Jerzy P. Łukaszewicz

Determination of carbon porosity from low-temperature nitrogen adsorption data. A comparison of the most frequently used methods

Abstract This paper compares the most frequently used procedures for carbon porosity determination, i.e. the Dubinin Radushkevich, Dubinin-Izotova, t and αS plot, Horvath-Kawazoe (HK) and micropore analysis methods. The correlations between the obtained results are presented, and the importance of the choice of reference material for t and/or αS plot construction is displayed. It is concluded that only the HK method predicts smaller pore sizes. Our results show also that nitric acid oxidation of carbon and desorption in a flow of He in the temperature range 493–573 K leads to considerable changes in its porosity. However, for carbon previously oxidized and desorbed at 573 K, a pore-blocking effect occurs which probably results from the production of anhydrides in the carbon micropores.

Porosity of carbon films applied to chemical sensor construction

Investigations on the basic properties of carbons applicable to the construction of semiconducting gas sensors are presented. Development of pore structure of such carbons is considered as the function of carbonisation temperature and chemical modification of the carbons. The chemical modification consisted in the premixing of furfuryl alcohol with an aqueous solution of sodium acetate. The carbons tested were prepared by simulating the “spry pyrolysis” technique. The Na-modification resulted in an increase of the Wo value (the Dubinin-Radushkevich adsorption model) of the carbon films upon increasing the carbonisation temperature while the average pore diameter L was constant. The pore structure in the case of Na-modified carbons was the result of Na2CO3 microcrystallite formation (from CH3COONa) inside the carbon skeleton and their subsequent reaction with the carbon matrix.

Nanoscale Phenomena Occurring during Pyrolysis of Salix viminalis Wood

Selective utilisation of unique properties of Salix viminalis wood enables preparation of materials of nanotechnologic properties. Thermal decomposition of lignin-cellulose organic matter results in the formation of a nanostructured porous carbon matrix (charcoal). Narrowed pore size distribution (PSD) in the subnanometer range allows to consider the charcoals as carbon molecular sieves (CMSs), which are capable of separating even chemically inert gases like neon, krypton, and nitrogen. High tolerance of Salix viminalis to heavy metal ions enables enriching living plant tissues with metal ions like lanthanum and manganese. Such ions may later form LaMnO3 with parallel transformation of plant tissues (organic matter) to carbon matrix using a heat treatment. In this way, one gets a hybrid material: a porous carbon matrix with uniformly suspended nanocrystallites of LaMoO3. The crystallites are in the catalytically active phase during the conversion of n-butanol to heptanone-4 with high yield and selectivity.

Energetic Willow (Salix viminalis) – Unconventional Applications

Salix viminalis (Common Osier, Basket Willow, Energetic Willow) is a plant belonging to the SRWC group (Short Rotation Woody Crops) (Borjesson et al., 1994; Christersson & Sennerby-Forsse, 1994). Such a qualification points out possible applications resulting from a fast growth and annual yield of biomass. The woody stems of Salix viminalis can be cut frequently and serve as burnable biomass. Therefore Salix viminalis wood is often called a “green fuel”. In general, willows (genus Salix) are popular plants since more than 400 species occur in Nature (including Salix viminalis). Particularly, Northern Hemisphere is a natural region for different willow species bearing sometimes traditional and very unique names like Sageleaf Willow, Goat Willow, Pussy Willow, Coastal Plain Willow, Kimura, Grey Willow, Sand Dune Willow, Furry Willow, Heartleaf Willow, Del Norte Willow, American Willow, Drummonds Willow, Eastwoods Willow, Mountain Willow, Sierra Willow etc. The variety of willow species partly results from ease of hybrid formation by cross-fertile of particular Salix genotypes in a natural process and/or by planned cultivation. Table 1 contains systematic botanic classification of willows.