CrV Bimetallic Phillips Catalyst Prepared by Citric Acid‐Assisted Impregnation on Ethylene Polymerization

Abstract

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/macp.202000010. Three CrV bimetallic Phillips catalysts are developed by a citric acid-assisted impregnation method and studied in ethylene homopolymerization and ethylene/1-hexene copolymerization. The method benefits to the dispersion of bimetallic active sites, especially for the V ones. The electron binding energy shift of V 2p 3/2 in CrV-1/2-CA suggests the increased electron deficiency of V active center. The CrV-1/2-CA, CrV-1/3-CA catalysts present higher activity, broader molecular weight distribution, than the counterparts without CAassisted impregnation, suggesting more active sites involved in the reaction. The 1-hexene is higher inserted in the polyethylene by CrV-1/2 than the CrV-1/2-CA. But the results of temperature rising elution fractionation-successive selfnucleation and annealing (TREF-SSA) show the thinner platelet thickness at the high molecular weight parts of high-density polyethylene by CrV-1/2-CA, suggesting the higher insertion of 1-hexene and higher tensile properties. The CrV-1/2-CA also shows the more hydrogen-regulated response in the polymerization. The deconvolution of the gel permeation chromatography curves presents the higher fractions of high molecular weight polymer component.

Controlling Polyethylene Molecular Weights and Distributions Using Chromium Complexes Supported by SNN-Tridentate Ligands

“…Generally, different classes of polyethylenes result from the use of specific metal-based catalysts, of which the design and synthesis are expensive, time-consuming, and not always as rewarding as expected. Therefore, the development of tunable catalytic systems that could produce different polyethylenes is highly desirable but challenging. , One of the industrially most relevant catalyst is the chromium-based Phillips catalyst (CrO x /SiO 2 ). − Discovered in 1951 by Hogan and Banks at Phillips Petroleum, this heterogeneous catalyst allows the manufacture of one-third of the high-density polyethylene (HDPE) commercialized, which is the most widely used polymer . Although the Phillips catalyst has been studied for over 70 years by both academic and industrial scientists, the nature of the initiation process, the coordination environment and the oxidation state of the metal in the active species, and the catalytic mechanism remain a hot and sometimes controversial topic. − Furthermore, much effort has been dedicated to the development of well-defined homogeneous Cr-based catalysts, ,− that are more amenable to detailed spectroscopic and structural studies than heterogeneous catalysts.…”

Study on Denitration Performance of Solid Waste Blast Furnace Slag Catalysts under Different Preparation Processes

“…Citric acid could promote the combination of Mn on the surface of the carrier and the active site, but excessive citric acid would change the acidity of the catalyst surface and the distribution of active sites when the amount of citric acid was very large, resulting in decreased catalytic activity. 46 , 47 …”

“…The performance of the Mn-based slag catalyst with 0.01% citric acid was better than that of the others, and the total NO treatment rate reached 41.03%. Citric acid could promote the combination of Mn on the surface of the carrier and the active site, but excessive citric acid would change the acidity of the catalyst surface and the distribution of active sites when the amount of citric acid was very large, resulting in decreased catalytic activity. , …”

Polyolefin microstructural deconvolution methods: The good, the bad, and the ugly

“…[51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66] Similar deconvolution studies were used to understand the effect of polymerization conditions and catalyst formulations for the polymerization of ethylene and α-olefins with Ziegler-Natta [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81] and Phillips/chromium catalysts. [82][83][84] Other studies used MWD deconvolution to identify active site populations for the polymerization of 1-octene, [85] 1-hexene, [86][87][88][89] and 1-butene [90,91] with Ziegler-Natta catalysts. An alternative MWD deconvolution algorithm, using the cumulative version of Flory distribution, has also been proposed but has not been widely adopted.…”