanol/THF washing of spent catalysts. The activity of as-received Zn-5 catalyst was preserved under successive use in catalytic tests. The activity of thermally treated Zn-5 salt (at 140 °C) did not restore after methanol/THF washing and during subsequent use of Zn-5-140 catalyst its activity successively decreased.     

Room temperature transesterification of soybean oil to biodiesel catalyzed by rod-like CaxSiOx + 2 solid base

Rod-like Ca_xSiO_x + 2 catalysts were synthesized by using one-pot hydrothermal method. Catalysts calcined at 550 °C were used in the transesterification reaction of soybean oil with methanol. Under methanol reflux condition, FAME yields of 82% and 95% were achieved on Ca₄SiO₆ in a reaction time of 1 and 2 h, separately. Also, the FAME yields on different Ca_xSiO_x + 2 catalysts were correlated with their basic properties. Besides, a FAME yield of ca. 80% can be achieved under room temperature over Ca₄SiO₆ catalyst.     

Kalsilite based heterogeneous catalyst for biodiesel production

Kalsilite (KAlSiO₄) was used as a heterogeneous catalyst for transesterification of soybean oil with methanol to biodiesel. Kalsilite showed relatively low catalytic activity for transesterification reaction. The catalytic activity of this catalyst was significantly enhanced by introducing a small amount of lithium nitrate by the impregnation method. A biodiesel yield of 100% and a kinematic viscosity of 3.84 cSt were achieved at a mild temperature of only 120 °C over this lithium modified kalsilite catalyst (2.3 wt.% Li).     

Transesterification of soybean oil to biodiesel using CaO as a solid base catalyst

In this study, transesterification of soybean oil to biodiesel using CaO as a solid base catalyst was studied. The reaction mechanism was proposed and the separate effects of the molar ratio of methanol to oil, reaction temperature, mass ratio of catalyst to oil and water content were investigated. The experimental results showed that a 12:1 molar ratio of methanol to oil, addition of 8% CaO catalyst, 65 °C reaction temperature and 2.03% water content in methanol gave the best results, and the biodiesel yield exceeded 95% at 3 h. The catalyst lifetime was longer than that of calcined K₂CO₃/γ-Al₂O₃ and KF/γ-Al₂O₃ catalysts. CaO maintained sustained activity even after being repeatedly used for 20 cycles and the biodiesel yield at 1.5 h was not affected much in the repeated experiments.     

Polyethylenes produced with zirconocene immobilized on MAO-modified silicas

The effect of Al content on MAO-modified silicas was evaluated on catalyst activity, on polymer properties and on residual metal content in the resulting polyethylenes. MAO-modified silicas were prepared by impregnating MAO toluene solutions in concentration range between 0.5 and 20.0 wt% Al/SiO₂. Commercial MAO-modified silica (Witco) containing 24.4 wt% Al/SiO₂ was used for comparative reasons. The resulting modified-silicas were employed as supports for grafting (nBuCp)₂ZrCl₂. Using external MAO as cocatalyst (Al/Zr=2000) no difference in catalyst activity was observed. Nevertheless, for Al/Zr=500, catalyst activities were shown to be higher for supported zirconocene systems containing 0.0-2.0 wt% Al/SiO₂ range. According to DSC analysis, one T_m peak was detected for polymer obtained with catalyst prepared with 0.5 wt% Al/SiO₂ (135 °C), but two T_m peaks were observed for polymers obtained with catalysts prepared with 10.0 wt% Al/SiO₂ (136 and 141 °C) and 20.0 wt% Al/SiO₂ (133 and 141 °C).     

Transesterification of palm oil on KyMg1 − xZn1 + xO3 catalyst: Effect of Mg-Zn interaction

The Mg-Zn interaction effect of K_yMg_1 − xZn_1 + xO₃ heterogeneous type catalyst and its performance on transesterification of palm oil have been studied using the response surface methodology and the factorial design of experiments. The catalyst was synthesized using the co-precipitation method and the activity was assessed by transesterification of palm oil into fatty acid methyl esters. The ratio of the Mg/Zn metal interaction, temperature and time of calcination were found to have positive influence on the conversion of palm oil to fatty acid methyl ester (FAME) with the effect of metal to metal ratio and temperature of calcination being more significant. The catalytic activity was found to decrease at higher calcination temperature and the catalyst type K₂Mg_0.34Zn_1.66O₃ with Mg/Zn ratio of 4.81 gave FAME content of 73% at a catalyst loading of 1.404 wt.% of oil with molar ratio of methanol to oil being 6:1 at temperature of 150 °C in 6 h. A regression model was obtained to predict conversions to methyl esters as a function of metal interaction ratio, temperature of calcination and time. The observed activity of the synthesized catalyst was due to its synergetic structure and composition.     

Acid base catalyzed transesterification kinetics of waste cooking oil

The present study reports the results of kinetics study of acid base catalyzed two step transesterification process of waste cooking oil, carried out at pre-determined optimum temperature of 65 °C and 50 °C for esterification and transesterification process respectively under the optimum condition of methanol to oil ratio of 3:7 (v/v), catalyst concentration 1%(w/w) for H₂SO₄ and NaOH and 400 rpm of stirring. The optimum temperature was determined based on the yield of ME at different temperature. Simply, the optimum concentration of H₂SO₄ and NaOH was determined with respect to ME Yield. The results indicated that both esterification and transesterification reaction are of first order rate reaction with reaction rate constant of 0.0031 min^− 1 and 0.0078 min^− 1 respectively showing that the former is a slower process than the later. The maximum yield of 21.50% of ME during esterification and 90.6% from transesterification of pretreated WCO has been obtained. This is the first study of its kind which deals with simplified kinetics of two step acid-base catalyzed transesterification process carried under the above optimum conditions and took about 6 h for complete conversion of TG to ME with least amount of activation energy. Also various parameters related to experiments are optimized with respect to ME yield.     

Biodiesel from fried vegetable oils via transesterification by heterogeneous catalysis

Three solid catalysts have been tested in the transesterification of fried oils: CaO, SrO, K₃PO₄. For CaO and SrO the different efficiency, between their use as powder or granules, has been examined. Another investigated aspect has been the catalytic activity at different catalyst loadings and recycles. At the end granules have been employed in a catalytic bed reactor, comparing results with batch systems. Results have shown that using catalyst as granule does not affect the yields after 3 h of reaction. The use of the catalytic bed reactor has given the possibility to perform the transesterification maintaining the catalyst separated from the reactants, without loss of efficiency; in fact the comparison between trials in batch reactor and in catalytic bed system has not shown differences in yields. After 3 h of reaction, at 65 °C, 5 wt% of catalyst, we have had the following FAME yields: 92% for CaO, 86% for SrO, 78% for K₃PO₄. The transesterification reaction has shown a sensitive influence respect to K₃PO₄ granules amount used; in fact the yield has reached the 85% using 10 wt% of catalyst. The reutilization of the catalyst, without regeneration, has shown a loss of efficiency of about 10-20% in decreasing yield.     

Transesterification of edible and non-edible oils over basic solid Mg/Zr catalysts

A series of Mg–Zr catalysts with varying Mg to Zr ratios was prepared by co-precipitation method. These catalysts were characterized by BET surface area, X-ray diffraction, X-ray photo electron spectroscopy and temperature programmed desorption of CO₂. The catalytic activity of these catalysts was evaluated for the room temperature transesterification of both edible and non-edible oils to their corresponding fatty acid methyl esters. The catalyst with Mg/Zr (2:1 wt./wt.%) exhibited exceptional activity towards transesterification reaction within short reaction time. The effects of different reaction parameters such as catalyst to oil mass ratio, reaction temperature, reaction time and methanol to oil molar ratio were studied to optimize the reaction conditions. The reasons for the observed activity of these catalysts are discussed in terms of their basicity and other physico-chemical properties.     

Biodiesel Production from Sunflower Oil Using K2CO3 Impregnated Kaolin Novel Solid Base Catalyst

Kaolin clay material was loaded with potassium carbonate by impregnation method as a novel, effective, and economically heterogeneous catalyst for biodiesel production of sunflower oil via the transesterification reaction. The structural and chemical properties of the produced catalysts were characterized through several analyses including the X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and Brunauer–Emmett–Teller specific surface area. These revealed the best catalyst for the investigated reaction among different ones prepared based upon various impregnation extent of the potassium carbonate. The influence of this parameter was examined through a comparison of the catalytic activity of differently produced catalysts. The impregnation amount of 20 wt% K₂CO₃ upon the kaolin achieved the highest catalytic activity attributed to its highest basicity. To expand upon the efficiency of transesterification, such reaction parameters including the molar ratio between methanol and oil, reactor loading of the catalyst, and time duration of the reaction were optimized. The highest yield of biodiesel over the K₂O/kaolin catalyst was around 95.3 ± 1.2%, which was achieved using the kaolin support impregnated with 20 wt% of K₂CO₃ under optimum reaction conditions of the catalyst, reactor loading of 5 wt%, reaction temperature of 65 °C, methanol:oil molar ratio of 6:1, and reaction duration time of 4 hours. Ultimately, this optimized catalyst was demonstrated to successfully withstand the aforementioned optimum criteria up to five consecutive reaction cycles while experiencing a rather negligible loss of about 10% of its activity.     

The Optimization of the Production of Methyl Esters from Corn Oil Using Barium Hydroxide as a Heterogeneous Catalyst

In recent years, vegetable oils, as renewable raw materials, became a promising feedstock for chemicals and biodiesel production. The main products derived from oils are esters of fatty acids, especially methyl esters, obtained by their transesterification with methanol, in presence of acid or alkaline catalysts. The use of such catalysts implies the need for washing operations, which leads to environmental pollution. In the present paper, the response surface methodology based on a central composite design, has been developed to optimize the process of transesterification of corn oil. Ba(OH)₂ in presence of diethyl ether was used as catalyst. A quadratic polynomial equation was obtained. It correlates the reaction parameters [methanol/oil molar ratio (x _r), reaction time (x _t) and catalyst concentration (x _c)] with methyl esters yield. Analysis of variance analysis showed that only methanol/oil molar ratio and catalyst concentration have had the most significant influences on the conversion. The maximum methyl esters yield was obtained using the following optimum parameters: methanol/corn oil ratio of 11.32, reaction time of 118 min and catalyst concentration of 3.6 wt%.     

Soybean oil transesterification over zinc oxide modified with alkali earth metals

Fatty acid methyl esters, derived from vegetable oils or animal fats and better known as biodiesel, have received considerable attention because of their environmental benefits and the limited resources of fossil fuels. Most biodiesel is usually produced by the transesterification of vegetable oils with methanol in the presence of a catalyst. This study reports on the preliminary results of using alkaline earth metal-doped zinc oxide as a heterogeneous catalyst for transesterification of soybean oil. The highest catalytic activity was obtained with ZnO loaded with 2.5 mmol Sr(NO₃)₂/g, followed by calcination at 873 K for 5 h. When the transesterification reaction was carried out at reflux of methanol (338 K), with a 12:1 molar ratio of methanol to soybean oil and a catalyst amount of 5 wt.%, the conversion of soybean oil was 94.7%. Besides, tetrahydrofuran (THF), when used as a co-solvent, could increase the conversion up to 96.8%. However, the recovered catalyst exhibited the lower catalytic activity with a conversion of soybean oil of 15.4%. Furthermore, DTA-TG, IR and the Hammett indicator method were employed for the catalyst characterizations.     

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.