Adsorbents bead activated carbon

The commercialization by Kureha Chemical Co. of Japan of a new, highly attrition-resistant, activated-carbon adsorbent as Beaded Activated Carbon (BAC) allowed development of a process employing fluidized-bed adsorption and moving-bed desorption for removal of volatile organic carbon compounds from air. The process has been marketed as GASTAK in Japan and as PURASIV HR (91) in the United States, and is now marketed as SOLD ACS by Daikin Industries, Ltd. 

Fixed-bed, temperature-swing processes rarely turn onl to be economical for bulk separations. Moving-bed and fluidized-bed processes based on thermal regeneration may prove to be much more economical because of lower heal requirements per unit of feed. The key to the success of these processes lies in the development of highly attrition-resistant adsorbent particles such as Kureha s bead activated carbon.2... 

The commercial sample, spherical bead activated carbon, was supplied by Kureha Chemical Industry. This activated carbon is referred to as Kureha carbon, which has a total micropore volume of 0.56 cm g" and a BET surface area of 1300 m g . The detailed textural properties of Kureha carbon are reported elsewhere [9]. The pore size distribution was evaluated in terms of the simulation of the density hmctional theory (DFT) using the isotherm data of nitrogen adsorption at 77 K and relative pressures up to 0.2. Only micropores contribute to the total pore volume and surface area. This was further confirmed by mercury intrusion porosimetry, no significantly additional porosity was observed in the pore size range from 2 nm to 100 pm. So, the investigated adsorbent is a purely microporous material and its pore size distribution covers the range from 0.4 to 1.9 nm [9]. 

These Deloxan beads have an inert siloxane matrix which is advantageous over other adsorbents such as activated carbon or organic polymer-based resins and fibers because (1) valuable API product is not adsorbed and lost as is the case when activated carbons are used and (2) they are chemically resistant to most solvents and stable over a wide pH range (0-12). 

We assume that the adsorbent mass used in the kinetic test consists of a sphere of radius R. It may be composed of several microsize particles (such as zeolite crystals) bonded together as in a commercial zeolite bead or simply an assemblage of the microparticles. It may also be composed of a noncrystalline material such as gels or aluminas or activated carbons. The resistance to mass transfer may occur at the surface of the sphere or at the surface of each microparticle. The heat transfer inside the adsorbent mass is controlled by its effective thermal conductivity. Each microparticle is at a uniform temperature dependent on time and its position in the sphere. 

A recently developed variation on these polymeric resins is the carbonaceous adsorbents. They are composed of hard, black, nondusting beads whose chemical composition is between that of activated carbon and polymeric adsorbents. 

Dependence of the diffusion coefficient on the degree of bead saturation is also known for porous adsorbents with a rigid structure, such as activated carbons [14, 15]. In this case, two processes - Knudsen diffusion (diffusion in porous materials) and migration of sorbate molecules along the pore... 

In order to impart hydrophilicity to neutral hydrophobic hypercrosslinked adsorbing resin CHA-101 (also obtained by post-crosslinking chloromethylated styrene-DVB copolymer), the latter was subjected to heating at 100°C within 12h in nitrobenzene in the presence of FeCb (6g per 30 g of sorbent beads) [92]. The resulting resin, NDA-702, was stated to be directly wetted by water. A comparative study of dimethyl phthalate adsorption at 10°C onto NDA-702, XAD-4, and AC-750 activated carbon showed that the sorbents take 500, 400, and 300 mg/g of the ester, respectively. The loading capacity of the sorbents decreases by 50-100 mg/g with temperature rising to 40°C. 

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]. 

One of the other studies on the influence of suspended solid materials on the mass transfer coefficient is that of Alper et al. (5).They employed various stirred cells of different designs,however,in all of the experiments gas-liquid interfacial area remained reasonably flat and could be taken as equal to the geometrical area.The values of k. was low so that the liquid film thickness was bigger than 50 pm.In agreement with above studies, their data showed that no effect of particles on k, values when inert particles,such as finely powdered quartz sand and oxirane acrylic beads,were employed.However,a completely different picture was obtained with highly porous particles of strong adsorbing property,such as activated carbon,which increased k considerably(5),... 

The Purasiv HR process is an improved fluidized bed, activated carbon process based on the use of a spherical beaded adsorbent developed by Kureha Chemical of Japan. The process was introduced in the United States and Canada by Union Carbide Corporation in 1978 (Union Carbide Corp., 1983). The unique form of the carbon adsorbent represents the key feature of the process. The beads, which are about 0.7 mm in diameter, create a homogeneous fluidized bed in the adsorption section and a free-flowing dense bed in the desorption section while providing a much higher resistance to attrition than conventional granular or pelletized material. The beads are produced by a proprietary process that involves shaping molten petroleum pitch into spherical particles which are subsequently carbonized and activated under controlled conditions. 

As previously mentioned, GC is a two-phase system that consists primarily of a stationary (solid and/or liquid) and mobile (gas) phase. When a liquid stationary phase is used (GLC), the liquid is immobilized as a thin film supported on a finely divided, inert solid support usually consisting of siliceous earth, crushed firebrick, glass beads, or in some cases, the inner wall of a glass tube. In GSC, the stationary phase is an active adsorbent, such as alumina, silica gel, or carbon, which is tightly packed into a tube. 

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