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Title: A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga( i-Bu) 3 Grafted onto γ-Alumina and Silica

Abstract

The reactions of Ga( i-Bu) 3 ( i-Bu = CH 2CH(CH 3) 2) with the dehydrated and partially dehydroxylated surfaces of alumina (Al 2O 3–500) and silica (SiO 2–700) were studied by IR, high field solid-state NMR and EXAFS spectroscopies, as well as elemental analysis. Grafting onto Al 2O 3–500 occurs selectively by protonolysis at individual surface hydroxyl groups, resulting in the formation of mononuclear [(≡AlO)Ga( i-Bu) 2L] (L = surface oxygen) sites as the major surface organometallic entities. Conversely, grafting on silica affords dinuclear species [(≡SiO) 2Ga 2( i-Bu) 3] by a combination of protonolysis and isobutyl group transfer to Si. Further evidence for the difference in nuclearity was obtained by analysis of the WT-EXAFS. The mononuclear alumina-supported Ga sites show much higher activity in propane dehydrogenation than their dinuclear silica-supported counterparts. The propane dehydrogenation reaction may require the presence of Al–O–Ga bonds to promote heterolytic C–H bond activation. In conclusion, comparisons with benchmark catalysts and related systems show that the effect of the catalyst diluent is significant under the reaction conditions and must be carefully assessed in order to attribute reactivity correctly.

Authors:
 [1];  [2]; ORCiD logo [3];  [1];  [4];  [1];  [3]; ORCiD logo [3]; ORCiD logo [2];  [1]
  1. Univ. Lyon, Villeurbanne Cedex (France)
  2. Univ. of California, Santa Barbara, CA (United States)
  3. Univ. Lille, Lille (France)
  4. Univ. of California, Santa Barbara, CA (United States); Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1476169
Grant/Contract Number:  
AC02-76SF00515; FG02-03ER15467; FR 2638
Resource Type:
Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 8; Journal Issue: 8; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; alumina; benchmarking; gallium; propane dehydrogenation; silica; surface organometallic chemistry; wavelet transform EXAFS

Citation Formats

Szeto, Kai C., Jones, Zachary R., Merle, Nicolas, Rios, César, Gallo, Alessandro, Le Quemener, Frederic, Delevoye, Laurent, Gauvin, Régis M., Scott, Susannah L., and Taoufik, Mostafa. A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)3 Grafted onto γ-Alumina and Silica. United States: N. p., 2018. Web. doi:10.1021/acscatal.8b00936.
Szeto, Kai C., Jones, Zachary R., Merle, Nicolas, Rios, César, Gallo, Alessandro, Le Quemener, Frederic, Delevoye, Laurent, Gauvin, Régis M., Scott, Susannah L., & Taoufik, Mostafa. A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)3 Grafted onto γ-Alumina and Silica. United States. doi:10.1021/acscatal.8b00936.
Szeto, Kai C., Jones, Zachary R., Merle, Nicolas, Rios, César, Gallo, Alessandro, Le Quemener, Frederic, Delevoye, Laurent, Gauvin, Régis M., Scott, Susannah L., and Taoufik, Mostafa. Mon . "A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)3 Grafted onto γ-Alumina and Silica". United States. doi:10.1021/acscatal.8b00936. https://www.osti.gov/servlets/purl/1476169.
@article{osti_1476169,
title = {A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)3 Grafted onto γ-Alumina and Silica},
author = {Szeto, Kai C. and Jones, Zachary R. and Merle, Nicolas and Rios, César and Gallo, Alessandro and Le Quemener, Frederic and Delevoye, Laurent and Gauvin, Régis M. and Scott, Susannah L. and Taoufik, Mostafa},
abstractNote = {The reactions of Ga(i-Bu)3 (i-Bu = CH2CH(CH3)2) with the dehydrated and partially dehydroxylated surfaces of alumina (Al2O3–500) and silica (SiO2–700) were studied by IR, high field solid-state NMR and EXAFS spectroscopies, as well as elemental analysis. Grafting onto Al2O3–500 occurs selectively by protonolysis at individual surface hydroxyl groups, resulting in the formation of mononuclear [(≡AlO)Ga(i-Bu)2L] (L = surface oxygen) sites as the major surface organometallic entities. Conversely, grafting on silica affords dinuclear species [(≡SiO)2Ga2(i-Bu)3] by a combination of protonolysis and isobutyl group transfer to Si. Further evidence for the difference in nuclearity was obtained by analysis of the WT-EXAFS. The mononuclear alumina-supported Ga sites show much higher activity in propane dehydrogenation than their dinuclear silica-supported counterparts. The propane dehydrogenation reaction may require the presence of Al–O–Ga bonds to promote heterolytic C–H bond activation. In conclusion, comparisons with benchmark catalysts and related systems show that the effect of the catalyst diluent is significant under the reaction conditions and must be carefully assessed in order to attribute reactivity correctly.},
doi = {10.1021/acscatal.8b00936},
journal = {ACS Catalysis},
number = 8,
volume = 8,
place = {United States},
year = {2018},
month = {7}
}

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