The discovery of carbon nanostructures, essentially carbon nanotubes (CNT) and carbon nanofibres (CNF) has led to a big effort devoted to their synthesis, characterization, surface modification and use. Indeed, these structures have encountered application in a wide range of technological fields, such as adsorption, catalysis, hydrogen storage or electronics. Apart from the filamentous arrange of graphene sheets conducting to CNT or CNF, carbon can bond in other different ways to create structures with dissimilar properties. The pairing of pentagonal and heptagonal carbon rings can result in the formation of carbon nanospheres (CNS). This novel nanostructure has only now started to attract significant research activity. In its spherical arrangement, the graphite sheets are not closed shells but rather waving flakes that follow the curvature of the sphere, creating many open edges at the surface. Contrary to the chemically inert C 60 , the unclosed graphitic flakes provide reactive ''dangling bonds'' that are proposed to enhance surface reactions, establishing CNS as good candidates for catalytic and adsorption applications. Despite the embryonic stage of the field and the existing data being too scattered, this work is aimed to provide a comprehensive review of the existing literature related to CNS, exploring the different preparation routes employed, the critical characterization results as well as the applications studied so far.

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The influence of the amount of two clay binders (montmorillonite and bentonite) on the acid properties and performance of Pd/HZSM-5 zeolite with different Si/Al ratios for the hydroisomerization of n-butane has been studied. Temperature-programmed desorption of ammonia, atomic absorption spectroscopy, chemisorption, and surface area measurements were used to characterize the catalysts. After agglomeration, some zeolite protons are neutralized by clay sodium and, consequently, a lower n-butane conversion is obtained. The product selectivity is also strongly influenced by the binder due to the fact that zeolite hydrogen transfer activity, metal/acid site balance, and diffusion of products are modified. If the appropriate binder is selected, the decrease in conversion will be compensated by a much higher isobutane selectivity. Thus, a catalyst based on Pd/HZSM-5, with a zeolite Si/Al ratio of 25, and agglomerated with bentonite in a zeolite/clay ratio of 35/65 wt/wt, showed not only an adequate mechanical resistance but also high isobutane selectivity and isobutane yield (87.1 and 23.9 mol %, respectively). It should be remarked that, under the same reaction conditions, the parent catalyst without binder showed worse isomerization activity (18.5 mol % isobutane yield with 47.3% isobutane selectivity).

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In this paper, the optimization of typical reaction variables for a pilot scale synthesis of carbon nanofibers (CNFs) using a fixed-bed reactor has been carried out to provide a more economically viable large scale production of these materials. Using a Ni/SiO 2 catalyst (10 wt % Ni) and ethylene as the carbon source, the optimum value of temperature, space velocity, and H 2 /C 2 H 4 ratio (v/v) in terms of carbon yield was 600 °C, 10000 h -1 , and 1:4, respectively. The modification of these variables caused a significant change in the type and amount of solid carbon recovered. Carbon product characterization demonstrated that CNFs with mesoporous character, large external surface, and good thermal stability and crystallinity were obtained. Finally, results demonstrated a successful scale-up by a factor of 45 in the pilot plant scale; a CNFs yield of 106 g CNFs /g catalytic metal could be obtained at optimal conditions during a reaction time of 60 min at optimal conditions in the pilot plant scale. For the same reaction conditions, only 80 g CNFs /g catalytic metal were obtained in the laboratory reactor.

h i g h l i g h t s O 3-EO enhances by 2.5 times the mineralization of phenol when compared to O 3 alone. O 3-EO reduces by half the time to achieve a phenol mineralization >90%. Ozonation alone fails on phenol mineralization and on diminishing toxicity. Toxicity onto Latuca sativa is only eliminated by the coupled treatment (O 3-EO).