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Surface chemistry and kinetics of the hydrolysis of isocyanic acid on anatase

Paper ID Volume ID Publish Year Pages File Format Full-Text
48786 46522 2007 9 PDF Available
Title
Surface chemistry and kinetics of the hydrolysis of isocyanic acid on anatase
Abstract

In order to meet the stricter NOx and particulate emission limits for commercial vehicles, the selective catalytic reduction (SCR) with urea is currently seen having the highest potential. The conversion of urea into ammonia and carbon dioxide consists of two consecutive reactions, in which isocyanic acid is an intermediate that is hydrolyzed over TiO2. The intrinsic kinetics and the surface chemistry for this reaction are explored. Up to a temperature of 132 °C the reaction was in the intrinsic kinetic regime (EA = 73 kJ/mol), while at higher temperatures the reaction was limited by pore and external diffusion constraints, respectively. In the presence of NO, NH3 and NO2, the catalytic activity was negatively influenced, increasing in severity in the sequence mentioned indicating that nitrates formed from NO2 were most effective in blocking cations and anions of TiO2. IR spectroscopy indicates that dissociative adsorption of HNCO on TiO2 forms Ti–NCO and hydrogen bonded OH species. In the presence of water, isocyanic acid was so rapidly hydrolyzed that only adsorbed ammonia was observed on the catalyst surface. The presence of NO, NH3 and NO2 retards hydrolysis leading to the appearance of isocyanate species on the surface.

Keywords
Diesel emission; SCR; DeNOx; Urea; Hydrolysis; Isocyanic acid; Isocyanate; Adsorption; Inhibition; TiO2
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Surface chemistry and kinetics of the hydrolysis of isocyanic acid on anatase
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 70, Issues 1–4, 31 January 2007, Pages 91–99
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us