Linzhou Zhuang

Structure design of a hyperbranched polyamine adsorbent for CO2 adsorption

An amino-terminated hyperbranched polymer (HBP-NH2) has been prepared through the Michael addition reaction between amines and methyl acrylate (MA) at 0 °C, followed by self-condensation of the addition reaction products at 100 °C and 140 °C. A novel CO2-“imprinted” hyperbranched polymeric adsorbent (IHBPA) with a high amino density was conveniently prepared by using glutaraldehyde to crosslink HBP-NH2 which had pre-adsorbed CO2. Through comparing the adsorption capacities of the IHBPA with HBPA, which was prepared with a similar procedure to that of IHBPA but without CO2 pre-adsorption, it could be found that the pre-adsorbed CO2 on HBP-NH2 would occupy the reactive sites of amino groups, and play the role of “imprinting” in the preparation of the adsorbent. The adsorption capacity of the IHBPA could thus be improved. After reducing the imino groups of the IHBPA to alkyl amine by NaBH4, the adsorption capacity of the reducing solid amine adsorbent (IHBPA-R) can be further improved. The prepared solid amine adsorbents also showed promising regeneration performance, which could maintain almost the same adsorption capacity for CO2 after 10 adsorption and desorption recycles. The high CO2 adsorption capacity (7.65 mmol g−1) of IHBPA-R can be attributed to its high amino density, terminal amine and hyper-branched structures.

Design of a viscose based solid amine fiber: effect of its chemical structure on adsorption properties for carbon dioxide.

A solid amine fiber VF-AM-TETA was designed with viscose (VF) substrate for efficient CO2 capture, where its hydroxyl groups could serve synergizing effect in CO2-amine reaction. When grafting modification and subsequent amination were applied to VF, effect of structures of grafting monomers as well as amines on its CO2 adsorption properties was taken into account. Amines with different 1° and 2° amine ratios were investigated as amination agents in terms of amine efficiency, so as to afford the fibrous adsorbent with maximum effective reactive amine sites for CO2 capturing. Results suggested that higher content in primary amine can facilitate CO2 adsorption onto the fiber by stronger basicity and smaller steric hindrance. Consequently, optimal chemical structure provided VF-AM-TETA with satisfactory adsorption capacity of 4.08 mmol/g when amine content was 8.74 mmol/g. Constant adsorption behavior within 6 adsorption-desorption cycles indicated its desirable regeneration performance in practical use due to excellent mechanical properties of VF-AM-TETA.

Magnetism and high magnetic-field-induced stability of alloy carbides in Fe-based materials

Understanding the nature of the magnetic-field-induced precipitation behaviors represents a major step forward towards unravelling the real nature of interesting phenomena in Fe-based alloys and especially towards solving the key materials problem for the development of fusion energy. Experimental results indicate that the applied high magnetic field effectively promotes the precipitation of M23C6 carbides. We build an integrated method, which breaks through the limitations of zero temperature and zero external field, to concentrate on the dependence of the stability induced by the magnetic effect, excluding the thermal effect. We investigate the intimate relationship between the external field and the origins of various magnetics structural characteristics, which are derived from the interactions among the various Wyckoff sites of iron atoms, antiparallel spin of chromium and Fe-C bond distances. The high-magnetic-field-induced exchange coupling increases with the strength of the external field, which then causes an increase in the parallel magnetic moment. The stability of the alloy carbide M23C6 is more dependent on external field effects than thermal effects, whereas that of M2C, M3C and M7C3 is mainly determined by thermal effects.

Author Correction: Magnetism and high magnetic-field-induced stability of alloy carbides in Fe-based materials

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Preparation and Properties of A Hyperbranch-Structured Polyamine adsorbent for Carbon Dioxide Capture

A fibrous adsorbent with amino-terminated hyperbranch structure (PP-AM-HBP-NH2) was prepared by grafting hyperbranched polyamine (HBP-NH2) onto the acrylamide-modified polypropylene (PP) fibers. The grafting of AM on PP fibers provided the active sites for introducing HBP-NH2 onto the PP fibers. This kind of “grafting to” procedure to synthesize hyperbranch-structured fiber could overcome the disadvantages of stepwise growth procedure, avoiding the complicated synthesis process and the requirement of strict experimental conditions. The grafted HBP-NH2 was three-dimensional dentritic architecture and had a large number of pores existing within the grafted polymers, which is favorable for CO2 molecules to diffuse into the HBP-NH2. Therefore, the as-prepared PP-AM-HBP-NH2 fibers showed a high adsorption capacity (5.64 mmol/g) for CO2 in the presence of water at 25 °C, and the utilization efficiency of alkyl amino groups could reach 88.2%, demonstrating that the hyperbranched structure of adsorbents can greatly promote adsorption capacity and efficiency. This could be attributed to better swelling properties and lower mass transfer resistance to CO2 of the hyperbranched adsorbent. PP-AM-HBP-NH2 also showed excellent regeneration performance, and it could maintain the same adsorption capacity for CO2 after 15 recycle numbers as the fresh adsorbent.