RESUMO
Catalytic oxidation is a feasible method for remediating volatile organic compounds (VOCs), due to its lower energy consumption and mineralization of VOCs into H2O and CO2. Noble metal-based catalysts are preferred for the catalytic oxidation of VOCs because of their superior activity, but they are usually deactivated by thermal aging which sinters the metal particles. Here, we report that Pt-Pd/Al2O3 thermally aged at 700-900 °C in air showed enhanced catalytic activity for toluene oxidation in humid conditions. There were electronic and structural changes in the thermally aged Pt-Pd/Al2O3, as confirmed by numerous analyses. Both Pt and Pd existed in a metallic rather than oxidized state without additional reduction steps. The noble metal particles were assembled to form Pt-Pd alloy, in the form of isolated Pd atoms surrounded by Pt atoms. This specific alloy structure was found to be crucial to the observed enhancement in catalytic toluene oxidation at low temperature.
Assuntos
Tolueno , Compostos Orgânicos Voláteis , Ligas/química , Dióxido de Carbono , Catálise , Eletrônica , Metais , Oxirredução , Compostos Orgânicos Voláteis/químicaRESUMO
In this work, the effect of the addition of vanadium to the Pt/TiO2 catalyst on the selective catalytic oxidation (SCO) of NH3 to N2 was investigated. It was found that the addition of vanadium significantly enhanced catalytic activity at all tested temperatures. The Pt/V/TiO2 catalyst exhibited the highest NH3 conversion (â¼100%) and NH3 to N2 conversion (â¼81%) at 250°C. The physicochemical characteristics of the catalysts were investigated via Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NH3 temperature-programmed desorption (TPD), NH3 temperature-programmed oxidation (TPO), and in situ Fourier-transform infrared (FTIR) spectroscopy. It was found that the addition of V to the catalyst enhanced the conversion of NH3 as a result of the formation of new acid sites. The increase in the number of acid sites resulted in increased NH3 to N2 conversion via the internal selective catalytic reduction (i-SCR) mechanism. This mechanism involves the SCR of NOx, which are formed by the oxidation of NH3. Based on experimental results and analyses of the catalysts modified by the addition of V, it was shown that there was a close relation between reaction selectivity and the surface oxygen species of the catalyst and N2 yield. Furthermore, the addition of V increased the durability of SO2 by inhibiting the formation of ammonium bisulfate (ABS).
Assuntos
Amônia , Vanádio , Catálise , Oxirredução , Difração de Raios XRESUMO
OBJECTIVE: This research is focused on modeling the diagnostic knowledge in traditional medicine. Unlike the previous studies which have dealt mainly with the standardized heuristic knowledge for diagnosis, we investigated the logical procedures and a set of source knowledge which the standardized diagnosis has been based on. These procedures and knowledge are related to Yin-Yang principle and their medical derivatives which are believed to interact with the heuristic knowledge for diagnosis through analogical reasoning. METHOD: we analyzed disorders which have been specified in traditional medicine and their signs and symptoms on the diagnostic criteria defined by Korean Institute of Oriental Medicine. Based on the conventional knowledge, all the symptoms were analyzed into elementary abstractive concepts so that we represented their properties by the principles mentioned above. And then we analyzed the procedures to link the disorders to their assigned sign and symptoms. RESULTS: Based on the proposed methodology, the diagnostic knowledge in traditional medicine was represented as rules in our ontology which was written by OpenCyc system. By applying these rules to the properties of the symptoms that have been derived from a patient, the patient's disorder can be determined. And this preliminary algorithm was implemented to be able to obtain a limited diagnostic result for individual patients. CONCLUSION: This research developed an analytic and consequently flexible diagnostic knowledge system for traditional medicine than the previous studies. These results will be extended to developing an analogical reasoning algorithm by the authors. It is also necessary, however, to improve them both by providing more practical diagnostic knowledge in such medicine and by carrying out clinical evaluations.
Assuntos
Humanos , Hidróxido de Alumínio , Carbonatos , Sistemas Inteligentes , Remoção , Lógica , Medicina Tradicional do Leste Asiático , Medicina Tradicional , Yin-YangRESUMO
The purpose of the present study was to elucidate the possible involvement of the medial vestibular nucleus (MVN) and inferior vestibular nucleus (IVN) following acute hypotension in the vestibulo- autonomic reflex through vestibulosolitary or vestibuloventrolateral projections. Acute hypotension- induced cFos expression was assessed in combination with retrograde cholera toxin B subunit (CTb) tract tracing. After injection of CTb into the solitary region, CTb-labeled neurons were located prominently around the lateral borders of the caudal MVN and medial border of the IVN. The superior vestibular nucleus also had a scattered distribution of CTb-labeled neurons. After injection of CTb toxin into the unilateral VLM, the distributions of CTb-labeled neurons in the MVN and IVN were similar to that observed after injection into the solitary region, although there were fewer CTb-labeled neurons. In the caudal MVN, about 38% and 13% of CTb-labeled neurons were double-labeled for cFos after injection of CTb into the solitary region and the VLM, respectively. In the IVN, 14% and 7% of CTb-labeled neurons were double-labeled for cFos after injection of CTb into the solitary region and the VLM, respectively. Therefore, the present study suggests that acute arterial hypotension may result in activation of vestibulosolitary pathways that mediate behavioral and visceral reflexes, and vestibuloventrolateral medullary pathways that indirectly mediate vestibulosympathetic responses.
