Duan-Jian Tao

Multi-Molar Absorption of CO2 by the Activation of Carboxylate Groups in Amino Acid Ionic Liquids

A new strategy for multi-molar absorption of CO2 is reported based on activating a carboxylate group in amino acid ionic liquids. It was illustrated that introducing an electron-withdrawing site to amino acid anions could reduce the negative inductive effect of the amino group while simultaneously activating the carboxylate group to interact with CO2 very efficiently. An extremely high absorption capacity of CO2 (up to 1.69 mol mol(-1) ) in aminopolycarboxylate-based amino acid ionic liquids was thus achieved. The evidence of spectroscopic investigations and quantum-chemical calculations confirmed the interactions between two kinds of sites in the anion and CO2 that resulted in superior CO2 capacities.

SO3H-functionalized Brønsted acidic ionic liquids as efficient catalysts for the synthesis of isoamyl salicylate

Six Bronsted acidic ionic liquids (BAILs) composed of [HSO4] were prepared, characterized, and used as catalysts of low dosage in the synthesis of isoamyl salicylate. The effects of various parameters such as the kind of BAILs, temperature, catalyst loading, and molar ratio of the reactants on the conversion of salicylic acid were also examined in detail. The results suggested that the catalytic performances of BAILs were of close relevance to their Hammett acidities. The SO3H-functionalized BAILs 1-(4-sulfonic acid) butyl-3-methylimidazolium hydrogen sulfate ([BSmim][HSO4]) and N-(4-sulfonic acid) butyl triethylammonium hydrogen sulfate ([BSEt3N][HSO4]) of strong acidities exhibited excellently catalytic activities and selectivities in the esterification of salicylic acid with isoamyl alcohol. The fully optimized geometries of [BSmim][HSO4] and [BSEt3N][HSO4] further manifest that their strong acidities are derived from the strong interactions between the anion with the sulfonic acid group. In addition, it was found that [BSmim][HSO4] could be also recovered easily and used repetitively at least six times without obvious decline in activity and quantity.

MOR zeolite supported Brønsted acidic ionic liquid: an efficient and recyclable heterogeneous catalyst for ketalization

In order to widen the application of ionic liquids as efficient and renewable heterogeneous catalysts, supported ionic liquids (SILs) have received considerable attention. A novel heterogeneous catalyst MOR zeolite supported Bronsted acidic ionic liquid (BAIL@MOR) was therefore prepared, characterized and applied in the ketalization reaction. The influences of reaction temperature, time, and catalyst loading have also been investigated in detail. Combined characterization results of XRD, FT-IR, SEM, TG-DTG and N2 adsorption–desorption suggested that the BAIL [CPES-BSIM][HSO4] was successfully immobilized on the surface of MOR zeolite by covalent bonds. Moreover, the catalytic performance tests demonstrated that the catalyst BAIL@MOR exhibited excellent catalytic activities in the ketalization of cyclohexanone with glycol, 1,2-propylene glycol and 1,3-butylene glycol under mild reaction conditions, as comparable with the homogeneous catalysis of the precursors [BSmim][HSO4] and H2SO4. In addition, the catalyst BAIL@MOR was also found to be reusable five times without a significant loss of its catalytic activity. Thus, the heterogeneous catalyst BAIL@MOR can act as a promising candidate for the ketalization reaction.

Tetrabutylphosphonium amino acid ionic liquids as efficient catalysts for solvent-free Knoevenagel condensation reactions

Five tetrabutylphosphonium amino acid ionic liquids ([P4444][AA]) were prepared, characterized, and used as catalysts for solvent-free Knoevenagel condensation reactions. The tetrabutylphosphonium prolinate ([P4444][Pro]) showed excellent catalytic activity and selectivity in Knoevenagel condensation reactions of active methylene compounds with various aromatic aldehydes, and all the yields of corresponding products were more than 85% under mild conditions. Furthermore, a plausible reaction mechanism for the excellent performance of [P4444][Pro] has been proposed, and [P4444][Pro] could be used repetitively at least six times without obvious decrease in activity and quantity.

Facile synthesis of fructone from ethyl acetoacetate and ethylene glycol catalyzed by SO3H-functionalized Brønsted acidic ionic liquids

SO3H-functionalized Bronsted acidic ionic liquids (BAILs) were synthesized and utilized as highly efficient catalysts for the production of fructone via the acetalization reaction of ethyl acetoacetate with ethylene glycol. In comparison with conventional H2SO4 and cation exchange resins, the BAILs N-(4-sulfonic acid) butyl triethylammonium hydrogensulfate ([BSEt3N][HSO4]) of strong acidities exhibited excellent catalytic activities. The effects of various parameters such as different BAILs, reaction temperature, catalyst dosage, and molar ratio of the reactants on the conversion of ethyl acetoacetate were investigated in detail. The experimental results indicated that the catalytic performance of BAILs were closely related to their Hammett acidities. Moreover, it was found that [BSEt3N][HSO4] could be also recovered easily and used repetitively six times without obvious decline in activity and quantity, showing great potential application in industry.

Synthesis of Ditetrahydrofurfuryl Carbonate as a Fuel Additive Catalyzed by Aminopolycarboxylate Ionic Liquids

A new series of aminopolycarboxylate ionic liquids were designed, synthesized, and applied for efficient and selective synthesis of ditetrahydrofurfuryl carbonate (DTC). Tetraethylammonium nitrilotriacetate ([N2222]3[NTA]) was demonstrated to show the best catalytic performance, in which DTC could be obtained at a yield of 80% under optimum conditions.Graphical Abstract

Kinetics Study of the Esterification of Acetic Acid with Methanol using Low-Corrosive Brønsted Acidic Ionic Liquids as Catalysts

The kinetics for the esterification of acetic acid with methanol was studied systemically in the presence of low-corrosive Brønsted acidic ionic liquids (BAILs) as catalysts. The effect of various parameters such as catalyst type, agitation speed, temperature, catalyst loading, and molar ratio of the reactants on the conversion of acidic acid was studied in detail to obtain the optimal reaction conditions. Moreover, the pseudo-homogeneous (PH) kinetic model was utilized successfully to correlate the experimental data in the temperature range from 323.15 to 343.15 K. Thus, a complete kinetic equation for describing this esterification system was developed that provides to obtain the kinetic information for the simulation and design of catalytic distillation column in the synthesis of methyl acetate.

Remarkably efficient hydrolysis of cinnamaldehyde to natural benzaldehyde in amino acid ionic liquids

The hydrolysis of cinnamaldehyde to natural benzaldehyde was investigated systematically using tetramethylammonium- based amino acid ionic liquids as homogeneous catalysts. The results indicated that tetramethylammonium prolinate ([N1111][Pro]) can be a powerful catalyst for the highly efficient hydrolysis of cinnamaldehyde, in which natural benzaldehyde was obtained with almost 94% yield and over 99% selectivity in 1 h. Moreover, kinetic study showed that compared with other catalysts, the catalytic system of [N1111][Pro] has a lower activation energy of 38.30 kJ·mol−1 in the hydrolysis reaction, indicating superior catalytic performance of [N1111][Pro]. Quantum-mechanical calculations further manifested that such high performance originates from the cooperative catalysis of the secondary amino and carboxyl group in the anion [Pro].

Facile One-Pot Synthesis of Flavanones Using Tetramethylguanidinum-Based Ionic Liquids as Catalysts

Several tetramethylguanidinum-based ionic liquids (TMGILs) were prepared, characterized and used as catalysts in one-pot synthesis of flavanones. The results indicated that TMGILs composed of phenolate anion was beneficial for one-pot synthesis of flavanones, and [TMG][4-MeO–PhO] induced the good yields of flavanones owing to the electron-donating effect of methoxy substituent on phenolate anion. Furthermore, [TMG][4-MeO–PhO] was found to be used repetitively at least five times without obvious decrease in activity and quantity.Graphical Abstract

Co-N-C catalysts synthesized by pyrolysis of Co-based deep eutectic solvents for aerobic oxidation of alcohols

The selective oxidation of alcohols to the corresponding aldehydes and ketones is of great importance in the academic and industrial fields. A series of excellent nanostructured catalysts comprising cobalt nanoparticles supported on nitrogen-doped carbon (Co-N-C) were thus prepared by pyrolysis of a deep eutectic solvent Co(NO3)2·6H2O/[Bmim]Br supported on commercial carbon. The catalytic activity of the Co-N-C materials was studied in the selective aerobic oxidation of alcohols with molecular oxygen under base-free conditions. The results indicated that the optimized Co-N-C/700 catalyst exhibited excellent catalytic performance in the selective oxidation of both aryl and alkyl alcohols, giving their corresponding aldehydes and ketones in good to excellent yields. Furthermore, the combination of the catalytic results of the control group and the different characterization methods showed that such high catalytic activity is due to the synergistic interaction between the nitrogen-doped carbon support and Co-N species in Co-N-C/700. In addition, the magnetically recoverable Co-N-C catalyst could be easily separated from the reaction system by using an external magnetic field and reused at least five times without an obvious decrease in the catalytic efficiency.