PILC

New Adsorbent Materials. SihcaUte and other hydrophobic molecular sieves, the new family of AlPO molecular sieves, and steadily increasing families of other new molecular sieves (including stmctures with much larger pores than those now commercially available), as well as new carbon molecular sieves and pillared interlayer clays (PILCS), will become more available for commercial appHcations, including adsorption. Adsorbents with enhanced performance, both highly selective physical adsorbents and easily regenerated, weak chemisorbents will be developed, as will new rate-selective adsorbents. 

The hydroamination of alkenes has been performed in the presence of heterogeneous acidic catalysts such as zeolites, amorphous aluminosilicates, phosphates, mesoporous oxides, pillared interlayered clays (PILCs), amorphous oxides, acid-treated sheet silicates or NafioN-H resins. They can be used either under batch conditions or in continuous operation at high temperature (above 200°C) under high pressure (above 100 bar). 

The original epoxidation with titanium-tartrate is homogeneous, but it can be carried out heterogeneously without diminishing enantioselectivity by using titanium-pillared montmorillonite catalyst (Ti-PILC) prepared from titanium isopropoxide, (+)-DAT, and Na+-montmorillonite.38 Due to the limited spacing of Ti-PILC, the epoxidation becomes slower as the allylic alcohol gets bulkier. 

Oxidation intermediates and reaction pathways of wet hydrogen peroxide oxidation of p-coumaric acid over (Al-Fe)PILC catalyst... 

Previous studies carried out with clay based catalysts pillared by Fe hydroxo complexes [13] or mixed (Al-Cu or Al-Fe) complexes, have shown that the mixed PILCs lead to the most promising results for organic compounds total oxidation in water, by using hydrogen peroxide as oxidant [14-16],... 

In the present study, we have focused our attention on the catalytic wet peroxide oxidation of p-coumaric acid over (Al-Fe)PILC. This phenolic molecule was chosen as a representative of the biologically recalcitrant polyphenolic compounds present in olive oil processing and wine distillery wastewaters. 

The intercalant solution was prepared by titration of an Al3+/ Fe3+cationic solution with 0.2 molL"1 NaOH. The cationic solution contained 0.18 and 0.02 molL"1 of A1C13 and FeCl3, respectively. The NaOH solution was slowly added to the cationic solution at 70°C until the OH/cation molar ratio was equal to 1.9. The intercalant solution was added to the clay suspension under stirring. The final ( Al+Fe) /clay ratio was equal to 3.8 mmol/g of dry clay. After aging for 24h, the pillared clay precursor was washed until total elimination of chloride ions, dried at 60°C and finally calcined at 500°C for 5h. The resulting material is (Al-Fe)PILC. 

Fig 1 shows the rate of p-coumaric acid solution (500ppm) and TOC removals during the phenolic compound oxidation over (Al-Fe)PILC catalyst (0.5g/l), as well as the uncatalysed reaction in slurry at 70°C. 

It can be seen that p-coumaric acid was slowly oxidised without catalyst, only 20% of substrate was converted and 5% of TOC was removed in 4hours of reaction. The use of (Al-Fe)PILC catalyst remarkably increased the rates of both p-coumaric acid and TOC removals in the reaction mixture under mild reaction conditions (temperature of 70°C, atmospheric pressure, [H2O2]=2.10"2M). The fact that the fast removal of p-coumaric acid was accompanied by a rather slower TOC reduction implies that intermediates which are stable and resistant to further total oxidation had been formed. 

Figure 2. Concentration profile of p-Coumaric acid (A) p-hydroxybenzoic acid ( ) and p-hydroxybenzaldehyde ( ). ([p-coumaric] = 500 ppm, pHi= 3.5, T=343 K, [H202] = 2xl0 2 M, 0.5g/l (Al-Fe)PILC).

Pillared interlayer clays (PILCs), 1 655 Pill-box cell, 13 417-419 Pilling, reduced, 11 211 Pillow cases, number produced from one bale of cotton, 8 133t Pilot plant(s), 19 457-471... 

Table 1 Chemical analyses and basal spacing of the original clays and of the PILC calcined at 300°C. The chemical compositions, on a dry basis, are referred to the silica content of the original clay.

Preparation of the PILC. As seen in Table 1, two factors determine the extent of A1 fixation (% Al O ) by the clay the final pH of the solution and the size of the clay particles. The influence of pH is readily explained by the equilibrium of formation of the polymer and by a competitive exchange w th the protons. The surface area increases from 42 to 180-360m /g upon intercalation, as reported on Table 1, and seems to be determined by the amount of A1 fixation. It appears that on sample G the extent of A1 fixation reaches a plateau at Al/clay=5. After this, diffusional limitations control the exchange on the large particles.The N2 adsorption gives a typical type IV isotherm, with 70% of the surface area localized in micropores smaller than 20A, after dehydration at 300°C. 

Acidity of the PILC. Acidic properties were studied by infrared spectrometry adsorbing pyridine as probe molecule on self supported wafers prepared by pressing the PILC into thin films (15... 

PILC. The hydrothermal stability of the PILC depends dramatically on the mode of preparation. After steaming at 650°C for 17 hours the conversion is 42% for sample G5 and 82% for sample B6. Hydrothermal stability at 700°C, from MAT results, can be obtained by simply decreasing the size of the particles of the original clay. The selectivity for coke is high, as expected, and changes with conversion (see on Figure 5). 

The influence of the K O content of the PILC can be investigated, comparing the present results with those reported for an Al-PILC prepared from a similar clay and containing a lower amount of K O (18b) (see Table 6). 

The aluminium content of the two samples is comparable, when referred to the silica content of the original clay, and the two PILC have comparable surface areas after calcination at 300°C. The ACH bentonite was formed into small extrudates and flash-dried, whereas sample G5 was dried in a thin cake. In both cases, crushing to a fine powder was easy. Sample G5 retains a higher surface area at 800°C in spite of a higher potassium content. Therefore the K O content of the PILC is not the predominant factor for the thermal stability. 

When rare earth Y-zeolite (REY) was added to the PILC or to the parent clay, the dried PILC or "as received" clay was reslurried in water and the calcined REY added to the 10 wt % level. This slurry was then mixed, filtered, dried, and calcined at 500 C for 2 hours in air. The calcined REY was obtained from Union Carbide and contained 14.1 wt % rare earth elements, primarily lanthanum and cerium. Portions of the PILC were pretreated by one of the methods listed below prior to the microactivity testing. 

Figure 3. PILC surface area versus solution age. See Figure 2 for symbols.

Cracking Activity. In the previous section, we demonstrated that aging conditions affect the surface area of pillared clays. Here, we discuss the cracking activities of some selected aged PILCs. 

After the Initial thermal pretreatments, conversion Is directly related to the nature of the microstructure developed In aged PILC. In the early stages of collapse of the microstructure. 

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