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Detailed Mechanism of Ethanol Transformation into Syngas on Catalysts Based on Mesoporous MgAl 2 O 4 Support Loaded with Ru + Ni/(PrCeZrO or MnCr 2 O 4 ) Active Components
Topics in Catalysis ( IF 2.8 ) Pub Date : 2020-02-05 , DOI: 10.1007/s11244-020-01222-1
Vladislav A. Sadykov , Nikita F. Eremeev , Ekaterina M. Sadovskaya , Yurii A. Chesalov , Svetlana N. Pavlova , Vladimir A. Rogov , Mikhail N. Simonov , Aleksei S. Bobin , Tatiana S. Glazneva , Ekaterina A. Smal , Anton.I. Lukashevich , Aleksei V. Krasnov , Vasilii I. Avdeev , Anne-Cecile Roger

Mechanism of ethanol partial oxidation into syngas over catalysts based on mesoporous MgAl2O4 spinel loaded with fluorite PrCeZrO or spinel MnCr2O4 oxides and promoted by Ru + Ni was studied by in situ FTIRS and 18O SSITKA. Surface species (ethoxy, adsorbed ethanol, acetaldehyde, acetate, etc.) were identified and their thermal stability and reactivity were estimated. Analysis of kinetics of the 18O transfer into reaction products (CO, CO2, CH3CHO) allowed to estimate the rates of steps and present a scheme of the reaction mechanism including (1) fast CH3CHO formation on mixed metal oxide sites; (2) rate-limiting stage of surface oxygen species incorporation into acetaldehyde or ethoxy species with C–C bond rupture yielding CO and CO2 along with H2 and H2O; (3) water gas shift reaction by redox mechanism affecting CO/CO2 ratio and their oxygen isotope fraction. Strong interaction of PrCeZrO or MnCr2O4 oxides with MgAl2O4 support results in decreasing constants of main reaction steps in comparison with those for catalysts based on bulk fluorite and spinel oxides, correlating with a higher surface oxygen bonding strength and its low coverage revealed by pulse microcalorimetry. DFT analysis confirmed a low energy barrier of the step of Ru–O oxygen incorporation into C–C bond of ethoxy species with its rupture explaining a higher syngas selectivity for Ru-doped catalysts.



中文翻译:

负载Ru + Ni /(PrCeZrO或MnCr 2 O 4)活性组分的介孔MgAl 2 O 4载体上乙醇在催化剂上转化为合成气的详细机理

通过原位FTIRS和18 O SSITKA研究了以Ru + Ni为助剂的萤石PrCeZrO或尖晶石MnCr 2 O 4氧化物负载介孔MgAl 2 O 4尖晶石在催化剂上乙醇部分氧化为合成气的机理。鉴定表面种类(乙氧基,吸附的乙醇,乙醛,乙酸盐等),并评估其热稳定性和反应性。分析18 O转移至反应产物(CO,CO 2,CH 3 CHO)的动力学,可以估算步骤的速率,并提出反应机理的方案,其中包括(1)快速CH 3在混合金属氧化物位点上形成CHO;(2)表面氧物种掺入乙醛或乙氧基中的限速阶段,CC键断裂,产生CO和CO 2以及H 2和H 2 O;(3)通过氧化还原机理的水煤气变换反应影响CO / CO 2比及其氧同位素分数。PrCeZrO或MnCr 2 O 4氧化物与MgAl 2 O 4的强相互作用与基于块状萤石和尖晶石氧化物的催化剂相比,该载体可降低主要反应步骤的常数,这与较高的表面氧键合强度和由脉冲量热法显示的低覆盖率有关。DFT分析证实了Ru–O氧掺入乙氧基的C–C键中的步骤具有较低的能垒,其破裂说明了掺Ru催化剂的合成气选择性更高。

更新日期:2020-02-05
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