Study of the Nature and Location of Silver in Ag-Exchanged Mordenite Catalysts. Characterization by Spectroscopic Techniques

 Catalysts based on Na-mordenite (symbolized as M) exchanged with 5, 10, and 15 wt % of Ag were characterized by X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine line structure (EXAFS), X-ray absorption near edge spectroscopy (XANES) and UV-vis diffuse reflectance spectroscopy (DRS) to investigate the effect of different treatments on the chemical state and surface concentration of the silver species. The AgxM catalysts were analyzed in oxidizing (O2) or reducing (H2/Ar) atmospheres and also after being used in the selective catalytic reduction of NOx or in successive cycles of toluene adsorption/desorption. In calcined samples, EXAFS profiles showed two types of AgO spheres of coordination, one due to a dispersed phase of silver oxide and the other due to Ag+ ions in interaction with the oxygen of the zeolite framework. The UV-vis DRS spectra showed the coexistence of isolated Ag+, Agn(delta)+ (n < 10) cationic clusters and AgxO particles. In addition, through the modified Auger parameter (alpha), calculated from XPS measurements, it was possible to identify Ag+ ions at exchange sites (alpha = 722 eV) and AgxO ( alpha = 725 eV) highly dispersed on the surface. Both species constitute stable active centers for the selective catalytic reduction of NOx under severe reaction conditions. However, during the adsorption-desorption of toluene, the reduction of silver oxides produces Ag(0) due to thermal hydrocarbon decomposition.   Fil: Aspromonte, Soledad Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Investigaciones En Catálisis y Petroquímica; Argentina. Universidad Nacional del Litoral; ArgentinaFil: Mizrahi, Martin Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Schneeberger, Florencia A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Investigaciones En Catálisis y Petroquímica; ArgentinaFil: Ramallo Lopez, Jose Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Boix, Alicia Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Investigaciones En Catálisis y Petroquímica; Argentina. Universidad Nacional del Litoral; Argentin

Study of the nature and location of silver in Ag-exchanged mordenite catalysts: characterization by spectroscopic techniques

Catalysts based on Na-mordenite (symbolized as M) exchanged with 5, 10, and 15 wt % of Ag were characterized by X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine line structure (EXAFS), X-ray absorption near edge spectroscopy (XANES) and UV-vis diffuse reflectance spectroscopy (DRS) to investigate the effect of different treatments on the chemical state and surface concentration of the silver species. The AgxM catalysts were analyzed in oxidizing (O2) or reducing (H2/Ar) atmospheres and also after being used in the selective catalytic reduction of NOx or in successive cycles of toluene adsorption/desorption. In calcined samples, EXAFS profiles showed two types of AgO spheres of coordination, one due to a dispersed phase of silver oxide and the other due to Ag+ ions in interaction with the oxygen of the zeolite framework. The UV-vis DRS spectra showed the coexistence of isolated Ag+, Agn(delta)+ (n < 10) cationic clusters and AgxO particles. In addition, through the modified Auger parameter (alpha), calculated from XPS measurements, it was possible to identify Ag+ ions at exchange sites (alpha = 722 eV) and AgxO ( alpha = 725 eV) highly dispersed on the surface. Both species constitute stable active centers for the selective catalytic reduction of NOx under severe reaction conditions. However, during the adsorption-desorption of toluene, the reduction of silver oxides produces Ag(0) due to thermal hydrocarbon decomposition.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Immune Response to SARS-CoV-2 Third Vaccine in Patients With Rheumatoid Arthritis Who Had No Seroconversion After Primary 2-Dose Regimen With Inactivated or Vector-Based Vaccines

Objective. The aim of this study was to assess the immune response after a third dose of SARS-CoV-2 vaccine in patients with rheumatoid arthritis (RA) with undetectable antibody titers after the primary regimen of 2 doses. Methods. Patients with RA with no seroconversion after 2 doses of SARS-CoV-2 vaccine and who received a third dose of either an mRNA or vector-based vaccine were included. Anti-SARS-CoV-2 IgG antibodies, neutralizing activity, and T cell responses were assessed after the third dose. Results. A total of 21 nonresponder patients were included. At the time of vaccination, 29% were receiving glucocorticoids and 85% biologic disease-modifying antirheumatic drugs (including 6 taking abatacept [ABA] and 4 taking rituximab [RTX]). The majority (95%) received the BNT162b2 vaccine and only one of them received the ChAdOx1 nCoV-19 vaccine. After the third dose, 91% of the patients presented detectable anti-SARS-CoV-2 IgG and 76% showed neutralizing activity. Compared to other treatments, ABA and RTX were associated with the absence of neutralizing activity in 4 out of 5 (80%) patients and lower titers of neutralizing antibodies (median 3, IQR 0-20 vs 8, IQR 4-128; P = 0.20). Specific T cell response was detected in 41% of all patients after the second dose, increasing to 71% after the third dose. The use of ABA was associated with a lower frequency of T cell response (33% vs 87%, P = 0.03). Conclusion. In this RA cohort, 91% of patients who failed to seroconvert after 2 doses of SARS-CoV-2 vaccine presented detectable anti-SARS-CoV-2 IgG after a third dose. The use of ABA was associated with a lower frequency of specific T cell response.Fil: Isnardi, Carolina A.. No especifíca;Fil: Cerda, Osvaldo L.. No especifíca;Fil: Landi, Margarita. Austral University Hospital; LiberiaFil: Cruces, Leonel Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; ArgentinaFil: Schneeberger, Emilce E.. No especifíca;Fil: Montoro, Claudia Calle. Austral University Hospital; LiberiaFil: Alfaro, María Agustina. No especifíca;Fil: Roldán, Brian M.. No especifíca;Fil: Gómez Vara, Andrea B.. No especifíca;Fil: Giorgis, Pamela. No especifíca;Fil: Ezquer, Roberto Alejandro. No especifíca;Fil: Crespo Rocha, María G. No especifíca;Fil: Reyes Gómez, Camila R.. No especifíca;Fil: de Los Ángeles Correa, Mária. No especifíca;Fil: Rosemffet, Marcos G.. No especifíca;Fil: Abarza, Virginia Carrizo. No especifíca;Fil: Pellet, Santiago Catalan. Austral University Hospital; LiberiaFil: Perandones, Miguel. No especifíca;Fil: Reimundes, Cecilia. Austral University Hospital; LiberiaFil: Longueira, Yesica Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; ArgentinaFil: Turk, Gabriela Julia Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; ArgentinaFil: Quiroga, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; ArgentinaFil: Laufer, Natalia Lorna. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; ArgentinaFil: Quintana, Rosana Maris. No especifíca;Fil: de la Vega, María Celina. No especifíca;Fil: Kreplak, Nicolás. No especifíca;Fil: Pifano, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Maid, Pablo. Austral University Hospital; LiberiaFil: Pons Estel, Guillermo J.. No especifíca;Fil: Citera, Gustavo. No especifíca