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Article

High Active Zn/Mg-Modified Ni–P/Al2O3 Catalysts Derived from ZnMgNiAl Layered Double Hydroxides for Hydrodesulfurization of Dibenzothiophene

1
Provincial Key Laboratory of Oil & Gas Chemical Technology, College of Chemistry & Chemical Engineering, Northeast Petroleum University, Daqing 163318, China
2
Key Laboratory of Enhanced oil & Gas Recovery of Education Ministry, College of Petroleum Engineering, Northeast Petroleum University, Daqing 163318, China
*
Author to whom correspondence should be addressed.
Catalysts 2017, 7(7), 202; https://doi.org/10.3390/catal7070202
Submission received: 14 June 2017 / Revised: 29 June 2017 / Accepted: 29 June 2017 / Published: 4 July 2017

Abstract

:
A series of ZnMgNiAl layered double hydroxides (LDHs) containing 20 wt.% Ni and different Zn/Mg molar ratios were prepared by a coprecipitation method, and then were introduced with H2PO4 via a microwave-hydrothermal method. With the resulting mixtures as the precursors, Zn/Mg-modified ZnMgNi–P/Al2O3 catalysts were prepared. The Zn/Mg molar ratio affected the formation of Ni2P and Ni12P5 in nickel phosphides. The ZnMgNi–P/Al2O3 catalyst with a Zn/Mg molar ratio of 3:1 exhibits the best dibenzothiophene hydrodesulfurization (HDS) activity. Compared with the Ni–P/Al2O3 catalyst prepared from the impregnation method, the ZnMgNi–P/Al2O3 catalyst shows a higher HDS activity (81.6% vs. 54.3%) and promotes the direct desulfurization of dibenzothiophene.

Graphical Abstract

1. Introduction

Sulfur removal has gained growing attention since the stringent fuel standards have been enacted throughout the world [1,2]. Among the existing sulfur removal methods, catalytic hydrodesulfurization (HDS) is a very efficient way to eliminate sulfur from fuel oil [3,4]. However, the existing commercial HDS catalysts fail to meet the regulated levels [5]. Studies on the hydrotreation properties of metal phosphides show that nickel phosphide is the most promising candidate for the preparation of next-generation HDS catalysts [6,7,8].
Layered double hydroxides (LDHs, [ M 1 - x 2 + M x 3 + ( OH ) 2 ] x + ( A x / n n ) m H 2 O ) are lamellarly-mixed hydroxides and a class of anionic clays having a hydrocalcite-like structure, which consist of positively charged mixed metal hydroxide layers and negatively charged interlayer anions [9]. LDHs have been demonstrated as effective precursors for the preparation of nickel phosphide catalysts. For instance, a Ni2P/Al2O3 catalyst prepared from LDHs shows higher HDS activity than that prepared from the impregnation method, but the Ni loading up to 64.4 wt.% is unfavorable for the dispersion of active components [10].
The addition of other metals to LDH-derived catalysts contributes to HDS. For instance, the incorporation of Zn and Mg improved the catalytic activities for HDS. Chen et al. [11] found that Zn-doped NiAlMoW catalyst prepared from a NiZnAl-layered hydroxide precursor could improve 4,6-dimethyl dibenzothiophene HDS activity. The higher HDS activity is attributed to the promoter effect of Zn, since Zn decreases the interaction between alumina and active components (Ni, Mo, and W) that forms Ni(Zn)–Mo(W)–S active species. CoMgMoAl catalysts drived from CoMgAl-terephthalate LDHs both enhanced the thiophene HDS and cyclohexene hydrogenation activities along with the increasing Mg content [12]. Nevertheless, research on development of a Zn/Mg-modified layered precursor for HDS is rare.
In the present work, aseries of ZnxMg1−xNi–P/Al2O3 (x is the Zn/(Zn+Mg) molar fraction) catalysts were prepared by using NH4H2PO4 as the phosphorous precursor and ZnxMg1−xNiAl LDHs as the nickel precursor. In addition, the effects of Zn/Mg molar ratio on the structure and HDS performance of ZnxMg1−xNi–P/Al2O3 catalyst were investigated.

2. Results and Discussion

2.1. Characterization of Catalysts

Figure 1 shows the X-ray diffraction (XRD) patterns of ZnxMg1−xNiAl LDHs with different Zn/Mg molar ratios. Clearly, all the ZnxMg1−xNiAl LDHs show typical XRD patterns of LDHs, including a high intensity peak (003) at 2θ = 11.4–11.7°, two weak peaks (006) and (009) at 2θ = 22.9–23.2° and 34.6–34.7°, respectively, and two smaller peaks (110) and (113) of transition metal oxides at 2θ = 60–63°. These results confirm the successful preparation of ZnxMg1−xNiAl LDHs [13]. No peaks of impurities were discerned, which indicates the high purity of the products.
The structural parameters of ZnxMg1−xNiAl LDHs are listed in Table 1. The lattice parameters a and c are both almost the same among different ZnxMg1−xNiAl LDHs, despite the different Zn/Mg molar ratios. Then, the crystallite sizes at the a- and c-directions were calculated by the Scherrer formula based on the (110) and (003) reflections, respectively. It was found Zn0.75Mg0.25NiAl LDHs had much smaller crystallite size than the other catalysts.
The XRD patterns of ZnxMg1−xNi–P/Al2O3 are shown in Figure 2. Clearly, ZnNi–P/Al2O3 shows the peaks at 2θ = 40.7°, 44.6°, 47.3°, and 54.1° attributed to Ni2P, and the typical peaks of AlPO4, Zn3(PO4)2, and Zn2P2O7. After the introduction of Mg, Ni still existed as Ni2P, while the diffraction peaks of Zn2Mg(PO4)2 appeared at x = 0.75 (Zn0.75Mg0.25Ni–P/Al2O3). With a further increase of Mg dosage, in addition to the Ni2P, the peaks of Ni12P5 also appeared at 2θ = 47.0° and 49.0° at x = 0.5 (Zn0.5Mg0.5Ni–P/Al2O3). At x = 0.25 (Zn0.25Mg0.75Ni–P/Al2O3), the diffraction peaks of Ni2P are weakened until nearly invisible. For MgNi–P/Al2O3, Ni and Mg only existed as Ni12P5 and Mg3(PO4)2.
Textural characteristics of typical catalysts are listed in Table 2. Clearly, all catalysts almost have the same pore volume. The Zn0.75Mg0.25Ni–P/Al2O3 has significantly higher specific surface area, but significantly smaller pore diameter and narrower pore size distribution (mainly concentrated in 2.3 nm) compared with ZnNi–P/Al2O3 and MgNi–P/Al2O3 (Figure 3a). Furthermore, MgNi–P/Al2O3 showes typical IV N2 adsorption isotherms with obvious hysteresis loops at relative pressures between 0.43 and 0.95 (Figure 3b), which confirms the presence of mesopores. Zn0.75Mg0.25Ni–P/Al2O3 and ZnNi–P/Al2O3, however, show typical II N2 adsorption isotherms.
Figure 4 shows the X-ray photoelectron spectroscopy (XPS) spectra of ZnxMg1−xNi–P/Al2O3, and the corresponding binding energies and surface composition are listed in Table 3. For ZnxMg1−xNi–P/Al2O3, the peaks at 852.2–853.7 and 129.2–129.6 eV are assigned to Niδ+ (0 < δ < 2) and Pδ− (0 < δ < 1) [14] (Figure 4a), respectively. The Niδ+ has higher binding energy than elemental Ni (852.5–852.9 eV), but lower than NiO (853.5–854.1 eV), indicating that the Ni in Ni2P bears partial positive charge. The binding energy of Pδ− is below the reported value of elemental P (Figure 4b). In nickel phosphides, because of a covalent bond between the Ni and P atoms and a charge transfer from Ni to P, the electron-deficient Ni formed. Moreover, the peaks at 856.1–857.2 and 134.0–134.5 eV are assigned to Ni2+ and P5+ [7,15], respectively. In addition, a broad shake-up peak appears at the binding energy of ~5.0 eV, which is higher than that of Ni2+ [16,17]. These peaks can be assigned to its satellite peaks, although they are located close to those of Ni3+ and nickel oxysulfide [18,19]. Moreover, the other broad peaks at higher binding energy are ascribed to the Ni 2p of nickel oxide [20].
For Zn0.75Mg0.25Ni–P/Al2O3, the interaction between the Ni2P particles and the support leads to decrease of the binding energy of Niδ+ (853.1 eV) [10,21]. As reported, the hydrogenation ability of the Ni site reduces with the decrease of electron density [22,23]. For MgNi–P/Al2O3, the binding energy of Niδ+ in Ni12P5 phase declines further (852.2 eV). Compared with Zn0.75Mg0.25Ni–P/Al2O3, the binding energy of Niδ+ in MgNi–P/Al2O3 is further reduced, indicating that less electron density is transferred from Ni to P in Ni12P5 compared with Ni2P. Sawhill et al. [15] also reported that the Ni in Ni12P5 has a higher electronic density than Ni2P.
The superficial atomic ratios of the catalysts were determined by XPS and the results are listed in Table 3. As shown from these results, the P/Ni molar ratio determined from the surface composition is far larger than the stoichiometric ratio of Ni2P or Ni12P5, which confirms the occurrence of surface P enrichment in the catalysts. Nonetheless, the Niδ+/ΣNi ratio is lower than 1 for all the catalysts, which indicates the presence of a large proportion of nickel oxide. The phosphorus on the catalyst surfaces essentially exists as PO43−. In addition, the P/Ni molar ratio is the lowest in Zn0.75Mg0.25Ni–P/Al2O3, which indicates that more Ni sites on the catalyst surface are exposed under the same Ni loading.
XRD of ZnxMg1−xNi–P/Al2O3 (Figure 2) shows that Ni, Zn, and Mg all could react with P, thereby affecting the formation of Ni2P and Ni12P5. Thus, how the single loading of ZnO or MgO would affect the formation of Ni2P and Ni12P5 was further studied. The XRD patterns of different nickel phosphate catalysts are shown in Figure 5. For Ni–P/Al2O3, Ni and P only exist as Ni2P, without any other phase, indicating that the active phase is Ni2P. For Zn0.75Mg0.25Ni–P/Al2O3 and Ni–P/ZnO, Ni and P mainly exist as Ni2P, accompanied by a small amount of AlPO4 and Zn3(PO4)2, respectively. For Ni–P/MgO, Ni, P and Mg exist as MgNiO2 and Mg3(PO4)2.

2.2. Catalytic Activity

Figure 6 shows the HDS of dibenzothiophene (DBT) over ZnxMg1−xNi–P/Al2O3 at varying temperatures. Clearly, the DBT conversion increases with the increase in temperature for all the catalysts (Figure 6a). The DBT conversion is promoted slowly with a further temperature rise above 613 K. Moreover, with the increase of Mg content, the DBT conversion over ZnxMg1−xNi–P/Al2O3 first increases and then decreases compared with ZnNi–P/Al2O3. At the reaction temperature of 653 K, and at the Zn/Mg molar ratio of 3:1 (i.e., x = 0.75), the DBT conversion over Zn0.75Mg0.25Ni–P/Al2O3 is maximized to 81.6%, and under the same conditions the conversion rates of ZnNi–P/Al2O3 and MgNi–P/Al2O3 are 70.6% and 54.6%, respectively. From the perspective of active phase composition, for ZnxMg1−xNi–P/Al2O3, XRD shows the nickel phosphide exists as Ni2P at x ≥ 0.75; the composition at x = 0.5 is mainly Ni2P and a small amount of Ni12P5; the composition at x = 0.25 is mainly Ni12P5 and a small amount of Ni2P; at x = 0, only Ni12P5 exists (Figure 2). For nickel phosphides, Ni2P shows much higher hydrogenation activity than Ni12P5 [6]. In addition, the HDS reaction mainly occurs on metal sites. From the perspectives of active phase composition/distribution and active particle size, XPS shows that more nickel sites are exposed on the surfaces of Zn0.75Mg0.25Ni–P/Al2O3 compared with ZnNi–P/Al2O3 (Table 3). The particle sizes of Ni2P in Zn0.75Mg0.25Ni–P/Al2O3 and Zn0.5Mg0.5Ni–P/Al2O3 calculated by the Scherrer formula are 29.4 and 34.8 nm, respectively. The smaller sizes of active Ni2P particles could promote the dispersion of the active Ni2P phase as well as the active specific surface area. Furthermore, compared with ZnNi–P/Al2O3 and MgNi–P/Al2O3 modified by a single metal, the modification by double metals (Zn+Mg) could reduce the mesoporous size and increase the micropore amount of Zn0.75Mg0.25Ni–P/Al2O3.
The reaction scheme for the HDS of DBT is presented in Scheme 1. The HDS of DBT occurs via direct desulfurization (DDS) and hydrogenation (HYD), which mainly form biphenyl (BP) and cyclohexylbenzene (CHB), respectively. The BP formed during DDS would undergo slow hydrogenation to form CHB, while the intermediates tetrahydrodibenzothiophene (THDBT) and hexahydrodibenzothiophene (HHDBT) formed during HYD were hydrogenated to CHB, which was further hydrogenation to bicyclohexyl (BCH). It was found that the HDS products of DBT on ZnxMg1−xNi–P/Al2O3 are only BP and CHB. Similar product distributions have been reported [24,25,26]. As showed in Figure 6b, the selectivity of BP increases and that of CHB decreases with the increase in temperature for all catalysts. The proportions of BP are larger over all the samples, indicating that DBT is mainly desulfurized via the DDS pathway. This conclusion agrees with Song et al. [10] who prepared Ni2P/Al2O3 catalysts from Ni–Al–CO32− LDHs. Interestingly, the selectivity of BP over Ni12P5 is higher than that of Ni2P for ZnxMg1−xNi–P/Al2O3, which indicates that Ni12P5 is more active in DDS than Ni2P.
For comparison, the HDS of DBT over different catalysts is shown in Figure 7. The HDS activities of the catalysts change in the order of Zn0.75Mg0.25Ni–P/Al2O3 > Ni–P/Al2O3 > Ni–P/ZnO > Ni–P/MgO. Compared with the widely-studied Ni–P/Al2O3, Zn0.75Mg0.25Ni–P/Al2O3 enhances not only HDS activity (from 54.3% to 81.6%), but also the selectivity of BP (from 54.6% to 87.8%) and the DDS pathway. XRD shows that the active phase is Ni2P and not Ni12P5 for both Zn0.75Mg0.25Ni–P/Al2O3 and Ni–P/Al2O3 (Figure 2). As reported, Ni2P has two types of sites, including tetrahedral Ni(1) sites and square pyramidal Ni(2) sites, which are responsible for HDS by the DDS route and desulfurization by the HYD route, respectively [27]. Therefore, Zn0.75Mg0.25Ni–P/Al2O3 prepared from LDHs enhances the Ni(1) sites compared with Ni–P/Al2O3. The HDS activity of Ni–P/MgO is the lowest, because the preferential reactions between P and Mg inhibits the formation of Ni2P and Ni12P5.

3. Experimental

3.1. Materials

Al(NO3)3·9H2O, Ni(NO3)2·6H2O, Zn(NO3)2·6H2O, and Mg(NO3)2·6H2O were purchased from Beijing Shuanghuan Chemical Reagents Company (Beijing, China). NaOH was provided by Tianjin Yongda Chemical Reagent Co., Ltd. (Tianjin, China). Na2CO3 was supplied by Tianjin Damao Reagents Company (Tianjin, China). HNO3 was obtained from Haerbin Chemical Reagent Company (Haerbin, China). NH4H2PO4 was purchased from Beijing Chemical Company (Beijing, China). A model oil was prepared by C12H8S (AccuStandard Inc., New Haven, CT, USA), C10H18 (Beijing Chemical Company, Beijing, China), and C14H30 (Tianjin North Chemical Reagents Company, Tianjin, China). All the chemicals were of analytical grade and used with no further treatment. Deionized water was used for solution preparation.

3.2. Catalyst Preparation

A series of ZnxMg1−xNiAl LDHs with M2+/M3+ molar ratio of 3:1 and different Zn/Mg molar ratios were prepared from coprecipitation under ambient atmosphere. Each time, a mixed solution of Mg(NO3)2·6H2O, Zn(NO3)2·2H2O, Ni(NO3)2·6H2O, and Al(NO3)3·9H2O was adjusted to pH 10 by adding a NaOH and Na2CO3 aqueous solution dropwise under stirring. The resulting suspension was aged at 333 K for 6 h. The precipitate was filtered and washed several times with deionized water. Then, ZnxMg1−xNi–P/Al2O3 catalysts were prepared by a microwave-hydrothermal treatment and temperature programmed reduction, as described in our previous work [10]. Typically, ZnxMg1−xNiAl LDHs were impregnated with an ammonium dihydrogenphosphate solution with a Ni/P molar ratio of 1:2 and treated using a microwave-hydrothermal method for 20 min at 363 K under reflux. After drying at 393 K for 12 h, the resulting materials were pressed into discs, crushed, and sieved to particles with 16–30 meshes. After calcination at 773 K for 3 h, the materials were reduced in a H2 flow (200 mL/min) while the temperature rose to 973 K at a rate of 2 K/min and was then maintained at 973 K for 2 h. Then, the materials were cooled to room temperature in a H2 flow, and passivated in a 20 mL/min O2/N2 flow (0.5 vol.% O2).
For comparison, Ni–P/Al2O3 (Ni–P/ZnO and Ni–P/MgO) catalyst was prepared by dissolving a Ni(NO3)2·6H2O, NH4H2PO4, Al(NO3)3·9H2O (Zn(NO3)2·6H2O, and Mg(NO3)2·6H2O) mixed solution in HNO3. After evaporation, the resulting solids were calcined, and reduced by heating to 873 K at a rate of 2 K/min in a H2 flow. The Ni/P molar ratio and theoretical Ni loading were 1:2 and 20 wt.%, respectively, for all catalysts.

3.3. Catalyst Characterization

XRD patterns were measured on a Rigaku D/max-2200 X-ray diffractometer operated at 40 kV and 40 mA using Cu Kα radiation. The textural properties of the catalysts were analyzed by the Brunauer-Emmett-Teller (BET) method using a Tristar II3020 surface area and porosity analyzer. XPS spectra were acquired with a K-Alpha electron spectrometer (Thermofisher Scientific Company, Waltham, MA, USA) using an Al Kα radiation source (1486.6 eV). The binding energy was calibrated by setting the C1s transition at 284.8 eV.

3.4. Catalytic Hydrogenation Activity Test

The HDS reaction of DBT was performed on a fixed-bed reactor [10]. Prior to the reaction, 0.65 g of a passivated catalyst was activated in H2 (40 mL/min) at 773 K for 2 h. After activation, the hydrotreation reaction was carried out at 553 K, 3.0 MPa. The liquid reactant, which consisted of a decalin solution of DBT (1 wt.%), was pumped into the reactor. The weight hourly space velocities (WHSV) and H2/oil ratio (V/V) were 2.0 h−1 and 500, respectively. Liquid product compositions of the samples collected at a 2-h interval were determined on a GC-14C gas chromatograph equipped with a SE-30 capillary column.

4. Conclusions

Zn/Mg-modified ZnxMg1−xNiAl LDHs with different Zn/Mg molar ratios were prepared. Briefly, H2PO42− was introduced by the microwave-hydrothermal method, and ZnxMg1−xNi–P/Al2O3 catalysts were prepared with the mixture as the precursor. In the precursors, under the hydrogenation atmosphere and during temperature programmed reduction, both Zn and Mg reacted with phosphorus substances, which impacted the formation of nickel phosphates. The nickel phosphate mainly existed in the form of Ni2P at x ≥ 0.5, but Ni12P5 at x < 0.5. Compared with the single-metal-modified catalysts (Zn or Mg), the Zn/Mg-modified (Zn/Mg molar ratio of 3:1) Zn0.75Mg0.25Ni–P/Al2O3 effectively reduced the pore sizes of catalysts, increased the pore counts, and had the smallest Ni2P particles. The catalyst prepared from this method showed the highest dibenzothiophene hydrodesulfurization activity and promoted the direct desulfurization of dibenzothiophene.

Acknowledgments

The authors acknowledge the financial supports from the Education Department of Heilongjiang Province (12541060) and the Graduate Innovation Project of Northeast Petroleum University (YJSCX2016-020NEPU).

Author Contributions

Feng Li, Cuiqin Li and conceived and designed the experiments; Feng Li, Jinrong Liang and Wenxi Zhu performed the experiments; Hua Song, Keliang Wang and Cuiqin Li analyzed the data; Feng Li contributed reagents/materials/analysis tools; Feng Li and Cuiqin Li wrote the paper.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. X-ray diffraction (XRD) patterns of ZnxMg1−xNiAl layered double hydroxides (LDHs).
Figure 1. X-ray diffraction (XRD) patterns of ZnxMg1−xNiAl layered double hydroxides (LDHs).
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Figure 2. XRD patterns of ZnxMg1−xNi–P/Al2O3.
Figure 2. XRD patterns of ZnxMg1−xNi–P/Al2O3.
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Figure 3. N2 adsorption-desorption isotherms (a) and corresponding pore size distributions (b) for ZnNi–P/Al2O3, Zn0.75Mg0.25Ni–P/Al2O3, and MgNi–P/Al2O3.
Figure 3. N2 adsorption-desorption isotherms (a) and corresponding pore size distributions (b) for ZnNi–P/Al2O3, Zn0.75Mg0.25Ni–P/Al2O3, and MgNi–P/Al2O3.
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Figure 4. XPS spectra of ZnNi–P/Al2O3, Zn0.75Mg0.25Ni–P/Al2O3, and MgNi–P/Al2O3: (a) Ni 2p; (b) P 2p.
Figure 4. XPS spectra of ZnNi–P/Al2O3, Zn0.75Mg0.25Ni–P/Al2O3, and MgNi–P/Al2O3: (a) Ni 2p; (b) P 2p.
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Figure 5. The XRD patterns of different nickel phosphate catalysts.
Figure 5. The XRD patterns of different nickel phosphate catalysts.
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Figure 6. Evolution of conversion (a) and selectivity (b) of dibenzothiophene (DBT) hydrodesulfurization (HDS) over ZnxMg1−xNi–P/Al2O3 catalysts, P = 3 MPa, weight hourly space velocities (WHSV) = 2.0 h−1 and H2/oil ratio = 500 (V/V).
Figure 6. Evolution of conversion (a) and selectivity (b) of dibenzothiophene (DBT) hydrodesulfurization (HDS) over ZnxMg1−xNi–P/Al2O3 catalysts, P = 3 MPa, weight hourly space velocities (WHSV) = 2.0 h−1 and H2/oil ratio = 500 (V/V).
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Scheme 1. Simplified reaction pathways for the HDS of DBT.
Scheme 1. Simplified reaction pathways for the HDS of DBT.
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Figure 7. HDS of DBT over different catalysts, T = 653 K, P = 3 MPa, WHSV = 2.0 h−1 and H2/oil ratio = 500 (V/V).
Figure 7. HDS of DBT over different catalysts, T = 653 K, P = 3 MPa, WHSV = 2.0 h−1 and H2/oil ratio = 500 (V/V).
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Table 1. Analysis of XRD patterns for ZnxMg1−xNiAl LDHs.
Table 1. Analysis of XRD patterns for ZnxMg1−xNiAl LDHs.
LDHsd (nm)Lattice Parameter 1Crystallite Size 2
(003)(006)(009)(110)acac
ZnNiAl0.760.380.260.150.302.3019.29.2
Zn0.75Mg0.25NiAl0.760.380.260.150.302.3014.19.6
Zn0.5Mg0.5NiAl0.770.390.260.150.302.3320.610.1
Zn0.25Mg0.75NiAl0.780.380.260.150.302.3220.59.4
MgNiAl0.770.380.260.150.302.3116.09.4
1 Lattice parameters a = 2d110 and c= d003 + d006 + d009, nm; 2 Crystallite sizes in direction a and c, nm.
Table 2. Textural characteristics of ZnNi–P/Al2O3, Zn0.75Mg0.25Ni–P/Al2O3, and MgNi–P/Al2O3.
Table 2. Textural characteristics of ZnNi–P/Al2O3, Zn0.75Mg0.25Ni–P/Al2O3, and MgNi–P/Al2O3.
CatalystSurface Area
(m2·g−1)
Pore Volume
(cm3·g−1)
Average Pore
Diameter (nm)
dc 1
(nm)
ZnNi–P/Al2O35.50.02518.239.2
Zn0.75Mg0.25Ni–P/Al2O311.80.0268.829.4
MgNi–P/Al2O36.70.02716.5
1 Calculated from the dc = Kλ/βcos(θ) (Scherrer formula) based on the Ni2P (111) (2θ = 40.7°).
Table 3. Spectral parameters obtained by X-ray photoelectron spectroscopy (XPS) analysis.
Table 3. Spectral parameters obtained by X-ray photoelectron spectroscopy (XPS) analysis.
SampleBinding Energy (eV)Surface Atomic Ratio
Ni 2p3/2P 2p3/2
Niδ+Ni2+SatellitePδ−P5+Niδ+/ΣNiP/NiSurface Composition
ZnNi–P/Al2O3853.7856.9861.0129.6134.00.447.41Zn8.6Ni5.9P43.7Al41.8
Zn0.75Mg0.25Ni–P/Al2O3853.0855.3860.6129.4133.80.191.87Zn1.1Mg9.2Ni20.0P37.4Al32.3
MgNi–P/Al2O3852.2855.5860.6129.2133.90.264.42Mg21.9Ni9.9P43.8Al24.4

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Li, F.; Liang, J.; Zhu, W.; Song, H.; Wang, K.; Li, C. High Active Zn/Mg-Modified Ni–P/Al2O3 Catalysts Derived from ZnMgNiAl Layered Double Hydroxides for Hydrodesulfurization of Dibenzothiophene. Catalysts 2017, 7, 202. https://doi.org/10.3390/catal7070202

AMA Style

Li F, Liang J, Zhu W, Song H, Wang K, Li C. High Active Zn/Mg-Modified Ni–P/Al2O3 Catalysts Derived from ZnMgNiAl Layered Double Hydroxides for Hydrodesulfurization of Dibenzothiophene. Catalysts. 2017; 7(7):202. https://doi.org/10.3390/catal7070202

Chicago/Turabian Style

Li, Feng, Jinrong Liang, Wenxi Zhu, Hua Song, Keliang Wang, and Cuiqin Li. 2017. "High Active Zn/Mg-Modified Ni–P/Al2O3 Catalysts Derived from ZnMgNiAl Layered Double Hydroxides for Hydrodesulfurization of Dibenzothiophene" Catalysts 7, no. 7: 202. https://doi.org/10.3390/catal7070202

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