Homogeneous Phase Copolymerizations of Vinylidene Fluoride and Hexafluoropropene in Supercritical Carbon Dioxide

Copolymerizations of vinylidene fluoride (VDF) and hexafluoropropene (HFP) were carried out in homogeneous phase with supercritical carbon dioxide up to complete VDF conversion using conventional peroxide initiators. The HFP monomer feed ratios, f_HFP, were varied between 0.65 and 0.20. Depending on f_HFP amorphous or semi‐crystalline copolymers were obtained. f_HFP also determines the minimum pressure required to allow for homogeneous phase reactions. For example, HFP‐rich copolymerizations in 70 wt.‐% CO₂ at 100 °C require a pressure of around 500 bar. Further, bulk copolymerizations in homogenous phase were feasible for f_HFP = 0.65 at 900 bar up to complete VDF conversion. Copolymerizations in the presence of perfluorinated hexyl iodide carried out at 75 °C gave access to low dispersity polymers. Due to homogeneous phase conditions the use of any surfactants or fluorinated cosolvent is avoided.

     

The Magnetic Field Effect on the Polymerization of Styrene in Supercritical Carbon Dioxide

Over the past decade there has been a growing interest in using supercritical fluids (SCFs) to promote reactions and to replace hazardous solvents with environmentally benign solvents, such as supercritical CO2 and H2O. Many reactions in SCFs have been studied1, including polymerization in scCO22. It is known that a small change in the pressure near critical point of a fluid causes a significant change in density-dependent properties such as the solubility parameter, viscosity, and dielect…     

The Effect of Neodymia on the Activity of Hydrocarbon Synthesis Catalysts from Carbon Dioxide

Inrecentyears,ironbasecatalystswereusedforcarbondioxidehydrogenationtolightolefinathighpressure'-'andatnormalpressure,Fe-Cobimetalliccatalystshowsgoodcarbondioxidehydrogenationactivitytolightolefins'6.Althoughhydrocarbonisthermodynamicfavoredthanthatofcarbonmonoxideatlowertemperature,thecatalysisactivityofFe-Cobimetalliccatalystisnothighenoughforhydrocarbonsynthesis.Inthispaper,neodymiawasaddedintothecatalysttoimproveitsactivityandlightolefinselectivity.TheFe-Cobimetalliccatalystswereprepare…     

The Functionality of Surface Hydroxy Groups on the Selectivity and Activity of Carbon Dioxide Reduction over Cuprous Oxide in Aqueous Solutions

Carbon dioxide (CO₂) reduction in aqueous solutions is an attractive strategy for carbon capture and utilization. Cuprous oxide (Cu₂O) is a promising catalyst for CO₂ reduction as it can convert CO₂ into valuable hydrocarbons and suppress the side hydrogen evolution reaction (HER). However, the nature of the active sites in Cu₂O remains under debate because of the complex surface structure of Cu₂O under reducing conditions, leading to limited guidance in designing improved Cu₂O catalysts. This paper describes the functionality of surface‐bonded hydroxy groups on partially reduced Cu₂O(111) for the CO₂ reduction reaction (CO₂RR) by combined density functional theory (DFT) calculations and experimental studies. We find that the surface hydroxy groups play a crucial role in the CO₂RR and HER, and a moderate coverage of hydroxy groups is optimal for promotion of the CO₂RR and suppression of the HER simultaneously. Electronic structure analysis indicates that the charge transfer from hydroxy groups to coordination‐unsaturated Cu (Cu_CUS) sites stabilizes surface‐adsorbed COOH*, which is a key intermediate during the CO₂RR. Moreover, the CO₂RR was evaluated over Cu₂O octahedral catalysts with {111} facets and different surface coverages of hydroxy groups, which demonstrates that Cu₂O octahedra with moderate coverage of hydroxy groups can indeed enhance the CO₂RR and suppress the HER.     

Effect of Substituents of Cerium Pyrazolates and Pyrrolates on Carbon Dioxide Activation

Homoleptic ceric pyrazolates (pz) Ce(RR’pz)₄ (R = R’ = tBu; R = R’ = Ph; R = tBu, R’ = Me) were synthesized by the protonolysis reaction of Ce[N(SiHMe₂)₂]₄ with the corresponding pyrazole derivative. The resulting complexes were investigated in their reactivity toward CO₂, revealing a significant influence of the bulkiness of the substituents on the pyrazolato ligands. The efficiency of the CO₂ insertion was found to increase in the order of tBu₂pz < Ph₂pz < tBuMepz < Me₂pz. For comparison, the pyrrole-based ate complexes [Ce₂(pyr)₆(µ-pyr)₂(thf)₂][Li(thf)₄]₂ (pyr = pyrrolato) and [Ce(cbz)₄(thf)₂][Li(thf)₄] (cbz = carbazolato) were obtained via protonolysis of the cerous ate complex Ce[N(SiHMe₂)₂]₄Li(thf) with pyrrole and carbazole, respectively. Treatment of the pyrrolate/carbazolate complexes with CO₂ seemed promising, but any reversibility could not be observed.     

Effect of the Preparation Conditions on the Phase Composition and Texture of Mesoporous Zirconium Dioxide

Changes in the phase composition and textures of zirconium dioxide depending on the composition of the reaction medium and the conditions of the subsequent hydrothemal and thermal treatment have been elucidated. The conditions for preparing uniformly mesoporous zirconium dioxide with pore sizes of 50-64 have been determined. It has been established that treatment of zirconium dioxide hydrogel in alkaline solutions facilitates the formation of nano-sized particles, stable to agglutination.     

On the Role of Alkali-Metal-Like Superatom Al12P in Reduction and Conversion of Carbon Dioxide

Developing efficient catalysts for the conversion of CO₂ into fuels and value-added chemicals is of great significance to relieve the growing energy crisis and global warming. With the assistance of DFT calculations, it was found that, different from Al₁₂X (X=Be, Al, and C), the alkali-metal-like superatom Al₁₂P prefers to combine with CO₂ via a bidentate double oxygen coordination, yielding a stable Al₁₂P(η²-O₂C) complex containing an activated radical anion of CO₂ (i.e., CO₂^.−). Thereby, this compound could not only participate in the subsequent cycloaddition reaction with propylene oxide but also initiate the radical reaction with hydrogen gas to form high-value chemicals, revealing that Al₁₂P can play an important role in catalyzing these conversion reactions. Considering that Al₁₂P has been produced in laboratory and is capable of absorbing visible light to drive the activation and transformation of CO₂, it is anticipated that this work could guide the discovery of additional superatom catalysts for CO₂ transformation and open up a new research field of superatom catalysis.     

Effect of the Linking Structure of Nonlinear Optical Side Groups on the Phase Behavior of an Aromatic Polyester Backbone

Summary: The phase behavior of poly(p‐phenylene terephthalate)s (PPT) with pendant side groups, N‐(4‐nitrophenyl)ethylaminoethanol (NPE) and N‐(4‐nitrophenyl)‐L ‐prolinol (NPP) has been studied by using differential scanning calorimetry (DSC), wide‐angle X‐ray scattering (WAXS), and second harmonic generation (SHG). PPT‐NPE showed a layered liquid crystalline morphology while PPT‐NPP showed a completely amorphous structure. Compressive or shear stress applied on the polymer melt surface at 210 °C induced a more prominent layered structure of PPT‐NPE whereas the amorphous structure of PPT‐NPP remained unchanged under the stress. In order to understand this phase difference in terms of the repeat structure, we attempted theoretical ab initio Hartree‐Fock, and DFT calculations for the monomers and molecular dynamics for the bulk state. The results indicated that molecular configurations are a good way of microscopically understanding the phases of rigid backbone polymers with functional side groups: The NPT (constant particle number, pressure, and temperature) simulation data at 210 °C agree qualitatively with the experimental data and the difference between PPT‐NPE and PPT‐NPP could be understood using rotational energy barrier, steric hindrance and inter‐chain interactions. X‐ray diffractometer (XRD) simulation patterns for the oligomers are also in qualitative agreement with the experimental WAXS data and the structural parameters of stacks of PPT‐NPE chains are estimated to be layer distance (4.6 Å), backbone distance (21.5 Å), and side distance (12 Å).

     

On the Activation of Methane and Carbon Dioxide by [HTaO]+ and [TaOH]+ in the Gas Phase: A Mechanistic Study

The thermal reactions of [Ta,O,H]⁺ with methane and carbon dioxide have been investigated experimentally and theoretically by using electrospray ionization mass spectrometry (ESI MS) and density functional theory calculations. Although the activation of methane proceeds by liberation of H₂, the activation of CO₂ gives rise to the formation of [OTa(OH)]⁺ under the elimination of CO. Computational studies of the reactions of methane and carbon dioxide with the two isomers of [Ta,O,H]⁺, namely, [HTaO]⁺ and [Ta(OH)]⁺, have been performed to elucidate mechanistic aspects and to explain characteristic reaction patterns.     

烷基芳基磺酸盐结构对微乳液相行为的影响

用Winsor相图法研究了自制的6种不同结构的烷基芳基磺酸盐/不同醇/正癸烷/NaCl/水体系在不同温度下所形成的微乳液。 探讨了烷基芳基磺酸盐结构对微乳液相行为的影响。 同时考察了温度和醇对微乳液相行为的影响。 结果表明,随着烷基芳基磺酸盐长烷基链的增长,中相形成盐度S1、中相消失盐度S2、中相盐宽ΔS和最佳盐浓度S*值均减小,最佳中相体积V*M和最佳增容量σ*值均增大;随着烷基芳基磺酸盐分子的芳环向长烷基链中间位置移动,S1、S2、ΔS、S*值均减小,V*M和σ*值均增大;随着温度升高,V*M和σ*值均减小,S1、S2、ΔS、S*值均增大,在25 ℃时,体系无中相微乳液形成;随着正构醇碳原子数的增加,V*M和σ*值均增大,S1、S2、ΔS、S*值均减小。     

Effect of Chain Length on Enzymatic Hydrolysis of p-Nitrophenyl Esters in Supercritical Carbon Dioxide

The effect of chain length on the enzymatic hydrolysis of various p-nitrophenyl esters was investigated. Specifically, the hydrolysis of various esters p-nitrophenyl butyrate (PNPB), p-nitrophenyl caprylate (PNPC), p-nitrophenyl laurate (PNPL), p-nitrophenyl myristate (PNPM) and p-nitrophenyl palmitate (PNPP) was studied in supercritical carbon dioxide (ScCO₂) with lipase (Novozym 435). This indicates that the conversion of nitrophenyl esters decreases with increasing chain length. The effect of various parameters such as amount of water added, temperature, and enzyme loading was studied. The optimum temperature for the hydrolysis of PNPB and PNPC was 50°C but was 55°C for PNPL, PNPM, and PNPP in ScCO₂. The reactions were also conducted in acetonitrile as the solvent, and it was found that the reactions reach equilibrium much faster in ScCO₂ than in acetonitrile. The kinetics of the hydrolysis reactions were modeled using a Ping Pong Bi Bi model.     

超临界二氧化碳参与的两相体系及其在有机合成反应中的应用

均相催化剂具有催化活性高、选择性好等优点, 但是产物难于纯化、催化剂不易回收等问题一直制约它的应用. 两相体系为这些问题的解决提供了一条新途径. 超临界二氧化碳参与的两相体系是使用超临界二氧化碳作流动相, 其它一些对环境友好的反应介质, 如: 水、离子液体、聚乙二醇等, 用于固定催化剂, 进行金属络合物催化的有机合成反应. 其显著特点是将反应与分离两步操作并于一个过程中完成, 即所谓“均相反应、非均相分离”过程, 实现均相催化过程的连续化. 综述了近几年来超临界二氧化碳促进的两相体系的研究进展, 并介绍其在有机合成反应中的应用.     

无机氧化物载体对催化CO_2与环氧化合物合成环状碳酸酯的促进作用(英文)

以一系列无机氧化物与四丁基溴化铵为双组分催化剂体系,考察了其催化CO2和环氧化合物合成环状碳酸酯的反应性能.结果表明,在四丁基溴化铵与这些本身并没有催化活性的无机氧化物共同作用下,反应活性明显提高,表现出很强的协同催化作用.另外,通过对SiO2的表面硅烷基化,考察了其表面羟基数量对反应活性的影响,发现当SiO2的表面经过硅烷基化以后,反应活性大幅度降低,表明无机氧化物表面羟基对CO2环加成反应活性有非常显著的促进作用.     

A Computational Study on the Mechanism for the K_2CO_3-catalyzed Reaction of Carbon Dioxide and 1-Chlo-2-propanol

The microcosmic reaction mechanism of K2CO3-catalyzed 1-chlo-2-propanol and carbon dioxide has been investigated by density functional theory(DFT) at the GGA/PW91/DNP level.We optimize the geometric configurations of reactants,intermediates,transition states,and products.The energy analysis calculation approves the authenticity of intermediates and transition states.According to our calculations,four feasible reaction pathways are found.The main pathway of the reaction is ReA → IMA1 → TSA1 → IMA2 → IMA5 → TSA5 → P.Besides,we also in-vestigate the reaction mechanism of 1-chlo-2-propanol and carbon dioxide without K2CO3-catalyzation by the same theory and level.The computational results indicate that the activation barrier with K2CO3-catalyzed is smaller than the activation barrier without K2CO3-catalyzed.That is to say,K2CO3 can promote the reaction to give the product in a high yield,which is in agreement with the experimental results.     

Studies on the Adsorption and Dissociation of Methane and Carbon Dioxide on Nickel

The adsorption and dissociation of methane and carbon dioxide for reforming on nickel catalysts were extensively investigated by TPSR, TPD, XPS and pulse reaction methods. These studies showed that the decomposition of methane results in the formation of at least three kinds of surface carbon species on supported nickel catalysts. Carbidic Cα, carbonaceous Cβ and carbidic clusters Cγ surface carbon species formed by the decomposition of methane demonstrated different surface mobility, thermal stability and reactivity. Carbidic Cα is a very active and important intermediate in carbon dioxide reforming with methane, and the carbidic clusters Cγ species might be the precursor of surface carbon deposition. The partially dehydrogenated Cβ species can react with H2 or CO2 to form CH4 or CO. On the other hand, it was proven that CO2 can be weakly adsorbed on supported nickel catalysts, and only one kind of CO2 adsorption state is formed. The interaction mechanism between the species dissociated from CH4 and CO2 during reforming was then hypothesized.     

超临界二氧化碳中聚氨酯吸附小分子的影响因素

研究了超临界ＣＯ２中降压时间以及小分子的溶度参数、亲电性和芳香性等因素对聚氨酯吸附小分子的影响,考察了小分子比蒸发速率对小分子在聚氨酯中解吸的影响。结果表明聚氨酯易于吸附亲电性试剂和多数芳香剂族小分子,通常比蒸发速率大的小分子在聚氨酯中解吸也快。     

二氧化钛薄膜的液相沉积法制备研究

常温下,采用锐钛矿型二氧化钛纳米晶为诱导剂,采用液相沉积法制备了二氧化钛薄膜,采用XRD、SEM、AFM对其晶型、平均晶粒尺寸和形貌进行表征。结果表明,室温所制的二氧化钛薄膜为锐钛矿型,平均粒径为5．8nm,二次粒子平均粒径为10nm,薄膜上观察不到明显的孔洞和裂纹,表面均匀平整,以苯酚的光催化氧化作为目标反应,评价了二氧化钛薄膜的光催化活性。