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Mesoporous Zeolite ZSM-5 Supported NiP Catalysts with High Activity in the Hydrogenation of Phenanthrene and 4,6-Dimethyldibenzothiophene Wenqian Fu, Lei Zhang, Dongfang Wu, Quanyong Yu, Ting Tang, and Tiandi Tang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b01583 • Publication Date (Web): 13 Jun 2016 Downloaded from http://pubs.acs.org on June 19, 2016

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Industrial & Engineering Chemistry Research

Mesoporous Zeolite ZSM-5 Supported Ni2P Catalysts with High Activity in the Hydrogenation of Phenanthrene and 4,6-Dimethyldibenzothiophene

Wenqian Fu,a,b Lei Zhang,a Dongfang Wu,b,* Quanyong Yu,a Ting Tang,b Tiandi Tang,a,c,* a

Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical

Engineering, Changzhou University, Changzhou, Jiangsu 213164, P. R. China. E-mail: [email protected] b

School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, P. R. China.

E-mail: [email protected] c

College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, P. R. China.

E-mail: [email protected]

KEYWORDS: Mesoporous Zeolite ZSM-5, Ni2P catalyst, Phenanthrene, 4,6Dimethyldibenzothiophene, Hydrogenation.

ACS Paragon Plus Environment


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ABSTRACT: Mesoporous zeolite ZSM-5 (ZSM-5-M) was synthesized and used as support for the preparation of highly efficient nickel phosphide catalyst (Ni2P/ZSM-5-M) in the deep hydrogenation of phenanthrene and in the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DM-DBT). Compared with Ni2P catalysts supported silica and high surface area hexagonal mesoporous silica (HMS) (Ni2P/SiO2 and Ni2P/HMS), Ni2P/ZSM-5-M exhibits higher hydrogenation and HDS activity. The phenanthrene conversion and deep hydrogenation products selectivity over Ni2P/ZSM-5-M (95% and 83%) are much higher than those over Ni2P/SiO2 (61% and 73%) and Ni2P/HMS (69% and 45%) under mild conditions. The 4,6-DM-DBT conversion over Ni2P/ZSM-5-M (93%) was higher than that over Ni2P/SiO2 (62%). This feature is attributed to the difference in surface properties of support. A large amount of acidic hydroxyl groups on the zeolites can interact strongly with catalyst precursor, resulting in the formation of highly dispersed Ni2P particles with small sizes, which provide abundant hydrogenation active sites.


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1. INTRODUCTION The reduction of the aromatics and sulfur content in diesel fuel has received much attention owing to stringent environmental legislations in recent years. To achieve deep dearomatization and desulfurization for producing ultraclean transportation fuel, even polyaromatics must be saturated and highly refractory sulfur compounds such as 4,6-dimethyldibenzothiophene must be completely removed.1-3 For this purpose, developing highly active hydrotreating catalyst has become very important with the ever-increasing supply of heavy crudes. Conventional metal sulfide catalysts supported on γ-Al2O3, such as CoMo/γ-Al2O3 and NiMo/γ-Al2O3 are widely used in the hydrotreating process,4-6 however, deep saturation of polyaromatic hydrocarbons as well as deep hydrodesulphurization over these type catalysts are difficult because of the low hydrogenation activities of these catalysts.7-9 In the last decades, transition metal phosphides such as Co2P10,11, WP11,12, MoP13 and Ni2P14,15, especially Ni2P, have received much attention due to their high intrinsic hydrotreating activity. Generally, SiO2 is the most commonly used support for Ni2P catalyst (Ni2P/SiO2).16,17 However, the activity of the SiO2 supported Ni2P catalyst is still limited owing to the lower Ni2P dispersion.18,19 An improvement of the Ni2P dispersion can be achieved by utilization of ordered mesoporous molecular sieve (MCM-41 and SBA-15) with large surface area,20,21 but the activity of the catalysts is unsatisfactory. The relatively low thermostability of MCM-41 and SBA-15 also limits their practical application.22 On the other hand, many studies have shown that the morphology of the Ni2P active phase also greatly affects its catalytic performance.18,23,24 The Ni2P active phase with small particles provides a more hydrogenation active sites, enhancing its hydrogenation activity.23,24 Therefore, increasing the dispersion of the Ni2P active phase and decreasing the Ni2P particle size could greatly improve its hydrogenation performance.



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As is well known, crystalline aluminosilicate zeolites exhibit large surface area, uniform porous structure, and unique surface properties (acidic hydroxyl) as well as a negatively charged framework. They are widely used as supports for the preparation of highly active metal catalysts.25-28 The surface properties and the negatively charged framework of the zeolite favor the enhancement of the metalsupport interaction, which could increase the dispersion of the metal catalysts.29,30 Furthermore, introducing mesoporous into zeolite could benefit the mass transfer of the bulk molecules, and improve the catalytic performance of their supported metal catalysts.31-33 Recently, we reported that Ni2P catalyst supported on mordenite nanosheet assemblies (Ni2P/NS-HMOR) has high activity in the hydrodesulfurization (HDS) of the 4,6-DM-DBT.34 Nevertheless, this type of catalyst precursor must be pretreated in a hydrogen stream at high temperature (500-600 °C) to reduce the Ni and P species. Herein, in this work, we synthesized mesoporous zeolite ZSM-5 (ZSM-5-M) by templating with a cationic copolymer containing quaternary ammonium groups. After impregnation of ammonium hypophosphite (NH4H2PO2) and nickel chloride (NiCl2·6H2O) solution with ZSM-5-M, the dried catalyst sample was directly reduced in H2 atmosphere at a low temperature of 400 °C. The obtained catalyst (Ni2P/ZSM-5-M) has high activity in the deep hydrogenation of phenathrene as compared to the Ni2P catalysts supported on SiO2 (Ni2P/SiO2) and high surface area mesoporous silica (Ni2P/HMS) as well as the NiMo catalysts supported mesoporous zeolite ZSM-5 and γ-Al2O3. Usually, deep hydrogenation of aromatics and desulfurization of the sulfur-containing compounds in the diesel fuel simultaneously occurs on hydrotreating catalysts.35-37 Generally, the refractory sulfur compounds in the diesel fuel are the dialkyldibenzothiophenes, such as 4,6-dimethyldibenzothiophene (4,6-DM-DBT).33,38 Conventional metal sulfide supported on γ-Al2O3 as well as Ni2P supported on SiO2 catalysts have difficulty removing 4,6-DM-DBT due to the steric hindrance of the methyl groups at the 4 and 6 positions.33 In the present work, we also investigated the possibility of sulfur removal by


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the conversion of 4,6-DM-DBT at mild reaction conditions (300 °C and 5 MPa) over Ni2P/ZSM-5-M catalyst. The results show that the hydrodesulfurization activity of the Ni2P/ZSM-5-M catalyst is higher than that of the Ni2P/SiO2 catalyst. 2. EXPERIMENTAL METHODS 2.1. Material Synthesis Mesoporous zeolite ZSM-5 (MZSM-5) was synthesized in the presence of tetraethylammonium hydroxide (TPAOH) from an aluminosilicate gel with a molar composition of Al2O3/89.6SiO2/24.5Na2O/0.012COPQA/3TPAOH/3000H2O. The COPQA was a cationic copolymer containing quaternary ammonium groups, which was used as mesoporous template.39 In a typical run, 17.6 mL of water glass, 11.2 mL H2O and 2.8 mL 25 wt.% TPAOH was mixed for stirring 1 h. 6 mL COPQA were slowly added to the mixture under vigorous stirring. After stirring at room temperature for 2 h, an acidic Al2(SO4)3 aqueous solution (0.03 mol·L-1) was added. The mixture was further stirred for 2 h to yield an aluminosilicate gel. The gel was transferred into a stainless steel autoclave for static crystallization at 170 °C for 2 days. After filtration and washing, the sample was dried at 120 °C overnight and calcined in air at 550 °C for 5 h. The mesopore-free ZSM-5 zeolite was synthesized by the same procedure in the absence of COPQA. Mesoporous zeolite Beta (Beta-M) was synthesized according to the procedure described in our previous work.22 The as-synthesized ZSM-5-M zeolite was converted to the H-form by ion exchange with 1 M NH4NO3 solution at 80 °C for 4 h, followed by calcination at 550 °C in air for 4 h. This process was repeated twice. The obtained sample was designated as HZSM-5-M. High surface area hexagonal mesoporous silica (HMS) was synthesized as follows: 1.1 g of cetyltrimethyl ammonium bromide was dissolved in 25 mL of deionized water followed by addition of 12 mL NH3·H2O (28 wt.%) and 5.0 mL tetraethylorthosilicate (TEOS). After stirring the mixture at



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room temperature for 1 h, sulfuric acid solution (4.0 M) was added to adjust the pH=10. The mixture was further stirred for 3 h at 45 °C to yield a gel. The gel was transferred into a stainless steel autoclave for crystallization at 100 °C for 3 days. After filtration and washing, the sample was dried at 120 °C overnight and calcined in air at 550 °C for 5 h. SiO2 was purchased from Shanghai GUOYAO Chemical Industry Co., Ltd. 2.2. Catalyst preparation The Ni2P catalysts were prepared by the incipient wetness impregnation method using an aqueous solution containing the required amount of ammonium hypophosphite (NH4H2PO2) and nickel chloride (NiCl2·6H2O). The Ni:P molar ratio in the impregnation solution was 1:2. The Ni loading was 6.0 wt.%. After impregnation, the sample was placed in air at ambient temperature for 20 h, and dried at 60 °C for 24 h. The dried samples were tableted (15 MPa), and crushed and sieved to 40-60 mesh particles. For characterization of the catalyst, the particle sample was pre-reduced in a H2 flow (160 mL·min-1) from room temperature to 400 °C with a heating rate of 2 °C·min-1 and kept for 2 h under 400 °C, then naturally cooled to room temperature in a continuous H2 flow. The obtained catalyst was passivated in a mixture of O2 and N2 (0.5 vol.% of O2) with a flow rate of 30 mL·min-1 for 2 h. The catalysts on the different supports were denoted as Ni2P/ZSM-5-M, Ni2P/HZSM-5-M, Ni2P/ZSM-5, Ni2P/Beta-M, Ni2P/SiO2 and Ni2P/HMS. 2.3. Characterization. The X-ray diffraction (XRD) pattern of the supports and passivated catalysts was obtained with a RIGAKU Smart Lab diffractometer using Cu Kα radiation. The nitrogen physisorption experiment was performed consistent with previous work.34 A transmission electron microscopy (TEM) image was obtained on a JEM-2100 microscope with a limited line resolution capacity of 1.4 Å, under a voltage of 200 kV. The reduced sample was dispersed in ethanol and dropped onto a carbon membrane-coated Cu grid before TEM experiment.


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The acidity of the supports and catalysts was measured using temperature-programmed desorption of ammonia (NH3-TPD) on a Micromeritics ASAP2920 instrument. The measurement procedure of the support acidity was in line with previous work.34 For the catalyst, 200 mg of the passivated sample was placed in a quartz tubular reactor and reduced in a H2-Ar (10 vol.% H2) stream at 400 °C for 2 h with a heating rate of 5 °C·min-1. After the sample was cooled to 120 °C in the He flow, NH3-He mixed gas (10 vol.% NH3) was passed over the sample for 30 min. After removal of physically adsorbed NH3 by flowing helium for 90 min at 120 °C, the sample was heated to 500 °C with a heating rate of 10 °C·min-1. The nature and change in the surface hydroxyls on supports and dried Ni2P catalysts were measured by infrared spectroscopy (IR) on a Bruker TENSOR 27 instrument equipped with an in situ reactor cell. Before the IR measurement, the He stream flowed over the sample at 60 °C for 3 h. Temperature programmed reduction (TPR) of the dried catalyst sample was conducted on a Micromeritics ASAP2920 instrument equipped with a cold trap (-80 °C, filling with a mixture of isopropanol and liquid nitrogen) that was installed in front of the thermal conductivity detector (TCD) entrance. Thus, the product caused by decomposition of the metal precursor in the sample could be trapped in the cold trap. 60 mg dried sample in a quartz tube was heated to 900 °C with a heating rate of 15 °C·min-1 in a gas mixture of H2-Ar (10 vol.% H2, 50 mL·min-1) stream. CO chemisorption was measured on a Micromeritics ASAP2920 instrument. 80 mg of passivated catalyst was pretreated in a quartz reactor to remove the passivation layer by heating to 340 °C at a rate of 5 °C min-1 in H2-Ar (10 vol.% H2, 40 mL·min-1) mixture gas for 2 h, and purging the sample at 340 °C for 60 min in a He flow. After that, the catalyst was naturally cooled to room temperature in a He flow at 30 mL·min-1. After pretreatment, 5 mL pulses of CO-He (5 vol.% CO) mixture gas were



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injected into a quartz reactor, and the CO uptake was measured by a TCD detector. CO-He (5 vol.% CO) mixture pulses were repeatedly injected until no further CO uptake occurred. For the calculation of the catalyst active sites, we assumed a 1:1 adsorption stoichiometry between CO and metal atom. X-ray photoelectron spectroscopic (XPS) measurement of the catalyst was performed on an ESCALAB MK II system. Before analysis, the dried catalyst was reduced in H2 gas (160 mL·min-1) from room temperature to 400 °C with a heating rate of 2 °C·min-1 and holding the temperature at 400 °C for 120 min. After cooling down to room temperature in a continuous H2 flow, the reduced catalyst was transferred under H2 stream into a bottle filled with absolute ethanol. For the XPS experiments, the ethanol in the bottle was removed and the residual was quickly moved to the sample holder, and then transferred into the analysis chamber in the XPS instrument. 2.4. Activity tests. The phenanthrene hydrogenation and 4,6-DM-DBT hydrodesulfurization were carried out in a fixed-bed continuous-flow stainless steel reactor (internal diameter 6.5 mm and length 500 mm). 0.3 g dried catalyst was diluted with 1.5 g SiC before being loaded into the reactor. Both ends of the catalyst bed were filled with extra 0.3 g SiC. The catalyst was directly reduced in the fixedbed reactor by heating to 400 °C at a rate of 2 °C·min-1 in a H2 flow (160 mL·min-1) and holding for 2 h, then naturally cooled to reaction temperature in a continuous H2 flow. The operating conditions of the phenanthrene hydrogenation were as follows, total pressure of 5.0 MPa, 1.0 wt.% phenanthrene in decalin, a H2 flow of 60 mL·min-1, the weight hourly space velocity (WHSV) of 15.4 h-1. For the HDS of the 4,6-DM-DBT, catalyst was tested under the following conditions: total pressure of 5.0 MPa, temperature of 300 C, 0.45 wt.% 4,6-DM-DBT in decalin, a H2 flow of 60 mL·min-1, weight hourly space velocity of 12.6 h-1. The product was collected and analyzed using an Agilent 7890B GC installed with a flame ionization detector (FID).


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To investigate the intrinsic activity of the catalyst, the mass transfer limitations were checked by means of the Weisz-Prater and Mears Criterion.40 0.05 g catalyst (40-60 mesh) was diluted with 1.8 g SiC (40-60 mesh) and then loaded into the reactor. After the reaction became stable, the phenanthrene conversion was kept a low level by changing the weight hourly space velocity. The internal and external diffusion limitations were examined by the Weisz-Prater Criterion (Cwp) and the Mears Criterion (CM),40 respectively (the detailed calculations are presented in the Supporting Information). The values of

and

were 0.00042 and 0.00082 for the Ni2P/ZSM-5-M catalyst under the

M

experimental conditions (see Supporting Information). Generally, the internal and external diffusion limitations can be neglected during the kinetic experiments when the values of

and

M

are below

1 and 0.15, respectively. In our case, the internal and external diffusion limitations can be neglected. In this case, the reaction rate (

) could be used to evaluate the intrinsic activity of the catalysts.40

The turnover frequencies (TOF, s-1) were calculated using the following equation in the phenanthrene hydrogenation:34 O where F is the reactant molar flow (mol· s-1), x is the phenanthrene conversion (%), W is the catalyst mass (kg). and M is the number of mole of loaded sites, which was determined by the CO uptake.

3. RESULTS AND DISCUSSION 3.1. Characterization Figure 1a shows the XRD patterns of the as-synthesized ZSM-5-M and Beta-M samples. The ZSM5-M sample exhibits typical peaks in the range of 5-50°associated with the MFI structure. The Beta-M



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sample exhibits typical peaks at 7.7, 21.4 and 22.6°characteristic for the Beta zeolite structure. The N2 sorption isotherms of ZSM-5-M and Beta-M exhibit a hysteresis loop at a relative pressure of 0.80-0.96 and 0.60-0.96 (Figure 1b), respectively, which is attributed to the presence of mesoporous structure in the ZSM-5-M and Beta-M samples. Correspondingly, the mesopore-size of the ZSM-5-M and Beta-M are mainly centered at 22 and 10 nm, respectively (Figure 1b, insert). The detailed textural parameters of the supports and catalysts are given in Table 1. The TEM images of the thin-sectioned ZSM-5-M and Beta-M give direct evidence for the presence of abundant hierarchical mesopores in the zeolite crystals (Figure S1, light areas, Supporting Information). The mesopore size of the ZSM-5-M and BetaM is in good agreement with that obtained from the N2 sorption (Figure 1b, insert). Figure 2 shows the XRD patterns of the Ni2P catalyst (PDF: 03-0953) and of the series of reduced catalysts. The diffraction peaks at 2θ=40.8°, 44.8°, and 47.6°are characteristic of Ni2P (Figure 1a).20,41 The characteristic diffraction peak at 47.6°for the Ni2P phase is overlapped with the diffraction peak of the ZSM-5-M (Figure 2, insert), while the two peaks at 40.6°and 44.8°are detected on the Ni2P/ZSM5 (Figure 2, insert), indicating that relative large Ni2P particles are formed on the outer surface of the mesopore-free ZSM-5. In contrast, the characteristics of Ni2P phase are not observed on the mesoporous zeolite supported Ni2P catalysts (Ni2P/ZSM-5-M and Ni2P/HZSM-5-M, Figure 2d and Figure 2e). These results indicate that the support with large mesoporous surface area benefit the formation of small Ni2P particles. Because of the small micropore size (0.53×0.56 nm),42 the Ni2P active phases is formed on the outer surface of the mesopore-free ZSM-5. The ZSM-5 has a lower external surface area (35 m2·g-1, Table 1), thus the Ni2P active phase with large particles is formed the outer surface of the ZSM-5 particles. In contrast, ZSM-5-M and HZSM-5-M have large external surface area (159, 167 m2·g-1, Table 1), which could benefit the formation of Ni2P phase with small particles in the mesopores and on the outer surface of the zeolite particles. This phenomenon is also


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obtained on the mesoporous zeolite Beta supported Ni2P catalyst (Figure S2, Supporting Information). The Ni2P/HMS and Ni2P/SiO2 catalysts were also examined by XRD analysis. The characteristic peaks of Ni2P are not noticeable on the Ni2P/HMS catalyst (Figure 3b), but are clearly observed on the Ni2P/SiO2 catalyst (Figure 3c). Indeed, the HMS with mesoporous surface area (663 m2·g-1) could facilitate the Ni2P dispersion, as compared to SiO2 (212 m2·g-1, Table 1). The Ni2P dispersion and the location were further investigated by the TEM experiment, and the results are shown in Figure 4. Relatively large Ni2P particles (5-20 nm) are observed on the outer surface of the Ni2P/ZSM-5 catalyst (Figure 4a). In contrast, well dispersed Ni2P active phases are mainly formed in the mesopores of the Ni2P/ZSM-5-M and Ni2P/HZSM-5-M catalysts (Figure 4b and Figure 4c, and Figure S3, Supporting Information). Small Ni2P particles with size of 3-5 nm are formed in the mesoporous channels of Ni2P/ZSM-5-M catalyst. Notably, less 3 nm Ni2P particles are highly dispersed in the mesoporous channels of Ni2P/HZSM-5-M catalyst. The Ni2P particles on the zeolite supports show a distinct crystal lattice spacing of 0.22 nm, which is consistent with the d-spacing of the Ni2P {111} crystallographic planes (Figure 4d).43,44 Small Ni2P particles with a size of 5 nm are also observed in the mesoporous channels of Ni2P/Beta-M catalyst (Figure S4, Supporting Information). In contrast, Ni2P particles with large size are formed on the SiO2 and HMS supported catalysts (Figure 4e and Figure 4f). The Ni2P active phase with small particle size highly dispersed in the mesopores of Ni2P/ZSM-5-M, Ni2P/HZSM-5-M and Ni2P/Beta-M catalysts could give more active sites, which is supported by the CO chemisorption data. The CO uptake of Ni2P/ZSM-5-M, Ni2P/HZSM-5-M and Ni2P/Beta-M catalysts (98.8, 125.3 and 81.3 µmol·g-1) are much higher than that of Ni2P/SiO2 (19.0 µmol·g-1) and Ni2P/HMS (34.1 µmol·g-1, Table 1) catalysts.



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Compared with SiO2 (212 m2·g-1) and HMS (663 m2·g-1) with large mesoporous surface area, ZSM-5-M and Beta-M show relatively low external surface area (159 and 146 m2·g-1, Table 1), but small Ni2P nanoparticles highly dispersed on the ZSM-5-M, HZSM-5-M and Beta-M, which should be attributed to difference in the surface properties of zeolite and silica. The details were interpreted as follows. The FT-IR spectra show that both acidic hydroxyl groups bonded to the framework aluminum atoms (Si-OH-Al, 3600 cm-1) and silanol groups (3740 cm-1) exist on ZSM-5-M and Beta-M (Figure 5a and Figure S5, Supporting Information),45,46 but only silica hydroxyl groups (3740 cm-1) exist on the SiO2 and HMS (Figure 5b and Figure 5c). The NH3-TPD results also indicate that large amounts of acidic sites are present on the zeolite surface (Figure 6a and Figure S6, Supporting Information). Both SiO2 and HMS supports show very small and weak acidic sites (Figure 6a). During the catalyst preparation, the metal precursor might interact with both the silanol and acidic hydroxyl groups. This suggestion was confirmed by the FT-IR results for the dried Ni2P/ZSM-5-M, Ni2P/SiO2 and Ni2P/HMS samples. It shows that the 3740, 3662 and 3600 cm-1 absorption band intensities of Ni2P/ZSM-5-M and the 3740 cm-1 absorption band intensity of Ni2P/SiO2 decreased after loading of Ni and P species (Figure 5), indicating that the Ni species interact with the acidic hydroxyl or silanol groups. However, the Ni species strongly interact with the acidic hydroxyl groups on the zeolite, and interact weakly with the silanol groups on the SiO2 and HMS.34 In addition, compared with the amorphous characteristics of SiO2 and HMS, the ZSM-5-M and Beta-M with negatively charged frameworks could strengthen the interaction of Ni species with zeolites.34 In this case, the small Ni2P particles are highly dispersed on the ZSM-5-M and Beta-M surface during the reduction process. These results indicate that the acidic sites of supports play an important role in the formation of small Ni2P particles with high dispersion. This can be supported by combining NH3-TPD results of supports and corresponding catalysts.


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SiO2 and HMS have almost no acidity (Figure 6a), but after loading of Ni and P species and reduction, the Ni2P/SiO2 and Ni2P/HMS catalysts present significant acidity (Figure 6b). These additional acidities could be caused by the PO-H groups (Brønsted acidity) of the Ni2P active phases.47 In contrast, after loading of Ni and P species and reduction, the acidity of the Ni2P/ZSM-5-M catalyst hardly increased and was similar to that of ZSM-5-M (Figure 6b). This means that the original acidic sites on the ZSM-5-M interact with the Ni species during the impregnation and drying processes, and are covered by the Ni2P phase in the catalyst reduction. In addition, strong acidic sites exist on the HZSM-5-M. After loading of Ni and P species and reduction, a small number of strong acidic sites are still present on the Ni2P/HZSM-5-M catalyst (Figure 6b). This result further confirms that the Ni species easily interact with the acidic sites on the zeolites. Compared with the Ni/SiO2 and Ni2P/HMS catalysts, the strong Ni-support interaction in the zeolite-supported Ni2P catalysts was investigated by H2-TPR experiments. For comparison, Ni supported on ZSM-5-M, HZSM-5-M, SiO2 and HMS catalysts (Ni/ZSM-5-M, Ni/HZSM-5-M, Ni/SiO2 and Ni/HMS) were also prepared. From Figure 7a, the reduction temperature peaks of the Ni/SiO2, Ni/HMS, Ni/ZSM-5-M and Ni/HZSM-5-M catalysts ordered at 335, 355, 376 and 391 °C, indicating that a relatively strong Ni-support interaction existed in Ni/ZSM-5-M and Ni/HZSM-5-M catalysts. After loading of Ni and P species, and drying, a negative peak in the temperature range of 180-201 °C appeared for all the catalysts (Figure 7b). This signal could be induced by the PH3 gas that was generated from the decomposition of the catalyst precursors under heating condition in reduction atmosphere, which could react with Ni species to form Ni2P phases. 44 Similar phenomenon was investigated in detail by d’Aquino and co-workers.48 They studied the reduction behavior of the SiO2, γ-Al2O3 and acidic amorphous SiO2-Al2O3 (ASA) supported Ni2P catalysts by TPR-MS technique in a mixture of H2-Ar (10 vol.% H2), and the obtained results show that the peaks at 224, 234 and 288 °C



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for the Ni2P/ SiO2, Ni2P/γ-Al2O3 and Ni2P/ASA are caused by the decomposition of the catalyst precursor of Ni(H2PO2)2 into PH3. Compared with Ni2P/SiO2 and Ni2P/HMS catalysts (133 °C), the starting decomposition temperature of the catalyst precursors on Ni2P/ZSM-5-M and Ni2P/HZSM-5-M samples appeared at relatively higher temperature (175 °C), indicating that the catalyst precursors have difficulty generating phosphorus species on the Ni2P/ZSM-5-M and Ni2P/HZSM-5-M relative to the Ni2P/SiO2 and Ni2P/HMS samples. These results suggest that the interaction between catalyst precursors and supports are relative stronger on Ni2P/ZSM-5-M and Ni2P/HZSM-5-M than on Ni2P/SiO2 and Ni2P/HMS samples. A reduction peak around 800 °C could relate to the reduction of the phosphate species that appeared on the Ni2P/SiO2 and Ni2P/HMS catalysts, whereas that was absent on Ni2P/ZSM-5-M and Ni2P/HZSM-5-M catalysts. To determine if the zeolite Al species interact with the P species to generate AlPO4 during the reduction process, the reduced Ni2P/ZSM-5-M sample was analyzed by infrared spectroscopy. The infrared spectroscopy in Figure S7 (Supporting Information) shows that the characteristic AlPO4 absorption band at 1120 cm-1 is not observed in the Ni2P/ZSM-5-M FT-IR spectrum.49 The surface composition of the reduced catalysts was analyzed by the XPS technique and the results were shown in Figure 8 and Table S1 (Supporting Information). The two contributions of the Ni 2p core level spectra for all the reduced catalysts are observed (Figure 8a). The binding energy near 852.5-852.9 eV is assigned to Niδ+ in the Ni2P phase, very close to that reported for Ni0 (852.0-853.0 eV).50,51 The binding energy near 856.2-856.9 eV could correspond to Ni2+ ions interaction with unreduced HPO3H- or phosphate ions induced by superficial oxidation.44 From Figure 8b, the lower binding energy around at 129.3 eV is assigned to Pδ- in the Ni2P phase,52 which is clearly observed on the Ni2P/ZSM-5-M and Ni2P/HZSM-5-M catalysts, while that on the Ni2P/HMS and Ni2P/SiO2 is not obvious (Figure 8b). That all samples show the broad bands at 133-135.0 eV associated with unreduced


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HPO3H- or phosphate species, which should be induced by surface oxidation of phosphorus during sample transfer process in the XPS instrument. 44,50 3.2. Phenanthrene hydrogenation The phenanthrene hydrogenation is a consecutive reaction (Figure 9), in which first dihydrophenanthrene (DHP) and 1,2,3,4-tetrahydrophenanthrene (THP) are created, followed by formation of symmetric and asymmetric octahydrophenanthrene (OHP) as well as perhydrophenanthrene (PHP). Generally, OHP and PHP are considered as the deep hydrogenation products (DHPS). The phenanthrene conversion and the DHPS selectivity over various catalysts at different temperatures are shown in Figure 10. Obviously, the phenanthrene conversions over Ni2P/HZMS-5-M and Ni2P/ZSM-5-M catalysts are much higher than those over the Ni2P/ZSM-5, Ni2P/HMS and Ni2P/SiO2 catalysts at all reaction temperatures (Figure10a). For example, the phenanthrene conversion over the Ni2P/HMS (69%) and Ni2P/SiO2 (61%) catalysts are much lower than that over the Ni2P/HZSM-5-M (95%) and Ni2P/ZSM-5-M (99%) catalysts at 280 °C. Correspondingly, the DHPS selectivity over the Ni2P/ZSM-5-M and Ni2P/HZSM-5-M catalysts is much higher than that over the Ni2P/HMS and Ni2P/SiO2 catalysts (Figure 10b). For instance, the DHPS selectivity over the Ni2P/ZSM-5-M and Ni2P/HZSM-5-M is 83 and 98%, and that over the Ni2P/HMS and Ni2P/SiO2 is 45 and 73 % at 280 °C, respectively. These results indicate that the mesoporous zeolites are better supports to prepare the Ni2P catalyst with high hydrogenation activity. To shed light on the intrinsic hydrogenation activity of the catalysts, the mass transfer in the reaction was ruled out (see Supported Information), and the obtained reaction rate ( phenanthrene hydrogenation over various catalysts is presented in Table 2. The


) and TOFs for and TOF of


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Ni2P/HZSM-5-M (13.2×10-4 mol·kg-1·s-1 and 8.2×10-3 s-1) and Ni2P/ZSM-5-M (4.2×10-4 mol·kg-1·s-1 and 5.6×10-3 s-1) catalysts are much higher than those of the Ni2P/HMS (3.5×10-4 mol·kg-1·s-1 and 5.2×10-3 s-1) and Ni2P/SiO2 catalysts (2.7×10-4 mol·kg-1·s-1 and 4.4×10-3 s-1). Furthermore, the TOF of the Ni2P/ZSM-5-M catalyst is also much higher than that of the NiMo catalysts supported mesoporous zeolite ZSM-5 (1.5×10-3 s-1) and γ-Al2O3 (0.89×10-3 s-1) reported by our previous work.40 These results indicate that the mesoporous zeolite supported Ni2P catalyst exhibits very high intrinsic hydrogenation activity as compared to those of the SiO2 and HMS supported Ni2P catalysts as well as conventional metal sulfide catalysts. The superior catalytic performance of the Ni2P/ZSM-5-M catalyst should be attributed to the well-dispersed Ni2P phases and porous structure as well as acidity. Because the molecular dimension of the phenanthrene is larger than the micropore size (0.53×0.56 nm) of ZSM-5,42,53 the hydrogenation reaction mainly occurs in the mesopores and on the outer surface of the catalysts. From Table 1, it is clearly that the outer surface area of ZSM-5 is only 35 m2·g-1, and the ZSM-5-M has a mesoporous surface area of 159 m2·g-1. Thus, the mesoporous structure in the ZSM-5-M supported Ni2P catalyst favors the mass transfer of the bulk phenanthrene molecules, as compared to the Ni2P/ZSM-5 catalyst. In addition, the large mesoporous surface area in the ZSM-5-M favors the Ni2P particles dispersion, and forms more Ni2P active phases in the mesopores. Therefore, compared with the Ni2P/ZSM-5 catalyst, the Ni2P/ZSM-5-M catalyst can provide abundant accessible active sites for phenanthrene molecules, enhancing its hydrogenation activity. The TEM results show that small Ni2P particles are highly dispersed in the mesoporous channels of the Ni2P/ZSM-5-M catalyst, and that the large Ni2P particles are formed on the outer surface of the Ni2P/ZSM-5 catalyst. The CO uptake on the Ni2P/ZSM-5-M catalyst (98.8 μmol g-1) is much higher than that on Ni2P/ZSM-5 (12 μmol·g-1), indicating that large amounts of active sites exist on the Ni2P/ZSM-5-M catalyst.


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Compared with ZSM-5-M (159 m2·g-1), although SiO2 (212 m2·g-1) and HMS (663 m2·g-1) have large mesoporous surface area, the activity of the Ni2P/SiO2 and Ni2P/HMS catalysts is much lower than that of the Ni2P/ZSM-5-M catalyst for all the reaction temperature regions. This is due to the change in the surface properties in the ZSM-5-M (or HZSM-5-M) and SiO2 (or HMS) supports. Large amounts of acidic sites exist on the ZSM-5-M and HZSM-5-M, which can favor the creation of a strong metal-support interaction, and result in small Ni2P particles highly dispersed in the mesopores of ZSM-5-M and HZSM-5-M as discussed above. The Ni2P active phase with small particle size is responsible for its high hydrogenation activity. It has been reported that there are two types of active sites in the Ni2P phase, tetrahedral Ni(I) sites and square pyramidal Ni(II) site.15,18 The Ni(I) sites are the direct desulfurization sites in the hydrodesulfurization reaction, while the Ni(II) sites are the hydrogenation sites. The number of Ni(II) sites increased with a decrease in crystallite size of the Ni2P active phase.18 In our case, the Ni2P particles with smaller size (less than 5 nm) are highly dispersed on Ni2P/ZSM-5-M and Ni2P/HZSM-5-M, but relatively larger Ni2P particles are formed on the Ni2P/SiO2 (5-15 nm) and Ni2P/HMS (5-10 nm) catalysts. Therefore, the Ni2P/ZSM-5-M and Ni2P/HZSM-5-M catalysts expose more hydrogenation active sites than the Ni2P/SiO2 and Ni2P/HMS catalysts in the phenanthrene hydrogenation reaction. Additionally, compared with SiO2 and HMS, ZSM-5-M and HZSM-5-M have many acidic sites (Figure 6a), which could benefit the phenanthrene adsorption and further improve the activity of their supported Ni2P catalysts.34 It is notable that although ZSM-5-M and HZSM-5-M have a similar external surface area (159, 167 m2·g-1, Table 1), the phenanthrene conversion and DHPS selectivity over the Ni2P/HZSM-5-M catalyst are higher than those over the Ni2P/ZSM-5-M catalyst when the reaction temperature is lower 290 °C (Figure 10). This could be due to the difference in the dispersions and sizes of Ni2P particles on the Ni2P/ZSM-5-M and Ni2P/HZSM-5-M catalysts. Compared with the Ni2P/ZSM-5-M catalyst (3-5 nm),



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relatively smaller Ni2P particles (less 3 nm) are formed in the mesoporous channels of the Ni2P/HZSM5-M catalyst. The CO-chemisorption also confirms that the CO uptake on the Ni2P/HZSM-5-M catalyst (125.3 μmol g-1) is higher than that of Ni2P/ZSM-5-M (98.8 μmol g-1). Meanwhile, the strong acidic sites existed on the Ni2P/HZSM-5-M catalyst could also improve its catalytic activity. Importantly, the Ni2P/ZSM-5-M catalyst has a good catalyst life in the phenanthrene hydrogenation (Figure 11). The good catalyst life of the Ni2P/ZSM-5-M catalyst is one of the key factors in the practical industrial applications. Not only the Ni2P/ZSM-5-M catalyst but also the Ni2P/Beta-M catalyst has excellent hydrogenation activity and good catalyst life in the phenanthrene hydrogenation (Figure 11). 3.3. Hydrodesulfurization of 4,6-DM-DBT Generally, 4,6-DM-DBT undergoes HDS over the Ni2P catalyst via two parallel reaction pathways: direct desulfurization (DDS) to give 3,3′-dimethylbiphenyl (DM-BP) and hydrogenation (HYD) to give the desulfurization products 3,3′-dimethylcycohexylbenzene (DM-CHB) and 3,3′-dimethylbicyclohexyl (DM-BCH).29 The hydrogenated sulfur-containing intermediates, such as 4,6dimethyltetrahydrodibenzothiophene (DM-THDBT), 4,6-dimethylhexahydrodibenzothiophene (DMHHDBT), and 4,6-dimethylperhydrodibenzothiophene (DM-PHDBT) are obtained from the HYD pathway (Figure 12). Because of the steric hindrance of the methyl groups in the 4 and 6 positions, the desulfurization of 4,6-DM-DBT mainly occurs through the hydrogenation pathway.29,34 Therefore, improvement of the hydrogenation activity of the catalyst could increase its HDS activity. As discussion above, the Ni2P/ZSM-5-M catalyst has highly dispersed Ni2P particles with small size, as comparison to Ni2P/SiO2 catalyst. The small Ni2P particles provide abundant hydrogenation active sites, which should be increase the hydrogenation activity of the catalyst and facilitate the conversion of the


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4,6-DM-DBT. This suggestion was supported by the 4,6-DM-DBT HDS experimental data that are shown in Figure 13 and Table 3. Clearly, the 4,6-DM-DBT conversion of the Ni2P/ZSM-5-M is much higher than that of the Ni2P/SiO2 catalyst. The selectivity toward the DM-CHB and DM-BCH products generated through the HYD route over the Ni2P/ZSM-5-M catalyst is 88%, but that over Ni2P/SiO2 catalyst is only 73%. These results indicate that the hydrogenation activity of the Ni2P/ZSM-5-M catalyst is much higher than that of the Ni2P/SiO2 catalyst in the HDS of the 4,6-DM-DBT. On the other hand, the 4,6-DM-DBT molecule are more easily adsorbed on the small Ni2P particles by interaction of Ni2P with the S atom, and the acidic sites on the catalyst could adsorb the4,6-DM-DBT by sulfur-acidic site interaction, which enhance the catalyst activity.34,54 In our case, the very small Ni2P particles and the large amounts of acidic sites on the ZSM-5-M could benefit the adsorption of the 4,6-DM-DBT molecule, improving the HDS activity of the Ni2P/ZSM-5-M.

4. CONCLUSION Mesoporous zeolite ZSM-5 was synthesized and applied for the preparation of highly active Ni2P catalysts. Compared with Ni2P catalysts supported on SiO2 and HMS, Ni2P catalysts supported on mesoporous zeolite ZSM-5 catalysts show very high activity in the deep hydrogenation of phenanthrene as well as in the HDS of the 4,6-DM-DBT. This is attributed to the change in the surface properties of zeolites with SiO2 and HMS. The acidic hydroxyl groups on the mesoporous zeolite could interact strongly with Ni, which facilitates the formation of highly dispersed Ni2P active phase with small particle size during reduction. The small Ni2P particles exhibit large amount hydrogenation active sites showing high hydrogenation activity.

AUTHOR INFORMATION Author Contributions



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The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Tiandi Tang and Dongfang Wu proposed the research direction and guided the project. Wenqian Fu and Lei Zhang performed the material synthesis and activity test experiments. Tiandi Tang and Wenqian Fu analyzed and discussed the experimental results and drafted the manuscript. Wenqian Fu and Lei Zhang characterized the catalysts, and analyzed characterization results. Quanyong Yu and Ting Tang performed some supporting experiments and characterization.

ACKNOWLEDGMENT This work was supported by National Natural Science Foundation of China (U1463203 and 21476030) and the Natural Science Foundation of Zhejiang Province of China (LZ14B060003).

SUPPORTING INFORMATION Calculation of Weisz-Prater Criterion and Mears Criterion, TEM images of the thin-sectioned (a) ZSM5-M and (b) Beta-M samples (Figure S1), XRD patterns of the Ni2P (PDF: 03-0953) and Ni2P/Beta-M samples (Figure S2), TEM images of the thin-sectioned Ni2P/ZSM-5-M sample (Figure S3), TEM images of the thin-sectioned Ni2P/Beta-M sample (Figure S4), FT-IR spectra of the (a) HZSM-5-M and dried Ni2P/HZSM-5-M, and (b) Beta-M and dried Ni2P/Beta-M samples (Figure S5), NH3-TPD curves of the Beta-M and Ni2P/Beta-M samples (Figure S6), FT-IR spectra of the (a) ZSM-5-M and Ni2P/ZSM-5-M, and (b) Beta-M and Ni2P/Beta-M samples (Figure S7), Surface chemical element composition of the reduced catalyst obtained by XPS analysis (Table S1). This Supporting Information is available free of charge via the Internet at http://pubs.acs.org.

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(43) Song, L. M.; Li, W.; Wang, G. L.; Zhang, M. H.; Tao, K. Y. A New Route to Prepare Supported Nickel Phosphide/Silica–alumina Hydrotreating Catalysts from Amorphous Alloys. Catal. Today 2007, 125, 137. (44) Song, H.; Dai, M.; Song, H. L.; Wan, X.; Xu, X. W. A Novel Synthesis of Ni2P/MCM-41 Catalysts by Reducing A Precursor of Ammonium Hypophosphite and Nickel Chloride at Low Temperature. Appl. Catal. A 2013, 462-463, 247. (45) Xu, B.; Bordiga, S.; Prins, R.; van Bokhoven, J. A. Effect of Framework Si/Al Ratio and Extraframework Aluminum on the Catalytic Activity of Y zeolite. Appl. Catal. A 2007, 333, 245. (46) Li. X. F.; Prins, R.; Van Bokhoven, J. A. Synthesis and Characterization of Mesoporous Mordenite. J. Catal. 2009, 262, 257. (47) Li, K. L.; Wang, R. J.; Chen, J. X. Hydrodeoxygenation of Anisole over Silica-supported Ni2P, MoP, and NiMoP Catalysts. Energy Fuels 2011, 25, 854. (48) d’Aquino, A. I.; Danforth, S. J.; Clinkingbeard, T. R.; Ilic, B.; Pullan, L.; Reynolds, M. A.; Murray, B. D.; Bussell, M. E. Highly-active Nickel Phosphide Hydrotreating Catalysts Prepared in situ Using Nickel Hypophosphite Precursors. J. Catal. 2016, 335, 204. (49) Chen, T.; Yang, B. L.; Li, S. S.; Wang, K. L.; Jiang, X. D.; Zhang, Y.; He, G. W. Ni2P Catalysts Supported on Titania-modified Alumina for the Hydrodesulfurization of Dibenzothiophene. Ind. Eng. Chem. Res. 2011, 50, 11043. (50) Song, H.; Dai, M.; Song, H. L.; Wan, X.; Xu, X. W.; Zhang, C. Y.; Wang, H. Y. Synthesis of A Ni2P Catalyst Supported on Anatase–TiO2 Whiskers with High Hydrodesulfurization Activity, Based on Triphenylphosphine. Catal. Commun. 2014, 43, 151.


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(51) Landau, M. V.; Herskowitz, M.; Hoffman, T.; Fuks, D.; Liverts, E.; Vingurt, D.; Froumin, N. Ultradeep Hydrodesulfurization and Adsorptive Desulfurization of Diesel Fuel on Metal-rich Nickel Phosphides. Ind. Eng. Chem. Res. 2009, 48, 5239. (52) Korányi, T. I.; Vít, Z.; Poduval, D. G.; Ryoo, R.; Kim, H. S.; Hensen, E. J. M. SBA-15-supported Nickel Phosphide Hydrotreating Catalysts. J. Catal. 2008, 253, 119. (53) Meng, X. C.; Wu, Y. X.; Li, Y. D. Tailoring the Pore Size of Zeolite Y as the Support of Diesel Aromatic Saturation Catalyst. J. Porous Mater. 2006, 13, 365. (54) Song, H.; Wan, X.; Dai, M.; Zhang, J. J.; Li, F.; Song. H. L. Deep Desulfurization of Model Gasoline by Selective Adsorption over Cu–Ce Bimetal Ion-exchanged Y Zeolite. Fuel Process. Technol. 2013, 116, 52.



FIGURES

Intensity (a.u.)

a Beta-M

ZSM-5-M

10

20

30

40

50

-1

b

1.6

10

1.2

22

600

0.8

3

-1

dV/dlog(D) Pore Volume (cm g )

2 Theta (deg.)

Quantity Adsorbed (cm g STP)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 42

0.4 0.0

400

Beta-M

10 Pore Diameter (nm)

ZSM-5-M

200

0.0

0.2

0.4

0.6

0.8

1.0

Relative Pressure (P/P0)

Figure 1. (a) XRD patterns and (b) N2 adsorption isotherms of the ZSM-5-M and Beta-M samples (inset, mesoporous size distribution of the ZSM-5-M and Beta-M samples. The Isotherms of Beta-M sample have been offset by 180 cm3·g-1 along the vertical axis for clarity. The mesopore size distribution of Beta-M sample has been offset by 1.1 cm3·g-1 along the vertical axis for clarity).


e d

Intensity (a.u.)

c b a 42

45

48

2 Theta (deg.)

e d c b a 10

20

30

40

50

2 Theta (deg.) Figure 2. XRD patterns of (a) Ni2P (PDF: 03-0953), (b) ZSM-5-M, (c) Ni2P/ZSM-5, (d) Ni2P/ZSM-5M and (e) Ni2P/HZSM-5-M catalysts.

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Intensity (a.u.)

Page 29 of 42

c

b a 10

20

30

2 Theta (deg.)

40

50

Figure 3. XRD patterns of (a) Ni2P (PDF: 03-0953), (b) Ni2P/HMS and (c) Ni2P/SiO2 catalysts.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 42

Figure 4. TEM images of the (a) Ni2P/ZSM-5, (b) Ni2P/ZSM-5-M, (c) Ni2P/HZSM-5-M, (d) highresolution TEM image and FFT (inset) of the Ni2P particles on zeolite, (e) Ni2P/SiO2 and (f) Ni2P/HMS samples.


Page 31 of 42

0.5 3662

a

3600

0.4

Absorption

ZSM-5-M

0.3 3740

0.2 Ni2P/ZSM-5-M

0.1 0.0 4000

3900

3800

3700

3600

3500

3400

3500

3400

3500

3400

-1

Wavenumber (cm )

Absorbance

0.8

3740

b SiO2

0.6 0.4 0.2

Ni2P/SiO2

0.0 4000

3900

3800

3700

3600 -1

Wavenumber (cm ) 1.2 1.0

c

3740 HMS

Absorbance

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.8 0.6 0.4 Ni2P/HMS

0.2 0.0 4000

3900

3800

3700

3600 -1

Wavenumber (cm )

Figure 5. FT-IR spectra of the (a) ZSM-5-M and dried Ni2P/ZSM-5-M, (b) SiO2 and dried Ni2P/SiO2 and (c) HMS and dried Ni2P/HMS samples.



0.06

a

ZSM-5-M HZSM-5-M SiO2

0.04

TCD Signal

HMS

0.02

0.00 200

300

400

500

Temperature (C)

0.06

Ni2P/SiO2

b

Ni2P/HMS Ni2P/ZSM-5-M

TCD Signal

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 42

Ni2P/HZSM-5-M

0.04

0.02

0.00 200

300

400

Temperature (C)

500

Figure 6. NH3-TPD profiles of the various (a) supports and (b) corresponding catalysts.


Page 33 of 42

a

391

TCD Signal (a.u.)

Ni/HZSM-5-M

376 Ni/ZSM-5-M

355 Ni/HMS

335 Ni/SiO2

200

400

600

800

Temperature (C)

b TCD Signal (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Ni2P/HZSM-5-M

174

Ni2P/ZSM-5-M

200

Ni2P/HMS

133 201

Ni2P/SiO2

194

182

200

400

600

800

Temperature (C) Figure 7. H2-TPR profiles of the dried (a) Ni/SiO2, Ni/HMS, Ni/ZSM-5-M and Ni/HZSM-5-M samples, and the dried (b) Ni2P/SiO2, Ni2P/HMS, Ni2P/ZSM-5-M and Ni2P/HZSM-5-M samples.



Intensity (a.u.)

a 852.8856.6

Ni2P/HZSM-5-M

852.8 856.6

852.6

Ni2P/ZSM-5-M

856.4

Ni2P/HMS

852.7 856.4

850

Ni2P/SiO2

860

870

880

890

Binding Energy (eV) 133.8

b 129.2

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 42

134.2

Ni2P/HZSM-5-M

134.1

Ni2P/ZSM-5-M

129.3

Ni2P/HMS

134.8

Ni2P/SiO2

128

132

136

140

Binding Energy (eV) Figure 8. XPS Ni2p (a) and P2p (b) spectra of the reduced Ni2P/SiO2, Ni2P/HMS, Ni2P/ZSM-5-M and Ni2P/HZSM-5-M catalysts.


Page 35 of 42

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 9. Reaction network of the hydrogenation of phenanthrene. (PHE: Phenanthrene; DHP: 9,10Dihydrophenanthrene; Octahydrophenanthrene

THP:

1,2,3,4-Tetrahydrophenanthrene;

(symmetric

octahydrophenanthrene)

OHP: or

1,2,3,4,5,6,7,8,1,2,3,4,4a,9,10,10a-

Octahydrophenanthrene (asymmetric octahydrophenanthrene); and PHP: Perhydrophenanthrene).



Phenanthrene Conversion (%)

100

a

99 95

80 69

60 61 36

40 20 0 260

100

270

280

Temperature (C)

290

98

b

83

DHPS Selectivity (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 42

80 73

60 45

40 20

13

0 260

270

280

290

Temperature (C) Figure 10. The phenanthrene conversion (a) and DHPS selectivity (b) at different temperatures over ▼ Ni2P/HZSM-5-M, ■ Ni2P/ZSM-5-M, ● Ni2P/HMS, ♦ Ni2P/SiO2 and ▲ Ni2P/ZSM-5 catalysts.


Page 37 of 42

100


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


80

60

40

20

0 0

20

40

60

80

100

Time on Stream (h)

Figure 11. Dependence of the phenanthrene conversion on reaction time over ■ Ni2P/ZSM-5-M and ● Ni2P/Beta-M catalysts at the temperature of 280 °C.

Figure 12. Network of 4,6-DM-DBT hydrodesulfurization.



100

4,6-DM-DBT Conversion (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 42

80

60

40

20 5

10

15

20

25

30

35

Time on Stream (h)

Figure 13. Dependence of the 4,6-DM-DB conversion on reaction time over ■ Ni2P/ZSM-5-M and (♦) Ni2P/SiO2 catalysts.


Page 39 of 42

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TABLES Table 1. Textual properties of supports and corresponding catalysts CO uptake

SBET (m2·g-1)ɑ

Vmic (cm3·g-1)b

Sext (m2·g-1)c

ZSM-5-Md

372

0.09

159

-

HZSM-5-Md

384

0.09

167

-

Beta-Md

655

0.20

146

-

SiO2d

663

0.12

212

-

HMSd

687

-

663

-

ZSM-5d

347

0.12

35

-

Ni2P/ZSM-5-M

165

0.05

70

98.8

Ni2P/HZSM-5-M

234

0.06

63

125.3

Ni2P/Beta-M

315

0.09

86

81.3

Ni2P/SiO2

263

0.02

219

19

Ni2P/HMS

178

-

163

34.1

Ni2P/ZSM-5

153

0.05

21

12

Samples

μmol·g-1)

ɑ

BET surface area. bMicroporous volume. cExternal surface area, including mesoporous surface area.

d

The samples are the powder form, and the others are tableted at 15 MPa.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 40 of 42

Table 2. Intrinsic activity of the Ni2P/ZSM-5-M, Ni2P/HMS and Ni2P/SiO2 catalysts in the phenanthrene hydrogenation.a robs×104 Catalyst mol∙kg-1∙s-1)

TOF×103

Product selectivity (%)

(s-1)

DHP

THP

OPH

PHP

Ni2P/ZSM-5-M

4.2

5.6

50

40

10

-

Ni2P/HZSM-5-M

13.2

8.2

52

29

19

-

Ni2P/HMS

3.5

5.2

52

40

8

-

Ni2P/SiO2

2.7

4.4

42

44

14

-

a

Reaction conditions: 0.05 g catalyst, total pressure of 5.0 MPa, temperature of 280 C, a H2 flow of 60

mL∙min-1, and 1.0 wt.% phenanthrene in decalin (The phenanthrene conversion over the catalysts is controlled about 40% by changing the weight hourly space velocity).


Page 41 of 42

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48


Table 3. Product selectivity of the Ni2P/ZSM-5-M and Ni2P/SiO2 catalysts at the reaction time of 27 h.a 4,6-DM-DBT Product selectivity (%) Catalyst Conv. (%)

DM-BP

DM-THDBT

DM-HHDBT

DM-PHDBT

DM-BCHb

DM-CHBb Tol.+MCHc

Ni2P/ZSM-5-M

93.5

4.8

1.5

0.6

0.6

28.3

59.8

4.4

Ni2P/SiO2

61.7

4.5

11.9

4.5

6.3

27.5

45.3

-

a

Reaction conditions: 0.3 g dried catalyst, total pressure of 5.0 MPa, temperature of 300 C, H2 flow rate of 60 mL∙min-1, weight

hourly space velocity of 12.6 h-1, a H2 flow of 60 mL·min-1, 0.45 wt.% 4,6-DM-DBT in decalin. bDM-BCH and DM-CHB are the hydrogenation products followed by desulfurization through the hydrogenation routes. cTol. and MCH denote toluene and methylcyclohexane, respectively.



For Table of Contents Only

100


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 42 of 42

Ni2P/HZSM-5-M 80

Ni2P/SiO2

60 40

Ni2P/ZSM-5

20 0 260

270

280

Temperature (C)

290


42

Mesoporous Zeolite ZSM-5 Supported Ni2P ... - ACS Publications

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