Politecnico di Torino
Chemical engineering
In the frame of methane steam reforming (MSR) process intensification for H2 production , catalysts based on Ruthenium (Ru) supported on Alumina (Al2O3) on cor-dierite monolith have been studied in terms of catalytic performance, mass and... more
In the frame of methane steam reforming (MSR) process intensification for H2 production , catalysts based on Ruthenium (Ru) supported on Alumina (Al2O3) on cor-dierite monolith have been studied in terms of catalytic performance, mass and heat transfer effects. Firstly, we compared the catalytic activity of Ru and Rh supported catalysts. Secondly, we study the effect of catalyst loading by varying the amount of carrier and active metal phase corresponding to 3.20, 6.45 and 12.89 mg cm-2. Then, we evaluated the mass/heat transfer effects and controlling regimes for the best-selected catalyst. Finally, the best-selected catalyst was characterized by means of Brunauer-Emmet-Teller (BET), X-Ray diffraction analysis (XRD) and Field-emission scanning electron microscopy (FESEM). The experiments were carried out in the temperature range of 550 to 850 °C, steam to carbon molar ratio (S/C) of 3.0 and different weight hourly space velocity (WHSV= 750, 1500 and 3000 Nl h −1 gcat −1). The catalyst with 1.5% Ru on 10% Al (1.5Ru10Al) was found to be the most promising toward the MSR reaction in terms of CH4 conversion and H2 production.
In this study, kinetic and mass transfer resistances (pore and interphase diffusion) were evaluated by varying the Co3O4 amount in the catalyst (PdO/Co3O4) supported on the zirconia open cell foam (Zir-OCF) of 30 ppi. The catalytic... more
In this study, kinetic and mass transfer resistances (pore and interphase diffusion) were evaluated by varying the Co3O4 amount in the catalyst (PdO/Co3O4) supported on the zirconia open cell foam (Zir-OCF) of 30 ppi. The catalytic performance was examined toward the methane combustion in lean conditions (0.5 and 1.0 vol.% CH4 inlet concentration, O2/CH4 molar ratio 8, WHSV 30, 60 and 90 NL h −1 gcat −1). Pore and strut geometry of the bare foam were evaluated by SEM images and X-CT data analysis. Solution combustion synthesis was employed to line the Co3O4 spinel on the foam, while the wetness impregnation for the PdO on the spinel. The various resistances were evaluated and compared at different WHSV by varying the Co3O4 amount. Finally, we derived a correlation that describes the mass transfer in OCFs at low Reynolds numbers. Graphical Abstract 2
Coated ceramic open cells foams (OCFs) with catalysts offer an attractive alternative to packed bed reactors for process intensification. Here, the effect of 3 wt.% PdO on Co3O4 coated on three different OCFs (alumina, silicon carbide and... more
Coated ceramic open cells foams (OCFs) with catalysts offer an attractive alternative to packed bed reactors for process intensification. Here, the effect of 3 wt.% PdO on Co3O4 coated on three different OCFs (alumina, silicon carbide and zirconia) was investigated toward the reaction of CH4 combustion in lean conditions. The OCFs were characterized by Raman spectroscopy and FESEM analysis. The operating regime of each OCF catalyst was investigated using a series of mass transfer resistances assuming pseudo first order reaction (large excess of oxygen). The thermal conductivity of OCFs plays an important role on the overall performance of the combustion reaction in terms of heat and mass transfer. The best OCF structured catalyst was tested up to 250 hours of time-on-stream, demonstrating good stability. PdO dispersion over the structured catalyst at the fresh and aged status was assessed by STEM analysis.
The application of ceramic foams as structured catalyst supports is clearly expanding due to faster mass/heat transfer and higher contact efficiency than honeycomb monoliths and, mainly, packed beds. In this paper, alumina open-cell foams... more
The application of ceramic foams as structured catalyst supports is clearly expanding due to faster mass/heat transfer and higher contact efficiency than honeycomb monoliths and, mainly, packed beds. In this paper, alumina open-cell foams (OCFs) with different pore density (20, 30 and 40 ppi) were coated with Rh/CeO 2 catalyst via a two steps synthesis method involving: (i) the solution combustion synthesis (SCS) to in-situ deposit the CeO 2 carrier and (ii) the wet impregnation (WI) of the Rh active phase. The catalytic coatings were characterized in terms of morphology and adhesion properties by SEM/EDX analysis and ultrasounds test. Permeability and form coefficient were derived from pressure drop data. Catalytic performance was evaluated towards biogas Steam Reforming (SR) and Oxy-Steam Reforming (OSR) processes at atmospheric pressure by varying temperature (800-900 • C) and space velocity (35,000-140,000 NmL•g −1 •h −1). Characteristics time analysis and dimensionless numbers were calculated to identify the controlling regime. Stability tests were performed for both SR and OSR over 200 h of time-on-stream (TOS) through consecutive start-up and shutdown cycles. As a result, homogenous, thin and high-resistance catalytic layers were in situ deposited on foam struts. All structured catalysts showed high activity, following the order 20 ppi < 30 ppi ≈ 40 ppi. External interphase (gas-solid) and external diffusion can be improved by reducing the pore diameter of the OCF structures. Anderson criterion revealed the absence of internal heat transfer resistances, as well as Damköhler and Weisz-Prater numbers excluded any internal mass transfer controlling regime, mainly due to thin coating thickness provided by the SCS method. Good stability was observed over 200 h of TOS for both SR and OSR processes.
Co 3 O 4 |α-Al 2 O 3 |cordierite structured catalysts were developed, optimizing washcoating procedure, active phase loading, and its deposition method via impregnation and solution combustion synthesis (SCS). The catalysts were... more
Co 3 O 4 |α-Al 2 O 3 |cordierite structured catalysts were developed, optimizing washcoating procedure, active phase loading, and its deposition method via impregnation and solution combustion synthesis (SCS). The catalysts were thoroughly characterized by XRD, μRS, SEM/EDS, and BET, revealing that the catalyst layer deposited over cordierite carrier, consists of a washcoated micrometric α-Al 2 O 3 (0.1-0.3 µm grains), where spinel nanocrystals (30-50 nm) were uniformly dispersed. It was found out that the SCS method to synthesize and finely disperse spinel nanoparticles results in significant better catalytic performance in low-temperature N 2 O decomposition than the classic impregnation method. The effectiveness factor evaluated, based on catalyst morphological features and deN 2 O catalytic results, was found to be ≈1. The determined mass transfer coefficients and type of the catalyst working regime (purely kinetic in the whole temperature range) provides the useful platform for rational design of a real deN 2 O catalyst.
Microplastics pollution is one of the main environmental challenges of our time, even though microplastics were observed for the first time almost 50 years ago. Microplastics—little plastic fragments smaller than 5 mm in size—are released... more
Microplastics pollution is one of the main environmental challenges of our time, even though microplastics were observed for the first time almost 50 years ago. Microplastics—little plastic fragments smaller than 5 mm in size—are released from bigger plastic objects during their use, maintenance, or disposal. As their release is uncontrolled and mostly uncontrollable, microplastics end up in the environment and are easily transported across the world, polluting nearly every ecosystem, especially the aquatic ones. Hence, microplastics represent a huge menace for many living species: they are ingested unintentionally by smaller animals and transferred along the food chain up to human beings, even threatening our health. It is therefore vital to take action against microplastics and many technologies have been designed in recent years with this purpose in mind. This paper provides an overview of the main solutions developed thus far to reduce further microplastic emissions and to colle...
- by melania fiore
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