Catalysis of the Phillips Petroleum Company Polyethylene Process

Ordered Oxide Surfaces on Metals: Chromium Oxide

“…For example, Cr 2 O 3 is an anti-ferromagnetic insulator [1] and CrO 2 is a half-metallic ferromagnetic material [2]. Supported chromium oxide based catalysts are crucial in the chemical industry for the production of several important commodity chemicals [3][4][5][6][7][8][9][10][11][12]. Besides the known bulk phases and applications of chromium oxide, we might consider that highly ordered ultra thin films grown on metal surfaces comprise new classes of this material.…”

The Nature of Surface CrOx Sites on SiO2 in Different Environments

“…The original catalyst system has since been fine-tuned and ethylene polymerization by silica supported CrO x catalysts is now responsible for *40-50 % of all high-density polyethylene (HDPE) produced [3]. In spite of the extensive research studies that have been performed about the supported CrO x /SiO 2 catalyst system over the past six decades, the same fundamental structural and mechanistic questions are still being debated [1][2][3][4]. For example, the initial molecular structure of the oxidized surface Cr ?6 O x site has been proposed to be present as isolated surface dioxo CrO 4 , isolated surface mono-oxo CrO 5 , and dimeric surface Cr 2 O 7 , while the chromia oxidation state during ethylene polymerization has been proposed to be reduced Cr ?2 and Cr ?3 .…”

“…In the early 1950s, J. P. Hogan and R. L. Banks of Phillips Petroleum Company made the discovery that ethylene can be converted to polyethylene by a chromium oxide-silicaalumina catalyst [1] that was subsequently commercialized. The Phillips type catalyst system, CrO x supported on an amorphous support, such as silica, is one of three types of catalysts currently used for olefin polymerization.…”

“…The other two types are Ziegler-Natta and single-site homogeneous catalysts or supported homogeneous catalysts, both of which require an activator. The appeal of the Phillips catalyst lies in its many advantages: (i) yielding over 50 different types of polyethylene, (ii) functioning without activators, and (iii) operating at low temperatures and pressures [1][2][3]. The original catalyst system has since been fine-tuned and ethylene polymerization by silica supported CrO x catalysts is now responsible for *40-50 % of all high-density polyethylene (HDPE) produced [3].…”

Review of the Phillips Chromium Catalyst for Ethylene Polymerization

“…1 , often used as the chromium source in laboratory studies, starts out as Cr(VI) and remains so after calcining. Although bulk CrO 3 begins to decompose above 200 • C into O 2 and Cr 2 O 3 , a certain amount is stabilized on silica even up to 1000 • C [24,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. The most common commercial source of chromium is basic chromium(III) acetate [25][26][27][28].…”