This article reviews the purification techniques involved in producing high-purity glycerol in the biodiesel industry. Utilization of glycerol by-products (contains less than 50 wt.% of glycerol and the remaining contents are water, salts, unreacted alcohol and catalyst) in biodiesel production affords greener and less costly processes. Research has focused on several purification steps that are capable of producing high-purity glycerol. Various new techniques for purifying glycerol promise better quality and lower cost and technologies are required to fulfil increasing worldwide demand. Neutralization, ultrafiltration, the use of ion exchange resins, vacuum distillation and other methods have been utilized in single or multiple stages. Recent studies have demonstrated that the combination of more than one technique produces high-purity glycerol (>99.2%). Purifications cost can be as low as 0.149 USD$/kg. For many applications, high-purity glycerol is more useful. In some cases, it is even necessary, particularly in the fields of hydrogen production, methanol production, pharmaceuticals and food additives.

Recently, TiO2/multi-walled carbon nanotube (MWCNT) hybrid nanocatalysts have been a subject of high interest due to their excellent structures, large surface areas and peculiar optical properties, which enhance their photocatalytic performance. In this work, a modified microwave technique was used to rapidly synthesise a TiO2/MWCNT nanocatalyst with a large surface area. X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller measurements were used to characterise the structure, morphology and the surface area of the sample. The photocatalytic activity of the hybrid nanocatalysts was evaluated through a comparison of the degradation of methylene blue dye under irradiation with ultraviolet and visible light. The results showed that the TiO2/MWCNT hybrid nanocatalysts degraded 34.9% of the methylene blue (MB) under irradiation with ultraviolet light, whereas 96.3% of the MB was degraded under irradiation with visible light.

X-Ray photoelectron spectroscopy (XPS) and Temperature-programmed Reduction (TPR) of 2%(Ru_1/2-Sn_1/2)/Al₂O₃ prepared by the microwave-assisted method have been studied. 2%(Ru_1/2-Sn_1/2)/Al₂O₃ have previously been evaluated as a catalyst in the reduction reaction of 4-nitrophenol. XPS and TPR studies of 2%(Ru_1/2-Sn_1/2)/Al₂O₃ was performed to confirm the metal state of Ru and Sn and reducibility of the sample, respectively. XPS data suggested that the formation of metal Ru(0) and Sn(0) in all samples. The XPS spectra of Ru 3p_3/2 and Sn 3d_5/2 shows binding energy peak at ~ 461.0 ± 0.2 eV and ~ 484,1 eV, respectively. The correlation of TPR and XPS characterization will be discussed further.

X-Ray photoelectron spectroscopy (XPS) and Temperature-programmed Reduction (TPR) of 2%(Ru_1/2-Sn_1/2)/Al₂O₃ prepared by the microwave-assisted method have been studied. 2%(Ru_1/2-Sn_1/2)/Al₂O₃ have previously been evaluated as a catalyst in the reduction reaction of 4-nitrophenol. XPS and TPR studies of 2%(Ru_1/2-Sn_1/2)/Al₂O₃ was performed to confirm the metal state of Ru and Sn and reducibility of the sample, respectively. XPS data suggested that the formation of metal Ru(0) and Sn(0) in all samples. The XPS spectra of Ru 3p_3/2 and Sn 3d_5/2 shows binding energy peak at ~ 461.0 ± 0.2 eV and ~ 484,1 eV, respectively. The correlation of TPR and XPS characterization will be discussed further.

Preparation method plays an important role to produce and improve the properties of materials. Microwave-assisted preparation method has developed rapidly as a benign preparation procedure due to its fast and uniform heating mechanisms. To study the effect of preparation method, bimetallic Ru-Sn based catalyst has been synthesized by using conventional and microwave impregnation methods. In this study, microwave power used was 700 W. Metallic reduction process of ion Run+ and Snn+ were monitored using UV-Vis spectrometer. Samples were then characterized using XRD, SEM and TEM. According to TEM results, morphology of catalyst strongly depends on the preparation route and stabilizing agent. Sample with PVP (polyvinyl pyrrolidone) has better metallic nanoparticles distribution. The sample prepared by conventional method shows agglomeration of nanoparticles on the support. Catalytic activities of both samples were examined in reduction reaction of pollutant, i.e. 4-nitrophenol. The catalytic examination has shown that reaction rate of 4-nitrophenol reduction by using microwave-assisted sample has improved 3.5 times faster than conventional impregnation sample.   Keywords: microwave, bimetallic, nanomaterial, Ruthenium-Tin, catalyst