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首页> 外文期刊>Fuel >Initial coke deposition on hydrotreating catalysts. Part II. Structure elucidation of initial coke on hydrodematallation catalysts
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Initial coke deposition on hydrotreating catalysts. Part II. Structure elucidation of initial coke on hydrodematallation catalysts

机译：在加氢处理催化剂上的初步焦炭沉积。第二部分加氢脱金属催化剂上初始焦的结构解析

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Kuwait atmospheric residue (KAR) was hydrodemetallized (HDM) over a commercial Mo/Al_2O_3 catalyst using a fixed-bed reactor unit. Initial coke deposition on the catalyst vs. time-on-stream (TOS) was studied by solid-state ~(13)C NMR to derive structural information on the initial coke deposited in the first 240 h of TOS. ~(13)C NMR spectral editing (cross-polarization technique in combination with the polarization inversion pulse sequence) was applied to distinguish on the one hand between quaternary and tertiary aromatic carbon and on the other hand between secondary and primary aliphatic carbon. Structural parameters, derived from those NMR measurements in combination with the aromaticity from single pulse excitation ~(13)C NMR and the H/C ratio from elemental analysis, have been used to assemble the hypothetical structure of initial coke. The 1 h coke has nearly the same H/C ratio as the KAR and represents an intermediate between heavy coke generating molecules from KAR and real coke. In the following 12 h, aromatic carbon is accumulated and aromatic rings are dealkylated but the coke is still rich in hydrogen. As the carbon deposition slows down (after 50 h) further aromatic carbon is built-up and aliphatic carbon decreases. After 120 h the hydrogenation activity of the HDM catalyst is still high and prevents the coke from getting hydrogen depleted, merely the degree of alkyl-substitution has dropped compared with the start of ran. With further increase of run time, carbon deposition reaches a steady state (240 h). As the analysis of a spent HDM catalyst (6500 h) from an industrial ARDS unit shows, throughout the following months of operation the porous hydrogen rich coke is increasingly converted into highly condensed polynuclear aromatic coke. THF-extraction of the used catalysts (TOS; 1, 12, 120, and 6500 h) has mainly removed small aromatic compounds with a high degree of alkyl-substitution.
机译：使用固定床反应器单元，在市售Mo / Al_2O_3催化剂上将科威特常压残渣（KAR）加氢脱金属（HDM）。通过固态〜（13）C NMR研究了催化剂上初始焦炭沉积与运行时间（TOS）的关系，以得出关于在TOS前240小时内沉积的初始焦炭的结构信息。应用〜（13）C NMR光谱编辑（交叉极化技术结合极化反转脉冲序列），一方面区分季芳族碳和叔芳族碳，另一方面区分仲脂肪族和伯脂肪族碳。从那些NMR测量结果结合单脉冲激发〜（13）C NMR的芳香性和元素分析的H / C比得出的结构参数已用于组装初始焦炭的假设结构。 1 h焦炭的H / C比与KAR几乎相同，代表了来自KAR的重质焦炭生成分子与真实焦炭之间的中间产物。在接下来的12小时内，芳烃碳积累，芳环脱烷基，但焦炭仍富含氢。随着碳沉积的减慢（50小时后），更多的芳族碳会堆积，脂肪族碳会减少。 120小时后，HDM催化剂的氢化活性仍然很高，可防止焦炭贫氢，与运行开始相比，仅烷基取代度降低了。随着运行时间的进一步增加，碳沉积达到稳态（240小时）。正如对来自工业ARDS单元的废HDM催化剂（6500小时）的分析所显示的那样，在接下来的几个月的运行中，多孔的富氢焦炭越来越多地转化为高度冷凝的多核芳烃。使用过的催化剂（TOS，1、12、120和6500 h）的THF萃取主要去除了烷基取代度高的小芳族化合物。

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