Fischer-Tropsch Synthesis

Team #1Junghye Chang, Austin Hughes, Hannah Hunter, Yasmin Moez,

Jane Njihia, Brianna Sheard

Introduction and Background

[1] Mena Subiranas, A. & Schaub, G. (2009). Combining Fischer-Tropsch (FT) and Hydrocarbon Reactions under FT Reaction Conditions: Model Compound and Combined-Catalyst Studies. International Journal of Chemical Reactor Engineering, 7(1), pp. -. Retrieved 30 Jan. 2020, from doi:10.2202/1542-6580.2022[2] Zhang, Q.; Deng, W.; Wang, Y. Recent Advances in Understanding the Key Catalyst Factors for Fischer-Tropsch Synthesis. Journal of Energy Chemistry 2013, 22 (1), 27–38.

2

What is Fischer-Tropsch Synthesis ?

Heterogeneous reaction process that converts synthesis gas (CO and H2) to hydrocarbons

(2n + 1) H2 + n CO → CnH2n+2 + n H2O

Why Fischer-Tropsch?

▪ Environmental demands▪ Technological developments▪ Decreasing fossil energy

resources

Introduction and Background

3

Benefits of Fischer-Tropsch

▪ Produces synthetic fuel of higher quality than conventional means

▪ Low-sulfur diesel fuel▪ Economic benefits

[1] Mena Subiranas, A. & Schaub, G. (2009). Combining Fischer-Tropsch (FT) and Hydrocarbon Reactions under FT Reaction Conditions: Model Compound and Combined-Catalyst Studies. International Journal of Chemical Reactor Engineering, 7(1), pp. -. Retrieved 30 Jan. 2020, from doi:10.2202/1542-6580.2022[3] Gruber, H.; Groß, P.; Rauch, R.; Reichhold, A.; Zweiler, R.; Aichernig, C.; Müller, S.; Ataimisch, N.; Hofbauer, H. Fischer-Tropsch Products from Biomass-Derived Syngas and Renewable Hydrogen. Biomass Conversion and Biorefinery 2019..

Schematic of biomass gasification using excess electricity, recycled CO2 and FTS to produce hydrocarbons

Main Points of Design Interest

▪ Exothermic, needs cooling to operate ▪ Gas to liquid (GTL) reaction involving

catalyzed adsorption- Metal catalysts are used

▪ Produces hydrocarbon molecules of various chain lengths

Reactors

4

Reactor Types

Operating Conditions

▪ High Temperature: 320 - 350 °C▪ Low Temperature: 220 - 250 °C▪ Pressure: Typically 2 - 3 MPa▪ Higher CO partial pressure → Longer carbon chains

[4] Steynberg, A. P., & Dry, M. E. (Eds.). (2004). Fischer-Tropsch Technology (Vol. 152). Elsevier.

Reactors

5

Advantages and Disadvantages

Slurry Phase

▪ + Highest diesel yield▪ + Easy to operate▪ - More downstream processing▪ - Lower overall CO conversion

Fluidized Bed (Sasol Advanced Synthol)

▪ + Higher capacity▪ + Highest gasoline and alkene yield▪ - High methane production▪ - Higher catalyst loading & losses

Diagram of slurry phase FT reactor. Slurry phase with Co catalyst is ideal for diesel production.

[4] Steynberg, A. P., & Dry, M. E. (Eds.). (2004). Fischer-Tropsch Technology (Vol. 152). Elsevier.

Catalysts

6[5] Abelló, S.; Montané, D. Exploring Iron-Based Multifunctional Catalysts for Fischer–Tropsch Synthesis: A Review. ChemSusChem 2011, 4 (11), 1538–1556. https://doi.org/10.1002/cssc.201100189.

Cobalt and Iron Catalyst Comparison

Cobalt Catalyst

Kinetics

7

Iron Catalyst

Zimmer- man (1990)

Riedel(2003)

kFT(mol/s∙ kg∙ Pa)

8.58 1.77

EA,FT(kJ/mol)

86 72

aFT 4.8 33

bFT 0.33 2.7

kFT,240°C(mol/s∙ kg∙ Pa2)

1.26 x 10-12

kFT,220°C(mol/s∙ kg∙ Pa2)

8.85 x 10-13

EA,FT(kJ/mol)

92.7 - 94.5

aFT,240°C(Pa-1)

1.16 x 10-5

aFT,220°C(Pa-1)

2.23 x 10-5

[1] Subiranas, A. M., & Schaub, G. (2007). Combining Fischer-Tropsch (FT) and Hydrocarbon Reactions under FT Reaction Conditions -- Catalyst and Reactor Studies with Co or Fe and Pt/ZSM-5. International Journal of Chemical Reactor Engineering, 5(1), 11–12. doi: 10.2202/1542-6580.1522

Kinetic Rate Law Expression and Parameter Values

ASPEN

8[6] Pondini, M., & Ebert, M. (2013). Process synthesis and design of low temperature Fischer-Tropsch crude production from biomass derived syngas . Department of Energy and Environment, Division of Heat and Power Technology, CHalmers University of Technology.

Type of Reactor

▪ RStoich

▪ Simulates a Slurry Reactor with FT kinetics

Complications with Kinetics

▪ Large number of hydrocarbon products with a series of very complicated rate laws

Work Around from Literature

▪ Use one aggregate rate law equation in ASPEN Plus▪ Use probability distribution models in Excel to get actual

hydrocarbon product distribution

Integrating Fischer-Tropsch Synthesis into ASPEN

Examples and Applications

9

Sasolburg, South Africa (Sasol)

▪ Fixed bed and slurry phase reactors with Fe catalyst▪ Leading producer of paraffin wax

Secunda, South Africa (Sasol)

▪ Fluidized bed reactors with Fe catalyst▪ Wider product spectrum → more complex separation

Sasol Secunda plant. Circulating fluidized bed reactors are seen on the right, and Advanced Synthol reactors on the left.

[4] Steynberg, A. P., & Dry, M. E. (Eds.). (2004). Fischer-Tropsch Technology (Vol. 152). Elsevier.