Structural and mechanistic investigation of a phosphate-modified HZSM-5 catalyst for methanol conversion.

被引：52

作者：

Abubakar, SM ^{[1
]}

Marcus, DM ^{[1
]}

Lee, JC ^{[1
]}

Ehresmann, JO ^{[1
]}

Chen, CY ^{[1
]}

Kletnieks, PW ^{[1
]}

Guenther, DR ^{[1
]}

Hayman, MJ ^{[1
]}

Pavlova, M ^{[1
]}

Nicholas, JB ^{[1
]}

Haw, JF ^{[1
]}

机构：

[1] Univ So Calif, Dept Chem, Los Angeles, CA 90089 USA

来源：

LANGMUIR | 2006年 / 22卷 / 10期

关键词：

D O I：

10.1021/la0534367

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

Phosphorus modification of a HZSM-5 (MFI) zeolite by wet impregnation has long been known to decrease aromatic formation in methanol conversion chemistry. We prepared and studied a catalyst modified by introducing trimethylphosphine under reaction conditions followed by oxidation. Magic-angle spinning (MAS) NMR shows that extensive dealumination occurs, resulting in a catalyst with a much higher framework SiO2/Al2O3 ratio, as well as extraframework aluminum and approximately 1.4 equiv of entrained phosphoric acid (under working conditions) per aluminum. Upon dehydration or regeneration, the phosphoric acid is converted, reversibly, to entrained P4O10. The aromatic selectivity of the modified catalyst is significantly lower than that of an unmodified zeolite with a similar, increased framework SiO2/Al1O3 ratio. By comparing the rates of H/D exchange in propene under conditions similar to those in methanol conversion chemistry, we determined that the acid site strength is indistinguishable on modified and unmodified zeolites, and this is consistent with theoretical modeling. On the phosphorus-modified zeolite, the rate of propene oligomerization is greatly suppressed, suggesting that entrained phosphate is an impediment to sterically demanding reactions.

引用

页码：4846 / 4852

页数：7

共 28 条

[1] SOLID-STATE NMR-STUDIES OF THE SHAPE-SELECTIVE CATALYTIC CONVERSION OF METHANOL INTO GASOLINE ON ZEOLITE ZSM-5 [J].