Juana M. Rosas

Recent Inventions in Glycerol Transformations and Processing

Many patents claiming new processes for the conversion of glycerol into valuable-added chemicals are appearing in recent years as a result of glycerol availability since it is the main by-product in the biodiesel production and in other processes concerning biomass as raw material. In a future biorefinery glycerol will remain as a platform molecule. Present review describes a selection of such patents and shows the potential of glycerol as raw material in such future chemical industries (biorefineries).

Preparation of different carbon materials by thermochemical conversion of lignin

Lignin valorization plays a crucial role within the modern biorefinery scheme from both the economic and environmental points of view; and the structure and composition of lignin becomes it an ideal precursor for the preparation of advanced carbon materials with high added-value. This review provides an overview of the different carbonaceous materials obtained by thermochemical conversion of lignin, such as activated carbons, carbon fibers, template carbons; high ordered carbons; giving information about the new strategies in terms of the preparation method and their possible applications.

Biomass Waste Carbon Materials as adsorbents for CO2 Capture under Post-Combustion Conditions

A series of porous carbon materials obtained from biomass waste have been synthesized, with different morphologies and structural properties, and evaluated as potential adsorbents for CO2 capture in post-combustion conditions. These carbon materials present CO2 adsorption capacities, at 25 oC and 101.3 kPa, comparable to those obtained by other complex carbon or inorganic materials. Furthermore, CO2 uptakes under these conditions can be well correlated to the narrow micropore volume, derived from the CO2 adsorption data at 0 oC (VDRCO2). In contrast, CO2 adsorption capacities at 25 oC and 15 kPa are more related to only pores of sizes lower than 0.7 nm. The capacity values obtained in column adsorption experiments were really promising. An activated carbon fiber obtained from Alcell lignin, FCL, presented a capacity value of 1.3 mmol/g (5.7 %wt). Moreover, the adsorption capacity of this carbon fiber was totally recovered in a very fast desorption cycle at the same operation temperature and total pressure and, therefore, without any additional energy requirement. Thus, these results suggest that the biomass waste used in this work could be successfully valorized as efficient CO2 adsorbent, under post-combustion conditions, showing excellent regeneration performance.

Easy fabrication of superporous zeolite templated carbon electrodes by electrospraying on rigid and flexible substrates

Electrospraying of colloidal suspensions of superporous zeolite templated carbon (ZTC) nanoparticles in ethanol is herein proposed for the controlled deposition of continuous carbon coatings over different substrates, both rigid and flexible. By simple tuning of the concentration, feed rate, voltage and treatment time, different electrode thicknesses can be obtained avoiding the difficult manipulation of ZTC nanopowder formed by around 200 nm size particles. The addition of sulfonated tetrafluoropolyethylene (Nafion) in low amounts into the ZTC suspension improves the adhesion, increases the allowable surface loading and enhances the electrochemical performance of ZTC electrodes. ZTC/Nafion coatings from 0.1 to 1.5 mg cm−2 have been successfully arranged over graphite sheet and conductive carbon paper substrates. The obtained electrodes have been electrochemically characterized in 1 M H2SO4 electrolyte, demonstrating the unique and well-known pseudocapacitive features of ZTC, while showing capacitances as high as 700 mF cm−2 and outstanding rate performance thanks to the improved arrangement and connectivity of the ZTC nanoparticles. A supercapacitor using electrosprayed ZTC electrodes is constructed, showing specific capacitance higher than 60 F g−1, capacitance retention of 63% when the current density is raised from 2.5 to 80 A g−1, energy density of 6.6 W h kg−1 and maximum deliverable power greater than 240 kW kg−1. These are promising results that make feasible the use of electrospraying for processing nanostructured carbon materials into electrodes of tunable thickness and deposited on substrates of different compositions and morphologies.

Coaxial Electrospinning for Nanostructured Advanced Materials

Electro-hydro-dynamic (EHD) compound jets, with diameters in the micro and nanometric size range, from conical menisci of two co-flowing liquids, is a consolidated platform for the production of nanofibers with inner structure, in a process so-called coaxial electrospinning or co-electrospinning. In contrast to other multi-step template based procedures, the EHD methodology is much more simple and general since, firstly, a solid template is needless and, secondly, the process is seldom affected by the chemistry of the liquids. This gentle process allows selecting the liquid precursors depending on the application sought for the nanofibers. Here, we review different products obtained by this EHD technique: (1) solid and hollow carbon nanofibers from different precursors (polyacrylonitrile, polyvinylpyrrolidone and lignin), (2) nanofibers of biocompatible polymers encapsulating liquids in the form of beads, (3) spinning nanofibers of alginate and (4) in-fiber encapsulation of active microgels.