Saran charcoal

Surface Diffusion of Low Boiling Gases on Saran Charcoal... 

Hydrogen, deuterium, neon, argon, and methane flow through saran charcoal by both Knudsen and surface flow. The latter is effected by the adsorbed molecules sliding from site to site across the surface. This is equivalent to a two-dimensional Knudsen flow where the adsorption site acts as the wall of the three-dimensional case, and a slide across the surface is the same as a flight across the pore. The activation energy for surface diffusion is 75 to 80% of the heat of adsorption. It is possible to calculate theoretically the relative contribution of each mechanism, while comparison with He, which does not adsorb, permits its experimental determination. The efficiency of surface flow is the ratio of the measured to the calculated value this decreases as the size of the molecule increases, being 80% for Ne and 12% for CH4. 

Poly(vinylidene chloride) may be obtained from The Dow Chemical Co. as a white powder, designated saran A. To prepare saran charcoal from this powder it is first pressed into a convenient shape by use of a hydraulic press and steel die at a pressure of 15,000 p.s.i. The compressed polymer is then heated slowly in vacuo, starting at 125° C. and gradually increasing the temperature up to 750° C. The heating process takes about 3 weeks and the resulting piece of carbon retains the shape of the original polymer but is reduced in size in all directions by about 20%. 

Saran charcoal is a hard, strong, and highly porous form of carbon. The pores are believed to be very fine and uniform, slotlike in cross section, and between 12 and 15 A. in width in their narrowest dimension (6). 

A pioneering investigation of the adsorption of water vapour by Saran charcoal (an ultramicroporous carbon) was carried out by Dacey et al., (1958). The isotherm at 55°C had the well-defined Type V character with a steep riser at p/p° 0.5-0.6. There was a small amount of low-pressure hysteresis, but the isotherm appeared to be completely reversible at p/p° > 0.55. 

Saran13 charcoal is prepared by the slow carbonization of compressed blocks of polyvinylidine chloride. Saran charcoal is very... 

FIGURE 2.5 Adsorption of iso-octane vapours on different Saran charcoal. 

FIGURE 2.6 Linear Langmuir plots for adsorption of iso-octane on different Saran charcoal [own work]. 

FIGURE 4.6 Adsorption of water vapor on Saran charcoal before and after pore blocking by deposition of sulphur. (After Bansal, R.C., Bala, S., and Sharma, N., Indian J. Technol., Tl, 206, 1989. With permission.)... 

FIGURE 4.9 Adsorption isotherms of heptane vapors on Saran charcoal before and aflerpore blocking by benzene pyrolysis. (After Sharma, N., Ph.D. thesis submitted to Panjab Univ.,... 

FIGURE 4.12 (a) Absorption isotherms of iso-octane vapours on Saran charcoal at different temperatures, (b) Absorption isotherms of iso-octane vapors on Saran-120 at different temperatures. (c) Absorption isotherms of a-pinene vapors on Saran charcoal at different temperatures, (d) Adsorption isotherms of a-pinene vapors on Saran-120 charcoal at different temperatures. (After Bansal, R.C. and Dhami, T.L., Carbon, 18, 207, 1980. With permission.)... 

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