Liquefaction Of Lignocellulosic Biomass Research Articles

Advancements and challenges in catalytic hydrothermal liquefaction of lignocellulosic biomass: A comprehensive review

Hydrothermal liquefaction (HTL) is one of the leading technologies for converting lignocellulosic biomass waste into liquid bio-oil to meet the growing energy demands and alleviate environmental crises. In this comprehensive review, an examination and comparison were conducted on three distinct technologies: HTL, Microwave-Assisted Hydrothermal Liquefaction (MA-HTL), and Co-hydrothermal Liquefaction (Co-HTL). The assessment encompassed various parameters, including production efficiency, bio-oil quality, production cost, and operational conditions. Furthermore, the pivotal role of catalysts in enhancing the bio-oil quality was explored. The corresponding catalytic attributes, spanning homogenous, heterogeneous, and combined catalysts, along with the associated mechanisms such as depolymerization, decarboxylation, decarbonylation, hydrogenation, dehydration, deoxygenation, and hydrodeoxygenation, were thoroughly examined. Additionally, the review delved into upgrading technologies and potential applications of bio-oil to broaden its utility. The current challenges and future prospects concerning bio-oil production using HTL technologies were also addressed.

Machine learning prediction of bio-polyol yields and hydroxyl values from acid-catalyzed liquefaction of lignocellulosic biomass

Amid the escalating demand for alternatives to petroleum resources and the imperative to decrease carbon emissions, there is an increasing interest in transforming lignocellulosic biomass into valuable chemicals. This study utilized machine learning models to analyze the acid-catalyzed liquefaction process of lignocellulosic biomass and to predict and characterize the yield and hydroxyl value (HV) of bio-polyols. A total of 612 yield data samples and 229 HV data samples were collected and analyzed. From these data, four machine learning models were constructed: Random Forest (RF), Gradient Boosting Regression (GBR), Gaussian Process Regression (GPR), and Support Vector Regression (SVR). The Bayesian Optimization Algorithm (BOA) was applied to refine the hyperparameters of the models, thereby enhancing their predictive accuracy. To clarify the effects of input features on predictive outcomes and to understand their interactive dynamics, one-dimensional and two-dimensional Accumulated Local Effects (ALE) analyses were performed. The results show that the GBR model was particularly precise in forecasting the yield and HV of bio-polyols, with corresponding test set determination coefficients (R2) of 0.82 and 0.91. The most influential factors on yield were reaction time (15.1 %), lignin content (13.1 %), and glycerol mass (12 %), while for HV, they were glycerol mass (28.9 %), particle size (15.1 %), and liquid-to-solid ratio (11.1 %). The ALE analysis also exposed the intricate interaction mechanisms between feedstock composition and liquefaction conditions. The verification results confirmed that the optimal model displayed exceptional generalization capabilities, with a Mean Absolute Percentage Error (MAPE) of 9.18 %. Utilizing this model, a user-friendly software package has been developed to enable rapid and precise prediction of the lignocellulosic biomass conversion process. This research not only delivers strategies to cut down on experimental costs and time but also offers a novel perspective on the industrial utilization of biomass-derived polyols.

Operational experience with miscanthus feedstock at the bioliq® fast pyrolysis plant

Fast pyrolysis is a thermochemical process for direct liquefaction of lignocellulosic biomass that offers flexibility in terms of feedstock variability since all biomass macromolecules are converted. In contrast to this expectation, it is also obvious that there are limits to feedstock flexibility once a fast pyrolysis plant has been built. This relates to the simple fact that any pretreatment is to a certain extent specific for one type of biomass, but also to the observation that liquid yield can vary widely depending on the feed. Different bio-oil yields directly affect heat management and volume flows in an installation. Laboratory equipment has very limited suitability to assess flexibility of a large scale implementation. To address this shortcoming, a change in feedstock with significantly different bio-oil yield was conducted in the bioliq® pilot unit that was designed for wheat straw with a feedstock capacity of 500 kg h−1. Miscanthus was used in two experimental campaigns that each lasted two weeks. While steady state operation succeeded, feedstock capacity had to be reduced significantly to around 200 kg h−1 to allow for a better control of pressure fluctuations in the hot gas section. An evaluation of volume flow rates reveals that these fluctuations are not due to an increased volatile yield. It is concluded that plugging issues caused by an increased reactivity of the produced volatiles likely caused the observations and limitations to plant capacity. The specific heat demand for the reactor of the fast pyrolysis unit was estimated to be approx. 0.83 and 0.76 MJ kg−1 for both miscanthus campaigns and ca. 0.67 MJ kg−1 for wheat straw. Heat supply to the reactor was not a limiting factor when changing the feedstock because the low feedstock rate outweighed the increase in specific heat demand. The yield distribution from miscanthus has been compared to experiments conducted in parallel in a smaller process development unit with a feedstock capacity of 10 kg h−1. The results impressively show the influence of ash content on the yield distribution and also the importance to focus on (earth) alkali metals to better describe their catalytic activity during biomass pyrolysis.

Upgrading of fast pyrolysis bio-oils to renewable hydrocarbons using slurry- and fixed bed hydroprocessing

Liquefaction of lignocellulosic biomass through fast pyrolysis, to yield fast pyrolysis bio-oil (FPBO), is a technique that has been extensively researched in the quest for finding alternatives to fossil feedstocks to produce fuels, chemicals, etc. Properties such as high oxygen content, acidity, and poor storage stability greatly limit the direct use of this bio-oil. Furthermore, high coking tendencies make upgrading of the FPBO by hydrodeoxygenation in fixed-bed bed hydrotreaters challenging due to plugging and catalyst deactivation. This study investigates a novel two-step hydroprocessing concept; a continuous slurry-based process using a dispersed NiMo-catalyst, followed by a fixed bed process using a supported NiMo-catalyst. The oil product from the slurry-process, having a reduced oxygen content (15 wt%) compared to the FPBO and a comparatively low coking tendency (TGA residue of 1.4 wt%), was successfully processed in the downstream fixed bed process for 58 h without any noticeable decrease in catalyst activity, or increase in pressure drop. The overall process resulted in a 29 wt% yield of deoxygenated oil product (0.5 wt% oxygen) from FPBO with an overall carbon recovery of 68%.

Agricultural Waste Liquefied Hydrothermally using Heterogeneous Catalyst

Due to its abundance and sustainability, lignocellulosic biomass is a possible replacement for petroleum oil in the production of energy and chemicals. Numerous thermochemical processes have been used in significant study to turn biomass into products with added value. One of the best methods for creating bio-fuels and bio-based compounds among them is hydrothermal liquefaction (HTL). However, a number of technological obstacles still need to be removed before HTL technology can be widely used in industry. Hydrothermal liquefaction is now thought to be amongst the most popular effective processes to converting moist biomass for bio crude, but it requires costly renovation procedures to be utilized as biofuel. It is crucial to employ catalysts that may straightforwardly improve the bio crude yield as well as the efficiency of the reaction process; the benefit of raising the operation’s overall production; the impacts of adding heterogeneous catalysts and how they affect the bio-crude yield. In lignocellulosic biomass hydrothermal liquefaction, a typical catalytic activity was discovered, dividing the various catalysts into four separate groups (transition metal, lanthanide oxide, alkaline metal oxide, and zeolite). The purpose study is to objectively evaluate the hydrothermal liquefaction of lignocellulosic biomass and know effecting of adding a zeolite catalyst on it, with a focus on increasing the production and efficiency of the biofuel. In addition, it has drawn attention to the natural stimulatory effects associated with zeolite catalysts.

Hydrothermal liquefaction of lignocellulosic biomass with potassium phosphate and iron and their binary mixture: A comprehensive investigation on the yields and compositions of biocrude and solid residue

Hydrothermal liquefaction of corn, soybean, rice and wheat straws with K3PO4, Fe and Fe + K3PO4 at 320 °C for 30 min was examined. The addition of K3PO4 led to the highest biocrude yields from hydrothermal liquefaction of rice straws (39.20 wt%). Particularly, the biocrude yields from K3PO4-catalyzed hydrothermal liquefaction of corn and rice straws were ∼ 10 wt% higher than those from non-catalytic run (19.4 and 27.8 wt%). Catalytic hydrothermal liquefaction with K3PO4 had minimal impact on the elemental compositions of biocrudes and solid residue. Furthermore, K3PO4 promoted the enrichment of low-boiling components in biocrudes by 2.02 wt%. for hydrothermal liquefaction of wheat straw. Moreover, the incorporation of K3PO4 induces the occurrence of dense porous structure on the surface of solid residue, making it highly suitable as an adsorbent or catalyst carrier. Finally, potential reaction network and mechanisms of catalytic hydrothermal liquefaction of straw have been proposed and discussed detailly.

Synergistic Hydrothermal Conversion of Aqueous Solutions of CO2 and Biomass Waste Liquefaction into Formate.

CO2 utilization by conversion into useful chemicals can contribute to facing the problem of increasing CO2 emissions. Among other alternatives, hydrothermal transformation stands out by the high conversions achieved, just using high-temperature water as the solvent. Previous works have demonstrated that several organic compounds with hydroxyl groups derived from biomass can be used as reductants of NaHCO3 aqueous solutions as inorganic CO2 sources. Formate was obtained as the main product as it was produced by conversion both of the inorganic carbon and of the organic reductants, whose transformation into formate was promoted by the addition of NaHCO3. Based on these results, in this work, the hydrothermal conversion of NaHCO3 is performed together with the liquefaction of lignocellulosic biomass (sugarcane bagasse and pine needles) in a one-pot process. Results show that yields to formate of 10% wt/wt (with respect to the initial concentration of biomass) are achieved by hydrothermal treatment of NaHCO3 and lignocellulosic biomass at 250 °C with a residence time of 180 min. Other products, such as acetic acid and lactic acid, were also obtained. These results demonstrate the feasibility of the hydrothermal reduction of CO2 combined with the hydrothermal liquefaction of residual biomass in a simultaneous process.

Improving the Yield of Fermentable Sugars Through Alkaline Pretreatment and Continuous Flow Hydrothermal Liquefaction of Lignocellulosic Biomass

Improving the Yield of Fermentable Sugars Through Alkaline Pretreatment and Continuous Flow Hydrothermal Liquefaction of Lignocellulosic Biomass

Use of a Lewis acid, a Brønsted acid, and their binary mixtures for the hydrothermal liquefaction of lignocellulose

The main objective of the present study is to investigate the effect of a Lewis acid, Brønsted acid, and their combined use on the hydrothermal liquefaction of lignocellulosic biomass. Hydrothermal liquefaction of teak wood was conducted at 250, 300 and 350 °C for 15, 30 and 60 min. Hydrothermal liquefaction of teak wood was carried out at 300 °C for 30 min (the best optimum conditions) without and with the use of Mg(ClO4)2, HClO4, and HClO4/Mg(ClO4)2 at various loadings (2–10 mmol/15 g wood). The highest bio-oil yield was obtained with the non-catalytic run. All tested catalysts have negative effect on bio-oil yields. The bio-oil yields generally decreased with increasing the catalyst loadings. The deoxygenation degree in bio-oils changed depending on the type of catalyst and loading. A high degree of de-oxygenation took place with Mg(ClO4)2 catalysts. An increased catalyst loading led to decreased aromatic contents of bio-oils catalysed by either Mg(ClO4)2 or HClO4. The use of a catalyst increased total naphtha fractions in bio-oils. The highest heating value of the bio-oil was estimated to be approximately 30 MJ/kg. Gas chromatography–mass spectrometry analysis revealed that the bio-oils from the non-catalytic and catalytic runs contained aldehydes, ketones, phenols, acids, esters and alcohols. The relative yields of the oxygenated compounds were affected by catalyst type.

Liquefaction of lignocellulosic biomass through biochemical conversion pathway: A strategic approach to achieve an industrial titer of bioethanol

Owing to fossil fuel depletion, the conversion of lignocellulosic biomass into bioethanol has gained momentum in the field of transportation sector. In the present study, liquefaction of sorghum stalks has been performed for the production of fermentable sugars and their subsequent conversion into bioethanol. Pretreatment, delignification, enzymatic hydrolysis are three sequential steps involved in the liquefaction process. About 82% of hemicellulose hydrolysis was attained by the pretreatment of sorghum stalks at 121 °C with 0.2 M sulfuric acid for 120 min. Further, the pretreated residue was de-lignified with 1–5% (w/v) sodium hydroxide which resulted in 85–98.7% removal of lignin. Subsequently, around 65–99.6% of cellulose hydrolysis was attained at an optimum enzyme loading of 30 mg protein/g of glucan. The optimum liquefaction condition of sorghum stalks was achieved by performing the pretreatment process at 121 °C with 0.2 M sulfuric acid for 120 min, delignification at 121 °C with 2% NaOH for 20 min and enzymatic hydrolysis at 50 °C with 30 mg protein/g of glucan for 72 h. Furthermore, 18.4 g/L and 74.7 g/L xylulosic and cellulosic ethanol was produced from pretreatment and enzymatic hydrolysis derived hydrolysates, respectively. Finally, 97.7% of sorghum stalks liquefaction was achieved, in which 84% of holocellulose (cellulose and hemicellulose) converted into 494 g of fermentable sugars which is further converted into 225 g or 285 mL ethanol per kg of sorghum stalks (equivalent to 285 L ethanol per ton of biomass).

Polyurethane Foams and Bio-Polyols from Liquefied Cotton Stalk Agricultural Waste

Cotton is planted on a large scale in China, especially in the Xinjiang Region. A large amount of agricultural waste from cotton plants is produced annually, and currently poses a disposal problem. In this study the product after liquefaction of cotton stalk powder was mixed with diphenylmethane diisocyanate to prepare polyurethane foams. The effects of the liquefaction conditions on the properties of the polyols and polyurethane foams produced using cotton stalk were investigated. The optimal processing conditions for the liquefied product, considering the quality of the polyurethane foams, were studied as a function of the residue fraction. Bio-polyols with promising material properties were produced using liquefaction conditions of 150 °C, reaction time of 90 min, catalyst content of 3 wt.%, and 20 w/w% cotton stalk loading. We investigated the optimal processing conditions for producing bio-foam materials with mechanical properties comparable to those of petroleum-based foam materials. This study demonstrated the potential of cotton stalk agricultural waste for use as a feedstock for producing polyols via liquefaction. It was shown that polyethylene glycol 400 (PEG400) and glycerin can be used as alternative solvents for liquefaction of lignocellulosic biomass, such as cotton stalk, to produce bio-polyol and polyurethane foams.

Ball milling promoted direct liquefaction of lignocellulosic biomass in supercritical ethanol

In the present work, ball milling was applied for the pretreatment of lignocellulose to obtain high conversion and bio-oil yield in supercritical ethanol. Ball milling substantially decreased the crystallinity and particle size of lignocellulose, thereby improving its accessibility in ethanol solvent. An increased bio-oil yield of 59.2% was obtained for the ball milled camphor-wood sawdust at 300°C, compared with 39.6% for the original lignocellulose. Decreased crystallinity significantly benefited the conversion of the cellulose component from 60.8% to 91.7%, and decreased particle size was beneficial for the conversion of all components. The obtained bio-oil had a high phenolic content, as analyzed by gas chromatography-mass spectrometry. Methoxylation and retro-aldol condensation were observed during alcoholysis, and the reaction pathways of lignocellulose in supercritical ethanol were attributed to the action of free radicals.

Co-hydrothermal Liquefaction of Lignocellulosic Biomass with Kukersite Oil Shale

The co-hydrothermal liquefaction of black pine wood (BPW) with Kukersite oil shale (KOS) at different blend ratios of BPW/KOS (1:1, 1:2, and 2:1) was conducted at 300 °C for 30 min. No synergistic ...

Directional liquefaction of lignocellulosic biomass for value added monosaccharides and aromatic compounds

Using lignocellulosic biomass as a feedstock for sustainable production of platform molecules is of great significance. We examined the directional liquefaction coupled with efficient stepwise fractionation of bamboo biomass into two groups of chemicals: monosaccharides and aromatic products. When sulfuric acid was used as the catalyst, a conversion of 70% was achieved with a 40% yield of monosaccharides and a 20% yield of aromatics were obtained at 180 °C for 30 min when the catalyst loading was 3.0% per 6.0 g bamboo. The production of 5-hydroxymethylfural (HMF), 5-ethoxymethylfurfural (EMF), ethyl levulinate (EL) and furfural was analyzed in terms of by-products formation. Due to similar physiochemical properties in each fraction, the platform molecules could broaden a new paradigm of bamboo biomass utilization for renewable energy and value-added biochemicals.

Supercritical carbon dioxide fractionation of bio-crude produced by hydrothermal liquefaction of pinewood

The supercritical carbon dioxide extraction of bio-crude, produced by hydrothermal liquefaction of lignocellulosic biomass, was investigated for pressures and temperatures in the range 112–400 bar and 40–120 °C, corresponding to solvent densities in the range 548–882 kg/m3. Total extraction yields ranged from 17 to 42%. For a given solvent density, temperature increase drastically improved both the process operability and efficiency. The extracts showed reduced density as well as 40% reduction of total acid number compared to the feed. The residue resulted to be partially deoxygenated. Ketones, 1-ring phenols and low molecular weight fatty acids were concentrated in the extract, with recoveries up to 80%, with ketones and phenols exhibiting the highest distribution factors. Observed selectivities suggest the feasibility of downstream separation of the key classes of extractives using supercritical carbon dioxide as a solvent.

Renewable diesel via hydrothermal liquefaction of oleaginous yeast and residual lignin from bioconversion of corn stover

Oleaginous yeast can produce high yields of lipids from hydrolyzed lignocellulosic carbohydrates, but the difficulty and cost of extracting the lipids from the bioreactor broth, as well as the lack of profitable options for valorizing feedstock lignin are major barriers to cost-competitive production of renewable diesel from corn stover via bioconversion. Hydrothermal liquefaction of lignocellulosic biomass effectively breaks down and converts lignin into biocrude oil products, but provides relatively low yields of biocrude from feedstock carbohydrates. In the present study, bioconversion and hydrothermal liquefaction were integrated in a new hybrid approach that combines the advantages of both processes to produce a high quality distillate fuel blendstock. Eight bioreactor cultures of the oleaginous yeast Lipomyces starkeyi were grown in pretreated corn stover hydrolysate or simulated hydrolysate media, with dry cell mass yields from sugar of up to 0.43 g/g, and yields of intracellular triglyceride lipids from sugar (measured as fatty acid methyl esters) of up to 0.26 g/g. The lipid-rich cell mass in the bioreactor broth was pooled and mixed with pretreated corn stover lignin to produce a slurry intermediate with a total mass of 23.5 kg. The slurry was fed to a continuous hydrothermal liquefaction reactor at a dry solids loading of 16.3% to produce biocrude oil with a carbon yield of 55% and a mass yield of 40% from the feedstock. The biocrude was then hydrotreated to produce a renewable hydrocarbon fuel blendstock, with the majority of the product boiling in the distillate range. Techno-economic analysis suggested that a biorefinery employing this integrated, hybrid conversion approach could produce approximately twice as much distillate fuel blendstock than contemporary biorefinery designs that rely solely on lipids solvent-extracted from oleaginous yeast for production of distillate blendstocks from corn stover hydrolysate. Sensitivity analysis of the proposed biorefinery design suggested that the cost of production could be reduced to $3/gasoline gallon equivalent or less by addressing identified research gaps, such as optimizing the separation of biocrude to recover additional hydrocarbon from the aqueous phase of the reactor effluent. Our results provide a proof-of-concept for a new hybrid biorefinery design that could enhance domestic production of renewable diesel, jet, and marine fuel from corn stover or other forms of lignocellulosic biomass.

Liquefaction of poplar biomass for value-added platform chemicals

This study shows that two groups of value-added platform chemicals, namely glucosides and phenolic compounds, can be obtained from the liquefaction of lignocellulosic biomass. The liquefaction of biomass was conducted in a methanol medium with H2SO4 as a catalyst at 120–220 °C. The effects of liquefaction temperature on the yield and distribution of the liquefied product and the change in liquefied residue were investigated. The maximum liquefaction rate was 91.13% at 220 °C based on the whole feedstock. The target products were glucosides and phenolic compounds, which were derived from the liquefaction of carbohydrates and lignin part in poplar biomass respectively, and could be effectively separated after liquefaction. The yields of glucosides and phenolic compounds reached 48.83 and 25.96% at 200 °C respectively. The glucosides mainly contained pentose and hexose glucosides with high a purity of 91.67% at 200 °C. The phenolic products were separated into four fractions with different molecular weight distributions. Overall, it achieved the simultaneous transformation of carbohydrates and lignin fractions in biomass into high value-added chemicals.

Liquefaction behaviour of twelve tropical hardwood species in phenol

Liquefaction of ligno-cellulosic biomass is one of the chemical conversion technologies for developing new materials, adhesives and energy systems. The liquefaction process also provides an opportunity to utilize ligno–cellulosic wastes such as saw-dust, woody wastes, branches and twigs, agro-residues, etc. for the development of value added products. This paper presents the liquefaction behaviour of wood meal of twelve tropical hardwood species in phenol as liquefying media to produce chemically active liquid which has potential to be used as a raw material for developing different products. The liquefaction was carried out at 140°C temperatures for 120 minutes at different liquid ratios. In all the cases, a viscous and sticky black liquid was obtained after the stipulated reaction time. The liquefaction efficiency was found to vary with species and liquid ratio. The highest liquefaction efficiency of 93% was achieved in balsa wood at 1:3 (wood: phenol) liquid ratio. The liquefied wood and residues were characterized by FTIR spectroscopy. The liquefied wood was found to be highly acidic in nature. Viscosity of liquefied wood at higher liquid ratio was independent of wood species. Correlation analysis revealed a strong negative relationship between wood basic density and liquefaction efficiency.

Valorization of pyrolysis water: a biorefinery side stream, for 1,2-propanediol production with engineered Corynebacterium glutamicum

BackgroundA future bioeconomy relies on the efficient use of renewable resources for energy and material product supply. In this context, biorefineries have been developed and play a key role in converting lignocellulosic residues. Although a holistic use of the biomass feed is desired, side streams evoke in current biorefinery approaches. To ensure profitability, efficiency, and sustainability of the overall conversion process, a meaningful valorization of these materials is needed. Here, a so far unexploited side stream derived from fast pyrolysis of wheat straw—pyrolysis water—was used for production of 1,2-propanediol in microbial fermentation with engineered Corynebacterium glutamicum.ResultsA protocol for pretreatment of pyrolysis water was established and enabled growth on its major constituents, acetate and acetol, with rates up to 0.36 ± 0.04 h−1. To convert acetol to 1,2-propanediol, the plasmid pJULgldA expressing the glycerol dehydrogenase from Escherichia coli was introduced into C. glutamicum. 1,2-propanediol was formed in a growth-coupled biotransformation and production was further increased by construction of C. glutamicum Δpqo ΔaceE ΔldhA Δmdh pJULgldA. In a two-phase aerobic/microaerobic fed-batch process with pyrolysis water as substrate, this strain produced 18.3 ± 1.2 mM 1,2-propanediol with a yield of 0.96 ± 0.05 mol 1,2-propanediol per mol acetol and showed an overall volumetric productivity of 1.4 ± 0.1 mmol 1,2-propanediol L−1 h−1.ConclusionsThis study implements microbial fermentation into a biorefinery based on pyrolytic liquefaction of lignocellulosic biomass and accesses a novel value chain by valorizing the side stream pyrolysis water for 1,2-PDO production with engineered C. glutamicum. The established bioprocess operated at maximal product yield and accomplished the so far highest overall volumetric productivity for microbial 1,2-PDO production with an engineered producer strain. Besides, the results highlight the potential of microbial conversion of this biorefinery side stream to other valuable products.

Hydro-liquefaction of rice stalk in supercritical ethanol with in situ generated hydrogen

Bio-crude oil derived from sub- and supercritical liquefaction of lignocellulosic biomass has received considerable interests, but it cannot be directly used as a fuel because of its high oxygen content. In this work, a novel hydro-liquefaction process with the hydrogen generated in situ during the oxidation of aluminum by supercritical ethanol was investigated. X-ray diffraction analyses showed that η-, κ-, θ-, and α-Al2O3 mixtures were formed as a result of aluminum oxidation. Proposed reaction pathways revealed that ethanol reforming reactions occurred with additional hydrogen produced. A maximum energy recovery around 75% from feedstock to bio-crude oil was achieved with the addition of aluminum. Investigation on the chemical composition showed that liquefaction of rice stalk in the presence of aluminum decreased the yield of aldehyde, acid, and nitrogenous groups, and increased the yield of bicyclic phenolics, ketones, and hydrocarbons in the oil. In addition, the volatile fraction of the oil was increased. Overall, aluminum assisted liquefaction significant increase in the degree of deoxygenation, and may be a promising way to convert lignocellulosic into biofuels.