Pyrolysis Oil Stabilisation by Catalytic Hydrotreatment, RH Venderbosch and HJ Heeres, Biofuel's Engineering Process Technology, pp 386
Stabilization of biomass-derived pyrolysis oils, R.H. Venderbosch, A.R. Ardiyanti, J. Wildschut, A. Oasmaa and H.J. Heeres, J Chem Technol Biotechnol 2010; 85: 674–686
Catalytic Hydrotreatment of Fast Pyrolysis Oil: Model Studies on Reaction Pathways for the carbohydrate Fraction, J. Wildschut, J. Arentz, C.B. Rasrendra, R.H. Venderbosch, H.J. Heeres, Environmental Progress & Sustainable Energy, 2009
Hydrotreatment of fast pyrolysis oil using heterogeneous noble-metal catalysts, J Wildschut., FH Mahfud, RH Venderbosch, HJ Heeres, 2009, Industrial and Engineering Chemistry Research, 48(23), 2009, Pages 10324-10334
Insights in the hydrotreatment of fast pyrolysis oil using a ruthenium on carbon catalyst, Wildschut J., Iqbal M.H., Melián Cabrera I.V., Venderbosch R.H., Heeres H.J., 2010, Energy Environ. Sci., DOI:10.1039/b923170f
Pyrolysis oil upgrading by high pressure thermal treatment, De Miguel Mercader F., Hogendoorn J.A., Venderbosch R.H., Kersten S.R.A., Groeneveld M.J., 2010, Fuel, 89(10), 2829-2837.
Stabilisation of biomass derived pyrolysis oils, RH Venderbosch, AR Ardiyanti, J Wildschut, A Oasmaa, HJ Heeres, 2010, J. Chem. Techn. Biotechn., 85, 674-686
Process-product studies on pyrolysis oil upgrading by hydrotreatment with Ru/C catalysts, AR Ardiyanti, RH Venderbosch, HJ Heeres, Proceedings of the 2009 AIChE Spring National Meeting, Tampa, 2009
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Pyrolysis oil is a liquid produced from a variety of biomass feedstock (see Pyrolysis), but as such it is not suitable for direct use as a transportation fuel. Further treatment of the oil will be required.
Two different routes are currently considered to produce biofuels from pyrolysis oil:
- Hydrodeoxygenation (HDO) of pyrolysis oil to produce an oil refinery compatible feedstock or final biofuel.
- Syngas production from pyrolysis oil, and subsequently synthesized to a transportation fuel.
Hydrodeoxygenation of pyrolysis oil (HDO)
In the ‘HDO process’, pyrolysis oil is treated with hydrogen at elevated pressure in the presence of a catalyst. The aim is to stabilize the oil, and to enable further treatment/upgrading to a transportation fuel. In the past, stabilisation of pyrolysis oil essentially meant decreasing its oxygen content, as this parameter was considered to be the main cause for loss in thermal stability. However, it is not the oxygen content per se that is important, but merely the way the oxygen is bound. For example, If present, the oxygen should be there as an alcohol group rather than as a keton, or sugar group.
This approach was further developed in the FP6 project BIOCOUP. After mild hydrogenation, the stabilized PO can be co-fed in a conventional Fluid Catalytic Cracking (FCC) unit or Hydrotreater of a conventional oil refinery. On small scale, it was demonstrated that shown that 20% of VGO (Vacuum Gas Oil) could be replaced by the renewable, stabilized pyrolysis oil. This 20% replacement would already unlock a huge potential for renewable biofuels.
Alternatively, the stabilized oil can be further treated with hydrogen to obtain a product which is for example miscible with mineral diesel and an oxygen content which is (close to) zero. However, the most critical step is the first stabilisation step. In co-operation with the Boreskov Institute of Catalysis (Russia) and the RijksUniversiteit Groningen (Netherlands), this initial stabilisation step has been further developed. This cooperation has led to the filing of a joint patent, and this proprietary catalyst is now used by BTG in the 1st step of the pyrolysis oil upgrading process.
Syngas production from pyrolysis oil
Syngas or synthesis gas is produced from a variety of feedstocks like e.g. coal, petcoke, natural gas and naphtha. The raw syngas from gasifiers or reformers is further cleaned and fed to a synthesis process to produce for example methanol, ammonia or Fischer-Tropsch liquids. The synthesis processes do have in common that high process pressures are applied. Contrary to solid biomass, pyrolysis oil can be easily pressurized. In addition, pyrolysis oil is virtually free of minerals and a catalyst might be applied. Therefore, two different approaches are further evaluated within BTG:
- Pressurized, oxygen blow (non-slagging) Entrained flow gasification
- Autothermal Catalytic Reforming (ACR)
Entrained flow gasification
Entrained flow reactors use atomised liquid, slurry or dry pulverised solid as a feedstock. Once pumped inside the gasifier, the feedstock is gasified with oxygen in a co-current flow. The residence time is only a few seconds. The temperatures are usually very high: typically 1,300 to 1,500 °C. BTG carried out experiments on a small scale to evaluate the entrained flow gasification of pyrolysis oil ( ~ 1 kg/hr). Subsequently, Shell and BTG conducted a successful experiment in 2002 using the atmospheric entrained flow gasifier of UET in Freiberg. During this test more than 1 ton of pyrolysis oil was gasified. Within the so-called SupraBio project new tests are scheduled in an oxygen blown, pressurized entrained flow gasifier. The pyrolysis oil gasification tests will be carried out in co-operation with ETC (Pitea, Sweden).
Autothermal Catalytic Reforming (ACR)
Autothermal Catalytic Reforming is a well-known process in the chemical industry. In the top of the reformer the fuel is partially combusted with oxygen to achieve the required temperature for reforming. The 2nd part of the gasifier is filled with a steam reforming catalyst. Typically, Ni or PGM based catalysts are used to enable high conversions at temperatures significantly lower than used in entrained flow gasification. At BTG an ACR-type reactor has been constructed to develop this process for pyrolysis oil reforming. Currently, the unit operates with air and ambient pressure. Both fixed bed and monolith catalysts are tested.