Meaning of mass transfer limitation and diffusion limitation

Mar 29, 2007 1 Replies
H

Hi! evveryone I am reading a article about metallocene catalyzed polymerization. There is a below writings :



" In a semibatch slurry reactor,the concentration of macromonomers increases with time,while the concen-tration of ethene may decrease due to mass transfer limitations. Diffusion limitations also broaden the molecular weight distribution in copolymerizations."



I would like to know the meanings of mass transfer limitations and diffusion limitations.



Would you inform me about that? I majored the chemistry, so I am not familiar with a term about polymer.



Thank you



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J

Mass transfer includes both diffusion and convection of matter.

Diffusion is decreases as the molecular weight increases, so the ethene, being a smaller molecule than the macromonomer, will diffuse faster. As it reacts, it's concentration decreases thereby increasing the concenctration of the remaining monomers - the macromonomer in this case.

John Aspen Research, -

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