Elucidating the effect of oxides on the zeolite catalyzed alkylation of benzene with 1-dodecene

In the present work, the effect of oxides on the alkylation of benzene with 1-dodecene was comprehensively investigated over MCM-49 n-heptanol, n-heptaldehyde and n-heptanoic acid were selected as the model oxides herein, and obvious decrease of lifetime could be caused by only trace amount of oxides added in the feedstocks. However, the deactivated catalysts were difficult to be regenerated by extraction with hot benzene. Additionally, coke-burning was also proved to be incapable to regenerate the deactivated catalysts mainly for the dealumination during calcination. Further characterizations complementary with DFT calculations were conducted to demonstrate that the deactivation was mainly due to the firm adsorption of oxides on the acid sites.

Experimental study of partially decoupled oxidation of ethane for producing ethylene and acetylene

With increasing amount of unconventional natural gas,the production of ethane,propane and other low alkanes continues to increase.In our previous works,a partially decoupled process(PDP) was proposed for conversion of ethane based on numerical simulations,which showed higher acetylene and ethylene selectivities than the original partial oxidation process.In the current work,the PDP of ethane for producing acetylene and ethylene was studied experimentally to verify the PDP concept.In the PDP of ethane,coke-oven gas or other cheap gas combusts with stoichiometric oxygen as heat carrier,and ethane is mixed with the heat carrier and undergoes pyrolysis at high temperatures.The jet-in-cross-flow(JICF) reactor was designed and manufactured to realize the PDP.A positioning device of 0.1 mm accuracy and a mass spectrometer were used to measure the spatial profiles of the species concentrations.The maximum combined yield(52.7%) of acetylene and ethylene was obtained even at the condition of heat loss,confirming that the PDP of ethane was advantageous over the partial oxidation process and at least comparable to the steam cracking process.

Ethylene glycol purification by melt crystallization:Removal of 2-methoxyethanol impurity

The coal(syngas)-to-ethylene glycol(CTEG),is contaminated with the naughty impurity 2-Methoxyethanol(ME)generated during the hydrogenation stage,which affect the quality of EG for fiber-grade polyester production.Distillation,is the employed separation process in industrial,which makes production complicated because of the heat sensitivity of the impurities system.Melt crystallization has been regarded as an effective technology to obtain high-purity organic compounds based on the melting points difference,which could avoid the problems by heating.In this work,we have explored the feasibility of the static melt crystallization on the separation of EG/ME in a jacketed crystallization tube.The experimental parameters were investigated,which covers crystallization and sweating stage in each step.The results showed that the purity of EG could reach≥99.8%from the binary system studied via the quaternary separation process.

Liquid-holdup regions research of novel reactive distillation column for C5 fraction separation

Recent advances in technologies of reactive distillation(RD) offer various design concepts for chemical processes.For separation of cracking C5 fraction, one of the main challenges is improving the conversion of cyclopentadiene(CPD) and the recovery of isoprene(IP). In the current work, a novel reactive distillation column with several liquid-holdup regions was designed, since it allows long residence time and provides flexibility for narrowing the efficiency gap between reaction and distillation. By use of Aspen Plus, a corresponding mathematic model was established and verified to be accurate. Following that, comprehensive studies were carried out for the design of liquid-holdup regions position. Details and principles about the separation performance with the liquid-holdup regions were revealed and optimized parameters were determined with 100 theoretical plates,feed position of 35 th plate, and four liquid-holdup regions at 25 th, 60 th, 75 th and 90 th plate. The designed RD column could well meet the technical requirement, and influence of other important factors including residence time, operating pressure and reflux ratio was further investigated.

CFD simulations of quenching process for partial oxidation of methane:Comparison of jet-in-cross-flow and impinging flow configurations

A new quenching process using the cold pyrolysis gas has been proposed for the partial oxidation(POX) of methane to recover the heat. The mixing of hot product gas and cold pyrolysis gas in milliseconds is critical to this new approach. Two most widely-used rapid mixing configurations, i.e. the jet-in-cross-flow(JICF) and impinging flow configurations, are compared in terms of mixing and quenching performances using computational fluid dynamics(CFD) coupled with detailed reaction mechanism Leeds 1.5. The mixedness, residence time distribution, temperature decreasing rate and loss ratio of acetylene during the quenching are systematically studied. The results show that the impinging flow has a more uniform mixing and narrower residence time distribution than the JICF.However, the temperature decreasing rate of the mainstream is faster in the JICF than in the impinging flow. The loss ratio of acetylene in the quenching process is 2.89% for the JICF and 1.45% for the impinging flow, showing that the impinging flow configuration is better and feasible for the quenching of POX of methane.

Enhancement of acetylene and ethylene yields in partially decoupled oxidation of ethane by changing the composition of heat carrier

In our previous work,a partially decoupled process(PDP)was proposed for efficient conversion of ethane to increase the ethylene yield and a new structural reactor called forward-impinging-back reactor(FIB)was proposed for scale-up.In this work,the influence of changing the composition and temperature of the heat carrier was investigated by simulations with detailed chemistry to further increase of the C_(2)(C_(2)H_(2)+C_(2)H_(4))yield in the PDP of ethane.At ideal mixing conditions,the C_(2) yield is 75.3%without steam addition and it is 82.9%at steam addition ratio of β=1.4.In comparison,the C_(2) yield in an FIB reactor is 62.4%without steam addition and it increases to 78.5%with steam addition(β=1.4).The requirement of high mixing efficiency is diminished by steam addition,which is favorable for reactor scale-up.

Coupling CO_(2)reduction with ethane aromatization for enhancing catalytic stability of iron-modified ZSM-5

The shale gas revolution and the carbon-neutrality goal are motivating the landscape toward the synthesis of value-added chemicals or fuels from underutilized ethane with the assistance of greenhouse gas CO_(2).Combining ethane aromatization with CO_(2)reduction offers an opportunity to directly produce liquid products for facile separation,storage,and transportation.In the present work,Fe/ZSM-5 catalysts showed promise in the simultaneous CO_(2)reduction and ethane aromatization at atmospheric pressure and 873 K.The catalysts were further investigated using X-ray diffraction(XRD)and X-ray absorption fine structure(XAFS)measurements under in-situ conditions,indicating that most of Fe species existed in the form of Fe oxides and a portion of Fe was incorporated into the ZSM-5 framework generating Lewis acid sites.Both types of Fe species remained almost unchanged under reaction conditions,contributing to an enhanced aromatization activity of Fe/ZSM-5.The effects of CO_(2)and steam on the acid sites and in turn aromatization activity were also investigated by transient studies,which exhibited a reversible modification behavior.Moreover,CO_(2)was identified to be critical to enhance coke resistance and in turn catalyst stability.This work highlights the feasibility of using CO_(2)to assist the upgrading of abundant ethane from shale gas to aromatics over non-precious Fe-based zeolite catalysts.

Simulation of bubble column reactors using CFD coupled with a population balance model

Bubble columns are widely used in chemical and biochemical processes due to their excellent mass and heat transfer characteristics and simple construction.However,their fundamental hydrodynamic behaviors,which are essential for reactor scale-up and design,are still not fully understood.To develop design tools for engineering purposes,much research has been carried out in the area of computationalfluid dynamics(CFD)modeling and simulation of gas-liquidflows.Due to the importance of the bubble behavior,the bubble size distribution must be considered in the CFD models.The population balance model(PBM)is an effective approach to predict the bubble size distribution,and great efforts have been made in recent years to couple the PBM into CFD simulations.This article gives a selective review of the modeling and simulation of bubble column reactors using CFD coupled with PBM.Bubble breakup and coalescence models due to different mechanisms are discussed.It is shown that the CFD-PBM coupled model with proper bubble breakup and coalescence models and interphase force formulations has the ability of predicting the complex hydrodynamics in differentflow regimes and,thus,provides a unified description of both the homo-geneous and heterogeneous regimes.Further study is needed to improve the models of bubble coalescence and breakup,turbulence modification in high gas holdup,and interphase forces of bubble swarms.

Hydrodynamic behavior of an internally circulating fluidized bed with tubular gas distributors

To better understand the hydrodynamic behavior of an internally circulating fluidized bed, solids holdup in the down-comer （Eso）, solids circulation rate （Gs） and gas bypassing fraction （from down-comer to riser y^R, and from riser to down-comer yRD） were experimentally studied. The effects of gas velocities in the riser and in the down-comer （UR and UD）, orifice diameter in the draft tube （dor）, and draft tube height （HR） were investigated. Experimental results showed that increase of gas velocities led to increase in Gs and yDR, and slight decrease in yeD. Larger orifice diameter on the draft tube led to higher 8sD, Gs and yDR, but had insignificant influence on YRD. with increasing draft tube height, both Gs and YDR first increased and then decreased, while yRD first decreased and then increased. Proposed correlations for predicting the hydrodynamic parameters agreed reasonably well with experimental values.