CALCULATE THE STANDARD ENTHALPIES OF COMBUSTION, FORMATION AND MELTING OF THE COMPLEX ROSEOFUNGIN WITH α-, β- and γ-CYCLODEXTRIN

One of the most important quantities in chemical thermodynamics and thermochemistry is the enthalpy of combustion. Of the currently existing methods for calculating the heat of combustion of natural and synthetic organic compounds, the most acceptable and correct in our case was the Karash method. In this study, the standard enthalpy of combustion, the standard enthalpy of formation, and the melting enthalpy of the antibiotic roseofungin and its cyclodextrin derivatives were calculated. As a result of the study, the thermodynamic constants of the standard enthalpies of combustion, standard enthalpies of formation, and the enthalpies of melting of the above compounds were calculated, which are of interest for physicochemical modeling of processes with their participation, serve as initial information arrays for loading into fundamental thermodynamic data banks and reference books, and is also important for standardization and certification of these complexes. It should be noted that the presence of a large number of hydroxyl groups in the structures of the studied complexes allows them to be attributed to polar compounds.

Pivotal Role of Chirality in Photoelectrocatalytic (PEC) Water Splitting

For decades, the over-exploitation of fossil fuel has made it urgent to develop alternative energy. Photoelectrochemical (PEC) water splitting is a promising approach to generate hydrogen, which is referred to as the fuel of the future due to its high enthalpy of combustion and zero pollution. Though impressive progress has been made over the years, PEC water splitting efficiency is still far from volume production of hydrogen, and more efforts are required to reduce the overpotential, inhibit the yield of hydrogen peroxide by-product, improve the PEC current density, improve light-harvesting capability, and develop low-cost earth-abundant catalysts. Recently, chirality has shown to play a pivotal role in addressing the issues of PEC water splitting via the effect of chiralinduced spin controlling and chiral-enhanced light harvesting. It is high time to pay attention to the art of chirality in promoting water splitting efficiency. Herein, recent progress in this field is reviewed, the approaches to introducing chirality into photo/electronic catalysts for PEC water splitting are summarized, characterization techniques applied in this research field are summed up, the challenges of chirality-enhanced PEC water splitting are discussed, and based on the present achievements, its bright future is anticipated.

Stacked-cup multiwall carbon nanotubes as components of energy-intensive suspension jet fuels

Objectives. The addition of high-density carbon materials to jet fuels can lead to a significant increase in the volumetric energy of the fuel combustion. The purpose of the current study was to thermodynamically analyze the possibility of obtaining model hydrocarbon fuels from toluene and T-1 using stacked-cup multiwall carbon nanotubes (MWCNTs). Methods. Bomb combustion calorimetry was used to define the combustion energy of the MWCNTs in the crystalline state. The temperature dependence of the MWCNTs’ heat capacity in the range 5–370 K and the fusion parameters were estimated using low-temperature adiabatic calorimetry. The physical density of MWCNTs was measured using the pycnometric method. The sedimentation stability of the mixtures of MWCNTs with liquids was determined using centrifugation at 7000 g. The calculations were carried out in MS Excel. Results. The energy and enthalpy of combustion of a technical sample of MWCNTs in the crystalline state were determined. Based on the smoothed heat capacity values, the standard thermodynamic functions (enthalpy, entropy, and Gibbs reduced energy) of MWCNTs in the crystalline state were obtained in a temperature range of 0–2000 K. The extrapolation of the MWCNTs’ heat capacity was carried out at a temperature of up to 2000 K using the heat capacity of crystalline graphite. It has been established that mixtures of MWCNTs with liquids containing more than 33 mass % of MWCNTs are stable during centrifugal sedimentation at 7000 g. For the toluene–MWCNTs and fuel T-1–MWCNTs model systems, the specific and volumetric combustion energies, the adiabatic combustion temperatures, and the conditional final maximum speed of the model rockets with fuel of various compositions were also calculated. Conclusions. The thermodynamic analysis showed that the addition of MWCNTs can significantly increase the volumetric energy intensity of traditional jet fuels, which can in turn improve the operational characteristics of drones and rockets.

Modified Brayton Cycle for Turbofans

In the present study, a design point analysis of twin-spool turbofan engines is carried out, considering fuel injection of Aviation Turbine Fuel (ATF) in the initial stages of the compressor instead of combustor The two-phase compression brings about intercooling in the modified Brayton cycle, by injecting the atomized fuel directly in the initial stages of axial-flow compressor. The intercooling effect results in reduction of compressor work while reinforcing the enthalpy of combustion of fuel due to change of state of fuel from liquid to vapor state. This brings about an improvement in the thrust and thermal efficiency of the modified cycle. Effect of the intercooling is investigated for different performance parameters namely Fuel flow rate ṁf Total thrust Fs, Thermal efficiency ηth, Overall efficiency ηo and Modified cycle factor MCF over the varying compressor pressure ratio (CPR). Injecting the fuel in the 2nd stage of compression results in percentage increase of total thrust by 21.14%, MCF by 31.35%, ηo by 14.92% and decrease in Fuel flow rate ṁf by 7%. While injecting the fuel in the 5th stage of compression results in increased ηo by 17.54 %, MCF by 37.30%, total thrust by 5.68% and decrease in Fuel flow rate ṁf by 22% at a CPR = 30 and Turbine Inlet Temperature (TIT) = 1260K vis-à-vis conventional cycle. Injecting the fuel in latter stages of compressor brings about a decrease of total thrust as well as efficiency.

Chemical, Enantioselective, and Sensory Analysis of a Cholinesterase Inhibitor Essential Oil from Coreopsis triloba S.F. Blake (Asteraceae)

The fresh leaves of Coreopsis triloba S.F. Blake, collected at Cerro Villonaco in Loja, Ecuador, were investigated with respect to their essential oil (EO). The chemical composition was determined qualitatively through gas chromatography coupled with mass spectrometry (GC-MS) and quantitatively by gas chromatography coupled with flame ionization (GC-FID), using relative response factors (RRF) based on the enthalpy of combustion. The essential oil contained between 92.5% and 93.4% of monoterpene hydrocarbons, with (E)-β-ocimene being the main component (35.2–35.9%), followed by β-phellandrene (24.6–25.0%), α-pinene (15.3–15.9%), myrcene (10.9–11.0%), sabinene (2.2–2.4%), (Z)-β-ocimene (1.5%), and germacrene D (1.2–1.3%). The enantiomeric distribution of α-pinene, β-pinene, limonene, and germacrene D was also determined. The main components responsible for the aroma were identified through aroma extract dilution analysis (AEDA), a gas chromatography-olfactometry (GC-O) based technique, being α-pinene, β-pinene (0.6%), terpinolene (0.1%), α-copaene (0.1–0.3%), β-phellandrene, and (E)-4,8-dimethyl-1,3,7-nonatriene (0.1–0.2%) the main olfactory constituents according to the decreasing factor of dilution (FD) order. The biological tests showed IC50 inhibition values of 42.2 and 6.8 µg/mL for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), respectively.

Microwave influenced laminar premixed hydrocarbon flames: Spectroscopic investigations

Low laminar burning velocity’s and slow reactions propagation are among a key problem in combustion processes with low calorific gas mixtures. The mixtures have a laminar burning velocity of 10 cm/s to 15 cm/s or even below which is 37% of natural gas. Thermal use of these gases could save considerable amounts of fossil fuel and reduce CO2 emissions. Due to low burning velocities and low enthalpy of combustion, ignition and stable combustion is complex, often preventing utilization of these gases. Microwave-assisted combustion can help to solve these problems. With microwave assistance, these gas mixtures could be burned with a higher burning velocity without preheating or co-firing. Therefore, this effect could be used for flame stabilization processes in industry applications. Microwaves could also change the combustion properties, for example radical formation and flame thickness. In this paper, we explore a possibility of using microwaves to increase the burning velocity of propane as one component in low calorific gas mixtures and also show higher productions of OH* and CH* radicals with an increase of the input microwave power. Different compositions of low calorific fuels were tested within a range of equivalence ratios from φ= 0.8 to φ= 1.3 for initial temperatures of 298 K and atmospheric conditions and microwave powers from 120 W to 600 W. For the experiments, a standard WR340 waveguide was modified with a port for burner installation and filter elements allowing for flue gas exhaust and optical access from the side. A 2.45 GHz CW magnetron was used as microwave source, microwave measurements were carried out with a 6-port- reflectometer with integrated three stub tuner. An axisymmetric premixed burner was designed to generate a steady conical laminar premixed flame stabilized on the outlet of a contoured nozzle under atmospheric pressure. The burner was operated with a propane mass flow of 0.2-0.4 nl/min at an equivalence ratio of φ= 0.8 to φ= 1.3. The optical techniques used in the current study are based on the flame contours detection by using the OH* chemiluminescence image technique. For every experimental case, 150 pictures were taken and averaged. Additionally, spectroscopic analysis of the flames was undertaken. The results suggest that production of OH* radicals in the flame front increases with microwave power. For evaluation, a picture based OH* chemiluminescence and a spectrographic method was used. In addition, a 9.9% increase of the burning velocity was observed in the premixed propane-air mixture for a 66 Watt absorbed microwave power. This effect is attributed to the increased OH* (~310nm) and CH* (~420nm) radical formation, which also reduces the flame thickness. It was found that absorption of microwaves in flames is generally low, but could be improved by a customized applicator design.

Calorimetric Computation of Enthalpy of Formation of Trisacetylacetonato Chromium(III) [Cr(C5H7O2)3(c)]

From thermochemical studies of organometallic compounds, a host of thermodynamic parameters viz., heat capacity, entropy, Gibbs energy etc., can be evaluated. The present communication deals with the evaluation of enthalpy of combustion and thereby estimation of enthalpy of formation of crystalline trisacetylacetonato chromium(III) [Cr (C5H7O2)3 (c)] or [Cr (acac)3 cH) and enthalpy of formation fH° –1 –1 respectively. Experimental data obtained are in good agreement with one another.