Mechanical stability of mesoporous molecular sieve MCM-48 studied by adsorption of benzene, n-heptane, and cyclohexane

The synthesis of MCM-48 has been performed in a 5 L autoclave, and the prog ress of the synthesis has been monitored by X-ray powder diffraction and Si -29 MAS NMR. The formation of MCM-48 progresses via an intermediate phase, whose conversion into the cubic phase is triggered by condensation of the s ilanol groups. The mechanical stability of silica mesoporous material MCM-4 8 has been investigated employing powder X-ray diffraction, nitrogen adsorp tion, and subcritical organic vapor (benzene, n-heptane, and cyclohexane) a dsorption isotherms and breakthrough curves. The adsorption capacity is aff ected considerably by mechanical compression between 20 and 400 N mm(-2), w hile the material is destroyed to a large extend at 480 and 600 N mm(-2), w hich is reflected by a dramatic decrease in adsorption capacity and poor X- ray diffraction patterns. As a result of its three-dimensional structure, t he mechanical stability of MCM-48 is larger compared to that of MCM-41 but still low compared to that of crystalline structures such as zeolites.