Safia Hamoudi

Sulfonic acid-functionalized periodic mesoporous organosilica

A series of periodic mesoporous organosilicas (PMOs) containing different amounts of sulfonic acid bearing groups were synthesized using bis(trimethoxysilyl)ethane (BTME) and mercaptopropyltrimethoxysilane (MPTMS) as framework precursors under basic conditions in the presence of cetyltrimethylammonium chloride (CTAC) surfactant. Conversion of the mercaptopropyl groups into sulfonic acid moieties was achieved via oxidation using hydrogen peroxide. Ordered cubic-like mesostructures with high surface areas (up to 950 m2/g) and narrow pore size distributions (up to 3.50 nm) were obtained. The structural ordering was shown to be retained after oxidation. The effect of the amount of mercaptopropylsilane incorporated in the synthesis gels on the structural properties, morphology, thermal behavior as well as the acidity of the synthesized materials was examined.

Catalytic oxidation of aqueous phenolic solutions catalyst deactivation and kinetics

Abstract The catalytic oxidation of aqueous phenol over MnO 2 /CeO 2 mixed oxide catalyst was shown to be accompanied with undesirable formation of heavy polymers on the catalyst surface leading thereby to its deactivation. This deactivation was proved experimentally through comprehensive quantitative and qualitative experimental measurements such as elemental analysis of deactivated cata-lyst, X-ray photoelectron spectroscopy, and temperature-programmed oxidation coupled with mass spectrometry. Using the Langmuir–Hinshelwood–Hougen–Watson approach, a deactivation-reaction network kinetic model was developed to predict the fate of the various carbon lumps involved in phenol wet oxidation. It was postulated that deactivation was the resultant of blockage of active sites by fouling species issued from polymerization of parent reactant (phenol) and its daughter intermediate dissolved partially oxidized products. The kinetic model was verified by comparing the experimental results with those foreseen in the simulation for different experimental conditions.

Periodic mesoporous organosilica from micellar oligomer template solutionElectronic supplementary information (ESI): available: TG/DTG data. See http://www.rsc.org/suppdata/cc/b2/b207134g/

Periodic mesoporous organosilica (PMO) with two-dimensional hexagonal symmetry was synthesised using a bridged silsesquioxane (CH3O)3Si-CH2-CH2-Si(CH3O)3 as precursor and polyoxyethylene non-ionic surfactant (Brij-56) as template. The hybrid material was characterised by X-ray diffraction, N2 adsorption, TEM, and solid-state 29Si MAS NMR spectroscopy.

Adsorptive removal of dihydrogenphosphate ion from aqueous solutions using mono, di- and tri-ammonium-functionalized SBA-15

Adsorption of monovalent phosphate anions from aqueous solutions on mono, di- and tri-ammonium-functionalized mesoporous SBA-15 silica was investigated. The adsorbent was prepared via a post-synthesis grafting method, using 3-aminopropyltrimethoxysilane (N-silane), [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane (NN-silane) and 1-[3-(trimethoxysilyl)-propyl]-diethylenetriamine (NNN-silane), followed by acidification in HCl solution to convert the attached surface amino groups to positively charged ammonium moieties. The loading of amino moieties on the SBA-15 surface was varied from 5% to 40% as organoalkoxysilane/silica molar ratio. The adsorption experiments were conducted batchwise at room temperature. Results showed that adsorption capacity increased with increasing the concentration of functional groups on the SBA-15 adsorbent whatever the nature of the functional group. In the case of monoammonium functional groups, the adsorption capacity increased from 0.64 to 1.07 mmol H(2)PO(4)(-)/g when the molar ratio organoalkoxysilane/silica was varied from 5% to 40%, respectively. Similar tendency was observed in the case of diammonium and triammonium organic functional groups. Also, for the same organoalkoxysilane/silica molar ratio, the adsorption capacity increased markedly with the increase of the number of protonated amines in the functional groups. Therefore, maximum adsorption capacities of 1.07, 1.70 and 2.46 mmol H(2)PO(4)(-)/g adsorbent were obtained using mono-, di- and tri-ammonium-functionalized SBA-15, respectively.

Catalytic oxidation of 4-chloroguaiacol reaction kinetics and catalytic studies

Abstract This paper describes the non-catalytic oxidation and the solid-catalysed oxidation of a chlorinated organo-compound contained in softwood pulp mill effluents. The oxidation of 4-chloroguaiacol was catalysed efficiently using Pt/alumina, manganese/cerium and cobalt/bismuth composite oxide catalysts. Self-inhibition of the parent pollutant, recalcitrance of highly stable organic by-products, and catalyst deactivation were the main causes that prevented full mineralization of the waste-water organic load. A comprehensive homogeneous–heterogeneous deactivation reaction network model was used to account for the distribution of carbon in the liquid, in the gas and on the solid phases. The model combined a two-parallel reaction scheme for the non-catalytic oxidation and a Langmuir–Hinshelwood approach for the catalyst-mediated oxidation.

Cubic Mesoporous Silica with Tailored Large Pores

MCM-48 silica was synthesized using GEMINI surfactant and its pore size was enlarged via a post-synthesis procedure in the presence of dimethyldecylamine (DMDA) as swelling agent. The effects of the amount of DMDA as well as the post-synthesis temperature on the pore size of the MCM-48 material were investigated. It was found that pore sizes up to 11.2 nm could be obtained. Generally, the pore size distributions were reasonably narrow and the pore volumes quite high (up to 2.6 cm3/g). The present work demonstrated the possibility to tailor the pore sizes of the MCM-48 silica.

Value-Added Processing of Lactose: Preparation of Bioactive Lactobionic Acid Using a Novel Catalytic Method

The microaerial oxidation of an aqueous solution of lactose to lactonionic acid (LBA) over the heterogeneous bimetallic catalyst Bi-Pd supported on mesoporous SBA-15 material was carried out in an agitated semi-batch reactor in alkaline medium within the pH range of 7 to 9.The present work focused on the synthesis and characterization of the bimetallic catalyst as well as optimization of the reaction operating conditions. To this purpose, the effect of both active metals loading on the support, metal/lactose ratio, reaction pH and dissolved oxygen concentration on the oxidation performances was examined at a very mild temperature of 65 oC.The bimetallic catalyst 1.02%Pd, 0.64%Bi/SBA-15, (Bi/Pd molar ratio of 0.3) showed the highest activity (96 % lactose conversion) and 100 % selectivity towards the targeted LBA product. Furthermore, the formulated catalyst proved to be stable in the reaction medium as both metals leaching was insignificant. Based on XRD and XPS analyses, it is suggested that the metals constituting the bimetallic catalyst active sites assemble into an intermetallic alloy having Bi1.75Pd stoichiometry.

Synthesis and Characterization of Titanium-Substituted Large Pore SSZ-42 Zeolite

Titanium-substituted large pore SSZ-42 zeolite was synthesized for the first time using the corresponding borosilicate as starting material. Substitution of boron by titanium took place via either high temperature treatment with TiCl4 vapor or by treatment with Ti(OiPr)4 in dry toluene at 120°C. Both deboronated and boron-containing samples were found to be suitable for post-synthesis incorporation of titanium in the zeolite framework. The obtained materials were characterized by FTIR, UV-visible and XPS. Titanium-modified SSZ-42 was found to be active for phenol hydroxylation and cyclohexene epoxidation.

Sulfur Promotion in Conjugated Isomerization of Safflower Oil over Bifunctional Structured Rh/SBA‐15 Catalysts

The sulfur effect on conjugated linoleic acid isomer (CLA) formation during the combined hydrogenation/directed isomerization of safflower oil over a bifunctional (hydrogenation and isomerization) highly structured rhodium‐based catalyst (Rh/SBA‐15) was investigated either by direct addition of increased concentrations of 3‐mercapto‐1,2‐propanediol to the reaction medium or by doping Rh/SBA‐15 with the same sulfur‐based compound yielding the sulfur‐doped Rh‐catalyst (S–Rh/SBA‐15). These catalysts exhibited interesting activity, stability, and recyclability.

Investigation of Ammonium Ion Removal from Aqueous Solutions Using Arene- and Propylsulfonic Acid Functionalized Mesoporous Silica Adsorbents

To counter environmental threats to the water resources polluted by NH, which is common in wastewaters and agricultural runoff, adsorption using mesoporous functional materials represents a promising alternative to existing treatment methods. In this study, adsorption of NH ions from aqueous solutions was investigated on arene- and propylsulfonic acid functionalized SBA-15 mesoporous silica materials. The adsorbents were synthesized via co-condensation and post-synthesis grafting procedures. Adsorbents were characterized by means of X-ray diffraction, N physisorption, titration, and elemental analyses. The effects of pH, NH initial concentration, temperature, adsorbent loading, organosilane molar ratio, and presence of competitive species on the performance of the adsorbent materials were examined. All the adsorbents having an organosilane/silica molar ratio of 1:5 displayed maximum adsorption capacity around approximately 25 mg g NH at the lowest temperature investigated, 5°C. This capacity decreased with increasing temperature. For a given initial NH concentration, the removal efficiency () increased with increasing adsorbent loading. For instance, increased from 24 to 59% when the adsorbent loading was increased from 2 to 10 g L at 25°C. The adsorption isotherms were well described by a Langmuir model equation. Adsorption capacity improved with increasing organosilane/silica molar ratio, reaching 42 mg g NH with a ratio of 2:5 at 25°C. Arene- and propylsulfonic acid functionalized SBA-15 materials synthesized via co-condensation and post-synthesis grafting proved to be effective high-capacity adsorbents for the removal of NH ions from aqueous solutions.