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The efficient strategy for waste conversion and resource recovery is of great interest in the sustainable bioeconomy context. This work reports on the catalytic upcycling of waste corrugated cardboard (WCC) into lactic acid using lanthanide triflates catalysts. WCC, a primary contributor to municipal solid wastes, has been viewed as a feedstock for producing a wide range of renewable products. Hydrothermal conversion of WCC was carried out in the presence of several lanthanide triflates. The reaction with erbium(III) triflate (Er(OTf)

Microwave irradiation assists the transformation of acid-insoluble Klason lignin into a green adhesive at a low reaction temperature (100 °C) and short reaction time (10 min).

The catalytic condensation of furfural and 2-methylfuran was performed to produce C15 diesel precursors using sulfonated acidic carbon catalysts, including multi-walled carbon nanotubes, graphene oxide, carbon aerogel, activated carbon, and carbon black. Sulfonated multi-walled carbon nanotubes were prepared with mild sulfonate grafting procedure, and displayed negligible modification of their pore structures. They exhibited the highest turnover frequency, indicating that the acid strength, depicted by the pKa, determined the catalytic condensation activity. The pKa values of the catalysts needed to be less than 4 for enabling the condensation of furfural and 2-methylfuran, and catalysts with pKa values greater than 4 exhibited poor condensation. The pKa, or acid strength, was determined by the environment of the surface sulfonates, which were electronically modified to adjust the stability of the sulfonate anions to release protons.

Despite the recognized efficacy of rhenium (oxide) for promoting hydrogenolysis of the C O bond of biomass-derived oxygenates when combined with a hydrogenation metal such as Pd or Ru, the hydrogenation function of rhenium itself is relatively unexplored. Herein, we investigated the activity and selectivity of rhenium nanoparticles supported on various metal oxides for the hydrodeoxygenation of guaiacol, i.e., 2-methoxyphenol. Catalytic experiments performed at 280 °C and 20 bar H2 in a batch reactor revealed that rhenium itself adequately catalyzes the demethoxylation and dehydroxylation of guaiacol, producing completely deoxygenated products of cyclohexane/benzene. The reduced and unreduced rhenium catalysts (Re vs. ReOx) exhibited similar catalytic activity, and both bulk rhenium oxide (ReO3 and Re2O7) and supported rhenium oxide, i.e., ReOx/SiO2, were completely reduced to metallic rhenium after the reaction, suggesting that metallic rhenium is mainly responsible for the hydrogenolysis of guaiacol. Among the catalysts tested, Re/SiO2 exhibited the highest guaiacol conversion (98%) and the highest selectivity for fully deoxygenated cyclohexane (58%), followed by TiO2, Al2O3, ZrO2, and CeO2. The catalytic activity was generally correlated with the rhenium dispersion as measured by transmission electron microscopy and CO-chemisorption. Despite its high activity, sintering and leaching of rhenium occurred for SiO2 support, whereas the second most active TiO2-supported rhenium catalyst was leaching-resistant. Using Re/TiO2 as a benchmark catalyst, the effects of the rhenium loading, the mesoporosity of TiO2, and reaction conditions on the conversion of guaiacol were further explored.

For the first time, three-dimensional Zeolitic Imidazole Framework (3D) ZIF-7 (Zn(BeIM)2, BeIM = benzimidazole) supported on two-dimensional (2D) Zn(BeIM)OAc (Zinc–Benzimidazole–Acetate) was synthesized by reacting Zn(OAc)2 and benzimidazole in a one-pot reaction. By modulating the amount of diethylamine during the reaction, the ZIF-7/Zn(BeIM)OAc with a 1 to 1 molar ratio was obtained when the reactant molar ratio of Zn(OAc)2 and benzimidazole was 1 to 1.5. It was found that 3D-ZIF-7 was synthesized first and then transformed into 2D-Zn(BeIM)OAc by the reaction with remaining Zn(OAc)2. The synthesized ZIF-7 (Zn(BeIM)2) supported on Zn(BeIM)OAc (1/1) showed enhanced catalytic performance in the methoxycarbonylation of aniline with dimethyl carbonate. The yield of methyl N-phenyl carbamate reached 92.0% in 2 h at 190 °C, which was higher than yields obtained using the single component catalysts ZIF-7 (69.9%) and Zn(BeIM)OAc (35.4%). Furthermore, this catalyst was successfully reused four times, maintaining an MPC yield of 92.0%–95.8%.

The preparation of LaAlO3 perovskite catalysts for the oxidative coupling of methane (OCM) using a very simple solid-state method with good reproducibility is described. To obtain high performance LaAlO3 catalysts, preparation conditions such as time, temperature, and oxygen content, which have a strong effect on the catalytic activity, are controlled during the calcination process. As the calcination time and temperature increase, the catalytic activity of LaAlO3 improves due to the good homogeneity and high crystallinity of LaAlO3 perovskite. Especially, the LaAlO3 catalyst calcined at 1350 °C for 24 h shows the highest selectivity and yield of C2 hydrocarbons. LaAlO3 catalysts calcined at various oxygen fractions show a volcano-shaped curve with respect to oxygen content in calcination gas, and the LaAlO3 catalyst prepared with an oxygen content of 5 % exhibits the best catalytic performance in this reaction. The appropriate oxygen fraction provides the LaAlO3 catalyst with a large amount of electrophilic lattice oxygen species and a sufficient amount of adsorption oxygen species, which are known to play key roles in the OCM reaction. This study clearly reveals this simple, highly reproducible, and mass-productive solid-state method as a promising preparation method for high performance LaAlO3 perovskite catalysts for OCM.

Perovskite-supported alkaline-earth metal oxide catalysts were prepared for application in the oxidative coupling of methane (OCM). The selective production of C2+ compounds, including ethane, ethylene, acetylene, propane, and propylene, was observed at reaction temperatures

The Diels-Alder reaction of biomass-derived dimethyl 2,5-furandicarboxylate (DMFDC) with ethylene followed by dehydrative aromatization is a sustainable route for the production of terephthalic acid, a monomer used for the synthesis of polyethylene terephthalate (PET). In this work, a series of heteropolyacid (HPA) catalysts with different supports, in this case SiO2, TiO2 and ZrO2, and hetero-addenda atoms, here phosphotungstic acid (HPW), silicotungstic acid (HSiW) and phosphomolybdic acid (HPMo), were used as catalysts, and their structure-activity correlation in the conversion of DMFDC to terephthalate was examined based on the density and strength of the acid sites. Characterization by XRD and Raman indicated that the Keggin structures of HPAs were well preserved on the SiO2 support compared to other supports, resulting in strong Bronsted acidity. The silica-supported HPW and HSiW catalysts exhibited significantly higher activity for terephthalate production than other supports and HPMo catalysts, but their activity were not correlated with the total acidity as measured by NH3-TPD. In contrast, the catalyst acid strength, as determined by the NH3 desorption temperature, decreased in the order HPW/SiO2 > HSiW/SiO2 >> HPW/ZrO2 > HPW/TiO2 > HPMo/SiO2 and was well correlated with the turnover rate for terephthalate production, suggesting that the higher activity of HPW/SiO2 is at least partly due to its stronger Bronsted acidity and that promoting the dehydration step of this reaction is a key to improving the selectivity to terephthalate. The effects of reaction conditions, in this case the acid loading amount, solvent used, temperature, and time, were also investigated with the most active silica-supported HPW catalysts to optimize the terephthalate yield. The 25%-HPW/SiO2 catalyst demonstrated a remarkable terephthalate yield of ∼60% with almost complete conversion under the optimum condition.

This study examined the effects of oxygen species on the unsteady-state oxidative coupling of methane (OCM) using a lengthy catalyst bed of Na2WO4/Mn/SiO2. The reaction conditions, including the methane-to-oxygen ratio, ratio of feed gas dilution by N2, quantity of catalyst, and feed flow rate were adjusted for the continuous flow fixed bed reaction system. While the O2 gas initiated methyl radical formation from methane, the surface lattice oxygen atoms improved the dehydrogenation of paraffins to olefins without significant activation of methane. The addition of CO2 as a mild oxidizing agent was also tested and slightly improved OCM selectivity with slightly lower methane conversion were observed.

SiO2@MnOx@Na2WO4@SiO2 core–shell catalysts were prepared and their fabrication was confirmed using transmission electron microscopy. The formation of Mn-based nanosheets on the silica spheres is important for the deposition of nanoscopic Na2WO4. The SiO2@MnOx@Na2WO4@SiO2 core–shell catalysts were used for the oxidative coupling of methane at a temperature of 700–800 °C at which the nanostructures were completely destroyed. Although the core–shell structures did not survive the high-temperature oxidative coupling of methane, the selective production of olefins and paraffins can be attributed to highly dispersed Na2WO4 derived from confined core–shell structures.

Biogas is a promising renewable energy source, however, it needs to be upgraded to increase its low calorific value. In this study, oxidative coupling of methane (OCM) was selected to convert it to a higher fuel standard. Prior to establishing the scaled-up OCM process, the effect of organic/inorganic binders on catalytic activity was examined. The selection of the binders and composition of the catalyst pellet influenced the pore structure, fracture strength, and catalytic activity of the catalyst pellets. It was also observed that the O2 supply from the inorganic binder is a key factor in determining catalytic activity, based on which the composition of the catalyst pellets was optimized. The higher heating value increased from 39.9 (CH4, Wobbe index = 53.5 MJ/Nm3) to 41.0 MJ/Nm3 (OCM product mixture, Wobbe index = 54.2 MJ/Nm3), achieving the fuel standard prescribed in many countries (Wobbe index = 45.5–55.0 MJ/Nm3). The reaction parameters (temperature, gas hourly space velocity, size of the reaction system, and the CH4/O2 ratio) were also optimized, followed by a sensitivity analysis. Furthermore, the catalyst was stable for a long-term (100 h) operation under the optimized conditions.

The issues over increases in energy demand and environmental pollution attributed to excessive use of fossil fuel have been the driving forces of the exploration for eco-friendly resource. Lignocellulosic biomass consisting of carbohydrates and lignin can be a renewable feedstock for replacing fossil fuels in the future because it is a plentiful and carbon neutral material. Especially, lignin, cross-linked phenolic polymers, is a topic of interest owing to its abundant production from pulp/paper industries as well as lignocellulose based biorefinery. The large potential of platform chemicals and biofuels from lignin has opened up an extensive range of opportunities to develop thermal and catalytic conversion technology. Over a few decades, several lignin conversion processes including catalytic pyrolysis, catalytic depolymerization, and catalytic oxidation have been developed to improve target products yields and to suppress side reactions. More recently, lignin-first approaches which maintain carbohydrates intact by selective extraction of lignin as valuable phenolics from whole biomass has been suggested. This review introduces recent ten years progress on thermal and catalytic conversion technology in terms of process type, catalyst development, and target products. This review is expected to offer an influential information for future research into the thermal and catalytic conversion of lignin as well as lignocellulosic feedstock.

Oxidative coupling of methane (OCM) was conducted over LaAlO3_X catalysts that were prepared by a co-precipitation method using different co-precipitation pH values (X = 6–10). The aim is to investigate the effect of pH values on the catalytic activity of LaAlO3 catalysts in this reaction. The results showed that the co-precipitation pH value affected greatly on the formation of chemical species of precipitate precursors in the co-precipitation step, leading to different phases of the finally obtained LaAlO3 catalysts. When the co-precipitation pH value increased up to 8, the lanthanum-related phases such as La2O3 and La(OH)3 were gradually formed as by-products, preventing the formation of LaAlO3 perovskite crystalline structure and facilitating the formation of oxygen vacancies on catalyst surface. However, at pH value of 9 or higher, the lanthanum content in the precipitate precursor was increased greatly. Not LaAlO3 perovskite but lanthanum-related phases were developed as main phases, reducing their catalytic activities in this reaction. Among LaAlO3 catalysts, the one prepared at pH = 8 showed the highest C2 yield due to its well-developed oxygen vacancies and electrophilic lattice oxygen. Therefore, the co-precipitation pH value strongly affected the LaAlO3 catalyst activity in OCM reaction. A precious pH control should be required to prepare various perovskite catalysts for the OCM.

Catalytic descriptors were studied to design optimum catalysts for the oxidative coupling of methane (OCM) by combining density functional theory (DFT) calculations and actual reaction experiments. SrTiO3 perovskite catalysts, selected for OCM, were modified using metal dopants, and their electronic structures were calculated using the DFT method. The CH3 adsorption energy Eads(CH3) and the oxygen vacancy formation energy Ef(vac) exhibited volcano-type correlations with the C2+ selectivity and O2-consumption for the formation of COx, respectively. The optimum catalytic activity, represented by the C2+ selectivity, was obtained for Eads(CH3) = −2.0 to −1.5 eV, indicating that overly strong adsorption of methyl radicals (or easily dissociated C H bonds of methane) and relatively insufficient oxygen supplementation to the catalyst surface improve deep oxidation to CO and CO2. Praseodymium (Pr)- and neodymium (Nd)-doped SrTiO3 catalysts confirm the DFT-predicted optimum electronic structure of the OCM catalysts.

A calcium carbonate (CaCO3)-supported Ru catalyst (Ru/CaCO3) prepared by a wet impregnation method was used for the hydrodeoxygenation (HDO) of eugenol, a lignin model compound representing coniferyl alcohols, and was shown to surpass Ru supported on neutral (ZrO2) and basic supports (MgAlOx, hydrotalcite, and MgO) in terms of deoxygenation activity. The production of deoxygenated compounds was observed during the batch reduction of eugenol with H2 (room-temperature-equivalent pressure = 50 bar) over Ru/CaCO3 at 250 °C, and the yields of compounds with no oxygen atoms (0-O) and one oxygen atom (1-O) were determined as 25.5 and 48.2%, respectively. X-ray photoelectron spectroscopy revealed that the improved hydrodeoxygenation activity could be ascribed to the increased electron density of catalytically active Ru species because of electron donation from the support.

Although numerous studies on the liquefaction of lignin for the production of high-yield and high-quality bio-oil have been performed in a batch reactor, studies using a continuous flow reactor are...

Although chloride-ligated Pt compounds like (bpym)PtCl 2 , K 2 PtCl 4 , and (DMSO) 2 PtCl 2 has been reported to be highly active catalysts for the methane oxidation to methyl bisulfate (MBS) in oleum media, their applications is hampered by the catalyst deactivation to PtCl 2 . In this study, we investigated Pt black catalyzed methane oxidation, which has no ligand. A MBS yield of 82.1% with a selectivity of 96.5% was obtained at a catalyst loading of 1.6 mM at 180 °C, which proved the highest catalytic activity of Pt-black for this reaction. The reaction was thought to proceed by the dissolved Pt species, and no deactivation was observed during four consecutive experiments. However, at a concentration of over 30 mM, MBS yield fell due to the decomposition of MBS to CO 2 on the surface of heterogeneous Pt(0). Vacuum distillation experiments showed the potential for isolating MBS from the oxidation product mixture as a major component.

A novel bifunctional catalyst that enables an efficient one-pot conversion of furfural into γ-valerolactone (GVL) has been developed by anchoring heteropolyacid (HPA) on Zr-Beta zeolite. The catalysts were prepared by a post-synthesis procedure, which consists of the dealumination of Al-Beta, incorporation of Zr into the beta framework through solid-state ion-exchange and impregnation of the HPA. Zr-Beta is used as a Lewis acid catalyst to catalyze the transfer hydrogenation of furfural and levulinic acid/ester using 2-propanol as a hydrogen donor. To deal with the inability of Zr-Beta to catalyze the hydrolytic ring-opening of furans toward GVL, phosphotungstic acid (HPW) and silicotungstic acid (HSiW) were introduced to the Zr-Beta as BrOnsted acid sites. The characterization of the catalysts using XRD, UV–vis and XPS as well as TPD of ammonia and FT-IR spectroscopy of the adsorbed pyridine revealed that the HPA/Zr-Beta possesses both isolated Lewis and BrOnsted acid sites. When they were applied to the one-pot cascade conversion of furfural, the initial activity of the HPA/Zr-Beta toward GVL production were 2–3 times greater than that for Zr-Beta due to the enhanced hydrolytic ring-opening of the furans promoted by the added BrOnsted acidity. Especially, HPW loaded Zr-Beta demonstrated a remarkable GVL yield of ∼70% at 433 K after 24 h due to its high thermal stability and stronger BrOnsted acidity, and its activity far surpasses that of the conventional Sn-Al-Beta zeolite (∼40%). Overall, this study demonstrates that an incorporation of HPA into Lewis acid Sn- or Zr-Beta zeolites is an effective strategy to create isolated Lewis and BrOnsted acid sites within a single catalyst, thereby allowing the selective cascade catalysis for the cost-effective production of high-value chemicals.

Organosolv lignin extracted from the four representative lignocellulose feeds of oil palm empty fruit bunch (agricultural waste), oak (hardwood), pine (softwood) and Miscanthus giganteus (grass) is depolymerized using Ru/H-zeolite β to produce phenolic hydrocarbons. The bulky methoxy functionality, which is rich in oak and pine, sterically hindered the ether bonds, decreasing the yields of phenolic monomers and improving the β–β coupling to repolymerize lignin fragments. Both depolymerization and repolymerization are improved at a higher reaction temperature. The structures and the reaction behavior of organosolv lignin are observed using NMR, GPC, N2-physisorption, SEM and DLS analysis methods.

The selective condensation of 2-methylfuran and furfural to C15 compounds is performed using supported phosphotungstic acid catalysts in a continuous-flow fixed-bed reactor. The formation of unwanted viscous tetramers (C20) is suppressed when the continuous-flow reaction system is used. Stronger acids, as measured by pKa, improved the condensation of furans, but the number of acid sites was rather weakly correlated with the catalytic activity. Suppressed catalytic activity in tiny pores smaller than 2.8–6.3 nm was also observed. Based on the observations of the acidity and pore structures, a strategy with which to design optimum catalysts for the condensation of furan compounds is suggested.

Previous work has shown that sulfonation and oxidation of chemi-thermomechanical pulps (CTMPs) significantly enhanced enzyme accessibility to cellulose while recovering the majority of carbohydrates in the water-insoluble component. In the work reported here, modified (sulfonated and oxidized) CTMPs derived from hard-and-softwoods were used to produce a DL-mix of lactic acid via a chemo-catalytic approach using lanthanide triflate (Ln (OTf)3) catalysts (Ln = La, Nd, Er, and Yb). It was apparent that sulfonation and oxidation of chemi-thermomechanical pulps (CTMPs) also enhanced Ln(OTf)3 catalyst accessibility to the carbohydrate components of the pulps, with the Er(OTf)3 catalysts resulting in significant lactic acid production. Under optimum conditions (250 °C, 60 min, 0.5 mmol catalyst g−1 biomass), 72% and 67% of the respective total carbohydrate present in the hard-and-softwood CTMPs could be converted to lactic acid compared to the respective 59% and 51% yields obtained after energy-intensive ball milling.

This study examined the effects of oxygen species on the unsteady-state oxidative coupling of methane (OCM) using a lengthy catalyst bed of Na

SiO

A complete hydrodeoxygenation(HDO) of vanillin to yield cycloalkanes was performed using bifunctional Ru loaded HZSM-5 catalysts with different metal loadings (0.1, 0.5, 1, 3, and 5 wt%) and Si/Al2 ratios (Si/Al2 = 23,300) in n-octane/water biphasic system. Both the reaction pathway and product distribution were influenced by the metal/acid balance of the catalysts. Higher metal/acid ratio promoted Caryl-C cleavage reaction, resulting in the increased yield of cyclohexane. Synergetic effect of metal and acid sites was observed in the bifunctional catalyst, attaining as high as 40-fold increase of metal efficiency in the ring hydrogenation reaction, compared to lone metal site catalyst. The effect of solvent composition was evaluated, revealing that the presence of water promoted the overall HDO reaction. By balancing metal/acid and introducing appropriate solvent system, efficient catalytic system that minimized carbon loss and improved metal efficiency for vanillin HDO was obtained.

The application of naturally abundant resources as alternative raw materials has been intensively studied because it is more economical and is also able to reduce solid waste generated by various industries. In this study, SiO2 was successfully extracted from sugarcane bagasse ash and pumice stone by using a low-temperature alkaline extraction method and acid precipitation process with high purity levels (98.4% and 96.3%, respectively). The extracted SiO2 was used as a catalyst support for Ag2O, where the two components were integrated with the impregnation method. The resulting catalysts were characterized to understand their structural features, as well as to see the catalytic performance. All samples of catalysts succeeded to reduce 4-nitrophenol, with differences in their reaction rates. The sample of Ag2O/SiO2, in which SiO2 was extracted from pumice stone, shows higher catalytic activity than that of sugarcane bagasse ash. From the analysis in this study, it is found that the aforementioned phenomenon is closely related to the structural properties of both Ag2O and SiO2 as the catalyst and its support.

The oxidative coupling of methane using silica-supported Na2WO4 (Na2WO4/SiO2) catalysts is observed by adjusting additives in order to understand the roles of additives and to design more efficient catalysts. By observing the effects of additives on the catalytic OCM activity of Na2WO4/SiO2 catalysts, the reducibility of metal additives, quantified by the standard reduction potentials, is observed to improve the methane conversion and olefin selectivity, indicating that the active sites of activating methane and dehydrogenating paraffin are identical. The supply of oxygen atoms from more easily reducible additives to tungsten oxide manipulate the OCM activity as described by the standard reduction potentials of the additives. The crystal and electronic structures of the catalysts depend on the additives, which can also be used to adjust the catalytic activity.

In this study, oxidative coupling of methane (OCM) was carried out to produce C2 and C3 hydrocarbons directly from methane in a plasma-catalyst hybrid system. Since catalyst only reaction requires high temperature above 700 °C, dielectric barrier discharge (DBD) plasma was applied as plasma source to lower the reaction temperature. Among various supports, only SiO2 showed the higher yield than plasma only reaction when combined with DBD plasma, which led us to focus on the SiO2-based catalyst. It was found that Ag/SiO2 demonstrated the highest C2+ hydrocarbon yield of about 9.7% at 385 °C. In this process, oxygen was proved to play an essential role in the coupling of methane to C2+ hydrocarbons over Ag/SiO2 catalyst. However, Ag/SiO2 catalyst under plasma condition became deactivated with time-on-stream because of coking. It was demonstrated that plasma regeneration at 378 °C gave rise to the full recovery of activity while thermal regeneration did not due to the partial removal of coke and the sintering of Ag.

We have previously shown that an activated carbon-supported ruthenium catalyst promoted with ReO x (RuRe/AC) is highly active for the hydrodeoxygenation (HDO) of lignin-derived phenols (e.g., guaiacol). In this work, we have investigated the effect of carbon supports on the structure and HDO activity of bimetallic RuRe particles using three different carbon supports, i.e., activated carbon (AC), carbon black (Vulcan carbon, VC), multi-walled carbon nanotube (MWCNT). The MWCNT- and VC-supported catalysts show remarkably enhanced activity and hydrocarbon selectivity for the HDO of a range of phenolic molecules (i.e., guaiacol, eugenol, benzyl phenyl ether) compared to RuRe/AC. STEM-EDS and XPS analyses reveal that bimetallic RuRe particles are more common than monometallic Ru or Re particles in the VC- and MWCNT-supported catalysts, and hexavalent rhenium species are more easily reduced to tetravalent rhenium during the HDO reactions in these catalysts, suggesting that Ru and Re in close proximity are required for the efficient hydrogenolysis of phenols. The formation of bimetallic particles on the AC surface is likely hindered by high microporosity and high surface oxygen functionalities, both of which restrict the mobility of Re and Ru for assembly.

The two-step hydrodeoxygenation of pine sawdust pyrolysis oil, or bio-oil, is performed using pairs of first-step hydrotreating and second-step hydrodeoxygenating catalysts. The reaction results demonstrate that the combination of hydrotreating carbon-supported 5 wt% Pd (5 wt% Pd/C) and hydrodeoxygenating tungstate-zirconia-supported 3 wt% Ru (3 wt% Ru/WZr) catalysts produced the highest yield of oil products and the lowest yield of cokes and tars. The hydrodeoxygenated liquid products are further analyzed using FT-IR, which indicates the removal of carbonyls and hydroxyls along with an increase of methyls. The roles of hydrotreating Pd/C are further studied using GC/MS results of the hydrotreated liquid products; these results indicate that the hydrogenation of carbonyls to alcohols and the saturation of furans occur during the first step of the hydrotreating process. The removal of carbonyls and unsaturated furans can suppress their strong adsorption to noble metal surfaces and then their carbonization to cokes.

This study investigates the use of combination of metal and solid-base catalysts for effective depolymerization of lignin into monophenol-rich bio-oil in supercritical ethanol through a synergy of base-catalyzed solvolysis and metal-catalyzed hydrogenolysis. The results showed that a combined catalyst of Ru/C and MgO/ZrO2 resulted in a significant decrease in the molecular weight of bio-oil, an increase in the yield of phenolic monomers, and the improved deoxygenation degree of bio-oil compared to the single catalyst condition. The synergic role of metal and base catalysts during lignin depolymerization was examined through comprehensive analysis of reaction products.

Strong adsorption of phenolics on zeolite acid sites causes high trapping inside zeolite channels and low catalytic activity of zeolite-supported catalysts in atmospheric pressure hydrodeoxygenation (HDO) of lignin-derived phenolics. This adsorption is more severe at low temperatures, and restricts the atmospheric HDO of phenolics to high reaction temperatures. The purpose of this research was to develop a catalyst with low phenolic trapping potential and high HDO efficiency under mild reaction conditions. Among the tested catalysts (Fe/HBeta, FeReOx/HBeta, Fe/MCM-41, ReOx/MCM-41, FeReOx/MCM-41, Fe/ZrO2 and FeReOx/ZrO2), the novel catalyst of FeReOx/ZrO2 exhibited the highest catalytic efficiency for mild-condition (pressure: 1 atm and temperature x/ZrO2 displayed remarkably enhanced performance, and its catalytic activity for the HDO of m-cresol at 350 °C was almost twice higher than that of Fe/HBeta(38) at 500 °C. Importantly, FeReOx/ZrO2 revealed a high HDO efficiency (BTX yield of 50.5 wt% with phenolic trapping below 5 wt%) at a low temperature of 250 °C, while Fe/HBeta(38) almost lost its entire catalytic activity at this temperature, and gave a low BTX yield of 3.0 wt% with a high trapped phenolic yield of 83.1 wt%. The remarkable catalytic activity of FeReOx/ZrO2 in the HDO of phenolics at atmospheric pressure and temperatures as low as 250 °C is a result of its mesoporosity and oxophilicity as well as its well-balanced acidity induced by both rhenium oxide and zirconia support causing a high dehydration efficiency.

Oxidative coupling of methane (OCM) was performed over three structurally different LaAlO3 perovskite catalysts prepared using the citrate sol-gel (LaAlO3_C), solid-state (LaAlO3_S), and hard-templating (LaAlO3_H) methods. Although three LaAlO3 perovskite catalysts were successfully prepared, the catalytic activity of the catalysts was significantly different depending on their preparation method. The preparation method, and thereby the crystallinity of the LaAlO3 perovskite catalysts, has a strong influence on the amount of surface lattice oxygen species, which play a key role in producing C2 compounds in OCM. Consequently, the C2 yield over LaAlO3 catalysts shows the same order as that shown by their relative crystallinity (LaAlO3_C > LaAlO3_S > LaAlO3_H). In other words, high crystallinity enabled LaAlO3 catalysts to retain a large amount of surface lattice oxygen species, resulting in a higher C2 yield. Among the tested catalysts, LaAlO3_C, prepared using the citrate sol-gel method, retained the highest amount of lattice oxygen species owing to its high crystallinity and exhibited the highest C2 yield (ca. 12% at 750 °C) for OCM.

Recent studies show that fast hydropyrolysis (i.e., pyrolysis under hydrogen atmosphere operating at a rapid heating rate) is a promising technology for the conversion of biomass into liquid fuels (e.g., bio-oil and C4+ hydrocarbons). This pyrolysis approach is reported to be more effective than conventional fast pyrolysis in producing aromatic hydrocarbons and also lowering the oxygen content of the bio-oil obtained compared to hydrodeoxygenation (a common bio-oil upgrading method). Based on current literature, various non-catalytic and catalytic fast hydropyrolysis processes are reviewed and discussed. Efforts to combine fast hydropyrolysis and hydrotreatment process are also highlighted. Points to be considered for future research into fast hydropyrolysis and pending challenges are also discussed.