Linear Alkanes Research Articles

Energy-efficient extraction of linear alkanes from various isomers using structured metal-organic framework membrane

Extraction of low concentration linear alkanes (C5-C7) from various isomers is critical for the petrochemical industry. At present, the separation of alkane isomers is mainly accomplished by distillation, which results in substantial energy expenditure. Metal-organic frameworks (MOFs) with well-tailored nanopores have been demonstrated to be capable of realizing molecule-level separation. In this study, oriented HKUST-1 membranes are formulated according to the morphology-biased principle and finally realized with a low dose synthesis method for terminating undesired crystal nucleation and growth. The fully exposed triangular sieving pore array of the membrane induces configuration entropic diffusion to split linear alkanes from mono-branched and di-branched isomers as well as their cyclical counterparts. Typically, the current separation technique consumes 91% less energy than vacuum distillation. Furthermore, our membranes can realize one-step extraction of normal-pentane, normal-hexane and normal-heptane from a ten-component alkane isomer solution that mimics light naphtha.

Effects of genotype and host environment on the cuticular hydrocarbon profiles of Lysiphlebus parasitoids and aggression by aphid-tending ants.

Parasitoids in the genus Lysiphlebus specialize on ant-tended aphids and have previously been reported to mimic the cuticular hydrocarbon (CHC) profiles of their aphid hosts to avoid detection by ants. However, the precise mechanisms that mediate reduced ant aggression toward Lysiphlebus spp. are not known, nor is it clear whether such mechanisms are broadly effective or specialized on particular aphid hosts. Here we explore the effects of wasp genotype and host environment on Lysiphlebus CHC profiles and ant aggression. Rearing asexual Lysiphlebus lines in different host aphid environments revealed effects of both wasp line and aphid host on wasp CHCs. However, variation in genotype and host affected different features of the CHC profile, with wasp genotype explaining most variation in linear and long-chain methyl alkanes, while aphid host environment primarily influenced short-chain methyl alkanes. Subsequent behavioural experiments revealed no effects of host environment on ant aggression, but strong evidence for genotypic effects. The influence of genotypic variation on experienced ant aggression and relevant chemical traits is particularly relevant in light of recent evidence for genetic divergence among Lysiphlebus parasitoids collected from different aphid hosts.

Algae pyrolysis in alkaline molten salt: Products transformation

Algae pyrolysis in alkaline molten salt is a promising technology for hydrogen production, but the pyrolysis products transformation has not clearly been described up-to-date. Moreover, the complex bio-oil especially heavy bio-oil fraction directly influences the products transformation pathways, while limiting the hydrogen production yield and application. Both the light and heavy bio-oil fractions are investigated in detail and the effect of alkaline molten salt on products transformation is obtained. Molten salt promotes the cyclization and aromatization of linear alkenes, thereby increasing aromatic compound content and hydrogen production. The decarbonation of Na2CO3 and the deoxygenation of NaOH lead to the methane release, in turn reducing hydrogen production. The heavy compounds tend to polymerize at higher temperatures into compounds with higher molecular weights and unsaturation, while generating hydrogen. As the temperature rises, char reacts with molten salt to form hydrogen and disappears at 650 °C, while aromatics in light compounds condense into heavy compounds, which then grow to form soot-like at 600 °C, accompanying hydrogen release. Based on the relationship between products transformation, hydrogen release and alkaline molten salt effect, strategies to improve the hydrogen yield and purity of AMSP process are proposed.

Limits of alkanes confined in mesoporous silica as a probe for geometrical tortuosity. An NMR relaxation study

Diffusion Nuclear Magnetic Resonance experiments offer a means to determine the geometrical tortuosity of a porous matrix, assuming that the interaction between the confined fluid and the confining matrix is negligible. In this, alkanes play a crucial role as molecular probes for polar mesoporous systems, with silica being particularly relevant due to its wide range of technological applications. Despite their inherent hydrophobicity, NMR measurements reveal that alkane/silica interactions become significant when the pore diameter approaches the size of the molecules. This fact is clearly demonstrated through the examination of the longitudinal (T1) and transverse (T2) relaxation times of linear and cyclic alkanes confined within silica mesopores of mean pore sizes: 3, 6, and 15 nm. Noticeably, the interactions are practically negligible in 6 and 15 nm pores, but they become relevant in the smallest ones. T1-T2 correlation maps evidence that relaxation times are influenced by molecular length, shape, and pore diameter. These empirical results not only corroborate previous theoretical findings but also highlight the ratio T1/T2 as a valuable, rapid, and cost-effective experimental tool for assessing the feasibility of a given solvent as a molecular probe for determining geometrical tortuosity.

C(sp3)-H hydroxylation of Broad-Spectrum Alkanes Catalyzed by an Artificial P450 Peroxygenase Driven by ω-Pyridyl Fatty Acyl Amino Acids

Selective hydroxylation of C(sp3)–H bonds is a long-standing challenge in the organic synthesis field. We herein report an artificial P450 peroxygenase system facilitated by ω-pyridyl fatty acyl amino acids that can hydroxylate broad-spectrum alkanes, including linear and cyclic alkanes and benzylic and allylic alkane chains. Compared with the previously reported dual-functional small molecule (DFSM) with imidazole as a catalytic group (Im-DFSM), pyridyl DFSM (Pyd-DFSM) produced substantially higher total turnover numbers (TTNs) for the hydroxylation of medium-chain alkanes and cycloalkanes (C6–C8), e.g., 12.0-fold and 17.1-fold increased TTNs of P450 mutant F87A/T268V for heptane and cycloheptane, respectively. In addition, Pyd-DFSM altered the enantioselectivity of benzylic hydroxylation, e.g., it almost inverted the configuration observed in the benzylic hydroxylation of ethylbenzene and tetralin. More importantly, Pyd-DFSM showed excellent regioselectivity for allylic hydroxylation over epoxidation of terminal alkenes and cycloalkenes, e.g., up to 94% allylic hydroxylation of 1-hexene was observed. This work significantly enhances the catalytic toolbox of the DFSM-facilitated P450 peroxygenase system; it not only substantially expands the chemical space of P450 enzymes, but also provides an alternative solution for the selective hydroxylation of C(sp3)–H bonds.

Evaluating the potential of NUIG2 metal–organic framework for adsorption of short linear alkanes at low pressure

Evaluating the potential of NUIG2 metal–organic framework for adsorption of short linear alkanes at low pressure

Lack of evidence for chemical integration of the cuckoo-bee Stelis nasuta (Latreille, 1809) and Coelioxys aurolimbata (Förster, 1853) with their main host Megachile parietina (Geoffroy, 1785)

Megachileparietina is a solitary megachilid species, which sometimes nests in large aggregations. Such a condition attracts a diverse entomological fauna, including several parasites. Here, we focused on two cuckoo-bees of this species, Stelis nasuta and Coelioxys aurolimbata (Megachilidae) and investigated if chemical integration with the host favours their reproductive success. Lipids on the epicuticle and in the Dufour’s gland secretion, possibly contributing to protecting the eggs against dehydration, of the three species showed species-specific mixtures of long-chained linear alkanes and alkenes. Moreover, contrary to what has been reported for some cuckoo-bees of the genus Nomada, we found no evidence that the mandibular glands of parasite males contribute to female chemical mimicry. Therefore, we found no indication that chemical integration is part of the adaptive strategies of these two brood parasites.

One-Pot Synthesis of Polycyclic 4,5-Dihydropyridazine-3(2H)-ones by Inverse Electron-Demand Diels-Alder (IEDDA) Reactions from Alkenes.

In the classical Inverse Electron-Demand Diels-Alder (IEDDA) reactions between alkenes and tetrazines, 4,5-dihydropyridazines are formed. 4,5-Dihydropyridazines are rapidly converted to the more energetically stable 1,4-dihydropyridazines by 1,3-prototropic isomerization. In this study, instead of 1,4-dihydropyridazines, 4,5-dihydropyridazine-3(2H)-ones were obtained as a result of IEDDA reactions between tetrazines with leaving groups at the 3,6-positions, and norbornene and barrelene-derived polycyclic alkenes in the presence of moisture in air or solvent. To show that this new method works not only on strained polycyclic alkenes but also on monocyclic and linear alkenes, the corresponding 4,5-dihydropyridazine-3(2H)-ones were obtained in high yields from the reactions performed with styrene and cyclopentene as well. The chemical structures of the polycyclic 4,5-dihydropyridazine-3(2H)-ones were determined by NMR and HRMS analyses. In addition, the exact structures of the polycyclic 4,5-dihydropyridazine-3(2H)-ones were also experimentally proven by converting them to pyridazine-3(2H)-ones known in the literature.

Illuminating the impact of the proximity communication modes between redox metallic and acidic zeolite sites during hydro-conversion of n-heptane

The unique physicochemical properties of “redox-acid” bifunctional zeolites make them an essential tool in the petrochemical industry, especially in the hydro-conversion of linear alkanes to deliver high-octane fuels. The current research activities in this domain are primarily tailored towards evaluating the “intimacy/proximity” criteria among two catalytically active sites and minimizing the loading of noble metals (e.g., Pd or Pt) in catalysis. However, the chemistry behind the communication mode (i.e., “through-space” or “through-bond” interaction between metallic and acid sites) has remained vastly underexplored during the hydro-conversion of n-alkanes over Pt or Pd/zeolites. To dig deeper into this uncharted territory, this work demonstrates that both “through-space” (cf. metals in extra-framework position in/on zeolite) and “through-bond” (cf. metals on the zeolite framework) bifunctionality favors the hydroisomerization step, while the later partially also promote the hydro-cracking. Their working protocol was probed by the diverse material characterization techniques that improved the understanding of the zeolite-catalyzed hydrocarbon conversion processes.

Valorization of oily sludge waste using biosurfactant-producing bacteria.

Oily sludge generated by the petroleum industry is not only an environmental hazard, but since it contains crude oil too, it is a valuable resource as well. This study demonstrates a methodology for the valorization of the oily sludge that allows the recovery of oil fractions by the action of microbes producing surface-active metabolites. Two bacterial isolates were used in the study that were producing different biosurfactants, identified via FTIR analysis as well as through genomic mapping of the biosurfactant pathways using RAST, ANTISMASH 7.0, STRING databases. Serratia spp. AKBS12, produced a mono-rhamnolipid, while Acinetobacter spp. AKBS16, produced emulsan. Although recovery efficiency of both biosurfactants was similar, the recovery profile with respect to the class of hydrocarbons differed. The rhamnolipid produced by Serratia spp. AKBS12 extracted mono-chained paraffins and linear alkanes, while emulsan, produced by Acinetobacter spp. AKBS16 could extract heavier paraffins. The extraction procedure is simple and involves mixing the biosurfactant with oily sludge at a temperature of 30 °C with an incubation of 9days. Sulphuric acid precipitation releases the oil trapped in the oily sludge. The study is the first step in developing user-friendly, innovative technologies that can be linked to the concept of a circular economy.

Selective Characterization of Olefins by Paternò-Büchi Reaction with Ultrahigh Resolution Mass Spectrometry.

Petroleum olefins play important roles in various secondary processing procedures and are important feedstocks for the modern organic chemical industry. It is quite challenging to analyze petroleum olefins beyond the gas chromatography (GC)-able range using mass spectrometry (MS) due to the difficulty of soft ionization and the matrix complexity. In this work, a Paternò-Büchi (PB) reaction combined with atmospheric pressure chemical ionization and ultrahigh resolution mass spectrometry (APCI-UHRMS) was developed for selective analysis of olefins. Through the PB reaction, C═C bonds were transformed into four-membered rings of oxetane with improved polarity so that soft ionization of olefins could be achieved. The systematic optimization of PB reaction conditions, as well as MS ionization conditions, ensured a high reaction yield and a satisfied MS response. Furthermore, a sound scheme was set up to discriminate the coexisting unsaturated alkanes in complex petroleum, including linear olefins, nonlinear olefins, cycloalkanes, and aromatics, making use of their different behaviors during the PB reaction and chemical ionization. The developed strategy was successfully applied to the analysis of olefins in fluid catalytic cracking oil slurry, a complex heavy oil sample. This method extended the characterization of petroleum olefins from lower to higher with high efficiency and selectivity to provide a comprehensive molecular library for heavy petroleum samples and process optimization.

Highly productive framework bounded Ni2+ on hierarchical zeolite for ethylene oligomerization

The production of higher linear olefins via ethylene oligomerization is an applied industrial process using homogeneous catalysts in the liquid phase. Heterogeneous catalysts based on Ni supported on zeolites are attractive materials for gas phase oligomerization but typically offer a low selectivity or low conversion. Here, we investigate a tailored method to introduce the Ni2+ species within the hierarchical zeolite crystallization step (in situ) and compare it with the standard impregnation procedure (ex situ). The in situ engineered catalyst has a very high concentration of Ni2+ species, seamlessly inserted and well dispersed into the zeolite framework, with increased accessibility through meso- and micropores. This catalyst has a unique 1-butene cumulative productivity (32.7 g of 1-butene per g of catalyst) and stability for at least 48 h. This framework bounded Ni2+ promotes oligomerization over isomerization, cracking, and hydride transfer, while the hierarchical zeolite structure enables the discharge of coke precursors. These results pave the way for a more efficient and effective ethylene oligomerization process.

Production of jet fuel range hydrocarbons using a magnetic Ni–Fe/SAPO-11 catalyst for solvent-free hydrodeoxygenation of jatropha oil

A novel, multifunctional Nix–Fe/SAPO-11 catalyst was synthesized and characterized, and its activity was evaluated for the solvent-free hydrodeoxygenation of jatropha oil. The catalyst has a spherical structure and moderate acid strength, and exhibited excellent cyclization and deoxidation activity. The inclusion of iron facilitated the dispersion of active components. Consequently, the iron-nickel alloy particle size remained small, resulting in an optimal distribution of the product. The composition of the products is linear alkanes (59.83%), isoparaffins (4.16%), aromatics (8.41%), and naphthenes (12.03%), where jet fuel components are relatively high, accounting for 55.04% of C8–C16 hydrocarbons. Interestingly, the iron present in the catalyst allowed the use of an external magnetic field for the rapid separation and recycling of the catalyst. Despite multiple uses, the recycled catalyst maintained high activity following five cycles, with hydrocarbon content consistently above 85%. The synergic effect of the metallic and acid sites of the catalyst, let to realize one-pot hydrodeoxygenation, isomerization, aromatization, and cracking of substrate forming bio-jet fuel range hydrocarbons.

(Invited) Metal Organic Frameworks for the Storage, Separation, and Purification of Gaseous Fuels

We have seen a surge of interest in metal organic frameworks (MOFs) over the past decades with more than 100,000 structures reported today. This interest is based on the modular building-block nature of their structure, which makes them tunable and widely applicable to many applications. Of particular interest is the storage, separation, and purification of gaseous fuels with MOFs as a much-needed alternative to the energy-intense processes currently in use. My talk will focus on results of a variety of MOFs that have been obtained by a close integration of synthesis, in situ vibrational spectroscopy, and ab initio materials modeling. In particular, we report on the development and characterization of four MOFs for the purpose of separating linear, mono, and dibranched alkane isomers through selective molecular sieving, which is of significant value in the petrochemical industry. The separation of such alkane isomers is a challenging and important industrial process for the production of premium gasoline, blending components with high research octane number. I will also show recent results that point towards non-standard kinetics in certain separation processes in MOFs as well as results for ultramicroporous MOFs that have the ability to effectively perform separations in the presence of water.

Fischer–Tropsch Synthesis Catalysts for Selective Production of Diesel Fraction

The Fischer–Tropsch process is considered one of the most promising eco-friendly routes for obtaining synthetic motor fuels. Fischer–Tropsch synthesis is a heterogeneous catalytic process in which a synthesis gas (CO/H2) transforms into a mixture of aliphatic hydrocarbons, mainly linear alkanes. Recently, an important direction has been to increase the selectivity of the process for the diesel fraction. Diesel fuel synthesized via the Fischer–Tropsch method has a number of advantages over conventional fuel, including the high cetane number, the low content of aromatic, and the practically absent sulfur and nitrogen impurities. One of the possible ways to obtain a high yield of diesel fuel via the Fischer–Tropsch process is the development of selective catalysts. In this review, the latest achievements in the field of production of diesel via Fischer–Tropsch synthesis using catalysts are reviewed for the first time. Catalytic systems based on Al2O3 and mesoporous silicates, such as MCM-41, SBA-15, and micro- and mesoporous zeolites, are observed. Together with catalytic systems, the main factors that influence diesel fuel selectivity such as temperature, pressure, CO:H2 ratio, active metal particle size, and carrier pore size are highlighted. The motivation behind this work is due to the increasing need for alternative processes in diesel fuel production with a low sulfur content and better exploitation characteristics.

Highly selective and recyclable homogeneous hydroformylation of olefins with [Rh(cod)Cl]2/PPh3 regulated by Et3N as additive

Rh-catalyzed hydroformylation of different olefins toward the corresponding aldehydes were performed under syngas atmosphere in the presence of triethylamine (Et3N) as additive. The influence of various reaction parameters including the phosphine ligands, solvents, additives have been investigated. It was found that, by involving Et3N as additive in the [Rh(cod)Cl]2/PPh3 catalytic system, the conversion of substrates (including cyclic, internal and linear olefins, up to 99%) and chemo/regioselectivity of the products were improved (up to 99%), the applicability for the synthesis of important aldehydes was wider in the absence of solvent. More importantly, the catalytic system could be recycled more than 7 times through vacuum distillation operation and provided a new synthesis method for the pesticide dinotefuran (Tetrahydrofuran-3-formaldehyde) and perfume (Lily aldehyde) intermediates.

Catalytic membrane reactors for alkane dehydrogenation applications: an integration of catalysis and separation process

Abstract Catalytic dehydrogenation of saturated hydrocarbons to corresponding alkenes by the release of the stoichiometric amount of hydrogen is the paramount solution for safe storage of hydrogen. The utilization of a catalytic membrane reactor for this process enhances the reaction yield beyond thermodynamic equilibrium by selectively and simultaneously removing the produced H2 during the reaction. To this end, the present review is focused on the integration of H2 permeable membranes with the catalysts for dehydrogenation of lighter alkanes for coproduction of olefins and high-purity hydrogen in a single step. Besides, this review also covers dehydrogenation of liquid organic hydrogen carriers for safe storage of hydrogen. Herein, different types of H2 perm-selective membranes used for the dehydrogenation reaction are highlighted and the effect of hydrocarbon on H2 permeation through these membranes are discussed in detail. Furthermore, the simulation studies along with the experimental investigation performed on the membrane reactors for dehydrogenation of linear and cyclic alkanes are critically reviewed to find the coherence between simulation and experimental findings. Systematic discussion is done on the different types of alkane dehydrogenation reactions and the parameters affecting the reaction performance. Finally, directions are provided to prepare a cheaper and large industrial scale membrane reactor for dehydrogenation reaction. The concept of coupling an exothermic reaction with the endothermic dehydrogenation reaction is provided as a future direction study to enhance the overall yield and energy efficiency of the integrated membrane reactor.

Alkane biosynthesis is promoted in methyl jasmonate-treated sweet cherry (Prunus avium) fruit cuticles.

The cuticle plays an important role in the survival of plants, and it is important to preserve the quality of fleshy fruits like sweet cherry. Plant hormones play a role in cuticle formation. In this sense, jasmonates have been shown to induce cuticle biosynthesis, but until today this has not been demonstrated in sweet cherry fruit. Therefore, the effect of exogenous methyl jasmonate (MeJA) application at the fruit set stage on the expression levels of cuticle synthesis-related genes and the wax composition of the isolated cuticle was studied in developing and ripe fruits of sweet cherry (Prunus avium 'Bing'), respectively. MeJA treatment resulted in up-regulation of the cuticle biosynthesis-related gene expression, such as PaWINA, PaWINB, PaKCS1, PaKCS6, PaLACS1, PaLACS2, PaWS, and PaWBC11. These genes play a vital role in the elongation and transport of fatty acids, and wax biosynthesis. Analysis of cuticular components in ripe fruit showed an increase in long-chain linear aliphatic wax compounds, particularly C27, C28, C29, C30, and C31 alkanes. Exogenous MeJA application at the fruit set stage of sweet cherry has a significant effect on the wax composition of the ripe fruit cuticle, particularly in terms of alkane biosynthesis. The results of this study may provide insights into the regulation of cuticle biosynthesis by jasmonates and be useful for improving fruit quality and storage life. © 2023 Society of Chemical Industry.

Ethylene Copolymerization with Linear and End-Cyclized Olefins via a Metallocene Catalyst: Polymerization Behavior and Thermal Properties of Copolymers

Olefin solution polymerization can be used to obtain high-performance polyolefin materials that cannot be obtained via other polymerization processes. Polyolefin elastomers (POE) are a typical example. Due to cost, only a few linear α-olefins (e.g., 1-butene, 1-hexene, and 1-octene) are used as comonomers in solution polymerization in industry. However, α-olefin comonomers with other structures may have different effects on polymerization in comparison with common linear ones. Moreover, the properties of the corresponding materials may differ significantly. In this work, copolymers of ethylene with linear and end-cyclized α-olefins are synthesized using a metallocene catalyst. The copolymerization of ethylene with linear α-olefins results in a higher turn-over frequency (TOF) and lower incorporation than copolymerization with end-cyclized α-olefins, which may indicate that end-cyclized α-olefins have a higher coordination probability and lower insertion rate. In this reaction, the comonomer is distributed randomly in the polymer chain and efficiently destroys crystallization. End-cyclized α-olefins exhibit a much stronger crystallization destructive capacity (CDC) in the copolymer than linear α-olefins, possibly because linear α-olefins act mainly in the radial direction of the main chain of the polymer, while end-cyclized α-olefins act mainly in the axial direction of the main chain.

Thermochemical study of 2-adamantanone

The results of a thermochemical study of the standard molar enthalpy of combustion of 2-adamantanone in the crystalline phase state by isoperibol combustion calorimetry are presented. Two different approaches of combustion-calorimetry data processing (one from 1956 traditionally used in the field and another from 2021 updated with respect to equations and reference values) were compared and shown to give nearly indistinguishable results for 2-adamantanone (composed of only C, H, O elements). The results allowed resolving the observed inconsistency in the literature values of the enthalpy of formation of 2-adamantanone in the crystalline phase state published to date. The experimental standard enthalpy of formation for crystal was combined with the enthalpy of sublimation available in the literature to give the enthalpy of formation for gas, which is in excellent agreement with the gas-phase enthalpy of formation computed according to one of the most reliable quantum-chemical protocols. The enthalpy effect of the substitution of a methylene fragment with a carbonyl group was analyzed in a series of linear, branched, and cyclic alkanes. The evaluated effect indirectly confirms the absence of any measurable strain in 2-adamantanone in comparison to the parent molecule of adamantane.