Abstract
Microporous carbon spheres of different morphology and porosity were synthesized from resorcinol-formaldehyde solutions by a simple and fast procedure. Polymeric spheres were shaped by means of microwave heating. Carbonization and activation with carbon dioxide were then applied to obtain the intended final carbon spheres. The influence of the pH, heating time and thermal treatments on the morphology and porosity of the carbon spheres was investigated. It was found that the size of the spheres, can be easily controlled during the synthesis process, specifically by modifying the pH of the precursor solution. An increase in the pH value from 3 to 5 led to carbon spheres with sizes of 4 μm and 3.5 μm, respectively, whereas time seemed to have no effect. These results have been attributed to the chemical mechanisms of the polymerization reaction. On the other hand, microporosity was tailored during the thermal treatments. Carbon spheres with surface areas of 630 m2/g and 1500 m2/g were obtained by applying carbonization and physical activation, respectively. Furthermore, the synthesis method proposed allows to obtained liquid polymerized inks that can be further used to coat ceramic supports by a simple spray-drying process, which enhances the potential of these materials for several applications.
Highlights
Over the last few decades, there has been an explosive growth in the synthesis, characterization and application of carbon spheres, due to the fact that their size, Associado LSRE/LCM, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, R
Microporous carbon spheres of different morphology and porosity were synthesized from resorcinol-formaldehyde solutions by a simple and fast procedure
Carbon spheres with surface areas of 630 m2/g and 1500 m2/g were obtained by applying carbonization and physical activation, respectively
Summary
Over the last few decades, there has been an explosive growth in the synthesis, characterization and application of carbon spheres, due to the fact that their size,. The widely-recognized advantages of RF solutions as carbon precursors (which include the possibility of tailoring their porous properties or of doping them with metals and heteroatoms [11, 24]), confer on them great potential for preparing carbon spheres that offer optimum performances in a wide variety of applications, such as adsorption [1, 25], ultrafiltration [26], catalysis [16] or electrochemical systems [9, 13, 15, 17] In some of these applications carbon spheres are used as coating of surfaces, nanoparticles or supports and, in these cases, spray-drying methods are preferable. The method presented here has demonstrated to be an easy and suitable way to coat surfaces of ceramic solid catalysts, thereby extending the range of applications of carbon spheres prepared from RF precursor solutions
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