Coke Formation and Characterization During 1-Hexene Isomerization and Oligomerization over H-ZSM-5 Catalyst under Supercritical Conditions
Coke Formation and Characterization During 1-Hexene Isomerization and Oligomerization over H-ZSM-5 Catalyst under Supercritical Conditions
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DOI：
10.1021/ie801466d
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发表时间：
2009-09
影响因子：
4.2
通讯作者：
Jiawei Wang;Faiza Hassan;Peter I. Chigada;S. Rigby;B. Al-Duri;J. Wood
中科院分区：
文献类型：
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作者：
Jiawei Wang;Faiza Hassan;Peter I. Chigada;S. Rigby;B. Al-Duri;J. Wood
在亚临界和超临界条件下，在220 - 250 °C的温度范围和10 - 70 bar的压力范围内，在下流式固定床反应器中，在ZSM-5催化剂上研究了1-己烯的异构化和低聚。催化剂的活性和产物的选择性被发现依赖于操作条件。反应在具有10和0.5g催化剂的床上进行，较小的床用于模拟较大床的顶层中的焦化。1-己烯在10 g催化剂床上的转化率在83 - 99%的范围内，这取决于操作条件，并且在试验期间是稳定的。反应温度从220 - 250 °C升高导致更高的低聚选择性，反应压力在10 - 70巴范围内升高也是如此。沉积在催化剂上的焦炭的量从在亚临界区域中在235 °C和10巴下的18.8重量%降低到在超临界区域中在235 °C和40巴下的10.4重量%。DRIFTS表明沉积焦主要是聚烯烃。氮吸附表明，在较短的接触时间内初始浅孔填充后，孔隙口随后被堵塞，焦炭主要在沸石微晶的外部形成。当用0.5g催化剂操作时，在亚临界条件下发生一些失活，尽管在超临界条件下没有。似乎在较小的催化剂质量下，低聚物保留在ZSM-5的孔结构内。研究的结果表明，操作温度和压力的调节可以用来调整反应的产物选择性，并且通过在超临界条件下操作来减少沉积在催化剂上的焦炭的总量。
The isomerization and oligomerization of 1-hexene was studied over ZSM-5 catalyst under sub- and supercritical conditions within a down-flow fixed bed reactor in the temperature range of 220−250 °C and pressure range 10−70 bar. The catalyst activity and the product selectivity were found to be dependent on the operation conditions. Reactions were carried out over beds with 10 and 0.5 g catalyst, the smaller bed being used to simulate coking in the top layer of the larger bed. The conversion of 1-hexene over the 10 g bed of catalyst was in the range 83−99%, depending upon the operating conditions and was stable during the test period. An increase of the reaction temperature from 220−250 °C led to higher selectivity toward oligomerization, as did increases in reaction pressure in the range 10−70 bar. The amount of coke deposited on the catalysts decreased from 18.8 wt % at 235 °C and 10 bar in the subcritical region to 10.4 wt % at 235 °C and 40 bar in the supercritical region. DRIFTS showed that deposited coke is mainly polyolefinic. Nitrogen sorption showed that following initial shallow pore filling over shorter contact times, the pore mouth subsequently became blocked and coke mainly formed on the outside of the zeolite crystallites. When operating with 0.5 g catalyst, some deactivation occurred under subcritical conditions, although not under supercritical conditions. It appeared that with the smaller catalyst mass oligomers were retained within the pore structure of ZSM-5. The results of the study demonstrate that adjustment of the operating temperature and pressure can be used to tune the product selectivity of the reaction and the total amount of coke deposited upon the catalyst is reduced by operating under supercritical conditions.