Hydrothermal liquefaction is a promising technology for the conversion of a wide range of bio-feedstock into a biocrude; a mixture of chemical compounds that holds the potential for a renewable production of chemicals and fuels. Most research in hydrothermal liquefaction is performed in batch type reactors, although a continuous and energy-efficient operation is paramount for such process to be feasible. In this work an experimental campaign in a continuous bench scale unit is presented. The campaign is based on glycerol-assisted hydrothermal liquefaction of aspen wood carried out with the presence of a homogeneous catalyst at supercritical water conditions, 400 • C and 300 bar. Furthermore, in the experimental campaign a water phase recirculation step is incorporated to evaluate the technical feasibility of such procedure. In total, four batches of approximately 100 kg of feed each were processed successfully at steady state conditions without any observation of system malfunctioning. The biocrude obtained was characterized using several analytical methods to evaluate the feasibility of the process and the quality of the product. Results showed that a high quality biocrude was obtained having a higher heating value of 34.3 MJ/kg. The volatile fraction of the biocrude consisted mostly of compounds having number of carbon atoms in the C 6 -C 12 range similar to gasoline. In terms of process feasibility, it was revealed that total organic carbon (TOC) and ash significantly accumulated in the water phase when such is recirculated for the proceeding batch. After four batches the TOC and the ash mass fraction of the water phase were 136.2 [g/L] and 12.6 [%], respectively. Water phase recirculation showed a slight increase in the biocrude quality in terms on an effective hydrogen-to-carbon ratio, but it showed no effects on the product gas composition or the pH of the water phase. The successful operation demonstrated the technical feasibility of a continuous production of high quality biocrude.

No abstract

No abstract

Nanostructured materials have drawn much attention because of the dramatically different properties observed on going from bulk material to nanosized particles. Nanoparticles have properties that lie between the quantum effects of atoms and molecules and the bulk properties of materials. In the nanometer range (1-100 nm) the particle size affects structural characteristics (e.g., lattice symmetry, unit-cell dimension), electronic properties (e.g., band gap), and therefore also the physical (e.g., wetting, melting point) and chemical properties (e.g., catalytic effects) of a material. The applications of nanomaterials include lithium-based batteries, fuel cells, [1, 2] thin films, inorganic-organic hybrid materials, [3] sensors, piezoelectric devices, and catalysts. [4,5] In all production methods for nanomaterials, a key requirement is the ability to control nanoparticle size, shape, and crystallinity. Special attention has been devoted to metal oxides. These can adopt many different crystal structures and have metallic, semiconducting, or insulating properties.[5] Their chemical properties range from strong catalytic reactivity to chemical inertness and high-temperature stability, and the application of metal oxides is a multibillion-dollar industry.Several wet-chemistry synthesis routes are capable of producing nanomaterials, [6] but the sol-gel technique has become the standard method for fabricating metal oxides because of the possibility of obtaining high chemical homogeneity at low temperature and under mild chemical conditions. [5,7] The downside is the relatively long process time and the need for posttreatment (e.g., calcination), which make the process less attractive for industry. The solution appears to be synthesis in supercritical fluids, which provides unique control of chemistry and nanocrystal properties. [8][9][10][11][12][13][14][15][16][17] Use of supercritical fluids as solvents in sol-gel processes enhances the kinetics by more than an order of magnitude. Furthermore, supercritical fluids exhibit particularly attractive properties such as gaslike mass-transfer behavior, liquidlike densities, and changed dielectric properties. These properties can be fine-tuned by simple changes in pressure and temperature; for example, the solubility of a compound can be dramatically changed to cause very fast precipitation.To manipulate the properties of nanomaterials and synthesize new materials with unprecedented properties, the main challenge is to understand the nucleation, crystallization, and growth processes.[5] This requires development of analytical tools capable of following nanoparticle formation in real time. In situ measurements by dynamic light scattering (DLS) have been used to study particle growth and stabilization of primary particles by surfactants. [18] In situ synchrotron powder diffraction has become a widely used tool for following solid-state reactions and crystallization processes. [19][20][21] The crux of this technique is the high intensity of the synchrotron beam, which allow...

Supercritical carbon dioxide (sCO2) extraction was applied on a raw bio-crude, obtained by hydrothermal liquefaction of pinewood. The extractions were carried out in semicontinuous mode, in the range 80 to 150 °C and 330 to 450 bar. Extraction yields from 44 to 53 wt% were achieved. The extracts were richer in lower molecular weight (MW) compounds, with fatty acids and aromatic hydrocarbons concentrated up to 14 and 24 wt%, respectively. For comparable MWs, lower polarity compounds concentrated in the extracts. Compared to the feed, the extracts exhibited lower density (from 1030 kg/m 3 down to 914 kg/m 3 ), lower water content (from 5.7 wt% down to 1.3 wt%) and lower oxygen content (from 10.0 wt% down to 5.0 wt%). In addition, the metal content was drastically reduced (from 8500 mg/kg down to 170 mg/kg on average). In the context of biofuel production, the sCO2 extracts are a better feed for catalytic hydrotreating.