Continuous process and equilibrium constant.

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Discussion Overview

The discussion revolves around the production of methanol in a chemical plant, focusing on the manipulation of equilibrium constants and the effects of operational conditions on yield. Participants explore the implications of maintaining specific temperature and pressure conditions during the production process and the separation of products.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that specific pressure, temperature, and flow rates can produce reactions with specific equilibrium constants, questioning if these conditions are maintained throughout the process, including in pipelines.
  • Another participant inquires if the discussion pertains to the conventional two-step process using a catalyst for methanol production.
  • There is a suggestion that while theoretical yield can be calculated using the equilibrium constant, actual yield may be less due to various factors such as catalyst effectiveness and residence time.
  • Concerns are raised about the potential impact on equilibrium position when changing conditions for separating water and methanol.
  • One participant mentions that condensation and distillation are physical processes where no reactions occur, leading to confusion regarding their influence on yield.
  • A later reply discusses the effect of condensation on the position of equilibrium for exothermic reactions, questioning the output if the reaction were endothermic.
  • Another participant concludes that condensation and distillation would not affect yield significantly due to the low rates of reactions, emphasizing the necessity of a catalyst for the final reaction step.

Areas of Agreement / Disagreement

Participants express differing views on the impact of operational conditions on equilibrium and yield, with some asserting that changes in separation processes do not affect yield, while others question the implications of reaction conditions on equilibrium position. The discussion remains unresolved regarding the extent of these effects.

Contextual Notes

Participants acknowledge the complexity of the interactions between reaction conditions and physical separation processes, with some assumptions about the nature of the reactions and their thermodynamic properties remaining unaddressed.

goggles31
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Assuming that we have a chemical plant which produces methanol through the following equations:
CH4 + H2O <--> CO + 3H2
CO + 2H2 <--> CH3OH
CO2 + 3H2 <--> CH3OH + H2O
I know that with specific pressure, temperature and flow rates, I can produce reactions with specific equilibrium constants. Are these conditions maintained until water and methanol are separated, even in the pipelines? I'm guessing that I can calculate the theoretical yield by applying the equilibrium constant. Is that correct? Thank you for your time.
Edit: Also, wouldn't I risk changing the position of equilibrium if I change the conditions to separate water and methanol?
 
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Are you referring to the conventional 2-step process using a catalyst for the final conversion of the syngas to methanol?
 
Yes, but that does not matter. I'm interested in the equilibrium constant manipulation.
 
goggles31 said:
Are these conditions maintained until water and methanol are separated, even in the pipelines?
I would think so, because the pipelines roughly maintain the same temperature and pressure.

goggles31 said:
I'm guessing that I can calculate the theoretical yield by applying the equilibrium constant. Is that correct?
Yes, but actual yield could be somewhat less. There's usually a compromise between catalyst, residence time, and yield.

goggles31 said:
Also, wouldn't I risk changing the position of equilibrium if I change the conditions to separate water and methanol?
Do you mean change the conditions of the reactions, or change the conditions of the water/methanol separation process?
 
The conditions of the reactions; condensation then distillation comes to mind, although it may not be the one used by the industry.
 
goggles31 said:
The conditions of the reactions; condensation then distillation comes to mind, although it may not be the one used by the industry.
I'm confused by this reply. Condensation and distillation are physical operations where no reactions take place.
 
Condensation is a cooling process. If we consider the third equation which is an exothermic reaction, the position of equilibrium would move to the right during condensation which would be ideal for this reaction since we are generating more methanol. But what if the reaction was actually endothermic? Wouldn't we be decreasing our potential output?
 
Now I understand. No, the condensation and distillation will have no effect on the yield because the rates of the reactions are insignificant. (That is why a catalyst is necessary for the final reaction step.)
 

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