On the deactivation of alkali solid catalysts for the synthesis of glycerol carbonate from glycerol and dimethyl carbonate

Abstract

The deactivation of alkali solid catalysts for the synthesis of glycerol carbonate from glycerol and dimethyl carbonate was investigated. Calcium oxide, calcium hydroxide and calcium methoxide were chosen as the representatives of the alkali solid catalysts. When the catalysts were recycled, the yield of glycerol carbonate decreased dramatically. The alkali solid catalyst was converted to the basic calcium carbonate Ca x (OH) y (CO 3 ) z , which was the cause of the decrease of glycerol carbonate yield. It was found that the chemical interactions of the alkali solid catalyst with glycerol and glycerol carbonate led to the formation of the basic calcium carbonate Ca x (OH) y (CO 3 ) z , for which the mechanism was proposed. Based on the deactivation mechanism, calcium diglyceroxide was adopted as a new catalyst for the transesterification of glycerol and dimethyl carbonate. Compared to calcium oxide, calcium hydroxide and calcium methoxide, calcium diglyceroxide showed excellent reusability for the transesterification of glycerol and dimethyl carbonate. For calcium oxide, calcium methoxide and calcium diglyceroxide, there were dissolution losses of the catalysts in the reaction medium. For calcium hydroxide, the catalyst dissolution loss in the reaction medium was nearly negligible. For calcium diglyceroxide, the dissolution of the catalyst in the reaction medium did not influence the yield of glycerol carbonate significantly.

Phenomenological kinetic model of the synthesis of glycerol carbonate assisted by focused beam reflectance measurements

“…2, the conversion after 1 h of operation and the TOF value were negligible and the TOF value were negligible at 55°C. Quantitative yields of GC were obtained using benzene [36] and tetrahydrofurane [37] as reaction media as opposed to the solventless operation approached in this study, in which a conversion of barely 3% was obtained at 60°C.…”

Kinetics of the production of glycerol carbonate by transesterification of glycerol with dimethyl and ethylene carbonate using potassium methoxide, a highly active catalyst

“…The utilization of calcium methoxide had already been investigated for the transesterification of DMC and glycerol and it was observed that this catalyst suffered from deactivation. Such deactivation process takes place through a complex reaction network in which calcium methoxide is eventually transformed into basic calcium carbonate, represented by the formula Ca x (OH) y (CO 3 whose basic strength is much lower than the original Ca(CH 3 O) 2 or calcium diglyceroxide, which is the species initiating the reaction mechanism for reaction {a} [42]. Subsequently, Models {a}3 and {a}4 are herein presented to take into account a first order catalyst deactivation in which an analogous basic potassium carbonate species would be formed.…”

“…Additionally, potassium methoxide has been utilized jointly with the ionic liquid [BMIM][Br] to achieve the electrochemical valorisation of CO 2 giving DMC as a product [41]. Finally, the solid catalyst calcium methoxide has also been used for the transesterification of glycerol with DMC [42].…”

Experimental and modelling approach to the catalytic coproduction of glycerol carbonate and ethylene glycol as a means to valorise glycerol

“…For example, in the case of calcium methoxide, when used for the production of glycerol carbonate, deactivation proceeds by a successive hydration to form the hydroxide followed by carbonation to render a mixed hydroxide-carbonate, a much less effective catalyst for transcarbonation reactions [50] . If potassium is considered, mixed salts are not expected as they are fully soluble (which is not the case of the alkaline earth element), but potassium hydroxide is scarcely soluble in organic solvents, even in glycerol at low to moderate temperatures.…”