Selective Production of Phenol on Bifunctional, Hierarchical ZSM-5 Zeolites.

Mono- and bimetallic Ni-, Ru- and Pt-modified hierarchical ZSM-5 materials were prepared by impregnation technique and characterized by X-ray diffraction (XRD), N2 physisorption, temperature-programmed reduction (TPR-TGA), ATR-FTIR and solid state NMR spectroscopy. Formation of finely dispersed nickel, ruthenium and platinum species was observed on the bimetallic catalysts. It was found that the peculiarity of the used zeolite structure and the modification procedure determine the type of formed metal oxides and their dispersion and reducibility. The samples' acidity was studied via FTIR spectroscopy of adsorbed pyridine. The changes in the zeolite structure were studied via solid-state NMR spectroscopy. The catalysts were investigated in a gas-phase hydrodeoxygenation, transalkylation and dealkylation reaction of model lignin derivative molecules for phenol production.

Hydrodemethoxylation/Dealkylation on Bifunctional Nanosized Zeolite Beta.

Mono-, and bimetallic Ni-, Ru-, and Pt-modified nanosized Beta zeolite catalysts were prepared by the post synthesis method and characterized by powder X-ray diffraction (XRD), nitrogen physisorption, HRTEM microscopy, temperature-programmed reduction (TPR-TGA), ATR FT-IR spectroscopy, and by solid-state MAS-NMR spectroscopy. The presence of nanosized nickel-oxide, ruthenium-oxide, and platinum species was detected on the catalysts. The presence of Brønsted and Lewis acid sites, and incorporation of nickel ions into zeolite lattice was proven by FT-IR of adsorbed pyridine. The structural changes in the catalyst matrix were investigated by solid state NMR spectroscopy. The catalysts were used in a gas-phase hydrodemethoxylation and dealkylation of 2-methoxy-4-propylphenol as a lignin derivative molecule for phenol synthesis.

Tamoxifen Delivery System Based on PEGylated Magnetic MCM-41 Silica.

Magnetic iron oxide containing MCM-41 silica (MM) with ~300 nm particle size was developed. The MM material before or after template removal was modified with NH2- or COOH-groups and then grafted with PEG chains. The anticancer drug tamoxifen was loaded into the organic groups' modified and PEGylated nanoparticles by an incipient wetness impregnation procedure. The amount of loaded drug and the release properties depend on whether modification of the nanoparticles was performed before or after the template removal step. The parent and drug-loaded samples were characterized by XRD, N2 physisorption, thermal gravimetric analysis, and ATR FT-IR spectroscopy. ATR FT-IR spectroscopic data and density functional theory (DFT) calculations supported the interaction between the mesoporous silica surface and tamoxifen molecules and pointed out that the drug molecule interacts more strongly with the silicate surface terminated by silanol groups than with the surface modified with carboxyl groups. A sustained tamoxifen release profile was obtained by an in vitro experiment at pH = 7.0 for the PEGylated formulation modified by COOH groups after the template removal. Free drug and formulated tamoxifen samples were further investigated for antiproliferative activity against MCF-7 cells.

Oxidation of 5-Chloromethylfurfural (CMF) to 2,5-Diformylfuran (DFF).

2,5-Diformylfuran (DFF) is an important biorenewable building block, namely for the manufacture of new polymers that may replace existing materials derived from limited fossil fuel resources. The current reported methods for the preparation of DFF are mainly derived from the oxidation of 5-hydroxymethylfurfural (HMF) and, to a lesser extent, directly from fructose. 5-Chloromethylfurfural (CMF) has been considered an alternative to HMF as an intermediate building block due to its advantages regarding stability, polarity, and availability from glucose and cellulose. The only reported method for the transformation of CMF to DFF is restricted to the use of DMSO as the solvent and oxidant. We envisioned that the transformation could be performed using more attractive conditions. To that end, we explored the oxidation of CMF to DFF by screening several oxidants such as H2O2, oxone, and pyridine N-oxide (PNO); different heating methods, namely thermal and microwave irradiation (MWI); and also flow conditions. The combination of PNO (4 equiv.) and Cu(OTf)2 (0.5 equiv.) in acetonitrile was identified as the best system, which lead to the formation of DFF in 54% yield under MWI for 5 min at 160 °C. Consequently, a range of different heterogeneous copper catalysts were tested, which allowed for catalyst reuse. Similar results were also observed under flow conditions using copper immobilized on silica under thermal heating at 160 °C for a residence time of 2.7 min. Finally, HMF and 5,5'-oxybis(5-methylene-2-furaldehyde) (OBMF) were the only byproducts identified under the reaction conditions studied.

CO2 Adsorption on the N- and P-Modified Mesoporous Silicas.

SBA-15 and MCM-48 mesoporous silicas were modified with functionalized (3-aminopropyl)triethoxysilane (APTES) by using the post-synthesis method, thus introducing N- and P-containing groups to the pore surface. The structure of the newly synthesized modifiers (aldimine and aminophosphonate derivatives of (3-aminopropyl)triethoxysilane and their grafting onto the porous matrix were proved by applying multinuclear NMR and FTIR spectroscopies. The content of the grafted functional groups was determined via thermogravimetric analysis. The physicochemical properties of the adsorbent samples were studied by nitrogen physisorption and UV-Vis spectroscopy. The adsorption capacity of CO2 was measured in a dynamic CO2 adsorption regime. The modified silicas displayed an enhanced adsorption capacity compared to the initial material. The 13C NMR spectra with high-power proton decoupling proved the presence of physically captured CO2. A value of 4.60 mmol/g was achieved for the MCM-48 material grafted with the Schiff base residues. The total CO2 desorption was achieved at 40 °C. A slight decrease of about 5% in CO2 adsorption capacities was registered for the modified silicas in three adsorption/desorption cycles, indicating their performance stability.

Comparative studies of carbon capture onto coal fly ash zeolites Na-X and Na-Ca-X.

The combustion of coal in Thermal Power Plants generates fine dust particles (coal fly ash, CFA), which are collected from the flue gas streams and deposited as solid wastes. One of the technologically reliable solutions for utilization of CFA is its alkaline conversion into zeolites. The present study focuses on the influence of calcium content in CFA on the chemical and phase composition, morphology and surface properties of coal fly ash zeolites. Comparative studies of the capacity of zeolites of Na-X and Na-Ca-X types from coal fly ash to capture carbon emissions under static and dynamic conditions have been performed. The present study answers a key question from a practical point of view, how does moisture in flue gases affect the adsorption of carbon dioxide on zeolites. The development of efficient adsorbents from CFA with varying composition will contribute to a number of environmental benefits and to the development of efficient CO2 capture technologies in the context of the circular economy.

CO2 Adsorption on Modified Mesoporous Silicas: The Role of the Adsorption Sites.

The post-synthesis procedure for cyclic amine (morpholine and 1-methylpiperazine) modified mesoporous MCM-48 and SBA-15 silicas was developed. The procedure for preparation of the modified mesoporous materials does not affect the structural characteristics of the initial mesoporous silicas strongly. The initial and modified materials were characterized by XRD, N2 physisorption, thermal analysis, and solid-state NMR. The CO2 adsorption of the obtained materials was tested under dynamic and equilibrium conditions. The NMR data revealed the formation of different CO2 adsorbed forms. The materials exhibited high CO2 absorption capacity lying above the benchmark value of 2 mmol/g and stretching out to the outstanding 4.4 mmol/g in the case of 1-methylpiperazin modified MCM-48. The materials are reusable, and their CO2 adsorption capacities are slightly lower in three adsorption/desorption cycles.

Progress in the Utilization of Coal Fly Ash by Conversion to Zeolites with Green Energy Applications.

Fly ash (FA) from lignite coal combusted in different Thermal Power Plants (TPPs) was used for the synthesis of zeolites (FAZs) of the Na-X type by alkaline activation via three laboratory procedures. FAZs were characterized with respect to their morphology, phase composition and surface properties, which predetermine their suitability for applications as catalysts and adsorbents. FAZs were subsequently modified with metal oxides (CuO) to improve their catalytic properties. The catalytic activity of non-modified and CuO-modified FAZs in the total oxidation of volatile organic compounds was investigated. FAZs were studied for their potential to retain CO2, as their favorable surface characteristics and the presence of iron oxides make them suitable for carbon capture technologies. Thin films of FAZs were deposited by in situ crystallization, and investigated for their morphology and optical sensitivity when exposed to pollutants in the gas phase, e.g., acetone. This study contributes to the development of novel technological solutions for the smart and valuable utilization of FA in the context of the circular economy and green energy production.

Studies on non-modified and copper-modified coal ash zeolites as heterogeneous catalysts for VOCs oxidation.

The present study is aimed at investigations on the catalytic activity for total oxidation of volatile organic compounds (VOCs), such as toluene, acetone, n-hexane and dichlorobenzene onto zeolite-like materials synthesized from coal fly ash (FA) directed to development of an economically efficient approach for degradation of VOCs. Fly ash zeolites (FAZ) were prepared by alkaline conversion of FA collected from Thermal Power Plants supplied with lignite coal from "Maritza-East" basin in Bulgaria. Different synthesis procedures double stage fusion-hydrothermal activation, fusion-atmospheric crystallization and atmospheric aging were applied. The synthesis products were identified by X-ray diffraction, and were assigned to zeolite Na-X. Scanning electron microscopy images reveal submicron dimensions of the composing crystallites. Nitrogen adsorption/desorption measurements reveal a mixed micro-mesoporous structure and specific surface area between 116 and 396 m2/g for the obtained FAZ. Relationships between surface properties, iron content and the catalytic activity of FAZ were investigated and discussed. Copper-modified fly ash zeolites (Cu-FAZ) were prepared by incipient wetness impregnation technique with copper acetylacetonate. The loading of 5 wt. % copper on the zeolite samples was achieved. The catalytic activity of FAZ and Cu-FAZ in the total oxidation of model VOCs mixture containing n-hexane, acetone, toluene, 1,2 dichlorobenzene was evaluated.

Verapamil delivery systems on the basis of mesoporous ZSM-5/KIT-6 and ZSM-5/SBA-15 polymer nanocomposites as a potential tool to overcome MDR in cancer cells.

ZSM-5/KIT-6 and ZSM-5/SBA-15 nanoparticles were synthesized and further modified by a post-synthesis method with (CH2)3SO3H and (CH2)3NHCO(CH2)2COOH groups to optimize their drug loading and release kinetic profiles. The verapamil cargo drug was loaded by incipient wetness impregnation both on the parent and modified nanoporous supports. Nanocarriers were then coated with a three-layer polymeric shell composed of chitosan-k-carrageenan-chitosan with grafted polysulfobetaine chains. The parent and drug loaded formulations were characterized by powder XRD, N2 physisorption, thermal analysis, AFM, DLS, TEM, ATR-FT-IR and solid state NMR spectroscopies. Loading of verapamil on such nanoporous carriers and their subsequent polymer coating resulted in a prolonged in vitro release of the drug molecules. Quantum-chemical calculations were performed to investigate the strength of the interaction between the specific functional groups of the drug molecule and (CH2)3SO3H and CH2)3NHCO(CH2)2COOH groups of the drug carrier. Furthermore, the ability of the developed nanocomposites to positively modulate the intracellular internalization and thereby augment the antitumor activity of the p-gp substrate drug doxorubicin was investigated in a comparative manner vs. free drug in a panel of MDR positive (HL-60/Dox, HT-29) and MDR negative (HL-60) human cancer cell lines using the Chou-Talalay method.

Vapor-Phase Hydrogenation of Levulinic Acid to γ-Valerolactone Over Bi-Functional Ni/HZSM-5 Catalyst.

The hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) in vapor-phase is economically more viable route if compared to reaction in liquid-phase. To improve the GVL yield in the vapor-phase reaction, the optimization of nickel modified zeolite as bi-functional catalyst (Ni/HZSM-5) was studied. Ni/HZSM-5 materials with fixed Al/Si molar ratio of 0.04 and different nominal Ni/Si molar ratios (from 0.01 to 0.05) were synthesized without the use of organic template and with the most affordable sources of silica and alumina. Materials were characterized by X-ray powder diffraction, SEM-EDX, TEM-EDX, pyridine TPD and DRIFTS, H2-TPR, N2 physisorption and isoelectric point. In the synthesized materials, 61-83% of nickel is present as bulk NiO and increases with nickel content. Additionally, in all catalysts, a small fraction of Ni2+ which strongly interacts with the zeolite support was detected (10-18%), as well as Ni2+ acting as charge compensating cations for Brønsted acid sites (7-21%). Increasing the nickel content in the catalysts leads to a progressive decrease of Brønsted acid sites (BAS) and concomitant increase of Lewis acid sites (LAS). When BAS/LAS is approaching to 1 and at the same time the amount of NiO reducible active sites is around 80%, the bi-functional Ni/HZSM-5-3 catalyst (Ni/Al = 0.59) leads to 99% conversion of LA and 100% selectivity to GVL at 320°C. This catalyst also shows stable levulinic acid hydrogenation to GVL in 3 reaction cycles conducted at 320°C. The concerted action of the following active sites in the catalyst is a key element for its optimized performance: (1) Ni metallic active sites with hydrogenation effect, (2) Lewis acid sites with dehydration effect, and (3) nickel aluminate sites with synergetic and stabilizing effects of all active sites in the catalyst.