Transesterification of vegetable oil to biodiesel using heterogeneous base catalyst

doi:10.1016/j.cattod.2004.06.007

Catalysis Today

Volumes 93–95, 1 September 2004, Pages 315-320

https://doi.org/10.1016/j.cattod.2004.06.007 Get rights and content

Abstract

Biodiesel produced by the transesterification of vegetable oils (VOs) is a promising alternative fuel to diesel regarding the limited resources of fossil fuel and the environmental concerns. In this work, an environmentally benign process for the production of biodiesel from VOs using heterogeneous catalyst was developed. Na/NaOH/γ-Al₂O₃ heterogeneous base catalyst was firstly adopted for the production of biodiesel. A study for optimizing the reaction conditions such as the reaction time, the stirring speed, the use of co-solvent, the oil to methanol ratio, and the amount of catalyst, was performed. The Na/NaOH/γ-Al₂O₃ heterogeneous base catalyst showed almost the same activity under the optimized reaction conditions compared to conventional homogeneous NaOH catalyst. The basic strength of Na/NaOH/γ-Al₂O₃ catalyst was estimated and the correlation with the activity towards transesterification was proposed.

Introduction

Air pollution is one of the most serious environmental problems all over the world. Since diesel engines of buses and trucks exhaust a huge amount of NO_x and particulates, a clean alternative fuel is highly demanded. For the recent few decades, many efforts to develop a clean fuel have been under way in many countries. Among many possible sources, biodiesel fuel derived from vegetable oil (VOs) attracts attention as a promising one to be substituted for conventional diesel fuels [1], [2]. Continuously increasing use of petroleum will intensify local air pollution and accelerate the global warming problems caused by CO₂. If pure or blend biodiesel is used as fuel, the net production of CO₂ can be highly suppressed. Sharmer et al. have estimated that in the case of using 1 kg of pure biodiesel instead of the fossil fuel, 3.2 kg of CO₂ production could be reduced [3].

Biodiesel can be blended at any level with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with little or no modifications. Biodiesel not only has proper viscosity, boiling point, and high cetane number [4], but also is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics [5].

One hundred years ago, Rudolf Diesel tested VOs as fuel for his engine. With the advent of cheap petroleum, appropriate crude oil fractions were refined to be used as fuel, and diesel fuels and diesel engines were evolved together. In the 1930s and 1940s, VOs were used as diesel fuels from time to time, but usually only in emergency situations. Recently, because of rise in crude oil prices, limited resources of fossil oil, and environmental concerns, there has been a renewed focus on VOs to make biodiesel fuels.

Biodiesel has been produced by transesterification of triglyceride (VOs) to methyl esters with methanol using sodium or potassium hydroxide dissolved in methanol as catalyst, as represented by the following equation.

In this conventional method, a large amount of waste water was produced to separate and clean the catalyst and the products. Therefore, for the development of an environmentally benign process and the reduction of the production cost, a new process using heterogeneous catalyst should be introduced.

In this work, Na/NaOH/γ-Al₂O₃ heterogeneous base catalyst was firstly adopted for the production of biodiesel. Na/NaOH/γ-Al₂O₃ catalyst was prepared by the successive treatment of γ-Al₂O₃ with sodium hydroxide and sodium at 320 °C under nitrogen following the method proposed by Suzukamo et al. [6]. In their reports, Na/NaOH/γ-Al₂O₃ catalyst had basic sites stronger than H_ = 37 and exhibited high activity on olefin isomerization. The formation of the basic sites was studied with XRD, XPS and TPD analysis. And then, a correlation between the basic strength and the activity towards transesterification was proposed.

Section snippets

Preparation of the catalyst

To eliminate chemical species adsorbed on the surface, γ-Al₂O₃ was pretreated at 550 °C for 12 h. The pretreated γ-Al₂O₃ was introduced into a stainless steel vessel equipped with a continuous stirring system, a nitrogen flow line, and two small solid reagent holders cooled to ambient temperature with cold circulating water flow. The vessel was heated up to 320 °C, into which predetermined amount of sodium hydroxide had kept in the reagent holder was added (0–30 wt.%). The stirring was continued

Catalyst characterizations

The measured BET surface area, pore volume, and pore diameter are shown in Table 2. The BET surface areas as well as the pore volumes decreased with loading sodium and sodium hydroxide, and this tendency was more outstanding in the case of sodium. As shown in the XRD analysis presented in Fig. 2, sodium aluminate was formed by the introduction of the sodium hydroxide. The crystal structure of sodium aluminate seems to be formed by the reaction with γ-Al₂O₃ according to the following equation: $Al_{2}$

Conclusions

Na/NaOH/γ-Al₂O₃ heterogeneous base catalyst was firstly used for the production of biodiesel from the soybean oil. Both the sodium aluminate formed by loading sodium hydroxide on γ-Al₂O₃, and the ionization of sodium, originated the strong basic sites of the catalysts. The activities of the heterogeneous base catalysts correlated with their basic strengths. The reaction conditions for the system were optimized to maximize the biodiesel production yield. A utilization of a co-solvent was found

Acknowledgements

The authors appreciate the support by research grants from the Korea Science and Engineering Foundation (KOSEF) through the Applied Rheology Center (ARC) at Korea University.

References (12)

D. Laforgia et al.
Bioresource Technol.
(1995)
L.G. Schumacher et al.
Bioresource Technol.
(1996)
A. Srivastava et al.
Renew. Sustain. Energy Rev.
(2000)
K. Sharmer, Umweltaspekte bei Herstellung und Verwendung von RME, in: RME Hearing, Ministry for Agriculture, Vienna,...
T.W. Ryan et al.
JAOCS
(1984)
G. Suzukamo, M. Fukao, M. Minobe, Chem. Lett. (1987)...

There are more references available in the full text version of this article.

Cited by (679)

Advances in photocatalytic biodiesel production: Preparation methods, modifications and mechanisms
2024, Fuel
The increased demand for fossil fuels, environmental pollution, and global warming calls for an alternative renewable energy source to power the world. Biodiesel has emerged as a potential candidate in place of petroleum-based diesel as a green and sustainable energy source. Biodiesel is the result of the (trans)esterification of oils or fats with single-chain alcohol. With the increasing demand for biodiesel, several new strategies have been proposed to synthesize biodiesel efficiently in less time. Several heterogeneous catalysts have been developed to enhance the rate of (trans)esterification reaction, but they still have drawbacks, such as harsh reaction conditions and high energy consumption. Photocatalytic biodiesel production is an eco-friendly, energy-efficient, new strategy for synthesizing biodiesel using semiconductor photocatalysts under light irradiation. Various metal oxide-based photocatalysts have been utilized for photocatalytic biodiesel production with efficiencies of over 95 %. However, metal oxides have a higher bandgap, which requires high-energy light to generate electron-hole pairs. Scientists are still working on the development of new photocatalysts for biodiesel production under visible light, and the field of photocatalytic biodiesel production is still in its initial stage. The present review article highlights the efficiency of various photocatalysts investigated for biodiesel production. The effect of various parameters affecting photocatalytic biodiesel production has been discussed. Based on the studies, strategies to enhance the photocatalytic biodiesel yield, limitations of the present photocatalysts and the scope of future research have also been proposed. The mechanism of photocatalytic biodiesel production has also been discussed to help readers design novel photocatalysts with enhanced properties for biodiesel synthesis.
An artificial intelligence approach to model and optimize biodiesel production from used cooking oil using CaO incorporated zeolite catalyst
2023, Energy Conversion and Management: X
The current work investigated the possibility of employing chicken eggshell-zeolite composite as a cheap and recyclable heterogeneous catalyst for used cooking oil (UCO) conversion into its corresponding methyl ester (UCOME) via methanolysis process. Various catalysts were formulated by loading eggshell on the zeolite and calcined at different temperatures to obtain CaO incorporated zeolite (CaO-Zel) catalyst. The catalyst sample calcined at 800 °C for 4 h (CaO-Zel-800) exhibited best activity for methanolysis process and was analyzed using various techniques, including BET, surface basicity, TPD-CO₂, TGA/DTA, SEM, XRD and FTIR. The transesterification process was modeled using artificial intelligence approach viz. artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) while optimization of the operating variables (temperature, catalyst loading, time and molar ratio) was performed by interfacing the developed models with ant colony optimization (ACO) algorithm. The closeness of coefficient of determination (R²) to unity and low mean square error (MSE) indicated that the methanolysis of UCO was adequately described by the developed models with ANFIS model (R² = 0.9997 and MSE = 0.1271) superior to ANN model (R² = 0.9953 and MSE = 2.0762). The highest UCOME yield of 99.45 $\pm$ 0.51 wt% was achieved with ANFIS-ACO under the condition; reaction temperature (72.97 °C), methanol/UCO molar ratio (7.14:1), reaction time (131.97 min) and catalyst dosage (5.39 wt%). The results of the sensitivity analysis revealed that all the operating variables influence UCOME yield, and none could be discarded. The CaO-Zel-800 catalyst was reused for five consecutive reaction cycles, and its activity only decreased by about 12%.
Acidic and basic sites on the surface of sodium montmorillonite active for catalytic transesterification of glycerol to glycerol carbonate
2023, Applied Clay Science
Montmorillonite (Mt) as a solid acid catalyst or support has been widely used in catalytic reactions. However, the existence and catalytic activities of its surface basic sites have rarely been revealed. Here, the surface and structure of Na-Mt are modulated by thermal treatment, providing both acidic and basic sites for the transesterification of glycerol with dimethyl carbonate (DMC) to glycerol carbonate (GLC). The experimental results showed that the thermally activated Na-Mt exhibited bifunctional catalytic properties in glycerol transesterification. The Na-Mt calcined at 400 °C had a basic site density of 1.38 mmol/g and led to a glycerol conversion of 96.8% and a GLC yield of 94.5%. Edge surfaces of Na-Mt provided M^II (M^III) atoms as Lewis acidic sites for facilitating the generation of glyceroxide anions from activated glycerol and -M-OH groups as Brønsted and Lewis basic sites for enhancing the carbonyl activation of DMC. This work revealed the co-existence of acidic and basic sites over thermally activated Na-Mt for synergetic catalysis in the transesterification of glycerol to GLC, making the development of Mt-based materials as bifunctional catalysts for one-pot acid-base catalytic processes possible.
Na-modified carbon nitride as a leach-resistant and cost-effective solid base catalyst for biodiesel production
2023, Fuel
Na-modified graphitic carbon nitrides were utilized for the transesterification of soybean oil and methanol. Graphitic carbon nitrides have not yet been widely applied in biodiesel production, despite their chemical stability and basicity. The catalysts were obtained via the co-thermal polymerization of NaOH and melamine. Catalyst prepared using conventional impregnation method was applied for comparison. The copolymerized catalyst with the optimum Na content showed over 90% biodiesel yield for 10 repeated cycles. The prepared catalysts were characterized by Fourier transform infrared spectrometry, X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy, CO₂-diffuse reflectance infrared Fourier transform spectroscopy, and X-ray photoelectron spectroscopy. The elaborate rigid bonds between Na and N contributed to the leaching-resistance and catalytic activity. While the majority of Na species in impregnated catalysts existed in the form of Na-O, which was easily leached out to the reaction medium showing rapid catalyst deactivation over the repeated cycles. The basicity derived from the electron transfer from the Na to N atoms was confirmed from the density functional theory and CO₂-diffuse reflectance infrared Fourier transform spectroscopy.
Novel and robust machine learning model to optimize biodiesel production from algal oil using CaO and CaO/Al<inf>2</inf>O<inf>3</inf> as catalyst: Sustainable green energy
2023, Environmental Technology and Innovation
In recent years, significant endeavors have been made to develop environmentally friendly fuels due to the detrimental effects of fossil fuels on ecosystem such as global warming, acid rain and air pollution. Alternative biodiesel transport fuel (ABTF) has shown their noteworthy potential of application due to having significant advantages such as negligible toxicity and excellent biodegradability. In this paper, Neural Network-based approaches were employed to create predictions in this work, including Multilayer Perceptron, Boosted Multilayer Perceptron, and Bagging Multilayer Perceptron. The regression issue has three input features: Reaction duration, catalyst amount, and methanol/oil ratio, and the only output is FAME yield. All three versions of these neural network models were tuned using their critical hyper-parameters and chose the optimal mix. Then, some standard measures are used to evaluate their performance. Multilayer perceptron, Boosted Multilayer perceptron, and Bagging Multilayer perceptron has error rates of 0.998, 0.998, and 0.877, respectively, and have MSE errors of 2.87, 1.19, and 5.57. Additionally, considering the MAPE 1.51E−02, 1.09E−02, and 2.26E−02 values acquired. Finally, the boosted multilayer perceptron is the most general and accurate model. Additionally, the optimal output value is 98.99 when the input vector is (x1 $=$ 158, x2 $=$ 1.25, x3 $=$ 33.75).
Various methods for enhancement in heterogeneous catalysed biodiesel production reaction rate
2023, Journal of the Indian Chemical Society
The biodiesel can be produced by transesterification and esterification reaction with edible and non-edible oil respectively. These reactions are catalysed by both homogeneous and heterogenous catalyst. The transesterification reactions for heterogeneous catalysts proceed at a relatively slow rate. The heterogeneous reaction mixture constitutes a three-phase system, oil/alcohol/catalyst therefore the mass transfer limitation controls the reaction rate. In the present study Tetra-hydrofuran, Hexane and Heptane as co-solvent have been tested for the transesterification and esterification reaction. Tetra-hydrofuran, assists in decreasing the mass transfer between the oil and methanol phases. Tetra-hydrofuran was found to be the best co-solvent. It also represents that the presence of Tetra-hydrofuran only enhance the solubility of phases not final equilibrium yield. Results are compared with homogeneous and heterogeneous catalysed reaction. Ultrasonic irradiation influenced the mixing of the reaction mixture and resulted in higher yields, for each co-solvent case.

View all citing articles on Scopus

View full text