| Summary: |
Authorities all over the world are gradually attempting to bring the concept of circular and self-sufficient bio-based economy into practice. The LigTech project is in line with this concept, aiming at unlocking lignin from black liquor, the waste stream from pulp processing, for production of value-added chemicals - vanillin and syringaldehyde - by taking initial steps to the development of a cutting-edge photoelectrocatalytic technology. Pulp industry is one of the major lignin worldwide producers but almost all lignin is being burned as low-value fuel. To change this scenario, it is urgent to provide efficient and environmentally sound technological solutions for lignin recovery. The project covers the demonstration of the technology feasibility, ranging from the basic principles to the experimental proof-of-concept (technology readiness level (TRL) of 3). The new technology will begreen, scalable, robust and potentially capable of providing the maximum vanillin and syringaldehyde yields predetermined by the lignin structure, or at least nearly maximum yields. To meet the overall project goal, three specific objectives have to be achieved: (1) Development of groundbreaking transparent photoanodes, (2) Development of a pioneering photoelectrocatalytic flow reactor, and (3) Application of the photoelectrocatalytic technology (photoanodes + reactor) for the selective oxidation of lignin from black liquor. The project will start by the fabrication and characterization of photoanodes (Task 1). They will be made up of a glass substrate coated with a conductive layer and a photocatalyst layer. Fluorine-doped tin oxide (FTO) will be preferred for transparent conductive layer since it is a very well-stablished and stable material. Different materials will be applied as photocatalyst, namely hematite, zinc oxide and titanium dioxide, at least, in the presence or absence of a dopant or a co-catalyst. At the same time, the photoelectrocatalytic system will be  |
Summary
Authorities all over the world are gradually attempting to bring the concept of circular and self-sufficient bio-based economy into practice. The LigTech project is in line with this concept, aiming at unlocking lignin from black liquor, the waste stream from pulp processing, for production of value-added chemicals - vanillin and syringaldehyde - by taking initial steps to the development of a cutting-edge photoelectrocatalytic technology. Pulp industry is one of the major lignin worldwide producers but almost all lignin is being burned as low-value fuel. To change this scenario, it is urgent to provide efficient and environmentally sound technological solutions for lignin recovery. The project covers the demonstration of the technology feasibility, ranging from the basic principles to the experimental proof-of-concept (technology readiness level (TRL) of 3). The new technology will begreen, scalable, robust and potentially capable of providing the maximum vanillin and syringaldehyde yields predetermined by the lignin structure, or at least nearly maximum yields. To meet the overall project goal, three specific objectives have to be achieved: (1) Development of groundbreaking transparent photoanodes, (2) Development of a pioneering photoelectrocatalytic flow reactor, and (3) Application of the photoelectrocatalytic technology (photoanodes + reactor) for the selective oxidation of lignin from black liquor. The project will start by the fabrication and characterization of photoanodes (Task 1). They will be made up of a glass substrate coated with a conductive layer and a photocatalyst layer. Fluorine-doped tin oxide (FTO) will be preferred for transparent conductive layer since it is a very well-stablished and stable material. Different materials will be applied as photocatalyst, namely hematite, zinc oxide and titanium dioxide, at least, in the presence or absence of a dopant or a co-catalyst. At the same time, the photoelectrocatalytic system will be developed, as well as a simple batch system for preliminary tests (Task 2). The reactor will be based on conventional filter-press electrochemical cells but employing (i) a photoanode and a window at an end face for photoanode illumination, and (ii) a stainless steel cathode with a mechanically imprinted network, called NETmix, for fluid circulation, with a unique flow distribution scheme and a heat exchanger. Black liquor will be provided by The Navigator Company and lignin will be isolated (Task 3) for preparation of pure lignin solutions to be used as feedstock. Afterwards, photoanodes efficiency will be preliminary assessed and improved by a combined theoretical and experimental approach (Task 4). Finally, the performance of the NETmix photoelectrocatalytic technology for lignin valorization will be evaluated (Task 5). The LigTech project will bring together researchers with complementary competences. The PI has expertise inelectrochemical and photocatalytic systems; the co-PI, V. Vilar and R. Boaventura have developed/are developing NETmix-based systems for water/air remediation and CO2 reduction; M. Dias has wealth of knowledge in all NETmix features and applications as she is its co-inventor; A. Rodrigues has a vast experience in valorization of lignin from black liquor; and D. Morais is a FCT PhD student focused on photoelectrocatalysis applied to organic synthesis. Furthermore, a research fellow will be hired and four collaborations (three international and one national) will be established to support the preparation, characterization and validation of photoanodes. The PI was awarded a FCT Junior Researcher contract(CEECIND/02196/2017) to develop a work plan with similar goals to those covered in the LigTech project, which will provide part of the funds to support her work plan. The co-PI and V. Vilar have FCT contracts (Junior Research-CEECIND/01386/2017 and Principal Researcher-CEECIND/01317/2017, respectively) for the development of NETmix-based technologies. |
| Results: |
Espera-se que os fotoânodos desenvolvidos apresentem elevada conversão e seletividade para a oxidação da lignina em vanilina e siringaldeído. A aplicação deste fotoânodos no reator fotoeletrocatalítico com transferência de massa intensificada, ou seja, a aplicação da nova tecnologia fotoeletrocatalítica, potencialmente induzirá os rendimentos máximos atingíveis de produção de vanilina e siringaldeído, predeterminados pela estrutura da lignina ou, pelo menos, valores próximos dos máximos. A nova tecnologia irá também favorecer a utilização de um processo sustentável de síntese de vanilina e siringaldeído, tendo em conta as suas características verdes: (i) capacidade de usar temperatura e pressão ambiente, (ii) capacidade de usar uma baixa voltagem, (iii) uso de regime laminar, (iv) uso de elétrodos com materiais seguros, e (v) ausência de produção de produtos químicos nocivos. Para além disso, os fotoânodos produzidos também podem inspirar uma série de aplicações em optoeletrónica, sensores, ciências de materiais, etc., e o reator fotoeletrocatalítico desenvolvido pode ser útil não só na oxidação seletiva de compostos orgânicos, mas também na fixação de azoto e redução de dióxidos de carbono. |