The desilication-dealumination process allowed the production of structurally more stable submicrometric Y zeolites with hierarchical porosity and high crystallinity.

Producing nanosized zeolites Y has been restricted to a Si/Al ratio lower than 2.0, requiring prolonged crystallization periods. This study employed temperature ramps during nucleation and crystallization to synthesize nanosized zeolites Y with a Si/Al ratio of 2.4, ranging from 47 to 100 nm, in just one day. Sequential post-synthesis desilication and dealumination treatments were used to modify the pore structure and acidity of the zeolites, leading to hierarchical zeolite formation. These modifications enhanced the structural stability and porosity of the zeolites while preserving their high crystallinity. Desilicated zeolites, unlike dealuminated ones, possessed straighter and more uniform mesoporous within their crystals, with diameters smaller than 5 nm. Additionally, successive desilication produced a greater number of intracrystalline mesoporous. The solids obtained from both processes exhibited porosity within the zeolite structure connected to the external surface, potentially improving the mass transfer limitations of the original zeolite due to the lack of mesoporous. Catalysts were prepared using modified nanozeolites for evaluation in the propylene oligomerization reaction. Catalysts based on dealuminated and desilicated nanosized zeolite Y showed high conversions above 20%, especially for dealuminated zeolites with conversions of 50%. Additionally, the catalysts demonstrated selectivity towards hydrocarbons in the C5-C7 range, suggesting better diffusion and access of propylene molecules to the active sites, favoring the formation of medium-sized hydrocarbon fractions. Conversely, the formation of longer hydrocarbon chains (C12⁺) was not favored, possibly due to insufficient mesoporous for larger molecule diffusion and a distribution of acid sites that encourages the union of longer hydrocarbon chains.

In the field of hydrocracking reactions, achieving optimal middle distillate yields remains a persistent challenge with commercially available zeolite Y catalysts. This limitation is attributed to challenges related to diffusion constraints within the catalyst. In response, we present a promising solution not only to these problems but also to the challenges encountered in nanosized Y zeolites when attempting to generate acidic sites within their structure and when analyzing their performance in vacuum gas oil hydrocracking. NiMo catalysts based on nanosized Y zeolites with different crystal sizes exchanged with lanthanum, effectively address diffusion issues and significantly enhance catalyst performance compared to dealuminated nanosized and commercial Y zeolite under the same reaction conditions. The catalysts were characterized by TGA, ICP-OES, XPS, N₂ physisorption, FT-IR for pyridine acidity, TEM-mapping, and the 3-methyl thiophene reaction to test the hydrogenating capacity. Surface analysis and microscopy showed greater porosity in the catalysts with smaller zeolites and different arrangements of their components. The catalysts based on steamed protonated nanosized Y zeolites with a larger size and lanthanide nanosized Y zeolite with a smaller size yielded more middle distillates. Research provides a comprehensive analysis, providing a correlation between the catalytic performance and the size of the nanosized Y zeolite.

In this study, a carbonaceous material was obtained from the thermal decomposition of a non-pretreated rice husk in a pyrolysis system with controlled nitrogen at 700, 800, 900, and 1000 °C. The characterization of the material was performed using various analytical techniques. The results of these characterizations indicate that the obtained carbonaceous material can achieve a surface area of 450 m²/g, with a microporous volume of 0.15 cm³/g. Furthermore, the presence of oxygenated function groups, predominantly hydroxyl (C-OH) and epoxy (C-O-C), along with amorphous silicon, was identified. Additionally, the material’s CO₂ adsorption capacity was assessed, revealing a maximum capacity of 1.0 mmol/g. The findings of this study suggest that the CO₂ adsorption effectiveness can be impacted by the presence of specific functional groups. These groups have been shown to enhance the material’s affinity for CO₂, along with its porosity and surface area. In this sense, a notable correlation was identified between the oxygenated function group content and CO₂ adsorption capacity. Also, the adsorption isotherm modeling showed an excellent fit to the Langmuir model, indicating monolayer adsorption on a homogeneous surface.

Síntesis de zeolita beta en presencia de metales alcalinosNa+ y K+ y su evaluación en hidrocraqueo de gasóleo de vacío