Effects of macropores on reducing internal diffusion limitations in Fischer–Tropsch synthesis using a hierarchical cobalt catalyst

Li, Hansheng; Wang, Jungang; Chen, Congbiao; Jia, Litao; Hou, Bo; Li, Debao

doi:10.1039/c6ra27166a

Cited by 44 publications

(24 citation statements)

References 36 publications

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“…The support with a smaller pore size diameter enhances the dispersion of cobalt in cobaltbased catalysts but limits the diffusion of syngas and products, thus providing light hydrocarbons. In contrast, the support with a larger pore size diameter improves the reducibility, favors the diffusion of syngas and products, and thus produces heavy hydrocarbons (Li et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Pore size effect of mesoporous support on metal particle size of Co/SiO2 catalyst in Fischer-Tropsch synthesis

al.¹

2018

Int. j. adv. appl. sci.

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Fischer Tropsch (FT) synthesis is an alternative route to produce ultrahigh pure hydrocarbon fuels. The length of hydrocarbon chain produced from FT synthesis taking place over the cobalt supported catalysts is depended upon the reactant and product diffusion as well as the metal particle size of the catalyst. Some works were reported that the pore size diameter of the support can control the metal dispersion. Therefore, the pore size can be considered as an important parameter for supported FT catalysts. This work aims to study the effect of pore size of mesoporous silica on metal particle size of cobalt-based catalysts and FT performance. The synthesized silica with the average pore size diameter of 7.2 nm and the commercial silica with the average diameter of 6.7 nm were used as supports to prepare CS catalyst samples. The cobalt supported on synthesized SiO2 shows larger cobalt oxide particle with lower dispersion compared to the results of the catalyst prepared using the commercial silica. Large cobalt oxide particle of supported catalyst decreases the interaction between metal and support which results in the increasing reducibility of cobalt oxide species and provides large cobalt metal particle after the reduction process. The FT tests were carried out under atmospheric pressure at 220 ᵒC, GHSV of 300 h -1 and H2/CO feed ratio of 2. The enhancement of selectivity towards long chain hydrocarbons (C5 + ) and FT activity were obtained from the catalyst with larger cobalt particle size. The growth of hydrocarbon chain during polymerization can be facilitated by the large surface of active site formed in the large pore size of support. Thus, the pore size diameter of support is an important key for the FT catalytic performance of cobalt catalyst supported on mesoporous silica materials.

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Section: Introductionmentioning

confidence: 99%

Pore size effect of mesoporous support on metal particle size of Co/SiO2 catalyst in Fischer-Tropsch synthesis

al.¹

2018

Int. j. adv. appl. sci.

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“…This ratio helps to produce water that inhibits methane production over time, while still providing enough H2 for polymerization [72]. As previously mentioned, H2 migrates faster than CO [70], but CO adsorption is stronger than that of H2 on the catalyst which, at a 2:1 ratio, facilitates polymerization for liquid fuel production through carbon-tocarbon coupling instead of releasing short carbon chains. This, in turn, limits methane formation [72].…”

Section: Effect Of Feed Ratio On Catalyst Activity (Zone D)mentioning

confidence: 92%

“…The reactant stoichiometry is important for the selectivity of the FT reaction. Increased H 2 in the feed gas, as in the 3:1 feed ratio, decreases the probability of chain growth (less probability of producing liquid fuels) [68,69] because H 2 diffuses faster than CO [70] leading to excess H 2 moving towards the center of the catalyst and inhibiting the formation of long chains of hydrocarbons. As a result, the selectivity to methane increases.…”

Section: Effect Of Feed Ratio On Catalyst Activity (Zone D)mentioning

confidence: 99%

Is the Fischer-Tropsch Conversion of Biogas-Derived Syngas to Liquid Fuels Feasible at Atmospheric Pressure?

et al. 2019

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Biogas resulting from anaerobic digestion can be utilized for the production of liquid fuels via reforming to syngas followed by the Fischer-Tropsch reaction. Renewable liquid fuels are highly desirable due to their potential for use in existing infrastructure, but current Fischer-Tropsch processes, which require operating pressures of 2–4 MPa (20–40 bar), are unsuitable for the relatively small scale of typical biogas production facilities in the EU, which are agriculture-based. This paper investigates the feasibility of producing liquid fuels from biogas-derived syngas at atmospheric pressure, with a focus on the system’s response to various interruption factors, such as total loss of feed gas, variations to feed ratio, and technical problems in the furnace. Results of laboratory testing showed that the liquid fuel selectivity could reach 60% under the studied conditions of 488 K (215 °C), H2/CO = 2 and 0.1 MPa (1 bar) over a commercial Fischer–Tropsch catalyst. Analysis indicated that the catalyst had two active sites for propagation, one site for the generation of methane and another for the production of liquid fuels and wax products. However, although the production of liquid fuels was verified at atmospheric pressure with high liquid fuel selectivity, the control of such a system to maintain activity is crucial. From an economic perspective, the system would require subsidies to achieve financial viability.

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“…The meso-macroporous SiO 2 monoliths were prepared by a sol-gel method similar with our previous studies. 31,32 By controlling the rates of phase separation and sol-gel process, the interconnected macropores with various diameter were obtained while the mesopores were from ammonia etching. The prepared meso-macroporous monoliths were ground into 10-20 mesh as supports and labeled as S0, S50, S150, S280, S440, S1100, S2100 and S6000 respectively according to the diameter of the macropores.…”

Section: Catalyst Preparationmentioning

confidence: 99%

“…In recent years, the hierarchical pore structured catalysts have been extensively applied in adsorption 22,23 and catalysis. [24][25][26][27][28][29][30] However, contrary to plenty of reports in FTS focusing on the novel preparation methods of the hierarchical structure and structure-activity relationships, [31][32][33][34][35][36][37] little attention has been devoted to the detailed reaction-diffusion process in a hierarchical structured catalyst pellet. Xu et al 38 prepared a bimodal catalyst and elucidated the reaction-diffusion process inside the pellet by numerical simulation.…”

Section: Introductionmentioning

confidence: 99%

Mass transfer advantage of hierarchical structured cobalt‐based catalyst pellet for Fischer–Tropsch synthesis

Niu

Li²,

Xia

et al. 2021

AIChE Journal

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The low effectiveness factor of catalyst pellet caused by high internal diffusion limitation is a common issue in fixed-bed reactor. Nevertheless, hierarchical structured catalyst provides a promising solution for the contradiction between reaction activity and diffusion efficiency in large catalyst pellets. Herein, we studied the effect of pore structure parameters of the meso-macroporous catalyst on Fischer-Tropsch synthesis performances through experiment and pellet scale reaction-diffusion simulation.The pellet simulation firstly elucidated the reason for the significant improvement on activity and product selectivity for the meso-macroporous catalyst observed in our experiment. Further optimization via pellet simulation indicated the critical influences of wax filling degree and that the perfect matching between reaction and mass transfer rates by increasing macropore size and adjusting porosity within pellet enables the C 5+ space-time yield to the maximum. This work could provide a theoretical guideline for the engineering design of the hierarchical structured catalyst pellet.

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Effects of macropores on reducing internal diffusion limitations in Fischer–Tropsch synthesis using a hierarchical cobalt catalyst

Abstract: Internal diffusion limitations in Fischer–Tropsch catalysts strongly affects their catalytic activities and product selectivities.

Cited by 44 publications

References 36 publications

Pore size effect of mesoporous support on metal particle size of Co/SiO2 catalyst in Fischer-Tropsch synthesis

Pore size effect of mesoporous support on metal particle size of Co/SiO2 catalyst in Fischer-Tropsch synthesis

Is the Fischer-Tropsch Conversion of Biogas-Derived Syngas to Liquid Fuels Feasible at Atmospheric Pressure?

Mass transfer advantage of hierarchical structured cobalt‐based catalyst pellet for Fischer–Tropsch synthesis

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