Sulfur Carriers 259
9.3.1.5 Sulfurized Fatty Oil (Black Color)
See Section 9.3.2.2 (Figure 9.5).
9.3.1.6 Sulfurized Fatty Oil/Olefi n Mixture (Light Color)
This special group of sulfur carriers is outstanding in properties as they combine the positive effects
of sulfurized olefi ns (e.g., hydrolytic stability, high sulfur content) with the excellent lubricity and
fi lm-forming properties of sulfurized fatty oils (Figure 9.6).
9.3.2 CURRENT COMMERCIAL PRODUCTION PROCESSES
9.3.2.1 General Aspects
In any current sulfurization process, the raw material is based on unsaturated compounds (olefi ns
or unsaturated esters). All reactions are addition reactions to olefi nic double bonds, and textbook
chemistry applies to this kind of reaction (catalytic conditions, mechanisms, addition patterns—
Markovnikov–anti-Markovnikov orientation).
Today’s large-scale production technology in general avoids any halogen-containing reaction
steps because there are low limits (maximum 30 ppm chlorine) in the fi nal lubricants that may
not be exceeded, for example, in automotive gear oils. Also, expensive removal/workup steps, for
example, by washing, can be avoided if halogens are not used.
Chromophoric group
O
O
O
O
O
O
S
S
S
S
S
S
S
S
S
R1
R2
R2
R1
S
FIGURE 9.5 Sulfurized fatty oil (black color).
n
O
O
R1
O
O
R1
S
S
S
FIGURE 9.4 Sulfurized synthetic esters (light color).