Research group of Professor Gao Guohua of East China Normal University: development of polyionic liquid microreactor for hydrolysis of vinyl carbonate

Introduction polyionic liquid is a kind of polymer containing ionic liquid group on the repeating unit of polymer chain It is gradually applied to heterogeneous catalysis in recent years, combining the advantages of the diversity and designability of ionic liquid anion and anion structure and the polyphase characteristics of polymer As we all know, heterogeneous catalysis plays an important role in modern chemical industry However, due to the difficulty of fully exposing its catalytic activity center, its catalytic activity is often low According to the structural characteristics of polyionic liquids, the design and synthesis of heterogeneous catalysts with special structural properties (such as porous structure, nanostructure, solvability and enrichment), so as to improve the dispersion of catalytic active center in the reaction substrate, is an effective way to prepare efficient catalysts Recently, the research group of Professor Gao Guohua of East China Normal University has successfully prepared a kind of polyionic liquid microreactor that can quantitatively enrich reactants, and it is used to efficiently catalyze the hydrolysis of vinyl carbonate to prepare glycol (green chem., DOI: 10.1039 / c7gc03773b) Professor Gao Guohua's research group is mainly engaged in the research of the related fields of ionic liquid catalysis and carbon dioxide resource utilization, including the synthesis and application of ionic liquid and polyionic liquid catalysts, the conversion and utilization of carbon dioxide, supramolecular recognition and separation membrane materials Guided by the characteristics of ionic liquids, the research group is committed to solving the problems of resource utilization and environmental pollution control Typical work includes the preparation of fine chemicals by fixing carbon dioxide with ionic liquid catalyst, the preparation of porous polyionic liquid catalyst, the research of soluble expanded polyionic liquid catalyst, and the application of soluble expanded polyionic liquid in dye adsorption and oil-water separation The main research directions of the research group include catalytic chemistry, ionic liquid chemistry, carbon dioxide resource utilization, and the development of functional membrane materials Gao Guohua, professor and doctoral supervisor of the Department of chemistry, East China Normal University He obtained bachelor's degree in Chemistry Department of Inner Mongolia University in 1986, doctor's degree in Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences in 1992, senior engineer in Yanshan Branch of Beijing Institute of chemical engineering, Sinopec from 1993 to 1997, research assistant in Department of chemical engineering, National University of Singapore from 1997 to 1999, catalyst Chemistry Research Center, Hokkaido University, Japan from 1999 to 2002 He served as a doctoral researcher; from 2002 to 2003, he worked as a postdoctoral researcher in the Department of chemistry, Ottawa, Canada; in December 2003, he was employed as a professor and doctoral supervisor in the Shanghai Key Laboratory of green chemistry and chemical process greening, Department of chemistry, East China Normal University He has cooperation and development experience with famous domestic and foreign enterprises such as Sony Company of Japan, Sinopec development department and Sinopec catalyst company He was invited to be the leader of physical chemistry group of East China Normal University and member of ionic liquid Professional Committee of Chinese chemical society Presided over 5 general projects of NSFC, participated in one key and major project respectively, and participated in one national key R & D plan In the past five years, he has published more than 30 scientific research papers in international core journals, such as chem Rev., chem SCI., green chem., chem Commun., ACS macro Lett., EUR J.Org Chem Research achievements: development of polyionic liquid microreactor for hydrolysis of vinyl carbonate A series of innovative experiments have been carried out on the synthesis of polyionic liquid catalysts They have synthesized a kind of polyionic liquid which can be swelled in the reaction substrate Without any pore structure or nanostructure, this kind of catalyst can absorb the swelling of reaction substrate into the polymer, so as to fully disperse the active center Therefore, the catalytic activity of 3-phenyl-2-oxazolidinone prepared from aniline and vinyl carbonate is equivalent to that of homogeneous catalyst (ACS macro Lett., 2016, 5, 435 – 438) Due to the different forces between the polyionic liquid and the reaction substrate, the reactants can be enriched to different degrees The research group further prepared the polyionic liquid catalyst which can quantitatively enrich specific reactants In the process of catalytic hydrolysis of ethylene carbonate to ethylene glycol, since polyionic liquid can quantitatively enrich the reactants with the best water ester ratio into the micro reactor, the high water ester ratio in the catalyst can be maintained without increasing the overall water consumption, so that the catalytic reaction can be carried out with high efficiency Figure 1 Performance of polyionic liquid microreactor for water enrichment and its catalytic effect on hydrolysis of vinyl carbonate to prepare glycol (source: Green chem 2018, 20, 1594-1601) the author first copolymerized N-vinyl imidazolium ionic liquid monomer, sodium acrylate and crosslinker to prepare a series of swelling polyionic liquids (as shown in Figure 2), and investigated the influence of polyionic liquids on the enrichment performance and structure of reaction substrate Figure 2 Synthesis of crosslinked polyionic liquids (source: Green chem 2018, 20, 1594 – 1601) in order to study the water enrichment performance of polyionic liquids in the mixed solvent of water and vinyl carbonate, the author added the prepared polyionic liquids to the mixed solution of water and vinyl carbonate (molar ratio r = 1.5), and the water and vinyl carbonate were dissolved and absorbed into the polyionic liquids to varying degrees Determine the content of water and vinyl carbonate in the internal and external solvents of polyionic liquid respectively, so as to calculate the water ester ratio R in of the internal solvent of polyionic liquid and the water ester ratio r out of the remaining solvent (see Table 1) The ratio, R in / r out, is used to measure the water enrichment capacity of the internal polyionic liquid, expressed by EW When EW > 1, it indicates that water is enriched in the polyionic liquid; on the contrary, when EW < 1, it indicates that vinyl carbonate is enriched in the polyionic liquid Through comparison, the author found that the ability of polyionic liquids to enrich water is positively related to the hydrophilicity of polyionic liquids The ability of polyionic liquids to enrich water can be controlled by introducing hydrophilic groups such as ether bonded hydroxyl groups into its 3-substituent structure, so as to design a catalyst to enrich reactants in a certain amount Table 1 The swelling degree of polyionic liquids in water and vinyl carbonate and the enrichment ability of polyionic liquids in mixed solvents (source: Green chem 2018, 20, 1594 – 1601) the author observed the micro morphology of polyionic liquids after swelling in water, vinyl carbonate and mixed solvents by cryo-SEM The swelling polyionic liquid gel was cooled by liquid nitrogen and then cross section, vacuum drying was used to sublimate the water on the cross section, while ethylene carbonate and polymer chain were left behind because they could not sublimate As shown in Fig 3a, the cross section of polyionic liquid is smooth after swelling in vinyl carbonate However, when the polyionic liquid swells in water, due to the sublimation of water, the three-dimensional network structure of the polymerization chain is exposed, as shown in Fig 3B The surface porosity (ϕϕϕϕϕϕϕϕϕϕϕϕϕϕϕϕϕϕϕϕϕϕϕϕ It can be seen from the cryo-SEM figure that the polyionic liquid chain can be fully dispersed in the solvent after swelling in the mixed solvent Therefore, when polyionic liquid is used as catalyst to catalyze the reaction of vinyl carbonate with water, this highly dispersed three-dimensional network structure is likely to greatly improve the mass transfer of reactants in the catalyst and the utilization of active center Fig 3 Frozen scanning electron micrograph of swelling state of polyionic liquid (source: Green chem 2018, 20, 1594 – 1601) Figure 4 shows the relationship between the water ester ratio in the polyionic liquid and the corresponding catalytic activity It can be seen that the moderate enrichment ability of polyionic liquids can make the reaction substrate be quantitatively adsorbed into the micro reactor, so that the proportion of reactants around the catalytic activity center can be optimized, and the catalytic activity of polyionic liquids can be improved When the enrichment capacity is too low, water molecules are difficult to be enriched, while when the enrichment capacity is too strong, the reactant vinyl carbonate is difficult to contact with the catalyst, so the reaction is not used The quantitative enrichment ability of the polyionic liquid microreactor in the reaction substrate can improve the catalytic efficiency and reduce the energy consumption while reducing the water consumption, which provides a new way for the design of high activity heterogeneous catalyst Figure 4 The relationship between the catalytic activity of polyionic liquids and the water ester ratio in the catalyst (source: Green chem 2018, 20, 1594 – 1601) the research results were published on green chem Zhang YONGYA, doctoral candidate of East China Normal University, was the first author of the paper The research work was supported by NSFC (2177306821573072), national key R & D plan (2017yfa0403102), Shanghai Key Discipline Construction Project (b409), etc Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information, chembeango app, chembeango official microblog, CBG wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the domestic representative research group, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.