Juan José Villaverde

Miscanthus x giganteus Extractives: A Source of Valuable Phenolic Compounds and Sterols

The chemical composition of the lipophilic extracts of bark and core, of the Miscanthus x giganteus stalk, was studied by gas chromatography-mass spectrometry (GC-MS). Aromatic compounds, sterols, and fatty acids, followed by long-chain fatty alcohols, were the major families of components present in the M. x giganteus stalk. Aromatic compounds are more abundant in the M. x giganteus bark (521 mg/kg of bark), with vanillic acid, vanillin, and p-hydroxybenzaldehyde as the major compounds of this family. In the M. x giganteus core, sterols represent about 949 mg/kg of dry core with beta-sitosterol, 7-oxo-beta-sitosterol, stigmasterol, and campesterol as the major components. The detection of small amounts of esters in the GC-MS analysis with short columns explains the small increase in the abundance of the identified families after alkaline hydrolysis. The high content of valuable sterols and aromatic compounds in M. x giganteus and, particularly, in the core, which is considered a residue in most applications, can open new perspectives for the integrated upgrading of this grass within the biorefinery perspective.

Delignification of Miscanthus×Giganteus by the Milox process

Miscanthus x giganteus stalks were subjected to delignification with formic acid-hydrogen peroxide-water in two stages. A face-centered experimental design was used to study the effects of different variables (formic acid and hydrogen peroxide concentrations, time and temperature) on yield, lignin content and viscosity of pulps on the first stage. Fitting equations described satisfactorily the system behaviour and showed that hydrogen peroxide concentration and temperature were the most influencing variables. A set of independent variables (90% formic acid, 1.5% hydrogen peroxide, 60 min, and 67 degrees Celsius) produced a pulp with low lignin content (kappa 17.2) and high viscosity (899 cm(3)/g), in the first stage. For the second stage a treatment time of 30 min was the more suitable, producing good quality pulps (kappa number 4.6, viscosity 788 cm(3)/g). Phenolic hydroxyl and carboxyl group contents were higher lignins from the first stage.

Miscanthus x giganteus as a Source Of Biobased Products Through Organosolv Fractionation: A Mini Review

This paper deals with the chemical treatments with selected organic compounds that have been applied to Mis- canthus to upgrade it, for pulp production or fractionation purposes. Organosolv processes have demonstrated their effec- tiveness as fractionation treatments; therefore special emphasis is placed on these systems and, in particular, those making use of carboxylic acids. That is, Acetosolv process that uses acetic acid-water-hydrochloric acid mixtures as delignifying agents, the process with formic acid-water-hydrochloric acid and the Milox process, which replaces the hydrochloric acid in the medium by hydrogen peroxide, thus forming peroxyacetic acid. Furthermore, we present the results of the charac- terizations that have been made in relation to extractives and lignin of Miscanthus. It also is analyzed the major changes undergone by lignin during organosolv treatments. Finally, some progresses in the field of TCF bleaching of the cellulose pulps obtained are summarized.

Bleaching Miscanthus x giganteus Acetosolv pulps with hydrogen peroxide/acetic acid. Part 1: Behaviour in aqueous alkaline media

Miscanthus x giganteus bark samples subjected to fractionation by the Acetosolv process under optimal conditions were bleached using hydrogen peroxide and acetic acid in aqueous media under alkaline conditions. The influence of the main operational variables in the bleaching of Acetosolv pulps of M. x giganteus (i.e. hydrogen peroxide concentration, 3-7%; temperature, 55-75 degrees C; pH 9-11), obtained after treatments, have been assessed on pulp yield, kappa number, viscosity and brightness of bleached pulps. For this purpose, a rotatable and orthogonal second-order factorial design of experiments was used, in order to identify the optimum operating conditions. The obtained empirical mathematical models demonstrate that, in general, the bleaching was efficient, achieving pulps with kappa numbers below 10. The chemical composition and physicochemical properties of the bleached pulps fulfilled the requirements for forthcoming bleaching stages. Moreover, an alkaline extraction stage to eliminate saponifiable groups of Acetosolv pulps was studied, as well as the necessity of use chelating agents in the stage with hydrogen peroxide.