Optimization of ultrasonic-assisted heterogeneous biodiesel production from palm oil: A response surface methodology approach

doi:10.1016/j.fuproc.2009.12.002

Fuel Processing Technology

Volume 91, Issue 5, May 2010, Pages 441-448

https://doi.org/10.1016/j.fuproc.2009.12.002 Get rights and content

Abstract

The use of ultrasonic processor in the heterogeneous transesterification of palm oil for biodiesel production has been investigated. Response surface methodology was employed to statistically evaluate and optimize the biodiesel production process catalyzed by two alkaline earth metal oxide catalysts i.e. BaO and SrO. SEM, surface analysis, AAS analysis and the Hammett indicator methods were used for characterization of the catalysts. Four different variables including reaction time (10–60 min), alcohol to oil molar ratio (3:1–15:1), catalyst loading (0.5–3.0 wt.%) and ultrasonic amplitude (25–100%) were optimized. Mathematical models were developed and used to predict the behavior of the process. The models were able to accurately predict the biodiesel yield with less than 5% error for both catalysts. The basic strength of the catalysts was the main reason of their high activities. This study confirmed that the ultrasonic significantly improved the process by reducing the reaction time to less than 50 min and the catalyst loading to 2.8 wt.% to achieve biodiesel yields of above 95%. The optimum alcohol to oil ratio was found to be at 9:1 while the best amplitudes were ∼ 70 and ∼ 80% for the BaO and SrO catalysts, respectively.

Introduction

Recently, particular focus is been given on global warming and exhaustion of non-renewable resources. These problems are primarily attributed to the heavy consumption of fossil fuels. Much attention has been given to biomass resources as alternatives for energy sources. The typical biodiesel fuel is produced by the transesterification of vegetable oils with low alcohol in the presence of homogeneous base-catalyst such as KOH or NaOH [1]. Transesterification can occur in the absence of a catalyst, but it can be effectively intensified by the use of suitable catalyst [2]. However, for the satisfactory use of the product as diesel fuel, the catalyst must be removed from the product mixture and this requires cumbersome purification processes while huge amount of wastewater is generated at the same time [3].

Heterogeneous catalytic process is expected to be future biodiesel production process. This process lowers the cost and minimizes the environmental impacts due to the simpler production steps and purification processes which are normally carried out under very mild conditions. The heterogeneous catalysts capable to be used are such as, titanium-silicates [4], alkaline earth metal compounds and hydroxides [4], [5], [6], and alkali metal hydroxides or salts supported on γ-alumina [7], [8], [9] or zeolites [10]. The common problem associated with the heterogeneous biodiesel production process is its low reaction rate due to poor interaction between the oil and alcohol during the reaction due to their mutual immiscibility [4], [5].

The demand for biodiesel in the world is sharply increasing. Thus, increasing the production rate for biodiesel in order to meet the demand seems to be essential. Therefore, new accelerating technologies are of great interest among researchers in this area. Ultrasonic radiations can accelerate the biodiesel production rate with homogenous catalyst [1], [11]. Hanh et al. [2] found that the methanolysis of oil in aqueous catalyst solutions (e.g. NaOH, KOH) can be accelerated by low frequency ultrasound which led to the intensification of the overall process. Reports on the beneficial use of ultrasound for homogeneous catalytic process for biodiesel production are also published very recently [1], [2], [12]. Despite widely investigated for accelerating homogeneous reaction systems, heterogeneous biodiesel production process has never been intensified using ultrasonic energy. The benefit offered to the homogeneous process is theoretically possible in the case of heterogeneous process in a similar manner. However, report on the use of ultrasonic-assisted heterogeneous process for the production of this renewable fuel is still hardly found in the literature.

Fig. 1 shows the five step reaction mechanism generally proposed for the role of metal oxide catalyst in the transesterification reaction. Steps 1 and 2 describe the adsorption of alcohol and fatty acid on two neighboring free catalytic sites, respectively. In step 3, the two adsorbed groups react to form a surface intermediates. These surface intermediates will further decompose in step 4 and finally desorb (step 5). According to Hattori et al. [13], the rate-determining step of this mechanism with catalysts having a higher basicity, such as BaO and SrO, is the surface reaction step. Forward reaction promotes the formation of esters to result in high biodiesel yield. In this respect, higher alcohol ratios are preferred but too high could dilute the reactants leading to lower reaction rate [11].

The main objective of this study was to elucidate the effects of ultrasonic irradiation on production conditions of palm oil transesterification with methanol using heterogeneous catalysts. In this study, BaO and SrO catalysts were used as they have been reported to be successful for this reaction by few researchers [5], [6].The experimental data obtained were used for the optimization of the process conditions by means of response surface methodology (RSM) under a historical design. RSM is an effective statistical technique for optimizing multifactor experiments, building models, evaluating the effects of several factors for desirable responses. The eventual objective of RSM is to determine the optimum operating conditions for the system, or to determine the region which satisfies the operating specifications [14].

Analysis of variance (ANOVA) provides the statistical results and diagnostic checking tests which enable researchers to evaluate adequacy of the models [15]. Historical design is generally used to fit the experimental data when data are available without the need for prior experimental design. In this study, the data obtained from the experimental work by varying one factor at a time were fitted to the historical design and overall trend was to be characterized while the accuracy of the models developed were simultaneously evaluated. It is of great interest to demonstrate the overall behavior of the ultrasonic-assisted process as the ultrasonic could affect the overall course of reaction leading to specific catalytic behaviors. However, thorough discussion on the catalyst reutilization is deemed beyond the specific scopes of the present work and is not discussed in detail in this manuscript.

Section snippets

Materials and chemicals

Commercial cooking palm oil (Vesawit, Malaysia) was purchased from a local market and used without any further purification. Methanol used for the transesterification process was supplied by Thermo Fisher Scientific Inc. (USA), while, n-hexane was purchased from Merck (Germany). Reference standards, such as methyl myristate, methyl palmitate, methyl oleate, methyl stearate and methyl linoleate were obtained from NuChek Prep. Inc., Australia. All the chemicals used were of analytical grade.

Catalyst preparation

The

Experimental design and analysis of variance (ANOVA)

The results for each experimental run for BaO and SrO catalysts are shown in Table 2. A quadratic regression model was developed using coded values from the estimation of data. The model was modified based on the insignificancy of some model terms. The model equations based on coded values for the biodiesel yield using BaO and SrO catalysts under ultrasonic conditions are represented by Eqs. (2), (3), respectively. The significance of each coefficient in Eqs. (2), (3) was determined by Student t

Conclusion

This study proved the effectiveness of ultrasonic irradiation in improving the transesterification process towards biodiesel production. The optimization of the process for BaO and SrO catalysts using ultrasonic energy was successfully conducted by fitting the experimental data into a historical design and a response surface methodology was then performed. Two mathematical models were developed by the software and they were able to accurately predict the biodiesel yield at any point in the

Acknowledgements

The authors gratefully acknowledge Felda Research Grant from Felda Foundation and Research University (RU) Grant from the Universiti Sains Malaysia to support their biodiesel research works.

References (25)

F.F.P. Santos et al.
Fuel Process. Technol.
(2009)
A. Kawashima et al.
Bioresour. Technol.
(2008)
C.J. Shieh et al.
Bioresour. Technol.
(2003)
G. Arzamendi et al.
Catal. Today
(2008)
A. Kawashima et al.
Bioresour. Technol.
(2009)
G. Arzamendi et al.
Chem. Eng. J.
(2007)
W. Chen et al.
Catal. Comm.
(2008)
X. Li et al.
Catal. Comm.
(2007)
G.J. Suppes et al.
Appl. Catal. A
(2004)
C. Stavarache et al.
Ultrason. Sonochem.
(2007)

H.D. Hanh et al.

Renew. Energ.

(2009)

A.A.L. Zinatizadeh et al.

Biochem. Eng. J.

(2007)

Cited by (112)

Heterogeneously catalyzed palm biodiesel production in intensified fruit blender
2023, Arabian Journal of Chemistry
This research investigated palm biodiesel production via solid base-catalyzed transesterification in an intensified kitchen fruit blender. Studied parameters included methanol to palm oil molar ratio, CaO catalyst loading, reaction temperature, and reaction volume. XRD analysis showed a pure CaO phase after calcination while other characteristics illustrated good functionality of the catalyst. An optimal condition was achieved with 15:1 of methanol to palm oil molar ratio, 5 wt% of CaO dosage, 60 °C of reaction temperature, and 1,000 mL of reaction volume, obtaining the highest FAME production of 97.58% and yield efficiency of 1.47 × 10⁻³ g/J. The FT-IR illustrated an alteration of various functional groups through a reusability experiment demonstrating exceptional activity stability. The catalyst activity was decreased by only 15.8% in the 5th consecutive cycle. Properties of produced biodiesel conformed to international standards. This proved that biodiesel production using the CaO catalyst in the intensified kitchen fruit blender provides a positive effect on reuse, reduces wastewater from the washing process, lowers production costs, and is environmentally responsible to achieve high FAME yield due to the cavitation phenomena inside the reactor to generate fine emulsion of oil and methanol which could be easier to reach the active site of the CaO catalyst.
Efficient production of biodiesel at low temperature using highly active bifunctional Na-Fe-Ca nanocatalyst from blast furnace waste
2022, Fuel
In this study, nanocatalysts for biodiesel production were prepared via wet impregnation of blast furnace dust (BFD) in Na₂CO₃ (Na-BFD) and CaCO₃ (Ca-BFD) suspension solutions and calcination at 500 and 600 °C, respectively. Biodiesel yields of 100.0 wt% (Na-BFD₅₀₀) and 98.3 wt% (Ca-BFD₆₀₀) were achieved at 65 °C. Synthesized catalysts showed outstanding activity and recyclability, due to the transition of CaCO₃, Na₂CO₃ and Fe₂O₃ to nanocrystals of NaFeO₂ (29.9 nm), Ca₂Fe₂O₅ (10.5 nm), CaO (100.1 nm) and Ca₂Fe₂O₅ (50.0 nm). Na-BFD₅₀₀ achieved 95.8 wt% biodiesel yield with 16 cycles, whereas Ca-BFD₆₀₀ reached 94.1 wt% biodiesel yield with 7 cycles via magnetic separation. BFD containing convertible magnetic and active components (Fe₂O₃ and CaCO₃) was an ideal raw material to synthesize catalyst for biodiesel production with high catalytic efficiency and easy separation. The study provided a practical utilization of industrial solid waste for biodiesel production.
Insight into the sulfonation conditions on the activity of sub-bituminous coal as acidic catalyst during the transesterification of spent corn oil; effect of sonication waves
2022, Sustainable Chemistry and Pharmacy
The impact of the sulfonation conditions on the catalytic activity of coal as an acidic catalyst was assessed by normal stirring (NS.Coal) and sonication waves (SS.Coal) based on the Response Surface methodology. The NS.Coal exhibits acid density and surface area of 8.8 mmol/g and 27.8 m²/g, respectively. This was obtained after 90 min at sulfonation conditions of 150 °C temperature and 95% H₂SO₄ concentration. In the existence of sonication waves for 60 min (240 W), SS.Coal shows acid density and surface area of 14.2 mmol/g and 45.8 m²/g, respectively. This demonstrates significant efficiency for the sonication-induced sulfonation processes during the synthesis of sulfonated coal as an acidic catalyst. The activities of NS.Coal and SS.Coal acidic catalysts were evaluated during the transesterification of corn oil. The best yield was obtained by NS.Coal (4 wt, %) is 99.3% after 60 min at 60 °C in the presence of 14:1 methanol/oil ratio. The archived yields using SS.Coal at loading values of 2 wt, %, 3 wt, %, and 4 wt, % are 99.6%, 99.84%, and 99.85%, respectively after 20 min. The kinetic properties of reactions were illustrated based on the Pseudo-First order assumption. The thermodynamic studies demonstrate the endothermic properties of the corn oil transesterification reactions. The determined activation energy by NS.Coal and SS.Coal are 26.22 kJ/mol and 17.7 kJ/mol, respectively reflect the possible use of them as effective catalysts at low energy and mild conditions.
Synthesis of MgO/MgSO<inf>4</inf> nanocatalyst by thiourea–nitrate solution combustion for biodiesel production from waste cooking oil
2022, Renewable Energy
A novel MgO/MgSO₄ nanocatalyst was synthesized using solution combustion method with thiourea as the fuel. The in-situ inducement of sulfonated group over the basic catalyst, MgO, was carried out for the first time using thiourea for the production of biodiesel. The synthesized nanocatalyst with its bi-functional characteristics performed efficiently in the simultaneous transesterification and esterification of high free fatty acid (FFA) containing waste cooking oil (WCO) into biodiesel in the presence of ultrasound. The newly developed nanocatalyst was characterized by XRD, FESEM, EDS, FTIR and BET analyses. The resulting nanocatalyst possesses a specific surface area of 82 m²/g and a pore volume of 0.047 cm³/g. The high sulfur content of 13.65% of the novel catalyst developed facilitates its high acidic characteristics suitable for the esterification step. The optimization of the process carried out by the response surface methodology (RSM) predicted the optimized parameters as follows: methanol to oil molar ratio-9.4:1, catalyst loading-8.9 wt%, ultrasonic power-402 W and reaction time-46 min. The optimum yield of biodiesel predicted by the RSM was 98.8%. The synthesized nanocatalyst demonstrated high stability which established significant future perspective for industrial production of biodiesel from low cost, high FFA containing feedstock.
Various methods of biodiesel production and types of catalysts
2022, Biofuels and Bioenergy: Opportunities and Challenges
Biodiesel is considered as the best alternative renewable source of energy with low carbon monoxide, particulates, and hydrocarbon emission. They are considered to be nontoxic, biodegradable, and ecofriendly and contain traces of sulfur. However, commercialization of biodiesel production faces many challenges due to high cost, extensive demand, and complex conversion process. Pyrolysis, microemulsion, catalytic and noncatalytic transesterification, supercritical methanol transesterification, ultrasound- and radio frequency–assisted transesterification, microwave irradiation–assisted transesterification, and in situ assisted transesterification techniques are used in the production of biodiesel. The role of catalyst is significant in the transesterification process for enhancing the conversion efficiency as well as improving the physicochemical properties of the biodiesel. 100% conversion efficiencies have been achieved by using microwave irradiation transesterification. Nanoparticles such as ZnO, MgO, CaO, nanocomposites, and ionic liquids act as efficient catalyst and assist in enhancing the conversion yield and reducing the production cost. Choosing the suitable catalyst, technique, and feedstock can reduce the overall cost of biodiesel and thus help in commercialization of biodiesel.
Pelletized biomass fly ash for FAME production: Optimization of a continuous process
2021, Fuel
Circularity in the resources usage is one of the current challenges in the development of our civilization. At the same time, there is an imperative need for cleaner and competitive energy sources, alternatives to those of fossil origin. In this context, the present work aimed to optimize a continuous process for fatty acid methyl esters (FAME) production using residual resources, namely waste cooking oil (WCO) and pelletized biomass fly ash as catalyst. A fixed bed tubular continuous reactor was designed and built. The pelletized catalyst performance was assessed in the reaction system, which was fed with a mixture of refined palm oil (RPO), WCO and methanol at 60 °C. The effect of three operating variables (residence time, WCO/RPO mass ratio and methanol/oil molar ratio) on FAME concentration was studied, using experimental the Box-Benhken design and the Response Surface Methodology (RSM). The maximum FAME concentration achieved was c.a. 89.7% under the following operating conditions: 124 min of residence time, 74.6 wt% WCO/RPO and 12:1 methanol/oil molar ratio. The catalyst kept stable over the 32 h of continuous operation, without noticeable deactivation. Thus, the pelletization of an industrial biomass fly ash, with bifunctional catalytic properties, allowed its application to the FAME production in a continuous regime, with high performance even when high percentages of WCO were used as feedstock.

View all citing articles on Scopus

View full text

Optimization of ultrasonic-assisted heterogeneous biodiesel production from palm oil: A response surface methodology approach

Abstract

Introduction

Section snippets

Materials and chemicals

Catalyst preparation

Experimental design and analysis of variance (ANOVA)

Conclusion

Acknowledgements

Fuel Process. Technol.

Bioresour. Technol.

Bioresour. Technol.

Catal. Today

Bioresour. Technol.

Chem. Eng. J.

Catal. Comm.

Catal. Comm.

Appl. Catal. A

Ultrason. Sonochem.

Renew. Energ.

Biochem. Eng. J.