Benzene Yield Research Articles

Pyrolysis–Gas Chromatography of Lakhra Coal: Effect of Temperature and Inorganic Matter on the Product Distribution

The objective of this article was to study the effect of pyrolysis temperature and mineral matter on the distribution of the products of C1-C6 hydrocarbons. Pakistani lignite named Lakhra 6B was used to study the effect of inorganic substances on the reactivity of coal. The experiments were performed using pyrolysis gas chromatography to investigate the activity of virgin coal, HCl acid-washed coal, and acid-washed coal with (Ca(C2H3O2)2, Mg(C2H3O2)2, NaC2H3O2, KC2H3O2), added respectively. The products obtained were monitored by a gas chromatograph. The main products identified were methane, ethane, ethylene, propane, 1-butene, n-butane, 1-pentene, n-pentane, and benzene. The results showed that coal conversion to methane increased with an increase in temperature and the amount of this hydrocarbon was high among all the hydrocarbons formed. It was observed that the addition of metal ions affected the yields of the products selectively. The yield of benzene was observed to be high in the case of calcium and magnesium form coals. The other cations form coals produced a smaller quantity of benzene in the temperature range studied. From the results, it can be concluded that metal ions played a selective role in controlling the yield of C1-C6 hydrocarbons products from coal pyrolysis in general and benzene yield in particular.

Two-stage pyrolysis of polystyrene: Pyrolysis oil as a source of fuels or benzene, toluene, ethylbenzene, and xylenes

The recycling rate of plastic waste needs to be improved worldwide. In that context, pyrolysis, through which petrochemical feedstock and alternative fuel can be obtained, has received significant attention. In this study, pyrolysis of polystyrene was conducted in a continuous two-stage process that has an auger reactor and a fluidized bed reactor connected in series. The main objective was to produce oils rich in benzene, toluene, ethylbenzene, and xylenes instead of typical polystyrene pyrolysis oils, which contain high amounts of styrene monomers with low thermal-oxidative stability. The effects of different reaction temperatures (in both reactors) and the type of fluidizing medium on the product distribution and composition were investigated. The maximum yield of benzene, toluene, ethylbenzene, and xylenes (26.3 wt%) was obtained at a temperature of 780 °C in the fluidized bed reactor. The oil and styrene yields at 780 °C were 86 and 26 wt%, respectively. To evaluate the fuel properties of the pyrolysis oil, its calorific value, API gravity, viscosity, density, ash content, pour point, flash point, and pH were examined. The results indicate that the pyrolysis oil can be both a good source of benzene, toluene, ethylbenzene, and xylenes and can potentially be used as a substitute source to gasoline or diesel fuels when it is mixed with oils with a low aromatic content.

Bimetallic Mo-Co/ZSM-5 and Mo-Ni/ZSM-5 catalysts for methane dehydroaromatization: A study of the effect of pretreatment and metal loadings on the catalytic behavior

Methane dehydroaromatization is studied using different loadings (0.2 wt%, 0.6 and 1 wt%) of Co and Ni additives on a 6 wt% Mo/ZSM-5 catalyst to evaluate the promoting effect of Ni and Co on reactivity and stability of the catalysts. A synergy between Mo and the additives is observed when combining a reduction/carburization pretreatment with an optimum additive loading: benzene yield and catalytic stability are both improved. The fresh and spent samples were characterized by X-Ray Diffraction, 27Al Magic-Angle Spinning Solid State Nuclear Magnetic Resonance Spectroscopy, Temperature-Programmed Reduction and Thermogravimetric Analysis. The results suggest that catalytic enhancement in precarburized Mo-Co and Mo-Ni samples is due to a combination of effects: extraction of Al from the ZSM-5 framework to form inactive Al2(MoO4)3 is reduced, interaction of Mo with the additives enhances the retention of Mo species within the zeolite channels, prevents Mo aggregation in reaction and modifies the reducibility of the Mo sites.

Valorization of biomass derivatives through the conversion of phenol over silica-supported Mo-Re oxide catalysts

Liquid-phase hydrodeoxygenation of phenol over silica-supported MoOx-ReOx catalysts was investigated at 300 °C and 5 MPa of H2. Mixed-oxides catalysts with similar surface metal density (2.3 atoms of metal per nm2 of SiO2) but different relative Mo and Re loadings were prepared by incipient wetness impregnation. The catalysts were characterized by N2 adsorption, temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), ultraviolet visible diffuse reflectance (UV–vis-DR) spectroscopy, X-ray diffraction (XRD) and temperature programmed desorption of NH3 (TPD-NH3). All the catalysts were highly active and selective towards deoxygenated products. However, MoOx/SiO2 was the most selective towards cyclohexane formation. Higher amount of benzene was produced with the Re-containing catalysts than it was over the MoOx/SiO2 catalyst, indicating that ReOx favored direct deoxygenation over hydrogenation of the aromatic ring. The catalyst containing equimolar amounts of MoOx and ReOx exhibited the highest yield of benzene. This result can be attributed to a synergistic effect that arises from electronic interaction between rhenium and molybdenum oxides which favors the formation of new oxygen vacancy sites. The study reveals that benzene selectivity is mainly influenced by ReOx sites and the activity can be tuned by a balance of MoOx and ReOx sites.

Ring Enlargement of Methylcyclopentane over Pt/(HZSM-48+pseudoboehmite) Catalysts

Platinum catalysts loaded on a hybrid support, composed of HZSM-48 and pseudoboehmite, were applied to the synthesis of benzene through methylcyclopentane (MCP) reforming in order to investigate the effect of the addition of pseudoboehmite to Pt/HZSM-48 for ring-enlargement reaction. A total of 0.5 wt% of platinum was impregnated on the hybrid support by using the incipient wetness method. Catalyst characterization was performed with nitrogen sorption, X-ray diffraction, temperature-programmed desorption of NH3, and infrared spectroscopy of adsorbed pyridine. It was found that mesoporous structures were well-developed in Pt/(HZSM-48 + pseudoboehmite) catalyst as a result of the pseudoboehmite addition, of which the average pore size was in the range of 7–8 nm. The presence of pseudoboehmite in the catalyst increases the total amount of acid sites and weakens the acid strength, compared with those of the Pt/HZSM-48 catalyst. Lewis acid sites were more abundant than Brönsted acid sites over the Pt/(HZSM-48+pseudoboehmite) catalysts. It was found that selectivity to the ring-enlargement reaction is dominant over selectivity to the ring-opening reaction over the Pt/(HZSM-48 + pseudoboehmite) catalysts. The benzene yield over Pt/(HZSM-48 + pseudoboehmite, 1:1) catalyst reached 65.1% at 450 °C and 0.3 h−1. As well as being influenced by the mesoporous structure, the higher activity and selectivity in MCP reforming was also determined by appropriate acidity of the Pt/(HZSM-48 + pseudoboehmite) catalysts.

Utilization of Synthesized Zeolite for Improved Properties of Pyrolytic Oil Derived from Used Tire

This paper reports the investigation of zeolite NaY synthesized from kaolin, a locally abundant soil material found in the Benin City metropolis, Nigeria, as a suitable catalyst and its effect on the properties of pyrolytic oil produced from used tires. The pyrolysis process was conducted from a range of 1 to 10 wt.% of catalyst concentration to the used tire at an operating temperature of 600°C, heating rate of 15°C/min, and particle size of 6 mm. An increase in the catalyst weight gave a maximum yield of catalytic pyrolytic oil (CPO) of 21.3 wt.% at a catalyst-to-tire ratio of 7.5 wt.%. Although this was lower than the noncatalyzed pyrolytic oil yield (34.40 wt.%), the quality in terms of chemical composition and hydrocarbon fuel range varied from that of the noncatalyzed pyrolytic oil, as indicated by the FT-IR, NMR, and GC-MS analyses. From the GC-MS result, the CPO gave a benzene yield higher than that of noncatalyzed pyrolytic oil. The CPO benzene yield can be ranked as CPO (5 wt.%) > CPO (1 wt.%) > CPO (10 wt.%) > CPO (7.5 wt.%) > noncatalyzed pyrolytic oil. The catalyst also improved the yield of other valuable chemicals such as ethylbenzene, o- and p-xylene, styrene, toluene, quinoline, pyrene, thiophene, P-cresol, phenol, and limonene in the pyrolytic oil. For hydrocarbon range, the catalyst displayed the potential to increase the yield of carbon range (C6–C15), which is similar to gasoline (C6–C12) and kerosene (C11–C14), with a lower yield of diesel and fuel oils (C11–C20) when compared to the noncatalyzed pyrolytic oil.

Evaluation on a double-chamber gas-liquid phase discharge reactor for benzene degradation

A double-chamber gas-liquid phase DBD reactor (GLDR), consisting of a gas-phase discharge chamber and a gas-liquid discharge chamber in series, was designed to enhance the degradation of benzene and the emission of NOx. The performance of the GLDR on discharge characteristics, reactive species production and benzene degradation was compared to that of the single-chamber gas phase DBD reactor (GPDR). The effects of discharge gap, applied voltage, initial benzene concentration, gas flow rate and solution conductivity on the degradation and energy yield of benzene in the GLDR were investigated. The GLDR presents a higher discharge power, higher benzene degradation and higher energy yield than that of the GPDR. NO2 emission was remarkably inhibited in the GLDR, possibly due to the dissolution of NO2 in water. The benzene degradation efficiency increased with the applied voltage, but decreased with the initial concentration, gas flow rate, and gas discharge gap, while the solution conductivity presented less influence on benzene degradation. The benzene degradation efficiency and the energy yield reached 61.11% and 1.45 g kWh–1 at 4 mm total gas discharge gap, 15 kV applied voltage, 200 ppm benzene concentration, 0.2 L min−1 gas flow rate and 721 μS cm−1 water conductivity. The intermediates and byproducts during benzene degradation were detected by FT-IR, GC-MS and LC-MS primarily, and phenols, COx, and other aromatic substitutes, O3, NOx, etc, were determined as the main intermediates. According to these detected byproducts, a possible benzene degradation mechanism was proposed.

Hydroconversion of Aromatic Hydrocarbons over Bimetallic Catalysts

Bimetallic catalysts (BMC) for hydroconversion of aromatic hydrocarbons (ArH) have been designed by modification of Ni/Al2O3 with chromium(0) compounds and phosphoromolybdic heteropolyacid (HPA). Catalysts were tested in hydrogenation of benzene and toluene, in hydrodemethylation of pure toluene and they were shown to possess a high activity, selectivity and sulfur tolerance under conditions of the processes above. The activity of BMC in these processes was much higher as compared with that of two-component (Ni-Cr, Ni-HPA) or conventional Ni/Al2O3 catalysts. Using BMC, hydrogenation of benzene and toluene proceeds with activity increased (up to 34–38 mol/kg·h) and toluene hydrodemethylation may be performed with improved selectivity (90.3%) and benzene yield (81%). The high sulfur tolerance of BMC was demonstrated by performing hydrodemethylation of toluene containing up to 500 ppm S.

Enhanced yield of benzene, toulene, and xylene from the co-aromatization of methane and propane over gallium supported on mesoporous ZSM-5 and ZSM-11

In this work, mesopore was introduced to ZSM-5 and ZSM-11 to increase the yield of benzene, toluene, and xylene (BTX) from the co-aromatization of methane and propane. Co-aromatization of methane and propane (10:1 M ratio) at 550 °C revealed that gallium oxide (2 wt%) supported on mesoporous zeolites showed higher BTX selectivity and BTX yield than that on microporous zeolites. In particular, the BTX yield of GaOy/meso-HZSM-11 (13.94%) was higher than that of GaOy/meso-HZSM-5 (11.20%), in addition to showing more stable activity up to 6 h. H2-TPR analysis indicated that GaOy/meso-HZSM-11 contains more mobile Ga2O species and GaO+ ion than GaOy/meso-HZSM-5. In addition, NH3-TPD analysis confirmed that such highly dispersed Ga species interact with Brönsted-Lowry acid sites of zeolites to produce medium acid site acting as Lewis acid more abundantly in the former than the latter. In summary, the superior co-aromatization performance with the highest reactant conversion of GaOy/meso-HZSM-11 was achieved by the synergetic effect of Lewis acid site formed by dispersed Ga species and Brönsted-Lowry acid sites of mesoporous HZSM-11.

Benzene purification from thiophene using dimethylformamide as an entrainer in thermally coupled extractive distillation columns

Thiophene (T) is one of the main sulfur-containing impurities in crude benzene produced by coke production. One effective way to remove the majority of thiophene from crude benzene is extractive distillation (ED) with dimethylformamide (DMF), which has been reported to increase the relative volatility of the benzene–thiophene (B–T) pair from 1.13 to 1.46–1.5 or 1.8–2.18. The aim of this work is to investigate the possibility of increasing the benzene yield from the initial fraction and reducing the ED heat demand of the separation of the B–T mixture with DMF as an entrainer by using an extractive distillation system with partially thermally coupled distillation columns (PTCED). To achieve this goal, both a conventional extractive distillation (CED) and a PTCED system were optimized. The total energy consumption in the column reboilers was selected as the optimization criterion. The same yield of benzene was achieved in the PTCED system at a lower column reboiler heat demand. As the benzene yield was increased, the energy savings of PTCEDS over CED increased. In addition, the production of the thiophene fraction required a significantly smaller reflux ratio in the side section of the PTCED system (1.0–2.28) than in the recovery column of the CED system (7.17–73.13).

Influence of solvents on pore structure and methane adsorption capacity of lacustrine shales: An example from a Chang 7 shale sample in the Ordos Basin, China

The dissolution of soluble organic matter by solvents can increase the porosity and pore connectivity of shale, which is conducive to the exploitation of shale gas. To explore the influence of solvents on the pore structure and methane adsorption capacity of extracted shale, a sample of the Chang 7 shales from the Ordos Basin, China is extracted using acetone, tetrahydrofuran (THF), carbon disulfide (CS2), and benzene, respectively. Low pressure gas (CO2 and N2) adsorptions and methane adsorption experiments were carried out on the studied sample before and after extraction. The results indicate that the extraction yields of THF, CS2, benzene and acetone were 0.84%, 0.63%, 0.34%, and 0.31%, respectively, which is jointly influenced by the molecular dynamics diameter, aromaticity, boiling point, and polarity. The extraction yield of acetone (0.31%) is the lowest, which may be attributed to its low boiling point. The extraction yield of CS2 is about 2 times higher than acetone. It may be related to that the CS2 can destroy ionic crosslinks in organic matter, improving the extraction yield significantly. The highest extraction yield (0.84%) of THF is consistent with its aromatic structure, high boiling point, and strong polarity. The extraction yield (0.34%) of benzene is relatively low among the used solvents, which may be aroused by its larger dynamic diameter and weak polarity. Interestingly, the size ranges of pores that increased after extraction are strongly controlled by solvents. Acetone is easier to enter the micropores due to its smaller dynamics diameter. Therefore, the organic matters in micropores were more easily dissolved in acetone, which results in the significant increases in micropore volume and surface area. Comparably, mesopore volume and surface area increased greatly after CS2 extraction. One possibility is that CS2 mainly dissolved the organic matters in mesopores. Another possibility is that a part of micropores were enlarged to mesopores by extraction. The macropore volumes of the sample extracted by benzene and THF obviously increased due to their larger dynamics diameters. The methane adsorption capacity of the extracted sample is stronger than the raw sample. The type of adsorption isotherm was not changed. The acetone extracted sample has the highest methane adsorption capacity, followed by THF, CS2, and benzene, which is positively related with their micropore surface areas.

Enhanced direct deoxygenation of anisole to benzene on SiO2-supported Ni-Ga alloy and intermetallic compound

Herein, Ni/SiO2 and bimetallic NixGa/SiO2 (Ni/Ga atomic ratio x = 6 and 3) catalysts were prepared by the impregnation method followed by reduction at 550 °C and tested in the vapor hydrodeoxygenation of anisole at 0.1 MPa and 300 °C. Ni-Ga alloy and Ni3Ga intermetallic compound (IMC) formed in Ni6Ga/SiO2 and Ni3Ga/SiO2, respectively, where the Ga atoms break contiguous Ni ones reducing the ensembles of Ni atoms and the H2 uptakes. Also, a charge transfer from Ga to Ni increased the electron density of Ni, and hydrogen spill-over occurred on NixGa/SiO2. In contrast to Ni/SiO2, NixGa/SiO2 improved not only the hydrodeoxygenation activity but also the selectivity to benzene. At the similar anisole conversion (˜31%), the selectivity to benzene was 75.2%, 83.0% and 92.6% on Ni/SiO2, Ni6Ga/SiO2 and Ni3Ga/SiO2, respectively. Reactivity evaluation, anisole-TPD and TPSR results show that the direct CArOCH3 bond cleavage (CAr represents the carbon in benzene ring) to benzene was more preferential on NixGa/SiO2 than on Ni/SiO2. Isotope tracing experiment indicates that the spilt-over hydrogen at the interface between the Ni3Ga particles and support participated in the reaction. We suggest that the synergetic effect between Ni and Ga facilitated the direct CArO bond cleavage. Moreover, NixGa/SiO2 were less active for benzene hydrogenation and CC bond hydrogenolysis than Ni/SiO2, contributing to higher selectivity to benzene. Significantly, methanol, derived from the direct the CArOCH3 bond cleavage, dominatingly decomposed to CO and H2 and methanation scarcely occurred on NixGa/SiO2, however, it was mainly converted to methane on Ni/SiO2. Low activities for benzene hydrogenation, CC bond hydrogenolysis and methanation on NixGa/SiO2 (especially Ni3Ga/SiO2) are attributed to the geometric and electronic effects of Ga in alloy and IMC. The finding is significant in rationally designing the catalyst with high benzene yield and low H2 consumption.

Study on catalytic pyrolysis of eucalyptus to produce aromatic hydrocarbons by Zn-Fe co-modified HZSM-5 catalysts

Eucalyptus was pyrolyzed over metal modified HZSM-5 for producing aromatics. The untreated HZSM-5 catalyst and Zn-Fe co-modified HZSM-5 were evaluated by XRD, SEM, NH3-TPD and N2 physical adsorption. The PY-GC/MS and TGA methods were used to perform pyrolysis of eucalyptus, exploring the product distribution of eucalyptus catalytic pyrolysis and the coking characteristics of the catalysts. Experiment resulted that the products yields and composition were significantly influenced by the use of every catalysts. Under the catalysis of 1 wt.%Zn-4 wt.%Fe/HZSM-5, the yields of benzene, toluene, xylene and naphthalene were 98.3%, 80.9%, 26.4% and 49.0% higher than those catalyzed by HZSM-5 only. The difference between TG curves of after-pyrolysis and unused catalysts reflected that 1 wt.%Zn-4 wt.%Fe/HZSM-5 looks less prone to coke than 5 wt.%Fe/HZSM-5 and 5 wt.%Zn-5 wt.%Fe/ HZSM-5. Based on all the analyses of pyrolysis characteristics, it is found that eucalyptus catalytic pyrolysis to produce aromatics is feasible, and 1 wt.%Zn-4 wt.%Fe/HZSM-5 is the optimal catalyst among modified HZSM-5 in this work.

Electroreductive dechlorination of γ-Hexachlorocyclohexane catalyzed by Rh2(dpf)4 in nonaqueous media, where dpf = N,N′-Diphenylformamidinate (1-) ion

The electroreductive dechlorination of γ-hexachlorocyclohexane (lindane) was investigated in non-aqueous media using as a catalyst the dirhodium complex Rh2(dpf)4, where dpf=the anion of N, N′-diphenylformamidinate. Rh2(dpf)4 undergoes two reversible one-electron redox processes in pyridine and/or N,N′-dimethylformamide (DMF), corresponding respectively to Rh24+/Rh25+ and Rh24+/Rh23+. Electrochemical and spectroelectrochemical measurements indicate that lindane reacts with the Rh23+ center in singly reduced [Rh2(dpf)4]−, giving a transient carbon-bonded dirhodium complex along with Cl−. Further catalytic dechlorination of lindane subsequently occurs with the activity of Rh2(dpf)4 as a catalyst depending upon the solvent conditions. Rh2(dpf)4 shows a higher catalytic reduction current in pyridine than in DMF for the degradation of lindane. This catalytic current can be further enhanced if 6% water (v/v) is added to the pyridine solution. Bulk controlled-potential electrolysis combined with GC–MS verified that although the addition of water to the neat pyridine increased the catalytic activity of Rh2(dpf)4, neat pyridine is still a better solvent for the formation of more extensively dechlorinated products of lindane. In neat pyridine, lindane can be converted stepwise to tetrachlorocyclohexene, dichlorobenzene isomers, chlorobenzene and the fully dechlorinated product benzene, the last of which becomes predominant at the end of the electrolysis. In pyridine having 6% added water, other than those dechlorinated products seen above, trichlorobenzene isomers are formed upon lindane degradation. Meanwhile, the relative concentrations of dichlorobenzene isomers and chlorobenzene become higher, while the yield of benzene becomes lower than the corresponding results obtained in neat pyridine. Based on the measured distribution of the products under the different solvent conditions, an overall pathway for the degradation of lindane is proposed.

An improved catalytic pyrolysis concept for renewable aromatics from biomass involving a recycling strategy for co-produced polycyclic aromatic hydrocarbons

Catalytic pyrolysis of crude glycerol over a shaped H-ZSM-5 zeolite catalyst with (partial) recycling of the product oil was studied with the incentive to improve benzene, toluene, and xylene (BTX) yields.

Microwave-induced pyrolysis of waste truck tyres with carbonaceous susceptor for the production of diesel-like fuel

Microwave-induced pyrolysis technique was utilised to pyrolyse waste truck tyres (TT) into useful pyrolysis oil with the aid of activated carbon. The effect of temperature was studied to determine the truck-tyre pyrolysis oil (TTPO) yield, hydrocarbon fractions, chemicals composition, energy yield and fuel properties. The activated carbon functions as microwave absorber to elevate the pyrolysis temperature for enhancing production of pyrolysis oil. The optimal pyrolysis temperature of 500 °C produces highest TTPO yield of 38.12 wt% with calorific value of 42.39 MJkg−1 and energy yield of 40.55 wt%. Detailed analysis shows the TTPO contained large amount of aromatic hydrocarbons and limonene (14.29%) compared to pyrolysis oil from personal car tyre. Among the important chemical compounds also discovered in TTPO are benzene, toluene, xylene (BTX). The relative yields of toluene obtained at 400 °C is 14.85%, whereas the relative yields of benzene and xylene at 450 °C were 0.85 and 7.60%, respectively. The physiochemical properties of TTPO500 are rather similar to conventional diesel, except the slightly lower flash point and calorific value for the former. This work shows that microwave-induced pyrolysis is a promising technique to recover diesel-like fuel for use as supplemental alternative fuel.

Investigation into the yields and characteristics of products from lignite low-temperature pyrolysis under CO2 and N2 atmospheres

A slow pyrolysis experiment was performed in a fixed-bed reactor to investigate the effects of a CO2 atmosphere on lignite pyrolysis behavior. Four different reaction temperatures of 450, 500, 550, and 600 °C with 30 min pyrolysis were considered. Results indicate that lignite pyrolysis in a CO2 atmosphere gives higher gas and water yields compared with those in a N2 atmosphere. Meanwhile, CO2 creates higher yields of small molecule gases such as CO, CH4, C2H6, and C3H6; however, the yield of H2 in a CO2 atmosphere is lower than that in a N2 atmosphere at 600 °C. There are higher yields of benzene, toluene, ethylbenzene, xylene (BTEX), polycyclic aromatic hydrocarbons (PAHs), and phenols in the CO2 atmosphere at 450 °C. All of the results clarify that the CO2 atmosphere promotes cleavage of the 3–5 ring structure in char and of the aliphatic side chain in the volatiles at 450 °C. Also, the CO2 atmosphere enhances thermal cracking of the 3–5 ring structure in char and volatile matter evolved from the thermal degradation of lignite and also reacts with volatile matter at 600 °C.

Catalytic properties of microporous zeolites in the catalytic cracking of m-diisopropylbenzene

The catalytic cracking of m-diisopropylbenzene, which is produced as a byproduct of the phenol production process, was studied over various microporous zeolite catalysts. The zeolites had different acidity and pore structures. The highest conversion of m-diisopropylbenzene in catalytic cracking was achieved on the MWW zeolite catalyst. BEA and FAU zeolite catalysts also showed considerably high conversion. The MWW zeolite exhibited a high selectivity for benzene and cumene compared to the other zeolites. The conversion of m-diisopropylbenzene on a MWW zeolite catalyst exceeded 90% at 400 °C. The yield of cumene plus benzene was approximately70% in catalytic cracking over MWW zeolite. The deactivation of MWW zeolite catalysts by carbon deposition on the catalyst could be neglected at high reaction temperatures, whereas it was quite serious on the zeolite catalysts with the MOR structure. Benzene might be produced by a secondary reaction of intermediates in the large pore channels during the retention time.

Benzene Purification from Thiophene by Extractive Distillation with Dimethylformamide

Thiophene (T) is the one of the main sulfur-containing impurities in the composition of crude benzene by coke production. The effective way to remove the main amount of thiophene from crude benzene is an extractive distillation (ED) with dimethylformamide (DMF) when the relative volatility of the benzene-thiophene pair increases from 1.13 to 1.8–2.18. The aim of this work is to investigate the possibility to increase benzene yield from the initial fraction and to reduce ED heat demand of B-T mixture with DMF as entrainer by using an extractive distillation system with partially thermally coupled distillation columns (PTCEDS). To achieve the goal, the conventional extractive distillation (CED) and the PTCEDS were subjected to parametric optimization. The total energy consumption in the column reboilers (Qreb) was selected as a criterion. It was found that the same yield of benzene is achieved in PTCEDS at lower heat demand in the columns' boilers than in CED. With an increase in the yield of benzene, energy savings are increased compared to conventional ED. Also, the production of the thiophene fraction in the side section of the PTCEDS requires a significantly smaller reflux ratio (1.0 – 2.28) than in the recovery column of the CED (7.17 – 73.13).

Non-oxidative dehydroaromatization of methane over Mo/H-ZSM-5 catalysts: A detailed analysis of the reaction-regeneration cycle

Of several Mo/H-ZSM-5 catalysts (Mo loading = 1, 3, 5, 7 wt%), 5Mo/H-ZSM-5 (5 wt%) exhibited the best catalytic performance for methane conversion and benzene yield for methane dehydroaromatization at 700 °C. It was observed that deactivation of zeolite acid sites precedes deactivation of the Mo2C sites. Increasing the number of accessible Mo carbide sites with minimizing isolated surface acid sites is required for high benzene selectivity and stability. Under oxidative conditions, bifunctional metal-acid sites were reversibly regenerated at 450 °C; at higher temperatures of 550–850 °C, irreversible deactivation was observed. The selective recovery of Brønsted acid sites near Mo sites other than isolated acid sites is sufficient to restore the catalytic activity in terms of benzene formation. Spectroscopic studies revealed that high-temperature oxidative regeneration induced (MoO42−)n oligomerization and subsequent carburization of bulk Mo carbide cluster. The 5Mo/H-ZSM-5 underwent MoO3 sublimation and loss of Brønsted acidity during oxidative regeneration at 850 °C. Reductive regeneration required a temperature higher than 700 °C for coke removal, but resulted in thermal degradation of the catalyst. Theoretical calculations indicated that partial oxidation of coke precursor (i.e. naphthalene) at 450 °C was more favorable than its partial hydrogenation at 850 °C on the Mo clusters in ZSM-5 channel. Overall, oxidative regeneration at 450 °C can maintain high Mo2C dispersion and efficient coke removal during 60 h of methane reaction.