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众所周知,人们在理想完好的单晶表面上的动力学研究已取得了很大的成功[1],然而对许多实际催化剂来说,传统催化理论和实验之间不符的情况仍然俯拾皆是.现在人们对造成这种情况的原因已经有了更加深入的认识:大量的实验事实表明,在表面催化反应体系中,不但催化剂表面具有复杂的分形结构,而且催化剂表面上的活性中心分布也具有复杂的分形特性[2].“分形”是指那些具有分数维数的几何对象.这些对象往往是不规则的,不能用通常的欧氏几何来描述[3].将分形引入催化科学中最早的是Pfeifer和Avnir等[4]人,至今已有近二十年的历史,现… 相似文献
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用XRD技术从定性和定量上对ZrO_2,特别是超强酸催化剂的物相和四方相ZrO_2的含量进行了详细的考察。结果表明,的引入使的晶化温度比ZrO_2大约提高了100K,并且使亚稳态四方相ZrO_2得以稳定。亚稳态四方相ZrO_2的含量主要受处理液浓度和焙烧温度的影响。处理液浓度越大,四方相含量越高;焙烧温度越高;四方相含量越低。强酸性的H_2SO_4溶液比弱酸性的(NH_4)_2SO_4溶液对四方相的生成更有利。在无定形ZrO_2、四方相ZrO_2和单斜相ZrO_2上的稳定性依次减小。 相似文献
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A new process of low-temperature methanol synthesis from CO/CO2/H2 based on dual-catalysis has been developed. Some alcohols, especially 2-alcohol, were found to have high catalytic promoting effect on the synthesis of methanol from CO hydrogenation. At 443 K and 5 MPa, the synthesis of methanol could process high effectively, resulting from the synergic catalysis of Cu/ZnO solid catalyst and 2-alcohol solvent catalyst. The primary results showed that when 2-butanol was used as reaction solvent, the one-pass average yield and the selectivity of methanol, in 40 h continuous reaction at temperature as low as 443 K and 5 MPa, were high up to 46.51% and 98.94% respectively. The catalytic activity was stable and the reaction temperature was 80 K or so lower than that in current industry synthesis process. This new process hopefully will become a practical method for methanol synthesis at low temperature. 相似文献
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液态及超临界CO_2萃取八角茴香油的研究 总被引:14,自引:0,他引:14
本文用液态及超临界CO_2对八角茴香油进行了萃取研究,在萃取压力为20.0~25.0MPa的条件下,详细地考察了临界温度上下萃取温度和解析温度对出油率和油的表观相态的影响,结果表明,萃取温度越高和/或解析温度越低出油率越低;用液体CO_2萃取比用超临界CO_2萃取的出油率要高得多;萃取温度大约在318K以下或解析温度在临界温度以下时,萃取所得八角茴香油都有明显分层现象. 相似文献
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