Synthesis of ZSM-48 zeolites and their catalytic performance: a review

Abstract

ZSM-48 is first discovered as an impurity phase in the synthesis of ZSM-39. ZSM-48 has a framework based on the ferrierite sheet with noninterpenetrating linear 10-ring channels which the dimensions...

Construction of Submicron Spherical ZSM-48 Zeolite: Crystallization Mechanism and Catalytic Application

“…However, for the F − -free system, rod twin crystals begin to appear on the surface of the ellipsoidal crystal in the final stage of crystallization (Figure 7e−h). Combined with the results of OH-IR and 29 Si MAS NMR, a tentative conclusion can be obtained: F − ions promote the condensation of silanol groups on the surface of primary rod crystals, and the final product shows more perfect spherical aggregates, while in the F − -free system, the free silanol groups induce the formation of twins as active silicon sites. In summary, two well-established conclusions about the role of F − ions can be proposed: (i) F − ions significantly short the crystallization induction period by accelerating the dissociation and rearrangement of disordered silica−aluminum polymeride.…”

“…ZSM-48 zeolite, a kind of zeolite with a disordered framework (*MRE topology) and unidimensional 10-membered-ring channels, generally exhibits a high silica–alumina ratio (SAR) property . The uncrossed one-dimensional channel structure makes it exhibit an excellent shape-selective performance in alkane and xylene isomerism. − However, like other one-dimensional zeolites, ZSM-48 zeolites usually exhibit rod or rod-bundle morphology with large aspect ratios .…”

“…When the x value reaches 0.1, the product shows a nearly uniform spherical crystal with a diameter of about 500 nm and rod twin crystals are rarely observed (Figure 2d,i), while when the x value continues to increase to 0.15, the product size tends to increase and the particle size distribution also widens, although the spherical morphology is maintained (Figure 2e,j). The formation of large crystals is a typical phenomenon when NH 4 F is introduced, which can be attributed to its ability to balance the positive charge of templates that is balanced by crystal defects in the F − -free system 40 To learn more about the role of NH 4 F, OH-IR and 29 Si MAS NMR were performed. Generally, the IR signal at 3740 cm −1 is attributed to the external free silanol groups for zeolite samples.…”

“…Catalyst Characterization. The characterization techniques involved in this work included X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 adsorption−desorption analysis, 27 Al, 19 F, and 29 Si solid-state magic-angle-spinning nuclear magnetic resonance ( 27 Al/ 19 F/ 29 Si MAS NMR), X-ray photoelectron spectroscopy, UV-Raman spectral analysis, Fourier transform infrared, X-ray fluorescence, dynamic light scattering (DLS), thermogravimetric analysis (TGA), ammonia temperatureprogrammed desorption (NH 3 -TPD), and testing of the pxylene diffusion performance of the catalyst. Details of various techniques are listed in the Supporting Information.…”

Construction of a One-Dimensional Al-Rich ZSM-48 Zeolite with a Hollow Structure

“…Zeolites are crystalline materials with well-defined micropores and tailorable acidity, and they have been applied in a wide range of catalytic processes and other industrial processes. − As an important branch of zeolite materials, one-dimensional (1D) zeolites exhibit specific applications in the fields of isomerization. − Generally, 1D zeolites are easy to grow into rods or needles along the main channel direction, leading to severe diffusion limitation. − Moreover, such morphologies are harmful to human health as they easily penetrate into the respiratory system . Hence, changing the growth trend of 1D zeolites and overcoming the problem of limited diffusion on the premise of good shape selectivity are of great importance.…”