Eleonora Stefanelli

Removal of CO2 from flue gas at high temperature using novel porous solids

Since the CO2 separation is the first and most energy intensive step of carbon capture and storage (CCS) technology, many research have targeted at improving the current technologies or developing new approaches of CO2 separation and capture. In this study, lithium orthosilicate-based pellets were developed and characterized as potential regenarable high-temperature CO2 sorbents. A mechanical method was used for pelletization of the powdered materials, namely K2CO3-doped lithium silicate (Li4SiO4). For increasing the performance of the pellets over multiple cycles an activation strategy was applied: the powdered sorbents were pelletized with a binder for enhancing their porosity by applying a thermal activation before adsorption process. Different amounts of binders (layered graphite and carbon nanotubes) were added to powered doped-sorbent in order to identify the optimal amount to ensure an adequate porosity into the pellets. The CO2 sorption properties of the obtained pellets were investigated by using a thermal gravimetric analyzer (TGA) in a controlled gas flow environment at low CO2 partial pressure (0.04 atm). Compared to the pure K2CO3-doped lithium silicate pellets, the sorbents prepared using layered graphite showed greater CO2 capture capabilities, which were ascribed to the higher porosity developed as a result of the activation. At 580 °C and a CO2 partial pressure of 0.04 atm, the uptake of CO2 in pellets prepared with 20 % of graphite reached about 200 mg CO2/g sorbent within 120 minutes corresponding to a Li4SiO4-conversion of 72.1 %. During multiple sorption/desorption cycles, a decay of the sorption capacity of the pellets was observed due to a partial sintering of the materials.

Novel Sustainable Composites Based on Poly(hydroxybutyrate-co-hydroxyvalerate) and Seagrass Beach-CAST Fibers: Performance and Degradability in Marine Environments

In order to produce sustainable, bio-based and highly biodegradable materials, composites based on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and fibers of Posidonia oceanica (PO), a dominant Mediterranean seagrass, were produced by simple melt mixing and characterized in terms of thermal stability, morphology and rheological/mechanical properties. In view of their potential application in marine environments, degradation of the developed composites was evaluated under simulated and real marine environmental conditions for 1 year. Using 10 wt % of acetyl tributyl citrate (ATBC) as a plasticizer, smooth processing was achieved for up to 30 wt % of PO fibers, despite the reduction of the melt fluidity observed with increasing fiber loading. The tensile modulus slightly increased (from 2 to 2.4 GPa) while the tensile strength and the elongation decreased (from 23.6 to 21.5 MPa and from 3.2 to 1.9%, respectively) by increasing the PO fiber content from 0 to 30 wt %. Interestingly, the impact resistance of the composites increased with the increasing of the PO content: the Charpy’s impact energy increased from 3.6 (without fiber) to 4.4 kJ/m2 for the composite with 30 wt %. The results of the aerobic biodegradation under simulated marine conditions showed that the presence of PO fibers favored the physical disintegration of the composite increasing the biodegradation rate of the polymeric matrix: after 216 days, the composite with 20 wt % PO fibers showed a biodegradability of about 30% compared to 20% of the composite without fibers. Under real marine conditions, the specimens containing PO fibers showed higher weight losses and deterioration of tensile properties compared to those without fibers. Presumably, biodegradation occurred after colonization of the specimen, and the specimens with 20 wt % PO fibers showed well-developed biofilm consisting of bacteria and fungi on the surface after only 3 months of incubation in marine sediments, unlike the no-fiber specimens. Consequently, the persistence of an adequate mechanical performance for a relatively long period (1 year), due to a moderate rate of biodegradation in the marine environment, make the developed PHBV/PO composites particularly suitable for the production of relatively low-cost and biodegradable items which are usable in the sea and/or sand dunes, increasing the market opportunities for biopolymers such as PHBV and, at the same time, finding an eco-sustainable valorization for the PO fibrous residues accumulated in large quantities on Mediterranean beaches, which represents a problem for coastal municipalities.

Levulinic acid from orange peel waste by hydrothermal carbonization (HTC)

With the awareness of the need for optimal and sustainable use of natural resources, hydrothermal treatment of biomass and biomass waste for energy and resource recovery has received increasing attention. The hydrothermal carbonization (HTC) of a biomass is achieved using water as the reaction medium and applying mild temperatures (180-250 ° C) under saturated pressure (autogenous or provided by a gas) for several hours. The thermochemical process applied to biomass includes simultaneous reactions of hydrolysis, dehydration, decarboxylation, condensation, polymerization and aromatization of the original precursor. The main resulting products are a carbon-rich solid, known as hydrochar, and a water phase containing soluble organic compounds. In this work, an experimental study on HTC process of orange peels to assess the yield of levulinic acid in water phase during the acid-catalyzed hydrolysis is reported. The results are promising, and comparable with other lignocellulosic biomass sources.

Manufacturing Technology of Ceramic Pebbles for Breeding Blanket

An open issue for the fusion power reactor is the choice of breeding blanket material. The possible use of Helium-Cooled Pebble Breeder ceramic material in the form of pebble beds is of great interest worldwide as demonstrated by the numerous studies and research on this subject. Lithium orthosilicate (Li4SiO4) is a promising breeding material investigated in this present study because the neutron capture of Li-6 allows the production of tritium, 6Li (n, t) 4He. Furthermore, lithium orthosilicate has the advantages of low activation characteristics, low thermal expansion coefficient, high thermal conductivity, high density and stability. Even if they are far from the industrial standard, a variety of industrial processes have been proposed for making orthosilicate pebbles with diameters of 0.1–1 mm. However, some manufacturing problems have been observed, such as in the chemical stability (agglomeration phenomena). The aim of this study is to provide a new methodology for the production of pebbles based on the drip casting method, which was jointly developed by the DICI-University of Pisa and Industrie Bitossi. Using this new (and alternative) manufacturing technology, in the field of fusion reactors, appropriately sized ceramic pebbles could be produced for use as tritium breeders.

Sol-gel synthesis of Li4SiO4 nanoparticles for CO2 capture at high temperature

Sol-gel Synthesis of Li4SiO4 Nanoparticles for CO2 Capture at High Temperature Monica Puccini, Takuya Harada, Eleonora Stefanelli, Sandra Vitolo, T. Alan Hatton Dipartimento di Ingegneria Civile e Industriale, University of Pisa, Largo Lucio Lazzarino 1, 56122 Pisa, Italy b Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States monica.puccini@unipi.it