Novel Niobosilicates Molecular Sieves: Potential Heterogeneous Catalysts for Biomass Conversion into Biofuels and Fine Chemicals

High purity glycerol is an important industrial feedstock that has applications in the food, cosmetics, and pharmaceutical industries, amongst others. However, it is expensive to refine crude glycerol, especially in medium-sized or small plants. Research in both academic and industrial laboratories has therefore focused on the development of innovative processes for the conversion of pure and crude glycerol into valuable products. Glycerol is considered one of the top twelve building block chemicals that can be derived from carbohydrates and converted to valuable commodity chemicals such as glyceric acid, propylene glycol, 1,3- and 1,2-propanediol, branched polyesters, and polyols. These chemicals can be formed using different routes including selective oxidation, hydrogenolysis, dehydration, transesterification, etherification, oligomerization, and polymerization. Glycerol oxidation or reduction is achieved by means of a complex pathway of reactions that can lead to a large number of useful intermediate substances or value-added chemicals. The use of zeolite-based catalysts containing niobium with the specific aim of producing value-added products using glycerol as raw material has not been widely reported in the literature. This study reports the synthesis of novel niobiosilicate using organic structure directing agents (SDA) derivates of chiral amines by sol-gel chemistry method. The niobiosilicate was characterized by XRD, MEV, XPS, DTA/TG and ²⁹Si MAS NMR. XRD analysis showed three peaks of high intensity at 2θ = 7^o, 12^o, 19^o and two peaks of low intensity at 2θ = 14^o, 18^o. MEV images showed that the morphology is built up of crystalline needles of 50 nm size. ²⁹Si MAS-NMR revealed a resonance peak at -95 ppm attributed to the chemical environment (3Si,1Nb). These data support the incorporation of niobium in the crystallographic structure of molecular sieve. Niobiosilicate catalysts has promoted high glycerol conversions (80%) with high selectivity for acrolein (30%).