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ZSM-5-based micro-/mesoporous composites have attracted extensive attention as a promising material that could be industrialized in the near future. The hierarchical structure and catalytic performance of the ZSM-5-based hierarchical composite are highly dependent on its treatment conditions. Of these synthesis parameters, dissolution alkalinity is the most important one. However, systematic studies on the effects of dissolution alkalinity, specifically those that discuss the relationship between porosity, acidity, and catalytic performance in ZSM-5-based hierarchical composites by the combined dissolution and self-assembly method, have not yet been reported. In this article, the porosity and acidity of ZSM-5-based micro-/mesoporous composite samples made by select dissolution alkalinities are systematically investigated. Various characterization techniques illustrate that three different groups of ZSM-5-based micro-/mesoporous composites are classified based on their distinctive indexed hierarchical factor values, I through III. Group I, treated with 0 to 0.5 mol L−1 NaOH, is mesoporous ZSM-5 attached by Al-MCM-41-like ordered mesostructures and has a high yield for liquid petroleum gas. Group II, treated with 0.5 mol L−1 to 1.0 mol L−1 NaOH, is a mixture of ZSM-5 zeolite phase and Al-MCM-41-like ordered mesostructure phase and has a high yield of light oil. Group III, treated with 1.0 mol L−1 NaOH, is formed by complete collapse of ZSM-5 crystals and formation of Al-MCM-41-like ordered mesostructures and exhibits a high yield of total liquid oil. Due to increasingly enhanced accessibility of acid sites (indexed as accessibility index), all three groups of ZSM-5-based micro-/mesoporous composites show comparable conversion for vacuum gas oil cracking compared with their parent counterpart. These results are of vital importance during the selection of the synthesis conditions and scale-up tests of ZSM-5-based micro-/mesoporous composites to selectively produce liquid petroleum gas, light oil, and total liquid oil. [ABSTRACT FROM AUTHOR]

The mass transfer processes in REUSY zeolites and fluid catalytic cracking (FCC) catalyst particles have been measured and distinguished in this study by uptake method with an intelligent gravimetric analyser (IGA) and by the frequency response (FR) technique. The results indicate that the diffusion time constants in the FCC catalyst particles are smaller than those in the REUSY zeolites, and the limiting steps for the overall mass transfer processes in the FCC catalyst particles are the diffusion process in the length scale of macropore of the matrix or/and the mass transfer at the zeolite–matrix interface rather than the intracrystalline diffusion one in the micropores of the zeolite crystals. [ABSTRACT FROM AUTHOR]

ZSM-5 zeolite crystals with controllable b-axis length (sheet-like, S-ZSM-5; chain-like, C-ZSM-5) have been synthesized by using urea and starch as additives in the starting aluminosilicate gels. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images show that these zeolite samples have good crystallinity. Transmission electron microscopy (TEM) images show that there is a strong chemical interaction between the stacked crystals in C-ZSM-5 samples. N2 sorption isotherms indicate that C-ZSM-5 crystals are mesoporous. Catalytic tests for the formation of p-xylene from m-xylene isomerization show that, compared with other zeolite catalysts, C-ZSM-5 catalysts give both high conversion and improved p-xylene selectivity, which are attributed to the combination of relatively long b-axis length and the present mesoporosity in the crystals. The improvement of p-xylene selectivity in catalytic m-xylene isomerisation is of great importance for selective industrial production of p-xylene in the future. [ABSTRACT FROM AUTHOR]

Abstract: NaY zeolites ion-exchanged with rare earth (RE) cations (La3+, Ce3+, Pr3+, Nd3+) were prepared by a double-exchange double-calcination method. The position, occupation and coordination of the zeolite extra-framework RE cations were identified by powder X-ray diffraction with the Rietveld refinement. The results indicate that Ce species were insusceptible to migration into the sodalite cages compared with others under the same circumstances, which may be attributed to the facile formation of CeO2(IV) based on Ce(OH)2+ and oxygen as well as the retarded migration of tetravalent cerium. Furthermore, the stability and activity of REY zeolites increased with decreasing ionic radii of RE elements. [Copyright &y& Elsevier]

Abstract: Mesopore ZSM-5 was prepared by alkali treatment of parent ZSM-5 zeolite and applied for butene catalytic cracking. The zeolite was treated in the NaOH solutions with different concentrations at 85°C. XRD showed that the intrinsic MFI structure of ZSM-5 zeolite was preserved and corresponding crystallinity remained unchangeableness when ZSM-5 was treated with low concentration NaOH solutions. However, excessive NaOH led to the destruction of zeolite structure. The BET surface area increased obviously after desilication, and the N2 adsorption/desorption curves indicated a number of mesopores generation. The experiment of butene catalytic cracking was carried out in a fixed-bed to investigate the influence of mesopores. The results showed that catalytic performances can be greatly improved through introducing the mesopores into parent ZSM-5 by alkali treatment. Highest yield of ethylene plus propylene were obtained when the treated concentration of NaOH solution is 0.1–0.2M. [Copyright &y& Elsevier]

After modifications of rare earth and phosphorus, the acidity density and the strength in the pores of zeolite Y (PREUSY) are improved effectively; the surface acidity is suitably reduced and weakened owing to the interaction of rare earth cation and phosphate anion. NH3-TPD analysis showed that the acid distribution of the modified zeolite is more concentrated on the range of intermediate and strong acidity. This kind of modification can direct more hydrocarbons to enter into the pores to be converted and remarkably reduces the possibility of naphtha olefins forming through a surface cracking reaction. In addition, because naphtha olefin reduction does not completely depend on olefin saturation through secondary hydrogen transfer reaction, this kind of reaction mode can decrease the excessive cracking of mediate distillate and can improve the diesel oil yield (LCO) effectively. Some reaction pathways were proposed. [Copyright &y& Elsevier]

Correlation between the adsorption-transformation behaviors of 2-methylthiophene and 3-methylthiophene and the active sites of NaY, HY and rare earth ion-exchanged ultra-stable Y (REUSY) zeolites have been studied by using an in situ FTIR technique and an intelligent gravimetric analyser-mass spectrometer (IGA-MS) coupling technique. The results show that the bridging hydroxyls (OH) of Si and Al atoms located in the supercage of zeolites Y are the preferred active sites, leading to the protonation and cracking reactions of the methylthiophenes. The AlO + active sites in the HY, and the Al(OH) 2+ and RE(OH) 2+ active sites in the REUSY both can make the oligomerization reaction occur at 303 and 373 K, and especially, the RE(OH) 2+ active sites significantly improve the oligomerization abilities. Besides, the activities and selectivities of the protonated 2-methylthiophene and 3-methylthiophene play a decisive role in the oligomerization pathways. As system temperatures of > 473 K, the oligomerization reaction is restricted, while the cracking reaction is improved. Thereby, modulation of the key active sites in adsorbents and system temperatures will be a good prospect for ultra-deep desulfurization in the future. [ABSTRACT FROM AUTHOR]

Abstract: The aluminum–silicon distribution and mesoporosity of Y zeolites prepared by sequential NaOH desilication and ammonium hexafluorosilicate (AHFS) dealumination are compared with that of Y samples prepared via AHFS dealumination only. AHFS treatment led to severe non-uniform dealumination and substantial surface silicon deposition. Y samples obtained by sequential desilication and dealumination had substantially better dealumination uniformity and aluminum–silicon distribution. The mesopore formation in these zeolites is discussed in detail. The desilication creates defects in the framework of the parent NaY zeolite. These defects improve the intra-crystalline transport and induce mesopore formation during dealumination. The desilication- plus dealumination-treated zeolites showed higher initial activity and lower deactivation tendency in the case of 1,3,5-triisopropylbenzene cracking, and higher conversion rate of cumene than those zeolites modified by AHFS treatment only. These catalytic data indicate that the former could be a viable catalyst in the catalytic cracking of heavy hydrocarbons. [Copyright &y& Elsevier]

Abstract: NaY/kaolin composite microspheres were synthesized by an in situ method using calcined kaolin microspheres as raw material. By mixing the modified NaY/kaolin composite microspheres and additive microspheres containing ZSM-5, a novel fluid catalytic cracking (FCC) catalyst for maximizing propylene yield in FCC unit was prepared. The catalyst was characterized by X-ray diffraction (XRD), temperature-programmed desorption of ammonium (NH3-TPD), and N2 adsorption–desorption techniques and tested in a bench FCC unit. The characterization results indicated that the catalyst has more meso- and macro-pores and more acid sites than the reference catalyst and thus can increase propylene yield by 1.27%. [Copyright &y& Elsevier]

• A process to make P containing Y zeolite more stable. • P is incorporated into the framework by P for Si(4Al) isomorphous substitution. • Si(4Al) becomes the more stable site P(4Al) in the Y zeolite framework. • The P species in DPY zeolite are more difficult to loss than usual P modify. • The distribution of P species in DPY zeolite is more uniform. It's a dream to make zeolites more stable so as to keep the activity and stability of the catalyst. Phosphorus modification is an effective method, however, the known post-modification predominantly presents as non-framework P, and the P-loss is a big trouble in application. We have discovered that in the reaction of PCl 3 or SiCl 4 + PCl 3 with NaY zeolite, a portion of P enters the framework of the zeolite, forming a PO 4 -AlO 4 structure. Further investigations revealed that P cannot be incorporated into the framework through P for Al isomorphous substitution, but rather through isomorphous substitution with Si(4Al). PCl 3 exhibits two effects in reaction: at lower quantities, it mainly undergoes isomorphous substitution with Si(4Al); at higher quantities, it leads to zeolite dealumination generating aluminum vacancies, which disrupt the zeolite framework or promotes Si for Al isomorphous substitution. After hydrothermal aging at 800 °C for 4 h, the stable presence of framework PO 4 -AlO 4 implies that the weakest site Si(4Al) becomes the more stable site P(4Al) in the Y zeolite framework. Compared with the JPY (prepared by impregnating (NH 4) 2 HPO 4 solution to high silica Y zeolite) sample, after 10 cycles of hydrothermal and water washing treatment, the P 2 O 5 loss rate of DPY (prepared by SiCl 4 + PCl 3 with NaY) zeolite ranged from 0.4 % to 3.5 %, significantly lower compared to the range of 18.7 % to 25.9 % observed in the JPY sample. This indicates that in DPY zeolite, the interaction between P and the zeolite is stronger and less prone to loss. Moreover, P is more uniformly distributed on the surface and bulk phase of DPY than JPY sample. [ABSTRACT FROM AUTHOR]

Abstract It is of great significance to identify the destructive role of high deposited vanadium on the USY-based cracking catalysts and find a facile approach to vanadium passivation for processing residue oil. Herein, the destruction degree of the steam-treated vanadium-contaminated USY zeolites, which also contained a certain amount of Na ions, was investigated by N 2 physical adsorption, NH 3 -TPD, HRTEM, 27Al MAS NMR and catalytic cracking evaluation. The results reveal that high deposited vanadium causes severe damage to the structure of USY, resulting in a sharp deterioration in cracking performance. Furthermore, CeO 2 and La 2 O 3 were studied as vanadium passivating agents. The introduction of La 2 O 3 using physical mixing could preserve the zeolite structure to a large extent without altering the properties of USY. The superior passivation performance might be mainly attributed to the fact that La 2 O 3 introduced by simple physical mixing prefers to interact with vanadium species, rather than migrate into the channels and cavities of zeolites USY. Graphical abstract Image 1 Highlights • High deposited vanadium causes severe damage to the crystal structure of zeolite USY. • Vanadium deposition deteriorates the cracking performance of USY-based FCC catalysts. • Introducing La 2 O 3 by simple physical mixing is an efficient way to passivate vanadium. • La 2 O 3 prefer to interact with vanadium instead of migrating into the channels of zeolite USY. [ABSTRACT FROM AUTHOR]

Optimizing the accessibility of zeolite Y, the main active component in fluid catalytic cracking (FCC) catalyst, is a crucial strategy to improve the heavy oil cracking performance of FCC catalysts. Four FCC catalysts with different Y zeolite content were prepared via in-situ crystallization method by adjusting the crystallization time. The distribution characteristics of the Y zeolite in in-situ crystallized catalysts have been characterized by scanning electron microscopy (SEM), laser confocal fluorescence microscopy and high-resolution field emission scanning electron microscopy (HR-FESEM). A unique structural feature of the FCC catalysts has been achieved, with the Y zeolite component mainly distributing in the outer layer of microspheres. The results of adsorption rate of macromolecule probes reveal that the appropriate zeolite layer thickness and topology were beneficial to the mass transfer performance and acid accessibility of FCC catalyst. The effective utilization ratios of zeolite in the novel FCC catalysts for heavy oil cracking on advanced catalyst equipment (ACE) is in good correspondence with the mass transfer performance of macromolecules and the accessibility of acid sites. It could be confirmed that the excellent heavy oil conversion performance of a FCC catalyst does not depend on the content of zeolite, but rather on the distribution characteristics are in favor of the accessibility of zeolite components. [Display omitted] • An interested FCC catalyst with unique zeolite distribution was obtained by in-situ crystallization of kaolin microspheres. • Y zeolite component is effectively controlled to grow over the skin layer of FCC catalyst microspheres. • The excellent diffusivity and the accessibility of heavy oil molecular have been significantly optimized. • The in-situ crystallization FCC catalyst display excellent heavy oil conversion performance. [ABSTRACT FROM AUTHOR]

Tunable mesoporosity was successfully generated by introducing Fe cations into the framework of NaY as starting points, and then by sequential ammonium ion exchange and steaming deferrization–dealumination treatment. Accordingly, the pore diameter and volume of mesopores depended on the content of framework Fe. The zeolite products were characterized by a complementary combination of X-ray diffraction (XRD), N 2 physisorption, TEM, DSC, Py-IR, and 27 Al MAS NMR. The results show that the mesopore volumes of the Fe-induced mesoporous ultra-stable Y (USY Fe ) zeolites, which prepared via sequential deferrization-dealumination by steaming, are all higher than 0.21 cm 3 g −1 with an additional thermal stability. The highest one reaches 0.23 cm 3 g −1 , over 53% of enhancement compared to USY (0.15 cm 3 g −1 ) without deteriorating acidity. Furthermore, the most probable mesopore distributions can be finely tuned, typically in the range of 9–17 nm. In addition, it is found that large mesopores (8–50 nm) are surprisingly boosted with the increase in the Fe content used for the preparation of USY Fe samples. In the catalytic cracking of adsorbate molecule of 1,3,5-triisopropylbenzene, the mesopores-enriched zeolites exhibit higher activity and lower deactivation tendency than USY with time on stream. The results demonstrated that the mesoporous material originating from the modification of zeolite with the pre-set Fe sites aided the diffusion into and out of the micropores via mesopores, and thus produced a positive influence on the catalytic performance. [ABSTRACT FROM AUTHOR]

Rare earth compounds were employed as vanadium traps in USY zeolite. USY zeolites containing La 2 O 3 , CeO 2 and LaPO 4 were prepared by precipitation method and characterized by means of BET, TEM, XPS, XRD and Rietveld refinement. The results indicated that the rare earth oxides were highly dispersed in zeolites and some of rare earth cations moved to zeolite cages, which improved the hydrothermal stability and catalytic activity of zeolites. In LaPO-USY zeolite, rare earth specie, as LaPO 4 , was distributed on the zeolite surface and did not affect the properties of catalyst. With rare earth elements at the same contents, the vanadium resistances of zeolites followed a descending order of LaPO-USY > Ce-USY > La-USY > USY. The significant differences between activation energies of zeolite destruction can be attributed to various vanadium tolerances. [ABSTRACT FROM AUTHOR]

Realumination of dealuminated HZSM-5 zeolites by acid treatment has always been controversial and puzzling. Through characterizations of XRD, nitrogen adsorption, NH 3 -TPD, IR, XPS and 27Al MAS NMR, this work confirmed realumination of dealuminated HZSM-5 zeolites could indeed be achieved after treated with HCl solution. And it was found mainly a portion of the penta-coordinated extra-framework aluminia (EFAl) were reinserted into the framework during the process of realumination. Moreover, the characterizations of ICP-AES and UV–Vis-DRS of Co2+-exchanged zeolites indicated the realumination capacity was closely related to the distribution of framework Al (Al F). Realumination was more likely achieved when there was lower content of Al pairs and less Al F located in the channel intersections in HZSM-5. Finally, realuminated zeolites exhibited a higher conversion of n -octane due to its more Brønsted acid sites than dealuminated HZSM-5 in catalytic cracking reaction. The significantly lower content of Al pairs in realuminated zeolites compared to parent HZSM-5 inhibits the hydride transfer process to a certain extent, resulting in a higher selectivity of propylene. [Display omitted] • Realumination of dealuminated HZSM-5 zeolites achieved by treatment with the aq HCl solution. • A portion of the penta-coordinated EFAl reinserted into the framework during realumination. • Realumination capacity is strongly dependent on the distribution of Al F in HZSM-5 zeolites. • Fewer Al pairs and more Al F located in the straight and sinusoidal channels are easier for realumination. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mesoporous aluminosilicate with acidity and hydrothermal stability was developed. [•] Hydrothermal stability was improved by Beta zeolite precursors in zeolite walls. [•] Al was introduced into the mesophases, and thus the acidity was improved. [•] Bimodal zeolites demonstrated superior catalytic properties for heavy oil FCC. [Copyright &y& Elsevier]

A facileand direct approach for the synthesis of mesoporous zeolite Y by using[(CH3O)3SiC3H6N(CH3)2-C18H37]Cl as templateis presented. Under the basic condition of the Y synthesis system,(CH3O)3Si– bonds hydrolyze to −Si–OH,and yield −Si–O–Al– and −Si–O–Si–linkages that anchor the template in zeolite framework. Afterward,micelles formed by −C18H37lead to theformation of mesoporosity within zeolite Y crystals. This material,which introduces intracrystalline mesoporosity into zeolite Y, showssuperior catalytic performance when used in heavy oil catalytic cracking. [ABSTRACT FROM AUTHOR]

Highlights: [•] Compared the performance of CeY obtained by liquid-, and solid-state ion exchange. [•] Strong Brönsted acids are unfavorable for the selective adsorption desulfurization. [•] Strong chemical adsorption or protonization of thiophene and cyclohexene occurs. [•] The nature of the influence from aromatics is competitive adsorption. [•] Oligomers of olefins hinder the adsorption of sulfur compounds. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zeolite-supported Pt catalysts are prepared by incipient wetness impregnation. [•] Mesoporous Beta catalyst performs excellently in the combustion of toluene. [•] Mesoporous Beta catalyst has higher activities and longer life than conventional one. [•] Mesoporosity in zeolite is favorable for mass transfer and Pt particles dispersion. [•] Reduced mesoporous Pt catalyst performs much lower activation energies (37–46kJ/mol). [Copyright &y& Elsevier]

Through a combination of Y zeoliteprecursors and the pH-adjustingmethod, bimodal aluminosilicates (denoted as LFs) with strong acidityand excellent hydrothermal stability were synthesized. The hydrothermalstability of the resulting aluminosilicates was improved greatly bytaking advantage of Y zeolite precursors (the retaining ratio of thetotal surface area was 33% after hydrothermal treatment in 100% watervapor at 800 °C for 15 h). When the mesostructure was basicallyformed in the first crystallization, the pH of the reaction systemwas adjusted from strong acid to neutral, followed by the second hydrothermalcrystallization, during which a large amount of Al could be introducedinto the mesophases. XRF and Al NMR showed that LFs possessed a highalumina loading (with SiO2/Al2O3molarratio of 24.4) and most of the Al was tetrahydrally coordinated. NH3-TPD results indicated that the total amount of acid sitesincreased 12.9 times compared with that of ZF (without pH adjustment).The resulting aluminosilicates with simultaneously enhanced acidityand hydrothermal stability showed superior catalytic properties whenused in heavy crude oil catalytic cracking. Our achievements havedeveloped a general synthetic route of bimodal aluminosilicates withstrong acidity and excellent hydrothermal stability. [ABSTRACT FROM AUTHOR]

Abstract: The acidity of catalytically active component, e.g., ultra stable Y zeolite (USY), plays an important role in determining their cracking activity and selectivity. To develop advanced sulfur reduction catalytic cracking catalysts, different type of elements were used to modify USY and the resulting catalysts were evaluated in a confined fluidized bed reactor and a micro-activity testing unit. The relation between the acidity of the zeolite and the conversion of sulfur compounds as well as the distributions of fluid catalytic cracking (FCC) products were discussed. The results showed that the rare earth (RE) metal can stabilize the catalyst and increase the conversion, but cannot increase the selectivity to thiophene compounds; V can reduce the sulfur content by 36.3m%, but decreases the overall conversion compared with the base catalyst. An optimum catalyst was obtained by the combined RE and V modification, over which the sulfur content in FCC gasoline can be decreased and the selectivity for the target products can be improved, with the sulfur content reduced by 30m% and the selectivity to coke even decreased by 0.20m% at a comparable conversion level of the base catalyst. [Copyright &y& Elsevier]

• Excellent sulfur adsorption capacity can be achieved by the zeolite Cu(I)-Y-0.28. • Effective desulfurization active sites in the Cu(I)-Y zeolites are re-defined. • Thiophene separately adsorb on each effective active site, rather than the oligomerization. • The role of [Cu-O-Cu]2+ and [Cu-O 2 -Cu]2+ species for thiophene capture is revealed. • The building direction of adsorption sites in Cu-containing adsorbents can be indicated. Cu-containing materials attracted much attentions to adsorption desulfurization due to their excellent sulfur adsorption capacities. The chemical properties of adsorption active sites in the adsorbents and adsorption desulfurization mechanism, however, still remained ambiguous, which had impeded the development of a potential desulfurization adsorbent. This work aimed to address the aforementioned challenges by using Cu(I)-Y zeolites obtained via liquid phase ion exchange method. The implication of Cu/Al ratios on the chemical properties of active sites, the adsorption desulfurization performance and the mechanism was the major focus of this work. The desulfurization experimental results indicate that the remarkable sulfur breakthrough adsorption capacity (ca. 0.95 mmol S/g) can be achieved by the sample Cu(I)-Y-0.28, which is about ca. 2.0 folds as high as the best one reported. In this work, a new insight is put forward that except for the Brønsted acid sites and Cu+ species, the dimeric [Cu-O-Cu]2+ and [Cu-O 2 -Cu]2+ species located in the supercages of Cu(I)-Y adsorbents are identified and can be considered as the effective desulfurization active sites by employing in situ FTIR spectroscopy, IGA, XPS, and H 2 -TPR techniques. Furthermore, we also discover that the thiophene molecules can be independently adsorbed on the abovementioned adsorption active sites, rather than the thiophene oligomerization even if in the presence of Brønsted acid sites. DFT calculation further reveals the respective role of dimeric [Cu-O-Cu]2+ and [Cu-O 2 -Cu]2+ species for the thiophene capture, due to its different adsorption modes [(η1C) and (O-μ 1 -C, η1C, O-μ 1 -S)]. This study to distinguish effective adsorption active sites in the Cu(I)-Y zeolites should play an instructive role in the development of excellent desulfurization adsorbents in aspects of sulfur adsorption capacity and even adsorption selectivity. [ABSTRACT FROM AUTHOR]