Soft-templating pathway to create nanostructured Mg–Al spinel as high-temperature absorbent for SO2

Interest in reducing SO₂ emission from the fluid catalytic cracking (FCC) crude oil has been encouraging the development of new materials to achieve such goal. The nanostructured Mg–Al spinel (MgAl₂O₄) was prepared by co-precipitation and post hydrothermal treatment in the presence of glucose and followed by elimination of the organic components by calcination at 700 °C for 3 h. Physical and chemical properties were characterized by XRD, N₂ sorption, TG, FTIR, SEM, and TEM methods. Mesoporous nanostructured MgAl₂O₄ with a high surface area of 324 m² g^?1 were obtained. The organic components contributed to the development of mesoporosity, functioning as a soft template. SO₂ adsorption tests showed that the nanostructured MgAl₂O₄ had a 51.58 % increase of SO₂ sorption capacity than MgAl₂O₄ prepared without glucose. These results showed that the nanostructured MgAl₂O₄ is a promising candidate as catalyst for flue gas desulfurization in FCC process. Three kinetic models were also applied to analyze the SO₂ adsorption kinetics; the pseudo-second order kinetic model fit well with a correlation coefficient (R²) of 0.991 for nanostructured MgAl₂O₄.     

SO2 abatement over nanocrystalline MgAl2O4 spinel-supported catalysts

Thermally stable magnesium-rich MgAl₂O₄ spinel with mesoporous nanostructures and high surface area has been prepared by co-precipitation and post hydrothermal treatment, using glucose as organic template. Physical and chemical properties were characterized by XRD, N₂ sorption, TG, FTIR, SEM, and TEM. The synthesized MgAl₂O₄ showed a surface area of 324 m² g^?1 and centralized mesopore distribution (ca. 3.3 nm pore width) after calcination at 700 °C for 3 h. The prepared MgAl₂O₄ were impregnated with metal oxides as sulfur transfer catalysts for high-temperature SO₂ adsorption reaction. The results showed that ferric doped MgAl₂O₄ had the highest SO₂ pick-up capacity up to 58 % and best regeneration up to 81 %. These results showed that thermally stable nanostructured MgAl₂O₄ are a promising candidate as catalyst for desulfurization in fluid catalytic cracking process.     

A Hierarchical Trust Model for Peer-to-Peer Networks

Trust has become an increasingly important issue given society’s growing reliance on electronic transactions. Peer-to-peer (P2P) networks are among the main electronic transaction environments affected by trust issues due to the freedom and anonymity of peers (users) and the inherent openness of these networks. A malicious peer can easily join a P2P network and abuse its peers and resources, resulting in a large-scale failure that might shut down the entire network. Therefore, a plethora of researchers have proposed trust management systems to mitigate the impact of the problem. However, due to the problem’s scale and complexity, more research is necessary. The algorithm proposed here, HierarchTrust, attempts to create a more reliable environment in which the selection of a peer provider of a file or other resource is based on several trust values represented in hierarchical form. The values at the top of the hierarchical form are more trusted than those at the lower end of the hierarchy. Trust, in HierarchTrust, is generally calculated based on the standard deviation. Evaluation via simulation showed that HierarchTrust produced a better success rate than the well-established EigenTrust algorithm.     

Polarization resistance studies on Corrosion inhibition of 304 austenitic and 430 ferritic stainless steels in H2SO4 solutions

The corrosion of 304 Austenitic and 430 Ferritic Stainless steels in sulphuric acid solutions has been investigated using polarization resistance (Rp) technique. Different organic inhibitors were used in this study and these contain an allylic group (CH₂ ? CH₂ ? ). The effect of acid and inhibitor concentrations, temperature, and addition of chloride ion was studied. Acid concentration was varied between 2 and 12 M and the reaction rate was found to be maximum at approximately 6 M. The inhibition efficiencies of various compounds were found to depend on concentration and varies from one alloy to another. For 304SS the efficiency lies between 40–100%. For 430SS some of these compounds behave as corrosion accelerator at certain concentrations and inhibitors at others. Chloride ion was found to improve considerably the inhibition efficiency with some exceptions. Various kinetic parameters were evaluated and they are reported. In addition the reaction mechanism is briefly discussed.