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Title: CATALYSTS FOR HIGH CETANE ETHERS AS DIESEL FUELS

A tungstena-zirconia (WZ) catalyst has been investigated for coupling methanol and isobutanol to unsymmetrical ethers, i.e. methyl isobutyl ether (MIBE) and compared with earlier studied sulfated-zirconia (SZ) and Nafion-H catalysts. In all cases, the ether synthesis mechanism is a dual site S{sub N}2 process involving competitive adsorption of reactants on proximal acid sites. At low reaction temperatures, methylisobutylether (MIBE) is the predominant product. However, at temperatures >135 C the WZ catalyst is very good for dehydration of isobutanol to isobutene. The surface acid sites of the WZ catalyst and a Nafion-H catalyst were diagnosed by high resolution X-ray photoelectron spectroscopy (XPS) of N 1s shifts after adsorption of amines. Using pyridine, ethylenediamine, and triethylamine, it is shown that WZ has heterogeneous strong Broensted acid sites. Theoretical study located the transition state of the alcohol coupling reaction on proximal Broensted acid sites and accounted well for XPS core-level shifts upon surface acid-base interactions. While computations have not been carried out with WZ, it is shown that the SZ catalyst is a slightly stronger acid than CF{sub 3}SO{sub 3}H (a model for Nafion-H) by 1.3-1.4 kcal/mol. A novel sulfated zirconia catalyst having proximal strong Broensted acid sites was synthesized and shown tomore » have significantly enhanced activity and high selectivity in producing MIBE or isobutene from methanol/isobutanol mixtures. The catalyst was prepared by anchoring 1,2-ethanediol bis(hydrogen sulfate) salt precursor onto zirconium hydroxide, followed by calcination to remove the -(CH{sub 2}CH{sub 2})- bridging residues.« less
Authors:
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Publication Date:
OSTI Identifier:
823645
DOE Contract Number:
FG26-98FT40113
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Mar 2003
Research Org:
Lehigh University (US)
Sponsoring Org:
(US)
Country of Publication:
United States
Language:
English
Subject:
10 SYNTHETIC FUELS; 33 ADVANCED PROPULSION SYSTEMS; ADSORPTION; AMINES; BROENSTED ACIDS; CALCINATION; CATALYSTS; DIESEL FUELS; ETHERS; ETHYL ETHER; FASTENING; GLYCOLS; METHANOL; PYRIDINE; RESIDUES; X-RAY PHOTOELECTRON SPECTROSCOPY; ZIRCONIUM HYDROXIDES