Diethylbenzene Research Articles

Low-temperature selective transformation of diethylbenzene to isobutane and cyclohexanes via the interplay of Pt and acid centres in Pt/H-*BEA zeolites

The hydrocracking of aromatic hydrocarbons on bifunctional catalysts comprises parallel reactions that provide a wide distribution of products and byproducts. This work demonstrates on diethylbenzene (DEB) hydrotreatment that Pt/H-Al-rich *BEA zeolite catalysts can significantly reduce the hydrocracking temperature so that only the selected reaction mechanisms prevail in the process, providing high selectivity. The interplay of high activity of Pt clusters in hydrogenation/dehydrogenation and Brønsted acid sites in acid-catalysed reactions allows selective hydrocracking of DEB to isobutane and methylcyclopentane by the paring reaction at 200 °C. Low-temperature hydrocracking consists of hydrogenation of DEB to diethylcyclohexane, its rapid skeletal hydroisomerization to C10 branched alkylcycloalkanes followed by their A type β scission providing isobutane and methylcyclopentane with 80% selectivity at 68% DEB conversion, practically without subsequent reactions of the formed products. The reactive CC bond in tribranched alkylcycloalkanes selectively undergoes A type β scission, while more stable CC bonds in less or unbranched hydrocarbon chains or rings do not crack to a substantial extent at low temperatures. The study demonstrates that the low-temperature hydrotreatment of aromatics over highly active catalysts allows controlling the involvement of individual reaction mechanisms in the complex hydrocracking process and provides tailored selectivity.

Methanol to Gasoline Conversion over CuO/ZSM-5 Catalyst Synthesized Using Sonochemistry Method

AbstractIn this research, the catalytic conversion of methanol to gasoline range hydrocarbons has been studied over CuO (5 %)/ZSM-5 and CuO (7 %)/ZSM-5 catalysts prepared via sonochemistry methods. Conversion of methanol to gasoline (MTG) has been carried out in a fixed bed reactor under atmospheric pressure and 400˚C temperature, over copper oxide on the synthesized ZSM-5 catalyst. The samples were characterized by XRD, SEM, TEM, BET, and FTIR techniques; in which good crystallinity and high specific surface area of synthesized zeolite were proved after impregnation of zeolite with copper. The present investigation suggests that the CuO/ZSM-5 catalyst made by sonochemistry method can increase the yield toward hydrocarbon production. It was concluded that impregnation of zeolite with copper oxide can alter the Brønsted/Lewis acid sites ratio and provide new Lewis acid sites over the surface of the ZSM-5. The main products of methanol to gasoline reaction over the catalyst that prepared via sonochemistry method were toluene, xylene, ethylbenzene, ethyl toluene, tetra methylbenzene, diethyl benzene and butylbenzene. The total amount of aromatics in the products was 80 % by using this catalyst. Our results suggest that catalyst synthesized by using sonochemistry shows better production yield toward hydrocarbons by affecting the distribution of active sites on the surface of the ZSM-5.

Catalytic liquefaction of Spirogyra gratiana transeau alga with supercritical solvents

ABSTRACTSpirogyra gratiana transeau alga was liquefied in organic solvents with and without catalyst in a cylindrical reactor at temperatures of 493, 513, and 533 K under supercritical conditions. The liquefied compounds were extracted with diethyl ether and benzene using an extraction procedure. The product yields in supercritical methanol, ethanol, and acetone were found to be 15.5, 23.7, and 34.4% at 533 K, respectively. The highest conversion to liquid products was obtained in supercritical ethanol with 10% sodium hydroxide as catalyst at the same temperature in the catalytic runs. Main chemical compounds present in the liquid product obtained in acetone without catalyst at 533 K were analyzed and characterized by gas chromatography-mass spectrometry (GC-MS).

Supercritical liquefaction of common reed (Phragmites australis) with alkali catalysts

ABSTRACTMilled Phragmites australis was liquefied in organic solvents with and without catalyst in a cylindrical reactor at temperatures of 533, 553, and 573 K under supercritical conditions. The liquefied compounds were extracted with diethyl ether and benzene using an extraction procedure. The product yields without catalyst in supercritical methanol, ethanol, and acetone were found to be 55.4%, 64.4%, and 73.5% at 573 K respectively. The highest conversion to liquid products was obtained in supercritical acetone with 10% sodium hydroxide as catalyst at the same temperature in the catalytic runs. Main chemical compounds present in the liquid products obtained in ethanol without catalyst and acetone with sodium hydroxide catalyst at 573 K were analyzed and characterized by gas chromatography–mass spectrometry (GC-MS).

Crystal dimension of ZSM-5 influences on para selective disproportionation of ethylbenzene.

Crystal size and crystal dimensions are vital role in shape selective feature. Para selective disproportionation of EthylBenzene (Dip-EB) was investigated over ZSM-5 synthesized in acidic medium. The catalysts were prepared by hydrothermal process with various Si/Al ratios (50, 75 and 100) using fluoride ion precursor. This fluoride ion precursor dissolves the ZSM-5 nutrients below it neutral pH between 4 and 6. The synthesized material was subjected into various physico chemical characterizations such as XRD, SEM, TGA and BET analyses. The XRD patterns showed high crystalline nature and their resulting SEM images were also indicate thin prismatic crystals of large dimension compared with alkaline medium synthesized one. The BET results earned good textural property. Catalytic activity of vapor phase Dip-EB was carried out between 523 and 673 K. As their result, diethylbenzene (DEB) isomers were obtained, but para selective Diethylbenzene (p-DEB) was observed higher than others. The high selectivity towards p-DEB was due to large crystal dimension of ZSM-5 catalysts synthesized in fluoride medium. Hence it is good commercial application for petrochemical feed stock production.

Ethylation of Ethylbenzene with Ethanol over Mordenite-Based Catalysts: Effects of Acidity, Desilication and Kinetics Analysis

Abstract This communication reports the kinetics analysis of ethylation of ethylbenzene (EB) with ethanol over large pore size mordenite catalysts. In this regard, two different catalyst samples are selected with SiO2/Al2O3 = 180 and 21, respectively. The higher acidic sample (SiO2/Al2O3 = 21) is desilicated to study the effects of desilication on the EB ethylation. The EB ethylation experiments are conducted in a fluidized CREC Riser Simulator using equimolar amount of EB and ethanol as feed. Under the studied reaction conditions, diethylbenzene (DEB) is the main product while a small amount of benzene and lighter gases are also produced. In addition to DEB, the higher acidic mordenite sample also produces benzene via dealkylation of EB. On the other hand, the large pore size mordenite sample gives triethylbenzene (TEB) as a secondary alkylation product. The desilicated sample shows slightly higher DEB selectivity but the EB conversion with this sample is low. Power law–based kinetics evaluation also confirms the above observations by showing low activation energy for DEB formation while high activation energies for benzene and TEB formations.

Kinetics Study of Ethylbenzene Alkylation with Ethanol over Medium and Large Pore Zeolites

The alkylation of ethylbenzene (EB) with ethanol has been studied over medium and large pore zeolite based catalysts in a fluidized-bed reactor. Focus is made on the effects of pore structure of zeolites on activity, selectivity, and reaction kinetics of EB ethylation. In this regard ZSM-5 and mordenite are selected as a medium and large pore zeolite, respectively. The catalysts considered have similar acidity. The EB ethylation experiments are conducted using 1:1 EB to ethanol molar ratio and at various temperature levels and different contact times. The product analysis shows that diethylbenzene (DEB) is the main product. However, the large pore size mordenite catalyst also produces a small amount of triethylbenzene. Phenomenological based kinetics models are developed based on the experimental conversion and selectivity data. The Langmuir–Hinshelwood mechanism with surface reaction control is considered for both the medium and large pore zeolites. The analysis of the developed model suggests that a Langmuir–Hinshelwood mechanism with weakly adsorbed EB and strongly adsorbed ethanol and product DEB fits the experimental data adequately. The kinetic analysis also shows that the modenite requires significantly low activation energy (45.2 kJ/mol) as compared to the ZSM-5 zeolite (112 kJ/mol). On the contrary, the estimated enthalpy of adsorption of product DEB on mordenite (85.3 kJ/mol) is significantly higher than the value on the ZSM-5 sample (67.7 kJ/mol). The enthalpy of adsorption of ethanol is found to be 32.4 and 52.4 kJ/mol on mordenite and ZSM-5 samples, respectively.

Dodecatungstophosphoric Acid Supported on Acidic Clay Catalyst for Disproportionation of Ethylbenzene in the Presence of C8 Aromatics

Vapor-phase disproportionation of ethylbenzene (EB) to diethylbenzene (DEB) in a single step is industrially relevant. Diethylbenzene is an important raw material for the conversion of divinylbenzene monomer. Conventionally, it is prepared from diacetophenone by reduction. It is also prepared by vapor-phase alkylation of ethylbenzene with ethylene/ethanol using zeolitic catalysts. In the current work, the efficacy of dodecatungstophosphoric acid (DTPA) supported on acid-treated clay has been evaluated in the disproportionation of ethylbenzene. A 20% (w/w) DTPA/K-10 clay catalyst was found to be efficient and robust. An industrial feed having different compositions of ethylbenzene and xylene isomers was used for the experimentation. Hence, they were expected to hinder the movement of reactant molecules on the catalyst surface. It was observed that irrespective of feed composition the concentration of the xylene isomers was intact in the product. There was no other byproduct formation like p-ethylmethylbenzene. Optimization of process parameters is presented. The effect of varying the concentration of aromatic compounds in the feed on ethylbenzene conversion and product distribution over the plain clay (K-10) and heteropolyacid-loaded clay catalyst have been discussed. The effect of catalyst bed length to inner diameter of reactor (L/D) ratio on the ethylbenzene conversion and selective formation of p-diethylbenzene (p-DEB) are also discussed.

Organosulfur Compounds in CS<sub>2</sub> Extractable-Fractions from Four Chinese Coals Oxidized with NaOCl

Four Chinese coals were oxidized with NaOCl aqueous solution under mild conditions. The reaction mixture was extracted with diethyl ether, carbon disulfide, petroleum ether, acetic ester and benzene sequentially. A series of organosulfur compounds (OSCs) were identified in the carbon disulfide fraction from the oxidized coals by GC/MS analysis but no OSCs were detected from other fractions except for 3 thiophene polycarboxylic acids found in ether-extraction. Some new types of sulfur function groups were also detected in the coal oxidation products which were not previously reported from coals. The results revealed that macromolecule OSCs in coals can be effectively degraded to water soluble small molecules with NaOCl aqueous solution, which can be enriched by carbon disulfide. Understanding the distribution of OSCs forms in coals matrix is useful in high value-added utilization of coals and coal desulphurization technologies.

Design and control of the ethyl benzene process

AbstractThe ethyl benzene (EB) process involves the reaction of benzene with ethylene to form the desired EB product. However, ethylene can also react with EB to form an undesired product of di‐ethyl benzene (DEB) if reactor temperatures or ethylene concentrations are high. An unusual feature of the EB process is the ability to recycle “to extinction” all the DEB formed in the reactor (no net DEB product produced), since DEB reacts with benzene to form EB. Since DEB is the highest‐boiling component in the system, it comes out the bottom of the two distillation columns, so there is little energy penalty in having a large DEB recycle. Recycling benzene is more expensive because it goes overhead in the first distillation column. The economic optimum steady‐state design is developed that minimizes total annual cost (capital and energy). An effective plantwide control structure is also developed. © 2010 American Institute of Chemical Engineers AIChE J, 2011

Development of a Novel Conversion Equation as a Function of Catalytic Reaction Conditions in Tubular Reactors

A comprehensive conversion equation was developed to simulate the catalytic reaction conditions (include temperature, pressure, residence time, and reaction composition) in tubular reactors: X M = 1 − exp [ − exp ( A + B / T r + C T r ) p r n p 0 + n p 1 p r τ r n τ 0 + n τ 1 τ r ∏ i = 1 m y i n y 0 + n y 1 y i ] . This conversion equation is based on the characteristics of the power-exponential function as well as the “variable reaction order” and “virtual reactant” concepts. Its validity was verified by fitting experiment data from three different catalytic systems such as the dehydrogenation of diethyl benzene, the hydrogenation of ethylbenzene, and the hydrodesulfurization of thiophene. The results show that the influences of reaction temperature, pressure, residence time, and reactant composition on the conversion of the reactant can be determined within a wide range of values. By comparison with the experimental data, the calculated conversions were all found to have a total average relative deviation of less than 2%. This suggests that the conversion equation is not limited to a specific catalyst system but could be suitable for various catalyst systems in tubular reactors. ： 根据幂指函数g(u) = u a+bu 的特点, 借用“虚拟反应组分”和“变动级数”的概念, 提出了管式反应器系统中反应转化率与工艺条件的关系式 X M = 1 − exp [ − exp ( A + B / T r + C T r ) p r n p 0 + n p 1 p r τ r n τ 0 + n τ 1 τ r ∏ i = 1 m y i n y 0 + n y 1 y i ] . 为了验证该转化率方程的普适性, 考察了二乙苯催化脱氢、乙苯加氢和噻吩加氢脱硫等, 并利用 Matlab 软件分别对这三个催化体系的实验数据进行拟合. 结果表明, 此方程在较宽的范围内均能很好地反映温度、反应压力、空速和物料比对转化率的影响. 预测结果与实验数据之间的总平均相对偏差均小于 2%, 说明该方程并不是针对某一特定的催化反应或催化剂, 可用于大多数的管式反应器催化反应系统中. A comprehensive conversion equation was developed to simulate catalytic reaction conditions in tubular reactors. This equation is not limited to a specific catalyst system and is suitable for various catalyst systems.

Deactivation of PtH-MFI bifunctional catalysts by coke formation during benzene alkylation with ethane

The alkylation reaction of benzene with ethane was studied at 370 °C over two Pt-containing MFI catalysts with Si/Al ratios of 15 and 40. The deactivation of the PtH-MFI-15 catalyst was found to be more significant, when compared with the PtH-MFI-40 catalyst, as a result of differences between the two catalysts in the formation of coke. The differing locations of the coke deposition were found to profoundly affect the product selectivity and deactivation behaviour of the two PtH-MFI catalysts. Results from gas sorption and X-ray diffraction experiments showed that coke is preferentially formed towards the centre of crystallites of the PtH-MFI-15 catalyst, as opposed to coke deposition on the outside surface of the PtH-MFI-40 crystallites, subsequently blocking entrance to the zeolite channels. Partial blockage of the internal pore structure of the PtH-MFI-15 catalyst with coke decreased the diffusion length within the PtH-MFI-15 crystallites. The effect of this reduction in the diffusion length within the PtH-MFI-15 crystallites is consistent with the observed decreasing para-selectivity of the diethylbenzene (DEB) isomers with time-on-stream. These findings are in contrast to the typical effect of coking, where, generally, the selectivity of para- isomers would be enhanced with coke deposition.

Kinetic Investigation of Benzene Ethylation with Ethanol over USY Zeolite in a Riser Simulator

The ethylation of benzene with ethanol over USY zeolite catalysts has been investigated at three different temperatures (300, 350, and 400 °C) for reaction times of 3, 5, 7, 10, 13, and 15 s with constant benzene to ethanol mole ratio of 1:1. Significant benzene conversion was found in the ethylation of benzene with ethanol over USY-2 catalyst as compared with the negligible conversion observed over USY-1 catalyst of lower acidity. The cracking of ethylbenzene (EB) was found to dominate at high temperatures (350 and 400 °C) in the ethylation of benzene with ethanol over USY-2 catalyst while ethylbenzene ethylation becomes significant at lower temperature (300 °C). Considerable amount of toluene was observed in the ethylation of benzene over USY-2 catalyst and was found to increase with increasing reaction temperature. The effect of reaction conditions on ethylbenzene selectivity, toluene selectivity, toluene-to-EB ratio, and total diethylbenzene (DEB) selectivity, are reported. Kinetic parameters for the ethylation of benzene with ethanol (E1), cracking of EB (E2), ethylation of ethylbenzene with ethanol (E3), and the cracking of diethylbenzene (E4) over USY-2 catalyst were determined using the catalyst activity decay function based on time-on-stream model. The apparent activation energies were found to decrease as follows: E2 > E3 > E4 > E1.

Third-phase formation in the extraction of thorium nitrate by N,N-dihexyloctanamide

N,N-dihexyloctanamide (DHOA) is an alternative candidate to tri-n-butylphosphate (TBP) for the reprocessing of spent nuclear fuels including those based on thorium. This paper reports the thirdphase formation behavior of Th(IV) with varying phase modifiers, diluents, extractant/nitrate ion concentration and temperature using DHOA/n-dodecane as solvent. The Th(IV)-LOC (limiting organic concentration) values increased with increasing concentration of the alcohols (modifiers) and that of DHOA in the organic phase. No third phase was observed when diethyl benzene (DEB) and decahydronaphthalene (decalin) were used as diluents. There was a sharp increase in Th(IV)-LOC value from 39.6 g/L (1M HNO3) to 48.6 g/L (1M HNO3 + 1M NaNO3) beyond which a saturation behavior was observed for Th(IV)-DHOA/n-dodecane system. The Th(IV)–LOC values increased with temperature but decreased with the aqueous phase acidity.

Characterization and Testing of Periodic Mesoporous Organosilicas as Potential Selective Benzene Adsorbents

The effects of surface imprinting on the adsorption and desorption properties of benzene- and diethylbenzene-bridged periodic mesoporous organosilicas (PMOs) acting as GC stationary-phase preconcentration sorbents for benzene and xylene were examined. Surface-imprinted and nonimprinted PMOs with diethylbenzene (DEB), benzene (BENZ), and ethane (BTSE) bridges and nonimprinted mesoporous silica (MCM-41) were prepared via well-established surfactant templating synthetic methods. The imprinted materials were synthesized using a surfactant demonstrated to produce trinitrotoluene (TNT) selective sorbents with increased adsorption capacity for cresol and 4-nitrophenol as well as TNT. Powder XRD and nitrogen sorption measurements revealed that all of the materials were mesoporous with the DEB materials having a random pore structure and lower surface area than the other materials which had ordered pore structures. Results for maximum uptake of benzene and p-xylene indicate a small but consistent positive effect on the adsorption of benzene and p-xylene due to surface imprinting. Comparing the surface area normalized uptakes (mg/m(2)) for materials having the same organic bridge with and without imprinting (DEB vs TDMI-DEB and BENZ vs TDMI-BENZ) shows that in seven of eight comparisons the imprinted analogue had a higher aromatic uptake. The imprinted samples showed higher weight normalized uptakes (mg/g) in five of eight cases. When used as a GC stationary phase, the organosilica materials yield more symmetrical chromatographic peaks and better separation than MCM-41, indicating superior trapping of BTX analytes, particularly at low concentrations. Additionally, these materials rapidly desorb the preconcentrated compounds.

Comparative Study Between Ethylbenzene Disproportionation Reaction and its Ethylation Reaction with Ethanol over ZSM-5

Ethylation of ethylbenzene with ethanol has been studied over ZSM-5 catalyst in a riser simulator that mimics the operation of a fluidized-bed reactor. The feed molar ratio of ethylbenzene:ethanol is 1:1. The study was carried out at 350, 400, 450, and 500 °C for reaction times of 3, 5, 7, 10, 13, and 15 s. Comparisons are made between the results of the ethylbenzene ethylation reaction with that of ethylbenzene disproportionation reaction earlier reported. The effect of reaction conditions on ethylbenzene reactivity, p-diethylbenzene selectivity, total diethylbenzene (DEB) isomers selectivity, p-DEB-to-m-DEB ratio, benzene-to-DEB molar ratio, and benzene selectivity, are reported. Benzene selectivity is about 10 times more in the EB disproportion reaction as compared to its ethylation reaction with ethanol at 350 °C. In addition, the results showed a p-DEB/m-DEB ratio for the EB ethylation reaction varying between 1.2–1.7, which is greater than the equilibrium values. Increase in temperature shifts the alkylation/dealkylation equilibrium towards dealkylation, thereby decreasing conversion and selectivity to DEB.

Ethylbenzene Transformation over a ZSM-5-Based Catalyst in a Riser Simulator

The transformation of ethylbenzene has been studied over a ZSM-5-type catalyst in a riser simulator that mimics the operation of a fluidized-bed reactor. The study was conducted at 350, 375, 400, 450, and 500 °C for reaction times of 3, 5, 7, 10, 13, and 15 s. The effect of reaction conditions on the ratio of cracking to disproportionation products (C/D), the distribution of diethylbenzene (DEB) isomers (m-DEB and p-DEB), and the ratio of benzene/diethylbenzenes (B/DEB) are reported. The experimental results were modeled using quasi-steady-state approximation. Disproportionation was determined to dominate at low temperatures (350−400 °C), while cracking reaction becomes significant as higher temperatures (>400 °C). Thus, two mechanisms were postulated to represent the disappearance of ethylbenzene during the transformation reaction (one mechanism for low temperature, and another for the complete temperature range considered). Kinetic parameters that were used for the disappearance of ethylbenzene during t...

Role of diluents in uranium transport across a supported liquid membrane using di(2-ethylhexyl)isobutyramide as the carrier

The extraction and transport behaviour of uranium from nitric acid medium across a supported liquid membrane has been studied using di(2-ethylhexyl)isobutyramide as the carrier. The effects of experimental parameters such as nature of diluents, e.g., n-dodecane, benzene, chloroform, tert-butyl benzene, diethyl benzene, n-octanol, 1,2-dichlorbenzene, and 2-nitrophenyl octyl ether, the membrane thickness, and the nitrate ion concentration, on the extraction/transport behaviour of uranium are reported. The experimentally obtained and the theoretically calculated values of permeability coefficients for uranium transport have been compared for different diluents.

Nanoporous Organosilicas as Preconcentration Materials for the Electrochemical Detection of Trinitrotoluene

We describe the use of nanoporous organosilicas for rapid preconcentration and extraction of trinitrotoluene (TNT) for electrochemical analysis and demonstrate the effect of template-directed molecular imprinting on TNT adsorption. The relative effects of the benzene (BENZ)- and diethylbenzene (DEB)-bridged organic-inorganic polymers, having narrow or broad pore size distributions, respectively, on electrochemical response and desorption behavior were examined. Sample volumes of 0.5-10 mL containing 5-1000 ppb TNT in a phosphate-buffered saline buffer were preconcentrated in-line before the detector using a microcolumn containing 10 mg of imprinted BENZ or DEB. Square-wave voltammetry was used to detect the first reduction peak of TNT in an electrochemical flow cell using a carbon working electrode and a Ag/AgCl reference electrode. Imprinted BENZ released TNT faster than imprinted DEB with considerably less peak tailing and displayed enhanced sensitivity and an improvement in the limit of detection (LOD) owing to more rapid elution of TNT from that material with increasing signal amplitude. For imprinted BENZ, the slope of signal versus concentration scaled linearly with increasing preconcentration volume, and for preconcentrating 10 mL of sample, the LOD for TNT was estimated to be 5 ppb. Template-directed molecularly imprinted DEB (TDMI-DEB) was 7-fold more efficient in adsorption of TNT from aqueous contaminated soil extract than nonimprinted DEB.

Separation of diethylbenzene isomers by distillative freezing

Due to the close boiling points of the mixed diethylbenzene (DEB) isomers, it is rather complicated to separate them by distillation. A new separation technique, distillative freezing (DF), is successfully applied to separate p-DEB from the diethylbenzene isomers in this study. Basically, the DF process operates at a triple point condition, in which the liquid mixture is simultaneously vaporized and solidified due to the three-phase equilibrium. It results in the formation of pure crystals along with the liquid phase and vapor phase of the mixtures. The process can be continued until the liquid phase is completely eliminated and only the pure solid crystals remain in the feed. A model, whereby the DF process is simulated in a series of equilibrium stage operations, is proposed to direct the DF operation. In the model, each stage is operated under an adiabatic condition at a three-phase equilibrium. The experiments show that, in the p-DEB/ m-DEB mixtures, p-DEB can be purified from 80% to 99% through several DF operations with the experimental recovery rate of p-DEB in one DF operation ranging from 58% to 77%. The unique feature of this new separation technique is that no filtration and crystal washing is required after the p-DEB crystals are obtained by DF.