Sorption Based Separations

Porosity and pore structure are properties that control diffitsive transport, selective reaction, and sorption-based separations of gases in adsorbents and catalysts [1,2]. Sorption porosimetry may be used to characterize the porosity of both mesoporous and microporous solids. The pore size distribution F H) is obtained from the experimental isotherm /[/ )... 

Branched hydrocarbons are preferred to linear hydrocarbons as ingredients in petrol because they enhance the fuel octane number. By catalytic isomerisation linear hydrocarbons are converted into mono and di branched hydrocarbons, and it becomes necessaiy to separate the mixture. A variety of zeolites may be used for this purpose, either on the basis of sorption thermodynamics or on the basis of sorption kinetics. Such data are relevant to the development of sorption based separation methods, but also they provide key information regarding the catalytic isomerisation over zeolites themselves. 

Keywords Natural gas, carbon capture, membrane technology, sorption based separations, separation enhanced reactors... 

The systems selected to serve as major examples include amino acids and different ion exchange resins. This selection was done due to representativity of amino acids as an example of biochemical substances (labile charge, ability to form zwitterions that is almost specific for bio-products, tendency to form associates, etc.) while structures of these materials are well-known. Functional polymers and, particularly, ion exchange resins are materials of first choice for sorption-based separation of such substances. 

Membrane-based separation processes to capture either H2 or CO2 from the gasifier are new and less studied methods of CO2 separation and capture. Membranes separate the desired gas component without requiring phase changes or chemical or physical sorption. The cost of membrane separation is generally dictated by the overall pressure drop. Membranes made of various types of materials such as polymers, metals, and rubber composites have been investigated. Palladium and molecular sieves are currently under study. ° ... 

ACs are the most commonly used form of porous carbons for a long time. Typically, they refer to coal and petroleum pitch as well as coconut sheUs-based AC. In most cases, ACs are processed to be filled with rich micropores that increase the surface area available for gas sorption and separation. For this category, to get a definite classification on the basis of pore structure is difficult due to their countless products as well as their complex pore features. Based on the physical characteristics, they can be widely classified into the following types powdered, granular, extruded, bead ACs, etc. For the pore structure of ACs, actually, all the three types of pores (micropore, mesopore, and macropore) are included in one product (Fig. 2.1), with a wide pore size distribution [1, 2]. Up to now, many kinds of ACs have been well commercialized in gas sorption/separation including CO2 capture. For example, the BPL type with specific area of 1,141 m g is able to adsorb 7 mmol g CO2 under the conditions of 25 °C and 35 bar, while under the same conditions MAXSORB-activated carbon with specific area of 3,250 g can capture up to 25 mmol g [3]. 

Physisorption based gas-sorption and separation techniques using solid state adsorbents are considered as a viable alternative for energy intensive cryogenic distillation and liquid extraction [3]. The solid state adsorbents are generally porous few... 

The research on guest-inclusion complexes of calixarene based molecular crystals paved the way for different type of gas-sorption studies in these materials under various conditions. Although these materials generally dcai t possess uniform pore nor have high surface area (unlike traditional porous materials such as zeolite, molecular sieves or MOFs), their unique void structures make them attractive candidates for selective gas-sorption and separation applications. It should be noted that no uniform method were used to analyze the gas-sorption capacity (or separation capability) of these... 

Ionization is the process of separation or dissociation of a molecule into particles of opposite electrical charge (ions). The presence and extent of ionization has a large effect on the chemical behavior of a substance. An acid or base that is extensively ionized may have markedly different solubility, sorption, toxicity, and biological characteristics than the corresponding neutral compound. Inorganic and organic acids, bases, and salts may be ionized under environmental conditions. A weak acid HA will ionize to some extent in water according to the reaction ... 

The use of HPLC in all its forms is growing steadily and may eventually exceed that of GC. This is because all four sorption mechanisms can be exploited and the technique is well suited to a very wide range of compound types including ionic, polymeric and labile materials. The most appropriate choice of mode of HPLC for a given separation problem is based on the relative molecular mass, solubility characteristics and polarity of the compounds to be separated and a guide to this is given in Figure 4.43. 

Surfactants are selected based primarily on the degree of solubilization. Other factors to be considered include toxicity, biodegradability, surfactant sorption, and surfactant solubility and compatibility with the separation process. Surfactants have the ability to lower the interfacial tension between water and the contaminant by as little as a factor of three to four orders of magnitude. Combined with a sufficient reduction in capillary forces, this allows pumped groundwater theoretically to move the DNAPL toward the recovery or extraction well. This is accomplished by injecting surfactant solution into the contaminated zone. Impacted groundwater characterized by an increase in the concentration of the contaminant is then recovered and treated. 

The main emphasis in this chapter is on the use of membranes for separations in liquid systems. As discussed by Koros and Chern(30) and Kesting and Fritzsche(31), gas mixtures may also be separated by membranes and both porous and non-porous membranes may be used. In the former case, Knudsen flow can result in separation, though the effect is relatively small. Much better separation is achieved with non-porous polymer membranes where the transport mechanism is based on sorption and diffusion. As for reverse osmosis and pervaporation, the transport equations for gas permeation through dense polymer membranes are based on Fick s Law, material transport being a function of the partial pressure difference across the membrane. 

Chromatographic methods for the separation of technetium from fission products are based on the strong sorption of pertechnetate from weakly acidic, neutral, and... 

For a detailed description of the separation processes that may take place at the sensing microzone, the foundation of which is closely related to non-chromatographic continuous separation techniques based on mass transfer across a gas-liquid (gas diffusion), liquid-liquid (dialysis, ultrafiltration) or liquid-solid interface (sorption), interested readers are referred to specialized monographs e.g. [3]). 

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