Methyl transesterification of waste cooking oil using a laboratory synthesized reusable heterogeneous base catalyst: Process optimization and homogeneity study of catalyst Meena Yadav, Veena Singh, Yogesh C. Sharma ⇑ Department of Chemistry, Indian Institute of Technology (Banaras Hindu University) Varanasi, Varanasi 221005, India article info Article history: Received 17 April 2017 Received in revised form 7 June 2017 Accepted 8 June 2017 Keywords: Biodiesel Homogeneous contribution Leaching Potassium impregnated zinc oxide Transesterification Waste cooking oil abstract A novel heterogeneous base catalyst, potassium impregnated zinc oxide was synthesized via precipita- tion method. It was modified by impregnation method and was used for synthesis of biodiesel using waste cooking oil as feedstock. The synthesized catalyst was characterized using various sophisticated techniques. The catalyst having a K/Zn atomic ratio of 60:40 was calcined at 900 °C, provided the highest catalytic activity. Effect of different reaction parameters on biodiesel conversion efficiency were scruti- nized. The experimental results showed that highest biodiesel conversion of 98% was achieved at opti- mized reaction conditions, at catalyst loading of 2.5 wt%, oil: methanol molar ratio of 1:18, 600 rpm and 65 °C for 50 min reaction time. Kinetics of the transesterification reaction was studied at varying reaction temperature (45–65 °C) and the reaction marked the highest rate constant at 65 °C. The activa- tion energy of the reaction was 14.54 kJ/mol. The reusability and homogeneous contribution of the cat- alyst was examined and it was investigated that leaching of active components from catalyst into the reaction media was responsible for catalyst deactivation and homogeneity. The synthesis of biodiesel was ascertained by ATR-FTIR and NMR ( 1 H and 13 C) analysis. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Energy is a critical input for global socio-economic develop- ment. As indicated by International Energy Agency (IEA-2014), energy demand up to 81.7% was contented by fossil fuel reservoirs especially by petroleum, coal and natural gas and has been expand- ing day by day [1,2]. During 1971–2001, world energy consump- tion has been doubled and at end of the year 2030, it will increase through 53% [3]. The price instability of fossil fuels in the world market and contribution to environmental deterioration in term of global warming necessitate the clean and sustainable diversification of conventional fuel [4]. Moreover, uneven distribu- tion of fossil fuel over the world also promotes countries to search some alternative sources of fuel for socio-economic independence [5]. According to World Energy Outlook (WEO) report, the energy scenario of India represents gloomy data as domestic production of crude petroleum satisfies only 18% of national requirement, while the rest nearly 172 million tones is met from imported crude petroleum (MoPNG, 2012) [3,6]. Reports of IEA-2013 indicate that India’s primary energy demand will increase from 750 Mtoe in 2011 to 1258–1647 Mtoe in the 2035 year [7]. For developing countries such as India, it is obligatory to search some environ- mental benign alternatives, particularly for petroleum products, in order to sustain continued energy supply and foreign exchange savings. In this context, energy derived from biomass based resources i.e. biofuels is appraised as most propitious alternative source due to its wide availability and cost effective nature [6]. Biodiesel, a potential substitute to petroleum diesel can be applied in existing internal combustion and ignition diesel engines without any modifications for low blends of 5–30% with petroleum diesel [8,9]. It is a clean burning, high energy return (90%), oxy- genated (10%), low hydrocarbon aroma and sulphur free fuel [10,11]. American society for testing and materials (ASTM) defines biodiesel as ‘‘the monoalkyl esters of long chain fatty acids derived from the renewable liquid feedstock, such as vegetable oils and animal fats, for use in compression ignition (CI) engines” [12]. The current feedstocks for commercial production of biodiesel are food based virgin oils such as soybean, rapeseed, corn, sun- flower, peanut and palm oil that contributes worldwide instability of food reserves and safety. Also, the higher prices of feedstock than conventional petroleum based diesel fuel are other major impediments in commercialization of biodiesel [13,14]. Alves et al. [15] and Farooq et al. [16] deliberated that the cost of feed- http://dx.doi.org/10.1016/j.enconman.2017.06.024 0196-8904/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: ysharma.apc@iitbhu.ac.in (Y.C. Sharma). Energy Conversion and Management 148 (2017) 1438–1452 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman