Silica-Based Solid Acid Catalyst with Different Concentration of H 2 SO 4 and Calcination Temperature: Preparation and C
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ORIGINAL PAPER
Silica-Based Solid Acid Catalyst with Different Concentration of H2SO4 and Calcination Temperature: Preparation and Characterization Aneu Aneu 1 & Karna Wijaya 1 & Akhmad Syoufian 1 Received: 19 May 2020 / Accepted: 25 September 2020 # Springer Nature B.V. 2020
Abstract Silica-based solid acid catalysts have been successfully prepared and characterized. This research aimed to study the effect of sulfuric acid and calcination temperature on the properties of silica-based solid acid catalyst chemically and physically. The catalyst was synthesized with tetraethyl ortho silicate (TEOS) as precursor of SiO2 through the sol gel method using sulfuric acid (H2SO4) with various concentrations (1 M, 2 M, and 3 M). Next, the gel formed was calcined with various temperatures (500, 600, 700, 800, and 900 °C). The synthesized sample was then tested for total acidity determination and was characterized using various instrumentations: FTIR, XRD, Gas Sorption Analyzer (GSA), and SEM. The total acidity increased with the increasing acid concentration and calcination temperature up to 700 °C. The N2 adsorption-desorption data showed a relatively large surface area 410,97 m2/g which can provide space for catalytic reaction for fatty acids. The catalytic study was carried out for esterification reaction using reflux system to reduce free fatty acids (FFA) content up to 49% and be possibly to be selected as pretreatment step for low grade feedstock biodiesel conversion. Keywords Solid acid catalyst . Mesoporous silica . Tetraethyl ortho silicate . Sulfuric acid . Calcination temperature
1 Introduction Solid acid catalysts have great potential for biodiesel conversion, especially for low-grade feedstocks [1, 2] such as waste cooking oil [3, 4]. Waste cooking oil is categorized as lowgrade feedstocks due to its high free fatty acids (FFA) content. Free fatty acids arise from the hydrolysis of triglycerides from the frying process. Free fatty acids in waste cooking oil are considered as impurities that must be removed by acidcatalyzed esterification as a pretreatment step prior to alkaline catalyzed transesterification [2]. Synthesis of sulfated metal oxide as a solid acid catalyst has been studied for various catalytic reactions [5–7]. This is supported by several advantages of a solid acid catalyst when compared to homogeneous catalysts, which is the ease of separation and its reusability [8]. There are various kinds of acid catalysts that have been used for esterification reactions, such as sulfuric acid * Karna Wijaya [email protected] 1
Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Yogyakarta, Indonesia
(H2SO4). This catalyst belongs to homogeneous catalyst type and has been widely used for esterification of used cooking oil. However, the weakness of the catalyst is that it is corrosive and reactive if it is not treated properly. So that the use of heterogeneous acid catalysts is chosen and has been widely studied for esterification of fatty acids from used cooki
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