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Developing functional materials from biomass is a significant research subject due to its unique structure, abundant availability, biodegradability and low cost. A series of chitosan–lignin (CL) composites were prepared through a hydrothermal method by varying the weight ratio of chitosan and lignin. Subsequently, these CL composites were combined with titania (T) to form a nanocomposite (T/CL) using sol–gel and hydrothermal based methods. T/CL nanocomposites exhibited improved photocatalytic performance in comparison with sol–gel and hydrothermally prepared pristine titania (SGH-TiO2), towards the selective oxidation of benzyl alcohol (BnOH) to benzaldehyde (Bnald) under UV (375 nm) and visible light (515 nm). More specifically, the 75T/CL(25 : 75) nanocomposite (a representative photocatalyst from the 75T/CL nanocomposite series) showed very high selectivity (94%) towards Bnald at 55% BnOH conversion under UV light. Whereas, SGH-TiO2 titania exhibited much lower (68%) selectivity for Bnald at similar BnOH conversion. Moreover, the 75T/CL(25 : 75) nanocomposite also showed excellent Bnald selectivity (100%) at moderate BnOH conversion (19%) under visible light. Whereas, SGH-TiO2 did not show any activity for BnOH oxidation under visible light. XPS studies suggest that the visible light activity of the 75T/CL(25 : 75) nanocomposite is possibly related to the doping of nitrogen into titania from chitosan. However, according to UV-visible-DRS results, no direct evidence pertaining to the decrease in band-gap energy of titania was found upon coupling with the CL composite and the visible light activity was attributed to N-doping of titania. Overall, it was found that T/CL nanocomposites enhanced the photocatalytic performance of titania via improved light harvesting and higher selectivity through mediation of active radical species.

The designing and synthesis of novel photocatalysts are the most important parts, with TiO2-based materials to be consider as prosperous candidates for the selective photo-oxidation of aromatic alcohol. Herein, we established an ultrasound-assisted (500 kHz) precipitation synthetic protocol which led to titanate nanorods of 30 nm maximum length, decorated with nanoclusters of size 1–3 nm. The physicochemical features of the synthesized catalysts were characterized by various techniques. The 1-D nanomaterial obtained at low ultrasound power revealed highest yield towards selective photo-oxidation of benzyl alcohol to benzaldehyde comparing to the material synthesized at higher ultrasound power, in silent, and the commercial TiO2-P25.

Commercial TiO2 (P25), alone or in the presence of graphite oxide (GO), was exposed to ultrasound treatment (US) with the objective to modify the surface of nanoparticles through introducing defects and chemical heterogeneity, and to build the composite with GO of synergistic features. The obtained materials were extensively characterized using XRD, HR-TEM, TA-MS, FTIR, XPS, potentiometric titration, adsorption of nitrogen, and UV/Vis diffuse reflectance techniques. The results showed that the US treatment/activation led to the formation of defects on the surface of the TiO2 nanoparticles, which were associated with an increase in the amount of terminal hydroxy groups, and which resulted in narrowing of the band gap energy. The composite formed upon the ultrasonic activation contained partially reduced GO particles deposited on the surface of TiO2 aggregates and bonded with the titania phase through its carboxylic groups existing at the edges of small defectous graphene particles, leading to a high volume of mesopores formed between the particles/aggregates of the nanoparticles. The US-treated materials showed a superior bifunctional detoxification performance, to adsorb and photocatalytically decompose vapors of a chemical warfare agent surrogate, as a result of the surface alteration/activation and an increase in the porosity.

In nuclear power plants, the concentration of hydrogen generated during the reaction of water with the zircaloy is diminished using the passive autocatalytic recombiners. Pd–Ni/Al\(_{2}\)O\(_{3}\) catalysts were tested in the recombination reaction and compared with the results for Pd/Al\(_{2}\)O\(_{3}\) and Pt/Al\(_{2}\)O\(_{3}\) catalysts. The catalytic reaction was performed in the flowing system under atmospheric pressure with a mixture of 0.5 % H\(_{2}\)-air in the stream in dry and wet conditions. The bimetallic, nickel-containing low-priced catalysts revealed a little lower activity than the high-priced Pd/Al\(_{2}\)O\(_{3}\), but their activity per active metal is promising. The lower atomic percentage of palladium in the active Pd–Ni phase resulted in higher turnover frequencies. Small amounts of water in the reaction mixture greatly decreased the catalytic performance but simple drying of the reaction mixture eliminated this effect.

Two series of highly dispersed supported Pd–Cu catalysts were prepared using different supports: highly acidic aluminum fluoride HS-AlF3, characterized by high surface area, and active carbon, both prepared by different preparation methods (fluorolytic sol–gel method and co-impregnation). A variety of techniques: chemisorption of hydrogen, XRD, TEM, and catalytic performance in two hydrogen-related probe reactions (in n-pentane hydroisomerization and CCl4 hydrodechlorination) were employed to probe metal dispersion and the extent of interaction between two metal components. A reasonable degree of bimetal intermixing in Pd–Cu/HS-AlF3 catalysts synthesized by fluorolytic co-gelation was recognized by the catalytic behavior in bifunctional hydroisomerization of n-pentane. A significantly decreased, compared to pure palladium, hydrogenation–dehydrogenation potential of Pd–Cu alloys led to a weaker performance of bimetallic catalysts. Similarly, it was found that incipient wetness co-impregnation of active carbon resulted in the formation of catalysts characterized by good metal dispersion and significant extent of Pd–Cu alloying. Although the monometallic 2 wt% Cu/carbon catalyst is nearly inactive in CCl4 hydrodechlorination, copper addition to palladium in the co-impregnated catalysts had very pronounced effect, vastly increasing the selectivity toward longer than methane hydrocarbons.

A series of new inorganic-organic hybrid materials based on TiO2 and new biochar-based supports (biochar obtained by pyrolysis of Miscanthus Straw Pellets (MSP) and Soft Wood Pellets (SWP) at 550 and 700 oC) were successfully prepared using ultrasound-assisted methodology. The resulting composites were characterized by a wide range physicochemical techniques and investigated in water and gas phase photocatalytic test reaction. Our best composite (TiO2/SWP700) achieved phenol degradation of 64.1% (under UV light) and 33.6% (under visible light). In addition, it also showed an extraordinarily high activity (~90 %) in selective oxidation of methanol to methyl formate in flow gas phase, high selectivity to methyl formate (~80 %) and high yield of methyl formate (~88 %) after 240 minutes of illumination. It can be noticed that when TiO2 is supported on biochar, presented a superior photocatalytic ability and could be recycled at least 5 times in both photocatalytic runs tests with reproducible high photocatalytic efficiency.

We report an operando XRD/MS experiment on nanocrystalline Pt supported on silica, monitoring quick growth of Pt in an NO atmosphere. XRD data following NO flow show structural changes typical of surface reconstruction. Although a small pressure of NO lifts surface reconstruction of a clean surface, a higher pressure of NO causes the surface to reconstruct again. TEM photographs show formation of clusters of Pt nanoparticles, pointing to growth controlled by coalescence. As surface reconstruction is the phenomenon that we always see accompanying quick growth, we postulate a mechanism of self-lifting cyclic reconstruction that drives the transport of whole clusters and their fusion.

International audience; HAlBEA zeolite is prepared by calcination of parent TEABEA zeolite at 823 K for 3 h in air following ionic exchange with NH4NO3 solution. NixHAlBEA zeolites are prepared by impregnation of HAlBEA with an aqueous solution of Ni(NO3)2, following a drying at 333 K to obtain NixHAlBEA. The calcination of HAlBEA and NixHAlBEA at 773 K for 3 h in air leads to the formation of C-HAlBEA and C–NixHAlBEA with appeared, for the latter, an octahedral and tetrahedral Ni(II) species incorporated in BEA framework as evidenced by XRD, DR UV–vis and XPS. Red-C-HAlBEA and red-C–NixHAlBEA are investigated as the catalysts in dehydrochlorination of 1,2-dichloroethane into vinyl chloride monomer in the presence of hydrogen at 503–523 K. Red-C-HAlBEA and red-C–Ni1.0HAlBEA show an excellent selectivity toward vinyl chloride (∼100%). Activity of HAlBEA and NixHAlBEA in the catalytic conversion of 1,2-dichloroethane strongly depends on the acidic properties of these materials and for the latter the catalytic activity depend on metal dispersion. The small Ni particles favor the dehydrochlorination of 1,2-dichloroethane to vinyl chloride. With increasing nickel particles size decreases activity of the red-C–NixHAlBEA catalysts. For these catalysts after kinetic run sintering of nickel phase is observed. Besides of carburization the nickel sintering is the main cause of red-C–NixHAlBEA deactivation. It is stronger for spent-red-C–Ni2.0HAlBEA with larger nickel particles than for red-C–Ni1.0HAlBEA containing smaller nickel particles (smaller than 5 nm).

The average size of the TiO2 nanoparticles was controlled at around 30 nm on Starbon 800 without using any surfactant, which is attributed to the hydrolysis and condensation (it is also proposed to be a plausible condensation with the carboxylate groups on the carbon surface) of the dissolved titanium(IV) isopropoxide into TiO2 by ultrasonic waves. As the Starbon in the composites has very good contact with the TiO2 nanoparticles (there is no Ti leaching after 240 min of photocatalysis, XRF analysis) it enhances the photo-electron conversion (better than Norit and graphene oxide carbons) of TiO2 by reducing the recombination of photo-generated electron–hole pairs. We have prepared an excellent new hybrid photocatalyst for aqueous phase phenol total mineralization.

Platinum and palladium supported on nanoscopic high surface area aluminum trifluoride (HS-AlF3) were prepared by the sol–gel synthesis. The properties of the HS-AlF3 support, catalyst precursors and catalysts were characterized by XRD, TEM, H2 chemisorption and FTIR-PAS of adsorbed pyridine. Both Pt/HS-AlF3 and Pd/HS-AlF3 catalysts were tested in the hydroconversion of n-pentane showing very good activity, stability and selectivity towards isomerization (80–90%) at 350 °C. The performance of catalysts was related to their bifunctional character. Very strong acidity of HS-AlF3 is the prerequisite for isomerization but the presence of metal is also essential to maintain a high conversion level.

Correction for ‘A novel biomass-based support (Starbon) for TiO2 hybrid photocatalysts: a versatile green tool for water purification’ by Juan Carlos Colmenares et al., RSC Adv., 2013, 3, 20186–20192.

Pd/Nb 2 O 5 –Al 2 O 3 catalysts exhibited interesting properties in the hydrodechlorination of dichlorodifluoromethane. Introduction of niobia to alumina increases the selectivity for CH 2 F 2 , from ∼40% (for Pd/ Al 2 O 3 ) up to ∼75%, for similar metal dispersions. High-temperature reduction (773 K, HTR) of Pd/Nb 2 O 5 –Al 2 O 3 generates the SMSI state, understood as blocking the Pd surface by (partly) reduced niobia. The extent of SMSI effect is judged from a direct comparison between the performance of differently pretreated Pd/Nb 2 O 5 –Al 2 O 3 catalysts tested in n -hexane conversion (hydrogenolysis/isomerisation). After HTR of the niobia-containing Pd catalysts, the hydrodechlorination activity disappeared, however the SMSI state became reversed during hydrodechlorination. It is speculated that CCl 2 F 2 and liberated HCl, interact with NbO x decorants, converting them into volatile niobium oxychloride species.

During reduction in dihydrogen at 873 K, a silica-supported palladium catalyst is initially converted to Pd4Si which further reacts with silicon-containing species to a Pd3Si phase. Such a stepwise phase change suggests that the mechanism of Pd silicide formation involves incorporation of silicon into a palladium phase, not vice versa, as was suggested in our previous work. This transformation has a great effect on catalytic properties of Pd–silica-containing systems in 2,2-dimethylpropane hydroconversion.

International audience; Influence of copper addition to nickel containing zeolite on activity and product selectivity in the hydrodechlorination of 1,2-dichloroethane was investigated. Ni2.0SiBEA and Cu2.0Ni2.0SiBEA zeolites were prepared by a two-steps postsynthesis method which consist of (1) creation of vacant T-atom sites by dealumination of calcined BEA zeolite with nitric acid and then (2) impregnation of as resulting SiBEA with aqueous nickel nitrate solution or co-impregnation with aqueous nickel and copper nitrate solution, respectively. Calcination at 773 K for 3 h in air and then reduction at 873 K over 3 h in flowing 10% H2/Ar of Ni2.0SiBEA and Cu2.0Ni2.0SiBEA, with an isolated pseudo-tetrahedral Ni(II) and Cu(II) species incorporated into BEA framework, leads to formation of red-C-Ni2.0SiBEA and red-C-Cu2.0Ni2.0SiBEA catalysts with very well dispersed metal nanoparticles. The state of nickel and copper in catalysts after calcination, reduction and reaction was characterized by XRD, low-temperature N2 sorption, TPR and XPS. The red-C-Ni2.0SiBEA and red-C-Cu2.0Ni2.0SiBEA catalysts were active in hydrodechlorination of 1,2-dichloroethane with very high selectivity into ethylene (90 and 96% respectively), desired product of this reaction. Thus, the simultaneous introduction of copper and nickel ions in SiBEA in the second step of postsynthesis procedure allows obtaining bimetallic red-C-Cu2.0Ni2.0SiBEA catalyst with well dispersed, separated Cu and Ni particles with higher selectivity toward ethylene than red-C-Ni2.0SiBEA catalyst. TEM experiments have shown that after catalytic run a very small agglomeration of metal particles took place. According to TPH and XPS measurements chlorine containing species are present in spent zeolite catalysts.

Big variations in overall activity and product selectivity in the cyclopentane/deuterium exchange reaction were found in effect of various pretreatments of two chlorine‐free Pd/γ‐Al2O3 catalysts. The most important changes are observed when severely prereduced (at 600 °C) Pd/Al2O3 catalysts have been reoxidised and mildly rereduced: the multiple type of exchange, typical of mildly pretreated Pd catalysts, is replaced by a stepwise mode, and a big increase in catalytic activity occurs. At this state, the Pd/γ‐Al2O3 catalysts retain some water (as surface hydroxyls) generated by reoxidation and mild reduction. Deuterium spillover from Pd onto alumina and changes in acidity of alumina are invoked to rationalize the kinetic results. Changes in the state of Pd after various pretreatments, as probed by temperature‐programmed hydride decomposition, can hardly be correlated with changes in the catalytic behaviour in the exchange reaction.

Correction for ‘Titania/chitosan–lignin nanocomposite as an efficient photocatalyst for the selective oxidation of benzyl alcohol under UV and visible light’ by Ayesha Khan et al., RSC Adv., 2021, 11, 34996–35010. DOI: 10.1039/D1RA06500A