Assessing and improving the catalytic activity of K-10 montmorillonite (original) (raw)
Related papers
A study of the surface acidity of acid-treated montmorillonite clay catalysts
Journal of Molecular Catalysis A: Chemical, 2001
The surface acidity of a series of commercial Süd Chemie acid-treated montmorillonite clays (K-catalysts) has been evaluated by a wide range of complementary experimental techniques. The different methods applied allow a rather complete characterisation of the surface acidity providing a complete picture of the Lewis/Brønsted acid strength/density of the surface sites. IR data show that the Brønsted sites on these catalysts are relatively weak and provide evidence for a slight increase of the strength and the density of Brønsted sites in the order K5 < K10 ∼ K20 < K30 in full agreement with the trend in iso-butene conversion, which is a measure of the strength and/or the abundancy of Brønsted sites. The apparent contradiction of these data with those obtained from the ammonia adsorption and iso-propanol conversion experiments can be explained by the structural and chemical modification of the clays upon acid treatment.
Preparation of acidic forms of montmorillonite clay via solid-state ion-exchange reactions
Catalysis Letters, 1992
A solid-state procedure has been developed which enables A13+ and Fe3+ ion-exchanged montmorillonite to be prepared via co-grinding of the clay with the appropriate metal nitrate at room temperature. Pyridine adsorption/infrared spectroscopic studies indicate that montmorillonite treated in this manner contains Brønsted and Lewis acid sites in significant quantities, suggesting that these easily prepared materials may be of interest as acid catalysts.
This paper discusses the mechanism of montmorillonite structural alteration and modification of bentonites' properties (based on samples from clay deposits Taganskoye, Kazakhstan and Mukhortala, Buriatia) under thermochemical treatment (treatment with inorganic acid solutions at different temperatures, concentrations and reaction times). Treatment conditions were chosen according to those accepted in chemical industry for obtaining acid modified clays as catalysts or sorbents. Also, more intense treatment was carried out to simulate possible influence at the liquid radioactive site repositories. A series of methods was used: XRD, FTIR, ICP-AES, TEM, nitrogen adsorption, and particle size analysis. It allowed revealing certain processes: transformation of montmorillonite structure which appears in the leaching of interlayer and octahedral cations and protonation of the interlayer and –OH groups at octahedral sheets. In turn, changes in the structure of the 2:1 layer of montmorillonite and its interlayer result in significant alterations in the properties: reduction of cation exchange capacity and an increase of specific surface area. Acid treatment also leads to a redistribution of particle sizes and changes the pore system. The results of the work showed that bentonite clays retain a significant portion of their adsorption properties even after a prolonged and intense thermochemical treatment (1 M HNO 3 , 60 • C, 108 h).
Chemical Modification of Montmorillonite K10 and Its Catalytic Activity
Asian Journal of Chemistry, 2020
Montmorillonite K10 (Mt-K10) was chemically modified using a silica-zirconia mixture and the resulting product was named SZMK. The product had an increased total surface acidity, catalytic activity, porosity, and thermal stability. Ammonia adsorption tests and further verification with FTIR and TGA/DTA showed that the acidity of SZMK was higher (0.16 mmol/g) than that of Mt-K10. Catalytic performance was analyzed on the esterification reaction of lauric acid. Refluxing lauric acid and methanol (molar ratio of 1:20) for 20 h with a 20 % (w/w) catalyst showed that catalytic activity of SZMK is high, i.e. methyl laurate production 98.18% (w/w) was achieved.
Evolution of Porosity and Surface Acidity in Montmorillonite Clay on Acid Activation
Industrial & Engineering Chemistry Research, 1995
Evolution of surface acidity and porosity in montmorillonite clay on treating with sulfuric acid has been studied. It is observed that the clay treated with 4 N sulfuric acid shows the maximum surface acidity. Acid strength distribution as measured by Benesi's technique of nonaqueous titration shows acidity range mainly between HO +4.6 and +3.3. Nitrogen adsorption-desorption hysteresis data indicate the transformation of pores from slit-shaped to spheroidal or ink bottle type as the acid concentration is increased from 1 to 8 N. These observations are explained in terms of structural modifications of clay on treatment with acid.
Solid acid catalysts from clays
Applied Catalysis A: General, 2000
Alumina-pillared and double-pillared montmorillonite and saponite samples have been prepared and characterised from the point of view of their thermal stability, porosity and structure. Surface acidity was studied by ammonia TPD, iso-propanol conversion and n-butene skeletal isomerisation catalysis, and by FT-IR spectroscopy of the surface hydroxy-groups, and of adsorbed acetonitrile and pivalonitrile.
Surfactant-Treated K10 Montmorillonite: A High-Surface-Area Clay Catalyst
Journal of Porous Materials
Hydrothermal surfactant treatment was used to transform K10 montmorillonite (M), which is one of the acid activated clays used as a catalyst and/or adsorbent, into a surfactant-treated K10 montmorillonite (SM). The material was characterized by X-ray diffraction, isopropanol probe reaction, N 2 adsorption-desorption, pyridineadsorption-FTIR, and TPR-MS. All the results show that SM is a new type of mesoporous material having high surface area (408 m 2 /g), high thermal stability, and high catalytic activity for isopropanol conversion.