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Article

ZnO Particles Stabilized in Polymeric Matrix for Liquid-Phase Methanol Synthesis

by
Valentin Yu. Doluda
1,
Olga P. Tkachenko
2,
Antonina A. Stepacheva
1,
Alexander I. Sidorov
1,
Alexey V. Bykov
1,
Mikhail G. Sulman
1,* and
Yury Yu. Kosivtsov
1
1
Department of Biotechnology, Chemistry and Standardization, Tver State Technical University, 170026 Tver, Russia
2
Laboratory of Developments and Study of Polyfunctional Catalysts, N.D. Zelinsky Institute of Organic Chemistry of Russian Academy of Science, 119991 Moscow, Russia
*
Author to whom correspondence should be addressed.
Catalysts 2023, 13(1), 116; https://doi.org/10.3390/catal13010116
Submission received: 21 November 2022 / Revised: 26 December 2022 / Accepted: 28 December 2022 / Published: 4 January 2023
(This article belongs to the Special Issue Application of Metal-Based Nanocatalysts for Environment and Energy)
Browse Figures
Versions Notes

Abstract

:
ZnO supported on hypercrosslinked polystyrene was developed for liquid-phase methanol synthesis. The synthesized catalyst was characterized using the low-temperature nitrogen physisorption, TEM, XPS, XAS, and CO DRIFT methods. The analysis showed that the catalyst has a high specific surface area (720 m2/g) and is characterized by the micro-mesoporous structure typical of the polymer used. The active phase is represented by ZnO species with a hexagonal wurtzite structure. ZnO-HPS showed high activity, selectivity, and stability in liquid-phase methanol synthesis in comparison with the industrial catalyst. The activity of the proposed catalyst was found to be 1.64 times higher than that of the conventional Cu/ZnO/Al2O3.

1. Introduction

Methanol is one of the key reactants in various fields of industry, i.e., pharmaceutical, cosmetic, perfumery, and fine chemistry. Methanol is also widely used for biodiesel production and can be applied as an alternative fossil fuel [1,2,3,4]. The production of methanol from biomass through gasification and subsequent CO hydrogenation is considered to be one of the prospective directions in green and sustainable chemistry [5,6,7].
Methanol can be produced in different ways: methane oxidation [8], the Christiansen process [9], two-step synthesis from methane through methyl-halide formation as an intermediate [10], and from synthesis gas [11,12,13,14]. The last process is currently used worldwide.
The synthesis of methanol from synthesis gas can be realized by either two- (gas phase) [15,16,17,18] or three-phase (liquid phase) processes [19,20]. Although gas-phase synthesis is widely studied, the high exothermic effect of the reaction requires the development of complex reactor systems [21]. Thus, liquid-phase methanol synthesis seems to be a promising method because of the simple reactor design, effective heat transfer, and lower process temperature [22,23,24,25]. Alcohols are the most often used solvents in liquid-phase methanol synthesis [26,27,28]. One of the main limitations of the liquid-phase process is considered to be the high catalyst deactivation rate [29,30]. However, this problem can be solved by the development of a stable and effective catalytic system.
In the industry, methanol synthesis from synthesis gas is carried out at the temperature of 240–270 °C and a pressure of 4.0–7.0 MPa. The typical catalyst used in this process is CuO/ZnO/Al2O3 [31,32,33,34,35,36,37,38,39,40]. The catalyst contains CuO (from 20 to 80%), ZnO (15–50%), and alumina (4–30%). Moreover, some additives can be used as promoters (i.e., MgO [41,42], ZrO2 [43,44,45], Cr2O3 [43], and rare-earth metal oxides [41]). Cu particles are considered to be the main active components in methanol synthesis catalysts, while ZnO mainly provides the Cu dispersion [46,47]. However, some researchers showed that ZnO tends to be the active site in CO’s hydrogenation into methanol [48,49]. Thus, in this work, the use of ZnO particles supported on an inert polymeric matrix of hypercrosslinked polystyrene (HPS) in methanol synthesis is proposed. The use of polymers to stabilize the nanoparticles of transition metals and their oxides is an attractive possibility for the synthesis of efficient and stable catalysts, allowing modification of catalytic properties. The rigid polymers have a high surface area and both small and large mesopores, which are suitable for the formation of the active phase and substrate transport to the active sites [50,51,52].

2. Results and Discussion

2.1. Characterization of Catalyst Samples

Three catalyst samples—initial, treated with hydrogen, and after catalysis—were analyzed by low-temperature nitrogen physisorption. The obtained isotherms (IV type) of nitrogen adsorption for all studied samples correspond to those for micro-mesoporous materials (Figure 1a) [53]. The form of the hysteresis loop (H4 type) indicates the presence of narrow slit-like pores for the studied samples (Figure 1b). Table 1 shows that during Zn incorporation into the polymer matrix a slight decrease in surface area is observed. Moreover, the decrease in the external surface area indicates the formation of ZnO particles in the polymer mesopores. For the catalyst treated with hydrogen at the reaction conditions, the surface area slightly decreases in comparison with the as-received catalyst. It indicates that no sufficient changes in the catalyst surface take place during the catalyst treatment. The decrease in surface area for the catalyst after the reaction can be connected with the absorption of reaction products into the pores of the polymer.
TEM images of the three catalyst samples—initial, treated with hydrogen, and after catalysis, are presented in Figure 2. The study of the initial ZnO-HPS catalyst sample (Figure 2a) showed the presence of Zn-containing nanoparticles with a mean diameter of 8 nm. The treatment with hydrogen (Figure 2b) led to a slight increase in the particle size up to 8.5 nm. The catalyst sample after methanol synthesis (Figure 2c) also showed slight aggregation up to the size of 9.6 nm. A further increase in ZnO nanoparticle size was not observed.
The survey XPS spectra for the Zn-HPS-based catalyst samples show the presence of oxygen, carbon, zinc, and nitrogen on the polymer surface (Figures S1–S3). Chlorine was also observed as one of the contaminating agents. Moreover, chlorine ions can be absorbed by the polymer during its synthesis. From Table 2, it is seen that the treatment of the as-received catalyst with hydrogen at the reaction conditions leads to a negligible increase in Zn content on the catalyst surface from 1.2 up to 1.6 at. %, which can be attributed to the formation of additional ZnO clusters during the catalyst’s saturation. However, such a difference is not significant and is within the permissible range of error. After the catalysis, a significant increase in the Zn surface content was observed (up to 3.6 at. %), which can be explained by the slight aggregation of the catalyst’s active phase.
The deconvolution of the high-resolution XPS Zn 2p spectra (Figure 3a) results in one type of reactive species that can be attributed to ZnO [54,55,56]. Slight shifts in the binding energies for both Zn and O to higher values are attributed to the differential charging of the catalyst surface. The presented data are in accordance with those obtained in the XAS study. The formation of ZnO crystals on the HPS surface was additionally confirmed by the XRD study (Figure S4) [57,58]. The analysis of XPS O 1s high-resolution spectra showed that the oxygen atoms present on the catalyst surface are attributed to ZnO species. However, for the as-synthesized catalyst sample, an additional peak at ~535.5 eV attributed to the adsorbed water was observed (Figure 3b).
To estimate the structure of the catalytically active sites of the ZnO-HPS catalyst, the three samples—ZnO-HPS initial (as received), treated with H2, and after catalysis—were studied by XAS analysis. Figure 4 shows the Zn K XANES of these zinc samples with the ZnO reference compound. The position of the Zn K-edge in all spectra of the ZnO-HPS catalysts is similar to that in the spectrum of the ZnO reference. This means that Zn in all catalyst samples exists in the Zn2+ electronic state, as was expected.
Furthermore, one can deduce by analyzing the intensity of the white line that the Zn species in the initial sample is, on average, surrounded by more electron-acceptor neighbors, whereas both treated samples and samples after the reaction demonstrate more electron-donor neighbors, which can be attributed to dynamic morphology changes in the catalyst structure, mainly due to the saturation of ZnO clusters with hydrogen and partial ZnO reduction, thus leading to changes in oxidation potential and surface energy [59].
The Fourier transformation of EXAFS oscillations for the three ZnO-HPS samples and references is presented in Figure 5. There are two narrow peaks in the spectrum of the ZnO reference. The first peak corresponds to the first and second coordination shells containing, respectively, one and three oxygen atoms at 1.79 and 2.04 Å real distances from the central Zn atom. The second peak corresponds to the third and fourth coordination shells containing, respectively, six and six zinc atoms at 3.21 and 3.25 Å real distances from the central Zn atom [60].
The FT EXAFS spectra of both ZnO-HPS treated samples and samples after catalysis are similar to those of the ZnO reference, whereas the FT EXAFS spectra of the ZnO-HPS initial sample show second peaks at a higher uncorrected distance. In addition, the intensity of the second peak differs in the FT EXAFS spectra of all three ZnO-HPS samples. The first and second peaks of the Zn FT EXAFS spectra were fitted in both r- and k-spaces with a two-shell model—oxygen and zinc shells around the central absorbing Zn atom (Figures S5–S7). The results of the model fit are presented in Table 3.
It is seen that the first shell contains three O atoms at a real distance of 2.04 Å and the second shell contains five Zn atoms at a real distance of 3.26 Å in the initial sample. The first shell contains three O atoms at a real distance of 2.00–2.02 Å in both treated samples and samples after the reaction. The second shell contains 10–11 Zn atoms at a real distance of 3.22 Å in these samples. The increase in Zn atom content in the structure of the ZnO active site can be connected with a partial reduction in ZnO species. As was proposed by [61], the decrease in oxygen content in zinc oxide clusters leads to a decrease in the interface energy, thereby leading to the enhancement of the catalyst–substrate interaction and an increase in catalytic activity. Thus, the treatment of the initial catalyst with hydrogen allows an increase in the catalytic performance. The insufficient changes in Zn atom content in the case of the used catalyst indicate that the catalyst maintains its morphology and thereby its activity. Thus, it can be proposed that the active site of the synthesized catalyst has a Zn–O–Zn cluster structure, where Zn atoms are dissolved in ZnO. Moreover, the saturation of catalysts with hydrogen leads to the formation of larger clusters (in comparison with the as-received catalyst) with a plane form.
Figure 6 represents the IR spectra of CO diffusion reflection registered for the three ZnO-HPS catalysts: initial, treated with hydrogen, and after the catalysis.
After CO adsorption at room temperature, one low-intensity absorption band at 2167 cm−1 is observed in the spectra of the initial sample (Figure 6a). This band corresponds to the valent vibrations of the CO molecule adsorbed on Zn2+ in the linear form. In the spectra of the catalyst sample treated with hydrogen, an absorption band at 2174 cm−1 attributed to the valent vibrations of CO adsorbed on Zn2+ in linear form is observed (Figure 6b). After holding the sample at room temperature for 17 h, the intensity of the absorption band at 2174 cm−1 decreased, while the band at 2359 cm−1 was attributed to the appearance of adsorbed CO2 molecules. In the IR spectra of the catalyst sample after catalysis (Figure 6c), the adsorption bands at 2170 cm−1 and 2357 cm−1 attributed to the vibrations of CO and CO2 adsorbed on Zn2+, respectively, are observed.

2.2. Catalytic Performance Study

The synthesized catalyst testing in methanol synthesis showed that the methanol yield reached up to 513 g(MeOH)/(kg(cat)∙h), compared to 312 g(MeOH)/(kg(cat)∙h) in the case of the conventional Cu/ZnO/Al2O3 catalyst reported in [24], as well as to the MEGAMAX® 700 catalyst, which afforded a methanol yield reaching up to 118 g(MeOH)/(kg(cat)∙h). The formation of methane as the main byproduct for the synthesized catalyst reached up to 86 mg(CH4)/(kg(cat)∙h), while, for MEGAMAX® 700, methane formation was over 350 mg(CH4)/(kg(cat)∙h). Moreover, the developed catalyst showed high activity at a lower temperature (170 °C) compared to a commonly applied temperature of 250–270 °C. Figure 7 shows that the ZnO-HPS catalyst maintains and even slightly increases its activity and selectivity up to 100 h, while, for the industrial catalyst, there was observed a slight decrease in catalytic performance at long-term operation (see Table 4).

3. Materials and Methods

3.1. Materials

Hypercrosslinked polystyrene (HPS) Macronet MN100 (functional groups—tert-amino groups, weak base capacity 0.5 mol/L, moisture 55–62%, swell factor max ±5%, specific gravity 1.04 g/mL, specific surface area 790 m2/g) was purchased from Purolite Int. (Llantrisant, U.K.) and used as received as a catalyst support. Zinc acetate (chemical grade, Sigma Aldrich, St. Louis, MO, USA) was used as a ZnO precursor. Tetrahydrofuran (chemical grade, Sigma Aldrich, USA) and methanol (chemical grade, Sigma Aldrich, St. Louis, MO, USA) were used as received for catalyst preparation. Isopropyl alcohol (IPA) (chemical grade, Kupavna Reactive, Moscow, Russia) and n-dodecane (chemical grade, Kupavna Reactive, Moscow, Russia) were used as solvents in methanol synthesis. H2 (99.9%, GasProduct, Tver, Russia), N2 (99.9%, GasProduct, Tver, Russia), CO (99.9%, GasProduct, Tver, Russia), and CO2 (99.9%, GasProduct, Tver, Russia) were used for methanol synthesis.

3.2. ZnO Catalyst Synthesis

The catalyst was prepared by the wet impregnation of HPS with 0.4225 g of Zn(Ac)2 in a solution containing 5.0 mL of tetrahydrofuran, 1.0 mL of methanol, and 3.0 mL of distilled water for 3.0 g of MN-100. The suspension was continuously stirred for 10 min to allow the adsorption of the solution by the polymer granules. Then, the resulting granules were dried at 75 °C for 1 h. The catalyst was washed with water at pH 6.4–7.0 and dried at 75 °C for 3 h and then heated up to 250 °C for 5 h under a nitrogen flow to form ZnO. Zn content was found to be 5.0 wt. % by X-ray fluorescent elemental analysis using Zeiss Jena VRA-30 (Zeiss, Jena, Germany).

3.3. Catalyst Characterization

The specific surface area, porosity, and pore size distribution of the catalyst samples (initial, after saturation with hydrogen, and after catalysis) were determined by nitrogen low-temperature adsorption using a Beckman Coulter SA 3100 (Coulter Corporation, Brea, CA, USA) analyzer. Before the analysis, the samples were outgassed in a Beckmann Coulter SA-PREP (Coulter Corporation, Brea, CA, USA) apparatus for sample preparation at 120 °C in a vacuum for 1 h. To estimate the specific surface area and total pore volume, the t-plot and Brunauer–Emmett–Teller models were used. Pore size distribution was evaluated using the Harkins–Jure equation.
The transmission electron microscopy (TEM) study of the catalyst samples (see before) was performed using a JEOL JEM1010 scanning transmission electron microscope (JEOL Ltd., Tokyo, Japan) operating at 80 kV. The polymer-based samples were embedded in an epoxy resin and microtomed in cross-sections. Images of the resulting thin sections (ca. 100 nm thick) were collected with a Gatan digital camera (Gatan Inc., Pleasanton, CA, USA) and analyzed with the Adobe Photoshop software package and the Scion Image Processing Toolkit (Scion Corporation, Chicago, IL, USA).
X-ray photoelectron spectroscopy (XPS) analysis of ZnO-HPS was performed using an ES-2403 spectrometer (Institute for Analytical Instrumentation RAS, St. Petersburg, Russia) modified with an analyzer, the PHOIBOS 100 produced by SPECS GmbH (Berlin, Germany), equipped with a MgKα/AlKα XR-50 X-ray radiation source. The spectra were acquired at an X-ray power of 200 W and an energy step of 0.1 eV. Before the analysis, the samples were allowed to outgas for 180 min. The data analysis was performed using CasaXPS (Casa Software Ltd, Teignmouth, U.K.).
X-ray absorption spectroscopy measurements were carried out on the BM23 station of The European Synchrotron Radiation Facility (Grenoble, France). Zn K (9659 eV) X-ray absorption spectra were recorded in the transmission mode using a Si (111) double-crystal monochromator. The samples, pressed into self-supporting wafers, were measured at 30 K. The spectrum of a metal foil was recorded simultaneously between the second and a third ionization chamber for energy calibration purposes. Special care was taken to avoid ambient atmosphere contamination. For sample preparation, the optimum weight to maximize the signal-to-noise ratio was pressed into a 13 mm diameter pellet in a glove bag (a dried He atmosphere) and completely wrapped in polyimide (Kapton, DuPont, Wilmington, DE, USA) adhesive tape. The analysis of the EXAFS spectra was performed with the software VIPER (Oriux, Houston, TX, USA) for Windows. The required scattering amplitudes and phase shifts were calculated by the ab initio FEFF8.10 code [62,63] for ZnO. At least duplicate spectra were recorded to ensure data reproducibility. The fitting was done in the k- and r-spaces. The shell radius r, coordination number N, Debye–Waller factor σ2, and adjustable “muffin-tin zero” ΔE were determined as fitting parameters. The errors of the fitting parameters were found by decomposition of the statistical χ2 function near its minimum, taking into account maximal pair correlations.
IR spectra of CO diffusion reflection were registered using an IR spectrometer, the NICOLET “Protege” 460 (Thermo Fisher Scientific, Waltham, MA, USA). Before the analysis, the catalyst samples were pretreated in a vacuum for 3 h at room temperature. Carbon monoxide was used as a test molecule. The adsorption of CO was performed at room temperature at a pressure of 12 mm Hg. CO desorption was carried out in a vacuum. Spectra were registered in the range of 6000–400 cm−1 with a step of 4 cm−1.

3.4. Catalytic Performance Study

The catalyst testing was performed in the flow-mode reactor reported in [64]. The catalyst was preliminarily treated at the reaction temperature (170 °C) in 30 mL/min hydrogen flow before the reaction to saturate the catalyst’s active sites with hydrogen. As is known [65], Zn oxide cannot be reduced to the metal state at this temperature, so we expected the presence of ZnO particles in the treated catalyst. A typical experiment was carried out as follows: 0.5 g of the catalyst in 45.0 mL of a solvent consisting of 15.0 mL of isopropyl alcohol (IPA) and 30.0 mL of dodecane was loaded in the reactor, which was equipped with a propeller mixer (stirring rate 250 rpm). Then, the hydrogen pressure was set at 3.0 MPa with a flow of 45 mL/min and the mixture was heated up to 170 °C. After the catalyst’s saturation for 1 h, hydrogen was substituted for synthesis gas composed of 79.38% H2, 0.12% N2, 20.49% CO, and 0.01% CO2, and the stirring rate was increased up to 750 rpm. The synthesis gas pressure was set at 2.0 MPa with a gas feeding rate of 270 mL/min. The reaction temperature was 170 °C. Under the same conditions, we also tested an industrial Cu-Zn-containing catalyst MEGAMAX® 700 (Süd-Chemie AG, Moosburg an der Isar, Germany). The outgoing steam-gas flow was directed into the chromatographic system of an online analysis tool (Kristallux 4000, Meta-Chrom, Yoshkar-Ola, Russia) along the heated line through the return pressure valve and removed from the system through a flow meter.

4. Conclusions

A ZnO-HPS catalyst was synthesized and applied for liquid-phase methanol synthesis. The catalyst has a high specific surface area, allowing the transfer of the reactants and products to the active sites. The characterization of the synthesized catalyst showed that the active phase of ZnO-HPS is represented by ZnO species with a mean particle diameter of approximately 8 nm, formed on the surface of the polymer. The ZnO nanoparticles have a hexagonal wurtzite structure. Moreover, the catalyst structure practically does not change during the reaction. The synthesized ZnO embedded into a polymeric matrix of HPS was found to be an active, selective, and stable catalyst for liquid-phase methanol synthesis, allowing a decrease in the reaction temperature from the conventional 250–270 °C to 170 °C.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal13010116/s1, Figure S1: The survey XPS spectra for the initial Zn-HPS; Figure S2: The survey XPS spectra for the Zn-HPS treated with hydrogen; Figure S3: The survey XPS spectra for the Zn-HPS after catalysis; Figure S4: XRD pattern for the Zn-HPS; Figure S5: Model fits of Zn K EXAFS of ZnO-HPS initial samples in k-space (a) and r-space (b); Figure S6: Model fits of Zn K EXAFS of ZnO-HPS treated samples in k-space (a) and r-space (b); Figure S7: Model fits of Zn K EXAFS spectrum of ZnO-HPS after catalysis sample in k-space (a) and r-space (b).

Author Contributions

Conceptualization, V.Y.D., A.I.S., M.G.S.; methodology, A.I.S.; investigation, O.P.T., A.V.B., V.Y.D., A.A.S.; writing—original draft preparation, A.A.S.; writing—review and editing, A.A.S.; project administration, Y.Y.K. All authors have read and agreed to the published version of the manuscript.

Funding

The financial support for the work was provided by the Russian Science Foundation (grant No 20-69-47084).

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Catalysts 13 00116 g001 550
Figure 1. Results of BET studies: (a) adsorption isotherms; (b) pore size distribution for the catalyst samples: 1—HPS; 2—ZnO-HPS; 3—ZnO-HPS treated with hydrogen; 4—ZnO-HPS after catalysis.
Figure 1. Results of BET studies: (a) adsorption isotherms; (b) pore size distribution for the catalyst samples: 1—HPS; 2—ZnO-HPS; 3—ZnO-HPS treated with hydrogen; 4—ZnO-HPS after catalysis.
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Catalysts 13 00116 g002 550
Figure 2. TEM images and particle size distribution histograms of the catalyst samples: (a,d) initial; (b,e) treated with hydrogen; (c,f) after catalysis.
Figure 2. TEM images and particle size distribution histograms of the catalyst samples: (a,d) initial; (b,e) treated with hydrogen; (c,f) after catalysis.
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Catalysts 13 00116 g003 550
Figure 3. High-resolution XPS spectra: (a) Zn 2p detailed regions; (b) O 1s detailed regions: red line—as-synthesized catalyst; yellow line—catalyst treated with hydrogen; violet line—catalyst after testing.
Figure 3. High-resolution XPS spectra: (a) Zn 2p detailed regions; (b) O 1s detailed regions: red line—as-synthesized catalyst; yellow line—catalyst treated with hydrogen; violet line—catalyst after testing.
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Figure 4. Zn XANES of the Zn samples: 1—ZnO reference; 2—ZnO-HPS initial; 3—ZnO-HPS treated; 4—ZnO-HPS after the catalysis.
Figure 4. Zn XANES of the Zn samples: 1—ZnO reference; 2—ZnO-HPS initial; 3—ZnO-HPS treated; 4—ZnO-HPS after the catalysis.
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Figure 5. FT of Zn K EXAFS spectra of the Zn samples: 1—ZnO reference; 2—ZnO-HPS initial; 3—ZnO-HPS treated; 4—ZnO-HPS after catalysis.
Figure 5. FT of Zn K EXAFS spectra of the Zn samples: 1—ZnO reference; 2—ZnO-HPS initial; 3—ZnO-HPS treated; 4—ZnO-HPS after catalysis.
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Figure 6. CO DRIFT spectra for the ZnO-HPS catalyst samples: (a) initial, (b) treated with hydrogen, (c) after catalysis.
Figure 6. CO DRIFT spectra for the ZnO-HPS catalyst samples: (a) initial, (b) treated with hydrogen, (c) after catalysis.
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Figure 7. Methanol and methane formation curve in the presence of ZnO-containing catalysts.
Figure 7. Methanol and methane formation curve in the presence of ZnO-containing catalysts.
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Table
Table 1. Catalyst surface area and pore volume.
Table 1. Catalyst surface area and pore volume.
SampleVpores, mL/gSBET, m2/gt-Plot Surface Area, m2/gDpores, nm
HPS (MN-100)0.57 ± 0.02770 ± 1External 135 ± 1
Micropore 635 ± 1		4–20
Initial ZnO-HPS0.53 ± 0.02723 ± 1External 100 ± 1
Micropore 623 ± 1		4–20
Treated ZnO-HPS0.53 ± 0.02720 ± 1External 98 ± 1
Micropore 622 ± 1		4–20
ZnO-HPS after catalysis 0.50 ± 0.02693 ± 1External 82 ± 1
Micropore 611 ± 1		4–20
Table
Table 2. Elemental composition of the catalyst surface.
Table 2. Elemental composition of the catalyst surface.
SampleElemental Composition, at. %
CONZnCl
Initial ZnO-HPS85.7 ± 1.110.8 ± 0.21.8 ± 0.11.2 ± 0.10.5 ± 0.1
Treated ZnO-HPS88.8 ± 1.17.5 ± 0.21.6 ± 0.11.6 ± 0.10.5 ± 0.1
ZnO-HPS after
catalysis 		81.8 ± 1.112.3 ± 0.21.7 ± 0.13.6 ± 0.10.6 ± 0.1
Table
Table 3. Parameters of the best model fit of Zn K EXAFS spectra of ZnO-HPS samples.
Table 3. Parameters of the best model fit of Zn K EXAFS spectra of ZnO-HPS samples.
SamplePathR, ÅCNσ × 10−3, Å−2Δ E, eV
InitialZn–O2.04 ± 0.013.3 ± 0.28.2 ± 111.6 ± 0.9
Zn–Zn3.26 ± 0.014.7 ± 0.69.8 ± 123.1 ± 1.3
TreatedZn–O2.00 ± 0.023.2 ± 0.65.2 ± 2.313.9 ± 3.4
Zn–Zn3.22 ± 0.0511.3 ± 1.16.1 ± 0.77.5 ± 0.8
After
catalysis		Zn–O2.02 ± 0.023.4 ± 0.77.6 ± 2.015.0 ± 3.2
Zn–Zn3.22 ± 0.0110.2 ± 1.17.8 ± 0.86.8 ± 1.0
Table
Table 4. Catalyst testing results.
Table 4. Catalyst testing results.
SampleCO Conversion, mol.%MeOH Selectivity, mol.%Selectivity after 100 h, mol.%
ZnO-HPS67.299.899.8
MEGAMAX® 70030.497.595.3
Cu/ZnO/Al2O3 [24]44.599.497.8
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Doluda, V.Y.; Tkachenko, O.P.; Stepacheva, A.A.; Sidorov, A.I.; Bykov, A.V.; Sulman, M.G.; Kosivtsov, Y.Y. ZnO Particles Stabilized in Polymeric Matrix for Liquid-Phase Methanol Synthesis. Catalysts 2023, 13, 116. https://doi.org/10.3390/catal13010116

AMA Style

Doluda VY, Tkachenko OP, Stepacheva AA, Sidorov AI, Bykov AV, Sulman MG, Kosivtsov YY. ZnO Particles Stabilized in Polymeric Matrix for Liquid-Phase Methanol Synthesis. Catalysts. 2023; 13(1):116. https://doi.org/10.3390/catal13010116

Chicago/Turabian Style

Doluda, Valentin Yu., Olga P. Tkachenko, Antonina A. Stepacheva, Alexander I. Sidorov, Alexey V. Bykov, Mikhail G. Sulman, and Yury Yu. Kosivtsov. 2023. "ZnO Particles Stabilized in Polymeric Matrix for Liquid-Phase Methanol Synthesis" Catalysts 13, no. 1: 116. https://doi.org/10.3390/catal13010116

APA Style

Doluda, V. Y., Tkachenko, O. P., Stepacheva, A. A., Sidorov, A. I., Bykov, A. V., Sulman, M. G., & Kosivtsov, Y. Y. (2023). ZnO Particles Stabilized in Polymeric Matrix for Liquid-Phase Methanol Synthesis. Catalysts, 13(1), 116. https://doi.org/10.3390/catal13010116

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