Selective Hydrogenolysis of Tetrahydrofurfuryl Alcohol to 1,5-Pentanediol over MgAl₂O₄-Modified Pt/WO₃/γ-Al₂O₃ Catalyst

Abstract

Tetrahydrofurfuryl alcohol, a cost-effective biomass derivative, offers a sustainable path for synthesizing 1,5-pentanediol through hydrogenolysis. To develop the efficient production of 1,5-pentanediol from this alcohol, we have prepared a series of MgAl₂O₄-modified Pt/WO_x/γ-Al₂O₃ catalysts with varying compositions via impregnation–calcination methods. The physicochemical properties of these catalysts were subsequently characterized using diverse techniques. Characterization revealed that magnesia–alumina spinel modification enhanced Pt particle dispersion, CO adsorption on Pt/WO_x/γ-Al₂O₃, reduced Pt particle reduction temperature, diminished the acid content in the catalysts, and increased the surface oxygen vacancy concentration. These alterations appear to influence the catalyst performance, though other factors cannot be ruled out. Catalytic activity tests demonstrated that magnesia–alumina spinel modification improved tetrahydrofurfuryl alcohol hydrogenolysis activity and the 1,5-pentanediol selectivity of Pt/WO_x/γ-Al₂O₃. Optimal performance was achieved at 12% magnesia–alumina spinel loading, with a tetrahydrofurfuryl alcohol conversion of 47.3% and 1,5-pentanediol selectivity of 88.4%.

1. Introduction

Biomass resources constitute a renewable and environmentally benign source of chemical feedstocks, thereby imparting significant value to their conversion and utilization in the pursuit of sustainable development [1,2]. Tetrahydrofurfuryl alcohol (THFA), serving as a pivotal platform compound, can be derived from the conversion of biomass resources [3,4]. The hydrogenolysis of THFA to produce 1,5-pentanediol (1,5-PeD) represents a highly desirable transformation pathway, given the high market demand for 1,5-PeD, which finds extensive applications in the synthesis of polyesters, polyurethanes, lubricants, perfumes, and advanced solvents, among others [5,6,7]. However, the industrial application of 1,5-PeD produced via THFA hydrogenolysis is constrained by the limitations of current catalysts. Therefore, the development of an efficient catalyst for the production of 1,5-PeD from THFA holds immense significance.

The selective cleavage of the sec-C–O bond in THFA to yield 1,5-PeD, while avoiding the attack on the C–C bond and other C–O bonds, is crucial [8,9]. There is a notable number of reports focusing on nonhomogeneous catalysts for the hydrogenolysis of THFA to produce 1,5-PeD. Soghrati et al. [10] examined the catalytic decomposition of THFA over a Ni-WO_x/SiO₂ nonprecious metal–metal catalyst, achieving a 28.7% conversion of THFA and a 47.3% selectivity for 1,5-PeD after 4 h of reaction at 250 °C and 3.4 MPa. Despite the promising performance of this Ni-based catalyst, it lags behind noble metals in terms of stability and activity. Koso et al. [11] formulated a 4 wt% Rh-ReO_x/SiO₂ catalyst for the hydrolysis of 1,5-PeD in THFA, achieving a high yield of 77% after 24 h of reaction. Wang et al. [12] synthesized a 4 wt% Ir-MoO_x/SiO₂ catalyst for the hydrogenation of 1,5-PeD in THFA, achieving a 70% conversion of THFA and a selectivity of around 68% for 1,5-PeD in a fixed-bed reactor at 6 MPa and 200 °C. Although Rh-loaded and Ir-loaded nonhomogeneous catalysts exhibit excellent performance, their industrial application for 1,5-PeD production remains challenging due to the high cost of Rh and Ir and the typical requirement for large industrial catalyst dosages. Given the chemical similarities between Pt, Ir, and Rh, Pt emerges as a cost-effective alternative that better aligns with industrialization demands [13].

In the development of catalysts aimed at the catalytic conversion of THFA to 1,5-PeD, the WO_x/γ-Al₂O₃ composite was selected as the primary catalyst carrier due to the γ-Al2O3’s high specific surface area and outstanding thermal stability [14]. These properties facilitate the dispersion and anchoring of active components. Additionally, WO_x, an economical solid acid material [15], is valued for its ability to produce H_xWO₃ species, whose Brønsted acid sites significantly contribute to the selective ring opening of THFA, thus favoring the production of 1,5-PeD [16].

MgAl₂O₄ exhibits superior thermal stability and mechanical strength, serving as a modified material that integrates the beneficial properties of various catalyst carriers [17]. Li et al. [18] observed that MgAl₂O₄ stabilizes Pt nanoparticles on its surface, suggesting that its modification on the carrier surface could potentially enhance catalyst reactivity. Furthermore, water, an environmentally benign solvent with high H₂ solubility, facilitates the diffusion of H⁺ on oxide surfaces, thus promoting the hydrogenation reaction of metal oxide-loaded catalysts [19,20]. Consequently, an aqueous solution of THFA was employed as the reaction feedstock.

The objective of this study was to enhance the efficiency of 1,5-PeD production via THFA by modifying the Pt-WO₃/γ-Al₂O₃ catalyst with MgAl₂O₄. We conducted thorough characterizations of the modified catalysts to analyze the structural and property alterations resulting from the introduction of MgAl₂O₄. Furthermore, we assessed the catalytic prowess of the MgAl₂O₄-modified catalyst in promoting the hydrogenolysis of THFA for 1,5-PeD synthesis in a fixed-bed reactor.

2. Results and Discussion

2.1. Catalyst Characterization

Figure 1 presents the XRD patterns of Pt/WAl catalysts modified with varying MgAl₂O₄ concentrations. A comparative analysis with the standard card of γ-Al₂O₃ (JCPDS Card No. 10-0425) reveals that the Pt/WAl catalysts exhibit diffraction peaks characteristic of γ-Al₂O₃ at 2θ values of 19.5°, 31.9°, 37.6°, 39.5°, 45.9°, 60.9°, and 67.0°. We are assuming that a very dispersed MgAl₂O₄ phase is formed, undetectable by XRD. Upon the introduction of MgAl₂O₄, the diffraction peaks corresponding to the (400) and (440) crystal planes of γ-Al₂O₃, positioned near 45.9° and 67.0°, undergo a gradual shift towards smaller angles. This shift may be attributed to the partial substitution of Al³⁺ in γ-Al₂O₃ by larger ions (e.g., Mg²⁺) in MgAl₂O₄, leading to an expansion of the γ-Al₂O₃ cell parameters and a corresponding shift in the diffraction peaks towards smaller angles [21], and the introduction of MgAl₂O₄ exerted a distinct influence on the crystalline morphology of the Pt/WAl catalyst. Furthermore, the absence of diffraction peaks corresponding to Pt and WO_x in the XRD spectra of the catalysts suggests their presence in a highly dispersed state within the catalyst matrix.

The textural properties (BET surface area, pore volume, and pore size diameter) of Pt/WAl catalysts modified with varying MgAl₂O₄ concentrations were ascertained through N₂ adsorption analysis. Upon scrutinizing the data presented in

Table 1. Specific surface area, pore volume, pore size, and total acid content of WAl carriers modified in MgAl₂O₄ with different contents.

Samples	Specific Surface Area (m2/g)	Pore Volume (cm3/g)	Pore Size Diameter (nm)	Total Acid Content (μmol/g)
WAl	163	0.50	13.9	181
6MgAl2O4@WAl	138	0.45	13.9	165
12MgAl2O4@WAl	133	0.42	13.9	127
18MgAl2O4@WAl	122	0.38	13.9	124

, it is evident that the specific surface area and pore volume of WAl carriers exhibit a decremental trend with the incremental incorporation of MgAl₂O₄. Notably, despite the augmentation in MgAl₂O₄ content, the pore size of WAl carriers remains unaltered. This reduction in surface area and pore volume can be attributed to the incorporation of MgAl₂O₄, which occupies a portion of the surface and pore channels within the WAl carriers. However, the pore size remains constant, indicating that the pore structure of the WAl carriers is not significantly affected by the addition of MgAl₂O₄.

To assess the N₂ adsorption–desorption isotherms of various carriers, Figure 2 depicts the amount of N₂ adsorbed and desorbed by each carrier as a function of relative pressure (P/P0). The isothermal adsorption curves of yMgAl₂O₄@WAl carriers conform to the characteristic IUPAC IV-type adsorption isothermal curves, accompanied by an H1-type hysteresis loop [22]. This indicates that the modification of MgAl₂O₄ did not alter the original pore structure of the WAl carrier, maintaining its mesoporous nature.

The influence of MgAl₂O₄ modification on the acid strength of the catalyst surface was explored using the NH₃-TPD technique. The findings, presented in Table 1, demonstrate a decreasing trend in the acid amount of WAl carriers with increasing MgAl₂O₄ modification content. This trend is likely attributed to MgAl₂O₄’s limited acidity and its effect on reducing the specific surface area and pore volume of WAl, thereby decreasing the number of acidic sites. Upon examining the data presented in Table 1, it is evident that the disparity in the total acid content between the 12MgAl₂O₄@WAl and 18MgAl₂O₄@WAl carriers is negligible. This observation suggests a relative stability in the total acid content of the carriers, which remains largely unchanged even with an increase in the MgAl₂O₄ content within a specified range (ranging from 12% to 18% of the WAl carrier’s mass).

To elucidate the influence of MgAl₂O₄ modification on the Pt particle dispersion on the Pt/WAl catalyst surface, we standardized the samples using the CO chemisorption technique. The Pt dispersions were calculated assuming a one-to-one ratio of CO molecules to Pt atoms adsorbed on the catalyst surface. The CO chemisorption experiments were performed at room temperature on a fully automated adsorbent apparatus (model TP-5080-B) from Tianjin Xianquan Company using 0.2 g (20–40 mesh) of catalyst. The results are summarized in

Table 2. The CO adsorption capacity and Pt dispersion of samples modified with different contents of MgAl₂O₄.

Samples	CO Adsorption Capacity (μmol/g)	Pt Dispersion (%)
12MgAl2O4@WAl	0.0	0
Pt/WAl	15.6	15
Pt/6MgAl2O4@WAl	35.0	34
Pt/12MgAl2O4@WAl	40.5	40
Pt/18MgAl2O4@WAl	38.0	37

.

As evident from Table 2, WO_x/γ-Al₂O₃ and MgAl₂O₄ did not adsorb CO in the Pt/yMgAl₂O₄@WAl catalysts. Notably, the MgAl₂O₄ modification enhanced the Pt dispersion on the Pt/WAl catalyst surface and increased the amount of adsorbed CO. The Pt/12MgAl₂O₄@WAl catalyst exhibited the highest CO adsorption capacity of 40.5 μmol/g and Pt dispersion of 40%. However, when the MgAl₂O₄ modification content reached 18% of the WAl mass, the CO adsorption and Pt dispersion decreased compared to the Pt/12MgAl₂O₄@WAl catalyst. This decrease may be attributed to the excessive introduction of MgAl₂O₄, leading to localized coverage of the active components in the Pt/WAl catalyst.

To examine the impact of MgAl₂O₄ modification on the size and distribution of Pt particles loaded onto the catalyst surface, transmission electron microscopy (TEM) analysis was employed. Figure 3a,b clearly illustrates the Pt metal particles loaded onto the carrier. By selecting 100 points on the TEM spectra of both catalysts, a statistical analysis was conducted to determine the Pt particle size distribution and average particle size on the catalyst surface. The average Pt particle sizes for the Pt/WAl and Pt/12MgAl₂O₄@WAl catalysts were found to be 1.86 nm and 1.48 nm, respectively. This indicates that the Pt particle size on the MgAl₂O₄-modified Pt/WAl catalyst is reduced. These findings reinforce the notion that MgAl₂O₄ modification enhances the dispersion of Pt particles on Pt/WAl catalysts.

In hydrogenolysis reactions, the noble metal Pt typically requires reduction to a low valence state to exhibit catalytic activity. To characterize the reduction properties of noble metals on solid catalyst surfaces, H₂-TPR is frequently employed. Figure 4 depicts the H₂-TPR profile of the Pt/yMgAl₂O₄@WAl catalyst, where y represents the percentage of MgAl₂O₄ to WAl (y = 0, 6, 12, 18). The profile reveals a broad reduction peak in the range of 100–400 °C, attributed to the reduction of PtO_x [23]. Notably, the reduction peak temperature of the Pt/WAl catalyst is 262 °C, which decreases upon modification with MgAl₂O₄. This reduction in peak temperature likely results from the improved dispersion of Pt particles on the MgAl₂O₄-modified catalyst, enhancing the contact area between PtO_x and H₂, thereby facilitating the reduction reaction at lower temperatures. The lowest PtO_x reduction temperature observed for the Pt/18MgAl₂O₄@WAl catalyst may be attributed to a combination of factors, including the promotional effect of MgAl₂O₄ and the acidic–alkaline properties of the catalyst surface. In summary, we observed a reduction in the reduction temperature of PtO_x in Pt/WAl catalysts modified with MgAl₂O₄, leading to an enhancement in their reduction performance. Additionally, a strong reduction signal was observed in the range of 600–800 °C, potentially representing the reduction process of WO_x [24], though the peak temperature could not be precisely determined due to experimental limitations.

To elucidate the alterations in the valence states of the active components on the Pt/WAl catalyst surface following MgAl₂O₄ modification, XPS characterization was performed. Figure 5a depicts the XPS spectra of O 1s for various MgAl₂O₄-modified catalysts. After peak fitting, three distinct peaks were observed in the O 1s spectra, corresponding to adsorbed oxygen (O_α), lattice oxygen (O_β), and bound oxygen (O_γ) on the catalyst surface. Specifically, the peaks centered at 529.8, 531.2, and 532.4 eV represent O_α, O_β, and O_γ, respectively [25]. Notably, the O_α peak at 529.8 eV originates from chemisorbed O₂ at oxygen vacancy [26]. Consequently, the percentage of O_α serves as an indirect indicator of the oxygen vacancy concentration on the carrier surface. As evident from Figure 5b, the O_α percentage exhibits an upward trend with increasing MgAl₂O₄ content, suggesting that moderate MgAl₂O₄ modification enhances the concentration of oxygen vacancy on the catalyst surface. Oxygen vacancies have been documented to enhance the catalytic activity and selectivity of Pt-loaded catalysts, attributed to their ability to modify the electronic states and surface properties of the catalysts [27,28].

The XPS spectra of W 4f for Pt/WAl catalysts modified with varying MgAl₂O₄ contents are presented in Figure 5c. The Pt/yMgAl₂O₄@WAl catalysts primarily exhibit W in their n-pentavalent and n-hexavalent forms. Specifically, the binding energies of W⁶⁺ 4f_7/2 and W⁶⁺ 4f_5/2 are approximately 35.8 eV and 37.8 eV, while the binding energies of W⁵⁺ 4f_7/2 and W⁵⁺ 4f_5/2 are around 34.9 eV and 36.7 eV [29,30]. As depicted in Figure 5d, the proportion of W⁶⁺ on the surface of the Pt/WAl catalyst experiences a noteworthy increase upon modification with MgAl₂O₄. An elevated proportion of W⁶⁺ may significantly contribute to the enhancement of the catalyst’s activity in the reaction.

2.2. The Activity of Catalysts for Hydrogenolysis of THFA to 1,5-PeD

To examine the influence of MgAl₂O₄ modification on the Pt/WAl-catalyzed THFA hydrogenolysis reaction, the performance of Pt/yMgAl₂O₄@WAl catalysts (y = 0, 6, 12, 18) was evaluated in a fixed-bed reactor at 150 °C, 4 MPa, and weight hourly space velocity (WHSV) of 0.2 h⁻¹. The products were sampled at regular intervals over a 30 h reaction period, and the resulting data are presented in

Table 3. The hydrogenation performance of THFA on WAl catalysts modified with different contents of MgAl₂O₄.

Catalysts	THFA Conversion (%)	Selective (%)
		1,5-PeD	1,2-PeD	n-Pentanol
Pt/WAl	26.0	86.9	0.8	12.3
Pt/6MgAl2O4@WAl	43.6	88.9	0.8	10.3
Pt/12MgAl2O4@WAl	47.3	88.4	0.4	11.3
Pt/18MgAl2O4@WAl	34.7	90.0	0.6	9.4

. Notably, the introduction of MgAl₂O₄ enhanced the catalytic performance of Pt/WAl, with the Pt/12MgAl₂O₄@WAl catalyst (containing 12% MgAl₂O₄ by mass of the WAl carrier) exhibiting the highest performance. This catalyst achieved a THFA conversion of 47.3% and a 1,5-PeD selectivity of 88.4%.

2.3. Discussion

By integrating catalyst characterization results with catalytic reaction test data, we have thoroughly investigated the structure–function relationship of Pt/yMgAl₂O₄@WAl catalysts under THFA hydrogenolysis conditions. BET analyses reveal that MgAl₂O₄ modification significantly impacts the physical properties (BET surface area, pore volume, and pore size) of Pt/WAl catalysts. NH₃-TPD characterization demonstrates that MgAl₂O₄ incorporation significantly decreases the total acid amount of the catalyst. Furthermore, CO chemisorption and TEM analyses indicate that MgAl₂O₄ modification enhances Pt particle dispersion on the catalyst surface, potentially increasing the density of Pt active sites per unit area. Conversely, H₂-TPR characterization shows that MgAl₂O₄ modification improves the reduction performance of the catalysts. Additionally, the XPS results reveal that MgAl₂O₄ modification not only elevates the concentration of oxygen vacancies but also enhances the W⁶⁺ ratio in the catalyst.

After a rigorous analysis of the experimental data, we established a negative correlation between the catalyst’s total acid content and its selectivity towards 1,5-PeD. Specifically, higher total acid amounts resulted in reduced selectivity towards 1,5-PeD. This led us to infer that optimizing the total acid amount of the catalyst is crucial for enhancing the selectivity of 1,5-PeD. Furthermore, we observed a positive correlation between Pt dispersion on the catalyst surface, CO adsorption, and THFA conversion. This can be attributed to the fact that improved Pt dispersion increases the density of active Pt sites per unit area, thereby enhancing the contact frequency with the reactant THFA and ultimately improving conversion efficiency. Additionally, factors such as enhanced catalyst-reducing properties, an increased concentration of oxygen vacancies, and a higher W⁶⁺ ratio are likely to contribute significantly to the improved performance of the catalyst.

The present study reveals promising performance and industrial prospects for MgAl₂O₄-modified Pt/WAl catalysts. However, avenues for further optimization and enhancement, including refinement of the preparation methodology and employment of a superior active carrier, remain unexplored.

3. Experimental Section

3.1. Catalyst Preparation

The following experimental procedure was utilized to prepare the catalysts. All chemicals, except for γ-Al₂O₃ and (NH₄)₆H₂W₁₂O₄₀·nH₂O, were purchased from Sinopharm Chemical Reagent Co. (Shanghai, China), while γ-Al₂O₃ and (NH₄)₆H₂W₁₂O₄₀·nH₂O were sourced from Aladdin and Across Organics (Geel, Belgium), respectively. The requisite quantities of (NH₄)₆H₂W₁₂O₄₀·nH₂O and γ-Al₂O₃ were thoroughly mixed in purified water and maintained at 85 °C for 24 h. Following this, the mixture was extruded into noodle-like shapes using a catalyst molding extruder after cooling to 110 °C, a humidity conducive to molding. The extruded samples were then dried at 110 °C and subsequently calcined at 800 °C for 3 h. The resulting tungsten–aluminum composite oxide (WO_x/Al₂O₃) carrier, labeled WAl, was ground to a particle size range of 20–40 mesh, with a tungsten content of 10 wt%. To modify the WAl carrier with MgAl₂O₄, Mg(NO₃)₂·6H₂O and Al(NO₃)₃·9H₂O were dissolved in purified water at a Mg:Al molar ratio of 1:2, with constant stirring until complete dissolution. The resulting solution, containing a theoretical amount of 0.1 g/mL MgAl₂O₄, was then used to impregnate 30 g of WAl carrier with an equal volume of the MgAl₂O₄ solution. This mixture was allowed to stand for 12 h at room temperature to ensure thorough impregnation. Subsequently, the impregnated samples were dried at 110 °C and calcined in a muffle furnace at 800 °C for 3 h. Following the sequential process, a MgAl₂O₄-modified WAl carrier was synthesized, with a 6 wt% incorporation of MgAl₂O₄ relative to the WAl carrier. To achieve varying MgAl₂O₄ concentrations, the aforementioned procedure was iterated multiple times. The resulting product, labeled as yMgAl₂O₄@WAl carrier, contained MgAl₂O₄ in varying proportions of y wt% concerning the WAl carrier, where y was set at 0, 6, 12, and 18. The pre-prepared yMgAl₂O₄@WAl carriers were impregnated with a precisely measured volume of H₂PtCl₆·6H₂O solution. This impregnation was allowed to proceed at room temperature for 12 h. Subsequently, the impregnated material was dried at 110 °C to remove excess water. Finally, the Pt/yMgAl₂O₄@WAl catalyst was calcined at 450 °C for 3 h. The catalyst possessed a Pt content constituting 2 wt% of the yMgAl₂O₄@WAl carrier.

3.2. Characterization of Catalysts

X-ray diffraction (XRD) analysis was conducted on a Smart Lab X-ray diffractometer from Rigaku, Japan, utilizing CuKα as the radiation source. The instrument was operated at a tube voltage of 40 kV and a tube current of 100 mA, with a scanning speed of 10°/min and a scanning range of 2θ = 10–80°.

To characterize the specific surface area, pore volume, and pore size of the catalysts, a fully automated 3H-2000PS series-specific surface and pore size analyzer from Best Instrument Technology Co. (Beijing, China) was employed. Before testing, the samples underwent a pretreatment process to guarantee accurate results. This pretreatment involved placing the samples in a vacuum environment at 300 °C for up to 3 h to eliminate physically adsorbed moisture, which could potentially occupy the surface and pores of the samples, thereby influencing the subsequent determination of specific surface area and pore size. Once the samples cooled to room temperature, they were placed in a liquid nitrogen environment, and N₂ was used as the adsorbent for adsorption and desorption testing. By measuring the adsorption amount of N₂ at different pressures, the adsorption isotherms of the samples were obtained. Utilizing the BET equation, the specific surface area of the samples was accurately calculated. Additionally, the BJH method was implemented to determine the pore volume and pore size of the samples.

The NH₃-temperature programmed desorption (NH₃-TPD) analysis was performed using a Tianjin Xianquan TP-5080-B fully automated adsorbent apparatus (Tianjin Xianquan Company, Tianjin, China). Before the experiment, 0.3 g (20–40 mesh) of the carrier was pretreated in a nitrogen atmosphere at 450 °C for 1 h. The sample was then equilibrated at 100 °C and adsorbed with high-purity NH3 for 1 h. To stabilize the baseline, the sample was purged with He at 100 °C for 1 h. Subsequently, the temperature was raised to 800 °C at a rate of 10 °C/min, and the desorption of NH₃ was monitored using a thermal conductivity detector (TCD). Calibration was performed by injecting a known amount of NH₃ to accurately measure the desorbed NH₃.

For the H₂-temperature programmed reduction (H₂-TPR) analysis, the same Tianjin Xianquan TP-5080-B apparatus was utilized. Initially, 0.2 g of the catalyst (20–40 mesh) was pretreated in a high-purity N₂ atmosphere at 300 °C for 1 h to remove surface impurities. Following this, the temperature was reduced to 30 °C, and a gas mixture of 10% H₂ and 90% N₂ was introduced at a flow rate of 30 mL/min to saturate the catalyst with hydrogen. After baseline stabilization, the temperature was gradually increased to 800 °C at a rate of 10 °C/min, during which the reduction reaction on the catalyst progressed and hydrogen was consumed.

The CO chemisorption experiments were conducted using a fully automated adsorption meter (model TP-5080-B) from Tianjin Xianquan Company. A 0.2 g sample (20–40 mesh) was pretreated under a continuous flow of H₂ gas (30 mL/min) at 300 °C for 2 h. Following this, the catalyst was purged with He gas (30 mL/min) at 300 °C for 30 min. Subsequently, upon cooling to 30 °C, regular injections of high-purity CO were performed for pulse adsorption. Each injection consisted of 100 μL of CO, and this process was repeated until saturation was achieved. The amount of CO adsorbed was determined by analyzing the peak area. Additionally, the dispersion of Pt in the catalyst and the amount of CO adsorbed were calculated using the method outlined in Ref [31]. This calculation assumes that each Pt atom can adsorb only one CO molecule.

Transmission electron microscopy (TEM) was performed using a TM3000 transmission electron microscope from JEOL, Tokyo, Japan. A minute quantity of catalyst powder was dispersed in ethanol via ultrasonic treatment for 30 min. Subsequently, 10 μL of the supernatant was deposited onto a carbon-coated copper mesh and allowed to dry at room temperature for analysis.

X-ray photoelectron spectroscopy (XPS) measurements were conducted on a KRATOS AXIS SUPRA instrument from Shimadzu, Kyoto, Japan. Monochromatic AlKa (1486.6 eV, 15 kV) was employed as the incident radiation. Before testing, the samples underwent reduction treatment in hydrogen at 300 °C for 3 h, adhering to the catalyst reaction conditions. Charge correction was standardized using the C 1s binding energy of 284.5 eV.

3.3. Catalytic Performance Evaluation

The catalyst performance was evaluated in a continuous flow fixed-bed reactor with a 10 mm reaction tube diameter and 3.5 g (20–40 mesh) catalyst. Before the reaction, the catalysts underwent a pretreatment step: reduction at 300 °C and 4.0 MPa with high-purity hydrogen (50 mL/min) for 2 h. Once the reaction system had cooled to the desired temperature, a 50 wt% aqueous THFA solution was steadily introduced via a double piston pump, operating under a reaction pressure of 4.0 MPa and a hydrogen flow rate of 50 mL/min. At the reactor inlet, the hydrogen and aqueous THFA streams were thoroughly blended, and subsequently, the liquid and gas streams were cooled and recovered efficiently in a gas–liquid separator.

The gaseous reaction products were analyzed on a GC-3900 gas chromatograph, equipped with a hydrogen flame ionization detector (FID), sourced from Ruineng Analytical Instruments Ltd., situated in Tengzhou City, Shandong Province, China. The liquid products were analyzed using the same GC-3900 gas chromatograph, with pure nitrogen as the carrier gas and a capillary SE-54 column (30 m × 0.32 mm × 0.5 μm). The evaporator, detector, and column temperatures were set at 230 °C, 280 °C, and 140 °C, respectively. The results were quantified using the area normalization method.

4. Conclusions

We synthesized a series of Pt/WAl catalysts modified with varying MgAl₂O₄ concentrations through impregnation–calcination methods and examined the influence of MgAl₂O₄ content on the material characteristics and catalytic efficiency. Our findings indicate that MgAl₂O₄ modification not only elevates the conversion of THFA but also enhances the selectivity for 1,5-PeD to a certain extent. This enhancement may be attributed to improvements in Pt particle dispersion on the catalyst surface, an increase in active sites on the support, and a higher concentration of oxygen vacancies on the catalyst surface. The optimal Pt/12MgAl₂O₄@WAl catalyst, achieved with 12% MgAl₂O₄ relative to WAl mass, exhibited a THFA conversion of 47.3% and a 1,5-PeD selectivity of 88.4%. This study provides valuable insights for optimizing the performance of Pt/WO_x-based catalysts in the hydrogenolysis of THFA to produce 1,5-PeD.