Experimental and Modeling Study of Catalytic Hydrogenation of Glucose to Sorbitol in a Continuously Operating Packed-Bed Reactor

Sorbitol is an alternative sweetener and a platform chemical for a wide variety of compounds. Selective hydrogenation of glucose to sorbitol over a commercial Ru/C catalyst was studied both experimentally and with the aid of detailed mathematical modeling. The experiments were conducted in a laboratory-scale trickle bed and in a semibatch stirred tank reactor. Sorbitol was obtained from the packed-bed reactor as the main product, typically with ∼90% selectivity within the studied temperature range (90–130 °C), while the side product was mannitol. The factors of interest were the temperature- and concentration-dependent reaction kinetics, deactivation, internal diffusion and heat conduction within particles, radial heat conduction and mass dispersion in the selected reactor section, liquid holdup, gas–liquid mass transfer, pressure drop, and axial dispersion. A mass-balance-based axial dispersion model (using temperature-dependent kinetics and deactivation modeled using the final activity concept) was capable of explaining the observed continuous packed-bed behavior rather well. The stirred tank reactor behavior could be described by a mass-balance-based model. Parameter estimation revealed that the main difference between semibatch and continuous operations arose from the more-severe deactivation in the packed bed. Simultaneous solution of heat and mass transfer for the top-most reactor section and for a catalyst particle revealed that heat-transfer limitations were not severe

Kinetics of Catalytic Wet Peroxide Oxidation of Phenolics in Olive Oil Mill Wastewaters over Copper Catalysts

During olive oil extraction, large amounts of phenolics are generated in the corresponding wastewaters (up to 10 g dm^–3). This makes olive oil mill wastewater toxic and conventional biological treatment challenging. The catalytic wet peroxide oxidation process can reduce toxicity without significant energy consumption. Hydrogen peroxide oxidation of phenolics present in industrial wastewaters was studied in this work over copper catalysts focusing on understanding the impact of mass transfer and establishing the reaction kinetics. A range of physicochemical methods were used for catalyst characterization. The optimal reaction conditions were identified as 353 K and atmospheric pressure, giving complete conversion of total phenols and over 50% conversion of total organic carbon content. Influence of mass transfer on the observed reaction rate and kinetics was investigated, and parameters of the advanced kinetic model and activation energies for hydrogen peroxide decomposition and polyphenol oxidation were estimated

Direct Amination of Dodecanol over Noble and Transition Metal Supported Silica Catalysts

Direct amination of 1-dodecanol with NH₃ and H₂ over Rh, Pt, Ir, Ru, Ni, Cu, and Co catalysts on SiO₂ has been studied. Catalyst synthesis was performed to allow high metal dispersion. The catalysts were characterized by TPO/TPR-MS, N₂ physisorption at 77 K, transmission electron microscopy, ICP analysis, and XPS. Through this characterization it was possible to relate the physical properties of the catalysts with activity and selectivity in 1-dodecanol amination. Iridium and ruthenium catalysts showed the highest conversion, about 77% after 24 h, and the selectivity of 78% and 81%, respectively, toward the desired product 1-dodecylamine. The Ru catalyst exhibited the highest yield of the desired product. In the conditions studied, the conversion increased in the order Cu < Ni < Rh < Pt < Co < Ir < Ru, and the selectivity was the highest for Ni and Co after 24 h. Both activity and selectivity of an oxidized Ir/SiO₂ catalyst increased considerably as the reaction progressed showing clearly that <i>in situ</i> catalyst reduction occurs being beneficial for dodecanol amination. High activity of Ir was also related to high metal dispersion

Fluidized-Bed Isobutane Dehydrogenation over Alumina-Supported Ga₂O₃ and Ga₂O₃–Cr₂O₃ Catalysts

Dehydrogenation of isobutane to isobutene over supported gallium oxide microspherical catalysts was investigated in a fluidized-bed reactor. A partially crystallized nanostructured aluminum hydroxide-oxide, which is a product of gibbsite centrifugal thermal activation (CTA) obtained using a CEFLAR technology, was used as a catalyst support. The structural and textural properties of Ga₂O₃/Al₂O₃ catalysts were characterized by a range of techniques including XRD, N₂-physisorption, TPD of NH₃ and CO₂, IRS of adsorbed pyridine, and selective adsorption of a series of acid–base indicators. A Ga–Al oxide catalyst exhibited a stable performance close to activity of Cr–Al oxide catalysts not containing soluble hexavalent chromium. Upon addition of Cr₂O₃ (6 wt % of Cr), in amounts lower than in an industrial chromia/alumina catalyst (10.9% Cr), and 1% ZrO₂ to 6%Ga/Al₂O₃ catalytic activity in isobutane dehydrogenation reaches the performance of the industrial KDM catalyst (“Sintez”, Russia)

Extraction of Lipids from <i>Chlorella</i> Alga by Supercritical Hexane and Demonstration of Their Subsequent Catalytic Hydrodeoxygenation

Extraction of lipids from <i>Chlorella</i> algae with supercritical hexane resulted in the high lipids yield of approximately 10% obtained at optimum conditions in terms of extraction time and agitation compared to the total content of lipids being 12%. Furthermore, an easiness of hexane recovery may be considered as economically and ecologically attractive. For the first time, in the current work catalytic hydrodeoxygenation (HDO) of <i>Chlorella</i> algal lipids was studied over 5 wt % Ni/SiO₂ at 300 °C and under 30 bar total pressure in H₂. The conversion of lipids was about 15% as the catalyst was totally deactivated after 60 min. The transformation of lipids proceeded mostly via hydrogenation and hydrogenolysis with formation of free fatty acid (FFA). Lower activity might be attributed to deactivation of catalysts caused by chlorophylls and carotenoids. Even though the conversion is low, future studies in HDO of lipids extracted from other algae species having higher lipid content could be proposed. A coke resistant catalyst might be considered to improve catalytic activity