444
activity, size, shape, and degree of crystallinity play a major role in overall catalyst
design for Fischer-Tropsch synthesis [44]. These factors can be achieved by selecting suitable support materials. The support materials generally improve the catalyst
activity by providing mechanical resistance to the catalyst. For example, supports
provide porosity with high surface areas and uniform morphology with strong
mechanical resistance. As a result, these support materials retain Fe or Co as
nanoparticles in its framework and improve the dispersion of metals (Fe, Co or
promoters like Ru, K, etc.) that help catalysts to be active and stable during the
Fischer-Tropsch synthesis for longer time on stream. Supports such as Al 2 O 3 , TiO 2 ,
SiO 2 , ZrO 2 , zeolite, and carbon nanofibers are generally used for heterogeneous
catalysis because of their high surface areas and excellent mechanical strength [45].
Metal-support interactions play an important role in catalyst development in
terms of activity and selectivity. The study of these interactions is a key factor for
the catalyst development for the Fischer-Tropsch synthesis is are presented in two
case studies below. Case study-1 describes the catalyst screening in the silicon
microreactors fabricated by conventional microfabrication techniques discussed in
the previous section. The second case study describes the catalyst screening in the
3D printed stainless steel microreactor.
3.2.1 Case Study-1: Catalyst Screening for FT Synthesis
in Silicon Microreactor
The reactions are carried out by aligning the silicon microreactor in the reaction line
without breaking and ensuring that the graphite gasket perfectly seals the inlets and
outlets in the reactor. The catalyst to be used for FT synthesis is coated into the
microchannels. The small microchannel features in the reaction zone play an important and challenging role during experiments for FT synthesis. The methods like dip
coating, incineration, and in-situ catalyst growth are few coating techniques that are
generally used in FT studies.
Our studies in Si-microreactor published in 2010 [46] covered different methods
for the deposition of catalysts in the channels of Si-microreactor. Zhao et al. [30]
studied the effect of ruthenium, ~0.4% by weight, as a promoter on silica-supported
iron- and cobalt-based catalysts synthesized by sol-gel technique for FT synthesis
in silicon microreactor. The addition of Ru to Fe-Co-SiO 2 increased the CO conversion by 16% at 200 °C at 1 atm with a syngas ratio of 3:1.
In order to understand how each metal interacts with SiO 2 in terms of
CO-conversion and selectivity of hydrocarbons, Mehta et al. [31] used a silica solgel- based catalyst coated into the microchannels with a modified closed channel
infiltration method called mCCI for FT synthesis. Figure 10 shows the SEM image
of the microchannels in the silicon microreactor coated with the FT catalyst. The FT
experiments with Fe-SiO 2 , Co-SiO 2 , and Ru-SiO 2 catalysts, prepared by sol-gel
technique (see Table 2 below), were conducted at different temperatures to find the
optimum performance of each catalyst with syngas molar ratio (H 2 :CO) of 2:1 and
3:1 at atmospheric pressure. As shown in Fig. 11, the metal type, temperature, and
N. Mohammad et al.
activity, size, shape, and degree of crystallinity play a major role in overall catalyst
design for Fischer-Tropsch synthesis [44]. These factors can be achieved by selecting suitable support materials. The support materials generally improve the catalyst
activity by providing mechanical resistance to the catalyst. For example, supports
provide porosity with high surface areas and uniform morphology with strong
mechanical resistance. As a result, these support materials retain Fe or Co as
nanoparticles in its framework and improve the dispersion of metals (Fe, Co or
promoters like Ru, K, etc.) that help catalysts to be active and stable during the
Fischer-Tropsch synthesis for longer time on stream. Supports such as Al 2 O 3 , TiO 2 ,
SiO 2 , ZrO 2 , zeolite, and carbon nanofibers are generally used for heterogeneous
catalysis because of their high surface areas and excellent mechanical strength [45].
Metal-support interactions play an important role in catalyst development in
terms of activity and selectivity. The study of these interactions is a key factor for
the catalyst development for the Fischer-Tropsch synthesis is are presented in two
case studies below. Case study-1 describes the catalyst screening in the silicon
microreactors fabricated by conventional microfabrication techniques discussed in
the previous section. The second case study describes the catalyst screening in the
3D printed stainless steel microreactor.
3.2.1 Case Study-1: Catalyst Screening for FT Synthesis
in Silicon Microreactor
The reactions are carried out by aligning the silicon microreactor in the reaction line
without breaking and ensuring that the graphite gasket perfectly seals the inlets and
outlets in the reactor. The catalyst to be used for FT synthesis is coated into the
microchannels. The small microchannel features in the reaction zone play an important and challenging role during experiments for FT synthesis. The methods like dip
coating, incineration, and in-situ catalyst growth are few coating techniques that are
generally used in FT studies.
Our studies in Si-microreactor published in 2010 [46] covered different methods
for the deposition of catalysts in the channels of Si-microreactor. Zhao et al. [30]
studied the effect of ruthenium, ~0.4% by weight, as a promoter on silica-supported
iron- and cobalt-based catalysts synthesized by sol-gel technique for FT synthesis
in silicon microreactor. The addition of Ru to Fe-Co-SiO 2 increased the CO conversion by 16% at 200 °C at 1 atm with a syngas ratio of 3:1.
In order to understand how each metal interacts with SiO 2 in terms of
CO-conversion and selectivity of hydrocarbons, Mehta et al. [31] used a silica solgel- based catalyst coated into the microchannels with a modified closed channel
infiltration method called mCCI for FT synthesis. Figure 10 shows the SEM image
of the microchannels in the silicon microreactor coated with the FT catalyst. The FT
experiments with Fe-SiO 2 , Co-SiO 2 , and Ru-SiO 2 catalysts, prepared by sol-gel
technique (see Table 2 below), were conducted at different temperatures to find the
optimum performance of each catalyst with syngas molar ratio (H 2 :CO) of 2:1 and
3:1 at atmospheric pressure. As shown in Fig. 11, the metal type, temperature, and
N. Mohammad et al.