Showing papers by "Gongying Wang published in 2022"

The effect of modifying group on the acid properties and catalytic performance of sulfonated mesoporous polydivinylbenzene solid acid in the Bisphenol-A synthesis reaction

Abstract: A series of sulfonated mesoporous polydivinylbenzene solid acids were prepared with various ways. The effect of sulfonation method and modifying group on the acid properties and catalytic performance of these solid acids was studied with the synthesis of Bisphenol-A as a probe reaction. The characterization results revealed that post sulfonation method was beneficial for grafting more sulfonic acid groups to improve the acid densities of sulfonated mesoporous polydivinylbenzene solid acids. In particular, for sulfonated mesoporous polydivinylbenzene modified by different groups, the electron withdrawing groups could enhance the acid strength of sulfonated mesoporous polydivinylbenzene. Then the strong acid sites not only had high catalytic efficiency but also were beneficial for producing target product Bisphenol-A to improve the selectivity. Trifluoromethanesulfonyl modifying sulfonated mesoporous polydivinylbenzene solid acid (PDVB-SO2CF3-SO3H) had the strongest acidity and optimal catalytic behavior. The phenol conversion of 36% (phenol theoretical conversion of 40%) and the Bisphenol-A selectivity of 90% were obtained at 90 °C for 4 h. In addition, PDVB-SO2CF3-SO3H had excellent reusability and could be reused at least 6 times. This work highlighted the effect of modifying groups with different electronic effects on the acidity of the sulfonated mesoporous polydivinylbenzene, and provided methods and references for regulating the acidity of other polymer solid acids.

The effect of alkali metals doping on properties of CuMgCe for isobutanol synthesis from syngas

Abstract: Four types of alkali metals Li, Na, K and Cs carbonate doped CuMgCe catalysts were prepared by an incipient wetness impregnation method, and the effect of alkali metals doping on the catalytic performance of catalyst for isobutanol synthesis from syngas was studied. Only the doping of K and Cs improved isobutanol selectivity, and the catalytic performance of K-CMC was better. All the catalysts characterized by XRD, BET, SEM, TEM, XPS, H2-TPR, CO-TPD, CO2-TPD and NH3-TPD to further reveal the effect of alkali metals on catalysts for isobutanol synthesis. We found that the alkali metals doping reduced the reducibility of the catalysts, but increased the strength and density of basic sites and reduced the density of acidic sites, thereby leading to diverse catalytic performance of the catalysts for isobutanol synthesis. Compared with K-CMC, the insufficient performance of Cs-CMC was attributed to CO2 oxidation of Cu and CO2 neutralization of basic sites.

Controlled synthesis of aliphatic polycarbonate diols using dimethyl carbonate and various diols

Abstract: Polycarbonate diols (PCDLs) are mainly used as soft segments for the synthesis of high-performance polyurethanes. In this work, dimethyl carbonate (DMC) and aliphatic diols are selected as reactants and CH3COONa is used as a catalyst to synthesize a series of PCDLs with different structures and different molecular weights by ester exchange polymerization reaction. The chemical structures of the PCDLs are characterized by FT-IR, 1H NMR, and 13C NMR, and the components of the distillates in the ester exchange stage are analyzed by gas chromatography. Due to the azeotropic problem of DMC and by-product methanol during the ester exchange process, It is difficult to design and control the reactions of PCDLs to obtain the target molecular weight products. Based on the reaction process of PCDLs, we proposed a method to design and synthesize the target molecular weight of PCDLs by using the reaction molar ratio of DMC and aliphatic diols involved in the transesterification reaction, which is not affected by the conditions of transesterification reaction and is applicable to the reactions of DMC with various diols.

Preparation of poly(melamine‐formaldehyde‐2,2′‐bis(trifluoromethyl)benzidine) high‐performance fibers

Abstract: Melamine formaldehyde fiber is widely used in various fields because of its excellent heat resistance and flame-retardant properties. In this study, melamine and paraformaldehyde are used as the main raw materials, 2,2′-bis(trifluoromethyl)benzidine (TFMB) is successfully introduced into the molecular chain. The TFMB modified spinning solutions (MF-TFMB) are obtained by one-step copolymerization, the TFMB-modified melamine-formaldehyde fibers (MFF-TFMB) are prepared by dry spinning. The surface contact angle and surface energy are measured by a contact angle measuring instrument. The thermal stability and mechanical properties of the fibers are measured by a thermogravimetric analyzer and a single-fiber strength tester. The results show that the introduction of the TFMB group reduces the surface free energy of the polymer and effectively improves the heat resistance and mechanical properties of the fiber. When the addition amount of TFMB is 3%, the MFF-TFMB-3% fiber has smooth surface and bubble-free inside, the breaking strength is 2.25 cN/dtex and the elongation at break is 11.85%. The limiting oxygen index is 32.5%, and the mass loss rate is decreased from 63.88% to 51.36% at 400°C. The fiber has excellent thermal stability and flame-retardant properties.

An Efficient Thiol and Trifluoromethanesulfonyl Difunctional Sulfonated Mesoporous Polydivinylbenzene Solid Acid: Cooperative Effect of Steric Hindrance and Acidity

Abstract: For acid-catalyzed chemical reactions with forming isomers of the target product, the isomer by-products cannot be well inhibited only by adjusting the acid properties. At this point, it is an effective strategy to design functional acid catalysts to decrease by-products through increasing the steric hindrance of forming isomer by-products. In this paper, thiol and trifluoromethanesulfonyl functional sulfonated mesoporous polydivinylbenzene solid acids were prepared. The Bisphenol-A synthesis reaction was used as a probe reaction to verify the cooperative effect of thiol and trifluoromethanesulfonyl on the catalytic performance of prepared solid acids. The results confirmed that thiol functionalizing sulfonated mesoporous polydivinylbenzene solid acid could reduce the by-product o′p-bisphenol-A through steric hindrance effect and then improved the selectivity of the target product p′p-bisphenol-A. Trifluoromethanesulfonyl functionalizing sulfonated mesoporous polydivinylbenzene could promote the catalytic efficiency and the selectivity of p′p-bisphenol-A by enhancing the acidity of solid acids. Thiol and trifluoromethanesulfonyl difunctional sulfonated mesoporous polydivinylbenzene (PDVB-SO2CF3-SO3H-SH) had the optimal catalytic performance due to the cooperative effect of steric hindrance and strong acidity. The phenol conversion of 37 % and the p′p-bisphenol-A selectivity of 97 % were obtained over PDVB-SO2CF3-SO3H-SH under 90 °C for 4 h.

Synthesis and properties of high performance thermoplastic polycarbonate polyurethane elastomers through a non-isocyanate route

Abstract: Thermoplastic polycarbonate polyurethane elastomers (TPCUEs) are synthesized through a solvent-free non-isocyanate melt polycondensation route. The route starts with the synthesis of 1,6-bis(hydroxyethyloxycarbonylamino)hexane (BHCH) from ethylene carbonate and 1,6-hexanediamine, and then the TPCUEs are prepared by the melt polycondensation of BHCH and polycarbonate diols (PCDLs). The TPCUEs are characterized by GPC, FT-IR, 1H NMR, XRD, AFM, DSC, TGA and tensile testing. The TPCUEs prepared have linear structures and high molecular weights, with Mn over 3.0 × 104 g mol−1. And these TPCUEs exhibit excellent thermal and mechanical properties, with Tg ranging from −18 to −1 °C, Tm ranging from 93 to 122 °C, Td,5% over 240 °C, tensile strength between 28.1–47.3 Mpa, elongation at break above 1000%, Young's modulus between 13.8–32.7 Mpa and resilience at 200% fixed-length between 70–90%, which makes them a promising alternative to products synthesized through the isocyanate route. In addition, the effects of the hard segment contents and the molecular weights of soft segment on the properties of TPCUEs are researched.

MIL-53(Al) catalytic synthesis of poly(ethylene terephthalate)

Abstract: Poly(ethylene terephthalate) (PET) is one of the world's five major engineering plastics and is widely used in various fields. At present, the main catalysts used in the synthesis of PET are antimony, titanium, and aluminum metal compounds. Among them, antimony-based catalysts are poisonous and the titanium-based catalyst products are relatively yellow in hue. The aluminum-based catalyst has the advantages of low price and environmental friendliness, but current research shows that the organoaluminum catalyst has the problem of hydrolysis, and MIL-53 (Al) has good stability and will not affect the environment, so we add a catalyst before the esterification reaction, and uses thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM), and N2 low-temperature physical adsorption characterizes the thermal stability and structure of MIL-53(Al). At the same time, the effects of different content, polycondensation time, before and after activation and polycondensation temperature on the properties of PET were investigated. The research results show that when the molar content of catalyst is 0.05% and the reaction temperature is 280 oC for 150 min, the product obtained is relatively excellent. The catalytic activity has almost no effect before and after activation, indicating that the polycondensation reaction is carried out on the surface of the catalyst. Therefore, MIL-53 (Al) has great potential in PET industrial catalysis.

Gradient Concentration Control of Active Components on the Industrial Cs-P/γ-Al2O3 Catalyst

Abstract: For supported catalysts, it is particularly important to ensure the effective loading of the active component on the support. A new industrial Cs-P/γ-Al2O3 catalyst with controllable distribution of active components was developed and applied to the aldol condensation reaction of methyl propionate and formaldehyde. The distribution of active components was controlled by adjusting the preparation conditions, especially the adsorption time, to form the catalyst with a gradient concentration of active components, which had been confirmed by the EMPA and SEM-EDS characterization. In addition, the kinetic equations including pseudo-first- and pseudo-second-order kinetic models as well as isotherm equations based on Freundlich and Langmuir models were used to describe the adsorption process to provide valuable process parameters for industrial production of catalysts.