Maria Lezanska

Novel nitrogen-containing mesoporous carbons prepared from chitosan

In this study, synthesis of novel nitrogen-containing mesoporous carbons with the use of both colloidal silica as a template and chitosan as a new promising carbon precursor was performed. The prepared materials were characterized by adsorption of nitrogen, high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy, Raman spectroscopy, and elemental analysis. The use of the silica template makes it possible to achieve products of the pore volume as high as 4.31 cm3 g−1, with only insignificant contribution of microporosity. The present method enables the synthesis of nitrogen-containing carbons in a simple manner, using an inexpensive and readily available biopolymer.

Al-MCM-41 modified with carbonaceous deposits : Characterisation by nitrogen adsorption measurements

Aluminosilicate MCM-41 samples in the as-prepared form and modified by deposition of carbonaceous compounds formed during conversion of cyclohexene were investigated by nitrogen adsorption. The amount of the deposits decreases with the reaction temperature and increases with the quantity of aluminium incorporated into the materials. The formation of coke occurs primarily in the aluminium-rich pores. The modification leads to a lowering of adsorption capacity, surface area, pore volume and relative pressure corresponding to the adsorption isotherm step that reflects the capillary condensation. The nitrogen adsorption measurements appeared to be a useful tool for characterisation of structural and surface properties of both the original and the novel surface-modified porous materials.

Al-MCM-48: synthesis and adsorption properties for water, benzene, and nitrogen

Mesoporous aluminosilicate molecular sieves with the MCM-48 structure have been synthesised using the method of grafting aluminium onto the purely siliceous material. The products were characterised with XRD and adsorption techniques. The obtained materials exhibited high surface areas and high total pore volumes. Adsorption of nitrogen, benzene, and water on the materials with various contents of Al proceeded similarly despite different physicochemical properties of the adsorptives as well as different adsorbent-adsorbate interactions.

Nitrogen-containing carbon replicas of SBA-15 and MLV prepared from pyrrole as carbon precursor

The nitrogen-containing carbonaceous replicas of siliceous materials were prepared and studied with the nitrogen adsorption, TEM, TGA, XPS, and EDX methods. The carbons obtained using SBA-15 as a matrix exhibited well-developed and highly ordered porous structures. Those from the MLV material showed lower sorption capacities and 3-D structures less ordered as in the case of the SBA-15 replicas.

Al-MCM-48 as a template for synthesis of porous carbons-adsorption study

Porous carbons were prepared by polymerisation and subsequent carbonisation of furfuryl alcohol adsorbed on mesoporous Al-MCM-48 molecular sieves. The carbonaceous products were examined with XRD, TEM, and adsorption. The carbons exhibited a developed mesoporous structure with a contribution of micropores. The adsorption isotherms of nitrogen, benzene, ethanol, and water provided information on mechanisms of the adsorption processes.

Preparation and catalytic characterisation of Al-grafted MCM-48 materials

Samples of Al-MCM-48 were prepared by grafting Al onto the pure siliceous material and used as catalysts for cumene cracking and conversion of 2-propanol. The former reaction yielded mainly benzene and propene, which indicated the presence of strong Bronsted acid sites in the catalysts. The conversion of 2-propanol resulted mainly in dehydration of the substrate, yielding propene and diisopropyl ether. The catalytic activity of Al-MCM-48 grew with both the Al content and reaction temperature. The concentrations of the Bronsted and Lewis acid sites increased with the Al content of the material as well.

24-P-22-Volatile products of the conversion of cyclohexene over Al-MCM-41

Publisher Summary This chapter presents the analysis of volatile products of the conversion of cyclohexene over aluminium (Al)-MCM-41. The analysis of volatile products reveals that the reaction runs mainly according to two mechanisms known as “cyclohexene skeletal isomerization (CSI)” and “cyclohexene hydrogen transfer (HT).” The results exhibit which of the two schemes predominate, depending on the reaction temperature and the Al content of the catalyst. The processes of CSI and HT are accompanied by cracking and alkylation, which are proved by the presence of products with 1 to 9 carbon atoms even though the C 6 compounds strongly prevail in all cases. Composition of the volatile products of the conversion depends on both concentration and strength of BrOnsted and Lewis acid centres.