Steam Conversion of Methane on Fechral
- PDF / 213,173 Bytes
- 3 Pages / 612 x 792 pts (letter) Page_size
- 107 Downloads / 209 Views
T COMMUNICATIONS
Steam Conversion of Methane on Fechral A. L. Tarasova,*, A. L. Kustova,b, A. N. Kalenchuka,b, P. V. Sokolovskiia, V. N. Bogdanovc, and I. G. Gilyadovc a Zelinsky
Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia of Chemsitry, Moscow State University, Moscow, 119992 Russia c OOO Ecotrans-M, Moscow, Russia *e-mail: [email protected]
b Departmenrt
Received January 28, 2020; revised January 28, 2020; accepted February 11, 2020
Abstract—The vapor conversion of methane on Ni-containing catalysts on structured metal supports made from a Fe–Cr–Al alloy (fechral) is studied. A very high hydrogen content is observed in the products of the reaction for low percent 1% Ni/fechral catalysts (around 75% at 870°C). Keywords: steam conversion, methane, catalysts, fechral DOI: 10.1134/S0036024420090289
INTRODUCTION The problems of finding new catalysts for converting natural gas into liquid products and obtaining pure hydrogen via methane conversion have become highly relevant in recent years. Methane can be converted into liquid fuels in three ways [1]: steam conversion (steam reforming),
СН4 + Н2О = СО + 3Н2, ΔH = +226 kJ/mol, the partial oxidation of methane with oxygen,
СН4 + 1/2О2 = СО + 2Н2, ΔH = –44 kJ/mol, and carbon dioxide methane conversion (dry reforming) СН4 + СО2 = 2СО + 2Н2, ΔH = +261 kJ/mol. The main reaction in the process of methane steam conversion proceeds on a nickel catalyst at 800– 1000°C and space velocities of around 1000 h−1. The equilibrium constant is 1 at 780°C. The reaction of CO methanation proceeds at lower temperatures. The process is typically conducted at a ratio of CH4 : H2O = 3 : 1, yielding gas with a (CO2 + H2)/(СО + СО2) ratio close to 3, which is suitable for the synthesis of ammonia. The lower H2/CO ∼ 2 ratio needed for the synthesis of methanol and hydrocarbons is obtained by adding CO2 or O2. To prevent carbon deposition by the Boudoir reaction
2СО = С + СО2,
ΔH = +172 kJ/mol
at temperatures below 630°C, water vapor is taken in excess, which also prevents the decomposition of methane at temperatures above 820°C:
СН4 = С + 2Н2,
ΔH = +75 kJ/mol.
Active catalysts for methane steam reforming are Group VIII metals deposited on a variety of supports. The order of their activities is Rh, Ru > Ni > Ir > Pd, Pt Co, Fe. Cobalt and iron are oxidized and deactivated under conditions of methane steam reforming, and noble metals are expensive. The only industrial catalyst for this reaction is therefore Ni deposited on oxide supports. However, this technology is characterized by exceptionally high energy consumption along with carbon dioxide conversion, both of which are highly endothermic. Partial oxidation is an exothermic process, which is the main advantage of partial oxidation. The main disadvantage of all three techniques is the rapid deactivation of the catalyst due to the formation of soot, which becomes thermodynamically advantageous at temperatures above 700°C. An important area in the development of methane conversion catalysts i
Data Loading...
