Supporting information

Promotional effect of Co and Ni on MoO3 catalysts for hydrogenolysis of

dibenzofuran to biphenyl under atmospheric hydrogen pressure

Jie Zhang a, Chuang Li a, Weixiang Guan a, Xiaozhen Chen a, Xiao Chen a, Chi-Wing Tsang b,

Changhai Liang a,*

a State Key Laboratory of Fine Chemicals, Laboratory of Advanced Materials and Catalytic

Engineering, School of Chemical Engineering, Dalian University of Technology, Dalian

116023, China

b Faculty of Science and Technology, Technological and Higher Education Institute of Hong

Kong, Hong Kong, China

* To whom correspondence should be addressed: Fax: + 86-411-84986353; E-mail: changhai@dlut.edu.cn; Homepage: http://amce.dlut.edu.cn

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CoMoO4 was prepared using a precipitation method staring from the correspondent

metal salt (NH4)6Mo7O24 and Co(NO3)2 dissolved in water. The solutions were prepared with

a Co/Mo molar ratio of 1 and stirred for 24 h at 80 °C to form the violaceous solid. And then

the obtained solid was washed using ethanol. After drying at 80 °C, the sample was then

treated in air at 400 °C for 2 h (5 °C min-1). The synthetic method of NiMoO4 was the same

as above.

When Co(Ni)MoO4 were used to the reaction of DBF, they were not reduced with

hydrogen before catalytic tests.

In order to determine the elemental distribution, SEM-EDX analysis was performed and

the images are shown in Fig. S1 and S2. The mapping images show that there is a good

correspondence of Co(Ni) elemental map formed with the intensity of Mo element,

indicating the Co(Ni) uniformly distributed on the surface of MoO3.

Effect of temperature was investigated to calculate the apparent activation energy (Ea)

of the conversion of DBF (Fig. S6). The Ea value over MoO3 was 152 kJ mol-1, much higher

than that over Co/MoO3 catalyst (131 kJ mol-1) and Ni/MoO3 catalyst (140 kJ mol-1). This

discrepancy between MoO3 and Co(Ni)/MoO3 implies that there exists great difference in the

activation barriers and further in the reaction activity. During the entire reaction temperature

range, MoO3 exhibited relatively poor activity (Fig.S6a). On the contrary, there existed a

markedly increasing trend in the conversion with the addition of Co(Ni), illustrating that

Co(Ni) favored the improvement of the catalytic activity. Especially, due to the existence of

Co, the conversion increased significantly from 19 % at 340 °C to 91 % when reacted at 380

°C (Fig.S6a). However, the selectivity of BP remained 100 % over three catalysts at the

studied reaction temperature and 0.1 MPa. It is noteworthy that the determined TOF values,

in consistent with the conversion, followed the same trend: Co/MoO3 > Ni/MoO3 > MoO3.

The activity of Co(Ni)/MoO3 catalysts at different reduction temperature was explored

as shown in Fig. S7 and the corresponding reaction rates were shown in Table S2. The

results showed that the activity of Co(Ni)/MoO3 catalysts reduced at 300 °C and 350 °C was

higher than that reduced at higher temperature. And the activity of Co/MoO3 was higher that

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of Ni/MoO3 in the studied reduction temperature, which is consistent with our results. Then

the catalysts at different reduction temperature were characterized by XPS and NH3-TPD.

The results were shown in Fig. S8, S9, S10 and S11.

At the reduction temperature of 300 °C and 350 °C, the acidity and the active Mo

species over Co/MoO3 and Ni/MoO3 had the little difference, which results in the similar

reaction rates. The increased acidity over Co(Ni)/MoO3 catalysts could increase the reaction

rates (Fig. S10a and S11a). On the other hand, the Mo species over Co/MoO3 and Ni/MoO3

presented the relatively large difference. The Mo5+ and Mo6+ species both showed the

relatively excellent activity, although the activity of Mo6+ species is inferior to the activity of

Mo5+ species. Therefore, the percentages of both the Mo5+ and (Mo5++Mo6+) species were

shown in the Fig. S10b and S11b. With the reduction temperature increasing from 350 °C,

the Mo5+ species gradually decreased over Co/MoO3 (Fig. S8), which leads to the decreased

activity. However, the Mo5+ species maintained stable over Ni/MoO3 with the increased

reduction temperature, whereas the Mo6+ species obviously decreased companied with the

increased reduction temperature (Fig. S9), and then resulted in the more inactive Mo4+. So it

contributed to the lower activity over Ni/MoO3. These results led to the same conclusion that

the acidic sites and Mo5+ species are the active sites for the reaction.

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Fig. S1. SEM and mapping of calcined Ni/MoO3 catalyst.

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Fig. S2. SEM and mapping of calcined Co/MoO3 catalyst.

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Fig. S3. H2-TPR for calcined MoO3, Co(Ni)/MoO3 and Co(Ni)MoO4 catalysts.

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Fig. S4. NH3-TPD of MoO3, Co(Ni)/MoO3 and CoMoO4 catalysts reduced at 300 °C for 2 h.

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Fig. S5. Selectivity as a function of WHSV (gDBF/gcatalyst∙h) during the hydrogenolysis of DBF over Ni/MoO3 catalyst reduced at 300 °C for 2 h.

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Fig. S6. The conversion for the hydrogenolysis of DBF as a function of reaction temperature at 0.44 gDBF/gcatalyst∙h (a) and the corresponding natural logarithm of TOF versus inversed temperature during the hydrogenolysis of DBF over MoO3 and Co(Ni)/MoO3 catalysts reduced at 300 °C for 2 h.

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Fig. S7. The conversion as a function of WHSV (gDBF/gcatalyst∙h) during the hydrogenolysis of DBF over Co/MoO3 (a) and Ni/MoO3 (b) at different reduction temperature for 2 h.

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Fig. S8. X-ray photoelectron spectra of the Mo (3d) energy region in Co/MoO3 catalysts reduced at 300 °C (a), 350 °C (b), 400 °C (c) and 450 °C (d) for 2 h. The ratios displayed correspond to the proportion of oxidation states of Mo6+, Mo5+ and Mo4+.

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Fig. S9. X-ray photoelectron spectra (XPS) of the Mo (3d) energy region in Ni/MoO3

catalysts reduced at 300 °C (a), 350 °C (b), 400 °C (c) and 450 °C (d) for 2 h. The ratios displayed correspond to the proportion of oxidation states of Mo6+, Mo5+ and Mo4+.

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Fig. S10. The relationship between reaction rates and acidity (a) or the active Mo species (b) over Co/MoO3 catalyst at different reduction temperature (left to right: 450 °C, 400 °C, 300 °C, 350 °C).

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Fig. S11. The relationship between reaction rates and acidity (a) or the active Mo species (b) over Co/MoO3 catalyst at different reduction temperature (left to right: 450 °C, 400 °C, 300 °C, 350 °C).

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Fig. S12. XPS spectra of the Co and Ni in (a) Co/MoO3 and (b) Ni/MoO3 reduced at 300 °C for 2 h, respectively.

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Table S1 Physical texture of calcined samples determined by BET.

Samples S(m2 g-1)

Vp

(cm3 g-1)dp

(nm)MoO3 17 0.035 8.4

Co/MoO3 11 0.029 10.3Ni/MoO3 11 0.024 10.6

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Table S2. The reaction rates of Co(Ni)/MoO3 catalysts at different reduction temperature.

Catalysts Reaction rates (μmol∙gcat-1∙s-1) at different reduction temperature

300 °C 350 °C 400 °C 450 °C

Co/MoO3 0.29 0.29 0.21 0.19Ni/MoO3 0.26 0.30 0.18 0.11

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Table S3. The activity of MoO3, Co(Ni)/MoO3 and Co(Ni)MoO4 catalysts (reduction at 300 °C for 2 h) at 0.44 gDBF/gcatalyst∙h.

Catalysts Activity

Conversion (%) Initial reaction rates (μmol∙gcat

-1∙s-1)Initial reaction rates

(μmol∙molMo-1∙s-1 102)

MoO3 25 0.18 0.66Co/MoO3 40 0.29 1.02CoMoO4 30 0.21 1.17Ni/MoO3 36 0.26 0.92NiMoO4 28 0.20 1.07

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