Journal of Catalysis p. 390 - 401 (1994)
Update date:2022-08-12
Topics:
Ruckenstein, Eli
Khan, Ashraf Z.
The oxidative methylation of acetonitrile with methane to acrylonitrile occurs more actively and selectivelybialkali promoted CaO catalysts thanany monoalkali promoted system.The most effective catalytic systems are obtained with LiA + CsA, NaA + CsA, or KA + CsA (A = SO42- , OH-, Cl-, CH3COO-, CO32-, or NO3-) supported on CaO, containing total alkali loadings of 10 molpercent with equal molar amounts of both alkalis.At 750 deg C, under atmospheric pressure, at CH4 : O2 : CH3CN : He partial pressure ratios of 5.0 : 1.0 : 1.5 : 6.5, and at a space velocity of 15,000 cm3 g-1 h-1, the highest selectivity to acrylonitrile (70.0 molpercent) and yield (25 percent) are obtained(5 molpercent Na+ + 5 molpercent Cs+)/CaO (prepared from the sulfate precursors).Any bialkali-promoted system containing Rb was less effective, whereas the Li-containing systems, though active initially, gradually lost the activity due to its volatility.The performances of the effective bialkali systems, after an initial increase, remained almost unchanged for a period of 60 h.In contrast, the stability of any monoalkali promoted system with time-on-stream was very low and the maximum initial yield of acrylonitrile was only 11.5 percent under the aforementioned conditions.The synergistic increase in the catalytic performance of the bialkali promoted CaO is reflected in the synergistic increase of the surface basicity (leading to superbasicity) caused by the high enrichment of the surface layer with the alkali ions.The relationship between the catalytic performances and the physicochemical characteristics of the catalysts revealed by XPS, AAS, and basicity measurement is explored.
View MoreDoi:10.1080/15421400701495674
(2007)Doi:10.1016/j.apcata.2010.05.003
(2010)Doi:10.1016/S0277-5387(00)83847-4
(1989)Doi:10.1021/ol016430r
(2001)Doi:10.1016/j.electacta.2011.02.090
(2011)Doi:10.1002/pola.23931
(2010)