[diss] Kemian tekniikan korkeakoulu / CHEM

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  • Scaling up the production of value-added bio-based products to industrial scale
    (2025) Forssell, Susanna
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-06-27
    Due to global challenges, such as climate change and depletion of fossil resources, there is increasing interest in utilizing bio-based products for value-added applications. Cellulose and lignin are abundantly available biopolymers, and as such, they are attractive raw materials for the production of bio-based materials. Kraft lignin is a byproduct from the pulping industry, which is currently mainly incinerated for energy. If noncombustible energy were utilized in pulp mills instead, lignin could be used for materials production. It has been proposed that epoxidized kraft lignin (EKL) can be used as a coating or as a formaldehyde-free option to phenol-formaldehyde adhesives as it possesses fire- and water-resistant properties. In addition, cellulose nanocrystals have attractive properties, including their mechanical properties, adaptable surface chemistry, and optical transparency. As a result, they have been proposed for use in polymer reinforcement, biomedical and packaging applications. Novel production methods for epoxidized kraft lignin and carboxylated cellulose nanocrystals have been demonstrated on a laboratory scale. The purpose of this research was to design industrial-scale production processes for these bio-based products and to conduct techno-economic analyses in order to evaluate the feasibility of the processes. The capital and operating costs were evaluated based on the developed mass and energy balances. Epoxidized kraft lignin is produced by lignin solution preparation, epoxidation reaction, solvent separation, solvent recycling, and isolation of the product. A negligible amount of waste and no greenhouse gas emissions are emitted in the production process. If wind or solar energy were available, the greenhouse gas emissions from utility usage would fall to almost zero. Bio-based solvents and reagents can be utilized in the process, and the recycling rate of the unreacted solvents is over 99%. The minimum selling price of the EKL product was estimated to be 0.7 €/kg when the production facilities are integrated to a biorefinery or a pulp mill. Solvent recycling is a key profitability factor of the production process. Production of EKL is both technically and economically feasible in the current adhesives and coatings markets. The capacity of the carboxylated cellulose nanocrystals (c-CNCs) plant was designed to be 8 kt/a of c-CNCs per dry matter, where the final product is a 1 wt.% solution. The recycling of the hydrogen chloride gas utilized for the acid hydrolysis is implemented in the process. Experimental testing shows that conventional industrial equipment can be utilized for the product purification and dispersion into c-CNCs. The minimum selling price was found to be 4.3 €/kg per dry matter. The scale-up of the process was found to be favorable. The KTH Royal Institute of Technology (KTH) Innovation Readiness Level Analysis showed that the development of both processes is progressing in a relatively balanced matter. Each of the sustainable production processes shows potential to be economically viable and to enter markets with high volumes. The c-CNC process development is further along regarding the technology development, whereas the EKL development has progressed more in terms of gathering team capabilities and necessary intellectual property rights. Although the innovation readiness levels remain relatively low at this stage, both products demonstrate the potential to generate added value within the bioeconomy, making them promising candidates for continued scale-up to the industrial level.
  • Engineering cellulose nanofibril hydrogels with bioactive phytochemicals: toward functional biomaterials
    (2025) Huynh, Ngoc
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-06-26
    Plants have historically been important sources of materials and medicine. However, the emergence of regenerative medicine and tissue engineering has favoured synthetics for tunable mechanics and animal-based materials for biological relevance. Despite this, synthetics often lack biocompatibility, and ethical and sustainability concerns challenge animal-based options. These limitations can be overcome by employing plant-based materials–an underutilised resource offering more sustainable solutions and tools for biomedical research. This thesis explores plant-derived hydrogels as non-animal substrates for biomedical applications. Cellulose nanofibrils (CNFs) show promise as functional nanomaterials but require enhanced mechanical performance and bioactivity for cell interactions. In this thesis, cellulose nanofibrils were combined with extracts from willow bark (WBE) and Aloe vera (AV), to create novel hydrogels with improved strength and bioactivity. In the development of these novel materials, several aspects of CNFs were examined, such as their interactions with water and living cells. These explorations revealed that the phenolic compounds from willow bark extracts improved flowability via a lubricating effect and salt ions densified the CNF network, thereby resulting in higher moduli, lower water uptake and swelling ratios. Meanwhile, the AV’s polysaccharide fraction behaved as a flexible matrix that enabled load transfer across the CNF network, and this synergy produced a series of hydrogels with significantly higher stiffness and elasticity. These novel hydrogels are anticipated to serve as valuable biomaterials for biomedical research, with particular relevance to tissue engineering. In this context, cell-material interactions play an important role in determining the biocompatibility of a given material and govern cell fate and biological functions. Various aspects of these cell-material interactions, such as blood compatibility, cell viability and physicochemical interaction forces with living cells, were investigated using haemolysis assay, LIVE/DEAD assay and advanced force spectroscopy techniques based on atomic force microscopy (AFM). Quantitative data on cellular adhesion in various cell-substrate and cell-cell systems revealed valuable insights into spheroid formation–a process heavily depending on cell-matrix and cell-cell adhesion. Although CNFs lack specific ligands for cell interactions, they interacted with cells without disrupting cell-cell adhesion. This enables a biomimetic environment that supports spheroid formation in both liver cancer cells and induced pluripotent stem cells. In summary, plant-based hydrogels from cellulose nanofibrils and plant extracts demonstrated enhanced mechanical performance and improved processability. The introduction of these plant extracts improved hydrogel functionality in several aspects, including antioxidant activity and water interaction management. Additionally, cellulose nanofibrils provide an environment that is conducive to spheroid formation. These plant-based hydrogels are competitive candidates for biomedical research, particularly in cases where non-animal and sustainable approaches are required.
  • From fibers to sugars Harnessing gaseous hydrogen chloride for cellulose conversion
    (2025) Wang, Yingfeng
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-06-26
    According to the so-called fringed-fibrillar model, the short, disordered regions in cellulose microfibrils are more susceptible to acid hydrolysis, which gives rise to the leveling-off degree of polymerization (LODP). In addition, one severe drawback of acid hydrolysis is the production of humins as an unwanted side reaction to glucose conversion. This dissertation utilizes a new pathway for cellulose degradation, namely using hydrogen chloride (HCl) gas, where the fiber morphology is minimally affected in the entire process. Purification of the products is relatively unproblematic from a gas-solid mixture, and a gaseous catalyst is more straightforward to recycle than the aqueous counterpart. The aim of this thesis was to explore the use of anhydrous HCl gas for producing sugars and nanocellulose from biomass by suppressing humin formation and analyzing the LODP behavior. Here, we investigate how various cellulose polymorphs/materials were hydrolyzed by HCI gas with a water content of 30–50 wt.%. The 50–70% glucose yields were obtained from cellulose I and II polymorphs, while a >90% monosaccharide conversion was acquired from cellulose IIIII after a mild post-hydrolysis. In addition, alcoholysis has raised attention because it can significantly increase biopolymers' solubility and depolymerization rate, inhibit harmful humin formation, and produce valuable platform chemicals. The cotton-based cellulose fibers were firstly soaked in various alcohols (ethanol, 2-propanol, t-butanol, and ethylene glycol) and exposed to anhydrous HCl gas as an acid catalyst, and the impact of these different systems on the leveling-off degree of polymerization (LODP) was explored. Ethylene glycol and t-butanol reached the LODP under the default conditions, i.e., 50 wt.% alcohol and without moisture. Cellulose nanofibrils (CNFs) have attracted significant attention due to their extraordinary mechanical and optical properties. In a foundational effort, we investigated the formation of CNF production from agricultural waste, namely from potato fibers, which are side streams with a global production of millions of tons annually. Remarkably, we obtained short CNFs (~500 nm) simultaneously in a one-step HCl(g) hydrolysis process involving alkali treatment, NaClO2 addition, and gaseous HCl hydrolysis. Subsequent film preparation demonstrated that even short CNFs could form strong transparent films. Overall, these findings provide a foundational understanding of the practical implementation of HCl gas hydrolysis with various cellulose polymorphs/materials. The study presents potential pathways for the HCl (g) hydrolysis of biomass and its use in the generation of nanocellulose and platform chemicals from various sources.
  • Virus-mimetic structures through protein engineering and nucleic acid origami
    (2025) Seitz, Iris
    School of Chemical Engineering | G5 Artikkeliväitöskirja | Defence date: 2025-06-18
    Viruses are fascinating and ubiquitous nanostructures that have intriguing biological properties. Their proteinaceous capsids are uniform in size and shape and serve to protect the viral genome and gate the flux of small molecules. Combined with their unique self-assembly properties, viruses have gained attention as versatile building blocks for bottom-up nanofabrication. However, the resulting virus-based assemblies are typically limited to specific morphologies. Gaining control over the assembly process to produce purpose-built nanostructures with programmable size and shape would be desirable in the development of new delivery systems and vaccines, among others. In this doctoral thesis, the use of nucleic acid origami to template functional virus-mimetic structures was explored. In publication I, the applicability of DNA origami as a binding platform to direct the assembly of virus capsid proteins was investigated. The results demonstrated precise control over the dimensions and morphology of the formed capsid protein-DNA origami assemblies, and that the approach is not limited to only one type of capsid protein. Moreover, the capsid protein coating enhanced the structural stability of DNA origami in endonuclease-rich environments. In publication II, the effect of the internal design of mR A-DNA origami on the folding and translation properties was explored. Extracellular translation studies revealed the importance of the position of the start codon within the mRNA-DNA origami for a successful translation initiation. The translation could be regulated by triggering a structural change in the structure, resulting in the accessibility of the start codon. Furthermore, the mRNA-DNA origami were complexed with virus capsid proteins, which enhanced the cellular uptake, leading to protein translation inside cells while exhibiting low toxicity. In publication III, a protein-based two-component coating, consisting of a targeting and a camouflaging agent, was applied on top of the DNA origami. Once the assembled complexes were illuminated, photolytic degradation of the camouflaging agent was triggered, resulting in the dissociation of the camouflaging agent from the DNA origami and hence the display of the targeting moiety. Finally, in publication IV, a biocatalytic nanoreactor was developed by utilizing DNA origami to spatially organize enzymes and to facilitate the assembly of virus capsid proteins. The findings also highlighted the ability of the assembled and well-defined protein shell to control enzyme-substrate interactions. In conclusion, the results demonstrate the applicability of nucleic acid origami to, in a controllable manner, template highly ordered virus-mimetic structures. Additionally, the nucleic acid origami serve as a pegboard to precisely place functional moieties or employ mRNA as a scaffold, thereby broadening the application range of virus-mimetic structures. The established methods could promote the development of functional and responsive nucleic acid origami-based multipurpose systems.
  • Experimental studies and thermodynamic modeling of metal-slag-refractory interactions in non-ferrous pyrometallurgical processes
    (2025) Jeon, Junmo
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-06-17
    In the non-ferrous pyrometallurgical processes, such as Cu/Ni making processes, the liquid phases, such as Ni alloys, matte, and slag phases exhibit complex behavior. Moreover, refractory lining materials generally react with the liquid phases, such as slag phases under extreme conditions at high temperatures in the Cu/Ni smelting and converting furnaces. Therefore, various solid and liquid solutions can be formed, and the fayalite FeOx-SiO2 slags including CaO, MgO, ZnO, and impurities can penetrate and corrode the lining refractory materials of the furnace, such as MgO-Cr2O3, MgO-Al2O3, and/or MgO-C. In order to increase efficiency of Cu/Ni processes and save costs, it is needed to understand and predict the complex behavior of liquid phases and the corrosion behavior of refractory materials against liquid slags. Thermodynamic modeling can be used to understand the behavior of liquid phases and refractory corrosion against slag phases using thermochemical software, such as FactSage. The thermodynamic modeling is used to calculate phase equilibria based on Gibbs free energy minimization methodology. The Gibbs free energy of non-ideal solution phases can be expressed mathematically by several thermodynamic models, such as Bragg-Williams random mixing model and Modified Quasichemical Model. The parameters of models can be optimized using the Calphad methodology in order to fit calculated phase equilibria and thermodynamic properties with experimentally determined data. The thermodynamic calculations based on the optimized parameters can be used to interpret and predict the behavior of liquid phases and slag-refractory reactions. In this doctoral thesis, the parameters of the ternary Ni-Co-C, CaO-MgO-ZnO, and MgO-ZnO-SiO2 systems were optimized using FactSage based on own experimental phase equilibria studies, as well as data from the scientific literature. The Bragg-Williams model was used for solid solutions, while the modified quasi-chemical model was used for the liquid solutions. All the optimized systems agreed well with the phase equilibria studies within the error limits of the experimental data. Moreover, the corrosion behavior of refractory materials against liquid slag was studied and interpreted using FactSage. Interfacial reactions between MgO-Cr2O3, MgO-Al2O3, and MgO-C refractories and CaO-FeOx-SiO2 slags were studied with experimental work, such as sessile drop and immersion tests. The experimental results also showed good agreement with thermodynamic calculations using FactSage. With the new thermodynamic databases developed in this work, pyrometallurgical processes can be optimized further in the future, taking into account metal-slag-refractory interactions.
  • Toward higher purities of diols and polyols by solid-liquid equilibrium modeling and cooling crystallization
    (2025) Ila, Mitra
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-06-17
    Developing biorefinery processes to convert lignocellulosic biomass, such as forestry and agricultural residues, into value-added products including different diols and polyols (e.g., sugar alcohols, glycols, and by-products such as glycerol) requires the integration of efficient downstream processes. The purification of monoethylene glycol (MEG) from close-boiling and azeotrope-forming impurities and the heat sensitivity issue of both MEG and glycerol has been a challenge. In this thesis, melt crystallization, a technique offering low-temperature operation, was investigated and adapted for relatively high-viscosity mixtures of MEG + 1,2-pentanediol and glycerol + diethylene glycol. This adaptation aimed to enhance the overall efficiency of the process, including the production of high-purity MEG and glycerol at high crystallization yields and reasonable crystal growth rate. Initial studies showed conventional solvent-free layer melt crystallization had poor purification efficiency with an impurity distribution coefficient of crystal layer close to 1. Alternatively, the effect of adding assisting solvents on solid-liquid equilibrium (SLE) phase behavior, crystal growth rate, and purification yield was investigated. Acetone was used for the MEG melt, while 1-butanol and a combination of acetone and 1-butanol (binary solvent) were used for the glycerol melt, chosen for their low viscosity, high vapor pressure, and lack of azeotrope formation based on the predicted vapor-liquid equilibrium data. A comparative study on the driving force for crystallization, using thermodynamic models, crystal growth rate, and viscosity, showed that the impact of the solvents on growth rates varied among MEG and glycerol mixtures due to different rate-limiting factors. Nevertheless, under controlled operating conditions, the distribution coefficient of impurity in the MEG crystal layer decreased to 0.13-0.55 with 15-25 mol.% acetone at crystal growth rates of 1.6×10-7 to 4.7×10-7 m/s. In the binary solvent and single solvent systems of glycerol, this value decreased to 0.13-0.3 and 0.2-0.35 in the first crystallization stage with a total 25 mol.% of solvent(s) at growth rates between 2×10-7 and 6.1×10-7 m/s, and 1.8×10-7 and 5.5×10-7 m/s respectively. Higher crystal purity was achieved in the binary solvent system, especially with increasing crystal growth rates in the second crystallization stage. The positive effect of the assisting solvent was evident in both systems, via increased product purity at higher crystal growth rates in glycerol mixtures and at a controlled rate in MEG mixtures. On the other hand, employing layer melt crystallization for the purification of xylitol obtained from fermented hemicellulose hydrolysate was influenced by the impurity content. High concentrations of impurities in the feed, along with the presence of heat-sensitive and colored compounds, can limit the feasibility of this method as the final purification step following solution crystallization. In addition, the efficiency of crystallization was investigated for downstream separation and purification of D-mannitol in the presence of major impurities produced by two biosynthesis routes using lactic acid bacteria (LAB) and Yarrowia lipolytica yeast strains. The crystallization pathways and maximum theoretical yield for the selective crystallization of mannitol from solutions with different erythritol concentrations, a major by-product of mannitol biosynthesis by yeast, were evaluated based on the predicted ternary solid-liquid phase diagram using a group contribution model. Despite the effect of impurities on crystal yield, controlled cooling crystallization showed high purification efficiency in both synthetic mannitol-erythritol mixtures and LAB fermentation broth containing lactate and acetate as major impurities.
  • Porous media modification with atomic layer deposition: Catalyst performance protection with an inert coating on a Cobalt-based Fischer-Tropsch catalyst
    (2025) Heikkinen, Niko
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-06-17
    Atomic layer deposition (ALD) is a gas phase thin film preparation method with many practical applications, from planar surface microelectronics to porous and tortuous structures such as catalysts. Precise control of reactant deposition inside porous media is achieved with self-limiting chemisorption, where instead of the amount of introduced reactant, the surface itself controls the deposition process. At full reactant saturation, the thin film formation is limited by the number of surface reaction sites and all excess reactants and by-products are removed from the surface prior to the next chemisorption cycle. Although ALD is a method of preparing conformal coatings on even complex structures, the process conditions must be appropriate and designed for each deposition surface and set of structural properties (e.g. pore size and surface area). One important consideration in ALD process design related to particulate materials such as heterogeneous catalysts is that the particle shape has a distinctive effect on the ALD reactant diffusion inside the particle. For this thesis the ALD process was studied for three particle geometries: slab, cylinder and sphere. Comparison of the different particle geometries was conducted with a one dimensional, coupled partial differential equation ALD diffusion–reaction model. The most significant finding was that in comparison to slab particles, only ~1/3 and ~1/2 the reactant exposure (Pa s) was required to fully coat spherical and cylindrical particles, respectively. The lower exposure required to achieve fully coated particles is due to the spherical and cylindrical particles decreasing in volume towards the core. In addition to the modelling work, this thesis experimentally studied the effects of ALD-prepared Al2O3 coatings (with a trimethylaluminum and water ALD process at 150˚C) on the performance of cobalt-based γ-Al2O3 and TiO2-supported catalysts in a Fischer-Tropsch reaction. The experimental work utilised eggshell type ALD coatings to prolong the catalyst lifetime and enhance performance in Fischer-Tropsch synthesis. The ALD coating started from the catalyst surface and reached 10–20 μm penetration depth. The particle size for the γ-Al2O3 support was 50–150 μm and for the TiO2 support 400 μm. The coating thickness was 1 to 4 nm (4 to 40 ALD cycles), while the average catalyst pore diameter was 10–28 nm. Before the Fischer-Tropsch reaction experiments, a post-ALD annealing process was conducted to create porosity in the ALD coating and partially recover the coating-covered active metal (cobalt) sites. The experimental results show that with both the γ-Al2O3 and TiO2-supported catalysts the ALD coating decreased Co removal through leaching during the Fischer-Tropsch reaction. The extent of leaching was suppressed by increasing ALD cycles. However, increasing the number of ALD cycles reduced the cobalt active site recovery and active site availability. Also, a general trend in terms of catalyst selectivity was that increasing the number of ALD cycles decreased the desired C5+ hydrocarbon selectivity and increased undesired CH4 selectivity.
  • Techno-economic assessment at different production scales for sustainable production of bio-based products
    (2025) Khalati, Elham
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-05-28
    This research assesses different aspects of eco-friendly production plants on pilot and commercial scales and develops technical and efficient processes that produce value-added sustainable products. It begins from a lignin-based production plant on pilot scale. The process involves the formation of colloidal lignin particles (CLPs) via self-assembly when lignin dissolution contacts water. This transformation improves the dispersibility of lignin in different media, thereby enabling its application in various areas. This research takes a systematic approach to design a safe and viable pilot plant to optimize the production process. Such an approach allows testing and validating the setup in conditions that closely mirror a full-scale production environment. For detailed design, the technical, safety, and environmental aspects of the pilot plant were examined. Process models were created to conduct process simulation and optimization, perform process safety analysis, and consider regulations to protect human health and the environment. Process safety analysis was conducted by classifying hazardous areas based on the incident rate and extent of the explosive gas atmosphere. In addition, European Union chemicals legislation was considered to assess health and environmental impacts. In the next research phase, the focus moved to developing a commercial-scale closed-cycle extraction process with supercritical CO2 (scCO2). Compared to conventional techniques, scCO2 extraction is considered a clean technology that mitigates environmental issues and enhances extraction yields. Similarly to the pilot plant, after developing process models, the process plant was simulated. Based on the generated technical diagrams, a structured and systematic system examination and risk analysis were performed. Compared to pilotscale setup, a commercial production plant requires more comprehensive techno-economic assessments to develop a viable and safe process. Therefore, cost assessments were conducted via estimating capital and total operating costs. The profitability of the process was also assessed based on calculating the net present value, payback period, and internal rate of return. Conducting sensitivity analysis also facilitated the determination of important variables impact on the process profitability. This investigation has led to thoroughly evaluating different aspects of pilot-scale CLP production as well as commercial multiproduct scCO2 extraction plants. The assessment results provide the opportunity to show their similar and distinct design aspects, which emphasize their roles in developing eco-friendly feasible processes. The approach applied to the CLP production covers new aspects of process design, which are not generally considered for technical, safety, and environmental features of the bench-scale process. This research can be applied in similar processes that involve lignin dissolution and solvent recovery unit optimization before scale-up. In the case of the full-scale plant, developing a mobile and multiproduct scCO2 extraction plant constitutes a new design concept which was developed and assessed in this study. This safe and eco-friendly process not only economically competes with conventional extraction techniques but also provides novel employment opportunities in rural areas.
  • Fractionation of softwood into lignin-containing fibres and fibrils and lignosulphonates through neutral sulphite pulping
    (2025) Hanhikoski, Saara
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-05-28
    The forest industry plays an important role in the production of sustainable materials, chemicals, and energy to meet current and future demands. Driven by economic and environmental factors, the forest industry is increasingly focused on enhancing resource efficiency and developing higher value-added products. In the wood pulping industry, maximising pulp yield and optimising the use of dissolved organic residues represent complementary strategies for the comprehensive utilisation of wood raw material. In this context, the potential of semi-chemical pulping processes, such as the commercial neutral sulphite semi-chemical (NSSC) pulping, to implement these strategies remains largely unexplored. Thus, this thesis provides insights into the fractionation of Scots pine using sodium-based neutral sulphite (NS) pulping within a pH range of 7‒10, as an alternative process to produce lignin-containing high-yield fibres and recoverable organic compounds in the spent liquor. The various sodium sulphite cooking conditions investigated enabled the production of pulp with yields ranging from 80% to 55% on o.d. wood. The analysed compositions showed that a high content of carbohydrates was preserved in the pulps, largely due to the stabilisation of galactoglucomannan. In contrast, delignification under the applied conditions was limited, and to achieve a pulp yield lower than that of typical NSSC pulps (<70% o.d. wood) required long cooking times at high temperatures or the use of anthraquinone as a catalyst. In the spent liquors, lignosulphonates and carboxylic acids, mainly acetic and formic acids, constituted the primary dissolved components. The lignin balances, compiled from lignosulphonates in the pulps and spent liquors, revealed that the pulps contained a residual lignosulphonate fraction that was readily alkali-soluble. The characteristics of this fraction were close to those of spent liquor lignosulphonates, indicating the potential for recovering and utilising both as by-products. Due to their high hemicellulose content and anionic charge, the fibres were relatively easy to fibrillate into nanosized material, although their fibrillation behaviour varied depending on lignin content. As a result of this characteristic, the fibres presented a promising source for lignin-containing cellulose nanofibrils, which may create new application opportunities for the fibres. The findings on Scots pine fractionation under various NS pulping conditions, summarised in this thesis, provide a basis for evaluating softwood NS pulping as an alternative process for producing lignin-containing high-yield fibres and fibrils, as well as lignosulphonates. In addition, the analysed characteristics of fibres and lignosulphonates facilitate the identification of their potential end-use applications. Considering the forest industry's emphasis on strategies to enhance resource efficiency through comprehensive utilization of wood, semi-chemical pulping processes present a viable option.
  • Fabrication of bio-inspired films and surfaces
    (2025) Daghigh Shirazi, Hamidreza
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-05-23
    Nature provides a wealth of optimized principles and functional structures that inspire the development of advanced materials to meet the demands of future technologies. This thesis explores bio-inspired approaches for fabricating films and surfaces using three distinct methods: direct replication of natural surface structures, independent tailoring of hierarchical surface structures, and film production via a spinning technique. These fabrication strategies aim to harness nature-inspired functionalities to advance material design and performance. The replication of leaf surface structures, specifically leek leaves, was achieved through soft lithography, enabling the transfer of superhydrophobic and anisotropic wetting properties of the leaves to the replicas. Furthermore, the replicated surface structures lead to additional optical functionalities. Three approaches were employed: all-biobased replicas using cellulose-based substrates coated with carnauba wax, elastomeric replicas coated with a candle soot layer, and elastomeric encapsulation for solar cells. The results demonstrated improvements in the efficiency of perovskite solar cells through light management. Furthermore, self-cleaning functionalities derived from the leaf structures was enabled owing to the superhydrophobic surfaces, in which dust and dirt are removed when water droplets roll off the surface. In the case of solar cells, this selfcleaning property ensures maximum incident light exposure and along with suitable encapsulation can promote both the lifetime and efficiency of photovoltaic systems. The thesis further delves into independently tailoring hierarchical surface structures by coupling optical patterning of azopolymers with thermal shrinkage of a bilayer with mismatching mechanical properties, combining surface features in two distinct length scales. This method provided anisotropic wetting properties and can also pave the path toward facile fabrication of templates, instead of direct usage of leaves, to transfer the surface structure. Additionally, a cellulose nanofibril (CNF) film-spinning approach was introduced to produce partial CNF alignment, inspired by cellulose orientation in natural systems like wood. The films showed optical transparency and anisotropic humidity actuation reminiscent of, e.g., pine cones. The developed fabrication routes highlight the potential of bio-inspired strategies to produce multifunctional films and surfaces in straightforward and simple manners. The versatility of the presented methods allows for their integration with a wide range of techniques and materials by researchers in future studies, enabling the potential to achieve even more impactful outcomes.
  • The Potential of Lignocellulosic Materials for Supercapacitors and Hydrogen Storage: Activated Carbon Synthesis and Cellulose Separator Development
    (2025) Selinger, Julian
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-05-16
    Energy storage devices are in growing demand, driven by the transition towards a more sustainable future and the increasing use of electronic devices, increasing use of electric and hydrogen−powered vehicles, as well as renewable energy systems. However, energy storage devices are often linked with environmental concerns, as they may contain non−biobased and non−degradable components. This concern is addressed in the following dissertation by exploring the use of bio−based materials for supercapacitor electrodes, hydrogen storage materials and separators. In a first phase optimized activation parameters for bio−based activated carbons were investigated using cellulose−chitosan IONCEL fibers as model precursors to achieve the best balance between surface area, pore size distribution and yield. Optimal conditions were identified with an activation temperature of 800 °C and pre−carbonized material−to−KOH ratio of 1:5. Industrial side streams from the coffee and sugar producing industries were subsequently activated under these conditions. Specific BET surface areas of up to 3,300 m2g−1 could be achieved, with pore size distributions favorable for hydrogen adsorption capacities of up to 2.8 wt.% at 1 bar and 5.8 wt.% at 37 bar, both measured at 77 K. Additionally, the microporous structures of the activated carbons significantly enhanced the performance of aqueous supercapacitors, achieving capacitances of up to 236 F g−1 (at 5 mV s−1). These results outperformed the benchmark material (YP80F) by approximately 100%. To increase the share of bio−based materials in supercapacitors, the aim was to produce cellulose−based separators while considering key design aspects. By incorporating microfibrillated cellulose into paper hand sheets, the thickness was reduced to below 40 μm, and pore sizes were adjusted to fulfill the requirements for supercapacitor separators. A crosslinking−approach using butanetetracarboxylic acid significantly enhanced the wet strength, increasing it by over 6,000%, while maintaining the dimensional stability under wet conditions. The electrochemical characterization demonstrated that the cellulose based separators perform comparable to that of commercial benchmark materials. This dissertation highlights that bio−based materials are a sustainable resource and can reach parity with or even outperform commercial benchmarks. It offers a path for the development of more environmentally friendly energy storage technologies.
  • Lignin-derived compounds valorization on metal-free carbon catalysts
    (2025) Yang, Mingze
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-05-09
    Biomass is a promising alternative to fossil fuels, addressing rising energy demands and supporting carbon neutrality. Among biomass components, lignin is abundant but challenging to utilize fully, making its valorization an important focus. Common methods like oxidative dehydrogenation (ODH) and alkylation-hydrodeoxygenation often require toxic agents or noble metal catalysts, which present environmental concerns. Metal-free, sustainable routes are needed, and carbon catalysts show potential as eco-friendly substitutes. This thesis investigated lignin valorization pathways using carbon catalysts, discussing the mechanisms and comparing their performance with traditional metal-based methods. The biaryl structural unit was synthesized using an air-oxidized activated carbon (oACair) catalyst in an ODH reaction from lignin-derived ketones. The oACair catalyst demonstrated a 74% biphenyl yield with a 9.1×10-2 h-1 reaction rate constant, showing excellent recyclability over six runs and a broad substrate scope across 15 substituted compounds. The quinoidic carbonyl active site and positively charged intermediated were proposed based on surface oxygen functional group analysis, model compound, functional group blocking, and Hammett plot. Similarly, the diaryl amine N-phenyl-1-naphthylamine (P1NA) was produced from lignin-derived aniline and 1-tetralone via an oACair-catalyzed tandem ODH (TODH) reaction, achieving a 71% yield of P1NA with a 0.23 h-1 Max. TOF. The reaction’s robustness was confirmed by its five-run recyclability and compatibility with 10 substrates, with the carboxylic acid group exhibiting cocatalytic effects. Free radical scavenger tests and simulations suggest a single-electron transfer free-radical mechanism for the TODH reaction. The alkylation of alcohols and phenolic compounds was another pathway explored in this thesis. Lignin-derived acidic carbon (SLC400) displayed a high acid density of 2.92 mmol·g-1 with dominated Bronsted acid sites. SLC400 exhibited good catalytic performance in the alkylation with a Max. TOF of 14.2 h⁻¹ in the dehydration step and a Max. TOF of 0.5 h⁻¹ in the alkylation step. Additionally, zeolite-supported tungsten oxide (WO₃/HY500) was applied for guaiacol ethanol alkylation (GEA), confirming pentaethylphenol as the main product and suggesting an alkylation-demethylation mechanism based on product structure and reaction monitoring. Surface acid analysis identified weak and strong Lewis acid sites as the primary active sites for this reaction. These routes offer practical methods to valorize lignin-derived compounds in an environmentally friendly and sustainable way, emphasizing the importance of metalfree carbon catalysts. The investigation of the kinetics, active site, and mechanism enhances the understanding of carbon catalysts and contributes to the further optimization of these routes.
  • Dewatering of single- and multilayer nanopapers
    (2025) Ahadian, Hamidreza
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-04-25
    During the past decade, the paper and board industry has increasingly explored the application of nanomaterials in furnish components. This is due to their potential to create innovative, high-value products that will dominate future markets. This includes cellulosic nanomaterials such as microand nanofibrillated cellulose (MNFC). MNFC consists of cellulose micro- and nanofibrils obtained by deaggregating cellulose macrofibers. These fibrils are considerably smaller and bind more water than the parent pulp fibers. MNFC presents opportunities to innovate natural fiber products with enhanced performance characteristics, including greater mechanical and barrier properties. However, the small size, high swelling, and large surface area of MNFC causes processing issues such as poor water removal properties. This thesis focuses on forming and dewatering sheets containing cellulose nanomaterials and investigates possible solutions to overcome the dewatering challenges. The main hypothesis is to help dewatering by restructuring the fiber network and increasing the permeability of the wet web. The reduced permeability of the wet web is directly related to sheet sealing, which is an established phenomenon in the papermaking process. Different mechanisms of sheet sealing are presented, and we propose approaches to prevent sheet sealing. We show that the enrichment of small fibrils on the exit layer should be avoided. MNFC/fiber flocs and their agglomeration in the suspension are modified through the addition of cationic micro-and nanobubbles. This also changes the z-distribution (localized concentration) of the MNFC fibrils in the web so that there will be more located in the upper layers, which reduces sheet sealing. This method allows for easier dewatering and producing samples with up to 25% MNFC content. Multilayer forming of sheet is suggested as a direct way of structuring. We show that the application of a very thin fibre layer (as thin as 5 gsm) on the screen has a significant effect on the dewatering rate. We also investigate the application of engineered fibers that provide desired functional properties and maintain dewatering properties. This material involves enhanced external fibrillation of fibers without generating excess flake fines and fiber fragments. The composition of this highly swelling material with parent pulp fibers provides low-density, highstrength paperboards. The work summarized in this thesis delivers new insights into dewatering challenges of novel paper/board grades containing nanomaterials and identifies potential routes to overcome these challenges.
  • Superstructured wood-based carbon materials for broadband light absorption and CO2 capture
    (2025) Zhao, Bin
    School of Chemical Engineering | G5 Artikkeliväitöskirja | Defence date: 2025-04-11
    Light is an abundant resource; however, stray light can significantly impact the performance and longevity of optical systems. Adverse effects such as reduced image contrast and signal degradation highlight the need for advanced solutions to effectively mitigate these challenges. Superblack materials, with near-zero light reflectance, are in high demand to enhance several light-based technologies. In this study, we developed wood-based spectral shielding materials with exceptionally low reflectance across the UV-VIS-NIR (250–2500 nm) and MIR (2.5–15 μm) ranges. Using a straightforward top-down approach, we produced robust superblack materials by removing lignin from wood and carbonizing the delignified wood at 1500 °C. This process induced shrinkage stresses in subwavelength severed wood cells, forming vertically aligned carbon microfiber arrays (~100 μm thick) with light reflectance as low as 0.36 %. We further synthesized multiscale carbon supraparticles (SPs) through a soft-templating process involving lignin nano- and microspheres bound with cellulose nanofibrils (CNFs). Following oxidative thermostabilization, these lignin SPs exhibited high mechanical strength due to their interconnected nanoscale networks. In further work, by inserting lignin particles (LPs) into delignified wood and carbonizing the structure, we created a carbonized reconstituted wood (cRW) system with enhanced dimensional fidelity and finely tuned light-absorbing fibrillar microstructures. They resulted in broadband light traps that achieved superabsorbance, exceeding 99.8% across a wide range of wavelengths, from infrared to ultraviolet. Tiled cRW structures, optically welded for customizable size and shape, demonstrated superior laser beam reflectivity compared to commercial light stoppers, eliminating thermal ghost reflections. This makes them promising candidates as reference infrared radiators for thermal imaging device calibration. Beyond optical applications, the carbon SPs also offer hierarchical adsorption sites, achieving a CO₂ adsorption capacity of 77 mg CO2·g-1. This innovation in the area of carbon capture was shown to solve the diffusion and kinetic limitations of conventional nanoparticle-based systems. Overall, this thesis summarizes wood-derived solutions that go from multispectral shielding to carbon capture technologies.
  • Advanced Characterization for Studying Ni-rich Cathode Materials for Li-ion Batteries
    (2025) Colalongo, Mattia
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-03-28
    Li-ion batteries (LiBs) are energy storage devices which are able to convert chemical energy into electrical energy. Due to the recent excessive consumption of fossil fuels resulted in the uncontrolled release of carbon dioxide and significant amounts of greenhouse gases into the atmosphere, the need for sustainable energy growth becameevident. Hence, there is a critical need for high-performance energy storage devices exhibiting both high energy and power density to ensure the sustainability and safety of storing renewable energy. In this thesis, by means of synchrotron radiation facility we explored the most efficient way to Zr bulk doping a Ni-rich layered cathode material upon two different pathways, during lithiation and co-precipitation step. High resolution x-ray diffraction and x-ray absorption spectroscopy measurements revealed, for the coprecipitation step, the absence of every Zr based impurity and a local environment compatible with its inclusion in the cathode host structure. Whereas for the lithiation step, Zr tended to only form extra-phase impurities. The Zr-doped Ni-rich cathode material synthesized via the co-precipitation method exhibited improved electrochemical performance compared to the undoped sample. To investigate these enhancements, operando high-energy x-ray diffraction and exsitu x-ray absorption spectroscopy were utilized. X-ray diffraction analysis revealed a reduced formation rate of the detrimental H3 phase in the doped samples, while x-ray absorption spectroscopy indicated a decrease in transition metal dissolution from the cathode material. These findings underline the importance of studying trace amount dopants to advance the development of more robust Ni-rich cathode materials. The undoped material in the operando studies revealed the presence of a phase segregation upon cycling at high voltages. To understand the nature of the phase segregation formation mechanism, a nanobeam approach was involved. An initial operando experiment by means of scanning x-ray diffraction microscopy was carried out to probe multiple single particles and follow the Li+ heterogenities upon cycling. However, the experiment faced challenges due to cell holder instability, and beam damage. Progress continued with further experiments at the IDOl ESRF beamline, allowing successful ex-situ examination of inter- and intra-particle heterogeneities in polycrystalline particles. Up to date, the operando challenges in nanoprobe studies remain a critical area to address in order to advance the research in the field of Li-ion battery materials.
  • Effects of Nickel in Copper Production: Implications for High-Purity Copper Electrorefining
    (2025) Sahlman, Mika
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-03-26
    The demand for high-purity copper is increasing due to the electrification of society. At the same time, the ore bodies are getting poorer, and there has been an increased emphasis on metal recycling. Most of the world’s high-purity copper is produced by electrorefining. Nickel is one of the main impurities in copper electrorefining, and the previously mentioned factors have resulted in increased nickel concentrations at the smelters and tankhouses, especially in operations that specialise in treating complex raw materials. This thesis studies the effects of Ni on Cu electrorefining and discusses the implications of the results for industrial electrorefining plants. Three main themes were investigated: Ni's contamination of the copper cathode, Ni’s effects on anode slime flow behaviour, and the impact of Ni on the physical quality of the cathode, i.e., roughness and nodule formation. Regular laboratory-scale copper electrorefining experiments were performed in traditional sulfuric acid media, with the focus of the thesis being on the behaviour of anode Ni and electrolyte Ni. Both industrial and synthetic electrolytes were used to investigate electrolyte Ni’s effects on copper electrorefining. Industrial anode samples were used to examine the impact of anodes on copper electrorefining. Anode slime detachment and cathode growth study results were verified in a bench-scale electrorefining cell. No definite upper limit for the anode Ni concentration could be determined. An upper limit of 20 g/L of Ni was proposed for the electrolyte due to the increased risk of rougher cathodes and cell passivation. Particle entrapment was the primary contamination mechanism of copper cathodes in the case of Ni. Synthetic anode slime composed of NiO and Fe2O3 did not cause cathode nodulation. Nodulation was observed with industrial anode slimes, but the industrial anode slime with less Ni (10.3 wt.%) resulted in more nodules than the industrial anode slime with higher Ni concentration (20.4 wt.%). Electrolyte inclusions were deemed plausible, but major micronodulation in the presence of conductive graphite was required for significant contamination. The electrodeposition of Ni does not happen in typical Cu electrorefining conditions. Increasing anode and electrolyte nickel concentrations led to an increased upward flow of anode slimes, at least during passivation. Increasing anode Ni concentrations increased upward flow of anode slimes throughout the electrolyte. In the case of the electrolyte, however, this phenomenon occurred only in the vicinity (1 mm) of the anode surface. The impact of electrolyte Ni was attributed to the increased porosity of the anode slime layer, while the changing anode slime mineralogy might explain the effect of anode Ni. Both anode and electrolyte Ni promoted the clustering of anode slime. Average, maximum and minimum anode slime settling velocities were 0.12 mm/s, 1.65 mm/s and -1.08 mm/s, respectively, during anode passivation (at 25 °C). At 60 °C, the anode slimes settled on average with a velocity of 1.4-49.6 mm/s, and upwards-moving slime could flow with a velocity of 2.5 mm/s. Design of Experiments (DOE) was used in combination with partial least square regression (PLSR) modelling to determine the impact of Ni and electrolyte additives (gelatine, thiourea and chloride) on the cathode roughness (Rz and Sm). Ni increased the Rz roughness of the Cu cathodes from 469 μm to 945 μm in the absence of additives. Ni alone did not affect the Sm roughness, but thiourea and Ni were found to have synergistic effects on smoothening the cathode surface. Laboratory cathodes were compared to industrial samples, and samples from both sources had similar surface roughnesses. While increasing Ni might cause rougher cathodes, variable importance in projections (VIP) suggests that additives have a more notable impact on cathode surface quality.
  • Electrochemical CO2 Reduction Mechanism Exploration: An Integrated Thermodynamic and Kinetic Approach
    (2025) Khakpour, Reza
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-03-26
    The electrochemical reduction of CO₂ (eCO₂RR) presents a promising strategy to address sustainable energy challenges by converting CO₂ into value-added chemicals and fuels. This thesis employs density functional theory (DFT) to investigate the reaction mechanisms of eCO₂RR, focusing on enhancing computational mthodologies and understanding catalyst performance. Key challenges such as the low reactivity of CO₂ and competition with the hydrogen evolution reaction (HER) are addressed through a systematic evaluation of molecular catalysts including metal porphyrins and phthalocyanines. The research develops advanced computational approaches to accurately model proton-coupled and decoupled electron transfers, essential for analyzing reaction pathways. The findings highlight bicarbonate as a more favorable intermediate compared to CO₂ under neutral pH conditions. Mechanistic insights into post-CO reactions including the formation of C1, C2, and C2+ products elucidate the role of catalyst design and reaction conditions in achieving multi-carbon product formation form single atom catalysts (SACs). Additionally, the study explores pH-dependent selectivity for formaldehyde and methane which aligns computational results with experimental observations. By providing a comprehensive framework for understanding eCO₂RR pathways, this thesis contributes to the rational design of catalytic systems and optimization of reaction conditions for sustainable energy applications and efficient electrocatalysis.
  • Molecular simulations of crystalline cellulose interfacial interactions
    (2025) Kou, Zhennan
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-03-21
    Crystalline nanocellulose, especially cellulose nanocrystals (CNCs), is widely used in many fields, such as pharmaceutical and biomedicine materials, paper making and alimentation industries, in reinforcement of polymer composites, but also as support matrices and packaging materials. The interactions between CNC surfaces and other materials can influence the properties of CNCbased materials, which can widen the usage of CNC materials. In this thesis, CNC interactions with water, ions, and lignin-carbohydrate complexes (LCCs) are studied, since these interactions can heavily affect the properties of CNC materials but also the wood-like and wood-based materials. We first studied the interactions between CNC surfaces and Na+ and Cl- ions in water solutions. After that, the interactions between CNC surfaces and LCCs were studied. A very small amount of ions can affect CNC surface interactions strongly. In this thesis research, in a 0.6 %wt CNC solution, 0.25 mM NaCl in the solution was sufficient to significantly change the viscosity. Our results show that the presence of NaCl as ions can change the water dipole orientation, which influences the interactions between CNCs. The hydration layer ordering at the position of the ion can increase. The change at the binding sites is enough to change the interaction between CNC surfaces, affecting solution viscosity. This kind of water molecule orientation change can help merge the hydration layers of surfaces, which increases the connections of CNCs in solution. Thus the viscosity increased. The interactions between LCCs and CNCs are dependent on the CNC surface crystal facet. We examined simple model LCCs to obtain insight. The main driving force of interaction between hydrophilic CNC surfaces and the model LCCs was hydrogen bonding, with lignin playing a bigger role when the hemicellulose chains are short. For hydrophobic CNC surfaces, the interaction was more through van der Waals and dipole-dipole forces. In summary, interactions between CNC surfaces common in CNC solutions and in wood-like and wood-based materials are studied in this thesis. This can help understanding and control the properties of these materials. The findings may help product design in these fields to be more productive and environment-friendly.
  • Bioinspired living coating system for wood protection
    (2025) Poohphajai, Faksawat
    School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2025-03-21
    The bioinspired living coating system offers an innovative, sustainable approach to wood protection, relying on natural substances with minimal environmental impact and low maintenance requirements. While promising as an alternative to conventional coatings, key aspects remain poorly understood. Although Aureobasidium pullulans (A. pullulans) has been identified as the optimal fungal species, it is essential to further validate that this fungus meets crucial criteria for effective protection. Additionally, the impacts of natural weathering on substrate properties, bioreceptivity, microbial colonization rates, and the survival of fungal cells within the coating under varied conditions require further investigation. This thesis aims to 1) explore A. pullulans' resilience in biofilm formation across different wood substrates and environmental conditions, 2) assess the performance of wood treated with this biofilm-based coating, and 3) examine fungal cell survival throughout its service life. The evaluation of fungal colonisation on wood surfaces exposed to diverse climate conditions and a range of coated and non-coated biobased façade materials revealed that specific species, notably A. pullulans, emerged as predominant primary colonisers on weathered wood surfaces, regardless of geographical location, cardinal direction, and surface treatment. The adaptability and capacity to thrive in a relatively broad range of ecological conditions make this fungal strain suitable as a protective layer for building materials. The assessment of fungal colonisation on wood surfaces coated with Biofinish following a 9-month exposure period revealed that the majority of the detected species belonged to the genera Aureobasidium, specifically A. pullulans. These results indicate the survival and effective antagonistic action of A. pullulans, the living and active ingredient of the coating, against other wooddecaying fungi. The performance of Scots pine (Pinus sylvestris L.) wood treated with Biofinish was evaluated against uncoated reference wood following a 12-month natural weathering trial. Biofinish exhibited superior performance across all examined aspects compared to the uncoated reference. The entirely bio-based composition of the Biofinish coating enhances its sustainability and compatibility with natural environments, rendering it an appealing alternative to contemporary wood surface protection solutions. The results from this thesis will facilitate the control and optimisation of fungal biofilm and contribute to the development of novel bioinspired protection coatings based on optimised fungal biofilm working in synergy and not against nature.
  • Electrochemical Reduction of CO₂ on Molecular Catalyst: Unfolding Operation Parameters Influence on Product Selectivity
    (2025) Hossain, Md Noor
    School of Chemical Engineering | Doctoral thesis (article-based)
    The electrochemical reduction of CO₂ (eCO₂R) using renewable electricity offers a promising way to convert waste CO₂ into valuable chemicals and fuels, achieving a negative carbon emission footprint. Industrializing eCO₂R for chemical production requires durable, selective, and active electrocatalysts capable of generating high current density at low overpotentials. This thesis focuses on the design and development of a cobalt tetraphenyl porphyrin/multi-walled carbon nanotube (CoTPP/MWCNT) composite for eCO₂R to one-carbon (C₁) chemicals and fuels, and the evaluation of this composite in various electrochemical cells. The electrochemical reduction of CO₂ on CoTPP/MWCNT was investigated in two electrochemical cells: H-cell and industrially relevant flow cell. In both electrochemical cells, selected potential values and a temperature range of 20-50°C were investigated in a 0.1 M KHCO3 electrolyte. The local reaction environment during eCO₂R on the composite was investigated using a differential electrochemical mass spectrometry (DEMS) technique. A similar temperature range as in previous studies was employed. The H-cell studies reveal that the composite produces a mixture of liquid and gas products. The product selectivity strongly depends on the applied potentials and temperatures. At lowest applied temperature, CO₂ is mainly converted to CO and CH3OH while H2 production remains minimal. As the temperature increases H2 production becomes dominant over eCO₂R related products. Flow cell studies reveal that composite mainly produces gas products such as CO and H2 at all applied potentials and temperature. Like H-cell, product selectivity strongly depends on the applied potentials and temperatures. Interestingly, at 20°C and highest applied negative potential, the composite is highly selective for CO formation, reaching a Faradaic efficiency (FE) of 98%. However, increasing the temperature significantly reduces CO selectivity while increasing H2 production. Furthermore, this study demonstrates that the syngas (a mixture of CO and H2) ratio can be controlled by adjusting the temperature. DEMS studies identify key fragments of reaction products evolving from the electrode/electrolyte interface. Experimental results reveal that onset potential of reaction products is strongly affected by temperature, particularly onset potential of CH3OH formation decreased approximately 300 mV at highest temperature. The reduction of onset potential is economically beneficial for large-scale industrial chemicals production. Overall, DEMS studies enhance our knowledge on the mechanisms of CH3OH and CH4 production on the CoTPP/MWCNT composite.