Selective hydrodeoxygenation of biomass derived 5-hydroxymethylfurfural over silica supported iridium catalysts

Catalytic performance of iridium supported on SiO2 was investigated for 5-hydroxymethylfurfural (HMF) transformation. Ir/SiO2 catalysts exhibiting different metal loading (1, 3, and 5¿wt.%) were tested in the preliminary experiments in the hydrogenation of two probe molecules, e.g. ethyl pyruvate (EP) and ketopantolactone (KP) to evaluate the Ir dispersion on the catalyst activity in CO hydrogenation. In the transformation of HMF the influence of metal dispersion, iridium precursor and addition of H2SO4 were studied revealing that 2,5-bis-(hydroxymethyl)furan (BHMF) was the main product with 83% selectivity at 70% conversion of HMF over chlorine free Ir/SiO2 together with H2SO4 at 333¿K in THF under 10¿bar H2 pressure. On the other hand, one-pot synthesis of HMF to 2,5-dimethylfuran (DMF) was promoted in the presence of chlorine containing 1%Ir/SiO2(Cl) and H2SO4. Both of these products are considered high value-added chemicals from biomass-derived 5-hydroxymethylfurfural. The exposed iridium atoms together with the total acid sites are an important catalytic descriptor for hydrogenation of HMF to BHMF.Peer ReviewedPreprin

Glycerol Valorization over ZrO2-Supported Copper Nanoparticles Catalysts Prepared by Chemical Reduction Method

Copper nanoparticles (NPs) and ZrO2-supported copper NPs (Cu NPs/ZrO2) were synthesized via a chemical reduction method applying different pH (4, 7 and 9) and evaluated in a glycerol dehydration reaction. Copper NPs were characterized with transmission electron microscopy (TEM) and UV–vis spectroscopy. Transmission electron microcopy (TEM) results revealed a homogeneous distribution of copper NPs. A hypsochromic shift was identified with UV–vis spectroscopy as the pH of the synthesis increased from pH = 4 to pH = 9. Zirconia-supported copper NPs catalysts were characterized using N2 physisorption, X-ray diffraction (XRD), TEM, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), temperature-programmed desorption of ammonia (NH3-TPD) and N2O chemisorption. The presence of ZrO2 in the chemical reduction method confirmed the dispersion of the copper nanoparticles. X-ray diffraction indicated only the presence of tetragonal zirconia patterns in the catalysts. XPS identified the Cu/Zr surface atomic ratio of the catalysts. TPR patterns showed two main peaks for the Cu NPS/ZrO2 pH = 9 catalyst; the first peak between 125 and 180 °C (region I) was ascribed to more dispersed copper species, and the second one between 180 and 250 °C (region II) was assigned to bulk CuO. The catalysts prepared at pH = 4 and pH = 7 only revealed reduction at lower temperatures (region I). Copper dispersion was determined by N2O chemisorption. With NH3-TPD it was found that Cu NPs/ZrO2 pH = 9 exhibited the highest total quantity of acidic sites and the highest apparent kinetic constant, with a value of 0.004 min−1. The different pH applied to the synthesis media of the copper nanoparticles determined the resultant copper dispersion on the ZrO2 support, providing active domains for glycerol conversion

Selective hydrodeoxygenation of biomass derived 5-hydroxymethylfurfural over silica supported iridium catalysts

Catalytic performance of iridium supported on SiO2 was investigated for 5-hydroxymethylfurfural (HMF) transformation. Ir/SiO2 catalysts exhibiting different metal loading (1, 3, and 5¿wt.%) were tested in the preliminary experiments in the hydrogenation of two probe molecules, e.g. ethyl pyruvate (EP) and ketopantolactone (KP) to evaluate the Ir dispersion on the catalyst activity in CO hydrogenation. In the transformation of HMF the influence of metal dispersion, iridium precursor and addition of H2SO4 were studied revealing that 2,5-bis-(hydroxymethyl)furan (BHMF) was the main product with 83% selectivity at 70% conversion of HMF over chlorine free Ir/SiO2 together with H2SO4 at 333¿K in THF under 10¿bar H2 pressure. On the other hand, one-pot synthesis of HMF to 2,5-dimethylfuran (DMF) was promoted in the presence of chlorine containing 1%Ir/SiO2(Cl) and H2SO4. Both of these products are considered high value-added chemicals from biomass-derived 5-hydroxymethylfurfural. The exposed iridium atoms together with the total acid sites are an important catalytic descriptor for hydrogenation of HMF to BHMF.Peer Reviewe

Turning glycerol to value-added chemicals in the absence of external hydrogen over copper catalysts supported on SBA-15-type materials containing zirconium

Nowadays, many industrial processes depend on fossil resources to obtain high-added-value chemical compounds, bringing with it significant environmental deterioration. Therefore, the implementation of green alternatives considering the use of biomass residues in hydrogen-free catalytic processes is of great relevance. In this work, a set of copper catalysts prepared by impregnating SBA-15 and Zr-SBA-15 (different Si/Zr ratios) supports were catalytically tested in the glycerol dehydration. The copper catalysts were characterized by ICP, SEM-EDS, N2 physisorption, XRD, HRTEM, FT-IR, UV–Vis DRS, XPS, H2-TPR, N2O chemisorption, and TPO analyses. ICP revealed a suitable agreement between nominal and actual copper content in the catalysts. Copper catalysts exhibited textural and structural properties of mesoporous materials which are affected by increasing Zr content. Pyridine FT-IR indicated that copper catalysts with lower Zr content possess the highest values of Lewis acid sites. Higher Zr content makes the copper reduction more difficult, and the dispersion is unfavored. The catalytic system was studied using an 80% wt. aqueous glycerol solution in inert conditions at 220 °C without diffusional limitations according to the Weisz–Prater and Mears criteria. The highest values of specific initial reaction rate and rate constant were obtained in catalysts with zero (Cu/B catalyst, 1.50¿×¿10-3 molgl/min gcat, 7.79¿×¿10-4 min-1) and low (Cu/B10 catalyst, 1.53¿×¿10-3 molgl/min gcat, 8.27¿×¿10-4 min-1) Zr loading. Hydroxyacetone (HA) and 1,2-propanediol (1,2-PDO) were the main formed products. HA formation reached values greater than 90% selectivity in the first minutes of the reaction, while 1,2-PDO achieved a progressive evolution over time up to 9% selectivity. Initial formation rates of HA (3.29¿×¿10-4 molHA/min gcat) and 1,2-PDO (2.13¿×¿10-5 mol1,2-PDO/min gcat) were optimized on the Cu/B10 catalyst containing the lowest Zr load. 1,2-PDO generation in the absence of external hydrogen with a high concentration of glycerol simulating industrial wastes is highlighted. Finally, the Zr load in the copper catalysts modulates the textural, structural, acidic, surface, and reducible properties, which can also be considered as descriptors to understand the catalytic activity together with exposed copper species, stability against copper leaching, sintering, and carbon deposition.Peer ReviewedPostprint (author's final draft

Revealing the effects of high Al loading incorporation in the SBA-15 silica mesoporous material

High aluminum loading incorporation in the SBA-15 silica structure was investigated. Different Si/Al molar ratios (15, 10, and 2) were evaluated. The SBA-15 and the aluminum-containing materials (Al-SBA-15) were prepared by the “pH adjusting” method with modifications. The mesoporous structure of the materials was demonstrated by the type IV isotherms. The SBA-15 pore changed from a cylindrical to a slit-like structure in the presence of higher aluminum content. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) pointed out that the structural order is compromised in the presence of a higher aluminum load in the Al-SBA-15 materials, although the mesoporous structure was preserved. Higher Al loading increases the total quantity of Lewis acid sites as well as generates Brönsted acid sites. CO adsorption FTIR spectroscopy suggests aluminum incorporation into the SBA-15 and generation of acid sites. The Si–O–Al linkage in the aluminum-containing materials was corroborated by UV–Vis DRS due to the presence of a peak centered at 241 nm related to the Al-O bond, which is ascribed to four-coordinated framework aluminum in the SBA-15 structure. XPS spectra of Al 2p suggested that the Al species are less oxidized than the Al2O3 phase giving some indication of Al incorporation into the SBA-15 framework. 27Al MAS NMR results revealed that the aluminum species are in a tetrahedral oxygen coordination environment for Al-SBA-15 with Si/Al molar ratios of 15 and 10. Aluminum species in both tetrahedral and octahedral environments were evidenced for Al-SBA-15 with a Si/Al molar ratio of 2.Peer ReviewedPostprint (author's final draft