Click-based porous cationic polymers for enhanced carbon dioxide capture

Imidazolium based porous cationic polymers were synthesized using an innovative and facile approach, which takes advantage of the Debus Radziszewski reaction to obtain meso- and microporous polymers following click chemistry principles. In the obtained set of materials, click based porous cationic polymers have the same cationic backbone, whereas they bear the commonly used anions of imidazolium poly(ionic liquid)s. These materials show hierarchical porosity and a good specific surface area. Furthermore, their chemical structure was extensively characterized using ATR FTIR and SS NMR spectroscopies, and HR MS. These polymers show good performance towards carbon dioxide sorption, especially those possessing the acetate anion. This polymer has an uptake of 2 mmol per g of CO2 at 1 bar and 273 K, a value which is among the highest recorded for imidazolium poly(ionic liquid)s. These polymers were also modified in order to introduce N-heterocyclic carbenes along the backbone. Carbon dioxide loading in the carbene-containing polymer is in the same range as that of the non-modified versions, but the nature of the interaction is substantially different. The combined use of in situ FTIR spectroscopy and microcalorimetry evidenced a chemisorption phenomenon that brings about the formation of an imidazolium carboxylate zwitterion.Comment: 29 page, 33 figure

CO2 adsorption on different organo-­‐modified SBA-­‐15 silicas: a multidisciplinary study on the effects of basic surface groups

Hybrid organic–inorganic SBA-15 silicas functionalized with increasing amounts of amino groups were studied in this work aiming to evaluate the effects of their physico-chemical properties on CO2 capture ability. Three different amino-silane species were used: 3-aminopropyltriethoxysilane (APTS), 3-(2-aminoethyl)- aminopropyltrimethoxysilane (EAPTS) and 3-[2-(2-aminoethyl)aminoethyl] aminopropyltrimethoxysilane (PAPTS). More specifically, samples were prepared by using two methods, following a post-synthesis grafting procedure and a one-pot preparation method. Experimental and computational techniques were used to study the structural and textural properties of the obtained samples and their surface species in relation to the adopted preparation method. For the most reactive samples, additional hints on the interactions of organosilane species with the silica surface were obtained by a combination of IR and SS-NMR spectroscopy, with particular emphasis on the effects of the silane chain length on the mobility of the organic species. Advanced complementary solid-state NMR techniques provided deeper information on the interactions of organosilane species with the silica surface. Finally, the amount of CO2 adsorbed was estimated by comparing the classical microcalorimetric analysis method with a new type of screening test, the Zero Length Column analysis, which is able to evaluate small amounts of samples in a very short time and the adsorption properties of the adsorbents. The reactivity of the amino-modified silica samples is deeply influenced by both the preparation route and by the type of organosilane used for the functionalization of the materials. In particular, samples prepared by the post-synthesis grafting procedure and containing higher amount of amino groups in the chain are more reactive, following the order PAPTS 4 EAPTS 4 APTS

Anterior cingulate cortex : contributions to social cognition

It has been suggested that the Anterior Cingulate Cortex (ACC) plays an important role in decision-making. Activity in this area reflects processing related to two principles of Reinforcement Learning Theory (RLT): (i) signalling the predicted value of actions at the time they are instructed and (ii) signalling prediction errors at the time of the outcomes of actions. It has been suggested that neurons in the gyrus of the ACC (ACCg) process information about others' decisions and not one's own. An important aim of this thesis is to investigate whether the ACCg processes others' decisions in a manner that conforms to the principles of RLT. Four fMRI experiments investigate activity in the ACCg at the time of cues that signal either the predicted value of others' actions or that signal another's predictions are erroneous. • Experiment 1: Activity in the ACCg occurred when the outcome of another's decision was unexpectedly positive. • Experiment 2: Activity in the ACCg varied parametrically with the discrepancy between another's prediction of an outcome and the actual outcome known by the subject, in a manner that conformed to the computational principles of RLT. • Experiment 3: Activity in the ACCg varied with the predicted value of a reward, discounted by the amount of effort required to obtain it. • Experiment 4: Activity in the ACCg varied with the value of delayed rewards that were discounted in a manner that conformed to a social norm. These results support the hypothesis that the ACCg processes the predicted value of others' actions and also signals when others' predictions about the value of their actions are erroneous, in a manner that conforms to the principles of RLT.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Micro-sized TiO2 photocatalyst for the purification of air from acetone and acethaldeide

In the last years increasingly restrictive regulations about the concentration limit of pollutants in air enhanced the development of more efficient treatment processes. In particular, advanced oxidation processes (AOPs) are chemical oxidation technologies that rely on the formation of the hydroxyl radical (OH\u2d9) to further oxide organic contaminants which are completely mineralized or converted to less harmful products. AOPs based on UV radiation involve photocatalysts, such as titanium dioxide (TiO2) mostly in nanometric size. However, nanoparticles give rise to many problems such as the catalyst-recovering, hindering their commercial application, other than possible damages on both human safety and environment. The present paper reports a comparative study on the application of nano (P25 by Evonik) and micro-sized (1077 by Kronos) TiO2 samples as photocatalyst on degradation of acetone (AC) and acetaldehyde (AD). Photocatalytic degradations of both pollutants were performed in a Pyrex glass cylindrical reactor of 5 L with 0.05 g of photocatalyst. The gaseous mixture in the reactor was obtained by mixing hot chromatographic air, humidified at 4, 40 and 75%, and an initial concentration of pollutant of 400 ppmV verified by an online micro-GC. The irradiation is carried out by an iron halogenide lamp (Jelosil, model HG 500) emitting in the 315-400 nm wavelength range (UV-A) with power of 30 W/m2. As shown in Fig. 1 the activity of the micro-TiO2 is comparable with that of the nano-sized one even if it is a little bit slower. In both cases, micro-GC analyses detected the formation of CO2 after the degradation: experimental results indicate the formation of CO2 at 100%, confirming a full degradation of the starting molecule (acetone).Considering these outcomes, the employment of microsized TiO2 as a photocatalyst turns out to be a valid alternative to the nano-sized catalysts. Moreover, in order to complete this study, TiO2 samples have been also doped with F to verify the influence of such a dopant on the material photoefficiency

Aerogel and xerogel WO3/ZrO2 samplesfor fine chemicals production

WO3/ZrO2 systems were prepared by sol-gel technique using different procedures for the solvent extraction: evaporation in vacuum at RT (xerogel) and extraction in supercritical conditions (aerogel). Two reactions of industrial interest were investigated under mild conditions: (i) acylation of veratrole with acetic anhydride; (ii) acylation of anisole with benzoic anhydride. Several techniques were employed in order to study the influence of the synthetic parameters on texture and catalytic activity: N2 physisorption, FT-IR spectroscopy, XPS, TPR and TPO analyses. The solvent extraction strongly influences metal reducibility, surface area, pores organisation, W/Zr surface density and metal interaction. The aerogel sample shows the best catalytic results for both conversion and yield. The supercritical extraction plays a central role especially in the recycling: by proper air activation, the aerogel sample attains the complete restoration of the catalytic activity even after three runs

Characterization and Modeling of Reversible CO2 Capture from Wet Streams by a MgO/Zeolite Y Nanocomposite

The synthesis of CO2 sorbents capable of working on combustion flue gases is a challenging topic in the field of carbon capture and sequestration. Indeed, the presence of moisture in combustion exhausts makes most of the materials capturing CO2 through physisorption ineffective, their affinity being larger for H2O than for CO2. In this work, we investigate a novel nanocomposite sorbent based on a Mg overexchanged zeolite Y (MgOHY), showing single Mg2+ ions and nanoconfined (MgO)(n) clusters. The interaction of CO2 with the material is studied thoroughly by combining IR spectroscopy and simulation, comparing dry and wet conditions. IR spectroscopy shows that while in dry conditions the adsorption is mainly driven by the Mg2+ ions, in wet ones, the (MgO) clusters react with carbon dioxide by forming (bi)carbonate-like species. These easily decompose at mild temperatures (25-200 degrees C). Density functional theory simulations are used to investigate the origin of the CO2 interaction with representative (MgO) clusters in the periodic zeolite structure and their enthalpy of formation as a function of the water coverage. The calculations disclose a synergic effect between CO2 and H2O that, while favoring the CO2 fixation, results in the formation of (bi)carbonate-like species less stable than those formed in the absence of water