New Catalysts from Spent Catalysts - Spent Hydroprocessing Catalysts - page 255

Figure 9.12: Effect of firing temperature on metal concentration in leachate [From ref. 427 .
Reprinted with permission].

study, Sokolov et al. [569] showed that NiO-containing spent catalysts with alumina carrier
was suitable for manufacturing alumina bearing refractory cement.

9.4.3.3 Synthetic Aggregates

Al-Fulaij et al. [570] investigated the possibility of producing non-leachable materials of high
compressive strength such as synthetic aggregates from spent hydroprocessing catalysts. The
potential for the use of such synthetic aggregates in cement concrete production was also
evaluated as part of the study. The process involved mixing about 4 wt.% of the spent catalyst
in the form of a fine powder (particle size less than 180 m) with clay (20 wt.%), gatch

(68 wt.%), sand (8 wt.%) and water, shaping the wet mix into small balls of about 20 mm
diameter, drying the balls at 110 ◦ C for 12 h and then heating them at high temperature in the
range 1150-1300 ◦ C. The effects of temperature on leachability and compression strength of
the synthetic aggregate are shown in Figs 9.12 and 9.13 [427] , respectively. The results
revealed that synthetic aggregate materials with minimum leaching ( < 1 ppm) and maximum
compressive strength were produced when the firing temperature was around 1175 ◦ C
[360,478] . The cement concrete prepared from the spent catalyst-based synthetic aggregate
had a compressive strength of 461 kg/cm 2 , while that of natural aggregate was 485 kg/cm 2 .
These results clearly indicated that the spent catalyst-based synthetic aggregates were stable
and non-leachable and they could be used in the construction industry for concrete production
by incorporating in a cement matrix.

9.4.3.4 Bricks Production

The study conducted by Acchar et al. [571] indicates on a potential of utilization of spent
hydroprocessing catalysts in manufacturing of red-clay based materials such as bricks.