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Dry-gel synthesis of Ti-beta for epoxidation of unsaturated fatty acid methyl esters (FAMEs)
(2026-09-01)
Yomthong, Krissanapat
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Saenluang, Kachaporn
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Soyphet, Asadawut
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Ittisanronnachai, Somlak
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Padchasri, Jintara
The Ti-beta was synthesized via a dry-gel conversion approach with the direct incorporation of titanium from titano-aluminosilicate nanobeads (Ti-SiAl-NB). At first, the Ti-SiAl-NB was prepared and employed as the precursor for zeolite crystallization. Powder XRD (PXRD) patterns confirm the amorphous nature of the nanobeads. These Ti-SiAl-NB precursors were subsequently converted to the Ti-beta zeolite via the dry-gel conversion approach. Structural characterization using PXRD, high-resolution TEM, and selected area electron diffraction (SAED) confirmed the formation of a beta zeolite framework, with dominant lattice planes indexed to (101) and (302). UV-vis DRS indicated that Ti existed as a tetrahedrally coordinated (TiIV) and non-framework Ti. Unfortunately, the as-synthesized Ti-beta exhibited a low catalytic activity in methyl oleate (MO) epoxidation, which is attributed to the prevalence of closed site TiIV [Ti(OSi)<inf>4</inf>] species that restrict substrate accessibility to active sites. To address this limitation, a post-synthetic treatment involving framework etching was applied to generate open site TiIV [Ti(OSi)<inf>3</inf>OH] species. As a result, MO conversion increased by approximately 2.73-fold, with epoxide selectivity up to 70%. Catalyst stability tests demonstrated sustained MO conversion of 65–72% and epoxide selectivity above 65% over several consecutive catalytic cycles. This work highlights a sustainable catalyst design strategy that combines the dry-gel conversion process with mild post-treatment to enhance active site accessibility and catalytic performance in the epoxidation of bulky molecules.
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Combination of natural silica and alumina sources for synthesis of MCM-22 zeolite
(2023-08-01)
Tanwongwan, Worapak
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Chollacoop, Nuwong
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Faungnawakij, Kajornsak
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Assabumrungrat, Suttichai
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Nakhanivej, Puritut
Zeolite has become a promising material that can potentially play a pivotal role in resolving environmental crises. Among zeolite families, MCM-22 zeolite shows outstanding intrinsic properties associated with the topology and porous structure, offering ion-exchange advantages for catalytic activity processes. The synthesis of MCM-22 zeolite becomes challenging when concerning the cost and catalytic performance. To overcome this bottleneck, we demonstrate a sustainable route of a hydrothermal process using natural resources as starting materials. Rice husk from agricultural waste was used as a silica source while natural clays (kaolin and bentonite) were applied as alumina sources. The products from natural sources were compared with the use of commercial starting materials, e.g., NaAlO<inf>2</inf> (for alumina) and Na<inf>2</inf>SiO<inf>3</inf> and TEOS (for silica), in points of crystal, compositional, and morphological views. We showed that the high purity of MCM-22 zeolite can be obtained from rice husk silica (RHS) and aluminosilicate gel (ASG) extracted from kaolin, while the use of ASG extracted from bentonite tended to be unsuitable to generate the zeolite formation. We also studied the effects of reaction time and the ratio of RHS/ASG on the crystallinity and surface area of MCM-22. The architecture and acidity of an optimal product were explored by Nuclear magnetic resonance spectroscopy and Temperature-programmed desorption of ammonia, demonstrating the success of achieving well acidity.
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DFT Investigation of the catalytic conversion of acetic acid to acetone on the zeolite H-ZSM5
(2022-12-01)
Konsue, Adchatawut
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Gleeson, M. Paul
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Gleeson, Duangkamol
Biomaterials processing has become increasingly important in the chemical industry. Identification and optimization of processes to facilitate biomass conversion is therefore recognized as being of great importance. Carboxylic acids derived from biomaterials are important building blocks that can be used in a wide variety of industrial applications. As such, methods to process them in an efficient and cost-effective manner are highly desirable. In this study we report the use of theoretical methods to explore the catalytic conversion of acetic acid to acetone on the zeolite H-ZSM5. We have employed a 46T DFT cluster model to explore mechanistic proposals reported in the literature. We investigate the relative energetics associated with the formation of the proposed intermediates, including acyl-zeolite complexes, enols, acylium cations, ketenes, anhydrides, and beta-keto acids, that could potentially connect acetic acid to the desired product, acetone. This assessment would allow us to identify the most probable mechanism connecting the reactant to products. We predict a low energy pathway starting with the generation of a surface acyl, followed by an anhydride, with the rate determining step involving methyl group migration. The reaction is predicted to be bi-molecular and involves C-C bond formation, in line with proposals based on isotopic labelling experiments.
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Direct Synthesis of Liquefied Petroleum Gas from Carbon Dioxide Using a Copper/Zinc Oxide/Zirconia/Alumina and HY Zeolite Hybrid Catalyst
(2021-07-27)
Natakaranakul, Jaru
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Thongkam, Montree
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Li, Hangjie
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Suchamalawong, Phorndranrat
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Tsubaki, Noritatsu
Conversion of CO<inf>2</inf> to lower hydrocarbons (HCs) is a high potential process that could reduce and sustainably control this greenhouse gas. In accord with The Sustainable Development Goal from The United Nation Development Program, liquefied petroleum gas (LPG) is viewed as environmentally friendly and is widely used. Small HCs can be directly synthesized from CO<inf>2</inf> hydrogenation over a hybrid catalyst. The main purpose of this study was to investigate the direct synthesis of LPG from CO<inf>2</inf> hydrogenation using a copper/zinc oxide/zirconium/alumina (CZZA) mixed metal and HY zeolite as a hybrid catalyst. The study was conducted in a fixed bed reactor using hydrogen/CO<inf>2</inf>/carbon monoxide as the reactant gas and evaluating four types of production condition, method of catalyst combination, reaction temperature, CZZA/HY zeolite mass ratio, and catalyst weight/volume flow rate. The mixing type between the CZZA and HY zeolite catalysts markedly influenced the HC selectivity with strong suppression of reverse water gas shift reaction. At the optimum condition, a 27.39 % CO<inf>2</inf> conversion level and a high HC (98.70 %) and LPG (66.56 %) selectivity were obtained.
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Pressure Swing Absorption Oxygen Concentrator equipped with Remote Monitoring Pulse Oximeter
(2021-01-01)
Ongtrakul, Salila
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Thitiratannapong, Anyarin
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Pintavirooj, Chuchart
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Treebupachatsakul, Treesukon
The new COVID-19 disease was first identified in China at the end of 2019 and has spread rapidly all over the world. It has been projected that, by March 2021, the number of infections could reach 300 million cases and over two million deaths. One of the main implications for COVID-19 patients is pneumonia where the lung is infected, hence patients suffering from insufficient oxygen in the blood. As the number of COVID-19 cases have significantly increased, the demand for oxygen generators have also skyrocketed. This research concerns the design and construction of emergency low-cost oxygen concentrators used for mild COVID-19 symptoms, of which are forced to be treated at home. Our absorption-based oxygen concentrator uses zeolite packed in a sieve canister. An Oil-free compressor is then used to pump air in. Zeolite will absorb nitrogen from the air leaving oxygen free to travel towards the outlet. To evaluate the treatment, we have equipped the system with a pulse oximeter to measure the percent saturation oxygen, pulse rate and temperature. To prevent COVID-19 infections between patients and caretakers, we have designed an android application to remotely control the oxygen concentrator. Experiment has shown that our emergency low-cost oxygen concentrator can supply oxygen with an 85% purity rate.

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