This document discusses catalyst process technology for steam reforming of hydrocarbons. It covers the chemical reactions involved, catalyst design considerations like shape and chemistry, and carbon formation and removal. Key points discussed include the conversion of hydrocarbons to syngas, reforming and shift reactions, factors that influence methane conversion, reformer design, optimizing catalyst shape for heat transfer and pressure drop, using alkali-doped catalysts to prevent carbon formation, and tailored catalyst requirements.

1. C2PT Catalyst Process Technology
By Gerard B Hawkins
Managing Director

2. Steam Reforming Catalysis :
◦ Chemical reactions
◦ Catalyst shape design
◦ Catalyst chemistry
◦ Carbon formation and removal

3. The conversion of hydrocarbons to a mixture of
CO, CO2 and H2
Two reactions: Reforming and Shift
Steam Reforming (very endothermic)
CH4 + H2O CO + 3H2
CnH2n+2 + nH2O nCO + (2n + 1)H2
Water gas shift (slightly exothermic)
CO + H2O CO2 + H2
Overall the reaction is highly endothermic

4.  Both reforming and shift reactions are
reversible
 Rate of shift is fast compared to reforming
 Methane conversion favored by:
– low pressure
– high temperature
– high steam to carbon ratio

5. Steam
Secondary
Reformer
Steam
Steam + Gas
Steam
Reformer
Air / Oxygen500°C
780°C
450°C
1200°C
950°C
10% CH4 0.5% CH4

6.  The primary reformer is a heat exchanger
 Its function is to heat up process gas
 Catalyst and reaction in the tubes
 Combustion on the shell side
 Dominant heat transfer by radiation

8. 0 0.2 0.4 0.6 0.8 1
200
300
400
500
600
700
800
900
fraction down tube
temperature(°C)
gas temp
Eq temp
ATE

9.  Nickel on a ceramic support
 Three key factors in catalyst design:
– geometric surface area
– heat transfer from tube to gas
– pressure drop
 Also of concern:
– packing in the tube
– breakage characteristics

10. Top Fired Reformer
0 0.2 0.4 0.6 0.8 1
660
680
700
720
740
760
780
800
820
840
860
fraction down tube
tubewalltemperature(°C)
base case
base case with twice GSA
base case with twice heat transfer

11. Outside tube wall
temperature 830°C
Bulk Process
Gas Temp.
715°C
1200°C
Fluegas
Inside tube wall
temperature 775°C
Gas film
Tube
Wall

12.  Need to minimize thickness of gas film at tube
wall
 Smaller catalyst particles improve heat transfer
from wall to bulk gas and reduce tube
temperatures
 Smaller particles increase pressure drop
 Catalyst shape should be optimized for high
heat transfer with low pressure drop

13.  The traditional catalyst shape is a ring
 Smaller rings give high activity and heat
transfer but higher pressure drop
 Optimized catalysts offer high surface
area and heat transfer with low PD
 Important that shape also provides good
packing and breakage characteristics

14. Relative
Pressure Drop
Relative HTC
Voidage
1 0.9 0.9 0.8
1 2 3 4
1 1.3 1.1 1.0
0.49 0.6 0.58 0.59
1 2 3 4

15. Design of catalyst shape is a complex
optimization of:
– Higher surface area (needed for activity -
diffusion control)
– Higher heat transfer (needed for cooler
reformer tubes)
– Lower pressure drop (efficiency consideration)
Need also to consider breakage
characteristics and loading
pattern inside the reformer tube

16. Catalyst loading
can be improved
using various
dense loading
techniques

18.  Carbon formation is totally unwanted
 Causes catalyst breakage and
deactivation
 Leads to overheating of the tubes
 In extreme cases carbon formation
causes a pressure drop increase

19. Carbon Formation and
Prevention
Giraffe
Necking
Hot TubeHot Band
Reformer tube appearance - Carbon laydown

20.  Cracking
– CH4 C + 2H2
– C2H6 2C + 3H2 etc
 Boudouard
– C + CO2 2CO
 Gasification
– C + H2O CO + H2

21.  Under normal conditions carbon
gasification by steam and CO2 is favored
(gasification rate > C formation rate)
 Problems of carbon formation occur when:
– steam to carbon ratio is too low
– catalyst is not active enough
– higher hydrocarbons are present
– tube walls are too hot
– catalyst has poor heat transfer characteristics
 Use of a potash doped catalyst reduces
probability of carbon formation

22. Methods of preventing carbon formation:
– Use more active catalyst
– Use better heat transfer catalyst
– Reduce level of higher hydrocarbons
– Increase the steam ratio
– Use VSG-Z102 (3-7) -hole tailored catalysts
catalyst (potash-promoted)

23.  Alkali greatly accelerates carbon removal
 Addition of potash to the catalyst support
reduces carbon formation in two ways:
a increases the basicity of the support
b promotes carbon gasification
 Potash is mobile on the catalyst surface
 Potash doped catalyst is only needed in
the top half of the reformer tube
C + H2O CO + H2
OH -

24.  Increasing the content of alkali (potash)
– Higher heat flux possible for light feeds
– Heavier hydrocarbons can be steam reformed
– Lower steam to carbon ratios
– Faster carbon removal during steaming

25. Fraction Down TubeTop Bottom
Non-Alkalised
Catalyst
Ring Catalyst
Optimised Shape
(4-hole Catalyst)
Inside Tube Wall
Temperature
920 C
(1688 F)
820 C
(1508 F)
720 C
(1328 F)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Alkalised
Catalyst
Carbon Forming
Region
O
O
O
O
O
O

26. For light feeds and LPG etc using lightly
alkalised catalyst VSG-Z101
– Potash is chemically locked into catalyst
support
– Potash required only in the top 30-50% of the
reformer tube
– Catalyst life influenced by
 Poisoning
 Ni Sintering
 Process upsets etc
VSG-Z101
VSG-Z102

27. 0
0.5
1
1.5
2
2.5
3
1.2m 3m 5m 6m 9m
Catalyst samples at various depths down
reformer tube
Fresh
1 year
2 years
4 years
6 years
wt% of potash
VSG-Z102
VSG-Z102

28. Requirements :
◦ High and stable activity
◦ Low pressure drop
◦ Good heat transfer
◦ High resistance to carbon
◦ High strength
◦ Robust formulation/simple operation
Best achieved with VSG-Z101 (3-7) -hole
tailored catalysts