Catalyst by ion exchange

Met-X A continuous process for removing traces of metals from cracking catalysts by ion-exchange. Developed by Atlantic Refining Company and first operated in Philadelphia in 1961. 

Kang and co-workers [79,80,84] prepared Au/NaY and Au-Fe/NaY catalysts by ion exchange from a solution of HAuCR. When only gold was present, they obtained gold particles of 10 to 40 nm diameter, while in the presence of iron, the mean diameter decreased to 5-8 nm. These results suggest that the presence of iron retards the sintering of metallic gold. 

In literature, a succesfull attempt has been reported, where Ru(II)-BINAP is sulfonated and immobilized by the supported aqueous phase technique [3]. We successfully immobilized this type of complexes in two different ways In a first system, we incorporated the Ru(II)-BINAP in a polydimethylsiloxane (PDMS) matrix [4]. In this paper, a second way of immobilizing the Ru(II)-BINAP catalyst, by ion exchange of the sulfonated complex on anionic minerals, is described. 

The Fe species formed during the preparation of Fe/ZSM-5 catalysts by ion exchange in aqueous medium or in the solid state were studied. XRD, EPR, Mdssbauer spectrocopy (MOSS) and chemical analysis (AAS) were used to sample characterization. The catalysts were evaluated through the propane oxidation in the range from 373 to 773 K. The MOSS data evidenced the presence of Fe" species in charge-compensation sites and a more content of hematite (Fe203) in the catalysts prepared in aqueous medium. In the propane oxidation, the activity of the Fe/ZSM-5 can be correlated with the amount of Fe-cationic species, confirming that they are the responsible for the catalytic activity. 

Catalytically active metal ions can be uniformly applied to the catalyst by ion exchange or impregnation. Subsequent reduction to the metal is also possible. 

In order to control the concentration of lower dibasic acid by-products in the system, a portion of the mother liquor stream is diverted to a purge treatment process. Following removal of nitric acid by distillation (Fig. 3, K), copper and vanadium catalyst are recovered by ion-exchange treatment (Fig. 

A cationic molybdenum sulfide cluster [Mo3S4(H20)9] " with incomplete cubane-type structure and a cationic nickel-molybdenum mixed sulfide cluster [Mo3NiS4Cl(H20)9p " with complete cubane-type structure were introduced into zeolites NaY, HUSY and KL by ion exchange. Stoichiometry of the ion exchange was well established by elemental analyses. The UV-visible spectra and EXAFS analysis data exhibited that the structure of the molybdenum cluster remained virtually intact after ion exchange. MoNi/NaY catalyst prepared using the molybdenum-nickel sulfide cluster was found to be active and selective for benzothiophene hydrodesulfurization. 

The cluster 2 was also introduced into NaY by ion exchange. After the ion exchange, 99% of molybdenum and nickel were loaded on NaY the Ni/Mo ratio did not change. The Cl/Mo ratio suggests that excess chlorine was present on the catalyst. 

Platinum catalysts were prepared by ion-exchange of activated charcoal. A powdered support was used for batch experiments (CECA SOS) and a granular form (Norit Rox 0.8) was employed in the continuous reactor. Oxidised sites on the surface of the support were created by treatment with aqueous sodium hypochlorite (3%) and ion-exchange of the associated protons with Pt(NH3)42+ ions was performed as described previously [13,14]. The palladium catalyst mentioned in section 3.1 was prepared by impregnation, as described in [8]. Bimetallic PtBi/C catalysts were prepared by two methods (1) bismuth was deposited onto a platinum catalyst, previously prepared by the exchange method outlined above, using the surface redox reaction ... 

Monolayer uptakes were obtained by extrapolating isotherms to zero pressure. Dispersions for all catalysts were determined using four separate methods H2 chemisorption, CO chemisorption, O2 chemisorption, and H2-O2 titration (PC-0 + 3/2H2 -Pt,-H + H20) [36]. Fractional dispersions for the Pt/SBA-15 series range from 0.13 to 0.31 based on total H2-O2 titration uptakes. A 3.2% Pt/Si02 catalyst prepared by ion exchange (Pt/ Si02-IE) [37] serving as a standard had an irreversible... 

It is well known that Rh(I) complexes can catalyze the carbonylation of methanol. A heterogenized catalyst was prepared by ion exchange of zeolite X or Y with Rh cations.126 The same catalytic cycle takes place in zeolites and in solution because the activation energy is nearly the same. The specific activity in zeolites, however, is less by an order of magnitude, suggesting that the Rh sites in the zeolite are not uniformly accessible. The oxidation of camphene was performed over zeolites exchanged with different metals (Mn, Co, Cu, Ni, and Zn).127 Cu-loaded zeolites have attracted considerable attention because of their unique properties applied in catalytic redox reactions.128-130 Four different Cu sites with defined coordinations have been found.131 It was found that the zeolitic media affects strongly the catalytic activity of the Cd2+ ion sites in Cd zeolites used to catalyze the hydration of acetylene.132... 

Several strategies to immobilize the p-oxo catalysts on an electrode surface or in a membrane have been employed. However, no available data about their efficiency as modified electrodes for water oxidation have been given.482-486 It should be noted that [ (bpy)2RuIII(OH2) 2(M C))]4+ is also an excellent electrocatalyst for oxidation of chloride to chlorine (better than for the oxidation of H20 into 02) at 1.20 V vs. SCE in 0.05 M HC1 solution,487 or at a modified electrode prepared by incorporation of the complex by ion-exchange into polystyrene sulfonate or Nafion films.482,4 8... 

Pt/H-MCM-22 catalysts for methane combustion have been prepared by ion-exchange of a highly crystalline H-MCM-22 zeolite using [Pt(NH3)4](N03)2. The activation procedure of the catalyst precursor has been optimized and all steps monitored by HRTEM, SEM and FTIR of CO adsorbed. The preliminary decomposition/calcination of the ion exchanged sample is very crucial in that influence the final properties of platinum active species. 

Catalysts were prepared from an alkali form of ferrierite, NaK-FER, with a Si/Al = 9 (TOSOH Co., Japan). The monometallic Co-HFER (3 wt. % Co) was obtained by ionexchanging the NH4-FER form with a Co(CH3COO)2 solution. The bimetallic Co/Pd-HFER sample (0.3 wt. % of Pd, 3wt. % Co) was then prepared by ion-exchanging it with a solution of Pd(NH3)4(N03)2. Further details are given elsewhere [10], UV-Vis/RDS spectra were carried out on a Varian Cary 5000 UV-VIS-NIR spectrophotometer. H2-TPR experiments were performed using samples of 130 mg of catalyst, under a mixture of 5% H2/Ar from RT to 1000°C (7.5°C min"1). 

---