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991.
Akihiro Hayakawa Yuta Hirano Ekenechukwu C. Okafor Hirofumi Yamashita Taku Kudo Hideaki Kobayashi 《Proceedings of the Combustion Institute》2021,38(2):2409-2417
Ammonia has widely attracted interest as a potential candidate not only as a hydrogen energy carrier but also as a carbon free fuel for internal combustion engines, such as gas turbines. Because ammonia contains a nitrogen atom in its molecule, nitrogen oxides (NOx) and other pollutants may be formed when it burns. Therefore, understanding the fundamental product gas characteristics of ammonia/air laminar flames is important for the design of ammonia-fueled combustors to meet stringent emission regulations. In this study, the product gas characteristics of ammonia/air premixed laminar flames for various equivalence ratios were experimentally and numerically investigated up to elevated pressure conditions. In the experiments, a stagnation flame configuration was employed because an ammonia flame can be stabilized by using such a configuration without a pilot flame. The experimental results showed that the maximum NO mole fraction was about 3,500 ppmv, at an equivalence ratio of 0.9 at 0.1 MPa. The NO mole fraction decreased as the equivalence ratio increased. In addition, the maximum value of the NO mole fraction decreased with an increase in mixture pressure. Furthermore, it was experimentally clarified that the simultaneous reduction of NO and unburnt ammonia can be achieved at an equivalence ratio of about 1.06, which is the target equivalence ratio for emission control in rich-lean two-stage ammonia combustors. Comparison of experimental and numerical results showed that even though the reaction mechanisms employed have been optimized for predicting the laminar burning velocity of ammonia/air flames, they failed to satisfactorily predict the measured species in this study. Sensitivity analysis was used to identify elementary reactions that control the species profiles but have negligible effects on the burning velocity. It is considered that these reaction models need to be updated for accurate prediction of product gas characteristics of ammonia/air flames. 相似文献
992.
Masanari Kimura Hidetaka Fujimatsu Akihiro Ezoe Kazufumi Shibata Masamichi Shimizu Satoru Matsumoto Yoshinao Tamaru 《Angewandte Chemie (International ed. in English)》1999,38(3):397-400
Regio‐ and stereoselective homoallylation of saturated aldehydes and ketones to give bishomoallyl alcohols 1,3‐anti‐ 1 is achieved with [Ni(acac)2] (cat.) and Et2Zn [Eq. (a)]. This new catalyst system thus complements the previously reported combination of [Ni(acac)2] with Et3B, which offers advantages in the homoallylation of unsaturated and aromatic aldehydes. acac=acetylacetonato. 相似文献
993.
Kuiling Ding Akihiro Ishii Koichi Mikami 《Angewandte Chemie (International ed. in English)》1999,38(4):497-501
The most effective catalyst system for the enantioselective alkylation of an aldehyde on the basis of “asymmetric activation” can be found by super high throughput screening of chiral ligands (L*) and activators (A*) for the diethylzinc complex. The product, an optically active alcohol, could be obtained with 99% ee and in up to 100% yield (see reaction scheme). R=benzylidene. 相似文献
994.
James C. W. Chien Yasumasa Iwamoto Marvin D. Rausch 《Journal of polymer science. Part A, Polymer chemistry》1999,37(14):2439-2445
Isotactic polypropylene (i-PP) and syndiotactic polypropylene (s-PP) obtained with single-site C2- and Cs-symmetric zirconocenes, respectively, activated with triphenyl carbenium tetrakis(pentafluorophenyl)borate (3) are immiscible with one another. Physical mixture of the two PPs is macrophase separated and crystallizes very slowly as is characteristic of s-PP. A solution of C2- and Cs-symmetric zirconocenes with 3 also produces an incompatible mixture of i-PP and s-PP. However, in the presence of an excess of a crossover agent such as triisobutylaluminum (TIBA), a new polymeric material is obtained that exhibits lower Tm and ΔHf than either of the two homosteric polymers and a much faster rate of crystallization than that of s-PP or its physical mixture with i-PP. Thermal annealing of this product markedly reduces the relative amount of crystalline phase compared to the amorphous phase and atomic force microscopy finds only microphase separation but not macroscopic phase separation. Fractionation and 13C-NMR showed the material to contain not only the homosteric i-PP and s-PP but also a stereoblock PP (i-PP-b-s-PP). The stereoblock fraction acts as a compatibilizing agent; it probably is produced by the exchange of propagating polymer chains between the syndiospecific and the isospecific sites assisted by the crossover agent. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2439–2445, 1999 相似文献
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998.
Akihiro Abe 《Macromolecular Symposia》1997,118(1):23-32
The conformation of chain molecules participating variously in the formation of liquid crystalline mesophase has been elucidated. Two examples are mentioned: (1) the side chain flanking the α-helical backbone of polypeptides, and (2) the spacer joining mesogenic units in mainchain liquid crystals. Flexible segments play an important role in determining thermodynamic properties of these systems. 相似文献
999.
Seiichi Tokura Norio Nishi Kiyohisa Takahashi Akihiro Shirai Yasumitsu Uraki 《Macromolecular Symposia》1995,99(1):201-208
A porous chitin foam was regenerated from chitin dope in calcium chloride dihydrate saturated methanol. The porous chitin foam was shown to have cationic property, because chitin foam tended to adsorb anionic dyes through ionic binding and hydrophobic interaction. A pendant type of polymeric drug was prepared applying peptide spacer composed of phenylalanine at amino end and two step hydrolyses of polymeric drug were shown to release active drug at the final step using lysozyme and chymotrypsin in vitro. 相似文献
1000.