Volatile Reaction Research Articles

Effect of volatile reactions on the yield and quality of tar from pyrolysis of Shenhua bituminous coal

Pyrolysis was an important route for coal conversion and also the fundamental for clean and efficient utilization of coal. As an important product of pyrolysis, coal tar can be used as the raw material for producing premium liquid fuels and high value-added chemicals (benzene-toluene-xylene, naphthalene, phenols, etc.). The products’ distribution and quality were significantly affected by the secondary reaction of volatiles. In this work, Shenhua bituminous coal was pyrolyzed with a two-stage reactor at a relatively low temperature, and the released volatiles underwent secondary reactions at various temperatures and residence time. The yields and quality of coal tar were characterized by gas chromatography–mass spectroscopy (GC–MS) and Fourier transformed infrared spectroscopy (FTIR). The results showed that secondary volatile reactions decrease tar yield but increase gas and coke yield. The volatile reaction results in a decrease in the content of aliphatics and phenols, and an increase in the content of arenes and polar compounds. The volatile reaction includes the following reactions: dehydroxylation, deoxygenation, cleavage of long chain aliphatic structures into short ones, and condensation of aromatic clusters, etc. The higher heating rate of pyrolysis reduces the content of aliphatic and polar compounds while increases that of arenes and phenols in the light tar (HS).

Influence of non-monetary information signals of the USA on the Ukrainian stock market volatility

The Ukrainian PFTS stock index volatility reaction as a whole and its constituent economic sectors (“Basic Materials”, “Financials”, “Industrials”, “Oil & Gas”, “Telecommunications”, “Utilities”) to seven non-monetary US information signals (“Consumer price index”, “Personal spending”, “Unemployment rate”, “Gross domestic product”, “Industrial production”, “Consumer confidence”, “Housing starts”) was carried out for the period 2000–2017 on the basis of closing stock quotations in the trading day format. To assess the “surprise” component direct influence nature of the USA selected non-monetary information signals on the PFTS stock index, an AR-GARCH econometric modelling device was used. The results achieved clearly indicate the presence of some PFTS stock index economic sectors heterogeneous reaction to the United States individual non-monetary information signals announcement. For example, such economic sectors as “Basic Materials”, “Financials”, and “Oil & Gas” volatility response to the US non-monetary information signal “Consumer price index” “surprise” components the opposite of the overall PFTS stock index reaction. It can also be concluded that the United States non-monetary information signals influence on the Ukrainian stock market volatility depends not only on the financial cycle phase and data frequency, but also on the PFTS stock index economic sector.

Effect of Different Drying Methods on Nutrient Quality of the Yellow Mealworm (Tenebrio molitor L.).

Yellow mealworm (Tenebrio molitor L.) represents a sustainable source of proteins and fatty acids for feed and food. Industrial production of mealworms necessitates optimized processing techniques, where drying as the first postharvest procedure is of utmost importance for the quality of the final product. This study examines the nutritional quality of mealworm larvae processed by rack oven drying, vacuum drying or freeze drying, respectively. Proximate composition and fatty acid profile were comparable between the dried larvae. In contrast, larvae color impressions and volatile compound profiles were very much dependent on processing procedure. High-temperature rack oven drying caused pronounced darkening with rather low content of volatiles, pointing toward the progress of Maillard reaction. On the other hand, vacuum drying or freeze drying led to enrichment of volatile Maillard reaction and lipid oxidation intermediates, whose actual sensory relevance needs to be clarified in the future. Beyond sensory and visual importance drying intermediates have to be considered with regard to their metal ion chelating ability; in particular for essential trace elements such as Zn2+. This study found comparable total zinc contents for the differently dried mealworm samples. However, dried larvae, in particular after rack oven drying, had only low zinc accessibility, which was between 20% and 40%. Therefore, bioaccessibility rather than total zinc has to be considered when their contribution to meeting the nutritional requirements for zinc in humans and animals is evaluated.

Estimating Stock Returns Volatility and the Risk-Return Nexus in the Nigerian Stock Market in the Presence of Shift Dummies

Volatility and the trade-off between risk and return in stock markets is an important subject in financial theory which play significant role in investment decision making, portfolio selection, options pricing, financial stability, hedging and pair trading strategy among others. This study estimates stock return volatility and analyses the risk-return trade-off in the Nigerian stock market using symmetric GARCH (1,1)-in-mean, asymmetric CGARCH (1,1)-in-mean and EGARCH (1,1)-in-mean models with Generalized Error Distribution and Student-t innovation. Data on daily closing all share prices of the Nigerian stock exchange for the period 2nd January, 1998 to 9th January, 2018 are utilised. The data is further divided into three sub-periods of pre-crisis, global financial crisis and post crisis periods to allow volatility behaviour and the risk-return trade-off to be investigated across the sub-periods. Results showed evidence of volatility clustering, leptokurtosis, high persistence of shocks to volatility and asymmetry without leverage effects across the study periods. The persistence of shocks to volatility increased during the global financial crisis period with delayed reactions of volatility to market changes. However, by incorporating the exogenous breaks into the volatility models for the full study period, the shock persistence drastically reduced with faster reactions of volatility to market changes. The results of this study also found supportive evidence for a significant positive risk-return relationship in Nigerian stock market across various study sub-periods and model specifications meaning that investors in Nigerian stock market should be compensated for holding risky assets. The empirical findings of this study further suggest that the recent global financial crisis have not altered the market dynamics to distort the risk-return trade-off in Nigerian stock market indicating that expected returns are not driven by changes in the stock market volatility. The study provides some policy recommendations for investors and policy makers in the Nigerian stock market.

Determination of Antioxidant Capacity, Phenolics and Volatile Maillard Reaction Products in Rye-Buckwheat Biscuits Supplemented with 3β-d-Rutinoside.

The Maillard reaction (MR) is responsible for the development of color, taste and aroma in bakery products though the formation of numerous aroma compounds such as pyrazines, pyrroles and aldehydes, nonvolatile taste active compounds and melanoidins. In this article, we investigate the effect of quercetin 3β-D-rutinoside (rutin) supplementation, at the level of 5–50 mg per 100 g, of rye-buckwheat biscuits on the formation of phenolics and volatile Maillard reaction products (MRPs) such as pyrazines, furfuryl alcohol and furfural, determined by headspace solid phase microextraction followed by gas chromatography–mass spectrometry (HS-SPME/GC–MS), in addition to the effect on the antioxidant capacity. The study confirmed that rutin was stable under baking conditions as showed by its content in rye-buckwheat biscuits. Supplementation of biscuits with increasing amounts of rutin resulted in the progressive increase of total phenolics and antioxidant capacity measured by DPPH and OxHLIA assays, but it had no effect on their sensory quality. From the eighteen compounds identified by HS-SPME/GC–MS in the volatile fraction of biscuits were quantitated as a compounds-of-interest: methylpyrazine, ethylpyrazine, 2,3-; 2,5- and 2,6-dimethylpyrazines, as well as furfural, furfuryl alcohol and hexanal. The rutin supplementation of biscuits might be one of the factors to influence the formation of both desirable volatile compounds and undesirable toxic compounds. In conclusion, this study indicates for the significant role of polyphenols on the formation of volatile compounds in biscuits with possible future application in the development of healthy bakery products with high antioxidant capacity.

Volatiles reaction during pyrolysis of corn stalk – Its influence on bio-oil composition and coking behavior of volatiles

Reaction of nascent volatiles is unavoidable during biomass pyrolysis and significantly influences the product yield, bio-oil quality and coking on the reactor wall. However, experimental studies in this aspect are still very limited. This work aims to advance the knowledge in this aspect using a two-stage reactor. Volatiles were generated in-situ from pyrolysis of corn stalk at 540 °C and swept off to the second-stage reactor preheated at 440–650 °C with a residence time of 1.5–4.7 s. The bio-oil quality was evaluated using simulated distillation gaschromatography. Results show that with increasing the volatiles temperature, the bio-oil yield decreases but the quality is improved: the contents of phenols, aldehydes and monocyclic aromatics increase significantly, those of esters and alcohols increase slightly and the contents of ketones, acids and furans decreases. Effect of volatiles residence time on the bio-oil quality depends on the volatiles temperature: becoming worse at 440 °C and better at 600 °C with increasing the residence time. The volatiles reaction also generates a few tetrahydrofuran-insoluble compounds, depositing on the downstream wall of the second-stage reactor (termed coke-wall) or suspending in bio-oil (termed soot-oil). The coke-wall yield increases with increasing volatiles temperature and residence time and is generally higher than the soot-oil yield.

The reaction behavior of volatiles generated from lignite pyrolysis

The reactions of volatiles generated from coal pyrolysis determined the tar yield and composition. In order to investigate the effect of the reaction behavior of volatiles on the distribution of pyrolysis products, especially the tar yield and composition, the reactions of volatiles generated from the Shengli lignite (SL) pyrolysis using a two-stage fixed-bed reactor, with the first stage for lignite pyrolysis and the second stage for reactions of volatiles, were investigated in this paper. It was found that the reactions of volatiles resulted in an increase in gas and coke yield and a decrease in tar yield during lignite pyrolysis. And the effect of reaction temperature in the range of 700–900 °C on the distribution of light tar is significantly greater than that of the volatiles’ residence time in the range of 4–14 s. Reactions of volatiles shortened the carbon chain length of alkanes and increased the content of arenes and phenols in light tar under certain conditions. When the volatiles’ reaction temperature was 700 °C and the volatile’s residence time was 8 s during coal SL pyrolysis at the heating rate of 10 °C/min, the phenols content was 1.5 times higher than that of raw light tar. It was found that the more heavy components content the volatiles contained, the more heavy components content the final tar contained after the volatiles reaction.

Design Principles for a Compartmentalized Enzyme Cascade Reaction

Compartmentalization of enzyme cascade reactions can both create a safe space for volatile reaction intermediates, where they are protected from cellular degradation mechanisms, and a quarantine fo...

Effect of volatiles’ reaction on composition of tars derived from pyrolysis of a lignite and a bituminous coal

In coal pyrolysis, the reaction of volatiles plays an important role in determination of tar yield and composition but has not been studied in detail in the literature. This work studies the volatiles’ reaction in pyrolysis of a bituminous coal (SM) and a lignite (HLBE) using a two-stage fixed-bed laboratory reactor with the second-stage temperature of 440–700 °C and the residence time of 1.5–6.9 s. The tars were characterized by solvent extraction with tetrahydrofuran (THF) and hexane, and by simulated distillation (SIMDIST) of the THF soluble matter and high performance liquid chromatography (HPLC) analysis of the hexane soluble matter. It was found that the main component of the tars was oil, which was more in the HLBE tar than in the SM tar. As much as >50 wt% oil and tar retained in the chromatograph columns. The volatiles reacted at temperatures as low as 440 °C and the rate was more pronounced at 600 °C in 4.2 s. The volatiles’ reaction reduced the oil yield while increased the pitch yield. The aromatics in the hexane soluble matter were mainly 2-ring compounds and their content increased by the volatiles’ reaction. The major tar fractions have boiling points of 200–538 °C and their content varied systematically in the volatiles reaction. The findings are important for design of efficient coal pyrolysis reactors.

A Study on the Asymmetric Effect to Housing Market Price Volatility

The objective of this paper empirically analyzes the relations between information and housing market volatility using the housing price index of Seoul, San Francisco and Los Angeles for the time period from January 1995 to July 2019. For the empirical test of the asymmetric effect of information on housing market volatility, this paper employs GJR-GARCH model which enable good information and bad information to have impact on volatility. The analysis results are as follows. First, it was found that the GJR-GARCH (1,1) model is suitable for analyzing the asymmetric reaction of housing price volatility for information types. Second, it was found that for information types, Seoul, San Francisco, and Los Angeles all displayed asymmetric housing price volatility. It was found that Seoul reacted greater to volatility for unexpected positive earnings rate information than unexpected negative earnings rate information, while on the contrary, San Francisco and Los Angeles showed that they reacted greater to unexpected negative earnings rate information than to unexpected positive earnings rate information. These findings support the hypothesis. Third, for sensitivity to volatility, Seoul was found to be about five times higher than San Francisco and Los Angeles. It is necessary to differentiate the housing price volatility prediction model and portfolio composition according to the information type.

Material weakness disclosures and restatement announcements: The joint and order effects

AbstractWe examine differences in stock price, option volatility, and litigation reactions to restatement announcements that are associated with a material weakness (MW) disclosure. Contrasted with restatements that are not associated with any MW disclosure, our analyses reveal that firms that announce both a restatement and an associated MW experience significantly more negative market returns, greater implied volatility, and higher likelihood of class action lawsuits. Separating the restatements into timely reporters, where the MW precedes the restatement, and non‐timely reporters, where the MW is concurrent with or follows the restatement, we find that timely reporters experience more negative returns at the time of the restatement, relative to non‐timely reporters, suggesting that investors perceive the early MW disclosure to signal more pervasive control‐related problems. Interestingly, we find that timely and non‐timely reporters are equally likely to be sued, consistent with the argument that wrongdoing (through either a timely or non‐timely MW disclosure) provides stronger grounds for establishing scienter. However, timely reporters appear to secure more favorable litigation outcomes: they face higher likelihood of lawsuit dismissals and pay much lower settlements, compared to non‐timely reporters. Overall, our evidence provides new insights into how market participants incorporate information about internal control weaknesses into their perceptions regarding the economic implications of financial restatements, and financial reporting quality.

Influence of Pyrolysis Gas on Volatile Yield and CO2 Reaction Kinetics of the Char Samples Generated in a High-Pressure, High-Temperature Flow Reactor

The influence of pyrolysis atmosphere on volatile yield, structural characteristics, and CO2 reaction kinetics have been examined on chars generated from Pittsburgh No. 8 coal at 6.2 bar pressure and 1100 °C in a high-pressure, high-temperature flow reactor (HPHTFR) in Ar, N2, 50 (vol. %) CO2 and N2 (i.e., CO2/ N2) atmospheres. The chars were characterized for volatile yield, thermal swelling ratio, surface area, pore size distribution, crystallite structure, defects to graphitic intensity ratio, and char-CO2 reactivity. Coal pyrolyzed in CO2/N2 showed higher volatile yield (27%) compared to coal pyrolyzed in argon (~16%) and nitrogen (~19%). Except for volatile yield, there was no significant difference in structural properties for chars generated in different pyrolysis atmospheres. The difference in volatile yield was found to be due to presence of unconverted tetrahydrofuran (THF) soluble tar/soot. The results also showed that the intrinsic reactivity was highest for char generated in N2 atmosphere and lowest for char generated in CO2/N2 atmosphere. The kinetic parameters (activation energy and pre-exponential factor) for the char-CO2 reaction were ascertained using nth order model. The activation energies did not differ significantly among the chars generated in different pyrolysis atmospheres. The order of reaction was found to follow: CO2/N2 char > N2 char ≈ Ar char.

Post-Brexit Stock Market Volatility and European Central Bank Reaction Function

The European stock markets experienced enormous volatility in stock markets post-Brexit era, which wasn’t observed before the shock. The volatility in financial markets has disturbed economic fundamentals including capital flow and economic growth in several European countries. To avoid such disturbances the monetary authorities have to implement a monetary reaction function by adopting an appropriate range for short-term interest rate consistent with the volatility of stock markets and depreciation of British pound. The monetary reaction function in this case shouldn’t be only based on traditional Taylor’s rule but also needs to take into account the volatility of stock markets and depreciation of pound versus major currencies. The goal of this paper is twofold. First, it tries to estimate the effects of Brexit on stock market volatility index for British FTSE, German DAX, and French CAC using econometric models and a dummy variable for post-Brexit. Second, it uses a Vector Auto Regression (VAR) model to stimulate the monetary reaction function of the European Central Bank (ECB) to find out how it may neutralize the adverse effects of stock market volatility on macroeconomic fundamentals.

Storage stability of bioactive compounds of pomegranate leather (pestil) produced by refractance window drying

AbstractFruit leathers are commonly produced with several fruits for consuming out of harvesting seasons. It is rich in nutritional and bioactive compounds. However, the bioactive compounds are sensitive to processing and storage conditions. Therefore, the chemical properties of the pomegranate leather produced by refractance window drying during storage at three different storage temperatures were investigated in the present study. The bioactive compounds of pomegranate leathers gradually decreased during storage, especially in high storage temperatures. The degradation of anthocyanins fit the second‐order reaction kinetics. HMF content and volatile nonenzymatic browning reaction products were increased during storage especially at 35 °C. Moreover, storing at 35 °C for short period of time caused a volatile composition similar to the storing for a long period at 22 °C. Overall, leather must be stored at low temperatures to increase the stability of bioactive compounds.Practical applicationsRefractance window drying has gained more and more attention from the food industry due to its scalability, cost‐effectiveness, and continuous production opportunity. Many papers have shown the effectiveness of refractance window drying over different drying techniques. However, the fate of refractance window dried materials during storage is absent in the literature. Therefore, the storage stability of pomegranate leather was determined in the present study.

The primary products of cellulose pyrolysis in the absence of extraparticle reactions

Cellulose pyrolysis leads to formation of char, gases and condensable species, with levoglucosan being one of the main components among the latter. However, the literature is not conclusive regarding which of these pyrolysis products are primary as opposed to form through reactions of volatiles in the pyrolyser once they have been released from the cellulose particle. To understand these cellulose pyrolysis pathways, cellulose, levoglucosan and cellulose/levoglucosan mixtures were pyrolyzed in a wire mesh reactor, which suppresses interactions between volatiles released from one particle and other particles. The product distribution and levoglucosan yield were compared at different temperatures in slow and fast heating rate. Above 60% levoglucosan was obtained at low temperature and in slow pyrolysis. Fast pyrolysis produced a large amount of small particles/aerosols in liquid phase. Gas was mainly formed in the initial stage of pyrolysis possibly due to the amorphous cellulose decomposition. The levoglucosan did not undergo secondary reactions. For cellulose/levoglucosan mixture, the vaporization of levoglucosan was not affected by cellulose pyrolysis. These results showed that levoglucosan and low molecular weight species are both formed directly from cellulose in reactions taking place in parallel. The alternative sequential pathway where levoglucosan is produced initially and then reacts to form low molecular weight species was not observed in these conditions.

Description of the char conversion process in coal combustion based on premixed FGM chemistry

This work presents and assesses a tabulation approach to represent the complex coal combustion chemistry at low computational costs. It should enable to include the process of volatiles conversion and char burnout in scale resolving simulations (such as large eddy simulations) of realistic coal combustion chambers. It is based on premixed flamelets and gets investigated with respect to its capability to accurately describe char conversion. In this approach the gas phase chemistry is mapped onto a four-dimensional manifold controlled by two mixture fractions, the enthalpy and a reaction progress variable. Accordingly, mixing between oxidizer, volatiles and gaseous char conversion products is accounted for besides non-adiabatic physics and finite rate chemistry effects. In a previous work (Knappstein et al., 2017), several modeling assumptions with regard to the description of the volatiles reaction using tabulated chemistry were already assessed. For the full description of the coal combustion process the model functionality was extended to account also for char conversion in the present work. Here, special emphasis is therefore put on aspects related with the conversion of char. The consistency of the model formulation and its implementation is demonstrated by the examination of mass, species and energy balances in generic test cases for which analytical solutions are derivable. Furthermore, results of a simulation adopting the presented model are compared against a detailed chemistry reference solution accounting for the full reaction mechanism. This situation approximates a particle essentially consisting of char that is exposed to hot oxygen-containing product gases. Thereby, capabilities of the presented modeling approach with respect to prediction accuracies for the model’s intended application in LES can be estimated.

NOX formation in oxy-fuel combustion of lignite in a bubbling fluidized bed – Modelling and experimental verification

This paper reports results of experimental and numerical studies of NOx formation in a 30 kWth lab-scale bubbling fluidized bed running in oxy-fuel mode. The numerical model is based on the GRI-mech 3.0 mechanism to compute the kinetics of homogeneous reactions of volatiles and char combustion products and takes into account the flue gas recirculation. The impact of the oxygen excess and of the fluidized bed temperature was examined. Both the numerical simulations and the experiments shown a significant correlation of NOX formation with the excess of oxygen, where a higher oxygen concentration enhances the fuel-bound nitrogen oxidation to NOX. It was also found that there is no correlation of the NOx formation and resulting emissions with the fluidized bed temperature in temperature range typical for bubbling fluidized bed combustors (840–960 °C), but the numerical simulations showed an increased NOX concentration when the temperature raised more (up to 1360 °C). The agreement of experimental and numerical results shows that the numerical model can provide useful insight into the mechanism of NOX formation.

Soot formation during biomass pyrolysis: Effects of temperature, water-leaching, and gas-phase residence time

Soot particles from biomass incomplete combustion, as a major source of particulate matter, arouse significant concerns due to its harmful impacts on environment and human health. In this paper, the effects of pyrolysis temperature, volatile residence time and water-leaching of biomass on soot formation during biomass pyrolysis were studied in a lab-scale furnace. The physicochemical characteristics of soot particles were comprehensively analyzed. Results show that soot is formed by the secondary reactions of volatiles from biomass thermal-cracking requiring a certain high temperature and long volatile residence time. With a short volatile residence time of 0.2 s, no soot is formed at 900–1200 °C. When the residence time increases to 2 s, soot is significantly formed at >1000 °C, when onion-like shell/core structures is observed. With pyrolysis temperature increasing, the soot particle size decreases and becomes uniform, the carbon content in soot increases, and the ordered structure of carbonization is enhanced, which leads to the degradation of soot oxidation reactivity. The water-leaching pretreatment for biomass leads to the increases of soot yield, particle size, and carbon content, as well as the KCl absence in soot and significantly lowered oxidation reactivity of soot. This indicates strong catalysis of potassium on soot production and consumption. Both gas and tar analyses support soot formation mechanism: (1) H2 yield increases due to formation of soot, but C2H2 yield reaches peak at 1000–1100 °C; (2) tar is dominated by PAHs, which molecules grow with the increase of temperature and residence time.

Effects of Secondary reaction of Primary Volatiles on Oil/gas Yield and Quality from Oil Shale Pyrolysis

The reaction behaviors of primary volatiles from oil shale pyrolysis were investigated using a two-stage reactor under different in-situ thermal reaction conditions. The reaction parameters of secondary reactor, such as, reactor temperature, atmosphere and residence time, were studied for their effects on the pyrolysis oil/gas yield and quality. The results showed that the reaction temperature had profound influence on the oil and gas yield. The pyrolyzed shale oil and gas yield reduced by 15% and 20% (mass) respectively, with the temperature of 2nd stage reactor increasing from 600 to 650 °C under optimized reaction condition of 1st stage. Comparing with nitrogen atmosphere, the liquid oil yield could be enhanced by 5% when steam was added as the reaction atmosphere in the second stage, and the corresponding oil was mainly concentrated in the gasoline and diesel distillations (that is, boiling point < 350 °C). The GC-MS analysis illustrated that the secondary reaction at the residence time of 0−3 s was mainly pyrolysis while the presence of steam could increase the content of aromatics in the oil and meanwhile suppress the condensation of aromatics. When the residence time was greater than 3−5 s, the secondary reaction was mainly condensation of poly-aromatics, which led to the increase of coke. Meanwhile, the gasoline and diesel oil yield remained stable, and the VGO fractions decreased by about 30%.

Kinetic study of high-intensity ultrasound-assisted Maillard reaction in a model system of d-glucose and glycine

A kinetic model for a high-intensity ultrasound-assisted Maillard reaction model system of d-glucose and glycine was proposed; activation energy (Ea) for each reaction step was calculated. Results showed that the generation of dicarbonyl compounds was significantly promoted by high-intensity ultrasound (e.g. Ea values for 1-deoxyglucosone were 60.9 ± 9.7 kJ mol−1 and 105.5 ± 9.9 kJ mol−1 in ultrasonic and thermal Maillard reaction, respectively), which resulted in a significantly higher concentration of colored and volatile Maillard reaction products generated in ultrasound-assisted Maillard reaction compared with that in thermal Maillard reaction. However, as a competitive reaction, the isomerization of d-glucose was suppressed and required significantly higher Ea values in ultrasound-assisted Maillard reaction (100.8 ± 6.2 kJ mol−1) compared with that in thermal Maillard reaction (84.2 ± 5.7 kJ mol−1). These finding may be attributed to an extremely high temperature and pressure environment, despite of being only momentarily, generated by high-intensity ultrasound.