How to Valorize Peanut Shells by a Simple Thermal-Catalytic Method

Topics in Catalysis - In this work, a simple thermal-catalytic system was used to valorize peanut shells (Arachis hypogaea), the residual biomass from the peanut industry. To accomplish this...     

Synthesis and Characterization of Al-MCM-41 and Al-MCM-48 Mesoporous Materials

A novel route in the synthesis of Al-MCM-41 and Al-MCM-48, using tetraethoxysilane (TEOS) and sodium aluminate (NaAlO₂) as Si and Al source has been obtained. The effect of surfactant nature and the synthesis conditions such as surfactant/Si ratio and hydrothermal treatment time on the formed mesostructure regularity has been studied. Different methods of template removal have also been evaluated. The samples were characterized by X-ray diffraction, nitrogen physisorption, FT-IR, and solid-state MAS NMR spectroscopy.     

Dodecatungstocobaltate supported over ZSM-5 zeolite as novel solid catalyst in selective sulfide oxidation

The catalytic behavior of a Keggin type potassium dodecatungstocobaltate (II) salt supported on ZSM-5 zeolite for wet peroxide oxidation of 2-(methylthio)benzothiazole, as a model organic sulfide, was thoroughly studied. Microporous ZSM-5 zeolite was obtained by the hydrothermal crystallization method. The Keggin salt was incorporated in the MFI zeolite matrix by the wet impregnation method followed by calcination at 350 °C. Catalysts were further characterized by X ray diffraction, UV–Vis diffuse reflectance spectroscopy and scanning electron microscopy-EDAX techniques. Supported and bulk Keggin dodecatungstocobaltate (II) were compared with pure H-ZSM-5 zeolite as catalysts for the sulfide oxidation. When the reaction was not catalyzed, just a 9 mol% of sulfide conversion was obtained. Reaction parameters, such as nature of the solvent, hydrogen peroxide concentration, reaction time, catalyst mass, substrate initial concentration and reaction temperature, were evaluated to reach the optimum reaction conditions, considering substrate conversion and sulfoxide and sulfone selectivities. Catalyst stability in several oxidation cycles was also examined.     

Studies on the synthesis of diacetyl over oxidation zeolite catalysts

Diacetyl (2,3-butanedione) synthesis from methyl ethyl ketone over oxidation zeolites using O₂ as oxidant was studied. Various zeolites with Fe, V and Ti as active sites were employed. VS-1, Ti-NCL, Ti-MCM-41 and FeBEA type materials were synthesized and characterized by BET, FTIR, XRD, pyridine adsorption and template desorption. The detailed study of the effect of reaction temperature, the effect of concentration of oxygen and the addition of water was realized. The most active catalyst was zeolites with V as oxidation center.     

Nature of the active sites in H-ZSM-11 zeolite modified with Zn(2+) and Ga(3+)

H-ZSM-11 zeolite modified with zinc and gallium by ion exchange was investigated using XRD, IR and TPD of ammonia. The modification of the material by zinc produced a lowering of the strong Brønsted acidic sites generating new and strong Lewis sites. Unlike zinc-zeolites, the gallium is localized preferentially on the outer surface of microcrystallites blocking a few Brønsted centers.     

Methane transformation into aromatic hydrocarbons by activation with LPG over Zn‐ZSM‐11 zeolite

Methane (C₁) can be activated by interaction with liquefied petroleum gas (LPG) even at very high C₁ molar fractions in the feed (C₁/(C₁ + LPG)=0.85) at temperatures of 450–550°C, GHSV(LPG)=2240 and 810 ml/g h, over Zn‐ZSM‐11 (molar fraction Zn²⁺/(Zn²⁺H⁺=0.86) and total pressure of 1 atm. The isobutane (i‐C₄) of LPG could be the main responsible of this interaction. Aromatic hydrocarbons were the main products in the whole range of C₁ molar fractions (0.4–0.85) studied, reaching excellent levels of 10–45%. This revised version was published online in July 2006 with corrections to the Cover Date.     

In-containing H-ZSM5 zeolites with various Si/Al ratios for the NO SCR in the presence of CH4 and O2. PAC, TPAD and FTIR studies

A series of In-loaded ZSM5 catalysts with Si/Al ratios of 17, 27 and 50 was studied. The catalytic activity for the NO reduction followed the 27 > 17 = 50 order. The acid properties were investigated by FTIR of pyridine as probe molecule desorbed in vacuum at different temperatures and by Temperature-Programmed Ammonium Desorption (TPAD) of NH₄–In–ZSM5. The nature of the In-species was determined by the Perturbed Angular Correlation (PAC) technique using ¹¹¹In as a probe. The contribution of indium to the acidity nature of the samples seems to be important taking into account that the number of Brönsted acid sites was reduced after the In exchange. In the same way new and strong electron-donor acceptor sites were generated. The PAC results indicate that there exists an important fraction of the indium present in the active sample coordinated as in the In₂O₃ case, while another one corresponding to a non-well defined near-In-neighborhood, is present too in a small fraction.     

Transalkylation of naphthalene with mesitylene over H-ZSM-11 zeolite

The transalkylation reaction between mesitylene and naphthalene has been studied over pentasil zeolites, type H-ZSM-11. The main product was 2-methylnaphthalene. The influence of external and total surface area of the catalysts on catalytic activity and selectivity was investigated. From these observations, it was found that the external surface of zeolites played a key role in the synthesis of 2-methylnaphthalene. This revised version was published online in July 2006 with corrections to the Cover Date.     

Zn-ZSM-11 zeolite catalyst for LPG aromatization

LPG transformation into aromatic hydrocarbons using Zn²⁺ modified pentasil zeolites has been studied at 450–540 °C and 10–58 g h/mol. The conversion and selectivity to aromatics obtained over Zn-H-ZSM-11 catalysts with different degree of exchange suggest, the primary role of the Zn²⁺ species is in C-H activation and the transformation of the intermediates into aromatic hydrocarbons.     

Catalytic conversion of natural gas with added ethane and LPG over Zn-ZSM-11

The higher hydrocarbons (C2+) from natural gas (NG), such as ethane (C2), propane (C3) and butane (C4) reached excellent levels of conversion over Zn-ZSM-11 at temperatures between 550–640°C and 1 atm total pressure, but the methane (C1) present in NG could not be converted. The C1 transformation by activation with co-reactants such as C2 and liquefied petroleum gas (LPG), over Zn-ZSM-11 was studied. The addition of amounts of C2 to a feed of commercial NG allowed to activate the C1 reaching excellent values of conversion and yield to aromatic hydrocarbons (AH). The high Lewis/Bronsted sites ratio of Zn-ZSM-11 catalyst determined by pyridine desorption at different temperatures followed by FT-IR spectroscopy, allowed us to suggest that electron-donor–acceptor complex, formed between C2+ species and unoccupied molecular orbital of the zinc species present in the catalyst, favored the interaction of C2+ through carbenium intermediate to activate methane.