Sviluppo di tecniche in regime transitorio per lo studio di reazioni di catalisi eterogenea

The research activities reported in this PhD thesis focus on one class of time-depending input variables: temperature and reactant concentration. Specifically, reactivity parameters (reagents conversion and products formation) were recorded as a function of temperature in temperature-programmed experiments with variable feed conditions (reducing or oxidizing atmospheres) and spent materials were characterized with surface analyses (SEM, EDS) to correlate their activity to chemical (mass and heat transfer) and physical (aggregation, segregation) phenomena. Also, the common feature between the catalytic materials investigated is the oxygen-storage capacity, i.e. their ability to store and release oxygen in oxygen-lean conditions, that represents a critical feature for more flexible operations, highly-selective oxidations and safer working conditions. Two model materials were selected as oxygen-donors for two distinct applications: CuO was chosen to correlate the effect of different reaction parameters to its morphological features, long-time stability during redox cycles (H2-O2) and formation of peculiar superficial nanostructures while LaFeO3 (perovskite) was identified as a possible candidate for the oxidative function, in automotive converter by taking advantage of oxygen diffusion in the lattice to transform CO into CO2. The last class of materials (CuY zeolites) was studied in CH4 activation to assess their potential application to an industrial-relevant reaction (methane-to-methanol, MTM) in which the oxygen provided by the zeolites selectively reduces the extent of over-oxidation products in favour of the partial oxidation to methanol.The research activities reported in this PhD thesis focus on one class of time-depending input variables: temperature and reactant concentration. Specifically, reactivity parameters (reagents conversion and products formation) were recorded as a function of temperature in temperature-programmed experiments with variable feed conditions (reducing or oxidizing atmospheres) and spent materials were characterized with surface analyses (SEM, EDS) to correlate their activity to chemical (mass and heat transfer) and physical (aggregation, segregation) phenomena. Also, the common feature between the catalytic materials investigated is the oxygen-storage capacity, i.e. their ability to store and release oxygen in oxygen-lean conditions, that represents a critical feature for more flexible operations, highly-selective oxidations and safer working conditions. Two model materials were selected as oxygen-donors for two distinct applications: CuO was chosen to correlate the effect of different reaction parameters to its morphological features, long-time stability during redox cycles (H2-O2) and formation of peculiar superficial nanostructures while LaFeO3 (perovskite) was identified as a possible candidate for the oxidative function, in automotive converter by taking advantage of oxygen diffusion in the lattice to transform CO into CO2. The last class of materials (CuY zeolites) was studied in CH4 activation to assess their potential application to an industrial-relevant reaction (methane-to-methanol, MTM) in which the oxygen provided by the zeolites selectively reduces the extent of over-oxidation products in favour of the partial oxidation to methanol

Efficient hydrothermal deoxygenation of tall oil fatty acids into n-paraffinic hydrocarbons and alcohols in the presence of aqueous formic acid

Hydrothermal deoxygenation of tall oil fatty acids (TOFA) was investigated in the presence of aqueous formic acid (0.5–7.5 wt%) as a H2 donor in the presence of subcritical H2O pressure (569–599 K). Pd and Ru nanoparticles supported on carbon (5% Pd/CSigma, 5% Ru/CSigma, 10% Pd/CO850_DP, and 5% Ru/COPcomm_DP) were found to be efficient catalysts for deoxygenation of TOFA. The reaction pathway was mainly influenced by the concentration of formic acid and the catalyst. In case of Pd catalysts, in the presence of 0–2.5 wt% formic acid, decarboxylation was the dominant pathway producing n-paraffinic hydrocarbons with one less carbon atom (heptadecane yield up to 94 wt%), while with 5–7.5% formic acid, a hydrodeoxygenation/hydrogenation mechanism was favored producing C18 deoxygenation products octadecanol and octadecane as the main products (yields up to 70 wt%). In contrast, Ru catalysts produced a mixture of C5-C20 (n-and iso-paraffinic) hydrocarbons via decarboxylation, cracking and isomerization (up to 58 wt% C17 yield and total hydrocarbon yield up to 95 wt%) irrespective of formic acid concentration. Kinetic studies showed that the rates of deoxygenation displayed Arrhenius type behavior with apparent activation energies of 134.44 ± 31.36 kJ/mol and 148.92 ± 3.66 kJ/mol, for the 5% Pd/CSigma and 5% Ru/CSigma catalyst, respectively. Furthermore, the experiments with glycerol tristearate, rapeseed oil, sunflower oil, rapeseed biodiesel, and hydrolyzed rapeseed oil produced identical products confirming the versatility of the aforementioned catalytic systems for deoxygenation of C18 feedstocks.Bio4Energ

Mesoporous CuO/TiO2 catalysts prepared by the ammonia driven deposition precipitation method for CO preferential oxidation: Effect of metal loading

Supported CuO catalysts onto a highly crystalline mesoporous TiO2 material are produced via an ammonium driven deposition precipitation method and tested for prefere degrees ntial oxidation of CO in H-2-rich gases. The effect of Cu loading on the oxidation activity is investigated by producing samples with final Cu content varying between 2.5 and 10 wt%. According to the analysis results, the chemical nature of the CuO species differs in each sample depending on the Cu loading. All materials tested are highly selective towards CO oxidation up to 160 degrees C. The 5 wt% Cu loaded material demonstrates the optimum CO-PROX performance, which is ascribed to the formation of finely dispersed and easily reducible copper oxide nanoparticles. Stability and durability of the latter sample are assessed by performing multiple testing cycles corresponding to >100hrs on stream as well as by the separate and combined addition of CO2 and H2O in the feeding stream