Liquefaction Solvent Research Articles

Recent Advances of Solvent Effects in Biomass Liquefaction Conversion

Liquefaction conversion technology has become one of the hottest biomass conversion methods due to its flexible material selection and extensive product applications. Exploring biomass liquefaction conversion focuses on catalysts, biomass/water ratio, and reaction temperature. However, it is found that solvents are crucial in the biomass liquefaction process and significantly impact the type of liquefied products and bio-oil yield. Given the current rapid development trend, timely sorting and summary of the solvent effect in the biomass liquefaction process can promote the subsequent development and industrialization of more efficient and cleaner biomass liquefaction technology. Therefore, this review first introduces the characteristics of water as the liquefaction solvent, then summarizes the effects of organic solvents on liquefaction, and finally elaborates on the synergistic effect of co-solvents, which provides a more systematic overview of solvent effects in the liquefaction process. Meanwhile, prospects are put forward for the future development of biomass liquefaction conversion.

Hydrothermal liquefaction of composite household waste to biocrude: the effect of liquefaction solvents on product yield and quality.

The hydrothermal liquefaction (HTL) of composite household waste (CHW) was investigated at different temperatures in the range of 240-360 °C, residence times in the range of 30-90 min, and co-solvent ratios of 2-8 ml/g, by utilising ethanol, glycerol, and produced aqueous phase as liquefaction solvents. Maximum biocrude yield of 46.19% was obtained at 340 °C and 75 min, with aqueous phase recirculation ratio (RR) of 5 ml/g. The chemical solvents such as glycerol and ethanol yielded a biocrude percentage of 45.18% and 42.16% at a ratio of 6 ml/g and 8 ml/g, respectively, for 340 °C and 75 min. The usage of co-solvents as hydrothermal medium increased the biocrude yield by 35.30% and decreased the formation of solid residue and gaseous products by 19.82% and 18.74% respectively. Also, the solid residue and biocrude obtained from co-solvent HTL possessed higher carbon and hydrogen content, thus having a H/C ratio and HHV that is 1.01 and 1.23 times higher than that of water as hydrothermal medium. Among the co-solvents, HTL with aqueous phase recirculation resulted in higher carbon and energy recovery percentages of 9.36% and 9.78% for solid residue and 52.09% and 56.75% for biocrude respectively. Further qualitatively, co-solvent HTL in the presence of obtained aqueous phase yielded 33.43% higher fraction of hydrocarbons than the pure water HTL and 7.70-17.01% higher hydrocarbons when compared with ethanol and glycerol HTL respectively. Nitrogen containing compounds, such as phenols and furfurals, for biocrudes obtained from all HTL processes, were found to be present in the range of 8.30-14.40%.

Theoretical analysis of hydrogen solubility in direct coal liquefaction solvents

The cyclic hydrogenation technology in a direct coal liquefaction process relies on the dissolved hydrogen of the solvent or oil participating in the hydrogenation reaction. Thus, a theoretical basis for process optimization and reactor design can be established by analyzing the solubility of hydrogen in liquefaction solvents. Experimental studies of hydrogen solubility in liquefaction solvents are challenging due to harsh reaction conditions and complex solvent compositions. In this study, the composition and content of liquefied solvents were analyzed. As model compounds, hexadecane, toluene, naphthalene, tetrahydronaphthalene, and phenanthrene were chosen to represent the liquefied solvents in chain alkanes and monocyclic, bicyclic, and tricyclic aromatic hydrocarbons. The solubility of hydrogen X (mol/mol) in pure solvent components and mixed solvents (alkanes and aromatics mixed in proportion to the chain alkanes + bicyclic aromatic hydrocarbons, bicyclic saturated aromatic hydrocarbons + bicyclic aromatic hydrocarbons, and bicyclic aromatic hydrocarbons + compounds containing heteroatoms composed of mixed components) are determined using Aspen simulation at temperature and pressure conditions of 373–523 K and 2–10 MPa. The results demonstrated that at high temperatures and pressures, the solubility of hydrogen in the solvent increases with the increase in temperature and pressure, with the pressure having a greater impact. Furthermore, the results revealed that hydrogen is more soluble in straight-chain alkanes than in other solvents, and the solubility of eicosanoids reaches a maximum of 0.296. The hydrogen solubility in aromatic ring compounds decreased gradually with an increase in the aromatic ring number. The influence of chain alkanes on the solubility of hydrogen predominates in a mixture of solvents with different mixing ratios of chain alkanes and aromatic hydrocarbons. The solubility of hydrogen in mixed aromatic solvents is less than that in the corresponding single solvents. Hydrogen is less soluble in solvent compounds containing heteroatoms than in compounds without heteroatoms.

Hydrogen-donating behavior and hydrogen-shuttling mechanism of liquefaction solvents under Fe- and Ni-based catalysts

The H-donating solvent plays a crucial role in both oil yield and products distribution during direct coal liquefaction. Meanwhile, liquefaction catalyst significantly influences the H-donating behavior of the solvent and the pathways of hydrogen transfer. In view of insufficient understanding on the impact of catalysts on H-donating behavior of solvent and hydrogen transfer pathways in direct liquefaction, in this study, non-H-donating solvents including naphthalene, 1-methylnaphthalene and pyrene (Py) and H-donating solvents including tetralin (THN) and 9,10-dihydroanthracene (DHA) were chosen as the solvents. The Shenhua nano-sized Fe-based and the prepared Ni/Al2O3 catalysts were used to investigate their effect on H-donating behavior of the solvent and H-shuttling mechanism. Results show that liquefaction solvent obviously affects coal conversion and products distribution no matter Fe-based or Ni-based catalyst was used. When non-H-donating solvent is used as liquefaction solvent, coal conversion is lower than that with THN or DHA as solvent. The addition of Py to THN as solvent improves the utilization of effective hydrogen in non-catalytic liquefaction, which is ascribed to hydrogen transfer effect of Py; however, hydrogen transfer mainly occurs through direct combination of gaseous H2 with radicals generated from coal pyrolysis in presence of Fe-based catalyst, with minimal shuttle action of solvent hydrogen. On the contrary, the Ni-based catalyst aids in enhancing the hydrogen shuttle effect of the solvent, and the hydrogen transfer path primarily involves H2 to solvent and then to coal, which is ascribed to good hydrogenation ability of Ni-based catalyst. Under the action of Fe-based catalyst, DHA as liquefaction solvent exhibits lower H-donating capability compared to THN, and approximately 65% of total hydrogen consumption is effectively utilized for coal liquefaction, along with about 35% of total hydrogen consumption for the hydrogenation, ring opening, and side-chain scission reactions of DHA. However, about 96% of total hydrogen consumption is effectively utilized for coal liquefaction when THN used as solvent, indicating that THN as liquefication solvent is more conducive to the transfer of gaseous hydrogen to free radical fragments from coal pyrolysis compared to DHA.

Production of sugars from lignocellulosic biomass via biochemical and thermochemical routes

Sugars are precursors to the majority of the world’s biofuels. Most of these come from sugar and starch crops, such as sugarcane and corn grain. Lignocellulosic sugars, although more challenging to extract from biomass, represent a large, untapped, opportunity. In response to the increasing attention to renewable energy, fuels, and chemicals, we review and compare two strategies for extracting sugars from lignocellulosic biomass: biochemical and thermochemical processing. Biochemical processing based on enzymatic hydrolysis has high sugar yield but is relatively slow. Thermochemical processing, which includes fast pyrolysis and solvent liquefaction, offers increased throughput and operability at the expense of low sugar yields.

Optimization of liquefaction process based on global meta-analysis and machine learning approach: Effect of process conditions and raw material selection on remaining ratio and bioavailability of heavy metals in biochar

<abstract> <p>Although liquefaction technology has been extensively applied, plenty of biomass remains tainted with heavy metals (HMs). A meta-analysis of literature published from 2010 to 2023 was conducted to investigate the effects of liquefaction conditions and biomass characteristics on the remaining ratio and chemical speciation of HMs in biochar, aiming to achieve harmless treatment of biomass contaminated with HMs. The results showed that a liquefaction time of 1–3 h led to the largest HMs remaining ratio in biochar, with the mean ranging from 84.09% to 92.76%, compared with liquefaction times of less than 1 h and more than 3 h. Organic and acidic solvents liquefied biochar exhibited the greatest and lowest HMs remaining ratio. The effect of liquefaction temperature on HMs remaining ratio was not significant. The C, H, O, volatile matter, and fixed carbon contents of biomass were negatively correlated with the HMs remaining ratio, and N, S, and ash were positively correlated. In addition, liquefaction significantly transformed the HMs in biochar from bioavailable fractions (F1 and F2) to stable fractions (F3) (<italic>P</italic> < 0.05) when the temperature was increased to 280–330 ℃, with a liquefaction time of 1–3 h, and organic solvent as the liquefaction solvent. N and ash in biomass were positively correlated with the residue state (F4) of HMs in biochar and negatively correlated with F1 or F2, while H, O, fixed carbon, and volatile matter were negatively correlated with F4 but positively correlated with F3. Machine learning results showed that the contribution of biomass characteristics to HMs remaining ratio was higher than that of liquefaction factor. The most prominent contribution to the chemical speciation changes of HMs was the characteristics of HMs themselves, followed by ash content in biomass, liquefaction time, and C content. The findings of this meta-analysis contribute to factor selection, modification, and application of liquefied biomass to reducing risks.</p> </abstract>

Bio-Oil-Based Epoxy Resins from Thermochemical Processing of Sustainable Resources: A Short Review

Epoxy is the most prevalent thermosetting resin in the field of polymer composite materials. There has been a growing interest in the development of bio-based epoxy resins as a sustainable alternative to conventional petrochemical epoxy resins. Advances in this field in recent years have included the use of various renewable resources, such as vegetable oils, lignin, and sugars, as direct precursors to produce bio-based epoxy resins. In the meantime, bio-oils have been produced via the decomposition of biomass through thermochemical conversion and mainly being used as renewable liquid fuels. It is noteworthy that bio-oils can be used as a sustainable resource to produce epoxy resins. This review addresses research progress in producing bio-oil-based epoxy resins from thermochemical processing techniques including organic solvent liquefaction, fast pyrolysis, and hydrothermal liquefaction. The production of bio-oil from thermochemical processing and its use to inject sustainability into epoxy resins are discussed. Herein, we intend to provide an overall picture of current attempts in the research area of bio-oil-based epoxy resins, reveal their potential for sustainable epoxy resins, and stimulate research interests in green/renewable materials.

Solubility study of hydrogen in direct coal liquefaction solvent based on quantitative structure–property relationships model

Direct coal liquefaction (DCL) is an important and effective method of converting coal into high-value-added chemicals and fuel oil. In DCL, heating the direct coal liquefaction solvent (DCLS) from low to high temperature and pre-hydrogenation of the DCLS are critical steps. Therefore, studying the dissolution of hydrogen in DCLS under liquefaction conditions gains importance. However, it is difficult to precisely determine hydrogen solubility only by experiments, especially under the actual DCL conditions. To address this issue, we developed a prediction model of hydrogen solubility in a single solvent based on the machine-learning quantitative structure–property relationship (ML-QSPR) methods. The results showed that the squared correlation coefficient R2 = 0.92 and root mean square error RMSE = 0.095, indicating the model’s good statistical performance. The external validation of the model also reveals excellent accuracy and predictive ability. Molecular polarization (α) is the main factor affecting the dissolution of hydrogen in DCLS. The hydrogen solubility in acyclic alkanes increases with increasing carbon number. Whereas in polycyclic aromatics, it decreases with increasing ring number, and in hydrogenated aromatics, it increases with hydrogenation degree. This work provides a new reference for the selection and proportioning of DCLS, i.e., a solvent with higher hydrogen solubility can be added to provide active hydrogen for the reaction and thus reduce the hydrogen pressure. Besides, it brings important insight into the theoretical significance and practical value of the DCL.

Bio‐polyols synthesized by liquefaction of cellulose: Influence of liquefaction solvent molecular weight

AbstractCurrently, the plastics industry including polyurethanes is based on the use of petrochemicals. For this reason, scientists are looking for new types of renewable resources for the substitution of petrochemical substances. This work aims to evaluate the effect of polyethylene glycols (PEG) with different molecular mass impact on properties of bio‐based polyols synthesized via biomass liquefaction of cellulose. To date, research has mostly focused on the use of different biomass sources, but the area of bio‐polyols synthesis with PEG with various molecular weights has not been explored in depth. For this reason, polyols were synthesized using PEG with a molecular weight in the range of 200–600 g/mol. Depending on the type of liquefaction solvent, the bio‐polyols showed a hydroxyl value of 519–652 mgKOH/g, a viscosity of 0.736–1.415 Pa∙s, and a water content below 1%. Observed difference may be related to change of reactivity of the PEG chains caused by steric hindrance of longer chains and the difference in the amount of reactive OH groups. These findings add substantially to understanding of the influence of liquefaction solvent molecular mass on the properties of new bio‐polyols and those of polyurethane materials.

Thermochemical liquefaction of Brassica napus straw: Effect of liquefaction parameters on biocrude

Rape straw ( Brassica napus ) was used to prepare high-quality biocrude (ORS) through thermochemical liquefaction . The effects of liquefaction temperature, solid-liquid ratio (R 1 ), and solvent filling ratio (R 2 ) on the yield of ORS prepared from rape straw were studied. The yield of ORS reached the maximum value (22.11 %) at 340 °C, with R 1 10 % and R 2 20 %. GC-MS analysis indicated that at low liquefaction temperatures (≤300 °C) the compounds in ORS were mainly esters, whereas at higher temperatures they were mainly phenolic compounds . Analysis based on the boiling points indicated the presence of mainly C 8 , C 9 , and C 20 compounds. Elemental analysis and measurement of the higher heating value (HHV) showed that the HHV of ORS at 340 °C was 41.36 MJ/kg. The process described in this work not only effectively disposes of rape straw, but also converts it into a potential renewable transportation energy alternative. • Biocrude was prepared by liquefaction of rape straw. • The yield of biocrude reached the maximum value (22.11 %) at 340 °C (R 1 :10 %, R 2 :20 %). • The main compounds of biocrude produced at lower temperature (≤300 °C) were esters. • The carbon number of biocrude compounds mainly distributed in C 8 , C 9 and C 20 . • The higher heating value of biocrude at 340 °C reached 41.36 MJ/kg.

Regulation of radicals by hydrogen-donor solvent in direct coal liquefaction

Regulation of radicals by hydrogen-donor solvent in direct coal liquefaction

Novel insights into the catalytic effect of hydrogen bonds on aldehyde groups generation during direct coal liquefaction

Direct coal liquefaction (DCL) is considered to be the effective method for production of aviation fuel and valuable chemicals, while low rank coal is appropriate feedstock because of high thermal reactivity. Original hydrogen bonds could promote low-temperature crosslinking reactions. liquefaction solvents could partially break original hydrogen bonds by forming new species. Impacts of hydrogen bonds formed by solvents on DCL reactions have rarely been studied. In order to figure out role of hydrogen bonds in DCL, a conjoint study of DCL experiments and density functional theory (DFT) calculations was carried out. More carboxyl groups were promoted to decompose. Meanwhile more aldehyde groups were found in solid products with increase of liquefaction temperature. As aldehyde groups are generated, hydrogen consumption increases. In terms of mechanism, effect of stronger hydrogen bonds on cleavage of covalent bonds were investigated by DFT-based potential energy surface scan. It turns out that cleavage of CO bonds in carboxyl groups could be enhanced, so that stabilization of free radicals results in consumption of extra hydrogen, which is provided by tetralin. Results of experimental methods are consistent with DFT calculations. The catalytic mechanism of hydrogen bonds upon conversion of carboxyl groups during DCL is proposed. Hydrogen bonds between coal and liquefaction solvents promote decomposition of carboxyl groups and consequently improve hydrogen transfer and thermal reactivity of solid products. Consequently, hydrogen bonds modulation should be taken into account during preparation of DCL solvents, for suppression of crosslinking reactions.

A comparison of the solvent liquefaction of lignin in ethanol and 1,4-butanediol

This study compares the depolymerization of soda lignin via solvent liquefaction in ethanol and 1,4-butanediol (BD). The commercial soda lignin was fractionated based on solubility in ethyl acetate and methanol providing three fractions (F1 – soluble in ethyl acetate and methanol, F2 - insoluble in ethyl acetate and soluble methanol, F3 – insoluble in either) which varied mostly based on their molecular weight ranges with the average molecular weight following the order F1 <F2 <F3. The whole lignin and its factions were subjected to solvent liquefaction in ethanol and BD at 300 °C, to test the use of a high boiling solvent (BD) to reduce the required reaction pressure. Use of neat BD resulted in a bio-oil similar to that produced via pyrolysis of lignin, and which had a higher average molecular weight and fewer remaining methoxy groups than those produced in ethanol. This may be attributable to differences in lignin solubility in the two solvents. The addition of formic acid was also examined in each solvent. Use of formic acid in combination with BD promoted crosslinking resulting in bio-oil with higher molecular weight. The use of lignin bio-oils from each solvent were compared as feedstocks for the production of bio-pitch, finding that those produced in BD provided a coking value closer to that required for many applications.

Hydrothermal liquefaction of sugarcane bagasse to bio-oils: Effect of liquefaction solvents on bio-oil stability

Bio-oil produced from the hydrothermal liquefaction (HTL) of biomass is unstable and cannot be transported over long distances to a refinery for upgrading to transportation fuel. This study examined the effect of the liquefaction solvent on the stability of bio-oils derived from the HTL of sugarcane bagasse. The accelerated aging test (0–8 days at 80 °C) was used to assess the stability of these oils with the aid of indicators such as water content, molecular weight range, functional groups present, phase separation, thermal stability, and the amount of residue after thermal analysis of the oils. The HTL solvent mixture of ethanol/water was found to produce the most stable bio-oil when compared to crude glycerol/water or water on its own. The light oils fractionated by solvent extraction were more stable than their corresponding bio-oils. The higher heating values (HHVs) of the light oils during the agiging process were relatively stable and were between 33 and 35 MJ/kg. The maximum boiling temperature of the first peak in the DTG thermogram of the aged light oil derived from ethanol/water is 147 °C (cf. diesel of 157 °C), while that of crude glycerol/water light oil is up to 190 °C. The stabilities of the oils derived from either ethanol or crude glycerol are related to alkylation, esterification, and acetalization reactions. This study has demonstrated that the HTL of sugarcane bagasse in the presence of ethanol/water produces oils of good quality that have long shelf-lives and have been projected to be stored for up to 8 years with minor compositional and structural changes.

Polyvinyl alcohol based bio‐composite films reinforced by liquefaction products and cellulose nanofibrils from coconut coir

AbstractIn this study, coconut coir was chemically converted to coir‐polyols (CP) via atmospheric liquefaction under microwave assistance, during which a combination of polyethylene glycol 400 and glycerol, and 98% sulfuric acid were applied as the liquefaction solvents and catalyst, respectively. The obtained CP was then analyzed in terms of its molecular weight distribution, hydroxyl values, and functional groups. Later, CP/polyvinyl alcohol (PVA) bio‐composite films reinforced without and with coir cellulose nanofibrils (CCNF) were prepared. After comprehensive characterization, the CP/PVA films exhibited higher stability in medium‐temperature range, while the CCNF/CP/PVA films on the other hand possessed higher properties of tensile strength, elongation at break, and water resistance. The proper dosage of reinforcing agents for preparing PVA‐based ternary blend films were proposed at 3% of CCNF and 10% of CP (based on film dry weight), which exhibited the best balance of properties in the critical parameters such as tensile strength and elongation at break.

Techno-economic assessment of HTL integration to the Brazilian sugarcane industry: An evaluation of different scenarios

Hydrothermal liquefaction (HTL) has been identified as one of the most promising thermochemical technologies to produce liquid biofuels. Although the production cost of HTL biofuels has not yet reached a competitive price, Brazil is recognized worldwide by its mature and well-developed biomass chain, along with a very market-competitive sugarcane industry, which could be used to deploy HTL technologies in a large-scale. The present study carried out a techno-economic analysis to understand the economic performance of HTL in the Brazilian context and considered sugarcane bagasse as the feedstock in two main configurations: a HTL stand-alone facility and a HTL plant integrated with the Brazilian sugarcane industry. The integration of the HTL with a sugarcane ethanol distillery has significantly increased the internal rate of return (IRR) compared with the stand-alone, moving from 8.1%–12.6% per year, thus indicating that HTL have the potential of being economically feasible if integrated to a sugarcane mill. Moreover, the minimum fuel selling prices of biofuels (MFSP) produced in the best integrated scenario showed a very high market-competitiveness, estimated as 0.44, 0.48, 0.51 and 0.37 US$/L for gasoline, diesel, jet fuel, and marine fuel, which were slightly lower than fossil counterparts. This study has also demonstrated that the selection of liquefaction solvents is a highly sensitive parameter to the economic feasibility of HTL; water has showed the highest economic feasibility, suggesting that the utilization of ethanol as solvent may not be feasible at industrial scale.

Strength analysis of noncovalent interactions between lignite and direct liquefaction solvents: A joint study of DFT calculations and swelling ratio determination

Noncovalent interactions have achieved extensive attentions in thermal conversion of low rank coal, but have been little studied in direct coal liquefaction (DCL). In order to investigate strength of noncovalent interactions (hydrogen bonds and π–π stacking) between lignite and DCL solvents, experimental methods and DFT (density function theory) calculations were utilized. Aromatic components in industrial recycled solvents have been selected, including tetralin, 1,2–dihydronaphthalene (DHN), indane, 1–methylnaphthalene, naphthalene, indene and benzene. On one hand, total strength of noncovalent interactions between those aromatic components and lignite were integrally evaluated by swelling ratio determination. On the other hand, Spatial distribution and strength of noncovalent interactions were investigated by RDG (reduced density gradient) analysis, CVB (core–valence bifurcation) index and LOLIPOP (localized orbital locator integrated pi over plane) index, respectively. Overall, addition of DHN, indane and benzene resulted in significant swelling of lignite. Swelling of lignite in benzene and others (DHN and indane) was enhanced by stronger OH–π hydrogen bonds and π–π stacking, respectively. By conjoint study of swelling ratio and DFT calculations, both hydrogen bonds and π–π stacking play crucial roles in swelling of lignite. Adjustment of noncovalent interactions should be taken into account during design of DCL solvents, based on correlations between noncovalent interactions and structural characteristics of aromatic components.

Microwave-assisted lignin liquefaction in hydrazine and ethylene glycol: Reaction pathways via response surface methodology

Microwave assisted liquefaction (MAL) of alkali lignin in ethylene glycol (EG) in the presence of hydrazine was carried out using response surface methodology. Dielectric properties of mixtures of lignin/EG at different hydrazine concentrations were determined to enhance the understanding of the MAL process. MAL parameters were hydrazine concentration (1–3%), temperature (100-180 °C), time (5-45 min) with the maximum microwave heating power limited to 750 W. Lignin/EG ratio was fixed at 1 g:10 ml. Dielectric properties were significantly influenced by hydrazine concentration and temperature. Major products from the liquefaction process (as % of peak areas) were grouped into guaiacol and derivatives (17–42%), Nitrogen compounds (0–27%), and Hydroxylated products (8–22%), and their yields were modelled with polynomial equations. Product yields were significantly influenced by process parameters. Optimum parameters for maximizing yields of guaiacol and nitrogen containing compounds were 0.5%, 180 °C, 25 min and 2.5%, 130, 25 min for hydrazine concentration, temperature, and time, respectively. Low hydrazine concentration increases guaiacol yield at higher temperatures, indicating that at high temperatures hydrazine behaves as a hydrogen donor for lignin liquefaction. The yield of nitrogen containing compounds increases at relatively low temperatures and high concentration of hydrazine. Apart from playing the respective roles of liquefaction solvent and hydrogen donor, EG and hydrazine also take part in the reaction thereby significantly modifying the composition of reaction products. A mechanistic reaction mechanism was proposed to explain the formation of the liquefaction products.

A novel semi-batch autoclave reactor to overcome thermal dwell time in solvent liquefaction experiments

The thermal profile of solvent liquefaction experiments must be well-controlled to generate data suitable for process scaling and technoeconomic analysis. Acknowledging the differences in small-scale batch systems compared to continuous commercial processes is important. In particular, many experiments have long heating and cooling periods, which influence rates of reaction in ways that would not occur in commercial continuous reactors. To overcome this problem, a novel semi-batch autoclave (SBA) system was built to rapidly heat reactants and cool products while maintaining constant pressure during solvent liquefaction experiments. In this study, the performance of the SBA reactor was compared to an isobaric conventional batch autoclave (ICBA) reactor in the solvent liquefaction of lignin in n-butanol. Heat transfer affected both the apparent reaction rate and measured product yields. Solvent liquefaction limited by slow heating gave the misperception that reaction rates were faster than was actually the case and promoted the formation of char-like solids. Experiments constrained by slow heat transfer are of limited use in process modeling and reactor design, which would otherwise result in undersized reactors for desired processing rates. The SBA system facilitates the design and scale-up of commercial SL plants as it approximates the thermal profile of a continuous system.

Catalytic hydrothermal liquefaction of lignin over carbon nanotube supported metal catalysts for production of monomeric phenols

The catalytic hydrothermal liquefaction (HTL) of lignin was studied at different temperature (260, 280 and 300 °C) with different metal supported (Co, Ni and Fe) on carbon nanotube (CNT) in the presence of different solvents including water, ethanol and methanol for 30 min Reaction time. In comparison with water solvent liquefaction, the bio-oil yield significantly increased under alcoholic solvent (ethanol and methanol). As the reaction temperature increased from 260 to 300 °C, there was an increase in the conversion (70.9–86.9 wt%) of lignin. The highest bio-oil yield (66.2 wt%) was found with 10.wt.% Co/CNT catalyst using an ethanol solvent system at 280 °C. Moreover lower temperature showed lower yield of bio-oil. Catalyst acidity and surface area were seen to affects the alkali lignin depolymerization. Co/CNT and Ni/CNT catalysts are mainly responsible for the depolymerization of lignin into higher monomer phenolic compounds. A higher area percentage of vanillin obtained during catalytic liquefaction reaction as the presence of a catalyst, and alcoholic solvent accelerated the β-O-4 bond cleavages. Also elemental and GPC analysis showed that during the liquefaction reaction promotes the hydrogenation/hydrodeoxygenation and produced lower molecular weight bio-oils.