Production of powder catalysts

Abstract

A process for the production of a magnesium chloride powder for use in a catalyst, the process comprising vaporising magnesium chloride in a plasma torch and quenching the vapour with a liquid containing an electron donor to form a magnesium chloride-based powder catalyst wherein at least 80% by weight of the magnesium chloride is present as the hexagonal phase thereof. The invention also relates to a precursor for such a catalyst.

1 . A process for the production of a magnesium chloride powder for use in a catalyst, the process comprising vaporising magnesium chloride in a plasma torch and quenching the vapour with a liquid containing an electron donor to form a magnesium chloride-based powder wherein at least 80% by weight of the magnesium chloride is present as the hexagonal phase thereof.  
     
     
         2 . A process according to  claim 1  wherein the electron donor is dissolved in an organic diluent in an amount of at least 2 vol % based on the amount of diluent.  
     
     
         3 . A process according to  claim 2  wherein the electron donor is present in an amount of from 2.5 to 10 vol % based on the amount of diluent.  
     
     
         4 . A process according to any one of  claims 1  to  3  wherein the electron donor is selected from tetrahydrofuran (THF) , 1,3 dioxolane, dioxane, diethyl ether, methyl tert-butyl ether, diisobutyl phthalate, di-n-butyl phthalate, ethyl n-butyl phthalate, diethyl phthalate, ethyl i-butyl phthalate and mixtures thereof.  
     
     
         5 . A process according to any foregoing claim wherein the vapour is quenched at a temperature of below −10° C. to condense the magnesium chloride powder.  
     
     
         6 . A process according to any foregoing claim wherein the magnesium chloride is comprised in a furnace which has a bottom part thereof provided with electrical power thereby to enhance the vaporisation of the magnesium chloride.  
     
     
         7 . A process according to any foregoing claim wherein at least 85% by weight of the magnesium chloride is present as the hexagonal phase thereof.  
     
     
         8 . A process according to any foregoing claim wherein the plasma torch vaporises the magnesium chloride at a temperature of at least 2000° C.  
     
     
         9 . A process according to any foregoing claim wherein the quenching step is followed by a titanation step in which the magnesium chloride powder is titanated to form a titanated catalyst for polymerising alpha-olefins.  
     
     
         10 . A process according to  claim 9  wherein the titanated catalyst has a median particle size d50 of from 8 to 34 microns  
     
     
         11 . A precursor for a magnesium chloride-based catalyst for polymerising alpha-olefins, the precursor comprising a magnesium chloride/tetrahydrofuran complex wherein at least 80% by weight of the magnesium chloride is present as the hexagonal phase thereof.