Selective Catalytic Reduction of NOx over V2O5-WO3-TiO2 SCR Catalysts—A Study at Elevated Pressure for Maritime Pre-turbine SCR Configuration

  • Steen R. Christensen
  • Brian B. Hansen
  • Kim H. Pedersen
  • Joakim R. Thøgersen
  • Anker D. JensenEmail author


The selective catalytic reduction (SCR) of NOx using NH3 was studied at pressures up to 5 bar over a vanadium-based SCR catalyst (~1 wt% V2O5 and 10 wt% WO3/TiO2), relevant for the installation of SCR reactors upstream of the turbocharger at marine engines. Experiments were performed using both granulated catalyst in a lab-scale fixed-bed reactor and a monolith catalyst in a bench-scale setup. The residence time across the catalytic bed was kept constant, by increasing the (normalized (0 °C, 1 atm)) volumetric flow rate proportionally to the pressure. The results show that for the granulated catalyst, the NOx conversion was independent of the pressure, indicating that the SCR kinetics are not affected by the increased pressure up to 5 bar. NH3 temperature-programmed desorption experiments showed that the catalyst NH3 adsorption increased with more than 30% when the pressure was increased from 1 bar to 4.5 bar. On the other hand, when the adsorption temperature was increased from 150 to 300 °C, the adsorption capacity decreased by approximately 60% independent on the pressure. The SCR reaction was unaffected by the increased NH3 uptake caused by the increased pressure, because only a certain fraction of the sites (\( {\theta}_{N{H}_3}^{\ast } \) = 0.14) was found to be active in the SCR reaction, and these are filled up at lower NH3 partial pressure than the total number of sites. Experiments using a monolithic catalyst showed that at temperatures above 250 °C, the NOx conversion was lower at an increased pressure (3.1 bar) when the residence time was held constant. This decrease was ascribed to increased internal and external diffusion limitations at the elevated pressure.


Pre-turbo SCR SCR of NOx on ships High-pressure SCR of NOx NH3 TPD V/W/Ti catalyst 



Ammonium bisulfate


Ammonia to NOx ratio


Ammonium sulfate


Channels per square inch


Continuous stirred tank reactor


Exhaust gas recirculation


International maritime organization


Liquid natural gas


NOx emission control area


Nitrogen oxides, the sum of NO and NO2


Packed bed reactor


Residual sum of squares


Selective catalytic reduction


SOx emission control area


Sulfur oxides, the sum of SO2, SO3, and H2SO4


Vanadium-based SCR catalyst



Temkin kinetics parameter [−]


NH3 concentration [mol/m3]


Catalyst particle diameter [m]


Reactor tube diameter [m]


Binary diffusion coefficient [m/s2]


Hydraulic diameter [m]


Porosity [−]


Activation energy of the adsorption process of NH3 [J/mol]

\( {E}_d^0 \)

Activation energy for the desorption process of NH3 [J/mol]


Friction factor [−]


Graetz dimensional number [−]


NO first order rate constant [1/s]


Mass based NO first order rate constant [m3/s/kg]

\( {k}_a^0 \)

Pre-exponential factor of the adsorption process of NH3 [m3/mol/s]

\( {k}_d^0 \)

Pre-exponential factor for the desorption process of NH3 [1/s]

\( {K}_{{\mathrm{NH}}_3} \)

NH3 adsorption equilibrium constant [m3/mol]


Reaction rate constant calculate at the temperature Tref


Length of catalyst [m]


NH3 adsorption capacity (mol/m3 particles)

\( \varOmega ={\varOmega}^{\prime}\cdot \frac{1-\varepsilon }{\varepsilon } \)

NH3 adsorption capacity (mol/m3 reactor)


Reactor pressure [Pa]


Volumetric flow rate (normal (0 °C, 1 atm)) [Nm3/s]


Rate of adsorption of NH3 [1/s]


Rate of desorption of NH3 [1/s]


Reynolds dimensional number [−]


Density of catalyst [kg/m3]


Rate of NO disappearance [1/s]


Schmidts dimensional number [−]


Sherwood dimensional number [−]


Asymptotic Sherwood number [−]


Surface coverage of NH3 [−]

\( {\theta}_{{\mathrm{NH}}_3}^{\ast } \)

Fraction of active sites in the SCR reaction [−]


Surface coverage of vanadium [−]


Linear velocity [m/s]


Volume [m3]


volumetric flow rate [m3/s]


Weight of catalyst [kg]


Vectors containing the measured gas phase mole fraction [ppm]


Vectors containing the modeled gas phase mole fraction [ppm]


Axial coordinate [m]


Dimensionless axial coordinate [−]



This work is part of the Danish societal partnership, Blue INNOship, and partly funded by the Innovation Fund Denmark (IFD) under File No: 155-2014-10 and the Danish Maritime Fund. The authors gratefully acknowledge the funding support.

Compliance with Ethical Standards

The authors declare that they have no competing interests.

Supplementary material

40825_2019_127_MOESM1_ESM.docx (4.7 mb)
ESM 1 (DOCX 4763 kb)


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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Department of Chemical and Biochemical EngineeringTechnical University of DenmarkKgs. LyngbyDenmark
  2. 2.Umicore Denmark ApSKgs. LyngbyDenmark

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