![]() ![]() In polyolefins production the product of the bed is a granule in the order of 200 μm diameter. Acoustic emission is a good indicator of the onset of bed disorders such as unwanted agglomeration of particles. It is therefore easy to detect the onset of slugging behavior and to exercise a control measure.Ĭhange in particle size and morphology influence the flow regimes within the bed and the acoustic emission produced. As the bubble size changes the modulation frequency also changes. The passing of bubbles through the bed causes a low-frequency modulation of the acoustic emission amplitude. ![]() Anything in the fluid bed, which changes the velocity, size, or hardness, brings about a change in the acoustic emission signals detected. A resonant sensor, mounted on the outside wall of a fluid bed, senses the motion of the particles from their impact. This lifts the material in the top sections of the bed causing loss of solid material and very poor efficiency.įluid beds produce large levels of acoustic emission. In extreme cases when the bubble diameter approaches that of the vessel a phenomenon known as ‘slugging’ may develop. When bubbles grow too large they serve as conduits for gas by-pass thereby reducing gas–solid contact. The bubbles are responsible for much of the mass transport of particles and are an important part of the mixing process. ![]() In the wake of these pockets is a stream of high-velocity particles. These are pockets of gas moving upward through the bed. In dense beds a ‘bubble phase’ is often seen. The particles move upwards in the center of the bed and fall downwards, under gravity, at the walls. In a fluidized bed, an upward current of gas suspends particles. These are of particular interest in the food and pharmaceutical industries. The gas is the monomer ethylene or propylene.įluid beds are frequently used to produce granules or to dry particulate materials. The particles consist of growing polyolefin granules (polyethylene or polypropylene). In the petrochemicals industry they are used for producing polyolefins on a very large scale. Belchamber, in Encyclopedia of Analytical Science (Second Edition), 2005 Fluid Bedsįluid bed technology is important in the oil, petrochemical, pharmaceutical, and food industries.Ĭatalytic cracking is an important process in the oil industry where petroleum vapor passes through a low-density bed of catalyst, which causes the heavier fractions to ‘crack’ producing lighter more valuable products. Among the main topics related to energy and environment, catalytic oxidation is also considered as a key subject of this review.R.M. In particular, the focus will be on the conversion of energy-related feedstocks, such as methane and higher alkanes that are primary products of the oil and gas industry, and of their product of combustion, CO 2, whose efficient capture and conversion is currently indicated as a top priority for the environment. In this review the application of SOMC strategy for the design and preparation of catalysts for industrially relevant processes that are crucial to the energy and environment is discussed. These notions are the basis of the ''catalysis by design'' strategy (''structure-activity'' relationship) in which a better understanding of the mechanistic aspects of the catalytic process led to the improvement of catalyst performances. The objective is to enter a catalytic cycle through a presumed catalytic intermediate prepared from organometallic or coordination compounds to generate well defined surface organometallic fragments (SOMFs) or surface coordination fragments (SCFs). Surface organometallic chemistry (SOMC) is an established concept, associated with specific tools, for the design, preparation and characterization of well-defined single-site catalysts. ![]() The broad challenges of energy and environment have become a main focus of research efforts to develop more active and selective catalytic systems for key chemical transformations. ![]()
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