Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
Gasification of biomass is today facing several problems with the high amount of tar
produced and compounds such as alkali that can harm the catalyst in catalytic tar reformation.
This is why the focus in this master thesis study was to create a catalyst for secondary tar
steam reforming. The aim was to create a catalyst that was suitable for tar steam reforming
and also evaluate the effect that alkali had on the catalyst.
A catalyst composed of 20%Bronzes –ZrO2 impregnated with nickel was prepared in this
study and characterised with XRD and BET. The bronzes consisted of K0.25WO3 and was
prepared with two different methods and analysed with XRD to see if there was some
difference in the structure and purity. Three different weight loads of nickel: 5-,10- and 15
wt% , was prepared for each catalyst that was named Method 1 and Method 2. In total six
catalysts was tested in an experimental test rig that was situated at the Royal Institute of
Technology in Stockholm. In addition a blank test was performed for comparison of the
For the experiments 1-methylnaphthalene was decided to be used as a simulated tar. The
experiments were divided into two parts where in Part 1 a S/C ratio of 4 was used and Part 2 a
S/C ratio of 6 was used. The experiments were conducted at reactor temperatures of 700 °C
and 800 °C with or without alkali aerosols. Other parameters changed in the experiments were
the catalyst load, 1-methylnaphthalene flow and the gas hourly space velocity. Results were
analysed with 4 micro gas chromatographs and solid phase adsorption.
Results from the catalyst characterisation indicated that the wanted catalyst had been prepared
however in Method 2 a higher purity of the bronzes was reached compared to Method 1. The
results from the BET analysis gave a surface area of between 40-46 m2/g for the different
In the experiments from Part 1 a very high gas hourly space velocity was used and the results
indicated that there was almost tar reduction compared to the blank test. In Part 2 the gas
hourly space velocity was lowered and a higher tar reduction and was obtained. One test was
also conducted at 900 °C where the highest tar reduction was obtained, almost 40 %.
From the results it could be seen tar reduction and 1-MN/naphthalene ratio was increasing
with higher temperatures and nickel loadings. Catalysts prepared from Method 2 also showed
a higher tar reduction and 1-MN/naphthalene ratio compared to Method 1which could
indicate that it was more stable and had a higher purity of the bronzes. The results from
atomic absorption spectrophotometer showed that the mass of potassium in the catalyst before
the experiment decreased between 3-29 % compared to after the experiment. From the rather
low decrease in potassium the hexagonal structure of the bronzes clearly protects the
potassium from evaporating within the bulk. Also introducing alkali aerosols had a positive
effect on the tar reduction.
2015. , 74 p.