Problems with catalysts for hydrogen production from methanol and water vapor
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This post was last edited by *aoliren on 2019-4-28 at 15:41. Recently, the hydrogen production facility using methanol steam cracking experienced a power outage that lasted about two hours. After it was restarted, it was found that the amount of converted gas had decreased significantly. The facility uses copper-based catalysts, and at full load, approximately 28% of the unreacted methanol or other products remain in the scrubber. It is currently suspected that the catalysts are damaged or have lost their activity. I would like to ask the experts: what are the characteristics of oxidation of copper-based catalysts? What could be the causes of such oxidation? And what are the characteristics of carbon deposition on the surface of copper-based catalysts? What causes carbon deposition? There is no suspicion of crushing for now, as the pressure difference between the inlet and outlet of the converter has not increased. Thank you
I guess it’s because high temperatures make carbon deposition more likely
This post was last edited by Internet Invisible Man on 2019-5-3 22:03. As you described, the unit should not experience such a situation when it resumes operation after a sudden power outage. Moreover, as long as no air is introduced or nitrogen with an oxygen content of over 1% is used after the unit is stopped, catalyst oxidation will not occur, as there are no conditions for oxygen to get in. The oxidation of copper-based catalysts is commonly referred to as oxygen passivation, in which the single-crystal copper in the catalyst is oxidized to copper oxide, rendering the catalyst inactive; this process is carried out only when it is necessary to repair leaks in the conversion tube. Regarding carbon deposition, it should not occur in the methanol-to-hydrogen process; only overheating-induced sintering is possible. The pressure difference for conversion of inlet and outlet gases remains unchanged. This situation can only be explained by the pulverization of the catalyst in the conversion tubes and the removal of that dust, resulting in a loss of catalyst within those tubes. If catalyst is lost in some of the conversion tubes, it will cause differences in resistance across these tubes, leading to uneven flow of the reaction gas; the gas flowing through areas with lower resistance will move at a faster rate and will not have enough time to react, thereby causing an excess amount of methanol to remain behind. Consider it from this perspective; feel free to contact me via private message if needed.
Thank you very much. I’ll organize the materials again and then ask for your guidance
Recycle the discarded catalysts that have been replaced
13839963512 Zhao
Do you still have some headroom in terms of reaction temperature? Try increasing it to see what happens, or check whether the ratio of methanol to water is appropriate – either of these can be adjusted.
Was the catalyst protected in a timely manner during the power outage? When the reaction conditions are met, it is usually due to a problem with the raw materials; the methanol content in the washing tower is generally around 2-3%. In the case described above, the catalyst is likely partially deactivated.
Methanol cracking is an endothermic reaction; it should not be a sintering process. Sintering also causes an increase in resistance.
Methanol cracking is an endothermic reaction, along with a shift reaction. The operating temperature is usually above 260, unless an extremely low concentration of CO at the outlet is required. The operating temperature is generally around 280. After operating at this temperature for an extended period, a sudden drop in temperature occurs, which leads to the destruction of the crystal lattice of the catalyst’s metal copper; the direct consequence of this is a significant reduction in the catalyst’s activity.