Alkaline Earth Metal Modified H-Mordenites. Their Catalytic Properties in the Isopropylation of Biphenyl

Abstract

Alkaline earth metal modification of H-mordenite (MOR) was examined in the isopropylation of biphenyl (BP). Of interest was the chemical and textural changes on catalytic properties as a result of the modification. At low loadings of 0.2− 0.5 mmol/g of the metals, the isomerization of 4,4′-diisopropybiphenyl (4,4′-DIPB) was effectively prevented at temperatures as high as 300 °C, resulting in high selectivities for 4,4′-DIPB. Metals reduce the acid amounts by low loadings, and deactivate external acid sites. At the loading of 2 mmol/g, only BaMOR was active with high selectivities for 4,4′-DIPB; however, other metals lost catalytic activity with the increase in the loading. These differences are ascribed to changes of acidity and pore size. The modification of barium with high loading formed moderate acidities, and kept pores open for the access of bulky molecules, resulting in the selective formation of 4,4′-DIPB; however, other metals declined the activities by choking pores for magnesium and calcium or by losing acidity for strontium.

Glucose isomerisation into fructose over Mg-impregnated Na-zeolites: Influence of zeolite structure

“…XRD diffraction peaks for MgO were not detected for any of the magnesium-impregnated zeolites (2θ = 37.0, 43.0, 62.4, 74.8 and 78.7° [33,34]), meaning that any formed MgO entities are either amorphous or small enough in size to escape XRD detection. A reduction in intensity of the zeolite diffraction peaks has been noticed by several authors when impregnating Y, ZSM-5 and MOR zeolites with up to 15 wt.% of magnesium [31,[35][36][37][38]. The same authors also observed that MgO diffraction peaks were absent even at the highest percentages of magnesium.…”

“…MgO particles were also not observable by TEM, as the contrast between the elements in the zeolite framework and the metal oxide species was insufficient [36]. However, by coupling EDS analysis to TEM it was possible to investigate how homogeneous was the dispersion of MgO on the different zeolite structures.…”