Pusat Pengajian Sains Kimia - Tesis
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- PublicationSynthesis Of Silicoaluminophosphate Zeolite Catalysts Directed By Benzyltrimethylammonium Hydroxide Template For The Chemical Production Of Biofuel Additives(2025-08)Wang, GuanchenSilicoaluminophosphate (SAPO) zeolites are very useful catalysts. Usually, they are synthesized with aliphatic quaternary ammonium compounds as organic template. However, benzyltrimethylammonium hydroxide (BTMAOH) containing cyclic functional group as a template has not been studied. Here, the crystallization of SAPO-34 and SAPO-20 zeolites using BTMAOH is studied by following their evolutional formation. The BTMA+ has shown its effective structure-directing and pore-filling roles whereby pure SAPO-34 and SAPO-20 with unique surface properties (surface area, porosity, acidity) are formed after 24 and 42 h at 180 °C. Compared with SAPO-20, SAPO-34 with larger pore size exhibits better catalytic activity (conversion 100%, ethyl levulinate (EL) yield 72.5%) in microwave-assisted furfuryl alcohol (FA) ethanolysis. The spent SAPO-34 catalyst is stable and recyclable, offering it as a cost-effective catalyst for various petrochemical reactions. This work also studies the preparation of hierarchical SAPO-5 using various surfactants, namely dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TP), hexadecyltrimethylammonium bromide (CTA) and hexadecylpyridinium chloride (CP). The results show that these ionic compounds experience interactions with inorganic reagents during crystallization, which in turn altering the morphological (crystal size and shape) and structural (porosity and acidity) properties of SAPO-5. Among hierarchical SAPO-5 samples, TP-SAPO-5 with the highest hierarchical factor (HF = 0.074) and second highest acidity (0.73 mmol·g-1) is the best catalyst for producing ethyl pyruvate (EP) via esterification. After parametric optimization, its performance (conversion 92.0%, selectivity 85.9%) is comparable to homogeneous HCl and H2SO4 catalysts (conversion 88-92%, selectivity 84-92%) and much superior than H-Y, H-MOR, SAPO-34 zeolites (conversion 56-100%, selectivity 67-76%). The hierarchical TP-SAPO-5 is also reusable for up to five reaction cycles, making it as a green and excellent catalyst for biomass product conversion.
- PublicationSynthesis And Mechanistic Study Of Heterojunction Biobr-Based Composites For Antibiotics Photodegradation(2025-08)Sun, YanliPhotocatalysis based on semiconductors has garnered increasing attention due to its potential to utilize solar energy and applications in environmental remediation. Recently, BiOBr has emerged as a promising candidate owing to its non-toxicity, low cost, and distinctive physicochemical properties. However, the fast recombination of electron-hole (e-/h+) pairs in these materials often limits its practical applications. This study aims to explore BiOBr-based semiconductors for the degradation of various antibiotics under visible light. First, two pristine BiOBr photocatalysts (BiOBr-W and BiOBr-EG) were first synthesized using water and ethylene glycol, respectively.
- PublicationKaedah Penyimenan Galvani Untuk Memendakkan Emas Dari Larutan Sianida Pada Grafit(1996-06)Ngah, Che Wan Zanariah Che WanPemulihan emas dari larutan konvensional emas-sianida dengan kaedah penyimenan galvani menggunakan grafit poros sebagai katod dan logam zink sebagai anod akan dihurai. Membran pertukaran kation raipore RAI-4010 digunakan untuk mengelakkan percampuran di antara anolit dan katolit serta litar pintas ion-ion dalam larutan. Eksperimen dilakukan dalam sistem berkelompok (batch system) untuk melihat kecekapan pemulihan emas secara penyimenan galvani. Keputusan yang diperolehi menunjukkan kaedah iru berupaya memulihkan lebih 99% daripada emas dari larutan konvensional emas-sianida yang telah disediakan secara sintetik. Kemuatan awal emas pada grafit dan perubahan ph larutan katolit didapati tidak mempengaruhi peratus pemulihan emas dengan kaedah ini. Manakala kepekatan spesies ion-ion emas, sianida dan kalsium di dalam katolit pula didapati meningkatkan peratus pemulihan emas secara penyimenan galvani ini.
- PublicationKesan Saling Tindakan Antara Molekul Terhadap Kelikatan Bagi N-Alkil Klorida Dan Campuran Alkohol Dan Amina Alifatik(1997-02)Teoh, Soo BeeThe densities and viscosities ofn-alkyl chlorides from pentyl chloride to hexadecyl chloride were determined at temperatures between 15 - 80 oe at 5 oe intervals. The densities increase linearly with temperature and chainlength and their correlation coefficients were better than 0.9999. At constant temperature, the molar volume was a linear function of the number of methylene unit, n, in the chain for the homologous series. A four constants equation correlating the molar volume with the number of methylene units and temperature of the n-alkyl chlorides was formulated excellent agreements between the calculated and measured values of molar volume were obtained. This formula accurately predicted the molar volume and hence the density for all the n-alkyl chlorides at any temperature within the range. The intrinsic volumes of the n-alkyl chlorides were determined by extrapolation of the plot of fluidity against molar volume to zero fluidity. Plots of the logarithm of viscosity versus reciprocal absolute temperature were almost linear. The energies of activation for viscous flow for the n-alkyl chlorides were calculated and found to increase with increase in chainlength.
- PublicationMordenite Zeolites Synthesized From Bamboo Leaves Ash For Acetylation Of Glycerol With Benzaldehyde(2025-08)Gong, JiangtianBamboo leaves ash (BLA) is a cheap and sustainable silica source but under-utilized in industry. Annually, over 20 million tons of bamboo are harvested worldwide, generating about 200,000 tons of leaves waste often disposed of by open burning. Valorizing this waste hence offers an eco-friendly solution to environmental problems. In this work, mordenite and hierarchical mordenite zeolites synthesized from BLA are reported. By carefully studying crystallization conditions, mordenites with three distinct morphologies (nanostick, intergrown bulky ball, nanorod) are successfully synthesized. The mordenite with nanorod shape contains hierarchical micro/mesoporosity, and is the bestcatalyst (80.22.4% conversion, 54.40.3% dioxolane selectivity) among mordenite catalysts prepared in acetalization of benzaldehyde and glycerol.