With the depletion of fossil fuel reserves and the increasing concern about greenhouse gas emission, the need to develop technologies for using renewable and sustainable energy resources is becoming urgent. Solar, winds, geothermal, and hydro as well as nuclear energy are all considered as clean energy sources to (partially) substitute fossil fuels in energy generation. Biomass, however, remains the only renewable energy source consisting of hydrocarbon compounds, which is a necessity for making basic building blocks for chemical industries. The development of feasible gasification technologies to produce syngas (primarily H2 and CO) is considerably inhibited by the “tar issues”. The tar content in the product gas has to be extremely low in order to effectively use the gas downstream, such as for synthesizing liquid fuels and generating electricity. Although there are a wide range of options for removing, cracking, and catalyzing the tar, this review mainly discusses the catalytic reforming approach using char as catalysts, of which the importance of the carbon structure of chars will be underpinned because the char structure including matrix carbon structure and functional groups on the char surface not only affects the reactivity of nonmetal active sites but also largely dominates the role/fate of internally existing and externally added metal species.
In this study, biochars derived from waste fiberboard biomass were applied in tetracycline (TC) removal in aqueous solution. Biochar samples were prepared by slow pyrolysis at 300, 500, and 800 • C, and were characterized by ultimate analysis, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), etc. The effects of ionic strength (0-1.0 mol/L of NaCl), initial TC concentration (2.5-60 ppm), biochar dosage (1.5-2.5 g/L), and initial pH (2-10) were systemically determined. The results present that biochar prepared at 800 • C (BC800) generally possesses the highest aromatization degree and surface area with abundant pyridinic N (N-6) and accordingly shows a better removal efficiency (68.6%) than the other two biochar samples. Adsorption isotherm data were better fitted by the Freundlich model (R 2 is 0.94) than the Langmuir model (R 2 is 0.85). Thermodynamic study showed that the adsorption process is endothermic and mainly physical in nature with the values of H 0 being 48.0 kJ/mol, S 0 being 157.1 J/mol/K, and G 0 varying from 1.02 to −2.14 kJ/mol. The graphite-like structure in biochar enables the π-π interactions with a ring structure in the TC molecule, which, together with the N-6 acting as electron donor, is the main driving force of the adsorption process.
The fiberboard waste with about 10% adhesive as bonding materials will release a large amount of NO x into the atmosphere when being used for energy resources. To mitigate the emission, it is desirable to convert the waste biomass into material-based products, so that the N species could be possibly retained in the solids without being emitted into the air. Thus, this study aims to examine the effects of glucose addition on the N retention and migration in chars during the copyrolysis with fiberboard wastes, especially considering the N-doped solid char as a potential high value functional carbon material. The pyrolysis experiments were mainly conducted in a fixed-bed quartz reactor at various temperatures, and the resultant chars were subjected to XPS analysis and other characterizations. It was found that the introduction of glucose has significantly increased the N retentions by 2−3 times at all the examined temperatures compared to the pyrolysis of fiberboard alone. During the copyrolysis, the relative abundance of amine-N in char at 400 °C has greatly decreased, while 500 °C has seen only N-5 and N-6 remaining in the char. Therefore, the copyrolysis of fiberboard waste and glucose could considerably enhance the N retentions in chars as well as vary the transformation of N occurring forms by the reactions between the adhesive-derived volatiles and the O-containing groups from the decomposition of glucose.
a Dimensional stability is an important property of wood that is strongly influenced by its water uptake behavior. Heat treatment is one method to improve wood dimensional stability. This study investigated the effects of heat treatment on the water uptake behavior of wood using a wicking test. The thickness of the tested wood sample was similar to that of the surface wood panel in a 3-layer composite floorboard. It was treated at different temperatures ranging from 200 °C to 400 °C under a nitrogen atmosphere for 10 min to provide the test data to investigate the basic theory relating to dimensional stability of heat-treated wood processed at higher temperatures for a short length of time. During the test, the water uptake of larch (Larix gmelinii) and red oak (Quercus rubra) were recorded continuously. The heattreated wood had a much lower water uptake ability than untreated wood during the early stage of the wicking test; untreated wood exhibited higher total water uptake. Compared with the untreated sample, the red oak wood treated at 400 °C had an average water uptake rate that decreased from 0.28 mg/mm 3 per hour to 0.038 mg/mm 3 per hour.
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