Products of the initial reduction of the Phillips catalyst by olefins
Products of the initial reduction of the Phillips catalyst by olefins
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菲利普斯催化剂被烯烃初始还原的产物
DOI：
10.1016/j.jcat.2019.07.057
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发表时间：
2019
影响因子：
7.3
通讯作者：
Jentoft, Friederike C.
中科院分区：
文献类型：
--
作者：
Joseph, Jincy;Potter, Kelsey C.;Wulfers, Matthew J.;Schwerdtfeger, Eric;McDaniel, Max P.;Jentoft, Friederike C.
研究了Cr（VI）/二氧化硅与乙烯、丙烯、2-戊烯、1-己烯或环己烯在25 ° C至150 °C之间的温度下反应的有机产物，以了解对聚合具有活性的铬位点的形成。得到了各种各样的产品，直接或通过配体置换或萃取，这取决于具体的烯烃和条件。烃类产物在与商业操作相关的条件下释放，并表明聚合和酸催化：短烯烃低聚物（来自聚合）、烷烃（可能来自氢化物转移）、内烯烃（来自双键转移）和异烷基苯（来自稀释剂苯的骨架异构化和烷基化）。在极性有机萃取介质中发现了醛、酮和醇，一些是萃取介质中羟醛缩合的结果。表面羧酸盐，明显的原位红外光谱，可以从催化剂上分离，只有通过水解。脱附含氧化合物的高阈值意味着铬位点保留自生配体。这些配体的性质取决于还原剂，因此，结果可能是活性或非活性位点。一致地，通过各种烯烃还原Cr（VI）/二氧化硅导致具有不同聚合行为的催化剂，并且向Cr（II）/二氧化硅添加外部配体导致中毒或活性催化剂，这取决于配体。
The organic products of the reaction between Cr(VI)/silica and ethylene, propene, 2-pentene, 1-hexene, or cyclohexene at temperatures between 25 and 150 °C were investigated to understand the formation of chromium sites active for polymerization. A wide assortment of products were obtained, either directly or through ligand displacement or extraction, which depended on the specific olefin and the conditions. Hydrocarbon products were released under conditions relevant to commercial operation and indicated both polymerization and acid catalysis: short olefin oligomers (from polymerization), alkanes (possibly from hydride transfer), internal olefins (from double bond shift) and isoalkylbenzenes (from skeletal isomerization and alkylation of the diluent benzene). Aldehydes, ketones, and alcohols were found in polar organic extraction media, some the result of aldol condensations in the extraction medium. Surface carboxylates, evident by in situ IR spectroscopy, could be detached from the catalyst only through hydrolysis. The high threshold to desorb oxygenates implies that the chromium sites retain self-generated ligands. The nature of these ligands depends on the reductant, and, consequently, the result may be an active or an inactive site. Consistently, reduction of Cr(VI)/silica by various olefins resulted in catalysts with different polymerization behavior, and addition of external ligands to Cr(II)/silica led to a poisoned or to an active catalyst, depending on the ligand.
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DOI：
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发表时间：
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期刊：
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发表时间：
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