Honghai Liu

Preparation of phosphorus-modified PITQ-13 catalysts and their performance in 1-butene catalytic cracking

Abstract A series of phosphorus-modified PITQ-13 catalysts was prepared by wet impregnation of NH4H2PO4 solution into an HITQ-13 parent. The catalysts were characterized using XRD, N2 adsorption, MAS NMR and NH3-TPD. Their catalytic performance in 1-butene catalytic cracking was evaluated in a fixed fluidized bed reactor. The results showed that the crystallinity, surface area and pore volume of P-modified PITQ-13 catalysts decreased with the increasing amounts of P. The number of weak acid sites increased, whereas that of strong acidity decreased. The selectivity to propylene in 1-butene cracking reactions increased because of the decrease in strong acidity. The yield of propylene achieved 41.6% over PITQ-13-2 catalyst with a P content of 1.0 wt%, which was 5.1% greater than that achieved over HITQ-13 catalyst.

Cation location and migration in lanthanum-exchanged NaY zeolite

LaNH4Y and LaY zeolites were prepared using a double‐exchange double‐calcination method by La exchange of NaY zeolite. The distribution of the La cations was determined by powder X‐ray diffraction with Rietveld refinement. The results indicate that the La cations are initially located in supercages, and then their hydration shells are stripped off and they migrate to small sodalite structures located at SI´ during heating and dehydration. The changes in the T-O-T angles show significant distortion of the flexible framework and instability in LaNH4 Y obtained using a one‐exchange one‐calcination process. For La cations located at SI´ and coordinated with O3, the T-O3 bond distance increased, which indicates that the rare‐earth cations not only restrain framework dealumination, suppressing condensation of the unit cell, but also have an effect on the T-O3 bond distance, increasing the unit cell volume. The role of the rare‐earth species is to ensure the hydrothermal stability of the zeolite in order to control the acid site density and catalytic activity. The effects of La cations and NH4^+ cations on the zeolite acidity were studied using infrared spectroscopy and NH3 temperature‐programmed desorption, and the mechanism of rare‐earth stabilization of the Y zeolite is described.

Desilication by Alkaline Treatment and Increasing the Silica to Alumina Ratio of Zeolite Y

The framework silica to alumina ratio, the porosity, and the acidity properties of ultrastable Y zeolites prepared by ‘steaming’ and by the ‘sequential alkaline treatment and steaming’ of NaY zeolites are compared. The adaptability of the combined alkaline treatment method and steaming toward the type of starting NaY zeolites was studied. By comparison with single steaming treatment the combination of sequential alkaline treatment and steaming affords products with an obviously increased mesopore volume. The level of framework ultrastabilization and acidity of the final products were not affected. The mesopore volume of the ultrastable Y zeolite prepared by steaming dealumination only was no more than 0.14 cm3/g. The mesopore volume of the final product prepared by sequential desilication and dealumination was 0.22 cm3/g. The sequential desilication and dealumination method is suitable for the NaY zeolite with a high framework silica to alumina ratio. A small increase in the mesopore volume and severe micropore damage were evident when the NaY zeolite with a relatively low silica to alumina ratio (SiO2/Al2O3 = 4.8, determined by nuclear magnetic resonance) was used as the starting material for the combined desilication and dealumination treatment.

Unstable-Fe-site-induced formation of mesopores in microporous zeolite Y without using organic templates

A novel organic template-free strategy for generating mesoporosity in Y zeolites is reported. It is revealed that Fe(3+) functioned as unstable sites in the Fe-NaY zeolite, which promotes deferrization-dealumination, leading to enhanced formation of intra-crystalline mesopores as well as desirable interconnectivity. The mesopore-enriched zeolite exhibits a remarkable ability in conversion of the bulky substrate.

Hydrothermally stable mesoporous aluminosilicates with moderate acidity via degradation-assembly process and improved catalytic properties

Mesoporous aluminosilicates with hydrothermal stability and moderate acidity are synthesized via assembly of microporous zeolite precursors obtained by the degradation of zeolite NaY, denoted as “degradation-assembly” (DA) technique. By controlling the degradation degree of matrix NaY, precursors with larger spatial volume and stronger rigidity will be obtained. The characterization results showed that the walls of the mesophase in MDA (mesoporous aluminosilicate obtained by “DA” method) composed of the preformed zeolite Y building units and the moderate acidity was inherited from the introduced precursors. It was suggested that the more mature assembly units accounted for the increased acidity of MDA with more Al species retained in the framework of mesophases. The resulting aluminosilicates with simultaneously moderate acidity and hydrothermal stability showed superior catalytic properties when used in heavy oil catalytic cracking catalysts.

Hydrothermally stable macro-meso-microporous materials: synthesis and application in heavy oil cracking

Hydrothermally stable hierarchical materials with macro-meso-micropores were synthesized by combination of precursor assembly and PS/P123 dual templates. Precursor assembly aims at the formation of meso-micropores and improving the hydrothermal stability, and PS microspheres aim at the introduction of macropores. Moreover, worm-like mesopores vertical to the surface of PS microspheres were present, which achieve the full interconnection of macro-meso-micropores. The resulting aluminosilicates with hierarchical pores and high hydrothermal stability showed excellent catalytic cracking properties for heavy oil.

Fabrication of intracrystalline mesopores within zeolite Y with greatly decreased templates

Zeolite Y with intracrystalline mesopores has been emerging as one of the most potential materials in the catalytic cracking of large molecules. Our group has reported the synthesis of zeolite Y with intracrystalline mesopores with the formula [(CH3O)3SiC3H6N(CH3)2C18H37]Cl (denoted as “TPOACl”). However, the fabrication of mesoporous zeolite Y with a decreased organic template remains a significant challenge. In this study, a novel surfactant [(CH3O)3SiC3H6N(CH3)2C16H33]Cl (denoted as “TPHAC”) was designed and synthesized using low-cost industrial raw materials, which was found suitable for the formation of mesoporosity utilizing greatly decreased amount of the surfactant. The possible differences in the synthesis mechanisms of TPOACl and TPHAC have been discussed. The enhanced hydrophilicity of the hydroxyl groups and the subsequent decrease in the micelle aggregation number (MAN) are proposed to be the key to underline the decreased amount of surfactant in the successful synthesis. The material shows excellent hydrothermal stability and a higher mesoporous surface area ratio than TPOACl. The prepared mesoporous zeolite Y showed much higher catalytic activity and selectivity in heavy oil cracking than that prepared from TPOACl.

Effect of Lauryl Sodium Sulfate on the In situ Crystallization of Small-Grain NaY

The in situ crystallization of small-grain NaY in the presence of lauryl sodium sulfate was investigated. The product containing small-grain NaY was used as a matrix to prepare REUSY catalyst via ammonium ion exchange and rare earth ion exchange. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), and N-2 physical adsorption-desorption were used to characterize the samples, while the catalytic performance of prepared catalysts was evaluated by micro-activity evaluation device and advanced catalytic evaluation (ACE). It is indicated that the addition of lauryl sodium sulfate (5% of Kaolin microsphere mass) to in situ crystallization system can decrease the average grain size of the zeolite from 540 to 250 nm. Relative to the conventional in situ crystallization fluid catalytic cracking (FCC) catalysts, the catalyst prepared from in situ crystallization product containing small-grain NaY, exhibits improved performance in the conversion rate of feedstock, the selectivity of the cracking product, and the resistance to carbon deposition.