C4 Olefins Research Articles

Pd-Co Supported on Anodized Aluminium for VOCs Abatement: Reaction Mechanism, Kinetics and Applicability as Monolithic Catalyst

It has been found out that Pd-Co-based catalyst, supported on anodized aluminum, possesses very high activity in combustion reactions of C1–C6 alkanes and toluene. The catalyst characterization has been made by N2-pysisorption, XRD, SEM, XPS, FTIR, TEM, and EPR methods. In view of the great interest, methane combustion was investigated in detail. It is ascertained that the complete oxidation of methane proceeds by dissociative adsorption on PdO and formation of hydroxyl and methyl groups, the former being highly reactive, and it undergoes further reaction to oxygen-containing intermediates, whereupon HCHO is one of them. The presence of Co2+ cations promotes greatly oxygen adsorption. The dissociative adsorption is favored on neighboring Co2+ cations, leading to the formation of bridging peroxides. Further, the oxygen dissociates on the nearest Pd2+ cations. According to the results from the experimental data, instrumental methods, and the observed kinetics and DFT model calculations, it can be concluded that the reaction pathway over Pd+Co/anodic alumina support (AAS) catalyst proceeds most probably through Mars–van Krevelen. The obtained data on the kinetics were used for simulation of the methane combustion in a full-scale adiabatic reactor.

Steam cracking in a semi-industrial dual fluidized bed reactor: Tackling the challenges in thermochemical recycling of plastic waste

Steam cracking is an integral process in the plastic manufacturing industry. Conventional steam crackers are tubular reactors and use fossil-based feedstocks like naphtha and LPG. This work presents steam cracking in a dual fluidized bed (DFB) reactor as an alternative for the direct steam cracking of plastic waste. Experiments were performed on a semi-industrial DFB system using naphtha, clean polyolefins, real-life plastic wastes, and a polyolefin-derived pyrolysis oil. The results show that steam cracking in a DFB is fundamentally equivalent to steam cracking in tubular reactors. Selective production of light olefins and monoaromatics was achieved within a temperature range of 700–825 °C. Naphtha yielded up to 56 % light olefins and 7 % BTXS, with ethylene and BTXS production positively correlating with cracking severity, while C3 and C4 olefins show a negative correlation. These results confirm that the established steam cracking mechanisms also apply to large-scale DFB steam crackers. The yield of light olefins is consistently obtained at approximately 52 % relative to the polyolefin content of the feedstock, regardless of the non-polyolefin content. This highlights the DFB steam cracker’s ability to produce light olefins directly from plastic waste without presorting. However, steam cracking in DFB results in significantly higher CO and CO2 yields than conventional steam cracking, especially with feedstocks containing non-polyolefins like PET and cellulose. Additionally, steam cracking of an olefin-rich pyrolysis oil yields up to 50 % light olefins with minimal coke formation, highlighting the potential in processing plastic waste pyrolysis oils without pretreatment steps such as distillation and hydrotreatment.

Hydrodeoxygenation of Glycerol to Propene Over Molybdenum and Niobium Phosphate Catalysts

AbstractIn single‐step conversion of glycerol to propene, the intricate catalytic pathways with molybdenum and niobium catalysts remain elusive. While these catalysts can effectively accelerate the hydrogenolytic cleavage of the glycerol CO bonds, resulting in a high selectivity to propene, the routes have not been thoroughly studied. This study explores the reaction routes and the role hydrogen plays in determining the product distribution. The hydrodeoxygenation (HDO) of glycerol was investigated using various glycerol purities in both batch and continuous reaction modes. Remarkably, Mo(PO4)x and Nb(PO4)x demonstrated catalytic performance with raw glycerol, indicating that impurities had no detrimental effect on the catalyst's activity. In batch mode, a propene selectivity of 53% was achieved over Mo(PO4)x as the catalyst, highlighting the catalyst's stability under these conditions. In continuous operation, the highest product selectivity to propene (12%) was observed at low temperatures (573 K), while more C2 to C6 alkanes were formed at increased temperatures (623 and 673 K). Whereas a hydrogen atmosphere promotes formation of 2‐propenol, as primary precursor to propene, an inert atmosphere leads to increased formation of propanal and dissociation products. Our work has elucidated new routes to upcycle biorenewable glycerol to propene over Mo(PO4)x and Nb(PO4)x catalysts.

Molecular Compositions, Mutagenicity, and Mutation Spectra of Atmospheric Oxidation Products of Alkenes and Dienes Initiated by NOx + UV or Ozone: A Structure-Activity Analysis.

Photooxidation products resulting from volatile organic compounds (VOCs) reacting with sunlight are important contributors to gas-phase air pollution. We characterized the product-weighted mutagenic potencies (rev m3 mgC-1 h-1) in Salmonella TA100 of atmospheres resulting from the hydroxyl radical (OH)-initiated photochemical oxidation of 11 C4 or C5 alkenes or dienes in the presence of nitric oxide (NO) and from the ozonolysis of four VOCs without NO (isoprene; 1,3-pentadiene; 1,4-pentadiene; and 1,3-butadiene). Irradiated atmospheres from precursors with a single C═C bond (3-methyl-1-butene, 2-methyl-1-butene, cis/trans-2-pentene, 2-methyl-2-butene, 1-butene, and 1-pentene) had low potencies (<5), whereas linear dienes with terminal C═C bonds had high potencies (50-65). Dienes with a branched structure (isoprene) or internal C═C bonds (1,3-pentadiene) had intermediate potencies (15-20). No VOCs were mutagenic without photochemical oxidation. VOCs+O3 in the dark produced less mutagenic atmospheres than photochemistry in the presence of NO. Atmospheres induced primarily C to T and C to A mutations, the main base substitutions in nonsmoker lung cancer. Atmospheres from the photooxidation of isoprene and 1,3-pentadiene also induced GG to TT, the signature mutation of peroxyacetyl nitrate. Five molecular compositions identified by Chemical Ionization Mass Spectrometry (CIMS), most containing nitrogen, correlated (r = 0.76-0.85) with the mutagenic potencies of irradiated atmospheres; most had a likely nitrate functional group. Assessment of the mutagenicity of emitted VOCs should consider VOC photooxidation products, especially dienes with terminal C═C bonds, as these products likely contribute to overall health effects from ambient air pollution.

Tea polyphenols coating improves physiological properties, microstructure and chemical composition of cuticle to suppress quality deterioration of passion fruit during cold storage

The plant cuticle plays a crucial role in modulating postharvest quality and extending shelf life of horticultural crops. Passion fruit often suffers from quality degradation primarily due to peel wrinkling after harvest. Tea polyphenols (TPs) hold potential for enhancing postharvest preservation. However, the specific effects of TPs coating on preservation of passion fruit, as well as the underlying mechanisms involving cuticle regulation, have not been thoroughly investigated. This study demonstrated that treating ‘Qinmi no.9’ passion fruit with TPs at a concentration of 0.1 g L−1 significantly mitigates weight loss, maintains firmness, and reduces cell membrane permeability during storage at 10 °C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that TPs treatment notably enhances cuticle thickness and structural integrity. Furthermore, gas chromatography–mass spectrometry (GC–MS) and metabolomics analyses indicated that TPs treatment obviously promotes the accumulation of palmitic acid, stearic acid, and their derivatives—primarily 12-Octadecenoic acid and 10(E)-Octadecenoic acid—as well as increases the levels of 11-Octadecenoic acid, primary alcohols such as 1-Eicosanol, and long-chain alkanes (including C31 and C32 alkanes) in the fruit peel cuticle. These biochemical changes contribute to the quality maintenance of passion fruit during cold storage. The findings suggest that TPs treatment is a promising biological strategy for extending shelf life and mitigating quality degradation by regulating cuticle metabolism in postharvest passion fruit.

Electronic and geometric features controlling the reactivity of Mg-vanadate and V2O5 surfaces toward the initial C–H activation of C1–C3 alkanes – A DFT+U study

This work employs density functional theory (DFT+U) calculations to explore initial C–H activations in C1–C3 alkanes on V2O5, MgV2O6 (meta-vanadate), Mg2V2O7 (pyro-vanadate), and Mg3V2O8 (ortho-vanadate) surfaces. These materials are selective catalysts for the oxidative dehydrogenation (ODH) of alkanes into alkenes, which offers practical and thermodynamic advantages over non-oxidative alkane dehydrogenation. The geometric and electronic properties that govern the reactivity of these materials, however, have not been explored by theory despite their importance in controlling rate determining alkane initial C–H activation during ODH catalysis. In this work, we explore fourteen low-energy surfaces of MgxV2Ox+5 (x = 0–3) exposing 64 distinct O atoms (reaction sites). C–H activation barriers are largest on Mg3V2O8, lower and similar for Mg2V2O7 and MgV2O6, and lowest for V2O5 surfaces; these predicted trends are consistent with measured ODH reactivity in earlier studies. Barriers are lowest (on average) when alkanes react with O atoms bound to a single V atom, with bridging O atoms having slightly higher barriers, and three-fold O atoms having the largest activation barriers. However, there is scattering within each subset indicating that factors beyond O-atom coordination have a significant role in the barriers. Vacancy formation energies (VFE) and the O 2p band energies were found to be weak descriptors of surface O reactivity for alkane activation barriers. Hydrogen addition energy (HAE) and methyl addition energy (MAE) values, in contrast, were found to correlate well with alkane activation barriers. MAE, however, outperforms HAE correlations because of the tendency of H* to form H-bonds with nearby surface O atoms, and those H-bonds are absent in C–H activation transition states causing scatter in the correlation of barriers with HAE. Constrained-orbital DFT methods were used to establish a theoretical thermochemical cycle that decouples surface reduction by CH3* into three components: surface distortion, orbital localization, and bond formation. These results give insights into how Mg:V ratios, surface structure (O-atom coordination), and reducibility (HAE, MAE) impact the reactivity of vanadium-based metal oxides toward alkane activation.

Effect of Ni/tire rubber carbon as catalyst in the hydrodeoxygenation of used vegetable oil: biofuel evaluation in the reduction of atmospheric emissions

Abstract The sustainable valorization of discarded resources remains a challenge, and their requirements are crucial for long-term development. In this sense, we characterize biofuels of the diesel range obtained with used vegetable oils subjected to hydrodeoxygenation with Ni supported on tire rubber carbon obtained by the pyrolysis of waste tires. Under optimal reaction conditions, the vegetable oil conversion was 81.2 % with a selectivity of 82.3 % to C10–C18 alkanes, which is supported by the results of the catalyst characterization. A vertical direct injection engine was used to compare the behavior of the renewable biofuel and petroleum diesel blends. In comparison to petroleum diesel, the blends with renewable biofuel showed minimal power loss. In addition, the use of blends containing biofuels allowed a reduction of 25 % of CO and HC, as well as a decrease of 48 % is smoke compared to petroleum diesel, due to the fact that renewable biofuels improved evaporation after injection, reduced the density, and did not contain aromatic components.

Effects of Different Shade Treatments on the Epidermal Wax Deposition of Hosta Genotypes with Different Glaucousness of Leaf Surface

Epidermal wax is strategically situated at the interface between plants and air; therefore, it plays a key role in plants’ interactions with their surroundings. It is also unstable and susceptible to light intensity. Hosta plants are shade-loving herbs with admirable flowers and leaves. Hosta ‘Halcyon’ and Hosta ensata F. Maek. are two species of Hosta with a glaucous and a glossy appearance, respectively. Light intensity can affect the composition of epicuticular wax on the leaf surface, which influences the leaf color phenotype and ornamental value. In this paper, the crystal micromorphology, content, and components of epicuticular wax on the leaves of two species of Hosta under different light conditions (10%-, 30%-, 50%-, 70%-, and 100%-intensity sunlight, relative light intensity (RLI)) have been studied using pot experiments. The results indicate that the epicuticular wax crystals of H. ‘Halcyon’ and H. ensata are tubular and platelet-like, respectively. The wax crystals of H. ‘Halcyon’ melted and formed a thick crust under 100% RLI, and those of H. ensata melted and formed a thick crust under 70% and 100% RLI conditions. The primary ingredients of the epicuticular wax of the two species of Hosta contained primary alcohols, alkanes, fatty acids, and esters; β-diketones were only detected in H. ‘Halcyon’. The quantity of epicuticular wax of H. ‘Halcyon’ reduced at first and then increased with an RLI increase, achieving its lowest value at 50% RLI, but that of H. ensata declined little by little. The amounts of C28 primary alcohols, C31 alkanes, and C18 fatty acids were significantly higher than those of other carbon atoms in the two genotypes of Hosta. The C31β-diketones content decreased with the increase in light intensity, which caused the white frost phenotype to gradually weaken in H. ‘Halcyon’.

Effects of several typical plastic combustion residues on gasoline

Abstract In order to solve the interference caused by polymer materials on gasoline accelerants in arson cases, the characteristics of residues after combustion of some typical plastics are studied. Comparing it to the combustion residue of gasoline, we discussed the interference in gasoline detection. The results show that the combustion products of these plastics mainly interfere with the alkanes and aromatic hydrocarbons in gasoline. Polyethylene, polystyrene, and polyvinyl chloride mainly produce C9-C16 branched-chain and straight-chain alkanes. Polystyrene and ABS resin generated C5 and C6 alkanes, also generated C1-benzene, C2 - benzene, and styrene. It mainly affects the identification of aromatic hydrocarbons in gasoline combustion residues. Understanding the types and characteristics of products in the combustion residues of these plastics can provide powerful evidence for fire investigators and criminal technicians in physical evidence identification.

Comparative analysis of additive decomposition using one-dimensional and two–dimensional gas chromatography: Part II - Irgafos 168 and zinc stearate

Plastic production has experienced a significant increase in the last sixty years due to its cost-efficiency and adaptable characteristics, leading to the extensive use of additives to improve its performance and longevity. Due to the high demand for plastic, plastic waste production has increased, contaminating the environment and living beings by leaching additives, among other substances. Pyrolysis stands out among recycling techniques because it can handle mixed polymer waste feedstock. However, understanding the pyrolyzates distribution of additives is fundamental to assessing pyrolysis process of plastic waste. This study investigated the pyrolysis product distributions of two commonly used antioxidants, namely, Irgafos 168 and zinc stearate (ZnSt), using one-dimensional gas chromatography equipped with a quadruple mass spectrometer (GC–MS) and two-dimensional gas chromatography coupled to flame ionization detector and time–of–flight mass spectrometer (GC×GC–FID/TOF–MS). While GC separation technique provided limited information on product distribution, GC×GC offered enhanced resolution and identification of the decomposition products. In the pyrolysis of Irgafos 168 at 550 °C, GC identified 18 products, while GC×GC identified 198 products, representing an increase of approximately 11-fold. Similarly, for ZnSt, GC identified 67 products, while GC×GC identified 434 products, representing a 6-fold increase. GC×GC identified decomposition products from 15 different chemical classes for Irgafos 168 and 16 chemical classes for ZnSt, compared to 4 and 11 chemical classes identified by GC, respectively. Phenols and their derivatives were the major chemical class in the decomposition products of Irgafos 168 with a yield of 9.51 wt.%. In contrast, olefinic products were the dominant ones for ZnSt, with a yield of 9.73 wt.%. The major decomposition product of Irgafos 168 and ZnSt was 2‑tert‑butyl‑methylphenol (C11H16O) and C6 olefin (C6H12) with yields of 3.88 wt.%, and 1.13 wt.%, respectively. Utilizing the GC×GC separation method improved the ability to identify decomposition products, which can ultimately lead to a better understanding of antioxidant degradation that occurs during the pyrolysis process. GC×GC also provided thorough characterization of minor and co-eluted products along with major antioxidant degradation products. Additionally, the decomposition product distribution of Irgafos 168 and ZnSt was also compared with the primary antioxidants, Irganox 1010, Irganox 1076, and BHT, studied in part 1. The analysis indicated that the olefinic chemical class was the predominant one in Irganox 1010, Irganox 1076, and ZnSt, while ketones were the major chemical class in the decomposition of BHT and phenolics had the highest yield in Irgafos 168.

Production of C2−C4 Olefins with Fischer‐Tropsch‐Synthesis: The Effect of Cu Promoter Loading on an Fe−Cu−K/SiO2 Catalyst

AbstractIn this study we focus on the iron‐based catalyst to produce C2−C4 olefin hydrocarbons via the high‐temperature Fischer‐Tropsch synthesis. Promoters have a significant impact on catalyst stability, activity, and product selectivity. Therefore, we investigated the effect of the Cu promoter in an Fe−Cu−K/SiO2 catalyst. We compared the catalyst without Cu and 1, 2, 3, 4, and 5 wt % Cu loadings. The overall catalyst activity increased from 0 to 3 wt % Cu loading and started to decrease at 4 and 5 wt % Cu loadings. Although overall catalyst activity had an optimum with 3 and 4 wt % Cu loading, the Cu loading had a negligible effect on product selectivity. However, when compared to a non‐Cu promoted catalyst, the Cu addition increased the selectivity towards olefinic C2−C4 hydrocarbons. The Fischer‐Tropsch experiments were performed in a tubular reactor system at 300 °C, 21 bar and H2 : CO=2 at different feed volume flows, with hydrogen activation. According to the performed temperature‐programmed dynamic chemisorption analysis, the Cu promoter assisted the iron reduction, and the lower overall activity to 0–2 wt % Cu loading might relate to insufficient dissociated H surface species, rather than the availability of C from dissociated CO.

Impact of the material hydroxylation on the possibility of pentane isomers separation by UiO-66 (Zr) MOF: A combined 2H NMR and MD study

The mobility of the pentane isomers in the hydroxylated UiO-66 metal-organic framework has been characterized. 2H NMR spectroscopy was applied to measure the jump rate of alkanes guest molecules between adjacent cages and estimate the diffusivity. It is inferred that the difference in diffusion coefficients defines the kinetic separation selectivity, which is higher for the linear alkanes. The adsorption of pentane isomers in UiO-66 has been modeled with molecular dynamics (MD) simulation. The adsorbed quantity of isopentane is higher than that for n-pentane, providing the possibility of separation with selectivity α ≈ 8 in stationary conditions. The impact of the UiO-66 MOF hydroxylation state on the mobility of pentane isomers has been characterized by comparison with results obtained for the dehydroxylated UiO-66 material. The hydroxylated state of UiO-66 MOF has 6-time higher separation selectivity for pentane isomers compared to its dehydroxylated state (αhyd ≈ 76). MD calculations show that hydroxylated UiO-66 MOF is more efficient, as the separation selectivity is 4 times lower in the dehydroxylated material. The UiO-66 hydroxylation effect is compared for the mobility of C4 and C5 alkanes. The optimal conditions for C4/C5 alkanes kinetic separation by UiO-66 MOF are established.

Theoretical and experimental constraints on hydrogen isotope equilibrium in C1-C5 alkanes

Stable isotope ratios of C1–C5 alkanes, the major constituents of subsurface gaseous hydrocarbons, can provide valuable insights on their origins, transport, and fates. Equilibrium isotope effects are fundamental to interpreting stable isotope signatures, as recognition of them in natural materials indicates reversible processes and constrains the temperatures of equilibrated systems. Hydrogen isotope equilibrium of C1–C5 alkanes is of particular interest because evidence shows that alkyl H can undergo isotopic exchange with coexisting compounds under subsurface conditions. We present the results of a combined experimental and theoretical effort to determine equilibrium hydrogen isotope distributions in mixtures of these hydrocarbon compounds. We created two mixtures: one with C1, C2 and C3 (where C1 indicates methane, C2 ethane, etc., hereinafter called ‘C1–C3 mixture’) and another one with C2, C3, iC4, nC4, iC5 and nC5 (hereinafter called ‘C2–C5 mixture’); in both cases, the mixtures were created to start out of hydrogen isotope equilibrium. We tested the performance of several metal catalysts as aids to H isotopic exchange by exposing these mixtures to different metal catalysts at 100 or 200 °C and analyzing the compound-specific hydrogen isotope ratios of the product gases. The C1–C3 mixture exchanged hydrogen isotopes among the starting gas components rapidly in the presence of Ru/Al2O3 at 200 °C. The isotope ratios reach a steady-state (presumably equilibrium) after 72 h of heating (up to 120 h). The hydrogen isotopic ratios of alkanes in the C2–C5 mixture shifted significantly in the presence of Rh/Al2O3 at 100 °C and C3-C5 compounds approached steady state after 70 h, whereas C2 had not yet reached a steady state D/H ratio after 216 h of heating. We evaluated the reaction progress of isotope exchange for each compound as a function of time with a reaction-network model informed by constraints on chemical kinetics. The model indicates that C3, iC4, nC4, iC5 and nC5 in the C2-C5 mixture reached internal isotope equilibrium after 70 h, hence we used their values to calculate experimental equilibrium results. We also calculated equilibrium isotope fractionations with the Bigeleisen-Mayer theorem using vibrational frequencies computed from the density functional theory (B3LYP/aug-cc-pVTZ). We included torsional conformers and explicit H positions in the calculations. We found that the experimental results from both the 200 ˚C C1–C3 experiment and 100 ˚C C2–C5 experiment are consistent with theoretical equilibrium results within experimental uncertainty. Additionally, our reaction-network model for catalyzed hydrogen isotope exchange between alkanes succeeded in fitting our experimental results. This modeling framework can be adjusted to simulate exchange in natural settings for constraining temperature histories and sources of natural gases.

Solvent-free deoxygenation of biolipid into liquid alkanes over bifunctional Ni/B2O3-ZrO2 catalyst

The efficient deoxygenation of renewable biolipids into liquid alkanes within the diesel range is a key protocol for producing high-quality biofuels. In this work, the conversion of methyl palmitate and raw palm oil were accomplished utilizing a bifunctional catalyst of Ni catalysts supported on B2O3-ZrO2 under solvent-free conditions. Among various Ni loading ratios investigated, the catalyst featuring a 10 % Ni loading achieved 100 % conversion of methyl palmitate and 84.4 % of liquid yield, with approximately 65 % being C15 alkanes. Additionally, more than 91 % of hydrocarbons were also generated from raw palm oil. These results can be attributed to the synergistic interplay between the acid sites, following B2O3 modification, and the presence of Ni species. Furthermore, the analysis of product distribution, gas product detection and the kinetics calculation strongly supports that the deoxygenation process of methyl palmitate primarily follows the hydrodecarbonylation route, leading to the predominant formation of C15 alkane.

Synthesis, evaluation and structure-activity relationship studies of pterodontic acid acylated derivatives with anti-flu A virus (H1N1) activity in vitro

In order to develop antiviral drugs, we utilized pterodontic acid (Poa-1) as a lead compound and conducted various modifications, including oxidation, reduction, addition, esterification, and acylation, resulting in the synthesis of 29 derivatives, of which 25 were novel acylation derivatives. Cell-level validation demonstrated that 4 derivatives exhibited significant inhibitory effects on the influenza A virus (H1N1), with an IC50 = 4.04–36.13 μM. Notably, four acylation derivatives (compounds IIE5, IIE6, IIE9, and IIE17) exhibited specific antiviral activities against influenza A virus (H1N1) with low cytotoxicity, indicating favorable therapeutic indices (SI = 3.5–11.9). Structure-activity relationship studies indicated that C5–C6 olefins are essential groups for antiviral activity, C11–C12 conjugated olefins will not interfere with antiviral activity. Carboxylic acid is an essential group for activity. Moreover，Carboxylic acid acylation can improve antiviral activity, and the inclusion of guanidine, cyclic amine, and phenyl groups with electron-donating substituents could enhance the antiviral activity of the lead compound. Natural products structural modifications are capable of improving the biological activity of lead compounds, offering a rapid pathway for the development of potent new structures.

STUDYING THE INFLUENCE OF ALKALINE TREATMENT AND MODIFICATION OF ZEOLITE ON ITS PHYSICAL-CHEMICAL AND CATALYTIC PROPERTIES IN THE PROCESS OF PROPANE CONVERSION TO OLEFIN HYDROCARBONS

In this work, the effect of alkaline treatment of ZSM-5 zeolite with a modulus of 100 on its physicochemical properties and activity in the process of converting propane into olefin hydrocarbons was investigated. The growing demand for lower olefins is driving the search for new ways to improve existing technologies and develop new, more efficient catalysts. Catalytic dehydrogenation of light alkanes is an alternative to the petrochemical method for producing lower olefins from cheap and available gas and oil and gas feedstocks. At the same time, dehydrogenation reactions of light alkanes have a number of features and limitations that determine the range of possible catalysts. Zeolites are a class of supports that, due to their large surface area, nanometer-sized pores, and good thermal stability, can be used to prepare catalysts for the dehydrogenation of C2−C4 alkanes. An important feature of crystalline high-silica zeolites is the ability to change their acidic properties under the influence of various pre-treatments, which opens up great opportunities for their regulation and, accordingly, the selection of the most effective catalyst for a particular chemical process. It has been shown that alkaline treatment of zeolite leads to the formation of an additional amount of mesopores, which, in turn, affects its catalytic properties in the process of converting propane into olefinic hydrocarbons. The dependence of the activity and selectivity of the zeolite catalyst on the concentration of the alkali solution used for its treatment has been established. It was found that treatment of the zeolite catalyst with a 1.0 M NaOH solution leads to an increase in its selectivity with respect to the formation of C2–C4 olefins from propane, which at a process temperature of 650 °C reaches 32.0% with a propane conversion of 81%. It has been shown that additional promotion of desilicated zeolite with magnesium or manganese increases its activity with respect to the formation of olefinic hydrocarbons from propane. For citation: Vosmerikov A.A., Vosmerikova L.N., Vosmerikov A.V. Studying the influence of alkaline treatment and modification of zeolite on its physical-chemical and catalytic properties in the process of propane conversion to olefin hydrocarbons. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 50-58. DOI: 10.6060/ivkkt.20246708.11t.

Catalytic Biomass Transformation to Hydrocarbons under Supercritical Conditions over Nickel Supported on Schungite

Liquid fuel production from biomass-derived molecules has received great attention due to the diminished fossil fuel reserves, growing energy demand, and the necessity of CO2 emission reduction. The deoxygenation of oils and fatty acids is a promising process to obtain “green” diesel. Herein, we report the results of the study of the deoxygenation of stearic acid to alkanes as a model reaction. Series of Ni-supported on schungite were obtained by precipitation in subcritical water (hydrothermal deposition) and for comparison via wetness impregnation followed, in both cases, by calcination at 500 °C and a reduction in H2 at 300 °C. The catalyst obtained via hydrothermal synthesis showed a three-fold higher specific surface area with a four-fold higher active phase dispersion compared to the catalysts synthesized via conventional impregnation. The catalysts were tested in stearic acid deoxygenation in supercritical n-hexane as the solvent. Under optimized process conditions (temperature of 280 °C, hydrogen partial pressure of 1.5 MPa, and 13.2 mol of stearic acid per mol of Ni), a close to 100% yield of C10–C18 alkanes, containing over 70 wt.% of targeted n-heptadecane, was obtained after 60 min of reaction.

Tuning a Cr-Catalyzed Ethylene Oligomerization Product Profile via a Rational Design of the N-aryl PNP Ligands

An approach towards incorporating varied degrees of steric profiles around the ligand’s backbone, which were envisaged to alter the catalytic paths leading to targeted 1-C8/1-C6 olefin products, were explored. Cr-pre-catalysts designed with PNP ligands comprising a fused aryl moiety were delivered at a relatively higher C8 olefin selectivity (up to 74.6 wt% and C8/C6 of 3.4) when the N-connection to the aromatic unit was placed at the 2-position. A relatively higher C6 olefin selectivity (up to 33.7 wt% and C8/C6 of 1.9) was achieved with the PNP unit anchored at the 1- or 6-position. Based on detailed catalytic studies, we confirm the fact that by introducing a controlled degree of bulkiness on the N-site through a judicious selection of the N-aryl moiety of different sizes, the selectivity of the targeted olefin product could be tuned in a rational manner.

Integration of Deep Eutectic Solvents and Hydrotalcites for Biomass Conversion and Aldol Condensation: Toward Platform Chemicals and Jet Fuel Synthesis—A Review

AbstractThe abundance and renewability of lignocellulosic biomass have made it a suitable alternative to fossil fuels in the reduction of global warming. The complex nature of the cellulose–hemicellulose–lignin bonds in the biomass makes it difficult to directly obtain platform chemicals. Pretreatment of the biomass has become a solution to remove lignin and obtain cellulose and or hemicellulose to produce platform chemicals. Platform chemicals such as hydroxymethylfurfural, furfural, and levulinic acid are viable feedstocks for aldol condensation to produce C8–C15 fuels. This review reports on deep eutectic solvents and microwave‐assisted pretreatment as green techniques for the delignification and platform chemicals production. Emphasis is placed on the use of hydrotalcites (HTs) as catalysts in platform chemicals production and aldol condensation for C8–C15 alkane fuels. Additionally, the hydrogenation of furfural into cyclopentanone and successive conversion into C10 and C15 alkanes with HTs was reviewed.

UiO-66/PIM-1 Mixed-Matrix Membrane for Hexane Isomer Separation.

The separation of high-octane dibranched alkanes from naphtha is critical in the refining of gasoline. To date, research on the membrane-based separation of alkane isomers has been limited, with a particular paucity of investigations into mixed-matrix membranes. Herein, the continuous and dense UiO-66/PIM-1 mixed-matrix membrane, which was prepared through precise control of the interfacial structure, was first applied to the differentiation of C6 alkane isomers. Due to the synergistic combination of UiO-66 with differential adsorption capabilities for alkanes and PIM-1 that possesses a cross-linkable structure, the resulting UiO-66/PIM-1-(20) membrane demonstrated remarkable separation performance and high stability. Pervaporation measurements showed that the mass fraction of 2,2-dimethylbutane in the feed side was increased from 50.0 to 75.8 wt % while an excellent flux of 1700 g m-2 h-1 was maintained over a continuous 40 h period. The UiO-66/PIM-1-(20) membrane, characterized by its facile replication and processing, shows potential for large-scale fabrication. This study offers a new approach to the membrane separation of alkane isomers.