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

Ajay K Dalai
2017 International Journal of Petrochemical Science & Engineering  
The submerged arc discharge in liquid nitrogen technique was used to synthesize carbon nanohorns (CNHs) using 90A and 34V; generating other carbon by-products at the high temperature (>4000K) plasma zone, herein depicted as: "other carbon particles" (OCP) and "other fine carbon particles" (OCP f ). In the present work, a series of potassiumpromoted CoRhMo catalysts with compositions 9%K, 4.5%Co, 1.5%Rh, and 15wt.% Mo, respectively, were supported over these carbon nanomaterials (CNH, OCP f ,
more » ... OCP) and characterized by BET, FTIR, RAMAN, TGA, H 2 -TPR, XRD, and TEM. 30wt.% HNO 3 treatment at T=110°C under reflux conditions for 30 minutes enhanced the overall textural properties of the pristine supports and preserved their mesoporosity evidenced by the Type IV isotherms with surface area increments in the order: CNH (89 to 499)> OCP f (34 to 82) >OCP (10 to 19 m 2 /g). The functionalized supports evidenced the presence of carboxylic acid (-COOH) groups with the most defective sites exhibited by CNHs as revealed by the I D /I G ratios ascertained by Raman spectroscopy. All three KCoRhMo-supported catalysts prepared were thermally stable up to 400°C (CNH) and 650°C (OCP f and OCP), and metals reducibility characterized by H 2 -TPR analysis followed the trend: CNH >OCP f > OCP. Powder XRD revealed inhomogeneous particles dispersion on the OCP-supported catalyst as compared to its CNH & OCP f counterparts as corroborated by the TEM analyses; probably due to significant changes in textural properties. The extensive characterization of these catalysts provided insights into their characteristic catalytic performances for the conversion of syngas to higher alcohols conducted at temperatures, pressure, GHSV, and H 2 /CO ratio of 300-340°C, 8.3 MPa, GHSV=3600 mL (STP) /g cat. h, and 1.25, respectively. CO conversion evaluated under stable reaction conditions at 340°C recorded a maximum of 52% for the CNH-supported KCoRhMo catalysts as opposed to 38% and 25%, respectively, for its OCP f and OCP counterparts.
doi:10.15406/ipcse.2017.02.00023 fatcat:lxvyhblczbcuxo6jnqusutih7m