Aromatic Formation Research Articles

The carboxylates formed on oxides promoting the aromatization in syngas conversion over composite catalysts

Syngas to aromatics (STA) over bifunctional catalysts has attracted much attention in recent years, but the mechanism underlying the formation of aromatics remains controversial. The critical reaction intermediates, carboxylates, were first identified and then confirmed to essentially promote aromatization in the syngas conversion over a ZnCrAlOx&H-ZSM-5 composite catalyst. This study provides evidence that the carboxylates can be formed during the reactions of formate species and olefins. In addition, it is shown that the carboxylates favor the formation of aromatics over H-ZSM-5 even in the presence of H2. A novel mechanism for the formation of aromatics via the generation and transformation of carboxylate intermediates is proposed, and the transformation of carboxylates to aromatics via methyl-2-cyclopenten-1-one (MCPO) intermediates is indeed likely. A better understanding of the formation mechanism of aromatics would help optimize the composite catalyst.

Conversion of Oxygenates on H-ZSM-5 Zeolites—Effects of Feed Structure and Si/Al Ratio on the Product Quality

The conversion of different biogenic feedstocks to hydrocarbons is a major challenge when ensuring hydrocarbon and fuel supply in spite of the heterogeneity of this feed. Flexible adaptation to changing compositions is mandatory for the respective processes. In this study, different oxygenate model feeds, such as alcohols, aldehydes, carboxylic acids and esters, were converted at 500 °C and 5 barg H2 using H-ZSM-5 zeolite catalysts with various Si/Al ratios to identify the relationship between the feed structure and the final product distribution. As the main outcome, the product distribution becomes increasingly independent of the feed structure for Al-rich H-ZSM-5 catalyst samples at low Time on Stream (ToS). Some minor exceptions are the increased formation of aromatics during ToS for carbonyl oxygenates compared to primary alcohols and the dominance of initial deoxygenation products for Si-rich H-ZSM-5 samples. This is interpreted by a multi-stage reaction sequence, which involves the initial deoxygenation of the feed and the subsequent integration of the olefin intermediates into a reaction network. The results pave the way towards the achievement of a desired product distribution in the conversion of different oxygenates simply by the adaption of the Al content of H-ZSM-5.

Cross-interaction of volatiles from co-pyrolysis of lignin with pig manure and their effects on properties of the resulting biochar

Biomass and pig manure have distinct compositions and the co-pyrolysis of them has gained much attention. However, the influence of volatiles interaction on the properties of the char was still unclear. In this study, lignin was selected as the model component of biomass with pig manure for co-pyrolysis at 600 °C. The results indicate that volatiles from co-pyrolysis promoted re-condensation reaction, resulting in the higher char yield (48.0% in co-pyrolysis versus 31.0% in pyrolysis of single manure) and the formation of more aromatics in bio-oil. The co-pyrolysis also facilitated the dehydrogenation and dehydration reactions, which accounted for the elimination of oxygen and nitrogen contents and thus a higher carbon content (64.7% in the co-pyrolysis versus the averaged value of 46.4% from the pyrolysis of single feedstock), higher crystallinity and thermal stability of the char. The in-situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) characterization results demonstrated that the functionalities abundances of char with temperature was influenced by volatiles interaction via accelerating the carbonization reaction. In addition, the high heating value (HHV) of char was obviously improved by cross-interaction of volatiles during co-pyrolysis (24.4 MJ/Kg in co-pyrolysis versus averaged value of 15.1 MJ/Kg from single pyrolysis), implying that the co-pyrolysis enhanced the energy density of the resulting char.

Controllable hollow HZSM-5 for high shape-selectivity to light aromatics from catalytic reforming of lignite pyrolysis volatiles

Light aromatics could be produced by catalytic fast pyrolysis (CFP) of lignite over HZSM-5 with shape selectivity and accessible active sites. However, the catalytic reactivity in the center crystal has not been fully exploited. In this work, the different hollow hierarchical porosity-tunable ZSM-5 were synthesized using polyethylene glycol as a soft template by a steam-assisted crystallization process. Compared with commercial HZSM-5, the synthesized HZSM-5 exhibited higher selectivity for alkylbenzene (toluene and m/p-xylene) with the yield of 9.91 mg/g (7.31 mg/g over commercial HZSM-5). The hollow HZSM-5 with pore-size fine-tuning were favorable to control the tiny different intermediates for shape-selective of benzene and alkylbenzene in CFP. In addition, the unmodified synthetic hollow catalysts also kept highly stability after seven cycle experiments due to the enhancement of molecules diffusion in crystal center, especially the alkylbenzene yield was sustained at approximately 7.38 mg/g during cycle experiments. The work provides a great prospect to promote the formation of alkyl aromatics in CFP.

Identification of atomically dispersed Fe-oxo species as new active sites in HZSM-5 for efficient non-oxidative methane dehydroaromatization

Non-oxidative methane dehydroaromatization (MDA) provides a promising and efficient technology for the valorization of huge amount of CH4 resources. Fe-based HZSM-5 zeolite as the second most researched catalyst system for MDA, however, commonly showed a much lower activity or/and selectivity for aromatics’ formation, probably due to an unsuitable Fe phase in the zeolite. Different from the reported Fe/HZSM-5 catalysts by the traditional impregnation method with Fe(NO3)3, a Fe/HZSM-5 catalyst was specially designed for the title reaction which was prepared by ion-exchange method with a stable, soluble and divalent Fe salt, i.e., FeSO4. Interestingly, the Fe2+-exchanged HZSM-5 catalyst can show an extremely higher aromatics formation activity with a maximum selectivity of 75–80% at a CH4 conversion of about 15% than any other Fe3+-exchanged and Fe-impregnated HZSM-5 zeolite catalysts at 1073 K. With various characterizations (UV-vis, UV-Raman, CO-DRFIT, HADDF-STEM and, especially, 57Fe Mössbauer spectroscopy), atomically dispersed Fe-oxo species anchored at framework Al sites are recognized to be responsible for selectively activating CH4 into CHx species available for aromatics’ formation. By comparison, the common Fe/HZSM-5 catalysts prepared by impregnation method with Fe(NO3)3 had a large amount of reducible Fe3O4 clusters on zeolite surface, and as they were reduced and carburized, the resulted metallic Fe and Fe carbide were both favorable for CH4 decomposition only, probably due to their poor dispersion. Fortunately, the limited S residuals (about 0.05 wt%) in the Fe2+-exchanged HZSM-5 catalyst from FeSO4 did not show its negative side on strongly promoting C–H cleavage. By comparison, the two impregnated Fe/HZSM-5 catalysts from FeSO4 and Fe2(SO4)3 both showed a complete CH4 decomposition due to considerable SO42- remained. Thanks to the application of the ion-exchange method and FeSO4 as Fe precursor, a highly active and selective Fe-based HZSM-5 catalyst has been successfully modeled and Fe-oxo species are recognized as new active sites for MDA, which may give us a new insight into constructing a catalyst with better catalytic performance for MDA and other reactions.

Recycling of plastic waste using flash pyrolysis – Effect of mixture composition

Recovery of plastic waste is becoming crucial since the amount of such waste increases continuously. The objective of this study is to investigate the potential of the pyrolysis technique for the recovery of plastic waste. In that frame, the influence of temperature (550°C or 600°C) on the pyrolysis of pure polypropylene (PP), polyethylene (PE), polystyrene (PS) and polyethylene terephthalate (PET) was first studied. It is shown that whatever the type of polymer, aromatic compounds are mainly formed and could reach 55wt.-% of the oil fraction for PP and 31wt.-% for PE at 550°C. In a second step, a PP/PE mixture and a model mixture representative of the packaging plastic waste stream were pyrolyzed to investigate the influence of a combination of polymers on the proportions and composition of the different fractions. The pyrolysis of the polymer mixtures shows that, even if the aromatic compounds formed are similar to those obtained for the virgin polymers, the proportion of aromatic compounds is much more important than when the polymers are pyrolyzed alone. Indeed, mixing PE with PP at a 50/50 ratio does not affect the amount of liquid, gas and solid fractions but leads to the formation of a higher quantity of xylene (39 wt-%) at 550°C. The combination of the plastics in the model mixture has also led to a decrease of the amount of waxy compounds. Furthermore, it was shown that a higher amount of aromatics than expected was formed. As a conclusion, this study demonstrates that pyrolysis is an effective technique to recover plastic waste as aromatic compounds for the petroleum industry. In the specific conditions used in this study (proposed model mixture and pyrolysis conditions), it will favor the idea that sorting is not needed to recover plastic waste through pyrolysis since aromatics formation is favored when the stream is composed of a mixture of polymers.

Catalytic Cracking of Light-naphtha Fraction over Zeolite-based Composites for On-purpose Propylene Production

Catalytic cracking of light-naphtha fraction over zeolite-based composites in fixed-bed mode was investigated to establish an efficient method for on-purpose propylene production. The composite catalysts, consisting of MFI-type zeolites containing iron, gallium and aluminum species (Fe–Ga–Al-MFI) and metal-oxide binder (e.g., silicon oxide, aluminum oxide), were employed for cracking of light-naphtha fraction. Fe–Ga–Al-MFI zeolites as matrix, containing each heteroatom at adequate ratio in the zeolite framework, exhibited both overall acid strength suitable for selective formation of light olefins and enhanced activity for dehydrogenation of light alkanes to alkenes, so that high overall yields of light olefins (ethylene, propylene and butenes) were attained by suppressing aromatics formation compared to cracking of light-naphtha fraction using conventional Al-MFI zeolite (ZSM-5). The unique acidity of the Fe–Ga–Al-MFI zeolite was maintained in the extruded form by using neutral and inactive silicon–oxide binder, which was selected to enhance mechanical strength and/or reduce pressure drop during reaction. The zeolite-based composite (Fe–Ga–Al-MFI/SiO2) selectively converted light-naphtha fraction (n-hexane) into light olefins including propylene with catalyst lifetime longer than 2000 h, suitable for fixed-bed operation, due to its excellent resistance to coke formation. Furthermore, the cracking reactions proceeded in the absence of steam at moderate temperatures below 650 °C, so catalytic cracking using the present zeolite-based composite saved considerable thermal energy required in the reaction unit, and the total amount of hydrocarbon feedstock was reduced by ca. 15 %, compared to conventional thermal cracking at 850 °C. The present review discusses the excellent properties of these zeolite-based catalysts and catalytic cracking of light-naphtha fraction emphasizing the catalytic chemistry and reaction engineering of the catalytic process.

Crack spatial distributions and dynamic thermomechanical properties of 3D braided composites during thermal oxygen ageing

Thermal oxygen ageing behaviors of polymer matrix composites depend on resin and preform architecture. This paper concerns effects of braided architectures on thermo-oxidative ageing, including inner and surface crack initiations and propagations in 3D braided carbon fiber/epoxy composites. The ageing behaviors of unidirectional (UD) was also tested for comparison. Attenuated total reflectance Fourier transform infrared spectroscopy, two-dimensional infrared correlation spectrum, and micro-computer tomography technique have been used to characterize ageing behaviors. Aromatic formation was found ether on the surface of epoxy resin appeared prior to peroxide. The resin shrinkage could appear on the surface, and the changes of shrinkage rate of the UD composites and the 3D braided composites were consistent with cracks volume fraction. In addition, the cracks in the 3D braided composites initiated later and propagated slower than those in the UD composites. The 3D braided structure was beneficial for retaining the stiffness and damping properties after ageing.

Disaggregation mechanism of prion amyloid for tweezer inhibitor

The aggregation of amyloid has been an important event in the pathology of amyloidogenicity. A number of small molecules have been designed for Amyloidosis treatment. Molecular tweezer CLR01, a potential drug for misfolded β-amyloids inhibition, was reportedly bind directly to Lysine residues and interrupt oligomerization. However, the disaggregation mechanism of amyloid for this inhibitor is unclear. Here we used long timescale of molecular dynamic simulation to reveal the mechanism of disaggregation for pentamer prion amyloid. Molecular docking and molecular dynamics simulation demonstrate that CLR01 is attached with Lysine222 nitrogen by π-cation interaction of its nine aromatic rings and formation of salt bridge/hydrogen bond of one of the two rotatable peripheral anionic phosphate groups. Upon CLR01 binding, we found a major shifting occurs in initial conformation of the oligomer and stretch out the N-terminal chain A from the rest of the amyloid which seems to be the first stage of disaggregated the fibrils slowly yet efficiently. Moreover, the CLR01 remodelled the pentamer Prion220–272 into a compact structure which might be the resistant conformation for further oligomerization. Our work will contribute to better understand the interaction and deterioration mechanism of molecular tweezer for prions and similar amyloids, and offer significant insights into therapeutic development for Amyloidosis treatment.

In-situ catalytic co-pyrolysis of kukersite oil shale with black pine wood over acid zeolites

The thermal and catalytic co-pyrolysis of black pine wood (BPW) and Kukersite oil shale (KOS) over acid zeolites were investigated by thermogravimetric analysis (TGA) and tandem micro reactor-gas chromatography/mass spectrometry (TMR-GC/MS). TGA showed that BPW and KOS had different decomposition temperature regions due to differences in compositions. The maximum decomposition temperature (Tmax) of BPW was not changed by co-pyrolysis with KOS or additional catalyst. Although co-pyrolysis did not change the Tmax of KOS with BPW or the additional use of HZSM-5 (Si/Al2O3: 23), the Tmax was lowered to 424 °C and 428 °C using HBeta(25) and HY(30), respectively. The TMR-GC/MS results showed that oxygenates and light hydrocarbons were produced mainly by the non-catalytic pyrolysis of BPW and KOS, respectively. By applying catalytic pyrolysis (CP), these oxygenates and light hydrocarbons were converted to aromatic hydrocarbons over acid zeolites. HZSM-5(23) had the highest efficiency in the formation of aromatics from the CP of BPW and KOS, followed by HBeta(25) and HY(30) because of the catalyst acidity and pore properties. The co-feeding of KOS on the CP of BPW enhanced the synergistic effects on the formation of aromatics because of the effective Diels-Alder reaction between the CP intermediates of BPW and KOS.

Efficient production of aromatics by catalytic pyrolysis of fruit waste over zeolites with 3D pore topologies

Fruit waste collected from a juice factory was pyrolyzed over zeolite catalysts with different pore topologies. The production of aromatic compounds was directly influenced by zeolite topology type (i.e. pore opening size and pore channel dimensionality). Zeolites with three-dimensional (3D) pore topologies (e.g. MFI, BEA and FAU) favored aromatization reactions, which yielded up to 80% aromatic compounds, compared to <20% yield in the pyrolysis over FER and MOR zeolites with two- and one-dimensional pore channels, respectively. The catalytic performance of the 3D zeolites, MFI, BEA and FAU were more vulnerable to operating conditions such as catalyst to biomass ratio and pyrolysis temperature, compared to 2D FER and 1D MOR zeolites. The results were possibly explained by the interplays of diffusion limitations and space constrains, imposed by the pore topologies. By correlation analysis, applying FAU zeolite at catalyst to biomass ratio of 2:1 under 450, 550, or 650 °C was found to be optimal for aromatics formation, affording more mono aromatic hydrocarbons (45%) and less polycyclic aromatic hydrocarbons (30%). Moreover, the zeolites employed in the reactions with larger pore size tended to coke. This work potentially provides a guideline for efficient conversion of fruit waste to aromatic compounds enriched biofuels.

Efficient catalytic conversion of microalgae residue solid waste into lactic acid over a Fe-Sn-Beta catalyst

Microalgae residue was efficiently converted into lactic acid with a high yield (33.9%) under mild reaction conditions (210 °C, 2 h) over a Fe-Sn-Beta catalyst. Under the action of homogeneous H3O+ and distinct Lewis acid sites on the catalyst, the production of lactic acid from microalgae residue underwent three main reaction steps: hydrolysis, isomerization, and retro-aldol condensation. Results demonstrated that the lipid component had a strong inhibitory effect on the production of lactic acid due to the formation of aromatics, esters, and complex nitrogenous heterocyclic compounds, which covered or poisoned the Lewis acid sites of the catalyst. The protein component acted as a chemical buffer that enhanced the production of lactic acid by controlling the release of monosaccharides from the carbohydrate fraction of microalgae and maintaining the catalytic activity of the catalyst. Thus, microalgae residue demonstrated great promise for the production of value-added chemicals.

High-Efficiency Conversion of Methanol to BTX Aromatics Over a Zn-Modified Nanosheet-HZSM-5 Zeolite

A Zn-modified nanosheet-HZSM-5 zeolite (Zn-SH-HZSM-5) was prepared and tested as a catalyst in the methanol-to-aromatics (MTA) reaction. First, both an effective suppression of C9+ aromatics formation and a significantly enhanced yield of benzene, toluene, and xylene (BTX) aromatics were achieved by reasonably controlling the reactive pathways in this catalytic reaction system. Further alkylation of BTX aromatics to form C9+ byproducts was effectively limited by the significantly reduced retention time of BTX molecules in the micropore system, with a significantly shortened diffusion-reaction path. Furthermore, the conversion of methanol to BTX was significantly improved by introducing new surface Zn-Lewis acid sites, achieving a synergistic catalysis with Brönsted acid sites. Second, this catalyst also exhibited strong capabilities both to limit the formation and deposition of large-size coke molecules, thanks to its shortened diffusion-reaction path, and to accommodate carbon, due to the high external surface area and considerable stacking mesopores. As a result, our Zn-SH-HZSM-5 catalyst demonstrated good stability in a 100 h on-stream reaction, providing a BTX yield higher than 54.5%, with a C9+ aromatic byproduct formation lower than 5.1%. The present work may provide a promising way for developing an elegant catalyst for a more sustainable MTA process.

Catalytic flash pyrolysis of Monoraphidium sp. before and after lipid extraction

The use of biomass from Monoraphidium sp. microalgae before and after lipid extraction was investigated using flash catalytic pyrolysis to generate a bio-oil with improved characteristics. The biomass was obtained from intensive outdoor crops and exhibited an attractive biochemical composition to be used in thermochemical processes with high protein and carbohydrate content remaining after lipid extraction. Flash pyrolysis of biomass before and after extraction was developed at 500 °C in an analytical micro-pyrolyzer coupled to a gas chromatography/mass spectrometry (Py-GC/MS) instrument and the pyrolysis vapors were transported to a catalytic bed at 300 °C. Pyrolysis vapors were improved in the catalytic pyrolysis using zeolite HZSM-5 which promoted the deoxygenation and complete denitrogenation of the products. Furthermore, the formation of aromatics in the biomass was increased before and after extraction to 87.45% and 95.08%, respectively, thus demonstrating the potential of this process to generate a high quality bio-oil which can be used in several applications in chemical and fuel industries.

Probing pyrolysis chemistry of 1-heptene pyrolysis with insight into fuel molecular structure effects

The pyrolysis of 1-heptene was studied in a flow reactor using synchrotron vacuum ultraviolet photoionization mass spectrometry at 0.04 and 1 atm and in a jet-stirred reactor using gas chromatography at 1 atm. Flow reactor pyrolysis products, including the allyl radical, cycloalkenes and aromatics, were identified and quantified. Alkenes are found to be the dominant product family, among which ethylene is the most abundant product. A detailed intermediate-to-high temperature model of 1-heptene was developed and validated against the new pyrolysis data in this work, as well as previous data of 1-heptene combustion in literature over a wide range of pressures, temperatures and equivalence ratios. Rate of production analysis and sensitivity analysis were performed to reveal the key pathways in fuel decomposition and product formation. The allylic CC bond dissociation reaction is concluded as the most important pathway in 1-heptene decomposition. Reactions of allyl, propargyl and cyclopentadienyl radicals play important roles in the formation of cycloalkenes and aromatics. Furthermore, comparative pyrolysis experiments of 1-hexene and n-heptane were also performed in the jet-stirred reactor at 1 atm using gas chromatography to explore fuel molecular structure effects on pyrolysis reactivity and product distributions among 1-alkene and n-alkane fuels. The comparison between 1-heptene and 1-hexene pyrolysis demonstrates that similar fuel molecular structure results in the similarities in primary fuel decomposition pathways and pyrolysis reactivity. Ethylene is the most abundant product in both 1-alkene pyrolysis, and the feature in 1-heptene molecular structure leads to enhanced formation of ethylene in its pyrolysis. The abundant formation of ethyl and methyl radicals leads to higher production of 1-pentene and 1-butene in 1-heptene and 1-hexene pyrolysis, respectively. The comparison between 1-heptene and n-heptane pyrolysis reveals that the existence of CC double bond enhances the pyrolysis reactivity of 1-heptene. Different from 1-heptene consumption, n-heptane consumption is dominantly controlled by H abstraction reactions instead of unimolecular decomposition reactions. Propene and 1-butene are prone to be produced in 1-heptene pyrolysis, while 1-hexene has higher mole fractions in n-heptane pyrolysis.

Mechanisms of aromatization of dilute ethylene on HZSM-5 and on Zn/HZSM-5 catalysts

Catalysts with a Zn/H+ molar ratio ranging from 0 (H-ZSM5) to 1.8 (Zn/H-ZSM5), were prepared by wet impregnation from three commercial zeolites with Si/Al ratio of 15, 40 and 75. The texture, acidity and reactivity of the bifunctional catalysts were characterized by: N2, IR followed by adsorption of pyridine and NH3-TPD, and tested at 500 °C with low partial pressure of ethylene (PC2H4 = 0.005 MPa) and a high GHSV (ca 13,300 h−1).The intrinsic activity of protonic acid sites in ethylene transformation depends on their density or rather on the concentration of next nearest neighbours pairs of Al atoms. Brønsted acid pair sites converts ethylene into aromatics while isolated protonic site are almost inactive. Two apparent primary products were distinguished: iso-butene and propene, resulting from the oligomerization-cracking catalytic pool, followed at high conversion by the concomitant formation of alkanes and aromatics through hydrogen transfer.The deposition of Zn was achieved by wet impregnation of the nitrate precursor. The thermal decomposition of the ZnOH+ cation by calcination is a function of the fraction of Al atoms in the nearest neighbours. Three main species of Zn could be identified: i) oxo-binuclear Zn2+ cations (O−-Zn2+-O-Zn2+-O−), ii) mononuclear Zn2+ cations (O−-Zn2+-O− and iii) ZnO particles located on the external surface. These species were quantified from the residual Brønsted acid sites probed by pyridine. A correlation has been established: one neutralized protonic site generates one Zn Lewis acid sites which coordinates two pyridine molecules. The ethylene conversion is proportional to the concentration of oxo-binuclear Zn cations and mononuclear Zn cations only correlate with hydrogenation and hydrogenolysis of olefins, while bulk ZnO is inactive.A metallacyclic mechanism of ethylene aromatization involving cyclo-butyl-zinc species has been proposed accordingly.

Catalytic Process in Producing Green Aromatics through Fast Pyrolysis of Wood of Five Tropical Fast Growing Trees Species

The generation of liquid fuels and chemicals is potential through a catalytic fast pyrolysis (CFP) which is a rapid, inexpensive, and promising method utilizing tropical wood biomass as starting material. There is a little known in the potential of wood biomass from tropical fast-growing trees as starting materials for the production of liquid fuel and chemicals. In this study the formation of aromatics by pyrolytic-gas chromatography/mass spectroscopy (Py-GC/MS) is evaluated on the effect of wood species with different characteristics and its cellulose component to the formation of aromatics. Fast pyrolysis of eucalyptus wood characterized with low content of ash and high percentages of hollocellulose and α-cellulose produced much high relative peaks of levoglucosan and small relative peaks of lignin derived products. Meanwhile high content of vollatile matter and high crystallinity of cellulose attributed balsa and jabon woods as feedstock for fast pyrolysis. The catalytic process in fast pyrolysis of eucalyptus decomposed the most of oxygenated compound such as levoglucosan and furfural into aromatics in the presence of ZSM-5. Coke formation on the surface catalyst might lead partly of decomposition of levoglucosan and furfural to form aromatics in the catalytic fast pyrolysis of balsa wood. Cellulose component determined on the formation of benzene, toluene, styrene, p-xylene, indane, indene, and naphthalene in catalytic fast pyrolysis of wood.

C14H10 polycyclic aromatic hydrocarbon formation by acetylene addition to naphthalenyl radicals observed.

The formation of polycyclic aromatic hydrocarbons (PAHs) during combustion has a substantial impact on environmental pollution and public health. The hydrogen-abstraction-acetylene-addition (HACA) mechanism is expected to be a significant source of larger PAHs containing more than two rings. In this study, the reactions of 1-naphthalenyl and 2-naphthalenyl radicals with acetylene (C2H2) are investigated using VUV photoionization time-of-flight mass spectrometry at 500 to 800 K, 15 to 50 torr, and reaction times up to 10 ms. Our experimental conditions allow us to probe the Bittner-Howard and modified Frenklach HACA routes, but not routes that require multiple radicals to drive the chemistry. The kinetic measurements are compared to a temperature-dependent kinetic model constructed using quantum chemistry calculations and accounting for chemical-activation and fall-off effects. We measure significant quantities of C14H10 (likely phenanthrene and anthracene), as well as 2-ethynylnaphthalene (C12H8), from the reaction of the 2-naphthalenyl radical with C2H2; these results are consistent with the predictions of the kinetic model and the HACA mechanism, but contradict a previous experimental study that indicated no C14H10 formation in the 2-naphthalenyl + C2H2 reaction. In the 1-naphthalenyl radical + C2H2 reaction system, the primary product measured is C12H8, consistent with the predicted formation of acenaphthylene via HACA. The present work provides direct experimental evidence that single-radical HACA can be an important mechanism for the formation of PAHs larger than naphthalene, validating a common assumption in combustion models.

Effect of zeolite on the catalytic cracking of tar yields mahogany wood pyrolysis

In this study, the effects of zeolite were observed to investigate the formation of a pyrolysis product, which is tar yield. Tar yields receive the most attention because of their potential as a bio-oil and chemical feedstocks. For this reason, efforts to increase tar yield were made, one of which was by adding zeolite to the pyrolysis process. The role of zeolite here was a pyrolysis catalyst. This is a study that uses mahogany wood as the feedstock for a real, pilot plant pyrolysis reactor. Moreover, 0-50% of the feedstock's mass worth of zeolite was also introduced during the pyrolytic process. The temperatures set in this pyrolysis were 250 °C, 500 °C, and 800 °C. The test results were measured in terms of the tar yield's volume and mass. The volume of tar yields produced increased as the temperature increased due to more biomass decomposed. Then, the chemical composition of tar yield was tested using a Gas Chromatograph Mass Spectrometry (GC-MS) to measure the percentage of its chemical constituent compounds. Then, the formation mechanism of tar compounds from pyrolysis was described by using HyperChem simulation. The results showed that an increase in zeolite catalyst percentage would generate more volume of tar yields. It was due to the breaking of biomass hydrocarbon chains, increasing the production of tar yields. Zeolite also affected the formation of hydrocarbon chains in tar yields where the chains became shorter as the percentage of zeolite catalyst rose. The mechanism of increasing tar product was due to the role of zeolite as a catalyst in the catalytic cracking process which is almost similar to acid-base reactions of Brønsted-Lowry and Lewis. This reaction took place when the pyrolysis yields moved through the pores of zeolite, breaking the long hydrocarbon chains into shorter ones which were dominated by alkenes, aromatic, and acidic compounds formation. In addition, acidic compounds represented by acetic acid function as a flammable matter possess the potential of becoming oil-fuel.

Stochastic Modeling of the Formation of Aromatics in Combustion

Stochastic Modeling of the Formation of Aromatics in Combustion