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

Rawan Hakawati,Beatrice Smyth,Geoffrey Mccullough,David Rooney,Helen Daly

doi:10.3390/en12061031

Abstract

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.

Highlights

Global energy consumption is estimated to increase by 77% between 2008 and 2050 [1]; increases to date have been coupled with increases in gasoline and diesel fuel consumption [2]
As the mass of catalyst was increased from 0.2 g (R1) to 0.4 g (R2), the average carbon monoxide (CO) conversion after three days on stream at 488 K (215 ◦ C) increased from 2% to 7% (Figure 2), methane was the major product formed with 97% selectivity for the 0.2 g reaction (Figure 3) and 72% selectivity for the 0.4 g reaction (Figure 4)
Cooling the reactor to 373 K (100 ◦ C) in the presence of He helped regain catalyst activity at FT conditions, as CO conversion increased to 20% with higher selectivity to liquid fuels than methane

Summary

Introduction

Global energy consumption is estimated to increase by 77% between 2008 and 2050 [1]; increases to date have been coupled with increases in gasoline and diesel fuel consumption [2]. The combustion of fossil fuels results in damaging environmental effects associated with increasing greenhouse gas (GHG) emissions [3]. Primary energy production from biogas is on an upward trend and in Europe increased from 2.1 Mtoe in 2000 to 16.1 Mtoe in 2016 [9], with the number. The majority of biogas is combusted directly on site for electricity and/or heat generation with a growing proportion upgraded to biomethane (i.e., natural gas standard) [9]. Biogas can be used as a feedstock for syngas production using technologies that are currently applied extensively for reforming natural gas [11]

Objectives

Results

Conclusion