Surface area and pore texture of catalysts

Graphitic carbon nitride, g-C3N4, is a polymeric material consisting of C, N, and some impurity H, connected via tris-triazine-based patterns. Compared with the majority of carbon materials, it has electron-rich properties, basic surface functionalities and H-bonding motifs due to the presence of N and H atoms. It is thus regarded as a potential candidate to complement carbon in material applications. In this review, a brief introduction to g-C3N4 is given, the methods used for synthesizing this material with different textural structures and surface morphologies are described, and its physicochemical properties are referred. In addition, four aspects of the applications of g-C3N4 in catalysis are discussed: (1) as a base metal-free catalyst for NO decomposition, (2) as a reference material in differentiating oxygen activation sites for oxidation reactions over supported catalysts, (3) as a functional material to synthesize nanosized metal particles, and (4) as a metal-free catalyst for photocatalysis. Th...

Graphitic Carbon Nitride: Synthesis, Properties, and Applications in Catalysis

Endowed with unparalleled high catalytic activity and selectivity, enzymes offer enormous potential as catalysts in practical applications. These applications, however, are seriously hampered by enzymes’ low thermal and chemical stabilities. One way to improve these stabilities is the enzyme immobilization. Among various tested methods of this process that make use of different enzyme-carrier interactions, immobilization by adsorption on solid carriers has appeared most common. According to these findings, in this review we present a comparative analysis of the literature reports on the recent trends in the immobilization of the enzymes by adsorption. This thorough study was prepared in order to provide a deeper understanding of the process. Both carriers, carrier modifiers and procedures developed for effective adsorption of the enzymes are discussed. The review may thus be helpful in choosing the right adsorption scheme for a given enzyme to achieve the improvement of its stability and activity for a specific application.

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Enzyme immobilization by adsorption: a review

Catalytic NOx Abatement Systems for Mobile Sources: From Three-Way to Lean Burn after-Treatment Technologies Pascal Granger* and Vasile I. Parvulescu* Unit e de Catalyse et de Chimie du Solide, UMR CNRS 8181, University of Lille 1, 59655 Villeneuve d’Ascq, France Department of Organic Chemistry, Biochemistry and Catalysis, University of Bucharest, Romania, 412 Regina Elisabeta Boulevard, Bucharest 030016, Romania

Catalytic NOx Abatement Systems for Mobile Sources: From Three-Way to Lean Burn after-Treatment Technologies

Selective catalytic reduction (SCR) of NO with NH3 over manganese substituted iron titanate catalysts was fully studied. The low temperature SCR activity was greatly enhanced when partial Fe was substituted by Mn, although the N-2 selectivity showed some decrease to a certain extent. The Mn substitution amounts showed obvious influence on the catalyst structure, redox behavior and NH3/NOx adsorption ability of the catalysts. Among FeaMn1-aTiOx (a = 1, 0.75, 0.5, 0.2, 0) serial catalysts, Fe0.5Mn0.5TiOx with the molar ratio of Fe:Mn = 1: 1 showed the highest SCR activity, because the interaction of iron, manganese and titanium species in this catalyst led to the largest surface area and the highest porosity, the severest structural distortion and most appropriate structural disorder, the enhanced oxidative ability of manganese species, the highest mobility of lattice oxygen, the proper ratio of Bronsted acid sites and Lewis acid sites together with the enhanced NOx adsorption capacity. (C) 2009 Elsevier B.V. All rights reserved.

Effect of manganese substitution on the structure and activity of iron titanate catalyst for the selective catalytic reduction of NO with NH3

Monitoring Changes in Surface and Structural Properties of Porous Carbons Modified by Different Oxidizing Agents.

Temperature‐programmed desorption (TPD) and surface reaction (TPSR), and additionally FTIR spectroscopy of adsorbed NO molecules were used to characterise surface sites on pillared smectites modified with carbon and manganese. Much higher adsorption of NH3 than NO was found, but acidic pre‐treatment increased NO sorption to comparable values as well as catalytic performance in SCR of NOx. In this case formation of strongly bound NO3− species was recognised, which reacted with NH3 at a temperature 200 °C higher than weaker adsorbed NO.

Pillared smectite modified with carbon and manganese as catalyst for SCR of NOx with NH3. Part II. Temperature‐programmed studies

Nitrogen-promoted active carbons as DeNOx catalysts: 1. The influence of modification parameters on the structure and catalytic properties

Nitrogen promoted activated carbons as DeNOx catalysts. 2. The influence of water on the catalytic performance

The preparation of active carbons promoted with manganese was studied with low temperature argon sorption techniques temperature-programmed desorption and X-ray photoelectron spectroscopy. As supports, unoxidized and oxidatively pretreated carbons were used. The introduction of active material was accomplished by an adsorption method using solutions of KMnO4, KMnO4+H2SO4 or Mn(NO3)2. The oxidation state of the active phase and its distribution depended on the precursor and the amount/type of oxygen surface functionalities of their support. KMnO4 solutions led to the precipitation of Mn2O3/MnO2 crystallites, mostly on the outer surface of active carbon particles. Mn(NO3)2 solutions, when introduced onto unpretreated support, resulted in Mn3O4/MnO2 as large aggregates. When H2SO4 was added to KMnO4 solution, small clusters with a broad distribution of sizes were deposited. A monolayer coverage of manganese species could only be obtained when active carbon was pretreated in an oxidizing environment strong enough to produce a considerable amount of carboxylic functionalities. Additionally, the preparation procedures influenced the textural properties.

J. Klinik

Papers

Monitoring Changes in Surface and Structural Properties of Porous Carbons Modified by Different Oxidizing Agents.

Pillared smectite modified with carbon and manganese as catalyst for SCR of NOx with NH3. Part II. Temperature‐programmed studies

Nitrogen-promoted active carbons as DeNOx catalysts: 1. The influence of modification parameters on the structure and catalytic properties

Nitrogen promoted activated carbons as DeNOx catalysts. 2. The influence of water on the catalytic performance

Manganese supported catalysts for selective catalytic reduction of nitrogen oxides with ammonia Part 1 Characterization