How to Overcome the Water–Gas‐Shift Equilibrium using a Conventional Nickel Reformer Catalyst

Abstract

The catalytic water–gas‐shift (WGS) reaction into hydrogen and carbon dioxide was investigated using a commercial nickel reformer catalyst. The effects of temperature, flow rate, and catalyst nature on the course of reaction were evaluated. Hydrogen and carbon dioxide were generated in the temperature range between 125 and 475 °C. A reaction scheme was used to explain the formation of methane. The WGS reaction and the methanation reaction (MTN) were used to calculate the equilibrium composition at these conditions. A commercial hydrotalcite‐like sorbent arranged in a multilayer pattern of catalyst plus sorbent was used for carbon dioxide capture to enhance the WGS reaction. The performance of the catalyst was assessed by comparing the measured conversions, hydrogen yields, and selectivities at steady‐state conditions with equilibrium values and with selected results reported recently, as well as conversions, hydrogen yields, and selectivities during the transient period as the hybrid system consisting of catalyst plus sorbent is arranged in a multilayer pattern system. The multilayer pattern system consisting of catalyst plus sorbent can easily overcome the thermodynamic restrictions of the WGS reaction at an operating temperature of 400 °C because of the enhanced sorption effect during the reaction process. In addition, lower flow rate regimes, and higher pressures and steam/carbon ratios increase the initial breakthrough period. This sorption‐enhanced technique makes the use of Ni‐based catalysts for the WGS reaction attractive, and suitable for the adjustment of the hydrogen ratio in synthesis gas streams.

Syngas production by bi-reforming methane on an Ni–K-promoted catalyst using hydrotalcites and filamentous carbon as a support material

“…The most obvious explanation is the fact that BRM is an endothermic and volume increase reaction, meaning that the conversion of all the reactants involved an increase in temperature with higher inert gas ow rates, as thermodynamically proven in a previous study. 59 Considering the side reaction scheme proposed in our previous works, 9,10 in particular CMD, SRM and DRM, the results obtained from the thermodynamic equilibrium calculations for inert gas variations are effectively clear. The exception is the single WGS reaction equilibrium, also a possible side-reaction, is not affected by the total pressure or partial pressure of inert gas.…”

“…The exception is the single WGS reaction equilibrium, also a possible side-reaction, is not affected by the total pressure or partial pressure of inert gas. 59 The material selected as a support for the promoter and active phase, LDH, as shown in Fig. 5, exhibited poor catalytic activity at low temperatures and reasonable catalytic activity at very high temperatures of around 850 C and higher.…”

Low-Cost Syngas Shifting for Remote Gasifiers: Combination of CO2 Adsorption and Catalyst Addition in a Novel and Simplified Packed Structure

“…The temperature range achieved in the lower part of the packed bed shows that both catalytic reforming and CO 2 adsorption over zeolite are suitable in the operating conditions that were achieved. According to Cunha et al [61], water conversion into hydrogen through steam gasification reactions start being verified at around 120 • C with nickel-based catalysts, even if full conversion would require temperatures in the range of 200 • C. Moreover, CO 2 adsorption over zeolite has also been reported at atmospheric pressure levels and temperature ranges around 100 • C. Zhao et al [3], for instance, reported that zeolite can adsorb CO 2 over its surface with efficiencies above 5% under relatively low pressure and temperature levels. Considering such reported records together with the temperature registers, it is possible to affirm that the packed bed has activity in the syngas quality obtained from the gasifier.…”

Steam Prereforming of Natural Gas over Nanostructured Nickel/Magnesium Aluminate Spinel Catalysts: Effect of Support and Nickel Loading

“…This is due to the methanation of CO x (x = 1o r2 )a nd H 2 [Eqs. (3) and (4)], which are exothermic reactions.W ith decreasing temperature,C H 4 is produced from C 2 H 6 and C 3 H 8 faster than it is decomposed, which results in af ast increase in the selectivity to CH 4 .T his is probably due to the low reactivityofm ethane at lower temperature.…”

“…This providess everal benefits, including ad ecrease in potential carbon depositions in the tubularr eformer, increased feed flexibility,a nd reduced energy consumption. [2] Thea diabatic prereformingp rocess is based on as et of reactions: [3,4] steam reforming of hydrocarbons (1), followed by the watergas shift reaction (2), and methanation of CO x (3 and 4).…”