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CO2 adsorption process in a composite geopolymer/zeolite 13X material has been analysed for post combustion carbon capture application, in dynamic conditions for a CO2/N2 gas mixture. Such composite material represents a valid alternative to conventional sorbents owing to the affinity and synergy between zeolite and the geopolymer binder as well as improved mechanical resistance and lower cost. Experimental analysis has been focused both on complete adsorption tests to determine the material maximum adsorption capacity and on breakthrough tests in transient conditions in (cyclic adsorption/desorption). Particular care has been devoted to thermal effects associated to adsorption and their effect on adsorption capacity and kinetics. Experimental data have been employed to support the development of a novel numerical model, based on Sips adsorption approach for sorbent capacity, and capable to describe the adsorption process, accounting for both mass and energy transport in the sorbent bed. The model proved able to describe well the experimental data at different CO2 feed concentration, and thus it has been employed in a predictive way to inspect process operating parameters and sorbent bed design on the resulting adsorption capacity, breakthrough time, and temperature profile. In particular, the model compared the results obtained in a scaled-up configuration (suitable to an industrial application) with those of the lab-scale system.

Methane Chemical Looping mixed dry reforming - CLMDR (dry reforming and partial oxidation) is an integrate process that utilizes CO2 directly, in presence of carrier materials, for the production of syngas with tuneable H2/CO molar ratio. Herein Cerium oxide was selected as reference source of oxygen and its use in the CLMDR process was evaluated by means of thermodynamic tools of Aspen Plus process simulator. Crucial features such as reforming and regeneration operative temperature, oxygen to methane molar ratio and CO2 addition were investigated in order to identify the most suitable and effective conditions for process. Simulation results of the proposed metal oxide were compared on the basis of methane conversion and syngas purity. Relevantly, cerium-based oxide was found to be selective in syngas production even when CO2 was added to the reforming reactor. After the required thermodynamic validation, a fixed bed reactor on lab scale was specifically designed and fabricated, and cerium oxide oxygen carrier characterized by Thermogravimetric analysis. Thermodynamic results and experimental tests proved the solid/gas chemical reaction takes place with appreciable conversions, and they also demonstrated the stability of the oxygen carrier redox properties during several cycles, thus confirming the feasibility of this new process.

An innovative membrane-based process for the separation of gaseous streams has been developed and tested at lab-scale. The new process can be conveniently carried out on the same modules currently employed for conventional gas separation membrane systems, and it relies on periodic swing of the downstream pressure, while upstream conditions are kept constant. Such new unit operation is run with no need of switching streams, and it allows to process constant flow rate and composition of both feed and retentate, while permeate is collected at assigned frequency, resulting in an overall on-average steady state process. An on-off control strategy over time of permeate collection produces alternate sorption/desorption steps in the membrane, associated to increase/decrease cycles of downstream pressure in the process, in a similar fashion to pressure swing adsorption (PSA). Indeed, consistently with the hybrid nature of the new process, the specific dynamic control of downstream pressure allows the exploitation of both resistive (permeation) and capacitive (adsorption) properties of the membrane, and the associated characteristics in terms of selectivity. By changing the duration of pressure swing period, the resistive or capacitive properties of the membrane can be conveniently tuned in order to explore different performances of the process, in terms of key component recovery and separation factor

Aiming at the reduction of CO2 emissions in the atmosphere, solid adsorbent materials are being of great interest for the development of reliable and efficient carbon capture and sequestration technologies (CCS), following different process schemes. Several adsorbent materials (e.g. zeolites or metal organic frameworks) are thus prepared and the their ability to selectively capture CO2 is investigated. Geopolymers, namely alkali-bonded ceramics [1], were produced by reacting an aluminosilicate powder with an aqueous alkali hydroxide and/or alkali silicate solution. The microstructure of the geopolymer matrix consists nanoprecipitates and mesopores. Geopolymers can be used to develop porous near-net-shape components in the pore size range from nanometres to millimetres and total porosity from 30% up to 90% [2].

This study deals with the production of geopolymers as porous wicks in a LHP prototype and testing of the thermal performances.

The oxygen barrier properties of composite materials, consisting of a LDPE substrate coated by a thin layer of nanostructured hybrid organic/inorganic materials based on SiO2 and polyethylene-polyethylene glycol (PE-PEG) block copolymers, obtained via a sol-gel technique have been characterized at 35°C and 50°C. A significant decrease (25-40%) of the oxygen transfer rate has been observed for coated samples with respect to bare substrate both at 35°C and 50°C.

The mass transport properties of cyclohexane in different phase separated styrene blockcopolymer, namely polystyrene-block-polybutadiene-block-polystyrene [SBS], polystyrene-blockpolyisoprene- block-polystyrene [SIS] and polystyrene-block-poly(ethylene butylene)-blockpolystyrene [SEBS] were investigated. The solubility and diffusivity in films samples have been measured, as function of concentration, at 60ºC by means of sequences of differential vapor sorption experiments run in a pressure decay apparatus. The effects of both molecular architecture (linear and star-branched for SBS) and microstructure of the elastomer mid-segment (polybutadiene vs poly(ethylene butylene) and polyisoprene) were considered. The sorption results were interpreted and modeled in terms of contributions from rubbery and glassy phases. Comparison between the different data in the binary system as function of solute concentration revealed that friction factor for solute molecules in SEBS and SIS is significantly higher than in SBS. Such results were also confirmed by linear viscoelastic characterization of the different polymers that has been carried out performing small angle oscillatory shear experiments in a wide range of temperatures between the soft block Tg and room temperature. The latter experimental data were analyzed by Time-Temperature Superposition. The relaxation spectrum has been determined and the monomeric friction factor has been extracted. This value has been correlated with results from diffusion experiments leading to a substantial agreement.

Proprietà di superficie e proprietà barriera di sistemi ibridi organico-inorganici ottenuti attraverso processi di doppia reticolazione