Influence of the synthesis conditions on the incorporation of B and the acidity in B-MCM-41 materials

GINA PECCHI; VASCHETTO ELIANA GABRIELA; GRISELDA A. EIMER; SANDRA G. CASUSCELLI

MICROPOROUS AND MESOPOROUS MATERIALS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016

1387-1811

B-MCM-41 typenano-structured materials were prepared by direct hydrothermal synthesis. Thetime of hydrothermal treatment, the Si/B initial molar ratio and the nature ofthe hydroxide source in the synthesis process were analyzed. All the materialswere characterized by XRD, N2 adsorption, TEM, SEM, ICP-OES, FT-IRand adsorption of pyridine coupled to FT-IR spectroscopy. The role of hydroxidesource is essential to achieve the incorporation of boron in the mesoporousstructure. The relationship between the Boron content in the synthesis gel, thedegree of introduction of tetra-coordinated B into the framework, the formationof nest silanols and the relative density of the acidic sites have been discussed.We could corroborate that hydroxyl groups present in silanol nests are thedirect responsible of the moderate Brønsted acidity of our materials. Theenhancement in the density of acidic nest silanols was reached by increasingthe B content in the mesoporous structure. Finally, the use of NH4OH,as hydroxide source, Si/B initial molar ratio of 10 and 20 and a hydrothermaltreatment of 6 days resulted the optimum synthesis conditions to obtain the highestframework B incorporation and more abundant moderate Brønsted sites (silanol nests), thus improvingthe potencial catalytic properties of these materials.