Alkali-Promoted Trimetallic Co−Rh−Mo Sulfide Catalysts for Higher Alcohols Synthesis from Synthesis Gas: Comparison of MWCNT and Activated Carbon Supports

Abstract

Multiwalled carbon nanotubes (MWCNTs) and activated carbon were used as supports for the Co (4.5 and 6 wt %) promoted K (9 wt %) modified Rh-Mo catalysts (1.5 wt % Rh and 15 wt % Mo). The catalysts were extensively characterized in both oxide and sulfide phases. A drastic fall in surface area over the activated carbon-supported catalysts was observed after impregnating with metal species. Diffraction peaks were observed in the X-ray diffraction (XRD) patterns of the sulfided alkali-modified trimetallic catalysts, due to the characteristic reflections of the K-Mo-S mixed phase. H 2 -temperature programmed reduction (TPR) profiles showed that the reduction behavior of metal species was improved with the addition of Co. The activated carbon-supported trimetallic catalysts showed less activity and selectivity compared to the MWCNT-supported catalyst, and metal dispersions were higher on the MWCNT-supported catalysts. The MWCNT-supported, alkali-promoted trimetallic catalyst with 4.5 wt % Co showed the highest total alcohols yield of 0.244 g/(g cat h), ethanol selectivity of 20.1%, and higher alcohols selectivity of 31.4% at 320 °C and 8.28 MPa using a gas hourly space velocity (GHSV) of 3.6 m 3 (STP)/(kg catalyst h). A maximum total alcohol yield of 0.261 g/(g cat h) and a selectivity of 42.9% were obtained on the 4.5 wt % Co-Rh-Mo-K/MWCNT catalyst, at a temperature of 330 °C. The total alcohol yield increased from 0.163 to 0.256 g/(g cat h) with increased pressure from 5.52 MPa (800 psig) to 9.65 MPa (1400 psig) over the 4.5 wt % Co-Rh-Mo-K/MWCNT catalyst.

Tuning of higher alcohol selectivity and productivity in CO hydrogenation reactions over K/MoS2 domains supported on mesoporous activated carbon and mixed MgAl oxide

“…Further studies were performed with activated carbon [26][27][28][29][30][31][32] and multi-walled carbon nanotubes (MWCNT) http://dx.doi.org/10.1016/j.jcat.2015.01.015 0021-9517/Ó 2015 Elsevier Inc. All rights reserved. [17][18][19][33][34][35][36] as supports that enhanced productivity due to higher dispersion of MoS 2 domains. These studies showed that catalytic activity is enhanced by dispersing the MoS 2 over a support and that Mo-support interactions can affect the reactivity and product distribution of the catalyst by facilitating alcohol reaction pathways.…”

“…Higher alcohol synthesis has been investigated with different families of heterogeneous catalysts including noble metal Rh-based catalysts [3][4][5][6][7][8][9][10][11], modified Cu-based methanol synthesis catalysts [12][13][14][15][16], and modified FT catalysts based on Co, Ru, and Fe [5,8,[17][18][19]. A particularly promising non-noble metal family of catalysts, MoS 2 -based catalysts modified with potassium [20,21], has been widely studied due to its resistance to sulfur poisoning, less severe coke deposition, and ability to form higher alcohols with a high selectivity to ethanol.…”

Syngas Conversion to Higher Alcohols: Application of novel K-Promoted CoRhMo Catalysts Supported over Carbon Nanohorns and its by-Products

“…43 Moreover, whereas CO 2 evolution mostly occurs below 500°C and CO evolution proceeding above this temperature, both physisorbed and chemisorbed water are mostly released in the range of 100-450°C. 44,45 However, in the present work, quantitative evaluation of the corresponding evolved gaseous species was not determined. Nonetheless, the corresponding % mass loss for the supported catalysts investigated in the temperature range of 200-500°C followed the trend: Cat-CNH (9.4%)>Cat-OCP f (1.4%)>Cat-OCP (0.9%).…”

Heterogeneous Catalysis on Nanostructured Carbon Material Supported Catalysts

“…Alkali-modified trimetallic Co-RhMo sulfided catalysts supported on commercial ACs with different textural characteristics were tested for the synthesis of higher alcohols from synthesis gas and compared with a similar catalyst supported on MWCNTs. 150,151 Addition of metals (Co, Rh, and Mo) to the microporous and mesoporous activated carbons, and the MWCNT supports, increased the mean pore diameter and % mesoporosity of the catalysts. The difference in metal dispersion of the sulfided catalysts on different supports was: MWCNTs < ACs.…”