Thongthai Witoon

Biodiesel production from transesterification of palm oil with methanol over CaO supported on bimodal meso-macroporous silica catalyst

Calcium oxide-loaded porous materials have shown promise as catalysts in transesterification. However, the slow diffusion of bulky triglycerides through the pores limited the activity of calcium oxide (CaO). In this work, bimodal meso-macroporous silica was used as a support to enhance the accessibility of the CaO dispersed inside the pores. Unimodal porous silica having the identical mesopore diameter was employed for the purpose of comparison. Effects of CaO content and catalyst pellet size on the yield of fatty acid methyl esters (FAME) were investigated. The basic strength was found to increase with increasing the CaO content. The CaO-loaded bimodal porous silica catalyst with the pellet size of 325μm achieved a high %FAME of 94.15 in the first cycle, and retained an excellent %FAME of 88.87 after five consecutive cycles.

Direct synthesis of dimethyl ether from CO2 hydrogenation over Cu–ZnO–ZrO2/SO42−–ZrO2 hybrid catalysts: effects of sulfur-to-zirconia ratios

Sulfated zirconia catalysts were prepared by a direct sulfation method and were admixed with a CuO–ZnO–ZrO2 catalyst for the direct synthesis of DME from CO2 hydrogenation. The effects of sulfur-to-zirconia ratios on the physicochemical properties, activity, selectivity and stability of the catalysts were investigated. The sulfur loading content significantly influenced the structure and surface chemistry of the catalysts. The addition of a small amount of sulfur (5–15 wt%) created numerous mesopores on the catalyst surface, remarkably enhancing the surface area and total pore volume. However, at high sulfur loading (20–30 wt%), the mesopores tended to merge and form a larger pore. The detailed characterization by FT-IR, XANES and NH3-TPD reveals that the sulfated zirconia with low sulfur content (5–10 wt%) mainly contained weak acid sites and acted as Lewis acids. Increasing the sulfur loading (15–30 wt%) resulted in the formation of Bronsted acid sites, thus increasing the acid strengths. The sulfated zirconia catalyst with 20 wt% sulfur loading achieved a superior DME productivity of 236 gDME kgcat−1 h−1 at a reaction temperature and pressure of 260 °C and 20 MPa. However, after 75 h of a time-on-stream experiment, the sulfated zirconia catalyst lost approximately 16.9% of its initial activity while a commercial H-ZSM-5 catalyst was more stable as only a 2.85% reduction was observed.

Impact of pore characteristics of silica materials on loading capacity and release behavior of ibuprofen

Impact of pore characteristics of porous silica supports on loading capacity and release behavior of ibuprofen was investigated. The porous silica materials and ibuprofen-loaded porous silica materials were thoroughly characterized by N2-sorption, thermal gravimetric and derivative weight analyses (TG-DTW), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) to determine the physical properties of materials, amount of ibuprofen adsorbed and position of ibuprofen. The detailed characterization reveals that the ibuprofen molecules adsorbed inside the mesopores. Increasing the mesopore size from 5nm to 10nm increased the ibuprofen loading from 0.74 to 0.85mmol/g, respectively. Incorporation of macropore into the structure of porous silica materials enhanced the ibuprofen loading capacity of 11.8-20.3%. The ibuprofen-loaded bimodal meso-macroporous silica materials exhibited the highest dissolution of 92wt.% within an hour. The ibuprofen particles deposited on the external surface of the porous silica materials showed a lower dissolution rate than the ibuprofen adsorbed inside the mesopores due to the formation of ibuprofen crystalline.

Multimetallic catalysts of RuO2–CuO–Cs2O–TiO2/SiO2 for direct gas-phase epoxidation of propylene to propylene oxide

RuO2–CuO/SiO2 catalysts doped with Cs2O and TiO2 were investigated for the direct gas phase epoxidation of propylene to propylene oxide (PO) using molecular oxygen under atmospheric pressure. The optimal catalyst was achieved at Ru/Cu/Cs/Ti = 8.3/4.2/0.6/0.8 by weight and total metal loading of 21 wt% on SiO2 support. NH3 and CO2 temperature programmed desorption measurements of RuO2–CuO/SiO2 catalyst modified with Cs2O showed that the surfaces acidity decreased, resulting in enhanced PO selectivity. The addition of TiO2 increased the PO formation rate by promoting the synergy effect between RuO2 and CuO. Using the Box–Behnken design of experiments on the RuO2–CuO–Cs2O–TiO2/SiO2 catalyst, an extraordinarily high optimal PO formation rate of 3015 gPO h−1 kgcat−1 was obtained with a feed comprised of O2/C3H6 at a volume ratio of 3.1 and (O2 + C3H6)/He at a volume ratio of 0.26, all at 272 °C and 34 cm3 min−1. To the knowledge of the authors, this is the highest PO formation rate ever reported for direct propylene epoxidation via O2.

Effect of bimodal porous silica on particle size and reducibility of cobalt oxide

In this study, the effect of bimodal porous silica (BPS) on particle size and reducibility of cobalt oxide has been investigated. Unimodal porous silica (UPS) was used for comparison purposes. Both silica supports were impregnated with an aqueous solution of cobalt nitrate to obtain cobalt loadings of about 10 wt%. Pore structure, specific surface area, morphology and cobalt oxide crystallite size of the cobalt oxide loaded on porous silicas were systematically characterized by means of N2-sorption, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The reduction behavior profiles and the activation energy for the reducibility of the cobalt oxide were studied by dynamic thermal gravimetric under flow of H2. The average particle size of cobalt oxide loaded on the BPS sample was revealed to be slightly larger than that loaded on the UPS sample, likely because cobalt oxide particles were distributed both on mesopores and macropores. The reduction temperatures of the cobalt oxide loaded on the BPS sample were found to be evidentially lower than those of the cobalt oxide loaded on the UPS sample.

One step NaBH 4 reduction of Pt-Ru-Ni catalysts on different types of carbon supports for direct ethanol fuel cells: Synthesis and characterization

Abstract The ternary catalyst Pt75Ru5Ni20 was conducted on various types of carbon supports including functionalized Vulcan XC-72R (f-CB), functionalized multi-walled carbon nanotubes (f-MWCNT), and mesoporous carbon (PC-Zn-succinic) by sodium borohydride chemical reduction method to improve the ethanol electrooxidation reaction (EOR) for direct ethanol fuel cell (DEFC). It was found that the particle size of the metals on f-MWCNT was 5.20 nm with good particle dispersion. The alloy formation of ternary catalyst was confirmed by XRD and more clearly described by SEM element mapping, which was relevant to the efficiency of the catalysts. Moreover, the mechanism of ethanol electrooxidation reaction based on the surface reaction was more understanding. The activity and stability for ethanol electrooxidation reaction (EOR) were investigated using cyclic voltammetry and chronoamperometry, respectively. The highest activity and stability for EOR were observed from Pt75Ru5Ni20/f-MWCNT due to a good metal-carbon interaction. Ru and Ni presented in Pt-Ru-Ni alloy improved the activity and stability of ternary catalysts for EOR. Moreover, the reduction of Pt content in ternary catalyst led to the catalyst cost deduction in DEFC.