Liquefaction Catalysts Research Articles

Multiphysics Studies of 3D Plate Fin Heat Exchanger Filled with Ortho-Para-Hydrogen Conversion Catalyst for Hydrogen Liquefaction

Multiphysics Studies of 3D Plate Fin Heat Exchanger Filled with Ortho-Para-Hydrogen Conversion Catalyst for Hydrogen Liquefaction

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.

Role of oxophilic metal ions (Mo, Zr, Ti) impregnated Ni/γ-Al2O3 catalysts for hydrothermal liquefaction of kraft lignin

In this study, the effect of oxophilic metal ions (Mo, Zr, and Ti) loaded Ni/γ-Al2O3 (Al) catalysts was explored for the first time for the hydrothermal liquefaction of kraft lignin using IPA for 30 min/280 °C. The liquefaction of lignin was noticed to be 65.4 wt% with 10 wt% loaded Ni/Al with an 81.3% total conversion. The performance of Ni/Al was enhanced remarkably by using the oxophilic metal ions as promoters owing to an increase in the Lewis character of the catalyst's surface. The bio-oil yield was a maximum of 72 wt% with a 91.5% conversion using 3 wt% loaded Ti–10Ni/Al. The different alcoholic solvents such as methanol, ethanol, and IPA were also examined for the same. However, the best liquefaction was noticed with IPA owing to better H-donor tendency. Additionally, a series of IPA-water co-solvent examinations attributed to a significant improvement in the liquefaction to 74.8 wt% (50:50) IPA-water system. The optimum catalyst 10Ni–3Ti/Al was tested for four catalytic cycles, which indicated a slight loss in the catalytic activity because of blockage of the catalytic active site by char deposition. The GC-MS investigation of optimum catalytic bio-oil showed the highest selectivity of acetosyringone (68.5%) and 2-methoxy-phenol (22.8%), which was observed to be only 30.1 and 5.1% for non-catalytic bio-oil. The 1H NMR and FT-IR investigation of raw lignin and bio-oil proved the breakage of lignin's 3D structure into respective G-and S-type monomeric compounds. Additionally, catalysts were characterized using the XRD, BET, and XPS analysis.

Unraveling the effects of sodium carbonate on hydrothermal liquefaction through individual biomass model component and machine learning-enabled prediction

Despite sodium carbonate (Na2CO3) being commonly utilized as a catalyst in actual biomass hydrothermal liquefaction (HTL), its impact on individual biomass components hasn't been well-examined. This study thus delves into the role of Na2CO3 in HTL of biomass model components (carbohydrate, lignin, protein, and lipid) at varying conditions. Na2CO3 at 5 wt% amplified carbohydrate degradation into biocrude and aqueous-gaseous products (AG), resonating with previous work on carbohydrate-rich feedstocks. While Na2CO3 has a marginal effect on lignin HTL, it negatively influences lipid HTL. Here, 5 wt% and 13.5 wt% Na2CO3 decrease the biocrude yield from 95.6% to less than 10%, simultaneously increasing the AG yield to approximately 90%. This is presumably due to the interaction of lipid decomposition intermediates (fatty acids) with sodium cations, resulting in water-soluble soap. For protein HTL, a low Na2CO3 concentration (5 wt%) has no significant impact on product formation, but excessive Na2CO3 (27 wt%) converts a considerable portion of biocrude into AG. In addition to these explorations that provided insights for actual biomass HTL, we also developed a machine learning model to adequately predict HTL biocrude yield by taking Na2CO3 effect into consideration. The Adaboost machine learning model displayed the most satisfactory prediction performance (training and testing R2: 0.96, 0.8) among the three investigated machine learning models. The feature importance analysis reveals lipid content and Na2CO3 concentration as pivotal factors over HTL process conditions and other biochemical components. This research provides fundamental insights into the Na2CO3 role in HTL product formation pathway and offers an intelligent and precise prediction model for HTL biocrude yield, thereby advancing the development of more efficient and sustainable bioenergy production processes.

Hydrothermal liquefaction of pinecone kraft lignin into selective phenolic: Optimization of Ni and Mo impregnation on ceria

Pine is an abundant forestry waste and is a main cause of forest fires in China's mountain area owing to its flammable nature. Therefore, its utilization for the production of valuable phenolics can contribute a small to fix it. This study examined Ni-impregnated ZrO2, CeO2, and MgO catalysts for hydrothermal liquefaction of pinecone lignin, which was extracted by applying the kraft process. The 5 wt%-Ni/CeO2 catalyst was found to be efficient with a 59.2 wt% bio-oil yield corresponding to 77.6% of total conversion in ethanol. This bio-oil yield was enhanced significantly to 65.7 wt% on applying the 3 wt% Mo along with 5Ni/CeO2. The effect of diverse solvents e.g., water, ethanol, methanol, IPA, and co-solvent mixture was also explored to achieve the greatest liquefaction of this PC kraft lignin. Amongst all, methanol/water (1:1) was highly compatible with the maximum liquefaction of kraft lignin (77.8%) at optimum 280 °C/30 reaction conditions. The GCMS analysis of optimum bio-oil attributes the higher selectivity of vanillin (67.4%) and validates the presence of guaiacyl sub-aromatic units in the lignin. The elemental analysis of cat-M-W bio-oil exhibits a considerable improvement in calorific value (38.4 MJ/kg) compared to that of raw lignin (28.1 MJ/kg). Additionally, the reusability test of the 5Ni–3Mo/CeO2 catalyst attributes the best performance of the catalyst up to two cycles without applying any kind of regeneration. Additionally, XRD and BET analysis of catalysts showed the impregnation of both metals (Ni & Mo) at the CeO2 surface in the oxide form.

Comparison of the Efficiency of Hetero- and Homogeneous Catalysts in Cellulose Liquefaction.

Biomass liquefaction is a well-known and extensively described process. Hydrothermal processes are well understood and can be used in the fuel industry. The use of organic solvents can result in full-fledged products for use in the synthesis of polyurethanes. The plastics industry, including polyurethanes, is targeting new, more environmentally friendly solutions. One of these is the replacement of petrochemical polyols with compounds obtained from renewable sources. It is common in biomass liquefaction to use sulfuric acid (VI) as a catalyst. The purpose of the present study was to test the effectiveness of a heterogeneous catalyst such as Nafion ion-exchange resin on the cellulose liquefaction process. The results obtained were compared with the bio-polyols obtained in a conventional way, using a homogeneous catalyst (sulfuric acid (VI)). Depending on the catalyst used and the temperature of the process, bio-polyols characterized, among other things, by a hydroxyl number in the range of 740-400 mgKOH/g were obtained. The research provides new information on the possibility of using heterogeneous catalysts in cellulose liquefaction.

Reactivity and Stability of Natural Clay Minerals with Various Phyllosilicate Structures as Catalysts for Hydrothermal Liquefaction of Wet Biomass Waste

Reactivity and Stability of Natural Clay Minerals with Various Phyllosilicate Structures as Catalysts for Hydrothermal Liquefaction of Wet Biomass Waste

Effect of Hybridization of Inorganic/Organic Acid as the Liquefaction Catalyst on the Properties of Liquefied Kenaf Polyols

Effect of Hybridization of Inorganic/Organic Acid as the Liquefaction Catalyst on the Properties of Liquefied Kenaf Polyols

Adsorption and transfer behaviors of hydrogen on Fe1-xS catalysts for direct coal liquefaction

Direct coal liquefaction (DCL) is an important and effective method to convert coal into chemicals and fuel oil. Pyrite catalysts play an important role in improving the hydrogenation and liquefaction efficiency of coal. There have been many studies on its active component Fe1-xS in promoting pyrolysis of coal and producing active hydrogen, but studies about the hydrogen migration on Fe1-xS catalyst and the interaction between hydrogen and Fe1-xS catalyst were rarely reported. It is significant to study the hydrogen transfer behaviors on Fe1-xS in DCL and understand the influence of Fe1-xS on the hydrogen migration process. In this study, the chemical adsorption and desorption of hydrogen on Fe1-xS were firstly proved experimentally. After pre-sulfidation of Fe1-xS, the maximum amount of H chemically adsorbed in Fe1-xS is 8.20 mmol/g at 360 °C and 1.5 h. The dehydrogenation of Fe1-xS in an anthracene (ANT) system and re-hydrogenation of that in the hydrogen supply systems, such as H2 and 1,2,3,4-tetrahydronaphthalene (THN), were explored at different experiment conditions, which gave some quantitative results of hydrogen transfer. Particularly, the dehydrogenation of Fe1-xS in the ANT system was analyzed in thermodynamics. The enthalpy of dehydrogenation of Fe1-xS in the ANT system is 117.6 kJ mol−1. The results break the traditional view about Fe1-xS only as a medium for active hydrogen transfer and provides a new perspective for further understanding the hydrogen transfer process.

Numerical model improvement of a plate-fin heat exchanger filled with catalyst for hydrogen liquefaction

The continuous ortho-para hydrogen conversion technology represented by the plate-fin heat exchanger filled with catalyst (PFHEFC) is one of the key technologies for the breakthrough of large-scale hydrogen liquefaction system. An appropriate numerical model of the PFHEFC can provide reference and guidance for its design. The thermal-hydraulic behaviors of the catalyst filled layer (CFL) are essential for the model development of the PFHEFC. In this paper, the thermal-hydraulic correlations of the high-pressure and low-temperature hydrogen in the CFL are investigated by the numerical simulation and then used to improve the existing numerical models of the PFHEFC. The results show that the simulation results of the face centered cubic (FCC) packing structure are close to the results of some classical correlations of the CFL with most relative deviations within ±10% and can be used to approximate the actual CFL. And taking 40 K as the dividing point, the new thermal-hydraulic correlations of the high-pressure and low-temperature hydrogen in the CFL are obtained with the relative deviations within ±10%. Further, the New model of the PFHEFC is developed with the new thermal-hydraulic correlations. The New model has some margin in the heat transfer performance, considers the special thermal-hydraulic performances of the high-pressure and low-temperature hydrogen in the CFL, and is consistent with the existing numerical models in the ortho-para hydrogen conversion performance. It shows the New model is more suitable for the PFHEFC and can provide more accurate results for the design of the PFHEFC than the existing numerical models.

Catalytic hydrothermal liquefaction of microalgae over reduced graphene oxide support Ni catalyst

In this study, a reduced graphene oxide (RGO) material loaded with nickel was prepared, and to the best of the authors' knowledge, it was the first time that RGO material used as a catalyst in the hydrothermal liquefaction (HTL) of microalgae. The effect of RGO support Ni catalyst on the yield and quality of bio-oil derived from HTL of Spirulina was studied in this research. The results showed that the catalyst could improve the yield of bio-oil, and the performance in improving the quality of bio-oil was significantly increased. GC–MS analysis showed that RGO catalyst could promote the formation of hydrocarbons. When the loading amount of Ni was 5%, the oxygen content of bio-oil was the lowest (14.79%), and when the loading amount of Ni was increased to 25%, the content of hydrocarbons was the highest (11.41%). In addition, RGO catalyst also increased the content of low boiling point components (<400°C) in bio-oil from 68% to 81%. This study can provide valuable information for the further application of graphene in microalgae HTL and the production of high-quality bio-oil in the future.

Highly active and magnetically recoverable heterogeneous catalyst for hydrothermal liquefaction of biomass into high quality bio-oil

This article reports a safe, low-cost, and industrially applicable magnetite supported on activated carbon catalyst that can be magnetically retrieved from the solid and reused multiple times without the need of a regeneration step. The FeOx/C catalyst improved the bio-oil yield by 19.7 ± 0.96 % when compared to the uncatalysed reaction at 320 °C for the HTL of draff (brewer’s spent grains). The use of homogeneous Na2CO3 base as a catalyst and co-catalyst, improved carbon extraction into the aqueous phase. The exceptional catalytic activity can be attributed to the Fe3O4 phase which can produce in-situ H2 that improves the biomass decomposition and oil property with an energy recovery of ∼84 %. The FeOx/C catalyst was separated using magnetic retrieval and maintained its catalytic activity even up to 5 reaction cycles showing potential as a cheap catalyst for HTL reactions and can be scaled-up for industrial applications.

The impact of nitrogen-containing compounds on the S-vacancies over the iron-based catalysts for direct coal liquefaction during the pre-sulfurization process

To advance the direct coal liquefaction (DCL) technology by a “Catalytic cycle of hydrogen donor solvents” pathway, it wasimportantfor the iron-based DCL catalyst to be pre-sulfurized under a suitable condition. In this report, the effect of liquid medium in the slurry bed pre-sulfurization process on iron-based catalyst was studied. Catalysts were pre-sulfurized under a variety of liquid mediums including alkanes, aromatics and heteroatom-containing compounds and the activity were evaluated according to their performance on hydrogenation of naphthalene. It was observed that, the nitrogen-containing medium give rise to the significant negative influence on the catalytic activity (with only 2.5 %-15.3 % of naphthalene conversions). Multiple spectroscopic and microscopic analyses of catalysts exhibited that the decrease of S vacancies was mainly responsible for the low activity. It was due to the promotion effect on Fe1-xS crystallization and troilite generation. S vacancies of the iron-based catalysts was considered as Lewis acid sites to catalyze the hydrogenation reaction. The new findings from this work is beneficial for the development and optimization of pre-sulfurization technology.

In-situ catalytic hydro-liquefaction of Delonix regia lignocellulosic biomass waste in hydrogen-donor solvent

Wastes from forestry residues and tree felling have been a major waste management concern since a long time. This issue had been addressed in this work where utilization of waste Delonix regia biomass by hydro-liquefaction in a hydrogen-donor solvent (methanol) and in presence of Ni–Al co-precipitation catalyst at different temperatures and a fixed pressure have seen to provide synergistic results not only in terms of yield of liquid products but also their higher heating values. To the best of authors’ knowledge, no studies have been testified in the literature using such co-precipitation catalyst for Delonix regia biomass liquefaction. The hydrogen donating capability of alcoholic methanol solvent in the hydro-liquefaction process along with existence of hydrogen rich environment, caused by supply of initial external hydrogen pressure, explained high yield of liquid products. A maximum higher heating value (HHV) of 26.31 MJ/kg for biocrude, obtained at 200 °C and 80 bar final reactor pressure for 60 min reaction time, depicted the potentiality of Ni–Al catalyst in reducing oxygen content of biocrude by partial hydrogenation during the liquefaction process. Apart from this, biocrude showed presence of long chain alkanes, esters, aldehydes and ketones in them. The low phenol content of the biocrude as found from Gas Chromatography-Mass Spectrometry (GC-MS) results were an indication of its less hazardous and toxic nature. The free-flowability and porous nature of solid biochar from this hydro-liquefaction process was a sign of their effectiveness in soil remediation processes and wastewater treatment. Finally, physical properties and fuel potential of biocrude obtained in this process were superior compared to those of bio-oil obtained by catalytic, non-catalytic and hydro-catalytic pyrolysis of same biomass conducted at elevated temperature of 600 °C.

PolyE‐IL: A polymeric Brønsted acid ionic liquid catalyst for catalytic thermo liquefaction of sugarcane bagasse into carboxylic acids

AbstractThe present study demonstrates a catalytic thermo liquefaction (CTL) process for the liquefaction of sugarcane bagasse into carboxylic acids using recyclable polymeric Brønsted acid ionic liquids (PolyE‐ILs) catalyst. A series of acid catalysts such as mineral acids, imidazole‐based ionic liquid and PolyE‐ILs with variable counter ions were tested. Of the tested catalysts, [PEI]+[HSO4]− resulted in 51.84% levulinic acid, 53.07% formic acid and 100% acetic acid yields compared with their theoretical maximum with 81.40% feedstock conversion at 210 °C for 120 min. Under 10 bar N2 pressure. The carbon‐enriched side products (CTL‐oil), catalyst and carboxylic acids were separated by integrating the adsorption and membrane separation process with &gt;98% efficiency. The CTL‐oil with calorific a value of 25–26 MJ/kg can be explored for further energy and fuel applications. Thus, the use of a robust and recyclable catalyst at moderate operating conditions provides an efficient pathway for the valorization of sugarcane bagasse into carboxylic acids and CTL‐oil. © 2022 Society of Chemical Industry and John Wiley &amp; Sons, Ltd

Use of an alkaline catalyst with ethanol-water as a co-solvent in the hydrothermal liquefaction of the Korean native kenaf: An analysis of the light oil and heavy oil characteristics

Hydrothermal liquefaction of the Korean native kenaf, with ethanol–water as a co-solvent at 275–350 °C for 30 min with and without 1 wt% of the alkaline catalysts Ca(OH)2, Na2CO3, K2CO3, and KOH, was investigated to identify the effect of the alkaline catalyst addition on the characteristics of the light and heavy oil produced. Component, elemental, ICP-ASE, and GC-MS analyses were conducted to determine the characteristics of the light oil, heavy oil, and solid residue. The highest bio-crude oil yield of 61.81% at 275 °C was found using ethanol–water without an alkaline catalyst. The addition of alkaline catalysts prompted the decomposition of both the heavy oil and light oil fractions, and re-polymerization reactions were suppressed. In addition, there were increases in the area percentages of ketone and phenolics derived from holocellulose and monolignols, respectively. Calcium ion was mainly detected in the aqueous phase, while sodium and potassium existed as solids in the solid residue. The results show that the addition of a calcium-based alkaline catalyst in the hydrothermal liquefaction of kenaf can enhance the energy recovery ratio to 58% and calorific value to 32.27 MJ/kg of the light oil at 350 °C.

Effect of sulfidation temperature on component transformation and catalytic performance of direct coal liquefaction catalyst

A series of iron sulfide catalysts were prepared in 5% H2S/N2 atmosphere at different pre-sulfidation temperatures, and their catalytic activity for naphthalene hydrogenation was studied at 360°C in 1% H2S/H2 atmosphere at 5MPa. The component transformation of the catalyst under varied pre-sulfidation temperature and reaction conditions was researched using MES, XRD and XPS. The results revealed that the sulfidation process was in the form of sulfurizing from surface to interior in the order of FeS2→FeS, Fe1−xS→Fe3S4→Fe2O3 during which transferring sulfur to the body phase was benefited from the rise of temperature. After contacting 1% H2S/H2 gas, the particles rapidly transformed to Fe1−xS from outside to the inside. By adjusting sulfidation conditions, the Fe1−xS content was high while the particle size was small, which made it possible to obtain the greatest activity of the catalyst.

Research of hydrogen action during pre-sulfidation of direct coal liquefaction catalyst

A series of iron sulfide catalysts were prepared by pre-sulfidation at different temperatures and different hydrogen partial pressures, and their catalytic naphthalene hydrogenation activities were studied under 5 MPa 1% H2S-H2 atmosphere at 360 °C. By means of XRD, MES, SEM-EDS, ICP and GC-MS, the effect of hydrogen on the pre-sulfidation process at different temperatures is studied. The results show that the introduction of hydrogen during the pre-sulfidation process facilitates the transfer of sulfur, thereby promoting the sulfidation. Different temperatures are favorable for the formation of Fe1–xS, but the effect of hydrogen is different at different pre-sulfidation temperatures. When pre-sulfidation at 50 °C, the introduction of hydrogen can be beneficial to the transfer of sulfur, which increases the catalytic activity, a lot of elemental Fe and elemental S can be observed at this temperature; when pre-sulfidation at 150 °C, the catalytic activity is the best. The content of elemental Fe decreases and no elemental S is observed. With the increase of hydrogen partial pressure, the hydrogenation conversion rate of naphthalene increases from 60.6% to 69.1%. When pre-sulfidation at 300 °C, the catalytic activity decreased to varying degrees. Hydrogen reduces the sulfur on the catalyst surface to a low valence state and crystalline Fe3O4 is observed inside the catalyst particles, which is not conducive to the transfer of sulfur.

Valorization of the spent catalyst from flue gas denitrogenation by improving bio-oil production from hydrothermal liquefaction of pinewood sawdust

Normally, the spent catalyst (V2O5-WO3/TiO2, denoted as VWTi) is dumped as a solid waste after denitrogenation of flue gas through selective catalyst reduction (SCR). However, this used catalyst contains an abundant amount of acid sites and thus can be potentially utilized as the catalyst in hydrothermal liquefaction (HTL) to produce bio-oil. Thus, in this study, the influences of operational variables on the main HTL products distribution and physicochemical properties of bio-oil were evaluated at 240–320 °C for 0–60 min and 0–20 wt% of catalyst dosage. The results demonstrated that the spent VWTi catalyst significantly promoted the production of bio-oil, yielding the highest bio-oil yield (33.9 wt%) at 300 °C for 30 min with a 10 wt% of catalyst loading. The bio-oil obtained with catalyst under the optimal conditions has a HHV of 28.69 MJ/kg, along with an energy recovery of 51.93%. In addition, the use of the spent VWTi catalyst in the HTL could obtain a higher fraction of phenolics compounds with lower boiling point and lower molecular weight, as identified by TGA and GPC analysis. Overall, this study provides an alternative route to valorize the spent catalyst from flue gas denitrogenation by applying as a catalyst to produce high quality bio-oil production in the biomass HTL process.

Synergistic effects of metallic Fe and other homogeneous/heterogeneous catalysts in hydrothermal liquefaction of woody biomass

In order to determine the synergistic effects of the mixed additives of Fe and other catalysts on the yields and characteristics of bio-oil products, hydrothermal liquefaction (HTL) of pinewood sawdust (PW) was performed at 300 °C for 30 min (biomass/water mass ratio = 1:10) in the presence of metallic iron (Fe), other homogeneous/heterogeneous catalysts (Na2CO3, NaOH, FeSO4, MgO, Ru/C, FeS), as well as mixed additives. The results indicated that the metallic Fe could increase the yield and promote the degree of hydrodeoxygenation of bio-oil products. Noticeable synergistic effects on improving the bio-oil yields were found in the presence of mixed additives of Fe and an alkali catalyst (Na2CO3/NaOH) or FeS. The maximum bio-oil yield and the most energy recovery from bio-oil (81%) were obtained with Fe + Na2CO3. In addition, the combination of Fe + Ru/C produced bio-oil with the highest carbon and hydrogen contents, the highest HHV (30.93 MJ/kg), as well as the lowest contents of oxygenated compounds and the largest amount of hydrocarbons. In summary, this work demonstrates the synergistic effects of the mixed additives of Fe and several catalysts (Na2CO3, FeS and Ru/C) in HTL of woody biomass, promoting both yields and quality of bio-oil products.