Adrian Ungureanu

This study explores the performances of nickel‐based materials for the dry reforming of methane (DRM), an important process for hydrogen and syngas productions. Ni nanoparticles are issued from porous phyllosilicate phase exolution under reducing conditions (in situ or ex situ). Phyllosilicate precursors were obtained by deposition/precipitation with urea onto SBA‐15 porous silica, with metal loading up to 40 wt.%. Reaction was performed at 600–700 °C. The successful formation and stabilization of highly dispersed nanoparticles (2–6 nm) is revealed, even for highly loaded formulations (20 wt.% and 40 wt.%). In DRM‐700 (CH₄/CO₂=1, 20 % CH₄, 480,000 mL g_cat⁻¹ h⁻¹) the formulation at 20 wt.% metal loading (Ni_20 %) activated during reaction affords 50 % and 65 % of CH₄ and CO₂ conversions respectively at 700 °C. Ni_20 % is showing excellent resistance toward sintering after DRM stability test of 80 h. Characterizations made for spent catalyst show high resistance toward sintering and limited carbon formation.

Herein, we show that gallium oxide can function as an efficient promoter for the Cu-catalysed hydrogenation of cinnamaldehyde. SBA-15-supported Cu–Ga 2 O 3 nanoparticles with a constant Cu loading of 5 wt% and two Cu/Ga weight ratios of 5 and 2, respectively, were synthesised by incipient wetness impregnation followed by mild drying. Physico-chemical characterisation revealed that the metal dispersion, and thus the active surface area of copper, can be enhanced nine-fold upon the addition of gallium promoter, boosting the catalytic activity as compared with the unpromoted Cu/SBA-15 catalyst. Likewise, the presence of Ga 2 O 3 improved the selectivity to cinnamyl alcohol.

Alumina-functionalized ordered mesoporous silica SBA-15 particles have been proposed to stabilize Pickering emulsions. Functionalization of SBA-15 particles have been performed by depositing alumina using a two-step synthesis (first, silica condensation, followed by alumina precipitation). Three different Al to Si ratios have been prepared. The calcined materials have been characterized by TEM, SEM, XRD, N2 physisorption, zeta potential, in order determine key physico-chemical properties, and the alumina localization. The emulsifying and stabilizing properties of the calcined particles have been evaluated for water/toluene-based Pickering emulsions.

Xylose can be selectively converted to xylitol in water, with an optimized yield of 98 %, in the presence of a simple silica supported monometallic cobalt – Co/SiO₂ – catalyst. This catalyst displays initial outstanding catalytic properties in a proper solvent, the best results being obtained in pure water. Recyclability studies show a moderate deactivation of the catalyst, while selectivity to xylitol remains almost unchanged after 4 cycles, confirming that this catalyst formulation is very promising for the xylitol production process.

Conventional melt infiltration (over calcined SBA‐15 silica support) and optimized melt infiltration (over surfactant‐containing SBA‐15 support) were used for the first time to prepare MnO_x nanoparticles encapsulated within the support pores. A comprehensive study on the evolution of textural, structural, and morphological characteristics of the MnO_x‐silica composites as well as their redox and surface properties is reported herein by varying synthesis parameters, such as manganese loading (5, 10, 20 and 30 Mn wt.%), and post‐treatment temperature (300 and 500 °C). The catalytic performances of the materials prepared in this work have been evaluated in the catalytic oxidation of formaldehyde. The results show a high performance of the SBA‐15 supported manganese oxide at low‐ to moderate‐ temperatures of reaction (Temperature at 50 % of HCHO conversion into CO₂ ranging from 110° to 150 °C), activity being related to Mn oxidation state (from 2.3 to 4) and MnO_x phase location, confined with or without 2D spatial distribution in the support porosity or formed at the external surface of SBA‐15. A high stability (60 hours), under dry air and 50 % relative humidity air, is reported for MnO_x‐based nanocatalysts prepared by conventional and optimized melt infiltration procedures.