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Title: LDRD final report on new homogeneous and supported oligomerization catalysts (LDRD 42461).

Abstract

The overall purpose of this LDRD is multifold. First, we are interested in preparing new homogeneous catalysts that can be used in the oligomerization of ethylene and in understanding commercially important systems better. Second, we are interested in attempting to support these new homogeneous catalysts in the pores of nano- or mesoporous materials in order to force new and unusual distributions of a-olefins to be formed during the oligomerization. Thus the overall purpose is to try to prepare new catalytic species and to possibly control the active site architecture in order to yield certain desired products during a catalytic reaction, much like nature does with enzymes. In order to rationally synthesize catalysts it is imperative to comprehend the function of the various components of the catalyst. In heterogeneous systems, it is of utmost importance to know how a support interacts with the active site of the catalyst. In fact, in the catalysis world this lack of fundamental understanding of the relationship between active site and support is the single largest reason catalysis is considered an 'empirical' or 'black box' science rather than a well-understood one. In this work we will be preparing novel ethylene oligomerization catalysts, which are normally P-Omore » chelated homogeneous complexes, with new ligands that replace P with a stable carbene. We will also examine a commercially catalyst system and investigate the active site in it via X-ray crystallography. We will also attempt to support these materials inside the pores of nano- and mesoporous materials. Essentially, we will be tailoring the size and scale of the catalyst active site and its surrounding environment to match the size of the molecular product(s) we wish to make. The overall purpose of the study will be to prepare new homogeneous catalysts, and if successful in supporting them to examine the effects that steric constraints and pore structures can have on growing oligomer chains.« less

Authors:
;
Publication Date:
Research Org.:
Sandia National Laboratories
Sponsoring Org.:
USDOE
OSTI Identifier:
920453
Report Number(s):
SAND2004-5506
TRN: US200818%%21
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; HOMOGENEOUS CATALYSIS; CATALYSTS; CRYSTALLOGRAPHY; ETHYLENE; POLYMERIZATION; PORE STRUCTURE; CATALYST SUPPORTS; POROUS MATERIALS; SYNTHESIS; Catalysts-Analysis.; Oligomers.; Nanoscience.

Citation Formats

Hascall, Anthony G., and Kemp, Richard Alan. LDRD final report on new homogeneous and supported oligomerization catalysts (LDRD 42461).. United States: N. p., 2004. Web. doi:10.2172/920453.
Hascall, Anthony G., & Kemp, Richard Alan. LDRD final report on new homogeneous and supported oligomerization catalysts (LDRD 42461).. United States. doi:10.2172/920453.
Hascall, Anthony G., and Kemp, Richard Alan. 2004. "LDRD final report on new homogeneous and supported oligomerization catalysts (LDRD 42461).". United States. doi:10.2172/920453. https://www.osti.gov/servlets/purl/920453.
@article{osti_920453,
title = {LDRD final report on new homogeneous and supported oligomerization catalysts (LDRD 42461).},
author = {Hascall, Anthony G. and Kemp, Richard Alan},
abstractNote = {The overall purpose of this LDRD is multifold. First, we are interested in preparing new homogeneous catalysts that can be used in the oligomerization of ethylene and in understanding commercially important systems better. Second, we are interested in attempting to support these new homogeneous catalysts in the pores of nano- or mesoporous materials in order to force new and unusual distributions of a-olefins to be formed during the oligomerization. Thus the overall purpose is to try to prepare new catalytic species and to possibly control the active site architecture in order to yield certain desired products during a catalytic reaction, much like nature does with enzymes. In order to rationally synthesize catalysts it is imperative to comprehend the function of the various components of the catalyst. In heterogeneous systems, it is of utmost importance to know how a support interacts with the active site of the catalyst. In fact, in the catalysis world this lack of fundamental understanding of the relationship between active site and support is the single largest reason catalysis is considered an 'empirical' or 'black box' science rather than a well-understood one. In this work we will be preparing novel ethylene oligomerization catalysts, which are normally P-O chelated homogeneous complexes, with new ligands that replace P with a stable carbene. We will also examine a commercially catalyst system and investigate the active site in it via X-ray crystallography. We will also attempt to support these materials inside the pores of nano- and mesoporous materials. Essentially, we will be tailoring the size and scale of the catalyst active site and its surrounding environment to match the size of the molecular product(s) we wish to make. The overall purpose of the study will be to prepare new homogeneous catalysts, and if successful in supporting them to examine the effects that steric constraints and pore structures can have on growing oligomer chains.},
doi = {10.2172/920453},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2004,
month =
}

Technical Report:

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  • This report summarizes our findings during the study of a novel homogeneous epoxidation catalyst system that uses molecular oxygen as the oxidant, a ''Holy Grail'' in catalysis. While olefins (alkenes) that do not contain allylic hydrogens can be epoxidized directly using heterogeneous catalysts, most olefins cannot, and so a general, atom-efficient route is desired. While most of the work performed on this LDRD has been on pincer complexes of late transition metals, we also scouted out metal/ligand combinations that were significantly different, and unfortunately, less successful. Most of the work reported here deals with phosphorus-ligated Pd hydrides [(PCP)Pd-H]. We havemore » demonstrated that molecular oxygen gas can insert into the Pd-H bond, giving a structurally characterized Pd-OOH species. This species reacts with oxygen acceptors such as olefins to donate an oxygen atom, although in various levels of selectivity, and to generate a [(PCP)Pd-OH] molecule. We discovered that the active [(PCP)Pd-H] active catalyst can be regenerated by addition of either CO or hydrogen. The demonstration of each step of the catalytic cycle is quite significant. Extensions to the pincer-Pd chemistry by attaching a fluorinated tail to the pincer designed to be used in solvents with higher oxygen solubilities are also presented.« less
  • The synthesis of tetrachlorotetraphenylcyclopentadienyl group 5 metal complexes has been accomplished through two routes, one a salt metathesis with lithiumtetraphenylcyclopentadiende and the other, reaction with trimethyltintetraphenylcyclopentadiene. The reactants and products have been characterized by {sup 1}H and {sup 13}C({sup 1}H) NMR spectroscopy. The niobium complex promotes the silylcyanation of butyraldehyde. The grafting of metal complexes to silica gel surfaces has been accomplished using tetrakisdimethylamidozirconium as the metal precursor. The most homogeneous binding as determined by CP-MAS {sup 13}C NMR and infrared spectroscopy was obtained with drying at 500 C at 3 mtorr vacuum. The remaining amido groups can be replacedmore » by reaction with alcohols to generate surface bound metal alkoxides. These bound catalysts promote silylcyanation of aryl aldehydes and can be reused three times with no loss of activity.« less
  • Control of nanoparticle size is crucial to the development of nanotechnology. At this point in time, no general, rational synthetic strategy for controlling nanocrystal diameters and producing narrow diameter distributions has emerged. This is a reflection of a poor understanding of the mechanisms for nanocrystal growth. Based on previous studies of bismuth and gold nanoparticle growth, this work clearly establishes two new synthetic approaches to controlled growth of colloidal Pt nanocrystals, both based on aggregative-growth mechanisms, which afford narrow size distributions and size control over a wide and relevant size regime. The first new method is a phase transfer process,more » where growth is controlled by varying ligand stabilizer concentrations. The second method involves rapid reduction of a molecular platinum precursor in the presence of a polymer stabilizer. At present the size control is empirical, and incompletely understood and incompletely developed. However, the new synthetic pathways are amenable to kinetic study and analysis, establishing that a quantitative, rational control of sizes and size distributions can be achieved.« less
  • Re and Ir carbonyls, and other compounds, were chosen as precursors. MgO, La{sub 2}O{sub 3}, zeolite NaX and KL, among others, were chosen as supports. EXAFS was used to study the metal-support interactions. Structures formed on almost fully dehydroxylated MgO by HRe(CO){sub 5}, and on MgO by Ir{sub 4}(CO){sub 12}, were studied. A metal-oxygen distance of 2.15 {angstrom} holds in for the metal-support interface in oxide-supported metal clusters following reduction in H{sub 2} above 450 C; for reduction below 350 C, the distance is 2.5--2.7 {angstrom}.