Gerard B. Hawkins Managing Director

C2PT Catalyst Process Technology

Hydrogenation Process

Crushing Refining

Filtration

Blending/ Packaging/Delivery

Ni catalyst in

Ni catalyst out

Oil Seeds

Hydrogenation

Product

Post bleaching/

Deodorization

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

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

Equilibrium is determined by hydrogen concentration !

Ni(fa)2 + H2

low pressure/ hydrogen shortage

high pressure/ abundance of hydrogen

Ni + 2 ffa

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

0

5

10

15

20

25

0 0.1 0.2 0.3 0.4 0.5 0.6

1/H2 pressure (bar-1)

Dis

solv

ed N

i (pp

m)

2 bar 10 bar 30 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)

Reversible reaction More H2 reaction goes Less H2

Concentration of Ni soaps will vary with conditions

and time!

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

A : heat-up, catalyst in FA but no H2

Ni content in oil

time

Ni c

onte

nt (p

pm)

0 t0 t1 t2 t3

Neq

Nmax

Nf

A B C

• B : H2 present; reaction occurring

• C : H2 valve closed; drop-tank & filtration

Leads to higher residual Ni

Ni content in oil

time

Ni c

onte

nt (p

pm)

0 t0 t1 t2 actual t3 actual

Neq

Nmax

Nf

IV90

IV80

IV70

“Prevention is better than cure” Reduce FFA even further!

Try to minimize the formation of Ni soaps by

making conditions for it unfavorable

Shorten contact time in absence of H2 BEFORE reaction

Ni content in oil minimizing t1 (catalyst in oil without hydrogen before reaction)

time

Ni c

onte

nt (p

pm)

0 t0 t1 new t2 t3

Nmax

Nf

IV90

IV80

IV70Nf new

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

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

Ni c

onte

nt (p

pm)

0 t0 t1 t2 t3

Nmax

Nf

IV90

IV70Nf

Nf new

Filter immediately after hydrogenation is finished Increasing filter area for faster filtration Minimizing problem-causing impurities (e.g. P,

wax) Optimize temperature of filtration

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

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

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