One-pot preparation of sulfonated ordered mesoporous carbon and its catalytic performance

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

“…Nonetheless, Hara and co-workers were perhaps the first to identify these SO 3 H-modified carbons as versatile solid Brønsted acid catalysts. , Such functionalized acidic carbons have been obtained from a wide variety of inexpensive carbon sources including natural organic carbon matter such as sugars, carbohydrates, cellulosic materials, lignin, ,,,,− peat, agro-wastes (e.g., husk, straw, seed cover, cow manure, corn cob), − industrial waste carbons (oil-pitch, polycyclic aromatic compounds, petroleum coke, glycerol, char, etc. ), ,− and commercial polymer resins. , Similar acidic carbons have also been obtained by sulfonating more expensive carbon supports such as templated carbons (ordered mesoporous carbons, zeolite-templated carbons), − commercial carbon supports (glassy carbon, active carbon, carbon foam, and carbon fibers), ,− as well as nanostructured carbons (graphene, graphene oxide, nanotubes, and carbon dots). − Sulfonation of carbon supports is typically achieved by reacting it with a sulfonating reagent such as concentrated H 2 SO 4 , fuming H 2 SO 4 , gaseous SO 3 , ClSO 3 H, p -toluenesulfonic acid, or SO 3 H-containing aryl diazoniums to name a few. ,,,,− …”

“…The basic structural unit of these materials can be approximated by a flexible amorphous carbon (or oxidized carbon) framework which has been covalently linked with several sulfonic (SO 3 H) acid groups (Figure ). The sulfonic groups are usually introduced onto the carbon framework structure via chemical modification or functionalization techniques in a step commonly referred to as “sulfonation”, whereupon the sulfonic group density varies in the range of 0.05–7.3 mmol/g, depending on the sulfonation method used and framework structure of the parent carbon support. − ,,,− ,− These Brønsted acidic sulfated carbons may be subdivided into several categories on the basis of their textural and surface properties as outlined in Table . In fact, the nature of the carbon support and the method of SO 3 H functionalization have a direct impact on the resulting material properties and cost.…”

“…The sulfonated forms of carbon materials are typically characterized by an increased surface acidity, surface acidic strength, and hydrophilicity resulting from the incorporation of additional sulfonic (SO 3 H) acid groups. At the same time, the onset decomposition temperature ( T onset ) of sulfonated counterparts shows a decline at 245–250 °C, resulting from the limited thermal stability of C–S bonds; this effect is especially noticeable for acidic sulfonated carbons based on thermally stable nanostructured and graphite-like (sp2) carbon supports. − ,,,− ,− Nevertheless, the actual stability of sulfonic sites is also affected by the operational/process conditions (temperature, pressure, nature of reactants, presence of solvents and H 2 O). − The individual types of sulfonated carbons and their surface chemistry are discussed in detail in the sections below.…”

“…Structurally and chemically these acidic carbons are very different from inorganic solid acids due to their unique carbon framework (Table ). − ,,,− ,− …”

“…Among the known solid acids, the cation-exchangeable polystyrene- co -divinylbenzene sulfonic acid resins ,, are perhaps the closest chemical analogues of sulfonated carbons − ,,,− ,− as both materials present an analogous chemical (elemental) composition and are made up of a flexible carbon-based backbone that has been covalently linked to the strongly Brønsted acidic SO 3 H sites (Figure ). Nevertheless, in spite of their compositional similarities, sulfonated carbons present several advantages over the sulfonic acid resins including improved stability and low cost.…”