Kinetics of Chemisorption<sup>1</sup>

Taylor, H. Austin; Thon, Nathaniel

doi:10.1021/ja01136a063

Cited by 217 publications

(79 citation statements)

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“…The rates of chemisorption in many gas-solid systems have been shown (1) to obey the Elovich equation, where q is the amount of gas taken up a t time t, and a and a: are coi~stai~ts. The g-t relation can be expressed by an integrated form of the Elovich equation as 2.3 9 = loglo(t+k) + constant, I I where k is a constant, so that a plot of q versus loglo(tf k) is linear.…”

Section: Introductionmentioning

confidence: 99%

Rates of Adsorption of Hydrogen on Palladium and on Rhodium

Low¹

1960

Can. J. Chem.

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A study of the effects of temperature and initial gas pressure on the kinetics of chernisorption of hydrogen on alumina-supported palladium and rhodium catalysts revealed, for both gassolid systems, that the adsorption proceeded via three distinct and consecutive kinetic stages. Each stage could be described by the Elovich equation. The temporal range of existence of each kinetic stage was temperature-and pressure-sensitive, low initial pressures and high temperatures favoring early appearance of each stage. On increasing the temperatures from 0' to 400" C , the amounts of hydrogen adsorbed on both solids decrease. Over that temperature range the rates of adsorption on P d decrease, while those on Rh increase, with increasing temperature. The general effect of increasing the initial gas pressure over the range 10-60 mm H g is to increase both rates and extents of adsorption. INTRODUCTIONThe rates of chemisorption in many gas-solid systems have been shown (1) to obey the Elovich equation, where q is the amount of gas taken up a t time t, and a and a: are coi~stai~ts. The g-t relation can be expressed by an integrated form of the Elovich equation as 2.3 9 = loglo(t+k) + constant, I I where k is a constant, so that a plot of q versus loglo(tf k) is linear. In certain systeills I isothermal discontinuities (I), or breaks, have been reported, in that abrupt changes in 1 slope occurred in the q -loglo (tfk) plots, and such behavior was ascribed to adsorption on different sites (I). The change in slope correspoilded to relatively increased or to decreased rates of adsorption, changes in both directions sometimes occurring within the same gas-solid system (2). Preliminary experiments had shown that such breaks occurred in the system Hz-Pd and Hz-Rh, and suggested more extensive work. E X P E R I M E N T A L DETAILSThe uptake of gas by the solids was followed by measuring decreases in pressure with time in systems of constant volume, using previously described techniques (2-G). The adsorbents were: 20.46-g sample of 0.5% Pd supported on the exterior of 3 x 5 mm ~-A1203 pellets; 15.85-g sample of 0.5y0 Pd on exterior of 1 x 3 mm ?-A1203 extrudates. The unreduced commercial catalysts were black in color. 011 heating of the catalysts to 500" C in vacuo a copious evolution of gas occurred. A part of the gas was condensible and probably water. After pumping overnight a t 500° C a pressure < lop6 mm Hg was attained, the original black coloration being retained. On exposure to Hq the catalysts turned gray. A test was made for efficiency of reduction by (a) reducing the catalysts a t 500" for a specific time with Hz a t 20 1. N.T.P./hour, (b) degassing a t 500" overnight, I(c) measuring Ha uptake on the degassed surface. No significant change in adsorption 'n/Ianzdscript

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Section: Introductionmentioning

confidence: 99%

Rates of Adsorption of Hydrogen on Palladium and on Rhodium

Low¹

1960

Can. J. Chem.

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“…The transient behaviour of the metal adsorption process was analysed using Elovich and intra-particle diffusion kinetic models [31][32][33]. To study the simultaneous transient behaviour of 'Na' and 'As' adsorption properties, sodium arsenate containing aqueous solution with the initial arsenic concentration of 200 ppm was tested.…”

Section: Kinetic Studiesmentioning

confidence: 99%

The role of functionalised multiwalled carbon nanotubes based supercapacitor for arsenic removal and desalination of sea water

Mishra

Ramaprabhu

2012

Journal of Experimental Nanoscience

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“…According to Aharoni [25], the Elovich equation usually holds for the results of processes involving the chemisorption of an adsorbate on a sorbent with a heterogeneous surface. According to other authors, however, the Elovich equation cannot be applied unless other processes preceding those which obey such an equation are considered; in the light of this assertion, Taylor and Thon [38] assumed the presence of a so-called pre-Elovich process of infinite rate starting and ending at t 0/0. Also, Aharoni and Tompkins [37] assumed the presence of pre-Elovich adsorption at an infinite rate that gradually evolved to an Elovich process.…”

Section: Specificmentioning

confidence: 99%