The selective dehydration of isobutanol to linear butenes catalyzed by acidic ferrierite (H-FER) has been investigated by operando IR spectroscopy under close batch conditions and along a temperature ramp. The employed apparatus permits to alternatively acquire spectra of both the gas phase composition and the species adsorbed on the H-FER surface, thus providing fundamental insights onto the products formation and the reaction intermediates formed on the catalyst surface. In the gas phase, the high selectivity for linear butenes was confirmed in the first phases of the reaction, followed by a slower isomerization to isobutene and by the formation of heavier compounds due to secondary processes. Detailed MCR-ALS analysis of the adsorbed species’ spectra permitted to also identify and quantify adsorbed 2-butanol and trans-2-butene on the H-FER surface, providing a first indication of the alcohol isomerization as a key step in the reaction mechanism. The proposed mechanism was evaluated by microkinetic modelling of both gas phase and surface concentration profiles, showing that the consecutive isomerization of isobutanol to adsorbed 2-butanol followed by its dehydration to trans-2-butene is more favorable than the one-step dehydration-isomerization of isobutanol. In contrast, the direct dehydration of isobutanol to isobutene was found to be slower over the entire investigated temperature range.

The selective removal of oxygenates like phenol is a key challenge in upgrading biofuels. This study evaluates the adsorption performance and selectivity of zeolites (HY2.9, USY22, and USY40) and oxides (Al2O3, SBA-15) for phenol in the presence of fuel representative co-molecules (toluene, cyclohexane, and 2,3-dimethyl-2-butene) using batch experiments and, notably, operando ATR-IR spectroscopy. Batch adsorption capacities followed the order SBA-15 > HY2.9 > USY40 approximate to USY22 > Al2O3. Performance depends on a combination of factors such as specific surface area, pore size and pore density, as well as the density and nature of the acid sites. While cyclohexane had negligible impact, toluene and dimethylbutene induced competitive adsorption or site poisoning, with effects being nearly cumulative in complex mixtures. ATR-IR measurements not only corroborated batch trends but also provided molecular-level insights, demonstrating its relevance as a rapid, operando screening tool to assess adsorption mechanisms, selectivity, and regeneration potential with minimal material consumption. The findings highlight the advantage of weakly acidic or non-acidic adsorbents in complex mixtures and underscore the utility of ATR-IR for efficient adsorbent evaluation.

To address environmental pollution, the chemical industry is continually refining its standards. In the United States and Europe, regulations stipulate that the sulfur content in diesel fuel must not exceed 15 ppm. This stringent requirement has driven continuous research into advanced fuel upgrading techniques. One such promising method is oxidative desulfurization (ODS), which removes sulfur compounds by converting them into sulfones, thereby improving their extractability into other phases. This mini-review aims to provide a qualitative analysis of the fundamental principles of ODS. It examines the roles of various oxidizing agents, extraction solvents, and heterogeneous catalysts, highlighting their respective advantages and limitations. Furthermore, the review elucidates the integrated reaction-extraction approach and explores emerging technologies and challenges associated with biodiesel upgrading in the context of biofuels. A quantitative section synthesizes representative results to provide a comprehensive overview. In conclusion, this paper underscores the importance of understanding both the benefits and limitations of ODS and emphasizes the necessity for ongoing research in the field of biodiesel production.

The complexity of composition of bio-oil from biomass makes it difficult to produce upgraded bio-oil via hydrodeoxygenation. In this paper, acetone is thus considered as a model compound of the ketones family abundant in pyrolysis bio-oil. Results showed that high conversion rates of acetone between 86.6% and 91.9% were observed with the use of HZSM-5, 5% Ni2P/HZSM-5, and 10% Ni2P/HZSM-5 catalysts. In most cases, CO2, C2H6, C3H6, and C3H8 were the dominant non-condensable gas products. For liquid phase, the selectivity was evaluated for different catalysts relative to ethanol, acetaldehyde, and aromatic hydrocarbons. A lower temperature favoured the formation of acetaldehyde and methyl isobutyl ketone with the 5% Ni2P/HZSM-5 catalyst, while higher temperatures increased the proportion of aromatic hydrocarbons. The principal influencing parameters of acetone HDO were temperature and contact time followed by reaction pressure and H-2 partial pressure. Optimal conditions give a selectivity of 49% of aromatics (benzene, toluene, and xylene) with the use of the 5% Ni2P/HZSM-5 catalyst. The pathway of the main reactions of acetone HDO was also proposed. MIK and aromatic hydrocarbons were formed by a multiple step aldol condensation reaction of acetone molecules followed by further hydrogenation.

In the present work, the liquid-solid interaction of liquid N-heteroaromatic compounds, commonly present in the petroleum feedstocks of the refineries, with Y zeolites used as hydrocracking catalysts was followed using IR-ATR spectroscopy. The inhibition of the zeolitic acid sites by strongly basic pyridine and weakly basic indole was highlighted using a continuous flow IR-ATR cell. Results were assessed by Density Functional Theory calculations to compute the vibrational frequencies of pyridine and indole according to the nature of the interaction sites: silanol groups or acidic OH groups. The study points out that IR-ATR spectroscopy opens the way for investigating the interaction modes of low vapor pressure molecules (e. g. indole) that present an inherent difficulty to be operated in the gas phase. Moreover, the IR-ATR makes possible the analysis of the little-explored low wavenumber zone (<800 cm(-1)), that presents informative vibrational modes on the adsorption mode of N-molecules. Hence, this work points out that for pyridine, the bands at 686 and 727 cm(-1) are characteristic of pyridinium species formed over zeolitic OH groups, meanwhile, the signals at 703 and 750 cm(-1), are associated to pyridine in interaction with silanol groups. The IR-ATR study reveals that indole, a weakly basic compound, can be protonated on acidic Y zeolites as unambiguously evidenced by the formation of the bands at 1617, 1608, 1543 and 705 cm(-1). Findings here exposed are crucial for studying inhibitory effects exerted by weak nitrogenated compounds on acidic materials during hydrocracking processes.

The purification of second-generation biofuels is becoming an urgent issue due to the toxicity of the combustion products of residual phenol in these biofuels. The use of solid sorbents such as zeolites appears as a promising solution for ensuring the selective sorption of phenol towards aromatics (the main components of biofuel). In the present work, we have adopted a bottom-up approach for removing phenol from a synthetic biofuel feed containing isooctane, phenol (1 wt%), n-nonane (1 wt.%) and toluene (40 wt.%), using faujasite-type Y zeolites with Si/Al ratio = 2.5. The astonishing performance of HY zeolite to treat the synthetic biofuel has been highlighted by assessing the interaction modes of the molecules involved over the structural sites via the combination of theoretical molecular modeling and experimental adsorption experiments.

This paper investigates the parameters that influence the selective adsorption of phenol, toxic molecule, from a semi-model biofuel mixture containing alkanes and different proportions of aromatic compounds. The adsorption capacity, selectivity and regeneration ability of different adsorbents, i.e. zeolites, silica-based solids, alumina and activated carbon, were related to their textural properties and the nature, strength or location of their acidic sites. This work demonstrates that phenol differently adsorbs in the micropores and mesopores. In the micropores of faujasites, phenol is condensed into the supercages. Otherwise, in the mesopores of the zeolite, phenol interacts with the silanol groups. On purely siliceous adsorbents, a ratio of one phenol adsorbed on one silanol group could be established. As for selectivity, the strong acidic sites of the faujasites are necessary to favor phenol adsorption compared to toluene. By contrast, the amount of strong Brønsted and Lewis acid sites limits regeneration. Hence, a compromise has to be found and the best performances were obtained using a slightly dealuminated zeolitic adsorbent presenting both micro and mesopores.

The precursor of all-silica COK-14 zeolite (OKO topology) with interrupted framework was subjected to wet ball milling in the presence of aluminum isopropoxide. Alumination and particle size reduction of the zeolite crystals was combined in this way. Wet ball milling resulted in fragmentation of the platelet-shape COK-14 crystals while preserving crystallinity. Al-27 NMR spectroscopy of the fully condensed COK-14 zeolite, obtained by calcination of milled -COK-14 precursor, confirmed the incorporation of tetrahedrally coordinated Al atoms in the framework. The creation of Bronsted acid sites was confirmed by pyridine adsorption. Loaded with platinum, the sample showed ideal bifunctional catalytic behavior in hydroisomerization and hydrocracking of n-decane model alkane compound. Aluminum incorporation by milling is an alternative to the atomic layer deposition (ALD) process using trimethylaluminum and to thermal alumination. Wet ball milling in presence of aluminum isopropoxide shows great potential for making siliceous zeolites catalytically active.

The purification of biofuels becomes a challenging issue because of the harmfulness of remaining phenolic molecules for human health and engines. To this end, protonic Y zeolites with different Si/Al ratios were explored as effective adsorbent materials to remove phenol from isooctane solution by using a dual experimental/computational strategy. Phenol was selectively removed from isooctane over HY and USY zeolites with a maximal adsorption capacity of 2.2 mmol.g(-1), which corresponds to 3-4 phenol molecules per zeolitic supercage. The adsorption equilibrium was reached faster over dealuminated zeolites, due to the presence of large pores at the expense of microporosity as well as a low density of acidic sites. We further evidence that the presence of acid sites limits the regeneration capacity since phenol was strongly adsorbed on both Bronsted and Lewis acid sites. USY zeolite with the highest Si/Al ratio presents the best regeneration capacity since it has the lower aluminum loading. A fundamental understanding of these performances was obtained by coupling characterization (infrared spectroscopy, breakthrough curves, and desorption experiments) and modeling tools (Grand Canonical Monte Carlo and Density Functional Theory).

Chemisorption of probe molecules such as hydrogen and carbon monoxide on the surface of Pt particles is the most common chemical technique used to estimate the crucial parameters of metal catalysts, namely the dispersion (D), the particle size (d), and the metallic specific surface area (S-pt). However, it remains a controversy concerning the stoichiometry of adsorbate per surface metal atom, leading to an inaccurate estimation of D, CO d, and S-pt. A model describing the statistics of the surface atoms and sites on perfect cuboctahedron clusters was developed to assess values of D, d, and S-pv assuming the most favorable adsorption sites based on density functional theory (DFT) calculation of the literature. This model successfully predicted the experimental values of D, d, and S-pt determined from H or CO chemisorption data, and it allowed providing a set of simple equations for the accurate determination of these parameters from chemisorption experiments on Pt.

A superior isomerization–hydrocracking catalyst was fabricated using atomic layer deposition of aluminium on a hierarchical ZSM-5 zeolite.

The impact of the textural properties of H-ZSM-5 zeolites in the conversion of ethanol to hydrocarbons at 623 K and under 3.0 MPa pressure is investigated. We highlight that the lifetime of the catalysts is not correlated to the coking rate but to the number of pore mouths. The addition of macropores (fluoride leaching) or mesopores (alkaline leaching) to micron-sized zeolites is a simple approach to increase the number of pore mouths and reduce the diffusion path length of molecules in the micropores. However, the most efficient way is to reduce the zeolite crystal size to nanometers. The longest catalyst lifetime (>100 h) is obtained with a hierarchical nanometer-sized zeolite even though most of its acid sites are poisoned. The important impact of the nature of coke on the catalysts regeneration is also highlighted. (C) 2015 Elsevier Inc. All rights reserved.

Catalysts based on tungsten oxide supported on silica and containing up to 2.5 W atoms nm(-2) were studied for the purpose of establishing quantitative relationships between the nature and abundance of surface species, acidity, and catalytic activity. Synthesis conditions that maximize the formation of amorphous WO3 were adopted to assess its influence on the overall acidity and activity. The results were compared to those of conventionally prepared catalysts. The catalysts' structure was characterized by FTIR, Raman, and UV spectroscopies. The acidity of the solids was monitored by adsorption of 2,6-dimethylpyridine followed by FTIR, and their catalytic activity was tested for the reaction of propan-2-ol dehydration. A methodology for quantitation of W species (WOx surface species, amorphous or crystalline WO3 particles) detected following calcination at 673 or 773 K was developed. For both calcination temperatures, surface W species were first formed with initial W addition. Their abundance increased with increasing content up to ca. 0.7 atom W nm(-2) and levels off for higher W surface densities. The leveling off was concomitant with the detection and rapid development of amorphous or crystalline WO3 phase (catalysts calcined respectively at 673 or 773 K). The comparison of W speciation in both series indicated that amorphous WO3 phase is quantitatively transformed to crystalline WO3 on increasing the calcination temperature from 673 to 773 K. The observed development of Bronsted acidity of the solids was associated with W deposition. The abundance of these acid sites correlated directly with the catalytic activity. The study of structure activity relationship showed that all W species were active. Modeling of the results permitted an estimation of the intrinsic activity of each W species. The values thus obtained suggest that amorphous WO3 particles exhibit the highest activity per surface W atom.

This study reports on the catalytic performance of nanosized zeolite X crystals and their precursors in the reaction of benzaldehyde with ethyl cyanoacetate. Crystal growth kinetics of FAU-type zeolite is studied at low temperature (35 degrees C) in order to discriminate different crystallization stages. First X-ray crystalline material is detected after 6 days of hydrothermal treatment. The formation of the crystalline phase is preceded by changes in the ring structure of an aluminosilicate precursor as revealed by the combined Raman-HEXRD-solid-state NMR analyses. The set of experimental data shows that these changes are related to the reorganization of the gel structure and the formation of zeolite units. Prior to the appearance of crystalline material, the apparently amorphous solid exhibits chemical composition and short-range order organization similar to that of a crystalline FAU-type zeolite. Knoevenagel condensation was used to test the catalytic activity of a series of zeolite intermediates and nanosized zeolite crystals. The amorphous precursor obtained after 5 days of hydrothermal treatment showed the highest yield of ethyl alpha-cyanocinnamate. Superior catalytic performance of this material was attributed to the combination of strong basic sites and less restricted and more accessible structure of the semicrystalline zeolite units. Thus, the crystal growth kinetics of FAU-type zeolite can be used as a tool to tune the properties of a catalyst used in Knoevenagel condensation.

Last site standing: A new generation of hierarchical Pt/H-ZSM-22 zeolites is designed for the efficient processing of upcoming renewable feedstocks. The enhanced accessibility of the active sites is vital for the superior activity and exceptional selectivity in the hydroisomerization of model molecules such as nonadecane and pristane.

Ring-opening reactions of decalin and methylcyclohexane (MCH) over bifunctional catalysts (1.2Ir/WO3/Al2O3) were investigated. A series of catalysts containing up to 5.3at. W/nm2 and 1.2wt.% Ir was prepared. The acidity of the solids was monitored by low-temperature CO adsorption followed by infrared spectroscopy. Characterization of the Ir metal phase was performed by H2 chemisorption and X-ray diffraction. The activity and product selectivity patterns obtained for the decalin ring-opening reaction were compared with those observed for MCH. For both naphthenes, ring contraction precedes ring opening, suggesting a similar ring-opening mechanism. Kinetic modeling based on the proposed reaction network allowed the determination of the activation energies and initial rates. Based on the yields and products distribution obtained for the decalin reaction, the potential for improvement of the cetane number is discussed.