Structure and Catalysis of Cellulose‐Derived Amorphous Carbon Bearing SO₃H Groups

Abstract

The correlation between catalytic performance and structure of a cellulose-derived and carbon-based solid acid (CCSA), an amorphous carbon bearing SO(3)H, COOH, and phenolic OH groups, was investigated. Sulfonation of partially carbonized cellulose under a N(2) atmosphere resulted in the formation of a CCSA, which was amorphous carbon consisting of small polycyclic aromatic carbon sheets with a high density of SO(3)H groups (ca. 2 mmol g(-1)). CCSAs were prepared from carbon precursors, which were obtained at temperatures ≤723 K, and exhibited a high catalytic performance for the esterification of acetic acid with ethanol and for the hydrolysis of cellobiose, although the surface areas were small (<5 m(2) g(-1)). In contrast, CCSAs, which were prepared from carbon precursors obtained at ≥823 K, exhibited much lower catalytic activities for both reactions, although the CCSAs had sufficient amounts of SO(3)H groups. Structural analyses, including spectroscopic analysis of CCSAs with adsorbed probe molecules, revealed that cross-linking between the polycyclic aromatic carbon sheets caused the sharp decrease in activity.

Deactivation of sulfonated hydrothermal carbons in the presence of alcohols: Evidences for sulfonic esters formation

“…HC-SO 3 H showed high catalytic performance in the first use, with yields of 46% after 1 h and 75% after 4 h. Initial TOF (mmol converted per mmol of catalyst per second) was calculated using conversion after 1 h and considering the total sulfur content (by elemental analysis) as SO 3 H groups. The TOF value (17.4 × 10 −3 s −1 , Table 2) is higher than values reported for sulfonated carbons in analogue reactions, (e. g. 1.6 × 10 −3 s −1 with sulfonated mesoporous carbon [15] or 5.4 × 10 −3 s −1 with sulfonated incompletely carbonized glucose [11] in esterification of oleic acid with methanol, Table 2) and similar to values obtained in esterification of lower acids (16.7 × 10 −3 s −1 with sulfonated partially carbonized cellulose in esterification of acetic acid with ethanol [13], Table 2). However, a significant drop in the catalytic activity upon reuse was observed (Table 3).…”

“…In this case, as the solid was not washed or dried under vacuum, weakly physisorbed propanol should remain on the solid, but the high mobility of those molecules make them not detectable by CP technique due to the fast relaxation. In order to confirm this point, the direct polarization 13 In order to confirm the presence of chemically bound propyl groups, solids pretreated with 1-propanol were thoroughly washed with acetone and the 13 C-CP-MAS-NMR spectra were registered after drying under vacuum ( Figure 9). As can be seen the spectrum of the sample pretreated under reflux remains unchanged, showing that chemically bound propyl groups are mainly formed at high temperature.…”

“…1 H-13 C CP spectra (10000 scans) were measured using a 1 H /2 pulse length of 2.45 s, with a contact time of 2 ms, and spinal64 proton decoupling sequence of 4.6 s pulse length. Direct polarization 13 C{ 1 H} spectra (60 scans) were measured using a 13 C /2 pulse length of 4.5 s, and continuous wave proton decoupling of 4.5 s pulse length. …”

“…In fact, sulfonated carbons obtained by partial carbonisation of glucose or cellulose have been used as catalysts for esterification reactions [9][10][11][12][13], as well as monoliths prepared by one-pot synthesis in the presence of p-toluenesulfonic acid [14]. Sulfonated mesoporous carbon was obtained by replication of SBA-15 pores through carbonisation of sucrose, leading to highly active solids [15].…”

Transesterification of Triolein over Hydrophobic Microporous Carbon with SO3H Groups

“…However,sp 2 linkages amongt he carbon sheetsa lso proliferate at such high temperatures, so that the density and reactivity of SO 3 Hg roups bonded to the carbon material are significantly reduced. [7] Recently,w eh ave focused on microporous carbon synthesized by using zeolites as at emplate. [8a-c] The microporous carbon synthesized above 900 Kh as fewer hydrophilic functional groups and is composed of small carbon sheets or bands.…”