Advanced Materials Research Vols. 931-932

Abstract: The synthesis of dimethyl ether via methanol dehydration has been carried out over Beta zeolite (BEA) and ion-exchanged Beta zeolite from bagasse fly ash using hydrothermal method. The reactions were taken place in a fixed-bed reactor. The effects of nickel and zirconium ion-exchanged of BEA were investigated. Ni-BEA zeolite exhibited high methanol conversion rate and DME-resultant upon the reaction temperature from 200 to 225°C with equilibrium-limiting condition over 225°C; Furthermore, the Ni-BEA zeolite presented the best stable activity at 225°C over 1,200 minute. The Ni-BEA zeolite has also been interesting as a zeolite which suited to be one role importance to improve the properties for methanol dehydration to dimethyl ether.

Abstract: This work is an investigation of the effectiveness of chemical oxygen demand (COD) removal from synthesized lignin wastewater using photo-Fenton reaction over Fe-Ce-Zn catalysts. The synthesized lignin wastewater had the same COD concentration as the pulp processing wastewater. The treatment was done using photo-Fenton reaction with the metal catalysts (Fe-Ce-Zn). They were prepared by co-precipitation. The catalysts efficacies in reducing COD were tested. It was found that the addition of zinc influenced its reaction due to the increasing of semiconductor property to the light. Moreover, the high surface area of Fe-Ce-Zn catalyst enhanced the COD removal due to the synergy of the high adsorption capacity. Therefore, the Fe-Ce-Zn catalyst was studied to obtain the optimal condition for COD reduction. The conditions and parameters investigated were: pH, the concentration of hydrogen peroxide (H₂O₂), and the concentration of catalyst. The optimal condition was obtained using the Box-Behnken statistical experiment design (BBD) and the response surface methodology (RSM). It has been found that the pH and the concentration of catalyst had the significant effects on the reduction of COD. The concentration of H₂O₂ has no effect on the COD removal. The maximum COD removal (60%) was achieved at the pH of 5.2, 4 g/L of catalyst loading, and 366 mg/L of H₂O₂.

Abstract: Lignin was degraded by Fenton-like reaction using Cu-BG-MCM41, in which BG-MCM41 was synthesized by hydrothermal technique from Bagasse ash (BG) as a support. Cu was immobilized on BG-MCM41 by in situ hydrothermal and impregnation method and characterized by XRD and BET surface area. The Fenton-like reactions were carried out in a batch reactor using 5wt%CuO/SiO_2, 10wt%CuO/SiO₂, 5wt%Cu-BG-MCM41 and 10wt%Cu-BG-MCM41 at the pH of 3 and the temperature of 80°C. The Cu loading, pH, and temperature affected lignin degradation. The efficiency of lignin degradation obtained were 95% for 5wt%CuO/SiO₂, 95% for 10wt%CuO/SiO_2, 65% for 5wt%Cu-BG-MCM41 and 96% for 10wt%Cu-BG-MCM41 at the pH of 3 and 80°C for 30 min. The results show that pH and temperature affected the stability of Cu loading, in which it was leached into the aqueous solution and that the reaction will occur in the aqueous solution more than on the surface of catalyst. Thus, 5wt%Cu-BG-MCM41 has the highest stability for Fenton-like reactions.

Abstract: Dimethyl Ether (DME) an alternative fuel was synthesized by methanol dehydration over the silica-based catalysts. Silica extracted from both rice husk (A) and rice-husk ash (B) was used as the precursors for preparing the catalysts. The SiO₂/Al₂O₃ and the SAPO catalysts prepared from that silica were analyzed using X-ray diffraction (XRD), N₂ adsorption (BET surface area), X-ray fluorescence (XRF), NH₃ temperature-programmed desorption (NH₃-TPD), and thermal gravimetric analysis (TGA). The effects of reaction temperature on the methanol selectivity and conversion to dimethyl ether were investigated. The methanol dehydration reactions were carried out in a packed-bed reactor at the reaction temperature of 250-350°C. DME was the major product and formed with selectivity of 57% over SAPO-B. An increasing of the reaction temperatures resulted in the enhancing of methanol conversion. The highest methanol conversion of 93% was achieved at 325°C. The method of silica extraction had an effect on the selectivity to DME due to the higher BET surface area.

Abstract: The goal of this research was to synthesize two different catalysts, namely K-OMS-2 and MnO_x. The K-OMS-2 was an octahedral manganese complex prepared by hydrothermal method, while manganese oxide (MnO_x) was directly synthesized by precipitation method. Both catalysts were employed to decompose toluene, an organic solvent that is widely used in industries. The catalysts were characterized by means of X-ray diffraction (XRD) and N₂-physorption. The surface areas of K-OMS-2 and MnO_x were 83.50 and 20.04 m²/g, respectively. The precipitation route gave XRD patterns of γ-Mn₂O₃ structure_, and a successful structure of an octahedral molecular sieve manganese oxide was obtained by the hydrothermal method. The toluene degradation was carried out in gas hourly space velocity (GHSV) range of 20,000-60,000 h^-1 with toluene concentration of 7,700 ppmv. The higher GHSV over K-OMS-2 gave the lower contact time consequently resulting in the lower %toluene degradation, whereas the best GHSV over γ-Mn₂O₃ was suitable at 40,000 h^-1. The complete oxidation temperature of toluene over K-OMS-2 occurred at 260 °C and was lower than the temperature by γ-Mn₂O₃ at 300 °C. The higher surface area of K-OMS-2 may not facilitate internal toluene diffusion to active K-OMS-2 sites because molecular toluene (5.6 Å) cannot migrate through its smaller pore diameter (4.6 Å); however, the fully oxidized K-OMS-2 can provide higher average oxidation state (AOS) and higher amount of lattice oxygen assisting toluene degradation compared to γ-Mn₂O₃. The full factorial design of experiment (DOE) exhibited a strong effect of temperature and catalyst types on toluene removal; in contrast gas hour space velocity (GHSV) exhibited no significant effect on %toluene removal even with increasing GHSV.

Abstract: Methanol synthesis from synthesis gas (syngas, a mixture of hydrogen (H₂) and carbon monoxide (CO)) in the presence of copper/zinc oxide/alumina catalyst (Cu/ZnO/Al₂O₃) was investigated using semi-batch reactor. The process was operated at 280 °C under pressure 40 bar in a slurry reactor (Parr reactor model 4848). The catalyst weight, syngas molar ratio and residence time were optimized for methanol synthesis. Cu/ZnO/Al₂O₃ catalyst was prepared by a two-step surfactant assisted precipitation method using polyethylene glycol (PEG 6000). The catalysts surface area, crystallinity, reducibility and morphology were characterized by BET, XRD, H₂-TPR and SEM-EDS, respectively. The BET analysis indicated that the catalyst calcined at 300 °C gave the highest surface area (99.67 m²/g). The crystallite size of Cu in Cu/ZnO/Al₂O₃ catalyst was estimated to be 14.14 nm., after adding the surfactants. The maximum methanol yield (607.53) was achieved after 24 hours of residence time using 5 g of the catalyst under a stream of 2 to 1 molar ratio of H₂ and CO reactive mixed gas. Under these conditions, 38.26% of CO conversion and 93.11% of selectivity to methanol were achieved. When the residence time was decreased to 12 hours with molar ratio of 0.5 H₂ to 1 CO, the yield of methanol was 388.11, with a CO conversion of 38.53% and selectivity to methanol of 90.77%.

Abstract: Wet-air oxidation (WAO) and catalytic wet-air oxidation (CWAO) over CuO/Al2O3 and NiO/Al2O3 catalysts for aniline removal were investigated. The oxidation reaction was carried out in a 1000-ml high-pressure batch reactor. The temperatures of 160, 200 and 260C and the pressures of 5 and 10 bars were generally applied for 120 min. CuO/Al2O3 and NiO/Al2O3 catalysts were prepared by impregnation method. It is found from the results that aniline was completely degraded at these conditions. However, aniline was converted into other organic carbons which remained in the solution. So COD was found in the solution after the reaction. It is seen from the results that 56% of COD was removed by WAO at 200C and 10 bars for 120 min. The CWAO over CuO/Al2O3 catalyst showed higher COD removal (76%) than NiO/Al2O3 catalyst (60%). The types of metal oxide had an effect to the activity of COD removal; that is, CuO showed higher COD removal than NiO. The WAO and CWAO of COD removal in aniline solution were the first-order kinetic with the constant reaction rate and activation energy for CuO/Al2O3 of 0.234 s-1 and 11.772 kJ/mol, respectively.

Abstract: Aniline was removed by photocatalysis reaction using zinc oxide (ZnO, ZnO/Al₂O₃ and ZnO/SiO₂) as catalysts. The oxidation reactions were carried out in a batch reactor. The experiment was designed by Pleckett-Burman Full Factorial Design (FFD) for screening test. The FFD was used to factors screening of 3 factors: wt% of ZnO, catalyst loading and UV light source on aniline removal. The equation model for factors screening was well fitted to the experiment data, which was observed by R² coefficient of 0.95. The results show that wt% of ZnO and catalysts loading were the significant effects. The highest percentage aniline removal of 82.7% was achieved at the reaction condition; 0.5g of ZnO catalyst and 30wt%ZnO under UV-C irradiation. Moreover, it was found that Pleckett-Burman FFD was useful in factor screening of the aniline removal by photochemical reaction over ZnO-based catalysts.

Abstract: The synthesis of dimethyl ether via methanol dehydration has been carried out over untreated-diatomite catalyst (DM) and hydrochloric acid modified treatment on diatomite catalyst (DMHC). The reactions were carried out in a fixed-bed reactor. The effects of hydrochloric acid modifications of diatomite on its catalytic performance were studied. The characterization such as XRD, SEM, FT-IR and FT-Raman had no deformation after HCl-modified treatment on catalysts. DMHC catalyst apparently gave the higher methanol conversion rate than DM due to the acidity while the selectivity of dimethyl ether from 250 to 350°C was slightly changed. The acidity was depended upon Al^(IV) ions; nevertheless, both Al^(V) and Al^(VI) were affected and hence increasing the basic active sites. Not only was the competitively catalytic methanol dehydrogenation preferred with basic condition but also methanol-blocking water molecule interaction was the unwanted reaction. In this investigation, the chemical-bond arrangements of silicon and aluminium ions were proposed with solid MAS/NMR. The DMHC catalyst exhibited better DME yield than the DM catalyst, and it could be used as a selective catalyst for DME synthesis from methanol.