CuZSM-5@HMS composite as an efficient micro-mesoporous catalyst for conversion of sugars into levulinic acid

In the present work, the formulation and performance of the silica-aluminosilicate-based composites were studied for catalytic conversion of sugars to levulinic acid. Tailoring the acidity, surface area and the porosity of the catalysts were the main goal of the work. The acidities of the catalysts were provided by ZSM-5 zeolite and were modulated by microwave assisted solid state ion-exchange with copper. The high surface area and porosity of the catalysts were guaranteed by mesopores silica type HMS. The composites of HMS and CuZSM-5 with different contents of 30%, 50%, 60% and 70% were synthesized and the morphological and textural features and acidity of the materials were assessed using XRD, EDX, SEM, TEM, N₂-physisorption, and FTIR, FTIR with pyridine and NH₃-TPD. CuZ(60%)@H composite acted as the best catalyst with production of 45% yield and 30% yield of LA from glucose and cellulose conversion, respectively. High surface area, large pore size and volume of HMS in the best composite structure favored mass transfer of the substrates and products and higher performance of the catalyst especially in cellulose hydrolysis. In addition, tuned and balanced concentration, strength and type of CuZSM-5 acidity in the composite promoted the desired pathway, favored formation of levulinic acid and suppressed humins formation.