Role of Mo in catalysts based on noble metals in hydrodeoxygenation reactions

The use of bio-energy as a renewable alternative to fossil fuels is nowadays attracting more and more attention. The bio-fuel from biomass seems to be a potential energy substitute for fossil fuels since it is a renewable resource that could contribute to sustainable development and global environmental preservation and it appears to have significant economic potential1. The problem is its high oxygen content, which gives undesirable properties for combustion. To remove oxygen, catalytic hydrodeoxygenation (HDO) reactions are carried out. Monometallic Mo/Si, Pt/Si as well as bimetallic PtMo/Si catalysts were prepared and evaluated in the hydrodeoxygenation (HDO)reaction of dibenzofurane (DBF) as a model molecule in biomass derived bio-oil.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Controlled alcohol oxidation reactions by supported non-noble metal nanoparticles on chitin-derived N-doped carbons

A series of catalysts based on non-noble metal nanoparticles supported on chitin-derived N-doped carbons was prepared through a one-step protocol in the presence of EDTA as a ligand. Both the complexing properties of EDTA and the interaction of metal precursors with the nitrogen sites on the support surface allowed a good dispersion and a homogeneous distribution of the metal active sites. The synthesized materials were tested in the catalytic oxidation of alcohols to aldehydes and ketones. Particularly, the model reaction of oxidation of benzyl alcohol showed that iron- and even more molybdenum-based materials exhibited the best performance. At 130 degrees C and 20 bar, in the presence of air as an oxidant, the Mo-N/C-catalyzed reactions proceeded with excellent conversion and selectivity, both above 90%, towards the product of partial oxidation, benzaldehyde, and the catalytic performance was retained over 5 recycling runs without any loss of activity. The Mo-based system proved effective also for the conversion of some representative benzyl- and furyl-type alcohols bearing primary and secondary hydroxyl functions to the corresponding aldehydes/ketones, though the oxidation of aliphatic substrates was unsuccessful. All catalysts together with the Mo-N/C sample recovered after its use were fully characterized following a multi-technique approach involving XRD, N-2-physisorption, XPS, and HRTEM-EDX analyses. Textural, morphological and chemical properties were thus compared and related to the observed trend of catalytic activity

Orthogonal assisted tandem reactions for the upgrading of bio-based aromatic alcohols using chitin derived mono and bimetallic catalysts

The upgrading of a benzyl-type alcohols was explored via an orthogonal tandem sequence comprised of a first oxidative step producing the corresponding aldehydes, and a subsequent reductive amination to achieve both secondary and tertiary amines. To the scope, acetonitrile (ACN) was used as a solvent and a source/precursor of reactant amines, and different heterogeneous catalysts based on Rh and Mo, were designed as mono- and bi-metallic systems in the form of metal nanoparticles dispersed on a chitin-derived N-doped carbons. A parametric analysis carried out separately for the oxidation and the reductive amination allowed to choose the best performant catalyst for both the reactions of the tandem process. A one-pot two-step protocol was implemented accordingly: as an example, benzyl alcohol was quantitatively and selectively oxidised to benzaldehyde (>99%) which in turn, was converted to N-benzylethanamine (66%) or N-benzyl-N-ethylethanamine (60%) in the presence of [Rh(5%)-N/C-Mo(5%)]-N/C or [Rh(3%)-N/C-Mo(5%)]-N/C as catalysts, respectively. The tandem sequence proved successful also for other bio-based benzyl-type alcohols that afforded the corresponding secondary/tertiary amines in yields up to 53-93%. Overall, the study proved the viability of an innovative method aimed not only at process intensification for multistep synthesis, but also at the valorization of substrates (alcohols) and biopolymers (chitin) derived from biomass

Iron phosphide nanocatalysts for oxygen removal from biomass derived biofuel. Phenol as a model molecule

Silica-supported catalysts based on iron phosphides with different stoichiometries were synthesised and tested in the hydrodeoxygenation (HDO) reaction of phenol, a model molecule present in bio-oil derived from pyrolysis of biomass. Tests were performed in a fixed bed reactor under hydrogen pressure (1.5 and 3 MPa). The catalysts were characterized by several characterization techniques in order to evaluate structure, textural and acidic properties and correlate them with the catalytic tests. Characterisation results revealed that by increasing the amount of P, phosphorous rich iron phosphide phases were formed. The surface became enriched with P, and this was associated with the presence of surface P-OH groups that provided Brönsted acid sites to activate O-containing compounds as well as surface hydrogen species that minimised deactivation by coke deposition. Samples containing P/Fe ratios 1 and 2 were the most active in the HDO reaction, being cyclohexane and cyclohexene, the most important reaction products. The product distribution was strongly affected by the reaction pressure employed

On the selective transformation of ethanol over Mg- and/or La-containing mixed oxides catalysts

[EN] MgO-La2O3 catalysts with different Mg/La molar ratio were synthesized by a precipitation method and a subsequent calcination and then characterized by x-ray diffraction, N2 adsorption-desorption isotherms (at-196 degrees C), CO2- and NH3-thermoprogrammed desorption and x-ray photoelectronic spectroscopy. The coexistence of acid and basic sites promoted the selective transformation of ethanol into valuable products. Thus, MgO catalyst promoted the Guerbet reaction obtaining n-butanol as product while the incorporation of La2O3 in the catalytic system improved the ethanol conversion notably, obtaining ethylene as the main product due to a dehydration reaction. The highest ethylene yield was obtained for the catalyst with a Mg/La molar ratio of 1.The funding received for this study from the Spanish Ministry of Science and Innovation, PID2021-126235OB-C31 and PID2021-126235OB-C32 funded by MCIN/AEI/10.13039/501100011033 and FEDER funds, and projects TED2021-130756B-C31 and TED2021-130756B-C32 funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe" by the European Union NextGenerationEU/PRTR, is acknowledged.Ballesteros Plata, D.; Balestra, G.; Cecilia, J.; Barroso Martín, I.; Infantes-Molina, A.; Tabanelli, T.; Cavani, F.... (2024). On the selective transformation of ethanol over Mg- and/or La-containing mixed oxides catalysts. Catalysis Today. 429. https://doi.org/10.1016/j.cattod.2023.11447042

Iron phosphide nanocatalysts presenting different stoichiometry as catalysts in the HDO of phenol

Iron phosphide catalysts supported on silica with an iron loading of 15 wt% were synthesized and studied in the hydrodeoxygenation (HDO) of phenol. The amount of phosphorus varied in order to obtain iron phosphides with different stoichiometry. Catalysts containing Fe2P, FeP and FeP2 phases were obtained. The textural and structural properties of the prepared catalysts were evaluated by using different experimental techniques such as N2 adsorption-desorption at -196 °C, X-ray diffraction (XRD), Mössbauer spectroscopy, high resolution transmission spectroscopy (HRTEM), infrared spectroscopy (IR) of adsorbed CO at low temperature, X-ray photoelectron microscopy (XPS) and NH3 thermoprogrammed desorption (NH3-TPD). The catalytic activity was studied at 275 °C and at 15 and 5 bar of hydrogen pressure in the hydrodeoxygenation reaction of phenol. Characterization results evidenced that the initial P/Fe ratio employed in the synthesis not only governed the stoichiometry of the iron phosphide, but also the particle size, metallic surface exposure and acidity. The catalysts presenting unique phases were those presenting better activity in the HDO reaction of phenol. Moreover, Fe2P phase presented better results than FeP in terms of HDO conversion

Iron phosphides presenting different stoichiometry as nanocatalysts in the HDO of phenol

Iron phosphide catalysts supported on silica with an iron loading of 15 wt% were synthesized and studied in the hydrodeoxygenation (HDO) of phenol. The amount of phosphorus varied in order to obtain iron phosphides with different stoichiometry. Catalysts containing Fe2P, FeP and FeP2 phases were obtained. The textural and structural properties of the prepared catalysts were evaluated by using different experimental techniques such as N2 adsorption-desorption at -196 °C, X-ray diffraction (XRD), Mössbauer spectroscopy, high resolution transmission spectroscopy (HRTEM), infrared spectroscopy (IR) of adsorbed CO at low temperature, X-ray photoelectron microscopy (XPS) and NH3 thermoprogrammed desorption (NH3-TPD). The catalytic activity was studied at 275 °C and at 15 and 5 bar of hydrogen pressure in the hydrodeoxygenation reaction of phenol. Characterization results evidenced that the initial P/Fe ratio employed in the synthesis not only governed the stoichiometry of the iron phosphide, but also the particle size, metallic surface exposure and acidity. The catalysts presenting unique phases were those presenting better activity in the HDO reaction of phenol. Moreover, Fe2P phase presented better results than FeP in terms of HDO conversio

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