Al In Framework Research Articles

Production of jet fuel by hydrorefining of Fischer-Tropsch wax over Pt/Al-TUD-1 bifunctional catalyst

TUD-1 supported bifunctional platinum catalysts were prepared and characterized for structural and textural properties, acidity, and platinum dispersion. The acidity of TUD-1 was varied by isomorphous substitution of Al and Ti in the framework. The TUD-1 supports possess a three-dimensional amorphous structure as shown by XRD. BET-N2 adsorption and pyridine FTIR studies revealed that the incorporation of Al in the TUD-1 framework enhances the surface area and generates Brønsted acidity. The catalysts were screened for hydrorefining of Fischer-Tropsch wax with C8-C44 n-paraffins. The catalysts prepared with Si-TUD-1 and Ti-TUD-1 supports were not active for hydrocracking and hydroisomerization due to the absence of Brønsted acid sites, which was verified by pyridine FTIR. Increasing the amount of Al in the framework gradually increased the Brønsted acid sites and thus promoted hydrocracking and hydroisomerization of F-T wax. Pt/Al-TUD-1 catalyst with a Si/Al ratio of 10 produced more jet fuel range hydrocarbons. Hydrorefining of F-T wax was evaluated over an optimal Pt/Al-TUD-1 (Si/Al = 10) catalyst at different pressures and temperatures. Hydroisomerization was favored at low hydrogen pressure. Increasing the temperature shifted the hydrocarbon distribution more towards gasoline due to severe cracking. The temperature of 330 °C and a hydrogen pressure of 5 MPa were found to be optimum to produce jet fuel range hydrocarbons that meet the ASTM specification of cold flow properties. This study proves the feasibility of the production of renewable jet fuel that is directly compatible with fossil-based aviation engines, through hydrorefining of F-T waxes using a mesoporous bifunctional catalyst.

Sub-zeolite of FER topology derived from an interlayer modification of PLS-3 lamellar precursor

A simple HCl–EtOH solution treatment has been conducted to modify the structure of Al-PLS-3, a kind of FER lamellar precursor with various Si/Al ratios (60–∞). With prolonging the treatment time from 15min to 24h at 443K, the precursors underwent a variety of structural changes, including removal of occluded organic species, loss of layer stacking order and restoration of an ordered structure by interlayer pillaring. The post structural modification gave rise to a sub-zeolite of FER topology within a short time of 40min, which possessed disordered stacking of FER sheets, named as ECNU-8. The physicochemical properties of ECNU-8 were characterized by means of various techniques and in comparison to those of conventional FER topology. Still composed of a collection of FER sheets but without an ordered stacking manner along (100) direction, the structure of ECNU-8 was constructed by a reorientation of interlayer hydrogen bond moieties caused by partial removal of interlayer organic structure directing agent. The ECNU-8 materials with different Al contents possessed external surface areas enlarged by 23.1–36.8% in comparison to corresponding three-dimensional FER zeolites. Containing the FER laminates and tetrahedral Al in framework, but mitigating the spatial restrictions in particular for the bulk molecule reactions, ECNU-8 proved to be a promising solid acid catalyst for processing larger substrates.

Novel Three Dimensional Cubic Fm3m Mesoporous Aluminosilicates with Tailored Cage Type Pore Structure and High Aluminum Content

AbstractNovel three dimensional cubic Fm3m mesoporous aluminosilicates (AlKIT‐5) with very high structural order and unprecedented loadings of Al in the silica framework have been successfully prepared for the first time by using non ionic surfactant as a template in a highly acidic medium. The obtained materials have been unambiguously characterized in detail by several sophisticated techniques such as XRD, N2 adsorption, HRTEM, HRSEM, EDS, elemental mapping, 27Al MAS NMR, and NH3‐TPD. We also demonstrate that the nature, and the amount of Al incorporation in the silica framework can easily be controlled by simply varying the nH2O/nHCl and the nSi/nAl ratios, and the Al sources in the synthesis gel. Among the Al sources examined, the Al isopropoxide (AiPr) is superior over other Al sources. 27Al MAS NMR results reveal that the amount of tetrahedral Al in the framework can be controlled by simply adjusting the nSi/nAl ratio in the synthesis gel, which increases with increasing the Al incorporation. One of the interesting findings in the work is the increase of the specific surface area, specific pore volume and the pore diameter of AlKIT‐5 with increasing the Al incorporation in the silica framework (up to nSi/nAl ratio of 10) while retaining the well‐ordered three dimensional cage type porous structure, and the mechanism for the unusual behavior has been discussed in detail. Finally, the acidity and the catalytic activity in the acetylation of veratrole of the AlKIT‐5 catalysts have been studied and the results have been compared with the several zeolites catalysts. Among the catalysts examined, AlKIT‐5(10) is found to be superior over the zeolites catalysts such as mordenite, zeolite H‐Y, zeolite H‐β, and ZSM‐5.

29Si MAS n.m.r. studies of the distribution of Si and Al in the framework of zeolite LaHY

The distributions of Si and Al in the framework of LaHY zeolites were studied by 29Si MAS n.m.r. and the ordering schemes of the distribution of Si and Al in the LaHY framework were obtained according to the results of 29Si MAS n.m.r. It was found that the La ions can stabilize the Si (3Al) and Si (2Al) units of the framework of LaHY and can affect the coordination distribution of the next-nearest-neighbor Al atom ( i-NNN) for the original Al atom. Thus, the concentration and the strength of Brönsted acid sites in LaHY zeolites can be modified by La ions.