Benzene, Toluene And Xylene Yield Research Articles

Effects of parameters in the preparation of Mo/MWW-type catalysts on the dehydroaromatization of shale gas

The direct non-oxidative aromatization of shale gas offers an unconventional production route for BTX (benzene, toluene, and xylene), potentially alleviating the heavy dependence of BTX supply on petroleum-based processes. Zeolite-supported transition metal catalysts have been successfully applied in the aromatization of light alkanes, where the zeolites provide the appropriate shape selectivity and acidity that are beneficial for the production of aromatics. In addition to HZSM-5, MCM-22 has also been recognized to be an effective support, owing to the characteristic topology of MWW structure. Here, we present a systematic investigation into the preparation and optimization of Mo/MWW-type catalysts, aiming to maximize their performance in shale gas aromatization. Mo/MCM-22 exhibited a superior initial BTX yield compared to Mo/ZSM-5 with a comparable Si/Al ratio, but was rapidly deactivated. A moderate value of Si/Al (∼ 11) was required for optimal catalytic performance, as an excessive amount of Al during the synthesis of MCM-22 led to insufficient amount of strong acid sites that are favorable for the reaction. The inclusion of Ga in MCM-22 greatly deteriorated the aromatization activity, owing to a significant degree of degalliation under reaction conditions. Contrary to ZSM-5, pelletization of MCM-22 also had a noticeable impact on catalytic performance, which was attributed to the nature of MWW topology. These results provide a comprehensive understanding of designing MWW-type zeolites for their application in shale gas aromatization.

Selective production of aromatics from catalytic pyrolysis of biomass wastes: Effects of feedstock properties and key oxygenated intermediates on aromatics formation

The catalytic pyrolysis is a promising method for obtaining value-added aromatics, especially benzene, toluene and xylene (BTX). For different biomass-based materials, the dual catalyst system composed of CaO-based and ZSM-5-based catalysts showed an obvious selectivity for the BTX production. This study chose CaO derived from organic calcium precursors (Org-CaO) and nano-sized ZSM-5 (NZSM-5), and comprehensively investigated the effects mechanism of biomass components on the formation pathways of BTX via Py-GC/MS. Under the catalysis of NZSM-5, the BTX yields were only 7.8–30%. The BTX yields on Org-CaO/NZSM-5 were as follows: lipid (63.1%) > hemicellulose (55.4%) > cellulose (40.2%) > lignin (21.7%). Typical pyrolysis intermediates were employed to quantitatively reveal the intermediate reactions. Pyrolysis intermediates exhibited low BTX-forming reactivity over NZSM-5. The pre-catalysis of Org-CaO selectively converted part undesired intermediates (fatty acids and furans) into BTX precursors (short-chain olefins and ketones), facilitating the remarkable increase of BTX yield in the subsequent NZSM-5 catalysis process. However, the pre-catalysis of Org-CaO can hardly make the ring opening reaction of lignin-derived phenolic compounds that have very low reactivity on NZSM-5, and thence high-lignin biomass obtained low BTX production during catalytic pyrolysis by Org-CaO/NZSM-5. These findings afforded a new route for increasing the BTX yields by directionally forming BTX precursors or controlling biomass components.

High-efficiency hydrocracking of phenanthrene into BTX aromatics over a Ni-modified lamellar-crystal HY zeolite.

A new Ni-HY zeolite with lamellar-crystals was prepared as a catalyst for phenanthrene hydrocracking. It showed significantly improved reactivity and BTX (benzene, toluene and xylene) selectivity (up to 99.1% and 75.6%, respectively), depending on a reasonable synergistic effect between its excellent internal-diffusion and the high-efficiency concerted catalysis of surface metal-Ni active sites and acid sites. In particular, compared with a conventional Ni-HY with diamond-shaped crystals, its significantly shortened diffusion-reaction path of the micropore system in the lamellar crystals greatly enhanced the diffusion-reaction efficiency of large-molecule phenanthrene and polycyclic intermediates and remarkably improved the utilization of both pores and internal reactive sites, powerfully promoting phenanthrene into benzene series conversion. The much decreased diffusion-residence time of benzene-series products in shortened channels also effectively weakened the further cracking loss of the benzene-ring, leading to enhanced BTX selectivity. Moreover, this shorter-channel Ni-HY catalyst with a higher external surface area and mesoporous volume also exhibited greatly improved catalytic stability attributed to its stronger capabilities of accommodating coke and resisting coke-deposition. The phenanthrene conversion of >76.3% and the BTX yield of >46.3% were obtained during a 60 h on-stream reaction.

Effect of Biomass-Based Catalyst in Walnut Shell/Polypropylene to BTX

Four biomass-based catalyst carriers with different pore structures were prepared by using a carbonization-activation method, followed by employment in the copyrolysis of Walnut Shell/Polypropylene (WNS/PP) to produce Benzene, Toluene and Xylene (BTX). Ten cycles were performed in each copyrolysis test in a bench-scaled tube furnace to determine the suitable pore size of the catalyst and excellent cycling performance for BTX production. In addition, Zn, Ni, and Ce were loaded with the selected catalyst carriers to synthesize the most suitable biomass-based catalyst. Results showed that the pore size and active center of the catalyst were the key factors affecting the WNS/PP catalytic copyrolysis. Biomass-based carrier with a pore size in the range of 0.55-1.2 nm was the most suitable to produce BTX in the optimal 10 cycle performance; it realized a relative BTX content of 9-20 area%, and a BTX mass yield of 23-67 mg/(graw) in the liquid-phase products from the WNS/PP copyrolysis. A catalyst loaded with 10 wt% Zn possessed the best catalytic effect with a relative BTX content of 39.49 area%, and a BTX yield of 111.13 mg/(graw).

Synergistic effect for selective hydrodeoxygenation of anisole over Cu-ReOx/SiO2

Selective hydrodeoxygenation (HDO) of lignin derived oxygenated aromatic compounds has great significance for lignin utilization and chemicals production. Hereby, bifunctional catalysts of Cu-MOx/SiO2 (M = Re, Mo or W) were prepared to study the synergistic effect of Cu and MOx on the performance of anisole HDO. Characterizations indicated that Cu interacted strongly with the second metal species. As a result, more efficient sites exposed on catalysts surface, and metal dispersion and surface properties both were improved. Besides, adsorption strength for both oxygen atom and aromatic ring in reactant were all adjusted due to Cu-MOx interaction. Bimetallic catalyst Cu-ReOx/SiO2 showed the highest HDO activity, while Cu-MoOx/SiO2 and Cu-WOx/SiO2 both preferred transmethylation because of their prominent acid properties. The Cu-ReOx composition was found to evidently affect the anisole conversion and selectivity of benzene, toluene and xylene (BTX). The highest BTX yield of 50.5 % could be achieved when Cu/Re ratio was 3.

Enhanced Catalytic Performance of Zn‐containing HZSM‐5 upon Selective Desilication in Ethane Dehydroaromatization Process

AbstractThe effect of introducing mesoporosity on the catalytic stability and selectivity of Zn‐containing ZSM‐5 catalysts was investigated for direct conversion of ethane to high‐value aromatics. Voids and mesopores were created in the zeolite (Si/Al=40) by selective desilication (recrystallization) using ammonium hydroxide and cetyltrimethylammonium bromide. Zinc was incorporated in the samples by incipient wetness impregnation to achieve different concentrations of 0.5, 1 and 5 wt %. The samples were characterized by XRD, N2 physisorption, TGA, NH3‐TPD, ICP‐OES, FTIR, 1H, 27Al and 29Si solid‐state MAS NMR. The desilicated samples were compared to their parent analogues for ethane conversion to aromatics such as benzene, toluene and xylenes (BTX). All of the desilicated samples showed an improvement in BTX yield and catalytic stability. Thus, the presence of mesoporosity increases the accessibility to the active sites and facilitates the mass transfer of aromatic compounds, which result in higher performance and catalytic stability of the desilicated ZSM‐5 samples containing zinc.

Influence of physicochemical properties of metal modified ZSM-5 catalyst on benzene, toluene and xylene production from biomass catalytic pyrolysis

Biomass catalytic pyrolysis with various metals (Zn, Fe, Ca, Ce and La) modified ZSM-5 catalysts were analyzed, in order to investigate the relationship between the physicochemical properties of catalysts and the benzene, toluene and xylene (BTX) products. Results revealed that the BTX products were positively correlated with the strong acid site contents of the catalysts. Appropriate amount (0.5–4 wt%) of loaded Zn species increased the strong acid site contents of the catalysts as well as BTX yields, and the highest yield of BTX was observed under Zn loading amount of 2 wt%. While excessive metal loading amount (10 wt%) decreased both the acidity and the physical properties of the catalyst, resulting in poor diffusion of reactants and products in the channel and decreased the BTX yield. It is recommended that ZSM-5 catalyst with higher strong acid site content and pore volume should be used for BTX production.

Deoxygenation in anisole decomposition over bimetallic catalysts supported on HZSM-5

This work investigated the deoxygenation reaction in anisole decomposition over HZSM-5 (HZ(25)) zeolite supported bimetallic catalysts to produce benzene, toluene and xylene (BTX). Experiments were performed in order to evaluate the synergistic effect between the two active metals with the focus on the effect of temperature, metal type, and metal loading ratio. Experimental results showed that 1%Ni-1%Mo/HZ(25) led to both the highest BTX yield (i.e. 30.0 wt%) and selectivity (i.e. 83.7%). On the contrary, bimetallic catalysts containing Fe were less effective in promoting the BTX production. It was identified that the optimum temperature for BTX production over 1%Ni-1%Mo/HZ(25) catalysts was 500 °C. Characterization of fresh and spent catalysts showed microcrystal particles of bi-metal loadings highly dispersed on the zeolite surface, and some agglomeration of metallic particles were also observed. Large amount of carbonaceous deposit was observed on the spent catalysts mainly in the form of amorphous. Density Functional Theory (DFT) modelling was carried out in order to study the adsorption energy of anisole and phenol molecules onto Ni-Mo, Ni-Fe and Mo-Fe surfaces; and the interactions between phenol molecule and bimetal surfaces were further analysed. All the analysed bimetal surfaces exhibited strong interactions with the adsorbed molecule. Ni-Mo surface declined electrons energy levels mainly around 1.5 eV in the adsorbate molecule and released the highest adsorption energy; while Ni-Fe and Mo-Fe surface led to more electrons exchange with the adsorbate during the adsorption. The modelling results agreed well with experiments by revealing that the strong binding between phenolic compounds (Phs) and the Ni-Mo based catalysts bimetal surface would lead to a higher BTX production in the deoxygenation reaction in the decomposition of anisole.

Enhanced ethylene selectivity and stability of Mo/ZSM5 upon modification with phosphorus in ethane dehydrogenation

Nonoxidative conversion of ethane to ethylene and/or BTX (benzene, toluene, and xylene) suffers rapid deactivation due to coke deposition. We report here the effects of phosphorus modification on the stability and activity of Mo/ZSM5 for nonoxidative conversion of ethane. The results show that the ethylene and BTX yield and stability are significantly enhanced upon modification with 2.5 wt.% P. NH3 TPD, pyridine FTIR, 1H MAS NMR, 27Al MAS NMR, 31P MAS NMR, 129Xe NMR, XPS, UV–visible diffuse reflectance spectra (UV–vis DRS), and nitrogen physisorption were carried out to understand the effects of P on the structure of Mo/ZSM5 and its correlation with catalytic performance. The presence of P reduces the acid strength and density, changes the channel system of ZSM5 by forming thermally stable SAPO-like interfaces with the framework Al, and improves the dispersion of molybdenum. Rapid deactivation still occurs on Mo/ZSM5 with 1 wt.% P due to the existence of denser silanol groups, more isolated Mo species, and reduced aperture size with little change in effective micropore volume. A higher P loading (2.5 wt.%) leads to less dense silanol groups and less reduced but stable molybdenum species, and simultaneously reduces channel diameter and internal volume. Consequently, the ethylene selectivity is enhanced and the formation of coke precursors is restricted, resulting in improved stability.

Sugarcane bagasse ex-situ catalytic fast pyrolysis for the production of Benzene, Toluene and Xylenes (BTX)

The ex-situ catalytic pyrolysis of sugarcane bagasse with various HZSM-5 (23, 50, and 80) catalysts was studied in a tandem micro reactor-GC/MS at 400 °C, 450 °C, 500 °C and 550 °C with a catalyst to biomass (C/B) ratios ranging from 2 to 23. The yields of benzene, toluene and xylenes (BTX) were significantly affected by pyrolysis temperature and C/B ratio. The highest BTX yield of 22% was obtained for the HZSM-5 (23) catalyst at C/B ratio of 12.5 and a temperature of 475 °C. Finally, an experimental design was performed to determine the optimal process conditions for BTX yields.

The Aromatization of Propene Via Nano-Size HZSM-5

Zeolite (ZSM) catalysts are known to convert small-size alkenes, e.g., propene, into aromatic hydrocarbons, specifically benzene, toluene and xylenes (BTX), with both high efficiency and specificity. The efficiency of conventional and hierarchical nano-size ZSM-5 for propene aromatization was compared in this study using a Design of Experiments (DOE) approach combined with detailed product analysis. Contrary to our expectations, the former showed a significantly greater BTX yield than the latter. Analysis of the obtained data by DOE and additional experiments with soybean oil cracking using both catalyst types indicated that a reason for the observed reduced activity of nano-scale zeolites may be tenacious water adsorption, which may reduce the catalyst active site availability to the substrate.

BTX production by coaromatization of methane and propane over gallium oxide supported on mesoporous HZSM-5

2wt% GaOy catalysts supported on mesoporous HZSM-5 and microporous HZSM-5 (denoted as 2GaOy/meso-HZSM-5 and 2GaOy/micro-HZSM-5, respectively) were prepared for use in the BTX (benzene, toluene, and xylene) production by coaromatization of methane and propane. It was revealed that 2GaOy/meso-HZSM-5 catalyst showed higher reactant conversion and initial BTX yield than 2GaOy/micro-HZSM-5 catalyst due to the enhanced mass transfer through 2GaOy/meso-HZSM-5 catalyst. On the basis of this result, a series of XGaOy/meso-HZSM-5 (X=0.5, 1, 2, 4, and 6) catalysts with different gallium oxide loading (X, wt%) were prepared for BTX production by coaromatization of methane and propane. The effect of gallium oxide loading on the acid properties and catalytic activities of XGaOy/meso-HZSM-5 catalysts was investigated. It was found that total acidity of the catalysts served as a crucial factor determining the catalytic performance in the BTX production. Conversion of reactants and initial BTX yield increased with increasing total acidity of the catalysts. Among the catalysts tested, 2GaOy/meso-HZSM-5 catalyst with the largest total acidity showed the best catalytic performance in the BTX production. Thus, an optimal gallium oxide loading of XGaOy/meso-HZSM-5 catalysts was required for maximum production of BTX by coaromatization of methane and propane.

Selective hydrocracking of pyrolysis fuel oil into benzene, toluene and xylene over CoMo/beta zeolite catalyst

Cobalt promoted Mo/β (Beta zeolite) catalysts were prepared with different metallic loadings (0.5–1.5) by a co-impregnation method. The catalytic activities of the synthesized catalysts were investigated for the selective hydrocracking of tetralin and pyrolysis fuel oil (PFO) into mono-aromatic hydrocarbons (MAH) such as benzene, toluene and xylene (BTX) in a fixed-bed reactor system. Prior to using the CoMo/β catalyst for crude PFO hydrocracking, different reaction parameters (including metallic loading, temperature, H2 pressure, and LHSV) were investigated for the hydrocracking of a model feed, tetralin, to determine the best conditions for maximum BTX yield. The CoMo(0.5)/β catalyst with a Co/Mo ratio of 0.5 produced the highest MAH yield of 62.6% at 99.5% conversion of tetralin, continuously for 140 h of reaction time without any deactivation. Furthermore, the CoMo(0.5)/β catalyst was found to be superior among the tested CoMo/β catalysts for hydrocracking real feed PFO, and it produced a maximum MAH yield of 54.8% at 99.1% conversion of PFO. The synthesized catalysts were characterized using different characterization techniques, including BET, NH3-TPD, SEM-EDS and ICP, to evaluate their physiochemical properties and determine the active sites present in the catalysts.

Coking kinetics and influence of reaction-regeneration on acidity, activity and deactivation of Zn/HZSM-5 catalyst during methanol aromatization

The coking kinetics and reaction-regeneration on Zn/HZSM-5 (Zn/HZ) catalyst in the conversion of methanol to aromatics were investigated. The highest initial benzene, toluene and xylene (BTX) yield of ca. 67.7% was obtained on fresh Zn/HZ catalyst, which showed the worst catalytic stability. The cycle of reaction-regeneration significantly modified the texture and acidity of Zn/HZ catalyst, which in turn affected its catalytic performance and coking behavior in methanol conversion to BTX. The residual carbon located on the surface of Zn/HZ catalyst led to the decrease of acid sites and the change on the acid sites distribution, which played an important roles on its activity and deactivation. It was found that the high B/L ratio and the low total acid sites concentration of the Zn/HZ catalyst favored to the high BTX yield and good catalytic stability in methanol conversion.

Transformation of Bio‐oil into BTX by Bio‐oil Catalytic Cracking

Production of benzene, toluene and xylenes (BTX) from bio‐oil can provide basic feedstocks for the petrochemical industry. Catalytic conversion of bio‐oil into BTX was performed by using different pore characteristics zeolites (HZSM‐5, HY‐zeolite, and MCM‐41). Based on the yield and selectivity of BTX, the production of aromatics decreases in the following order: HZSM‐5>MCM‐41>HY‐zeolite. The highest BTX yield from bio‐oil using HZSM‐5 reached 33.1% with aromatics selectivity of 86.4%. The reaction conditions and catalyst characterization were investigated in detail to make clear the optimal operating parameters and the relation between the catalyst structure and the production of BTX.

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.

Product distribution from catalytic degradation of polyethylene over H-gallosilicate

For developing a novel technology to reuse plastic waste chemically, the degradation of low-density polyethylene into aromatic hydrocarbons was investigated with H-gallosilicate as a catalyst at 375–550°C. The gallosilicate produced valuable aromatic hydrocarbons, mainly benzene, toluene and xylenes (BTX). The BTX yield increased with reaction temperature and went up to over 58 wt.% at 500°C. The liquid products obtained at temperatures above 500°C consisted of aromatics only. For this simplified liquid composition and the high BTX yield, the catalytic degradation of polyethylene using H-gallosilicate is highly promising as a new technology for chemical recycling of polyolefins. The polyethylene degradation occurring at temperatures below 450°C involved aromatization by direct cyclization of the decomposed fragments that correspond to the liquid products with six or more carbon atoms. In addition to this, above that temperature, the aromatization also proceeded through the oligomerization of the C 4 and C 5 fractions formed in the degradation steps and subsequent cyclization. The latter mechanism contributed more to the formation of aromatics with increasing reaction temperature.

Catalytic hydrocracking reaction of nascent coal volatile matter under high pressure

The volatile matter evolved during the rapid pyrolysis of coal was hydrocracked over catalysts in the last stage to increase the yield of valuable products like benzene, toluene and xylenes (BTX). The effects of gas atmosphere, coal type, pyrolysis temperature, hydrocracking temperature and catalyst type were examined. The highest BTX yield, 10.4 wt%(daf), was obtained under the following conditions: Millmerran coal, H 2 pressure of 5 MPa, primary pyrolysis temperature of 800 °C, secondary hydrocracking temperature of 620 °C and with a NiMoS catalyst.

Direct post-cracking of volatiles from coal hydropyrolysis: 2. Influence of pressure

Direct post-cracking of volatile material produced by hydropyrolysis of bituminous coal at 580 °C under hydrogen pressure 1–5 MPa has been investigated at 700 °C under constant hydrogen pressure with 0.1 and 1 s residence times. Results show that pressure promotes the formation of benzene, toluene and xylenes (BTX) and naphthalenes during post-cracking, while phenol, cresols and xylenols (PCX) are not affected. The transformation of heavy Ohenols into PCX is not influenced by the hydrogen pressure. During post-cracking the BTX yield can be more than doyble that reached in simple hydropyrolysis. Post-cracking applied to high oil yield hydropyrolysis processes will be a valuable BTX source.