Higher Alcohol and Oxygenate Synthesis from Synthesis Gas and Ethanol over Supported K-(Co)MoS₂ Catalysts: Effect of Novel Ni-Containing Carbon Nanofiber Supports Formed as Byproducts from Methane Decomposition

Abstract

The supports nature employed greatly affects the catalytic activities and physicochemical characteristics of catalysts. In the present investigation, after the catalytic decomposition of methane using 82Ni-8Cu/Al 2 O 3 catalyst, an inactive catalyst containing a carbon nanofiber byproduct has been studied as a support for synthesis of higher alcohols and other oxygenates from syngas and ethanol conversion, respectively, over a K-modified Copromoted MoS 2 catalyst. The catalytic results have been compared with those of catalysts supported on Al 2 O 3 , carbon-coated alumina, and two types of fabric-activated carbon (NWA and AST). Besides, an unprompted (K)-MoS 2 catalyst supported on CNF-82Ni-8Cu/ Al 2 O 3 (CNFS) has been tested to investigate the mobility probability of Ni atoms from support to the KMoS 2 active phase. N 2 adsorption−desorption, X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to analyze the sulfided catalysts. On comparing CNFS-supported catalysts to alumina-based supports and fabric-activated carbons, the CNFS-supported catalysts demonstrated the highest ability to resist hydrogenation and water−gas shift reactions. This was due to the highest average stacking number and average slab length, which were likely caused by the minimal interaction between the active phase and CNFS support. As a result, it causes the atoms of potassium and cobalt to develop electronic states that are favorable for the higher synthesis of alcohols. KMoS 2 /CNFS has demonstrated the best selectivity toward ethanol and total liquid yield. The order of supported sulfided catalysts for synthesizing other oxygenates from ethanol conversion decreases as follows: KMoS 2 /CNFS > KCoMoS 2 /AST > KCoMoS 2 /NWA ≥ KCoMoS 2 /CNFS > KCoMoS 2 /CCA ≥ KCoMoS 2 /Al 2 O 3 . For the first time, the possibility of dynamics of nickel ions from support to the active phase has been proven.

A Study of the Effects of K-Modification and (Co, Ni, Fe)-Promotion on a Supported MoS2-Based Catalyst for Ethanol Conversion

“…Furthermore, it hinders the cleavage of C–O bonds in intermediates that are adsorbed on active sites and alters the selectivity from alkyl to alkoxide fragments. The incorporation of K has been found to have noticeable effects on catalytic performance . This suggests that the K cation plays a significant role in determining the characteristics of the pure MoS 2 phase, ultimately affecting the efficacy of the catalyst.…”

“…The data presented in Figure indicate that the alcohol yields exhibited an ascending trend as follows: MoS 2 < (Me)­MoS 2 < K-MoS 2 < K-(Me)­MoS 2 . The presence of K species has the potential to impact not only the generation of diverse oxidized precursors but also the microstructural, surface morphology, and electronic characteristics of active MoS 2 phases . K-addition also stabilizes alkoxy species, resulting in enhanced synthesis of alcohols.…”