Elucidating the Effect of Ion Exchange Protocol on the Copper Exchange Efficacy, Copper Siting, and SCR Activity in Cu-SSZ-13.

The front cover artwork is provided by Professor Jean-Sabin McEwen at Washington State University. The image shows how ion exchanges prepared with different copper precursors influence how the copper ultimately sites relative to the zeolite framework, which ultimately impacts its catalytic reactivity for the selective catalytic reduction (SCR) of NO in Cu-SSZ-13. Read the full text of the Research Article at 10.

Elucidating the Effect of Ion Exchange Protocol on the Copper Exchange Efficacy, Copper Siting, and SCR activity in Cu-SSZ-13.

The influence of the copper ion exchange protocol on SCR activity of SSZ-13 is quantified. Using the same parent SSZ-13 zeolite, four exchange protocols are used to assess how exchange protocol impacts metal uptake and SCR activity. Large differences in the SCR activity, nearly 30 percentage points at 160 °C at constant copper content, are observed for different exchange protocols implying that different exchange protocols lead to different copper species.

Water Is the Oxygen Source for Methanol Produced in Partial Oxidation of Methane in a Flow Reactor over Cu-SSZ-13.

Direct oxidation of methane to methanol is a long-standing challenge in the heterogeneous catalysis community. This Communication demonstrates that water, not dioxygen, is the main source of the oxygen present in the methanol produced in the partial oxidation of methane to methanol over Cu-SSZ-13 in a continuous-flow reactor. This is confirmed by experiments performed in the absence of molecular oxygen and with the use of O-labeled water.

Covalently functionalized uniform amino-silica nanoparticles. Synthesis and validation of amine group accessibility and stability.

This paper describes the synthesis and characterization of colloidally stable, 18 nm silica nanoparticles that are functionalized with amine groups. Electron microscopy, small-angle X-ray scattering (SAXS), and dynamic light scattering show the amine grafting does not impact particle size. SAXS and DLS confirm the particles do not aggregate at 10 mg mL and pH 2 for 30 days.

PFG NMR studies of lysine-silica solutions.

The formation process of silica nanoparticles in lysine-silica mixtures was studied using dynamic light scattering (DLS) and pulsed-field gradient (PFG) NMR measurements. (1)H NMR shows line broadening of the lysine resonances during TEOS hydrolysis/nanoparticle formation. Analysis of the TEOS hydrolysis kinetics show that TEOS hydrolysis is the rate-limiting step in particle formation, and has an activation energy of 20.

Phenylboronic acid functionalized SBA-15 for sugar capture.

The synthesis and characterization of organic-inorganic hybrid materials that selectively capture sugars from model biomass hydrolysis mixtures are reported. 3-Aminophenylboronic acid (PBA) groups that can reversibly form cyclic esters with 1,2-diols, and 1,3-diols including sugars are attached to mesoporous SBA-15 via different synthetic protocols. In the first route, a coupling agent is used to link PBA and SBA-15, while in the second route poly(acrylic acid) brushes are first grafted from the surface of SBA-15 by surface-initiated atom transfer radical polymerization and PBA is then immobilized.

PFG NMR investigations of TPA-TMA-silica mixtures.

Pulsed-field gradient (PFG) NMR studies of tetrapropylammonium (TPA)-tetramethylammonium (TMA)-silica mixtures are presented, and the effect of TMA as a foreign ion on the TPA-silica nanoparticle interactions before and after heating has been studied. Dynamic light scattering (DLS) results suggest that silica nanoparticles in these TPA-TMA systems grow via a ripening mechanism for the first 24 h of heating. PFG NMR of mixtures before heating show that TMA can effectively displace TPA from the nanoparticle surface.

Specific ion effects on nanoparticle stability and organocation-particle interactions in tetraalkylammonium-silica mixtures.

Tetramethylammonium (TMA)- and tetrapropylammonium (TPA)-silica mixtures containing monovalent salts were studied to determine how salt impacts nanoparticle stability and organocation-silica interactions. Dynamic light scattering (DLS) results show that salt concentrations as low as 5 mM can induce nanoparticle aggregation. The extent of aggregation increases with the ionic size of the alkali-metal cations, consistent with the Hoffmeister series.

Novel polypeptide/thiol--SBA-15 hybrid materials synthesized via surface selective grafting.

Novel hybrid materials are synthesized through the surface selective grafting of poly-L-lysine and thiols from SBA-15.

Layer structure preservation during swelling, pillaring, and exfoliation of a zeolite precursor.

MCM-22(P), the precursor to zeolite MCM-22, consists of stacks of layers that can be swollen and exfoliated to produce catalytically active materials. However, the current swelling procedures result in significant degradation of crystal morphology along with partial loss of crystallinity and dissolution of the crystalline phase. Fabrication of polymer nanocomposites and coatings with MCM-22 for separation, barrier, and other applications requires a swelling method that does not alter drastically the crystal morphology and layer structure and preserves the high aspect ratio of the layers.

Synthesis, characterization, and growth rates of aluminum- and Ge,Al-substituted silicalite-1 materials grown from clear solutions.

The synthesis, characterization, and growth rates of aluminum- and germanium,aluminum-substituted silicalite-1 (Al-silicalite-1, Ge,Al-silicalite-1) materials grown from clear solutions are reported. In the case of aluminum substitution, the crystallinity of the materials as determined by powder X-ray diffraction (PXRD) decreases with increasing aluminum content, as does the micropore volume determined by nitrogen adsorption and the growth rate determined by in situ small-angle X-ray scattering (SAXS). The final materials possess slightly lower Si/Al ratios than the initial synthesis mixtures based on X-ray fluorescence analysis.

Silicalite-1 growth from clear solution: Effect of alcohol identity and content on growth kinetics.

In situ small-angle X-ray scattering (SAXS) is used to investigate the influence of alcohol identity and content on silicalite-1 growth from clear solutions at 368 K. Several tetraalkyl orthosilicates (Si(OR)4, R = Me, Pr, and Bu) are used to synthesize silicalite-1 from clear solution mixtures comparable to those previously investigated (i.e.

29Si NMR studies of zeolite precursor solutions.

Solution 29Si NMR spectroscopy results of zeolite precursor solutions of composition 1 SiO2:4 C2H5OH:0.36/n R+n[OH-]n:20 H2O are reported. This work employs isotopically enriched 29Si materials to aid in spectral interpretation.

Synthesis and characterization of uniform alumina-mesoporous silica hybrid membranes.

The synthesis and characterization of alumina-mesoporous silica (alumina-MS) hybrid membranes are reported. The hybrids are formed using a variation of the evaporative-induced self-assembly (EISA) process reported by Hayward et al. (Langmuir 2004, 20, 5998) based on dip coating of an Anopore 200 nm membrane with a Brij-56/TEOS/HCl/H2O solution.

Anionic microemulsion-mediated low temperature synthesis of anisotropic silicalite-1 nanocrystals.

The low-temperature (368 K) synthesis of silicalite-1 nanocrystals in anionic microemulsions is reported. In the presence of AOT/isooctane mixtures silicalite-1 nanocrystals can be formed that are coffin-shaped and approximately 100 x 40 x 200 nm in size. This is in contrast to samples made without the microemulsion under the same conditions where irregular spherical particles approximately 100 nm in diameter are formed.

Engineering nanospaces: ordered mesoporous silicas as model substrates for building complex hybrid materials.

This contribution summarizes investigations of organic-inorganic hybrid materials wherein the inorganic phase is ordered mesoporous silica such as MCM-41 and SBA-15. The review, which covers work performed in the last three years, emphasizes studies of: (1) covalently attached functional groups, (2) new approaches to functionalization, (3) approaches for achieving high densities of uniform functional groups, (4) periodic mesoporous organosilicas (PMOs) with hierarchical ordering, (5) new functional chemistries, and (6) the application of new materials to enantioselective catalysis and emerging areas. The review concludes with the authors outlining some outstanding problems in the field.

Helical poly-L-glutamic acid templated nanoporous aluminium oxides.

The synthesis of porous aluminium oxide made in the presence of helical poly-L-glutamic acid is reported.

Poly-L-lysine templated silicas: using polypeptide secondary structure to control oxide pore architectures.

Utilizing polypeptide secondary structure as a means for controlling oxide pore architectures is explored. Poly-L-lysine is used as a model polypeptide as its folding behavior is well understood and compatible with the sol-gel chemistry of silica. Here, we show that silicas synthesized with poly-L-lysine in a alpha-helix conformation possess cylindrical pores that are approximately 1.

Modifying zeolite particle morphology and size using water/oil/surfactant mixtures as confined domains for zeolite growth.

Here we report the synthesis of silicalite-1 particles using microemulsions wherein the particle size and morphology can be varied.