Catalytic activity of nickel sulfide catalysts supported on Al-pillared montmorillonite for thiophene hydrodesulfurization.

Al-pillared clays, prepared by exchange with partly hydrolyzed aluminium nitrate solutions, dried in air or freeze-dried, and calcined, were used as supports for nickel sulfide catalysts. The catalysts were tested on their hydrodesulfurization (HDS) activity for thiophene. The catalysts show a high thiophene HDS activity. It appears that details in the preparation and calcination of the pillared clays have a strong influence on the catalytic activity

Catalytic activity of nickel sulfide catalysts supported on Al-pillared montmorillonite for thiophene hydrodesulfurization.

Al-pillared clays, prepared by exchange with partly hydrolyzed aluminium nitrate solutions, dried in air or freeze-dried, and calcined, were used as supports for nickel sulfide catalysts. The catalysts were tested on their hydrodesulfurization (HDS) activity for thiophene. The catalysts show a high thiophene HDS activity. It appears that details in the preparation and calcination of the pillared clays have a strong influence on the catalytic activity

Pillared clays : preparation and characterization of clay minerals and aluminum-based pillaring agents

After an extensive introductory chapter (Chapter I), in which the background and the aim of the research is dealt with, the hydrothermal synthesis and the characterization of Na-beidellite is discussed in Chapter II and III. The conditions of temperature, water pressure, and sodium activity under which Na-beidellite can be synthesized in the chemical system Na20-AI203-Si02-H20 are investigated in Chapter IV. The stability field is limited at low temperatures by the formation of kaolinite and at high temperatures by that of paragonite and quartz. In Chapter V solid-state magic-angle spinning 23Na NMR combined with XRD and TGA is used to study the interlayer collapse and the migration of sodium present at the interlayer during dehydration of synthetic Na-beidellite. It is shown that the Na+ surrounded by two water molecules is relocated in the hexagonal cavities of the tetrahedral sheet. The low-temperature synthesis of ammonium-saponites is considered in Chapter VI, while solid-state 27AI NMR combined with 29Si I\lMR provides evidence for the presence of AI at the octahedral and the interlayer sites as dealt with in Chapter VII. In Chapter VIII a model is developed for the crystallization of saponite based on the hydrothermal synthesis of ammonium-saponite at increasing periods of aging time. Chapter IX discusses the synthesis of Mg-saponites using gels containing different competing cations. Since the preparation of AI pillaring agents is highly important in the preparation of pillared clays, much work has been devoted to the study of the forced hydrolysis of AI3+. Chapter X to XV are dealing with NMR studies of the aqueous chemistry of AI3+. Chapter X to XIII concentrate on the formation, thermal stability, and aging of monomeric, oligomeric, and tridecameric A13+ species during forced hydrolysis. In Chapter XIII direct evidence based on NMR line broadening data for the existence of the [AI(OH)2] + species is provided. The aging of the tridecameric AI complex in partly hydrolyzed AI-sec-butoxide solutions and the reaction to fibrous boehmite are considered in Chapter XIV. Chapter XV and XVI deal with the characterization, thermal stability, and NMR properties of basic AI sulfate resulting from addition of sodium sulfate solution to partly hydrolyzed AI solutions containing the tridecameric AI species, such as described in Chapter X to XIII. Pillaring and thermal treatment of synthetic beidellite and natural montmorillonite is described in Chapter XVII and the catalytic conversion of thiophene over pillared clays into which nickel has been applied in Chapter XVIII. Finally in Chapter XIX some concluding remarks concerning the results obtained in this study and the implications for the applications of (synthetic) clay minerals in catalytic reactions are mad

Identification by RAMAN Microscopy of magnesian vivianite formed from Fe2+, Mg, Mn2+ and PO4 3- in a Roman camp near fort Vechten, Utrecht, The Netherlands

The presence of a magnesian vivianite (Fe2+)2.5(Mg, Mn, Ca)0.5(PO4)2. 8H2O, has been identified in a soil sample form a Roman camp near Fort Vechten, The Netherlands, using a combination of Raman microscopy and scanning electron microscopy. An unsubstituted vivianite and baricite were characterized for comparative reasons. The split phosphate-stretching mode is recognized around 1115, 1062 and 1015 cm-1, while the corresponding bending modes are found around 591, 519, 471 and 422 cm-1. The substitution of Mg and Mn for Fe2+ in the crystal structure causes a shift towards higher wavenumbers compared to pure vivianite. As shown by the baričite sample substitution causes a broadening of the bands. The observed broadening however is larger than can be explained by substitution alone. The low intensity of the water bands, especially in the OH-stretching region between 2700 and 3700 cm-1 indicates that the magnesian vivianite is partially dehydrated, which explains the much larger broadening than the observed broadening caused by substitution of Mg and Mn in vivianite and baričite

Complexity of Intercalation of Hydrazine into Kaolinite - A Controlled Rate Thermal Analysis and DRIFT Spectroscopic Study

Controlled rate thermal analysis (CRTA) allows the separation of adsorbed and intercalated hydrazine. CRTA displays the presence of three different types of hydrogen-bonded hydrazine in the intercalation complex: (a) The first is adsorbed loosely bonded on the kaolinite structure fully expanded by hydrazine–hydrate and liberated between approx 50 and 70 degrees Celsius (b) The second intercalated hydrazine is lost between approx 70 and 85 degrees Celsius. (c) The third type of intercalated-hydrazine molecule is lost in the 85–130 degrees Celsius range. CRTA at 70 degrees Celsius enables the removal of hydrazine–water and results in the partial collapse of the hydrazine-intercalated kaolinite structure to form a hydrazine-intercalated kaolinite. Removal of the adsorbed hydrazine enables the DRIFT spectra of the hydrazine-intercalated complex without any adsorbed hydrazine to be obtained. A band at 3626 cm−1 attributed to the inner surface hydroxyls of kaolinite hydrogen bonded to hydrazine is observed. The intercalation of hydrazine–hydrate into kaolinite is complex and results from the different types of surface interactions of the hydrazine with the kaolinite surfaces