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[Display omitted] • A synthetic route to novel high-energy–density biofuels from α-pinene. • Alkylation of α-pinene with lignin-based phenols followed by hydrodeoxygenation. • Potential biomass-based high-energy–density fuels with favorable properties. The present work investigated the alkylation performance of various lignin-based phenols as carbon-increasing blocks for α-pinene to create novel biomass-based high-energy–density fuels (HEDFs). H 3 PW 12 O 40 (HPW) was identified as an effective catalyst for the Friedel-Crafts alkylation of α-pinene and phenol substrates, with guaiacol showing the highest activity followed by phenol, anisole, 4-methylguaiacol, 4-ethylguaiacol, and 4-propylguaiacol. Moreover, guaiacol also displayed the best selectivity for monoalkylated products. Blended alkylated products of phenol, anisole, and guaiacol could be fully hydrodeoxygenated under the catalysis of HPW and Pd/C. However, the dialkylated components from 4-methylguaiacol, 4-ethylguaiacol, and 4-propylguaiacol were challenging to hydrodeoxygenation under the same conditions. After vacuum distillation, all refined products from different phenol substrates exhibited promising fuel properties, suggesting the potential for developing high-energy–density biofuels from α-pinene and lignin-based phenols using the approach outlined in this work. [ABSTRACT FROM AUTHOR]

• A series of novel Ni-M/MXene (M = Pd, Pt, Ru) bimetallic catalysts were prepared. • Ni-Pd/MXene provided the highest conversion of guaiacol (100%) and Y HDO (35.15%). • A "relay catalytic" effect induced by Ni and Pd is key to boost the guaiacols HDO. • Kinetic modelling based on the likely catalytic reaction network over Ni-Pd/MXene. Currently, traditional hydrodeoxygenation (HDO) catalysts have various shortcomings such as low activity levels and vulnerability to deactivation. Therefore, a series of MXene-supported Ni-M (M = Pd, Pt, Ru) bimetallic catalysts were designed and prepared. The above catalysts were also comprehensively characterized using XRD, BET, H 2 -TPR, NH 3 -TPD, XPS, SEM and TEM methods. Moreover, due to the largest particular specific surface area, moderate amount of acid sites and the strongest three-electron transfer channels between support and active metals of Ni-Pd/MXene catalyst, it exhibited the superior catalytic performance to achieve 100 % guaiacol conversion and 35.15 % highest overall yields of HDO products (Y HDO) under the optimal reaction conditions (at 340 °C for 8 h, utilizing in-situ hydrogen source: formic acid). Furthermore, a detailed discussion on the main reaction pathways and mechanism of guaiacol HDO catalyzed by Ni-Pd/MXene was provided, an unique bimetallic synergistic "relay catalytic" theory has been proposed. Kinetic studies revealed that phenol, one of the main HDO products, is primarily generated via guaiacol demethoxylation, while catechol dehydroxylation to phenol acts as the rate-determining step. This work introduces a new strategy for the development of HDO catalysts. [ABSTRACT FROM AUTHOR]

• The low loading of Ni/C catalysts are used for the HDO of guaiacol and bio-oil. • The guaiacol is completely converted to cyclohexanol over 5%Ni/C at 200 °C and 2 h. • The phenols derived from bio-oil are gradually converted to alcohols and cycloalkanes. • The C-O bond between benzene ring and methoxy group in guaiacol is first cleaved. It is significant to improve the quality of bio-oil to produce cyclohexanol and cycloalkane products through hydrodeoxygenation (HDO). Excellent and inexpensive catalysts facilitate the upgrading of bio-oils and phenols under mild conditions and subsequent industrial applications. Catalysts synthesized in previous studies have a high metal loading, resulting in increased production costs. Herein, a series of low loading of Ni/C catalysts (1–7%) were synthesized and applied for the HDO of lignin bio-oil and derived phenols. The characterization results demonstrated that 5%Ni/C possessed the smallest metal particle size and sufficient amount of Ni0, achieving a well conversion of phenols in bio-oil. A low loading of 5%Ni/C can produce enough reactive H species in a short time. Therefore, guaiacol was completely converted to cyclohexanol over 5%Ni/C at 200 °C and 2 h. The products of bio-oil conversion were gradually hydro-deoxidized to cyclohexanol compounds and cycloalkanes over 5%Ni/C. The deuterium experiment revealed that the major pathway for the transformation of guaiacol was to first break the C-O bond between the benzene ring and methoxy group. Besides, other bio-oil derived phenols (phenol, cresol and vanillin, etc.) were fully transformed to related cyclohexanols over 5%Ni/C. This study provides a prospective catalyst for the HDO of lignin bio-oil and derived phenols. [ABSTRACT FROM AUTHOR]

This study employed the DFT method to calculate the catalytic activity of various organic functional groups during phenol production on seaweed biochar. It also used machine learning to analyze the correlation between electronic structure parameters of different sites and their catalytic activity. Finally, it summarized the essential characteristics of the most active site. [Display omitted] • Establishing cluster models of algal biochar catalyst and its catalytic mechanisms for lignin upgrading using a DFT method. • Decision trees, random forests, gradient boosting, and extreme gradient boosting were used to establish prediction models. • The random forest method performs best in revealing catalyst reactivity. • Fukui function is an effective descriptor for evaluating the reaction activity of adsorption sites. With the continuous development of the industrialization process, the reserves of primary energy sources such as petroleum have sharply decreased. The development of efficient and economical catalysts is of great significance in promoting the rapid pyrolysis of biomass to produce high-quality liquid fuels and chemicals. In this study, density functional theory (DFT) and machine learning (ML) were used to explore the catalytic reaction mechanism of guaiacol pyrolysis over seaweed biochar catalyst. Models of algae biochar catalysts with oxygen-containing or nitrogen-containing functional groups were established, and the surface transformation mechanism of guaiacol over the biochar catalyst was calculated using DFT. Furthermore, four machine learning methods (decision tree (DT), random forest (RF), gradient boosting (GB), and extreme gradient boosting (XGBoost)) were used to establish a mathematical model based on catalyst characteristics for predicting key intermediate adsorption energy during catalysis reaction. The fitting results and performance analysis of each prediction model show that the RF method-trained model has the highest accuracy. Fukui function (f-) was proved as an effective descriptor to evaluate the reactivity of adsorbed sites. This study provides a pathway to developing more efficient biochar catalysts, which could lead to more sustainable and environmentally friendly energy solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Optimization of HDO reaction conditions for guaiacol with different catalysts. • The electron transfer between bimetals resulted in a high catalytic activity. • Guaiacol is converted to cycloalkanes by HDO under mild conditions. • Fe 10 Ni 1 /h-BN (10 %) shows good reusability after five cycles. Catalytic hydrodeoxygenation (HDO) was the essential step for fuel production through the conversion of lignin-derived phenolic compounds to C6-C9 cycloalkane. In this study, Fe-Ni supported on the hexagonal boron nitride (h-BN) catalysts were synthetized and applied in the hydrodeoxygenation of guaiacol derived from lignin to cycloalkanes. The performance of FeNi/h-BN was investigated. The synergistic effect of bimetals can make transition metals show the same catalytic performance as precious metals, among which Fe 10 Ni 1 /h-BN (10 %) catalyst had the highest catalytic activity for the generation of cycloalkanes. The conditions of reaction temperature and reaction time were optimized. Guaiacol had high conversion (>98 %) and cycloalkane selectivity (98.4 %) in decalin solvent, because the interaction between Ni and Fe promotes the reduction of metal sites and the adsorption of hydrogen, and the electron transfer of Fe to Ni weakens the C O bond of the substrate intermediate, leading to its cracking and promoting the formation of cycloalkanes. At the same time, cyclohexanol was the main product in the aqueous phase, and the yield of the target product cycloalkanes was low, only 15.9 %. The main reasons were the competition between the oxygen of the oxygenated solvent and the intermediate of the reactant, and the ring opening reaction of cyclohexane in the aqueous phase, which limits the reaction of HDO. According to the change trend of the products under different conditions, the reaction path of guaiacol hydrodeoxygenation to prepare cycloalkane fuel was obtained. Catalyst after cycle test 5 times, maintain a good activity, total hydrocarbon production rate remained at 79.3 %, conversion rate, at 82.6 %. [ABSTRACT FROM AUTHOR]

• First measurements laminar burning velocity for guaiacol. • Product quantification during jet-stirred reactor oxidation in extended conditions. • A new validated detailed kinetic model for anisole and guaiacol combustion. Anisole and guaiacol are both used as surrogates for lignin-derived biofuel. However, while the oxidation reaction mechanisms of anisole can be validated against a large set of experimental data, experimental measurements and models for guaiacol are limited. In this context, in addition to measuring adiabatic laminar burning velocities of both fuels using a flat flame burner, the oxidation of guaiacol was investigated at temperatures between 600 and 925 K. A near-atmospheric pressure jet–stirred reactor was used for three equivalence ratios (0.5, 1 and 2) with a high helium dilution. The experiments yielded mole fractions of 22 reaction products, among which two new species, benzodioxole and benzodioxole-2-one, were identified. All the measurements made in this work, along with extensive literature data on anisole, were compared with the predictions of a newly developed kinetic model. A good agreement was found between kinetic modeling and experiments, showing improved prediction for some species relative to the existing literature guaiacol oxidation models. Flow-rate analyses are also discussed both in flames and in the jet-stirred reactor, especially focusing on the formation of the newly detected products. [ABSTRACT FROM AUTHOR]

[Display omitted] • A poplar lignin derivate was significantly hydroconverted to cyclanes over Ni/β 25. • H...H and H+ are the main active hydrogen species for the catalytic hydroconversion. • DFT calculations combined with experiments further proved the reaction pathway. Upgrading lignin derivatives (LDs) to cyclanes by catalytic hydroconversion facilitates the value-added utilizations. Ni 20% /β 25 was prepared via a deposition-precipitation method and used for catalytically hydroconverting guaiacol and a poplar lignin derivate (PLD). Guaiacol was completely converted to cyclohexane (CH) as the main product in the yield of 93.3 mol% at 220 °C under initial hydrogen pressure of 4 MPa for 2 h, while the PLD was significantly converted to cyclanes over Ni 20% /β 25 for 8 h. Density functional theory combined with experiments explained the related mechanisms, i.e. , H 2 was activated to H...H, which was split to relatively mobile H+ and immobile H- over Ni 20% /β 25. H...H transfer to benzene ring (BR) leads to BR hydrogenation and subsequent H+ transfer to the oxygen atom in -OCH 3 and -OH connected to the hydrogenated BR induces the demethoxylation and dehydroxylation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metallic Co was successfully introduced into Co-promoted MoS 2 catalyst. • Metallic Co accelerated the H 2 dissociation and then enhanced the deoxygenation activity. • Co–Co 9 S 8 –MoS 2 catalyst allowed the reaction temperature for cleaving C aromatic –O bond lowered to 120 °C. • Co–Co 9 S 8 –MoS 2 catalyst exhibited high stability and good universality in the deoxygenation reactions. • Aromatics selectivity could maintain to 99.8 % even at 4.0 MPa H 2 pressure. The formidable challenge for the deoxygenation of lignin-derived aromatic oxy-compounds into arenes under mild conditions is how to engineer a robust catalyst. In this study, Co–Co 9 S 8 –MoS 2 catalyst was prepared via thermal decomposition, in–situ sulfidation and following by H 2 reduction, where Co was highly dispersed and mainly existed in the species of metallic Co and Co 9 S 8. This catalyst exhibited high activity, allowing the reaction temperature for cleaving C aromatic –O bond lowered to 120 °C, which was attributed to that metallic Co accelerated the H 2 dissociation and then enhanced the deoxygenation activity. Co–Co 9 S 8 –MoS 2 also presented a high stability: both the conversion and product selectivity were unchanged after 8 continuous cycles, and the characterization results evidenced almost no structure change and sulfur loss during the deoxygenation reaction. In addition, other 20 aromatic oxy-compounds including acid, ester, guaiacol and dimer lignin linkages were also successfully deoxygenated, and the arenes selectivity could maintain higher than 98 %. This work offered a new strategy for constructing metal–sulfide–MoS 2 type catalysts and provided an efficient route towards the practical application in bio-oil upgrading. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cotton stalk-derived soluble portion produce CHs and cyclanes over Ni/sepiolite via CHC. • Ni/sepiolite displayed a high activity of CHC in ODB, BOB, and guaiacol. • H...H and H+ are main active hydrogen species in CHC of ODB, BOB, and guaiacol. Catalytic hydroconversion (CHC) of a lignin-derived soluble portion to value-added chemicals is of great significance. Ni/sepiolite was successfully prepared via a impregnation method and used for the CHC of a cotton stalk-derived soluble portion (CSDSP). Cyclanes and cyclohexanols are the main products with total relative content of 64.7% from the CHC of CSDSP over Ni/sepiolite. To better understand the reaction mechanism, the CHC of oxydibenzene (ODB), benzyloxybenzene (BOB), and guaiacol over Ni/sepiolite were investigated. They were completely converted at 240 °C under 4 MPa of initial hydrogen pressure. According to the resulting products, H...H and H+ are the main active hydrogen species in the CHC and H+ transfer induces the cleavage of -CH 2 -O- bond in BOB followed by hydrogenating benzene ring (BR), while the CHC of ODB and guaiacol proceeds via the hydrogenation of BR and subsequent cleavage of -CH 2 -O- bond. [ABSTRACT FROM AUTHOR]

[Display omitted] • Non-noble CoNi alloy catalysts have efficient hydrogenation ability for guaiacol. • Synthesis of mesoporous rod-shaped catalysts through carbon reduction using MOF. • Guaiacol hydrodeoxidation reaction takes place in a mesoporous structure. • Hydrogen absorption capacity is key to reducing hydrogenation reaction conditions. Selective hydrodeoxygenation (HDO) of guaiacol is a green and sustainable method to produce cyclohexanol. However, developing an economically efficient and highly selective non-precious metal catalyst for the HDO reaction remains a significant challenge. Here, we synthesized rod-like CoNi alloy catalysts via calcination a precursor of CoNi-BTC metal–organic framework (MOF). And a selectivity up to 94.9% can be achieved for cyclohexanol under mild reaction conditions. According to the analysis of characterization, the specific surface area and pore size had a dual impact on the catalyst activity calcinated at different temperatures. The synergistic effect of the CoNi alloy also led to an enhanced hydrogen adsorption capability of the catalyst, resulting in a significant enhancement in catalytic activity compared to the monometallic catalyst. This article provides a reference for the rational design of alloy MOF materials for catalyzing high-performance HDO of guaiacol. [ABSTRACT FROM AUTHOR]

Highlights • Catalysts with tuneable acidity and surface area are produced by a scalable process. • Increasing the amount of silica in Al 2 O 3 -SiO 2 catalysts promotes the HDO reaction. • Supports' isoelectric points give easy access to the final catalysts performance. • Aromatic compounds are selectively obtained with good conversions (up to 91% in 1 h). • Both regenerated and bimetallic catalysts are prepared and successfully tested. Abstract The hydrodeoxygenation (HDO) of guaiacol is a model reaction for the upgrading of the lignin component of bio-oils, in the framework of the production of fuels from the most abundant and renewable biomass source. While Ni-based catalysts are now widely recognized as suitable catalysts for this reaction, the role of the catalyst support is far less investigated. In this work, Ni-based catalysts for the HDO reaction of guaiacol were prepared using a series of alumina-silica supports characterized by a different amount of silica (0–40%). A wide range of metal contents (0–45%) was also investigated. The reaction was performed in H 2 at 50 bar and 300 °C, determining conversion, product distribution and HDO degree. Besides a notable role played by the Ni amount, the catalyst performance is markedly affected by the morphological and surface features of the support. The measured isoelectric point of the bare supports appeared to be predictive of the final performance of the relative Ni-based catalyst: the more acidic the isoelectric point, the better the overall performance of the catalyst. A regeneration treatment in mild conditions was developed to fully restore the starting surface features of the catalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Deoxygenation of guaiacol with the synthesized Rh/ZrO 2 catalyst was achieved. • High yield of oxygen-free product (87.7mol%, cyclohexane) was obtained. • The suitable reaction conditions were 5 wt.% guaiacol, 300 °C, 7 MPa and 3 h. • Kinetics at four temperatures fit well to a pseudo-first-order kinetic model. Abstract To explore the mechanism for hydrodeoxygenation (HDO) of bio-oil, which contains large compounds that share similar molecular structures of phenyl ring with oxygen-containing functional groups, guaiacol as a typical model compound of lignin-derived bio-oil was hydrotreated at 150–350 °C under 3–7 MPa (H 2) using the synthesized zirconia-supported Rh catalyst in a batch reactor. With Rh/ZrO 2 catalyst, guaiacol can be completely converted where reaction temperature plays a decisive role and significantly affects the degree of hydrogenation. HDO Process was optimized with insight into effects of different reaction parameters, including H 2 pressure, reactant concentration, reaction time and temperature, on the whole process of HDO and formation of undesired oxygen-contained products. The optimum reaction conditions were 5 wt. % guaiacol, 300 °C and 7 MPa in which guaiacol could be completely deoxygenated with 87. 7 mol% oxygen-free product of cyclohexane in 3 h and the desired O/C and H/C ratios of products were obtained. A specific reaction network including three main steps: "guaiacol → 1-methyl-1,2-cyclohexanediol → cyclohexanone and cyclohexanol → completely deoxygenated compounds of cycloalkanes", was deduced by a comprehensive study on different reaction parameters and a typical key reaction network for HDO of lignin-derived bio-oil is proposed based on model compounds studies. Kinetic model for HDO of guiaacol with the Rh/ZrO 2 catalyst was proposed based on the credible pathway and it fits well to a pseudo-first-order kinetic model that the R 2 values obtained for the fittings were all above 0.98 at four temperatures. At low temperature of 150 °C, the kinetically relevant step is hydrogenation of the aromatic ring, yielding 90 mol% 1-methyl-1,2-cyclohexanediol, while at high temperature (≥300 °C), the kinetically relevant step is the complete deoxygenation of oxygen-containing functional groups which mainly yields cyclohexane. These results would be helpful to further understand the HDO mechanism of lignin-derived bio-oil, and the excellent performance of Rh/ZrO 2 demonstrated its potential application in bio-oil hydrodeoxygenative upgrading process. [ABSTRACT FROM AUTHOR]

Biomass gasification is a primary thermochemical conversion technology for transforming woody biomass feedstocks into a range of renewable fuels and chemicals. However in practice during biomass gasification, tar formation is practically unavoidable and tar removal during downstream synthesis gas cleaning is crucial to achieving high-quality synthesis gas at commercial scale. A category of catalytic tar reforming (tar cracking) catalysts typically utilizes precious metals including rhodium, which shows high reactivity toward gasification tar, resists coking and is more tolerant to sulphur compared to nickel. As such, they are similar to automotive exhaust after-treatment catalysts. In this study we evaluated how a commercial automotive catalyst performed as a gasification tar reforming catalyst. We tested the catalyst at bench scale for methanol reforming and tar reforming at 700 °C using 80/20 mixtures of methanol/water, and 79.5/20/0.5 mixtures of methanol/water/tar and methanol/water/guaiacol in flowing nitrogen. Methanol was 95% converted to synthesis gas at 700 °C and the catalyst did not deactivate during 48 h on stream. Methanol/water mixtures containing 4925 ppm gasification tar also reacted readily over the catalyst to produce syngas, but catalyst deactivation occurred over tens of hours of continuous operation, indicated by decreased conversion of the methanol/tar feed. The catalyst was regenerated by calcining in air at 500 °C, which allowed catalyst to operate for 120 h. Methanol/water/guaiacol mixtures also reacted readily to produce syngas, but as with tar, the catalyst deactivated over tens of hours continuous operation with methanol/guaiacol feed. SEM data confirmed that coking of the catalyst was the likely cause of deactivation. At relatively high reaction temperature and contact times of seconds used in this study, guaiacol was completely deoxygenated, but a fraction of the guaiacol was methylated over the catalyst to form methyl-substituted benzenes, toluenes and xylenes (BTX). [ABSTRACT FROM AUTHOR]

Understanding the pyrolysis mechanism of lignin is of great importance for improvement of thermochemical conversion processes and upgrading of biofuels. In this work, the pyrolysis of lignin model compound, guaiacol, at atmospheric pressure has been studied in a flow reactor by synchrotron vacuum ultraviolet photoionization mass spectrometry. Over 50 species were detected and identified in guaiacol pyrolysis, including alkanes, alkenes, cyclic alkenes, dienes, alkynes and aromatics. Major pathways proposed, including homolytic cleavage of O-CH 3 bond, isomerization, dehydrogenation and hydrogenation, were evaluated using quantum chemical calculations. In the proposed pathways, homolytic cleavage of O-CH 3 bond is regarded as an important route for the formation of catechol. H-atom and CH 3 -radical assisted demethoxylation mechanisms were proposed to interpret the formation of phenol and cresol, respectively. Furthermore, an energetically advantageous route including intramolecular H-immigration, ring-opening and decarbonylation was proposed to account for the formation of C 4 products. A series of aromatic products were detected in this work, which is helpful to understand the coking mechanism during pyrolysis of lignin. [ABSTRACT FROM AUTHOR]

Catalytic hydrodeoxygenation (HDO) is a promising technology for improving the properties of pyrolysis bio-oils. However, the role that intermolecular reactivity between the numerous chemical components of bio-oil plays on the overall performance of the process has been scarcely investigated. In order to gain additional insights into the network of chemical processes taking place during bio-oil upgrading, the present work investigates the hydrodeoxygenation of mixtures of guaiacol and propionic acid using Ni based catalysts supported on solids exhibiting different acidity and textural characteristics: hierarchical ZSM-5 (h-ZSM-5), SBA-15 and Al-SBA-15. In addition, to the products of the HDO of each component of the binary mixture, such cyclohexane and propane, this work shows that hydrodeoxygenation is coupled with esterification, which occurs as a consequence of the in situ formation of methanol by demethoxylation of guaiacol, and other alcohols produced by hydrogenation. Minor contributions of alkylation reactions to the final product distribution are also revealed. Those secondary processes increase the chain length of the products and they contribute positively to avoid carbon losses in the gas phase. Results reported here indicate that the use of acidic supports improves the catalytic behavior leading much higher HDO degree. In this sense, Ni/h-ZSM-5 catalyst shows HDO values close to 100% and significant esterification activity, becoming a very promising catalyst for improving bio-oils properties as advanced biofuel. [ABSTRACT FROM AUTHOR]

The effects of molecular weight on the pyrolysis products properties of alkali lignin were investigated by using thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TG-FTIR) and tube furnace. Four lignin samples, including pure alkali lignin (AL), more than 10 kDa lignin fraction (AL-10kDa), 5–10 kDa lignin fraction (AL-5kDa) and 1–5 kDa lignin fraction (AL-1kDa) were firstly prepared by ultrafiltration membrane technology. Then the thermal behavior and volatile evolution patterns of the four lignin samples were investigated by TG-FTIR, and the component properties of condensable and incondensable products obtained from tube furnace were characterized by the gas chromatography/mass spectroscopy (GC/MS) and gas chromatography (GC). TG-FTIR results indicated that the molecular weight of lignin was not significantly affected on the evolution temperature ranges and volatile product species, while has an obviously effect on the total yields of CH 4 , CO 2 , phenols and aromatics products. GC/MS and GC results indicated that low molecular weight helps to crack the methoxy groups of lignin leading to the yields of CH 4 , CO, CO 2 , phenol and alkyl phenol increased, while high molecular weight favored the generation of guaiacol and alkyl guaiacol. Meanwhile, the effect of molecular weight on the yields of aromatics was also affected by the pyrolysis temperature. [ABSTRACT FROM AUTHOR]

The performance of spark ignition engines is highly dependent on fuel anti-knock quality, which in turn is governed by autoignition chemistry. In this study, we explore this chemistry for various aromatic oxygenates (i.e., anisole, 4-methyl anisole, 4-propyl anisole, guaiacol, 4-methyl guaiacol, 4-ethyl guaiacol) that can be produced from lignin, a low value residual biomass stream that is generated in paper pulping and cellulosic ethanol plants. All compounds share the same benzene ring, but have distinct oxygen functionalities and degrees of alkylation. The objective of this study is to ascertain what the impact is of said side groups on anti-knock quality and, by proxy, on fuel economy in a modern Volvo T5 spark ignition engine. To better comprehend the variation in behavior amongst the fuels, further experiments have been conducted in a constant volume autoignition device. The results demonstrate that alkylation has a negligible impact on anti-knock quality, while the addition of functional oxygen groups manifests as a deterioration in anti-knock quality. [ABSTRACT FROM AUTHOR]

The promoting effect of Cu on Re/SiO 2 catalysts was studied for guaiacol hydrodeoxygenation. Cu(x)Re/SiO 2 catalysts containing from 0 to 1.91 wt% Cu and 13 wt% of Re were prepared by successive wet impregnation and characterized using X-ray diffraction (XRD), nitrogen sorption, CO chemisorption, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and surface acidity techniques. Batch reactions were carried out at 300 °C and 5 MPa of H 2 . The Cu(x)Re/SiO 2 catalysts displayed higher activities than the Re/SiO 2 catalyst with a maximum activity at 1.58 wt% Cu. At loadings above 1.5 wt%, aggregate formation and a loss of metallic Re active sites lead to a decreased activity. The increase of the activity was attributed not only to Cu increasing the Re reducibility, but also to Cu somehow increasing the metallic Re active sites favoring guaiacol conversion. All catalysts displayed the same product distribution, confirming that the Cu in the Cu(x)Re/SiO 2 not change the nature of the active site in the metallic Re nanoparticles. [ABSTRACT FROM AUTHOR]

Catalytic upgrading of raw bio-oil and liquid–liquid extracted bio-oil (high concentrated phenolic with trace acid and acetaldehyde) with methanol over ZSM-5 catalyst had been studied in this work. Temperature played vital function and leaded to increasing gas yield but less catalyst coking. It also changed both chemical distribution and selectivity on both gas and liquid products, with aromatic concentration increasing by 34.42%. Temperature of 400 °C was selected as the optimized reaction conditions with liquid yield of 10.47 wt.% and 75.00% aromatic hydrocarbon in liquid product from 100 g biomass, only with coke yield of 1.42 wt.%. Phenolic-rich extracted bio-oil obtained higher aromatic hydrocarbon yield (7.3 wt.% increased from 1.1 wt.%) and lower coke yield (1.42 wt.% decrease from 15.79 wt.%) than raw bio-oil. Catalyst regenerated from this type of feedstock also achieved higher activity and longer useable running times on aromatic yield compared to fresh catalyst. This result suggested that lignin derived phenolic and guaiacol compounds were not the only reason caused catalyst coking on ZSM-5 catalyst. Small high active molecules of acetic acid and acetaldehyde also acted as important precursors of catalyst coke formation. [ABSTRACT FROM AUTHOR]

Ni nanoparticles have been selectively loaded inside or outside commercial carbon nanotubes by the wet impregnation method, and their catalytic performance on the conversion of guaiacol in batch reactor at 5 MPa and 573 K has been studied. Different characterization techniques were used to investigate the effect of confinement in nanotubes. The catalysts showed different selectivity to cyclohexene compared to cyclohexane was enhanced when the nanoparticles were loaded inside. This result was attributed to the different adsorption mode of the molecule inside the nanotubes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-Fe alloy supported catalysts were prepared from layered double hydroxide precursor. • Ni-Fe alloy sites facilitate the aromatic ring hydrogenation. • Alkaline MgAlO x support promotes the demethoxylation and suppresses the dehydroxylation. • Synergistic effect between Ni-Fe alloy and basic sites improves cyclohexanol selectivity. The production of cyclohexanol from non-fossil biomass is green and sustainable. Here, a series of highly dispersed Ni-Fe alloy nanocatalysts (Ni-Fe/MgAlO x) were prepared for guaiacol hydrodeoxygenation to cyclohexanol. The results show that the doped Fe led to electron-rich Ni and the introduced Mg species of the support increased the basic sites. The kinetic studies indicate that guaiacol conversion to cyclohexanol included the aromatic ring hydrogenation and the demethoxylation steps. And the Ni-Fe/MgAlO x-1 with the sites of Ni-Fe alloy could significantly reduce the E a of aromatic ring hydrogenation. Meanwhile, the Ni-Fe/MgAlO x-1 with Mg-doped support exhibited much lower E a of demethoxylation. Thus, the synergistic effects between Ni-Fe alloy and basic sites brought about high performance to cyclohexanol. Hence the Ni-Fe/MgAlO x-1 gave the highest cyclohexanol yield of 92.1%. The strategy of optimization different catalytic sites for the corresponding reaction step can provide a particular view for designing efficient catalysts in multiple-step hydrogenation/hydrodeoxygenation reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon supported Fe 3 C catalysts were prepared and applied in lignin valorization. • Lignin was converted into guaiacols with 86 wt% selectivity at a 48 wt% conversion rate at the present of catalysts. • The acid sites as electron acceptors on the Fe 3 C/C catalyst break the C-O bonds of linkages. • The metal Fe (0) nanoclusters on Fe 3 C/C surface play an important role to break the C–C bonds for producing guaiacol monomers. One-pot lignin catalytic depolymerization (LDP) under supercritical ethanol was an effective strategy for converting lignin into value-added aromatic monomers. However, complex substructure and linkages in lignin limited the development of gaining high selectivity aromatic monomers. In this study, carbon supported Fe-Fe 3 C/C based catalysts prepared using high temperature reducing method were employed as LDP catalysts. GC–MS and 1H−13C 2D HSQC NMR results of lignin oil display that the optimum Fe-C-700 catalyst can converted lignin into lignin oil consisting of guaiacol and 4-alkyl guaiacols with an 86 wt% of selectivity at a 48 wt% of conversion rate. The XRD, Raman, HRTEM, TEM-EDS mapping, and the XPS characterization results of Fe-Fe 3 C/C catalysts show that the graphitized and amorphous carbon encapsulates iron carbide nanocrystal and metal iron nanoclusters. The NH 3 -TPD and CO 2 – TPD profiles revealed a system of strong acid-base sites on Fe-Fe 3 C/C catalysts which means acid sites are responsible for C-O bonds breaking and base sites are responsible for cleavage of C–C bonds. Metal Fe (0) was considered to be a key factor to activate the hydrogen source in order to promote the hydrogenation process. [ABSTRACT FROM AUTHOR]

Abstract: To shed light into the influences of the shape of the main hydrocarbon families constituting FCC feedstocks (naphthenes and alkanes) and of the phenolic molecules size on the MFI additive function during bio-oils and traditional Fluid Catalytic Cracking feedstocks co-processing, the transformations of n-heptane in presence of phenol and guaiacol were performed over an HMFI zeolite, at 350 and 450°C. For phenol, the results were compared with those previously obtained with methylcyclohexane. A lower impact of phenol was noticed for n-heptane than for methylcyclohexane due to the easier linear alkanes diffusion into the zeolite channels, which reveals that the phenolic molecules influence on the MFI additive function could not be as critical as envisaged for a purely naphthenic feedstock. Whatever the reactant, higher temperatures do not overcome phenol deactivating effect because, once inside the zeolite structure, phenol polar molecules diffusion is very limited. An increase of the coke molecules ramification and aromaticity was observed for the n-heptane transformation in presence of phenol, instead of a reduction of the coke production from the reactant, as noticed for methylcyclohexane. Therefore, for n-heptane the further HMFI deactivation due to phenol mainly proceeds by pore blocking, contrarily to that verified for methylcyclohexane. Furthermore, the greater the size of the phenolic molecules present in the hydrotreated bio-oils, the lower their effect on the MFI additive action. In fact, bulky oxygenated molecules are preferential adsorbed close to the zeolite outer surface, from which they are more easily removed at higher temperatures. This explains the lower guaiacol deactivating effect at 450°C, when compared with phenol. [ABSTRACT FROM AUTHOR]

• Bimetallic NiCo catalyst is employed to conduct HDO of pyrolysis lignin-oil. • 100% yield of cyclohexane products is obtained at 240 °C in guaiacol HDO. • Ni-Co interaction promotes the adsorption of hydrogen and weakens the C-O bond. • Specific kinetic study is conducted to verify the reaction pathway. • The apparent Ea of guaiacol HDO on NiCo/SiO 2 -ZrO 2 is 55.9 kJ·mol−1. Catalytic hydrodeoxygenation (HDO) is a popular route to upgrade the pyrolysis lignin-oil that is abundant of phenolic compounds, and the synergistic effect of bimetal enables to improve the catalytic activity significantly. In this work, a series of non-noble metal catalysts are synthesized and their HDO performances of guaiacol are compared. Optimized NiCo/SiO 2 -ZrO 2 catalyst expresses a 100% conversion and a 99.9% selectivity of cyclohexane product, which is higher than those over Ni/SiO 2 -ZrO 2 catalyst. Catalyst characterization results demonstrate that the interaction between Ni and Co promotes the reduction of metal site and the adsorption of hydrogen, which is the crucial factor during HDO process. Besides, the electron transfer from Co to Ni species weakens the C-O bond of substrate intermediate and results in its cleavage to transform cyclohexanol to cyclohexane. This is also the rate determining step in the HDO of guaiacol. Specific kinetic study is conducted to verify the reaction pathway and the structure–activity relationship. The HDO reaction of guaiacol on NiCo/SiO 2 -ZrO 2 fits the first order kinetic model well. The apparent E a of 55.9 kJ·mol−1 is lower than those of the noble metal catalysts reported in previous studies. In addition, the upgrading of raw pyrolysis lignin-oil on this non-noble bimetallic catalyst also achieves a high HDO efficiency, with the hydrocarbon contents increased from 4.2% to 60.6%. The good HDO performance of this cheap and easy-prepared NiCo catalyst proves its promising potential in the upgrading of lignin-oil for the production of hydrocarbon fuels. [ABSTRACT FROM AUTHOR]

[Display omitted] • High lignin conversion (67–69%) was achieved with Pd-metal oxide catalysts. • Pd-Mo/biochar promoted high selectivity (57%) to C9 monomers at 240 °C, 3 h. • The total monomer yield was high (42 wt%) with Pd-Mo/biochar with low amount of heavies. • Catalytic activity to form 4-propyl guaiacol is in line with electropositivity of metal oxides. Valorizing lignin to phenolic monomers and fine chemicals is an essential component of a sustainable biorefinery that uses lignocellulosic feedstocks. In this study, Pd-metal oxides (ZrO 2 , WO x , MoO 3) supported on activated biochar (ABC) catalysts were developed for hydrogenolysis of lignin. The metals (2% Pd, 5% Zr, 5% W, 5% Mo) were supported on activated biochar using the wetness impregnation method, and the catalysts were extensively characterized. The effect of addition of secondary metals on active surface properties such as acidity, Pd metal particle size and dispersion were also evaluated. The selectivity to C9 monomeric phenols followed the trend: 2Pd-5Mo/ABC (57.3%) > 2Pd-5Zr/ABC (49.2%) > 2Pd-5W/ABC (45%) > 2Pd/ABC (42.9%). The maximum C9 phenolic monomer yield achieved in this study was ~ 22 wt%. The fractional conversion of lignin was 67–69% with Pd-metal oxide catalysts. The presence of Mo in the catalyst inhibited the hydrogenation of aliphatic C α = C β in lignin and led to the formation of t -isoeugenol, while the presence of W and Zr resulted in selective formation of the hydrogenated product, propyl guaiacol. Using model compounds, it is proved that the formation of propyl guaiacol is via hydrogenation of t -isoeugenol, and not through dehydroxylation of propanol guaiacol. The dehydroxylation activity of the catalysts is attributed to the higher Lewis acidity and electropositive nature of the metals. A notable carbon atom economy of 47–50% towards total phenolic monomers was achieved with 2Pd/ABC, 2Pd-5Mo/ABC and 2Pd-5Zr/ABC catalysts. [ABSTRACT FROM AUTHOR]