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The photocatalyst composition can significantly affect their physicochemical properties that are directly related to their photocatalytic activity. In this work, the influence of the Pd-TiO 2 /ZSM-5 catalyst composition on hydrogen production by photocatalytic water splitting was studied. The ZSM-5 zeolite was use as support for the active phase of titanium dioxide; palladium was also incorporated as a metallic co-catalyst. The concentrations of TiO 2 and Pd were varied during catalyst synthesis according to a factorial rotational experimental design. The catalysts were characterized and employed in hydrogen production under ultraviolet radiation. Empirical models were obtained for relating physicochemical properties and hydrogen production as functions of palladium and titanium dioxide content. Relative crystallinity of the support and specific surface area were affected only by the titanium dioxide contend while band gap energy and hydrogen production were affected by nominal percentage of metallic co-catalyst and active phase. The most active catalyst was the 1.5%Pd-28%TiO 2 /ZSM-5, which promoted hydrogen production rate of 1148 μmol g cat −1 h −1 under low power irradiation font. [ABSTRACT FROM AUTHOR]

It is possible to produce hydrocarbons by hydrocracking of biomass, such as those produced by crude oil cracking. This product can be incorporated as raw material in petrochemical industry and used as petroleum fractions without any changes on engines. The hydrocracking process was performed over NaZSM5 and HZSM5, where the improvement of this acidity was carried out by ion exchange with ammonia followed by calcination. The reactions were performed on a stainless steel fixed bed reactor. The catalyst was evaluated at 723 K and 138 kPa, under flow of hydrogen gas, with weight hourly space velocity (WHSV) of 4 h −1 . Products are analysed by gas chromatography with mass spectra detector (GC–MS) and by nuclear magnetic resonance (NMR) of 1 H. For the fresh catalyst, all triglyceride was converted to hydrocarbon by the process. For NaZSM5, the catalyst activity is high but has a high decrease over the time of reaction. It was changed for HZSM5, where the catalyst maintained a high activity even after 90 min of reaction. This treatment improved also the product, where a high yield of gaseous hydrocarbon was changed to a high yield of liquid hydrocarbon, especially by the presence of aromatics molecules. [ABSTRACT FROM AUTHOR]

• Pd-TiO 2 /ZSM-5 catalyst was used in water splitting under UV light. • Empirical models were obtained for effects of operational conditions on H 2 production rate. • H 2 production was mainly affected by catalyst concentration and ethanol content. • Initial pH presented negative effect on photocatalytic H 2 production. Operational variables effects on hydrogen production in photocatalytic water splitting system were evaluated using Pd-TiO 2 /ZSM-5. This material was synthetized and had its physicochemical properties properly characterized. Using experimental design techniques allowed the simultaneous evaluation of the effects of catalyst concentration, ethanol (sacrificial reagent) content and initial solution pH on hydrogen production rate. It was verified that an increase in catalyst concentration or ethanol content has a positive influence on system productivity until a maximum point is reached, from which a decrease on gas evolution rate occurs. In contrast, an increase in the initial solution pH presented a linear negative effect on hydrogen production in all analyzed experimental region. Among evaluated conditions, the highest total hydrogen production rate, 712 μmol h−1 (791 μmol g cat −1 h−1), was obtained using a catalyst concentration of 1.5 g L−1, a 16% ethanol content and initial solution pH equal to 4. [ABSTRACT FROM AUTHOR]

A static batch arrangement composed of anti-leak vials coupled to gas chromatography is proposed as a complementary system for performance assessment of biogas desulfurization by adsorption. For testing, a modified commercial activated carbon produced by controlled thermal treatment in the presence of iron(III) species improved biogas desulfurization. The adsorbents showed a superior hydrogen sulfide removal compared to ordinary one. Pseudo-first-order, pseudo-second-order, and Bangham's kinetic models were used to fit experimental data. All studied samples followed pseudo-first-order model, indicating the predominance of physisorption, and Bangham's model, confirming that the micropores structure played an important role for gases diffusion and adsorbent capacity. Additionally, the materials were characterized by N2 adsorption–desorption, X-ray diffraction, infrared spectroscopy, scanning electron microscopy and energy-dispersive spectroscopy. The thermal treatment associated with iron impregnation caused significant modifications in the surface of the materials, and the iron species showed two main benefits: an expressive increase in the specific area and the formation of specific adsorption sites for hydrogen sulfide removal. The results reinforce the advantages of iron-modified adsorbents in relation to their non-modified counterparts. The analytical methodology based on the confinement of multiple gases contributes to improving the understanding of the hydrogen sulfide adsorption process using pressure swing adsorption technology. [ABSTRACT FROM AUTHOR]