Research articles
ScienceAsia 50S (2024):ID 2024s002 1-11 |doi:
10.2306/scienceasia1513-1874.2024.s002
Tunable organosulfonic acid-functionalized natural
rubber/wormhole-like mesostructured silica nanocomposites
for enhancing the esterification of carboxylic acids with
methanol
Krongkiat Na Lumphoona, Sukunya Ngampradita, Satit Yousatitb, Toshiyuki Yokoic, Chawalit Ngamcharussrivichaib,d,e, Sakdinun Nuntanga,*
ABSTRACT: Organosulfonic acid-functionalized natural rubber/wormhole-like mesostructured silica (NR/WMS?
SO3H) nanocomposites, which are solid acid catalysts, are used in esterification due to their extensive surface
area, shape-selective characteristics, extremely acidic sites, and hydrophobic behavior. Herein, NR/WMS?SO3H
catalysts with different mesoporosity and acidity values were synthesized via an in-situ sol?gel technique, in which
tetraethylorthosilicate mixed with different primary amines (CnH2n+1NH2
, n = 12, 14, and 16) as structural templating
agents were simultaneously condensed with 3-mercaptopropyl trimethoxysilane in an NR colloidal solution, followed
by oxidation with hydrogen peroxide. The X-ray diffraction analysis and transmission electron microscopy revealed
a wormhole-like framework of the NR/WMS?SO3H composites. The use of amine templates with longer alkyl chains
provided the NR/WMS?SO3H catalysts with a larger pore diameter, acidity, and enhanced hydrophobic properties. This
study exhibited the development and production of customized acidic hybrid mesoporous silica catalysts with specific
characteristics such as mesoporosity, acidity, and hydrophobicity. Moreover, the NR/WMS?SO3H catalysts demonstrated
improved catalytic efficacy in comparison to regular organosulfonic acid?functionalized wormhole-like mesostructured
silica in the esterification of acetic, octanoic, and palmitic acids with methanol. The hydrophobic properties of
the NR/WMS?SO3H composites prevented a readsorption of H2O produced by the esterification. Furthermore, the
mesoporosity and acidity of the NR/WMS?SO3H catalysts might be a crucial factor in enhancing acid conversion
during esterification. Additionally, the NR/WMS?SO3H catalyst has the potential to be regenerated and reused in
the esterification of palmitic acid with methanol.
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| a |
Industrial Chemistry Innovation Programme, Faculty of Science, Maejo University, Chiang Mai 50290 Thailand |
| b |
Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330 Thailand |
| c |
Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 Japan |
| d |
Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University,
Bangkok 10330 Thailand |
| e |
Center of Excellence in Catalysis for Bioenergy and Renewable Chemicals (CBRC), Faculty of Science,
Chulalongkorn University, Bangkok 10330 Thailand |
* Corresponding author, E-mail: Sakdinun.nt@gmail.com
Received 3 Feb 2024, Accepted 24 Sep 2024
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