Influence of forced feed composition cycling on catalytic methanol synthesis

Abstract

Studies have been carried out between 230 and 270°C and 1.97 and 2.93 MPa total pressure on the synthesis of methanol over an industrial catalyst of the copper‐zinc oxide‐alumina type using a gradientless reactor. Two modes of forced feed composition cycling were explored: periodic variations of the mole fraction of H2 and CO and periodic variation of the CO2 content. The latter mode substantially improved methanol production and suppressed the parasitic formation of methane, while the former mode had just the opposite effect. Measurements of methanol, methane and CO during a cycle as well as separate observations of the response to step‐changes in concentration indicated substantial storage of CO on the catalyst surface. Rapid response of methane to the CO2 content suggests over‐reduced areas of the catalyst surface are responsible for methane formation and that these regions are readily oxidized. CO2 or H2O associated with methane formation appear to relate to the dynamics of methanol formation.

An Experimental Study of Concentration Forcing Applied to the Methanol Synthesis Reaction

“…Both improvements occurred when oscillating between carbon monoxide and hydrogen while keeping a constant source of carbon dioxide. Both improvements are significantly higher than that obtained by Nappi et al (1985) in their study of concentration forcing between carbon monoxide and hydrogen with no carbon dioxide source. Thus, as is true for steady-state operation, the addition of carbon dioxide in the feed favorably affects the methanol production rate during concentration-forcing operation.…”

Methanol Synthesis – Industrial Challenges within a Changing Raw Material Landscape

“…However, as the direct hydrogenation of CO does scarcely occur on commercial catalysts, a certain amount of CO 2 needs to be present in the reactor feed to enable WGS and CO conversion to methanol , , , , . A maximum methanol formation rate was experimentally observed by various researchers at a molar CO 2 concentration of approximately 2 mol.‐% of carbon in the reactor feed , , , .…”

Methanol synthesis under periodic operation: An experimental investigation

“…Two modes of periodic operation were explored: 1) cycling between two feeds of different H2/C0 mole ratio in the absence of C02, and 2) periodically pulsing a feed of constant H2/C0 ratio with a feed containing 2 vol % C02. Nappi et al (1985) found that cycling between different H2 and CO mole fractions failed to increase the methanol synthesis at all cycle periods employed; however a significant improvement, about 27%, was seen when C02 pulsing was employed. This latter observation was based on just several experiments.…”

“…Our research group has studied forcing methanol synthesis before. Nappi et al (1985) used a three component catalyst with the nominal composition: 27% CuO, 44% ZnO, and 29% A1203 by mass. This catalyst produced small amounts of methane.…”