Synthesis and characterization of titanium pillared clays Influence of the temperature of preparation

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.

Influence of Operational Parameters on Photocatalytic Degradation of Linuron in Aqueous TiO2 Pillared Montmorillonite Suspension

TiO2 pillared clay was prepared by intercalation of titan polyoxocation into interlamelar space of an Algerian montmorillonite and used for the photocatalytic degradation of the linuron herbicide as a target pollutant in aqueous solution. The TiO2 pillared montmorillonite (Mont-TiO2) was characterized by X-ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD), X-Ray fluorescence (XRF), scanning electronic microscopy (SEM), thermogravimetry and differential thermal analysis (TG-DTA), Fourier transformed infra-red (FT-IR), specific area and porosity determinations. This physicochemical characterization pointed to successful TiO2 pillaring of the clay. The prepared material has porous structure and exhibit a good thermal stability as indicated by its surface area after calcination by microwave. The effects of operating parameters such as catalyst loading, initial pH of the solution and the pollutant concentration on the photocatalytic efficiency and COD removal  were evaluated. Under initial pH of the solution around seven, pollutant concentration of 10 mg/L and 2.5 g/L of catalyst at room temperature, the degradation efficiency and COD removal of linuron was best then the other operating conditions. It was observed that operational parameters play a major role in the photocatalytic degradation process. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Titania-Clay Mineral Composites for Environmental Catalysis and Photocatalysis

The use of titania-based composite materials in the field of heterogeneous catalysis and photocatalysis has a long and rich history. Hybrid structures combining titania nanoparticles with clay minerals have been extensively investigated for nearly four decades. The attractiveness of clay minerals as components of functional materials stems primarily from their compositional versatility and the possibility of using silicate lamellae as prefabricated building blocks ready to be fitted into the desired nanoconstruction. This review focuses on the evolution over the years of synthetic strategies employed for the manufacturing of titania–clay mineral composites with particular attention to the role of the adopted preparative approach in shaping the physical and chemical characteristics of the materials and enabling, ultimately, tuning of their catalytic and/or photocatalytic performance.

Low-temperature catalytic aqueous phase oxidation of microcystin-LR with iron-doped TiO2 pillared clay catalysts

TiO₂-PILCs and iron-doped TiO₂-PILCs were employed in order to destroy toxic microcystin-LR in the presence of H₂O₂ under the UV light. While less than 5% of the initial microcystin-LR and TOC disappeared in 240 min with the TiO₂-PILCs, almost complete conversion of microcystin-LR could be achieved in 180 min on the 10 wt% iron-doped TiO₂-PILC-A. On the exterior surface of the iron-doped TiO₂-PILCs were mainly located iron particles which had nano-sized diameter and Fe²⁺/Fe³⁺ cations together. Through Fenton-type oxidation on iron particles with H₂O₂, the big microcystin-LR molecules were converted primarily into smaller intermediate organic molecules of hydrocarbons, carboxylic acids and organic amines. The smaller intermediate molecules were believed to be diffused into the pores of the iron-doped TiO₂-PILCs and to be further mineralized into CO₂ and H₂O through the action of photocatalysis on the TiO₂ pillars. However, complete conversion of TOC could not be obtained due to the iron particle deactivation. XPS, TPO and TEM studies showed the continuous accumulation of carbonaceous materials onto the surface of iron particles.

Photocatalytic and adsorption properties of TiO2-pillared montmorillonite obtained by hydrothermally activated intercalation of titanium polyhydroxo complexes

We report on a new approach for the synthesis of TiO₂-pillared montmorillonite, where the pillars exhibit a high degree of crystallinity (nanocrystals) representing a mixture of anatase and rutile phases. The structures exhibit improved adsorption and photocatalytic activity as a result of hydrothermally activated intercalation of titanium polyhydroxo complexes (i.e., TiCl₄ hydrolysis products) in a solution with a concentration close to the sol formation limit. The materials, produced at various annealing temperatures from the intercalated samples, were characterized by infrared spectroscopy, differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA), X-ray diffraction, dynamic light scattering (DLS) measurements, and liquefied nitrogen adsorption/desorption. The photocatalytic activity of the TiO₂-pillared materials was studied using the degradation of anionic (methyl orange, MO) and cationic (rhodamine B, RhB) dyes in water under UV irradiation. The combined effect of adsorption and photocatalysis resulted in removal of 100% MO and 97.5% RhB (with an initial concentration of 40 mg/L and a photocatalyst-sorbent concentration of 1 g/L) in about 100 minutes. The produced TiO₂-pillared montmorillonite showed increased photocatalytic activity as compared to the commercially available photocatalyst Degussa P25.

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.

TiIV Exchanged K10-Montmorillonite: Characterisation and Catalytic Properties in Liquid-Phase Sulfide Oxidation

Titanium-containing K10 has been synthesised and characterised by X-ray diffraction, UV-visible reflectance, solid state NMR spectroscopy, N2 nitrogen adsorption at 77K and chemical analysis. Two different titanium species have identified with a high dispersion in K10. The first is in an isolated penta- and hexa-coordinated state and the second is in the form of polymerised hexacoordinated species, which contains Ti-O-Ti bonds. These titanium species were found to be the catalytic sites that readily interact with oxidant to offer an active and selective catalytic system for the oxidation of sulfides. This catalytic system was studied in the asymmetric oxidation of methyl phenyl sulfide, using different types of chiral modifier, and gives excellent conversion and sulfoxide selectivity, together with a significant enantioselectivity in the range of 16–18% ee with (R)-binol.

Influência de argilas pilarizadas na decomposição catalítica do óleo de andiroba

Amostras de esmectitas oriundas do estado do Pará, região amazônica, Brasil, foram usadas em processo de pilarização no presente estudo. As matrizes pilarizadas e natural foram caracterizadas usando DRX e analise textural usando isotermas de adsorção-desorção de nitrogênio. Os íons de intercalação (Al13, Ti, Zr) foram obtidos através de reações químicas com soluções de AlCl(3)6H2O/ NaOH, etoxido de titânio/HCl, acetato de zircônio / HCl. Os resultados obtidos com o processo de pilarização apresentaram aumento do espaçamento basal de 15,6 para 20, 64 Å e área superficial de 44 para 358 m²/g (Zr-PILC). A estabilidade térmica da argila natural foi melhorada com o processo de pilarização. O material resultante foi submetido a um processo catalítico de decomposição do óleo de andiroba em um reator de leito fixo a 673 ± 1 K. A atividade catalítica foi determinada pelo produto de decomposição resultante da reação química. Os parâmetros físico-químicos foram obtidos usando DRX, FTIR e análise textural. As argilas pilarizadas apresentaram alta acidez de Brønsted, com alta concentração de hidrocarbonetos aromáticos e baixa concentração de hidrocarbonetos alifáticos.