Hydrotalcite Catalyst Research Articles

Depolymerisation of organosolv lignin by supported Pt metal catalysts

The conversion of lignocellulosic biomass into value-added chemicals and biofuels has been attracting the attention of researchers in recent years. Lignin is an abundant, natural polymer and a major component of lignocellulose comprising an aromatic structure with ether linkages, methoxy-, and hydroxyl groups. Therefore, it has great potential as a sustainable source to produce basic chemical products. In this study, precious metal-loaded hydrotalcite (HTC) catalysts for the depolymerization of organosolv lignin (OL) were investigated concerning minimizing coke formation and maximizing the value-added lignin oil fraction and lignin tar fraction. The influences of the catalyst support, the platinum loading as well as the loading with a second metal (Cu or Ni) were examined. The resulting depolymerization fractions (lignin oil, lignin tar, aqueous fraction, and coke) were determined gravimetrically. To compare the molecular mass distribution of the lignin oil and lignin tar fractions as well as the purchased OL, gel permeation chromatography (GPC) was used. The lignin oil fractions were analyzed quantitatively and qualitatively by gas chromatography-mass spectroscopy (GC–MS). Regarding the most suitable catalyst system (5%Pt-1%Ni/HTC), a design of experiment (DoE) was prepared to further minimize coke formation and maximize the value-added fractions (lignin oil and lignin tar). This optimization led to 18 wt% lignin oil fraction, 72 wt% lignin tar fraction, and 0.4 wt% coke formation.

Highly thermally stable multi-porous calcium aluminum hydrotalcite catalyst for efficient carbonate synthesis

In the context of a carbon–neutral era, conversion of greenhouse gas CO2via chemical catalysis is a powerful means. Using CO2and petroleum-derived alkylene oxide as the raw materials to produce high-value carbonate substances has been considered a green and economic path for carbon reduction and energy transition. We discovered a multi-porous calcium aluminum hydrotalcite material (Ca-Al HT), and found that it performs excellent catalytic ability on transesterification (an important reaction in the synthesis of carbonates). Being different from homogeneous basic catalysts such as soluble metal hydroxides and organic halide salts, and well-known solid basic catalyst CaO, which are difficult to recycle and suffer severe deactivation in long-term catalytic process, the robust Ca12Al14O33crystal phase in Ca-Al HT catalyst behaves much more stable catalytic performance during 4000 min efficient catalysis (63 % conversion and 100 % selectivity). The special crystal phase structure of Ca12Al14O33remains stable at even a very high temperature of 900 °C. In contrast, CaO as the reference catalyst is very sensitive to trace H2O in catalytic system, and deactivates immediately. The outstanding catalytic ability of Ca-Al HT is attributed to its super-strong alkali strength, large alkali amount, and quick mass transfer originating from the hierarchical pore system.

Comparative Physicochemical and Catalytic Study of Nanocrystalline Mg-Al Hydrotalcites Precipitated with Inorganic and Organic Bases.

Synthetic Mg-Al hydrotalcites (HT) are environmentally friendly solid bases frequently applied as catalysts in base catalyzed reactions. The most common synthesis method, using NaOH as precipitant, is problematized by the possibility of introducing undesired Na contamination. Alkali-free synthesis is usually performed with NH3aq, a precipitant which is less efficient in incorporation of Mg into HT lattice. In the present work, organic bases, tetrabutylammonium hydroxide and choline hydroxide, were successfully employed as precipitating agents in a new alkali-free route of Mg-Al HT synthesis. HT solids were also obtained with inorganic bases, NH3aq and NaOH. Characterization with X-ray diffraction, elemental analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy and thermogravimetry/differential scanning calorimetry, confirmed the formation of nanocrystalline HT compounds with all employed bases. HT prepared with NH3aq exhibited an Mg deficit, which was detrimental to the catalytic activity in base catalyzed reactions. The effect was attributed to the tendency of Mg2+ to form ammine complexes, a conclusion supported by quantum mechanical calculations. HT prepared with NaOH showed the highest crystallinity, which was unfavorable for catalytic application. The addition of starch to the synthesis medium provided a means by which to diminish the crystal size of all HT precipitates. Catalytic tests of the Baeyer–Villiger oxidation of cyclohexanone demonstrated that the highest yields of ε-caprolactone were obtained with fine-crystalline HT catalysts prepared with organic bases in the presence of a starch template.

Highly thermally stable multi-porous calcium aluminum hydrotalcite catalyst for efficient carbonate synthesis

<h2>Abstract</h2> In the context of a carbon-neutral era, conversion of greenhouse gas CO₂ via chemical catalysis is a powerful means. Using CO₂ and petroleum-derived alkylene oxide as the raw materials to produce high-value carbonate substances has been considered a green and economic path for carbon reduction and energy transition. We discovered a multi-porous calcium aluminum hydrotalcite material (Ca-Al HT), and found that it performs excellent catalytic ability on transesterification (an important reaction in the synthesis of carbonates). Being different from homogeneous basic catalysts such as soluble metal hydroxides and organic halide salts, and well-known solid basic catalyst CaO, which are difficult to recycle and suffer severe deactivation in long-term catalytic process, the robust Ca₁₂Al₁₄O₃₃ crystal phase in Ca-Al HT catalyst behaves much more stable catalytic performance during 4000 min efficient catalysis (63% conversion and 100% selectivity). The special crystal phase structure of Ca₁₂Al₁₄O₃₃ maintains stability at even a very high temperature of 900 °C. In contrast, CaO as the reference catalyst is very sensitive to trace H₂O in catalytic system, and deactivates immediately. The outstanding catalytic ability of Ca-Al HT is attributed to its super-strong alkali strength, large alkali amount, and quick mass transfer originating from the hierarchical pore system.

In depth thermokinetic investigation on Co-pyrolysis of low-rank coal and algae consortium blends over CeO2 loaded hydrotalcite (MgNiAl) catalyst

This study investigates the co-pyrolysis behavior of bituminous coal (100%BC), algae consortium (100%AC), and their blends at various blending ratios. The pure and coal-biomass blends were characterized using CHN-S, GCV, and FTIR analysis. Whereas, the co-pyrolysis of blends were performed in a TGA. The deviation between the experimental and calculated values of weight loss (WL%), the residue left (RL%), and the maximum rate of weight loss (wt%/min) was used to calculate the synergistic effects. Kinetic parameters were investigated using the Coats-Redfern integral method through eighteen (18) reaction mechanistic models. The activation energy (Ea) for 100%BC was 85.04 kJ/mol through the F3 model, whilst for 100%AC showed 78.22 kJ/mol using the D3 model. Thermodynamic parameters such as Enthalpy (∆H) and Gibbs free energy (∆G) showed positive values, while Entropy (∆S) was negative for each coal-biomass blend. The catalytic co-pyrolysis of the optimum blend (20BCE-80AC) was studied using CeO2 loaded MgNiAl (CeO2 @MNA) as a multifunctional catalyst. The increased WL% displayed a positive effect toward a higher yield of volatile matter. Ea of the optimum blend in co-pyrolysis was further reduced through catalytic co-pyrolysis and Ea in the first and second stages was 72.48 kJ/mol and 13.76 kJ/mol, while 3 wt% catalyst loading further reduced its Ea in both stages to 67.82 kJ/mol and 41.21 kJ/mol. The use of CeO2 @MNA at 3 wt% loading showed a reduction in the peak devolatilization temperature (Tp) of the optimum blend substantially increasing the reaction rate, and reducing the Ea required for the decomposition process.

Conversion of furfuryl alcohol to 1,5-pentanediol over CuCoAl nanocatalyst: The synergetic catalysis between Cu, CoOx and the basicity of metal oxides

A series of layered Cu-Co-Al hydrotalcite (LDHs) catalysts with different Cu/Co molar ratio were synthesized and applied for the hydrogenation of furfuryl alcohol to 1,5-pentanediol. The results indicated that the Cu0.2Co5.8/Al2O3 catalyst displayed an excellent catalytic efficiency compared to monometallic Co/Al2O3 or Cu/Al2O3 catalyst. The yield of 1,5-pentanediol reached 44.7% at 140°C, 4 MPa H2 within 2 h. In-situ XPS, H2-TPR, CO2-TPD analysis revealed that the high efficiency of this catalyst was attributed to the synergistic catalysis between the surface Cu0, CoOx and the basicity of metal oxides. Typically, Cu0 sites activate dissociated hydrogen, the basic sites anchor furfuryl alcohol by -OH to form an alcoholate species, inducing furfuryl alcohol with C2 oblique adsorption on the catalyst surface. The adjacent CoOx species adsorb and activate C2=C3 group in furfuryl alcohol. Subsequently, C2=C3 bond of furfuryl alcohol was partially hydrogenated, facilitating the cleavage C2-O1 bond to produce 1,5-pentanediol.

Biodiesel Production of Palm Oil Mill Effluent by Using Hydrotalcite Catalyst

Biodiesel is currently preferred for consumption and has been widely used as a substitute for diesel. This study aimed to determine the effect of various methanol-to-oil ratios in the esterification process and also the effect of hydrotalcite catalyst weight on the transesterification product. The catalyst was characterized with SEM, XRD, FTIR, and TG-DTG-DTA. The esterification process was operated at various oil-to-methanol ratios, i.e., 1:12-1:36 and the transesterification was performed using several catalyst weights, 0.5%-2.5%. The results showed that the optimum conditions of esterification were at the 1:30 molar ratio of oil-to-methanol, which decreased the amount of acid number by 95.75%, while the optimum condition of transesterification was at 1.5% catalyst weight. The characteristics of biodiesel using 0.5-2% hydrotalcite catalyst (acid number, total glycerol, free glycerol, ester levels, viscosity, density, oxidation stability) have met the Indonesian biodiesel standard of SNI-04-7182-2012.

Sorption enhanced steam reforming of methane over waste-derived CaO promoted MgNiAl hydrotalcite catalyst for sustainable H2 production

The waste-derived CaO promoted Mg-Ni-Al (MNA) based hydrotalcite hybrid catalysts were synthesized by co-precipitation and wet impregnation method and tested for sorption enhanced steam methane reforming (SESMR) for hydrogen (H2) production. The catalysts were characterized using X-ray diffractometer (XRD), Field emission scanning electron miscroscopy (FESEM), Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, Brauner Emmett teller (BET), laser particle size analyzer, Temperature programmed reduction (TPR), Thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). Various CaO loadings varying from 0% to 15% into the MNA-based hydrotalcite catalysts (MNA HTc) were assessed for SESMR in a fixed bed reactor. The results revealed that 10% CaO@MNA exhibited the best performance in terms of a longer pre-breakthrough period with respect to other compositions. The CH4 fraction, H2 purity, and CO2 production in the absence of CaO were marked at 60%, 55%, and 14% respectively. However, the CH4 fraction and H2 purity increased to 77% and 80%, while CO2 decreased to 3% in the pre-breakthrough period for 10% CaO @ MNA at 650 °C, WHSV 2000 mL CH4 g−1h−1 and S/C of 2.0. The nanocomposite 10%CaO@MNA was tested over three consecutive SESMR cycles at 650 °C to analyze its regeneration capacity. The hybrid catalyst was also tested at various temperatures from 650° to 850°C to investigate the effect of CaO sorbent. It was found that elevated temperatures > 750 °C likely reduced the carbonation reaction and shifted the technique to SMR. The spent catalyst exhibited negligible carbon formation on the catalyst surface. The catalytic performance of the reported catalyst-sorbent system is encouraging for further regeneration studies for SMR and other reforming techniques.

Influence of Co/Fe molar ratio on hydrotalcite catalysts prepared with or without microwave

Two series of mixed cobalt-iron oxides were synthesized by the conventional hydrotalcite route, without (CoxFe2-HT) or with microwave irradiations (CoxFe2-MW). Different molar ratios Co2+/Fe3+ were also investigated with 2 ≤ x ​≤ ​8. X-ray diffraction (XRD) analysis confirmed the formation of the desired hydrotalcite phase for all the materials before calcination whatever the molar ratio Co2+/Fe3+ is. After calcination of the latter materials at 500 ​°C, XRD evidenced the complete destruction of the hydrotalcite phase and, consequently, the formation of mixed oxides of cobalt and iron.After being characterized, the oxides materials were tested towards the total oxidation of the volatile organic compound (VOC) propene. Both the molar ratio and the preparation method have a significant effect on the catalytic properties. The light-off curves of CoxFe2-HT500 materials showed that the catalytic activity is improved for a molar ratio Co2+/Fe3+ > 2. Co6Fe2-HT500, with the ratio Co2+/Fe3+ equal to 3, showed the best catalytic performance. Furthermore, except for Co8Fe2-MW500, the materials that were subjected to microwave irradiations gave higher catalytic activities compared to those of the homologous ones prepared without such irradiations. Co6Fe2-MW500 was found to be the most catalytically active among all the materials of both series due to the higher specific surface area, the higher amount and easier reducibility of active species, higher proportion of mobile oxygen and of Co2+ on the surface. Furthermore, this catalyst did not show tendency to deactivation and coking even after 100 ​h under stream.

Evaluation of the reactivity, selectivity and lifetime of hydrotalcite-based catalysts using isopropanol as probe molecule

Hydrotalcite catalysts derived from NiAl and NiAlMg mixed oxides were successfully prepared by coprecipitation at a constant pH of 11. Physicochemical methods were investigated to determine their structural and textural properties. Using isopropanol as a probe molecule, the acid–base properties of the catalysts were investigated, and the evaluation of reactivity, selectivity and lifetime was established.

Study of the Catalytic Activity of the Compounds Hydrotalcite Type Treated by Microwave in the Self-Condensation of Acetone.

The self-condensation reaction of acetone, producing diacetone alcohol (DAA), is of great industrial importance. It was used to study the catalytic activity of Mg-Al catalysts synthesized by the coprecipitation method. For this purpose, we synthesized Mg-Al based hydrotalcite with a molar ratio of 3, obtained either after conventional heating or after microwave irradiation with of 100 W for three minutes. Structural and chemical properties of the obtained catalysts were characterized, using different techniques: X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscope (SEM), equipped with energy dispersive X-ray (EDX), and specific surface area of the catalysts were determined by the methylene blue (MB) adsorption method. Also, these catalysts were tested in the self-condensation reaction of acetone at 273 K in the liquid phase without solvent, a reaction which requires very high catalytic activity. The microwave treatment improves the catalyst activity, and the conversion of acetone to diacetone alcohol increases from 13.2 to 18.3% after 8 h of reaction. Moreover, the microwave-treated hydrotalcite catalyst, calcined at 723 K and rehydrated under a flow of N2, is the most active and gives conversion of acetone of 52% under the same reaction conditions.

SYNTHESIS AND APPLICATION OF Cu-Fe HYDROTALCITE IN ALDOL REACTION

The heterogeneous recyclable catalyst, Cu-Fe hydrotalcite, was synthesized by coprecipitation, activated at 200oC and then successfully applied in Aldol reaction. The Aldol products were obtained in moderate yield under mild conditions, simple and environmentally benign process, with the recovery of hydrotalcite catalyst up to 99%. This procedure also exhibited efficiency in the total synthesis of Abhexone, a flavor with high demand in the food and cosmetic industry.

Partial oxidation of methane over CeO2 loaded hydrotalcite (MgNiAl) catalyst for the production of hydrogen rich syngas (H2, CO)

In this work, partial oxidation of methane (POM) was investigated using Mg-Ni-Al (MNA) hydrotalcite promoted CeO2 catalyst in a fixed bed reactor. MNA hydrotalcite was synthesized using the co-precipitation process, while CeO2 was incorporated via the wetness impregnation technique. The CeO2@MNA samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) technique. The catalytic activity of CeO2 promoted MNA (CeO2@MNA) for POM reaction was evaluated for various CeO2 loading kept the feed ratio CH4/O2 = 2 at 850 °C. The catalyst containing 10 wt% cerium loading (10%CeO2@MNA) showed 94% CH4 conversion with H2/CO ratio above 2.0, that is more suitable for FT synthesis. The performance of catalyst is attributed to highly crystalline stable CeO2@MNA with better Ce-MNA interactions withstand for 35 h time on stream. Furthermore, the spent catalyst was examined by TGA, SEM-EDS, and XRD to evaluate the carbon formation and structural changes during the span of reaction time.

Continuous biodiesel production: A review of advances in catalysis, microfluidic and cavitation reactors

Biodiesel production can be achieved through different processes and different reactor types as well as varying reaction parameters such as catalyst dose, oil: alcohol ratio, reaction time, mixing intensity, free fatty acid content (<3% required) and reaction temperature. The present review presents the advances in catalytic biodiesel production with emphasis on the current challenges, and prospects in homogeneous and heterogeneous catalysts. Particularly, alkaline earth metal, metal mixed oxides, carbon-based and biomass-derived catalysts, and ionic liquids are discussed in detail. In addition, microfluidic, and acoustic reactors such as ultrasonic and hydrodynamic cavitation reactors are reviewed. The results from conducted studies revealed calcium oxide (CaO)-based catalysts derived from either residual biomass sources or synthetic chemicals are more favorable for biodiesel synthesis. Hydrotalcite catalysts and ionic liquids require harsh conditions such as higher temperature, higher oil: methanol ratio, and longer reaction time to achieve appreciable yield. The micro-reactors and cavitation reactors provide a faster reaction rate compared to conventional reactors because there is a drastic reduction in the time it takes for miscibility and diffusion of the reactant molecules and hence, eliminates the high energy requirement for mixing. The hydrodynamics reactor presents lower erosion challenges and energy input per unit of reactants when compared with the ultrasonic reactor. It is hoped that this study will provide detailed and recent knowledge on heterogeneous catalysts, microfluidic, and cavitation reactors for biodiesel synthesis.

Intercalated structured nickel-based hydrotalcite nanocatalyst for diphenylacetylene semihydrogenation

<p indent=0mm>A novel nickel-based hydrotalcite catalyst Ni/Mg₃Al₁O-PDA was fabricated by intercalating the complex formed by pyridine-2,3-dicarboxylic acid (PDA) and nickel ions into the layers of Mg-Al hydrotalcite. Compared with nickel-based nanocatalysts prepared by traditional impregnation method and co-precipitation method, this catalyst showed superior catalytic performance in the semi-hydrogenation of 1,2-diphenylacetylene. Results of X-ray powder diffraction, infrared spectrum, transmission electron microscopy and X-ray photoelectron spectroscopy showed that the intercalation effect of Ni-PDA effectively promoted the uniform dispersion of Ni precursors between hydrotalcite laminates, and increased the intercalation distance of hydrotalcite laminates from 0.76 to <sc>1.55 nm.</sc> This process not only facilitated the high dispersion of Ni nanoparticles, but also increased the specific surface area and pore volume of the catalyst, thus exposing more Ni active sites. Moreover, the formation of MgNiO₂ spinel structure in the catalyst precursors significantly improved the interaction between the active species and the support, promoted the dispersion of Ni nanoparticles, and improved the activity and stability of the obtained catalyst.

Photoelectrocatalytic Degradation of Congo Red Dye with Activated Hydrotalcites and Copper Anode

Photoelectrocatalysis is a novel technique that combines heterogeneous photocatalysis with the application of an electric field to the system through electrodes for the degradation of organic contaminants in aqueous systems, mainly of toxic dyes. The efficiency of these combined processes depends on the semiconductor properties of the catalysts, as well as on the anodic capacity of the electrode. In this study, we propose the use of active hydrotalcites in the degradation of Congo red dye through processes assisted by ultraviolet (UV) irradiation and electric current. Our research focused on evaluating the degradation capacity of Congo red by means of photolysis, catalysis, photocatalysis, electrocatalysis, and photoelectrocatalysis, as well as identifying the effect of the properties of the active hydrotalcites in these processes. The results show that a maximum degradation was reached with the photoelectrocatalysis process with active hydrotalcites and a copper anode at 6 h with 95% in a half-life of 0.36 h. The degradation is favored by the attack of the OH• radicals under double bonds in the diazo groups where the electrode produces Cu2+ ions, and with the photogenerated electrons, the recombination speed of the electron–hole in the hydrotalcite catalyst is reduced until the complete degradation.

Rape oil transesterification by methanol and ethanol on extruded hydrotalcite catalyst

This article is devoted to rape oil transesterification by methanol and ethanol on powder and extruded Mg/Al hydrotalcite catalyst in a stirred reactor under atmospheric pressure close to boiling point of alcohol with inserted perforated basket with extrudates. With 15 wt% of catalyst in relation to rape oil and molar ratio methanol/ester group of oil 13:1, the yield of monomethylester reached 99.5% within 48 h in the case of fresh catalyst. After recalcination, the same catalyst enabled the same yield of monomethylester within 72 h and third cycle of this catalyst after two recalcinations led to 98.5% of monomethylester yield also within 72 h. Extrudates enabled the same monoester yield as hydrotalcite powder within 24 (60–61%) up to 48 h (99%). Moreover, several experiments were done in the autoclave to assume temperature effect to reaction time. Enhanced temperature 140 °C provided nearly 99% monoester yield within 12 h. A new arrangement with extrudates in a perforated basket makes transesterification with heterogeneous hydrotalcite catalyst easily feasible. Differently from rather promising results in rape oil transesterification with methanol, ethanol worked in this reaction much more slowly. Not surprisingly water inhibits transesterification, as the reaction with 96% ethanol shows. Using 99.8% ethanol nearly without water makes transesterification significantly faster, but 51% monoester yield after 120 h reaction time is still insufficient. Nevertheless, ethanol remains a promising raw material for oil transesterification, as it can be prepared by a bioprocess, which makes the whole technology based on renewable sources.

Synergistic effects of gamma irradiation on the PET surface and heat treatment of hydrotalcite catalyst supported by Pt/TiO2 nanoparticles on PET depolymerization rate

Acquiring new methods to achieve the products with lesser molecular weight associated with minimum energy consumption in poly(ethylene terephthalate) (PET) recycling can improve the glycolysis reaction performance. The synergistic effects of gamma irradiation on the properties of PET wastes and heat treatment on the catalytic activity of novel hydrotalcite supported by 2‐wt% Pt/TiO2 nanoparticles (NPs) were studied. The PET samples treated by different gamma irradiation doses, γ, were degraded by glycolysis, which resulted in an increased yield of bis(2‐hydroxyethyl) terephthalate (BHET) monomer. The XPS analysis showed that the calcination temperature of the catalyst, T, affects the strength of the acid and/or basic sites of catalyst, degradation products, and reaction time. The NH3‐temperature‐programmed desorption (TPD) analysis showed the interaction between TiO2 and Pt led to a wide distribution of middle strength acid sites. Processing of PET by gamma irradiation showed that the average molecular weight of degradation products and reaction time decreased by increasing gamma dose. The composition (wt%) analysis indicated that the highest values of yield and selectivity of BHET were achieved in the optimum values of γ = 70 kGy and T = 450°C. The proposed procedure helps to attain minimize the residual oligomers and unreacted species during PET recycling.

Effect of the Solvent on the Basic Properties of Mg–Al Hydrotalcite Catalysts for Glucose Isomerization

We suggested the existence of a relationship between the base properties of Mg–Al hydrotalcite catalysts and the solvents employed in the industrially important isomerization of glucose produce fructose. We prepared Mg–Al hydrotalcite catalysts with different Mg/Al atomic ratios to tune the basic properties of the catalyst. The prepared catalysts were used in the glucose isomerization conducted in various solvents. Experimental results confirmed that the catalysts exhibited different activities in the different solvents. We also implemented the Hammett indicator method, which allows to analyze the basic properties of the catalysts in various solvents. According to evidence, the basic properties of the catalysts varied substantially in different solvents. Notably, increases in the catalysts’ base properties matched the observed increases in fructose yield of the glucose isomerization. Consequently, we suggested that, in order to prepare efficient Mg–Al hydrotalcite catalysts for glucose isomerization, the interaction between the solvent used to conduct the reaction and the basic properties of the catalyst, which are in turn influenced by the solvent, should be considered.

Production of Aromatic Compounds by Catalytic Depolymerization of Technical and Downstream Biorefinery Lignins.

Lignocellulosic materials are promising alternatives to non-renewable fossil sources when producing aromatic compounds. Lignins from Populus salicaceae. Pinus radiata and Pinus pinaster from industrial wastes and biorefinery effluents were isolated and characterized. Lignin was depolymerized using homogenous (NaOH) and heterogeneous (Ni-, Cu- or Ni-Cu-hydrotalcites) base catalysis and catalytic hydrogenolysis using Ru/C. When homogeneous base catalyzed depolymerization (BCD) and Ru/C hydrogenolysis were combined on poplar lignin, the aromatics amount was ca. 11 wt.%. Monomer distributions changed depending on the feedstock and the reaction conditions. Aqueous NaOH produced cleavage of the alkyl side chain that was preserved when using modified hydrotalcite catalysts or Ru/C-catalyzed hydrogenolysis in ethanol. Depolymerization using hydrotalcite catalysts in ethanol produced monomers bearing carbonyl groups on the alkyl side chain. The analysis of the reaction mixtures was done by size exclusion chromatography (SEC) and diffusion ordered nuclear magnetic resonance spectroscopy (DOSY NMR). 31P NMR and heteronuclear single quantum coherence spectroscopy (HSQC) were also used in this study. The content in poly-(hydroxy)-aromatic ethers in the reaction mixtures decreased upon thermal treatments in ethanol. It was concluded that thermo-solvolysis is key in lignin depolymerization, and that the synergistic effect of Ni and Cu provided monomers with oxidized alkyl side chains.