Selective Oxidation of Glycerol Catalyzed by Rh/Activated Carbon: Importance of Support Surface Chemistry

Abstract

Noble metal catalysts (Pt, Ir, Pd, Rh, Au) supported on activated carbon were assessed for glycerol oxidation. Rhodium is a highly efficient catalyst when the support has neutral or basic properties. The surface chemistry of activated carbon plays a key role in the performance.

Factors affecting activity and selectivity in the oxidation of glycerol promoted by platinum catalysts

“…The top-left panel shows the accumulation of the different products detected in our batch reactor, plotted in the form of turnover numbers (TONs), expressed in units of glycerol molecules consumed per number of platinum surface atoms in the catalyst (estimated using the Pt nanoparticle size distributions obtained from TEM measurements), versus time. The initial overall TOF in this catalytic run is about 40 min −1 , a value quite a bit higher than those seen with supported Pt catalysts in other reports [15][16][17][18]20,27,29,31 and also competitive with some Bimodified samples 15,16 (Table 1). Only three main products were seen in our kinetic runs, GLYALD, DHA, and GLA; no other compounds were detected within the detection limits of our experiments.…”

“…However, the published research in this area is sometimes confusing and not conclusive in terms of how to select the best catalysts for each individual application. 23,24 Many other parameters related to the characteristics of the catalyst as well as the operating conditions have been shown to influence the activity and selectivity of glycerol oxidation, including the nature of the support, 20,25,26 which often is a form of activated carbon, 6,10,19,27 the catalyst preparation method, 16,18 the metal loading, particle size, and particle shape, 13,17,22,28,29 the type of reactor used, 9 and the reaction conditions, including temperature and oxygen pressure. [6][7][8] It has been repeatedly shown that selectivity toward the oxidation of the secondary alcohol group can be enhanced by the addition of Bi to Pt catalysts, 6,[8][9][10][11][12][13][14][15][16][17] but the catalytic performance also varies significantly when using acidic versus basic media, 3,7,11,18 and only limited research has been carried out under neutral conditions.…”

Recent Advances in Catalytic Conversion of Glycerol

“…Therefore, for Au catalysts, to control over the distribution of particle sizes and to avoid the aggregation of Au particles are very important issues. Villa Aside from active metal components, tuning the support is also helpful to enhance the catalytic performances (220,221,222). For example, in comparison with Pt/activated carbon catalysts, Pt/multi-wall nanotube catalysts were more active.…”

“…For Rh-based catalysts, a remarkable influence of the surface of the support on the activity was also observed recently. When the support was neutral or alkaline, the supported Rh catalyst was more active (222). In addition, it was recently found that Au-Pd alloys/TiO 2 catalysts appeared peculiarly active (225,226).…”

Selective oxidation of glycerol over Pt supported on mesoporous carbon nitride in base-free aqueous solution

“…However, because of the complex nature of these reaction pathways, it is still a challenge to control the selectivity to give desired products. The aerobic oxidation of glycerol has been extensively studied by many groups using supported Pt [9,10], Pd [10,11], Au [10−22], Rh [23], Ir [24], and Cu-containing catalysts [25−28], and bimetals such as Pt-Bi [29], Au-Pd [30−33], Pd-Ag [34], and Au-Pt [35,36]. The activity and selectivity strongly depend on the reaction conditions (pH, temperature, and substrate to metal ratio) and the structure of the catalyst (metal, particle size, and support).…”