1,720,971 research outputs found
Defect-Rich Regulatory Activity Strategy: Disordered Structure for Enhanced Catalytic Interfacial Reaction of Chlorobenzene
No full textIn contrast to previous defect engineering methods, the preparation of amorphous materials can obtain abundant defect sites through a simple way, which is expected to effectively degrade Volatile Organic Compounds (VOCs) under milder conditions. However, in-depth and systematic studies in this area are still lacking. Novel types of amorphous CeMn x catalysts with abundant defects were prepared through simple hydrothermal synthesis and used for Cl-VOCs catalysis for the first time. Experimental characterizations and DFT calculations proved that Ce doping induced MnO2 lattice distortion, which led to the transformation of CeMn x into an amorphous structure and the formation of abundant defect sites. It was observed that CeMn0.16 was able to eliminate chlorobenzene (CB) at 200 degrees C, and the CO(2 )yields and the selectivity of inorganic chlorine was significantly higher than that of MnO2. The O-18 isotope kinetic experiments revealed that the interfacial reaction process followed the MVK mechanism. The large number of oxygen vacancies accelerated the migration of lattice oxygen from the interior to the exterior, enhancing the ability to trap gas-phase oxygen. Mn4+ acted as the main active center to participate in CB catalysis, and the resulting reactive oxygen species (ROS) and Mn3+-[O2-]-Ce4+ further accelerated the entire oxidation cycle
Mechanism of the generation of benzaldehyde and benzoic acid on Pd (111) surface during the destruction of toluene: Verification of experiments and models
No full textCatalytic oxidation technology is still the mainstream technology of VOCs treatment at present, and it is of great significance to study the main active components of catalysts and clarify the evolution and transformation process of intermediate products in the catalytic process for clarifying the reaction mechanism and guiding the catalyst design. Pd was identified as the main active component in catalytic oxidation of toluene, and the important intermediate products in the degradation of toluene, i.e., benzaldehyde and benzoic acid, were obtained through experiment and In-situ DRIFT spectra. However, the specific evolution process of intermediates is difficult to observe experimentally. The conversion of toluene on Pd (111) surface was studied by DFT calculation. Benzaldehyde was the most stable intermediate and benzoic acid was the most stable energy state of the reaction products. Then the activation energies and reaction energies of all possible reaction paths from toluene to benzaldehyde or benzoic acid were calculated, and the only transition state was obtained. Two pathways for the formation of benzaldehyde and benzoic acid were identified, in which the oxidation reaction after dehydrogenation may be the common rate-determining step of the two pathways, with a maximum energy barrier of 0.80 eV
Synthesis of Cu2O micro/nanocrystals for catalytic combustion of high-concentration CO: The crucial role of glucose
No full textCubic Cu2O micro/nanocrystals were successfully synthesized by liquid-phase reduction using copper salt of CuSO4 or CuCl2.2H2O, and glucose or ascorbic acid as reducing agent, respectively. The activity of the catalysts was evaluated by light-off curves of CO self-sustained catalytic combustion via temperature-programmed oxidation of CO (CO-TPO), with the results showing the activity of catalysts following the order of Cu2O-ClGLU > Cu2O-S-GLU > Cu2O-S-AA > Cu2O-Cl-AA, (Cl denotes CuCl2.2H2O, GLU denotes glucose, S denotes CuSO4 and AA denotes ascorbic acid, respectively), corresponding to the ignition temperature of 109 degrees C, 122 degrees C, 137 degrees C and 186 degrees C, respectively. The crystal structure, elemental valence, morphology and redox property of the prepared catalysts were analyzed by using various characterization techniques. Combined with in situ infrared spectrum, the CO self-sustained catalytic combustion over Cu2O catalysts mainly follows the Mars-van-Krevelen (M-v-K) mechanism: the adsorbed and activated CO reacts with lattice oxygen to yield CO2 and oxygen vacancy, and then the oxygen vacancy can be replenished by gaseous oxygen. Combined with catalytic performance of high-concentration CO, it is found that the catalysts prepared using glucose as reducing agent are more angular compared with ascorbic acid. The Cu2O-Cl-GLU synthesized with glucose and CuCl2.2H2O exhibits the best catalytic activity among all the catalysts tested, attributing to its more obvious edge and rough crystal surface. The unique structure of Cu2O-Cl-GLU leads to the high exposure rate and coordination unsaturation of atoms on the cubic Cu2O micro/nanocrystals that can improve the ability of activating gaseous O2 and low temperature reducibility, and consequently facilitating the catalytic activity
Modification of red mud catalyst using oxalic acid-assisted UV treatment for toluene removal
No full textAn innovative simplified modification method for red mud had been proposed, which enabled its utilization as an active Fe 2 O 3 -rich component for catalytic oxidation of toluene. The Box-Behnken design, based on Response Surface Methodology (RSM), was employed to optimize the modification of bauxite residue using oxalic acid combined with UV irradiation. Based on the experimental conditions, the optimal conditions for three independent parameters were determined: acid leaching time (2 hours), UV irradiation time (1 hour), and acid dosage (150 ml),which was in order to enhance the maximum catalytic efficiency of toluene at 300 degrees C. Under the optimal preparation conditions provided by the Box-Behnken design, the catalytic efficiency of toluene at 300 degrees C could reach 99.2%. In comparison to the acid -modified mud (MRM) and untreated bauxite residue (RM), the aluminum refinery residue modified with oxalic acid -assisted UV irradiation (MRM-UV) exhibited the formation of oxalate sub -iron precipitates, resulting in significantly lower catalytic temperatures (238 degrees C). Furthermore, through XRF, XRD, XPS, O 2- TPD, and H 2 -TPD analysis, it was discovered that a large amount of iron oxide and calcium oxide formed CaO+Fe 2 O 3 -> Ca 2 Fe 2 O 5 , strengthening the interaction between iron and calcium, augmenting the migration rate of lattice oxygen from the bulk phase to the surface. Consequently, T 50 were reduced by 20.9% and 31.8% when compared to MRM and RM. Moreover, the CO 2 selectivity of MRM-UV increased from 8.6% to 70.5% compared to RM at 300 degrees C. Using in situ DRIFTS, the reaction pathway of toluene on MRM-UV was identified as benzyl alcohol -> benzaldehyde or benzoyl -> benzoate -> maleic anhydride -> CO 2 and H 2 O. The process refinement reduced VOCs emissions and promoted sustainable waste management by combining oxalic acid with catalytically active red mud
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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