Sulfonated Carbon Catalyst Research Articles

Alternative carbon based acid catalyst for selective esterification of glycerol to acetylglycerols

Carbon-based acid catalysts with porous structure were prepared by sulfonation of carbonized sucrose. The catalysts have an amorphous porous structure with a good acid capacity and high thermal stability. The catalytic activity was evaluated by the esterification of glycerol with acetic acid. The sulfonated carbon catalysts showed that glycerol was completely transformed into a mixture of glycerol esters including a high selectivity of about 50% to triacetylglycerol (TAG).

Glycerol Etherification by tert-Butanol Catalyzed by Sulfonated Carbon Catalyst

The recent discovery of sulfonated carbon catalyst made from sugar attracts attention owing to its renewable source. The sulfonated carbon catalyst shows higher reactivity on esterification and transesterification reactions over the conventional solid acid catalysts such as nobic acid and amberlyst. These findings are remarkable because the sulfonated carbon catalyst has a surface area much smaller than any other solid acid catalysts tested for esterification and transesterification reactions. This study reports the characteristics of the sulfonated carbon catalyst and its reactivity on glycerol etherification by fe/f-butanol. Sulfonated carbon catalyst was prepared by sulphonation of the sugar char, prepared by pyrolyzing sugar (D-glucose) at 400°C for 15 h under nitrogen flow in a tube furnace. The catalyst was characterized by specific surface area, thermo-gravimetric analysis, FT-IR and total acidity, which showed that the sulfonated carbon catalyst has a surface area of less than 1 m2 g-1 and decomposed under inert gas at around 236°C. The catalyst has a total acidity of 4 mmol g-1, mainly contributed by -SO3 moiety as indicated by the FT-IR analysis. Etherification sample analyzed on GC-MS showed the presence of mono-glyceiyl ethers isomers and di-glyceiyl ether isomers; however, tri-glyceiyl ether was not detected. The capability of the catalyst to promote the production of glyceryl ethers is a new application of the newly discovered sulfonated carbon catalyst; however, more experiments are required to elucidated catalyst reactivity, stability and selectivity under different reaction conditions. Di-glyceryl ethers are useful products in many applications such as biodiesel fuel additives. © 2010 Asian Network for Scientific Information.

Preparation of a novel sulfonated carbon catalyst for the etherification of isopentene with methanol to produce tert-amyl methyl ether

Abstract A novel method for the preparation of acid carbon catalyst from glucose and 4-hydroxybenzenesulfonic acid (p-HBSA) was reported. Glucose was first hydrolyzed to hydroxymethylfurfural that reacted with p-HBSA (a phenol compound) to form a phenolic (PF)-like resin containing –SO3H groups. The resin was carbonized and sulfonated further in concentrated sulfuric acid at 443 K to form an amorphous carbon material with a surface area of 22 m2/g. This acidic carbon contained 3.1 mmol/g of strong surface acid sites (–SO3H), and thus exhibited good catalytic activity for the etherification of isopentene with methanol to produce tert-amyl methyl ether.

Activation and deactivation characteristics of sulfonated carbon catalysts

Recently, there have been reports in the literature on sulfonated carbon catalysts prepared from sugars exhibiting interesting acid catalytic properties. However, to date, little has been reported about their activation/deactivation characteristics. For this paper, the activation/deactivation behaviors of such sulfonated carbon catalysts were investigated through the esterification of free fatty acids (acetic acid and caprylic acid) and transesterification of triglycerides (triacetin, tricaprylin and soybean oil) with methanol. The catalytic properties of the sulfonated catalysts were compared with those of Nafion ® SAC-13 and sulfuric acid, other similar Brønsted acid catalysts. For the liquid-phase esterification of acetic acid and transesterification of triacetin with methanol, the sulfonated carbon catalysts exhibited catalytic site activities comparable to those for sulfuric acid, along with higher (by weight) specific catalytic activities but lower initial TOFs compared with Nafion ® SAC-13. Catalyst swelling was critical for catalytic activity of the sulfonated carbon catalysts. Poor swelling in the gas phase of the catalysts led to the appearance of an induction period and inferior catalytic performance in the gas-phase esterification of acetic acid. In the liquid-phase esterification of acetic acid, catalytic activity decreased during the initial reaction batch cycles but reached a plateau after several catalytic cycles at 60 °C. Elemental analysis, 1H NMR results of the liquid reaction mixtures after reaction, and the decreased activity of the catalysts after extensive solvent washing suggest that the initial catalyst deactivation was caused by the leaching of polycyclic aromatic hydrocarbons containing SO 3H groups. Cycling experiments involving large triglycerides actually showed a cumulative effect of slower catalyst swelling in the less-polar reaction mixtures moderated by deactivation of the catalyst due to leaching, resulting in increased activity in the early cycles followed by a loss of activity in later cycles.