One-pot synthesis of large-pore AlMCM-41 aluminosilicates with high stability and adjustable acidity

We report for the first time, a novel one-pot protocol for the synthesis of large-pore AlMCM-41 aluminosilica materials (i.e. LP-AlMCM-41(y), where y = Si/Al ratio). Assisted by a pore-expansion agent, i.e. N,N-dimethylhexadecylamine (DMHA) and the self-assembly process, aluminum incorporation and pore-enlargement were achieved in a single step, eliminating costly post-synthesis treatments. The LP-AlMCM-41s and the corresponding protonated materials, i.e. LP-H-AlMCM-41, were thoroughly characterized by ICP, N-2 adsorption desorption, TEM, Al-27 MAS NMR and FT-IR of adsorbed pyridine. The LP-AlMCM-41 materials exhibited relatively sharp and uniform pore size distribution profiles, BET surface areas of around 1000 m(2)/g and average pore diameters of 6-7 nm. No dealumination or structural degradation was observed upon pore-enlargement of AlMCM-41, which is a unique feature of this methodology. As opposed to purely siliceous LP-MCM-41, the LP-AlMCM-41(20) showed structural stability toward prolonged exposure to boiling water and steam. Thus, it is anticipated to be a good candidate for adsorption applications in aqueous media as well in processes utilizing steam for regeneration. Upon protonation, the catalytic activity of LP-H-AlMCM-41s was investigated in the acid catalyzed reaction of furfural with 2-methylfuran to produce 2,2'-(2-furylmethylene)bis(5-methylfuran) (FMBM). A superior catalytic performance was observed in the presence of LP-H-AlMCM-41(20), showing 49% furfural conversion with 71% selectivity to FMBM. Owing to the high BET surface areas and pore volumes as well as the large and uniform pore diameters preserved after protonation, these LP-H-AlMCM-41 aluminosilicates can be potential candidates for catalytic processes involving complex molecular structures such as petroleum heavy oil and biomass.