Influence of NH4 + on the preparation of carbonaceous spheres by a hydrothermal process

Qiao, Liang; Chen, Jie; Ying, Yao; Zheng, Jingwu; Jiang, Liqiang

doi:10.1007/s10853-012-7023-9

Cited by 9 publications

(14 citation statements)

References 20 publications

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“…The most dominant observation is that the added salts highly affect the growth of the particles, resulting in very big particles compared to experiments without such additives, this is in agreement with many previous studies [9,[28][29][30][31][32][33]. Although the system is very complex, with a variety of factors that influence the growth of the particles, such as time, temperature, concentration [19,20] and additives, it can be concluded from the literature that carbon spheres produced without additives usually have a mean diameter in a range between 100 nm and 2 µm [9,19,20,22,48,49], whereas the usage of additives, such as salts or acids, results in larger particles that vary between 1 and 15 µm [9,29,30,[32][33][34].…”

Section: Discussionsupporting

confidence: 91%

“…But what are the arguments in favor of coagulation of emulsion-like droplets? A first hint can be found in scanning-electron-microscopy (SEM) of different carbon spheres, displaying them in a state of partial coagulation, where two or more spheres have started merging without completing it [9,29,[36][37][38]. Additionally, in a previous publication it has been observed that the growth of the spheres continued after the conversion of the main building block of the spheres (HMF); thus, coalescence very likely took place [9].…”

Section: Introductionmentioning

confidence: 93%

“…Whereas many studies are focused on the formation of the particles without additives [19][20][21][22][23], others make use of different kinds of additives, such as acids, bases, or salts [24][25][26][27], during the synthesis of the particles. There are several examples in which the usage of an additive results in remarkable larger particles [9,[28][29][30][31][32][33][34]. Based on this observation, it is interesting to use additives as a tool to control the size of the particles.…”

Section: Introductionmentioning

confidence: 99%

“…(1) It is assumed that the additives have a catalytic impact on the reaction system, and therefore accelerate the polymerization and polycondensation reactions that form the particles, which further increases the size of the particles [28][29][30][31]35]. It has to be noted that the authors used this hypothesis (1) to explain their results, but did not confirm it based on their results.…”

Section: Introductionmentioning

confidence: 99%

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Hydrothermal carbonization of fructose—effect of salts and reactor stirring on the growth and formation of carbon spheres

Jung

Duman

Zimmermann

et al. 2021

Biomass Conv. Bioref.

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Hydrothermal carbonization (HTC) has become a promising technology for the production of hydrochar and carbon spheres. Several studies indicate a strong dependency of the reaction conditions on the sphere diameter. The usage of additives, such as salts, is one possibility to increase the size of the spheres. However, the growth mechanism which leads to larger particles is not fully understood. In this work, kinetic studies of HTC with fructose were performed with different salts as additives. The growth of the particles (the increase in size) has been compared to the formation rates (increase in yield) of hydrochar by using the reaction rate constants from the kinetic model. The results indicate that the acceleration of the growth rate is independent of the formation rate. It is therefore assumed that coagulation, as a growth mechanism, took place. With longer reaction times, the particles reached a stable particle size, independently from the added salts; therefore, it was assumed that the particles underwent some sort of solidification. The state of matter can therefore be described as an intermediate state between liquid and solid, similar to mesophase pitch. Experiments with a stirrer resulted in squashed particles, which supports the model, that the particles exhibit emulsion-like behavior.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Hydrothermal carbonization of fructose—effect of salts and reactor stirring on the growth and formation of carbon spheres

Jung

Duman

Zimmermann

et al. 2021

Biomass Conv. Bioref.

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“…46,47 The appearance of the latter peak was accompanied by the disappearance of the peak in 1700 cm À1 (carbonyl group), the reduction of C═O group was reported in nitrogenated HC. 48,49 Moreover, the intensity of the peak in 1160 cm À1 (C O C, asymmetric stretch) was also reduced in HC-SCG/5MU. 50 However, the intensity of the peak around 615 cm À1 (C O C outof-plane bending) was increased in the nitrogenized HC.…”

Section: The Incorporation Of N To the Hc During Htc And The Characte...mentioning

confidence: 94%

Thermal treatment versus hydrothermal carbonization: How to synthesize nitrogen‐enriched carbon materials for energy storage applications?

Alhnidi

Straten

Nicolae

et al. 2021

Intl J of Energy Research

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The thermal treatment of an activated carbon/chars with a nitrogen precursor is not a sustainable nor an efficient method for the incorporation of N into the carbon structure. This study proposes the use of hydrothermal carbonization (HTC) as an environmentally friendly method for the incorporation of N into the bulk of carbon materials. The authors propose the following sequence for the synthesis of Nenriched carbon materials (NCM) for energy storage applications: HTC of the N precursor and biomass ! activation of N-hydrochar (N-HC). To investigate the proposed method, HTCs of spent coffee grounds (SCG) with N precursors (urea and alanine) were conducted at 220 C for 5 hours. The resulted N-HCs were subjected to a mild thermal activation via pyrolysis at 600 C for 2 hours. The results showed that HTC enhances the incorporation of N into the carbon matrix via many reactions, for example, the Maillard reaction (MR) or the Mannich reaction, which may accompany the formation of HC via the solved-intermediate pathway or the solid-to-solid pathway, respectively. However, adjusting some parameters before HTC, for example, the concentration of the N precursor and the pH value of the slurry is important to avoid a significant reduction in the N-HC yield. The proposed method led to the synthesis of NCM with a N content of 10.3wt% The X-ray photoelectron spectroscopy (XPS) confirmed the incorporation of N into the bulk of NCM and showed a significant increase in the content of heterocyclic N compounds (pyridinic N, pyrrolic N, and graphitic N) in the NCM. The incorporation of N via the proposed method significantly improved the electrochemical properties of NCM as the values of the specific capacitance and the electrical conductivity in the NCM increased by five times and four times, respectively.

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A facile and environmentally friendly biomass-assisted stӧber method to fabricate dispersed carbon nanospheres

et al. 2018

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Influence of NH4 + on the preparation of carbonaceous spheres by a hydrothermal process

Cited by 9 publications

References 20 publications

Hydrothermal carbonization of fructose—effect of salts and reactor stirring on the growth and formation of carbon spheres

Hydrothermal carbonization of fructose—effect of salts and reactor stirring on the growth and formation of carbon spheres

Thermal treatment versus hydrothermal carbonization: How to synthesize nitrogen‐enriched carbon materials for energy storage applications?

A facile and environmentally friendly biomass-assisted stӧber method to fabricate dispersed carbon nanospheres

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