CSJ 11(2): December, 2020 ISSN: 2276 – 707X Muhammadu and Hamisu ChemSearch Journal 11(2): 15 – 23, December, 2020 Publication of Chemical Society of Nigeria, Kano Chapter Received: 06/08/2020 Accepted: 04/09/2020 http://www.ajol.info/index.php/csj Synthesis of Fatty Acid Methyl Ester (Biodiesel) using Environmentally Benign Catalyst (Yam Peel) Muhammadu Abdulsalam and *Hamisu Umar Farouk Department of Pure and Industrial Chemistry, Bayero University, P.M.B. 3011, BUK, Kano, Nigeria *Correspondence Email: [email protected] ABSTRACT Homogeneous alkali-catalyzed transesterification is the typical process used in biodiesel production, complicating the downstream separation processes and causing oversupply of glycerol as by-product. In this work the synthesis of biodiesel by solid heterogeneous acid catalysts using sulphuric and phosphoric acids functionalized yam peel as catalysts and fried oil as the source of glyceride was investigated. The solid acid catalysts were prepared by carbonization followed by direct sulfonation and phosphoration via reflux. The FTIR Spectra of the catalyst and the XRD confirmed the incorporation of sulphate and phosphate groups on the carbonized yam peels. The amount of catalyst loading was investigated on the biodiesel yield. Sulphuric acid treated catalyst showed highest yield of 62.6 % at 1.0 g catalyst load, with phosphoric acid treated catalyst having slightly lower at 61.2 % and 1.0 g load. The physicochemical analysis of the used oil showed acid value of 27.50 mg KOH/g, free fatty acid (FFA) value of 13.83, density 0.91 g/mL, saponification value 154.28 mgKOH/g. The presence of high free fatty acid in the oil feed indicate that the preferred catalyst to be used is heterogeneous catalyst. Keywords: Acid-catalyst, Carbonization, Phosphoration, Sulfonation, Transesterification INTRODUCTION significantly the emission of carbon dioxide (CO2) Energy is the chief mover of economic on a life cycle basis, carbon monoxide (CO), growth and plays a vital role in sustaining the unburned hydrocarbons and particulate matters by modern economy and society. The future of 78, 46.7, 45.2 and 66.7 %, respectively (Ezebor et economic growth depends on the long-term al., 2014). The likelihood of producing biofuels accessibility to energy from the sources that are from locally grown sources, as an alternative for easily available, safe and affordable. However, various petroleum products is one of the reliable with the increased use and depleting problem of methods of overcoming the energy crisis. Any fossil fuels there is a huge demand for an investments in biofuels will lead to a considerable alternative source of energy which can produce boost in economic development. It is expected that sufficient energy of preferred quality in various with suitable production process, biofuels will forms in a sustainable manner and at competitive produce significantly lesser greenhouse gas prices (Ouda et al., 2016). emissions than fossil fuels (Monisha et al., 2013). In recent years, there has been increased Transesterification is a conventional focus on global warming and the depletion of technique employed for the production of biodiesel. resources caused by the heavy consumption of It is a catalyzed reversible reaction which involves finite fossil resources. In order to resolve these a homogeneous or heterogeneous catalyst to problems, biomass is increasingly gaining produce biodiesel from oleaginous feedstock with international attention as a source of renewable the aid of short-chain alcohol. The triglycerides energy. Biodiesel fuel produced by the (TG) from the feedstock are converted into fatty transesterification of vegetable oils and animal fats acid alkyl esters (FAAEs) referred to as biodiesel is expected to be one of the biomass-based and producing glycerol as the by-product which alternatives to fossil resources due to its can be separated in a decantation funnel overnight renewability, lack of aromatic compounds, high or by centrifugation (Kirubakaran and Selvan, biodegradability, and low sulphur dioxide (SO2) 2018). The overall chemical equation is shown in and particulate matter content (Kawashima et al., the reaction process is shown in Scheme 1. Since 2007). Apart from the processing methods, this process occurs in a liquid-liquid two-phase biodiesel feedstock also requires some conversions system, its rate is constrained by the mass transfer to meet regulatory standards. The application of contributed by immiscibility of oil and alcohol. biodiesel in conventional diesel engines helps to Other factors such as high operating cost and remediate the global warming effect by reducing 15 CSJ 11(2): December, 2020 ISSN: 2276 – 707X Muhammadu and Hamisu energy requirements further limit its performance (Tiwari et al., 2018). Scheme 1: Catalytic Transesterification (Pereira et al., 2014) Catalytic transesterification using production (Endalew et al., 2011). Despite their methanol is the typical method employed for the high catalytic activities, they either suffer from low production of biodiesel due to the fact that acid densities, deactivation in the presence of methanol is relatively cheap and easily accessible. water, small pore size or poor stability (Lou et al., This results in huge production of glycerol as by- 2012). Researchers have reported the synthesis of product, creating the problem of oversupply and water-tolerant catalyst from carbon-bearing declining their market price (Marx, 2016). materials by incomplete carbonization followed by Therefore, manufacturing biodiesel via a novel sulfonation with concentrated sulphuric acid (Toda glycerol-free method can be more favorable to et al., 2005). Various carbon materials such as improve the processing economics and avoid the naphthalene, glucose, starch, cellulose, sucrose, by-production of glycerol. For instance, methyl vegetable oil asphalt are presently being used. A acetate can replace the alcohol reactant in prepared carbon-based catalyst from bagasse and transesterification reaction and form triacetin, a its catalytic activity was tested on the esterification higher added value by-product as compared to of oleic acid with methanol and transesterification glycerol. Catalyst is a crucial element in speeding of waste cooking oil containing a high amount of up the transesterification reaction for biodiesel FFAs 38.6 wt% (Lou et al., 2012). production. Nowadays, the commercial production In general, the catalysts used for of biodiesel makes use of homogeneous catalysts transesterification process can be bases, acids or (Domingues et al., 2013). This increases the overall immobilized enzymes. For the transesterification to operating cost due to downstream processes to give a high yield, the alcohol should be free of recover the catalysts. Thus, heterogeneous catalyst moisture and the free fatty acid content must be is preferable. However, although heterogeneous <0.5 % (Monisha et al., 2013). Transesterification alkaline catalyst offers high catalytic performance, is a reversible reaction but in the production of its activity is affected by feedstock with high free biodiesel, the backward reaction does not take fatty acid (FFA) content due to soap formation place or is negligible because the glycerol formed (Chakraborty et al., 2016). Heterogeneous acidic is immiscible with the product leading to a two- catalyst is suitable to be used under the conditions phase system. of high FFA content and water without soap In this work the synthesis of carbon-based formation (Ezebor et al., 2014). heterogeneous catalyst for both transesterification Solid acid catalysts are gaining a lot of of triglycerides and esterification of free fatty acids attention because of their ease in separation of in biodiesel production was carried out. The product without the need for high consumption of synthesis of solid acid catalysts was from waste energy and elimination of the problems associated yam peels through two methods; by direct with corrosion, toxicity and environmental sulfonation (via reflux by sulfuric acid) and pollution (Dawodu et al., 2014). These kinds of phosphoration (via reflux by phosphoricacid). catalysts are capable of catalyzing simultaneous The effects of operating parameters such esterification and transesterification of FFAs and as acid concentration and amount of catalyst triglycerides present in non-edible vegetable oils loading on the percentage yield of the biodiesel into biodiesel. Solid acid catalysts such as zeolites, was investigated. sulphated zirconia, niobic acid, perfluorosulfonated ionomers are currently being used for biodiesel 16 CSJ 11(2): December, 2020 ISSN: 2276 – 707X Muhammadu and Hamisu MATERIALS AND METHODS weight taken as W1 and then filled with oil sample MATERIALS and recorded as W2 and that of empty bottle was Fresh Yam peels were collected from W3 (Usman et al., 2013). The specific gravity of the Kabuga in Gwale Local government, Kano State, oil was calculated using equation 4. Nigeria, the yam peel sample was washed and dried o W1 – W3 for 48 hours at 60 C. The sample was crushed into Specific gravity = (4) fine powder using mortar and pestle. The fried W2 – W3 cooking oil was obtained at Rigiyar Zaki, Ungogo Catalyst preparation Local Government, Kano State. Phosphoric acid 85 Yam peel powder (10 g) was hydrolyzed % (H PO ), Sulphuric acid 98 % (H SO ), 3 4 2 4 using 200 mL of 1 M NaOH followed by refluxing Methanol (≥99.8 %), 1 M NaOH, distilled water, for 2 h, with repeated washings and filtering the fried oil (awara), Phenolphthalein