Science and technology of novel processes for deep desulfurization of oil refinery streams: a review☆ ☆

Catalytic removal of NO

The utilization of ceria in industrial catalysis

An overview is given on the ongoing activities in the area of the decomposition of nitrous oxide, N2O, over solid catalysts. These catalysts include metals, pure and mixed oxides, supported as well as unsupported, and zeolitic systems. The review covers aspects of the reaction mechanism and kinetics, focusing on the role of surface oxygen, the inhibition by molecular oxygen, water and other species, poisoning phenomena and practical developments.

Heterogeneous catalytic decomposition of nitrous oxide

By the early 1970s increased use of cars in some major cities had resulted in serious concerns about urban air quality caused by engine exhaust gas emissions themselves, and by the more harmful species derived from them via photochemical reactions. The three main exhaust gas pollutants are hydrocarbons (including partially oxidised organic compounds), carbon monoxide and nitrogen oxides. Engine modifications alone were not sufficient to control them, and catalytic systems were introduced to do this. This catalytic chemistry involves activation of small pollutant molecules that is achieved particularly effectively over platinum group metal catalysts. Catalytic emissions control was introduced first in the form of platinum-based oxidation catalysts that lowered hydrocarbon and carbon monoxide emissions. Reduction of nitrogen oxides to nitrogen was initially done over a platinum/rhodium catalyst prior to oxidation, and subsequently simultaneous conversion of all three pollutants over a single three-way catalyst to harmless products became possible when the composition of the exhaust gas could be maintained close to the stoichiometric point. Today modern cars with three-way catalysts can achieve almost complete removal of all three exhaust pollutants over the life of the vehicle. There is now a high level of interest, especially in Europe, in improved fuel-efficient vehicles with reduced carbon dioxide emissions, and “lean-burn” engines, particularly diesels that can provide better fuel economy. Here oxidation of hydrocarbons and carbon monoxide is fairly straightforward, but direct reduction of NO x under lean conditions is practically impossible. Two very different approaches are being developed for lean-NO x control; these are NO x -trapping with periodic reductive regeneration, and selective catalytic reduction (SCR) with ammonia or hydrocarbon. Good progress has been made in developing these technologies and they are gradually being introduced into production. Because of the nature of the diesel engine combustion process they produce more particulate matter (PM) or soot than gasoline engines, and this gives rise to health concerns. The exhaust temperature of heavy-duty diesels is high enough (250–400 °C) for nitric oxide to be converted to nitrogen dioxide over an upstream platinum catalyst, and this smoothly oxidises retained soot in the filter. The exhaust temperature of passenger car diesels is too low for this to take place all the time, so trapped soot is periodically burnt in oxygen above 550 °C. Here a platinum catalyst is used to oxidise higher than normal amounts of hydrocarbon and carbon monoxide upstream of the filter to give sufficient temperature for soot combustion to take place with oxygen. Diesel PM control is discussed in terms of a range of vehicle applications, including very recent results from actual on-road measurements involving a mobile laboratory, and the technical challenges associated with developing ultra-clean diesel-powered cars are discussed.

Progress and future challenges in controlling automotive exhaust gas emissions

The present and the future of structured catalysts - an overview. Reactors with structured catalysts where no convective mass transfer over a cross section of the reactor occurs (monolithic catalysts = honeycomb catalysts): ceramic catalyst supports for casoline fuel metal and coated-metal catalysts autocatalysts - past, present and future monolithic catalysts for the selective reduction of NOx with NH3 from stationary monolith reactors unconventional utilization of monolithic

Structured Catalysts and Reactors

The use of structured catalysts in the chemical industry has been considered for years. Conventional fixed-bed reactors have some obvious disadvantages such as maldistributions of various kinds (including a nonuniform access of reactants to the catalytic surface), high pressure drop in the bed, etc. Structured catalysts are promising as far as elimination of these setbacks is concerned. Two basic kinds of structured catalysts can be distinguished: Structural packings covered with catalytically active material, similar in design to those used in distillation and absorption columns and/or static mixers. Good examples of catalysts of this kind are those offered by Sulzer, clearly developed by Sulzer column packings and static mixers. As in packed beds, there is an intensive radial convective mass transport over the entire cross-section of these packings. Structural packing catalysts and the reactors containing them are, however, not within the scope of this review. Monolithic catalysts are continuou...

Monoliths in Heterogeneous Catalysis

Monolithic Reactors for Fine Chemicals Industries: A Comparative Analysis of a Monolithic Reactor and a Mechanically Agitated Slurry Reactor

Engineering Hierarchically Architectured Zeolites by Demetallation Au Allows Catalysis at Room Temperature The Fascinating Structure and the Potential of Metal Organic Frameworks (MOFs) Enzymatic Catalysis Today and Tomorrow The Wonderful World of Fenton Chemistry in Solid Catalyst Synthesis Challenges in Catalysis for Sustainability Catalytic Processing of Biomass into Chemicals Structured Reactors, a Wealth of Opportunities Zeolite Membranes in Catalysis: What is New and How Bright is the Future Microstructures on Macroscale: Microchannel Reactors for Medium- and Large-Size Processes Intensification of Heat Transfer in Chemical Reactors: Heat Exchanger Reactors Reactors Using Alternative Energy Forms for Green Synthetic Routes, New Functional Products and Nanotechnology Switching from Batch to Continuous Processing for Fine and Intermediate Scale Chemicals Manufacture Progress in Methods for Identification of Micro- and Macroscale Physical Phenomena in Chemical Reactors: Improvements in Scale-Up of Chemical Reactors

Andrzej Cybulski

Papers

Structured Catalysts and Reactors

Monoliths in Heterogeneous Catalysis

Monolithic Reactors for Fine Chemicals Industries: A Comparative Analysis of a Monolithic Reactor and a Mechanically Agitated Slurry Reactor

Novel Concepts in Catalysis and Chemical Reactors: Improving the Efficiency for the Future

Modelling of heat transfer in metallic monoliths consisting of sinusoidal cells