Lab-scale pyrolysis and hydrothermal carbonization of biomass digestate: Characterization of solid products

The aim of the present study is to investigate the production of biochar from anaerobic digestion (AD) digestate. Re-Cord selected digestate from real and representative (regarding the scale and the process technology) anaerobic digestion plant. Please click on the file below for full content of the abstract

Biochar from lab-scale pyrolysis: influence of feedstock and operational temperature

AbstractBiochar properties are highly dependent on the feedstock type and operational conditions during thermochemical processing, in particular slow pyrolysis. To clarify this aspect, nine biochars were produced by pyrolyzing in a macro TGA at 400, 550, and 650 °C three different decorticated and chopped biomasses. The studied biomasses are representative of conifer (black pine) and deciduous (poplar and willow) woods. Biochar surface area, size, and shape of pores were investigated by means of nitrogen adsorption isotherm, Hg porosimetry, and electron microscopy. The results indicate that biochars with high surface area can be obtained at high temperature, especially starting from pine feedstock. Regarding porosity, micro-pores (1–10 nm) are not remarkably affected by the starting feedstocks, while macro-pores (> 10 nm) are strictly connected with the morphology of the starting wood. More than the surface area, we found a strong correlation between the chemical composition (elemental composition and FTIR) of the biochars and their retention and release capacity of ions (cation exchange capacity, CEC). The trend in the CEC, determined via coupled approach by spectrophotometric and ion chromatography, reveals that the increase in the processing temperature has the effect of reducing the number of functional groups able of exchanging the cations with the equilibrium solution. This work represents a step forward in the characterization of the char produced by pyrolysis of biomass thanks to the development of a multi-technique approach allowing to obtain a structure-property correlation of the biochars. Our results and experimental approach can help in the optimization of the parameters used in the preparation of these materials.Graphical abstrac

Chemoselective Aerobic Oxidation of Unproteced Diols Catalyzed by Pd-(NHC) (NHC = N-heterocyclic carbene) Complexes

[[abstract]]Neutral Pd(X)(η3-allyl) (X = Cl, OAc (acetate)) complexes bearing mono-coordinating NHC ligands have been synthesized, characterized and employed to catalyze the aerobic oxidation of unprotected 1,2- and 1,3-diols selectively to hydroxy ketones. A comparison of the catalytic performance of these precursors with a reference system has shown that the precursor with the ligands N,N′-bis(adamantyl)imidazol-2-ylidene and chloride is the most efficient for the chemoselective oxidation of 1,2-diols is concerned. High-pressure 1H NMR (HPNMR) experiments in combination with catalytic batch reactions have provided valuable information on the activation of the precursor as well as on the stability of the catalysts

Performance and emissions of liquefied wood as fuel for a small scale gas turbine

This study investigates for the first time the combustion in a micro gas turbine (MGT) of a new bioliquid, a viscous biocrude, which is a liquefied wood (LW) produced via solvolysis of lignocellulosic biomass in acidified glycols. The test rig includes a modified fuel injection line, a re-designed combustion chamber and revised fuel injection positions. The main novelties of this work are: (1) producing of liquefied wood with pure ethylene glycol as a solvent, and methanesulfonic acid as a catalyst, to obtain a bio-crude with lower viscosity and higher lignocellulosics content than previous tested formulations(2) upgrading raw liquefied wood by blending it with ethanol to further reduce the viscosity of the mixture(3) utilizing a commercially available MGT Auxiliary Power Unit (APU) of 25%kW electrical power output, with notably reduced extent of adaptations to use the newly obtained fuel mixture. Fuel properties, and their impact on combustion performance using liquefied wood, are investigated by analyzing MGT performance and emissions response at different load and blend ratios. Emissions revealed that the presence of LW in the blends significantly affects CO and NOX concentrations compared to conventional fuels. CO roughly increased from 600%ppm (pure ethanol as fuel) to 1500%ppm (at 20%kW electrical power). The experimental study reveals that it is possible to achieve efficient MGT operation while utilizing high biocrude to ethanol ratios, but a number of adaptations are necessary. The achieved maximum share of liquefied wood in the fuel blend is 47.2% at 25%kW power output. Main barriers to the use of higher share of liquefied wood in these type of systems are also summarized

Characterization of microalga Chlorella as a fuel and its thermogravimetric behavior

.Microalgae are photosynthetic microorganisms living in marine or freshwater environment. In this study, samples of Chlorella spp. and Nannochloropsis from two different origins were analysed to settle a preliminary characterization of these microorganisms as intermediate energy carriers and their properties compared to a conventional lignocellulosic feedstock (pine chips). Both microalgae samples were characterized in terms of elemental composition (CHONS and P) and thermogravimetric behavior. This was investigated through non-isothermal thermogravimetric analysis in nitrogen atmosphere at heating rate of 15 °C min−1 and temperature up to 800 °C. Solid residues produced at 300 °C and 800 °C from TGA were also analysed to determine the ultimate composition of chars. Activation energy, reaction order and pre-exponential factor were calculated for the single step conversion mechanism of 1 g of Chlorella spp. and compared to literature data on Chlorella protothecoides and Spirulina platensis. Calculated kinetic parameters, given as intervals of several determinations, resulted to be: pre-exponential factor (A) 1.47–1.62E6 min−1, activation energy (E) 7.13–7.92E4 J mol−1, reaction order (n) 1.69–2.41. 1.2 kg of Chlorella spp. was then processed in a newly designed batch pyrolysis pilot reactor, capable of converting up to 1.5 kg h−1 of material, and pyrolysis liquid collected, analysed and compared with a sample of fast pyrolysis from pine chips. This preliminary investigation aimed at carrying out a first characterization of algae oil and optimise the operational aspects of the reactor, tested with the first time with this unconventional feedstock. The algae pyrolysis oil exhibited superior properties as intermediate energy carrier compared to pyrolysis oil from fast pyrolysis of pine chips, in particular higher HHV and carbon content and lower oxygen and water content. These data can potentially be used in the design and modelling of thermochemical conversion processes of microalgae

Performance and emissions of liquefied wood as fuel for a small scale gas turbine

Test of modified MGT with crude oil derived from wood liquefation

Organic dye-sensitized solar cells containing alkaline iodide-based gel polymer electrolytes: Influence of cation size

The electrolyte used in dye-sensitized solar cells (DSSCs) plays a key role in the process of current generation, and hence the analysis of charge-transfer mechanisms both in its bulk and at its interfaces with other materials is of fundamental importance. Because of solvent confinement, gel polymer electrolytes are more practical and convenient to use with respect to liquid electrolytes, but in-depth studies are still necessary to optimize their performances. In this work, gel polymer electrolytes of general formulation polyacrylonitrile (PAN)/ethylene carbonate (EC)/propylene carbonate (PC)/MI, where M+is a cation in the alkaline series Li-Cs, were prepared and used in DSSCs. Their ionic conductivities were determined by impedance analysis, and their temperature dependence showed Arrhenius behavior within the experimental window. FT-IR studies of the electrolytes confirmed the prevalence of EC coordination around the cations. Photo-anodes were prepared by adsorbing organic sensitizer D35 on nanocrystalline TiO2thin films, and employed to build DSSCs with the gel electrolytes. Nanosecond transient spectroscopy results indicated a slightly faster dye regeneration process in the presence of large cations (Cs+, Rb+). Moreover, a negative shift of TiO2flat-band potential with the decreasing charge density of the cations (increasing size) was observed through Mott-Schottky analysis. In general, results indicate that cell efficiencies are mostly governed by photocurrent values, in turn depending on the conductivity increase with cation size. Accordingly, the best result was obtained with the Cs+-containing cell, although in this case a slight reduction of photovoltage compared to Rb+was observed

Green/Yellow-Emitting Conjugated Heterocyclic Fluorophores for Luminescent Solar Concentrators

In this study, we report on the synthesis of new organic fluorophores containing either the benzo[1,2-d:4,5-d]bisthiazole or the dithieno[3,2-b:2,3-d]silole heterocyclic unit, and on their application for the fabrication of luminescent solar concentrators (LSCs) made of poly(methyl methacrylate) (PMMA) thin films. In solution, the new compounds absorbed light in the visible region and displayed a brilliant green emission in the 500-600 nm range with moderate-to-good fluorescence quantum yields (0.25-0.68). Dispersions of selected fluorophores in PMMA thin films mostly maintained the light absorption features observed in solution, although in the case of benzobisthiazole-based fluorophore 1a an evident fluorescence red-shift was observed when increasing the compound concentration in the film. In agreement with its promising optical properties, LSCs prepared with the latter compound yielded interesting optical efficiencies up to 6.42%, not far from those of state-of-the-art PMMA LSC devices