Biofuel compositions and methods based on co-processing aromatic-rich and aromatic-lean components

Abstract

Biofuel compositions obtained by the simultaneous hydroprocessing of at least two distinct hydroprocessing feedstocks, either or both of which are derived from biomass, are disclosed. The co-processing of these feedstocks can result in an upgraded product having suitable characteristics, in terms of composition (e.g., quantities of compounds such as aromatic hydrocarbons, present in relatively large amounts) and in terms of quality (e.g., quantities of compounds such as oxygenates, present in relatively small amounts) for use as a hydroprocessed biofuel such as hydroprocessed aviation biofuel.

Description

FIELD OF THE INVENTION[0001]The present invention relates to the hydroprocessing of both aromatic-rich and aromatic-lean components, either or both of which are derived from biomass, as well as hydroprocessed biofuels (e.g., aviation fuel) made from this co-processing. The present invention also relates to such hydroprocessing methods, utilizing hydrogen generated from biomass-derived C4− byproducts, in order to further reduce the carbon footprint of the biofuel.DESCRIPTION OF RELATED ART[0002]Environmental concerns over fossil fuel greenhouse gas (GHG) emissions have led to an increasing emphasis on renewable energy sources. Wood and other forms of biomass including agricultural and forestry residues are examples of some of the main types of renewable feedstocks being considered for the production of liquid fuels. Energy from biomass based on energy crops such as short rotation forestry, for example, can contribute significantly towards the objectives of the Kyoto Agreement in redu...

AI Technical Summary

Benefits of technology

[0010]Hydroprocessing of both aromatic-rich and aromatic-lean components advantageously provides simultaneous upgrading of at least these two components, which, optionally followed by fractionation of the resulting, hydroprocessed product, can provide a hydroprocessed biofuel meeting applicable composition and quality standards. In addition, the oxygenate content of the aromatic-rich component, which is generally significantly higher than that of the aromatic-lean component (e.g., derived from F-T synthesis), is diluted during hydroprocessing. This further simplifies the overall process, by reducing adiabatic temperature rise and the corresponding production of undesirable coke precursors. According to embodiments of the invention, a biofuel that does not require further blending with aromatic hydrocarbons, such as an on-spec aviation biofuel, is obtained after hydroprocessing and fractionation.

[0011]Embodiments of the invention therefore relate to novel production methods for fuel compositions that are at least partially, but often completely, derived from renewable carbon sources. These sources include an aromatic-rich biomass derived component and an aromatic-lean component that may likewise be biomass derived (e.g., from the BTL pathway, combining gasification and F-T synthesis, as described above). Representative methods comprise contacting these components with hydrogen together in a common hydroprocessing reactor to achieve efficiencies and other advantages, as discussed herein, compared to separately upgrading these components. Following fractionation of the hydroprocessed product, the resulting hydroprocessed biofuel (e.g., a hydroprocessed aviation biofuel, having a significant quantity of aromatic hydrocarbons) may be used in neat form (e.g., as an aviation fuel) or otherwise blended, for example, with conventional petroleum derived blending stocks. Whether or not the hydroprocessed biofuel is blended, the carbon footprint of the resulting neat biofuel or blended biofuel can be reduced.

[0012]Other embodiments of the invention relate to production methods for hydroprocessed biofuel exhibiting a GHG emission, based on a Life Cycle Assessment (LCA), which is further reduced by virtue of using a biomass-derived source of hydrogen for the hydroprocessing step. In particular, byproducts (e.g., light hydrocarbons) of hydroprocessing, F-T synthesis, and / or pyrolysis can be converted, according to an overall hydroprocessed biofuel production process, in an integrated hydrogen generation unit. For example, a catalytic steam reformer may be integrated with one or more of a catalytic hydroprocessing unit, a F-T synthesis unit, and / or a Rapid Thermal Processing (RTP) pyrolysis unit. Therefore, at least a portion of the byproducts of any one or more of these operations may be converted to hydrogen (e.g., by catalytic steam reforming), thereby generating at least a portion of the hydrogen required for hydroprocessing. Importantly, the generation of hydrogen in this manner (i.e., from byproducts obtained from the processing of feedstocks comprising renewable carbon) beneficially reduces the amount of hydrogen that must be obtained from external fossil sources (imported), thereby further lowering the lifecycle GHG emission value of the resulting hydroprocessed biofuel. According to other embodiments in which gasification and F-T synthesis are used to provide the aromatic-lean component, a portion of the syngas from gasification can be purified and used as a renewable source of hydrogen for hydroprocessing.

[0013]Representative production methods include (i) the pyrolysis of a first biomass feedstock to raw pyrolysis oil, to provide the aromatic-rich component and also (ii) the gasification of a second biomass feedstock, followed by F-T synthesis, to provide the aromatic-lean component. Alternatively, the aromatic-rich component may be obtained from other naturally occurring sources without pyrolysis, such as from tall oil or oils derived from aromatic foliage such as eucalyptols. The first and second biomass feedstocks may comprise the same or different types of biomass, and, according to particular embodiments, both components are derived from second generation (e.g., lignocellulosic) biomass feedstocks. The aromatic-rich and / or aromatic-lean components may optionally be obtained after separation from (e.g., by fractionation), and / or pretreatment of, the raw pyrolysis oil and / or the F-T synthesis product, respectively, prior to hydroprocessing. In any event, the subsequent hydroprocessing of the aromatic-rich and aromatic-lean components beneficially reduces their total oxygen content and increases their total heating value.

Problems solved by technology

Other properties of pyrolysis oil render it generally unusable, in any appreciable proportion, as a component of a transportation fuel composition.

Likewise, the products of Biomass to Liquid (BTL) pathways described above, which include the products of gasification followed by F-T synthesis, are generally of significantly lower quality, compared to their counterpart, paraffin-rich petroleum derived products used for fuel blending.

This quality deficit results from the presence of oxygenates and possibly olefins, with amounts of these non-paraffin impurities depending on the F-T catalyst and processing conditions used.

Moreover, the high overall paraffin content characteristic of products obtained from this reaction renders them unsuitable, even in the absence of their oxygenate and olefin impurities, for use in current commercial applications such as aviation fuel, unless blended with aromatic hydrocarbons.