Structural and energetic nonuniformities of pyrocarbon-mineral adsorbents

Several series of pyrocarbon-mineral adsorbents (carbosils) were studied us ing the nitrogen adsorption method to compute structural and energetic para meters within the scope of overall adsorption isotherm approximation applyi ng a regularization procedure with consideration for surface heterogeneity. A portion of pyrocarbon deposits (graphene clusters) fills mesopores of th e oxide supports, but another portion represents relatively large nonporous pyrocarbon globules formed on the outer surfaces of the oxide matrices. Co ntributions of these two types of pyrocarbon deposits depend on the nature of oxide matrices and carbonized precursors. The characteristics of pyrocar bon formed on the silica (silica gel, fumed silica) surfaces differ from th ose for deposits prepared on the surfaces of titania/silica and alumina/sil ica or by the pyrolysis of metal acetylacetonates (Zr(AcAc)(4), TiO(AcAc)(2 ), Ni(AcAc)(2), Zn(AcAc)(2),Cr(AcAc)(3), Co(AcAc)(2)) on mesoporous silica gel. The structural and energetic characteristics estimated using the adsor ption method with consideration for the adsorbent heterogeneity are fruitfu l for comparative analysis of the H-1 NMR spectra of water adsorbed on carb osils from the gas phase or unfrozen in the aqueous suspensions at T < 273 K. (C) 2001 Academic Press.