Yields Of HCN Research Articles

Density functional theory and ReaxFF MD study on steam-induced nitrogen migration mechanism during char gasification

The formation of nitrogen-containing species during char gasification is crucial for emission of nitrogenous pollutants. In this work, the detailed nitrogen migration mechanism during char gasification is studied. Density functional theory (DFT) coupled with ReaxFF MD methods are used to conduct an in-depth analysis on the intrinsic reaction mechanism during Char(N) and steam interaction. DFT results show that orbital electrons of carbon atoms on char surface are driven towards nitrogen atoms by nitrogen functional groups. The electron density of adjacent carbon atoms is weakened, which has a positive charge. Orbital electron properties show that the band energy gaps of three Char(N) models are 3.063 eV, 1.092 eV and 3.328 eV, indicating the reactivity order for three Char(N) models is as follows: Char(N)-2＞Char(N)-1＞Char(N)-3. DFT calculation indicates that the interaction between Char(N) and steam reduces unsaturated carbon atoms and lower the char decomposition activity, which will inhibit the yield of HCN. In contrast, through hydrogen transfer reactions, nitrogen atoms are easily combined with hydrogen atoms, which is more conducive to the formation of ammonia. ReaxFF MD modeling proves that HCN is the main product for Char(N) decomposition under inert atmosphere. Under steam atmosphere, nitrogen atoms in char are more likely to be converted into amino products. The induction of steam provides a large number of active hydrogen radicals, which is able to attack the nitrogen atoms of char and form N–H bonds, thus promoting the formation of ammonia.

Effect of NaCl/MgCl2 on generation of NOx precursors during aspartic acid pyrolysis: A experimental and theoretical study

This work studied the effect of NaCl/MgCl2 on the evolution of nitrogen during aspartic acid pyrolysis, focusing on the transformation pathways in molecular level. The generation of NOX precursors and other volatiles were detected by TG-FTIR, UV, and GC–MS. Notably, density functional theory was used to evaluate energy barrier and rate-determining step during pyrolysis. The yields of NH3, HCN, and HNCO were inhibited by NaCl/MgCl2 addition, especially on the second releasing stage (333–468 °C). The result of theoretical simulations showed that the rate-determining step in six pathways of aspartic acid pyrolysis was changed by NaCl/MgCl2 addition, especially for MgCl2, and the optimum generation pathway for nitrogen–containing products changed from NH3 formation to DKP formation. The highest energy barrier of NH3 and HCN generation increased to 327 kJ/mol and 432 kJ/mol after the addition of NaCl and MgCl2, respectively, leading to their lower release than raw aspartic acid. In addition, the presence of NaCl/MgCl2 decreased the energy barrier for the substitution of the amino group with the hydroxyl group, especially for NaCl, resulting in the fact that more nitrogen was retained in the char. The results first revealed how the NaCl/MgCl2 affected the nitrogen transformation during aspartic acid pyrolysis under molecular level.

Theoretical study on nitrogen migration mechanism during the pyrolysis of 2-pyrrolidone

Incineration is one of the mainstream techniques for the treatment of municipal waste. As the main component of municipal waste, kitchen waste incineration releases a large amount of NOx pollutants. Pyrolysis is the initial stage of incineration, during which nitrogen species in kitchen waste are converted into NOx precursors. In this study, nitrogen migration mechanism of NOx precursors (i.e., HNCO, HCN, and NH3) during the pyrolysis of 2-pyrrolidone, a typical lactam compound in kitchen waste, was investigated based on density functional theory calculations. Various formation pathways of HNCO, HCN and NH3 were discovered respectively. Meanwhile, the pathways of HNCO decomposition to HCN and NH3 at high temperature were illustrated. The formation and decomposition pathway of HCNO satisfactorily interpreted the experimental finding in which HNCO release curve decreased with the temperature rise. Furthermore, the reason for the high yield of HCN as the main product throughout the experimental temperature range and its insensitivity to temperature variation was also identified theoretically in this study.

The effects of alkali metals and alkaline earth metals on the mechanism of N-containing gases production during glutamic acid pyrolysis

Biomass contains Alkali and Alkaline Earth Metals (AAEMs) which, during the pyrolysis process of biomass, can affect the production of harmful gases such as NH3, HCN and HNCO. In this study, the effect of AAEMs on the mechanisms of amino acid pyrolysis was analysed with a combination of Thermogravimetric- Fourier Transform Infrared Spectroscopy (TG-FTIR) experiments and Density Functional Theory (DFT) calculations. Moreover, the four most abundant metals in biomass (K, Ca, Na and Mg) were selected, and glutamic acid (Glu), which accounts for the largest proportion of plant proteins, was studied. The results showed that all four metal chlorides had an inhibitory effect on the production of N-containing gases, while promoted the char formation. Sodium was the most effective in reducing the yields of NH3, HCN and HNCO. The alkaline earth metals (Ca and Mg) could influence the temperature range for gas release. Diketopiperazines (DKP) were produced from the pyrolysis of amino acids, and the precursor of HCN and HNCO. This study explained the effect of AAEMs on nitrogen conversion mechanisms during biomass pyrolysis and provided theoretical support for controlling the nitrogen element transfer.

Formation mechanism of NOx precursors during the pyrolysis of 2,5-diketopiperazine based on experimental and theoretical study

Incineration of food waste leads to the release of NOx pollutants, whereas the formation mechanism of the NOx precursors (HCN, NH3, and HNCO) during the initial pyrolysis process is far from well-studied, limiting the source control on NOx release. In this work, 2,5-diketopiperazine (DKP) was selected as the N-containing model compound to study the formation mechanism of NOx precursors in food waste pyrolysis, by combining experiments and density functional theory (DFT) calculations. The C1-N2 bond broken via the N2-to-N5 H-transfer possesses the lowest energy barrier, together with the largest reaction rate constants in the range of 400–800 °C. NH3 can be easily generated with low energy barriers and high rate constants at low temperatures (below 630 °C). Whereas, the rate constants of the pathways for HCN formation will exceed those for NH3 generation in the range of 630–740 °C. In addition, the DKP pyrolysis can also lead to the formation of HNCO with a very low energy barrier, and it can convert into HCN and NH3 through further hydrogenation and decomposition. These calculation results are exactly consistent with the experimental results that NH3 was the main precursor in the range of 400–600 °C, and the yield of HCN exceeded that of NH3 when the temperature was over 600 °C. Our current work on the formation mechanism of NOx precursors during the pyrolysis of DKP can provide theoretical guidance for the development of NOx control technology in the pyrolysis/combustion process of organic waste.

Updated yields of nitrogenated species in flames of ammonia/benzene via introducing an aniline sub-mechanism

Ammonia and cyclic aromatic compounds are principal products from combustion of various fractions of biomass. Yet, kinetic mechanistic models on formation of NOx from biomass de-couple the oxidation mechanism of ammonia from that of aromatic molecules. Literature kinetic models do not consider a plausible formation of aniline as the initial product from the interaction of amine radicals and benzene molecules (as the simplest aromatic molecule). Such reaction acts a sink for NH2 radicals, and thus may alter the yields of NOx and HCN. To fill in this gap, this study reports production pathways of aniline from NH2 + benzene reactions, maps out unimolecular decomposition pathways of aniline and its derived anilino radical into, and explores the effect of the title reaction on the yields of small nitrogenated species from co-combustion of ammonia and benzene. We find that anilino radical to preferentially decompose into iso-HNC and a cyclopentadienyl radical. The resonance-stabilized structure of the anilino radical enables it to undergo bimolecular reaction with the aniline molecule to generate N-analogous compounds of dioxins, namely diphenylamine, carbazole, and phenazine. Detail kinetic modeling discloses that decomposition of aniline initiates at 1100 K with ammonia and HCN signify the most abundant N-bearing species at intermediates and high temperatures, respectively. Introducing the newly constructed aniline sub-mechanism in NOx + benzene kinetic model from the literature (i.e., CERCK model) alters predicted concentrations of principal N species within factors of 1.2- 2 between 1100–1300 K. It is hoped that reaction rate constants and mechanistic pathways presented herein to improve the predictive performance of kinetic models that address NOx and HCN emission from flames of ammonia and aromatic-containing fuels in general.

Comparison of smoke component yields between room‐scale and bench‐scale experiments

SummaryA standard procedure is needed for obtainingaccurate values of the yields of fire effluent components that are associated with harm to people from a singleacute exposure to the effluent from a fire involving realistic commercial products. We compare yields of toxic gases generated by four bench‐scale apparatus to the yields from previously conducted room‐scale fires. The apparatus is the radiant apparatus in NFPA 269 and ASTM E 1678, the smoke density chamber in ISO 5659‐2, a controlled‐atmosphere version of the cone calorimeter (ASTM E 1354), and the tube furnace specified in ISO/TS 19700. The bench‐scale specimens were cut from the same products that were burned in the room‐scale tests: a sofa, bookcases, and household electric power cable. The yields of CO2 CO, HCl, and HCN were determined. The yields of other toxicants (NO, NO2, formaldehyde, and acrolein) were below the detection limits, but were shown to be of limited importance relative to the four measured gases. We developed a criterion of a factor of two for satisfactoryscale agreement. Using this, the yields from the modified cone calorimeter were the most promising, but still imperfect, match to the room fire yields. The results of this study provide an improved basis for obtainingaccurate combustion product yield data for fire hazard and risk modeling over what currently exists.

Experimental study on the effect of pyrolysis temperature on the NO emission and conversion during combustion

For realizing the coupling pyrolysis of coal and combustion of semi-coke, this paper explored the effect of pyrolysis temperature on the combustion characteristics and NO emission of Pingshuo semi-coke. The main physical and chemical properties, which might affect the NO emission, were also investigated systematically. As the pyrolysis temperature increased, the nitrogen content of semi-coke gradually decreased and the proportion of quaternary nitrogen (N-Q) gradually increased. CaO produced by the decomposition of CaCO3 would promote the transformation from HCN to NO. Pore structure was most developed at 750 °C, which was beneficial to the conversion of HCN and reduction of NO. Combustion experiments were carried out on a thermogravimetric–mass spectrometry. It was found that increasing the pyrolysis temperature would cause the combustion reaction to occur at a higher temperature. Evolved gases during the combustion were quantitatively analyzed by equivalent characteristic spectrum analysis. The yield of HCN during combustion first decreased and then increased and the yield of NO decreased while the pyrolysis temperature increased. There was an optimum pyrolysis temperature for the minimum conversion rate of fuel-N to NO and HCN. For Pingshuo bituminous, this optimum pyrolysis temperature was 750 °C.

Effects of calcium on the evolution of nitrogen during pyrolysis of a typical low rank coal

This study aims to investigate the effects of calcium on the migration of nitrogen in coal (coal-N) to N-containing gas species, particularly, NH3 and HCN (volatile-N) in volatiles, as well as the chemical transformation of the N in char during coal pyrolysis under different temperatures. The pyrolysis experiments of Shengli brown coal and its derived coal samples loaded with different contents of calcium were conducted under 600–800 °C in a novel fluidized bed reactor. The experimental results showed that during coal pyrolysis, the generation of NH3 is mainly derived from secondary reactions among volatiles, tar and char with the catalytic effect of mineral matter, especially calcium in coal. Increasing pyrolysis temperature from 600 to 800 °C could enhance the release of N in coal to volatiles. Meanwhile, the increased pyrolysis temperature could also inhibit the generation of NH3 while facilitating the formation of HCN. The release of HCN is more sensitive to pyrolysis temperatures. Specifically, under higher pyrolysis temperatures, more N-containing structures in coal would become thermally unstable and crack into HCN; On the other hand, higher pyrolysis temperature could also enhance the decomposition of N in coal to N-containing species in tar or N2, thus reducing the release of HCN and NH3. Nitrogen in tar could either undergo secondary decomposition reactions, generating NH3, HCN, N2 and other N-containing species in gas phase, or experience condensation polymerization by forming macromolecular structure and be retained in char at high pyrolysis temperatures. Calcium could significantly restrain the release of N from coal, thus reducing the yields of NH3 and HCN. During coal pyrolysis, calcium catalytically enhances the fracture and combination of chemical bonds, generating abundant free radicals. These free radicals could continuously attack N-containing structures and consequently release the N-containing gaseous products, such as NH3, HCN, N2 etc., resulting in the decrease of N in char. Calcium also plays important roles in nitrogen transformation in char during coal pyrolysis by catalytically intensifying the transformation of N in char from pyridinic nitrogen (N-6) and pyrrolic nitrogen (N-5) to quaternary type nitrogen (N-Q) during coal pyrolysis.

Radiation-based model reduction for the optimization of high temperature tube bundle reactors: Synthesis of hydrogen cyanide

Key intermediates of the chemical value chain such as hydrogen cyanide and synthesis gas are produced in high temperature tube bundle reactors. Process intensification plays an essential role toward a more sustainable production of these compounds. In this contribution the tube bundle arrangement is optimized for the case study of hydrogen cyanide production. Using physics-based model reduction, the bundle reactor is modeled in two dimensions. Gas layer emissivity and tube total view factors are identified as crucial parameters for radiative heat transfer in the furnace. Using an equidistant spacing of 0.052 m, the average yield of HCN is improved by 0.5% and the variance of tube yields is reduced. Overall, staggered arrangements are superior to aligned bundle arrangements. Based on these findings, rule-of-thumb-type tube bundle design heuristics can be derived for any specific furnace design having a potentially large impact on the economic and ecologic footprint of these processes.

Effect of Temperature and Mineral Matter on the Formation of NOx Precursors during Fast Pyrolysis of 2,5-Diketopiperazine

2,5-diketopiperazine (DKP) was used as a N-containing model compound to investigate the formation pathway of NOx precursors (HCN, NH3, and HNCO) during biomass pyrolysis. The experiment was carried out using a tube furnace coupled with a Fourier Transform Infrared Spectrometer in an argon atmosphere. The results showed that NH3, HCN, and HNCO were the major N-containing species formed during DKP fast pyrolysis. The largest yield was HCN, followed by NH3 and lastly HNCO. When the pyrolysis temperature was increased, the yield of NH3 increased slowly, but the yield of HCN decreased slightly at 800~950 °C and the change accelerate rapidly above 950 °C. Then NH3 became the main product above 1020 °C. The temperature influence was negligible on the selectivity between HCN and NH3 from pyrolysis of DKP. H radicals played an important role in competitive reactions. It was also noted that the presence of Na+, K+, Ca2+, and Mg2+ exhibited a catalytic effect on nitrogen conversion during the DKP fast pyrolysis process. K+ and Na+ were beneficial to the yield of NH3, but not to the yield of HCN. Ca2+ and Mg2+ could promote the formation of HCN, but prevent the formation of NH3.

Is Photolytic Production a Viable Source of HCN and HNC in Astrophysical Environments? A Laboratory-based Feasibility Study of Methyl Cyanoformate

Motivated by the possibility that cyano-containing hydrocarbons may act as photolytic sources for HCN and HNC in astrophysical environments, we conducted a combined experimental and theoretical investigation of the 193 nm photolysis of the cyano-ester, methyl cyanoformate (MCF). Experimentally, nanosecond time-resolved infrared emission spectroscopy was used to detect the emission from nascent products generated in the photolysis reaction. The time-resolved spectra were analyzed using a recently developed spectral reconstruction analysis, which revealed spectral bands assignable to HCN and HNC. Fitting of the emission band shape and intensity allowed determination of the photolysis quantum yields of HCN, HNC, and CN (A22 Π1)and an HNC/HCN ratio of ∼0.076 ± 0.059. Additionally, multiconfiguration self-consistent field calculations were used to characterize photoexcitation-induced reactions in the ground and four lowest singlet excited states of MCF. At 193 nm excitation, dissociation is predicted to occur predominantly on the repulsive S 2 state, with minor pathways via internal conversion from S 2 to highly excited ground state. An automated transition-state search algorithm was employed to identify the corresponding ground-state dissociation channels, and Rice-Ramsperger-Kassel-Marcus and Kinetic Monte Carlo simulations were used to calculate the associated branching ratios. The proposed mechanisms were validated using the experimentally measured and quasi-classical trajectory-deduced nascent internal energy distributions of HCN and HNC. This work, along with previous studies, illustrates the propensity for cyano-containing hydrocarbons to act as photolytic sources for astrophysical HCN and HNC and may help explain the observed overabundance of HNC in astrophysical environments.

Heterogeneous reactions between ions NH3+ and NH+ and hydrocarbons adsorbed on a tungsten surface. Formation of HCN+ in NH+-surface hydrocarbon collisions

Interaction of NH3+ (ND3+) and NH+ with a hydrocarbon-covered tungsten surface kept at room temperature or heated to 150 and 300°C showed a series of reactions between the projectile ion and hydrocarbons adsorbed on the tungsten surface. Collisions with NH3+ showed formation of NH4+, HCNH+, and CH2NH2+, with NH4+ strongly prevailing at low incident energies of the projectile ion. Analogously, collisions with ND3+ showed formation of ND3H+, HCND+, and CH2ND2+ with dominant contributions of ND3H+ at low incident energies. No formation of HCN+ (DCN+) could be positively identified. In reactions with NH+, formation of HCN+ was clearly observed; the dependence of the normalized yield of HCN+ on incident energy indicated a threshold at about 40eV which might be due to an activation energy or an endothermicity of the surface reaction of about 2.4–3.2eV.

Co-pyrolysis between microalgae and textile dyeing sludge by TG–FTIR: Kinetics and products

In this work, the kinetic behavior and evolution characteristics of the gaseous products of microalgae (MA) and textile dyeing sludge (TDS) blends during co-pyrolysis were investigated using TG–FTIR. The TDS was blended with MA in the range of 10–90wt.%, and then heated from 105°C to 900°C at 10, 20 and 40°C/min under N2 atmosphere with a flow rate of 80ml/min. The initial decomposition temperature of TDS was lower than MA, but the pyrolysis intensity of MA was higher than TDS. The co-pyrolysis of MA and TDS could avoid the drawbacks with each other and improve their pyrolysis performance. The synergistic interaction between MA and TDS was mainly due to the flowing and sticky bio-oil and alkali metals catalytic effect. Two iso-conversional methods of Ozawa–Flynn–Wall (OFW) and Kissinger–Akahira–Sunose (KAS) were used to calculate the activation energy, and low average activation energy was obtained when the blending ratio of MA was 80%. CO2, H2O, CH4, CO, HNCO, NH3, HCN, SO2, CH, CO and CO groups were the main gaseous products observed from the FTIR spectrums during co-pyrolysis. The origin of CO2, H2O, CH4, CO, HNCO, NH3, HCN, SO2, CH, CO and CO groups was analyzed combined with the decomposition order of the components in MA and TDS. The evolution of the gaseous products was consistent with the weight loss of the blends during co-pyrolysis. The yields of CO2, CH, CO, CO, CO, HNCO, NH3, HCN and SO2 did not monotonically change with the increasing blending ratio of MA, attributed to the synergistic interaction between MA and TDS. The blending ratio of MA reached 80% would obtain the highest yield of desired products. In order to get the low average activation energy and more desired products, the potential global optimum blending ratio of MA for co-pyrolysis of the blends was 80%.

Thermogravimetry–Mass Spectrometry Analysis of Nitrogen Transformation during Oxy-fuel Combustion of Coal and Biomass Mixtures

The nitrogen transformation during the oxy-fuel combustion of coal and biomass mixtures was studied through thermogravimetry–mass spectrometry (TG–MS). Influence factors, such as atmosphere and biomass share, were selected to study the release of four nitrogenous gases HCN, HNCO, NH3, and NO. With the presence of ≥20% O2, the combustion of Datong coal and biomass mixtures releases less HCN, NH3, and NO and more HNCO in the O2/CO2 atmosphere compared to the O2/N2 atmosphere. HCN and HNCO compete mutually during the formation of nitrogenous gases. The mixtures of Datong coal and biomass release more nitrogenous gases than Datong coal alone in both O2/CO2 and O2/N2 atmospheres during the devolatilization. With the O2 concentration in the O2/CO2 atmosphere increasing from 20 to 100%, the relative yields of NH3, HCN, and HNCO produced from the mixtures decrease, while the NO yield increases. The HNCO yield changes greatly with the increase of the O2 concentration because of the oxidation by OH. Increasing the biomass share in the mixtures improves the relative yields of nitrogenous gases. The biomass share can greatly affect the HCN and HNCO yields, owing to the different forms of N-containing structures between coal and biomass.

Parametric study of reburning of nitrogen oxide for superfine pulverized coal

An experimental investigation of process parameters design by superfine pulverized coal reburning on NOx reduction is carried out in a one-dimensional bench-scale combustion system. Reburning effectiveness for initial levels ranging from 600 to 650ppm is evaluated. It is found that for Shenhua bituminous coal, NOx reduction performance of superfine pulverized coal owns its unique advantage, 50% higher than conventional particle size. Medium reburning fuel fraction (RF20∼RF25) and low oxygen concentration are recommended to be ensured in this experiment. The yield of HCN and CH4 along the furnace axis does not seem to be decisive on the effect of particle size, but is closely related to the effect of reburning fuel fraction. Both exhaust and in-flame measurements are reported in this paper to provide valuable experimental data for practical engineering applications.

Effects of Solid Residence Time and Inherent Metal Cations on the Fate of the Nitrogen in Coal during Rapid Pyrolysis

Six coals with carbon contents ranging from 69 to 80 wt % dry ash-free (daf) were rapidly pyrolyzed at 1300 °C under a stream of high purity He in a free fall-type graphite reactor incorporating a graphite filter to control the residence time of coal particles. In this manner, the effects of both residence time and inherent mineral contents on N2 formation from char-N following devolatilization were examined. At a residence time of zero, 20–30% of the coal-N was released as volatile-N species, such as tar-N, HCN and NH3, while <15% was transitioned to N2 and the remainder (60–80%) was retained in the char. When the residence time was increased to 120 s, the yields of tar-N, HCN and NH3 were almost unchanged, irrespective of the coal type, although the N2 yield increased and the char-N decreased with increasing residence times, with the changes in yields of both species being roughly equal. When an Indonesian char sample already devolatilized at 1000 °C was pyrolyzed again by applying a slow heating rate o...

A comparative study of nitrogen conversion during pyrolysis of coconut fiber, its corresponding biochar and their blends with lignite

In the present study, the conversion of fuel-N to HCN and NH3 was investigated during rapid pyrolysis of raw biomass (coconut fiber), its corresponding biochar and their blends with lignite within a temperature range of 600-900°C. The results showed that the raw biomass and the biochar showed totally different nitrogen partitioning between NH3 and HCN. HCN was the dominant nitrogen pollutant from pyrolysis of raw biomass, while for the biochar pyrolysis the yield of NH3 was slightly higher than that of HCN. Synergistic interactions occurred within both raw biomass/lignite and biochar/lignite blends, especially for the biochar/lignite blend, and resulted in reduced yields of HCN and NH3, decreased the total nitrogen percentage retained in the char and promoted harmless N2 formation. These findings suggest that biochar/lignite co-firing for energy production may have the enhanced benefit of reduced emissions of nitrogen pollutants than raw biomass/lignite.

Effect of heating rate on migration and transformation of N during pyrolysis of Shengli brown coal

The effects of heating rate on migration, transformation and occurring forms of nitrogen during pyrolysis of Shengli brown coals were studied in a fixed-bed/fluidised-bed quartz reactor. The results indicate that the yields of NH3 and HCN from the fast pyrolysis were much higher than those from the slow pyrolysis. The difference in the yields of NH3 and HCN between the fast and slow heating rates increases with the increasing pyrolysis temperature. The maximum productions of NH3 and HCN mostly occur at 973 K, which is attributed to the enhanced condensation and secondary reactions with the increasing pyrolysis temperature. The release rate of char-N is faster than the weight loss rate of char itself at fast heating rate. The results from X-ray photoelectron spectroscopy (XPS) analysis imply that the pyrolysis process has facilitated the transformation of pyrrolic (N-5) to quaternary type nitrogen (N-Q) and pyridinic (N-6). It seems that the fast heating rate favors the formation of N-6 while the content of N-Q in char is relatively high at the slow heating rate.

NOx and N2O precursors (NH3 and HCN) from biomass pyrolysis: interaction between amino acid and mineral matter

Mineral matter in biomass influences nitrogen chemistry during pyrolysis. Amino acids, selected as the model compound in biomass, were pyrolyzed with the major mineral matters in biomass (potassium, calcium and iron) at 800°C to investigate the effect of mineral matter on the distribution of N-containing species from amino acid pyrolysis. HCN and NH3 were detected online with a Fourier transform infrared (FT-IR) spectrometer. The extent of interaction between amino acid and the mineral matter was determined by comparing the yields of HCN and NH3 from pyrolysis of amino acids with mineral matters with those from amino acid pyrolysis under the same condition. The results indicate that yields of HCN and NH3 and nitrogen conversion pathway from amino acid pyrolysis are influenced by the mineral matter. Mineral matter has catalytic effects on the primary decomposition reaction pathway of amino acid as well as the secondary cracking pathway of 2,5-piperazinedione. For amino acids with reactive side chains, the mineral matter also has catalytic effects on thermal cracking of nitrogen-containing char.