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Influence of H2O and H2S on the composition, activity, and stability of sulfided Mo, CoMo, and NiMo supported on MgAl2O4 for hydrodeoxygenation of ethylene glycol
Applied Catalysis A: General ( IF 4.7 ) Pub Date : 2017-12-10 , DOI: 10.1016/j.apcata.2017.12.008
Trine Marie Hartmann Dabros , Abhijeet Gaur , Delfina Garcia Pintos , Paul Sprenger , Martin Høj , Thomas Willum Hansen , Felix Studt , Jostein Gabrielsen , Jan-Dierk Grunwaldt , Anker Degn Jensen

In this work, density functional theory (DFT), catalytic activity tests, and in-situ X-ray absorption spectroscopy (XAS) was performed to gain detailed insights into the activity and stability of MoS2, Ni-MoS2, and Co-MoS2 catalysts used for hydrodeoxygenation (HDO) of ethylene glycol upon variation of the partial pressures of H2O and H2S. The results show high water tolerance of the catalysts and highlight the importance of promotion and H2S level during HDO.

DFT calculations unraveled that the active edge of MoS2 could be stabilized against SO exchanges by increasing the partial pressure of H2S or by promotion with either Ni or Co. The Mo, NiMo, and CoMo catalysts of the present study were all active and fairly selective for ethylene glycol HDO at 400 °C, 27 bar H2, and 550–2200 ppm H2S, and conversions of ≈50–100%. The unpromoted Mo/MgAl2O4 catalyst had a lower stability and activity per gram catalyst than the promoted analogues. The NiMo and CoMo catalysts produced ethane, ethylene, and C1 cracking products with a C2/C1 ratio of 1.5–2.0 at 550 ppm H2S. This ratio of HDO to cracking could be increased to ≈2 at 2200 ppm H2S which also stabilized the activity. Removing H2S from the feed caused severe catalyst deactivation. Both DFT and catalytic activity tests indicated that increasing the H2S concentration increased the concentration of SH groups on the catalyst, which correspondingly activated and stabilized the catalytic HDO performance. In-situ XAS further supported that the catalysts were tolerant towards water when exposed to increasing water concentration with H2O/H2S ratios up to 300 at 400–450 °C.

Raman spectroscopy and XAS showed that MoS2 was present in the prepared catalysts as small and highly dispersed particles, probably owing to a strong interaction with the support. Linear combination fitting (LCF) analysis of the X-ray absorption near edge structure (XANES) spectra obtained during in-situ sulfidation showed that Ni was sulfided faster than Mo and CoMo, and that Mo was sulfided faster when promoted with Ni. Extended X-ray absorption fine structure (EXAFS) results showed the presence of MoS2 in all sulfided catalysts. Sulfided CoMo was present as a mixture of CoMoS and Co9S8, whereas sulfided NiMo was present as NiMoS.



中文翻译:

H 2 O和H 2 S对负载在MgAl 2 O 4上的乙二醇加氢脱氧的硫化Mo,CoMo和NiMo的组成,活性和稳定性的影响

在这项工作中,进行了密度泛函理论(DFT),催化活性测试和原位X射线吸收光谱(XAS),以深入了解MoS 2,Ni-MoS 2和Co-的活性和稳定性。随H 2 O和H 2 S分压的变化而用于乙二醇加氢脱氧(HDO)的MoS 2催化剂。结果表明,该催化剂具有很高的耐水性,并突出了在HDO过程中促进和H 2 S含量的重要性。

DFT计算表明,通过增加H 2 S的分压或通过Ni或Co的促进作用,可以使MoS 2的活性边缘对S O交换稳定。本研究的Mo,NiMo和CoMo催化剂均具有活性在400°C,27 bar H 2和550–2200 ppm H 2 S的条件下对乙二醇HDO具有相当的选择性,转化率约为50–100%。未促进的Mo / MgAl 2 O 4催化剂的每克催化剂的稳定性和活性均低于促进的类似物。制得的乙烷,乙烯和的NiMo催化剂的CoMo,和C 1裂解产物与C 2 / C 1在550 ppm H 2 S时,比率为1.5–2.0。在2200 ppm H 2 S时,HDO与开裂的比率可以增加到≈2,这也使活性稳定。从进料中除去H 2 S会导致严重的催化剂失活。DFT和催化活性测试均表明,增加H 2 S浓度会增加催化剂上SH基团的浓度,从而相应地活化和稳定了催化HDO性能。原位XAS进一步证明,当催化剂在400–450°C的H 2 O / H 2 S比高达300的不断增加的水浓度下暴露时,它们对水具有耐受性。

拉曼光谱法和XAS分析表明,所制得的催化剂中的MoS 2以小的且高度分散的颗粒形式存在,这可能是由于与载体的强烈相互作用所致。在原位硫化过程中获得的X射线吸收近边缘结构(XANES)光谱的线性组合拟合(LCF)分析显示,Ni的硫化速度比Mo和CoMo快,而Mo则在被Ni促进时硫化得更快。扩展的X射线吸收精细结构(EXAFS)结果表明,所有硫化催化剂中均存在MoS 2。硫化的CoMo以CoMoS和Co 9 S 8的混合物形式存在,而硫化的NiMo以NiMoS形式存在。

更新日期:2017-12-10
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