Volumetric adsorption apparatus

For laboratory-scale modification, distinction has to be made between static and dynamic adsorption procedures. In a static procedure, the substrate is contacted with a known volume of gas at a well-defined pressure. The modifying gas may be stationary or circulating in a closed loop. Modification in a static gas adsorption apparatus allows the careful control of all reaction parameters. Temperature and pressure can be controlled and easily measured. Adsorption kinetics may be determined by following the pressure as a function of the reaction time. Figure 8.13 displays a volumetric adsorption apparatus, in which mercury is used, as a means to change the internal volume and for pressure measurement. 

A typical commercial volumetric adsorption apparatus is shown in Figure 6.8 [20], The volumetric sorption equipment is equipped with pressure transducers in the dosing volume compartment of the apparatus and high-precision pressure transducers dedicated to measure the pressure in the sample cell [21,22], Hence, the sample cell is isolated throughout equilibration, which assures a very small void volume, and as a result a highly accurate determination of the adsorbed amount [21],... 

FIGURE 6.8 Representation of a standard volumetric adsorption apparatus. (Taken from Thommes, M., in Nanoporous Materials Science and Engineering, Lu, G.Q. and Zhao, X.S. (eds.), Imperial College Press, London, UK, 2004, 317. With permission.)... 

A classical volumetric adsorption apparatus equipped with absolute capacitance pressures transducers can be used for the estimation of adsorption isotherms in the pressure range 10-3 mbaradsorption measurements the carbon black samples are extracted with toluene and water/methanol (1 1) and after drying degassed overnight at 200 °C at a pressure below 10 4 mbar. The time allowed for equilibrium of each point of the isotherm is 5-90 min depending on the sample and the adsorbed amount. 

The adsorption isotherms for water with five of the samples were obtained at 25° C. by using a volumetric adsorption apparatus described previously (13). Prior to adsorption measurements these samples were also outgassed at 160° and 10-6 mm. Hg. Each adsorption isotherm consisted of 20 to 40 experimental points covering the relative pressure range 0.01 to 0.95. 

BET measurements were performed in a conventional volumetric adsorption apparatus at the temperature of liquid N2 (77.4 K). Prior to measurements the samples were pretreated in vacuum at 573 K for 1 hour (Table 1, fourth column). 

The adsorption calorimetric measurements were carried out at 423 K on a SETARAM microcalorimeter of calvet-type connected with a standard volumetric adsorption apparatus. The pressure measurements were made using a MKS Baratron membrane manometer. Prior to the ammonia adsorption, the samples (900 mg) were carefully calcined in high vacuum at 673 K for 15 h. 

H2O, n-hexane and cyclohexane sorption capacities of SAPO-31 were determined gravimetrically using a vacuum microbalance (Cahn Instruments, USA). The size and the morphology of the crystals of SAPO-31 were examined using a JEOL (JSM-840 A) scanning electron microscope. The BET surface area was determined using a volumetric adsorption apparatus ( Model Omnisorb lOOCX, Coulter, USA). 

Boron Nitride and Metal Borides.—A new high-precision volumetric adsorption apparatus has been used to determine the energies of interaction of Ne, Ar, Kr, and Xe with hexagonal BN at 273 K. 

Ammoniation was carried out in a dynamic volumetric adsorption apparatus, as described elsehwere [3]. The ammonia uptake was measured volumetrically, whereas the surfce chlorine concentration was determined argentometrically [5]. Extreme care was taken to prevent the samples from hydrolysis, by handling them in a Na glove box or in vacuo. The total chlorine concentration was determined argentometrically after direct hydrolysis of the modified surface following reaction. 

Pure Nz and Oz adsorption isotherms were measured on the zeolites in our laboratory at approximately 30 and 70°C and in the gas pressure range of 0-1.5 atmospheres except for CaLSX where the isotherms were measured at 23 and 45°C. A conventional volumetric adsorption apparatus was used for these measurements [5]. The experimental isotherms are given in Tables 1-5 for easy access. Figures 1 and 2 respectively show the pure Nz and Oz isotherms (amount... 

Adsorption of CO2 and CH4. Adsorptions of CO2 and CH4 on the ACFs were carried out separately using a volumetric adsorption apparatus. Each ACF was evacuated to 10 2 ton at 150 C for Ih prior to the adsorption study. The gas volumes... 

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