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Title: Bifunctional Nature of a SiO2-Supported Ni2P Catalyst for Hydrotreating: EXAFS and FTIR Studies

Abstract

A Ni{sub 2}P catalyst supported on a high-surface area SiO{sub 2} (350 m{sup 2} g{sub -1}) was prepared by temperature-programmed reduction, and its structural and surface properties were studied. X-ray diffraction and extended X-ray absorption fine structure measurements were used to obtain structural parameters for the supported Ni{sub 2}P phase, and Fourier transform infrared (FTIR) analysis with the probe molecules CO and pyridine was carried out to characterize the surface properties. The catalytic activity was measured at 573 K and 3.1 MPa in a three-phase fixed-bed reactor for hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) using a model liquid feed. At standard conditions using 500 ppm S as 4,6-dimethyldibenzothiophene (4,6-DMDBT), 3000 ppm S as dimethyldisulfide, 200 ppm N as quinoline, and 1% tetralin in a tridecane solvent, the Ni{sub 2}P/SiO{sub 2} gave an HDS conversion of 85%, an HDN conversion of 100%, and a tetralin conversion of 37%, which were much higher than those of a commercial Ni-Mo-S/Al{sub 2}O{sub 3} catalyst, which gave an HDS conversion of 41%, an HDN conversion of 98%, and a tetralin conversion of 20% based on equal numbers of sites (240 {micro}mol) loaded in the reactor. The sites were counted by CO chemisorption for the phosphide andmore » by low-temperature O{sub 2} chemisorption for the sulfide. The Ni{sub 2}P/SiO{sub 2} catalyst favored the hydrogenation (HYD) pathway for 4,6-DMDBT HDS to generate methylcyclohexyltoluene and dimethylbicyclohexane with a relative HYD selectivity of 95%. It also favored hydrogenation for tetralin to give decalin with a relative HYD selectivity of 89%. The Ni{sub 2}P/SiO{sub 2} catalyst also showed better resistance to N-compounds than the Ni-Mo-S/Al{sub 2}O{sub 3} catalyst. The FTIR spectra of adsorbed CO showed that the Ni site in the Ni{sub 2}P phase gave rise to considerable {pi}-back bonding, which was related to the high activity of the Ni{sub 2}P/SiO{sub 2} catalyst in the hydrogenation of aromatics. The FTIR spectra of adsorbed pyridine showed that the Ni{sub 2}P phase had a P{single_bond}OH group associated with Br{o}nsted acidity that was active for the protonation of N compounds. These results thus suggest that the supported Ni{sub 2}P catalyst has bifunctional properties that are beneficial for catalytic activity in hydroprocessing.« less

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914196
Report Number(s):
BNL-78764-2007-JA
Journal ID: ISSN 0021-9517; JCTLA5; TRN: US200804%%327
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Catal.; Journal Volume: 239; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; NICKEL PHOSPHIDES; CATALYTIC EFFECTS; CATALYST SUPPORTS; SILICON OXIDES; CHEMICAL PREPARATION; MORPHOLOGY; SURFACE PROPERTIES; CARBON MONOXIDE; PYRIDINE; CHEMISORPTION; HYDROGENATION; DESULFURIZATION; DENITRIFICATION; POLYCYCLIC SULFUR HETEROCYCLES; DISULFIDES; QUINOLINES; CATALYSIS; national synchrotron light source

Citation Formats

Lee,K., and Oyama, S. Bifunctional Nature of a SiO2-Supported Ni2P Catalyst for Hydrotreating: EXAFS and FTIR Studies. United States: N. p., 2006. Web. doi:10.1016/j.jcat.2005.12.029.
Lee,K., & Oyama, S. Bifunctional Nature of a SiO2-Supported Ni2P Catalyst for Hydrotreating: EXAFS and FTIR Studies. United States. doi:10.1016/j.jcat.2005.12.029.
Lee,K., and Oyama, S. Sun . "Bifunctional Nature of a SiO2-Supported Ni2P Catalyst for Hydrotreating: EXAFS and FTIR Studies". United States. doi:10.1016/j.jcat.2005.12.029.
@article{osti_914196,
title = {Bifunctional Nature of a SiO2-Supported Ni2P Catalyst for Hydrotreating: EXAFS and FTIR Studies},
author = {Lee,K. and Oyama, S.},
abstractNote = {A Ni{sub 2}P catalyst supported on a high-surface area SiO{sub 2} (350 m{sup 2} g{sub -1}) was prepared by temperature-programmed reduction, and its structural and surface properties were studied. X-ray diffraction and extended X-ray absorption fine structure measurements were used to obtain structural parameters for the supported Ni{sub 2}P phase, and Fourier transform infrared (FTIR) analysis with the probe molecules CO and pyridine was carried out to characterize the surface properties. The catalytic activity was measured at 573 K and 3.1 MPa in a three-phase fixed-bed reactor for hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) using a model liquid feed. At standard conditions using 500 ppm S as 4,6-dimethyldibenzothiophene (4,6-DMDBT), 3000 ppm S as dimethyldisulfide, 200 ppm N as quinoline, and 1% tetralin in a tridecane solvent, the Ni{sub 2}P/SiO{sub 2} gave an HDS conversion of 85%, an HDN conversion of 100%, and a tetralin conversion of 37%, which were much higher than those of a commercial Ni-Mo-S/Al{sub 2}O{sub 3} catalyst, which gave an HDS conversion of 41%, an HDN conversion of 98%, and a tetralin conversion of 20% based on equal numbers of sites (240 {micro}mol) loaded in the reactor. The sites were counted by CO chemisorption for the phosphide and by low-temperature O{sub 2} chemisorption for the sulfide. The Ni{sub 2}P/SiO{sub 2} catalyst favored the hydrogenation (HYD) pathway for 4,6-DMDBT HDS to generate methylcyclohexyltoluene and dimethylbicyclohexane with a relative HYD selectivity of 95%. It also favored hydrogenation for tetralin to give decalin with a relative HYD selectivity of 89%. The Ni{sub 2}P/SiO{sub 2} catalyst also showed better resistance to N-compounds than the Ni-Mo-S/Al{sub 2}O{sub 3} catalyst. The FTIR spectra of adsorbed CO showed that the Ni site in the Ni{sub 2}P phase gave rise to considerable {pi}-back bonding, which was related to the high activity of the Ni{sub 2}P/SiO{sub 2} catalyst in the hydrogenation of aromatics. The FTIR spectra of adsorbed pyridine showed that the Ni{sub 2}P phase had a P{single_bond}OH group associated with Br{o}nsted acidity that was active for the protonation of N compounds. These results thus suggest that the supported Ni{sub 2}P catalyst has bifunctional properties that are beneficial for catalytic activity in hydroprocessing.},
doi = {10.1016/j.jcat.2005.12.029},
journal = {J. Catal.},
number = 2,
volume = 239,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • The effect of crystallite size on the activity of silica-supported Pt catalysts during CO oxidation has been investigated by kinetic studies and in situ infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectroscopies. Catalysts containing 2% w/w Pt on silica were prepared by two different methods, rendering catalysts with dispersion values ranging between 0.29 and 0.80. Kinetic results indicate that the turnover frequency (TOF) of CO oxidation increases with increasing particle size under O{sub 2}-rich conditions, confirming that the CO oxidation reaction over Pt/SiO{sub 2} catalysts is structure sensitive under an oxidizing environment. This characteristic is not only relatedmore » to the gas phase surrounding the supported catalyst but also to the crystallite size range analyzed. EXAFS results show the formation of completely metallic Pt particles upon reduction in H2 at 300 {sup o}C for 1 h regardless of the particle size, whereas after a subsequent oxidation pretreatment only the smallest particles are fully oxidized. At room temperature, the oxidized Pt surface does not adsorb CO, but under oxidizing conditions (1% CO, 10% O{sub 2} in He) the oxidized catalysts show activity at T>100 {sup o}C. Fourier-transform infrared spectroscopy indicates that even this low CO concentration leads to reduction of the oxidized surface under reaction conditions. The results presented here clearly show that the active surface of Pt/SiO{sub 2} catalysts during CO oxidation is the metallic Pt, and that different sites on a Pt crystallite have different oxidation rates depending on its size. These results show the sensitivity of CO oxidation activity to the preparation method, pretreatment, and most significantly to the reaction atmosphere.« less
  • A Ni2P/SiO2 catalyst that is highly active for hydrodesulfurization (HDS) reaction was studied by in situ extended x-ray absorption fine structure (EXAFS) under the real reaction conditions. The measurements were conducted at realistic conditions of high pressure (3 MPa) and high temperature (613 K) in the presence of model oil. We used a low-volume cell with cubic boron nitride windows. The obtained spectra revealed that the bulk Ni2P structure was stable at reaction conditions and that the active surface had Ni-S bonds under reaction conditions, which played an important role for HDS reactions.
  • Ni{sub 2}P catalysts supported on potassium ion-exchanged ultrastable Y zeolites (KUSY) were prepared by temperature-programmed reduction (TPR), and the effect of Ni{sub 2}P loading and initial Ni/P ratios on the hydroprocessing performance was studied. X-ray diffraction (XRD), and extended X-ray absorption fine structure (EXAFS) were used to obtain structural parameters. Transmission electron microscopy (TEM) analysis showed that the KUSY-supported Ni{sub 2}P samples consisted of nanoparticles, which were likely situated in the mesoporous cavities or the external surfaces of the zeolite crystals. The catalytic activity was measured at 613 K and 3.1 MPa in a three-phase fixed bed reactor for hydrodesulfurizationmore » (HDS) and hydrodenitrogenation (HDN) using a model liquid feed containing 500 ppm S as 4,6-dimethyldibenzothiophene (4,6-DMDBT), 500 ppm N as quinoline, and 3000-6000 ppm S as dimethyldisulfide (DMDS). Partial exchange with K enhanced the catalytic activity for the HDS of 4,6-DMDBT and resistance to N-compound inhibition. The Ni{sub 2}P/KUSY had high activity with an HDS conversion of 99%, and an HDN conversion of 100%, which were much higher than those of a commercial Ni-Mo-S/Al{sub 2}O{sub 3} catalyst with an HDS conversion of 80% and HDN conversion of 100%, based on equal sites (240 {mu}mol) loaded in the reactor. The sites were counted by CO chemisorption for the phosphide and by low-temperature O{sub 2} chemisorption for the sulfide. Deficiency of P in the Ni{sub 2}P resulted in deactivation, probably due to susceptibility to sulfidation. EXAFS analysis of the catalysts showed that the addition of extra P led to an increase in Ni-P coordination with lengthening of Ni-Ni bond distances, resulting in a high and stable catalytic activity.« less
  • This report discusses the use of N{sub 2}O method to determine the surface area of copper catalyst. Extreme x-ray absorption fluorescence spectroscopy is used to show that average particle diameter of Copper on silicon oxide is less than 25 {Angstrom}.
  • No abstract prepared.