Iver Schmidt

Improved Performance of Nano-Size H-BEA Zeolite Catalysts for the Friedel–Crafts Acetylation of Anisole by Acetic Anhydride

Nano-size zeolite H-BEA (n-H-BEA) prepared by “confined space synthesis” (CSS) within the pores of a carbon black matrix shows improved activity without loss in para-selectivity for the Friedel–Crafts acetylation of anisole by acetic anhydride. The turnover frequency (TOF) of n-H-BEA exceeds that of a conventional H-BEA catalyst of similar aluminum and thus acid site content by a factor of about three at intermediate conversion. The latter observation is attributed to enhanced access and better utilization of the whole zeolite intracrystalline volume by the reactants as well as to the easier desorption of the acetylated product, p-methoxyacetophenone.

Catalytic epoxidation of alkenes with hydrogen peroxide over first mesoporous titanium-containing zeolite

Novel mesoporous TS-1 catalyst is shown to be active in nepoxidation of oct-1-ene and significantly more active in epoxidation of ncyclohexene than conventional TS-1.

TEM stereo-imaging of mesoporous zeolite single crystals

Mesoporous zeolite single crystals with intracrystalline mesopores and metal oxide particles located in the zeolite mesopore are characterised by direct TEM stereo-imaging.

Preparation and characterization of mesoporous TS-1 catalyst

Highly crystalline titanium-containing zeolite TS-1 with an intracrystalline mesopore system has been prepared and characterized. The TS-1 zeolite is crystallized in a carbon nanoparticle matrix (18 nm particles), which is subsequently removed by heating, leaving a mesopore system with the same diameter as the carbon nanoparticles. The resulting mesoporous TS-1 zeolite is characterized using X-Ray diffraction, Inductively Coupled Plasma emission spectroscopy, UV/vis-spectroscopy, Raman spectroscopy, Hg-porosimetry and Scanning Electron Microscopy. The results show, that the TS-1 is highly crystalline, anatase-free and highly mesoporous with an average crystal size of ≈5 μm. The mesoporous TS-1 is shown to exhibit a smaller degree of diffusion limitations in the epoxidation of cyclohexene with aqueous hydrogen peroxide than conventional TS-1.

03-O-02-Mesoporous zeolites

Publisher Summary Mesoporous zeolite crystals exhibit promising properties in catalytic processes. This chapter discusses mesoporous zeolites. It also describes how mesoporous ZSM-5 crystals can be synthesized by a variation of the confined space synthesis method and how the synthesis conditions influence the morphology of the zeolites. The advantages of mesoporous zeolite crystals as heterogeneous catalysts are presented. High nucleation rates favor the formation of nanosized zeolites, whereas low nucleation rates favor the formation of mesoporous zeolites. The structure and morphology of the mesoporous zeolite crystals are illustrated by transmission and scanning electron microscopy. Mesoporous zeolites have high mesopore volumes and high mesopore surface areas.

Preparation and characterization of the first series of molybdenum(III) ammine complexes, fac-[MoX3 (NH3)3] (X = Cl, Br, I). Spectrochemical parameters for molybdenum(III)

Abstract A new series of molybdenum(III) triammines fac -[MoX 3 (NH 3 ) 3 ] (X = Cl, Br, I) has conveniently been prepared by reaction of fac -[Mo(CF 3 SO 3 ) 3 (NH 3 ) 3 ] with LiX dissolved in tetrahydrofuran or ethanol. By an entirely analogous method fac -[CrBr 3 (NH 3 ) 3 ] and the already known fac -[CrCl 3 (NH3) 3 ] were prepared as well. All compounds have been characterized by UV-Vi s diffuse reflectance spectroscopy, IR spectroscopy and chemical analysis. In agreement with the mononuclear formulation, room temperature magnetic moments for members of the fac -[MoX 3 (NH 3 ) 3 ] series were near the d3 spin-only value. The combined analysis of the diffuse reflectance spectra of the fac -[MoX 3 (NH 3 ) 3 ] complexes and the solution spectra of the [MoX 6 ] 3− ions yielded the following spectrochemical parameters for molybdenum(III): Δ(NH 3 ) = 3.0 μm −1 , Δ(Cl) = 1.9 μm −1 , Δ(Br) = 1.8 μm −1 and Δ (I) = 1.4 μm −1

Calcination of ZSM-5. An In Situ Synchrotron Powder Diffraction Study

The calcination of the zeolite ZSM-5 was studied by in situ X-ray synchrotron powder diffraction. Two samples were studied: One conventionally synthesized (CONV) and one synthesized in a charcoal matrix according to the confined space synthesis method (CSS). The powder diffraction data were collected between 375 K and 975 K in steps of approximately 8 K/5 min. and evaluated by Rietveld refinements. Both sets of powder diffraction patterns displayed the characteristic intensity changes for calcination, but neither of them showed the expected orthorhombic to monoclinic phase transition. Refinements of the extra-framework occupancy showed that the calcination starts at about 475 K and is essentially completed at 675 K for CSS, while the CONV calcination starts at 525 K and ends at 650 K. The refinement results agree very well with the TGA results. The carbon matrix of the CSS sample is combusted between 700 and 850 K. The unit cell dimensions continuously decrease from 475 to 975 K. An initial slow 1.2 % reduction between 375 and 875 K is followed by a fast 1.2 % reduction between 875 and 950 K for the CSS sample. This second unit cell reduction step is unrelated to the calcination process and does not involve any weight loss. It is suggested that this step is a recrystallisation/annealing process reducing the amount of defects and strain.

Non-Crystallographic Nanopores in Single Crystals: A New Approach in Nanomaterials Chemistry

Nanomaterials are the building blocks of nanotechnology. Recently, nanotube materials have attracted considerable attention due to their unique physical and chemical properties. Here we discuss how nanotubes can be used as templates for preparation of a new family of materials, the nanoporous single crystals, and for the preparation of metal sulfide nanotube materials. Today, the characterization of these materials depends heavily on electron microscopy. However, as rational synthesis schemes are becoming available, more well-defined, homogeneous nanotube samples will be produced and the role of diffraction techniques may increase.