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1.
何乐芹  张贵琴  边丽 《河北工业科技》2009,26(3):140-143,155
以γ-氨丙基三乙氧基硅基烷对MCM-41修饰,得到氨基修饰的MCM-41,进而通过接枝法将手性Salen-Mn(Ⅲ)配合物固载在介孔分子筛MCM-41上,制备了MCM-41负载的带隔离基团的C2-不对称Salen-Mn(Ⅲ)催化剂。分别利用FT-IR和DR UV-Vis等手段对负载催化剂进行了表征。以NaClO为氧化剂,考察了该负载Salen-Mn(Ⅲ)配合物催化非官能化烯烃不对称环氧化反应的性能及循环使用性能。  相似文献   

2.
采用化学键联和溶胶-凝胶相结合的方法制备锚链固定的多相化Salen-Mn(Ⅲ)催化剂,利用FT-IR,UV-vis,1H NMR等方法对催化剂及其前体进行表征。考察了该催化剂催化烯烃不对称环氧化反应及其循环使用的性能,实验发现,多相化催化剂催化活性有所降低,但延长了反应时间后,催化顺-β-甲基苯乙烯不对称环氧化的转化率达到95%,其环氧化产物的对映体过量值(ee值)为60%。  相似文献   

3.
在现今的科研领域中,针对有机催化的不对称合成反应是主要的研究热点,不对称Michele加成反应是大量手性合成子以及药物中间体的合成的重要方式。现今已有催化Michale加成反应的有机催化剂主要有脯氨酸及其衍生物、手性咪唑啉酮以及金鸡纳碱衍生物等。文章对多种有机催化剂在催化不对称Michael加成反应中的使用、不对称诱导反应的作用机制、催化剂分子结构、作用反应条件对催化活性以及不对称诱导作用的影响等方面进行了综述,期望为后续研究带来一定的参考。  相似文献   

4.
中石化石油化工科学研究院在传统水热合成TS-1分子筛的基础上,自主开发了TS-1分子筛重排改性工艺。该工艺具有制备重复性好的优点,经重排改性后的TS-1分子筛晶粒具有空心结构(商品牌号为HTS),催化苯酚羟基化反应的活性可提高2—4倍,催化环己酮氨肟化反应的活性亦有大幅度提高,且已成功应用于巴陵石化公司己内酰胺的工业化生产中。石油化工科学研究院在HTS用于催化丙烯环氧化反应的研究中,考察了成型黏结剂、反应温度对HTS催化丙烯环氧化反应的影响。  相似文献   

5.
日本出光公司采用金属茂催化剂成功合成一种新型的液态高级烯烃,这种新物质是一种碳原子数达20以上的高碳烯烃,在室温下为液态,可以在低温下使用,该烯烃挥发性低,可用于诸如环氧化等反应的一系列改性。  相似文献   

6.
着重介绍了L-脯氨酸催化不对称直接Aldol反应的特点及反应类型,认为L-脯氨酸及其类似物催化的不对称直接Aldol反应不仅具有理论上的研究价值而且具有潜在的工业化前景。  相似文献   

7.
对近些年来L脯氨酸(LProline)等6类有机小分子催化剂催化不对称直接Aldol反应的特点、实用范围及结果作了详细介绍,认为该领域具有广阔的发展前景。  相似文献   

8.
烯烃聚合反应是石油化工中的基础化学反应,催化剂在此类反应中尤其重要,而吡啶二亚胺铁配合物正是此类催化剂中的重要的一类,本文主要介绍吡啶二亚胺铁配合物的专利研究进展及其修饰方法,有助于更全面的了解吡啶二亚胺铁配合物及进一步进行研究。  相似文献   

9.
脯氨酸催化的直接不对称Michael反应   总被引:2,自引:1,他引:2  
综述了脯氨酸催化的直接不对称Michael反应的研究进展,包括脯氨酸作为催化剂在有机溶剂、离子液体溶剂条件下的反应以及脯氨酸催化的放大效应;介绍了脯氨酸衍生物作为催化剂的Michael反应,以及脯氨酸催化的Michael反应与其他反应的复合反应等。  相似文献   

10.
聚丙交酯(或聚乳酸)是一种可降解的塑料,符合环境友好的要求,而稀土金属配合物在催化丙交酯开环聚合方面具有活性高、反应条件温和、副反应少、残余催化剂无毒害等优势。文章从专利文献和非专利文献两方面分别进行了梳理,并从稀土金属配合物本身的特点出发分析了其产业化中存在的问题以及可能的解决途径。  相似文献   

11.
This study advances the proposition that applying core tenets of complexity theory is useful for solving the “crucial problem” in strategic management—describing, explaining, and predicting firm heterogeneity. The study describes the core tenets (e.g., the necessity of constructing models for cases with relationship reversals to a significant main effect—cases occur whereby both high and low scores of an antecedent condition indicate high scores in an outcome condition; asymmetric models are necessary because the causes of successful outcomes are not the mirror opposite of the causes of unsuccessful outcomes). Constructing “somewhat precise outcomes models” (SPOM) rather than null hypothesis statistical testing (NHST) is the principal analytic tool. The study describes asymmetric models of implemented strategy and competitive advantage for ROE, negation of ROE, and complex outcome statements for agribusiness firms (n = 247) across seven Latin America national as well as tests the predictive validities of models across specific nations for the models of sampled firms within Costa Rica, El Salvador, Guatemala, and Nicaragua. The findings support the propositions that constructing complex antecedent statements (i.e., algorithms/configurations/recipes/screens) are useful for indicating high performance or the negation of high performance consistently. Configural implemented strategy models have direct influences on both high and low performance outcomes, while competitive advantage models impact low, but not, high performance outcomes. Complex competitive advantage conditions contribute indirectly to high performance outcomes.  相似文献   

12.
The objective of this study is to examine asymmetric rivalry between strategic groups in a given industry. Two research hypotheses argue for the existence of asymmetric rivalry in the sense that strategic groups of small companies have a greater degree of response but a slower speed of response to the actions of strategic groups of large companies, than vice versa. To test this, we use an ex post approach that examines the news releases published on the strategic actions and reactions of firms. A third hypothesis compares ex ante competitive expectations with ex post asymmetric rivalry between strategic groups. To test this, we compare ex post news on actions/reactions with an ex ante approach that estimates conjectural variations. The empirical application carried out on bank deposits in the Spanish market defines strategic groups in terms of size due to the historical and institutional conditions of the industry (deregulatory change). The results obtained show that rivalry patterns between strategic groups in terms of company size can be predicted as asymmetric in the sense that smaller bank strategic groups have a greater degree of response (Stackelberg ‘leader–follower’ competitive interaction), and a slower speed of response to the actions of larger bank strategic groups than is found the other way around. Moreover, ex ante expectations of aggressiveness on the part of larger strategic groups characterize greater ex post reactions from the smaller‐size strategic groups. Therefore, the size distribution of strategic groups is valuable to research on complex industries with deregulation changes. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

13.
The purpose of this paper is to analyse the relationship development stages of asymmetric customer–supplier relationships. The structure of relationships between larger customers and smaller suppliers has been the focus of a number of studies in IMP (Industrial Marketing and Purchasing Group) research. But, there is a paucity of research that examines development stages in relationships where a difference in size between the parties exists. The paper links the characteristics of asymmetric customer–supplier relationships and the relationship development stages through a literature review. The findings from a set of five in-depth case studies of asymmetric customer–supplier relationships in the Taiwanese electronics industry are presented. The case studies involved 50 semi-structured interviews with customer and supplier executives and, in addition, multiple observations of customer–supplier interactions within each case study. Individual and cross-case analysis was conducted to examine the links between the characteristics of asymmetric customer–supplier relationships and relationship development stages. The findings revealed that asymmetric customer–supplier relationships in the Taiwanese electronics industry were very unbalanced and vulnerable in the exploratory stage of development. In the developing stage relationships were more likely to develop if suppliers and customers mirrored each other's behaviour and echoed each other's priorities. In the stable stage suppliers and customers worked on shared and balanced contributions to the relationship. The paper contributes to the understanding of how smaller suppliers and larger customers can identify and develop key sets of relationship characteristics through the exploratory, developing and stable stages of asymmetric relationship development from both customer and supplier perspectives.  相似文献   

14.
对过氧化氢氧化丙烯制备环氧丙烷工艺进行了初步设计,运用软件建立了丙烯环氧化工序的全流程模型,并对主要的塔设备进行了模拟计算和参数优化,对全流程进行了模拟计算。经计算得到的模拟结果对过氧化氢氧化丙烯制备环氧丙烷工艺的工业化有一定的参考价值。  相似文献   

15.
Previous literature has shown that potential buyers use a reference price or product to form their opinion about the value of a new product. Therefore, the pricing decision is an interactive process. We investigate the two generalizations of the cross-price effect (the neighborhood price effect and the asymmetric price effect) on consumer willingness-to-pay (WTP) for multiple similar products in an open-ended contingent valuation context. Results show that the cross-price effect on WTP is prominent, with the neighborhood price effect holding in contingent valuation. No conclusions are reached about the asymmetric price effect.  相似文献   

16.
This study investigates the use of private rules in exercising power in asymmetric business relationships. In asymmetric business relationships, the stronger party is likely to be able to dominate and exercise power over the conclusion of contracts and, thereby determine the processes and outcomes of the relationship. The study demonstrates how companies exercise their power in asymmetric relationships through private rules. Private rules are typically expressed in the General Terms and Conditions of Trade (GTCT) of the more powerful actor in a business relationship and are continually adapted to changing business and market requirements. Drawing on an empirical investigation in the German grocery retail business conducted in the years between 2011 and 2013, the present study demonstrates that power is exercised by the stronger parties through intervention–enforcement–sanctioning practices that are codified in private rules. Private rules frame, standardize and legitimize the terms and conditions under which exchanges among counterparts may take place thus institutionalizing the inherent power asymmetry.  相似文献   

17.
This study examines the supply response of the Greek beef market and the possible effect of the European Union’s Common Agricultural Policy (CAP) on the Greek beef sector during the period 1993–2005. A Generalized Autoregressive Conditional Heteroskedasticity (GARCH) process is used to estimate expected price, and price volatility, while several different symmetric, asymmetric and non-linear GARCH models are estimated. The empirical results show that price volatility and feed price are important risk factors in the supply response function, while the negative asymmetric price volatility that was detected implies that producers have a weak market position. Furthermore, the empirical findings confirm that the annual premium paid by the EU to beef producers had a positive impact on the production level and also, the change of the EU price support regime, after 2006, is having negative effects on beef production level in Greece.  相似文献   

18.
为了分析管理层盈余预测对盈余不对称及时性之间的关系,即发布消息的时间点和内容分类对盈余不对称及时性的影响,用Basu模型分段实证检验盈余预测对盈余不对称及时性的影响、正(负)向盈余预测与不对称及时性的关系,以及当期发布的盈余预警对盈余不对称及时性的影响。结果表明,不对称及时性对公司发布的未来盈余的影响不显著,公司发布预期盈余的时间及时性主要集中在负向盈余意外,这与价格引导盈余引起更多的未来盈余预测的向下有偏的不对称及时性系数相一致,当期发布盈余预警会降低盈余与收益的不对称及时性。管理层发布内部盈余预测,有助于缓解与外部信息使用者之间的信息不对称,满足利益相关者的决策需求,进而有助于促进证券市场向半强式有效市场转化。  相似文献   

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