Hydrogenation and Hydrodeoxygenation of Oxygen-Substituted Aromatics over Rh/silica: Catechol, Resorcinol and Hydroquinone
Hydrogenation and Hydrodeoxygenation of Oxygen-Substituted Aromatics over Rh/silica: Catechol, Resorcinol and Hydroquinone
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Rh/二氧化硅上氧取代芳烃的氢化和加氢脱氧：儿茶酚、间苯二酚和对苯二酚
DOI：
10.3390/catal10050584
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发表时间：
2020
期刊：
影响因子：
3.9
通讯作者：
S. Jackson
中科院分区：
文献类型：
--
作者：
Kathleen Kirkwood;S. Jackson
研究了二羟基苯异构体儿茶酚（1,2-二羟基苯）、间苯二酚（1,3-二羟基苯）和对苯二酚（1,4-二羟基苯）在Rh/silica催化剂上，在303-343 K和3 barg氢气压力下的加氢和加氢脱氧（HDO）反应。反应活性顺序为间苯二酚>儿茶酚>对苯二酚（间位>邻位>对）。动力学分析表明，儿茶酚为负序反应，对苯二酚和间苯二酚均为正半序反应，表明儿茶酚的吸附作用更强。儿茶酚和对苯二酚的活化能为~30 kJ·mol−1，间苯二酚的活化能为41 kJ·mol−1。间苯二酚和对苯二酚的氢解产物（环己醇、环己酮和环己烷）的累积收率较高，约为40%。相反，儿茶酚有利于加氢，特别是顺-1,2-二羟基环己烷。二羟基环己烯加氢形成顺式异构体，对顺式-1,2-二羟基环己烯的高选择性可以解释为1,2-二羟基环己烯相对于儿茶酚、间苯二酚或对苯二酚的其他环己烯中间体具有更高的稳定性。反式异构体不是由等价的顺式二羟基环己烷异构化形成的，而是由2/3/4-羟基环己酮直接加氢形成的。间苯二酚和对苯二酚对HDO具有较高的选择性，这可能与活性表面环己烯与羟基具有C=C双键β-γ有助于氢解有关。用氘代替氢表明，每一种同分异构体都有独特的动力学同位素效应，对环己烷的HDO影响很大。环己烷产生的延迟表明氘起到了抑制剂的作用，可能阻断了导致环己烷形成的特定HDO位点。用程序升温氧化法（TPO）检测了碳沉积，发现了三种表面物质。
The hydrogenation and hydrodeoxygenation (HDO) of dihydroxybenzene isomers, catechol (1,2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene) and hydroquinone (1,4-dihydroxybenzene) was studied in the liquid phase over a Rh/silica catalyst at 303–343 K and 3 barg hydrogen pressure. The following order of reactivity, resorcinol > catechol > hydroquinone (meta > ortho > para) was obtained. Kinetic analysis revealed that catechol had a negative order of reaction whereas both hydroquinone and resorcinol gave positive half-order suggesting that catechol is more strongly adsorbed. Activation energies of ~30 kJ·mol−1 were determined for catechol and hydroquinone, while resorcinol gave a value of 41 kJ·mol−1. Resorcinol, and similarly hydroquinone, gave higher yields of the hydrogenolysis products (cyclohexanol, cyclohexanone and cyclohexane) with a cumulative yield of ~40%. In contrast catechol favoured hydrogenation, specifically to cis-1,2-dihydroxycyclohexane. It is proposed that cis-isomers are formed from hydrogenation of dihydroxycyclohexenes and high selectivity to cis-1,2-dihydroxycyclohexane can be explained by the enhanced stability of 1,2-dihydroxycyclohex-1-ene relative to other cyclohexene intermediates of catechol, resorcinol or hydroquinone. Trans-isomers are not formed by isomerisation of the equivalent cis-dihydroxycyclohexane but by direct hydrogenation of 2/3/4-hydroxycyclohexanone. The higher selectivity to HDO for resorcinol and hydroquinone may relate to the reactive surface cyclohexenes that have a C=C double bond β-γ to a hydroxyl group aiding hydrogenolysis. Using deuterium instead of hydrogen revealed that each isomer had a unique kinetic isotope effect and that HDO to cyclohexane was dramatically affected. The delay in the production of cyclohexane suggest that deuterium acted as an inhibitor and may have blocked the specific HDO site that results in cyclohexane formation. Carbon deposition was detected by temperature programmed oxidation (TPO) and revealed three surface species.