V. Durga Kumari

Photocatalytic degradation of H-acid over a novel TiO2 thin film fixed bed reactor and in aqueous suspensions ☆

The present work is focused on the heterogeneous photocatalytic degradation of H-acid, a toxic and non-biodegradable dye intermediate, in TiO2 suspensions and TiO2 thin film fixed bed reactor (TFFBR). The degradation studies in slurry form are investigated using TiO2 Degussa P25 and different Millennium PC50, PC100 and PC500 photocatalysts under UV illumination. The study includes dark adsorption experiments in different pH conditions, influence of the amount of photocatalyst, effect of H-acid concentration, effect of pH on chemical oxygen demand (COD), biological oxygen demand (BOD) and the sulfate ion formation during the photocatalytic degradation. Photocatalytic treatment significantly reduces COD and increases the biodegradability of H-acid. The intermediates have been identified by LCMS. The study with slurry is extended to the immobilization of preformed TiO2 Degussa P25 in thin film using an acrylic emulsion by simple spray technique on inert Cuddapah stone. This method of immobilization does not require the thermal treatment of the catalyst at high temperatures. It may be used for the photocatalytic treatment of effluents at a higher scale.

Photocatalytic degradation of isoproturon herbicide over TiO2/Al-MCM-41 composite systems using solar light

The present investigation covers immobilization of TiO2 using a simple solid state dispersion technique over mesoporous Al-MCM-41 support for the treatment of isoproturon herbicide. Catalysts are characterized by XRD, X-ray photo electron spectroscopy (XPS), surface area, UV-Vis diffused reflectance spectra (DRS), SEM and TEM. A detailed photocatalytic degradation study of isoproturon under solar light in aqueous suspensions is reported. The 10 wt% TiO2/Al-MCM-41 composite system found to be optimum with high degradation activity. The reaction follows pseudo-first order kinetics. The parameters like TiO2 loading over Al-MCM-41, amount of catalyst, concentration of substrate, pH effect, durability of the catalyst, activity comparison of TiO2 and Al-MCM-41 supported system are studied. The mineralization of isoproturon is monitored by TOC. Based on the degradation products detected through LC-MS, a plausible degradation mechanism is proposed. The data indicates that TiO2/Al-MCM-41 composite system is an effective photocatalyst for treatment of isoproturon in contaminated water.

TiO2 supported over SBA-15 : An efficient photocatalyst for the pesticide degradation using solar light

Photocatalytic degradation and mineralization of pesticides are studied over TiO(2) supported mesoporous SBA-15 composite system using solar light. TiO(2) is immobilized over SBA-15 by solid sate dispersion method. The catalysts are characterized by XRD, surface area, UV-Vis diffused reflectance spectra, SEM and TEM. The detailed photocatalytic degradation studies are carried out over TiO(2), SBA-15 and different TiO(2) wt% supported SBA-15. The activity evaluation parameters such as catalyst amount, pH, and pollutant initial concentration are studied taking isoproturon as a model compound and established conditions for pesticide degradation. The optimum degradation is achieved over 10 wt% TiO(2)/SBA-15 within 30 min and the reaction is following pseudo-first order kinetics. The isoproturon mineralization is monitored with TOC reduction and it takes around 9h for disappearance. The commercial pesticide solutions containing imidacloprid and phosphamidon are also successfully degraded over these composites with the established conditions. The data indicates that 10 wt% TiO(2)/SBA-15 composite is an effective and highly active system for the pesticide degradations.

Calcined Mg–Al, Mg–Cr and Zn–Al hydrotalcite catalysts for tert-butylation of phenol with iso-butanol—a comparative study

Calcined hydrotalcites (CHTs) are studied for the tert-butylation of phenol using iso-butanol in the temperatures ranging from 350 to 500 °C. The major products of this reaction on calcined magnesium–aluminium hydrotalcites (CMA-HTs) are O-tert-butyl phenol (tert-butyl phenyl ether, OTBP) and 2-tert-butyl phenol (o-tert-butyl phenol, 2TBP) with O-butenyl phenol (butenyl phenyl ether, OBP) and 2-butenyl phenol (o-butenyl phenol, 2BP) as useful by-products. With a view to understand the reaction mechanism and the reaction path, tert-butylation of phenol is studied by changing both Mg[M(II)] and Al[M(III)] ions with Zn2+ and Cr3+, respectively. Thus, Mg–Al (MA), Mg–Cr (MC) and Zn–Al (ZA) hydrotalcites (with M2+:M3+ ratio=2) are prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), differential thermal analysis/thermo gravimetric analysis (DTA/TG), BET-surface area (BET-SA) and acidity–basicity measurements (temperature-programmed desorption (TPD) of NH3 and CO2). Mixed oxides obtained from CHTs are found to be more active over their individual oxides for the tert-butylation of phenol. The butylation activities of the three different CHTs are in the order CMA-HT>CZA-HT>CMC-HT. A different product distribution is obtained over calcined Mg–Cr and Zn–Al hydrotalcites for the tert-butylation of phenol showing the influence of acid–base properties on the activity of the catalysts. A probable mechanism based on the experimental observations has been proposed in order to explain the formation of butenyl phenols.

Synergistic effect of nanocavities in anatase TiO2 nanobelts for photocatalytic degradation of methyl orange dye in aqueous solution.

Nanocavities are empty voids exposed on the surface of one dimensional TiO2 nanostructured material. Often, they exhibited beneficial optical and electrical properties that leads to efficient photocatalytic reactions. This study reports formation of nanocavities on anatase TiO2 nanobelts (TNB) through dehydroxylation of surface hydroxyl groups during calcination process (350-600°C). The morphological and crystal structure analysis of TNB-500, -550 and -600 displayed the nanobelts shape with high density of nano-size cavities and increase in average diameter with calcination temperature. The SAED patterns confirm the anatase TiO2 phase. The enhanced light absorption properties of biphasic anatase/TiO2-B and anatase TiO2 than H2Ti3O7 are attributed to transformation of crystal structure upon calcination process. The catalytic activity was evaluated for degradation of methyl orange dye in aqueous solution under solar light irradiation. The reaction variables such as calcination temperature, amount of catalyst and pH of the methyl orange dye solution were studied and discussed in detail. Under optimal experimental conditions TNB-550 photocatalyst displayed highest degradation performance about 8 folds higher than H2Ti3O7. The high performance is explained as due to synergistic properties of one dimensional anatase TiO2 with high density of nanocavities leading to one dimensional transfer of electrons and high absorption co-efficient in UV-A spectrum are suitable for efficient red-ox reactions.

Correlation of activity and stability of CuO/ZnO/Al2O3 methanol steam reforming catalysts with Cu/Zn composition obtained by SEM–EDAX analysis ☆

Abstract A series of CuO/ZnO/Al 2 O 3 catalysts were prepared and characterized by TPR, surface area, metal area, XRD and SEM–EDAX analysis. These systems were evaluated in the development of a methanol steam reforming catalyst (MSR). A correlation of activity and stability of MSR catalysts with the Cu/Zn ratio derived by SEM–EDAX analysis is observed. The stable activity of these catalysts is also supported by the method of preparation, low temperature reducibility and the presence of reversibly oxidizable Cu species observed by TPR of fresh and used catalysts.

An integrated approach of solar photocatalytic and biological treatment of N-containing organic compounds in wastewater

In the present study the integration of TiO2-assisted solar photocatalysis and biological treatment for the degradation of organic nitrogen containing pyrazinamide (antituberculosis drug) synthesis process effluent is investigated. The experimental results showed that a considerable increase in the degradation efficiency of N-containing compounds is obtained by integration of photocatalysis and biological treatment when compared to either biological or photocatalysis treatment alone. The optimization parameter like amount of photocatalyst (TiO2 Degussa-P-25) was performed for photocatalytic treatment under solar irradiation. Furthermore BOD5/COD ratios were also evaluated. The optimum catalyst (wt.%) of 0.35 TiO2, and 40 times dilution are found to be optimum for achieving a maximum of 76, 83, 80% of COD, color and TOC removals respectively and an improved BOD5/COD ratio of 0.3 to 0.7 in a duration of 24 h. Also the formation of increased from 10 to 44 mg L−1 within 20 h of photocatalytic treatment. The effluent subjected to biological treatment for five days (120 h) has resulted 43% COD removal only, whereas the treatment method using integrated approach resulted a 91% COD removal in a duration of 44 h.

Steam Reforming of Glycerol for Hydrogen Production over Catalyst

The performance of catalyst for glycerol reforming has been investigated in fixed-bed reactor using careful tailoring of the operational conditions. In this paper, a commercial Engelhard catalyst has been sized and compared to gas product distribution versus catalyst size, water-to-carbon ratio, and stability of the catalyst system. catalysts of three sizes (, , and mm) are evaluated using glycerol: water mixture at to produce 2 L H2 g−1 cat h−1. The results indicate that mm size pellet is showing minimum coking and maintaining same level of conversion even after several hours of reforming activity. Whereas studies on and mm pellets indicate that carbon formation is affecting the reforming activity. Under accelerated aging studies, with 1 : 9 molar ratio of glycerol to water, 3 mg carbon g−1 cat h−1 was generated in 20 cycles, whereas 1 : 18 feed produced only 1.5 mg carbon g−1 cat h−1 during the same cycles of operation. The catalysts were characterized before and after evaluation by X-ray diffraction (XRD), BET surface area, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDAX), CHNS analysis, transmission electron microscopy (TEM), and X-ray photo electron spectroscopy (XPS).

Vapor phase isopropylation of quinoline over modified HY zeolites

The vapor phase isopropylation of quinoline was carried out over HY and modified HY zeolites in a fixed‐bed reactor at atmospheric pressure. The yield of 2‐isopropylquinoline was higher over modified zeolites, especially over doubly‐promoted LaKHY zeolite. The maximum yield of 2‐isopropylquinoline obtained was 48.8 wt% with 82.9% selectivity. The reaction favors on moderate Lewis acidic sites.

Tert-butylation of phenol with isobutanol over magnesium- aluminium hydrotalcites

Magnesium-aluminium hydrotalcites are prepared with Mg/Al atomic ratios 2- 7 and characterized by XRD, DTA, surface area measurements and acidity-basicity measurements. The tert-butylation of phenol is carried out on the calcined magnesium-aluminium hydrotalcites using isobutanol in the temperature range of 350- 500°C. The major products of this reaction are O-tert-butyl phenol and 2-tert-butyl phenol. Along with the normal alklyated products O-butenyl phenol and 2-butenyl phenols are also obtained. A correlation between the product distribution and the nature of acid-base properties of the catalyst is studied.