The role of triethylaluminum in Z-N catalysts
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The common view here is that triethylaluminum serves as an activator for titanium-based catalysts (TiCl4 supported on MgCl2), providing active centers for the polymerization reaction and also helping to remove certain impurities from the monomer. However, I have seen in some sources that for certain polymerization reactions the catalyst is TiCl3 alone, along with triethylaluminum; so what is the role of triethylaluminum in this case? Just removing impurities?
Actually, it’s just as you said............. it provides active centers for the polymerization reaction, and it also helps to remove certain impurities from the monomers (such as CO, moisture). TiCl3 or TiCl4 are merely catalysts of different generations..... but they still require the assistance of a co-catalyst, triethylaluminum (TEAL)
Reply to 2# PCMA: Our understanding is that TEAL reduces TiCl4 to TiCl3; it is the trivalent titanium that serves as the active center of the catalyst. I just want to know whether this is merely a reduction reaction or if there are other processes involved as well
They’re all the same; the active center is Ti, okay??
It has three functions: 1. Converting TiCl4 into TiCl3; 2. Forming an active center together with TiCl3. Allow propylene molecules to grow on it 3. Remove impurities
TEAL forms the active center for polymerization together with the main catalyst, while eliminating harmful substances in the raw materials and the system, thereby protecting the main catalyst. TEAL-N standard type, used in the production of polyethylene ； TEAL-S special type, used in the production of polypropylene.
It mainly exerts a promoter effect, forming catalytically active centers with Ti atoms.