Adsorbed product

The cyclic steady state SMB performance is characterized by four parameters purity, recovery, solvent consumption, and adsorbent productivity. Extract (raffinate) purity is the ratio between the concentration of the more retained component (less retained) and the total concentration of the two species in the extract (raffinate). The recovery is the amount of the target species obtained in the desired product stream per total amount of the same species fed into the system. Solvent consumption is the total amount of solvent used (in eluent and feed) per unit of racemic amount treated. Productivity is the amount of racemic mixture treated per volume of adsorbent bed and per unit of time. 

The vertex of a separation region points out the better operating conditions, since it is the point where the purity criteria are fulfilled with a higher feed flow rate (and so lower eluent flow rate). Hence, in the operating conditions specified by the vertex point, both solvent consumption and adsorbent productivity are optimized. Comparing the vertex points obtained for the two values of mass transfer coefficient, we conclude that the mass transfer resistance influences the better SMB operating conditions. Moreover, this influence is emphasized when a higher purity requirement is desired [28]. 

The kinetic expression was derived by Akers and White (10) who assumed that the rate-controlling factor in methane formation was the reaction between the adsorbed reactants to form adsorbed products. However, the observed temperature-dependence of the rate was small, which indicates a low activation energy, and diffusion was probably rate-controlling for the catalyst used. 

In the following we consider a surface with adsorbed atoms or molecules that react. We will leave out the details of the internal coordinates of these adsorbed species, but note that their partition functions can be found using the schemes presented above. Let us assume that species A reacts with B to form an adsorbed product AB via an activated complex AB ... 

Reaction products can also be identified by in situ infrared reflectance spectroscopy (Fourier transform infrared reflectance spectroscopy, FTIRS) used as single potential alteration infrared reflectance spectroscopy (SPAIRS). This method is suitable not only for obtaining information on adsorbed products (see below), but also for observing infrared (IR) absorption bands due to the products immediately after their formation in the vicinity of the electrode surface. It is thus easy to follow the production of CO2 versus the oxidation potential and to compare the behavior of different electrocatalysts. 

Similar to gasoline, the properties of DNAPLs such as immiscibility with water, volatility, and solubility of some of its components cause the presence of multiphase (pure product, solute, gas, and adsorbate) products and movement that is typical of the phenomena associated with DNAPL release. The theory associated with the interaction of gasoline with soil is applicable to DNAPLs. However,... 

Monte Carlo simulations have been also used to reproduce the dynamics of adsorbates associated with NO reduction reactions. As mentioned above, complex desorption dynamics have been observed experimentally in some instances. For example, the N2 produced from decomposition of N20 on Rh(110) leaves the surface in five peaks associated with both the N20 dissociation events and the desorption of the adsorbed products. Monte Carlo simulations of those spectra was possible by using a model that takes into account both channels of N2 desorption and also N20 O lateral interactions to stabilize N20 adsorption [18],... 

The three remaining steps (chemisorption of reactants, reaction on the surface, and desorption of adsorbed products) are all chemical in nature. It is convenient to employ the concept of a rate limiting step in the treatment of these processes so that the reaction rate becomes equal to that of the slowest step. The other steps are presumed to be sufficiently rapid that quasiequilibrium relations may be used. The overall rate of conversion will then be determined by the interaction of the rate of the process that is rate limiting from a chemical point of view with the rates of the physical mass transfer processes discussed above. 

The simplest case is one for which there is an adsorbed product. Equation (2.188) can then be used to establish the stoichiometric composition of the adsorbed species providing that they can be oxidised to volatile products and that the system can be calibrated, i.e. K determined. Thus, for adsorbed CO, n = 2. The CO can be oxidised off as C02 with the MS and current response being measured as a function of potential, allowing K to be calculated. 

As far as the Prigogine-type coupling between heat- and mass flow is operative from the catalytic active sites to the vigorously generating bubbles, the adsorbed products will be readily taken out and a large amount of vacant sites will be generated stationarily. Therefore, the restriction of equilibrium conversion (AG < 0) even becomes removable as a consequence of AG < AG by adopting the superheated liquid-film catalysis. 

Chemical reaction of the adsorbed reactants to adsorbed products (surface reaction - the intrinsic chemical step)... 

The process can be divided into four different sections. Section I is located between the desorbent and extraction node. The flow rate is higher than in all the other sections, which is necessary to remove the more strongly adsorbed product (here component B) from the adsorbent. Section II is located between the extract and the feed node. In this section the components B and C are formed. The less strongly adsorbed product (here component C) is desorbed and transported upstream together with the solvent, whereas B is still held on the adsorbent and transported to the extract port. The extract stream therefore contains the more strongly adsorbed product B. In Section III the conversion of component A takes place. Component B is retained and, thus, component C can be collected at the raffinate port. In Section IV component C is adsorbed and transported back to Section III together with the adsorbent, while the fluid phase is cleaned and recycled. 

For adsorption limited by mass transfer kinetics, the educt should be significantly less retained than the most strongly adsorbed product. 

Heavy wall tubing plain, coloured, striped tubing fabrications for instrumentation automotive push-pull cables industrial and process hydraulics and other fluids. .. Piping liners for glass-lined reactors, stainless steel reactors, glass equipment and mixers... Membranes, filter media, filter bags, cartridges, microfiltration membranes, vents and adsorbent products. .. 

Knitted, woven, braided or sewn fibres compression packing, sewing thread, membranes, filter media, filter bags, cartridges, microfiltration membranes, vents and adsorbent products... 

Finally, new developments in zeolite catalyst and adsorbent manufacture will be outlined in the form of a survey of recent open and patent literature. Patents are extensively cited as reference materials for this chapter however no effort is made to identify specific manufacturing techniques actually used by any particular company to manufacture zeolites or any catalytic or adsorbent products. This is because there is no way to determine whether manufacturing patents are practiced as is or whether further refinements have been accomplished subsequent to the filing of the patents that may be held by specific companies as trade secrets. 

Reid, Sherwood and Prausnitz [11] provide a wide variety of models for calculation of molecular diffusion. Dr is the Knudsen diffusion coefficient. It has been given in several articles as 9700r(T/MW). Once we have both diffusion coefficients we can obtain an expression for the macro-pore diffusion coefficient 1/D = 1/Dk -i-1/Dm- We next obtain the pore diffusivity by inclusion of the tortuosity Dp = D/t, and finally the local molar flux J in the macro-pores is described by the famiUar relationship J = —e D dcjdz. Thus flux in the macro-pores of the adsorbent product is related to the term CpD/r. This last quantity may be thought of as the effective macro-pore diffusivity. The resistance to mass transfer that develops due to macropore diffusion has a length dependence of R]. 

The basic adsorption process design. Sub-tasks within that include the adsorbent selection, made in view of aU of the requirements imposed on the dehydration process. The adsorption step time, regeneration and cooHng step times all need to be settled and these in view of mechanical details. The overall vessel configuration, for example, the vessel ID and length, which quantities are typically sized based on pressure drop. Finally we need to make some estimate of the expected service Hfetime for the adsorbent product. 

As was suggested in a previous paper dthe steady state etching of solid material by exposure to gas phase particles with or without a plasma is usually described by the following sequence of steps (1) nondissociative adsorption of gas phase species at the surface of the solid being etched (2) dissociation of this absorbed gas (i.e., dissociative chemisorption) (3) reaction between adsorbed radicals and the solid surface to form an adsorbed product molecule, e.g., SiF fads) (4) desorption of the product molecule into the gas phase and (5) the removal of nonreactive residue (e.g., carbon) from the surface. 

Clayson, Edward T., Lieutenant Colonel, U.S. Army, Program Director, Anthrax Vaccine Adsorbed Production Program, JPO-BD, telephone interview, August 22, 2001. 

The transition state leading to the dissociative complex of surface methoxy and water is shown in Fig. 13, as are the final adsorbed products. The transition state is product-like, indicating that the reaction barrier appears to be dominated by the breaking of the methanol C-O bond. The overall thermodynamics of dehydration were predicted to be between 2 kJ/mol endothermic and 5 kJ/mol exothermic, depending on the precise method and cluster model used. With respect to the side-on physisorbed complex, the activation energy was calculated to be 185 kJ/mol. 

For higher amounts of selenium dioxide in the feed (Z > 0.02), while the surface concentration of adsorbed oxygen ions gradually decreases, the surface concentration of adsorbed products becomes significant, and possibly results in the modifier s entering the catalyst lattice substitutionally, rather than interstitially, Cu2+, Cu+, or O" is replaced by selenium, forming a small unit of a covalent compound. Thus, both free... 

Let a be the fraction of the active surface which is covered with molecules of the reactant when the pressure of this is p, and let o be the fraction covered with molecules of the adsorbed product when the pressure of this is p. ... 

Union Carbide s OlefinSiv Process. Union Carbide s OlefinSiv process is used mainly to separate n-butylenes from isobutylene 31). The basic hardware is the same as for the IsoSiv process for n-paraffin separation, and the process uses a rapid cycle, fixed-bed adsorption. Since this process separates straight-chain olefins from branched-chain olefins, it is reasonable to assume that a 5A molecular sieve is used as the adsorbent. Product purities are claimed to be above 99% for both n-butylene and isobutylene streams. 

In certain cases and together with the electrode reaction, in particular that of oxygen reduction at metal surfaces, a non-electrochemical regeneration mechanism operates which is heterogeneous in nature and involves the adsorbed product [165] obviously, it is very dependent on the electrode material and the available surface states. The reaction scheme is thus of the type... 

Figure 2. An additional problem is the fact that only one highly purified (less-adsorbed) product can be produced, since part of this product is used to purge the more tightly adsorbed product and is lost with that product.

The net effect of this process is to produce, using a single adsorbing bed and two surge tanks, a constant flow of less tightly adsorbed product - primarily oxygen in this case - from a constant flow of air from a compressor. 

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