Distribution Of Reaction Products Research Articles

Understanding shape selectivity effects of hydroisomerization using a reaction equilibrium model.

We study important aspects of shape selectivity effects of zeolites for hydroisomerization of linear alkanes, which produces a myriad of isomers, particularly for long chain hydrocarbons. To investigate the conditions for achieving an optimal yield of branched hydrocarbons, it is important to understand the role of chemical equilibrium in these reversible reactions. We conduct an extensive analysis of shape selectivity effects of different zeolites for the hydroisomerization of C7 and C8 isomers at chemical reaction equilibrium conditions. The reaction ensemble Monte Carlo method, coupled with grand-canonical Monte Carlo simulations, is commonly used for computing reaction equilibrium of heterogeneous reactions. The computational demands become prohibitive for a large number of reactions. We used a faster alternative in which reaction equilibrium is obtained by imposing chemical equilibrium in the gas phase and phase equilibrium between the gas phase components and the adsorbed phase counterparts. This effectively mimics the chemical equilibrium distribution in the adsorbed phase. Using Henry's law at infinite dilution and mixture adsorption isotherm models at elevated pressures, we calculate the adsorbed loadings in the zeolites. This study shows that zeolites with cage or channel-like structures exhibit significant differences in selectivity for alkane isomers. We also observe a minimal impact of pressure on the gas-phase equilibrium of these reactions at typical experimental reaction temperatures 400-700K. This study marks initial strides in understanding the reaction product distribution for long-chain alkanes.

Thermodynamic property estimations for aqueous primary, secondary, and tertiary alkylamines, benzylamines, and their corresponding aminiums across temperature and pressure are validated by measurements from experiments

On Earth and beyond, organic chemistry often occurs in the presence of water within environments that deviate drastically from ambient conditions (25 °C and 1 bar). Accurately predicting aqueous organic reaction pathways is crucial toward understanding planetary scale processes such as the cycling of elements crucial for life (e.g., carbon and nitrogen). Advanced thermodynamic modeling can be utilized to determine the favorability of various organic reactions based on geologically relevant ranges of temperature and pressure, as well as compositional variables (e.g., pH). However, data that would otherwise allow for a diversity of organic compounds and environmental conditions to be modeled are sparse and rarely tested with experiments, particularly with regard to organic-nitrogen compounds. In this work, we develop a framework to estimate thermodynamic properties at ambient conditions that can then be extrapolated across ranges of temperature and pressure for aqueous primary, secondary, and tertiary amines and aminiums (protonated amines), specifically those structures containing linear alkyl chains and benzyl functional groups. We also performed hydrothermal experiments (250 °C, ∼40 bar) involving reactions of methylamines to test our resulting thermodynamic models, and we compare our models for other alkylamines and benzylamines to previous empirical measurements from the literature. Specifically, we use existing thermodynamic data along with our estimates at ambient conditions in combination with a variety of existing extrapolation methods related to the revised Helgeson-Kirkham-Flowers (HKF) equations of state to generate temperature- and pressure-dependent predictions of acid dissociation constants (i.e., pKa values) that strongly agree with previous empirical measurements. We use similar methods to predict product distributions for reactions involving primary, secondary, and tertiary amines/aminiums, as well as ammonia/ammonium and corresponding alcohols whose collective distributions depend on reversible substitution reactions. Our predictions are in good agreement with our experimental results involving the methylamine reaction system as well as previous experiments involving the benzylamine reaction system, for which we also produced thermodynamic estimates involving benzyl alcohol. The agreement between independent theoretical predictions and experimental measurements suggests that our estimated properties can be applied to modeling amine chemistry in other experimental and natural aqueous systems that range in temperature and pressure, providing new tools for planetary exploration.

Efficient and Homogenous Precipitation of Sulfur Within a 3D Electrospun Heterocatalytic Rutile/Anatase TiO2-x Framework in Lithium–Sulfur Batteries

AbstractLithium–sulfur (Li–S) batteries can potentially outperform state-of-the-art lithium-ion batteries, but their further development is hindered by challenges, such as poor electrical conductivity of sulfur and lithium sulfide, shuttle phenomena of lithium polysulfides, and uneven distribution of solid reaction products. Herein, free-standing carbon nanofibers embedded with oxygen-deficient titanium dioxide nanoparticles (TiO2-x/CNFs) has been fabricated by a facile electrospinning method, which can support active electrode materials without the need for conductive carbon and binders. By carefully controlling the calcination temperature, a mixed phase of rutile and anatase was achieved in the TiO2-x nanoparticles. The hybridization of anatase/rutile TiO2-x and the oxygen vacancy in TiO2-x play a crucial role in enhancing the conversion kinetics of lithium polysulfides (LiPSs), mitigating the shuttle effect of LiPSs, and enhancing the overall efficiency of the Li–S battery system. Additionally, the free-standing TiO2-x/CNFs facilitate uniform deposition of reaction products during cycling, as confirmed by synchrotron X-ray imaging. As a result of these advantageous features, the TiO2-x/CNFs-based cathode demonstrates an initial specific discharge capacity of 787.4 mAh g−1 at 0.5 C in the Li–S coin cells, and a final specific discharge capacity of 584.0 mAh g−1 after 300 cycles. Furthermore, soft-packaged Li–S pouch cells were constructed using the TiO2-x/CNFs-based cathode, exhibiting excellent mechanical properties at different bending states. This study presents an innovative approach to developing free-standing sulfur host materials that are well suited for flexible Li–S batteries as well as for various other energy applications. Graphical Abstract

Catalytic hydrothermal liquefaction of Camelina sativa residues for renewable biogasoline production

ABSTRACT Camelina sativa plant residue was used as feedstock for the production of biogasoline (a mixture of paraffinic and olefinic hydrocarbons) by catalytic hydrothermal liquefaction (cHTL) process. The experiments were conducted at temperature range 200–375°C and pressure range 10–19 MPa. Molecular hydrogen was added for the hydro-deoxygenation processes. Various experiments were performed to understand the contributions of process parameters such as temperature, pressure, hydrogen, and retention time on reaction conversion and products distribution. This was followed by screening of different catalyst supports – γ-Al2O3, HZSM-5, SiO2-Al2O3, SBA-15, and Al2O3-HZSM-5 to understand their impacts as well as catalytic activities. The Al2O3/HZSM-5 exhibited the best properties and was impregnated with a varying range of cobalt metal for the HTL of Camelina sativa. The 5%Co/γ-Al2O3-HZSM-5 catalyst exhibited highest liquefaction conversion (79%) and biogasoline yield (43%) at optimized reaction conditions due to the presence of strong brønsted acidity on the catalyst were that enhanced both the hydrocarbon cracking and hydrogenation leading to the production of low boiling point and low molecular weight hydrocarbon within the boiling point range of fossil gasoline. Across all the data point used in the work, the average deviation was within ± 3%, these are mostly indicated by the error bars.

Image enhancement and microstructure characterization of energy dispersive X-ray spectroscopy images of blended cement pastes

Energy dispersive X-ray spectroscopy (EDS) image analysis has been widely used to study the microstructure of cementitious materials, whereas in some cases the efficiency of the characterization suffered from the extremely long time for image acquisition. In this study, we proposed an EDS image analysis methodology including image enhancement, phase extraction, and characterization of reaction products. The guided filter and Logarithm correction were combined and employed to improve the resolvability of low-quality EDS images. Gaussian Mixture Model (GMM) algorithm was applied to segment the unreacted phases and two different groups of reaction products from the enhanced EDS images. Moreover, the spatial distribution and chemical composition of reaction products were characterized using the lineal-path function and simple lineal iterative clustering (SLIC) algorithm. Results showed that low-quality EDS images after enhancing could achieve the comparable performance with high-quality EDS images in terms of the phase proportions. This study offers a practical and effective methodology for enhancing and analyzing the low-quality EDS images, giving insights into the phase assemblage and microstructure evolution of cementitious materials.

Assessment of Cryogenic Coring to Preserve Vertical Distributions of Trichloroethylene and Reaction Products in an Aquitard

AbstractThere is not a clear understanding of the extent by which naturally occurring reactions can attenuate trichloroethene (TCE) and its daughter products within low permeability zones (LPZs), and addressing this knowledge gap requires advancement of methods to accurately measure in situ volatile chemical concentrations. In this study, a soil coring method that freezes the soil in‐situ (a.k.a., cryogenic coring) was utilized to measure depth‐discrete distributions of TCE and its volatile reaction products through a TCE‐impacted silty clay aquitard, and results were compared with those from adjacent soil cores taken using a conventional coring approach. Vertical concentration profiles of TCE, cis‐1,2‐dichloroethylene (DCE), vinyl chloride (VC), ethane, and methane were all compared between the two coring methods, and results indicate the two coring methods recovered statistically equivalent concentrations of volatiles across most depths of the fine‐grained cohesive clayey soil at the study site. Biotic reductive dechlorination was the dominant TCE reaction pathway at the site; several reduced gasses that are possible markers for abiotic reduction were detected, but their concentrations and intervals of occurrence were not sufficiently consistent to indicate whether they were from abiotic TCE reduction or unrelated biological processes. Overall, cryogenic coring yielded improved recovery of sand lenses compared to conventional coring, but offered no apparent benefits for improved recovery of TCE and its volatile reaction products in the low permeability aquitard material at the site.

Hierarchical porous Pt/Hβ catalyst with controllable acidity for efficient hydrogenation of naphthalene

A series of hierarchical porous Pt/Hβ catalysts with different mesopores-acidity were synthesized without using secondary template. The pore structures of the catalysts were altered by constructing mesopores through alkali etching to reduce the mass transfer resistance. Moreover, the metal-support interaction (MSI) was optimized to improve the dispersion of the Pt metal particles. The smaller metal species could expose more active sites during the hydrogenation process, along with a more pronounced electron-deficiency effect. Furthermore, the effect of acid sites distribution on the hydrogenation reaction path and product distribution were also investigated. The strong acid-mesopores-metal factor (X) was defined to describe the relationship with the yield of decalin. The yield of decalin was well correlated with a high R2 value of 0.97. The Pt/Hβ-75 catalyst showed the best synergistic effect between acidity, mesopore and Pt species, leading to the optimal naphthalene conversion (96.7%) and higher yield of decalin (76.7%) at a relatively low temperature, which exhibited a better activity than other catalysts reported in literature for hydrogenation of naphthalene at a similar reaction condition. Besides, the hydrogenation reaction mechanism of naphthalene over Pt supported catalysts was further investigated by density functional theory, and the effect of Pt NPs size on the catalytic reaction process and activity was preliminarily revealed.

A new generation pathway of singlet oxygen in heterogeneous single–atom Mn catalyst/peroxymonosulfate system

The function of heterogeneous catalyst in singlet oxygen (1O2) generation under acidic and neutral conditions and the effect of sulfate radical on the generation of 1O2 is still unclear. This study provided a novel generation pathway of 1O2 in the heterogeneous Mn single − atom catalyst (Mn SAC)/peroxymonosulfate (PMS) system. The MnN4 site with the ideal binding strength promoted the activation of PMS to generate sulfate radical (SO4•–), which would be adsorbed on the carbon/nitrogen sites forming SO4•–(s), reacting spontaneously to produce 1O2. The presence of MnN4 and carbon/nitrogen structure sites could shift the oxidation process from a bulk–phase oxidation to a surface oxidation. This shift has important implications in terms of reaction rate and product distribution, as the dual reaction sites decrease the required migration distance for the active species to form 1O2, avoiding the pointless consumption of active substances.

Mono- and Co- solvency based transesterification of Caryota urens seed oil

This study aims to comprehensively evaluate the reaction parameters and fuel properties of biodiesel derived from underutilized waste Caryota urens seed oil (CUO) using mono- and co-solvency-based transesterification. The CUO was extracted through both solvent extraction at the laboratory scale and mechanical screw press for large-scale purposes, with a maximum oil content of 7.76 ± 1.52% (wt%) reported. Transesterification of CUO was carried out using methyl, ethyl, and methyl-ethyl-based reaction systems employing KOH as a base catalyst and ethanol as a co-solvent. The highest yields were achieved under optimized reaction conditions: molar ratio of 1:9, catalyst concentration of 0.75, 0.6, and 0.6 wt%, reaction temperatures of 60, 75, and 70 °C, reaction times of 135, 90, and 40 min, and methanol to ethanol ratio of 4.5/4.5. Notably, the addition of ethanol in an equivalent ratio to methanol altered the reaction kinetics and product distributions, encouraged reactions at higher temperatures without any loss of solvent loss, reduced the overall reaction time, enhanced the overall ester yield, and exhibited the most favourable fuel properties. In fact, fuel properties of both CUO ethyl and methyl-ethyl esters, evaluated as per ASTM D6751 standards, reported enhanced calorific value (40.14 and 39.67 MJ/kg), cetane number (69.29 and 68.27), kinematic viscosity (5.27 and 5.03 mm2/s), and reduced density (870.76 and 871.41 kg/m3) than compared to CUO methyl esters. The findings of this research indicate that CUO esters, regardless of their form, hold significant potential as a promising source of biodiesel fuel.

Study on the process of producing crotonaldehyde from acetaldehyde catalyzed by Zr-β zeolite

As an essential raw material of chemical industry, crotonaldehyde is mainly used to produce sorbic acid, which is a kind of safe food preservative. The nowadays production process of crotonaldehyde adopts sodium hydroxide solution and acetic acid in series as catalysis, which cause serious problems such as salinity waste water and equipment corrosion. Therefore, Zr-β zeolite was developed to catalyze the production of crotonaldehyde from acetaldehyde gas–solid reaction process in our group. This catalyst showed the potential of industrial application for its 94 % selectivity and stability. This paper aims to develop a technological process to produce crotonaldehyde from acetaldehyde based on the newely-researched-out Zr-β zeolite catalyst. According to experimental results of reaction condition and product distribution, a technological process consisting of (1) aldol condensation reaction and raw material recovery section, (2) crotonaldehyde concentration and refinement section, (3) 2-methyl-2-cyclopenten-1-one (MCP) and acidic impurity removal section was established. Mechanical supercharging was employed in section (1) to elevate the heat grade of reactor effluent to heat the reactor feed. Pre-concentration followed by azeotropic distillation was proposed to purify croton aldehyde product. The removal of little MCP in the re-used water was accomplished by evaporating MCP at the top of the column based on our previous finding that MCP-water could form minimum azeotrope. As a result, the purity of crotonaldehyde reached 99.92 wt% and water content reduced below 10 ppm in product, which is much better than the product standard required crotonaldehyde purity 99.5 % and water content 2000 ppm. Based on optimum process, heat exchange network was further optimized with pitch point method, and at last the required heat load was 2.25 Gcal per ton of crotonaldehyde product. The problem of generating salinity waste water in the traditional process was solved thoroughly, which meant that this is a more environmentally friendly process to produce crotonaldehyde.

Real-Time Mass Spectrometry for Simultaneous Monitoring of Electrode Dissolution and Reaction Product Distribution during Organic Electrosynthesis

An organic electrosynthesis is an emerging tool for modern chemical manufacturing fitting the environmental and sustainability agenda. It utilizes polarized electrode surfaces as “traceless” oxidants or reductants, whereas its heterogeneous nature and exceptional tunability enable easy access to radical intermediates and novel mechanistic pathways. In the line of further energy input improvement, there is a growing demand for appropriate catalytic materials devoted to organic molecule transformations, for which the activity and selectivity have so far been most studied. Although the investigation of electrodes’ and electrocatalysts’ stability in the field of electrochemical energy conversion is well-established, there is still a lack of attention to the symmetrical studies for organic electrosynthesis. Nevertheless, electrode material losses shorten the reactor’s lifetime and can cause metal cathodic re-depositions, severely altering reaction product selectivity and final product contaminations. Although some reports on the ex-cell metal dissolution analysis are available, no information about its mechanism can be gained in such a way. To highlight the issue numerically, an analytical method to characterize rates and mechanisms of catalyst dissolution within a real-time response-enabled potential-, temperature-, or time-resolved parametrization of the electrocatalyst is highly demanded.Herein we present a system to study organic electrosynthetic protocols under dynamic operations to quantitatively monitor the electrode dissolution aligned with reaction products during organic molecules transformations. The instrument comprises an electrochemical flow cell (EFC) with exchangeable working electrodes, the outlet of which is interfaced with an online quadrupole mass spectrometer (OQMS) for the analysis of extracted by solid membrane gaseous products and an inductively coupled plasma mass spectrometer (ICP-MS) for the detection of dissolved metals. The system is exemplified by a benchmark Kolbe electrolysis over platinum Pt anode, commonly considered a stable and inert electrode material. Based on the literature, methanol has been used as a solvent of choice, while partially neutralized acetic acids with different bases were studied as objects. The methodology shed some light on understanding the role of platinum oxide formation on the electrode surface and can be used to study time- and potential-resolved catalyst stability and the possibility for dissolved transition metal-catalyzed electroorganic transformations.

A theoretical and modeling study of nitrogen chemistry in polycyclic aromatic hydrocarbons growth process

Ammonia blended with hydrocarbon fuels inhibits soot formation due to the chemical effect of NH3 in polycyclic aromatic hydrocarbons (PAHs) growth process. Nitrogenous species are highly concentrated intermediates in combustion of fuels doped with NH3, while their interaction with PAHs remains unclear for the lack of experimental data. In this work, hydrogen cyanide (HCN) reacts with benzene and naphthalene as isoelectronic species of C2H2 to complete the hydrogen-abstraction-acetylene-addition (HACA) chemistry reaction in PAHs growth process. The reaction pathways for HCN-benzene and HCN-naphthalene were investigated at G3(MP2, CC)//B3LYP/6-311G(d,p) level, and the rate coefficients were calculated using Rice-Ramsperger-Kassel-Marcus (RRKM) theory to analyze the yield distribution of various reaction products. Cyano-substituted species or N-PAHs may form in HCN-benzene and HCN-naphthalene reaction systems. The kinetic results show that the formation of cyano group dominates the HCN addition at high temperatures, which indicates that the Frenklach HACA route is more favorable in flame conditions. The branching ratios results show that HCN addition to benzene and naphthalene competes with C2H2 addition within the temperature range of 1000–2000 K. Besides, the yield of HCN reacting with naphthalene is considerable at low temperatures. The simulation results confirm the contribution of HCN addition to benzene by detecting the mole fraction of benzonitrile. Theoretical study and kinetic simulation identify the interaction between HCN and PAHs, blocking the formation of larger PAHs. These findings provided a deeper insight into the chemical effect of nitrogenous species on PAHs growth, which helps to explain the inhibitory effect of NH3 on soot formation.

Mass transfer and reaction mechanism of CO2 capture into a novel amino acid ionic liquid phase-change absorbent

In order to overcome high heat duty and poor regeneration efficiency of existing chemical absorbent, a novel aqueous amino acid ionic liquids (AAILs) phase change absorbent with tetraethylenepentamine (TEPA) as cation, L-proline (L-Pro) as anion and N-propanol (NPA) as phase separator was proposed in this study. [TEPAH][Pro]/NPA/H2O owned the maximum absorption loading of 2.01 mol CO2·mol absorbent−1, and the rich phase viscosity was only 8.06 mPa·s. Moreover, its desorption efficiency was 84.4% while the 5th cyclic loading kept above 1.61 mol CO2·mol absorbent−1. With the presence of NPA, the rich phase only accounted for 41% of the total volume while it contained 99.3% of CO2 products. The heat duty was only 2.39 GJ·t CO2-1, which was 37% lower than that of 30 wt% ethanolamine (MEA) aqueous solution. Meanwhile, the reaction mechanism and product distribution were revealed by 13C NMR and the mass transfer kinetics was investigated using the wetted wall column. The products in the rich phase mainly consisted of carbamate, hydrogen carbonate, propyl carbonate and water while the main component of the lean phase was NPA. The reaction followed a fast pseudo-first order reaction. At 313.15 K, the rate constant of fresh absorbent was 51346 s−1, which showed a decreasing trend with the increase of absorption loading at 313.15 K. The second order reaction rate was calculated by: k2 = 9.88 × 109exp(-3591.2/T), where the reaction activation energy was only 29.86 kJ·mol−1.

Effects of pressure and temperature on CO2 facilitation of amino acid salt-containing membranes for post-combustion carbon capture

Polymeric facilitated transport membranes (FTMs) that contain amino acid salts (AASs) provide a cost-effective option for reducing the CO2 emissions associated with burning fossil fuels. In the current work, we examined the effects of CO2 partial pressure and temperature on the CO2 absorption properties of three AAS mobile carriers, piperazine glycinate (PZ-Gly), 2-(1-piperazinyl)ethylamine glycinate (PZEA-Gly), and 2-(1-piperazinyl)ethylamine sarcosinate (PZEA-Sar), and their facilitation of CO2 transport by employing 13C NMR spectroscopy. The CO2 loading and the distribution of reaction products, i.e., carbamate and bicarbonate products, were analyzed and quantified for each AAS sample. The 13C NMR analysis revealed that PZEA-Sar had a greater CO2 loading and favored the more efficient bicarbonate pathway in comparison to PZ-Gly and PZEA-Gly. In addition, we noted marked differences in the formation of carbamate and bicarbonate products when the CO2 partial pressure and temperature were adjusted. The concentration gradient of the reaction products formed indicated that the diffusion of carbamate products was the most influential factor in CO2 transport under reduced CO2 partial pressure. However, as the partial pressure of CO2 increased, bicarbonate products began to play a more significant role. At elevated temperatures, a lower absorption of CO2 was observed, resulting in the reduced generation of both reaction products. This suggests that the enhanced CO2 permeance of FTMs is mainly attributed to the accelerated diffusion of the reaction products. The findings of this study contribute to a comprehensive understanding of the transport mechanism by which AAS carriers enhance CO2 facilitation, allowing for the refinement of more efficient FTM designs.

Quantifying the microstructure and phase assemblage of alkali-activated fly ash/slag materials by EDS mapping analysis

Accurately quantifying the proportions and distributions of reaction products is crucial for interpreting reaction mechanisms and microstructure evolution in alkaline activated fly ash/slag pastes. However, existing techniques are limited in their ability to provide a comprehensive and visual analysis. This paper presents a versatile energy dispersive X-ray spectroscopy (EDS) mapping analysis that enables image enhancement, phase extraction, and component classification in the alkaline-activated materials (AAMs) -irrespective of the nature and quality of element mappings. The proposed methodology effectively removes the detection noise that inherently existed in EDS mappings, subsequently reinforcing the accuracy of the clustering analysis. The phase extraction procedure allows for obtaining the proportion of pores, reaction products, and unreacted solid precursors (SPs). Moreover, the component classification procedure enables further categorization of the reaction products and unreacted SPs. By analyzing the element ratios and shortest distances, the chemical compositions and spatial distributions of various reaction products could be revealed. Through the application of different analysis schemes, a consistent tendency was obtained, validating the practicability and reliability of this methodology.

Effect of metal oxides on reaction route and product distribution of catalytic cellulose hydrogenolysis

The effects of CeO2, ZrO2, Nb2O5, and ZnO catalysts supported on carbon nanotubes (CNT) relative to cellulose hydrothermal hydrogenolysis in the presence of Ni/CNT and pressured H2 was studied in this work. The catalysts were characterized by inductively coupled plasma – optical emission spectrometry, X-ray diffraction, X-ray photoelectron spectrometry, transmission electron microscopy, NH3 temperature programmed desorption (TPD), and CO2-TPD. Glucose and its isomers were detected by mass spectrometry. The results showed that redox active CeO2/CNT with strong Lewis acid and strong Lewis base sites was active in C-C bong cracking, isomerization, dehydrogenation, and hydrodeoxygenation reaction, yielding 36.3% ethylene glycol and 17.2% 1,2-propylene glycol. The ZnO/CNT with Bronsted base accelerated isomerization, retro-aldol condensation, and dehydrogenation, yielding 20.7% 1,2-propylene glycol, 17.8% ethylene glycol, and 12.7% tetrahydrofuran dimethanol. The Nb2O5/CNT and ZrO2/CNT were inert to C-C bond cracking, whereas H+ in hot compressed water and the Bronsted acid in Nb2O5/CNT accelerated dehydration, yielding more sorbitol and sorbitans. The results provide reference for catalyst selection and product regulation in cellulose hydrogenolysis.

The electrocatalytic activity and selectivity of ethylene glycol oxidation into value-added chemicals at iron-group electrodes in alkaline media

Selective electrocatalytic conversion via ethylene glycol oxidation reaction (EGOR) at abundant Iron-group catalysts could be a promising and sustainable approach to produce value-added C1 and C2 chemicals. However, the corresponding intrinsic electrocatalytic activity and selectivity of EGOR on Iron-group electrodes are still ambiguous, which is urgent to be revealed. The linear scanning voltammetry (LSV) results show that Co and Ni rather than Fe exhibit considerably high activity, and the CoIV and NiIII sites formed at high potential might be crucial for the fast EGOR revealed by LSV and operando electrochemical impedance spectroscopy (EIS). Then, the in-situ electrochemical infrared absorption spectroscopy (IRAS) and high-performance liquid chromatography (HPLC) are used to obtain a general understanding of reaction pathways and product distributions in alkaline media. Specifically, a parallel C1 pathway (formate) without CO2 generation and C2 pathway (glycollate, oxalate) is confirmed on Co and Ni surfaces. The C1 pathway is dominated on the Ni surface with a ∼60% selectivity of formate, while the C2 pathway is favorable on the Co surface with a ∼43% selectivity of glycollate at 1.60 V vs. RHE. In addition, the Ni electrode showed a higher yield rate of carboxylate products. This work may offer theoretical guidance for the design of noble-metal-free electrocatalysts towards efficient selective electrooxidation of EG to value-added chemicals.

Co-pyrolysis of peanut shell with municipal sludge: reaction mechanism, product distribution, and synergy.

Biomass/sludge co-pyrolysis contributes to the high-efficiency resource utilization, harmless treatment, and reduction in volume of sludge. Due to the complexity of co-pyrolysis reaction, it is essential to evaluate the thermodynamic behavior, synergy, and reaction mechanism of this process to make it commercially viable. In this work, the pyrolysis properties, thermodynamic analysis and product distribution of municipal sludge (MS), peanut shell (PS), and their blends with various sludge mass ratios (SMRs) were investigated by a thermogravimetric analyzer and a fixed bed reactor. There was a considerable synergy existing in the process of PS/MS co-pyrolysis, and the synergy occurred mainly at the devolatilization phase, accelerating the mixture pyrolysis. When the conversion rate α was less than 0.7, the apparent activation energy decreased continuously with SMR at the same α; however, it increased dramatically with SMR when α was greater than 0.7. Reactants and reaction stages greatly affected the kinetic mechanism of fuel pyrolysis, and this finding was beneficial for the numerical simulation of mixture pyrolysis. Based on the conclusions and precision of this work, the mass ratio of PS to MS was recommended to be 6:4, which had the strongest synergy, with a gas yield of 26.69 wt.% at 600°C and a lower heating value (LHV) of pyrolysis gas of 14.89 MJ/Nm3.

Photochemical radical benzylic bromination with Br2: Computational modeling of the mechanism and microkinetic

Halogenation of organic compounds is an important functionalization process for further chemical transformation and the benzylic hydrogen is reactive towards the photochemically generated Br atom. This work reports the free energy profile of the several steps of the reaction of the Br atom with toluene leading to benzyl bromide, (dibromomethyl)benzene, and (tribromomethyl)benzene using reliable theoretical B2GP-PLYP method. A detailed microkinetic analysis of the reaction rate and product distribution was also performed. Our analysis points out that polar solvent increases the reaction rate in relation to apolar one. Substitution on the aromatic ring cannot be explained by the electrophilic mechanism in an apolar medium. The reactivity of different benzylic substrates was evaluated, and we have found that the cyano electron-withdrawing group in the aromatic ring retards the reaction, while the ortho-methoxy group, and oxygen and nitrogen atoms bonded to the benzylic carbon, enhance the reaction rate.

How Pulse Width Affects Laser Ablation of Organic Liquids.

Laser synthesis in liquids is often carried out in organic solvents to prevent oxidation of metals during nanoparticle generation and to produce tailored carbon-based nanomaterials. This work investigates laser ablation of neat organic liquids acetone, ethanol, n-hexane, and toluene with pulse widths ranging from 30 fs to 4 ps through measurements of reaction kinetics and characterization of the ablation products with optical spectroscopy and mass spectrometry. Increasing the pulse width from 30 fs to 4 ps impacts both the reaction kinetics and product distributions, suppressing the formation of solvent molecule dimers and oxidized molecules while enhancing the yields of gaseous molecules, sp-hybridized carbons, and fluorescent carbon dots. The observed trends are explained in the context of established ionization mechanisms and cavitation bubble dynamical processes that occur during ultrashort pulsed laser ablation of liquid media. The results of this work have important implications both for controlling the formation of carbon shells around metal nanoparticles during the ablation of solid targets in liquid and producing carbon nanomaterials directly from the ablation of organic liquids without a solid target.