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Chiang Mai J. Sci. 2014; 41(1) Chiang Mai J. Sci. 2014; 41(1) : 128-137 http://epg.science.cmu.ac.th/ejournal/ Contributed Paper
Biodiesel Production from Palm Oil Using Potassium Hydroxide Loaded on ZrO2 Catalyst in a Batch Reactor Pisitpong Intarapong [a], Sotsanan Iangthanarat [a], Apanee Luengnaruemitchai*[a,b] and Samai Jai-In [c] [a] The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand. [b] Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok 10330, Thailand. [c] The Royal Thai Navy, Bangkok 10700 Thailand. *Author for correspondence; e-mail:
[email protected] Received: 10 July 2012 Accepted: 18 March 2013
ABSTRACT A KOH/ZrO2 catalyst was used as a solid base catalyst for biodiesel production via transesterification of palm oil with methanol using a batch reactor. The catalytic activity of KOH/ZrO2 is associated with the active phase (K2O) and basic properties. The catalysts were characterized by using BET, XRD, SEM, CO2-TPD, and Hammett indicators.The highest methyl ester content of 99% was obtained when the highest basic strength (15< H_ 91%) is obtained when using K species as a precursor. Suppes et al. reported that the decrease in the conversion for Cs compared to that of K on their supports relates to the degree of ion exchange between a precursor and a support [12]. The large size of cesium cations limits the exchange capacity with the oxygen, resulting in less basicity. However, relatively few studies have been carried out on ZrO2 supports in comparison to the Al2O3 system as mention above. Therefore, ZrO2 is a promising candidate with strong potential as a support base catalyst due to its basic features and thermal stability under high calcination temperatures. The aim of this present work focused on the catalytic performance of KOH supported on ZrO2 in a batch reactor under various conditions. The influence of conditions such as catalyst size, reaction time, potassium loading, methanol-to-oil molar ratio, and amount of catalyst on the methyl ester (ME) content was investigated. The fuel properties of the produced biodiesel were also examined. 2. MATERIALS AND METHODS
2.1 Materials Refined palm oil (MW 849.61 kg/kmol) was obtained from the Naval Engineering Command, Thailand. The composition of refined palm oil is shown in Table 1. ZrO2 was obtained from Lab-Scan. Anhydrous methanol (Lab-Scan, 99.95%), potassium hydroxide (Lab-Scan), and sodium sulfate (Fisher Scientific) were used as chemicals for biodiesel production. Methyl heptadecanoate (puriss p.a., standard for GC, 99.7%) and heptane (Fisher Scientific, puriss p.a., 99.5% GC) supplied by Fluka, were used to measure the methyl ester content.
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Table 1. Composition of refined palm oil. Free Fatty Acid Methyl ester (wt%) 0.01 caprylic (C8:0) 0.01 carpic (C10:0) 0.20 Lauric (C12:0) 0.83 Myristic (C14:0) 40.29 Palmitic (C16:0) 3.70 Stearic (C18:0) 43.73 Oleic (C18:1) 10.64 Linoleic (C18:2) 0.19 Linolenic (C18:3) 0.30 Arachidic (C20:0) 2.2 Catalyst Preparation The KOH/ZrO2 catalyst was prepared by the impregnation method. The pore volume was 0.6 ml/g of ZrO2. The ZrO2 support was impregnated with an aqueous solution of KOH at various loadings of K(10 to 40 wt%). The prepared catalysts were dried in an oven at 110°C for 24 h and calcined at 500°C for 3 h. 2.3 Catalyst Characterization A Bruker X-ray diffractometer system (XRD; D8 Advance), equipped with a 2.2 kW Cu anode long fine-focus ceramic X-ray tube for generating CuKα radiation (1.5405 ), was used as the X-ray source to obtain the XRD patterns at running conditions of 40 kV and 40 mA. The detector scans in the 10° to 70° (2θ) range at a scan speed of 0.02° (2θ)/ 0.5 second was utilized. A scanning electron microscope (SEM), JOEL Model JSM 5200, was used to identify the microstructure and capture micrographs of the catalyst morphology. The specific surface area was determined by the Brunauer-Emmet-Teller (BET) method using a Sorptomatic model 1990 instrument (Thermo Finnigan). Before analyzing, the volatile species adsorbed on the surface were eliminated by out gassing at 300°C for 24 h. Helium gas was used as an adsorbate for blank analysis and nitrogen
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gas was used as the adsorbate for sample analysis. The basic strength of the catalysts was determined by using Hammett indicators of bromthymol blue (H_ = 7.2), phenolphthalein (H_ = 9.8), 2,4-dinitroaniline (H_ = 15.0), and 4-nitroaniline (H_ = 18.4). Temperatureprogrammed desorption (CO 2 -TPD), which used CO2 gas as a probe molecule, was used to determine the basic properties of the samples. 2.4 Transesterification A sample of palm oil was weighed and placed in a 500 ml three-necked flask, equipped with a magnetic stirrer (300 rpm) and a reflux condenser, and was heated to 65°C. Next, the modified catalyst and methanol were added to a three-necked flask. The reaction was carried out until it reached the desired reaction time. The reaction was stopped by instantly cooling, and the catalysts were separated from the product mixture by using a suction flask. The biodiesel (top phase) was separated from the glycerol (bottom phase) by using a separatory funnel. The biodiesel was loaded into a rotary evaporator to remove excess methanol. Finally, the methyl esters content was measured by gas chromatography (GC). The methyl ester content was analyzed by GC (HP 5890) with a capillary column of DB-WAX (30 m × 0.25 mm) and equipped with a flame ionization detector. Methyl heptadecanoate was used as an internal standard to determine the amount of methyl ester content. Methyl ester content is defined as follows. (ΣΑ)-AEI CEI ×VEI C= × AEI
m
× 100
where C is methyl ester content or fatty acid methyl ester (FAME). ΣA is the overall area of methyl ester from C12 to C24. AEI is the
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peak area which is aligned with the methyl heptadecanoate solution. CEI is concentration of methyl heptadecanoate solution (mg/ml). VEI is the volume of methyl heptadecanoate solution (ml), and m is the weight of the sample (mg). Mono-, di-, and tri-glyceride levels were determined by high performance liquid chromatography (HPLC) [13]. The fuel properties-flash point, water content, and sulfur content-of the biodiesel product were determined according to EN 14214 standards. 3. RESULTS AND DISCUSSION
3.1 Catalyst Characterization The XRD patterns of ZrO2 and KOH/ ZrO2 with various K loadings are shown in
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Figure 1. The XRD pattern of fresh ZrO2 shows typical diffraction peaks at 2θ = 28°, 31°, 34°, 49°, 50°, 54°, 55°, and 60°, indicating the monoclinic phase of ZrO2. When the K loading was increased from 10 to 15 wt%, the XRD patterns are almost the same as the XRD pattern of pure ZrO2. When the K loading was further increased from 20 to 30 wt%, a new phase was observed at 2θ = 31° which was attributed to the characteristic peaks of K2O. This result agrees with the results of KOH/Al2O3 [14]. With low K loading
