Tuning the metal–support interaction in supported K-promoted NiMo catalysts for enhanced selectivity and productivity towards higher alcohols in CO hydrogenation

Abstract

Ni–KMoS/MMO catalysts were obtained using encapsulated Mo-based precursors to tune metal–support interaction, and enhanced selectivity and productivity towards higher alcohols.

Tungsten-Doped Molybdenum Sulfide with Dominant Double-Layer Structure on Mixed MgAl Oxide for Higher Alcohol Synthesis in CO Hydrogenation

“…Compared with bulk MoS 2 -based catalysts, supported Mo-based catalysts are desired to enhance activity and to improve higher alcohol selectivity using SiO 2 , CeO 2 , MgO, Al 2 O 3 , and carbon-based materials as supports. ,− Among those supports, mixed Mg/Al oxide (MMO) can tune the interaction between Mo and MMO to improve the product distribution toward higher alcohols. , The special nature of MMO of weakening the alcohols dehydration and favoring oxygenate coupling reactions may be helpful for the high selectivity of C 2 + alcohols . On the basis of the “Rim–Edge” model of MoS 2 catalysts, hydrogenation reactions only occurred on rim and edge sites. , It has also been reported that the high dispersion of MoS 2 on MMO with a proper layer number and slab size for more exposure of edge sites can enhance higher alcohol selectivity. ,, On the other hand, group VIII metals possess the potential for enhancing the activity and improving the HA selectivity by balancing the CO/H 2 activation and alcohols formation. Among these elements, Ni and Co are regarded as superior additives .…”

Enhanced Higher Alcohol Synthesis from CO Hydrogenation on Zn-Modified MgAl-Mixed Oxide Supported KNiMoS-Based Catalysts

“…H 2 -TPR was carried out to examine the effects of Zn on the reducibility of K,NiMo/Zn 0.7 Al 0.3 , K,NiMo/Zn 0.35 Mg 0.35 Al 0.3 , and K,NiMo/Mg 0.7 Al 0.3 . Figure b and Table present two main peaks on three oxidic catalysts where the peak at low temperature can be ascribed to the reduction from Mo 6+ to Mo 4+ of octahedral molybdenum (Mo­(o)) oxide, and the peak located at high temperature can be assigned to the deep reduction of Mo species in tetrahedral sites (Mo­(t)) or the reduction of Mo 4+ to metallic Mo. ,, It is difficult to assign Ni reduction temperatures because the reduction peak of Ni may overlapped with Mo signals. , The TPR of K,Mo/Zn 0.7 Al 0.3 was also performed to investigate the overlap of the reduction of Ni and Mo species (Figure S2). The results suggest that the addition of Ni can promote the reduction of Mo species .…”

“…14,15 It is worth noting that Zn can also be used to tune the acidity/alkalinity by partially neutralizing inherent strong acidic sites. 16−19 Our previous work 3,4,20 showed that the integration of surfactant-encapsulated molybdenum precursors and hydrothermal methods can modulate the interaction between molybdenum species and supports, successfully increasing the selectivity of C 2+ OH and the total alcohol yield. The HAS performance is greatly influenced by acidic/alkaline and structural properties.…”

“…Among several typical catalysts, such as Rh-based noble, modified methanol synthesis catalysts, modified Fischer–Tropsch catalysts, and Mo-based catalysts, − alkaline-doped molybdenum sulfides (ADM) have been confirmed to be the promising catalysts because of their low cost and sulfur tolerance. , Supported Mo-based catalysts benefit from the high surface area and more active sites, but they are restricted by the poor C 2+ OH selectivity. ,, Some acidic metal oxide supports (e.g., Al 2 O 3 and ZrO 2 ) can inhibit the HAS and increase the dehydration of alcohol on the acidic sites of supports, indicating weak acidic or neutral supports more suitable. , It has been reported that alkali metal, mainly basic K, can significantly improve the HA selectivity. ,, In addition, group VIII metals (e.g., Co and Ni) also possess the potential for improving the HAS by facilitating the CO insertion process . A dual active site model is proposed in transition metal-promoted ADM catalysts for HAS where CO/H 2 activation and hydrocarbon formation are on the transition metal sulfide (MS x , M=Fe, Co, Ni), while CO insertion, chain growth, and alcohol formation are on the molybdenum-mixed sulfides (M-KMoS x ). , Recently, Chen et al , showed that the multimetallic bulk catalyst by the introduction of Zn to NiMoW exhibited high hydrodesulphurisation (HDS) activity owing to the synergism between active compound Ni/Mo and Zn, the inhibition about the formation of Al 2 (MoO 4 ) 3 , and the improvement in surface dispersion of Ni/Mo species.…”

“…Liu et al prepared unsupported NiZnMo catalysts by chemical coprecipitation for HDS where the addition of Zn increased the reducibility of Ni species, but the strong interaction between Zn and Mo/W inhibited the reducibility of Mo species. The HDS activity can be significantly improved by modulating the interaction between Ni/Co and Mo after the introduction of Zn. , It is worth noting that Zn can also be used to tune the acidity/alkalinity by partially neutralizing inherent strong acidic sites. − Our previous work ,, showed that the integration of surfactant-encapsulated molybdenum precursors and hydrothermal methods can modulate the interaction between molybdenum species and supports, successfully increasing the selectivity of C 2+ OH and the total alcohol yield. The HAS performance is greatly influenced by acidic/alkaline and structural properties .…”