Sol–gel La 2 O 3 –ZrO 2 mixed oxide catalysts for biodiesel production

The Effect of the ZrO2 Loading in SiO2@ZrO2-CaO Catalysts for Transesterification Reaction

“…The basicity of the catalysts was measured by CO 2 -TPD. This technique allows the description of the strength of the basic sites according to the CO 2 desorption temperature, as weak (T < 200 • C) and associated with -OH groups, medium strength (between 200 • C and 400 • C) associated with adsorbed bidentate carbonates, and strong basic sites (T > 400 • C) associated with monodentate carbonates formed as O 2− ions [11]. The CO 2 -TPD results indicated (see Figure S5 for desorption profiles) that the SiO 2 @ZrO 2 samples have very few basic sites (28, 69, and 46 µmol g −1 for SiO 2 @ZrO 2 0.04 M, SiO 2 @ZrO 2 0.06 M, and SiO 2 @ZrO 2 0.08 M, respectively).…”

“…This group is further divided into first, second, and third generations. The first generation is produced from edible oils, such as corn, sunflower [1,6], cotton [7], soybean [8], palm [2], rapeseed [9], and canola oils [10,11]. On the other hand, second generation biofuels are from non-edible oils, such as jatropha [12][13][14], karanja [15], castor [16], and linseed [17].…”

“…While the homogeneous catalysts are widely used in the biodiesel industry, the separation of catalysts from products, the corrosion of the reactor, as well as secondary reactions, have led us to explore heterogeneous catalysts as a potential alternative to improve biodiesel production. Solid catalysts, such as MgO [2] Li/TiO 2 [10], La 2 O 3 -ZrO 2 [11], CaO-La 2 O 3 [26], CaO [27][28][29], potassium-impregnated Fe 3 O 4 -CeO 2 [9], Li 2 SiO 3 [30], and Ag/CeO 2 [31], have been efficiently employed for biodiesel production. Nanomaterial catalysts have gained attention in academia and industry due to their properties in tuning chemical reactions [9,[32][33][34].…”

“…In general, ZrO 2 can be partially stabilized when doped with CaO [36,41,42]. In addition, when ZrO 2 can be partially stabilized for any doped agent, the crystalline structures can undergo changes because the ZrO 2 has an ability to embed foreign cations in their network [11,43]. Hence, calcium has been considered as a foreign cation that facilitates basic properties in a core-shell material capable of FAME production [44].…”

Solid Green Biodiesel Catalysts Derived from Coal Fly Ash

“…The numerous disadvantages of homogenous base and acid catalysts, such as soap formation, catalyst recovery, high corrosion, and inhibition by water [1,24] can be replaced using heterogeneous catalysts such as alkaline [25] and alkaline earth metal oxides [2,26,27], mixed oxides [28][29][30], modified layered double hydroxides [31][32][33][34], zeolites [35][36][37], sulfonated solids [38], ion exchange resins [39][40][41], supported heteropolyacids [42,43], etc. In order to design new catalysts based on the modern concept of environmental protection, greatest attention of many scientists is directed at investigation of different waste materials (fly ash from coal-fired power stations (CFPSs), biomass fly ash, agricultural and animal waste, industrial waste reach in calcium such as mud and slug, and natural sources) for potential catalyst synthesis, which can often be very dangerous and leave a lasting impact on the environment.…”