Main Hydrocarbon Products Research Articles

Fischer-Tropsch Synthesis for the Production of Sustainable Aviation Fuel: Formation of Tertiary Amines from Ammonia Contaminants.

Fischer-Tropsch synthesis combined with product workup is a promising route toward synthetic aviation fuel from renewable hydrogen and carbon sources like biomass, CO2, and waste. Cost savings can be achieved by reducing the number of gas treatment steps in new plants, but the consequence of contaminants in the feed needs investigation. While feeding 2.6 ppmV ammonia to a Fischer-Tropsch reactor, it was shown that ammonia was predominantly chemically converted into organic amines, with most nitrogen found in the water phase (89%), followed by heavy wax (7%) and light wax (1%). The concentration difference between water and light wax was shown to be due to the post-condensation separation of amines on polarity. Amines up to a chain length of 120 were detected in the heavy wax with MALDI-FT-ICR-MS, which, in combination with the high nitrogen content, suggests that amines have a similar chain growth probability compared to the main hydrocarbon products. Detailed product analysis with three independent analytical techniques showed that tertiary N,N-dimethylalkylamines were by far the most abundant amine class. This suggests that ammonia is decomposed on the cobalt surface and, potentially as a dimethylamine fragment, incorporated in the growing chain. Further evidence was obtained from the abundance of trimethylamine and from the reconciled nitrogen product analysis up to C100, which showed that the amine product distribution followed from naphtha onward the same ASF kinetics as alkanes and oxygenates while being distinctively different from the alkene distribution. The presented findings provide further avenues for studies of the Fischer-Tropsch reaction mechanism and indicate the opportunity of cost saving on gas treatment, while further validation is required to assess the impact on hydrocracking and product quality.

Experimental Investigation of the Photochemical Production of Hydrocarbons in Warm Gas Giant Exoplanet Atmospheres

In warm (equilibrium temperature <1000 K) gas giant exoplanet atmospheres, the observation of trace species in abundances deviating from thermochemical equilibrium predictions could be used as an indicator of disequilibrium chemical processes, such as photochemistry. To predict which compounds could be used as such tracers, it is therefore essential to study how photochemical processes affect their abundances. For this purpose, we investigated experimentally the efficiency of the photochemical formation of hydrocarbons in gas mixtures representative of warm gas giant atmospheres as a function of the gas temperature at millibar pressures. We find that, compared to thermal reactions alone, photochemistry efficiently promotes, under the studied conditions, the formation of hydrocarbons, with the detection of acetylene, ethane, and propane, as well as carbon monoxide. Therefore, our results confirm the importance of photochemistry in exoplanet atmospheres as a disequilibrium process. Ethane is the major hydrocarbon formed in our experiments, in apparent contradiction with the prediction by thermo-photochemical models that acetylene should be the main hydrocarbon product. We also observe an evolution of the hydrocarbon production efficiency as a function of the temperature, a behavior not reproduced by a 0D thermo-photochemical model. Additional studies are necessary to definitively understand the origin of the differences between the experimental and modeling results and to infer the importance of our results for understanding hydrocarbon formation in warm gas giant exoplanet atmospheres. Finally, our work demonstrates the importance of experimental studies together with modeling studies to accurately interpret, understand, and predict observations of exoplanet atmospheres.

Enhancing deoxygenation of waste cooking palm oil over CaO-MgO catalyst modified by K2O for green bio-fuel

There are challenges to replacing traditional fossil fuels completely, so producing efficient green biofuels is crucial. In this work, waste cooking palm oil (WCPO) was used as raw material to produce biofuel through pyrolytic catalysis cracking (PCC) over alkaline catalysts as CaO-MgO with various dopants at 0, 3, 6 and 9 wt% K2O contents. The WCPO reacted under atmospheric pressure without purging gases at 500, 525 and 550 °C, respectively. Catalysts were characterized by various techniques in terms of physical and chemical properties. The pyrolytic oil (PO) was separated from the crude oil product. Then, PO was characterized by TGA/DTG, CHNO, FTIR and GC–MS. The PO was distilled following an ASTM D86 method. The properties of biofuels, such as density, kinematic viscosity and acidity, were measured. The basicity of the catalyst increased with increasing K2O contents. K2O not only enhanced the pyrolytic-liquid product yield but also significantly reduced the oxygenated compounds in biofuel through the deoxygenation process to improve biofuel quality. The different reaction temperatures were observed in which low-temperature reaction provided incompletely cracking heavy molecules, and more gas product occurred at the high reaction temperature. Surprisingly, the fatty acid compounds of WCPO were transferred to hydrocarbon compounds by deoxygenation reactions confirmed by GC–MS and FTIR results. The highest pyrolytic oil yield was approximately 92 vol% compared with crude oil product, obtained from 3 wt% K2O-MgO/CaO and 525 °C. The paraffinic and olefinic compounds were the main hydrocarbon products with K2O doping catalysts, while ketone compounds were found in all catalysts via the ketonic decarboxylation mechanism. In this condition, pyrolytic oil was completely distilled to get gasoline, kerosene and diesel. The kinematic viscosity and density were under ASTM standards except for acidity. Remarkably, the acidity of biofuel with K2O doping was reduced about 2–3 times compared to MgO/CaO alone.

Pyrolysis study of N, N-dimethylformamide at low pressure

N, N-dimethylformamide (DMF) is a kind of general solvent in Li-ion industry and nitrogen-containing component of amines fuels. The trace vapor of DMF is very harmful to human and environment, which could be treated by pyrolysis. The pyrolysis of DMF was newly carried out in a flow reactor at 30 Torr within 873–1273 K. Synchrotron radiation single photoionization coupled with molecular beam mass spectrometry was employed to detect the reactants, intermediates and products. 26 species were identified and quantified. Products related to NOx, such as nitrosomethane, nitrosyl cyanide and N-methylformamide were identified. With the temperature increasing, the mole fractions of species tend to increase monotonically, while nitrosyl cyanide, ethyl radical, cyclopropane, carbon monoxide, ethanol, acetaldehyde and ethanol exhibit peak-shaped curves. Hydrogen abstractions and dissociations are the main initial pathways of DMF consumption. As the main hydrocarbon products, methane and ethylene are predominantly formed by the H abstraction reaction by methyl radical and the β-scission of ethyl radical, respectively. Carbon monoxide is mainly generated from the dissociation of DMF and its mole fraction is at the same level as the fuel DMF. HCN is the most abundant product among all the carbonitride species via H abstraction of CH2 =NH as well as the collisions of CN with alkanes and aldehydes. These results provide a theoretical basis for further study of treating DMF in the exhaust fumes through pyrolysis and have reference value for the clean utilization of amine fuels.

A DFT Study for Catalytic Deoxygenation of Methyl Butyrate on a Lewis Acid Site of ZSM-5 Zeolite

The catalytic deoxygenation mechanism of fatty acid esters on a Lewis acid site of ZSM-5 zeolite was elucidated via density functional theory (DFT) by using a methyl butyrate (MB) as the model compound for fatty acid esters. The configurations of the initial reactant, transition states, and products together with the activation barrier of each elementary reaction were determined. The activation barrier of different initial cracking reactions decreases in the order of α-C–C &gt; β-C–C &gt; α-C–O &gt; β-C–O. The best reaction path for catalytic deoxygenation of methyl butyrate over Lewis acid site is CH3CH2CH2C(OCH3)=O⋯Lewis → CH3CH2⋯Lewis⋯C(=CH2)OCH3 → CH2=CH2 + CH3COOCH3 + Lewis. The oxygen of methyl butyrate is mainly removed as CO2, methyl acetate, formaldehyde, and butyraldehyde, while ethylene, propylene, and butane are the main hydrocarbon products. In addition, the group generated by cracking of methyl butyrate form a bond with the Lewis acid site, promoting the transformation between a Lewis acid and a Brønsted acid. The corresponding intermediates have a high single point energy, but the poor stability leads to further deoxygenation and cracking reactions. This work provides a theoretical basis for the modification in the number of Brønsted acid and Lewis acid sites in the ZSM-5 zeolite.

Insight into the role of Fe5C2 in CO2 catalytic hydrogenation to hydrocarbons

Iron-based catalysts have been widely used to synthesize value-added hydrocarbons through CO2 hydrogenation. Fe carbide, Fe5C2, was proposed as the active phase responsible for CC coupling during the chain growth. However, the reaction mechanism over iron-based catalysts is still under debate due to the presence of multiple phases of Fe species. In this work, Fe5C2 and K-modified Fe5C2 were prepared and used to study the relationship between the Fe phase, catalytic performance and reaction pathways. CH4 and CO selectivities of 46.1 C-mol% and 2.8 C-mol% were obtained on Fe5C2 at a CO2 conversion of 49.8 %, with the main hydrocarbon products being alkanes. With the addition of the promoter K, the C2-C4= selectivity increased to above 38.0 C-mol%, and the selectivity to C5+ hydrocarbons increased to 23.9 C-mol% at a similar CO2 conversion. CH4 and C2+ hydrocarbons formed through the CO2→CO→hydrocarbons (indirect) route over K-modified Fe5C2, whereas the direct hydrogenation route occurred on unmodified Fe5C2 in addition to the indirect route of CO2 to CO to hydrocarbons through Fischer-Tropsch synthesis (FTS) processes. This work offers insights in direct CO2 hydrogenation over Fe5C2 and Fe3O4-Fe5C2 catalysts, which advances the understanding of the functions of active phases and reaction pathways of CO2 hydrogenation over iron-based catalysts.

Green C2-C4 hydrocarbon production through direct CO2 hydrogenation with renewable hydrogen: Process development and techno-economic analysis

This study proposes a novel process for the light hydrocarbons production from captured CO2 and renewable hydrogen (H2). The process consists of two main stages: i) A reaction stage in which CO2 is converted into alkene-range hydrocarbons over a K-promoted Fe catalyst, and ii) a separation stage in which multiple technologies are integrated for the recycling of CO2, carbon monoxide (CO), and H2 and the purification of the main C2-C4 hydrocarbon products (e.g., light olefins) and byproduct (C5+). The methane (CH4) and CO rejected in the separation stage are fed into a combined heat and power (CHP) process to generate utilities on-site while C5+ considered as by-product. In the rigorous process models developed in this work, the required sub-processes are integrated at a plant-wide level and the optimal operation conditions are determined to ensure high energy efficiency and low environmental impact, as well as compliance with the product specifications. As a result, the proposed process could achieve 99.2% and 42.0% carbon and energy efficiencies, respectively. The unit production cost for the C2-C4 hydrocarbons was estimated to be 3.58 USD/kg, and the CO2 emission was estimated to be negative (−1.85 kg CO2 per kg C2-C4 hydrocarbon). In addition, an economic sensitivity analysis was performed to identify the major cost-drivers, such as low CO2 conversion or high prices for renewable H2, and to propose solutions to these bottlenecks to allow the development of economically viable applications.

Non‐oxidative methane conversion in diffuse, filamentary, and spark regimes of nanosecond repetitively pulsed discharge with negative polarity

AbstractMethane conversion for higher hydrocarbons was carried out in the diffuse, filamentary, and spark regimes of nanosecond repetitively pulsed discharge with negative polarity in a pin‐to‐plate reactor. The diffuse discharge was characterized as a regime with low‐plasma energy, and only trace hydrogen and C2H6 were found in this regime. In filamentary regime, the conversion rate reached 2.2–7.6% with energy conversion efficiency (ECE) of 8.8–12.7%. Meanwhile the selectivity of C2H6, C2H4, C2H2, and C3 were 24.3–18.6%, 9.3–7%, 5.6–7.3%, and 0–5%, respectively. As for the spark regime, C2H2 became the main hydrocarbon product with the selectivity of 12.8%, conversion rate of 44.7–74.4% and ECE of 12.3%. Electrical measurements and ICCD photographs showed that the short pulse could prevent the streamer turning into spark discharge, and thus realize smooth transitions among each regime. Optical emission spectroscopy was used to investigate the plasma chemistry in each regime. It found that the highest spectral line, gas temperature, and electron density varied in these regimes. These results suggested that, comparing with electron impact reactions, the thermal chemistry became more and more important as the plasma energy increased.

Catalytic hydrothermal deoxygenation of fatty acids over palladium on activated carbon catalyst (Pd/C) for renewable diesel production

Renewable diesel, a potential substitute for petroleum diesel, is usually produced from biological sources by deoxygenating fatty acids in the presence of organic solvents with the addition of hydrogen. This could pose a health challenge and increase the cost of production. The current work was conducted in subcritical water without the addition of hydrogen using palmitic and oleic acids as fatty acids. The impact of temperature and reaction time was assessed using 5% palladium on activated carbon (Pd/C) catalyst. The recovered organic products were analysed for hydrocarbons using gas chromatography. The results show that the main hydrocarbon products from palmitic and oleic acids were pentadecane and heptadecane, respectively. The maximum value of the molar yield of pentadecane was 35.4% at the optimum conditions of 290 °C and 1.5 h, and that from heptadecane was 16.6% at 330 °C and 4 h. This shows that 5% Pd/C is active for catalysing the hydrothermal decarboxylation of the fatty acids to hydrocarbons. With these results, the cost of production can probably be reduced and the capacity to use hydrocarbons from a renewable resource to displace conventional diesel can be increased.

High Yield of Hydrocarbons from Catalytic Hydrodenitrogenation of Indole under Hydrothermal Conditions

We report herein on a new method to achieve a high yield of hydrocarbons from hydrothermal catalytic hydrodenitrogenation (HDN) of indole, which is higher than that from conventional pyrolysis methods. The main hydrocarbon products were aromatic hydrocarbons and alkanes, which are similar to fossil oils to be used as liquid fuels in the future. Catalyst screening experiments show that noble metal catalysts (e.g., 5 wt % Pt, Pd, or Ru) supported on porous solids (e.g., carbon, Al2O3) enhanced the conversion of indole to hydrocarbons under hydrothermal condition. Of those different catalysts, Pd/γ-Al2O3 shows the greatest influence on the yield of hydrocarbons, which we focus on the catalyst Pd/γ-Al2O3 in more details. On the basis of the Pd/γ-Al2O3 catalyst, the effects of time, temperature, and H2 pressure on the hydrocarbons were discussed. HDN of the indole reaction at 450 °C, 0.015 g/cm3 water density, 5 MPa H2, and 50 wt % Pd/γ-Al2O3 loading led to a maximum yield (51 mol %) of hydrocarbons at 120 min...

Controllable Product Selectivity on Polycrystalline Cu through Tunable Surface Morphology

Carbon dioxide (CO2) electroreduction (CO2ELR) has the advantage of using a gaseous waste stream accompanied with water, a catalyst and electricity from renewables and turn it to carbon neutral chemicals and fuels. The most valuable products of CO2ELR are formed predominantly on Cu-based catalysts, such as methane (CH4), ethylene (C2H4), ethanol, and formic acid. However, there are still hindrances that prevent the broad commercial use of the process and are associated mainly with catalyst performance, such as current efficiency, selectivity, and stability1, 2. Recent studies highlighted the importance of surface morphology which can improve faradaic efficiency (FE) and activity towards more desirable products (hydrocarbons) 3-6. Our recent study showed that Cu undergoes reconstruction under CO2 reduction conditions that influences the surface morphology and the crystal orientation7 which added more complexity to understanding morphology-driven performance. Understanding and identifying the factors behind the activity and selectivity improvement is of great importance since it will allow us to control and direct the reactions towards the targeted products though the optimal design of catalysts. This work examines the morphology-related factors (particle size, roughness, and crystal orientation) and copper oxidation state that drive the selectivity on rough Cu-based catalysts surfaces. Rough Cu-based catalysts were synthesized by electrodeposition and their morphological aspects were tuned through control of the parameters of potential applied and charge passed. A surface current distribution due to morphology was performed for each catalyst. The evaluation of each synthesized catalyst involved the examination of their surface morphology, reaction selectivity, and current efficiency. The surface morphology of each Cu-based catalyst was examined with capacitance measurements using cyclic voltammetry techniques, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). Micro gas chromatography (microGC) was used for the gaseous product analysis. The results present the factors that influence the selectivity and illustrate a direct relation between specific morphological aspects, current distribution, and product selectivity. In particular, lower roughness catalysts (1.6 roughness factor) covered with larger particles (3μm size particles) produced methane as the main hydrocarbon product; whereas, higher surface roughness catalysts (7.8 roughness factor) covered with smaller particles (300nm size) were associated with the higher formation of ethylene. Current distribution analysis illustrated lower current intensity on low roughness surfaces in comparison with higher roughness surfaces where the current intensity was higher. We will report that the crystal orientation of polycrystalline Cu is not the main factor that drives the selectivity and the oxidized Cu doesn’t seem to enhance the selectivity to C2H4 in comparison with metallic Cu.

Direct hydrodeoxygenation of algal lipids extracted from Chlorella alga

AbstractBACKGROUNDHydrodeoxygenation (HDO) of Chlorella algal oil extracted with supercritical hexane and stearic acid as a model compound was investigated over several supported Ni and Mo2N–MoO2 catalysts in a semibatch reactor at 300 °C under 30 bar in the presence of hydrogen.RESULTSThe results showed that all catalysts were very active in HDO of stearic acid. With crude algal oil, a maximum conversion of lipids of 35% was found with an acidic Ni‐HY‐80 zeolite catalyst after 360 min. The main products in algal oil HDO were fatty acids; whereas maximally only 7% hydrocarbons were formed with Ni‐HY‐80. The main hydrocarbon products were formed via decarbonylation, as the hydrogenation/dehydration route was suppressed.CONCLUSIONSHydrodeoxygenation of crude Chlorella algal oil was demonstrated over nickel supported on beta zeolite and with a molybdenum oxide–nitride catalyst. Strong catalyst deactivation occurred for the former catalyst, whereas the latter retained its activity. © 2016 Society of Chemical Industry

Evaluation of the Impact of Surface Reconstruction on Rough Electrodeposited Copper‐Based Catalysts for Carbon Dioxide Electroreduction

AbstractCarbon dioxide electroreduction (CO2ELR) can combine the use of a gaseous waste byproduct (CO2) with electricity from renewable sources to produce low‐carbon fuels and useful chemicals. Recent reports pointed out the superior performance of rough copper polycrystalline catalysts; however, reconstruction that takes place on such surfaces is under investigation. This report highlights the importance of copper surface reconstruction on rough surfaces during CO2ELR. Electrodeposited copper‐based catalysts composed primarily of Cu(111) were examined under CO2ELR conditions, and it was found that they underwent reconstruction towards Cu(200). The main hydrocarbon product of electrodeposited copper‐based catalysts with Cu(200) was CH4. The Cu/Cu catalyst achieved up to 40 % Faradaic efficiency (FE) to CH4 and low H2 efficiency (16 % FE) at −1.07 V versus the reversible hydrogen electrode (RHE), at a current density of −86 mA cm−2. This study provides new insights regarding the correlation of copper crystal orientation and selectivity on rough copper surfaces and the impact of copper reconstruction on the reaction.

Pyrolysis of waste tires: A modeling and parameter estimation study using Aspen Plus®

This paper presents a simulation flowsheet model of a waste tire pyrolysis process with feed capacity of 150kg/h. A kinetic rate-based reaction model is formulated in a form implementable in the simulation package Aspen Plus, giving the flowsheet model the capability to predict more than 110 tire pyrolysis products as reported in experiments by Laresgoiti et al. (2004) and Williams (2013) for the oil and gas products respectively. The simulation model is successfully validated in two stages: firstly against experimental data from Olazar et al. (2008) by comparing the mass fractions for the oil products (gas, liquids (non-aromatics), aromatics, and tar) at temperatures of 425, 500, 550 and 610°C, and secondly against experimental results of main hydrocarbon products (C7 to C15) obtained by Laresgoiti et al. (2004) at temperatures of 400, 500, 600, and 700°C. The model was then used to analyze the effect of pyrolysis process temperature and showed that increased temperatures led to chain fractions from C10 and higher to decrease while smaller chains increased; this is attributed to the extensive cracking of the larger hydrocarbon chains at higher temperatures. The utility of the flowsheet model was highlighted through an energy analysis that targeted power efficiency of the process determined through production profiles of gasoline and diesel at various temperatures. This shows, through the summation of the net power gain from the plant for gasoline plus diesel that the maximum net power lies at the lower temperatures corresponding to minimum production of gasoline and maximum production of diesel. This simulation model can thus serve as a robust tool to respond to market conditions that dictate fuel demand and prices while at the same time identifying optimum process conditions (e.g. temperature) driven by process economics.

Kinetics of Adsorption of Methylcyclopentadienyl Manganese Tricarbonyl on Copper Surfaces and Implications for the Atomic Layer Deposition of Thin Solid Films

The kinetics of the thermal chemistry of methylcyclopentadienyl manganese tricarbonyl on copper surfaces was followed by infrared absorption spectroscopy analysis of the gas surrounding the substrate. Dissociative adsorption of the MeCpMn(CO)3 precursor was seen at low temperatures, below 400 K, and was determined to occur via the initial loss of a single carbon monoxide ligand. Full decarbonylation was observed starting at a surface temperature of approximately 510 K, and full decomposition of the Mn precursor was seen to be complete by 540 K. All these transitions were determined to occur at temperatures at least 100 K lower than those reported on silicon oxide surfaces. Comparison with reference spectra afforded the identification of the main hydrocarbon product as a mixture of methylcyclopentadiene isomers. Isothermal measurements of MeCpMn(CO)3 partial pressure versus reaction time highlighted a deviation from first-order kinetics, an effect associated with changes in surface reactivity. A self-limit...

Catalytic Pyrolysis of Microcrystalline Cellulose with Five Molecular Sieve Based Catalysts in Py-GC-MS

Catalytic pyrolysis of biomass has the potential to produce bio-oil , which is rich in aromatic hydrocarbons and can be used as transportation fuel. In this paper, microcrystalline cellulose were pyrolysis with HZSM-5(Si/Al=25), HZSM-5(Si/Al=50), HZSM-5(Si/Al=100), HY, Hβin a CDS5200 pyroprobe at temperature ranging from 450-650̊C. GC-MS is used to analyze the liquid product in the catalytic pyrolysis. Except the catalysts and pyrolysis temperature, this work also evaluated the influences of heating rate, catalyst-to-biomass ratios on the production yield of aromatic hydrocarbons and product distribution. HZSM-5(Si/Al=50) has the highest yield among the five catalysts. Catalytic pyrolysis at 500̊C、20K/ms heating rate and 5:1catalyst to biomass ratio is most suitable to produce aromatic hydrocarbons. Benzene, toluene, xylene and naphthalene are the main aromatic hydrocarbon products in catalytic pyrolysis of microcrystalline cellulose.

Hydrodeoxygenation of Benzofuran over Silica–Alumina-Supported Pt, Pd, and Pt–Pd Catalysts

A series of monometallic Pt and Pd and alloyed Pt–Pd catalysts (mole ratio of Pt/Pd = 1, 4, and 0.25) were prepared with silica–alumina as support. CO chemisorption and X-ray diffraction (XRD) were applied to characterize the resulting samples. The performance of the catalysts for hydrodeoxygenation (HDO) for benzofuran (BF) was evaluated in a fixed-bed flow reactor at 280 °C and 3.0 MPa. Only one major route was found for the reaction network of HDO of BF among the catalysts. First, BF was transformed to 2,3-dihydrobenzofuran with the hydrogenation at the heterocyclic ring, followed by further conversion to octahydrobenzofuran at the benzene ring. The main hydrocarbon products are ethylcyclohexane and methylcyclohexane. The silica–alumina-supported catalysts also showed significant cracking activities, with the observation of the production of methylcyclohexane. The activity and product selectivity of Pt, Pd, and bimetallic Pt–Pd catalysts with the influence of the weight time were investigated in detail. Bimetallic Pt–Pd catalysts were higher in activity in the hydrogenation and the removal of oxygen from BF than their monometallic counterparts. The Pd4Pt1 catalyst presented the highest activity, with 99% conversion of BF and 100% selectivity toward 2,3-dihydrobenzofuran among all of the other catalysts at low weight time.

Detailed Product Analysis during Low- and Intermediate-Temperature Oxidation of Ethylcyclohexane

An experimental study of the oxidation of ethylcyclohexane has been performed in a jet-stirred reactor with online gas chromatography, under quasi-atmospheric pressure (800 Torr), at temperatures ranging from 500 to 1100 K (low- and intermediate-temperature zone including the negative temperature coefficient area), at a residence time of 2 s, and for three equivalence ratios (0.25, 1, and 2). Ethylcyclohexane displays important low-temperature reactivity with a well-marked negative temperature coefficient behavior. In addition to 47 products with a mass lower than ethylcyclohexane which have been quantified, many species with a C(8)H(14)O formula (molecular weight of 126) were detected by GC-MS and 7 of them were quantified. These molecules are cyclic ethers, ketones, and aldehydes with the same carbon skeleton as the reactant. Experiments were also carried on under the same conditions for two other C(8) hydrocarbons, n-octane and 1-octene, showing that the reactivity of ethylcyclohexane is close to that of the alkene and lower than that of the alkane. Simulations using a detailed kinetic model of the literature allow a good prediction of the global reactivity and of the main hydrocarbon products for temperatures above 800 K. The main reaction channels leading to the observed reaction products at both low (below 800 K) and intermediate temperature (above 800 K) are discussed.

Flash Pyrolysis of Lakhara Lignite Utilizing Effective Radical Transfer

AbstractFlash pyrolysis of raw and tetralin treated coal samples were carried out in nitrogen atmosphere. Two representative coal samples from Lakhra coalmines labeled Lakhra‐3 (L3) and Lakhra‐6B (L6B) were pyrolyzed in their raw state and after treatment with tetralin. Initial experiments were carried out at 700 °C with 2 milligrams of 80 mesh size samples. The main hydrocarbon products detected from both samples were methane, ethylene, ethane, propane, butane, pentane, benzene, toluene and xylene (BTX). The ratio of the total hydrocarbon yield from L3 and L6B raw samples is 1:1.49, respectively, while the relative yield of aliphatic C1‐C5 straight chain products to BTX are 7.65:5.49. Theses differences in product yields clearly indicate the compositional variation between the two samples. The total hydrocarbon yield (C1‐C5 +BTX) of tetralin swollen L3 coal and L6B coal was larger than the raw coal at all temperatures, and larger by 50.6% and 32.6%, respectively, at 700 °C. The treatment of coal samples has a more pronounced effect on BTX yield than C1‐C5 aliphatic hydrocarbons. BTX yield of tetralin treated L3 coals at 700 °C was 3.5 times higher while for L6B coal the BTX yield was 2.1 times higher than the raw samples. These significant increases in hydrocarbons yields can be explain in terms of the suppression of the cross‐linking reactions of coal fragments due to the penetration of tetralin in to the micropores of coal, as well as the effective H radicals transfer from tetralin to coal fragments during pyrolysis.

Carbon monoxide hydrogenation over molybdenum and tungsten carbides

Hydrogenation of carbon monoxide was studied over the face centered cubic (fcc) phases of molybdenum and tungsten carbides. Moderately high surface area unsupported molybdenum and tungsten carbides (95 and 52 m 2 g −1, respectively) were prepared using a temperature programmed synthesis method. The starting oxides were first converted to a cubic nitride by reacting with ammonia, which are subsequently transformed to the carbide in a methane/hydrogen mixture. The presence of the face centered cubic structure was confirmed by X-ray diffraction. The catalysts were tested in a slurry continuously stirred tank reactor (CSTR) at P=2 MPa, in the temperature range 494–573 K and space velocities that varied from 2.5 to 15 S l h −1 g cat −1 . The production of large amounts of carbon dioxide instead of water in the case of molybdenum carbide indicates a high water gas shift activity. In both cases the main hydrocarbon product is methane.