|Adding nickel and co-feeding H2 increased gasoline yield 32% relative to a conventional catalyst. Credit: Rao et al. Click to enlarge.|
Researchers at TU Delft (The Netherlands) and Universidad Rey Juan Carlos (Spain) have developed a new concept to increase the efficiency of the catalytic cracking of unsaturated vegetable oil to greatly increase the production of gasoline and light olefins (propene and butenes). A paper on their work is published in the journal ChemSusChem.
By incorporating nickel onto a base commercial FCC (fluid catalytic cracking) Ecat (equilibrium catalyst) and co-feeding hydrogen into the reaction system under realistic FCC operations (525 °C, 1.1 atm), the team found that gasoline production increased 32% relative to the standard Ecat.
They also found that the incorporation of platinum, with our without co-feeding hydrogen, is detrimental both to conversion and selectivity. Thus, they conclude, a “judicious choice of metal” is vital for performance during vegetable oil cracking.
This approach can be very promising and economical by utilizing recycle system for in-situ hydrogen produced to eliminate the hydrogen requirement from other sources. This concept can also lead to another potential application: co-processing of vegetable oils together with heavier petroleum feedstocks that contain metal, especially nickel, contaminants.
In that case, the great advantage is that metal incorporation onto the base FCC catalyst is not required while at the same time gasoline production from the vegetable oil fraction can be enhanced by exploiting the metal deposits present in the petroleum feedstock. These findings may certainly stimulate interest for directing future research in the rational design of new FCC catalysts for the production of biofuels.
—Rao et al.
Biofuels pathways. In the introduction to their paper, Rao et al. note that there are numerous conversion pathways for the production of different types of bio- and renewable fuels, including (but not limited to):
- Bioalcohols such as ethanol from the fermentation of sugars;
- Transesterification of plant-based oils or animal fats to biodiesel;
- Hydrotreatment of vegetable oils to renewable (“green”) diesel;
- Pyrolysis of biomass to bio-oil, and its upgrading;
- Gasification of biomass via Fischer-Tropsch synthesis via syngas; and
- Catalytic cracking of vegetable oils to gasoline, diesel and light olefins similar to the standard FCC process in refineries.
Depending on the feedstock type, some of the above-mentioned processes are already commercially available, but except for the FCC of vegetable oils, only the fermentation process is directly designed for gasoline production. In addition, some of the processes above are still under development because they are very energy- and capital-intensive.
Thus, catalytic cracking of biomass (e.g., vegetable oils) is the only process that is able to directly produce gasoline, along with diesel and light olefins components. Furthermore, the compatibility of vegetable oil processing with the existing infrastructure of the standard FCC process makes this process much more economically feasible than other methods.
—Rao et al.
T. V. M. Rao, M. M. Calvero, M. Makkee (2010) Effective Gasoline Production Strategies by Catalytic Cracking of Rapeseed Vegetable Oil in Refinery Conditions. ChemSusChem Volume 3, Issue 7, pages 807–810 doi: 10.1002/cssc.201000128