Tubular furnace

The general procedure was adapted from Fang et al. [48 (link)]; the carbon precursor and some operating conditions were changed to obtain a nanometric size and high surface area. The original method uses phenolic resol as the carbon precursor without a template, but the material yield is less than 10%. For this reason, resorcinol was used as a carbon precursor. Pluronic F127 was employed as a soft template, in order to obtain a porous structure.
Initially, a solution of resorcinol/formaldehyde (R/F) (molar ratio of 1:2), Pluronic F127 (concentration of less than 10⁻⁷ mol L⁻¹), and deionized water (molar relation water/resorcinol ratio of 5556:1) was stirred at 200 rpm, 25 °C, for 18 h. Parallel to this, the latex nanoparticles were placed in water with 0.05 mL of Span 80 to disperse hydrophobic particles in the aqueous medium, at 25 °C for 4 h and 200 rpm. After that, the carbon precursor was added to the system, which was followed by stirring for 30 min. The solution was placed in a hydrothermal reactor (Techinstro, Nagpur, India) with a capacity of 200 mL, for 24 h at 130 °C. The obtained polymer was cleaned with acetone for 3 days to remove the water inside the porous structure. After that, the material was carbonized in N₂ at 700 °C (1.5 °C min⁻¹) for 4 h, using a tubular furnace (Thermo Fisher Scientific, Waltham, USA).

The nanoparticles regeneration process starts from the asphaltene adsorption followed by their catalytic decomposition. The nanoparticles with adsorbed asphaltenes were subjected to a steam atmosphere in a tubular furnace (Thermo Scientific Lindberg/Blue, Waltham, MA, USA) at 240 °C for 2 h. For this, N₂ flow was fixed at 100 mL·min⁻¹ and steam injection was performed at a flow rate of 6.3 mL·min⁻¹ using a gas saturator with controlled temperature. In each regeneration cycle, part of the nanoparticles was taken to perform the thermogravimetric and X-ray photoelectron spectroscopy analyses.

The process was adapted from White et al. [35 (link)], using the latex template and defining particular concentrations of reagents and carbon precursor. The initial water:carbon precursor mass ratio was 1800:1 and the latex/carbon precursor mass ratio was 1:10. The latex nanoparticles were placed in water with 0.05 mL of Span 80 to disperse hydrophobic particles in the aqueous medium, at 25 °C for 4 h and 200 rpm. After that, the carbon precursor was added to the system, which was followed by stirring for 30 min. This solution was put in a hydrothermal reactor (Techinstro, Nagpur, India) with a capacity of 200 mL, at 180 °C for 24 h. After the reaction, the carbon gels were filtered and washed with excess deionized H₂O.
Later, gels are washed with acetone for 3 days, to permit the exchange of water molecules and preserve the porous structure during carbonization. Finally, the obtained polymer was dried at 120 °C for 12 h and carbonized under N₂ flow at 60 mL min⁻¹ and 500 °C (1 °C min⁻¹) for 6 h, using a tubular furnace (Thermo Fisher Scientific, Waltham, USA). CN.RON1 was obtained. After that, the same procedure was carried out at a lower molasses concentration. The cane molasses was diluted at a mass ratio (H₂O/carbon precursor) of 3600:1 to obtain smaller particle sizes. In this case, CN.RON2 was obtained.