Search

Lignin is a potential resource for biobased aromatics with applications in the field of fuel additives, resins, and bioplastics. Via a catalytic depolymerization process using supercritical ethanol and a mixed metal oxide catalyst (CuMgAlOx), lignin can be converted into a lignin oil, containing phenolic monomers that are intermediates to the mentioned applications. Herein, we evaluated the viability of this lignin conversion technology through a stage-gate scale-up methodology. Optimization was done with a day-clustered Box-Behnken design to accommodate the large number of experimental runs in which five input factors (temperature, lignin-to-ethanol ratio, catalyst particle size, catalyst concentration, and reaction time) and three output product streams (monomer yield, yield of THF-soluble fragments, and yield of THF-insoluble fragments and char) were considered. Qualitative relationships between the studied process parameters and the product streams were determined based on mass balances and product analyses. Linear mixed models with random intercept were employed to study quantitative relationships between the input factors and the outcomes through maximum likelihood estimation. The response surface methodology study reveals that the selected input factors, together with higher order interactions, are highly significant for the determination of the three response surfaces. The good agreement between the predicted and experimental yield of the three output streams is a validation of the response surface methodology analysis discussed in this contribution.

In this study, the development of lignin-based resins for wood adhesion applications was demonstrated. We investigated two lignin fractions: commercial Protobind 1000 lignin and methanol-soluble Protobind 1000 lignin fraction after mild solvolysis. Although lignin has previously been incorporated into various cross-linked systems, this is the first report on lignin-based thermosets obtained via thiol–yne “click” chemistry. In this approach, lignin was functionalized with terminal alkyne groups followed by cross-linking with a multifunctional thiol, resulting in polymeric network formation. The influence of the curing conditions on the resin characteristics and performance was studied, by varying the amount of reactive monomeric diluents. Additionally, a post-curing strategy utilizing the Claisen rearrangement was investigated. These resins were tested as a wood adhesive and were proven to possess a desirable performance, comparable to the state-of-art phenol-formaldehyde resins. Lignin-based thiol–yne resins turn out to be an alternative to phenol-formaldehyde resins, currently used as adhesives and coatings. Although it is possible to use lignin in phenol-formaldehyde resins, lignin addition is compromising the resin’s performance. The main benefits over the phenol-formaldehyde approach are that higher lignin loadings are possible to achieve, and no volatiles are emitted during the resin processing and use.

As a hard-to-decarbonize sector, the shipping industry is experiencing demands to accelerate the transition from fossil fuels to alternative low-carbon fuels, to significantly reduce the negative impacts on the environment. Biofuels are regarded as one of the solutions for decarbonization in the marine sector. This paper introduces a lignin-derived drop-in biofuel, 2-methoxy-4-propylphenol (2M4PP), from non-edible feedstocks and investigates engine performance using its 10% (by volume) blend with standard diesel fuel (DF) at variable engine speeds and loads. Results show insignificant difference between the in-cylinder pressures of the proposed blend and DF. The diesel-2M4PP blend emits less carbon monoxide (CO) and nitric oxide (NO x) than DF at all speeds by up to 39.6% and 10.7% respectively, although its brake-specific fuel consumption (BSFC) is higher. A Ricardo wave model, which is validated with engine experimental data at 2400 rpm speed and full load, is investigated by adjusting injection pressure, injection timing, injection duration and nozzle diameter. The optimal parameters, i.e., 214 bar injection pressure, 6° injection timing, 41.4° injection duration, and 0.37 mm injector orifice, lead to the best engine performance with improved brake power, reduced NO x emissions, and limited influence on BSFC and hydrocarbon emissions compared to DF.

There is an environmental concern regarding the use of petroleum-based lubricants, which are generally toxic and nonbiodegradable. Biobased lubricants, such as vegetable oils, are the alternative: they show excellent lubricity, are readily biodegradable and nontoxic. However, a major disadvantage of using vegetable oils in lubricant applications is their lack of thermo-oxidative stability, which can be improved by antioxidant additives. Here, we propose the use of lignin-based additives in biolubricant formulations to improve this feature, based on lignin’s known antioxidant properties. To ensure a stable dispersion in vegetable oil, lignin was partially esterified. Antioxidant properties of lignin before and after palmitoylation were demonstrated in a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Four different lignin-based fractions, commercial Protobind P1000 soda lignin from straw, solvolytically fractionated Protobind P1000 lignin and two lignin fractions from reductively catalyzed fractionation (RCF) of native birch wood, were tested in biolubricant formulations with castor oil as base oil. Those lignin fractions exhibited excellent performance compared to butylated hydroxytoluene (BHT), a commonly used petroleum-based antioxidant. Formulations of modified lignin in castor oil possess improved thermo-oxidative stability, as illustrated by their increased oxidation induction time. Additionally, rheological and tribological tests demonstrate similar, or in some cases improved, lubricating properties compared to castor oil. This study showcases the successful incorporation of lignin-based antioxidants in biolubricant formulations, tackling the major disadvantage of vegetable oils as environment-friendly lubricants.

A mild thermal solvolysis process using alcohols for the valorization of technical Protobind soda lignin into crude lignin oil (CLO) is presented. The solubilization process results in lower molecular weight lignin fragments (1250–1550 g mol−1cf. 2500 g mol−1 of parent lignin), while rejecting heavy compounds and other solid impurities. The influence of the reaction temperature (100–350 °C), residence time (0.5–4 h), lignin : solvent ratio (1 : 15–1 : 2 w/v) and alcohol solvent (methanol, ethanol, 1-propanol, 1-butanol, and 1-octanol) on the amount and type of products is investigated. At a high lignin loading (ratio < 1 : 5 w/v) and under optimum conditions for lignin solubilization (T = 200 °C, t = 0.5 h), the condensation reactions and solvent consumption are minimized. Methanol exhibits the highest solvolytic efficacy resulting in an overall lignin solubilization degree of 61 wt%, which includes some heavier lignin fractions originating from condensation reactions. The other alcohols resulted in a lignin solubilization degree of 57 wt% for ethanol, 53 wt% for 1-propanol, 51 wt% for 1-butanol and 38 wt% for 1-octanol. The solvent losses based on GC-MS analysis of the obtained CLOs were 1.1 wt% for methanol, 1.4 wt% for ethanol and 2.2 wt% for 1-butanol. Hansen solubility parameters are employed to discuss the effect of solvent on the solubilization process. Gel permeation chromatography and heteronuclear single quantum coherence NMR of solubilized fractions revealed cleavage of β-O-4 bonds during thermal solvolysis, explaining the molecular weight reduction. Methanol is the most favourable solvent and is utilized in solubilization of 5 different biorefinery lignins. In all cases, this led to CLO with a lower molecular weight of the lignin fragments, a lower polydispersity and an increased hydroxyl group content.

Lignin is a renewable and abundant source for production of bio-based chemicals and is a valuable alternative to crude oil to obtain aromatic building blocks. It is built from aromatic units with strong chemical linkages, which need to be cleaved to enable the use of the aromatic compounds in industrial applications. In addition to depolymerizing lignin, efficient fractionation and conversion of the resulting complex mixtures is an essential step in the valorization of lignin derivatives for different applications. In this work, we studied the separation of a lignin oil obtained by catalytic cleavage in supercritical ethanol (scEtOH) of technical lignin produced by means of soda pulping of wheat straw. The use of six commercial polymeric nanofiltration (NF) membranes and one in-house developed Grignard-functionalized ceramic membrane was investigated for the fractionation of a mixture of lignin derivatives. Separation by molecular weight (MW) was observed with the polymeric NP030 membrane but not with the other membranes tested. The development of a protocol using this membrane in the diafiltration mode for fractionation of crude lignin oils (CLOs) is discussed.

This paper presents systematic analysis of value creation chains and their economic and environmental hotspots within a multi-product biorefinery with the primary goal to promote sustainable biorefining. Lignocellulosic biorefinery producing ethanol, crude lignin oil (CLO) and electricity was analysed. The methodology involves transformation of technological model into an input-output one with the use of matrix notation for the analysis of economic and environmental attributes along value chains. The results show that the accumulation of biomass through energy supply grows by a factor of 1.2 for ethanol and electricity, and by 1.4 for CLO value chains, of which solid recovery, lignin solvolysis and biomass pretreatment are responsible for the most significant growth indicating the necessity for energy optimization of those steps. The analysis reveals a superfluous role of infrastructure in pretreatment and lignin drying processes. Of infrastructural costs related to the equipment required for the pretreatment step, wastewater treatment (WWT) facility is responsible for 58%, and of the costs of lignin drying, the combined heat and power plant is responsible for 56%. WWT determines 75% of infrastructural GHG emissions attributable to pretreatment, and 57% of those related to lignin drying. This points at an advantage of a biorefinery concept involving the removal of lignin fraction before the valorization of carbohydrates. Another hotspot, the lignin solvolysis technology, shows environmental and economic advantages of its further optimization in terms of production costs and GHG emissions. The proposed method is helpful for analyzing economic and environmental hotspots in new biorefinery concepts and integration pathways.

Life‐cycle inventory (LCI) is a fundamental phase in the quantification of the environmental performance of products. However, when it comes to the LCI of a multi‐product system, discussions about the choice of the appropriate methodology to allocate environmental impacts still continue. A further system subdivision and the implementation of a mechanism allowing environmental burdens to be tracked would help to improve model accuracy. This study focuses on the LCI modeling of a lignocellulosic biorefinery producing ethanol, lignin oligomers, and electricity, and demonstrates the application of the matrix‐based approach for detailed system subdivision and environmental burden tracking. Forty scenarios utilizing process‐specific allocation methods were tested to account for the global warming potential of outputs. The main findings of the paper are: (i) the importance of specific allocation methods applied to combined heat and power plants that stress the key role of internal energy supply in carrying environmental burdens; (ii) a negligible effect of allocation methods applied to wastewater treatment facilities; (iii) the inconsistency of results obtained via two allocation methods, one based on the total mass and the second based on the dry mass allocation, which raises questions about the validity of water accounting in the allocation procedure of related products; (iv) the role of upstream greenhouse gas (GHG) emissions in lignin‐derived outputs, which emphasizes the importance of a proper allocation methodology to be applied to this residue; and (v) an important role of the biomass pretreatment and lignin solvolysis processes in the accumulation of emissions, which highlights the importance of decreasing the amount of solids and methanol content in the processes discussed here.

We optimized the solvolysis step in methanol for two-step lignin-first upgrading of woody biomass. Birchwood was first converted via sulfuric acid methanolysis to cellulose pulp and a lignin oil intermediate, which comprises a mixture of lignin oligomers and C5 sugars in the methanol solvent. The impact of reaction temperature (140–200 °C), acid loading (0.24–0.81 wt%, dry biomass), methanol/biomass ratio (2.3/1–15.8/1 w/w) and reaction time (2 h and 0.5 h) was investigated. At high biomass loadings (ratio &lt, 6.3/1 w/w), operation at elevated pressure facilitates delignification by keeping methanol in the liquid phase. A high degree of delignification goes together to a large extent with C5 sugar release, mostly in the form of methyl xylosides. Gel permeation chromatography and heteronuclear single quantum coherence NMR of lignin fractions obtained at high acid (0.81 wt%) and low biomass (15.8/1 w/w) loading revealed extensive cleavage of β-O-4′ bonds during acidolysis at 180 °C for 2 h. At an optimized methanol/biomass ratio of 2.3/1 w/w and acid loading (0.24 wt%), more β-O-4′ bonds could be preserved, i.e., about 33% after 2 h and 47% after 0.5 h. The high reactivity of the extracted lignin fragments was confirmed by a second hydrogenolysis step. Reductive treatment with Pd/C under mild conditions led to disappearance of ether linkages and molecular weight reduction in the hydrotreated lignin oil.

With a view to boost practical implementation of lignin conversion technologies, this paper assesses the availability of industrial lignin and evaluates pricing strategies applicable to multi-product biorefineries. The biorefineries, producing either denatured ethanol or sugar hydrolysate as a main product, can yield 43% and 61% of lignin residue (LR) comprising 33% and 23% of lignin by mass, respectively, without sacrificing the output of the main product and before electricity import has become indispensable. Analysis of the pricing strategies reveals that LR must be treated as a low-value by-product, and its minimum selling price (MSP) is driven mainly by the prevailing electricity price. Under the biorefinery net zero energy balance, and taking into account the LR market price adequacy, as well as the main probabilistic conditions, the upper range for the MSP is calculated at $43–70 and $18–37 per ton for biorefineries producing ethanol and hydrolysate, respectively.

Much scientific research has been carried to convert lignin into valuable biobased chemicals or fuels. Most of these studies had the objective to develop active and selective catalysts for effective lignin depolymerization; this with little regard for the parameters that are necessary for later commercialization of these technologies. In this work, we have chosen as a case study a process that has been extensively studied and reported on earlier by our group. This process converts (technical) lignin into mainly aromatic compounds, using supercritical ethanol and a Cu–Mg–Al mixed oxide catalyst. Here, we investigate the impact of scaling up this process from lab to bench scale. More specifically, we study the influence of higher lignin loadings than previously reported on, amongst other parameters, monomer yield, solvent losses and catalyst fouling; all of which being critical performance parameters for industrial operation. After we examined the technical feasibility of our process at 4 L scale, we further looked into the economic viability of this technology, by introducing two performance criteria, both of which being a function of lignin monomer yield. The ratios (g/g) of yield over total feed, and yield over ethanol losses are presented as qualitative indicators for capital expenditure (CAPEX) and operational expenditure (OPEX), respectively. This exercise sheds some much needed light on the trade-off between yield optimization and cost minimization.

This paper explores the environmental and economic aspects of fast pyrolytic conversion of lignin, obtained from 2G ethanol plants, to transport fuels for both the marine and automotive markets. Various scenarios are explored, pertaining to aggregation of lignin from several sites, alternative energy carries to replace lignin, transport modalities, and allocation methodology. The results highlight two critical factors that ultimately determine the economic and/or environmental fuel viability. The first factor, the logistics scheme, exhibited the disadvantage of the centralized approach, owing to prohibitively expensive transportation costs of the low energy-dense lignin. Life cycle analysis (LCA) displayed the second critical factor related to alternative energy carrier selection. Natural gas (NG) chosen over additional biomass boosts well-to-wheel greenhouse gas emissions (WTW GHG) to a level incompatible with the reduction targets set by the U.S. renewable fuel standard (RFS). Adversely, the process' economics revealed higher profits vs. fossil energy carrier. (C) 2017 The Author(s). Published by Elsevier Ltd.