FIELD OF THE INVENTION Embodiments of the invention generally relate to a process for converting a biomass feed into valuable chemicals, wherein the biomass feed comprises lignin.

BACKGROUND Lignin is a waste material from wood processes when cellulose and hemi-cellulose have been extracted. Lignin comprises very large molecules that contains interesting chemical structures, i.a. aromatic compounds.

Today, lignin is used as a resource for production of some chemicals but the majority of lignin is used as fuel with a rather low value.

There is an increasing interest in obtaining bio-based alternatives to traditional feedstocks. Biomass is a feedstock that is available in large quantities in many countries, and at a low cost. As used herein, the term "biomass" includes lignin containing plants. Examples of sources of plant biomass are numerous types of plants, including all tree species. Often lignin is a residue when cellulose and hemi-cellulose is extracted from wood.

It is an object of the invention to provide a process arranged for decomposing lignin into smaller molecules where the functionality of the sub-molecules is preserved. It is also an object of the invention to produce high-value chemicals from the sub-molecules emanating from decomposition of lignin. It is also an object to produce high- value chemicals from in-expensive biomass feed at a cost level competing with the traditional market. Examples of valuable or high-value chemicals that may be extracted from lignin are benzene, phenol, toluene, and styrene.

SUMMARY OF THE INVENTION

Embodiments of the invention generally relate to a process for converting a biomass feed into valuable chemicals, wherein the biomass feed comprises lignin, said lignin comprising aromatic species having aromatic bonded carbon and/or bonds to functional groups, said process comprising the steps of:

a) using low temperature plasma to decompose lignin molecules in the lignin into smaller molecules, where chemical bonds crosslinking lignin molecules are broken whilst a substantial part of the aromatic bonded carbon and/or bonds to functional groups of the aromatic species are maintained, hereby obtaining a raw product stream comprising aromatic compounds and other products,

b) separating the raw product stream into a stream comprising aromatic compounds and a stream comprising other products.

The separation process of step b) is a phase separation combined with e.g. a distillation process. The phase separation may take place using a phase separation paper sep- arating the solvent phase from the aqueous phase. The distillation process may take place in a distillation column separating the species based on their boiling points.

The term "low temperature plasma" is meant to denote non-thermal plasma generated by electrons using an electric discharge. This may take place at temperatures as low as between 10 and 100 ^° C.

Low temperature plasma may be generated by a high frequency electric field. Using the high frequency generation of a low temperature plasma causes only a very moderate temperature increase. The low temperature plasma comprises an ionization field lead- ing to excitation, dissociation and ionization of molecules. The term "using low temperature plasma to decompose lignin molecules" is meant to denote the break of aliphatic bonds in the lignin polymer leading to smaller molecules. The term "valuable chemicals" is meant to denote chemicals that are attractive feedstocks for chemical productions like benzene, phenol, toluene, styrene and other aro- matics.

In an embodiment the stream comprising other products is used as a feed stream for syngas production. Such a syngas production is e.g. a second low temperature plasma process resulting in a synthesis gas stream and an aqueous waste stream.

In an embodiment the low temperature plasma is submerged into the aqueous phase. This means, that the generation of the electrons providing the plasma by the electric discharge is submerged into the aqueous phase.

In an embodiment the temperature of the low temperature plasma is between about 10°C and about 90°C. The temperature of the low temperature plasma is e.g. between about 40°C and about 75°C.

In an embodiment of the process, step a) of the process is a continuous process. Step b) of the process may be a continuous process or a batch process.

In an embodiment of the process, the biomass feed is a black liquor feed stream. Black liquor is a waste product from the kraft process when digesting pulpwood into paper pulp removing lignin, hemicelluloses and other extractives from the wood to free the cellulose fibres.

In an embodiment of the process, step a) of the process takes place within a low tem- perature plasma reactor, said low temperature plasma reactor comprising catalyst for catalysing the reaction. The catalyst is e.g. a hydrogenation catalyst or an oxidation catalyst that enable bond breaking by hydrogenation or oxidation of the carbon-carbon or carbon-oxygen bonds in the lignin molecule, respectively. The low temperature plasma reactor may e.g. be a batch process in a stirred tank or a continuous process in a fixed bed reactor.

BRI EF DESCRI PTION OF THE DRAWI NGS

Figure 1 is a diagram of the process according to the invention; and

Figure 2 shows an example of a possible lignin structure.

DETAI LED DESCRI PTION OF THE DRAWINGS The following is a detailed description of an embodiments of the invention depicted in the accompanying drawing. The embodiment is an example only and is not limiting the invention. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

Figure 1 is a diagram of the process 10 according to the invention. A biomass feed stream 1 comprising lignin is fed to a low temperature plasma reactor 20. I n the embodiment shown in Figure 1, the biomass feed stream 1 is a stream of aqueous lignin. Lignin is very large molecules that contain i.a. aromatic compounds. In the low temper- ature plasma reactor 20, the low temperature plasma is used to decompose lignin molecules in the stream of aqueous lignin into smaller molecules, where the functionality of the smaller molecules is preserved.

Thus, chemical bonds crosslinking lignin molecules are broken whilst a substantial part of the aromatic bonded carbon and/or bonds to functional groups of the aromatic compounds are maintained, hereby obtaining a raw product stream 2 comprising a mixture of aromatic compounds and other products.

The temperature of the low temperature plasma is between about 10°C and about 90°C. For example, the temperature of the low temperature plasma is between about 40°C and about 75°C.

In a separator 30, the raw product stream 2 comprising a mixture of aromatic compounds and other products is separated into at least two streams, viz. a stream 3 com- prising aromatic compounds and a stream 4 comprising other products.

Optionally, the stream 4 comprising other products may be fed to a second low temperature plasma generator 40 resulting in a synthesis gas stream 5 and an aqueous waste stream 6. The synthesis gas stream 5 may undergo further purification or other processes downstream the second low temperature plasma generator 40.

The synthesis gas comprises mainly hydrogen and carbon monoxide, and is a valuable feedstock for production of chemicals. The low temperature plasma will be capable of breaking the lignin structure into smaller molecules in a way that the interesting chemical structures, e.g. the aromatic compounds, are maintained. This is possible as a low temperature plasma may be tuned only to energize certain chemical bonds, meaning it is possible to selectively separate the lignin into smaller molecules in a controlled matter. These low tempera- ture plasmas may be designed in many forms and phases. Preferably, a plasma that will be submerged in a slurry phase containing the lignin e.g. black liquor, is used. This eases the handling and reduces overall cost.

Figure 2 shows an example of a possible lignin structure. Lignin is a huge molecule con- sisting of aromatic (benzene) structures cross linked with aliphatic bonds (C-C or C-O- C). The energy levels of a low temperature plasma are able to energize the aliphatic bond without significant effect on the aromatic bonds. This leads to the cleavage of the lignin molecule into small molecules of benzene with functional groups like phenol, toluene, etc.

In some embodiments, one or more heat exchange means or other means for heating or cooling the streams may be included to ensure the proper temperatures, e.g. for the separation phase. While the invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.