Special Issue "Automotive Emission Control Catalysts"

A special issue of Catalysts (ISSN 2073-4344).

Deadline for manuscript submissions: closed (31 January 2016)

Special Issue Editors

Guest Editor
Dr. Jae-Soon Choi

Fuels, Engines, and Emissions Research Center, Energy and Transportation Science Division, Oak Ridge National Laboratory, Knoxville, TN 37932, USA
Website | E-Mail
Fax: +1 865 946 1354
Interests: environmental catalysis; automotive catalysis; lean NOx catalysts; biofuels; spatiotemporally resolved measurement of catalytic reactions
Guest Editor
Dr. Petr Kočí

Department of Chemical Engineering, University of Chemistry and Technology, Prague, Technicka 5, CZ 166 28 Prague, Czech Republic
Website | E-Mail
Interests: heterogeneous catalytic reactors; exhaust gas aftertreatment; reaction kinetics; mathematical modeling; diffusion in porous materials

Special Issue Information

Dear Colleagues,

Emission control catalysts constitute an essential part of today’s vehicles powered by internal combustion engines, mitigating the harmful effects of pollutants in the exhaust gas. Despite the impressive advances made since the introduction of the first catalytic converters in the 1970s, there is a continued need for more effective after-treatment systems. Indeed, besides the ever tightening emission regulations, the automotive catalysts are expected to perform at progressively lower exhaust temperatures. Driven by public concern on energy security and climate change, the efficiency of internal combustion engines is improving at a rapid pace entailing a significant reduction in the exhaust temperature. To address this so-called low-temperature challenge—achieve over 90% conversion at 150 °C or lower—without compromising the catalyst cost and vehicle fuel economy, enhanced catalysts and operating strategies need to be developed. It necessitates further research on novel catalytic materials, fundamental details of catalyst structure, reaction mechanisms, kinetics, and deactivation processes.

This Special Issue focuses on recent developments in automotive emission control catalysts, including: (1) novel catalytic materials and catalyst designs; (2) scientific understanding of reaction pathways, kinetics, and deactivation mechanisms; (3) strategies for mitigation of catalyst deactivation and/or for catalyst regeneration; and (4) mathematical modeling.

Dr. Jae-Soon Choi
Dr. Petr Kočí
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


Keywords

  • Automotive catalysts
  • Exhaust gas after-treatment
  • Three-way catalysts
  • Diesel oxidation catalysts
  • Selective catalytic reduction
  • NOx storage-reduction
  • Lean NOx traps
  • Particulate filters
  • Hydrocarbon traps
  • Passive NOx adsorbers

Published Papers (9 papers)

View options order results:
result details:
Displaying articles 1-9
Export citation of selected articles as:

Editorial

Jump to: Research

Open AccessEditorial Automotive Emission Control Catalysts
Catalysts 2016, 6(10), 155; doi:10.3390/catal6100155
Received: 14 September 2016 / Accepted: 22 September 2016 / Published: 6 October 2016
PDF Full-text (160 KB) | HTML Full-text | XML Full-text
Abstract
Emission control catalysts constitute an essential part of today’s vehicles powered by internal combustion engines, mitigating the harmful effects of pollutants in the exhaust such as carbon monoxide, hydrocarbons, nitrogen oxides, and particulate matter [1].[...] Full article
(This article belongs to the Special Issue Automotive Emission Control Catalysts)

Research

Jump to: Editorial

Open AccessArticle Adsorption and Oxidation Investigations over Pt/Al2O3 Catalyst: A Microcalorimetric Study
Catalysts 2016, 6(5), 73; doi:10.3390/catal6050073
Received: 11 February 2016 / Revised: 27 April 2016 / Accepted: 5 May 2016 / Published: 17 May 2016
Cited by 2 | PDF Full-text (2728 KB) | HTML Full-text | XML Full-text
Abstract
The differential adsorption heats of oxygen and NO, as well as catalytic oxidation behavior during NO oxidation and NO2 dissociation reactions over supported Pt-catalysts, were investigated by microcalorimetric measurements. The average heat of adsorption (∆H) of oxygen ranged from 310 kJ/mol at
[...] Read more.
The differential adsorption heats of oxygen and NO, as well as catalytic oxidation behavior during NO oxidation and NO2 dissociation reactions over supported Pt-catalysts, were investigated by microcalorimetric measurements. The average heat of adsorption (∆H) of oxygen ranged from 310 kJ/mol at 200 °C to 289 kJ/mol at 400 °C. Over this temperature range formation of platinum oxides and coverage dependence caused variations in the apparent heat of adsorption. NO heat of adsorption from 50 to 150 °C was near constant with an average value of 202 kJ/mol over the temperature range. Full article
(This article belongs to the Special Issue Automotive Emission Control Catalysts)
Figures

Open AccessArticle Impact of Lubricant Additives on thePhysicochemical Properties and Activity of Three‐Way Catalysts
Catalysts 2016, 6(4), 54; doi:10.3390/catal6040054
Received: 1 February 2016 / Revised: 10 March 2016 / Accepted: 14 March 2016 / Published: 4 April 2016
Cited by 3 | PDF Full-text (5728 KB) | HTML Full-text | XML Full-text
Abstract
As alternative lubricant anti‐wear additives are sought to reduce friction and improve overall fuel economy, it is important that these additives are also compatible with current emissions control catalysts. In the present work, an oil‐miscible phosphorous‐containing ionic liquid (IL), trihexyltetradecylphosphonium bis(2‐ethylhexyl) phosphate ([P
[...] Read more.
As alternative lubricant anti‐wear additives are sought to reduce friction and improve overall fuel economy, it is important that these additives are also compatible with current emissions control catalysts. In the present work, an oil‐miscible phosphorous‐containing ionic liquid (IL), trihexyltetradecylphosphonium bis(2‐ethylhexyl) phosphate ([P66614][DEHP]), is evaluated for its impact on three‐way catalysts (TWC) and benchmarked against the industry standard zinc‐dialkyl‐dithio‐phosphate (ZDDP). The TWCs are aged in different scenarios: neat gasoline (no‐additive, or NA), gasoline+ZDDP, and gasoline+IL. The aged samples, along with the as‐received TWC, are characterized through various analytical techniques including catalyst reactivity evaluation in a bench‐flow reactor. The temperatures of 50% conversion (T50) for the ZDDP‐aged TWCs increased by 30, 24, and 25 °C for NO, CO, and C3H6, respectively, compared to the no‐additive case. Although the IL‐aged TWC also increased in T50 for CO and C3H6, it was notably less than ZDDP, 7 and 9 °C, respectively. Additionally, the IL‐aged samples had higher water‐gas‐shift reactivity and oxygen storage capacity than the ZDDP‐aged TWC. Characterization of the aged samples indicated the predominant presence of CePO4 in the ZDDP‐aged TWC aged by ZDDP, while its formation was retarded in the case of IL where higher levels of AlPO4 is observed. Thus, results in this work indicate that the phosphonium‐phosphate IL potentially has less adverse impact on TWC than ZDDP. Full article
(This article belongs to the Special Issue Automotive Emission Control Catalysts)
Figures

Open AccessFeature PaperArticle Mechanistic Investigation of the Reduction of NOx over Pt- and Rh-Based LNT Catalysts
Catalysts 2016, 6(3), 46; doi:10.3390/catal6030046
Received: 30 January 2016 / Revised: 29 February 2016 / Accepted: 2 March 2016 / Published: 15 March 2016
Cited by 2 | PDF Full-text (1654 KB) | HTML Full-text | XML Full-text
Abstract
The influence of the noble metals (Pt vs. Rh) on the NOx storage reduction performances of lean NOx trap catalysts is here investigated by transient micro-reactor flow experiments. The study indicates a different behavior during the storage in that the Rh-based
[...] Read more.
The influence of the noble metals (Pt vs. Rh) on the NOx storage reduction performances of lean NOx trap catalysts is here investigated by transient micro-reactor flow experiments. The study indicates a different behavior during the storage in that the Rh-based catalyst showed higher storage capacity at high temperature as compared to the Pt-containing sample, while the opposite is seen at low temperatures. It is suggested that the higher storage capacity of the Rh-containing sample at high temperature is related to the higher dispersion of Rh as compared to Pt, while the lower storage capacity of Rh-Ba/Al2O3 at low temperature is related to its poor oxidizing properties. The noble metals also affect the catalyst behavior upon reduction of the stored NOx, by decreasing the threshold temperature for the reduction of the stored NOx. The Pt-based catalyst promotes the reduction of the adsorbed NOx at lower temperatures if compared to the Rh-containing sample, due to its superior reducibility. However, Rh-based material shows higher reactivity in the NH3 decomposition significantly enhancing N2 selectivity. Moreover, formation of small amounts of N2O is observed on both Pt- and Rh-based catalyst samples only during the reduction of highly reactive NOx stored at 150 °C, where NOx is likely in the form of nitrites. Full article
(This article belongs to the Special Issue Automotive Emission Control Catalysts)
Figures

Open AccessArticle On the Effect of Preparation Methods of PdCe-MOR Catalysts as NOx CH4-SCR System for Natural Gas Vehicles Application
Catalysts 2015, 5(4), 1815-1830; doi:10.3390/catal5041815
Received: 1 September 2015 / Revised: 12 October 2015 / Accepted: 12 October 2015 / Published: 27 October 2015
Cited by 2 | PDF Full-text (942 KB) | HTML Full-text | XML Full-text
Abstract
In the present work, the effect of several parameters involved in the preparation of PdCe-HMOR catalysts active for NOxselective catalytic reduction with methane (NOx CH4-SCR) was studied. Results show that the catalytic performance of Pd-HMOR is better when
[...] Read more.
In the present work, the effect of several parameters involved in the preparation of PdCe-HMOR catalysts active for NOx selective catalytic reduction with methane (NOx CH4-SCR) was studied. Results show that the catalytic performance of Pd-HMOR is better when palladium is introduced by ion-exchange, namely at room temperature. It was also shown that Pd loading does not influence the formation of cerium species, namely surface Ce4+ (CeO2) species and CeO2 species in interaction with Pd. However, when Ce is introduced before Pd, more surface CeO2 species are stabilized in the support and less CeO2 become in interaction with Pd, which results in a worse NOx CH4-SCR catalytic performance. Full article
(This article belongs to the Special Issue Automotive Emission Control Catalysts)
Figures

Open AccessArticle Part I: A Comparative Thermal Aging Study on the Regenerability of Rh/Al2O3 and Rh/CexOy-ZrO2 as Model Catalysts for Automotive Three Way Catalysts
Catalysts 2015, 5(4), 1770-1796; doi:10.3390/catal5041770
Received: 3 August 2015 / Revised: 30 September 2015 / Accepted: 9 October 2015 / Published: 23 October 2015
Cited by 9 | PDF Full-text (15426 KB) | HTML Full-text | XML Full-text
Abstract
The rhodium (Rh) component in automotive three way catalysts (TWC) experiences severe thermal deactivation during fuel shutoff, an engine mode (e.g., at downhill coasting) used for enhancing fuel economy. In a subsequent switch to a slightly fuel rich condition, in situ catalyst regeneration
[...] Read more.
The rhodium (Rh) component in automotive three way catalysts (TWC) experiences severe thermal deactivation during fuel shutoff, an engine mode (e.g., at downhill coasting) used for enhancing fuel economy. In a subsequent switch to a slightly fuel rich condition, in situ catalyst regeneration is accomplished by reduction with H2 generated through steam reforming catalyzed by Rh0 sites. The present work reports the effects of the two processes on the activity and properties of 0.5% Rh/Al2O3 and 0.5% Rh/CexOy-ZrO2 (CZO) as model catalysts for Rh-TWC. A very brief introduction of three way catalysts and system considerations is also given. During simulated fuel shutoff, catalyst deactivation is accelerated with increasing aging temperature from 800 °C to 1050 °C. Rh on a CZO support experiences less deactivation and faster regeneration than Rh on Al2O3. Catalyst characterization techniques including BET surface area, CO chemisorption, TPR, and XPS measurements were applied to examine the roles of metal-support interactions in each catalyst system. For Rh/Al2O3, strong metal-support interactions with the formation of stable rhodium aluminate (Rh(AlO2)y) complex dominates in fuel shutoff, leading to more difficult catalyst regeneration. For Rh/CZO, Rh sites were partially oxidized to Rh2O3 and were relatively easy to be reduced to active Rh0 during regeneration. Full article
(This article belongs to the Special Issue Automotive Emission Control Catalysts)
Figures

Open AccessArticle Part II: Oxidative Thermal Aging of Pd/Al2O3 and Pd/CexOy-ZrO2 in Automotive Three Way Catalysts: The Effects of Fuel Shutoff and Attempted Fuel Rich Regeneration
Catalysts 2015, 5(4), 1797-1814; doi:10.3390/catal5041797
Received: 30 August 2015 / Revised: 8 October 2015 / Accepted: 8 October 2015 / Published: 23 October 2015
Cited by 9 | PDF Full-text (887 KB) | HTML Full-text | XML Full-text
Abstract
The Pd component in the automotive three way catalyst (TWC) experiences deactivation during fuel shutoff, a process employed by automobile companies for enhancing fuel economy when the vehicle is coasting downhill. The process exposes the TWC to a severe oxidative aging environment with
[...] Read more.
The Pd component in the automotive three way catalyst (TWC) experiences deactivation during fuel shutoff, a process employed by automobile companies for enhancing fuel economy when the vehicle is coasting downhill. The process exposes the TWC to a severe oxidative aging environment with the flow of hot (800 °C–1050 °C) air. Simulated fuel shutoff aging at 1050 °C leads to Pd metal sintering, the main cause of irreversible deactivation of 3% Pd/Al2O3 and 3% Pd/CexOy-ZrO2 (CZO) as model catalysts. The effect on the Rh component was presented in our companion paper Part I. Moderate support sintering and Pd-CexOy interactions were also experienced upon aging, but had a minimal effect on the catalyst activity losses. Cooling in air, following aging, was not able to reverse the metallic Pd sintering by re-dispersing to PdO. Unlike the aged Rh-TWCs (Part I), reduction via in situ steam reforming (SR) of exhaust HCs was not effective in reversing the deactivation of aged Pd/Al2O3, but did show a slight recovery of the Pd activity when CZO was the carrier. The Pd+/Pd0 and Ce3+/Ce4+ couples in Pd/CZO are reported to promote the catalytic SR by improving the redox efficiency during the regeneration, while no such promoting effect was observed for Pd/Al2O3. A suggestion is made for improving the catalyst performance. Full article
(This article belongs to the Special Issue Automotive Emission Control Catalysts)
Figures

Open AccessArticle VOx Surface Coverage Optimization of V2O5/WO3-TiO2 SCR Catalysts by Variation of the V Loading and by Aging
Catalysts 2015, 5(4), 1704-1720; doi:10.3390/catal5041704
Received: 24 August 2015 / Revised: 25 September 2015 / Accepted: 1 October 2015 / Published: 14 October 2015
Cited by 12 | PDF Full-text (385 KB) | HTML Full-text | XML Full-text
Abstract
V2O5/WO3-TiO2 selective catalytic reduction (SCR) catalysts with a V2O5 loading of 1.7, 2.0, 2.3, 2.6, 2.9, 3.2 and 3.5 wt. % were investigated in the fresh state and after hydrothermal aging at 600
[...] Read more.
V2O5/WO3-TiO2 selective catalytic reduction (SCR) catalysts with a V2O5 loading of 1.7, 2.0, 2.3, 2.6, 2.9, 3.2 and 3.5 wt. % were investigated in the fresh state and after hydrothermal aging at 600 °C for 16 h. The catalysts were characterized by means of nitrogen physisorption, X-ray diffraction and X-ray absorption spectroscopy. In the fresh state, the SCR activity increased with increasing V loading. Upon aging, the catalysts with up to 2.3 wt. % V2O5 exhibited higher NOx reduction activity than in the fresh state, while the catalysts with more than 2.6 wt. % V2O5 showed increasing deactivation tendencies. The observed activation and deactivation were correlated with the change of the VOx and WOx surface coverages. Only catalysts with a VOx coverage below 50% in the aged state did not show deactivation tendencies. With respect to tungsten, above one monolayer of WOx, WO3 particles were formed leading to loss of surface acidity, sintering, catalyst deactivation and early NH3 slip. An optimal compromise between activity and hydrothermal aging resistance could be obtained only with V2O5 between 2.0 and 2.6 wt. %. Full article
(This article belongs to the Special Issue Automotive Emission Control Catalysts)
Figures

Open AccessArticle Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst
Catalysts 2015, 5(3), 1535-1553; doi:10.3390/catal5031535
Received: 8 July 2015 / Revised: 25 August 2015 / Accepted: 28 August 2015 / Published: 4 September 2015
Cited by 2 | PDF Full-text (834 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The selective catalytic reduction (SCR) of NOx by NH3 has been extensively studied in the literature, mainly because of its high potential to remediate the pollution of diesel exhaust gases. The implementation of the NH3-SCR process into passenger cars
[...] Read more.
The selective catalytic reduction (SCR) of NOx by NH3 has been extensively studied in the literature, mainly because of its high potential to remediate the pollution of diesel exhaust gases. The implementation of the NH3-SCR process into passenger cars requires the use of an ammonia precursor, provided by a urea aqueous solution in the conventional process. Although the thermal decomposition and hydrolysis mechanisms of urea are well documented in the literature, the influence of the direct use of urea on the NOx reduction over SCR catalysts may be problematic. With the aim to evaluate prototype powdered catalysts, a specific synthetic gas bench adjusted to powdered material was developed, allowing the use of NH3 or urea as reductant for direct comparison. The design of the experimental setup allows vaporization of liquid urea at 200 °C under 10 bar using an HPLC pump and a micro injector of 50 μm diameter. This work presents the experimental setup of the catalytic test and some remarkable catalytic results towards further development of new catalytic formulations specifically dedicated to urea-SCR. Indeed, a possible divergence in terms of DeNOx efficiency is evidenced depending on the nature of the reductant, NH3 or urea solution. Particularly, the evaluated catalyst may not allow an optimal NOx conversion because of a lack in ammonia availability when the urea residence time is shortened. This is attributed to insufficient activity of isocyanic acid (HNCO) hydrolysis, which can be improved by addition upstream of an active solid for the hydrolysis reaction such as ZrO2. Thus, this µ-scale synthetic gas bench adjusted to powdered materials enables the specific behaviour of urea use for NOx reduction to be demonstrated. Full article
(This article belongs to the Special Issue Automotive Emission Control Catalysts)
Figures

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Effect of Fe2O3 Loading on FeVO4-Based NH3-SCR Catalysts
Authors
Alessandro Trovarelli
Affiliation:
Università di Udine Dipartimento di Chimica, Fisica e Ambiente via del Cotonificio 108 33100 Udine, Italy
Abstract:
FeVO4-Fe2O3 catalysts supported on TiO2-WO3-SiO2 (TWS) were studied for their application in the NH3-SCR reaction. All the catalysts were characterized by means of X-ray powder diffraction, B.E.T. surface area measurements and temperature programmed methods. Selective catalytic reduction of NO was measured in a laboratory set-up for powder tests. The work is focused to highlight the influence of different loadings of Fe2O3 on catalytic activity and stability of FeVO4/TWS previously investigated in our laboratories. It is shown that Fe2O3 plays an important role on thermal stability and catalytic activity. This is a consequence of the effect of hindering the phase transformation of TiO2 of the support from anatase to rutile.

Journal Contact

MDPI AG
Catalysts Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
E-Mail: 
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Catalysts Edit a special issue Review for Catalysts
logo
loading...
Back to Top