Preparation and Optimization of Macroalgae-Derived Solid Acid Catalysts

Abstract

Solid acid catalysts were synthesized from macroalgae Sargassum horneri via hydrothermal carbonization followed by sulfuric acid sulfonation. A three-variable Box-Behnken design and optimization was used to maximize surface acidity. The optimal preparation conditions were found to be at the carbonization temperature of 217 °C, the carbonization time of 4.6 h and the sulfonation temperature of 108.5 °C. Under these conditions, the highest surface acidity achieved was 1.62 mmol g −1 .Physical and chemical properties of prepared solid acid catalyst were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, and elemental analysis. The results proved the grafting of -SO 3 H groups on an amorphous carbon structure. The catalyst activity was evaluated by the esterification of oleic acid with methanol. The sample prepared achieved 96.6% esterification yield, which was higher than the 86.7% yield achieved by commercial Ambersyst-15 under the same reaction conditions. Graphical Abstract

SO3H-Containing Functional Carbon Materials: Synthesis, Structure, and Acid Catalysis

“…The same authors also showed that by addition of 50% acrylic acid during the hydrothermal treatment materials with 2-fold-enhanced COOH (2.88 mmol/g) and 1.2-fold-enhanced SO 3 H densities (1.53 mmol/g) were produced . Similarly, sulfonation of hydrothermally treated macroalgae produced sulfonated hydrochars with the concentration of SO 3 H sites being around 0.953–1.62 mmol/g . The higher degree of SO 3 H functionalization achieved over lignin- and lignocellulose-based hydrochars is most likely due to the presence of a more aromatized carbon framework structure in comparison to the sugar-based hydrochars.…”

“…The hydrochar-based sulfonated materials or sulfonated hydrothermal carbons (SHCs) have been successfully obtained by reacting hydrochars derived from glucose, ,− ,, xylose, , sucrose, cellulose, , as well as natural organic matter such as lignin, ,, wood meal, and macroalgae with a strong sulfonating agent (concentrated H 2 SO 4 , fuming H 2 SO 4 , and chlorosulfonic acid). These SHCs have been demonstrated to exhibit SO 3 H densities ranging between 0.57 and 1.58 mmol/g.…”

“…In spite of the lack of porosity resulting from a highly hydrogen-bonded interconnected structure, these materials have demonstrated excellent catalytic activity and selectivity in various organic reactions, particularly upon biomass conversion (polysaccharide hydrolysis, fatty acid esterification, biodiesel production, sugar dehydrations, and alike), and aqueous-phase reactions. The unusually high activity of SHCs was attributed to an enhanced adsorption of oxygenated reactants by hydrophilic surface functional groups and the unfolding of ultramicropores in polar reaction media (swelling). − ,,,,,− On the downside, the biggest drawbacks of these SHC are (a) the poor thermal (<200 °C) and hydrothermal stability which limit their applicability in high-temperature applications and (b) the highly hydrophilic surface and presence of low oxidation state sulfur species that are likely to contribute to the poisoning of catalytic sites though strong chemisorption of water, oxygenated molecules, and metal impurities present in reactant streams. ,,,, …”

Optimization and Characterization of Mesoporous Sulfonated Carbon Catalyst and Its Application in Modeling and Optimization of Acetin Production

“…The characterization of the OMSC catalyst was carried using various analytical methods. The sulfonic and total acid densities were estimated by the titration method, as reported in several literature articles with a slight modification [ 27 , 35 , 48 , 59 ]. Briefly, 0.05 g of the catalyst was mixed with a 15 mL 2 M NaCl solution and stirred at room temperature for 1 h. After that, the filtrate was titrated with 0.05 M NaOH solution using phenolphthalein indicator, and the sulfonic acid (SO 3 H) density was determined as the amount of NaOH solution consumed.…”

A Two-Step SO3H/ICG Catalyst Synthesis for Biodiesel Production: Optimization of Sulfonation Step via Microwave Irradiation

“…Four independent variables used in sulfonation of the ICG were sulfonation time (X1), volume H2SO4 (X2), power level of microwave (X3), as well as stirring rate (X4). These 4 parameters were selected based on the most significantly variables influencing the catalytic activity as well as from previous study [9]. Table 1 tabulates experimental level coded and range for independent variables.…”