Efficient upgrading of bio-derived mixtures into low-carbon-footprint fuels and chemicals is essential for sustainable development of our society. The hydroconversion of many individual reactants present in bio-oils has already been understood considerably. On contrary, the simultaneous transformation of reactants with different functional groups has been studied only scarcely, despite it is utmost importance to understand and describe possible inhibition and deactivation effects during co-processing and to design efficient hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) catalysts. This paper describes the performance of NiMo/Al2O3 catalyst in the conversion of lauric acid or anisole mixed with indole. The conversion of anisole in its mixture with indole is significantly hindered: indole and its derivatives suppress both the hydrogenation of the aromatic ring and the hydrogenolysis of the C-O bond, thereby preventing the successful production of cyclohexane as the ultimate HDO product. The co-conversion of lauric acid and indole proceeds via a partially changed reaction route of both components compared to their individual conversion. In particular, condensation reaction products are predominantly formed by reactions of indole and lauric acid hydrogenation intermediates. These intermolecular products were found to be advantageous as they contributed to an increase in the yield of fuel-range hydrocarbons. Finally, the transformation of ternary anisole-lauric acid-indole mixture confirmed that anisole was the "weak link" in HDO/HDN of complex mixtures as indicated in conversion of binary mixtures. The study proves that a successful conversion of real bio-oil mixtures into hydrocarbons requires a systematic work towards the optimization of both catalyst design and reaction conditions.

We report for the first time a one-pot catalytic route for the selective hydrogenation of biomass-derived 5-hydroxymethylfurfural (HMF) into 1,2,5-hexanetriol and related value-added products such as 1-hydroxyhexane-2,5-dione (HHD) and 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF) using a Ru/TiO2 catalyst. In particular, the influence of the solvent composition (water-dioxane) on the reaction pathways for HMF ring opening and ring reduction products was investigated, revealing that water acts not only as a sustainable solvent but also as a reactive substrate, promoting OH-group rearrangements. Under optimized conditions, BHMTHF was obtained in >99% yield in pure 1,4-dioxane, while HHD and 1,2,5-hexanetriol were produced at 90% and 75% yields, respectively, in pure aqueous media. DFT calculations on Ru(0001) surfaces indicate that water increases the concentration of surface hydroxyl species (OH*), facilitating selective ring-opening reactions. Catalyst characterization showed minor increases in Ru particle size and solvent-dependent metallic Ru availability, influenced by carbon deposition. Nevertheless, the Ru/TiO2 catalyst retained high activity and selectivity over several cycles in both solvents. This study demonstrates a solvent-directed, highly selective strategy for converting HMF into valuable chemicals, integrating experimental and theoretical insights to advance green catalytic processes.

Hydrodeoxyge nation (HDO) of lignin-derived phenolics is a key strategy for producing renewable fuels and value-added chemicals. Conventional Ni/Al2O3 catalysts lead to the formation of undesired saturated oxygenates, due to their high tendency toward aromatic-ring hydrogenation. Here, we report that Cu incorporation into Ni/Al2O3 selectively tunes reaction pathways in guaiacol and anisole HDO. The resulting Ni-Cu/Al2O3 catalysts suppress hydrogenation and (de)methylation to different extents. While anisole conversion shows minor selectivity changes, guaiacol exhibits a pronounced shift toward deoxygenation and methylation, due to stronger inhibition of hydrogenation. Kinetic modeling reveals unequal suppression of competing pathways and corresponding changes in rate-determining steps. Notably, the shift away from hydrogenated oxygenates toward deoxygenated and methylated products persists at elevated hydrogen pressures. At 270 degrees C and 40 bar H-2, 5% Ni-5% Cu/Al2O3 achieves >70% guaiacol conversion, and this produces cyclohexane and methylated naphthenics and phenolics as primary products.

Hydrodeoxygenation (HDO) of lignin-derived phenolics offers a sustainable pathway for producing sustainable aviation fuels (SAF) and value-added chemicals. In this study, anisole was employed as a model compound to investigate HDO over Ni supported on SBA-15 and AlSBA-15. AlSBA-15 supports with varying Al contents were synthesized via direct and post-synthesis methods, both of which led to the incorporation of framework and extra-framework Al species to enhance HDO. Increasing Al content in AlSBA-15 resulted in lower specific surface area, decreased NiO reducibility, and a higher density of Lewis and Brønsted acid sites. Anisole conversion was found to be directly proportional to Ni reducibility, making AlSBA-15 with lower Al content the preferred catalyst support. The presence of Brønsted acid sites in AlSBA-15 enhanced selectivity toward C₆ deoxygenation products (cyclohexane and benzene) by accelerating the demethoxylation of methoxycyclohexane. However, the catalysts with Lewis and especially Brønsted acid sites were found to lack initial stability, and Ni/SBA-15 was found to be the most stable catalyst. Nickel incorporation via the chemisorption–hydrolysis method produced smaller, more uniformly dispersed, and more readily reducible Ni particles than wet impregnation, resulting in higher anisole conversions. Product selectivity, however, was independent of Ni crystallite size and the metal incorporation method.

[This corrects the article DOI: 10.1021/acssuschemeng.5c04908.].

5-Hydroxymethylfurfural (HMF) is a platform chemical that can be catalytically valorized into high-value-added chemicals. Despite the extensive use of titania-supported metal catalysts in HMF conversion, the specific influence of the TiO2 support on the formation of metal active sites, their dispersion, and their role in HMF conversion is not addressed sufficiently. In this work, we investigated five TiO2 supports, four anatase- and one rutile-dominant, varying in surface area and acidity, which were loaded with 1 wt % Ru using RuCl3. Characterization results revealed that the Ru environment, charge distribution, and surface features (transition from Ru-Cl to Ru-O species) varied depending on the TiO2 support used. Their catalytic performance was assessed in HMF hydrogenation. Despite identical Ru loadings, the Ru/TiO2 catalysts exhibited remarkably different catalytic activities and selectivity. High-surface-area anatase TiO2 led to the formation of smaller Ru particles and supported the conversion of HMF to 5-methylfurfural. In contrast, lower surface area anatase and rutile supports favored the formation of larger Ru particles and redirected the reaction course from 5-MF toward the hydrogenation route, yielding primarily 2,5-bis(hydroxymethyl)furan. This study revealed the switchable behavior of Ru/TiO2 catalysts and exposed the critical role of TiO2 structural and morphological features for reaction pathways in HMF valorization over Ru/TiO2. These insights provide a refined framework for the rational design of oxide-supported catalysts tailored for the selective conversion of biomass.

Paper provides a comprehensive study of Ni-Cu catalysts on alumina, focusing on the effects of metal loading, reduction temperatures, and bimetallic interactions on catalyst properties and adsorption behaviour of model organic molecules. Introduction of metal reduces catalyst surface area. Low Cu loadings promote formation of isolated Cu sites, higher result in large CuO clusters. Ni catalysts have composition consisting of a mixture of NiO, NiO-like, and spinel species and the surface is primarily covered by NiO. Bimetallic Ni-Cu catalysts reveal Cu enhanced hydrogenation ability and reducibility. Acidity, primarily originating from alumina, decreases with increasing metal loading, however increasing nickel loading induces new type of sites capable of decomposing NH3. Reduced acidity limits anisole and guaiacol adsorption, while the presence of Cu provides additional adsorption sites for furfuryl alcohol. Organics exhibit distinct adsorption modes with following desorption and/ or decomposition during thermal heating influenced by metal loading, catalyst composition and organics type. Incorporating Ni and Cu affects coke deposits: the most deposits are formed on alumina after guaiacol adsorption, while anisole leaves no carbonaceous residues. The study highlights the importance of reduction conditions on catalytic performance, advocating further research on adsorption under reaction-like conditions to understand the catalysts' behaviour in practical applications.

Valorization of lignin-derived phenolics by hydrodeoxygenation (HDO) poses two major challenges. The first one is the reduction of oxygen content and the second one is to prevent the loss of C atoms from the feedstock while removing oxygen atoms in,-OCH3 groups. In this study, Ni/Al2O3 catalysts were found to be efficient for deoxygenation, and Cu/Al2O3 catalysts were used to selectively carry out reactions intended toward preventing C losses. HDO over Ni/Al2O3 catalysts resulted in the hydrogenation of the aromatic ring of guaiacol and anisole, followed by demethoxylation, as the major reaction pathway. The demethoxylation reaction was favored at lower H2 pressure. However, at lower pressure catalytic deactivation and the nonlinear Arrhenius nature of the aromatic ring hydrogenation limited guaiacol and anisole conversions at higher temperatures. It was found that with the increase in Ni loading the overall conversion was maximum at 10 wt% Ni. Since the demethoxylation reaction occurred only after aromatic ring hydrogenation, its rate showed a similar dependence on both Ni loading and reaction temperature as that of hydrogenation. In this work, (de)methylation reactions of guaiacol and anisole were carried out selectively over Cu/Al2O3 catalysts. Adsorption studies showed that alumina sites were responsible for the reactive adsorption which gave rise to the (de)methylation reactions; and the Cu sites further enhanced these reactions, especially at higher H2 pressures. We have achieved about 65 % molar conversion of guaiacol selectively towards the formation of catechol, phenol, and methylated catechols/phenols, accompanied by small quantities of toluene and xylenes.

The platform molecule 5-Hydroxymethylfurfural (HMF) can be derived from biomass feedstocks and catalytically hydrogenated into various high value molecules. Its conversion to 5-methylfurfural (5-MF), a versatile synthetic intermediate and perfuming agent is challenging as the selective hydrodeoxygenation of the C-OH group in HMF is far less favorable kinetically and thermodynamically than the hydrogenation of the C & boxH;O group, which leads to 2,5-bis(hydroxymethyl)furan (BHMF). Herein, for the first time we demonstrate that Ni/TiO2 catalysts can be tuned to promote the selective removal of a hydroxyl group in the presence of an aldehyde moiety, achieving a high 5-MF yield. Among various synthesis approaches, the direct ion-exchange incorporation of Ni into a TiO2 network prepared via an alginate synthesis route enabled identifying key factors directing the reaction selectivity toward 5-MF. The highest 5-MF selectivity (86%) at nearly full conversion was favored by high acidity and ultra-high dispersion of Ni atoms on the surface, while the crucial role of titania was discussed. By contrast, increasing the reduction temperature to 700 degrees C significantly lowered acidity and led to the formation of larger Ni particles, which favored C & boxH;O activation and in turn promoted a selectivity shift toward BHMF achieving 86% selectivity at nearly full conversion.

The simple hydration of physically mixed Mg and Al oxides results in the formation of an LDH (layered double hydroxide) phase via the dissolution-precipitation-crystallization mechanism. Nevertheless, the change in the properties and catalytic performances of these materials with respect to the hydration conditions has not been well explained to date. Therefore, in this study, we hydrated physically mixed Mg and Al oxides at T = 25 degrees C or 75 degrees C within a time range of 5 minutes to 7 days. Subsequently, we characterized the properties of the resulting materials using an array of appropriate methods and assessed their performances in aldol condensation of furfural and acetone. An increase in the hydration time and temperature promoted the formation of the desired LDH phase. Nevertheless, the performance of the catalysts did not improve accordingly. We assumed that the surprisingly inferior performance of the LDH-rich catalysts was due to the deposition of Al species on their external solid surface instead of being incorporated in the LDH phase, and these species blocked the access of reactants to the catalytically active sites in the HTC phase, resulting in a decreased catalytic activity. Thus, the maximum activity of the catalysts was observed at a relatively low concentration of water-soluble Al species and, accordingly, at a relative content of LDH phase of 20-25%. These results are beneficial for understanding the relationship between the hydration conditions of MgO + Al2O3 physical mixtures and the properties of the derived LDH-phase containing solids and have potential in the design of green, efficient and stable solid base catalysts.

Anisole is a model molecule for studying hydrodeoxygenation (HDO) of lignin -derived oxygenates. Here we elucidate its HDO pathway over 10 % Ni/Al2O3 catalyst. Adsorption experiments showed that anisole is adsorbed on the acidic sites of the Al2O3 . Anisole adsorption at 200 -300 degrees C is reactive in nature, and results in its demethylation. The catalyst was tested at 100 -300 degree celsius, 5 -40 bar H-2 pressure. Conversion of 78 % was obtained at 5 bar and 300 degrees C, restricted by hydrogenation -dehydrogenation equilibrium. HDO mainly starts through the ringhydrogenation pathway. This is followed by demethoxylation beyond 180 degree celsius. At 5 -12 bar, cyclohexane dehydrogenates to benzene. This was confirmed by conducting an HDO experiment with methoxycyclohexane. At lower pressure deoxygenation is favored; and demethylation is accompanied with methylation of the aromatic ring, for temperature >260 degree celsius Investigation of the initial reaction stages showed that anisole HDO on Ni/Al2O3 catalyst proceeds via two independent pathways i.e., reactive adsorption/(de)methylation and aromatic ring hydrogenation.

In recent decades, the high catalytic activity of MgAl mixed oxides (MOs) and rehydrated hydrotalcites (HTCs) has made them very promising basic catalysts for various organic reactions. The synthesis procedure as well as the mechanism of the formation of HTC structure has been well described. Despite this, little has been published on how synthetic parameters affect the physico-chemical properties, rehydration ability and performance of the hydrotalcite-derived catalysts. Here, a series of catalysts with the same molar ratio Mg/Al = 3 varied by the coprecipitation conditions (pH value, temperature, ageing duration) were synthesized and used as precursors for the preparation of the MgAl MOs and rehydrated HTCs. The set of methods (AAS, XRD, SEM, N2-physisorption, TGA and CO2-TPD) was used to establish a relation between the synthetic parameters and the physico-chemical properties of the prepared materials. Their catalytic performance was monitored in aldol condensation of furfural and acetone as a model reaction. Preparations at different pH values and temperature resulted in the formation of HTC samples with crystallite size evaluated by XRD in the range of 70-230 ?, (d003). Nevertheless, the crystallite size of the resulting MOs was similar in the range of 30-36 ?, (d003). The rehydration of the MOs for 5-120 min produced high-crystalline reconstructed HTC with a crystalline size in the range of 82-111 ?, (d003), i.e. the crystallite size of a large-size HTC precursor was not restored. Catalytic results revealed that the crystallite size of an as-prepared HTC precursor was a crucial parameter that affected the performance of both MOs and reconstructed HTCs in the condensation reaction. Furfural conversion over MOs and short-time rehydrated (5-10 min) materials in the reaction was strongly dependent on initial size of the as-prepared HTC crystallites. In contrast, the catalytic performance of the catalysts rehydrated for 120 min, was similar: furfural conversion was above 99% in all cases. Based on these results, the effect of the physico-chemical properties of the as-prepared HTCs on the catalytic performance of both MOs and reconstructed MgAl HTCs was established. A difference in the properties of the prepared samples was explained assuming the existence of extra-framework or partially framework Al-rich species that prevented the access of reactant molecules to catalytically active sites: the larger the crystallite size of the as-prepared precursor, the higher the excess of both structural defects and nonframework Al-rich species, and the lower the furfural conversion over these catalysts. Nevertheless, long rehydration time favored the involvement of the Al-rich species in the recrystallization of HTC structure as evidenced by SEM. As a consequence, furfural conversion increased over these catalysts. These results provide a new insight into the influence of synthetic parameters on the properties of MOs and rehydrated HTCs: the crystallite size of the as-prepared precursors determines the performance of the produced catalysts in aldol condensation by affecting the rehydration ability of the derived MOs.

The co-hydroconversion of lauric acid and anisole was carried out over Ni and NiMo catalysts T=260 and 280 degrees C and pH2=40 bar. Ni/Al2O3 demonstrated a high activity in converting anisole to cyclohexane, but lauric acid conversion was suppressed over this catalyst. In the co-conversion of their mixture the phenolic had no effect on the conversion of the acid, but the latter prevented the cleavage of the C-O bond in both anisole and reaction intermediates. It was assumed that the successful conversion of anisole in its mixture with lauric acid required that a catalyst should provide the fast consumption of the acid component. Accordingly, NiMo/Al2O3 possessed a high activity in lauric acid conversion, and a high cyclohexane yield from anisole was observed after the complete consumption of the acid. The results of the present study can be useful for the rational design of a catalyst for the effective hydroconversion of bio-oil.

The 5-Hydroxymethylfurfural (HMF) platform molecule can be derived from biomass feedstocks and catalytically hydrogenated into various added-value molecules. Its conversion to 5-methylfurfural (5-MF), a versatile synthetic intermediate and perfuming agent, is particularly challenging, the selective hydrodeoxygenation of the C–OH group in HMF being by far less favourable kinetically and thermodynamically than the hydrogenation of the C=O group that gives 2,5-bis-hydroxymethylfuran (BHMF). Herein, for the first time we showed that Ni/TiO2 catalysts can be tuned to promote the selective removal of a hydroxy group in the presence of an aldehyde moiety, and give high 5-MF yield. Among various synthesis approaches, the direct ion exchange incorporation of Ni into a TiO2 network prepared by an alginate synthesis route allowed the key-factors orientating the reaction selectivity towards 5-MF to be identified. The highest 5-MF selectivity (86%) at nearly full conversion was favoured by high acidity and ultra-high dispersion of Ni atoms at the surface, while the prime role of titania was discussed. By contrast, increasing the reduction temperature up to 700°C strongly lowered the acidity and formed larger Ni particles, which favour the C=O activation, and is thereby promoting the selectivity switch towards BHMF at 86% also at nearly full conversion.

Two supports (ZnO, ZrO 2 ) and four promoters (Al 2 O 3 , ZnO, CoO x , NiO) were investigated to design environmentally-friendly Cu-based hydrogenolysis catalysts.

Aiming at the valorization of furfural-derived compounds, the potential of (La-)NiCu catalysts for the hydrodeoxygenation of 4-(2-furanyl)-3-buten-2-one has been assessed. The impact of support acidity and the effects of modifying the support with La have been explored. While catalysts with non-acidic supports solely lead to hydrogenation, the acid sites enable furanic ring opening. Additionally, changing the support alters the metalsupport interaction strength, with stronger interactions reducing the NiCu alloy particle size and increasing activity. Furthermore, according to Density of States calculations, La further enhances the hydrodeoxygenation activity by increasing the adsorption strength. Also, for the acidic supports, it increases the relative abundance of NiCu alloy on the support surface, further increasing the specific activity. The La-NiCu-Al catalyst demonstrated was the best performing catalyst at 200 degrees C and 40 bar H 2 , achieving a high conversion rate of 77 mol kg cat - 1 h -1 with a combined selectivity of 29 % towards octane and BTHF at 99 % conversion, and stability over 5 hours Time-On-Stream. Additionally, isopropyl alcohol proved to be an excellent hydrogen donor, as the external H 2 pressure does not substantially impact the catalyst activity and selectivity, but H 2 itself proved to be important for the catalyst stability.

5-Hydroxymethylfurfural (HMF) is a versatile platform molecule that can be derived from biomass feedstocks and catalytically converted into various value-added chemicals. In this work, selective hydrogenation of HMF is investigated to produce valuable furan-based diols, namely 2,5-bis-hydroxymethylfuran (BHMF) and 2,5-bis-hydroxymethyltetrahydrofuran (BHMTHF), using TiO2 supported Ru catalysts. The catalyst performance was fine-tuned to achieve over 98% yield to BHMF and BHMTHF under optimized reaction conditions with very good recyclability. We pointed out several key factors allowing to maximize the yield towards the respective diols. Features such as the Ru nanoparticle size, the strength of metal-support interactions and the presence of residual chlorine were found to significantly influence the reaction. A characteristic volcano-shaped relationship was obtained between the particle size and the catalytic activity giving the highest diol yield for an optimum Ru nanoparticle size of 1.6 nm. Further, metal-support interactions were found to be responsible for providing optimum Ru-TiOx interfacial surface sites and chlorine was affecting the electronic properties of Ru nanoparticles, potentially benefiting to the selective formation of BHMF. The reaction time was shown to control the hydrogenation of the furan ring and the selectivity of the reaction, that can be directed optimally towards BHMF or BHMTHF.

In the context of 5-hydroxymethylfurfural (HMF) valorisation, TiO2 has emerged as a promising support. However, its intrinsic activity and underlying structural parameters remained undiscovered. This study elucidates the close relationship between structural and surface properties of TiO2 (e.g. crystalline size, surface area, and the number and type of acid sites) and its activity in HMF conversion. Lewis acid sites were found to be the exclusive acid sites present in anatase TiO2 samples, and their abundance correlated strongly with the overall surface area of TiO2. HMF conversion over TiO2 led to the simultaneous formation of 5-methylfurfural (5-MF) and 2,5-diformylfuran (2,5-DFF). Their formation was attributed to an intermolecular hydride transfer occurring over the Lewis acid sites. This opens up the possibility of selectively obtaining 5-MF and 2,5-DFF using solely TiO2 active sites. These findings provide valuable insights for designing TiO2-supported metal catalysts for future energy and environmental applications, aligning with green chemistry principles.