Pyrolysis

About: Pyrolysis is a research topic. Over the lifetime, 34918 publications have been published within this topic receiving 833524 citations.

Tuning Carbon Materials for Supercapacitors by Direct Pyrolysis of Seaweeds

Abstract: The sea provides a large variety of seaweeds that, because of their chemical composition, are fantastic precursors of nanotextured carbons. The carbons are obtained by the simple pyrolysis of the seaweeds under a nitrogen atmosphere between 600 and 900 °C, followed by rinsing the product in slightly acidic water. Depending on the origin of the seaweed and on the pyrolysis conditions, the synthesis may be oriented to give an oxygen-enriched carbon or to give a tuned micro/mesoporous carbon. The samples with a rich oxygenated surface functionality are excellent as supercapacitor electrodes in an aqueous medium whereas the perfectly tuned porous carbons are directly applicable for organic media. In both cases, the specific surface area of the attained carbons does not exceed 1300 m2 g−1, which results in high-density materials. As a consequence, the volumetric capacitance is very high, making these materials more interesting than activated carbons from the point of view of developing small and compact electric power sources. Such versatile carbons, obtained by a simple, ecological, and cheap process, could be well used for environment remediation such as water and air treatment.

Hydrotreatment of Fast Pyrolysis Oil Using Heterogeneous Noble-Metal Catalysts

Abstract: Fast pyrolysis oils from lignocellulosic biomass are promising second-generation biofuels. Unfortunately, the application range for such oils is limited because of the high acidity (pH∼2.5) and the presence of oxygen in a variety of chemical functionalities, and upgrading of the oils is required for most applications. Herein, we report an experimental study on the upgrading of fast pyrolysis oil by catalytic hydrotreatment. A variety of heterogeneous noble-metal catalysts were tested for this purpose (Ru/C, Ru/TiO2, Ru/Al2O3, Pt/C, and Pd/C), and the results were compared to those obtained with typical hydrotreatment catalysts (sulfided NiMo/Al2O3 and CoMo/Al2O3). The reactions were carried out at temperatures of 250 and 350 °C and pressures of 100 and 200 bar. The Ru/C catalyst was found to be superior to the classical hydrotreating catalysts with respect to oil yield (up to 60 wt %) and deoxygenation level (up to 90 wt %). The upgraded products were less acidic and contained less water than the original...

Structural chemistry and Raman spectra of niobium oxides

Abstract: The pyrolysis of TVSb has been investigated in a flow tube reactor using Dz and He carrier gases. For TVSb alone, the most likely pyrolysis reaction involves an Sbcentered reductive elimination pathway. A less likely possibility is pyrolysis via homolysis of the Sb-C bonds, yielding vinyl radicals. Unfortunately, examination of the organic byproducts in both He and D, yields insufficient information to form a definitive hypothesis. However, in He the pyrolysis rate for TVSb is more rapid than for TMSb. Since vinyl radicals form stronger bonds than methyl radicals, this datum contradicts the Sb-C bond homolysis mechanism. Again, the activation energy for pyrolysis is less than the expected Sb-vinyl bond strength. Finally, the addition of C7D, produces no CH,=CHD, indicative of the absence of vinyl radicals. To elucidate our understanding of GaSb growth by using TMGa and TVSb, the pyrolysis rates for this combination of reactants were also studied. CH, radicals from (CH3N), pyrolysis were found to enhance TVSb pyrolysis in He. TMGa also increases the TVSb pyrolysis rate, mainly due to the methyl radicals produced. A heterogeneous pyrolysis reaction appears a t high surface area. At V/III ratios normally used for OMVPE growth, carbonaceous deposits were formed. Thus, TVSb may be a useful precursor for OMVPE only a t V/III ratios less than unity.

Biomass derived hard carbon used as a high performance anode material for sodium ion batteries

Abstract: A porous hard carbon material was synthesized by the simple pyrolysis of H3PO4-treated biomass, i.e., pomelo peels, at 700 °C in N2. The as-obtained hard carbon had a 3D connected porous structure and a large specific surface area of 1272 m2 g−1. XPS analysis showed that the carbon material was functionalized by O-containing and P-containing groups. The porous hard carbon was used as an anode for sodium ion batteries and exhibited good cycling stability and rate capability, delivering a capacity of 181 mA h g−1 at 200 mA g−1 after 220 cycles and retaining a capacity of 71 mA h g−1 at 5 A g−1. The sodium storage mechanisms of the porous hard carbon can be explained by Na+ intercalation into the disordered graphene layers, redox reaction of the surface O-containing functional groups and Na+ storage in the nanoscale pores. However, the porous hard carbon demonstrated a low coulombic efficiency of 27%, resulting from the formation of a solid electrolyte interphase film and the side reactions of surface phosphorus groups.