Influence of sucrose solution's pH on hydrothermally synthesized carbon microspheres

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

“…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].…”

“…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.…”

“…(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.…”

Hydrothermal synthesis of carbon microspheres from sucrose with citric acid as a catalyst: physicochemical and structural properties

“…By taking these outstanding characteristics into account, a range of methods has been used to prepare the CMSs, including pyrolysis, chemical vapour deposition, and hydrothermal treatment [9][10][11]. The hydrothermal treatment of CMSs has recently received a great deal of attention due to its moderate reaction conditions, one-step synthetic procedure, low cost, and environmental friendliness [12]. The main advantage of the hydrothermal method is the high efficiency that can be achieved at mild temperature ( < 300°C) inside a sealed autoclave where there is no need to use any hazardous solvents [13,14].…”

“…Another main factor affecting the size of the CMSs is the pH of the solution. Zha et al [12] prepared CMSs from sucrose using hydrothermal carbonization and evaluated the effect of different pH values (0.1,1, 3, 5,7,10,12, and 14) on physicochemical properties of CMSs by adding hydrochloric acid (HCl) or sodium hydroxide (NaOH). The results revealed that while under acidic conditions, the particle size of CMSs appeared to be smaller, at alkaline pH, the size of CMSs was grown.…”