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Robust and Efficient processes and technologies for Drop In renewable FUELs for road transport

Periodic Reporting for period 2 - REDIFUEL (Robust and Efficient processes and technologies for Drop In renewable FUELs for road transport)

Reporting period: 2020-04-01 to 2022-01-31

The EU target for 2050 is to bring down the GHG emissions to only 5-20% of the 1990 levels. The road transport sector, which accounts for 95% of the EU’s 2016 total of transport GHG emissions, have to contribute with at least a 60% reduction. This represents a major challenge for the road transport sector, as the sector is nearly entirely based on internal combustion engines (ICE) using fossil fuels.

Besides electrifying short range transport of people and goods, particularly heavy-duty transport will rely on liquid energy carriers with high energy density for a long time to come. Thus, the ultimate solution is to fully switch this transport to 2nd or 3rd generation renewable fuels.

These fuels have to comply with the existing fueling infrastructure and engines to enable a fluent transition from fossil fuels. Thus, drop-in capable renewable fuels are needed, which can be mixed in any quantity with fossil-based fuels and comply with current fuels standards, i.e. EN590 and EN15940. Furthermore, they have to be cost competitive compared to both current fuels and other CO2-neutral powertrain technologies. A versatility in feedstock and large volume production are also crucial points to allows for a fluent transition to renewable fuels.

Hence, the overall objective of REDIFUEL is to enable the utilization of various biomass feedstocks (and also the use of H2 and CO2) for a renewable and sustainable EN590 Diesel. REDIFUEL’s ambition is to develop new technologies, solutions and processes to reach high conversion efficiencies for renewable fuel production. The proposed drop-in biofuel contains high-cetane C11+- bio-hydrocarbons and C6-C11 bio-alcohols which have exceptional performance with respect to combustion and soot-inhibition properties. The techno-economic mit-term target is to reach a highly competitive production cost level of € 0.90-1.00 per litre by 2030 at moderate production plant sizes.

The overall TRL of the process should be raised from ~3 to ~5 within this RIA. The biofuel produced matched the stated requirements very well, but today's production costs with the technologie available does not enable production costs of € 1.00 per litre. Still, the consortium could derive measures how to further reduce production cost in future. The environmental and societal aspects are taken into account by a Biomass-to-Wheel analysis showing that the overall CO2 reduction compared to fossil fuels is tremendous and beyond that of conventional biodiesel.
During the project, extensive lab-scale research on the synthesis and physicochemical characterization of Fischer-Tropsch catalysts based on cobalt as the major active metal has been done. More than 30 catalyst samples have been produced to enable testing their catalytic performance - at the lab scale and under conditions relevant for industrial application. The lab-scale studies revealed a trade-off between the overall conversion rate and the selectivity to olefins in the C5-C10 hydrocarbon product fraction. Catalysts more selective to said fraction showed to be less active per unit mass/volume than catalysts less selective to that product slate.

Overall, the performance of four catalyst samples was assessed prior to selection for upscaling activities. The catalyst finally chosen for demonstrator purpose enabled high olefin shares of >40%, what results in an alcohol content of up to 30% in the final fuel. Still, the overall activity of the catalyst has to be improved to enable an economic utilization of the process.
For the development of a catalytic system for an efficient hydroformylation/hydrogenation process, two possible catalytic systems have been developed which are able to transform the olefin feedstock in high selectivity to the desired alcohols. Within a catalytic system a rhodium catalyst in combination with water soluble phosphine ligands is used. The water soluble phosphine ligand allows for a recycling of the catalyst by immobilization in a water phase. An experimental setup to test this recycling strategy revealed very low leeching of the rhodium catalyst.

Due to volume limitation of the real REDIFUEL product, fuel analysis and engine tests have been conducted with commercially available surrogate fuels that match the composition of the real product from lab experiments very well. REDIFUEL’s composition has been proposed based on the properties optimization and process products, which consists of Gas-to-Liquid (GtL) and linear alcohols in a ratio of 70:30 vol %. Tailoring a fuel is always a conflict of interests, i.e. emission behavior, ignitability and density. A blend of REDIFUEL/UCOME was found to be most promising with a density of 798 kg/m3, which is very close to the minimum arctic grade EN590 density limit of 800 kg/m3. Due to the hydrophilicity of the alcohols, special attention must be paid on storage and transport of REDIFUEL to keep the overall water content of the fuel within the EN590 limits.

Engine tests with a single cylinder research engine, derived from a state-of-the-art heavy-duty engine, have shown that REDIFUEL significantly reduces pollutant without the need of any engine hardware or software changes. Generally, the particulate matter (- 20%), carbon monoxide (- 20%), and hydrocarbon emissions (- 30%) are reduced with increasing share of REDIFUEL thanks to its oxygen and paraffinic content. Moreover, all the blends of REDIFUEL with Diesel exhibited a rise in efficiency up to +0.5%-points.

The REDIFUEL was also investigated at a series production demonstrator truck. By means of a portable emission monitoring systems (PEMS), real-driving emissions could be investigated. According to the initial single cylinder engine test, also the truck tests revealed the superior emission formation compared to fossil fuel under latest EU VI legislation.

In order to fully exploit the potential of such a renewable fuel, CFD simulations are performed to design an optimal shape of piston bowl and injector nozzle. For validation of this model, optical investigations by means of High Pressure Chamber (HPC) experiments have been undertaken. The results have proven that REDIFUEL blends feature similar mixture formation as Diesel, but a faster self-ignition.
Within this project, the first EN590 compatible 100% renewable diesel fuel was derived and produced.

The high bio-alcohol share in the product enables the fuel to be compliant to the Diesel fuel legislation EN590. Other biogenic Diesel fuels, such as commercially available BioDiesel (FAME) and Hydrated Vegetable Oil (HVO) and other biogenic products with lower TRL such as di-methyl ether do not comply with EN590 and thus additional fuel standards had to be created for these fuels.

Hence, REDIFUEL will be a biogenic fuel that is compliant to EN590 and thus can be fueled in any existing Diesel vehicle without restraints.

The possible variety in feedstock will make REDIFUEL also able and easy to adapt to existing biomass producing infrastructure. The Well-to-Wheel LCA has proven the enormous potential in CO2 savings compared to fossil fuels. Given the current TRL ~ 5, today's production costs of course would be very high, but pathways could be derived how to bring production costs to ~€ 1.00 per litre on the short term.

The results have been disseminated via (open access) publications, conference presentations and proceedings, and online events with more than 300 participants from all over the world.
REDIFUEL Concept 2
REDIFUEL Concept 1