@article { ISI:000239326400010,
	title = {On the {\textquoteleft}{\textquoteleft}Active spacer and stabilizer{\textquoteright}{\textquoteright} role of Zn in Cu1-xZnxFe2O4 in the selective mono-N-methylation of aniline: XPS and catalysis study},
	journal = {Journal of Catalysis},
	volume = {241},
	number = {1},
	year = {2006},
	month = {JUL},
	pages = {83-95},
	publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE},
	type = {Article},
	address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA},
	abstract = {<p>A systematic catalytic methylation study on ferrospinel materials led to the selective production of N-methylaniline (NMA) with Cu1-xZnxFe2O4. Aniline methylation was carried out on Cu1-xZnxFe2O4 with a feed composition of CH3OH:PhNH2:H2O = 3:1:1 at 513-633 K. NMA was formed selectively on all of the catalyst compositions, with trace amounts of secondary products under most of the conditions. Cu0.5Zn0.5Fe2O4 composition showed high catalytic activity and stability up to 100 h. Although the Cu2+ was responsible for methylation activity, Zn2+ enhanced the overall stability of the catalyst system. XPS investigations revealed that the degree of Cu2+ reduction decreased dramatically from x = 0.05/0.25 to 0.5/0.75 on spent catalysts. TPR studies indicated that the reducibility of Cu2+ decreased from fully reducible at 523 K with Cu-rich compositions to partially reducible at 573 K on x = 0.5. Stable activity observed on Cu0.5Zn0.5Fe2O4 can be attributed to the highly heterogeneous distribution of metal ions. This heterogeneous distribution indicates an important role of zinc, likely as an {\textquoteleft}{\textquoteleft}active spacer cum stabilizee{\textquoteright} that hinders the reduction of active Cu2+ and contributes to prolonged activity. (c) 2006 Elsevier Inc. All rights reserved.</p>},
	keywords = {Aniline, Ferrite, N-methylaniline, N-methylation, spacer, stabilizer, surface distribution, TPR, XPS},
	issn = {0021-9517},
	doi = {10.1016/j.jcat.2006.04.010},
	author = {Vijayaraj, Munusamy and Gopinath, Chinnakonda S.}
}
@article { ISI:000245534900008,
	title = {Selective mono-N-methylation of aniline substrates on Cu1-xZnxFe2O4},
	journal = {Applied Catalysis A-General},
	volume = {320},
	year = {2007},
	month = {MAR},
	pages = {64-68},
	publisher = {ELSEVIER SCIENCE BV},
	type = {Article},
	address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS},
	abstract = {<p>Selective mono-N-methylation of substituted anilines (o-, m- and p-toluidines, 2,6-xylidine, p-anisidine and p-aminoacetophenone) was carried out with methanol as methylating agent under vapor phase reaction conditions on Cu1-xZnxFe2O4 systems. The catalytic reactions with each aniline substrate were carried out at optimum reaction conditions (MeOH:anilines:water = 3: 1: 1, space velocity = 3.58 h(-1)) between 543 and 603 K. The presence of a ring-directing group did not have any significant influence on the N-methylaniline(s) selectivity, which remains very high; the same initial conversion/yield was observed for at least 11 h. Electronic effects due to different groups in the above aniline substrates influence the reactivity of the substrates in terms of conversion and yield. Toluidine reactivity varies with respect to the position (ortho, meta and para) of the methyl group on the phenyl ring. Para-substituted anilines (p-toluidine and p-anisidine) exhibit comparable catalytic activity, while p-aminoacetophenone shows higher conversion. The perpendicular orientation of toluidine substrates on catalyst surfaces influences the conversion and N-methyltoluidine yield. Increased crowding at ortho-position and hence steric hindrance (aniline \&gt; o-toluidine \&gt; 2,6-xylidine) restrict the substrates interaction with the catalyst surface, and 2,6-xylidine shows no reactivity. The best catalytic activity observed with Cu0.5Zn0.5Fe2O4 was due to a heterogeneous distribution of metal ions on the surface with Zn serving as active spacer group as well as methyl species source. (c) 2007 Elsevier B.V. All rights reserved.</p>},
	keywords = {mono-N-methylation, N-methylaniline, N-methylation, selective N-methvlation, spinel},
	issn = {0926-860X},
	doi = {10.1016/j.apcata.2006.12.016},
	author = {Vijayaraj, Munusamy and Gopinath, Chinnakonda S.}
}
