Grape stem is a kind of agricultural and forestry waste. A fundamental understanding of grape stem pyrolysis behavior and kinetics is essential for its efficient thermochemical conversion. Thermogravimetric infrared spectroscopy and pyrolysis gas chromatography-mass spectrometry, combined with two model-free integral methods: Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) were used to investigate the weight loss behavior, the distribution and content of rapid pyrolysis products, the release law of small molecule pyrolysis gases, and the pyrolysis activation energy during pyrolysis. The results showed that the main pyrolysis reaction temperature ranged from 240 °C to 690 °C. The pyrolysis reaction of grape stems at 200 °C to 700 °C was divided into three stages: 0.15 < α < 0.35, 0.35 < α < 0.65, and 0.65 < α < 0.75, which corresponded to the main pyrolysis stages of hemicellulose, cellulose, and lignin, respectively. The products of rapid pyrolysis at 290 °C were mainly composed of acids and sugars, while the products at 355 °C were mainly phenolics. This study aims to provide a theoretical reference for the pyrolysis gasification test of grape stem.
Co-doping
of heteroatoms into the support of metal-supported catalysts
is a prevalent method to improve the catalytic performance by adjusting
metal–support interactions. This paper investigated the catalytic
performances of Ru supported on biomass-derived char (Ru@Char), N-doped
char (Ru@N-Char), and N,P-co-doped char (Ru@NP-Char)
in the emerging lignin-first depolymerization for both poplar (hardwood)
and pine (softwood) samples, with an emphasis on the production of
phenolic monomers. Various characterizations of the prepared catalysts
showed that the codoping of N,P not only facilitated the formation
of micropores in the char but also introduced weak and moderate acid
sites. Furthermore, the sizes of Ru nanoparticles on the codoped char
became smaller, and the proportion of metallic Ru species was increased,
resulting from electron transfer from Ru to the codoped char. The
yields of the phenolic monomers from poplar and pine over Ru@NP-Char
were as high as 57.98 and 17.53 wt % Klason lignin, respectively,
which were improved by factors of 1.4–2.5 in comparison to
Ru@Char and Ru@N-Char. Full delignification during the depolymerization
of both poplar and pine was also achieved over Ru@NP-Char.
The design of carbon materials with
high electrochemical performances
is desirable to fulfill the demands of next-generation supercapacitors.
In this study, porous nitrogen-doped carbon materials were prepared
by hydrothermal carbonization and KOH activation using a renewable
algae as the nitrogen source and partly carbon source. Addition of
glucose as a promoter was found to favor the formation of homogeneous
spherical structure and retention of nitrogen in the solid phase,
resulting in excellent capacitive properties. Under optimized conditions,
the algae-derived nitrogen self-doped porous carbon materials had
a high specific surface area of 1893.26 m2/g, a high nitrogen
content of 2.9 wt %, and a large gravimetric capacitance of 335.5
F/g in a 6 M KOH aqueous electrolyte. After 5000 cycles, the assembled
supercapacitor still maintained 89.41% of the initial capacitance,
demonstrating a good cycling stability. The results indicated that
renewable algae could be a promising nitrogen source for the production
of N-doped carbon materials.
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