Properties of Jatropha seed oil from Northeastern Thailand and its transesterification catalyzed by potassium supported on NaY zeolite
Introduction
Biodiesel is interesting as an alternative fuel because it is renewable, environmental benign, non-toxic, and biodegradable. It generates lower emission gases from combustion such as CO2, NOx, hydrocarbon particles [1], [2], [3]. Biodiesel can be produced from renewable sources such as vegetable oils, animal fats and waste cooking oils by transesterification [1], [2]. However, the fact that edible oils from sources such as palm and soybean are valuable as food supplies makes them less interesting as feed stocks for the biodiesel production. Consequently, oils from non-edible crops like Jatropha Curcas have gained attention for this purpose. J. Curcas is a drought resistant shrub grown well in Asia and Africa. Because it grows quickly with high-seed yield and high oil content, it is easy to establish as an oil source for biodiesel [4]. Because J. Curcas is also cultivated widely in our province, Nakhon Ratchasima which is in the northeastern part of Thailand, Jatropha seed oil was used in our work. The composition and properties of the oil should be investigated before using as a source for transesterification.
The transesterification or alcoholysis is a reaction between triglyceride from vegetable oils or animal fats and alcohol such as methanol in the presence of a catalyst such as homogeneous base (NaOH, KOH) or acid (H2SO4, HCl). As shown in Scheme 1, the products are esters (biodiesel) and glycerol [5].
In general, alkaline homogeneous catalysts provide good catalytic activity but a large amount of water is required for a removal of the catalyst, generating a large amount of wastewater. Therefore, heterogeneous catalysts are studied because the catalyst separation from the biodiesel product is simple and washing water is not required [6], [7]. In this work we investigated biodiesel production from Jatropha seed oil over heterogeneous catalysts containing potassium supported on zeolite Y, one of aluminosilicate materials with faujasite (FAU) structure.
Zeolites have been used as a support material for transesterification catalysts [8], [9], [10] and as a catalyst for esterification [11]. Suppes et al. [8] compared potassium and cesium-exchanged NaX (also in the FAU family) with NaOx/NaX obtained by loading sodium acetate or sodium azide on NaX and calcination at 500 °C. For transesterification of soybean oil at 60 °C for 24 h, the NaX exchanged potassium and cesium gave methyl ester yields of 10.3% and 7.3%, respectively, much lower than that from the NaOx/NaX which gave more than 80% yields. Because the occluded sodium oxide species were incorporated into NaX zeolites, the base strength and number of basic sites were increased compared to the parent NaX zeolite. Xie et al. [9] achieved a conversion of 85.6% at 65 °C for methyl esters at 8 h residence time using NaX zeolite loaded with KOH. Noiroj et al. [10] employed KOH loaded on Al2O3 and NaY zeolite as the catalysts for transesterification of palm oil with methanol. The 25 wt% KOH/Al2O3 and 10 wt% KOH/NaY showed good performance, at temperature below 70 °C within 2–3 h giving the biodiesel yield of 91.07%. However, high loading of KOH impacted the crystalline structure of zeolite causing collapses. For heterogeneous catalysis, it is necessary to maintain the pore structure of the support after loading with metal [9]. In this work, the other K precursor, CH3COOK in buffer solution pH ∼ 5 was used to produce the catalyst with preservation of the NaY structure.
The objective of this study was to develop an efficient catalytic process using a K/NaY zeolite catalyst with high activity for the production of biodiesel from Jatropha seed oil. The effect of the reaction variables including the ratio of methanol to oil, the reaction time and the amount of potassium loading on zeolite were also investigated.
Section snippets
Oil extraction and characterization
Jatropha seeds were collected from Field Crops in Chokchai District, Nakhon Ratchasima, dried, ground and extracted by hexane with a ratio of 1:4 (w/v) for 3 h. The extracted oil was filtered and the moisture was removed using anhydrous sodium sulfate (Na2SO4). The fatty acid composition of methyl esters and physical and chemical properties of the Jatropha seed oil were characterized by Industrial Metrology and Testing Service Centre, Thailand Institute of Scientific and Technological Research
Composition and properties of Jatropha seed oil
The fatty acid composition of the Jatropha seed oil is presented in Table 1. The major components were unsaturated fatty acids including oleic acid (C18:1) and linoleic acid (C18:2). Jatropha seed oil also consisted of saturated fatty acids, mainly palmitic acid (C16:0) and stearic acid (C18:0). Chemical characteristics of Jatropha seed oil are given in Table 2. The fatty acid composition and physicochemical properties of Jatropha seed oil from this work are similar to those reported in the
Conclusion
The extracted oil from Jatropha seed contained high amount of unsaturated fatty acids and it has potential as a biodiesel feed stock for biodiesel production via transesterification. Potassium supported on NaY zeolite as a heterogeneous catalyst can be prepared by impregnation of NaY with a solution buffer of potassium to keep the structure of NaY. In transesterification of Jatropha seed oil to biodiesel using xK/NaY, the 12K/NaY catalyst showed the best catalytic activity. The highest yield of
Acknowledgement
Funding for this research was from Suranaree University of Technology and scholarship for N. Supamathanon was from Rajamangala University of Technology Isan, Thailand.
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