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Title: The Role of Carbon in Catalytically Stabilized Transition Metal Sulfides

Abstract

Since WWII considerable progress has been made in understanding the basis for the activity and the selectivity of molybdenum and tungsten based hydrotreating catalysts. Recently, the focus of investigation has turned to the structure of the catalytically stabilized active catalyst. The surface of the catalytically stabilized MoS2 has been shown to be carbided with the formula MoSxCy under hydrotreating conditions. In this paper we review the basis for this finding and present new data extending the concept to the promoted TMS (transition metal sulfides) systems CoMoC and NiMoC. Freshly sulfided CoMoS and NiMoS catalyst have a strong tendency to form the carbided surface phases from any available carbon source.

Authors:
; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930649
Report Number(s):
BNL-81091-2008-JA
TRN: US200901%%14
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Catalysis A: General; Journal Volume: 322
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CARBON; CATALYTIC EFFECTS; CATALYSTS; MOLYBDENUM SULFIDES; HYDROGENATION; MOLYBDENUM CARBIDES; CATALYSIS; COBALT SULFIDES; NICKEL SULFIDES; national synchrotron light source

Citation Formats

Kelty,S., Berhault, G., and Chianelli, R. The Role of Carbon in Catalytically Stabilized Transition Metal Sulfides. United States: N. p., 2007. Web. doi:10.1016/j.apcata.2007.01.017.
Kelty,S., Berhault, G., & Chianelli, R. The Role of Carbon in Catalytically Stabilized Transition Metal Sulfides. United States. doi:10.1016/j.apcata.2007.01.017.
Kelty,S., Berhault, G., and Chianelli, R. Mon . "The Role of Carbon in Catalytically Stabilized Transition Metal Sulfides". United States. doi:10.1016/j.apcata.2007.01.017.
@article{osti_930649,
title = {The Role of Carbon in Catalytically Stabilized Transition Metal Sulfides},
author = {Kelty,S. and Berhault, G. and Chianelli, R.},
abstractNote = {Since WWII considerable progress has been made in understanding the basis for the activity and the selectivity of molybdenum and tungsten based hydrotreating catalysts. Recently, the focus of investigation has turned to the structure of the catalytically stabilized active catalyst. The surface of the catalytically stabilized MoS2 has been shown to be carbided with the formula MoSxCy under hydrotreating conditions. In this paper we review the basis for this finding and present new data extending the concept to the promoted TMS (transition metal sulfides) systems CoMoC and NiMoC. Freshly sulfided CoMoS and NiMoS catalyst have a strong tendency to form the carbided surface phases from any available carbon source.},
doi = {10.1016/j.apcata.2007.01.017},
journal = {Applied Catalysis A: General},
number = ,
volume = 322,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • One of the chief problems in upgrading shale oil is the presence of inherent arsenic, which is known to poison downstream catalysts. Highly dispersed transition metal sulfides formed in situ from the decomposition of dithiocarbamate (DTC) complexes of transition metals show excellent potential as dearsenation agents. The authors have studied the reaction of these sulfides with various arsenic compositions, and characterized the metal arsenides and arsenic metal sulfides formed as well as the ease of their formation. Thus, the reaction of bis(butyldithiocarbamato)Ni, (NiBuDTC), with model compounds was very facile and gave NiAs, NiAsS, and NiAs[sub 2[minus]x]S[sub x]. In general, themore » effectiveness of the sulfides for dearsenation followed the sequence Ni > Mo [much gt] Co, while iron sulfides were totally ineffective. Based upon these results, tests where run in autoclaves (as well as a fixed-bed flow-through unit) with Ni BuDTC and shale oil having 73 ppm inherent As. Under optimum conditions, dearsenation down to less than 1 ppm was obtained.« less
  • The study of the second row of transition metal sulfided catalysts well-dispersed on activated carbon and of a conventional NiMo/alumina sulfided catalyst shows that these sulfides can be classified into three families following their pyridine hydrodenitrogenation activity: the very poor catalysts (order 1) such as MiMo, Zr, Ag, and Nb; the active catalysts (order 10) such as Mo, Rh, and Pd; and the very active catalyst Ru. The selectivity of products differs greatly from one catalyst to another: the higher the concentration in saturated C{sub 5} hydrocarbons, the higher the activity; the higher the concentration in cracked hydrocarbons (C{sub 4},more » C{sub 3}, C{sub 2}, and C{sub 1}) the lower the activity. In addition, there is no simple correlation between the concentrations of the different intermediate amines (piperidine and pentylamines mainly) and activity, which excludes any simple kinetical explanation.« less
  • Results of a detailed kinetic study on the thiophene hydrodesulfurization reaction at atmospheric pressure over a set of carbon-supported transition metal sulfides, i.e., the sulfides of Co, Mo, Rh, and the mixed CoMo sulfide, are presented. It is found that (partially) hydrogenated thiophenes, i.e., 2,3-dihydrothiophene, 2,5-dihydrothiophene, and tetrahydrothiophene, are important intermediates in the reaction mechanism. The reaction orders of thiophene suggest that carbon-sulfur bond cleavage is rate limiting for most of the catalysts. The CoMo catalyst may have hydrogenative sulfur removal as the rate limiting step. This catalyst shows a strong decrease in apparent activation energy with temperature to bemore » ascribed to a large change in steady state surface coverage by thiophene (or H{sub 2}S) as a function of temperature. This is consistent with a strong interaction between catalyst and thiophene. The Rh catalyst most probably shows a phase transition leading to different kinetic parameters. A strong interaction between the metal sulfide and thiophene is important for a high HDS activity. 38 refs., 4 figs., 5 tabs.« less
  • Transition metal sulfide (TMS) catalysts were prepared by impregnation of an activated carbon support with aqueous solutions of first-, second-, and third-row (group V-VIII) transition metal salts, drying and in situ sulfidation. The catalysts were tested in the hydrodenitrogenation of quinoline (653 K, 5.5 MPa) in microautoclaves and microflow reactors. The first-row transition metal sulfides had low quinoline conversions to hydrocarbons, and their periodic trend formed a U-shaped curve with a minimum at Mn/C and Fe/C and maxima at V/C and Ni/C. The quinoline conversions to hydrocarbons of the second- and third-row TMS formed volcano curves with maxima at Rh/Cmore » and Ir/C and with Mo/C and W/C having the lowest conversions. The transition metal sulfide catalysts with a low quinoline hydrogenation (first-row transition metal sulfides, Mo/C and W/C) also had a low quinoline conversion to hydrocarbons. The transition metal sulfides with the highest quinoline conversions to hydrocarbons (Rh/C, Pd/C, Os/C, Ir/C and Pt/C) had a very highquinoline hydrogenation and a high selectivity for propylcyclohexane. Ru/C and especially Re/C had a good quinoline conversion to hydrocarbons, but also an exceptionally high selectivity for propylbenzene.« less
  • Both a systematic experimental study of the promoting effect of the first row transition metals on the hydrodesulfurization (HDS) activity of MoS/sub 2/ and a systematic theoretical study of the electronic structure of simple clusters which model these catalyst systems have been carried out. A comparison of measured trends in activity with calculated trends in electronic structure makes it possible to establish an electronic basis for the promotion effects observed in the MoS/sub 2/ systems. Both Co and Ni, which serve as promoters, have the ability to donate electrons to Mo, while Cu, which serves as a poison, withdraws electronsmore » from Mo. The other first row transition metals, which have little effect on the HDS activity of MoS/sub 2/, do not have the ability to donate to or accept electrons from Mo. Thus promotion is associated with an increase in electron density on Mo while poisoning is associated with a decrease in electron density. These results are consistent with previous results which related particular electronic factors to the HDS activity of binary sulfide catalysts.« less