Catalytic synthesis of biodiesel from pongamia glabra over zirconia and its modified forms

Zirconia & its modified forms such as Mo(VI)/ZrO₂, Pt-SO ₄ ^2? /ZrO₂, MgO & MgO-ZrO₂ mixed oxide were prepared by impregnation method. These catalysts were analyzed for surface acidity, surface basicity and crystallinity by using techniques such as TPD & powder X-ray diffraction. Mo(VI)/ZrO₂, Pt-SO₄ ^2?/ZrO₂ were used as solid acid catalysts for esterification of pongamia glabra (karanja) oil to reduce the concentration of free fatty acid and MgO and MgO-ZrO₂ mixed oxide were used as solid base catalysts for transesterification of karanja oil to produce biodiesel. These zirconia catalysts were found to be highly efficient for the synthesis of biodiesel with more than 90% yield of biodiesel. These solid catalysts can be effectively reactivated and reused.     

Biodiesel production from waste cooking oil over alkaline modified zirconia catalyst

Screening and catalytic activity of alkaline modified zirconia i.e. Mg/ZrO₂, Ca/ZrO₂, Sr/ZrO₂, and Ba/ZrO₂ as heterogeneous catalyst in biodiesel production from waste cooking oil (WCO) have been investigated. The catalysts were prepared via wet impregnation of alkaline nitrate salts supported on zirconia. Physico-chemical characteristics of the catalysts were analyzed by BET surface area, XRD, FESEM and CO₂–NH₃–TPD. Among the catalysts screened, Sr/ZrO₂ exhibited higher catalytic activities. Characterization results disclosed Sr/ZrO₂ catalyst possessed balanced basic and acid site concentrations with its pore volume, surface area as well as pore diameters suitable for biodiesel production. The balanced active sites facilitated simultaneous transesterification and esterification of WCO. A plausible mechanism has been suggested for the simultaneous reactions. The effects of operating process conditions such as methanol to oil molar ratio, reaction temperature and catalyst loading on biodiesel production in the presence of Sr/ZrO₂ were investigated. Methyl ester (ME) yield at 79.7% was produced over 2.7 wt.% catalyst loading (Sr/ZrO₂), 29:1 methanol to oil molar ratio, 169 min of reaction time and 115.5 °C temperature.     

Supported solid and heteropoly acid catalysts for production of biodiesel

Biodiesel has developed attraction of most researchers recently because of its renewable resources and environmental benefits. Transesterification process in the presence of catalysts is the most common way, which is used for biodiesel production. Heterogeneous acid catalysts are considered more reliable than any other catalysts to carry out most vital reactions related to green chemistry (biodiesel production), because the production of biodiesel from solid acid catalysts is considered economically favorable. Nowadays, biodiesel is preparing from low quality feedstock by using solid acids catalysts in many research laboratory throughout the world. This article discusses how much catalyst shapes affect the efficiency of catalyst during catalysis. Different types of supports (zinc oxide, alumina, zirconia, and silica) are used to increase the efficiency of catalysts. Supported Lewis acid, Brønsted acid, and heteropoly acid catalysts show good efficiency for the catalytic transesterification of oil with alcohol. Heteropoly acid catalysts are tremendous and environment friendly acid catalyst and have ability to tolerate contaminations of oil resources such as water contents and free fatty acids (FFAs) contents. Keggin-type heteropoly acids are easily available and having stable structure while Wells–Dawson-type heteropoly acids are included in super acid class, due to these reasons heteropoly acids are considered as best acidic catalysts for biodiesel production by catalytic transesterification process. Therefore, this review also focused on the deactivation, regeneration and advantages of supported solid acid catalysts used for the catalytic production of biodiesel through transesterification.     

Effects of Brønsted and Lewis Acidities on Catalytic Activity of Heteropolyacids in Transesterification and Esterification Reactions

Some salts of H₃PW₁₂O₄₀‐M_x/nH_3–xPW₁₂O₄₀ (abbreviated as M_x/nH_3–xPW) were prepared and used as acid catalysts for transesterification and esterification reactions. These catalysts have double acidity properties, i.e., Lewis acidity and Brønsted acidity, that are suitable for the conversion of waste cooking oil into biodiesel. The highest efficiency was 59.2 % and 94.7 % corresponding to transesterification and esterification reactions by Ti_0.6H_0.6PW with moderate Lewis acidity. The relationship between the acidic properties and the catalytic activity is discussed in detail.     

Solid superacid catalyzed glycerol esterification of free fatty acids in waste cooking oil for biodiesel production

The free fatty acids (FFAs) of waste cooking oil (WCO) are readily esterified with crude glycerol in the presence of the solid superacid SO/ZrO₂–Al₂O₃. This reaction lowers the acidity of WCO before biodiesel production. The solid superacid SO/ZrO₂–Al₂O₃ catalyzes both FFA esterification and TAG glycerolysis during the reaction. The conversion of FFA in the WCO with an acid value of 88.4 ± 0.5 mg KOH/g to acylglycerols was 98.4% under optimal conditions (mole ratio of glycerol to FFA = 1.4:1; reaction time = 4 h; reaction temperature = 200°C; catalyst loading = 0.3 wt%) obtained through an orthogonal experiment. The final FAME product with a FAME content of 96.9 ± 0.3 wt% yield was 94.8 wt%, after transesterification of the esterified WCO with methanol, catalyzed by potassium hydroxide. The FAME composition of the products produced by transesterification were identified and quantified by GC–MS. The results suggest that this new glycerol esterification process, using a solid superacid catalyst, affords a promising method to convert oils with high FFA levels, like WCO, to biodiesel. The process has the inherent advantage of easy separation steps for removing excess alcohol and significant savings in energy, when compared to acid catalyzed reactions with methanol to lower acidity. Practical applications : In this work, WCO with a high acid value was esterified with crude glycerol catalyzed by solid super acid, whose formula was expressed as SO/ZrO₂–Al₂O₃. There are distinct advantages to this new esterification process, which include easy separation of the excess crude glycerol by sedimentation or centrifugation, the use of the low cost reactant crude glycerol direct from the byproducts of transesterification, the potential to achieve a very low content of FFAs by post‐refining to improve the yield of the final product, and time and energy saving are found as compared to the traditional methanol esterification process. This new technology provides a promising alternative method for processing feedstocks of high acid value, such as WCO, for the production of biodiesel.     

Biodiesel production by the transesterification of cottonseed oil by solid acid catalysts

Methyl esters (biodiesel) were produced by the transesterification of cottonseed oil with methanol in the presence of solid acids as heterogeneous catalysts. The solid acids were prepared by mounting H₂SO₄ on TiO₂ · nH₂O and Zr(OH)₄, respectively, followed by calcining at 823K. TiO₂-SO₄ ²⁻ and ZrO₂-SO₄ ²⁻ showed high activity for the transesterification. The yield of methyl esters was over 90% under the conditions of 230°C, methanol/oil mole ratio of 12:1, reaction time 8 h and catalyst amount (catalyst/oil) of 2% (w). The solid acid catalysts showed more better adaptability than solid base catalysts when the oil has high acidity. IR spectral analysis of absorbed pyridine on the samples showed that there were Lewis and Br?nsted acid sites on the catalysts. Translated from The Chinese Journal of Process Engineering, 2006, 6(4): 571–575 [译自: 过程工程学报]     

Lewis acid-catalyzed transesterification and esterification of high free fatty acid oil in subcritical methanol

Lewis acid catalysts are active for both esterification and transesterification, but the reaction is very slow due to mass-transfer limitations between methanol and oil phase. Because oil, FFA and Lewis acid catalysts are all soluble in the subcritical methanol phase, the esterification and transesterification will be enhanced when they are carried out under subcritical conditions. In this work, the esterification and transesterification of high FFA oil to biodiesel via Lewis acid catalysts such as Pb(OOCCH₃)₂, Cd(OOCCH₃)₂ and Zn(OOCCH₃)₂ were carried out in the subcritical methanol phase (2 MPa, 180°C, reaction time 30 min). The results show that the esterification conversion reaches 79.8-96.4% with Palmitic acid as feedstock, and the transesterification conversion reaches 56.8-73.4% with soybean oil as feedstock. With the mixture of Soybean oil and Palmitic acid (FFA content of 20.3 wt%) as feedstock, the content of fatty acid methyl esters (FAME) in products reaches 67.3-83.4%.     

Activity of solid catalysts for biodiesel production: A review

Heterogeneous catalysts are promising for the transesterification reaction of vegetable oils to produce biodiesel. Unlike homogeneous, heterogeneous catalysts are environmentally benign and could be operated in continuous processes. Moreover they can be reused and regenerated. However a high molar ratio of alcohol to oil, large amount of catalyst and high temperature and pressure are required when utilizing heterogeneous catalyst to produce biodiesel. In this paper, the catalytic activity of several solid base and acid catalysts, particularly metal oxides and supported metal oxides, was reviewed. Solid acid catalysts were able to do transesterification and esterification reactions simultaneously and convert oils with high amount of FFA (Free Fatty Acids). However, the reaction rate in the presence of solid base catalysts was faster. The catalyst efficiency depended on several factors such as specific surface area, pore size, pore volume and active site concentration.     

制备生物柴油的固体酸催化剂研究进展

生物柴油是一种绿色可再生能源。目前,大多采用高活性的固体酸催化酯化、酯交换反应进行制备,该工艺具有产品与催化剂易分离、催化剂可回收再生且环保等优点。本文综述了固体超强酸、负载型固体酸、金属氧化物及复合物、沸石分子筛、阳离子交换树脂、离子液体及杂多酸等不同类型固体酸催化剂催化制备生物柴油的最新研究进展,包括催化剂的制备、活性、催化行为。最后,对制备生物柴油的固体酸在物理化学性质、成本等方面的研究进行展望。     

Biodiesel Production using Lewis Catalysts under Ultrasonic Activation

Biodiesel can be produced by transesterification of oil triglycerides, as well as by esterification of fatty acids using feedstock materials rich in free fatty acids)FFAs). Utilization of such feedstocks can gain substantial economical profit and solve a problem of disposal of residual raw materials. To find an effective method of biodiesel production from FFA, we developed esterification of FFAs under ultrasonic activation using Lewis acids as catalysts. Homologous catalyst BF₃ and heterogeneous AlCl₃ were highly effective in reactions of model FFAs methylation under ultrasonic activation, when the reaction yield reached 100 %. Ethylation at the same conditions was less successful.     

Synthesis of mesoporous SiO2–ZrO2 mixed oxides by sol–gel method

A series of SiO₂–ZrO₂ mixed oxides were prepared by sol–gel method in the presence of directing agent, with variable amounts of ZrO₂ between pure silica and pure zirconia, with the aim to obtain catalytic materials suitable as solid acid catalysts. SiO₂–ZrO₂ mixed oxides differ from the two pure starting oxides. While SiO₂ has a low OH density without peculiar acid character, the introduction of increasing amounts of Zr increases the density of the acid sites in the materials. Furthermore both SiO₂/ZrO₂ molar ratio and drying procedure are able to influence the physico-chemical characteristics (textural properties, acid sites distribution, etc.) of these mixed oxides.     

Simplistic transesterification approach for the synthesis of benzyl salicylate over honeycomb monoliths coated with modified forms of zirconia as catalysts: Kinetics

The catalysts such as Al₂O₃/ZrO₂ with 2–10?wt% of Al₂O₃ were coated on honeycomb monoliths by dip-and-dry technique. These catalysts were also prepared in their powder form. All the catalysts (honeycomb and powder form) were characterized for their surface acidity, crystallinity, functionality, elemental analysis, and morphology. The catalytic activity of all the catalysts was performed in the transesterification of methyl salicylate with benzyl alcohol to synthesize benzyl salicylate. Reaction conditions like reaction time, reaction temperature, and the molar ratio of the reactants were varied to obtain the highest yield of benzyl salicylate. The 6% Al₂O₃/ZrO₂ coated on honeycomb exhibited the highest conversion of methyl salicylate at 383?K in 60?min. Kinetic studies were conducted to determine the energy of activation and temperature coefficient. The rate constants in the case of 6AZ (HCM) was found to be 5.0?×?10^?3?min^?1 (373?K); 6.4?×?10^?3?min^?1 (383?K) and 2.2?×?10^?3?min^?1 (373?K); 3.2?×?10^?3?min^?1 (383?K) in the case of 6AZ (PF) catalyst, while the energy of activation (E_a) values were found to be 35.12 and 39.93 kJ mol^?1 for 6AZ (HCM) and 6AZ (PF), respectively. The reactant preadsorption study discloses that the transesterification follows the Eley–Rideal mechanism. Reactivation and recyclability of the catalysts were also examined and the results clearly indicate that Al₂O₃/ZrO₂ coated on the honeycomb is efficient and green catalytic system.     

Transesterification Catalysts from Iron Doped Hydrotalcite-like Precursors: Solid Bases for Biodiesel Production

Abstract Described are new solid base catalysts for transesterification of seed oil triglycerides to fatty acid methyl esters, a key step in biodiesel production. These were prepared by substituting Fe3+ ions substitute for a fraction of the Al3+ ions in the Mg/Al layered double hydroxide lattices of hydrotalcites (HTC) and calcining to give porous metal oxides (PMOs). These iron-doped PMOs are much stronger bases than those derived from undoped or Ga3+ doped HTCs and are effective catalysts for the methanol transesterification of triacetin (glycerol triacetate) and of soybean oil. Graphical Abstract New solid base catalysts for transesterification of seed oil triglycerides to fatty acid methyl esters, a key step in biodiesel production, were prepared by substituting Fe³⁺ for Al³⁺ cations in hydrotalcite (HTC) structures and calcining to give porous metal oxides.      

Transesterification of soybean frying oil to biodiesel using heterogeneous catalysts

In the present work, the transesterification reaction of soybean frying oil with methanol, in the presence of different heterogeneous catalysts (Mg MCM-41, Mg-Al Hydrotalcite, and K⁺ impregnated zirconia), using low frequency ultrasonication (24 KHz) and mechanical stirring (600 rpm) for the production of biodiesel fuel was studied. Selection of catalysts was based on a combination of porosity and surface basicity. Their characterization was carried out using X-ray diffraction, Nitrogen adsorption-desorption porosimetry and scanning electron microscopy (SEM) with energy dispersive spectra (EDS). The activities of the catalysts were related to their basic strength. Mg-Al hydrotalcite showed particularly the highest activity (conversion 97%). It is important to mention that the catalyst activity of ZrO₂ in the transesterification reaction increased as the catalyst was enriched with more potassium cations becoming more basic. Use of ultrasonication significantly accelerated the transesterification reaction compared to the use of mechanical stirring (5 h versus 24 h).     

Biodiesel Production Using a Carbon Solid Acid Catalyst Derived from β‐Cyclodextrin

A novel carbon solid acid catalyst was prepared by incomplete hydrothermal carbonization of β‐cyclodextrin into small polycyclic aromatic carbon sheets, followed by the introduction of –SO₃H groups via sulfonation with sulfuric acid. The physical and chemical properties of the catalyst were characterized in detail. The catalyst simultaneously catalyzed esterification and transesterification reactions to produce biodiesel from high free fatty acid (FFA) containing oils (55.2 %). For the as‐prepared catalyst, 90.82 % of the oleic acid was esterified after 8 h, while the total transesterification yield of high FFA containing oils reached 79.98 % after 12 h. By contrast, the obtained catalyst showed comparable activity to biomass (such as sugar, starch, etc.)‐based carbon solid acid catalyst while Amberlyst‐15 resulted in significantly lower levels of conversion, demonstrating its relatively high catalytic activity for simultaneous esterification and transesterification. Moreover, as the catalyst can be regenerated, it has the potential for use in biodiesel production from oils with a high FFA content.     

Feasibility of Palm Oil as the Feedstock for Biodiesel Production via Heterogeneous Transesterification

The production of biodiesel has become popular recently as a result of increasing demand for a clean, safe and renewable energy. Biodiesel is made from natural renewable sources such as vegetable oils and animal fats. The conventional method of producing biodiesel is by reacting vegetable oil with alcohol in the presence of a homogenous catalyst (NaOH). However, this conventional method has some limitations such as the formation of soap, usage of significant quantities of wash water and complicated separation processes. Heterogeneous processes using solid catalysts have significant advantages over homogenous methods. Currently, more than 90 % of world biodiesel is produced using rapeseed oil. The production of biodiesel from rapeseed oil is considered uneconomical, considering the fact that palm oil is currently the world's cheapest vegetable oil. Therefore, the focus of this study is to show the feasibility of producing biodiesel from palm oil using montmorillonite KSF as a heterogeneous catalyst. The heterogeneous transesterification process was studied using design of experiment (DOE), specifically response surface methodology (RSM) based on a four‐variable central composite design (CCD) with α = 2. The transesterification process variables were reaction temperature, x₁ (50–190 °C), reaction period, x₂ (60–300 min), methanol/oil ratio, x₃ (4–12 mol mol^–1) and the amount of catalyst, x₄ (1–5 wt %). It was found that the conversion of palm oil to biodiesel can reach up to 78.7 % using the following reaction conditions: reaction temperature of 155 °C, reaction period of 120 min, ratio of methanol/oil at 10:1 mol mol^–1 and amount of catalyst at 4 wt %. From this study, it was shown that montmorillonite KSF catalyst can be used as a solid catalyst for biodiesel production from palm oil.     

Synthesis and characterization of mono‐acylglycerols through the glycerolysis of methyl esters obtained from linseed oil

Here we investigate the production and characterization of mono‐acylglycerols through the glycerolysis of biodiesel, a methyl ester mixture, obtained from linseed oil. The biodiesel employed was derived from linseed oil through transesterification according to transesterification double step process 1 . The efficiency of H₂SO₄, CaO, and NaOH as catalysts was evaluated for the production of mono‐acylglycerols. The glycerolysis reactions were performed by varying the molar ratio of the reagents (biodiesel:glycerol), the type and amount of catalyst, reaction time and temperature. Systematic evaluation of reaction yield is shown as a function of these parameters. Reaction products were characterized through IR spectroscopy, hydrogen NMR, and the GC techniques. The study of three different catalysts indicated that the most efficient was 5% NaOH in a 1:5 biodiesel–glycerol molar ratio with 10 h reaction time. The reaction reached a maximum of 85% biodiesel conversion with a mono‐acylglycerol yield of 72% at 130°C.     

Transesterification of Pistacia chinensis oil for biodiesel catalyzed by CaO-CeO2 mixed oxides

This study investigates the use of CaO-CeO₂ mixed oxides as solid base catalysts for the transesterification of Pistacia chinensis oil with methanol to produce biodiesel. These CaO-CeO₂ mixed-oxide catalysts were prepared by an incipient wetness impregnation method and characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. The cerium improved the heterogeneous catalytic stability remarkably due to the defects induced by the substitution of Ca ions for Ce ions on the surface. The best catalyst was determined to be C0.15-973 (with a Ce/Ca molar ratio of 0.15 and having been calcined at 973 K), considering its catalytic and anti-leaching abilities. The effects of reaction parameters such as the methanol/oil molar ratio, the amount of catalyst amount and the reaction temperature were also investigated. For the C0.15-973 regenerated after five reuses, the biodiesel yield was 91%, which is slightly less than that of the fresh sample. The test results revealed that the CaO-CeO₂ mixed oxides have good potential for use in the large-scale biodiesel production.     

Synthesis of biodiesel from Scenedesmus sp. by microwave and ultrasound assisted in situ transesterification using tungstated zirconia as a solid acid catalyst

Oleaginous Scenedesmus sp. was cultivated phototrophically in an open pond for biofuels production. The culture was harvested and subsequently dewatered and dried. The chemical properties of the Scenedesmus sp. lipids were determined as per standard ASTM methods. Biodiesel was synthesized by in situ transesterification from dried biomass using microwave and sonication techniques with tungstated zirconia (WO₃/ZrO₂) as a solid acid catalyst. In situ transesterification allowed minimizing the requirement of solvents by merging the two steps (i.e. extraction of lipid and conversion to biodiesel) to a single step. The use of a solid catalyst effectively reduces the purification cost of biodiesel due to ease of separation and potential for reuse. The conversion of Scenedesmus sp. lipids to biodiesel was determined by GC. Box–Behnken design was used for optimization of the variables to optimize the biodiesel yield and conversion. The efficiency of the two processes was compared.     

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.