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A kinetic model of smouldering of pine wood is determined by thermo-gravimetric analysis (TGA), describing the reactions of wood pyrolysis, wood oxidation and char oxidation. Thermo-gravimetric experiments were conducted with constant heating rates ranging from 2.5 to 10 K/min in atmospheres of pure nitrogen and mixtures of nitrogen and oxygen (with 20.5%, 8.2% and 4.3% O2). At first wood pyrolysis and char oxidation experiments are carried out in an independent way. Then smouldering experiments are conducted, which combine the two previous reactions with wood oxidation. Finally, the heats of the reactions are determined by differential scanning calorimetry (DSC). The results are discussed, compared with the literature and the derived kinetic model is presented, which includes five components: three pseudo-components of wood – representing roughly cellulose, hemi-cellulose and lignin – as well as char and ashes.
The influence of heterogeneous secondary reactions on char oxidation reactivity, which can take place during slow pyrolysis processes in a woody biomass particle, is analyzed in this study. To this end, the oxidative behavior of primary char produced in a thermobalance with initial wood masses of a few milligrams is compared to the behavior of char produced under conditions enhancing secondary reactions, i.e., large particle and bed sizes in fixed-bed reactors. The influence of the Maximum conversion temperature, heating rate, and catalytic effect of inorganics is also studied to compare the effect of each parameter.
Results show that a significant reduction in reactivity takes place when char is produced under conditions enhancing These secondary reactions during pyrolysis. The effect is of similar order as the effect as a result of thermal annealing at 900 °C or the catalytic effect of alkali and alkaline earth metals. Therefore, the presence of heterogeneous secondary reactions during pyrolysis should be taken into account in studies addressing biomass char reactivity. Furthermore, it is shown that the reduction of reactivity as a result of secondary reactions is related to neither the loss of oxygen-containing functional groups nor the potential blocking of pores, specially micropores, resulting from the formation of this secondary char. The explanation may, therefore, lie on the deactivation or blocking of active sites by the secondary char.
We report a new sequence selective terpolymerisation in which three monomers (butylene oxide (BO) A, PhNCS B and phtalic thioanhydride (PTA) C) are selectively enchained into an (ABA′C)n sequence. PTA/PhNCS/BO ring-opening terpolymerisation ROTERP can be coupled with CS2 ROTERP to generate tetrapolymers and with εDL ROP in switchable catalysis for blockpolymer synthesis.
Preparation of graphene oxide by cyanuric chloride as an effective and non-corrosive oxidizing agent
(2016)
In this work, we report a new method for the synthesis of graphene oxide (GO) using cyanuric chloride as a non-corrosive oxidizing agent.
The mild conditions, simple purification, and scalability of this method are significant advantages over common approaches in which harsh oxidizing agents are used. Moreover, a major drawback with the Hummers' method, the production of toxic gases, is not an issue with this process. This method is a safe and large-scale alternative for the production of GO under mild conditions.
Comprehensive Characterization of APTES Surface Modifications of Hydrous Boehmite Nanoparticles
(2020)
Hydrous boehmite (γ-AlOOH) nanoparticles (BNP) show great potential as nanoscale filler for the fabrication of fiber reinforced nanocomposite materials. Notably, the particle−matrix interaction has been demonstrated to be decisive for improving the matrix-dominant mechanical properties in the past years. Tailoring the surface properties of the nanofiller enables to selectively design the interaction and thus to exploit the benefits of the nanocomposite in an optimal way. Here, an extensive study is presented on the binding of (3-aminopropyl)triethoxysilane (APTES), a common silane surface modifier, on BNP in correlation to different process parameters (concentration, time, temperature, and pH). Furthermore, a comprehensive characterization of the modified BNP was performed by using elemental analysis (EA), thermogravimetric analysis (TGA) coupled with mass spectrometry (TGA-MS), and Kaiser’s test (KT). The results show an increasing monolayer formation up to a complete surface coverage with rising APTES concentration, time, and temperature, resulting in a maximal grafting density of 1.3 molecules/nm². Unspecific multilayer formation was solely observed under acidic conditions. Comparison of TGA-MS results with data recorded from EA, TGA, and KT verified that TGA-MS is a convenient and highly suitable method to elucidate the ligand binding in detail.