One-Pot Transformation of Citronellal to Menthol Over H-Beta Zeolite Supported Ni Catalyst: Effect of Catalyst Support Acidity and Ni Loading

Citronellal was converted to menthol in a one-pot approach using H-Beta zeolite-based Ni catalyst in a batch reactor at 80 °C, under 20 bar of total pressure. The effects of H-Beta acidity (H-Beta-25 with the molar ratio SiO2/Al2O3 = 25 and H-Beta-300 with SiO2/Al2O3 = 300) and Ni loading (5, 10 and 15 wt %) on the catalytic performance were investigated. Ni was impregnated on H-Beta support using the evaporation-impregnation method. The physico-chemical properties of the catalysts were characterized by XRD, SEM, TEM, ICP-OES, N2 physisorption, TPR, and pyridine adsorption–desorption FTIR techniques. Activity and selectivity of catalysts were strongly affected by the Brønsted and Lewis acid sites concentration and strength, Ni loading, its particle size and dispersion. A synergetic effect of appropriate acidity and suitable Ni loading in 15 wt.% Ni/H-Beta-25 catalyst led to the best performance giving 36% yield of menthols and 77% stereoselectivity to (±)-menthol isomer at 93% citronellal conversion. Moreover, the catalyst was successfully regenerated and reused giving similar activity, selectivity and stereoselectivity to the desired (±)-menthol isomer as the fresh one. Graphical Abstract: [Figure not available: see fulltext.

Hydrodeoxygenation of Isoeugenol over Ni- and Co-Supported Catalysts

Hydrodeoxygenation (HDO) of isoeugenol was investigated over several Ni (Ni/SiO2, Ni/graphite) and Co (Co/SBA-15, Co/SiO2, Co/TiO2, Co/Al2O3) catalysts at 200 and 300 degrees C under 30 bar hydrogen pressure in a batch reactor. The catalysts were prepared by an impregnation method and systematically characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy dispersive analysis, organic elemental, and thermogravimetrical analysis before and after the reaction. Analysis of the liquid, solid, and gaseous products was performed to identify isoeugenol transformation pathways. The maximum yield of the desired propylcyclohexane (PCH) (63%) and the highest sum of masses of reactants and products in the liquid phase based on GC results (GCLPA) (79%) were obtained over 10 wt % Co/SBA-15. HDO of isoeugenol over 11 wt % Co/SiO2 resulted in 50% PCH yield with a rather similar GCLPA of 73%. Low yields of PCH and the liquid phase mass balance closure were obtained over highly dispersed 15 wt % Co/Al2O3 and 15 wt % Co/TiO2. PCH yield was 60% over Ni/graphite and 44% over Ni/SiO2 after 4 h with GCLPA values of 73 and 70%, correspondingly. Overall PCH yields increased in the following order: Co/TiO2 < Co/Al2O3 < Ni/SiO2 < Co/SiO2 < Ni/graphite < Co/SBA-15. Regeneration and reuse of industrially relevant 11 wt % Co/SiO2 was succesfully demonstrated

Hydrodeoxygenation of Isoeugenol over Alumina-Supported Ir, Pt, and Re Catalysts

Hydrodeoxygenation (HDO) of isoeugenol (IE) was investigated using bimetallic iridium rhenium and platinum rhenium catalysts supported on alumina in the temperature and pressure ranges of 200-250 degrees C and 17-40 bar in nonpolar dodecane as a solvent. The main parameters were catalyst type, hydrogen pressure, and initial concentration. Nearly quantitative yield of the desired product, propylcyclohexane (PCH), at complete conversion in 240 min was obtained with Ir-Re/Al2O3 prepared by the deposition-precipitation method using 0.1 mol/L IE initial concentration. High iridium dispersion together with a modification effect of rhenium provided in situ formation of the IrRe active component with reproducible catalytic activity for selective HDO of IE to PCH. The reaction rate was shown to increase with the increasing initial IE concentration promoting also HDO and giving a higher liquid phase mass balance. Increasing hydrogen pressure benefits the PCH yield

Selectivity control in Pt-catalyzed cinnamaldehyde hydrogenation

Chemoselectivity is a cornerstone of catalysis, permitting the targeted modification of specific functional groups within complex starting materials. Here we elucidate key structural and electronic factors controlling the liquid phase hydrogenation of cinnamaldehyde and related benzylic aldehydes over Pt nanoparticles. Mechanistic insight from kinetic mapping reveals cinnamaldehyde hydrogenation is structure-insensitive over metallic platinum, proceeding with a common Turnover Frequency independent of precursor, particle size or support architecture. In contrast, selectivity to the desired cinnamyl alcohol product is highly structure sensitive, with large nanoparticles and high hydrogen pressures favoring C=O over C=C hydrogenation, attributed to molecular surface crowding and suppression of sterically-demanding adsorption modes. In situ vibrational spectroscopies highlight the role of support polarity in enhancing C=O hydrogenation (through cinnamaldehyde reorientation), a general phenomenon extending to alkyl-substituted benzaldehydes. Tuning nanoparticle size and support polarity affords a flexible means to control the chemoselective hydrogenation of aromatic aldehydes

Mathematical modeling of starch oxidation by hydrogen peroxide in the presence of an iron catalyst complex

SSCI-VIDE+CDFA+ASOInternational audienceStarch oxidatio

Mathematical modeling of starch oxidation by hydrogen peroxide in the presence of an iron catalyst complex

SSCI-VIDE+CDFA+PTO:ASOInternational audienc

Oxidation of Starch by H2O2 in the Presence of Iron Tetrasulfophthalocyanine Catalyst: The Effect of Catalyst Concentration, pH, Solid-Liquid Ratio, and Origin of Starch

SSCI-VIDE+CDFA+PTO:ASOInternational audienceSeveral types of starches were oxidized by H2O2 in the presence of iron tetrasulfophthaloryanine catalyst (FePcS) in batch mode, and thekinetics of the H2O2 decomposition was followed when varying thecatalyst concentration and solid to liquid ratio of the starch andaqueous phase. Mainly, waxy corn starch with high content of amylopectinand potato starch were used, but also high amylose,starch was studied.The COOH content was determined for the final oxidized starch. It wasfound that, with 40 mg of catalyst and the starch present in a largeramount, the H2O2 decomposition followed a first order kinetics with aninitial decomposition rate in the range of 0.10 mol/L.h. Significantlyless starch slowed down the decomposition rate to 0.05 mol/L.h; however,when no starch was present, the decomposition increased to a maximum of0.14 mol/L. On the contrary, absence of catalyst resulted in a linearH2O2 decomposition profile. The FePcS catalyst concentration had a largeimpact on the decomposition of H2O2 regardless of the starch amount orthe starch origin. When using very low starch amounts in relation to thecatalyst amount, brown,solid residues were observed on the reactorwall, indicating that iron was defragmented from the catalyst

Improvement in carbohydrate and phlorotannin extraction from Macrocystis pyrifera using carbohydrate active enzyme from marine Alternaria sp as pretreatment

The commercial importance of brown seaweed has been increasing over the past decade, especially due to industries interested in the extraction of phycocolloids and, more recently, of polyphenol compounds such as phlorotannins. The objective of this work was to optimize the extraction conditions of carbohydrates and phlorotannins from Macrocystis pyrifera, evaluated enzymatic pretreatment and different parameters of extraction using design of experiment. The optimal conditions upon extraction of the carbohydrates and phlorotannins were determined by means of a pretreatment protocol taking advantage on a carbohydrate active enzyme, followed by an alkaline hydrolysis with 0.5 N NaOH at 100 degrees C, 180 min, and S/L ratio of 1/20. In order to extract the carbohydrates, the best conditions found for the pretreatment procedure were 37 degrees C, pH 7.0 for 24 h, and a S/L ratio of 1/10, giving an extraction yield (EY) of 89.67 +/- 12.3 wt.%. In turn, for the extraction of phlorotannins, the best conditions identified in terms of the pretreatment were 25 degrees C, pH 7.0 for 36 h, and a S/L ratio of 1/20, thus giving a yield (EY) of 2.14 +/- 0.25 wt.%. Statistical analysis of both processes revealed a maximum EY of 91.24 wt.% for carbohydrates and 3.31 wt.% EY for phlorotannins.CONICYT, AKA-ERNC 009 / Centre for Biotechnology and Bioengineering (CeBiB), FB-0001 / Academy of Finland, 268937 / Knut and Alice Wallenberg Foundation / Abo Akademi Universit