Amine‐Functionalized Mesoporous Silica Adsorbent for CO2 Capture in Confined‐Fluidized Bed: Study of the Breakthrough Adsorption Curves as a Function of Several Operating Variables

Carbon capture, utilization, and storage (CCUS) is one of the key promising technologies that can reduce GHG emissions from those industries that generate CO2 as part of their production processes. Compared to other effective CO2 capture methods, the adsorption technique offers the possibility of reducing the costs of the process by setting solid sorbent with a high capacity of adsorption and easy regeneration and, also, controlling the performance of gas‐solid contactor. In this work, an amine‐functionalized mesoporous sorbent was used to capture CO2 emissions in a confined‐fluidized bed. The adoption of a confined environment allows the establishment of a homogeneous expansion regime for the sorbent and allows to improve the exchange of matter and heat between gas and solid phase. The results illustrate how the different concentration of the solution adopted during the functionalization affects the adsorption capacity. That, measured as mg of CO2 per g of sorbent, was determined by breakthrough curves from continuous adsorption tests using different concentrations of CO2 in air. Mesoporous silica functionalized with a concentration of 20% of APTES proves to be the best viable option in terms of cost and ease of preparation, low temperature of regeneration, and effective use for CO2 capture

Monoclinic ZrO2 Powders. Some Features of the Interfacial Electrostatic Behaviour

The paper reports results of both surface charge vs pH measurements and of electrokametie determinations performed on suspension of monoelmic zirconia. The time length os the pre-conditioning of the oxide in the electrolyte (KNO3) appears to affect the value both of the c. !i. p. and of the i. e. p. and to modify the pattern of charge curves. The transition from »fast« to »slow« titrations also introduces remarkable differences in the degree of hysteresis and in the overal trend of charge curves. A common interpretation of these phenomena is proposed considering the high temperature of preparation of the samples and the possible consequent removal of the surface chemisorbed water

Binary separation in very thin nematic films: thickness and phase coexistence

The behavior as a function of temperature of very thin films (10 to 200 nm) of pentylcyanobiphenyl (5CB) on silicon substrates is reported. In the vicinity of the nematic/isotropic transition we observe a coexistence of two regions of different thicknesses: thick regions are in the nematic state while thin ones are in the isotropic state. Moreover, the transition temperature is shifted downward following a 1/h^2 law (h is the film thickness). Microscope observations and small angle X-ray scattering allowed us to draw a phase diagram which is explained in terms of a binary first order phase transition where thickness plays the role of an order parameter.Comment: 5 pages, 3 figures, submitted to PRL on the 26th of Apri

Inhomogeneity-induced second-order phase transitions in Potts model on hierarchical lattices

The thermodynamics of the $q$-state Potts model with arbitrary $q$ on a class of hierarchical lattices is considered. Contrary to the case of the crystal lattices, it has always the second-order phase transitions. The analytical expressions fo the critical indexes are obtained, their dependencies on the structural lattice pararmeters are studied and the scailing relations among them are establised. The structural criterion of the inhomogeneity-induced transformation of the transition order is suggested. The application of the results to a description of critical phenomena in the dilute crystals and substances confined in porous media is discussed.Comment: 9 pages, 2 figure

New membranes for hydrogen and syngas production

Syngas is an important feedstock for the production of higher hydrocarbons or methanol. It can be produced via conversion of methane and the most extensively used process for this conversion is the methane steam reforming reaction carried out in large furnaces. On the other hand, hydrogen is nowadays produced via conversion of methane to syngas and successive water gas shift reaction and purification. Methane steam reforming is a highly endothermic reaction which is industrially operated under severe conditions resulting in several undesirable consequences: sintering of the catalyst, very high carbon deposition and the use of high-temperature resisting materials. These drawbacks for methane steam reforming can be overcome by using membrane reactors, systems able to combine the separation properties of membrane with the typical characteristics of catalytic reactions. By using for example Pd-based membrane reactors, the hydrogen produced can be continuously withdrawn from the reaction system circumventing the thermodynamic limitations and making the methane steam reforming feasible at lower temperatures than the traditional systems. A potential alternative technique to steam reforming processes for producing syngas is the partial oxidation of methane with oxygen, having the disadvantage (economical and technological) that pure oxygen is required. Using air instead of pure oxygen is beneficial only if it can be performed by using a membrane reactor in which the membrane is perm-selective to oxygen. Another possible route for the partial oxidation of methane is the use of catalytic membrane reactors in which the membrane acts as both separation layer and reaction media. In this chapter new membranes to be used in syngas production and in hydrogen production will be discussed

Silica Monolith for the Removal of Pollutants from Gas and Aqueous Phases

In recent years, chemical industries have been focusing on sustainable development approaches, promoting materials that offer performance at lower costs and reducing significantly the environmental impact. In connection to these approaches, mesoporous materials have been synthesized and extensively studied for various applications. Nevertheless, the use of powders present different handling and recycling limitations. To overcome these problems there are two possible options: (i) the preparation of pellets starting from the pre-synthesized silica powders, or (ii) the direct preparation of monoliths. Among the different types of mesoporous materials, silicas have been widely used for environmental application, since meet most of the criteria for selection of adsorbents such as high specific surface area, large pore–size and chemical inertness; for these reason, mesoporous silicas have been used for adsorption of both organic and inorganic pollutants [1]. The preparation of silica monoliths can be a convenient way to fully exploit the structural and functional properties of the material by saving, at the same time, both reactants and time, in that a single-step synthesis is required [2]. In this work, mesoporous silica monoliths have been prepared by spinodal condensation reaction [3] and then tested as adsorbents of organic pollutants from aqueous or gaseous phase. The physico-chemical features of the silica monoliths have been determined by using different experimental techniques [4]. Textural properties were found to be homogeneous over the entire length of the monolith, which has an average surface area of ca. 850 m2 g−1 and a total pore volume of 1.2 cm3 g−1. The monoliths were tested for the removal of toluene, chosen as a model molecule of aromatic hydrocarbons, from gas phase. A combination of FT-IR spectroscopy and volumetric analysis was adopted to study the adsorption process and gain knowledge on the interactions between adsorbent surface and toluene molecule. Silica monoliths were found to be stable to water treatment (36 h at 50 °C), even if the treatment reduced the specific surface area. Finally, the ability of the same monoliths, before and after the water treatment, to remove Rhodamine B from aqueous solution was also studied by using UV-visible spectroscopy. After water treatment, the material was able to adsorb 50% of the Rhodamine B with respect to 70% of the control sample