Direct Oxidation of Hibiscus cannabinus Stalks to Vanillin Using CeO2 Nanostructure Catalysts

Biomass lignin can be used to produce vanillin through an oxidation process. Although its purity is high, the processing time and separation efficiency are not ideal. This research aims to produce vanillin directly from Kenaf stalks without separating the lignin first from the lignocellulosic biomas...

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Main Authors: Ramli, A., Khairul Anuar, N.A.S.I., Bakhtiar, N.A.A., Mohamad Yunus, N., Mohamed, A.R.
Format: Article
Published: Multidisciplinary Digital Publishing Institute (MDPI) 2023
Online Access:http://scholars.utp.edu.my/id/eprint/37506/
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spelling oai:scholars.utp.edu.my:375062023-10-04T13:23:07Z http://scholars.utp.edu.my/id/eprint/37506/ Direct Oxidation of Hibiscus cannabinus Stalks to Vanillin Using CeO2 Nanostructure Catalysts Ramli, A. Khairul Anuar, N.A.S.I. Bakhtiar, N.A.A. Mohamad Yunus, N. Mohamed, A.R. Biomass lignin can be used to produce vanillin through an oxidation process. Although its purity is high, the processing time and separation efficiency are not ideal. This research aims to produce vanillin directly from Kenaf stalks without separating the lignin first from the lignocellulosic biomass. This method is greener because it does not require the separation of cellulose and hemicellulose from the biomass, thus minimizing the use of acid and alkaline solutions and saving time. A high oxygen storage capacity and release capacity of ceria as an oxidation catalyst contribute to the reversable redox properties between Ce4+ and Ce3+ in ceria lattice. Cerium oxide nanostructures were synthesized using a hydrothermal method treated under alkaline NaOH, followed by drying at 120 °C for 16 h and calcining at different temperatures between 400 and 600 °C for the direct oxidation of Kenaf stalks to vanillin under microwave irradiation. The catalysts were characterized for their physicochemical properties using XRD, N2 adsorption�desorption isotherms and TEM. All synthesized CeO2 nanostructures showed the presence of diffraction peaks assigned to the presence of cubic fluorite. The N2 adsorption�desorption isotherms showed that all catalysts possess a Type IV isotherm, indicating a mesoporous structure. The TEM image shows the uniform shape of the CeO2 nanostructures, while HRTEM images show that the CeO2 nanostructures are single-crystalline in nature. All catalysts were tested for the direct oxidation of Kenaf stalks using H2O2 as the oxidizing agent in temperatures ranging from 160 to 180 °C for 10�30 min with 0.1�0.3 g catalyst loading under 100�500 W of microwave irradiation. The CeO2-Nps-400 catalyst produced the highest vanillin yields of 3.84 and 4.32 for the direct oxidation of Kenaf stalks and extraction of lignin from Kenaf stalks, respectively. Compared to our earlier study, the highest vanillin yields of 2.90 and 3.70 for direct biomass and extracted lignin were achieved using a Ce/MgO catalyst. © 2023 by the authors. Multidisciplinary Digital Publishing Institute (MDPI) 2023 Article NonPeerReviewed Ramli, A. and Khairul Anuar, N.A.S.I. and Bakhtiar, N.A.A. and Mohamad Yunus, N. and Mohamed, A.R. (2023) Direct Oxidation of Hibiscus cannabinus Stalks to Vanillin Using CeO2 Nanostructure Catalysts. Molecules, 28 (13). ISSN 14203049 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85164847284&doi=10.3390%2fmolecules28134963&partnerID=40&md5=0748f65f1eeefa501aadcd30a8e0d505 10.3390/molecules28134963 10.3390/molecules28134963 10.3390/molecules28134963
institution Universiti Teknologi Petronas
building UTP Resource Centre
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Teknologi Petronas
content_source UTP Institutional Repository
url_provider http://eprints.utp.edu.my/
description Biomass lignin can be used to produce vanillin through an oxidation process. Although its purity is high, the processing time and separation efficiency are not ideal. This research aims to produce vanillin directly from Kenaf stalks without separating the lignin first from the lignocellulosic biomass. This method is greener because it does not require the separation of cellulose and hemicellulose from the biomass, thus minimizing the use of acid and alkaline solutions and saving time. A high oxygen storage capacity and release capacity of ceria as an oxidation catalyst contribute to the reversable redox properties between Ce4+ and Ce3+ in ceria lattice. Cerium oxide nanostructures were synthesized using a hydrothermal method treated under alkaline NaOH, followed by drying at 120 °C for 16 h and calcining at different temperatures between 400 and 600 °C for the direct oxidation of Kenaf stalks to vanillin under microwave irradiation. The catalysts were characterized for their physicochemical properties using XRD, N2 adsorption�desorption isotherms and TEM. All synthesized CeO2 nanostructures showed the presence of diffraction peaks assigned to the presence of cubic fluorite. The N2 adsorption�desorption isotherms showed that all catalysts possess a Type IV isotherm, indicating a mesoporous structure. The TEM image shows the uniform shape of the CeO2 nanostructures, while HRTEM images show that the CeO2 nanostructures are single-crystalline in nature. All catalysts were tested for the direct oxidation of Kenaf stalks using H2O2 as the oxidizing agent in temperatures ranging from 160 to 180 °C for 10�30 min with 0.1�0.3 g catalyst loading under 100�500 W of microwave irradiation. The CeO2-Nps-400 catalyst produced the highest vanillin yields of 3.84 and 4.32 for the direct oxidation of Kenaf stalks and extraction of lignin from Kenaf stalks, respectively. Compared to our earlier study, the highest vanillin yields of 2.90 and 3.70 for direct biomass and extracted lignin were achieved using a Ce/MgO catalyst. © 2023 by the authors.
format Article
author Ramli, A.
Khairul Anuar, N.A.S.I.
Bakhtiar, N.A.A.
Mohamad Yunus, N.
Mohamed, A.R.
spellingShingle Ramli, A.
Khairul Anuar, N.A.S.I.
Bakhtiar, N.A.A.
Mohamad Yunus, N.
Mohamed, A.R.
Direct Oxidation of Hibiscus cannabinus Stalks to Vanillin Using CeO2 Nanostructure Catalysts
author_facet Ramli, A.
Khairul Anuar, N.A.S.I.
Bakhtiar, N.A.A.
Mohamad Yunus, N.
Mohamed, A.R.
author_sort Ramli, A.
title Direct Oxidation of Hibiscus cannabinus Stalks to Vanillin Using CeO2 Nanostructure Catalysts
title_short Direct Oxidation of Hibiscus cannabinus Stalks to Vanillin Using CeO2 Nanostructure Catalysts
title_full Direct Oxidation of Hibiscus cannabinus Stalks to Vanillin Using CeO2 Nanostructure Catalysts
title_fullStr Direct Oxidation of Hibiscus cannabinus Stalks to Vanillin Using CeO2 Nanostructure Catalysts
title_full_unstemmed Direct Oxidation of Hibiscus cannabinus Stalks to Vanillin Using CeO2 Nanostructure Catalysts
title_sort direct oxidation of hibiscus cannabinus stalks to vanillin using ceo2 nanostructure catalysts
publisher Multidisciplinary Digital Publishing Institute (MDPI)
publishDate 2023
url http://scholars.utp.edu.my/id/eprint/37506/
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85164847284&doi=10.3390%2fmolecules28134963&partnerID=40&md5=0748f65f1eeefa501aadcd30a8e0d505
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