Solid acid catalysts from clays (original) (raw)
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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.
Acidic and hydrocarbon catalytic properties of pillared clay
Catalysis Today, 1988
Pillared clays (PILC) are a special class of solid acid material which are synthesized by interlayering expandable clay minerals with large polyoxycations as pillars. With the purpose of exploring the potential af these solid acid minerals as hydrocarbon conversion catalysts in petroleum refining and in the petrochemical industries, our laboratory (refs. l-81, has been conducting research on PILC with a variety of polyoxycations as pillars and several kinds of clay materials as parent clays, and also paid attention to the relation between the acidity and the structure of PILC, the influence of pillaring, and their hydrocarbon conversion activities.
Clays as Catalysts in Petroleum Refining Industry
In the last century, catalysts became one of the most powerful tools in the petroleum refining industry. Clays are widely used as catalysts and catalyst supports for a quite broad range of processes. Clay catalysts have attracted much interest in catalytic application in petroleum refining industry. This review will focus on the using of clays and their modifications as catalysts and catalyst supports in the petroleum refining industry. Clays are used extensively for various processes such as catalytic cracking, hydrocracking, reforming, isomerization, hydrogenation, alkylation, etc. The most important clays used in the manufacture of catalysts are kaolin and montmorillonite. The largest use of kaolin is in catalyst substrates in the catalytic cracking of petroleum, in the matrix as catalysts of fluid catalytic cracking, synthetic of zeolite andalumina. Montmorillonites or acid-modified montmorillonites also have been used for numerous reactions. For example, the best clay base for pillaring is a high-swelling Na-montmorillonite. However, the interest on palygorskite and sepiolite clays is more recent, but their interesting application as catalyst supports.
Synthesis of Smectites and Porous Pillared Clay Catalysts: A Review
Journal of Porous Materials, 1998
This paper reviews the synthesis of smectites and porous pillared clay catalysts. Synthetic as well as natural smectites serve as precursors for the synthesis of Al, Zr, Ti, Fe, Cr, Ga, V, Si, and other pillared clays as well as mixed Fe/Al, Ga/Al, Si/Al, Zr/Al and other mixed metal/Al pillared clays. The use of these pillared clays in some catalytic reactions is also briefly reviewed.
Asian Journal of Chemistry
The preparation of aluminium pillared montmorillonite (Al-PILM) from Indonesian natural montmorillonite and its catalytic activity study in the bio-oil cracking has been investigated. The synthesis of Al-PILM catalyst was conducted through intercalation process of Al13 Keggin ion at the Al ratio of 5 mmol Al/g montmorillonite followed by dehydroxylation processing to get aluminium oxide pillar in montmorillonite interlayer. Catalyst characterization performed by XRD, surface area analyzer and surface acidity measurement and SEM. Activity test of material as catalyst in bio-oil cracking focused on the effect of Al-PILM utilization to the product distribution and liquid product composition. The result showed that Al-PILM has higher activity to produce lighter fraction of hydrocarbon than montmorillonite. The increase in liquid product and selectivity to produce smaller hydrocarbon compounds attributed to the improvement of catalyst performance after pillarization.
Journal of Porous Materials, 2001
Metal oxide pillared clay (PILC) possesses several interesting properties, such as large surface area, high pore volume and tunable pore size (from micropore to mesopore), high thermal stability, strong surface acidity and catalytic active substrates/metal oxide pillars. These unique characteristics make PILC an attractive material in catalytic reactions. It can be made either as catalyst support or directly used as catalyst. This paper is a continuous work from Kloprogge's review (J.T. Kloprogge, J. Porous Mater. 5, 5 1998) on the synthesis and properties of smectites and related PILCs and will focus on the diverse applications of clay pillared with different types of metal oxides in the heterogeneous catalysis area and adsorption area. The relation between the performance of the PILC and its physico-chemical features will be addressed.
Applied Catalysis A: General, 1998
Pillared clays were prepared by intercalation in a Wyoming montmorillonite with a partially hydrolyzed aluminum chloride solution containing Ce 3 ions as second, and Co 2 , or Ni 2 , or Zn 2 , or Mg 2 ions as third component. These multicomponent pillared materials were investigated by Fourier Transform Infra-Red (FT-IR) spectroscopy, X-ray diffraction (XRD), nitrogen (77 K) and ammonia (323 K) adsorption, thermogravimetric (TG) analysis and acidity measurement in order to determine both thermal stability and acidity. The catalyst obtained from a pillaring mixture of three cations (AlCeMg-PILC) showed the most interesting characteristics. # 1998 Elsevier Science B.V.
An improved route for the synthesis of Al13-pillared montmorillonite catalysts
Journal of Porous Materials, 2007
The distribution of Al13 pillars and the process of intercalation in montmorillonite can be enhanced through the application of an ultrasonic treatment. This paper describes the results of ultrasonic treatment in the preparation of Al-pillared montmorillonite with and without prior exchange with Na+. The resulting materials have been characterised by X-ray diffraction (XRD), N2 adsorption/desorption, Scanning Electron Microscopy and Atomic Force Microscopy (AFM). The catalytic activity was tested with the n-heptane hydroconversion test. Optimum results were obtained after ultrasonic treatment up to 20 min without prior Na-exchange before the Al13 intercalation. Longer ultrasonic treatment resulted in partial destruction of the pillared structure. The pore size diameter also increased with increasing ultrasonic treatment up to 20 min with values in the range of 4 nm. This behaviour can be explained by the loss of the typical house of cards structure after prolonged ultrasonic treatment. AFM showed that the pillars in the interlayer of the montmorillonite resulted in a distortion of the tetrahedral sheets of the clay. At atomic scale resolution it was clear that the pillar distribution is not homogenous, confirming earlier results using high resolution TEM. The effects of ultrasonic treatment on the catalytic activity is rather limited, although the pillared clays prepared with short ultrasonic treatments of 5 and 10 min performed slightly better.
CATALYTIC ACTIVITY OF SYNTHETIC SAPONITE CLAYS: EFFECTS OF TETRAHEDRAL AND OCTAHEDRAL COMPOSITION
Journal of Catalysis, 2005
Catalytic activity of synthetic saponite clays: effects of tetrahedral and octahedral composition. Journal of Catalysis, 231(2), 443-452. ABSTRACT This paper describes the catalytic characteristics of synthetic saponites with well-known chemical composition, thermal stability and acidity in three catalytic reactions: 1) catalytic cracking of n-dodecane, 2) hydro-isomerization of n-heptane and 3) Friedel-Crafts alkylation of benzene. Saponites with Mg in the octahedral position was by far the best catalyst for the catalytic cracking of n-dodecane, which can be explained by the higher surface area of these saponites compared to saponites with other compositions. All saponites performed better in the hydro-isomerization reaction of n-heptane and Friedel-Crafts alkylation compared to commercially available catalysts such as HZSM-5 and ASA. The shape selectivity in the Friedel-Crafts alkylation of benzene towards p-and o-DIOPB was remarkably high for the synthetic saponites.
Effect of Pt on Catalytic Activity of Al- and Zr-Pillared Smectite
Asian Journal of Chemistry, 2016
Clays are known as one of the inorganic materials with some applications especially as catalyst and adsorbent in industries. The potency of porosity and also modifiable structure of clays have been reported as high potential for developing smart inorganic materials. For those purposes, clays particularly smectite class are modified related to their application [1-3]. Smectite clays are modified with metals or oxides in order to enhance the activity regarding to the specific catalytic reactions instead of to cover the limitation related to its lack of the structure stability in high temperature. Metal oxide pillared clays are popular method in clay modification scheme. The pillarization process consists of the metal oxide insertion between the interlayer region of clays and have been reported to give sufficiently thermal stability. Among some metal oxide such as Ti, Cr, Zr and Zn, Al and Zr were intensively reported for catalysis purposes [4-8]. Preparation of Aland Zr-pillared smectite involving pillared montmorillonite and pillared saponite were reported to be active as catalyst in many reactions such as hydrogenation, esterification, etc. Not only as catalysts itself, both materials are potential to be utilized as catalyst support from their thermal stability and easily prepared. In previous works Al-pillared montmorillonite (Al-PILM) was reported to have high catalytic activity in hydro