[curiouscat]

What's a good re-activation procedure for a zeolite catalyst? I was using a beta zeolite for an acetylation reaction and initial run activity is superb (90+ % conversion) but unfortunately subsequent runs show a much reduced activity (~60% conversion).

Our current reuse protocol is centrifuge -> MeOH wash -> oven dry at 150 C for an hour.

Any other ideas? Strong acids? Oxidation?

My suspicion is strong product binding leading to deactivation. The catalyst color visibly darkens and on low conversion runs deactivation is lesser.

PS. I have emailed the catalyst vendor of course, but as is the norm big corporate responses suck.

[orgopete]

It appears there are two questions here. Does oven drying at 150 C restore or dry the zeolite to its previous condition? (I'm assuming that is what is being attempted.) What is causing the zeolite to become darkened and does this reduce the activity of the catalyst?

Let me assume the catalyst is not being restored. You could run a simple set of reactions in which you vary the drying tome from a few minutes to several hours. If the yield or conversion correlates with drying time, I think that should separate the two issues. If it is an impurity. Then once the zeolite is dried, the conversion should plateau.

I used to activate my zeolites by putting them in a microwave oven. I think this was referenced in Fieser and Fieser.

[curiouscat]

You just put them in a typical microwave neat, say in a glass dish? I've only about 30 gm of catalyst or so.

[orgopete]

Yup, that's how I did it, actually a beaker. They tended to get really hot so be careful.

[curiouscat]

Yup, that's how I did it, actually a beaker. They tended to get really hot so be careful.

Ok, thanks! How long did you microwave them usually? What qty approximately.

[orgopete]

This was quite sometime ago, so I don't remember. I just did it by the seat of my pants. I put some in a beaker, put it in the microwave and watched what happened. It drove water out and you could see it condense on the side of the beaker. That told me it was working. I didn't try to see how hot it might get though, you know like microwaving paper until it burns. I wasn't  even scientific about it. I just took fresh sieves from a bottle and zapped it before adding it to my solvent for drying.

I can't have been the only person to have done this. Can someone else give details?