Non-catalytic Conditions Research Articles

Conversion mechanism of thermal plasma-enhanced CH4-CO2 reforming system to syngas under the non-catalytic conditions

Thermal plasma activation of CH4-CO2 reforming (CRM) to syngas under non-catalytic conditions is an efficient and clean technology for the large-scale utilization of hydrocarbon resources and the conversion of greenhouse gases. This study investigates the equilibrium state and transformation mechanism of a CRM reaction system activated by thermal plasma through experimental, thermodynamic, and kinetic analyses. The experimental results illustrated that the CO2 conversion rate and H2 selectivity showed a downward trend with an increase in the CO2/CH4 molar ratio, whereas the CH4 conversion rate and CO selectivity showed the opposite trend. When CO2/CH4 molar ratio was 6/4, the selectivity for CO and H2 increased to 87.0 % and 80.8 %, respectively. Excess CO2 promotes the partial oxidation of CH4 to eliminate carbon deposition, resulting in an H2/CO molar ratio value closer to 1. Thermodynamic results show that the thermal-plasma-initiated CRM reaction can reach thermodynamic equilibrium more easily than the conventional catalyzed reactions, achieving much higher feedstock gas conversion without carbon deposition. The kinetic results obtained from the PSR model revealed that CH4 and CO2 were cleaved to form free radicals at the instant of contact with the plasma flame. O, H, and other particles generated in the form of free radicals rapidly collided with each other and transformed into CO and H2, accelerating the reaction process. The results presented in this study will help reveal the transformation mechanism of the CRM reaction activated by thermal plasma under non-catalytic conditions and provide a new perspective for studying CRM reactions.

Catalytic vs. uncatalyzed [2 + 2] photocycloadditions of quinones with alkynes.

Photoreactions of quinones with alkynes under catalytic and non-catalytic conditions were studied. In contrast to recent reports, simple irradiation with blue light is sufficient to trigger [2 + 2] photocycloadditions, which afford either fused cyclobutenes or reactive para-quinone methides (p-QMs) depending on the quinone structure. Revision of the chemo- and regioselectivity of the uncatalyzed photoreactions provided useful insight into their overlooked relatedness to the recently developed catalytic protocols. Experimental evidence indicates that the reactivity of the photochemically generated p-QMs is sufficient to perform uncatalyzed reactions with nucleophiles, which can help to explain the existing transformations and develop new cascade transformations involving quinones and alkynes.

Recycling Pomelo Peel Waste in the Form of Hydrochar Obtained by Microwave-Assisted Hydrothermal Carbonization.

Pomelo peel (PP) is a kind of solid waste that is produced in the processing industry of honey pomelo. This study deeply explored the feasibility of recycling PP in the form of hydrochar (HC) by microwave-assisted hydrothermal carbonization (HTC) technology. Under the non-catalytic reaction conditions, the yield of hydrochar initially increased with the rise of reaction temperature (150-210 °C) until it remained relatively stable after 210 °C. Under the CaO-catalytical reaction condition, the yield of hydrochar did not change much at first (150-190 °C) but decreased significantly when the reaction temperature exceeded 190 °C. After the microwave-assisted HTC treatment, the PP-derived HC presented higher aromaticity, carbonization degree, porosity, and caloric value. Compared with raw PP, the nutrients in HC were more stable (conducive to being used as slow-release fertilizer). The application of CaO increased the pH value of HC and effectively promoted the accumulation of phosphorus in HC. The HC produced at 210 °C without any catalyst possessing a high devolatilization ability. Additionally, the HC obtained at 190 °C with CaO as the catalyst presented a high combustion property. In general, PP-derived HC showed great application potential in the field of soil remediation/improvement and solid fuels. This preliminary study would undoubtedly provide some important fundamental understanding of the microwave-assisted HTC of PP.

Novel cobalt-based MOF facilitating reclaiming byproduct in wet magnesia desulfurization with ultrahigh dispersity and catalytic activity

In the wet magnesia desulfurization process, magnesium sulfite oxidation is essential to reclaim and resource utilization the byproducts. Therefore, it is of great significance to create reliable and effective catalysts. In this study, a novel and efficient catalyst, Co-MOF (BTC), was synthesized by an ultrasound assisted one-pot method. The oxidation rate of MgSO3 by Co-MOF (BTC) was 0.112 mmol·L−1·s−1, 13–14 times higher than under non-catalytic conditions, with an apparent activation energy of 26.82 kJ·moL−1. The catalytic efficiency is 4–5 times higher than previously reported Co-SBA-15 catalysts with the same loading. The characterization results of XRD, TEM and XPS confirm that the active component cobalt has a high dispersion on TMLA, and Co (II) plays an important role in improving the oxidation performance of catalysts. The results reveal that the rich hydroxyl group on surface of TMLA is conducive to the dispersion of Co for full contact with the reactants, and the Co (II) of Co-MOF (BTC) is favorable to the formation of Co-O bond, and then promotes its oxidative activity. The kinetics of the MgSO3 oxidation catalyzed by the prepared Co-MOF (BTC) was investigated in a bubble oxidation apparatus, indicating that the oxidation rate was dependent on the reaction temperature, pH value, oxygen partial pressure and air velocity.

Lithium salt-concentrated organogels prepared via one-step polymer network formation in acetonitrile-based solutions

We report lithium (Li) salt-concentrated organogel prepared via one-step gelation conducted in an acetonitrile (AN)-based solution containing tetra-arm poly (ethylene glycol) (TetraPEG) and the lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) salt at extremely high concentration. The polymer network formation via a Michael addition reaction between thiol-terminated and maleimide-terminated TetraPEG prepolymers successfully proceeded in concentrated LiTFSA/AN solutions under noncatalytic conditions at room temperature to yield a homogeneous polymer network with high reaction efficiency (>95%). We investigated the electrochemical properties of the concentrated organogel to apply it as a quasi-solid electrolyte material to the Li-ion capacitors comprising a graphite anode and activated carbon (AC) cathode. The concentrated organogel afforded the reversible Li-ion insertion/desertion into/from graphite; however, reactivity depended on the polymer concentration in the organogels. The reversible adsorption/desorption of TFSA anions into/from the AC was observed in the concentrated organogel, which was comparable to that of the corresponding electrolyte solution.

Efficient Access of Phenyl-Spaced 5,5′-Bridged Dinuclear Ruthenium Metal Complexes and the Effect of Dynamic Ligand Exchange on Catalysis

Herein, we present the synthesis, characterization, and light-driven hydrogen evolution activity of two dinuclear Ru-Pt complexes, Rup(ph)pPtX2 (X = Cl, I), comprising a new phenyl-spaced 5,5′-bis-phenanthroline p(ph)p bridging ligand. The two complexes only differ in the nature of the halide ligand at the catalytic center. Structural, photophysical, electrochemical, as well as photochemical characterization techniques revealed that the variations of single components of the intramolecular system provide a strong influence on the stability even in non-catalytic conditions. Interestingly, varying electron density at the catalytic center, mainly influenced by the coordinating halide at the catalytic center, as shown by 195Pt NMR spectroscopy, strongly influences the photocatalytic efficiency. Furthermore, intensive investigations on the potential catalytic mechanism showed that small structural variations (e.g., halide exchange) not only affect catalytic activity but can also switch the main catalytic mechanism from an initially molecular one to a fully heterogeneous, colloid-driven hydrogen evolution.

Atom-economic Michael reaction between hydroacridines and arylmaleimides without catalyst/additive

Previously unknown spiroderivatives of 3,1-benzoxazines were synthesized by the reaction of anthranilic acid with cyclic ketones. The interaction of 3,1-spirobenzoxazines with Vilsmeier-Haack reagent (POCl3 (PBr3)/DMF), depending on the amount of formulation agent, leads to the formation of hydroacridones or hydroacridines. Under catalyst- and additive-free conditions, N-arylmaleimides, like Michael's acceptors, are added to the hydroacridines in DMSO to form the corresponding adducts. The reaction proceeds stereoselectively with the formation of a mirror pair of diastereomers, if the products have only two chiral centers. In the presence of three chiral centers in the structure of Michael's adducts, the reaction is not stereoselective. The reaction proceeds by the sp3 hybrid carbon atom under non-catalytic conditions due to the imin-enamine tautomerism of chloro(bromo)hydroacridines. The presented reaction can also be considered as an effective atom-economical aza-ene reaction, which fully meets today's requirements for eco-friendly reaction. The synthesized compounds are potential biologically active substances and can also be used as "building-blocks" for organic synthesis.

Competition of hydrolysis, self-polymerization and graft coupling for n-dodecyltrimethoxysilane modified Al2O3 under non-catalytic conditions

Silane coupling agent (SCA) modification was a common method to improve the interfacial compatibility between fillers and matrix. In this paper, the competition of silane hydrolysis, self-polymerization and graft coupling during the modification process was investigated under non-homogeneous and non-catalytic conditions from the modification mechanism of SCA. It was found that the degree of hydrolysis, self-polymerization of SCA and graft coupling with Al2O3 surface could be controlled by regulating the reaction conditions and combination of nuclear magnetic resonance hydrogen spectroscopy, thermogravimetric analyzer and X-ray photoelectron spectroscopy is effective methods for measure quantitatively the degree of hydrolysis, self-polymerization of SCA and graft coupling. In addition, free silanes with different degrees of hydrolysis and self-polymerization had obviously influence on the fluidity and store stability of modified spherical Al2O3. Free silanes with smaller degrees of hydrolysis and self-polymerization had lubricating effect and could further reduce the viscosity and with larger degrees of hydrolysis and self-polymerization free products would lead to agglomeration. Therefore, we had a deeper investigation on the modification mechanism for SCA and the role of free silane, which was of guiding significance to control the modification conditions and analyze the stability for modified fillers (agglomeration and long-term storage) in industrial production.

Co-liquefaction of Tunçbilek lignite with algae (spirulina species): Effect of process parameters and characterization of chars and oils

Nowadays, to reduce the cost of coal liquefaction and to produce a new liquid fuel alternative to petroleum, it is considered a more convenient method to liquefy coal and biomass together instead of solely coal liquefaction. Liquefaction experiments were carried out by changing the solvent/solid ratio of 1/1–5/1, reaction temperature 320–400 °C, reaction time 30–90 min, and algae/lignite ratio in the range of 1/1–5/1. As a result of this study, the most suitable process parameters obtained by considering total conversion are; solvent/solid ratio 3/1, reaction time 60 min, algae/lignite ratio 4/1, and reaction temperature 380 °C. Under these conditions, the highest total conversion is approximately 80% and 77% in catalytic and non-catalytic conditions, respectively. Under non-catalytic conditions of co-liquefaction experiments due to the GC-MS results, cyclopentane (raw material of motor oil), pentadecane, 2-methyl-naphthalene, octa-ethylene glycol, ethylene oxide heptamer are the main products of optimum parameters aforementioned for oil. They are mainly used in fuel technology and used in the chemical industry as raw materials mean low-cost production as well.

Importance of char-volatiles interactions during co-pyrolysis of polypropylene and biomass components

This study reports the importance of plastic volatiles on char-volatiles interactions during co-pyrolysis of polypropylene (PP) and biomass components under non-catalytic conditions in a two-stage reactor. PP-volatiles were generated and interacted with biochar from cellulose and lignin downstream at different temperatures. Different experiment configurations were designed in order to explore the contribution of the tarry and waxy materials in PP-volatiles to the char-volatiles interactions. Experimental results showed that the char-volatiles interactions altered the yield and the chemical structure of PP-oil and biochar. The O-containing and aromatic species in biochar acted as active sites during interactions. Large aromatic rings in the biochar were predominant during the cracking of the tarry materials in PP-volatiles, while the O-containing species dominated during the recombination and polymerization of the waxy material in PP-volatiles. At higher temperatures, waxy and tarry materials released H-radicals inside the cellulose-char matrix, and strengthened the ring aromatic condensation reactions, while waxy and tarry materials were involved in heavier aromatic structures in lignin-char, leading to the fragmentation of lignin. In addition, even at low temperatures (e.g. 500 °C), waxy material can provide hydrogen and slightly enhance the condensation of the aromatic ring systems in lignin-char.

Influence of catalytic wall on the effective radius of a blunt body geometry in a nonequilibrium hypersonic flow

The effect of the surface catalycity on the effective radius of a blunt body geometry in hypersonic flow is numerically investigated. The blunt body geometry is defined in terms of a body radius with variation in both nose radius and the corner radius. Five different types of blunt body configurations are considered, that range from a flat-faced to a complete hemisphere geometry. The chosen blunt body configurations are investigated for four flow conditions with different levels of flow enthalpy. The effective radius is obtained by comparing the stagnation heat transfer of the blunt body geometry to that of the spherical geometry. To compute the stagnation heat transfer in the given blunt body configuration, a two-dimensional computational fluid dynamics (CFD) solver with thermochemical non-equilibrium is utilized. Both non-catalytic and fully-catalytic wall boundary conditions are considered in the computation. The obtained effective radius is additionally compared with the original data provided in the literature. The results show that surface catalycity influences the effective radius for the given blunt body configuration.

Non-catalytic, instant iridium (Ir) leaching: A non-negligible aspect in identifying Ir-based perovskite oxygen-evolving electrocatalysts

The large-scale application of proton exchange membrane water electrolysis technology requires the development of high-performance oxygen evolution electrocatalysts with as little iridium (Ir) as possible. Ir-based double perovskite oxides (A2B'IrO6; A = alkaline, alkaline-earth, or rare-earth elements; B' = transition metal or rare-earth elements) represent a class of oxides with great potential to replace the commercial catalyst IrO2. However, the structural evolution of Ir-based double perovskite oxides in electrolytes is incompletely understood, and foundational knowledge of the design principle of the “ideal” material is lacking. In this work, we report the unexpected phenomenon of instant Ir leaching from Ir-based double perovskite oxides in acid under non-catalytic conditions and discuss the implications of this phenomenon for mechanism investigation and material identification. Some well-known Ir-based double perovskite oxides, such as Ba2PrIrO6 and Sr2YIrO6, undergo instantaneous Ir leaching when they come into contact with acidic electrolytes. The Ir-leaching process is found to be non-persistent and non-thermodynamically determined, and its extent is correlated with the leaching of other B'-site elements in the perovskite oxides. Based on this observation, we revisit the Ir dissolution-precipitation process for surface IrOx formation during the perovskite-electrolyzed oxygen evolution reaction, emphasizing the non-negligible role of Ir species owing to acid corrosion in the electrolyte. Finally, we modify a screening protocol for low-Ir oxygen evolution electrocatalysts and propose an instant acid corrosion test as an indispensable process to evaluate the structural stability of potential catalysts.

Bio-Crude Production from Protein-Extracted Grass Residue through Hydrothermal Liquefaction

In the present study, the protein-extracted grass residue (press cake) was processed through hydrothermal liquefaction under sub and supercritical temperatures (300, 350 and 400 °C) with and without using a potassium carbonate catalyst. The results revealed that bio-crude yield was influenced by both temperature and the catalyst. The catalyst was found to be effective at 350 °C (350 Cat) for enhancing the bio-crude yield, whereas supercritical state in both catalytic and non-catalytic conditions improved the quality of bio-crude with reasonable HHVs (33 to 36 MJ/kg). The thermal behaviour of bio-crude was analysed and higher volatile contents (more than 50% under the range of 350 °C) were found at supercritical conditions. The overall TOC values in the residual aqueous phase varied from 22 to 38 g/L. Higher carbon loss was noticed in the aqueous phase in supercritical conditions. Furthermore, GCMS analysis showed ketones, acids and ester, aromatics and hydrocarbon with negligible nitrogen-containing compounds in bio-crude. In conclusion, the catalytic conversion of grass residue under subcritical conditions (350 Cat) is favourable in terms of high bio-crude yield, however, supercritical conditions promote the deoxygenation of oxygen-containing compounds in biomass and thus improve HHVs of bio-crude.

Production of Activated Carbon from Waste PET’ Chars

Activated carbon, which is used in many application areas such as gas purification, purification of pollution in water and wastewater, removal of odor and pollution, in the defense industry, in the production of protective clothing and in the health sector, was produced from solid products obtained by waste polyethylene terephthalate (wPET) liquefaction that was carried out under non-catalytic conditions, the reaction time of 15-90 min, and a reaction temperature of 325-425 °C in a batch reactor. The solid products obtained, after grinding, were made in a muffle furnace at 400-700°C in a nitrogen gas atmosphere for 30 min. The solid products obtained in the liquefaction of waste polyethylene terephthalate contain approximately 60% Carbon (C), 4% Hydrogen (H) and 36% Oxygen (O), and are composed of terephthalic acid (C₈H₆O₄) in crystalline form. According to Brunauer–Emmett–Teller (BET) analysis, BET surface area of 313.05 m²g^-1 and average pore diameter of 2.71 nm of ZnCl₂ activated carbons were obtained. They have formed largely mesoporous structures. According to Scanning Electron Microscopy (SEM) analysis, it was observed that medium and large porous structures were formed. Produced activated carbons have commercial product potential but there is a need to optimize the process parameters for better results.

Analysis of ammonium bisulfate/sulfate generation and deposition characteristics as the by-product of SCR in coal-fired flue gas

The generation and deposition of ammonium bisulfate (ABS) in flue gas caused serious blockage and corrosion to the air preheater, which seriously affect the safe and economic operation of coal-fired power plants. The generation and deposition of ABS/ammonium sulfate (AS) under non-catalytic conditions were studied on a simulated air preheater test bench, and FT-IR and XRD tests were performed to characterize the products under different conditions. Experimental results show that the generation of ABS/AS is complicated and controlled by the concentration of SO3 and NH3, the ratio of SO3 to NH3 (SO3/NH3) and deposition temperature. Under the same SO3 conditions, ABS/AS generation rate under different SO3/NH3 conditions is 1:2 > 2:1 > 1:1. The initial deposition temperature of ABS/AS will increase with the corresponding increase of SO3 and NH3 concentration, and is exponentially correlated with the product of SO3 and NH3 concentration in flue gas. In the temperature range 390–223 °C, ABS generated and deposited under all conditions, and in the temperature range 223–131 °C, the mixture of H2O, H2SO4, and ABS generated and deposited when SO3/NH3 is 2:1, and AS with a small amount of (NH4)3H(SO4)2 generated and deposited when SO3/NH3 is 1:1 and 1:2.

Diels–Alder Cycloadditions of Bio-Derived Furans with Maleimides as a Sustainable «Click» Approach towards Molecular, Macromolecular and Hybrid Systems

This mini-review highlights the recent research trends in designing organic or organic-inorganic hybrid molecular, biomolecular and macromolecular systems employing intermolecular Diels–Alder cycloadditions of biobased, furan-containing substrates and maleimide dienophiles. The furan/maleimide Diels–Alder reaction is a well-known process that may proceed with high efficiency under non-catalytic and solvent-free conditions. Due to the simplicity, 100% atom economy and biobased nature of many furanic substrates, this type of [4+2]-cycloaddition may be recognized as a sustainable “click” approach with high potential for application in many fields, such as fine organic synthesis, bioorganic chemistry, material sciences and smart polymers development.

Technological Aspects of Highly Selective Synthesis of Allyloxyalcohols—New, Greener, Productive Methods

Allyl ethers bearing free hydroxyl groups of CH2=CH-CH-O-A-OH type (hydroxyalkyl allyl ethers, allyloxyalcohols) are valuable chemicals in many environmentally friendly industrial applications. The development of technologically attractive methods for their production is necessary. The two pathways (L-L PTC and non-catalytic solvent-free conditions) were optimized for the highly selective and yield synthesis of 4-allyloxybutan-1-ol. Improvements in the PTC method (50% NaOH(aq), the equimolar ratio of NaOH to diol, cyclohexane as solvent) with a new highly selective and effective PT catalyst, i.e., Me(n-Oct)3N+Br− (0.3 mol%), resulted in 88% yield and 98% selectivity of 4-allyloxybutan-1-ol with minimal formation of allyl chloride hydrolysis by-products (<1%). In turn, application of non-catalytic solvent-free conditions and the change in the key substrate with an excess of diol and use of solid NaOH solely led to a mono-O-allylation product with an excellent yield of 99% in a relatively short reaction time (3.5 h), with trace amounts of by-products (<0.1%). This sustainable method is perfectly suitable for the synthesis on a larger scale (3 moles of the key substrate) and for the full O-allylation process.

Study on the detailed reaction pathway and catalytic mechanism of a Ni/ZrO2 catalyst for supercritical water gasification of diesel oil

Diesel oil, as a petroleum product, can be used as a model of oilfield wastewater to be gasified in supercritical water (SCW). This paper is aimed to obtain the gasification characteristics, detailed reaction pathway of diesel oil and the catalytic mechanism of a Ni/ZrO2 catalyst in SCW, providing some guidance for supercritical water gasification (SCWG) of oilfield wastewater. The SCWG of 6.8 wt% diesel experiments were carried out in a quartz reactor system with different temperatures (460, 500, 540 °C), reaction time range of 0–90 min. The carbon gasification efficiency achieved 97.5% at 500 °C with the Ni/ZrO2 catalyst, which was over 3 times higher than 27.6% under non-catalytic condition. The liquid intermediate was analyzed by gas chromatography-mass spectrometry, and naphthalene was the most difficulty intermediate to be gasified in diesel SCWG. A kinetic model was established to describe quantitatively the variation of gas yields with experimental conditions. The production and consumption of gases by SCWG of diesel oil under non-catalytic and catalytic conditions were analyzed in detail, and the mechanism of the Ni/ZrO2 catalyst was proposed. The Ni/ZrO2 catalyst effectively enhanced the steam reforming and pyrolysis reactions as well as inhibited the polymerization and aromatization reaction.

Investigation of the liquefaction possibility of Ermenek lignite as an alternative clean energy source

Coal liquefaction; can be defined as the transformation of coal into products that have a high energy density, can be easily stored and transported and do not create environmental pollution, to meet both fuel and chemical raw material requirements.
 This study was carried out to determine the yields of the products formed as a result of the liquefaction of Konya-Ermenek lignite in the N2 atmosphere and under non-catalytic conditions. Proximate and ultimate analysis of the obtained solid and liquid products was made. The composition of the oil product was determined by GC-MS. As a result of liquefaction, the char yield was 71.37%, the preasphaltene yield was 12.24%, the asphaltene yield was 2.23% and the oil + gas yield was 14.16%. It was determined that the higher heating value of 4199 kcal/kg in raw lignite is twice as high in liquefaction products. It was determined that the sulfur content of 3.94% in raw lignite decreased to 1.54%, 0.85% and 0.44% in char, preasphaltene and oil, respectively.

Electrocatalytic Reduction of Bromothiophenes vs Bromobenzenes on Gold and Silver Electrodes: Enhancement from S specific adsorption and modulation from substituent effects

A voltammetric comparative investigation on the electrochemical activity of substituted bromothiophenes vs bromobenzenes highlights the combined effects of the aromatic or heteroaromatic ring substituents and the sulphur atom on both the intrinsic reactivity (accounted for by experiments on a glassy carbon electrode, assumed to have negligible specific interactions) and the reactivity in the presence of electrocatalytic effects, working on Au or Ag electrodes. The two series of compounds share similarities concerning the dissociative electron transfer mechanism for the reductive cleavage of the C-Br bond, including substituent effects. However, the presence of the sulphur atom in the heteroaromatic series significantly promotes the process both in non-catalytic conditions, on account of electronic effects, and on catalytic electrodes, performing as adsorption auxiliary. The effect is particularly remarkable on Au, partially compensating for the effect of the very negative surface charge, and with significant modulation from the S position with respect to the Br leaving group. The nitrile group might act as an additional adsorption auxiliary besides the S atom. In dibromobithiophene systems Au and Ag catalytic surfaces can also induce a remarkable modification in molecular conformation in order to optimize Br and S interactions with the catalytic surface for both conjugated thiophene rings.