Olefin Polymerization on Supported Chromium Oxide Catalysts

High resolution X-ray photoelectron spectroscopic analysis of transformation of surface chromium species on Phillips CrOx/SiO2 catalysts isothermally calcined at various temperatures

“…With its unique product properties, the catalyst is still quite competitive against Ziegler-Natta and metallocene catalysts in some application areas like blow molding HDPE products [11,12]. Further improvements of this catalyst are in high demand in the industrial field but still remained as a challenging work due to poor mechanistic understanding of it even after 50 years of great research efforts in this field [13][14][15][16][17]. A clearer understanding of the physico-chemical states of surface Cr species on Phillips catalyst is expected to play an important role for further mechanistic exploration [15,17].…”

Photo-stability of surface chromate species on Phillips CrO /SiO2 catalysts isothermally calcined at various temperatures, probed by high resolution X-ray photoelectron spectroscopy

“…Nowadays, it is still responsible for producing over 7 million tons of high density polyethylene (HDPE) per year in the world, which covers about 40% of the world HDPE market. However, many mechanisms relating to the nature of active site and its polymerization are still open for discussion in spite of the great industrial success as well as 50 years of research efforts in this field [3][4][5][6][7]. Further improvements based on better mechanistic understanding of this catalyst system are in high demand from the industrial field but still remain a challenging work.…”

Selective Catalysis and Nanoscience: An Inseparable Pair

“…With the exception of the low-density polyethylene (LDPE), which is made by a high temperature/high pressure radical process, the other types of polyolefins are produced by using either homogeneous or heterogeneous catalysts operating at relatively low temperatures (353-453 K) and pressures (< 50 bar). Basically, three main classes of olefin polymerization catalysts can be distinguished: i) the Ziegler-Natta heterogeneous catalysts, [124][125][126][127][128][129][130] ii) the Phillips-type heterogeneous catalysts, [131][132][133][134][135][136] and iii) the single-site homogeneous catalysts (or supported homogeneous catalysts), such as metallocene catalysts. [137,138] Since the 1950s, most of the important polymers have been made by using catalysts with only limited control over the range of lengths of the polymer chains (low product selectivity), as well as over other structural features that govern the properties of the material.…”