Preparation and characterization of TiO2 incorporated Y-zeolite

Synthesis and Performance of Photocatalysts for Photocatalytic Hydrogen Production: Future Perspectives

Photocatalysis for “green” hydrogen production is a technology of increasing importance that has been studied using both TiO2–based and heterojunction composite-based semiconductors. Different irradiation sources and reactor units can be considered for the enhancement of photocatalysis. Current approaches also consider the use of electron/hole scavengers, organic species, such as ethanol, that are “available” in agricultural waste, in communities around the world. Alternatively, organic pollutants present in wastewaters can be used as organic scavengers, reducing health and environmental concerns for plants, animals, and humans. Thus, photocatalysis may help reduce the carbon footprint of energy production by generating H2, a friendly energy carrier, and by minimizing water contamination. This review discusses the most up-to-date and important information on photocatalysis for hydrogen production, providing a critical evaluation of: (1) The synthesis and characterization of semiconductor materials; (2) The design of photocatalytic reactors; (3) The reaction engineering of photocatalysis; (4) Photocatalysis energy efficiencies; and (5) The future opportunities for photocatalysis using artificial intelligence. Overall, this review describes the state-of-the-art of TiO2–based and heterojunction composite-based semiconductors that produce H2 from aqueous systems, demonstrating the viability of photocatalysis for “green” hydrogen production.

TiO2/porous adsorbents: Recent advances and novel applications

This article reviews two interrelated areas of research: the first is the use of TiO₂-supported adsorbent materials as enhanced heterogeneous photocatalysts and their application to various reactions for organic pollutant removal from air and water; the second is the combination of adsorbent materials with TiO₂ photocatalysts which aims to efficiently regenerate adsorbent materials using illumination. By reviewing both areas of research, the following topics are covered; (i) photocatalytic activation of TiO_2; (ii) related properties of photocatalytic TiO_2; (iii) shortcomings of photocatalytic processes; (iv) preparation methods of composite TiO₂/adsorbent materials and their photocatalytic performance; (v) properties of common adsorbents and their applications for pollutant removal from air and water; (vi) adsorbent regeneration methods and their economic and operational issues; (vii) conclusions and future outlooks. This topic has not been previously reviewed to such an extent, and considerable knowledge can be gained from assembling the large number of studies on adsorption-photocatalysis combinations. As such, this review provides guidance for researchers working in the fields of environmental and chemical engineering focussing on organic pollutant removal and the engineering of new high performance photocatalytic TiO₂-supported porous adsorbent materials.

Efficient photocatalytic degradation of organics present in gas and liquid phases using Pt-TiO2/Zeolite (H-ZSM)

TiO2-encapsulated H-ZSM photocatalysts were prepared by physical mixing of TiO2 and zeolites. Pt was immobilized on the surface of the TiO2-encapsulated zeolite (H-ZSM) catalysts by a simple photochemical reduction method. Different weight ratios of both TiO2 and Pt were hybridized with H-ZSM and the catalytic performance of the prepared catalysts was investigated for 2-propanol oxidation in liquid phase and acetaldehyde in gas phase reaction. Around 5-10 wt% TiO2-encapsulated H-ZSM catalysts was found to be optimal amount for the effective oxidation of the organics. Prior to light irradiation, Pt-TiO2-H-ZSM showed considerable amount of catalytic degradation of 2-propanol in the dark, forming acetone as an intermediate. In this study, Pt has played a major and important role on the total oxidation of 2-propanol as well as acetaldehyde. As a result, no residual organics were present in the pores of the zeolites. The catalysts could be reused more than three times without losing their catalytic activity in both phases. The Pt-TiO2-H-ZSM photocatalysts could overcome the problem of strong adsorption of organics in the zeolite pores (after the reaction). Thus, Pt-TiO2-H-ZSM can be used as a potential catalyst for both liquid and gas phase oxidation of organic pollutants.

An overview on limitations of TiO2-based particles for photocatalytic degradation of organic pollutants and the corresponding countermeasures

The pollutants classified as "persistent organic pollutants (POPs)", are being subject to high concern among the scientific community due to their persistence in the environment. TiO2-based photocatalytic process has shown a great potential as a low-cost, environmentally friendly and sustainable treatment technology to remove POPs in sewage to overcome the shortcomings of the conventional technologies. However, this technology suffers from some main technical barriers that impede its commercialization, i.e., the inefficient exploitation of visible light, low adsorption capacity for hydrophobic contaminants, uniform distribution in aqueous suspension and post-recovery of the TiO2 particles after water treatment. To improve the photocatalytic efficiency of TiO2, many studies have been carried out with the aim of eliminating the limitations mentioned above. This review summarizes the recently developed countermeasures for improving the performance of TiO2-based photocatalytic degradation of organic pollutants with respect to the visible-light photocatalytic activity, adsorption capacity, stability and separability. The performance of various TiO2-based photocatalytic processes for POPs degradation and the underlying mechanisms were summarized and discussed. The future research needs for TiO2-based technology are suggested accordingly. This review will significantly improve our understanding of the process of photocatalytic degradation of POPs by TiO2-based particles and provide useful information to scientists and engineers who work in this field.

Hybridization of zirconia, zinc and iron supported on HY zeolite as a solar-based catalyst for the rapid decolorization of various dyes

A Zr/Zn/Fe/HY nanocomposite catalyst with high photoactivity, good stability and a lower band gap energy was generated via a one-pot electrosynthesis.

Effective solar-based iron oxide supported HY zeolite catalyst for the decolorization of organic and simulated dyes

An excellent EGFe₂O₃/HY catalyst with a size of <30 nm and superior photoactivity was generated via one-pot electrosynthesis.

Facile synthesis of WO3 with reduced particle size on zeolite and enhanced photocatalytic activity

WO₃ supported on zeolite-Y (WO3-ZY) was successfully synthesized by a facile impregnation method and well characterized by various techniques.

An efficient Fe2O3/HY catalyst for Friedel–Crafts acylation of m-xylene with benzoyl chloride

Iron oxide supported on HY zeolite was prepared and exhibited excellent catalytic performance in the acylation of m-xylene with benzoyl chloride. It was characterized by XRD, BET, XPS, NH₃-TPD and Py-IR. The catalytic activity of Fe₂O₃/HY is enhanced with the increase of Lewis acidic sites. Furthermore, the reaction parameters were optimized. Finally, the catalyst was easily separated reused for five runs without appreciable loss of catalytic activity.

Preparation and characterization of TiO2/HZSM-11 zeolite for photodegradation of dichlorvos in aqueous solution

The TiO2/HZSM-11 materials were synthesized using titanium isopropoxide as a TiO2 precursor and HZSM-11 a medium pore size zeolite with high thermal and chemical resistance as support. The amount of titanium isopropoxide was varied in order to obtain TiO2 concentrations of 3, 10, 20, 30 and 50 wt% in the final material. They were characterized by a series of complementary techniques: X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (DRS), transmittance Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The surface area of the TiO2/HZSM-11 samples decreased with the increment of TiO2 loading. As result of the increment of the calcination temperature from 450 to 800°C an increase in the size of the anatase crystals was observed. However, the X-ray diffraction patterns of the solids only presented the characteristic peaks of the anatase phase. The catalytic activity of the materials in the photodegradation of Dichlorvos (DDVP) depended on the TiO2 amount the thermal treatment temperature. The sample containing 30% TiO2 calcined at 450°C showed the best catalytic performance and it can be reused without noticeable activity loss during at least four cycles. The catalytic performance was similar to that of the P25 Degussa used as a reference but its separation, recovery and reuse was easier.

Zeolites: Promised Materials for the Sustainable Production of Hydrogen

Zeolites have been shown to be useful catalysts in a large variety of reactions, from acid to base and redox catalysis. The particular properties of these materials (high surface area, uniform porosity, interconnected pore/channel system, accessible pore volume, high adsorption capacity, ion-exchange ability, and shape/size selectivity) provide crucial features as effective catalysts and catalysts supports. Currently, new applications are being developed from the considerable existing knowledge about these important and remarkable materials. Among them, those applications related to the development of processes with less impact on the environment (green processes) and with the production of alternative and cleaner energies are of paramount importance. Hydrogen is believed to be critical for the energy and environmental sustainability. It is a clean energy carrier which can be used for transportation and stationary power generation. In the production of hydrogen, the development of new catalysts is one of the most important and effective ways to address the problems related to the sustainable production of hydrogen. This paper explores the possibility to use zeolites as catalysts or supports of catalysts to produce hydrogen from renewable resources. Specifically, two approaches have been considered: reforming of biomass-derived compounds (reforming of bioethanol) and water splitting using solar energy. This paper examines the role of zeolites in the preparation of highly active and selective ethanol steam reforming catalysts and their main properties to be used as efficient water splitting photocatalysts.

Zeolite Y encapsulated with Fe-TiO2 for ultrasound-assisted degradation of amaranth dye in water

A new heterogeneous catalyst for sonocatalytic degradation of amaranth dye in water was synthesized by introducing titania into the pores of zeolite (NaY) through ion exchange method while Fe (III) was immobilized on the encapsulated titanium via impregnation method. XRD results could not detect any peaks for titanium oxide or Fe(2)O(3) due to its low loading. The UV-vis analysis proved a blue shift toward shorter wavelength after the loading of Ti into NaY while a red shift was detected after the loading of Fe into the encapsulated titanium. Different reaction variables such as TiO(2) content, amount of Fe, pH values, amount of hydrogen peroxide, catalyst loading and the initial dye concentration were studied to estimate their effect on the decolorization efficiency of amaranth. The maximum decolorization efficiency achieved was 97.5% at a solution pH of 2.5, catalyst dosage of 2 g/L, 20 mmol/100 mL of H(2)O(2) and initial dye concentration of 10 mg/L. The new heterogeneous catalyst Fe/Ti-NaY was a promising catalyst for this reaction and showed minimum Fe leaching at the end of the reaction.

Selective photocatalytic degradation of aquatic pollutants by titania encapsulated into FAU-type zeolites

The selective photocatalytic degradation of charged pollutants in water was achieved on titania encapsulated into FAU-type zeolites. The electrostatic attraction of cationic substrates and repulsion of anionic substrates by the negatively charged zeolite framework facilitated the selective photocatalytic degradation of charged substrates. The hybrid zeolite-titania photocatalysts were prepared through the ion-exchange method. The titania clusters were mainly well distributed within the cavities of FAU-type zeolites whereas no TiO(2) nanoparticles aggregates were observed on the external surface of zeolite crystals. The hybrid zeolite-titania photocatalysts were characterized by diffuse reflectance UV-visible spectroscopy, transmission electron microscopy, energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy. The selective degradation of charged pollutants was investigated by employing three pairs of oppositely charged substrates. The comparison between the cationic and anionic substrates clearly showed that the degradation rates for the cationic substrates on the hybrid photocatalysts are markedly higher than those for the anionic substrates. Among the cationic substrates, the smaller cations such as tetramethylammoniums were preferentially degraded. This enabled the selective removal of cationic substrates among the mixture. Such a selective photocatalytic degradation of water pollutants may provide a useful strategy for the development of economical photocatalytic process by targeting only the most recalcitrant pollutant.

Photocatalytic Degradation of Methyl Orange on Y Zeolite Supported TiO2

The photocatalytic activity of TiO2/Y photocatalyst was investigated. The experimental results showed that the activity of TiO2/Y photocatalyst prepared by sol-gel method was greatly affected by calcination temperature and the nature of Y-zeolite. Photocatalytic degradation efficiency increased with increasing content of TiO2 on NaY zeolite and reached its maximum rate of 12.4% when TiO2 content was 90%. When TiO2 content was in the range of 50% to 90% , the activity of TiO2/HY was better than pure TiO2. The activity of TiO2/FeY was comparatively low in the TiO2 content range of 50-90%. The enhancement of photocatalytic activity of TiO2 after loading on Y zeolite is not appreciable, indicating that Y type zeolite is not a promising support for TiO2 prepared by sol-gel method.

Photodegradation of an azo dye using immobilized nanoparticles of TiO2 supported by natural porous mineral

Natural mordenite, replacing the synthetic zeolites, has been employed as the support of TiO2, and its photocatalytic activity has been examined in methyl orange (MO) aqueous under UV light. AFM, TEM, XRD, FTIR and fluorescence spectra have been used to reveal the loading effects of TiO2 on mordenite. The results show that the photocatalytic degradation (PCD) reaction rates are sharply increased by natural zeolite supports. Since mordenite is photo-inert, the PCD-enhancement is mostly caused by the bonding effects of Ti-O-Si and Ti-O-Al. Moreover, another two distinct natural zeolites have been employed as the supports of TiO2, in order to check the universality of PCD-enhancement effect of natural zeolites on TiO2. And the factors of PCD reaction on TiO2-zeolite, such as pH and catalyst dose, have been investigated.