Lean NOx reduction by alternative fuels - with focus on catalysts for dimethyl ether
Doktorsavhandling, 2011

There is an increased demand for diesel engines running on non-fossil fuels such as dimethyl ether (DME), biodiesel and synthetic diesel. DME is a promising alternative fuel with potential for high energy efficiency and low CO2 emissions. However, during all high temperature combustion NOx is formed, which may require exhaust aftertreatment. Two technologies for NOx reduction under lean conditions utilizing the fuel as reducing agent are the lean NOx catalyst (LNC) and the lean NOx adsorber (LNA). Lean NOx reduction with alternative fuels was investigated in a flow reactor and showed that DME was an efficient reducing agent for NOx over a BaO-based LNA, but not over a Cu-ZSM-5-based LNC. Also methanol did not reduce NOx over Cu-ZSM-5, whereas higher ethers and alcohols did. Despite being more oxidised than DME, ethylene glycol reduced NOx. It was concluded that a C–C bond is required in hydrocarbon-based reducing agents for lean NOx reduction over Cu-ZSM-5. A comparison of biodiesel, synthetic diesel, conventional diesel and octane as reducing agents, showed that Cu-ZSM-5 reduced NOx at a lower temperature than Ag/Al2O3, which was more sensitive to the reductant used. RME gave the lowest, and octane the highest, NOx conversion over both catalysts. The oxygenated hydrocarbon triethylene glycol dimethyl ether (triglyme) efficiently reduced NOx over Ag/Al2O3, but not over Cu-ZSM-5. Adding a low amount of triglyme to propene as reducing agents drastically promoted the NOx conversion over Ag/Al2O3 at low temperature. A series of In2O3-, Ga2O3- or B2O3-promoted γ-Al2O3 catalysts were investigated for lean NOx reduction with DME. B2O3/Al2O3 and Ga2O3/Al2O3 catalysts gave a temperature window similar to Al2O3, but with higher NOx conversion. In2O3/Al2O3 showed the highest NOx conversion at low temperature, whereas pure In2O3 was inactive for NOx reduction with DME. It was concluded that a close interaction between In2O3 and Al2O3 is essential for the promoting effect of In2O3 at low temperature. In-situ DRIFT spectroscopy showed that the differences in activity of In2O3/Al2O3, pure Al2O3 and pure In2O3 correlated to differences in the amounts of surface species that are possible intermediates of the reaction.

biofuel

In2O3

lean NOx reduction

alumina

Cu-ZSM-5

Ga2O3

DME

hydrocarbon-SCR

alternative fuel

NOx storage

B2O3

Ag/Al2O3

FB-salen, Fysikgården 4, Chalmers
Opponent: Professor Bjerne Clausen

Författare

Sara U Erkfeldt

Chalmers, Kemi- och bioteknik

Kompetenscentrum katalys (KCK)

Lean NOx Reduction with Various Bio-Diesels as Reducing Agents

Topics in Catalysis,; Vol. 54(2011)p. 1219-1223

Artikel i vetenskaplig tidskrift

Influence of the reducing agent for lean NOx reduction over Cu-ZSM-5

Applied Catalysis B: Environmental,; Vol. 102(2011)p. 547-554

Artikel i vetenskaplig tidskrift

NOx Reduction Performance of Lean NOx Catalyst and Lean NOx Adsorber Using DME as Reducing Agent

Topics in Catalysis,; Vol. 42/43(2007)p. 149-152

Artikel i vetenskaplig tidskrift

Intresset för alternativa bränslen har ökat de senaste åren till följd av en oro för den globala uppvärmningen. Inom transportsektorn används en mycket stor andel fossila bränslen, vars förbränning ger ett tillskott av växthusgasen koldioxid (CO2). Detta har lett till ett ökat intresse för motorer som arbetar med syreöverskott t.ex. dieselmotorer, som ger lägre CO2 emissioner än traditionella bensinmotorer. Samtidigt ökar efterfrågan på icke-fossila bränslen. Dimetyleter (DME) tillverkad från biomassa är ett lovande alternativt bränsle, med hög energieffektivitet och låga CO2 emissioner. Vid förbränning i luft under hög temperatur bildas dock kväveoxider (NOx), som är giftiga och ger miljöproblem. De måste därför omvandlas till kvävgas. Fokus för avhandlingen är att studera NOx reduktion i syrerika avgaser med alternativa bränslen, främst DME, som reduktionsmedel. Syftet är att öka förståelsen för reduktionsmedlets inverkan på NOx reduktionen och att utveckla katalysatorer för DME. Katalysatorns förmåga att reducera NOx med olika reduktionsmedel studerades i en flödesreaktor. Reduktionsmedlet visade sig ha en stor inverkan. De katalysatorer som används för diesel var inte effektiva med DME. Nya katalysatormaterial för DME togs fram och med IR-spektroskopi identifierades olika komponenter på ytan under reaktionen. Denna kunskap kan användas för att utveckla förbättrade katalysatorer för NOx reduktion med alternativa bränslen vilket underlättar introduktionen av dessa bränslen.

The use of alternative fuels is increasing due to the issue of global warming. The majority of the energy consumed in the transport sector comes from fossil fuels, whose combustion contributes to increased levels of atmospheric carbon dioxide (CO2). This has led to a large interest in engines operating under oxygen excess such as diesel engines, which give lower CO2 emissions than conventional gasoline engines. There is also an increased demand for non-fossil fuels. Dimethylether (DME) produced from biomass is a promising alternative fuel, with high energy efficiency and low CO2 emissions. However, high temperature combustion in air forms nitrogen oxides (NOx), which are toxic and environmentally harmful. These must thus be converted to harmless nitrogen gas. The focus of this thesis is to study NOx reduction in oxygen excess with alternative fuels, principally DME, as reducing agents. The aim is to increase the understanding of the influence of the reducing agent on NOx reduction and to develop catalysts for DME. The catalysts ability to reduce NOx with various reducing agents was studied in a flow reactor. The reducing agent was found to have a large influence. The catalysts used for NOx reduction with diesel were not efficient with DME. New catalytic materials for DME was developed and studied with IR spectroscopy to identify components on the surface during the reaction. This knowledge can be used to develop new catalysts for NOx reduction with alternative fuels.

Drivkrafter

Hållbar utveckling

Styrkeområden

Transport

Energi

Materialvetenskap

Ämneskategorier

Kemiska processer

Annan kemiteknik

Annan kemi

Kemi

ISBN

978-91-7385-580-8

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie

FB-salen, Fysikgården 4, Chalmers

Opponent: Professor Bjerne Clausen

Mer information

Skapat

2017-10-08