The_Catalyst_Review_January_2024 - 9

SPECIAL FEATURE
The PO catalyst market value, on a global basis, is expected to
grow 5% from 2023-2026. From 2023-2029, growth will moderate
to 4.7% annually, assuming an initial limited impact by mechanical
recycling (TCGR, 2023). In the following paragraphs, the author
focuses his analysis on the polyolefin catalysts recent technology
advances, global supply chain and the competitive market
perspectives. The author is preparing another article, " Polyolefin
Technology Transfer Market, " to be published in a forthcoming
edition of The Catalyst Review, which will analyze and discuss the
polyolefin process technology advances, market and trends in the
frame of circularity and CO2
emission mitigation.
Technology Advances
Sustainability still demands improved polymer materials in
terms of down gauging (light weighting), or more efficient
catalysts improving polymer CAPEX and OPEX, while the
circular economy forces packaging designers to prioritize
durability over disposability, push polymer recycling
(mechanical and chemical) and use of more renewable raw materials. In the following sections, the recent catalyst, process, and
product technology advances made by some technology leader/innovators are reviewed.
PE Chromium-based Catalysts
One would think that advances in the development of chromium catalysts would be minimal. However, there are still ongoing
issues in improving these catalyst formulations, as well as operations. One of those challenges has been to move away from organic
solvents, which cause extended drying times and increase the cost of catalyst production.
* CPChem details in one recent patent the use of carboxylic or alcohol/acetic acid mixtures in an aqueous solution in
depositing the silyltitanium compound, which reduces this cycle but increases activity and melt flow index (MFI). In a
novel idea, CPChem reduces the Cr catalyst oxidation states by using a light beam at a UV-visible wavelength. CPChem
suggests a bimetallic catalyst using aqueous solution and Cr and V.
* Many producers have now turned to internal formulations, which do not impair catalyst activity, containing aliphatics and
alcohols, such as LyondellBasell's formulation formed by 0.6 wt% water, 6 wt% isopropanol, 30 wt% dodecylbenzenesulfonic
acid and 63.4 wt% n-heptane.
* SABIC claims a bimodal PE from two different types of chromium sites, with one reduced with a cycloalkylamine
compound, then adjusting the molecular weight distribution (MWD) by regulating the ratio between the CrOx and SC.
PE Ziegler-Natta Catalysts
Regarding the ZN PE catalysts, the more recent improvement activity has been carried out with activators. One advance has been
in catalysts for LLDPE, which have greater control over long chain branching (LCB). Historically, this was produced by blending
LDPE with ZN LLDPE. New advances of Univation in ZN catalyst allow, outside of metallocenes, controlling the LCB by adjusting the
amount/concentration of the alkyl aluminum co-catalyst. It has been found that the type of reducing agent deployed can influence
MWD and MW.
PE Metallocene and SSC
Advancements in PE metallocene and single-site catalysts have proliferated over the last few years. These include new and novel
architectures, as well as the use of combined metallocene catalysts and mixtures of metallocenes with different ZN and Cr catalysts.
* One development example by CPChem is the use of dual metallocenes to make LLDPE with bi- or multi-modal MW's
but also the control of LCB in the lower MW component.
* There is also a strong movement away from methylaluminoxane (MAO) activators with metallocenes, beyond borates.
There are multiple claims by different producers, with fluorides being the strongest alternative, but other electron
withdrawing anions including chloride, bromide, phosphate, triflate, bisulfate, sulfates or combinations are claimed.
CPChem is using different alkyl aluminums to control MW, using bridged half metallocene Ti's, Zr's as a proven
technique. Control of melt index ratio (MIR) and melt strength (MS) are crucial to maintaining good PE processability,
Figure 4. Global PO catalyst components & non-merchant catalysts
value 2022 (USD million).
Source: Author
The Catalyst Review
January 2024
9

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