Titania-pillared Clay Research Articles

Titanium-Pillared Clay: Preparation Optimization, Characterization, and Artificial Neural Network Modeling.

Titanium-pillared clay (Ti-PILC), as one of the most suitable types of porous adsorbents/(photo)catalysts, was prepared from a local type of Iranian clay and titanium isopropoxide. The production process was optimized by changing three operating parameters, including the clay suspension concentration (in the range of 0.5–10% w/v), the H+/Ti ratio (2–8 mol/mol), and the calcination temperature (300–700 °C). The largest specific surface area for the Ti-PILC was about 164 m2/g under the clay suspension of 0.5% w/v, H+/Ti = 6, with a surface area 273% larger than that of the raw clay. The surface areas obtained from more concentrated clay suspensions were, however, comparable (159 m2/g for 3% w/v clay and H+/Ti = 4). An increase in the calcination temperature has a negative effect on the porous texture of Ti-PILC, but based on modeling with artificial neural networks, its contribution was only 7%. Clay suspension and H+/Ti ratio play a role of 56 and 37% of the specific surface area. The presence of rutile phase, and in some cases anatase phase of TiO2 crystals was detected. FTIR and SEM investigations of Ti-PILCs produced under different operating parameters were analyzed.

Ruthenium-doped Titania-pillared Clay for The Selective Catalytic Oxidation of Cyclohexene: Influence of Ru Loading

A series of ruthenium-based catalysts supported on acid-activated montmorillonite (PILC) and interspersed with titanium (Ru/Ti-PILCs) were prepared with various amounts of ruthenium. Their catalytic performances in the selective oxidation of cyclohexene, using tert-butylhydroperoxide (TBHP) as oxidant were checked. The clay structure modification by acid activation and impregnation of transition metals resulted in an enhanced Lewis and Bronsted acidities. The Ru/Ti-PILCs materials were characterized using X-ray diffraction (XRD), surface area and pore volume measurements, surface acidity followed by Fourier transform infrared (FTIR) spectroscopy, chemical analysis, and Scanning Electron Microscopy (SEM). It was found that all catalysts can selectively oxidize cyclohexene through allylic oxidation leading mainly to 2-cyclohexene-1-one (Enone) as the major product, and 2-cyclohexene-1-ol (Enol) as secondary product. With the 5 %Ru/Ti-PILC, it was possible to reach 59 % cyclohexene total conversion, and 87 % selectivity into 2-cyclohexene-1-one and 13 % selectivity into 2-cyclohexene-1-ol.

Treatment of Methylene Blue and Methyl Orange Dyes in Wastewater by Grafted Titania Pillared Clay Membranes.

Background: Amphoteric membranes such as Titania Pillared Clay (TiPILC) membranes exhibit different charges at different pH ranges, subsequently show efficient separation for cationic and anionic organic pollutants in wastewater based on solution pH. The structural properties of such membranes determine their permeability and selectivity to a large extent. The present work is initiated to explore the possibility of enhancing the surface area of TiPILC membranes by grafting with 3-aminopropyltriethoxysilane.Method: Grafted TiPILC membranes were fabricated by colloidal sol- gel route followed by dip coating, drying and sintering the membranes at 300oC. X-ray diffraction (XRD) spectra of the pillared photocatalyst membranes show the presence of only anatase phase, which exhibits better photocatalytic activity. Fourier Transform Infrared (FT-IR) spectra reveal the formation of delaminated TiPILC material. The specific surface area of TiPILC membrane obtained at pH3.5 is 183m2/g.Results: Literature survey of 47 papers was carried out for the work. 10 papers were based on patents being dealt on degradation of organic dyes in wastewater by conventional methods, though reports of membrane technology are limited in literature. The rest 37 papers outlined the importance of widespread use of titania photocatalyst powder for degradation studies.Conclusion: The membrane material thus developed is efficient in complete decolouration of both Methylene Blue and Methyl Orange dyes on account of the high surface charge and high surface area in just one cycle of filtration.

Allylic oxidation of cyclohexene over ruthenium-doped titanium-pillared clay

Ruthenium-doped H-Montmorillonite (H-Mont) and Ti-pillared clay (Ti-PILC) were prepared then studied for oxidation of cyclohexene, with tert-butylhydroperoxide (TBHP) as the oxygen source.

Removal of elemental mercury by titanium pillared clay impregnated with potassium iodine

A new kind of titanium pillared clay (Ti-PILC) impregnated by potassium iodine (KI) was synthesized to remove the elemental mercury (Hg0) in the simulated flue gas. The effect of KI loading amount, temperature, flue gas components (O2, SO2, H2O and NO) on Hg0 removal efficiency was investigated with a bench-scale bed. The techniques of Brunauer–Emmett–Teller (BET), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS), were used to characterize the clays. Compared with the original clay or the KI-impregnated clay, the KI-impregnated Ti-PILC showed an excellent Hg0 removal ability due to its larger BET surface area and more mesopores of 2–10nm. O2 was found to be an important factor for Hg0 removal. The Hg0 removal efficiency was enhanced with the rise in temperature. SO2 had a slight promotion effect while H2O greatly inhibited Hg0 removal. In all these flue gas components, NO was the most effective composition on promoting Hg0 removal. During the adsorption process, chemisorption occurred between iodine and Hg0 on the surface of the material in the temperature range of 80–180°C. The major product was assumed to be HgI2. The experiments and kinetic models analysis manifested that both physisorption and chemisorption of Hg0 occurred on the surface of KI-Ti-PILC, whereas the adsorption process was mainly chemisorption.

The Preparation and Application of Environmentally Benign Titanium Pillared Clay Catalyst for Esterification of Ethanol and Acetic Acid

The Preparation and Application of Environmentally Benign Titanium Pillared Clay Catalyst for Esterification of Ethanol and Acetic Acid

The Preparation and Application of Environmentally Benign Titanium Pillared Clay Catalyst for Esterification of Ethanol and Acetic Acid

Aims: The study is aimed to develop an indigenous heterogeneous based catalyst and evaluate kinetic mechanism for the synthesis of ethyl acetate by esterification of acetic acid and ethanol. Study Design: Batch reactor system.

Ceria Modified MnOx/TiO2-Pillared Clays Catalysts for the Selective Catalytic Reduction of NO with NH3 at Low Temperature

Titania-pillared clays (TiO 2 -PILC) were synthesized by ion exchange and manganese was introduced as the active phase. The catalytic behavior of the x Mn/TiO 2 -PILC catalysts was studied for the low-temperature selective catalytic reduction (SCR) of NO with NH 3 . A series of Ce-doped 8%Mn- y Ce/TiO 2 -PILC catalysts were prepared and evaluated for their performance in the low-temperature SCR of NO with NH 3 , their resistance to water vapor (H 2 O), and their resistance to sulfur dioxide (SO 2 ). It was found that the NO conversion properties of the 8%Mn/TiO 2 -PILC catalysts could be significantly improved by adding Ce and all the catalysts gave high resistance to H 2 O but were sensitive to SO 2 . The catalyst with a Ce loading of 2% gave 95% NO conversion at 220 °C and exhibited a moderate SO 2 -poisoning resistance compared with the other catalysts. X-ray diffraction, N 2 adsorption-desorption, temperature-programmed desorption of NH 3 , X-ray photoelectron spectroscopy, and temperature-programmed reduction of H 2 were used to characterize the properties of the catalysts. The addition of Ce improved the diffusion of Mn on the surfaces of the catalysts, which enhanced the surface acidity and improved the reduction properties of the catalysts and these were the main influencing factors for the low-temperature SCR. 采用离子交换法制备了钛基层柱粘土 (TiO 2 -PILC), 并应用浸渍法将 Mn 负载于其上制得不同 Mn 含量的 x Mn/TiO 2 -PILCs 催化剂, 考察了催化剂低温 NH 3 选择性催化还原 NO (NH 3 -SCR) 活性, 研究了添加 Ce 对 8%Mn/TiO 2 -PILC 催化剂活性及其抗水蒸气抗 SO 2 特性的影响. 结果发现, TiO 2 -PILC 负载的锰基催化剂具有良好的抗水蒸气性能, 但在水蒸气和 SO 2 共存时失活严重. Ce 的添加对催化剂活性以及抗 SO 2 能力均有所提高, 其中 8%Mn-2%Ce/TiO 2 -PILC 在 200 o C 时 NO 去除率达到 95%, 同时 SO 2 失活速率明显比其他催化剂低. 采用 N 2 吸附-脱附、X 射线衍射、NH 3 程序升温脱附、H 2 程序升温还原和 X 射线光电子能谱等技术对催化剂结构和性质进行了表征. 结果表明, 所制备催化剂具有丰富的中孔结构和较大的比表面积; Ce 的添加使 Mn 在催化剂表面分散性更好, 提高了催化剂表面酸性和催化剂氧化还原性能, 从而使其活性和抗硫性能增加. The addition of Ce to 8%Mn/TiO 2 -pillared clays (PILC) catalysts significantly improved NO conversion during the SCR and the resistance to SO 2 during low temperature selective catalytic reduction. The higher catalytic activity of the 8%Mn-2%Ce/TiO 2 -PILC catalyst is due to its better reduction behavior at low temperature and its higher number of acid sites.

Comparison study of titania pillared interlayered clays and porous clay heterostructures modified with copper and iron as catalysts of the DeNOx process

Natural montmorillonite was used as a raw material for the preparation of titania pillared clays (Ti-PILC) and porous clay heterostructures (Ti-PCH). Ti-PILC was produced by direct exchange of interlayer sodium cations in montmorillonite (sodium form) for titanium oligocations. Ti-PCH was obtained by the surfactant directed method. Tetraethylorthosilicate and titanium isopropoxide were used as the source of silica and titania, respectively. Copper and iron were introduced to Ti-PILC and Ti-PCH by the ion exchange method. The obtained materials were characterized with respect to chemical composition (EPMA), structure (XRD) and texture (BET), coordination and aggregation of transition metal species (UV–vis-DRS) and surface acidity (FT-IR). Modified montmorillonites were found to be active and selective catalysts for the reduction of NO with ammonia (DeNOx process) and their catalytic performance depended on the type of support (Ti-PILC or Ti-PCH) as well as deposited transition metal (Cu or Fe) species.

Synthesis of metal-oxide pillared montmorillonite clay for the selective catalytic oxidation of H 2S

In the present work, titania-pillared clay (Ti-PILC) and zirconia-pillared clay (Zr-PILC) were synthesized, and their catalytic performance was studied for the selective oxidation of H 2S to elemental sulfur. The obtained pillared clays (PILCs) were characterized by X-ray fluorescence spectroscopy (XRF), infrared (FTIR) spectroscopy, BET surface area measurements, X-ray photoelectron spectroscopy (XPS), UV–vis-diffuse reflectance spectroscopy (UV–vis-DRS), temperature-programmed desorption of ammonia (NH 3-TPD), and thermogravimetric (TG) analysis. The reaction tests were carried out in a continuous flow fixed-bed reactor at temperature ranging from 220 to 300 °C. The conversion of H 2S increased with increasing temperature for all PILCs while the selectivity to SO 2 remained almost constant. The good catalytic performance of the metal-oxide pillared clays may be due to the high surface area and the presence of Brönsted and Lewis acid sites.

Catalytic performance of vanadia-doped titania-pillared clay for the selective catalytic oxidation of H 2S

A series of vanadia-doped titania pillared clay (V/Ti-PILC) with various amounts of vanadia were prepared and their performance for the selective catalytic oxidation of H 2S was investigated in this study. V/Ti-PILCs were characterized using X-ray diffraction (XRD), BET apparatus, and X-ray photoelectron spectroscopy (XPS). V/Ti-PILCs showed better catalytic performance than as such Ti-PILC at temperatures ranging from 220 to 300 °C without any considerable SO 2 emission. The H 2S conversion over V/Ti-PILC increased with increasing vanadia content up to 5 wt.%. This superior catalytic performance might be related to the uniform dispersion of vanadia in the form of monomeric and polymeric species. However, it decreased at 10 wt.% vanadia loading due to the decrease of surface area and to the formation of crystalline V 2O 5 phase. The presence of water vapor in the reactant mixture resulted in the decrease of the H 2S conversion.

Highly Thermostable Anatase Titania-Pillared Clay for the Photocatalytic Degradation of Airborne Styrene

Airborne styrene is a suspected human carcinogen, and traditional ways of mitigation include the use of adsorption technologies (activated carbon or zeolites) or thermal destruction. These methods presenttheir own shortcomings, i.e., adsorbents need to be regenerated or replaced regularly, and relatively large energy inputs are required in thermal treatment. Photocatalysis offers a potentially sustainable and clean means of controlling such fugitive emissions of styrene in air. The present study demonstrates a new type of well-characterized, highly thermostable titania-pillared clay photocatalysts for airborne styrene decomposition in a custom-designed fluidized-bed photoreactor. This photocatalytic system is found to be capable of destroying up to 87% of 300 ppmV airborne styrene in the presence of ultraviolet (UV) irradiation. The effects of relative humidity (RH: 0 or 20%) are also studied, together with the arising physical structures (in terms of porosity and surface characteristics) of the catalysts when subjected to relatively high calcination temperatures of 1000-1200 degrees C. Such a temperature range may be encountered, e.g., in flue gas emissions (1). It is found that relative humidity levels of 20% retard the degradation efficiencies of airborne styrene when using highly porous catalysts.

Vanadia-doped titania-pillared montmorillonite clay for the selective catalytic oxidation of H2S

Abstract The performance of vanadia-doped titania-pillared clay (V/Ti-PILC) in the selective catalytic oxidation of H 2 S was investigated in this study. A series of V/Ti-PILC with various amounts of vanadia were prepared and characterized. XRD analysis revealed the presence of titania anatase peak without any evidence of crystalline vanadia. V/Ti-PILC showed a very good catalytic performance towards H 2 S oxidation at temperatures ranging from 220–300 °C without the considerable emission of SO 2 . At 300 °C, all the catalysts showed high H 2 S conversion of about 85%. The H 2 S conversions over V/Ti-PILC increased with increasing vanadia content and temperature.

Preparation of organoclay having titania nano-crystals in interlayer hydrophobic field and its characterization

To prepare the material for cleaning up the water polluted by the toxic organic compounds with poor polarity such the endocrine disruptor chemicals, we attempted to prepare the cation-exchangeable titania-pillared clay by the hydrothermal synthesis. White powder obtained by the hydrothermal treatment of the montmorillonite with titania precursor in water still had the cation-exchangeable property. Both TEM image and XRD patterns showed that anatase-type nano-crystals (crystalline size: ca. 20 nm) were incorporated in the montmorillonite interlayer space. The organoclay having titania nano-crystals (OCT) could be prepare by intercalating the cetyltrimentylammonium cations to the montmorillonite with titania nano-crystals (CT) due to the cation-exchange reaction. The adsorption amount of bisphenol A (BPA) by the OCT from water was about 6th times larger than that by the CT, because the OCT has higher hydrophobicity than CT. From UV irradiation experiment by 300 W high-pressure Hg lamp, it was found that OCT exhibited the higher photocatalytic decomposition ability for BPA dissolved in water than both CT and titania nano-crystal powder, which was synthesized under the hydrothermal condition. Moreover, the present OCT exhibited the high durability against the continuous UV irradiation.

Oxidation of aniline over titania pillared montmorillonite clays

Titania pillared clays (Ti-PILC) have been synthesized employing conventional stirring (method I) and ultrasonic agitation (method II) techniques followed by hydrothermal treatment. The characterization results revealed the formation of Ti-PILC with significant reduction of time when ultrasonic method was used. Subsequent hydrothermal treatment on the samples has resulted in the increase in the crystallinity and the transformation of anatase TiO2 to rutile TiO2. The rutile phase is more prominent in the samples prepared by stirring method. UV–Vis studies on the samples exhibit blue shift in the absorption band due to the quantum size effect. This indicates that a major part of TiO2 in the pillared clay could be well below 10 nm in size, which is supported by XRD and the average pore size. The pillared clay catalysts have proved to be promising in aniline oxidation with H2O2, selectively forming azoxybenzene under the working conditions. The aniline conversion and the product distribution largely depended on the catalyst concentration, H2O2 to aniline mole ratio, the nature of the solvent and the oxidant. Higher conversion of aniline and greater selectivity for azoxybenzene was obtained with methanol as the solvent.

Vanadia-doped titanium-pillared clay: Preparation, characterization and reactivity in the epoxidation of allylic alcohol (E)-2-hexen-1-ol

A series of vanadia supported titanium-pillared clay (Ti-PILC) with various amounts of vanadium were prepared, characterized then studied for epoxidation of allylic alcohol (E)-2-hexen-1-ol with tert-butylhydroperoxide (TBHP) as oxygen source. The Ti-PILC support was prepared by hydrolysis of TiCl 4 or Ti(OC 3H 7) 4 with HCl. Using a stoichiometric molar ratio TBHP/alcohol, it was found that vanadia supported on Ti-pillared clay is more active than Ti-pillared clay for the epoxidation and the Ti-source does not play the main role in the epoxidation process. It was also shown that 1 wt.% V supported on Ti-PILC promotes the epoxidation of (E)-2-hexen-1-ol without vanadia leaching, leading to heterogeneous catalysis.

Selective catalytic reduction of NO with ammonia over V2O5 supported sulfated titanium-pillared clay catalysts: influence of V2O5 content

A series of V2O5 supported sulfated titanium-pillared clay catalysts with various amounts of vanadia were prepared and characterized by BET, DRX, XPS and NH3-TPD then studied for selective catalytic reduction (SCR) of NO by NH3 in the presence of oxygen. It was found that vanadia supported on sulfated Ti-pillared clay is more active at any temperature than sulfated Ti-pillared clay for the SCR of NO by NH3. The NO conversions over V2O5 supported sulfated Ti-pillared clay catalysts were found to increase with vanadia content, but the selectivity into nitrogen decreases upon sulfation, suggesting that there is an optimum of activity as a function of the number of acid sites.

Synthesis of titania-pillared montmorillonite via intercalation of titanium alkoxide dissolved in supercritical carbon dioxide

A new method for the synthesis of pillared clays using supercritical carbon dioxide (scCO2) has been developed. This scheme consists of two steps: (1) the hydrophobitization of the clay interlayer space, using an organic ion exchange method with interlayer cations in aqueous solution, and (2) the intercalation of a metal alkoxide dissolved in scCO2 followed by hydrolysis with adsorbed water present in the interlayer space. This method is expected to be advantageous in the structural and chemical design of pillared clays by allowing specific tailoring of the organic ions and metal alkoxides used during preparation. In this work, the synthesis of titania-pillared clay using montmorillonite (MNT) and titanium isopropoxide was investigated. Alkyltrimethylammonium cations were used to study the effect of organic ions on the clay structure. Titania pillared MNT were successfully prepared with the presence of hydrophobic interlayer ions, whereas intercalation was not successful on MNT without hydrophobitization of the interlayer space. Nano-sized anatase was observed on the calcined samples and the titania content was related to the hydrophobic nature of the organic ion used. The intercalated samples have both meso- and microporous structures and the microporosity was considered to be a factor related to the variety of organic ion used. An optimised pillared clay sample showed potential as a catalytic adsorbent for toxic volatile organic compounds in air.

Selective catalytic reduction of NO by NH3 on sulfated titanium-pillared clay

Structural, textural and surface properties of sulfated and non-sulfated titanium-pillared clay were correlated with catalytic tests in the reduction of NO by NH3 in the presence of oxygen. Lower specific surface areas and basal spacings but stronger acid sites were observed on sulfated Ti-pillared clay than on Ti-pillared clay. Sulfated Ti-pillared clays were more active than Ti-pillared clay. Accordingly, it is suggested that the strong Bronsted acidity generated by sulfate is responsible for the high reactivity of sulfated Ti-pillared clay at high temperature.

Enhanced Adsorption Capacity and Photo-Catalytic Oxidative Activity of Dyes in Aqueous Medium by Hydrothermally Treated Titania Pillared Clay

Titania pillared montmorillonite clay was prepared by two different routes viz. 1) conventional ion exchange method and 2) modified method wherein the post hydrothermal treatment after ion-exchange was employed. The influence of the post hydrothermal treatment on the textural properties of titania-pillared clays was studied. The calcined clay was characterized by different physico-chemical techniques such as XRD, EDX, low temperature (77 K) nitrogen adsorption and UV-Vis diffuse reflectance spectroscopy. The content of pillared titania remained unchanged irrespective of the method of preparation. The method of preparation and severity of the conditions employed for the hydrothermal treatment resulted in alteration of the crystallinity and crystallite size of the anatase. The changes in the average pore diameter was found to comensurate with the changes in crystallite size of anatase phase. The increase in total pore volume as a function of the severity of the post hydrothermal treatment resulted in the decrease in micropore volume. The severity of the post hydrothermal treatment governed the extent of the blue shift in UV-Vis DRS spectra.