The_Catalyst_Review_January_2024 - 11

SPECIAL FEATURE
continued to explore other more novel PP catalyst
formulations. This includes mixed metals within
procatalysts such as bismuth (Bi), zinc (Zn) and vanadium,
according to a LyondellBasell patent. In this example, by
substituting Bi up to 2 mole per mole of Mg, the catalyst
has higher activity and higher crystallinity. Heterophasic
copolymers can also be made.
* Borealis has been developing less expensive Sirius
PP catalyst formulations in their emulsion technology
replacing butyl ethyl magnesium with MgCl2
,
incorporating nucleators in situ and exploring spray
drying to produce narrower particle size distribution.
Exploration of modified silica supports have also
received considerable attention. In addition to fluroided
silica supports, components to control porosity, BrunauerEmmett-Teller
(BET) surface area and spray drying to
control the macroporosity between 0.18 cc/g and 0.30 cc/g are needed for the reduction of elimination of sheeting and/or
chucking during reactor operation.
Figure 7. Clariant Polymax 600/610 phthalate free PP catalyst features.
Source: Richter Lukesova, 2022
* The last few years have seen considerable development of PP donors and activators. SABIC has been very active in this field.
They have an interesting broad patent in which the catalyst is prepared by reacting Mg aloxide or aryloxide with Ti tetrachloride,
a monoester activator and an internal donor of carbamate. A similar patent using benzoate claims an activity increase of 17.5 to
26.2 kg/gr catalyst, the MWD increases from 6.97 to 8.0 and the xylene soluble (XS) decrease from 4.56 to 2.19. Another important
example of activator development in phthalate free ZN catalysts is formulating the addition of electron-donating compounds
containing oxygen and/or nitrogen after the ethylbenzonate one. Such compounds are described as 9,9-bisnethoxymethyl-9Hflourene
or 4-{(ethoxycarbonyl(methyl)amino}pentan-2-yl-ethyl} carbamate. This is a novel patent by SABIC, but it seems a very
expensive approach. Not to be outdone, other new electron donors to improve activity and crystallinity, such as propylbenzoates
and carboxylates have recently been patented by LyondellBasell. Grace has also been very active, suggesting the use of
dibenzoates added to diethers and spray dried; this allows higher activity and better morphology control, an improved H2
response, and improved MWD relative to catalysts based on single donors while PetroChina has explored diketones donors.
In summary, all PP catalyst manufacturers have pursued multiple internal donors and activators to tailor catalyst activities and
properties to enhance process productivity and improve product properties. Combined catalysts systems are also now common
commercially. Numerous patents describe combined Cr/ZN, ZN and metallocene and combined metallocenes into single catalysts for
bimodal MWD or other improved PP/PE properties.
Global Supply Chain and Competitive Perspectives
As presented earlier, Figure 1 depicts the polyolefins value chain in the frame of circularity. Manufacturers for producing polyolefins
need supply of catalysts and process technology
respectively from the catalyst, co-catalysts suppliers
and process technology licensors. Catalyst suppliers
manufacture the pro-catalyst types (ZN, Cr-based or
metallocene/SSC), using the needed chemical raw
materials as MgCl2
, TiCl4
, Cr oxide, proper ligands,
internal electron donors (stereo regulators) for PP and
various supports (e.g., silica, alumina). Usually, other
chemical suppliers manufacture certain PO catalyst
components as co-catalysts/activators (e.g., Al-Alkyls or
MAO for metallocenes) and external electron donors
for PP (silanes), which are supplied directly to PO
producers that use them during the polymerization
together with the pro-catalyst.
This section will discuss briefly in the following the
polyolefin global catalyst and components supply
chain, the roles of different components suppliers, the
synergies among them and the possible marketing
advantages for the suppliers that are capable to offer
more catalysts and components. Table 4 summarizes
the PO catalyst manufacturing site locations of all the
major PO catalyst merchant suppliers.
The Catalyst Review
Table 4. PE/PP catalyst production sites.
Source: Author
January 2024
11

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