HYDRODESULFURIZATION OF THIOPHENE OVER � -Mo2N CATALYSTS
147
CONCLUSIONS
port of this work. We also thank Professor Michael Myrick of the Depart-
ment of Chemistry at the University of South Carolina for assistance with
the scanning tunneling microscopic analyses and Dr. Dana Dunkelberger
of the Electron Microscopy Center at the University of South Carolina
for assistance with the scanning and transmission electron microscopic
analyses.
Macrocrystalline Mo2N has been synthesized from MoO3
macrocrystals by temperature programmed reaction in
N2/H2 and NH3 gases. In this work, Mo2N macrocrystals
2
were revealed to have a specific surface area of 44 m /g.
�
-Mo2N macrocrystals are relatively small, dark metallic-
REFERENCES
gray platelets of moderately porous material which have
visible dimensions varying from micrometer- to centimeter-
scaled proportions.
1
2
. Volpe, L., and Boudart, M., J. Solid State Chem. 59, 332 (1985).
. Ranhorta, G. S., Haddix, G. W., Bell, A. T., and Reimer, J. A., J. Catal.
108, 24 (1987).
. Choi, J.-G., Curl, R. L., and Thompson, L. T., J. Catal. 146, 218 (1994).
. Wise, R. S., and Markel, E. J., J. Catal. 145, 335 (1994).
. Roberts, K. L., and Markel, E. J., J. Phys. Chem. 98, 4083 (1994).
. Volpe, L., and Boudart, M., J. Phys. Chem. 90, 4878 (1986).
. Wise, R. S., and Markel, E. J., J. Catal. 145, 344 (1994)
8. Ranhorta, G. S., Bell, A. T., and Reimer, J. A., J. Catal. 108, 40 (1987).
. Oyama, S. T., Catal. Today 15, 279 (1992).
0. Schlatter, J. C., Oyama, S. T., Metcalfe, J. E., and Lambert, J. M., Ind.
Eng. Chem. Res. 27, 1648 (1988).
From scanning electron microscopic analyses, the synthe-
sis reaction appears to commence at the edges of the pla-
nar MoO3 macrocrystals and later convert the crystalline
MoO3 into a mat of layers each less than 200 nm thick.
However, the bulk of the porosity of the Mo2N macrocrys-
tals does not appear to be located in these exposed basal
planes, but instead in a fine pore structure. Scanning tunnel-
ing microscopy and X-ray diffraction shows that the solid
consists of Mo2N crystallites which are foreshortened in the
3
4
5
6
7
9
1
1
1. Choi, J.-G., Brenner, J. R., Colling, C. W., Demczyk, B. G., Dunning,
J. L., and Thompson, L. T., Catal. Today 15, 201 (1992).
[200] direction with either an amorphous surface phase or a
polycrystalline core. X-ray diffraction patterns from Mo2N 12. Markel, E. J., and Van Zee, J. W., J. Catal. 126, 643 (1990).
1
1
1
1
1
3. Nagai, M., Miyao, J., and Tsuboi, T., Catal. Lett. 18, 9 (1993).
4. Daage, M., and Chianelli, R. R., J. Catal. 149, 414 (1994).
5. Bertrand, O., and Dufour, L. C., Phys. Status Solidi A 60, 507 (1980).
6. Anderson, J., J. Physique, Suppl. 38, C7–C17 (1977).
7. Hillis, M. R., Kemball, C., and Roberts, M. W., Trans. Faraday Soc. 62,
3570 (1966).
macrocrystals indicate the presence of crystallites which are
locked in crystallographic alignment. TGA analyses of the
reduction/nitridation reaction indicate that the reaction is
slower in the macrocrystalline than equivalent powder syn-
theses. The rate of reaction is likely limited by solid-state
diffusion where the reduction reaction would possibly com-
mence at the edges of the MoO3 macrocrystal and consume
the oxide from the edges inward.
18. King, E. G., Weller, W. W., and Christensen, A. U., U.S. Bur. Mines,
Report, 1960.
1
2
2
9. Bursill, L. A., Proc. R. Soc. A 311, 267 (1969).
0. JCPDS X-ray Powder Diffraction Inorganic Reference Data, 1987.
1. Gusev, A. I., Phys. Stat. Sol. (B) 163, 17 (1991).
The thiophene desulfurization activity of macrocrys-
talline Mo2N is observed to be more than twice that of 22. Wise, R., and Markel, E., unpublished results.
2
3. Klug, H. P., and Alexander, L. E., in “X-Ray Diffraction Procedures,”
p. 511. Wiley, New York, 1962.
Mo2N powder on an area basis but is of equal activity on
a mass basis. The reason for this difference in area specific
activities is unknown. Product selectivities for butenes, bu-
tane, and butadiene for the thiophene desulfurization over
24. Colling, C. W., Choi, J.-G., and Thompson, L. T., J. Catal. 160, 35 (1996).
25. Burdick, S. E., and Markel, E. J., unpublished results.
26. Benson, S. W., and Bose, A. W., J. Am. Chem. Soc. 85, 1385 (1963).
Mo2N macrocrystal catalysts are in close agreement with 27. Chase, M. W., Davies, C. A., Downey, J. R., Frurip, D. J., McDonald,
R. A., and Syverud, A. N., JANAF Thermochemical Tables, 3rd ed.
8. Oyama, S. T., Schlatter, J. C., Metcalfe, J. E., and Lambert, J. M., Ind.
Eng. Chem. Res. 27, 1639 (1988).
9. Choi, J.-G., Brenner, J. R., Colling, C. W., Demczyk, B., Dunning,
J. L., and Thompson, L. T., Catal. Today 15, 201 (1992).
those observed for Mo2N powder catalysts. Thiophene is
desulfurized to form predominantly 1-butene with smaller
amounts of other C4 compounds observed.
2
2
ACKNOWLEDGMENTS
30. McCarty, K. F., Anderegg, J. W., and Schrader, G. L., J. Catal. 93, 375
1985).
(
This work was supported by the National Science Foundation Grant
OFR-9108772-02. The National Science Foundation also provided fund-
31. Osbaldiston, R. J. C., MS thesis, Univ. of South Carolina, 1993.
32. Desikan, P., and Amberg, C. H., Can. J. Chem. 41, 1966 (1963).
ing for the electron microscope (Equipment Grant DIR-9016370). K. L. 33. Kolboe, S., and Amberg, C. H., Can. J. Chem. 44, 2623 (1966).
Roberts also thanks the Department of Energy EPSCoR Fellowship pro- 34. Markel, E. J., Sauer, N. N., Angelici, R. J., and Schrader, G. L., J. Catal.
gram at the University of South Carolina and the Department of En-
ergy Samuel Massie Chair of Excellence in Environmental Engineering at
North Carolina Agricultural and Technical State University for their sup-
116, 11 (1989).
35. Sauer, N. N., Markel, E. J., Schrader, G. L., and Angelici, R. J., J. Catal.
117, 295 (1989).