Microcalorimetric Studies of Adsorption on the Surface of Pd-Cu/SiO2

Abstract

Abstract: Adsorption of H-₂, CO, O-₂and C-₂H-₄on m(Pd)/m(SiO-₂)=2%, m(Pd,Cu)/m(SiO-₂)[n(Pd)/n(Cu)}=1/1]=2%, m(Pd,Cu)/m(SiO-₂)[n(Pd)/n(Cu)=1/4]=2% and m(Cu)/m(SiO-₂)=8%, catalysts was investigated by using the techniques of microcalorimetric adsorption at room temperature.The effect of O-₂on adsorption of C-₂H-₄on the surface of the catalysts was also studied.It is found that the number of sites for H-₂adsorption on PdCu/SiO-₂is close to that on Pd/SiO-₂. Addition of Cu decreases the sites of stronger adsorption and increases the sites of weaker adsorption of H-₂and COon Pd.On the other hand, Pd can promote the dispersion of Cu on SiO-₂and accelerate the rate of O-₂adsorption on Cu/SiO-₂. These results suggest that Pd and Cu atoms are well mixed and Pd atoms are well dispersed in the PdCu/SiO-₂catalysts.Ethylene adsorbed on Pd/SiO-₂produces ethylidyne and σ and di-π species.The addition of Cu inhibits the formation of the dissociatively adsorbed species--ethylidyne but promotes the formation of undissociatively adsorbed species--π and di-σ species for ethylene adsorption on Pd-Cu/SiO-₂catalysts.Ethylene may react with O-₂adsorbed on Pd/SiO-₂at room temperature.Cu decreases the activity of adsorbed O-₂on Pd-Cu/SiO-₂. Hence, ethylene may be activated effectively on PdCu catalysts.

Key words: Ethylene, Calorimetric adsorption, Pd-Cu/SiO-₂catalysts

CLC Number:

O643

TrendMD:

LI MingShi, GE Xin, ZOU Hu, SHEN JianYi. Microcalorimetric Studies of Adsorption on the Surface of Pd-Cu/SiO₂[J]. Chem. J. Chinese Universities, 2000, 21(12): 1896.

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Microcalorimetric Studies of Adsorption on the Surface of Pd-Cu/SiO₂

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