The two first surface elementary steps of a gas/solid catalytic reaction are the adsorption/desorption at least one of the reactants leading to its adsorption equilibrium which can be or not disturbed by the others surface elementary steps leading to the products. The variety of the sites of a conventional catalyst may lead to the formation of different coadsorbed species such as linear, bridged and threefold coordinated species for the adsorption of CO on supported metal particles. The aim of the present article is to summarize works performed in the last twenty years for the development and applications of an analytical method named Adsorption Equilibrium InfraRed spectroscopy (AEIR) for the measurement of the individual heats of adsorption of coadsorbed species and for the validation of mathematical expressions for their adsorption coefficients and adsorption models. The method uses the evolution of the IR bands characteristic of each of coadsorbed species during the increase in the adsorption temperature in isobaric conditions. The presentation shows that the versatility of AEIR leads to net advantages as compared to others conventional methods particularly in the context of the microkinetic approach of catalytic reactions. Full article

The catalytic upgrading of bio-based platform molecules is a promising approach for biomass valorization. However, most solid catalysts are not thermally or chemically stable, and are difficult to prepare. In this study, a stable organic phosphonate–hafnium solid catalyst (PPOA–Hf) was synthesized, and acid–base bifunctional sites were found to play a cooperative role in the cascade transfer hydrogenation and cyclization of ethyl levulinate (EL) to γ-valerolactone (GVL). Under relatively mild reaction conditions of 160 °C for 6 h, EL was completely converted to GVL with a good yield of 85%. The apparent activation energy was calculated to be 53 kJ/mol, which was lower than other solid catalysts for the same reaction. In addition, the PPOA-Hf solid catalyst did not significantly decrease its activity after five recycles, and no evident leaching of Hf was observed, indicating its high stability and potential practical application. Full article

Beyond tailored and synthetic catalysts sought out for ozone decomposition, mineral dusts provide naturally mixed metal oxide materials. The steady-state uptake of O₃ evidenced across a wide concentration range signifies the catalytic decomposition of O₃. The geocatalytic properties of such natural mineral dust open up new perspectives in atmospheric chemistry and catalytic processes. Full article

The most recent progress obtained through the precise use of enabling technologies, namely microwave, ultrasound, and mechanochemistry, described in the literature for obtaining improved performance catalysts (and photocatalysts) for CO₂ hydrogenation, are reviewed. In particular, the main advantages (and drawbacks) found in using the proposed methodologies will be discussed and compared by focusing on catalyst design and optimization of clean and efficient (green) synthetic processes. The role of microwaves as a possible activation tool used to improve the reaction yield will also be considered. Full article

The present work describes the study of micro (H-ZSM-5) and mesoporous (AL-MCM-41) structures, aiming at their application in the production of renewable fuels through the thermos-catalytic pyrolysis process both were synthesized hydrothermally and characterized by X-ray diffraction, thermal analysis, infrared spectroscopy, nitrogen adsorption, and surface acidity. The catalytic effect of the materials mentioned, as well as their mechanical mixtures in the proportions of H-ZSM-5 (75% wt) and AL-MCM-41 (25% wt); H-ZSM-5 (50% wt) and AL-MCM-41 (50% wt); H-ZSM-5 (25% wt) and AL-MCM-41 (75% wt) were used in the thermal and thermo-catalytic pyrolysis of sunflower oil. The products obtained in the presence of H-ZSM-5 (25% wt) and AL-MCM-41(75% wt) showed selectivity for the conversion of hydrocarbons between C11 and C16, which is near that of the petroleum-derived kerosene and diesel (>C16). On the other hand, the H-ZSM-5 (75% wt) and AL-MCM-41 (25% wt) material, in which the majoritarian catalyst is the microporous, with active sites and a higher surface acidity, indicates selectivity for light hydrocarbons (C5-C10), in the range of gasoline obtained by the conversion of mineral oil. The presence of catalysts (AL-MCM-41and H-ZSM-5) favors the deoxygenation of the pyrolysis products of sunflower oil by decarbonylation reaction. Full article

In this work, the influence of the structure-forming agent on the composition, morphology and oxygen reduction reaction (ORR) activity of Fe-N-C catalysts was investigated. As structure-forming agents (SFAs), dicyandiamide (DCDA) (nitrogen source) or oxalic acid (oxygen source) or mixtures thereof were used. For characterization, cyclic voltammetry and rotating disc electrode (RDE) experiments were performed in 0.1 M H₂SO₄. In addition to this, N₂ sorption measurements and Raman spectroscopy were performed for the structural, and elemental analysis for chemical characterization. The role of metal, nitrogen and carbon sources within the synthesis of Fe-N-C catalysts has been pointed out before. Here, we show that the optimum in terms of ORR activity is achieved if both N- and O-containing SFAs are used in almost similar fractions. All catalysts display a redox couple, where its position depends on the fractions of SFAs. The SFA has also a strong impact on the morphology: Catalysts that were prepared with a larger fraction of N-containing SFA revealed a higher order in graphitization, indicated by bands in the 2nd order range of the Raman spectra. Nevertheless, the optimum in terms of ORR activity is obtained for the catalyst with highest D/G band ratio. Therefore, the results indicate that the presence of an additional oxygen-containing SFA is beneficial within the preparation. Full article

The catalyst preparation technique plays a significant role in its activity and durability. The present research investigated sodium hydroxide and sodium chloride as the precursor chemicals for impregnation on waste oyster shells that were tested as heterogeneous base catalysts for transesterification of soybean oil. Effects of precursor concentration and calcination temperature on the surface structure and the activity of the catalysts were studied via the one-factor-at-a-time method. The optimal impregnation concentrations of sodium hydroxide and sodium chloride were determined to be 6 mol/L and 2.43 mol/L, respectively. The optimal calcination temperature was determined to be 800 °C for both sodium hydroxide and sodium chloride-impregnated catalysts. Analyses of the catalysts via X-ray Diffraction and X-ray photoelectron spectroscopy indicated that different active species were formed on the surface depending on the calcination temperature. Results obtained from this study could be used to fine-tune the procedure for the synthesis of transesterification catalysts from aquatic animal shells. Full article

An electron-conducting mixed oxide, Co-Pt bronze was synthesized and examined as a candidate for a highly durable electrocatalyst for both the polymer electrolyte fuel cells and electrolyzers. The motivation of this study comes from the fact that this material has not been studied as an electrocatalyst in acidic media, although past studies showed a high electronic conductivity and a high corrosion resistance. Co-Pt bronze without metallic Pt was obtained by solid-state synthesis and hot aqua regia rinsing. The OER activity was found to be among the highest as a material without Ir and Ru in acidic media, and it showed extremely high electrochemical stability in the OER potential range. Its oxygen reduction reaction (ORR) was obtained after potential cycles down to the hydrogen region, which formed a thin Pt metallic layer over the oxide. While its specific activity was not more than that of pure platinum nanoparticles, its durability against the potential cycles was much higher. Full article

Chemical looping reforming (CLR) technique is a prospective option for hydrogen production. Improving oxygen mobility and sintering resistance are still the main challenges of the development of high-performance oxygen carriers (OCs) in the CLR process. This paper explores the performance of Ni/CeO₂ nanorod (NR) as an OC in CLR of ethanol. Various characterization methods such as N₂ adsorption-desorption, X-ray diffraction (XRD), Raman spectra, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (TPR), and H₂ chemisorption were utilized to study the properties of fresh OCs. The characterization results show the Ni/CeO₂-NR possesses high Ni dispersion, abundant oxygen vacancies, and strong metal-support interaction. The performance of prepared OCs was tested in a packed-bed reactor. H₂ selectivity of 80% was achieved by Ni/CeO₂-NR in 10-cycle stability test. The small particle size and abundant oxygen vacancies contributed to the water gas shift reaction, improving the catalytic activity. The covered interfacial Ni atoms closely anchored on the underlying surface oxygen vacancies on the (111) facets of CeO₂-NR, enhancing the anti-sintering capability. Moreover, the strong oxygen mobility of CeO₂-NR also effectively eliminated surface coke on the Ni particle surface. Full article

This study describes the decomposition of CO₂ using Dielectric Barrier Discharge (DBD) plasma technology combined with the packing materials. A self-cooling coaxial cylinder DBD reactor that packed ZrO₂ pellets or glass beads with a grain size of 1–2 mm was designed to decompose CO₂. The control of the temperature of the reactor was achieved via passing the condensate water through the shell of the DBD reactor. Key factors, for instance discharge length, packing materials, beads size and discharge power, were investigated to evaluate the efficiency of CO₂ decomposition. The results indicated that packing materials exhibited a prominent effect on CO₂ decomposition, especially in the presence of ZrO₂ pellets. Most encouragingly, a maximum decomposition rate of 49.1% (2-mm particle sizes) and 52.1% (1-mm particle sizes) was obtained with packing ZrO₂ pellets and a 32.3% (2-mm particle sizes) and a 33.5% (1-mm particle sizes) decomposing rate with packing glass beads. In the meantime, CO selectivity was up to 95%. Furthermore, the energy efficiency was increased from 3.3%–7% before and after packing ZrO₂ pellets into the DBD reactor. It was concluded that the packing ZrO₂ simultaneously increases the key values, decomposition rate and energy efficiency, by a factor of two, which makes it very promising. The improved decomposition rate and energy efficiency can be attributed mainly to the stronger electric field and electron energy and the lower reaction temperature. Full article

Conventional methanol synthesis process (CR configuration) consists of water-cooled and gas-cooled reactors in which methanol and water are condensed inside the gas-cooled reactor which deactivates the catalyst. In this study, two novel configurations (AW and ACW configurations) are represented to address this problem in which the gas-cooled reactor is replaced with adiabatic reactor. Moreover, a condenser is applied between adiabatic and water-cooled reactors in ACW configuration. Results show that temperature increases somewhat along the adiabatic reactor that prevents gas condensate formation. Besides, the adiabatic reactor maximum temperature is less than that of first reactor in CR configuration which prevents copper based catalyst thermal sintering. Moreover, a high cross section-to-length ratio of the adiabatic reactor leads to negligible pressure drop along the reactor and improvement in CO₂ conversion to methanol that has positive environmental effects. Also, water mole fraction decreases along the reactors of AW and ACW configurations to prevent the deactivation of catalyst active sites. Eventually, methanol production rates by AW and ACW configurations are improved around 25.5% and 43.1% in comparison with CR configuration. So, novel AW and ACW configurations provide many benefits including improvement in catalyst activity and durability, CO₂ conversion, and the methanol production rate. Full article

Chiral amines are important components of 40–45% of small molecule pharmaceuticals and many other industrially important fine chemicals and agrochemicals. Recent advances in synthetic applications of ω-transaminases for the production of chiral amines are reviewed herein. Although a new pool of potential ω-transaminases is being continuously screened and characterized from various microbial strains, their industrial application is limited by factors such as disfavored reaction equilibrium, poor substrate scope, and product inhibition. We present a closer look at recent developments in overcoming these challenges by various reaction engineering approaches. Furthermore, protein engineering techniques, which play a crucial role in improving the substrate scope of these biocatalysts and their operational stability, are also presented. Last, the incorporation of ω-transaminases in multi-enzymatic cascades, which significantly improves their synthetic applicability in the synthesis of complex chemical compounds, is detailed. This analysis of recent advances shows that ω-transaminases will continue to provide an efficient alternative to conventional catalysis for the synthesis of enantiomerically pure amines. Full article