Reactions Of Hydrocarbons Research Articles

DFT Studies of the Adsorption of Propane and Propene on Metallic Surfaces in Ag/ZrO2 Catalysts as a Model for Catalytic Combustion Reactions of Light Hydrocarbons

Molecular modelling studies were carried out at the DFT level of the adsorption of propane and propene on Ag surfaces as a model of the interaction of light hydrocarbons with Ag/ZrO2 catalysts for catalytic combustion reactions. It was found that the most stable mode of adsorption of propene through its π system on Ag atom has energies consistent with chemisorption and generates an elongation of the C1=C2 bond, which would explain the increase in the activity of the catalysts as a function of its metallic charge. The results obtained from the DFT calculations explain the different types of interactions between propene and propane with the metallic surface. The propene is chemisorbed on the Ag surface, distorting its bonds and generating its activation. This would imply that a higher metallic charge in the catalyst would increase the number of active sites in which this activation occurs, generating a higher activity. In addition, with the addition of O, the binding energy between the propene and the metal surface increased. On the other hand, the presence of a metallic surface is not enough for the activation of the propane molecule. This would explain why, by increasing the amount of metal in the catalyst, the activity for the combustion of propane is practically not affected.

Effect of Molecular Structure of C10 Hydrocarbons on Production of Light Olefins in Catalytic Cracking

The effect of the molecular structure of feedstock on the cracking reaction of C10 hydrocarbons to ethylene and propylene over H-ZSM-5 zeolite was investigated. To better compare the effect of decane on the production of light olefins, the thermal cracking and catalytic cracking performance of decane were first investigated. As a comparison, the thermal cracking and catalytic cracking of decane were studied by cracking over quartz sand and H-ZSM-5. Compared with the thermal cracking reaction over quartz sand, the catalytic cracking reaction of decane over H-ZSM-5 has a significantly higher conversion and light olefins selectivity, especially when the reaction temperature was lower than 600 °C. On this basis, the catalytic cracking reactions of decane and decene over H-ZSM-5 were further compared. It was found that decene with a double bond structure had high reactivity over H-ZSM-5 and was almost completely converted, and the product was mainly olefin. Compared with decane as feedstock, it has a lower methane yield and higher selectivity of light olefins. Therefore, decene was more suitable for the production of light olefins than decane. To this end, we designed a new light olefin production process. Through olefin cracking, the yield of light olefins in the product can be effectively improved, and the proportion of different light olefins such as ethylene, propylene and butene can be flexibly adjusted.

Effects of gold and platinum on the activity of catalysts for the complete oxidation reaction of hydrocarbons and carbon monoxide

This study presents synthesis results of catalysts made of perovskite-like oxide La2-xSrxCuO4 (x=0.0, 0.5, 1.0) using the citrate method and crystallisation at 800°C. The structure of the catalysts was characterised by X-ray diffraction (XRD). The perovskite-like oxide catalyst activity was enhanced with gold (Au) and platinum (Pt). Au was mounted on the perovskite-like oxide catalysts by the sol-gel method. The activity of the perovskite-like oxide La2-xSrxCuO4 (x=0.0, 0.5, 1.0) and the perovskite catalyst LaMnO3/LaCuO3 was evaluated by complete oxidation of volatile hydrocarbons (HCs) in a mixture of toluene and methyl ethyl ketone (MEK) and carbon monoxide (CO) in a microflow analysis system combined with gas chromatography. The results showed that the light-off temperature (the 50% conversion temperature of the catalysts) of the Pt, Au/perovskite catalyst samples decreased significantly. The light-off temperature of the Au/LaSrCuO4 Au nanoparticle catalysts in the complete CO oxidation reaction reached a temperature of 150°C, lower than the Pt/LaSrCuO4 catalyst (170°C), allowing replacement of previous Pt catalysts with Au nanoparticle catalysts. The LaSrCuO4 catalyst had better oxidising activities than the La2CuO4 catalyst, indicating that the addition of strontium (Sr) has increased the catalyst activity, and demonstrates the potential for application in catalytic converters in motorcycles.

Effect of molecular structure change on the properties of persistent free radicals during coal oxidation

This study is aimed at exploring the effect of molecular structure changes on the properties of persistent free radicals in coal during the heating process of coal spontaneous combustion (CSC). Therefore, the persistent free radicals and main functional groups variation characteristics in the process of coal oxidation were analyzed by means of in situ electron spin resonance and in situ infrared spectroscopy, and the change relationship between the molecular structure of coal and the persistent free radicals in coal during the reaction was further discussed by correlation analysis. The results showed that the concentration of persistent free radicals showed a stage change of “first decreasing, then increasing and then decreasing”. The g-factor decreases gradually and the heteroatom free radicals are consumed continuously. Dehydrogenation oxidation reaction causes the weakening of the “electron-proton” interaction, which narrows the line-width (ΔH) of free radicals. The phenolic hydroxyl as the electron donating group is converted into -CO functional group through dehydrogenation and oxidation reaction, which promotes the formation and accumulation of persistent free radicals in coal. Under the influence of phenolic hydroxyl, the relationship between the stretching vibration strength of aromatic ring CH and the properties of persistent free radicals in coal shows a similar change law with phenolic hydroxyl. In addition, the chain structure represented by –CH2-, –CH3/–CH2- is continuously consumed in the oxidative dehydrogenation reaction, triggering a series of free radical reactions. The free radicals formed in this process are affected by the steric hindrance of polymer networks and the electron delocalization of aromatic group in coal, so the persistent free radicals can be formed and accumulated. The dehydrogenation and oxidation reaction of the active group led to the reduction of g-factor and ΔH. Persistent free radicals play an important role in the free radical chain reaction that triggers CSC, so preventing the dehydrogenation and oxidation reaction of hydroxyl (especially phenolic hydroxyl) and aliphatic hydrocarbons (especially –CH2- and –CH3/–CH2-) is the key to prevent CSC.

Steam cracking of methyl ester: A modeling study on the influence of the hydrocarbon backbone

Biodiesel can be used to produce clean platform chemicals for the chemical industry, as an alternative to or blend with conventional steam cracking feedstocks. Research on the decomposition chemistry of biodiesel is crucial for understanding their combustion, aging and potential as source for base chemical production. Three methyl esters are studied with varying hydrocarbon chain length and a different degrees of saturation to evaluate the impact of these structural differences on the decomposition chemistry and the decomposition product composition. A new kinetic model is developed with the automatic kinetic model generation tool Genesys for the pyrolysis of methyl butanoate, methyl decanoate and methyl dec-4-enoate. New ab initio calculations are carried out for the pyrolysis of methyl butanoate and for retro-ene reactions in unsaturated hydrocarbons and methyl esters, because of their importance in the secondary decomposition chemistry. The first-principles based kinetic model is validated using in-house experimental data gathered in a tubular reactor and against literature experimental data gathered in a jet-stirred reactor for methyl decanoate pyrolysis. A rate of production analysis reveals the main channels towards the pyrolysis products. The presence of the double bond in the hydrocarbon chain leads to a higher production of aromatic species, at the cost of a lower ethylene and propylene production. The high selectivity to aromatics is caused by the fast formation of 1,3-cyclopentadiene from the unsaturated, resonantly stabilized radicals formed during the decomposition.

A hierarchical reduction method with selective targets for combustion modeling of large Hydrocarbons: A case study of 1,3,5-Trimethylbenzene skeletal mechanism

A novel hierarchical method of skeletal reduction for detailed hydrocarbon reaction mechanisms is proposed and applied to generate a skeletal mechanism of 1,3,5-trimethylbenzene (135TMB) which is relevant to practical fuels and their surrogates. The proposed reduction method is based on the hierarchical sensitivity analysis (HSA) implemented in a top-to-bottom manner in terms of carbon levels with selective reduction targets, such as autoignition delay time, laminar flame speed, flame extinction, speciation, etc. These reduction targets can be selected based on the desired combustion phenomena to be simulated and are only validated at their corresponding carbon levels where the respective chemistries are dominating. In contrast to the conventional global sensitivity analysis (GSA) in which species and reactions are randomly evaluated, HSA evaluates species and reactions following the oxidation sequence of fuel molecule, and therefore is able to generate skeletal mechanisms as compact as possible with significantly higher efficiency than GSA. In addition, quasi-steady-state approximation and reaction lumping are integrated in the current reduction process. Low-temperature reaction pathway is also optimized with reaction rates tuned using a particle swarm algorithm to better predict species fractions in the low-to-intermediate temperature regime. As such, based on the detailed 135TMB mechanism of Diévart et al. (2013) with 450 species and 4569 reactions, a skeletal mechanism with 46 species and 197 reactions has been successfully generated including both high- and low-temperature reaction pathways. Extensive validations of the resulting skeletal mechanism are performed against the detailed mechanism predictions and the literature experimental data over a wide range of conditions, and good agreements are observed. These results not only show the accuracy and reliability of the present skeletal 135TMB mechanism but also demonstrate the effectiveness and reduction efficiency of the proposed hierarchical reduction method.

Unexpected Structural Effects on the Onset of Thermal Reactions of Aromatic Hydrocarbons

This work aims to study the reactivity of a broad range of aromatic hydrocarbons to better understand the reactivities of more complex hydrocarbon mixtures. A set of closed-system pyrolysis experiments were conducted on a diverse range of ∼30 polycyclic aromatic hydrocarbons (PAHs) at the thermal onset reaction temperature of 400 °C to understand structural effects on reactivities and shed light on the early events of thermal reaction mechanisms. Thermal transformations, including methyl transfer (alkylation/dealkylation), rearrangement, condensation, molecular growth, and other chemical transformations, are often indicated by dark carbon materials composed of complex mixtures. Thermal transformation was confirmed by phenomenological changes (color and solubility) and chemical analysis using nuclear magnetic resonance, thermogravimetric analysis, gas chromatography, and electron spin resonance. Unsubstituted PAHs (e.g., phenanthrene, anthracene, pyrene, chrysene, etc.) were unaffected by heating at this temperature, with the exception of tetracene and pentacene which readily transformed into dark and insoluble materials. The reactivity of these unsubstituted PAHs is consistent with aromaticity predicted by the Clar theory. On the contrary, most alkyl-substituted PAHs can be transformed into carbon materials at 400 °C; however, alkyl-substituted phenanthrenes (2,7-dimethyl, 2-ethyl, or 7-ethyl) and benzenes (xylenes and pentamethylbenzene) were unreactive. CH2-containing PAH molecules were unreactive if in a five-membered ring (e.g., fluorene and benzofluorene) but became reactive if in a six-membered ring (9,10-dihydroanthracene), likely as a result of aromatization of the latter. The reactivity of the aryl–aryl linkage depends upon the aromatic moieties to which it is connected. While it is unreactive when connecting phenyl groups, such as in p-terphenyl, it is reactive when connecting pyrenes, such as in 1,1′-bispyrene. These results were unexpected and challenge the conventional thinking about hydrocarbon reactivities. Explanations and possible hypotheses are proposed, but more questions remain unanswered to understand the structural effects on reactivities. These findings are conducive to the sustainable use of aromatic hydrocarbons for higher value carbon materials and relevant to numerous pyrolysis studies on oil shale kerogens, biomass, and waste plastics.

Challenges and Opportunities for Platinum in the Modern Three-Way Catalyst

Gasoline vehicles have generally relied upon a combination of palladium and rhodium for more than 25 years to facilitate the required oxidative and reductive reactions of carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NOx). Recently, steady increases in the price of palladium relative to platinum have fuelled demand to reincorporate platinum into three-way catalysts (TWCs). However, the fundamental properties of platinum, including susceptibility toward sintering and inhibition under typical gasoline operating conditions, present significant challenges. This article presents an overview of the origins for these challenges, as well as select strategies for maximising platinum’s contribution to modern-day TWCs. Optimisation of ceria-zirconia supports is one route by which platinum’s performance can be significantly improved through tuning of the ceria-to-zirconia ratio. Additionally, alloying platinum with a secondary platinum group metal (pgm), such as rhodium, leverages complimentary properties of both metals, imparting stability and overall activity enhancements. Such routes not only enable pgm flexibility, but also provide opportunities to further improve TWC performance.

A Novel Reduced Reaction Mechanism for Diesel/2,5-Dimethylfuran Engine Application

The application of 2,5-dimethylfuran (DMF) as an alternative fuel for internal combustion engines has been gaining popularity. However, it has rarely been studied in previous research on the chemical kinetics of DMF for engine combustion simulations. In the present study, a reduced n-heptane/toluene/DMF-polycyclic aromatic hydrocarbon (PAH) reaction mechanism containing only 78 species amongst 190 reactions was proposed and applied to predict the combustion and emissions of a diesel engine using diesel/DMF blend fuel. First, a detailed reaction mechanism for DMF from the literature was chosen and reduced using combined mechanism reduction methods under engine-relevant conditions. Second, the reduced mechanism of DMF was incorporated into an existing reduced n-heptane/toluene-PAH mechanism to establish a three-component chemistry mechanism. Third, the predictive capability of the combined mechanism was improved by adjusting the rate constants of selected gas-phase reactions. Subsequently, the proposed three-component mechanism was compared and validated with experimental measurements of shock tube ignition delay times and premixed flame species profiles acquired from published papers. Moreover, new experimental data from a conventional diesel engine were used to evaluate the developed mechanism. Overall, the predicted results obtained by this proposed reduced n-heptane/toluene/DMF-PAH mechanism are in reasonable agreement with the available experiments.

Quantification of biodegradation rate of hydrocarbons in a contaminated aquifer by CO2 δ13C monitoring at ground surface

Ground surface analysis of CO2 emissions with δ13C determination is experimentally demonstrated to be a potential methodology to monitor, on line, the dynamics of petroleum-hydrocarbon biodegradation in soil aquifers, thanks to the improvement of the Isotopic Ratio Infra Red Spectroscopy technique. Biodegradation rate of remaining hydrocarbon substrates in groundwater can be quantified using basic application of the Rayleigh equations, by δ13CCO2 analysis released at ground surface above the pollution plume instead of usual approaches based on groundwater hydrocarbons δ13C analysis, when physical and chemical properties for the contaminated site meet appropriate conditions.The validation approach for that gasoline contaminated specific site is discussed and verified by comparison of first order attenuation rate constant determined from δ13CCO2 analysis emitted at ground surface and from δ13CTOLUENE analysis in ground water. A kinetic fractionation factor α of 0.9979 (or ε value of −2.1 ± 0.5‰) is estimated for the biodegradation of the most reactive hydrocarbon substrates (TEX). The treatment of this Rayleigh equations by linear regression of δ13CCO2 values along the predominant direction of groundwater flow leads to the following results and conclusions for that site: (i) first order biodegradation rate constants (and annual variation) are maximum after the activation of a Permeable Reactive Barrier (PRB) in May 2014: 0.92(+0.29–0.17) year−1, and during July and October: 0.46(+0.14–0.09) year−1 and minimum in mid-winter in February 2015: 0.17(+0.05–0.03) year−1, given by the estimation range for ε. These results are in the lower range with reported in literature for similar contaminated sites (1.6–18 year−1) considering natural attenuation under sulfate reducing conditions and (ii) the seasonal variation of the first order biodegradation rate constant is mainly correlated with the seasonal variation of the CO2 flux, where maximum values are in summers and minimum values in winters. Both seasonal variations are mainly due to the annual cycle of the natural biodegradation activity at the scale of the pollution plume, rather than the activation of the PRB.This work demonstrates that δ13CCO2 analysis released at ground surface from biodegradation of groundwater hydrocarbons could provide, under characterized and appropriate conditions, a non-intrusive (without soil samplings), fast, and low-cost online method to monitor and therefore to optimize soil remediation processes in real time. (Monitored Natural Attenuation or Enhanced Bioremediation).

A Metal-Free Cyclobutadiene Reagent for Intermolecular [4 + 2] Cycloadditions.

Cyclobutadiene is a highly reactive antiaromatic hydrocarbon that has fascinated chemists for over 60 years. However, its preparation and uses in chemical synthesis are sparing, in part due to its lengthy synthesis that generates hazardous byproducts including excess heavy metals. Herein, we report a scalable, metal-free cyclobutadiene reagent, diethyldiazabicyclohexene dicarboxylate, and explore its intermolecular [4 + 2] cycloaddition with various electron-deficient alkenes. We also demonstrate its utility in a three-step synthesis of dipiperamide G and a diverse array of product derivatizations including bromocyclobutadiene.

One pot synthesis of bridgehead amino alcohols from diamantoid hydrocarbons

An efficient approach for the synthesis of amino alcohols directly from cage hydrocarbons has been developed. Multigram scalability, good yields and one-pot procedure, that utilize readily available reagents along with synthetic convenience showed its usefulness. The proposed one-pot method includes sequential reactions of cage hydrocarbon with nitric acid, further amination of intermediate nitroxy derivative with urea, followed by oxidation of previously generated amine to amino alcohol on addition of conc. H2SO4.

Atomistic insight into the effects of electrostatic fields on hydrocarbon reaction kinetics.

Reactive Molecular Dynamics (MD) and Density Functional Theory (DFT) computations are performed to provide insight into the effects of external electrostatic fields on hydrocarbon reaction kinetics. By comparing the results from MD and DFT, the suitability of the MD method in modeling electrodynamics is first assessed. Results show that the electric field-induced polarization predicted by the MD charge equilibration method is in good agreement with various DFT charge partitioning schemes. Then, the effects of oriented external electric fields on the transition pathways of non-redox reactions are investigated. Results on the minimum energy path suggest that electric fields can cause catalysis or inhibition of oxidation reactions, whereas pyrolysis reactions are not affected due to the weaker electronegativity of the hydrogen and carbon atoms. MD simulations of isolated reactions show that the reaction kinetics is also affected by applied external Lorentz forces and interatomic Coulomb forces since they can increase or decrease the energy of collision depending on the molecular conformation. In addition, electric fields can affect the kinetics of polar species and force them to align in the direction of field lines. These effects are attributed to energy transfer via intermolecular collisions and stabilization under the external Lorentz force. The kinetics of apolar species is not significantly affected mainly due to the weak induced dipole moment even under strong electric fields. The dynamics and reaction rates of species are studied by means of large-scale combustion simulations of n-dodecane and oxygen mixtures. Results show that under strong electric fields, the fuel, oxidizer, and most product molecules experience translational and rotational acceleration mainly due to close charge transfer along with a reduction in their vibrational energy due to stabilization. This study will serve as a basis to improve the current methods used in MD and to develop novel methodologies for the modeling of macroscale reacting flows under external electrostatic fields.

Modeling the influence of chain length on secondary organic aerosol (SOA) formation via multiphase reactions of alkanes

Abstract. Secondary organic aerosol (SOA) from diesel fuel is known to be significantly sourced from the atmospheric oxidation of aliphatic hydrocarbons. In this study, the formation of linear alkane SOA was predicted using the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model that simulated multiphase reactions of hydrocarbons. In the model, the formation of oxygenated products from the photooxidation of linear alkanes was simulated using a nearly explicit gas kinetic mechanism. Autoxidation paths integrated with alkyl peroxy radicals were added to the Master Chemical Mechanism v3.3.1 to improve the prediction of low-volatility products in the gas phase and SOA mass. The resulting gas products were then lumped into volatility- and reactivity-based groups that are linked to mass-based stoichiometric coefficients. The SOA mass in the UNIPAR model is produced via three major pathways: partitioning of gaseous oxidized products onto both the organic and wet inorganic phases, oligomerization in the organic phase, and reactions in the wet inorganic phase (acid-catalyzed oligomerization and organosulfate formation). The model performance was demonstrated for SOA data that were produced through the photooxidation of a homologous series of linear alkanes ranging from C9–C15 under varying environments (NOx levels and inorganic seed conditions) in a large outdoor photochemical smog chamber. The product distributions of linear alkanes were mathematically predicted as a function of carbon number using an incremental volatility coefficient (IVC) to cover a wide range of alkane lengths. The prediction of alkane SOA using the incremental volatility-based product distributions, which were obtained with C9–C12 alkanes, was evaluated for C13 and C15 chamber data and further extrapolated to predict the SOA from longer-chain alkanes (≥ C15) that can be found in diesel. The model simulation of linear alkanes in diesel fuel suggests that SOA mass is mainly produced by alkanes C15 and higher. Alkane SOA is insignificantly impacted by the reactions of organic species in the wet inorganic phase due to the hydrophobicity of products but significantly influenced by gas–particle partitioning.

Zirconium-Catalyzed C-H Alumination of Polyolefins, Paraffins, and Methane.

C-H/Et-Al exchange in zirconium-catalyzed reactions of saturated hydrocarbons and AlEt3 affords versatile organoaluminum compounds and ethane. The grafting of commercially available Zr(OtBu)4 on silica/alumina gives monopodal ≡SiO-Zr(OtBu)3 surface pre-catalyst sites that are activated in situ by ligand exchange with AlEt3. The catalytic C-H alumination of dodecane at 150 °C followed by quenching in air affords n-dodecanol as the major product, revealing selectivity for methyl group activation. Shorter hydrocarbon or alcohol products were not detected under these conditions. Catalytic reactions of cyclooctane and AlEt3, however, afford ring-opened products, indicating that C-C bond cleavage occurs readily in methyl group-free reactants. This selectivity for methyl group alumination enables the C-H alumination of polyethylenes, polypropylene, polystyrene, and poly-α-olefin oils without significant chain deconstruction. In addition, the smallest hydrocarbon, methane, undergoes selective mono-alumination under solvent-free catalytic conditions, providing a direct route to Al-Me species.

Modeling daytime and nighttime secondary organic aerosol formation via multiphase reactions of biogenic hydrocarbons

Abstract. The daytime oxidation of biogenic hydrocarbons is attributed to both OH radicals and O3, while nighttime chemistry is dominated by the reaction with O3 and NO3 radicals. Here, daytime and nighttime patterns of secondary organic aerosol (SOA) originating from biogenic hydrocarbons were predicted under varying environmental conditions (temperature, humidity, sunlight intensity, NOx levels, and seed conditions) by using the UNIfied Partitioning Aerosol phase Reaction (UNIPAR) model, which comprises multiphase gas–particle partitioning and in-particle chemistry. The products originating from the atmospheric oxidation of three different hydrocarbons (isoprene, α-pinene, and β-caryophyllene) were predicted by using extended semi-explicit mechanisms for four major oxidants (OH, O3, NO3, and O(3P)) during day and night. The resulting oxygenated products were then classified into volatility–reactivity-based lumping species. The stoichiometric coefficients associated with lumping species were dynamically constructed under varying NOx levels, and they were applied to the UNIPAR SOA model. The predictability of the model was demonstrated by simulating chamber-generated SOA data under varying environments. For daytime SOA formation, both isoprene and α-pinene were dominated by the OH-radical-initiated oxidation showing a gradual increase in SOA yields with decreasing NOx levels. The nighttime isoprene SOA formation was processed mainly by the NO3-driven oxidation, yielding higher SOA mass than daytime at higher NOx level (isoprene / NOx < 5 ppb C ppb−1). At a given amount of ozone, the oxidation to produce the nighttime α-pinene SOA gradually transited from the NO3-initiated reaction to ozonolysis as NOx levels decreased. Nighttime α-pinene SOA yields were also significantly higher than daytime SOA yields, although the nighttime α-pinene SOA yields gradually decreased with decreasing NOx levels. β-Caryophyllene, which rapidly produced SOA with high yields, showed a relatively small variation in SOA yields from changes in environmental conditions (i.e., NOx levels, seed conditions, and sunlight intensity), and its SOA formation was mainly attributed to ozonolysis day and night. The daytime SOA formation was generally more sensitive to the aqueous reactions than the nighttime SOA because the daytime chemistry produced more highly oxidized multifunctional products. The simulation of α-pinene SOA in the presence of gasoline fuel, which can compete with α-pinene for the reaction with OH radicals in typical urban air, suggested more growth of α-pinene SOA by the enhanced ozonolysis path. We concluded that the oxidation of the biogenic hydrocarbon with O3 or NO3 radicals is a source of the production of a sizable amount of nocturnal SOA, despite the low emission at night.

Suppressing the aromatic cycle of the dimethyl ether to hydrocarbons reaction on zeolites

The influence of the zeolite framework type on the conversion of dimethyl ether (DME) to hydrocarbons (DTH) was investigated for *MRE, MFI and TON zeolite catalysts. Remarkable differences in the catalytic performance of the materials were observed. In particular, the *MRE zeolite showed an exceptionally high yield of olefins (90%) with a substantial ratio of products in the chain length range C5-C11. Additionally, the longevity of the *MRE zeolite clearly exceeded previously reported data. The comparison of mechanistic parameters (Hydrogen-Transfer-Index HTICi and C3/C2 ratio) demonstrated for this zeolite, that the formation of aromatics in the reaction network can be almost completely suppressed under suitable reaction conditions. By varying the reaction parameters temperature, DME partial pressure and weight hourly space velocity (WHSV), it was possible to identify the optimal combination of selectivity and deactivation resistance for each material. The olefin-rich DTH product of the *MRE zeolite offers manifold possibilities for further conversion to valuable renewably produced low-emission fuels like gasoline or jet fuel.

An iron-catalyzed C–S bond-forming reaction of carboxylic acids and hydrocarbons via photo-induced ligand to metal charge transfer

A photo-induced iron-catalyzed strategy that facilitates the transformation of carboxylic acids and hydrocarbons into thioethers and sulfoxides is herein reported.

Activation of perfluoroalkyl iodides by anions: extending the scope of halogen bond activation to C(sp3)-H amidation, C(sp2)-H iodination, and perfluoroalkylation reactions.

A simple, efficient, and convenient activation of perfluoroalkyl iodides by tBuONa or KOH, without expensive photo- or transition metal catalysts, allows the promotion of versatile α-sp3 C-H amidation reactions of alkyl ethers and benzylic hydrocarbons, C-H iodination of heteroaryl compounds, and perfluoroalkylations of electron-rich π bonds. Mechanistic studies show that these novel protocols are based on the halogen bond interaction between perfluoroalkyl iodides and tBuONa or KOH, which promote homolysis of perfluoroalkyl iodides under mild conditions.

Free and internal energies for the adsorption of short alkanes into the zeolite SSZ-13 from ab initio molecular dynamics simulations.

Electronic structure calculations have become a valuable tool in understanding chemical reactions of hydrocarbons in zeolite pores. However, commonly applied approaches to calculate free energies based on static electronic structure calculations significantly overestimate the entropic penalty for molecular adsorption into zeolite pores. Here, we use ab initio molecular dynamics (AIMD) simulations to model the adsorption of methane, ethane, and propane to purely siliceous and protonated SSZ-13. In our analyses we focus on the internal and Helmholtz free energies of adsorption of each molecule and compare our results to various approaches for the calculation of free energies based on static calculations. We find that only an approach that retains two thirds of the translational entropy of the adsorbate upon adsorption compares favorably with AIMD simulations. However, comparison to experimental measurements of Gibbs free energies of adsorption reported in the literature implies that we might not have captured the full complexity of alkane adsorption in our model. We expect that results in this work will help to develop a better understanding of alkane adsorption in zeolites, and that the provided data will serve as a benchmark for free energy calculations of alkane adsorption in zeolites in the future.