TY - JOUR
T1 - A density functional theory study of the interactions of H2O with H-ZSM-5, Cu-ZSM-5, and Co-ZSM-5
AU - Rice, Mark J.
AU - Chakraborty, Arup K.
AU - Bell, Alexis T.
PY - 1998/9/17
Y1 - 1998/9/17
N2 - The interactions of water with H-ZSM-5, Cu-ZSM-5, and Co-ZSM-5 have been investigated by density functional theory (DFT). Calculations were also performed to determine the thermodynamics of metal removal from the zeolite. For all three forms of ZSM-5, water adsorbs by direct interaction of the O atom with the cation and hydrogen bonding of one of the two H atoms with an oxygen atom in the zeolite framework. The magnitude of the energy of adsorption of one H2O molecule decreases in the order Cu-ZSM-5 (Cu as Cu+) > Co-ZSM-5 (Co as Co2+(OH)-) > H-ZSM-5 > Cu-ZSM-5 (Cu as Cu2+(OH)-). Adsorption of a second H2O molecule occurs with a smaller binding energy, which decreases in the order Cu-ZSM-5 (Cu as Cu+) > Cu-ZSM-5 (Cu as Cu2+(OH)-) > Co-ZSM-5 (Co as Co2+(OH)-) > H-ZSM-5. At 800 K, demetalation to form a gaseous metal hydroxide species is unfavorable thermodynamically but will occur spontaneously if the final product is a metal oxide. Demetalation of Cu is projected to occur much more readily than demetalation of Co, in good agreement with experimental observation.
AB - The interactions of water with H-ZSM-5, Cu-ZSM-5, and Co-ZSM-5 have been investigated by density functional theory (DFT). Calculations were also performed to determine the thermodynamics of metal removal from the zeolite. For all three forms of ZSM-5, water adsorbs by direct interaction of the O atom with the cation and hydrogen bonding of one of the two H atoms with an oxygen atom in the zeolite framework. The magnitude of the energy of adsorption of one H2O molecule decreases in the order Cu-ZSM-5 (Cu as Cu+) > Co-ZSM-5 (Co as Co2+(OH)-) > H-ZSM-5 > Cu-ZSM-5 (Cu as Cu2+(OH)-). Adsorption of a second H2O molecule occurs with a smaller binding energy, which decreases in the order Cu-ZSM-5 (Cu as Cu+) > Cu-ZSM-5 (Cu as Cu2+(OH)-) > Co-ZSM-5 (Co as Co2+(OH)-) > H-ZSM-5. At 800 K, demetalation to form a gaseous metal hydroxide species is unfavorable thermodynamically but will occur spontaneously if the final product is a metal oxide. Demetalation of Cu is projected to occur much more readily than demetalation of Co, in good agreement with experimental observation.
UR - http://www.scopus.com/inward/record.url?scp=0001363906&partnerID=8YFLogxK
U2 - 10.1021/jp981108s
DO - 10.1021/jp981108s
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:0001363906
SN - 1089-5639
VL - 102
SP - 7498
EP - 7504
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 38
ER -