Abstract
The main purpose of this manuscript is to report the new usage of tea waste (TW) as a catalyst for efficient conversion of palm fatty acid distillate (PFAD) to biodiesel. In this work, we investigate the potential of tea waste char as a catalyst for biodiesel production before and after sulfonation. The activated sulfonated tea waste char catalyst was characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffractometry (XRD), elemental composition (CHNS), nitrogen adsorption-desorption using Brunauer-Emmett-Teller (BET) and ammonia-temperature-programmed desorption (NH3-TPD). The activated tea waste char catalyst shows higher acid density of 31 μmol g−1 as compared to tea waste char of 16 μmol g−1 and higher surface area of 122 m2/g. The optimum fatty acid conversion conditions were found that 4 wt % of catalyst loading with 9:1 of methanol:PFAD for 90 min of reaction time at 65 °C gives 97% free fatty acid (FFA) conversion. In conclusion, the sulfonated tea waste (STW) catalyst showed an impressive catalytic activity towards the esterification of PFAD at optimum reaction conditions with significant recyclability in five successive cycles without any reactivation step.
Highlights
Energy is the key factor of the modern world
Surface area and active acid sites density are the two main factors to determine the level of catalyst activity
It was observed that the treatment of the incomplete carbonized tea waste with the phosphoric acid increased surface area of the TW
Summary
Energy is the key factor of the modern world. Fossil fuel is the leading energy provider among all energy basic sources. Depletion of fossil fuel resources is the hot topic among the energy providers and other stakeholders [1]. Biodiesel has been recognized as a substitute to commercial fuel due to similarity in their characteristics. Biodiesel is a blend of long chain alkyl esters produced through transesterification/esterification reaction of oils or fats with alcohol in the presence of catalyst [2]. The ester production is achieved through transesterification using a homogeneous catalyst i.e., potassium and sodium hydroxide [3]. Hydrochloric and sulfuric acid were used as homogeneous acid catalysts for the esterification process of feedstock containing high free fatty acids (FFA). The disadvantages of homogeneous acid catalysts are saponification or emulsion formation and Materials 2019, 12, 2293; doi:10.3390/ma12142293 www.mdpi.com/journal/materials
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