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The production of ethylene glycol (EG) from cellulose has garnered significant attention in recent years as an attractive alternative to fossil fuels due to the potential of cellulose as a renewable and sustainable feedstock. In this work, to the best of our knowledge, a series of low-cost Ni-W bimetallic catalysts supported on glucose/carbon nanotube hybrid carbons were synthesised for the first time and employed to transform cellulose into EG. Two different strategies were combined for the preparation of the carbons: the activation and addition of carbon nanotubes (CNTs) to obtain a hybrid material (AG-CNT). The catalytic conversion process proceeded through cellulose hydrolysis to glucose, followed by glucose retro-aldol condensation to glycolaldehyde and its subsequent hydrogenation to EG. Through the optimisation of the catalyst's properties, particularly the metals' content, a good synergistic effect of C-C bond cleavage and hydrogenation capabilities was assured, resulting in the highly selective production of EG. The balance between Ni and W active sites was confirmed to be a crucial parameter. Thus, total cellulose conversion (100%) was achieved with EG yields of 60–62%, which are amongst the best yields ever reported for the catalytic conversion of cellulose into EG via carbon-supported catalysts. [ABSTRACT FROM AUTHOR]

Different supported metal catalysts were tested for the one-pot transformation of corncob xylan to xylitol. The influence of several factors, such as catalytic support, nature of metal, metal loading, amount of catalyst, hydrogen pressure and reaction temperature, was investigated. The results revealed that xylan can be converted into xylitol with a yield close to 80% after 2 h of reaction using Ru supported on carbon nanotubes (CNT, 0.4 wt% metal loading) with excellent stability after repeated use, at a temperature of 170°C and an H2 pressure of 50 bar. The yield of xylitol achieved is one of the highest ever reported for the direct conversion of xylan to xylitol using an environmentally friendly process. [ABSTRACT FROM AUTHOR]

The catalytic reduction of nitrites over Pt-In catalysts supported on activated carbon has been studied in a semi-batch reactor, at room temperature and atmospheric pressure, and using hydrogen as the reducing agent. The influence of the indium content on the activity and selectivity was evaluated. Monometallic Pt catalysts are very active for nitrite reduction, but the addition of up to 1 wt% of indium significantly increases the nitrogen selectivity from 0 to 96%. The decrease in the accessible noble metal surface area reduces the amount of hydrogen available at the catalyst surface, this favoring the combination of nitrogen-containing intermediate molecules to promote the formation of N 2 instead of being deeply hydrogenated into NH 4+ . Several activated carbon-supported Pt-In catalysts, activated under different calcination and reduction temperatures, have been also evaluated in nitrite reduction. The catalyst calcined and reduced at 400°C showed the best performance considering both the activity and the selectivity to nitrogen. This enhanced selectivity is ascribed to the formation of Pt-In alloy. The electronic properties of Pt change upon alloy formation, as it is demonstrated by XPS., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The handling Editor declared a past co-authorship with the authors (AS, ER, MP)., (Copyright © 2021 Soares, Jardim, Ramos-Fernandez, Villora-Picó, Pastor-Blas, Silvestre-Albero, Órfão, Pereira and Sepúlveda-Escribano.)

Cryptomelane-type manganese oxides were synthesized by redox reaction under acid and reflux conditions. Different metals (cesium, lithium and titanium) were incorporated into the tunnel structure by the ion-exchange technique. Gold was loaded onto these materials (1wt%) by a double impregnation method. The obtained catalysts were characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectrometry, scanning electron microscopy, X-ray diffraction and temperature-programmed reduction. The catalytic activity of these materials was evaluated in the oxidation of carbon monoxide. The incorporation of Cs, Li or Ti into cryptomelane was detrimental in terms of catalytic activity. Further addition of gold to cryptomelane doped materials significantly improved the catalytic performance, especially for Cs-K-OMS-2 and Li-K-OMS-2 (to a smaller extent). Addition of gold to the Ti containing material did not show a significant improvement. The observed trends are related to the effect of gold on samples reducibility and to the gold particle size. The lattice oxygen can also be considered accountable for the activity of the materials, since the most active cryptomelane catalysts are those with higher lattice oxygen donating ability for the oxidation of the CO molecule., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Two catalysts containing ceria dispersed on the surface of multi-walled carbon nanotubes and activated carbon were investigated as ozonation catalysts for the mineralization of bezafibrate (BZF). The results were compared with those obtained in the absence of the catalyst and in the presence of the parent carbon materials, as well as in the presence of ceria (CeO2). Carbon materials containing ceria showed an interesting catalytic effect. Both materials enhanced the mineralization of BZF relatively to single ozonation and ozonation catalysed by the corresponding carbon materials. In the catalytic ozonation with these materials, both surface and bulk reactions are supposed to occur. The BZF ozonation catalysed by CeO2 leaded to the highest mineralization degrees, indicating that the reaction mechanism followed in the presence of CeO2 (free radical oxidation in solution) leads to the formation of intermediates more easily degradable, mainly after 120 min of reaction. Some primary products and refractory final oxidation compounds in single and catalytic ozonation of BZF were followed. The original chlorine present on the BZF molecule is completely converted to chloride anion and part of the nitrogen is mainly converted to NO3- along with smaller amounts of NO2- and NH4+. Microtox tests revealed that simultaneous use of ozone and CeO2 originated lower acute toxicity.

Two carbon materials (multi-walled carbon nanotubes, MWCNTs, and activated carbon) were investigated as ozonation catalysts for the mineralization of the antibiotic sulphamethoxazole (SMX). MWCNTs presented a higher catalytic performance than activated carbons, which was justified by their differences in surface chemistry and by the higher internal mass transfer resistances expected for activated carbons. 3-Amino-5-methylisoxazole and p-benzoquinone were detected as primary products of single and catalytic ozonation of SMX, whereas oxamic, oxalic, pyruvic and maleic acids were identified as refractory final oxidation products. The original sulphur of the SMX was almost completely converted to sulphate and part of the nitrogen was converted to NH4+ and NO3-. The presence of the radical scavenger tert-butanol during catalytic and single ozonation evidenced the participation of HO radicals in the oxidation mechanisms of SMX, especially in the mineralization of several intermediates. Microtox tests revealed that simultaneous use of ozone and MWCNTs originated lower acute toxicity. The time course of all detected compounds was studied and the transformation pathway for the complete mineralization of SMX by single and catalytic ozonation in the presence of the selected materials was elucidated., (Copyright © 2012 Elsevier B.V. All rights reserved.)