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Immobilization of catalytically active transition metal complexes on silica polyamine composite (SPC) surfaces offers many advantages for applications in catalysis particularly for catalyst recovery and reuse. We report here the immobilization of PONOP pincer complexes of Ru, Rh, Ni and Pd on the poly(allylamine) SPC, BP-1 using the Mannich reaction. Three different methods have been investigated for synthesizing the PONOP pincer transition metal complexes on BP-1: 1) direct reaction of the preformed pincer complexes using a two step Mannich reaction; 2) immobilization of the PONOP ligand using the Mannich reaction followed by the addition of a transition metal compound of a given metal; 3) the stepwise construction of PONOP on BP-1 followed by addition of a transition metal compound. The immobilized complexes on BP-1 were characterized by FT-IR, solid-state CPMAS 13 C and 31 P NMR, as well as elemental analysis. Anchoring of the complexes on BP-1 was also evaluated by the metal loading data obtained from the digestion of the loaded composites followed by Atomic Absorption Spectroscopy (AAS) or Inductively Coupled Plasma Atomic Emission Spectroscopy (ICPAES). The results showed that method 1 works better for the loading of pincer complexes on the SPC than methods 2 and 3. In the case of the Ru and Ni pincer complexes reasonable agreement with the phosphorous analysis was realized, while for the Pd complex values were high relative to the loading predicted from the phosphorus analysis, indicating the formation of the Pd nanoparticles on the surface during immobilization. For the Rh and Ru immobilized complexes with methods 2 & 3, metal loading was lower than the phosphorous analysis and this is attributed to entrained triphenylphosphine from the starting rhodium and ruthenium complexes based on the 13 C and 31 P CPMAS NMR data. Solution experiments using the PONOP pincer ligand and the Ru(PONOP) complex with n-butyl amine were conducted to model the site of electrophilic aromatic substitution on the pyridine ring. It was found that substitution both meta - and para -to the nitrogen takes place and this helped in the interpretation of the solid-state data. [ABSTRACT FROM AUTHOR]

A series of Pd-Ag mixed-metal nanocatalysts were prepared by reduction of Pd-Ag salts in the presence of poly(propylene imine) dendrimers, which were covalently bound to the surface of a silica polyamine composite, BP-1 (polyallylamine covalently bound to a silanized amorphous silica gel). Three different Pd-to-Ag ratios were evaluated (50:50, catalyst 1; 40:60, catalyst 2; 60:40, catalyst 3) with the goal of determining how the amount of Ag effects selectivity, rate and conversion in the selective , such as phenylacetylene and 1- or 4-octyne, to the corresponding alkenes. Conditions for the are reported where there is improved selectivity without a serious reduction in rate when compared with the analogous Pd-only catalysts. Catalyst 2 worked best for phenylacetylene and catalyst 3 worked best for the octynes. The catalysts could be reused seven times without loss of activity. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Modified silica polyamine composites (SPC) made from silanized amorphous nano-porous silica gel and polyamines have been used for the selective removal and recovery of oxyanions of heavy metals such as As and Se in the presence of excess sulfate. The SPCs were functionalized with phosphorus acid using the Mannich reaction, resulting in a phosphonic acid modified composite (BPAP) on which Zr(IV) was immobilized by complexation to the phosphonic acid group. Tungstate and molybdate anions strongly adsorbed on the ZrBPAP composite over a broad pH range of 2–10. The sorption mechanism is believed to be a complexation between the tungstate and/or molybdate and Zr(IV) immobilized-phosphonic acid complex of BPAP. However, complete regeneration of the composite was not successful. A second composite modeled after polymer based adsorbents containing tetraalkyl ammonium groups was synthesized by exhaustive alkylation of the poly(allylamine) composite, BP-1. This composite, BPQAM, composite shows a higher selectivity for tungstate over molybdate at a pH of 6 (WO42 −/MoO42 − = 3/1). Using 2MH2SO4 as the strip solution provided selectivity for molybdate (~ 90% purity). The significance of the observed selectivity is discussed in terms of the chemical properties of the oxyanion and the nature of the interactions with the immobilized metal site. Attempts to separate molybdate from nickel and vanadium using solution concentrations modeled after a contaminated creek in Western Australia are also reported. The use of ZrBPAP and the aminoacetate modified SPC, WP2, resulted in the efficient separation of molybdate but the separation of the nickel from vanadium proved more difficult. [Copyright &y& Elsevier]

Silica polyamine composites made from silanized amorphous silica gel and a polyamine (polyallylamine (BP-1) and poly(ethyleneimine) (WP-1)) were functionalized with ethylenediamine-N,N,N′,N′-tetraacetic (EDTA) anhydride resulting in the modified composites BP-ED and WP-ED respectively. Successful immobilization of the poly-acetate ligand was confirmed by weight gain, IR and elemental analysis. The modified composites had ligand loading values of 0.78 mmol/g and 0.58 mmol/g respectively. Adsorption characteristics were investigated for BP-ED and WP-ED by pH profiles, time dependent isotherms, concentration dependent isotherms, and the Langmuir and Freundlich adsorption models. Metal ion capacities (mmol of metal adsorbed per gram of adsorbent) were shown to increase with pH for BP-ED and WP-ED, which is in contrast with silica gel modified with EDTA anhydride via amino propyl silane without the use of a polyamine where the opposite trend is observed. The adsorption of Ni(II), Zn(II) and Co(II) onto BP-ED and WP-ED was shown to fit the Langmuir adsorption model, which indicates a monolayer, non-cooperative metal ion uptake. For both composites the divalent metal ion selectivity is as follows: Cu(II)>Ni(II)>> Zn(II), Co(II)>> Mn(II). Also the trivalent metal ion selectivity is as follows: Fe(III)>Ga(III)>> Eu(III)>Al(III). This is in close agreement with reported formation constants for EDTA in solution. Breakthrough and recovery tests were carried out using a 5cc packed column. The separation and recovery of Ni(II) from Co(II) when BP-ED was challenged with a solution containing 1.5 mg/L of both metals resulted in an acidic strip solution of greater than 97% Ni(II) purity. Further, selective separation of Ni(II) from a solution containing low levels of Co(II) and Zn(II) and high level Fe(II) at pH=1 was also achieved. Ni(II) was extracted at a flow rate of 0.1 column volumes per minute (0.5 mL/min) and recovered in greater than 90% purity by an acidic strip. Impurity in the strip was a consequence of Fe(II) oxidation to Fe(III). These tests demonstrate that well resolved separations of one divalent metal ion from one or more other divalent metal ions are possible through the use of EDTA anhydride modified silica polyamine composites with higher capacities than the previously reported amino propyl silane modified silica gel. [ABSTRACT FROM AUTHOR]

Details a study which described two modified silica-polyamine composite materials. Separation of metal ions; Efficiency composite materials in metal ion removal; Discussion and conclusion.

A novel silica–polyamine composite material, WP-1, was synthesized according to a new patented procedure for aqueous heavy metal ion removal. The effects of pH and initial concentration of metal ions on adsorption were investigated. Results showed that WP-1 has metal ion capacities in the order Cu(II) > Ni(II) > Fe(II) and generally works best in the 2–4 pH range. Kinetic studies showed the Cu(II) adsorption reaction occurs in a second-order fashion with a rate constant of 4.4 × 10-4 s-1. Two similar silica–polyamine materials, prepared by different procedures cited in the literature, were compared with WP-1 for Cu(II) ion capacity and mechanical durability. These tests showed that capacities were more than twice as high when the new patented procedure was used, indicating much better coverage of the silica gel. During repeated metal loading and unloading tests, WP-1 maintained up to 94% of its initial Cu(II) capacity and its mechanical integrity for 3000 cycles, whereas testing of the other materials had to be stopped prematurely due to degradation of the materials. [ABSTRACT FROM AUTHOR]