Formation Of Ethylbenzene Research Articles

B-Axis-Oriented ZSM-5 Nanosheets for Efficient Alkylation of Benzene with Methanol: Synergy of Acid Sites and Diffusion

ZSM-5 nanosheets are promising catalysts for the catalytic reactions controlled by diffusion limitations. This study reveals its significant application in the alkylation of benzene with methanol. The b-axis-oriented ZSM-5 nanosheets with similar acid property but varied thicknesses of about 30, 90, and 300 nm were prepared to investigate the effect of thickness on their catalytic properties for alkylation reactions. Comparative results demonstrate that the sample with a thickness of 30 nm exhibits higher benzene conversion, xylene selectivity, and methyl selectivity (up to 97%), accompanied by an ultralong lifetime (up to 1000 h, 10 times longer than that of the sample with a thickness of 300 nm) and lower byproduct ethylbenzene selectivity. This is ascribed to the shortened straight channel length, increased specific surface area, and enlarged mesopore volume that significantly facilitate the diffusion of reactants and products, increase the accessibility of acid sites, and decrease the coke formation. Moreover, compared with conventional ZSM-5 nanocrystals, ZSM-5 nanosheets deliver a substantially extended lifetime due to fewer framework defects. Most significantly, this study unravels the diffusion effect on ethylbenzene selectivity over ZSM-5 nanosheets with different thicknesses and illustrates the role of strong Brønsted acid sites in the dynamic changes of ethylbenzene selectivity. In light of the above analysis, we developed a precoking strategy and an introducing-heteroatom strategy to precisely tailor the catalyst acidity, further suppressing the ethylbenzene formation (<0.3%) while maintaining long-term stable operation (>300 h).

Ethylbenzene formation and its conversion towards coke in the side-chain methylation of toluene on a basic X zeolite

Ethylbenzene formation and its conversion towards coke in the side-chain methylation of toluene on a basic X zeolite

Enhancing the side-chain alkylation of toluene with methanol to styrene over the Cs-modified X zeolite by the assistance of basic picoline as a co-catalyst

Side-chain alkylation of toluene with methanol is a green pathway to realize the one-step production of styrene under mild conditions, but the low selectivity of styrene is difficult to be improved with by-products of ethylbenzene and xylene. In this study, a new way is introduced to improve the catalytic performance by means of assisting basic compounds as co-catalysts during the toluene side-chain alkylation with methanol to styrene. As a result, high activity of side-chain alkylation appears over the basic Cs-modified zeolite catalysts prepared by ion exchange and impregnation methods. This high performance should be mainly attributed to two co-catalysis actions: (1) the promotion of basic compounds for methanol dehydrogenation to formaldehyde as the intermediate for side-chain alkylation; (2) the suppression of the styrene transfer hydrogenation on basic Cs-modified zeolites to avoid the formation of ethylbenzene. Especially for Cs2O/CsX-ex catalyst, the addition of 2% mol/mol 2-picoline in reaction mixture could achieve both 12.3% toluene conversion and 84.1% styrene selectivity. Whereas the higher concentration of 2-picoline (>6% mol/mol) caused an inhibition to the catalytic activity because the excessive basic compound poisoned the combined acid-base pathway required for the side-chain alkylation process. In addition, two possible side-chain alkylation reaction routes on Cs-modified zeolite under the different 2-picoline absorption were described.

Regulating Electronic Status of Platinum Nanoparticles by Metal–Organic Frameworks for Selective Catalysis

Selective hydrogenation of alkynes to alkenes remains challenging in the field of catalysis due to the ease of over-hydrogenated of alkynes to alkanes. Favorably, the incorporation of metal nanopar...

Synthesis of Hierarchical Porous Ti-ZSM-5: A High Active Catalyst for Benzene Alkylation with Methanol

The major challenge in the production of xylene from benzene alkylation with methanol is to avoid the side reaction of methanol with olefins, and this leads to the low utilization efficiency of methanol and the generation of byproduct ethylbenzene. Hierarchical porous Ti-ZSM-5 with appropriate acidity was achieved by substituting part of Al by Ti in the synthesis process, which exhibited the high utilization efficiency of methanol and high suppression of the ethylbenzene formation by the efficient suppression of methanol to olefins.

Selective catalytic transformation of polystyrene into ethylbenzene over Fe-Cu-Co/Alumina

FeCuCo over aluminum oxide catalyst was prepared to catalytically degrade polystyrene (PS) into ethylbenzene (EB) under mild conditions. This catalyst was characterized by XRD, SEM, STEM-EELS, STEM-EDS, XPS, and physical properties. A significant selectivity toward EB formation at 250 °C was achieved in the absence of hydrogen with 82% liquid yield. End-chain session and cross-linking reactions are proposed to be the dominant pathways in the degradation of PS over FeCuCo to form EB.

Alkylation of Benzene by Methanol: Thermodynamics Analysis for Designing and Designing for Enhancing the Selectivity of Toluene and Para-Xylene

The process of benzene/methanol alkylation reaction was studied thermodynamically based on functional group contribution method of Benson. Results show that ortho-xylene (OX), Ethyl-benzene (EB) and tri-methylbenzene (TMB) are the main byproduct in alkylation of benzene by methanol and the suppression of OX, EB and TMB over hierarchical porous HZSM-5 or other types of acidic solid catalysts still remains a great challenge. To overcome these limitations, we modified hierarchical ZSM-5 with ruthenium (Ru) to evaluate the alkylation of benzene with methanol in a fixed-bed continuous flow reactor. It was found that the presence of a small amount of Ru in ZSM-5 catalyst would largely suppress the formation of EB, reduce the selectivity of OX and TMB, and also extend greatly the live time of the catalyst. Alkylation of benzene by methanol: thermodynamics analysis for designing and designing for enhancing the selectivity of toluene and para-xylene.

Alkylation of benzene with ethylene in the presence of dimethyldichlorosilane

The kinetics of the alkylation of benzene with ethylene in the presence of dimethyldichlorosilane (DMDCS) are studied and a kinetic equation for this homogeneous irreversible reaction of the second order is created. The circulation of the DMDCS catalyst does not reduce its initial activity in relation to the formation of ethylbenzene and diethylbenzenes. The presence of moisture in the initial C6H6+C2H4+DMDCS mixture reduces the catalyst activity. The dehydration of the starting mixture by removal of moisture from benzene was carried out using an azeotropic distillation. A reaction mechanism for the benzene alkylation with ethylene in the presence of DMDCS is formulated based on the generalized quantum-chemical principle and the theory of groups. The participation of DMDCS in the process of hydrocarbon conversion is confirmed experimentally and theoretically for the first time.

Studies of the decomposition of the ethylene hydrophenylation catalyst TpRu(CO)(NCMe)Ph

TpRu(CO)(NCMe)Ph is a catalyst for the conversion of benzene and ethylene to ethylbenzene. Previously, the formation of ethylbenzene has been shown to occur through a pathway that involves ethylene coordination to Ru, insertion of ethylene into the Ru–phenyl bond and Ru–mediated benzene C–H activation. The effect of ethylene pressure and catalyst concentration (between 0.2 and 0.01 mol % based on benzene) on the decomposition of TpRu(CO)(NCMe)Ph was examined. Studies have shown that there are two competing catalyst deactivation pathways. At higher concentrations of TpRu(CO)(NCMe)Ph, the dominant deactivation pathway is likely initiated by a binuclear reaction of two Ru complexes that leads to formation of unidentified paramagnetic species. Kinetic studies reveal that this pathway for catalyst decomposition occurs with a second-order rate of 0.007 (1) M−1 s−1. At lower Ru concentrations, ethylene C–H activation to form the allyl complex TpRu(CO)(η3-C4H7) is the predominant deactivation pathway. The effect of ethylene pressure on catalyst decomposition was also examined. At higher ethylene pressure nearly quantitative formation of TpRu(CO)(η3-C4H7) was observed.

Benzene alkylation with methanol over phosphate modified hierarchical porous ZSM-5 with tailored acidity

Abstract The acidity and acid distribution of hierarchical porous ZSM-5 were tailored via phosphate modification. The catalytic results showed that both benzene conversion and selectivity of toluene and xylene increased with the presence of appropriate amount of phosphorus. Meanwhile, side reactions such as methanol to olefins related with the formation of by-product ethylbenzene formation and isomerization of xylene to meta -xylene were suppressed efficiently. The acid strength and sites amount of Bronsted acid of the catalyst were crucial for improving benzene conversion and yield of xylene, whereas passivation of external surface acid sites played an important role in breaking thermodynamic equilibrium distribution of xylene isomers.

Kinetic study of alkylation of benzene with ethanol over bimetallic modified HZSM-5 zeolite catalyst and effects of percentage metal loading

Alkylation of benzene with ethanol was analyzed using shape selective boron–magnesium bimetallic HZSM-5 (Si/Al = 90) zeolite catalyst. The alkylation of benzene with ethanol (2:1 by volume) produces ethylbenzene as primary product and others like 1, 2-Diethylbenzene, 1, 4-Diethylbenzene, and xylene mixtures as secondary products. The physiochemical properties of catalyst were characterized by XRD, BET, TGA, FTIR, NH3-TPD, and FE-SEM. The feed and products were analyzed by gas chromatography and mass spectroscopy. B–Mg bimetallic catalysts supported on HZSM-5 zeolite catalyst with SAR = 90 were synthesized by the incipient wetness impregnation method and examined for alkylation of benzene with ethanol. Total metal loading of 5, 10, and 15% was used for catalyst synthesis. The highest selectivity of ethylbenzene (76.22%) was obtained by (Mg + B)-15%-HZSM-5 and the lowest ethylbenzene selectivity (49.15%) was obtained by (Mg + B)-5%-HZSM-5 using 2:1 benzene-to-ethanol ratio by volume. A reaction scheme with three parallel routes leading to the formation of ethylbenzene, diethylbenzene, and triethylbenzene was considered for the kinetic study. The kinetic parameters were determined using Langmuir–Hinshelwood–Hougen–Watson (LHHW)-type kinetic model. LHHW model could satisfactorily correlate the rate data and this model gives good fit between the experimental and calculated data.

Thermal and catalytic pyrolysis of a mixture of plastics from small waste electrical and electronic equipment (WEEE)

Pyrolysis seems a promising route for recycling of heterogeneous, contaminated and additives containing plastics from waste electrical and electronic equipment (WEEE). This study deals with the thermal and catalytic pyrolysis of a synthetic mixture containing real waste plastics, representative of polymers contained in small WEEE. Two zeolite-based catalysts were used at 400°C: HUSY and HZSM-5 with a high silica content, while three different temperatures were adopted for the thermal cracking: 400, 600 and 800°C. The mass balance showed that the oil produced by pyrolysis is always the main product regardless the process conditions selected, with yields ranging from 83% to 93%. A higher yield was obtained when pyrolysis was carried out with HZSM-5 at 400°C and without catalysts, but at 600 and 800°C. Formation of a significant amount of solid residue (about 13%) is observed using HUSY. The oily liquid product of pyrolysis, analysed by GC–MS and GC-FID, as well as by elemental analysis and for energy content, appeared lighter, less viscous and with a higher concentration of monoaromatics under catalytic condition, if compared to the liquid product derived from thermal degradation at the same temperature. HZSM-5 led to the production of a high yield of styrene (17.5%), while HUSY favoured the formation of ethylbenzene (15%). Energy released by combustion of the oil was around 39MJ/kg, thus suggesting the possibility to exploit it as a fuel, if the recovery of chemical compounds could not be realised. Elemental and proximate analysis of char and GC-TCD analysis of the gas were also performed. Finally, it was estimated to what extent these two products, showing a relevant ability to release energy, could fulfil the energy demand requested in pyrolysis.

Shape selectivity of beta and MCM-49 zeolites in liquid-phase alkylation of benzene with ethylene

NH3, pyridine and 2,4,6-trimethyl-pyridine were selected as the base probes to characterize the different pore acidity of H-beta and H-MCM-49 zeolites, revealing the essence in their catalytic performance from the view of shape selectivity in different pore systems. Based on the size of base probes, reactants, product, transition states and pore channels, the difference in catalytic performance over H-beta and H-MCM-49 was investigated. Easy diffusion of reactants into and long diffusion distance for ethylbenzene escaping out of confined space within beta are the main reason for superior activity and poorer ethylbenzene (EB) selectivity. As for H-MCM-49, acid sites located in 10 MR channels contributed little to the formation of EB due to transition state selectivity; Acid sites located in 12 MR cups on the outer surface with little restriction on the diffusion of reactant/product toward/from the active centers were the major active centers for EB formation, which could be detected by 2,4,6-trimethyl-pyridine; There was diffusion limitation on reactant/product in 12 MR supercages through 10 MR windows to influence activity/selectivity. The enhancement in activity and selectivity in liquid-phase alkylation of benzene with ethylene over MWW zeolites should be mainly focused on transforming confined 12 MR supercages into 12 MR cups with improved openness.

The effect of Si/Al ratio on the catalytic performance of hierarchical porous ZSM-5 for catalyzing benzene alkylation with methanol

High suppression of ethylbenzene formation could be successfully achieved by adjusting the Si/Al ratio of hierarchical porous ZSM-5.

COMPLEX REAGENTS BASED ON INDUSTRIAL CONCENTRATES AROMATIC HYDROCARBONS FOR THE FLOTATION OF HIGH-ASH COALS

In article are presented results of investigation of developing of complex reagent based on side product of ethyl benzene formation and light gasoline of catalytic cracking for high-ash coals flotation process in central ore-dressing factory (COF) Pechorskaya JSOC Vorkuta-Ugol. It is discovered that on vat residue of ethyl benzene rectification has 70-90 % vol. in reagent, coal yield increases on 10-16 % wt., extraction of combustible matter increases on 10-17 % wt., accordingly. High activity of flotation reagent, in our view, is connected of the presence of vat residue of ethyl benzene rectification of polyethylbenzenes (bi- and three), with increased adsorption activity and high hydrofobization capacity in compared to paraffin-naphthenic and aromatic hydrocarbons in gasoline fractions. It is established that using complex reagent UKF-1 gets to increase yield of concentrate on 1.4 % wt. in compare with regime with separating entrance collector-reagent and frothing-agent. It is founded that more reliable flow for developed reagent regime is 1.6 kg /ton, coal yield has 59,6 % wt., ash content locates in possible levels and has 9,0-9,1 % wt. A further increasing of the flow rate of the reagent to 2.0 kg/t reduces the selectivity of the flotation process. It is defined main physic-chemical properties for offered reagent according to requirements and standarts for flotation reagents. It is offered principal technological scheme of flotation of coal with complex reagent, characterized with high-economical indicators.

Phosphine and N-heterocyclic carbene ligands on Pt(II) shift selectivity from ethylene hydrophenylation toward benzene vinylation

A series of Pt(II) complexes of the type ([(L∼L)Pt(L′)(Ph)][BAr′4] (L∼L = 1,2-bis(dimethylphosphino)ethane, 1,2-bis(diphenylphosphino)ethane, (N-pyrrolyl)2P(CH2)2P(N-pyrrolyl)2, 1,3-bis(diphenylphosphino)propane, 1,1′-bis(diphenylphosphino)ferrocene, (bis-(diphenylphosphino)methyl)methylamine, 8-(diisopropylphosphino)quinoline, 1,1′-methylene-3,3′-di-tert-butylimidazol-2,2′-diylidine); L′ = THF or NCMe) has been synthesized and fully characterized. These complexes were screened as catalysts for ethylene hydrophenylation to yield ethylbenzene. All of the complexes exhibited selectivity for styrene production with low catalytic turnover. DFT calculations have been used to model reactivity of the [(dmpe)Pt(L')(Ph)][BAr′4] (dmpe = 1,2-bis(dimethylphosphino)ethane). It is shown that selective styrene formation is a result of a calculated ΔΔG‡ of 5 kcal/mol for the benzene C–H activation step in the catalytic cycles for styrene versus ethylbenzene formation.

Promoting effects of MgO and Pd modification on the catalytic performance of hierarchical porous ZSM-5 for catalyzing benzene alkylation with methanol

The dual modification catalyst (MgO and Pd) could effectively combine the effect of MgO for suppressing the side reaction of methanol to olefins and the effect of Pd for inhibiting the formation of ethylbenzene and coke.

Catalytic Activity of Pt Modified Hierarchical ZSM-5 Catalysts in Benzene Alkylation with Methanol

Hierarchical ZSM-5 zeolite showed an improved performance as compared to conventional ZSM-5 catalysts in the alkylation of benzene with methanol. However, ethylbenzene yet remains as a major problem. In this study, we modified hierarchical ZSM-5 with Pt to evaluate the alkylation of benzene with methanol in a fixed-bed continuous flow reactor. It was found that Pt modified hierarchical ZSM-5 could successfully combine the catalytic advantages of hierarchical ZSM-5 and the high suppression of Pt to ethylbenzene formation. Moreover, employing direct reduction could improve the utilization of Pt by avoiding Pt particles sintering. .

High suppression of the formation of ethylbenzene in benzene alkylation with methanol over ZSM-5 catalyst modified by platinum

The generation of ethylbenzene is difficult to be avoided in benzene alkylation with methanol over ZSM-5 catalysts to produce toluene and xylene. Moreover, the separation or removal of ethylbenzene from C8 aromatic yet remains as a major challenge. In this study, the effect of Pt addition on the catalytic performance of ZSM-5 for benzene alkylation was investigated. It was found that the presence of a small amount of Pt in ZSM-5 catalyst would largely suppress the formation of ethylbenzene and extend the life-span of the catalyst, which was mainly due to the hydrogenation of ethylene into ethane on Pt particles.

Pathway to Ethylbenzene Formation in Side-Chain Alkylation of Toluene with Methanol Over Cesium Ion-Exchanged Zeolite X

To control the styrene to ethylbenzene ratio in the products of side-chain alkylation of toluene with methanol over Cs-X-based catalysts, pathway to ethylbenzene was examined. Styrene underwent transfer hydrogenation with methanol much faster than hydrogenation with hydrogen to ethylbenzene. Addition of Cs2O and ZrB2O5 to Cs-X enhanced and suppressed, respectively, the transfer hydrogenation.