Synthesis by Precipitation and Characterisation of Antimony Tetraoxide

Antimony oxide has found application in various area including clarification, pigment, material synthesis and catalyst. This study investigated the influence of synthesis parameters (precipitating agent and solvent) on the formation of antimony oxide powder. Characterizations of the samples were carried out by Thermogravimetry Analysis (TGA), X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, BET surface area measurement and Scanning Electron Microscopy (SEM). Investigations on the influence of the type of precipitating agents (NaOH and NHIOH), on the formation of antimony oxide revealed that a-Sb204 was produced after the precursors were calcined. The precursors were a mixture of Sb40sC12 and Sb203 phase when precipitated with NaOH but only Sb203 phase when precipitated with NH40H. By varying the two precipitation agent, NH40H solution gave better surface areas and fine morphologies for the samples compared to NaOH solution. On the influence of solvent, ethanol gave full reflection of Sb203and different structure phase before calcination process. No phase of the antimony oxy chloride was obtained for these samples. After calcined process, all samples gave full reflection of the a-Sb204. Usage of the NaOH as a precipitating agent gave higher surface area compared to NH40H samples

Heterogeneous gold and palladium based catalysts for solvent-free oxidation of toluene

Catalyzed oxidation of aromatic hydrocarbons with molecular oxygen has been studied for several decades. For example, toluene can be converted into oxidation products such as benzyl alcohol, benzaldehyde, benzoic acid and benzyl benzoate. At present, the principal industrial production of benzoic acid via the oxidation of toluene involves the use of homogeneous cobalt catalysts in an air pressurized aqueous acetic acid mixture in the presence of Mn ions. However, the use of solvent causes difficulties in the separation of catalysts and products, equipment corrosion, and due to the environmental hazards associated with the use of liquid acids as solvent. Developing solvent free toluene oxidation having great activity has attracted special attention as a promising environmentally friendly reaction. Recently, gold based supported catalyst have been found to be highly effective oxidation catalyst where a number of important discoveries have been made such as in hydrogen peroxide synthesis and selective oxidation of alcohols to aldehydes. As a proof of concept for the following studies, oxidation of toluene and other aromatic hydrocarbons were carried out in round bottom flask with TBHP as oxidant. At mild condition (80 ºC), it was evident that Au-Pd supported catalyst is capable of oxidising aromatics C-H bonds on toluene and derivatives and TBHP as oxidant also have been discovered well in this thesis. The catalyst preparation method was shown to be very important in the formation of active site catalysts. The sol-immobilisation catalyst with a narrow distribution of small particles, was more active than Au-Pd alloy having Au-core palladium shell with PdO dominance on the surface via impregnation catalyst. In addition to that, the choice of support is crucial and this study discovered carbon as a preferred support give enhance on performance activity of toluene. At the same time, the distribution of products can be altered with the choice of preparation methods and support. The synergistic effect of Au and Pd was confirmed by superior catalytic activity compared to monometallic catalyst. Investigations of reaction conditions such as reaction time, reusability, pre-treatment conditions, metal ratio, and mass of catalyst were fully investigated. It was found that the activity and selectivity of the catalyst was highly dependent on these variables. Reaction mechanism was proposed and it was based on catalytic evaluation data. Even though, the proposed mechanism was contradicted by the EPR data study, it was believed that the reactive oxygen species (ROS) was involved in the surface of catalyst and give effect of the catalytic activity. Overall, the oxidation of toluene was successfully studied by using Au-Pd supported catalyst and can not be denied that the importance of TBHP as oxidant involve in this process has been proven.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Heterogeneous gold and palladium based catalysts for solvent-free oxidation of toluene

Catalyzed oxidation of aromatic hydrocarbons with molecular oxygen has been studied for several decades. For example, toluene can be converted into oxidation products such as benzyl alcohol, benzaldehyde, benzoic acid and benzyl benzoate. At present, the principal industrial production of benzoic acid via the oxidation of toluene involves the use of homogeneous cobalt catalysts in an air pressurized aqueous acetic acid mixture in the presence of Mn ions. However, the use of solvent causes difficulties in the separation of catalysts and products, equipment corrosion, and due to the environmental hazards associated with the use of liquid acids as solvent. Developing solvent free toluene oxidation having great activity has attracted special attention as a promising environmentally friendly reaction. Recently, gold based supported catalyst have been found to be highly effective oxidation catalyst where a number of important discoveries have been made such as in hydrogen peroxide synthesis and selective oxidation of alcohols to aldehydes. As a proof of concept for the following studies, oxidation of toluene and other aromatic hydrocarbons were carried out in round bottom flask with TBHP as oxidant. At mild condition (80 ºC), it was evident that Au-Pd supported catalyst is capable of oxidising aromatics C-H bonds on toluene and derivatives and TBHP as oxidant also have been discovered well in this thesis. The catalyst preparation method was shown to be very important in the formation of active site catalysts. The sol-immobilisation catalyst with a narrow distribution of small particles, was more active than Au-Pd alloy having Au-core palladium shell with PdO dominance on the surface via impregnation catalyst. In addition to that, the choice of support is crucial and this study discovered carbon as a preferred support give enhance on performance activity of toluene. At the same time, the distribution of products can be altered with the choice of preparation methods and support. The synergistic effect of Au and Pd was confirmed by superior catalytic activity compared to monometallic catalyst. Investigations of reaction conditions such as reaction time, reusability, pre-treatment conditions, metal ratio, and mass of catalyst were fully investigated. It was found that the activity and selectivity of the catalyst was highly dependent on these variables. Reaction mechanism was proposed and it was based on catalytic evaluation data. Even though, the proposed mechanism was contradicted by the EPR data study, it was believed that the reactive oxygen species (ROS) was involved in the surface of catalyst and give effect of the catalytic activity. Overall, the oxidation of toluene was successfully studied by using Au-Pd supported catalyst and can not be denied that the importance of TBHP as oxidant involve in this process has been proven

Synthesis and characterization of Fe2O3/CaO derived from Anadara Granosa for methyl ester production

Taufiq Yap Yun Hin/ Mohd Izham Saiman/ / Ibrahim M. Lokman In this study, the iron (III) oxide (Fe2O3) doped on natural CaO catalyst (Fe2O3/CaO) was prepared and utilized in biodiesel production from used frying oil by a single-step reaction process. The heterogeneous Fe2O3/CaO catalyst was synthesized using impregnation method; followed by calcination at 500 °C. The catalyst was characterized in detail by both qualitative and quantitative methods such as X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM), thermal gravimetric analysis (TGA), ammonia and carbon dioxide-temperature programmed desorption (NH3-TPD and CO2-TPD), and Brunauer-Emmett-Teller (BET) analyses. The operating parameters such as molar ratio of methanol, catalyst amount and reaction time were investigated in order to optimize the reaction condition for the biodiesel production. As a result, the optimum reaction parameters found were 15:1 methanol-to-oil molar ratio, 65 °C reaction temperature, 3 h of reaction time and 1 wt.% of the Fe2O3/CaO. The reported results revealed suggestively high potential of the heterogeneous Fe2O3/CaO catalyst for direct conversion of used frying oil to biodiesel-with the possibility to reuse at least 5 reaction cycles without any reactivation process

Effect of Gelatin-Stabilized Copper Nanoparticles on Catalytic Reduction of Methylene Blue

The synthesis of copper nanoparticles was carried out with gelatin as a stabilizer by reducing CuSO4.5H2O ions using hydrazine. Ascorbic acid and aqueous NaOH were also used as an antioxidant and pH controller, respectively. The effects of NaOH, hydrazine, and concentration of gelatin as stabilizer were studied. The synthesized copper nanoparticles were characterized by UV-vis spectroscopy, XRD, zeta potential measurements, FTIR, EDX, FESEM, and TEM. The formation of CuNPs@Gelatin is initially confirmed by UV-vis spectroscopic analysis with the characteristic band at 583 nm. XRD and TEM reports revealed that CuNPs@Gelatin (0.75 wt.%) is highly crystalline and spherical in shape with optimum average size of 4.21 ± 0.95 nm. FTIR studies indicated the presence of amide group on the surface of the CuNPs indicating the stability of CuNPs which is further supported by zeta potential measurements with the negative optimum value of −37.90 ± 0.6 mV. The CuNPs@G4 showed a good catalytic activity against methylene blue (MB) reduction using NaBH4 as a reducing agent in an aqueous solution. The best enhanced properties of CuNPs@G4 were found for the 0.75 wt.% gelatin concentration. Thermodynamic parameters (ΔH and ΔS) indicate that under the studied temperature, the reduction of MB by CuNPs@G4 is not feasible and had endothermic in nature

Electrochemical reduced graphene oxide-poly(eriochrome black T)/gold nanoparticles modified glassy carbon electrode for simultaneous determination of ascorbic acid, dopamine and uric acid

This work reports on the preparation of electrochemically reduced graphene oxide (ERGO)-poly(eriochrome black T) (pEBT) assembled gold nanoparticles for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA) in PBS pH 6.0. Characterisations of the composite were carried out by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. As a result of the synergistic effect, the modified glassy carbon electrode (GCE) possessed an efficient electrochemical catalytic activity with a high selectivity and sensitivity in oxidising AA-DA and DA-UA as compared to the bare GCE. The peak separations of AA and DA, DA and UA were 183 mV and 150 mV, respectively. The linear response ranges for AA, DA and UA were 10–900 μM, 0.5–20 μM and 2–70 μM with detection limits of 0.53 μM, 0.009 μM and 0.046 μM (S/N = 3), respectively. The sensitivity of ERGO-pEBT/AuNPs was measured as 0.003 µA/μM, 0.164 µA/μM and 0.034 µA/μM for AA, DA, and UA, respectively. The modified electrochemical sensor was used in the determination of AA, DA, and UA in vitamin C tablets and urine sample with good recovery

Preparation, characterization and catalytic activity of biomaterial-supported copper nanoparticles

Synthesis of copper nanoparticles was carried out with nanocrystalline cellulose (NCC) as a support by reducing CuSO4·5H2O ions using hydrazine. Ascorbic acid and aqueous NaOH were also used as an antioxidant and pH controller, respectively. The synthesized copper nanoparticles supported on NCC (CuNPs@NCC) were characterized by UV–vis, XRD, TEM, XRF, TGA, DSC, N2 adsorption-desorption method at 77 K and FTIR. The UV–vis confirmed the formation and stability of the CuNPs, which indicated that the maximum absorbance of CuNPs@NCC was at 590 nm due to the surface plasmon absorption of CuNPs. Morphological characterization clearly showed the formation of a spherical structure of the CuNPs with the mean diameter and standard deviation of 2.71 ± 1.12 nm. Similarly, XRD showed that the synthesized CuNPs@NCC was of high purity. The thermal analysis showed that the CuNPs@NCC exhibited better thermal behaviors than NCC. BET surface area revealed that the N2 adsorption–desorption isotherms of CuNPs@NCC featured a type IV isotherm with an H3 hysterisis loop. This chemical method is simple, cost effective, and environmentally friendly. Compared to NCC-supported CuNPs and unsupported CuNPs, the as-prepared CuNPs@NCC exhibit a superior catalytic activity and high sustainability for the reduction of methylene blue with NaBH4 in aqueous solution at room temperature. The CuNPs@NCC achieved complete reduction of MB with completion time, rate constant and correlation coefficient (R 2) of 12 min, 0.7421 min−1 and 0.9922, respectively

Sulfonated functionalization of carbon derived corncob residue via hydrothermal synthesis route for esterification of palm fatty acid distillate

Low-cost biodiesel was successfully produced through esterification of the high-free fatty acid (FFA) feedstock of palm fatty acid distillate over corncob residue-derived heterogeneous solid acid catalyst. Sulfonated functionalized carbon derived from corncob was synthesized via hydrothermal carbonization followed by chemical activation using concentrated H2SO4. The hydrothermal carbonization technique allows efficient carbonization because it is able to maintain active polar species in the corncob. H2SO4 activation can effectively improve the acid strength of HTC-S catalyst. The HTC-S catalyst was optimized via the OVAT technique, and 92% FFA with a FAME yield of 85% was achieved at optimum conditions of 2 h reaction time, 70 °C reaction temperature, 3wt.% catalyst loading, and 15:1 methanol-to-oil molar ratio. Regeneration of the reused HTC-S catalyst via H2SO4 treatment was an effective technique to maintain catalyst stability

Synthesis of bimetallic gold-pallidum loaded on carbon as efficient catalysts for the oxidation of benzyl alcohol into benzaldehyde

A series of catalysts consisting of palladium and gold nanoparticles loaded on carbon (Au-Pd/C) were synthesized and evaluated for the liquid phase oxidation of benzyl alcohol to benzaldehyde. These catalysts were prepared via two procedures: impregnation and sol immobilization. They were characterized by using a transmission electron microscope, a thermogravimetric analyzer, a surface area analyzer, and ammonia temperature-programmed desorption. The catalysts were evaluated for the oxidation of benzyl alcohol via a heterogeneous catalyst and 35% hydrogen peroxide as an oxidizing agent without the use of solvents. The experimental conditions and parameters, such as the effect of the preparation procedure, catalyst mass, temperature, time and the hydrogen peroxide ratio to benzyl alcohol oxidation, were optimized to obtain the optimum conversion percentage. Au-Pd/C prepared by sol immobilization showed excellent performance. A Fourier-transform infrared spectroscope was utilized to confirm the oxidation conversion of benzyl alcohol into benzaldehyde. Our result revealed the very facile and practical oxidation of benzyl alcohols with H2O2 under mild conditions and produced products with a high conversion rate within a short time with excellent performance for five cycles. With the advantage of using cost-effective H2O2 and the formation of water as a coproduct, the synthesized Au-Pd/C catalysts used in this work met the criteria for “green chemistry”