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Textural characterization of porous solids is commonly carried out by N 2 adsorption at 77 K. Additionally, CO 2 adsorption at 273 K and sub-atmospheric pressure was proposed as a complement to N 2 for the more complete characterization of the narrow microporosity. However, and contrary to the general assumption, CO 2 adsorption may be kinetically restricted in narrow pores (<0.3-0.4 nm), in spite of the high-temperature (273 K) at which the measurement is carried out, thus giving rise to an erroneous characterization.

8The experimental conditions for the pyrolysis of olive stones to produce a swelling of the particle and eventually the formation of 9 carbon foam are described and discussed. The greatest expansion of the material occurred when 200-300 g of precursor, in the presence 10 of steam at a pressure of 1 MPa, is introduced into a 1000 ml stainless steel reactor placed inside a sand-bath furnace previously heated to 11 500°C. In a few minutes the pyrolysis begins and this exothermic process leads to a more rapid pyrolysis. A relationship between heating 12 rate and degree of foaming for the resulting char is observed. The carbon foam obtained exhibits a low density, 0.2-0.3 g/cm 3 , due to the 13 presence of meso and macropores, mainly those of size larger than 1 lm. A mechanism is suggested to explain the formation of the foam 14 as a combination of a softening of the precursor and a fragmentation of the biopolymers to produce a ''melt''. A fast increase in tem-15 perature reduces the viscosity of the ''melt'' and facilitates the fragmentation to volatiles, responsible for the swelling of the particles and 16 the formation of the foam. 17

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Chloroform formation during the chlorination of simple organic molecules modeling humic substances, such as phenol and di-and trihydroxybenzenes, was studied by on-line membrane introduction mass spectrometry (MIMS). Under the reaction conditions employed, chloroform was rapidly formed from 1,3-dihydroxybenzene, 1,4-dihydroxybenzene, phenol and 1,2,3-trihydroxybenzene with yields of 17, 13, 7 and 5%, respectively. With the exception of aniline, which afforded a 17% chloroform yield, non-phenolic compounds, such as nitrobenzene, chlorobenzene, toluene, benzene and cyclohexanol, furnished low yields. Mechanistic studies showed that phenol is chlorinated consecutively and produces initially chlorophenol. It is suggested that chloroform might be formed mainly from chlorinated 3,5-cyclohexadienone-type intermediates. MIMS was also used to determine the reaction rates and to study the kinetics of the chlorination. A good Hammett linear correlation for an electrophilic substitution mechanism was found for the compounds C 6 H 5 X (X = NH 2 , OH, CH 3 , H, Cl and NO 2 ). Copyright

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