Ángel Peral

Zeolite crystallization from organofunctionalized seeds

A novel synthesis method has been applied to different zeolites (ZSM-5, ZSM-11 and Beta), based on the crystallization of silanized seeds, as a way to perturb the subsequent crystal growth step and to modify the zeolite textural properties. The zeolitic materials so obtained exhibit unique properties, such as the presence of ultra-small nanocrystals and supermicropores and enhanced overall and external surface areas. Moreover, these samples possess a high catalytic activity for the conversion of bulky molecules.

Controlling the generation of hierarchical porosity in ZSM-5 by changing the silanization degree of protozeolitic units

ZSM-5 zeolite with hierarchical porosity has been synthesized employing a new method based in the organofunctionalization of protozeolitic units using a silanization agent. The organosilane is grafted onto the external surface of the zeolitic nanounits hindering their further aggregation. The materials obtained exhibit hierarchical porosity and enhanced textural properties. In this work, we report the results obtained when the amount of silanization agent is varied as a means of controlling the contribution of the secondary porosity so generated, showing that the textural properties of the zeolite can be tailored by adjusting the organosilane/silica ratio during the protozeolitic silanization step.

Isosorbide Production from Sorbitol over Heterogeneous Acid Catalysts: Screening and Kinetic Study

The catalytic performance of two types of heterogeneous acid catalysts—sulfonic acid-functionalized materials and aluminum containing zeolites,—in the dehydration of sorbitol to isosorbide, in solventless and autogenous pressure conditions, has been studied. Catalysts screening evidenced strong differences between sulfonic acid-based materials and acid zeolites in terms of catalytic performance. Whereas sulfonic materials, such as Amberlyst-70 and SBA-15-Pr-SO3H, showed a very high catalytic activity, zeolites with beta structure evidenced good catalytic performance together with minimized promotion of side reactions (production of non-desired sorbitans, humins, etc.). Kinetic studies performed at different temperatures, adjusting to a Langmuir–Hinshelwood type model, allowed correlating the physicochemical properties of the acid materials with their catalytic performance in sorbitol dehydration. Thus, the analysis of initial selectivity through kinetic constants comparison indicated that commercial beta zeolite with a Si/Al ratio of 19 is the most selective catalyst for the production of isosorbide, though following a slower kinetics than the sulfonic materials. Furthermore, an equivalent hierarchical beta zeolite has been synthesised and evaluated, resulting in a slight improvement of the catalytic performance, in terms of both yield and selectivity to isosorbide. This improvement is attributed to the superior textural properties.