Effect of acid–base characteristics of ZrO2–Y2O3 on catalytic properties in carboxylation of methanol

Abstract

We have established that the calcination temperature for ZrO 2 -Y 2 O 3 catalysts changes their acid-base spectrum, which determines the direction of the conversions in the mixture MeOH + CO 2 . For samples with predominance of acid sites, the major product is dimethyl ether. As the content of base sites increases, methyl formate is formed. Activity in dimethyl carbonate synthesis is exhibited only by samples in which the basicity is higher than the acidity or close to it.In recent years, there has been increased interest in using zirconium oxide and its stabilized forms in various catalytic processes [1][2][3], which is connected with their physicochemical characteristics and in particular with their acid-base properties.Back in 1985, Tanabe et al. established that the behavior of ZrO 2 in catalysis is different depending on its calcination temperature. Zirconium dioxide calcined at 600°C exhibits the maximum activity relative to the reaction of hydrogenation of 1,3-butadiene, while a sample calcined at 800°C exhibits maximum activity relative to hydrogenation of cyclohexadiene [4]. The catalytic activity of zirconium oxide is due to the presence of both base and acid sites on its surface, which makes materials based on zirconium oxide promising for use in processes of heterogeneous acid-base catalysis occurring with participation of acid and base sites on the surface [5].One such process is the reaction of carboxylation of methanol, obtaining dimethyl carbonate (DMC), a valuable chemical product and a promising high-octane additive to motor fuels [6]. The prospects for this method for obtaining DMC involve the use of CO 2 , which is considered the main source of the "greenhouse effect" and causes global climate change [7]. The first studies of this reaction were conducted in the 1980s [8]. Only a few papers have been devoted to study of the reaction of methanol carboxylation in the presence of ZrO 2 [9, 10]. The metastable tetragonal modification t-ZrO 2 may be of special interest; stabilization of the latter is promoted by yttrium oxide additives. Therefore it was of interest to study ZrO 2 -Y 2 O 3 systems, characterized by an increased content of this metastable phase.The aim of this work was to determine the effect of the calcination temperature on the acid-base characteristics of ZrO 2 -Y 2 O 3 and to establish the connection between the acid-base characteristics and the catalytic properties of these samples in synthesis of dimethyl carbonate from methanol and carbon dioxide. EXPERIMENTALIn this work, we investigated samples of ZrO 2 stabilized by Y 2 O 3 (3.4 mole %) (YSZ series: yttrium stabilized zirconia), prepared at the A. A. Galkin Donets'k Physicotechnical Institute (National Academy of Sciences of Ukraine) by

Morphology control of ceria nanocrystals for catalytic conversion of CO2 with methanol

“…Combining the two proles together, we can see that the prepared CeO 2 catalysts possess both acid and basic sites, consistent with the results reported previously. [33][34][35] This result also reveals that CeO 2 is an acid-base bifunctional catalyst. Earlier work 10,11,16 has indicated that acid and base sites are both essential in direct synthesis of DMC synthesis.…”

Synthesis of diethyl carbonate from ethanol through different routes: A thermodynamic and comparative analysis

“…However, this route is most green as it involves direct utilization of CO 2 . It has been observed that a combination of acidic‐basic sites on a catalyst are important for selective synthesis of dialkyl carbonate as it involves adsorption of CO 2 and activation of alcohol . The co‐production of water also needs to be dehydrated which increased yield by 9 fold .…”

“…It has been observed that a combination of acidic-basic sites on a catalyst are important for selective synthesis of dialkyl carbonate as it involves adsorption of CO 2 and activation of alcohol. [41][42][43][44][45] The co-production of water also needs to be dehydrated which increased yield by 9 fold. [35] Synthesis of DEC from DMC is restricted by the formation of azeotropes.…”

Preparation of Zirconium Oxide Powder Using Zirconium Carboxylate Precursors

“…Due to its unique chemical properties (i.e., surface acidity and basicity [2,3]), it is a valuable catalyst for elimination, dehydration, hydrogenation, and oxidation. As reported previously [4,5], the properties of tetragonal zirconia (t-ZrO 2 ) that is employed in the aforementioned applications are highly dependent on the precursors used for its preparation.…”