Sustainable Synthesis of Dimethyl- and Diethyl Carbonate from CO2in Batch and Continuous Flow─Lessons from Thermodynamics and the Importance of Catalyst Stability
Abstract:Equilibrium conversions
for the direct condensation of MeOH and
EtOH with CO
2
to give dimethyl- and diethyl carbonate,
respectively, have been calculated over a range of experimentally
relevant conditions. The validity of these calculations has been verified
in both batch and continuous flow experiments over a heterogeneous
CeO
2
catalyst. Operating under optimized conditions of
140 °C and 200 bar CO
2
, record productivities of 235
mmol/L·h… Show more
“…Meanwhile, under the “stoichiometric” (alcohol/nitrile/CH 3 CN=50 : 25 : 100) and “alcohol‐excess” (100 : 25 : 100) conditions, the possible maximum amount of dialkyl carbonates is 25 mmol. Under these three conditions, we conducted the reactions using two different amounts of CeO 2 catalyst (0.17 g and 0.68 g), which and whose related materials have been reported by many research groups to exhibit good catalytic activity for non‐reductive conversion of CO 2 [4,21–27,34–57] . The results obtained with the smaller amount of CeO 2 catalyst (0.17 g) are reflected by the reactivity of alcohols and nitrile dehydrants over the catalyst surfaces, and those with the larger amount of CeO 2 (0.68 g) provide the information about the saturation level of the product formation.…”
Section: Resultsmentioning
confidence: 99%
“…Due to the unnecessity of alteration in the oxidation state of the carbon atom in CO 2 , the energy requirement for non‐reductive transformation is relatively low compared to reductive transformation. This advantage has attracted much attentions of researchers and made the synthesis of dialkyl carbonates central to the non‐reductive CO 2 transformation [1,3,4] . Organic carbonates including dialkyl carbonates have been used as electrolytes in lithium‐ion batteries and raw materials for polycarbonates, and dimethyl carbonate is also regarded as a promising fuel additive [3] .…”
Section: Introductionmentioning
confidence: 99%
“…This advantage has attracted much attentions of researchers and made the synthesis of dialkyl carbonates central to the non-reductive CO 2 transformation. [1,3,4] Organic carbonates including dialkyl carbonates have been used as electrolytes in lithium-ion batteries and raw materials for polycarbonates, and dimethyl carbonate is also regarded as a promising fuel additive. [3] Dialkyl carbonates have been synthesized conventionally by the reaction of alcohols with phosgene (COCl 2 ) or urea, (NH 2 ) 2 CO. [3] The reaction of alcohols with (NH 2 ) 2 CO to dialkyl carbonates can be interpreted as an indirect route from CO 2 because (NH 2 ) 2 CO is synthesized from CO 2 and ammonia.…”
Section: Introductionmentioning
confidence: 99%
“…Our previous results for the other nitrile dehydrants consisting of CH 3 CN [22] and benzonitrile [23] have also indicated that the formation rate of dialkyl carbonate is dependent on the combination of alcohol and nitrile. (4) Along with the equilibrium shift, the addition of 2cyanopyridine enhances the reaction rate of CO 2 and alcohols to corresponding organic carbonates. [27] This acceleration effect is due to the formation of strong base sites via the attachment of 2-cyanopyridine on the CeO 2 surface.…”
The shift of equilibrium by removing water with nitrile dehydrants is crucial for CeO2‐catalyzed synthesis of dialkyl carbonates from CO2 and alcohols. Two nitriles – 2‐cyanopyridine and 2‐furonitrile – were previously found as effective dehydrants, yet their detailed comparison as well as exploration of potential of 2‐furonitrile remain insufficient. Herein, the performance of 2‐cyanopyridine and 2‐furonitrile was compared in the synthesis of various dialkyl carbonates. 2‐furonitrile was found to be superior to 2‐cyanopyridine in the synthesis of dialkyl carbonates from CO2 and bulky or long‐chain (≥C3) alcohols. Namely, the yield of diisopropyl carbonate (up to 50 %) achieved using CeO2 and 2‐furonitrile is comparable to or even higher than previously reported ones. Meanwhile, 2‐cyanopyridine acted as a better dehydrant than 2‐furonitrile in the synthesis of dimethyl carbonate and diethyl carbonate. The adsorption experiments and density functional theory calculations have indicated that the better performance of 2‐furonitrile compared to 2‐cyanopyridine in the synthesis of dialkyl carbonates from bulky or long‐chain alcohols is due to the weaker interaction of 2‐furonitrile with the CeO2 surface. Such weak interaction of 2‐furonitrile offers a larger reaction field on the catalyst surface for both CO2 and alcohols.
“…Meanwhile, under the “stoichiometric” (alcohol/nitrile/CH 3 CN=50 : 25 : 100) and “alcohol‐excess” (100 : 25 : 100) conditions, the possible maximum amount of dialkyl carbonates is 25 mmol. Under these three conditions, we conducted the reactions using two different amounts of CeO 2 catalyst (0.17 g and 0.68 g), which and whose related materials have been reported by many research groups to exhibit good catalytic activity for non‐reductive conversion of CO 2 [4,21–27,34–57] . The results obtained with the smaller amount of CeO 2 catalyst (0.17 g) are reflected by the reactivity of alcohols and nitrile dehydrants over the catalyst surfaces, and those with the larger amount of CeO 2 (0.68 g) provide the information about the saturation level of the product formation.…”
Section: Resultsmentioning
confidence: 99%
“…Due to the unnecessity of alteration in the oxidation state of the carbon atom in CO 2 , the energy requirement for non‐reductive transformation is relatively low compared to reductive transformation. This advantage has attracted much attentions of researchers and made the synthesis of dialkyl carbonates central to the non‐reductive CO 2 transformation [1,3,4] . Organic carbonates including dialkyl carbonates have been used as electrolytes in lithium‐ion batteries and raw materials for polycarbonates, and dimethyl carbonate is also regarded as a promising fuel additive [3] .…”
Section: Introductionmentioning
confidence: 99%
“…This advantage has attracted much attentions of researchers and made the synthesis of dialkyl carbonates central to the non-reductive CO 2 transformation. [1,3,4] Organic carbonates including dialkyl carbonates have been used as electrolytes in lithium-ion batteries and raw materials for polycarbonates, and dimethyl carbonate is also regarded as a promising fuel additive. [3] Dialkyl carbonates have been synthesized conventionally by the reaction of alcohols with phosgene (COCl 2 ) or urea, (NH 2 ) 2 CO. [3] The reaction of alcohols with (NH 2 ) 2 CO to dialkyl carbonates can be interpreted as an indirect route from CO 2 because (NH 2 ) 2 CO is synthesized from CO 2 and ammonia.…”
Section: Introductionmentioning
confidence: 99%
“…Our previous results for the other nitrile dehydrants consisting of CH 3 CN [22] and benzonitrile [23] have also indicated that the formation rate of dialkyl carbonate is dependent on the combination of alcohol and nitrile. (4) Along with the equilibrium shift, the addition of 2cyanopyridine enhances the reaction rate of CO 2 and alcohols to corresponding organic carbonates. [27] This acceleration effect is due to the formation of strong base sites via the attachment of 2-cyanopyridine on the CeO 2 surface.…”
The shift of equilibrium by removing water with nitrile dehydrants is crucial for CeO2‐catalyzed synthesis of dialkyl carbonates from CO2 and alcohols. Two nitriles – 2‐cyanopyridine and 2‐furonitrile – were previously found as effective dehydrants, yet their detailed comparison as well as exploration of potential of 2‐furonitrile remain insufficient. Herein, the performance of 2‐cyanopyridine and 2‐furonitrile was compared in the synthesis of various dialkyl carbonates. 2‐furonitrile was found to be superior to 2‐cyanopyridine in the synthesis of dialkyl carbonates from CO2 and bulky or long‐chain (≥C3) alcohols. Namely, the yield of diisopropyl carbonate (up to 50 %) achieved using CeO2 and 2‐furonitrile is comparable to or even higher than previously reported ones. Meanwhile, 2‐cyanopyridine acted as a better dehydrant than 2‐furonitrile in the synthesis of dimethyl carbonate and diethyl carbonate. The adsorption experiments and density functional theory calculations have indicated that the better performance of 2‐furonitrile compared to 2‐cyanopyridine in the synthesis of dialkyl carbonates from bulky or long‐chain alcohols is due to the weaker interaction of 2‐furonitrile with the CeO2 surface. Such weak interaction of 2‐furonitrile offers a larger reaction field on the catalyst surface for both CO2 and alcohols.
“…They observed that performing DAC synthesis in CF conditions (scCO 2 at 200 bar, T = 140 °C, productivities of 235 mmol (L h) −1 for DMC and 241 mmol (L h) −1 for DEC) allowed for continuous removal of both water and DAC product, preventing progressive surface M–O–M hydrolysis on the heterogeneous catalyst and paving the road towards low-temperature direct carboxylation of alcohols. 58 Aricò and co-workers developed a scalable procedure for the synthesis of non-commercial symmetrical and unsymmetrical DACs incorporating alkyl, alkoxyalkyl, aminoalkyl, and thioalkyl moieties, depicted in Scheme 6. DAC synthesis occurred via TBD-promoted transcarbonylation (10% mol); interestingly, the reported procedure allowed for large-scale production of DACs (up to 100 mL) and DAC products were purified by distillation.…”
Section: Synthesis Of Dialkyl Carbonates (Dacs)mentioning
This review showcases a thorough analysis of reactions and applications of the most widespread linear and alkylene organic carbonates (DACs) as dimethyl-, diethyl-, ethylene-, and propylene- carbonates (DMC, DEC, EC,...
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