Hydrogenation Process Overview Filtration Dissolved Nickel Catalyst deactivation in fatty acids by corrosion Ni soap decomposition Nickel dissolution in the presence of hydrogen Formation of Nickel Soaps Dynamic State of Dissolved Nickel Soaps Dynamic State Brush Hydrogenation To lower Ni soap formation Reduce FFA in oil Prevent water or soap stock getting into reactor Minimize t1 Minimize t3 Find optimum filtration temperature

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

2. Hydrogenation Process
Crushing Refining
Filtration
Blending/
Packaging
/Delivery
Ni catalyst
in
Ni catalyst
out
Oil Seeds
Hydrogenation
Product
Post
bleaching/
Deodorization

3.  Reactor mix is filtered to remove the
catalyst
 There is usually a maximum allowed
residual nickel content in the product
 2 types of residual nickel
◦ (a) Particulate nickel - small black particles
◦ (b) Dissolved nickel - soluble nickel soaps,
salts, etc

4.  Majority of residual Ni cases are due to this
 Ni tolerances have been coming down
 ………but Fatty Acid levels haven’t
 => Increasingly difficult to keep dissolved Ni soaps
below detection

5. Equilibrium is determined by hydrogen concentration !
Ni(fa)2 + H2
low pressure/
hydrogen shortage
high pressure/
abundance of hydrogen
Ni + 2 ffa

6. Fate of nickel crystallites:
Nickel dissolution is chemically reversible, but catalytic surface
vanishes drastically thereby (loss of Nickel dispersion):
+ ffa
- ffa
+ Ni-soaps
fresh
catalyst 100 m²/g Ni
used
catalyst 10-20 m²/g Ni

8. 0
5
10
15
20
25
0 0.1 0.2 0.3 0.4 0.5 0.6
1/H2 pressure (bar-1)
DissolvedNi(ppm)
2 bar10 bar30 bar
Ni2+ = K.(H+)2/H2
Ni + 2H+ = Ni2+ + H2
Note Ni dissolution decreases by factor 100 for every pH unit rise!
(data based on fatty acid hydrogenation 180 C)

9.  Reversible reaction
 More H2 reaction goes
 Less H2
 Concentration of Ni soaps will vary with conditions
and time!

10.  Concentration of Ni soaps will vary depending on
◦ H2 concentration (pressure/mixing)
◦ Ni content
◦ FFA content
◦ Temperature
 These vary over the process
◦ Hence dissolved Ni content DYNAMIC

11.  A : heat-up, catalyst in FA but no H2
Ni content in oil
time
Nicontent(ppm)
0 t0 t1 t2 t3
Neq
Nmax
Nf
A B C
• B : H2 present; reaction occurring
• C : H2 valve closed; drop-tank & filtration

12.  Leads to higher residual Ni
Ni content in oil
time
Nicontent(ppm)
0 t0 t1 t2 actual t3 actual
Neq
Nmax
Nf
IV90
IV80
IV70

13.  “Prevention is better than cure”
 Reduce FFA even further!
 Try to minimize the formation of Ni soaps by
making conditions for it unfavorable

14.  Shorten contact time in absence of H2 BEFORE
reaction
Ni content in oil
minimizing t1 (catalyst in oil without hydrogen before reaction)
time
Nicontent(ppm)
0 t0 t1 new t2 t3
Nmax
Nf
IV90
IV80
IV70
Nf new

15.  Make addition of catalyst last possible operation
before opening H2 valve
 Dose to the reactor while under H2 pressure
 Melt catalyst only in cover fat

16.  Shorten contact time in absence of H2 AFTER reaction
Ni content in oil (Green Line )
minimizing t1 & t3 (catalyst in oil without hydrogen before and after
reaction)
time
Nicontent(ppm)
0 t0 t1 t2 t3
Nmax
Nf
IV90
IV70
Nf
Nf new

17.  Filter immediately after hydrogenation is finished
 Increasing filter area for faster filtration
 Minimizing problem-causing impurities (e.g. P,
wax)
 Optimize temperature of filtration

18.  Reactor mix is filtered to remove the catalyst
 There is usually a maximum allowed residual
nickel content in the product
 2 types of residual nickel
◦ (a) Particulate nickel - small black particles
◦ (b) Dissolved nickel - soluble nickel soaps, salts, etc
 Identifying which type:
◦ Can check if it is (a) by using a filter paper check and
particle analysis
◦ If no black dots on filter paper and still Ni in ICP
reading it is probably dissolved nickel

19.  Dissolved Nickel removed with
◦ post bleaching with citric or phosphoric acid
◦ use of bleaching earth
◦ reduction in FFAs and/or water in feed oil
◦ reduction in contact time without hydrogen

20.  Reduce FFA in oil
 Prevent water or soap stock getting into reactor
 Minimize t1
 Minimize t3
 Find optimum filtration temperature