Shaorui Yan,Ruinian Zhou,Feng Han,Mengmeng Feng,Chengxia Miao,Shuai Zhang,Shiyun Ai
A CO2-induced ROCO2Na/ROCO2H buffer solution is developed and employed in the carboxylative cyclization of propargyl alcohol to generate α-alkylene cyclic carbonates. The introduction of CO2 into the propargyl alcohol/sodium tertiary pentoxide system can provide the ROCO2Na/ROCO2H buffer solution with both basic and acidic species. The basic and acidic species can simultaneously promote the generation of a carbonate anion intermediate and the interaction between the alkyne moieties of propargyl alcohol and protons (H+), facilitating carboxylative cyclization. Furthermore, the bulky (n-C4H9)4N+ cation of tetrabutylammonium bromide as an additive plays a crucial role in enhancing the nucleophilicity of the carbonate anion intermediate. Various α-alkylene cyclic carbonates are obtained in this catalytic system with relatively good yields at 80 °C.
An unexpected CO 2 -induced dissolution of ZnO into ionic liquids was discovered. This process exhibited high dissolution speed and the dissociated mixture was applied as an efficient Zn-based catalytic system for the CO 2 -promoted hydration of propargylic alcohols under atmospheric pressure with broad substrate scope. Moreover, this system could be recycled and reused for at least 16 times with excellent yields continuously obtained, which is an unprecedented record for this reaction. Significantly, this system could employ waste pigments as the ZnO source and work even under flue gas atmosphere. In the mechanistic investigations, the interaction between ZnO, CO 2 and ionic liquids to give N-heterocyclic carbene/CO 2 adducts proved to be the key factor for this specific dissolution. These adducts were further identified to exhibit better reactivity than the normal CO 2 by experimental data and density functional theory (DFT) calculations, which might be responsible for the excellent performance of the abovementioned catalytic system.
Selective hydrogenation of alkynol compounds to produce high value-added enols is an important reaction in the fine chemical industry. The construction of selective hydrogenation catalysts for alkynols is challenging because the alkynyl group is prone to over hydrogenation and the selectivity in the hydrogenation is always low. Herein, a simple sacrificial template strategy was designed to prepare mesoporous CeO2, on which ultrafine and highly-dispersed bimetallic PdCu nanoparticles were anchored, obtaining the PdCu@CeO2 catalyst. Introducing non-precious metallic Cu can improve the selectivity of precious metal Pd catalysts for the selective hydrogenation of alkynols through electronic and geometric modulation. The obtained PdCu@CeO2 catalyst showed high selectivity (99%) and good recyclability for the selective hydrogenation of the probe compound propynol ethoxylate under mild conditions. The PdCu@CeO2 catalyst also exhibited excellent performance in the catalytic selective hydrogenation of various substituted alkynols. Therefore, this research work provides a feasible strategy for the effective regulation of catalytic performance, which has potential application for the efficient catalytic selective hydrogenation of alkynols in the fine chemical industry.
The liquid-liquid equilibrium data for the water + propargyl alcohol (PA) + solvents ternary system were measured at 308.2 K under 101.3 kPa, where solvents refer to ethyl acetate, methyl tert-butyl ether, methyl isobutyl carbinol and chloroform. The tie lines were displayed in ternary phase diagrams. The distribution coefficient and separation factor were calculated according to the measured tie-line data and employed to evaluate the capacity of solvents to extract PA from aqueous solution. The calculation results demonstrated that the selectivity was large enough for the extraction application. Meanwhile, the reliability of the experimental data was confirmed using the Othmer-Tobias and Hand equations. The UNIFAC model was applied for a comparison and predicting the LLE behaviors. The results indicated that the calculated data by UNIFAC model cannot agree well with the experimental ones. The NRTL and UNIQUAC models were used to correlate the experimental data and the binary interaction parameters were regressed. The root mean square deviations of the NRTL and UNIQUAC models were less than 0.6%, indicating that the LLE experimental data can be successfully correlated by the models.
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