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On Auger electron spectroscopic measurements of ZnCl2 —coal interaction
Journal of Electron Spectroscopy and Related Phenomena, 16 (1979) 119-121 0 Elsewer Sclentlflc Pubhshmg Company, Amsterdam - Printed III The Netherlands
Short communication
ON AUGER ELECTRON SPECTROSCOPIC MEASUREMENTS Z&l, +OAL INTERACTION
GEORGE
D PARKS
Phallaps Petroleum (USA) (Recewed
OF
Company,
Phdllps
Research
Center, Bartksvdle,
Oklahoma
74004
15 June 1978)
Zmc halides are known to be active catalysts for the hydrogenation of coal’ _ A recent electron spectroscopic study of ZnCl, impregnated coal has shown the presence of two “anomalous” lmes m the Zn Lj M, j M,+ 5 Auger regron separated by 4.2 eV mstead of the normal 9.1 eV separation observed m the Zn Auger lmes 2. These two lmes were presumed to be the Zn Auger lmes which had been shrfted due to mteractlons between the ZnCl, and the coal. It was further postulated that this unexpected shLft might be due to Zn bonded to coal free radicals and thus be related to the catalytic actnnty. Smce no Utah coal was avrulable, 10 g of Phillips Texas lignite was unpregnated with 6% Zn as Z&l, m the same manner as desmbed by Lee et a12. Samples of this matenal were then treated under flowmg H2 at 250,350 and 450” C. A sample with no ZnCl, was also treated at 450* C. The resultmg chars were exammed by XPS using a Varlan IEE spectrometer with Mg anode All samples of the ZnCl, unpregnated chars showed relatively strong Zn(2p 3/2) and C1(2p) lmes as well as the %nomalous” lmes at 343 and 352 eV (C(ls) = 285,OeV). These lmes became more dlstmct as treatment temperature increased, m agreement with behavior observed by Lee et a12. We also nolxed, however, that the same two lmes were present m the spectrum of the samples to which no ZnC12 had been added; m addition, neither the Zn (2~ 3/2) nor the Cl (2~) lmes could be detected for these spectra. The bmdmg enewes of the lmes on these blank samples (one vacuum dined and one treated at 450” C) were 347.7 and 351.0 eV. This data suggests that the “anomalous” lmes which Lee et al. assigned as shifted Zn L3 M,,:, M, 5 Auger lmes are probably Ca (2p) hnes from calcmm m the
362
358
354
(NOT
BINDING ENERGY CORRECTED FOR
350
(In eV1 CHARGING1
Figure 1 Ca(2p) spectra for wmpleo treated m Hz at 450° C
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342
121
coal samples. The calcium probably migrates to the surface dunng treatment at high temperatures, causmg the c&mm lmes to become more mtense compared to the zmc Auger Imes. The effect of the zmc can be seen m Fig. 1 which shows the Ca(2p) spectrum for samples treated at 450” C. The Ca(2pi ) line of the sample with ZnCl, overlaps with the Zn Auger lme at 354 eV, makmg It appear to be broadened and shlftmg its apparent bmdmg energy by about 1 eV The calcmm lmes of the char from the ZnCI, unpregnated hgnlte are obviously more intense than those of the char from the untreated hgnlte sample This mcrease m the amount of surface calcium effected by the ZnCl, may play a role m the catalytic actlvlty of ZnCl, for coal hydrogenatlon While mteractlons between ZnCl, and coal free radicals may occur and may play an Important role m the catalytic actlvlty of ZnCl,, the electron spectroscopic data on hgnlte coals provide no evLdence to support the exrstence of such mteractlons, and mdlcate that previous data may have been Interpreted mcorrectly Expenments conducted with Kruparowxtz coal and an instrument usmg Al Kcr X-rays would provide an unambiguous resolution of the question smce the Zn Auger hnes and the Ca(2p) photoelectron lmes will appear m different regons of the spectrum
REFERENCES 1
2
R E Wood and W H Wmer, Ind Eng Chem Process Des Dev, 16 (1976) 144 J M Lee, R E Wood and W H Wmer, J Electron Spectroec ReZat Phenom (1977) 493
, 12
Short communication
ON AUGER ELECTRON SPECTROSCOPIC MEASUREMENTS Z&l, +OAL INTERACTION
GEORGE
D PARKS
Phallaps Petroleum (USA) (Recewed
OF
Company,
Phdllps
Research
Center, Bartksvdle,
Oklahoma
74004
15 June 1978)
Zmc halides are known to be active catalysts for the hydrogenation of coal’ _ A recent electron spectroscopic study of ZnCl, impregnated coal has shown the presence of two “anomalous” lmes m the Zn Lj M, j M,+ 5 Auger regron separated by 4.2 eV mstead of the normal 9.1 eV separation observed m the Zn Auger lmes 2. These two lmes were presumed to be the Zn Auger lmes which had been shrfted due to mteractlons between the ZnCl, and the coal. It was further postulated that this unexpected shLft might be due to Zn bonded to coal free radicals and thus be related to the catalytic actnnty. Smce no Utah coal was avrulable, 10 g of Phillips Texas lignite was unpregnated with 6% Zn as Z&l, m the same manner as desmbed by Lee et a12. Samples of this matenal were then treated under flowmg H2 at 250,350 and 450” C. A sample with no ZnCl, was also treated at 450* C. The resultmg chars were exammed by XPS using a Varlan IEE spectrometer with Mg anode All samples of the ZnCl, unpregnated chars showed relatively strong Zn(2p 3/2) and C1(2p) lmes as well as the %nomalous” lmes at 343 and 352 eV (C(ls) = 285,OeV). These lmes became more dlstmct as treatment temperature increased, m agreement with behavior observed by Lee et a12. We also nolxed, however, that the same two lmes were present m the spectrum of the samples to which no ZnC12 had been added; m addition, neither the Zn (2~ 3/2) nor the Cl (2~) lmes could be detected for these spectra. The bmdmg enewes of the lmes on these blank samples (one vacuum dined and one treated at 450” C) were 347.7 and 351.0 eV. This data suggests that the “anomalous” lmes which Lee et al. assigned as shifted Zn L3 M,,:, M, 5 Auger lmes are probably Ca (2p) hnes from calcmm m the
362
358
354
(NOT
BINDING ENERGY CORRECTED FOR
350
(In eV1 CHARGING1
Figure 1 Ca(2p) spectra for wmpleo treated m Hz at 450° C
346
342
121
coal samples. The calcium probably migrates to the surface dunng treatment at high temperatures, causmg the c&mm lmes to become more mtense compared to the zmc Auger Imes. The effect of the zmc can be seen m Fig. 1 which shows the Ca(2p) spectrum for samples treated at 450” C. The Ca(2pi ) line of the sample with ZnCl, overlaps with the Zn Auger lme at 354 eV, makmg It appear to be broadened and shlftmg its apparent bmdmg energy by about 1 eV The calcmm lmes of the char from the ZnCI, unpregnated hgnlte are obviously more intense than those of the char from the untreated hgnlte sample This mcrease m the amount of surface calcium effected by the ZnCl, may play a role m the catalytic actlvlty of ZnCl, for coal hydrogenatlon While mteractlons between ZnCl, and coal free radicals may occur and may play an Important role m the catalytic actlvlty of ZnCl,, the electron spectroscopic data on hgnlte coals provide no evLdence to support the exrstence of such mteractlons, and mdlcate that previous data may have been Interpreted mcorrectly Expenments conducted with Kruparowxtz coal and an instrument usmg Al Kcr X-rays would provide an unambiguous resolution of the question smce the Zn Auger hnes and the Ca(2p) photoelectron lmes will appear m different regons of the spectrum
REFERENCES 1
2
R E Wood and W H Wmer, Ind Eng Chem Process Des Dev, 16 (1976) 144 J M Lee, R E Wood and W H Wmer, J Electron Spectroec ReZat Phenom (1977) 493
, 12