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Deactivation of emission control catalysts for heavy-duty vehicles: Impact of biofuel and lube oil-derived contaminants
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.ORCID iD: 0000-0002-5784-6686
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Catalytic emission control is used to reduce the negative impact of pollutants from diesel exhausts on our health and on the environment. For a heavy-duty truck, such a system consists of a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), a selective catalytic reduction (SCR) catalyst, and an ammonia slip catalyst (ASC). Due to greenhouse-gas induced global warming, it is necessary to decrease the emissions of such gases. Two strategies for this reduction are: 1) to produce engines that are more fuel efficient, 2) to use sustainably produced renewable fuels such as biodiesel and HVO. However, both these strategies may pose additional challenges for the emission control system: a colder exhaust due to the higher fuel-efficiency requires the use of highly active catalysts; catalyst deactivation related to impurities in biofuels, which requires very robust catalysts.   The objective of this thesis was to study the impact of biofuel as well as lubrication oil-related contaminants on the performance of emission control catalysts (DOC and SCR catalysts) for heavy-duty diesel engines. The main focus has been on the low-temperature performance of V2O5-WO3/TiO2 (VWTi) and Cu-SSZ-13 SCR catalysts.    Results from the project have shown that both Cu-SSZ-13 and VWTi catalysts capture and can be deactivated by phosphorus (P), while only the Cu-SSZ-13 is deactivated by sulfur (S). The degree of the P-related deactivation depends on the concentration in the catalyst, which depends on content of P in the exhaust and the exposure time, as well as the type of catalyst. S-deactivation of Cu-SSZ-13 is observed at low temperatures, where un-poisoned Cu-SSZ-13 are significantly more active than VWTi catalysts. As a contrast, the VWTi-performance can even be improved by sulfur; but alkali metals are severe poisons to VWTi catalysts. Partial performance-recovery of S-poisoned Cu-SSZ-13 can be obtained by exposing it to sulfur-free exhausts at elevated temperatures. The use of an upstream DOC, providing fast SCR conditions to the SCR catalyst, considerably improves the low-temperature performance of the VWTi, as well as sulfur-poisoned Cu-SSZ-13 catalysts. An upstream DOC also protects the SCR catalysts from phosphorus deactivation, as it can trap large amounts of P. However, if too much phosphorus is captured by the DOC, severe deactivation of this catalyst results, which lowers the overall performance of the exhaust treatment system.  Insights from this project will guide the development of robust exhaust treatment systems for various applications. Additionally, it could aid in developing more durable emission control catalysts.

Abstract [sv]

Katalytisk avgasrening används för att minska de negativa hälso- och miljöeffekterna av dieselavgaser. För tunga lastbilar består detta avgasreningssystem av flera komponenter, dieseloxidationskatalysator (DOC), partikelfilter, SCR-katalysator och ammoniaköverskottskatalysator. I och med de klimatnegativa effekterna av växthusgaser, inkl. koldioxid, måste även emissionerna av dessa från tunga fordon minska. Två sätt att uppnå detta är att 1) producera mer bränsleeffektiva motorer, 2) använda förnybara bränslen såsom biodiesel och hydrerad växtolja (HVO). Båda dessa strategier kan dock medföra tuffa utmaningar för efterbehandlingssystemet – kallare avgaser respektive katalysatordeaktivering relaterad till kontamineringsämnen i biobränslena. Detta kräver att katalysatorerna är både aktiva och tåliga.  Syftet med detta doktorandprojekt har varit att studera effekten av biobränsle- och motoroljerelaterade kontamineringsämnens påverkan på avgasreningskatalysatorer för tunga dieselmotorer.  Huvudfokuset har varit påverkan på lågtemperaturegenskaperna hos två olika typer av SCR-katalysatorer, V2O5-WO3/TiO2 (VWTi) och Cu-SSZ. Resultat från projektet har visat att fosfor kan ackumuleras i både VWTi och Cu-SSZ-13 och deaktivera dessa, medan svavel endast deaktiverar Cu-SSZ-13. Denna deaktivering syns vid låga temperaturer där Cu-SSZ-13 annars har en betydligt bättre prestanda än VWTi. Prestandan för svavelförgiftad Cu-zeolit kan delvis fås tillbaka genom att öka temperaturen i avgaserna i svavelfri miljö. Närvaro av ammoniak i avgasen underlättar regenereringen. VWTi-katalysatorn är däremot inte känslig för svavel utan får snarare en något förbättrad prestanda. Däremot är alkalimetaller ett starkt gift för VWTi.  En uppströms DOC kan väsentligt förbättra lågtemperaturprestandan för VWTi och för svavelförgiftad Cu-SSZ-13 genom att förse dessa med NO2 så att snabb SCR kan uppnås. DOCn kan också skydda SCR-katalysatorer från fosforförgiftning genom att själv fånga upp fosfor. För mycket fosfor på DOCn resulterar dock i förgiftning även av denna, vilket påverkar resten av avgasbehandlingssystemet negativt. Resultaten från detta projekt kan användas för att utveckla robusta avgasbehandlingssystem för olika typer av tillämpningar, och kan bidra till utvecklandet av mer tåliga katalysatorer.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2020. , p. 121
Series
TRITA-CBH-FOU ; 2020:10
Keywords [en]
NH3-SCR, Cu-SSZ-13, V2O5-WO3/TiO2, catalyst deactivation, diesel oxidation catalyst, sulfur, phosphorus, biodiesel, heavy-duty, emission control, regeneration, alkali metals
Keywords [sv]
NH3-SCR, Cu-SSZ-13, V2O5-WO3/TiO2, katalysatordeaktivering, dieseloxidationskatalysator, svavel, fosfor, biodiesel, tunga dieselmotorer, avgasrening, regenerering, alkalimetaller
National Category
Chemical Process Engineering Other Chemistry Topics Materials Chemistry
Research subject
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-267206ISBN: 978-91-7873-437-5 (print)OAI: oai:DiVA.org:kth-267206DiVA, id: diva2:1391259
Public defence
2020-02-28, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 2020-02-04

Available from: 2020-02-04 Created: 2020-02-04 Last updated: 2020-02-05Bibliographically approved
List of papers
1. Multivariate analysis of the effect of biodiesel-derived contaminants on V2O5-WO3/TiO2 SCR catalysts
Open this publication in new window or tab >>Multivariate analysis of the effect of biodiesel-derived contaminants on V2O5-WO3/TiO2 SCR catalysts
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2016 (English)In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 183, p. 377-385Article in journal (Refereed) Published
Abstract [en]

This study investigates the effect of biodiesel-derived contaminants on vanadia-based NH3-SCR catalysts in heavy-duty exhaust aftertreatment. The aim was to study, not only the effect of single contaminants on the catalyst performance, but also of possible interaction effects between poisons. The effect of six potential catalyst poisons (Na, K, Mg, P, S and Zn) was evaluated using an experimental design and multivariate data analysis. Monolithic V2O5-WO3/TiO2 catalysts were subjected to accelerated laboratory-scale aging, where the six contaminants were fed simultaneously using a wet impregnation method. In addition to NO conversion tests, the catalysts were characterized by means of ICP-OES, SEM-EDX, XPS, N-2 physisorption and NH3-TPD. The lab-aged samples were compared to fresh and vehicle-aged catalysts. The accelerated aging method showed good reproducibility and gave rise to surface compounds similar to those found in vehicle-aged catalysts. Despite plausible differences regarding penetration depth of the contaminants into the walls of the catalyst, the aging method appears to be an efficient way to point out significant chemical poisons. The model obtained from the experimental design was found to correlate well with the experimental data and can therefore be used to predict effects of the various poisons and poison interactions. Significant effects on the NOx conversion were found for P, S, Na, Mg and K as well as for the interactions P x Na, P x K and S x Na. A poisoning effect was found for Mg, Na, K, P x K, and P x Na, where Na and K exhibited the strongest poisoning effect. The deactivating effect of alkali was lowered in the presence of phosphorus and sulfur, which is explained by the formation of phosphates and sulfates, preventing the interaction of the alkali metals with the vanadia active sites.

Keywords
NH3-SCR, V2O5-WO3/TiO2, Chemical deactivation, Design of experiments (DoE)
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-180579 (URN)10.1016/j.apcatb.2015.10.045 (DOI)000367106200042 ()2-s2.0-84947104888 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20160121

Available from: 2016-01-21 Created: 2016-01-19 Last updated: 2020-02-04Bibliographically approved
2. Catalytic aftertreatment systems for trucks fueled by biofuels - Aspects on the impact of fuel quality on catalyst deactivation
Open this publication in new window or tab >>Catalytic aftertreatment systems for trucks fueled by biofuels - Aspects on the impact of fuel quality on catalyst deactivation
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2018 (English)In: Catalysis:: Volume 30, Royal Society of Chemistry, 2018, p. 64-145Chapter in book (Refereed)
Abstract [en]

The issue of sustainable energy supply is a global problem for pursuing future endeavours in the energy area. In countries such as China and India there is a tremendous growth at the moment, which is envisaged by an ever growing demand for vehicles. Hence, one of the grand challenges of society is to meet the demands for sustainable and environmentally-friendly technologies in the transport sector. One way to tackle the problem of growing concentrations of carbon dioxide, which is believed to contribute to global warming, is the use of biofuels. It is becoming more and more evident that global warming is partly due to increasing anthropogenic carbon dioxide emissions. An important contribution to these emissions is the use of fossil fuels in the transport sector. Hence, more efficient engines and an increased use of biofuels would be a step in the right direction. Although new propulsion systems are emerging, such as hybrid power-trains and fuel cell systems, analysis shows that combustion systems with excess oxygen, such as the diesel engine, will be the most important engine concept for the next 20 years. In this paper we will identify the specific challenges related to the production and use of biofuels in heavy-duty trucks and how they influence the catalytic units in the emission after-treatment system in the truck. Biofuels, such as biodiesel, contain potential poisons for the vehicle exhaust after-treatment, such as potassium, sodium, magnesium, phosphorus, zinc, sulfur and other compounds.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
Series
Catalysis, ISSN 0140-0568, E-ISSN 1465-1920 ; 30
National Category
Energy Systems
Identifiers
urn:nbn:se:kth:diva-236380 (URN)10.1039/9781788013048-00064 (DOI)2-s2.0-85049314296 (Scopus ID)9781788011518 (ISBN)978-1-78801-304-8 (ISBN)978-1-78801-476-2 (ISBN)
Note

QC 20181105

Available from: 2018-11-05 Created: 2018-11-05 Last updated: 2020-02-04Bibliographically approved
3. Chemical aging of Cu-SSZ-13 SCR catalysts for heavy-duty vehicles –Influence of sulfur dioxide
Open this publication in new window or tab >>Chemical aging of Cu-SSZ-13 SCR catalysts for heavy-duty vehicles –Influence of sulfur dioxide
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2018 (English)In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 320, p. 72-83Article in journal (Refereed) Published
Abstract [en]

Selective catalytic reduction of nitrogen oxides is an efficient technique for emission abatement in heavy-dutyvehicles. Cu-SSZ-13 SCR catalysts are more active than vanadium-based catalysts at low temperatures, but aremore sensitive to deactivation by sulfur. Consequently, there is a need to study poisoning by sulfur for thiscatalyst material. This experimental investigation focuses on the effect of sulfur on the low-temperature per-formance of Cu-SSZ-13 SCR catalysts. The effect of sulfur exposure temperature, and the influence of the NO 2 /NO x ratio, are considered and two different regeneration temperatures are compared. In addition, catalystsamples from an engine-aged catalyst are evaluated. The SO 2 exposure temperature is shown to have an im-portant impact on the deactivation of the Cu-SSZ-13 catalyst. The lowest sulfur exposure temperature (220 °C)results in the most severe deactivation, while the highest temperature during sulfur exposure (400 °C) results inthe lowest degree of deactivation. This was found to be related to the amount of sulfur on the catalyst.Additionally, SO 2 exposure was shown to decrease the N 2 O selectivity. The engine-aged catalyst has a decreasedperformance in terms of both decreased activity and increased N 2 O selectivity. For this catalyst, impurities fromfuel and engine-oil can play a role in the deactivation. Different deactivation mechanisms are seen for the lab-and engine-aged catalysts.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2018
Keywords
NH3-SCR, Cu-SSZ-13, Cu-CHA, chemical deactivation, sulfur, heavy-duty vehicles, engine-aging
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-259737 (URN)10.1016/j.cattod.2018.01.035 (DOI)000448295200009 ()2-s2.0-85044780771 (Scopus ID)
Note

QC 20191011

Available from: 2019-09-22 Created: 2019-09-22 Last updated: 2020-02-04Bibliographically approved
4. In-situ studies of oxidation/reduction of copper in Cu-CHA SCR catalysts:comparison of fresh and SO2-poisoned catalysts
Open this publication in new window or tab >>In-situ studies of oxidation/reduction of copper in Cu-CHA SCR catalysts:comparison of fresh and SO2-poisoned catalysts
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(English)In: Article in journal (Other academic) Accepted
Abstract [en]

SO2-poisoning results in deactivation of Cu-CHA SCR under standard SCR conditions; however regeneration at 700 ◦C completely restores the SCR performance. To understand the nature of these effects, Cu-species in the fresh and poisoned catalystswere characterized by in-situ temperature-dependent time-resolved Cu K-edge X-ray absorption spectroscopy using the multivariate curve resolution alternating least squares (MCR-ALS) approach and continuous Cauchy wavelet transforms. The extracted chemically-meaningful reference spectra of Cu-species were analyzed by DFT-assisted XANES calculations. Cu-bisulfates werefound as the most energetically favorable poisoned Cu-species. The response of Cu-species to a reducing environment differs inthe fresh and SO2-poisoned catalysts. Differences in reducibility are related to the formation of quasi-linear Cu-complexes in the SO2-poisoned catalyst formed during heating in H2/He. Heating in H2/He leads to partial desulfurization of the poisoned catalyst. Cooling in H2/He after heating results in more facile formation of Cu-metal clusters in fresh catalyst than in SO2-poisoned.

National Category
Chemical Process Engineering Materials Chemistry Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-267205 (URN)
Available from: 2020-02-04 Created: 2020-02-04 Last updated: 2020-02-04
5. Effect of biofuel- and lube oil-originated sulfur and phosphorus on the performance of Cu-SSZ-13 and V2O5-WO3/TiO2 SCR catalysts
Open this publication in new window or tab >>Effect of biofuel- and lube oil-originated sulfur and phosphorus on the performance of Cu-SSZ-13 and V2O5-WO3/TiO2 SCR catalysts
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Two different SCR catalysts, V2O5-WO3/TiO2 and Cu-SSZ-13, were exposed to biodiesel exhausts generated by a diesel burner. The effect of phosphorus and sulfur on the SCR performance of these catalysts was investigated by doping the fuel with P-, S-, or P+S-containing compounds. Elemental analyses showed that both catalysts captured phosphorus while only Cu-SSZ-13 captured sulfur. High molar P/V ratios, up to almost 3, were observed for V2O5-WO3/TiO2, while the highest P/Cu ratios observed were slightly above 1 for the Cu-SSZ-13 catalyst. Although the V2O5-WO3/TiO2 catalyst captured more P than did the Cu-SSZ-13 catalyst, a higher degree of deactivation was observed for the latter, especially at low temperatures. For both catalysts, phosphorus exposure resulted in suppression of the SCR performance over the entire temperature range. Sulfur exposure, on the other hand, resulted in deactivation of the Cu-SSZ-13 catalyst mainly at temperatures below 300-350 ºC. The use of an oxidation catalyst upstream of the SCR catalyst during the exhaust-exposure could protect the SCR catalyst from phosphorus poisoning. The results in this work will improve the 2  understanding of chemical deactivation of SCR catalysts and aid in developing durable aftertreatment systems.

Keywords
Cu-SSZ-13, V2O5-WO3/TiO2, NH3-SCR, phosphorus, sulfur, biodiesel exhaust
National Category
Other Chemical Engineering Materials Chemistry
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-267201 (URN)
Available from: 2020-02-04 Created: 2020-02-04 Last updated: 2020-02-04
6. Deactivation of a Pd/Pt Bimetallic Oxidation Catalyst Used in a Biogas-Powered Euro VI Heavy-Duty Engine Installation
Open this publication in new window or tab >>Deactivation of a Pd/Pt Bimetallic Oxidation Catalyst Used in a Biogas-Powered Euro VI Heavy-Duty Engine Installation
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2019 (English)In: CATALYSTS, ISSN 2073-4344, Vol. 9, no 12, article id 1014Article in journal (Refereed) Published
Abstract [en]

The reduction of anthropogenic greenhouse gas emissions is crucial to avoid further warming of the planet. We investigated how effluent gases from a biogas powered Euro VI heavy-duty engine impact the performance of a bimetallic (palladium and platinum) oxidation catalyst. Using synthetic gas mixtures, the oxidation of NO, CO, and CH4 before and after exposure to biogas exhaust for 900 h was studied. The catalyst lost most of its activity for methane oxidation, and the activity loss was most severe for the inlet part of the aged catalyst. Here, a clear sintering of Pt and Pd was observed, and higher concentrations of catalyst poisons such as sulfur and phosphorus were detected. The sintering and poisoning resulted in less available active sites and hence lower activity for methane oxidation.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
oxidation catalyst, emission control, catalyst deactivation, engine bench, biogas, methane
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-267181 (URN)10.3390/catal9121014 (DOI)000507336600043 ()2-s2.0-85076737466 (Scopus ID)
Note

QC 20200204

Available from: 2020-02-04 Created: 2020-02-04 Last updated: 2020-02-04Bibliographically approved

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