# Beneficial Effect of W Incorporation in Supported Mo-based Catalysts for the HDO of m-Cresol

Bertha Farah, Christine Lancelot, Pascal Blanchard, Frédéric Richard, Carole Lamonier

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Bertha Farah, Christine Lancelot, Pascal Blanchard, Frédéric Richard, Carole Lamonier. Beneficial Effect of W Incorporation in Supported Mo-based Catalysts for the HDO of m-Cresol. ChemCatChem, 2023, 15 (5), 10.1002/cctc.202201409. [https://hal-04039829v1](https://hal.science/hal-04039829v1)

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# Beneficial Effect of W Incorporation in Supported Mo-based
Catalysts for the HDO of m-Cresol

Bertha Farah,[a] Christine Lancelot,[a] Pascal Blanchard,[a] Frédéric Richard,*[b] and Carole Lamonier*[a]

The hydrodeoxygenation (HDO) of m-cresol was investigated at 340 °C under 30 bar as total pressure over molybdenum oxide-based catalysts. 10 wt.% Mo were first deposited on various supports (ZrO₂, TiO₂, Al₂O₃ and COK12). The use of oxophilic ZrO₂ and TiO₂ supports allowed to obtain the highest HDO catalytic performances. This result could be in link with the reducibility of Mo, which was found to be dependent on the support nature. Several catalysts containing both W and Mo in

oxide phase supported on ZrO₂ were then prepared using various heteropolyacids as precursors (H₄SiMoₓW₁₂ₓO₄₀ with x = 0, 3, 6, 9 and 12). A synergy was observed between Mo and W and the best catalytic performance was obtained for SiMo₉W₃/ZrO₂. More importantly, the presence of W improved the reducibility of Mo⁶⁺ to Mo⁵⁺ species, which quantity was correlated to catalytic activity suggesting that Mo⁵⁺ could be the active phase in HDO.

## Introduction

Aromatic hydrocarbons including benzene, toluene and xylene (BTX) are high value chemicals required for diverse industrial applications. They are mainly used as solvents in the manufacturing of daily products (detergents, soaps, dyes...) as well as additives in gasoline to obtain high-octane fuels. On the current market, aromatic compounds are mostly produced from petroleum-derived chemical processes, particularly from catalytic reforming of naphtha. However, as the demand for BTX rises nowadays, so do the issues of global warming caused by the release of greenhouse gases in the atmosphere from human activities, notably by fossil-fuel using refineries. Thus, the worldwide answer for aromatic production consists in the use of alternative, renewable and sustainable sources. In this context, ligno-cellulosic biomass represents a valuable feedstock for the production of fuels, chemicals and energy. Among its three major components (cellulose, hemi-cellulose and

lignin), lignin consists of three dimensional cross-linked methoxylated phenylpropane structures, which can be depolymerized by several techniques, such as pyrolysis or hydrothermal liquefaction, into liquids rich in phenolic compounds (guaiacol, phenol, cresol, anisole...) that can then be upgraded to aromatics, particularly BTX, through the hydrodeoxygenation (HDO) catalytic process.[1,2]

HDO consists of removing O atoms mainly as water from phenolic molecules in the presence of hydrogen at temperatures between 200 and 400 °C and under pressures going up to 200 bar.[3] Two types of deoxygenated products can be obtained from HDO reactions: aromatic hydrocarbons, produced from the direct cleavage of the carbon-oxygen bond through direct deoxygenation (DDO) pathway, and naphthenes, resulting from the hydrogenation of the aromatic ring (HYD). Catalyst choice plays an essential role in directing the HDO reaction pathway and product selectivity.[4]

Traditional hydrodesulfurization catalysts, sulfide Mo, CoMo and NiMo supported on γ-alumina, were first tested for the similar HDO reaction and showed excellent activities.[5,6] However, to avoid catalyst deactivation, a continuous sulfur source (H₂S, DMDS...) has to be provided throughout the reaction, which might result in the contamination of end-products or in the emission of H₂S.[7] Molybdenum oxide catalysts appear to be suitable alternatives. Prasomri et al. demonstrated that unsupported MoO₃ catalysts have interesting HDO activity and exhibit high tolerance to deactivation by coke deposits or water poisoning.[8] Regarding selectivity, it was shown that MoO₃ was effective to generate high yields of aromatic hydrocarbons from lignin-derived oxygenates, which was attributed to the Mo oxophilic character that allows to lower the energy barrier of the DDO pathway.[9,10] In HDO of phenolics over MoO₃ catalysts, it was proposed that the reduced Mo⁵⁺ species concomitant with oxygen vacancies could result in the removal of the oxygen atom from the phenolic compound upon the adsorption on the vacancy site, thus acting as the catalyst active site.[9,11] It was further demonstrated that efficient supports

<figure><img src="image_3.png" /></figure>

Supporting information for this article is available on the WWW under
https://doi.org/10.1002/cctc.202201409

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<footnote>[a] B. Farah, Dr. C. Lancelot, Dr. P. Blanchard, Prof. C. Lamonier
Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181-UCCS-Unité de Catalyse et Chimie du Solide
Université de Lille
Avenue Paul Langevin
59000 Lille (France)
E-mail: carole.lamonier@univ-lille.fr</footnote>

<footnote>[b] Dr. F. Richard
Institut de Chimie des Milieux et Matériaux de Poitiers, CNRS UMR 7285
Université de Poitiers
4 rue Michel Brunet
86022 Poitiers (France)
E-mail: frederic.richard@univ-poitiers.fr</footnote>
<figure><img src="image_5.png" /></figure>

could stabilize these Mo⁵⁺ species, hereby improving catalyst activity, selectivity and stability by slowing down the deactivation process.[12]

It is well known that the choice of a suitable support is an essential aspect of catalyst formulation. Various oxides were considered as support for MoO₃ such as Al₂O₃,[13] SiO₂,[14,15] TiO₂,[16,17] and ZrO₂.[11,18,19] When evaluated in m-cresol HDO under atmospheric pressure at 320 °C,[12] MoO₃/ZrO₂ and MoO₃/TiO₂ exhibited initial high activities whereas MoO₃/Al₂O₃, MoO₃/CeO₂ and MoO₃/SiO₂ were drastically less active. Whatever the catalyst, a strong deactivation was observed. Under more severe conditions (340 °C, 40 bar), no deactivation was noticed for the three catalysts used (MoO₃/Al₂O₃, MoO₃/SiO₂ and MoO₃/SBA-15), MoO₃/Al₂O₃ being the most active.[20] These Mo oxide supported catalysts that demonstrated high selectivity to the DDO pathway were nevertheless also reported less active than sulfide catalysts.[20,21] It appears then interesting to investigate the modification of the molybdenum oxide phase to obtain both activity and selectivity into aromatics enhancements. A synergetic effect between Mo and W was demonstrated in sulfide catalysts for HDS reaction.[22] The observed better sulfidation of both elements suggested their easier reducibility that could be beneficial in HDO where Mo⁵⁺ species are suggested as active sites.[9]

In this present work, after studying the support effect on Mo based catalysts by using relevant supports described in the literature (alumina, titania and zirconia) and a mesoporous silica (COK12) support, new supported MoW mixed oxides catalysts prepared from H₄SiMoₓW₁₂ₓO₄₀ heteropolyacids with x = 0, 3, 6, 9 and 12 have been characterized and evaluated in the HDO of m-cresol at 340 °C under 30 bar.

## Results and Discussion

### Support effect

Mo content in the prepared catalysts, determined by ICP-OES, was confirmed to be around the 10% set value as shown in Table S1 supplementary information. Textural properties of supports and Mo based catalysts, including surface area, pore volume and average pore diameter issued from N₂-physiorp- tion isotherms (Figure S1 supplementary information) are also reported in Table S1. The values obtained per gram of catalyst were recalculated per gram of support, in order to remove the weight gain due to the MoO₃ contribution. On Al₂O₃, ZrO₂ and TiO₂, the surface areas and pore volumes of the catalysts were close to those of the bare supports, which suggested that the Mo oxide phase was well dispersed. For Mo/COK12, a decrease of 36% of the support surface area and 28% of the pore volume was observed, probably due to pore blockage by large MoOₓ particles, the porous structure of COK12 being main- tained after Mo impregnation as evidenced by low-angle XRD analysis (Figure S2, supplementary information). Average pore diameter was barely modified by Mo deposition on the supports.

The diffractograms of Mo/Al₂O₃ and Mo/TiO₂ catalysts only showed reflections of the corresponding alumina and titania supports, indicating a good dispersion of Mo on these supports (Figure 1). For Mo/ZrO₂, two crystalline phases were detected: MoO₃ (peak at 27°) and Zr(MoO₄)₂ (peak at 23°),[18] present in small quantities on the catalyst surface. Over Mo/COK12, only MoO₃ phase was observed, with peaks of high intensity. These results were confirmed by Raman spectroscopy as shown in Figure 2. For Mo/TiO₂, a large peak at 976 cm⁻¹ corresponding to terminal Mo=O stretching modes was observed, evidencing the presence of well dispersed polymolybdate species.[23] In the case of Mo/Al₂O₃, the presence of the large peak at 946 cm⁻¹ together with that at 565 cm⁻¹ (Figure S3, supplementary information) suggests that Anderson-type heteropolymolybdate [Al(OH)₆Mo₆O₁₈]³⁻ anion, may have formed on the catalyst due to Al³⁺ extraction of the support.[24] For both Mo/COK12 and Mo/ZrO₂, peaks at 991 and 815 cm⁻¹ corresponding to sym- metrical O-Mo-O vibrational mode confirmed the presence of MoO₃. In addition, for Mo/ZrO₂ two small peaks at 943 and 742 cm⁻¹ were attributed to Zr(MoO₄)₂ phase.[25] To conclude, in agreement with textural characterizations showing an impor- tant loss of surface area, the observation of MoO₃ crystallo- graphic phase by XRD together with specific Raman lines of MoO₃, indicates a poor Mo dispersion at the COK12 surface (despite its high surface area) that is due to the weak interactions between Mo oxide entities and COK12 surface after deposition. On alumina and TiO₂ containing high quantity of

<figure><img src="image_6.png" /><figcaption>**Figure 1.** XRD patterns of the different supports and their corresponding MoO₃ based catalysts.</figcaption></figure>
<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /><figcaption>**Figure 2.** Raman spectra of supported MoO<sub>3</sub> catalysts.</figcaption></figure>

OH groups at the surface, their strong interaction with Mo entities leads to well dispersed molybdate based phase, thus preventing the formation of undesirable crystalline Mo phase.[26] On ZrO<sub>2</sub> a specific behavior is noticed due to its small pore volume, where the high concentration of Mo in the impregnating solution could explain the formation of small Zr(MoO<sub>4</sub>)<sub>2</sub> entities together with MoO<sub>3</sub> species, as evidenced by Raman and XRD.[27,28]

Reduction properties of the supported Mo oxide catalysts were investigated through H<sub>2</sub>-TPR (Figure 3). As expected, Al<sub>2</sub>O<sub>3</sub>, ZrO<sub>2</sub> and COK12 were not reduced in the temperature range of 100–1000 °C, while a low consumption of H<sub>2</sub> (0.28 mmol g<sup>-1</sup>) was observed around 600 °C on TiO<sub>2</sub>. The reduction of Mo based catalysts proceeded in two steps: the first at a temperature range between 400 and 600 °C, attributed to the reduction of octahedral Mo<sup>6+</sup> to Mo<sup>5+</sup>/Mo<sup>4+</sup>, and the second at temperatures higher than 700 °C attributed to further reduction to metallic Mo.[29,30] On Mo/ZrO<sub>2</sub>, an extra peak of H<sub>2</sub> consumption at 407 °C corresponded to the reduction of Mo in Zr(MoO<sub>4</sub>)<sub>2</sub> species.[18] Based on H<sub>2</sub> consumption values reported in Table S2 (supplementary information), the reducibility of Mo depends on the support nature: the Mo reduction was complete on Mo/ZrO<sub>2</sub>, while values of 92% for Mo/TiO<sub>2</sub>, 72% for Mo/Al<sub>2</sub>O<sub>3</sub> and 44% for Mo/COK12 were calculated. It can be seen that oxophilic supports like ZrO<sub>2</sub> and TiO<sub>2</sub> favored the global reducibility of Mo species. Considering that Mo<sup>5+</sup> could be the active sites in HDO,[9,11] the temperatures of the maximum of H<sub>2</sub> consumption corresponding to the Mo<sup>6+</sup> species reduction were compared, leading to the following order: Mo/ZrO<sub>2</sub> (407 °C) < Mo/TiO<sub>2</sub> (452 °C) < Mo/Al<sub>2</sub>O<sub>3</sub> (465 °C) <

<figure><img src="image_9.png" /><figcaption>**Figure 3.** H<sub>2</sub>-TPR profiles of the different supports and their corresponding MoO<sub>3</sub> based catalysts.</figcaption></figure>

Mo/COK12 (519 °C), showing that the formation of Mo<sup>5+</sup> could occur at lower temperature on ZrO<sub>2</sub> and TiO<sub>2</sub>.

The atomic proportions of the different oxidation states of Mo were then determined from XPS (Table 1). The Mo 3d level consists of two spin orbit split contributions, 3d<sub>5/2</sub> and 3d<sub>3/2</sub>, with binding energies for Mo<sup>6+</sup>, Mo<sup>5+</sup> and Mo<sup>4+</sup> of 232.5-233.2 eV, 231.0-232.0 eV and 228.5-229.5 eV, respectively.[31] Before reduction, for the oxidic precursors, only Mo<sup>6+</sup> species were observed over Mo/ZrO<sub>2</sub>, Mo/Al<sub>2</sub>O<sub>3</sub> and Mo/COK12, while 11% reduced Mo<sup>5+</sup> species were detected on Mo/TiO<sub>2</sub> in relation with TiO<sub>2</sub> surface reduction properties. Then, for the catalysts reduced under 1 bar at 340 °C for 1 h (spectra shown in Figure S4, supplementary information), it was seen that Mo<sup>6+</sup> remained the main species (between 78 and 99%) as reported in Table 1. Almost no reduction of Mo<sup>6+</sup> was detected for reduced Mo/COK12 and close quantities of Mo<sup>5+</sup>, in the range

<table><caption>**Table 1.** Atomic proportions of different oxidation state Mo species detected by XPS over the oxidic precursors and reduced catalysts.</caption><thead><tr><th rowspan="2">Catalyst</th><th colspan="3">Oxidic precursors</th><th colspan="3">Reduced catalysts under 1 bar, 340 °C, 1 h</th></tr><tr><th>[%]<br>Mo<sup>6+</sup></th><th>[%]<br>Mo<sup>5+</sup></th><th>[%]<br>Mo<sup>4+</sup></th><th>[%]<br>Mo<sup>6+</sup></th><th>[%]<br>Mo<sup>5+</sup></th><th>[%]<br>Mo<sup>4+</sup></th></tr></thead><tbody><tr><td>Mo/Al<sub>2</sub>O<sub>3</sub></td><td>100</td><td>0</td><td>0</td><td>78</td><td>18</td><td>4</td></tr><tr><td>Mo/ZrO<sub>2</sub></td><td>100</td><td>0</td><td>0</td><td>85</td><td>13</td><td>2</td></tr><tr><td>Mo/TiO<sub>2</sub></td><td>89</td><td>11</td><td>0</td><td>80</td><td>18</td><td>2</td></tr><tr><td>Mo/COK12</td><td>100</td><td>0</td><td>0</td><td>99</td><td>1</td><td>0</td></tr></tbody></table>
<figure><img src="image_10.png" /></figure>

of 13–18%, were calculated for the other catalysts. The proportions of Mo⁴⁺ remained at low levels, less than 4%.

All catalysts were evaluated in HDO of m-cresol at 340 °C and 30 bar for 6 hours on stream. The activity of the catalysts was determined at the same contact time (expressed as W/F value) fixed to 45 g·mol<sub>cresol</sub><sup>-1</sup>, m-cresol conversions ranging between 8 and 60% (Table 2). The following order of HDO activity, estimated by k<sub>HDO</sub> values, was: Mo/ZrO<sub>2</sub> > Mo/TiO<sub>2</sub> > Mo/Al<sub>2</sub>O<sub>3</sub> ≈ Mo/COK12. For all catalysts, the DDO route was largely predominant since the k<sub>DDO</sub>/k<sub>HDO</sub> ratio was greater than 0.8. Interestingly, regardless the catalyst, no deactivation was noticed during 6 hours on stream in accordance with results reported using similar experimental conditions.<sup>[20]</sup>

Products distributions obtained at iso-conversion (around 20–25%) are reported in Table 3. Toluene, obtained by the DDO pathway, was the main product observed, irrespective the catalyst, the highest selectivity reaching 91 mol% for Mo/ZrO<sub>2</sub>. Methylcyclohexene isomers (MCHenes) formed by the HYD

route were detected in low amounts (below 20 mol%). Despite the high H₂ pressure, the fully hydrogenated product (meth- ylcyclohexane (MCH)) was only detected in traces, indicating the poor hydrogenation ability of Mo based catalysts. These results are in accordance with the reaction network of m-cresol already reported in the literature (Scheme 1).<sup>[20]</sup>

According to literature,<sup>[9,11]</sup> Mo⁵⁺ species are proposed to be the active sites for HDO of phenolic compounds. In our solids, the detected amounts of Mo⁵⁺ species measured by XPS after reduction do not correlate with the catalytic properties, since the most efficient catalyst Mo/ZrO₂ possesses slightly lower Mo⁵⁺ content than those of less active Mo/TiO₂ and Mo/Al₂O₃ (Table 1). Similar results were observed for the support effect in m-cresol HDO study performed by Shetty et al.<sup>[12]</sup> The amounts of Mo⁵⁺ detected by XPS in their catalysts collected after 7.5 h of test were all close, the most active Mo/ZrO₂ having 36% Mo⁵⁺, while much less active Mo/Al₂O₃ had 38%.

It thus seems that the proportion of Mo⁵⁺ species is not the only parameter to explain the catalytic performances of Mo based catalysts when comparing different supports. Other parameters directly related to support properties could thus be involved, like acidity but also differences in dispersion of Mo in the oxidic precursor that could also affect the dispersion of Mo⁵⁺ species.

Nevertheless, reducibility of Mo cannot be ruled out as an important factor in HDO, since for Mo/COK12, which was not reduced after the reduction step, little catalytic activity was registered. In fact, the reducibility of Mo⁶⁺ evaluated by the TPR analysis through the temperature of the first maximum of H₂ consumption correlates with the catalytic activity. For the most active catalyst Mo/ZrO₂, the improved activity could be explained by the specific interaction between the Mo and the support through the formation of the Zr(MoO₄)₂ phase which was found to be easier to reduce than MoO₃ according to H₂-TPR. Ranga et al<sup>[18]</sup> proposed that the easier reduction of Zr(MoO₄)₂ could explain the higher catalytic activity for the HDO of anisole of Mo/ZrO₂. In a similar study, Shetty et al<sup>[11]</sup> compared the impact on catalytic activity of the phase in which Mo species are involved using three 25% MoO₃/ZrO₂ catalysts containing only MoO₃, Zr(MoO₄)₂, or a mixture of both phases. Unlike the previous work of Ranga et al, catalysts having only MoO₃ and the mixture of the two phases showed a similar activity superior to that of the catalyst with only Zr(MoO₄)₂, for which fewer amounts of redox-active MoOₓ species quantified from oxygen chemisorption data were observed. Thus, the effect of this phase needs to be further investigated.

As the ZrO₂ support allowed to obtain the most efficient Mo based catalyst, this support was selected for further studies using MoW catalysts.

## Effect of molybdenum-tungsten active phase

A series of SiMoₓW<sub>12-x</sub>/ZrO₂ catalysts was prepared starting from mixed H₄SiMoₓW<sub>12-x</sub>O₄₀ HPA with x=0, 3, 6, 9 and 12 and with 10 wt.% of total metal content (Table S4, supporting information). No significant loss of surface area, pore volume or average

<table><caption>**Table 2.** Apparent rate constants from HDO of m-cresol over supported MoO₃ catalysts at 340 °C, 30 bar and space time W/F = 45 g·mol<sub>cresol</sub><sup>-1</sup>.</caption><thead><tr><th rowspan="2">Catalyst</th><th rowspan="2">Conversion [%]</th><th colspan="3">Rate constants<br>[mol<sub>cresol</sub> mol<sub>Mo</sub><sup>-1</sup> h<sup>-1</sup>]</th><th rowspan="2">k<sub>DDO</sub>/k<sub>HDO</sub></th></tr><tr><th>k<sub>HDO</sub></th><th>k<sub>DDO</sub></th><th>k<sub>HYD</sub></th></tr></thead><tbody><tr><td>Mo/Al<sub>2</sub>O<sub>3</sub></td><td>12</td><td>3.0</td><td>2.7</td><td>0.3</td><td>0.9</td></tr><tr><td>Mo/ZrO<sub>2</sub></td><td>60</td><td>19.3</td><td>17.6</td><td>1.7</td><td>0.9</td></tr><tr><td>Mo/TiO<sub>2</sub></td><td>38</td><td>10.1</td><td>8.5</td><td>1.6</td><td>0.8</td></tr><tr><td>Mo/COK12</td><td>8</td><td>1.8</td><td>1.7</td><td>0.1</td><td>0.9</td></tr></tbody></table>

<table><caption>**Table 3.** Product selectivity at iso-conversion from HDO of m-cresol over supported MoO₃ catalysts at 340 °C and 30 bar.</caption><thead><tr><th rowspan="2">Catalyst</th><th rowspan="2">W/F<br>[g·h·mol<sub>cresol</sub><sup>-1</sup>]</th><th rowspan="2">Conversion<br>[%]</th><th colspan="3">Selectivity [mol%]</th></tr><tr><th>Toluene</th><th>MCHenes</th><th>MCH</th></tr></thead><tbody><tr><td>Mo/Al<sub>2</sub>O<sub>3</sub></td><td>90</td><td>21</td><td>89</td><td>11</td><td>0</td></tr><tr><td>Mo/ZrO<sub>2</sub></td><td>18</td><td>23</td><td>91</td><td>9</td><td>0</td></tr><tr><td>Mo/TiO<sub>2</sub></td><td>23</td><td>22</td><td>79</td><td>21</td><td>0</td></tr><tr><td>Mo/COK12</td><td>113</td><td>23</td><td>87</td><td>11</td><td>2</td></tr></tbody></table>

<figure><img src="image_11.png" /><figcaption>**Scheme 1.** Reaction network of m-cresol transformation at 340 °C and 30 bar over supported MoO₃ catalysts.</figcaption></figure>
<figure><img src="image_12.png" /></figure>

<figure><img src="image_13.png" /><figcaption>**Figure 4.** Raman spectra of HPAs and HPA-derived SiMo~x~W~12-x~/ZrO~2~ catalysts. (Not clear, figure added below)</figcaption></figure>

pore diameter was recorded for the materials after metal deposition on the ZrO~2~ support (Figure S5, Table S4, supplementary information). XRD diffractograms only showed reflections of the support, indicating that no other crystalline phase was present (Figure S6, supporting information).

The formation of the Keggin structure H~4~SiMo~x~W~12-x~/O~40~ HPAs (with x=0, 3, 6, 9 and 12) was confirmed by Raman spectroscopy (Figure 4) with typical spectra, characterized by a main peak at high wavelengths corresponding to symmetric Mo(W)-O~t~ terminal vibration together with peaks in the low Raman shift region (below 250 cm~⁻¹~) attributed to the stretching mode of the Mo(W)-O vibration (where O links Mo(W) and Si).[32] As the Mo content increases in the solids, the main peak shifts to lower wavenumbers, from 998 cm~⁻¹~ for H~4~SiW~12~/O~40~ to 983 cm~⁻¹~ for H~4~SiMo~12~/O~40~, in agreement with literature data.[33,34] In Raman spectra of SiMo~x~W~12-x~/ZrO~2~ oxidic precursors, the peaks of the ZrO~2~ phase hide peaks related to the Mo/W Keggin structure, nevertheless the characteristic peaks corresponding to Mo(W)-O terminal bond are still observed together with the peak in the range 235–245 cm~⁻¹~, thus evidencing the HPA preservation on ZrO~2~ support after drying.

H~2~-TPR profiles of the catalysts in the temperature range between 400 and 600 °C are presented in Figure 5. W is not reduced in these conditions and the observed peaks are attributed to the reduction of Mo~6~⁺ to Mo~5~⁺/Mo~4~⁺. The reduction profile of SiMo~12~/ZrO~2~ (Figure 5) is similar to that of Mo/ZrO~2~ (Figure 3), with the 2 peaks found at 417 and 449 °C. The similarity between the TPR profiles suggests that HPA structures were not preserved under increasing temperature, and that after HPA structure destruction, interactions between Mo species and the zirconia support on SiMo~12~/ZrO~2~ became close to those of HMA-derived Mo/ZrO~2~. As discussed above,

<figure><img src="image_14.png" /><figcaption>**Figure 5.** H~2~-TPR profiles of SiMo~x~W~12-x~/ZrO~2~ catalysts.</figcaption></figure>

the first peak at 417 °C was attributed to the reduction of Zr(MoO~4~)~2~. These species not detected by XRD in dried catalysts could then be formed during TPR analysis. For the mixed SiMo~x~W~12-x~/ZrO~2~ catalysts having lower Mo loadings (Table S4 supplementary information), only one peak was observed (between 418 and 423 °C) and was attributed mostly to the
<figure><img src="image_15.png" /></figure>

reduction of Zr(MoO₄)₂.[18] The experimental H₂ uptake values for the conversion of Mo⁶⁺ to Mo⁴⁺ were expectedly found to decrease with the Mo loading in the catalyst: SiMo₁₂/ZrO₂ with 10% Mo (0.41 mmol g⁻¹) > SiMo₉W₃/ZrO₂ with 6% Mo (0.23 mmol g⁻¹) > SiMo₆W₆/ZrO₂ with 3.4% Mo (0.10 mmol g⁻¹) > SiMo₃W₉/ZrO₂ with 1.5% Mo (0.06 mmol g⁻¹) > SiW₁₂/ZrO₂ (0.02 mmol g⁻¹).

XPS spectra were acquired on the oxidic precursors and reduced samples to probe the oxidation states of the surface Mo and W species and are shown in Figures S7 and S8 supplementary information. Atomic proportions of the different oxidation state Mo species are reported in Table 4. Analyses of the oxidic precursors confirm that the deposition on ZrO₂ of a Mo based Keggin heteropolyanion precursor, well-known to be easily reduced, induces the presence of Mo⁵⁺ species before the reduction step. For SiMo₁₂/ZrO₂, 11% of Mo⁵⁺ were formed, while only Mo⁶⁺ species were detected on the Mo/ZrO₂ catalyst prepared by impregnation with HMA solution. Moreover, it appears that the addition of W improves the initial reducibility of Mo in the mixed SiMoₓW₁₂ₓ/ZrO₂ oxidic precursors, the amount of Mo⁵⁺ increasing with W content. This trend with W content was also observed for the reduced catalysts. After reduction at 1 bar, proportions of Mo⁵⁺ species increased (between 11–32% to 21–46%). This observation agrees with previous results on sulfide MoW hydrotreating catalysts, reporting an increase of Mo sulfidation degree (Mo⁶⁺ to Mo⁴⁺) in the presence of W.[22,34] The atomic proportions of the different oxidation states of W species are reported in Table 5. XPS decompositions of the W4f spectral region of the catalysts reduced at 1 bar showed that W is not reduced under 1 bar H₂ at 340 °C. In order to analyze the oxidation states of Mo and W in the reaction conditions, the three mixed SiMo₃W₉/ZrO₂, SiMo₆W₆/ZrO₂ and SiMo₉W₃/ZrO₂ catalysts were reduced under

<table><caption>**Table 6.** Apparent rate constants from HDO of m-cresol over SiMoₓW₁₂ₓ/ZrO₂ catalysts at 340 °C and 30 bar for W/F equal to 45 g mol⁻¹.</caption><thead><tr><th rowspan="2">Catalyst</th><th rowspan="2">Conversion [%]</th><th colspan="3">Rate constants</th></tr><tr><th>[mol<sub>cresol</sub> mol<sub>metals</sub> h<sup>-1</sup>]</th><th>k<sub>DDO</sub></th><th>k<sub>HYD</sub></th></tr></thead><tbody><tr><td>SiMo<sub>12</sub>/ZrO<sub>2</sub></td><td>63</td><td>20.9</td><td>19.5</td><td>1.4</td></tr><tr><td>SiMo<sub>6</sub>W<sub>3</sub>/ZrO<sub>2</sub></td><td>61</td><td>25.1 (16)<sup>[a]</sup></td><td>24.3</td><td>0.8</td></tr><tr><td>SiMo<sub>6</sub>W<sub>6</sub>/ZrO<sub>2</sub></td><td>36</td><td>14.0 (11)<sup>[a]</sup></td><td>13.8</td><td>0.2</td></tr><tr><td>SiMo<sub>3</sub>W<sub>9</sub>/ZrO<sub>2</sub></td><td>22</td><td>8.9 (6)<sup>[a]</sup></td><td>8.8</td><td>0.1</td></tr><tr><td>SiW<sub>12</sub>/ZrO<sub>2</sub></td><td>3</td><td>1.4</td><td>1.3</td><td>0.1</td></tr></tbody></table>

[a] Apparent rate constants of MoW catalysts estimated from individual SiMo₁₂/ZrO₂ and SiW₁₂/ZrO₂ experimental apparent rate constants.

30 bar H₂ at 340 °C for 1 h. According to XPS analysis (Table 4), Mo appears to be more reduced at 30 bar (35–45% Mo⁶⁺) than at 1 bar (51–62% Mo⁶⁺). However, it can be noted that the atomic proportions of Mo⁵⁺ remained similar, while a noticeable increase in Mo⁴⁺ species was observed (0–5% to 11–19%). As for W, only around 10% of W⁵⁺ were formed for SiMo₆W₆/ZrO₂ and SiMo₃W₉/ZrO₂ reduced at 30 bar at 340 °C (Table 5 and Figure S8 supplementary information).

HDO reactions were performed in the same conditions as with the previous Mo supported catalysts at 340 °C and 30 bar and at a contact time (W/F) of 45 g mol⁻¹. Apparent rate constant values are presented in Table 6.

Tungsten alone exhibited poor activity in deoxygenation of m-cresol in these conditions. XPS results showed that W was barely reduced under 30 bar H₂, which confirms that reduction capability of the active oxide phase is essential to obtain efficient HDO catalysts.

The results also showed that the SiMo₁₂/ZrO₂ catalyst has a similar activity to that of Mo/ZrO₂ (kHDO = 20.9 and

<table><caption>**Table 4.** Atomic proportions of different oxidation state Mo species detected by XPS over the oxidic precursors and reduced SiMoₓW₁₂ₓ/ZrO₂ catalysts.</caption><thead><tr><th rowspan="2">Catalyst</th><th colspan="3">oxidic precursors</th><th colspan="8">Reduced catalysts at 340 °C, 1 h</th></tr><tr><th>[%] Mo⁶⁺</th><th>[%] Mo⁵⁺</th><th>[%] Mo⁴⁺</th><th>1 bar</th><th>[%] Mo⁶⁺</th><th>[%] Mo⁵⁺</th><th>[%] Mo⁴⁺</th><th>30 bar</th><th>[%] Mo⁶⁺</th><th>[%] Mo⁵⁺</th><th>[%] Mo⁴⁺</th><th>Number of Mo⁵⁺ atoms in reduced catalysts (x10¹⁹) [a]</th><th>Number of Mo⁴⁺ atoms in reduced catalysts (x10¹⁹) [b]</th></tr></thead><tbody><tr><td>SiMo<sub>12</sub>/ZrO<sub>2</sub></td><td>89</td><td>11</td><td>0</td><td>79</td><td>21</td><td>0</td><td>–</td><td>–</td><td>–</td><td>–</td><td>3.9</td><td>–</td><td>0.0</td></tr><tr><td>SiMo<sub>3</sub>W<sub>3</sub>/ZrO<sub>2</sub></td><td>78</td><td>22</td><td>0</td><td>62</td><td>38</td><td>0</td><td>–</td><td>45</td><td>44</td><td>11</td><td>4.4</td><td>5.0</td><td>0.0</td></tr><tr><td>SiMo<sub>6</sub>W<sub>6</sub>/ZrO<sub>2</sub></td><td>73</td><td>27</td><td>0</td><td>51</td><td>44</td><td>5</td><td>–</td><td>37</td><td>46</td><td>19</td><td>2.8</td><td>2.9</td><td>0.3</td></tr><tr><td>SiMo<sub>3</sub>W<sub>9</sub>/ZrO<sub>2</sub></td><td>68</td><td>32</td><td>0</td><td>52</td><td>46</td><td>2</td><td>–</td><td>35</td><td>50</td><td>15</td><td>1.3</td><td>1.4</td><td>0.1</td></tr></tbody></table>

–: Values not determined. [a] Calculated as follows: N(Mo⁵⁺) = n(Mo) in the reactor * Nₐ * % Mo⁵⁺ (XPS). [b] Calculated as follows: N(Mo⁴⁺) = n(Mo) in the reactor * Nₐ * % Mo⁴⁺ (XPS).

<table><caption>**Table 5.** Atomic proportions of different oxidation state W species detected by XPS over the oxidic precursors and reduced SiMoₓW₁₂ₓ/ZrO₂ catalysts.</caption><thead><tr><th rowspan="2">Catalyst</th><th colspan="3">oxidic precursors</th><th colspan="8">Reduced catalysts at 340 °C, 1 h</th></tr><tr><th>[%] W⁶⁺</th><th>[%] W⁵⁺</th><th>[%] W⁴⁺</th><th>1 bar</th><th>[%] W⁶⁺</th><th>[%] W⁵⁺</th><th>[%] W⁴⁺</th><th>30 bar</th><th>[%] W⁶⁺</th><th>[%] W⁵⁺</th><th>[%] W⁴⁺</th><th>Number of W⁵⁺ atoms in reduced catalysts (x10¹⁹) [a]</th></tr></thead><tbody><tr><td>SiMo<sub>3</sub>W<sub>3</sub>/ZrO<sub>2</sub></td><td>100</td><td>0</td><td>0</td><td>100</td><td>0</td><td>0</td><td>–</td><td>100</td><td>0</td><td>0</td><td>0</td><td>0</td></tr><tr><td>SiMo<sub>6</sub>W<sub>6</sub>/ZrO<sub>2</sub></td><td>100</td><td>0</td><td>0</td><td>100</td><td>0</td><td>0</td><td>–</td><td>87</td><td>13</td><td>0</td><td>0.8</td><td>0.8</td></tr><tr><td>SiMo<sub>3</sub>W<sub>9</sub>/ZrO<sub>2</sub></td><td>100</td><td>0</td><td>0</td><td>100</td><td>0</td><td>0</td><td>–</td><td>90</td><td>10</td><td>0</td><td>0.8</td><td>0.8</td></tr><tr><td>SiW<sub>12</sub>/ZrO<sub>2</sub></td><td>100</td><td>0</td><td>0</td><td>100</td><td>0</td><td>0</td><td>–</td><td>84</td><td>13</td><td>3</td><td>1.3</td><td>0.8</td></tr></tbody></table>

[a] Calculated as follows: N(W⁵⁺) = n(W) in the reactor * Nₐ * % W⁵⁺ (XPS).
<figure><img src="image_16.png" /></figure>

19.3 mol·cresol·mol·Mo⁻¹·h⁻¹ respectively). For MoW catalysts, activity increases with Mo content, as expected: k<sub>HDO</sub> (SiMo<sub>9</sub>W<sub>3</sub>/ZrO<sub>2</sub>) > k<sub>HDO</sub> (SiMo<sub>6</sub>W<sub>6</sub>/ZrO<sub>2</sub>) > k<sub>HDO</sub> (SiMo<sub>3</sub>W<sub>9</sub>/ZrO<sub>2</sub>), the activity of SiMo<sub>9</sub>W<sub>3</sub>/ZrO<sub>2</sub> surpassing also that of SiMo<sub>12</sub>/ZrO<sub>2</sub> with k<sub>HDO</sub> = 25.1 mol·cresol·mol·metals⁻¹·h⁻¹. Moreover, it appears that there is a synergy between Mo and W beneficial to hydrodeoxygenation. This is confirmed by the comparison between estimated apparent rate constants of mixed MoW catalysts, calculated from the experimental rate constants of SiMo<sub>12</sub>/ZrO<sub>2</sub> and SiW<sub>12</sub>/ZrO<sub>2</sub>, and their experimental values (Figure 6). All experimentally obtained values were greater than estimated ones, pointing to the advantage of Mo–W combination on activity, especially in the case of SiMo<sub>9</sub>W<sub>3</sub>/ZrO<sub>2</sub> for which a large difference between the two rate constants is observed (25.1 versus 16 mol·cresol·mol·metals⁻¹·h⁻¹ estimated).

Apparent k<sub>DDO</sub> values reported in Table 6 confirm that the DDO pathway is favorable for all catalysts. Product selectivity results determined at near iso-conversion (34–40%) are given in Table 7. Selectivities of the catalysts to the DDO pathway are also shown in Figure 6 together with catalytic activity for the MoW series. It can be seen that the selectivity to toluene improved in the presence of tungsten, reaching almost 100%. In particular, for the most active catalyst SiMo<sub>9</sub>W<sub>3</sub>/ZrO<sub>2</sub>, this selectivity was of 96% compared to 91% for SiMo<sub>12</sub>/ZrO<sub>2</sub>. It appears then that although W is much less active than Mo, it is

more selective to aromatics, which might be due to its higher oxophilicity.

Considering the different content of Mo in the catalysts, the numbers of Mo⁵⁺ and Mo⁴⁺ atoms in the MoW reduced catalysts were calculated based on the atomic proportions of Mo⁵⁺ and Mo⁴⁺ as determined by XPS (Table 4).

A linear relationship between k<sub>HDO</sub> determined experimentally and the number of Mo⁵⁺ atoms obtained for the reduced catalysts at 1 bar as well as 30 bar was observed as shown in Figure 7. On the other hand, the quantity of Mo⁴⁺ atoms formed on the reduced catalysts does not follow the activity (Table 4). As for W, no reduction was observed under 1 bar and only around 10% of W⁵⁺ is formed under 30 bar H₂ at 340 °C. Indeed, literature indicated that under higher temperature (500 °C), W was reduced to W⁴⁺ and W⁰ without the formation of W⁵⁺.[³⁶] W is thus not significantly reduced in our conditions, and the small amounts of W⁵⁺ in SiW<sub>12</sub>/ZrO<sub>2</sub> (10% of the total amount of W) do not lead to a significant conversion (only 3%).

These results then confirm that in our conditions Mo⁴⁺ cannot be considered as active phase for HDO, in agreement with previous literature work,[³⁵] and neither can reduced W species. Reduced Mo⁵⁺ species can thus be considered as the active sites for HDO reactions on a series of supported catalysts using the same support.[¹²] The increase in the number of Mo⁵⁺ atoms can be attributed to the presence of W, as seen for both the MoW oxidic precursors and reduced catalysts from XPS results (Table 4).

Conclusion

A series of supported Mo oxide catalysts were prepared and investigated for the HDO of m-cresol at 340 °C and 30 bar. It was observed that for different supports, the proportion of Mo⁵⁺ species detected on the reduced catalysts could not be

<figure><img src="image_17.png" /><figcaption>**Figure 7.** Relationship between k<sub>HDO</sub> and number of Mo⁵⁺ atoms for the reduced SiMo<sub>x</sub>W<sub>12-x</sub>/ZrO<sub>2</sub> catalysts at 1 and 30 bar.</figcaption></figure>

<figure><img src="image_18.png" /><figcaption>**Figure 6.** Catalytic activity and selectivity of SiMo<sub>x</sub>W<sub>12-x</sub>/ZrO<sub>2</sub> catalysts.</figcaption></figure>

<table><caption>**Table 7.** Product selectivity from HDO of m-cresol over SiMo<sub>x</sub>W<sub>12-x</sub>/ZrO<sub>2</sub> catalysts at 340 °C and 30 bar.</caption><thead><tr><th rowspan="2">Catalyst</th><th rowspan="2">W/F<br>[g h mol<sub>cresol</sub><sup>-1</sup>]</th><th rowspan="2">Conversion<br>[%]</th><th colspan="3">Selectivity [mol %]</th></tr><tr><th>Toluene</th><th>MCHenes</th><th>MCH</th></tr></thead><tbody><tr><td>SiMo<sub>12</sub>/ZrO<sub>2</sub></td><td>23</td><td>40</td><td>91</td><td>9</td><td>&lt; 1</td></tr><tr><td>SiMo<sub>9</sub>W<sub>3</sub>/ZrO<sub>2</sub></td><td>23</td><td>38</td><td>96</td><td>4</td><td>&lt; 1</td></tr><tr><td>SiMo<sub>6</sub>W<sub>6</sub>/ZrO<sub>2</sub></td><td>45</td><td>38</td><td>99</td><td>1</td><td>&lt; 1</td></tr><tr><td>SiMo<sub>3</sub>W<sub>9</sub>/ZrO<sub>2</sub></td><td>72</td><td>34</td><td>98</td><td>2</td><td>&lt; 1</td></tr><tr><td>SiW<sub>12</sub>/ZrO<sub>2</sub>*</td><td>522</td><td>16</td><td>98</td><td>2</td><td>&lt; 1</td></tr></tbody></table>

<footnote>*: Since SiW<sub>12</sub>/ZrO<sub>2</sub> is not active in HDO, the conversion cannot be further increased due to limitations in experimental conditions.</footnote>
<figure><img src="image_19.png" /></figure>

linked to the catalytic performances, suggesting that other parameters need to be considered, such as the reducibility of Mo, which was found to depend on the support nature and to correlate with activity: Mo/ZrO₂ > Mo/TiO₂ > Mo/Al₂O₃ > Mo/ COK12.

This work was then extended to a series of SiMoₓW₁₂ₓ catalysts supported on ZrO₂, starting from mixed H₄SiMoₓW₁₂ₓO₄₀ heteropolyacids having 10 wt.% total metal content. H₂-TPR and XPS results first showed that the less active catalyst SiW₁₂/ ZrO₂ is not significantly reduced under our experimental conditions, which confirms that the use of a reducible active phase is preferable for HDO reactions. Then, a correlation was found between the quantity of Mo⁵⁺ atoms on the reduced catalysts both at 1 and 30 bar and the catalytic activity, confirming that Mo⁵⁺ species can be considered as active sites for HDO. The increase of the amount of Mo⁵⁺ species was obtained using mixed MoW precursors, highlighting the positive effect of W on Mo reducibility. In particular, the most active catalyst SiMo₉W₃/ZrO₂ showed the highest number of Mo⁵⁺ atoms. A synergy between Mo and W was observed for all MoW catalysts for which the obtained experimental activities were higher than the expected ones. The presence of W increased the selectivity to the formation of toluene through the DDO pathway.

Experimental Section

Preparation of catalysts with different supports

10 wt.% Mo were deposited through incipient wetness impregnation method on different oxide supports: commercial γ-Alumina (ELF Solaize research center, ref SAG 1175), Zirconia (monoclinic, Saint Gobain, ref SZ 31164) and Titania (anatase, Saint Gobain, ref ST 61120), as well as ordered mesoporous silica COK12 synthesized in the laboratory according to the protocol of Jammaer and al.[37] Ammonium heptamolybdate (NH₄)₂Mo₇O₂₄·4H₂O (99%, Alfa Aesar) was chosen as Mo precursor. First, an aqueous solution of the Mo precursor was added dropwise to the support with frequent stirring. Then, the impregnation process is followed by a maturation step at room temperature for 3 h to allow the solution to diffuse well in the pores. The solid is then dried at 100 °C overnight in an oven, before being calcined under air at 500 °C for 4 h (1.5 °C/min) to decompose the salts and form the supported oxides.

Preparation of catalysts with different active phase
precursors

Monometallic and mixed H₄SiMoₓW₁₂ₓO₄₀ heteropolyacids with varying Mo/W atomic ratios were first synthesized according to previous reports. Five starting materials were obtained: H₄SiMo₁₂O₄₀ (SiMo₁₂),[³⁸] H₄SiW₁₂O₄₀ (SiW₁₂),[³²] H₄SiMo₃W₃O₄₀ (SiMo₃W₃),[³⁴] H₄SiMo₆W₆O₄₀ (SiMo₆W₆),[³⁴] and H₄SiMo₉W₃O₄₀ (SiMo₉W₃),[³⁴] .Their elemental composition and structures were confirmed by XRD and Raman spectroscopy.

Catalysts with 10 wt.% total metals were prepared by incipient wetness impregnation of the zirconia support with aqueous solutions of the aforementioned SiMoₓW₁₂ₓ crystals. After maturation for 3 h, the catalysts were dried at 100 °C overnight without further calcination.

All catalysts were finally crushed and sieved to a grain size of 200–300 µm before use.

Catalyst characterizations

Inductively coupled plasma optical emission spectroscopy analysis (ICP-OES-5110 Agilent) was performed on the oxidic precursors to determine the exact amount of Mo and/or W loadings. The samples were mineralized by mixing with an acidic aqueous solution containing nitric, hydrochloric and hydrofluoric acids.

Bare supports and oxidic precursors were characterized by N₂-
physisorption, X-Ray diffraction, Raman spectroscopy and H₂-
temperature programmed reduction.

N₂-physisorption was carried out at -196°C using a Micrometrics ASAP 2000 apparatus functioning in multipoint mode. The textural properties are determined from adsorption-desorption isotherms: the specific surface area is calculated according to the Brunauer-Emmett-Teller (BET) model and the pore size according to the Brunauer-Joyner-Halenda (BJH) theory. The samples were degassed beforehand under vacuum at 200°C for 5 h.

Powder X-ray diffraction (XRD) patterns were recorded in the 10–90° range on a BRUKER D8 type apparatus. The acquisition step was set to 0.02° and the acquisition time to 2 seconds per step. Low angle diffractions were also performed from 0 to 5° for the COK12 bare support and corresponding Mo supported catalyst, on a Bruker D8 Advance diffractometer, with the small divergence and scattering slits being 0.02° and the acquisition time being 15 seconds per step. Phase identification was determined from ICDD database search.

Raman spectroscopy was performed at room temperature on an
XPlora spectrometer (Horiba) equipped with a 532 nm visible green
laser operating at a power of 100 mW. An optical magnification of
50 times was used and the spectra were recorded from shifts
between 200 and 1200 cm⁻¹.

Temperature programmed reduction (H₂-TPR) analyses were per-
formed on a Micrometrics AutoChem II 2920 V3.05 instrument. The
sample is first pretreated under argon at 200 °C for 1 h. After
cooling down, it is subjected to a programmed temperature
increase from 100 to 1000 °C (10 °C/min) under a reducing mixture
of 5 vol% H₂/Ar (50 ml/min). The composition of the gas mixture is
measured at the outlet by a thermal conductivity detector (TCD).

Catalysts activated under H₂ at 340°C and 1 bar and catalysts
collected after test were characterized by X-ray photoelectron
spectroscopy (XPS) technique. XPS spectra were recorded on a
Kratos Axis Ultra DLD spectrometer using a monochromatic Al Kα
source (hn = 1486.6 eV, 150 W) and a charge neutralization system.
Data analysis was performed on the CasaXPS software (Version
2.3.23). Binding energies were first corrected to provide the C 1s
spectral component at 284.8 eV and then, after applying a Shirley
background subtraction, the individual spectral regions of Mo 3d
and W4f were decomposed using the GL (30) line shape to identify
the existing oxidation states. Three constraints were used for
deconvolution: equal full width at half maximum for Mo 3d₃/₂ and
Mo 3d₅/₂ as well as for W4f₅/₂ and W4f₇/₂, an area ratio of Mo 3d₃/₂ to
Mo 3d₅/₂ equal to 2/3 and of W4f₅/₂ to W4f₇/₂ equal to 3/4, and a
splitting energy of 3.15 eV for Mo 3d₃/₂ and Mo 3d₅/₂ and of 2.15 eV
for W4f₅/₂ and W4f₇/₂. Binding energies of Mo 3d transitions for all
the samples are shown in tables S3 and S5 in the supplementary
information and those of W 4f in table S6.
## Catalytic Tests

Catalytic activity and selectivity were studied for the hydrodeoxygenation reaction of m-cresol, chosen as model phenolic compound. 300 mg of catalyst were loaded in a down flow inox tubular fixed-bed reactor (length: 40 cm; inner diameter: 1.26 cm). The catalyst was first activated under 2 L h⁻¹ of H₂ at 340 °C and 30 bar for 1 h. The reaction starts at the same temperature and pressure conditions by sending through the liquid feed using an HPLC Gilson pump. The inlet feed is composed of 7 mol% m-cresol as reactant, 89 mol% n-heptane as solvent and 4 mol% n-decane as internal standard. The H₂/m-cresol ratio was fixed at 286 NL·L⁻¹ throughout the experiments.

Catalyst activity was determined by carrying out HDO reactions over a time space of 6 h. H₂ and feed flow rates were set to 6.80 L h⁻¹ and 0.23 mL min⁻¹ respectively, which corresponds to a space time τ (defined as the ratio of catalyst weight to molar flow rate of m-cresol W/F<sub>m-cresol</sub>) of 45.8 g h mol⁻¹. Gas products exiting the reactor were condensed at 10 °C in a Minichiller-Huber condenser. The resulting liquid was extracted every hour and was injected in a Varian 430 gas chromatographic system equipped with a DB1 capillary column (length: 30 m, inside diameter: 0.32 mm, film thickness: 5 µm) and an FID detector. Conversion X and activity k<sub>HDO</sub> of the catalysts were calculated as follows:

$$X (\%) = \frac{C_{\text{cresol(0)}} - C_{\text{cresol(0)}}}{C_{\text{cresol(0)}}} \cdot 100 \quad (1)$$

$$k_{\text{HDO}} (\text{mol c\text{resol} mol metals}^{-1} \text{h}^{-1}) = - \frac{F_{\text{m-cresol}}}{n_{\text{metals}}} \ln \left( 1 - \frac{X}{100} \right) \quad (2)$$

where C<sub>cresol(0)</sub> and C<sub>cresol</sub> are the molar fractions of m-cresol in the feed and in the collected liquid sample.

Selectivities of the different catalysts were compared at isothermal and were determined as follows:

$$S_j (\%) = \frac{C_i}{C_{m-cresol(0)} - C_{m-cresol}} \cdot 100 \quad (3)$$

where C<sub>i</sub> is the molar fraction of a given product.

## Acknowledgements

This work was financially supported by the University of Lille. Chevreul institute (FR 2638) is acknowledged for supporting this work. The authors thank Pardis Simon and Olivier Gardoll for their contribution in XPS and TPR measurements respectively. Frederic Richard acknowledges the financial support from the European Union (ERDF), "Region Nouvelle Aquitaine".

## Conflict of Interest

The authors declare no conflict of interest.

## Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

**Keywords:** Hydrodeoxygenation · MoOₓ reducibility · Mo⁵⁺ · support effect · Mo-W synergy

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Manuscript received: November 15, 2022

Revised manuscript received: January 23, 2023

Accepted manuscript online: February 1, 2023

Version of record online: February 13, 2023