Abstract
Natural silica has advantages in various fields such as catalysts, because it is easily obtained and applied in the chemical reaction process. The synthesis of natural silica-based magnetic acid catalyst, MSNP/SO42- aims to obtain a large yield from the reaction process between oleic acid and methanol to form methyl ester. Natural silica obtained from geothermal waste was washed with distilled water, then sol gel method was applied at pH of 4-6 to obtain SiO2 nanoparticles. FeCl3 was added to achieve the magnetic properties, and the cetyl trimethyl ammonium bromide (CTAB) is varied in order to attain optimal mesoporous size. Brunauer emmet teller (BET) results showed optimum results from 1: 2 molarity ratio between silica and CTAB with a surface area of 520.94 m2/g. The acidic properties were obtained by immersion using H2SO4 0.5 M. The catalyst were tested for the acidic and magnetic properties using temperature programmed desorption ammonia (TPD-NH3) and vibrating sample magnetometer (VSM) characterization resulting intotal acidity of 0.2488 mmol/g and. softmagnetic type, respectively. The BET surface area of the sulfate modified into MSNP/SO42-, was decreased by 114.44 m2/g. Application of MSNP/SO42- as a catalyst for forming methyl esters obtained a percentage of 85.41% yield based on the gas chromatography mass spectrometry (GC- MS) results.
Highlights
Silica is an inorganic material that is abundantly available in nature
We report the synthesis dan characterization of magnetic silica nanoparticles (MSNP) its sulfated form (MSNP/SO42-) derived from geothermal silica sludge
The catalyst based on sulfated magnetic silica nanoparticles was applied for the esterification of methanol and oleic acid whereas it was expected to provide a high percentage of total methyl esters observed using Gas Chromatography Mass Spectrometry (GC-MS)
Summary
Silica is an inorganic material that is abundantly available in nature. The synthesis of silica can be conducted by utilizing geothermal sludge as the precursor using the sol-gel method [1]. Silica magnetite can be obtained by two approaches, the encapsulation of iron oxide into silica shell and the immobilization of nanoparticles into silica surface using sol-gel method [4]. Another study showed that magnetic mesoporous silica nanoparticles using CTAB and TEOS as the precursor generated a surface area of 78.319 m2/g with a particle size of 7.44 nm [7]. To generate the heterogeneous acid catalyst, sulfonation or sulfated method may be applied for the mesoporous material. The nanoparticles were modified from iron salt and CTAB via the sol-gel method and modified by sulfuric acid to obtain the acid catalyst. The catalyst based on sulfated magnetic silica nanoparticles was applied for the esterification of methanol and oleic acid whereas it was expected to provide a high percentage of total methyl esters observed using GC-MS
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