Synthesis of spherical nano-ZSM-5 zeolite with intergranular mesoporous for alkylation of ethylbenzene with ethanol to produce m-diethylbenzene

Catalytic synthesis of m-diethylbenzene(m-DEB)through alkylation of ethylbenzene(EB)may be a promising alternative route in comparison with traditional rectification of mixed DEB,for which the top priority is to develop efficient and stable heterogeneous catalysts.Here,the spherical nano-ZSM-5 zeolite with abundant intergranular mesoporous is synthesized by the seed-mediated growth method for alkylation of EB with ethanol to produce m-DEB.The results show that the spherical nano-ZSM-5 zeolite exhibits better stability and higher alkylation activity at a lower temperature than those of commercial micropore ZSM-5.And then,the spherical nano-ZSM-5 is further modified by La_(2)O_(3) through acid treatment followed by immersion method.The acid treatment causes nano-ZSM-5 to exhibit the increased pore size but decreased the acid sites,and subsequent La_(2)O_(3) loading reintroduces the weak acid sites.As a result,the HNO_(3)-La_(2)O_(3)-modified catalyst exhibits a slight increase in EB conversion and DEB yield in comparison with unmodified one,and meanwhile,it still maintains high m-DEB selectivity.The catalyst after acid treatment achieves higher catalytic stability besides maintaining the high alkylation activity of EB with ethanol.The present study on the spherical nano-HZSM-5 zeolite and its modification catalyst with excellent alkylation ability provides new insights into the production of mDEB.

Scale up and stability test for oxidative coupling of methane over Na_2WO_4-Mn/SiO_2 catalyst in a 200 ml fixed-bed reactor

The study of scale up for the oxidative coupling of methane （OCM） has been carried out in a 200 ml stainless steel fixed-bed reactor over a 5wt% Na2WO4-1.9wt% Mn/SiO2 （W-Mn/SiO2） catalyst. The effects of reaction conditions were investigated in detail. The results showed that, with increasing reaction temperature, the gas-phase reaction was enhanced and a significant amount of methane was converted into COx; with the CH4/O2 molar ratio of 5, the highest C2 （ethylene and ethane） yield of 25% was achieved; the presence of steam （as diluent） had a positive effect on the C2 selectivity and yield. Under lower methane gaseous hourly space velocity （GHSV）, higher selectivity and yield of C2 were obtained as the result of the decrease of released heat energy. In 100 h reaction time, the C2 selectivity of 66%-61% and C2 yield of 24.2%-25.4% were achieved by a single pass without any significant loss in catalytic performance.

Conversion enhancement of tubular fixed-bed reactor for Fischer-Tropsch synthesis using static mixer

Recently, Fischer-Tropsch synthesis （FTS） has become an interesting technology because of its potential role in producing biofuels via Biomass- to-Liquids （BTL） processes. In Fischer-Tropsch （FT） section, biomass-derived syngas, mainly composed of a mixture of carbon monoxide （CO） and hydrogen （H2）, is converted into various forms of hydrocarbon products over a catalyst at specified temperature and pressure. Fixed-bed reactors are typically used for these processes as conventional FT reactors. The fixed-bed or packed-bed type reactor has its drawbacks, which are heat transfer limitation, i.e. a hot spot problem involved highly exothermic characteristics of FT reaction, and mass transfer limitation due to the condensation of liquid hydrocarbon products occurred on catalyst surface. This work is initiated to develop a new chemical reactor design in which a better distribution of gaseous reactants and hydrocarbon products could be achieved, and led to higher throughput and conversion. The main goal of the research is the enhancement of a fixed-bed reactor, focusing on the application of KenicsTM static mixer insertion in the tubular packed-bed reactor. Two FTS experiments were carried out using two reactors i.e., with and without static mixer insertion within catalytic beds. The modeled syngas used was a mixed gas composed of H2/CO in 2 ： 1 molar ratio that was fed at the rate of 30 mL（STP）·min^- 1 （GHSV ≈ 136 mL·gcat^-1 ·h^-1） into the fixed Ru supported aluminum catalyst bed of weight 13.3 g. The reaction was carried out at 180 ℃ and atmospheric pressure continuously for 36 h for both experiments. Both transient and steady-state conversions （in terms of time on stream） were reported. The results revealed that the steady-state CO conversion for the case using the static mixer was approximately 3.5 times higher than that of the case without static mixer. In both cases, the values of chain growth probability of hydrocarbon products （α） for Fischer-Tropsch synthesis were 0.92 and 0.89 for the case with and without static mixer, respectively.

On-Line Prediction of a Fixed-Bed Reactor Using K-L Expansion and Neural Networks

An on-line prediction scheme combining the Karhunen-Love expansion and a recurrent neural network for a wall-cooled fixed-bed reactor is presented.Benzene oxidation in a pilotscale,single tube fixed-bed reactor is chosen as a working system and a pseudo-homogeneous twodimensional model is used to generate simulation data to investigate the prediction scheme presentedunder randomly changing operating conditions.The scheme consisting of the K-L expansion andneural network performs satisfactorily for on-line prediction of reaction yield and bed temperatures.

A Simulation Study of the Steam Reforming of Methaneina Fixed-Bed Reactor

In this work a one-dimensional mathematical model was developed to simulate methane conversion and hydrogen yield in a fixed-bed reactor filled with catalyst particles. For the reason that reforming reactions are sorely endothermic process, the heat is supplied to the reactor through electrical heating. The reforming reactions have been investigated from a modelling view point considering the effect of different temperatures ranging from 500℃ and 977℃ on the conversion of methane and hydrogen yield. Simulation results show that the steam reforming of methane in a fixed-bed reactor can efficiently store high temperature end thermal energy. When the operating temperature is increased to 977℃, the conversion of methane is 97.48% and the hydrogen yield is 2.2408. As a conclusion, the maximum thermochemical efficiency will be obtained under optimal operating temperature (977℃) and the steam/methane (3.86) ratio.

Suiting Dynamic Models of Fixed-Bed Catalytic Reactors for Computer-Based Applications

This work investigated the applicability of heterogeneous and pseudo-homogeneous models to predict the dynamic behavior of a fixed-bed catalytic reactor. Some issues concerning the dynamic behavior of the system were discussed, such as the prediction of the inverse response phenomenon. The proposed models (Het- erogeneous I and II and Pseudo-homogeneous) were able to predict with qualitative similarity the main characteristics of the dynamic behavior of a fixed-bed catalytic reactor, including the inverse response. The computational time demanded for the solution of the heterogeneous models was 10 to 50% longer than in the case of the pseudo-homogeneous model, making the use of the former suitable for applications where computational time is not the major restriction (off-line applications). On the other hand, when on-line applications are required, the simplified model (Pseudo-homogeneous model) showed to be a good alternative because this model was able to predict (qualitatively) the dynamics of the reactor using a faster and easier numerical solution.

The adsorption properties of NaY zeolite for separation of ethylene glycol and 1,2-butanediol: Experiment and molecular modelling

The separation of ethylene glycol(EG)and 1,2-butanediol(1,2-BDO)azeotrope in the synthesis process of EG via coal and biomass is becoming of increasing commercial and environmental importance.Selective adsorption is deemed as the most promising methods because of energy saving and environment favorable.In this paper,NaY zeolite was used to separate 1,2-BDO from EG,and its adsorption properties was then investigated.The isotherms of EG and 1,2-BDO in vapor and liquid phases from 298 to 328 K indicated that they fitted Langmuir model quite well,and the NaY zeolite absorbent favored EG more than 1,2-BDO.The Grand Canonical Monte Carlo(GCMC)and molecular dynamics(MD)simulation techniques were conducted to investigate the competition adsorption and diffusion characteristics in different adsorption regions.It was observed that EG and 1,2-BDO molecules all have the most probable locations of the center of the 12-membered ring near the Na cations.The diffusivities of EG are lower than those of 1,2-BDO at the same adsorption concentration.At last,the breakthrough curves of the binary mixture regressed from the empirical Dose–Response model in fixed-bed column showed that the adsorption selectivity of EG could reach to as high as 2.43,verified that the NaY zeolite could effectively separate EG from 1,2-BDO.This work is also helpful for further separation of other dihydric alcohol mixtures from coal and biomass fermentation.

Effect of Active Zeolite in the Pyrolysis of Polypropylene and Low Density Polyethylene Types of Plastic Waste

Plastic is a basic need for humans,but it has also caused big problems for the environment.Then,the purpose of this study was to determine the effect of the type of plastic and the addition of a zeolite catalyst on the oil yield from the pyrolysis of plastic waste.The research stages were natural zeolite activation,pyrolysis reactor settings,pyrolysis of plastic waste(PP and LDPE types),and characterization.The results showed that the used natural zeolite had a mordenite phase and activated natural zeolite had a higher Si/Al ratio than the inactivated one.The addition of a zeolite catalyst had an effect on the produced yield.The yields of oil from plastic waste pyrolysis with zeolite catalyst for PP and LDPE plastics were about 75.9 and 76.9 w/w,respectively.The results of the GCMS analysis showed that the compounds of the pyrolysis oil were thought to be from the alkanes,cycloalkanes,alkenes,carboxylic acids with aromatic rings,and ketones.The results of the GC-MS test showed that the uncatalyzed pyrolysis product consists of compounds with a range of C5-C11 carbon chains.Meanwhile,the ranges of pyrolysis products with active zeolite catalyst were C6-C24 carbon chains.

A three dimensional CFD simulation and optimization of direct DME synthesis in a fixed bed reactor

In this study, a comprehensive three-dimensional dynamic model was developed for simulating the flow behavior and catalytic coupling reactions for direct synthesis of dimethyl ether （DME） from syngas including CO2 in a fixed bed reactor at commercial scale under both adiabatic and isothermal conditions. For this purpose, a computational fluid dynamic （CFD） simulation was carried out through which the standard κ-ε model with 10% turbulence tolerations was implemented. At first, an adiabatic fixed bed reactor was simulated and the obtained results were compared with those of an equivalent commercial slurry reactor. Then the concentration and temperature profiles along the reactor were predicted. Consequently, the optimum temperature, pressure, hydrogen to carbon monoxide ratio in the feedstock and the reactor height under different operation conditions were determined. Finally, the results obtained from this three-dimensional dynamic model under appropriate industrial boundary conditions were compared with those of others available in literature to verify the model. Next, through changing the boundary conditions, the simulation was performed for an isothermal fixed bed reactor. Furthermore, it was revealed that, under isothermal conditions, the performed equilibrium simulations were done for a single phase system. Considering the simultaneous effects of temperature and pressure, the optimum operation conditions for the isothermal and adiabatic fixed bed reactors were investigated. The results of the H2＋CO conversions indicated that, under isothermal condition, higher conversion could be achieved, in compared with that under adiabatic conditions. Then, the effects of various operating parameters, including the pressure and temperature, of the reactor on the DME production were examined. Ultimately, the CFD modeling results generated in the present work showed reasonable agreement with previously obtained data available in the literature.

Synthesis of Linear Alkylbenzene in a Novel Liquid-Solid Circulating Moving Bed Reactor

For the alkylation of benzene with long-chain olefins, using Hβ zeolite catalyst as replacement of HF or A1Cl3 has the advantages of no corrosion, less environmental pollution, and much more 2-phenyl isomer, which has the highest biodegradability and solubility, and better detergent properties among the related isomers. The characterization of the coke shows that the deactivation of catalyst is caused by the jam of bulkier molecules, such as naphthalene, indane and linear alkylbenzenes, which are too big to move quickly in the intracrystalline pores of catalyst. The deactivated catalyst can be regenerated by benzene washing at higher temperature. To make the processes of reaction and regeneration continuous, a novel moving bed reactor is developed. Comparing with the processes with fixed bed reactors, the processes in this work have the advantages of continuous operation, low temperature, low pressure, low mole ratio of benzene to olefins, and high weight hourly space velocity.Keywords t3 zeolite, alkylation, linear alkylbenzene, moving bed

生物沸石反应器在微污染水源水处理中的应用

随着我国经济社会的发展,水资源短缺和水质问题已成为制约发展的重要因素。因此,必须加强城市污水治理、提高再生水利用率。传统生物滤池在处理污水和再生水的过程中存在诸多问题,如占地面积大、易堵塞等。本文通过使用天然斜发沸石制备的生物沸石反应器进行试验研究,结果显示沸石具有良好的选择性和污染物去除效果,且抗冲击负荷能力强。得到主要结论如下:通过静态吸附试验得出当进水浊度小于5 NTU时,沸石出水浊度可降至0.2 NTU以下;当进水CODMn质量浓度大于3 mg/L时,沸石出水CODMn质量浓度均低于4 mg/L;当进水氨氮质量浓度小于8mg/L时,沸石出水氨氮浓度均低于1 mg/L。说明沸石具有良好的选择性。

加氢裂化尾油在不同结构催化剂上催化裂解制烯烃研究

为了明确分子筛孔道结构与酸性质对加氢裂化尾油催化裂解制备低碳烯烃的构效关系,寻找最优催化剂,实现加氢裂化尾油的高效转化,挑选了BEA,FER,TON,FAU,AEL,AFI,MFI等7种拓扑结构的分子筛,考察了加氢裂化尾油在不同孔道结构分子筛上的催化裂解反应性能,并通过以正己烷为探针的脉冲微反试验进一步分析了分子筛酸性对催化裂解反应过程中尾油反应性能及低碳烯烃产物分布的影响。加氢裂化尾油的催化裂解试验结果表明,反应转化率受孔径大小与孔道结构共同作用,具有尺寸为0.40 nm×0.65 nm的椭圆形一维孔道结构的SAPO-11分子筛为催化裂解反应最优催化剂。脉冲微反试验结果表明:分子筛弱酸酸量及中强酸酸量越大,越有利于目的产物乙烯和丙烯生成。

沸石颗粒填料固定床生物膜免曝气污水处理工艺

为降低污水处理能耗,利用沸石颗粒充当生物填料构建固定床生物膜反应器,通过序批式进水—排水的方式使反应器内填料表面生物膜处于交替厌氧—好氧环境,避免了传统污水处理曝气工艺所需的大量能耗,并能有效去除COD和脱氮。该工艺主要原理:在厌氧阶段(进水),污水与生物膜和沸石颗粒接触,聚糖菌(GAOs)将有机碳源转化为胞内聚羟基烷酸(PHAs),沸石吸附污水中的NH_(4)^(+)-N。在好氧阶段(排水),通过聚糖菌、硝化菌和反硝化菌的共同作用,将沸石吸附的NH_(4)^(+)-N转化为氮气,使得生物膜和沸石颗粒得以再生。沸石颗粒固定床生物膜反应器以活性污泥为接种污泥,在序批式厌氧—好氧交替运行模式下,2周内成功启动;长期运行中污水COD、NH_(4)^(+)-N和TN去除率分别为87%、83%和83%,且出水中未检出硝态氮;长期运行后,反应器内生物膜菌群以Thauera、Candidatus competitivebacter、Nitrospira细菌属为主,它们是去除COD和脱氮的关键微生物。

Deactivation and regeneration of TS-1/SiO2 catalyst for epoxidation of propylene with hydrogen peroxide in a fixed-bed reactor

TS-1/SiO2 catalyst for the epoxidation of propylene with hydrogen peroxide in a fixed-bed reactor has been investigated. The catalyst activity decreases gradually with the online reaction time, but the selectivity of propylene epoxide is kept at about 93%. The fresh, deactivated and regenerated catalysts were characterized with X-ray diffraction, Fourier transform infrared spectro- scopy, ultra-violet-visible diffuse reflectance, Brunner- Emmett-TeUer method and thermogravimetric analysis, and the deactivated catalyst was regenerated with H2O2/ methanol solution. Compared with the fresh catalyst, both the framework structure and the content of titanium in the framework of the deactivated and regenerated TS-1/SiO2 catalysts were not changed. The major reason of the catalyst deactivation was the blockage of the channels of the catalyst by bulky organic by-products, which covered the active centers of titanium in TS-1. The deposited materials on the deactivated TS-1/SiO2 catalyst could be removed by treatment with hydrogen peroxide/methanol solution or pure methanol; the higher the treatment temperature and the higher the concentration of H2O2 in methanol, the higher the extent of the regeneration. The regeneration treatment did not influence the product selectivity in the propylene epoxidation.

Constructing S-scheme 2D/0D g-C_(3)N_(4)/TiO_(2) NPs/MPs heterojunction with 2D-Ti3AlC2 MAX cocatalyst for photocatalytic CO_(2) reduction to CO/CH_(4) in fixed-bed and monolith photoreactors

Exfoliated 2D MAX Ti_(3) AlC_(2) conductive cocatalyst anchored with g-C_(3)N_(4)/TiO_(2) to construct 2D/0D/2D het-erojunction has been explored for enhanced CO_(2) photoreduction in a fixed-bed and monolith photoreac-tor.The TiO_(2) particle sizes(NPs and MPs)were systematically investigated to determine effective metal-support interaction with faster charge carrier separation among the composite materials.When TiO_(2) NPs were anchored with 2D Ti_(3) AlC_(2) MAX structure,10.44 folds higher CH_(4) production was observed com-pared to anchoring TiO_(2) MPs.Maximum CH_(4) yield rate of 2103.5μmol g^(−1) h^(−1) achieved at selectivity 96.59%using ternary g-C_(3)N_(4)/TiO_(2)/Ti_(3) AlC_(2)2D/0D/2D composite which is 2.73 and 7.45 folds higher than using binary g-C_(3)N_(4)/Ti_(3) AlC_(2) MAX and TiO_(2) NPs/Ti_(3)AlC_(2) samples,respectively.A step-scheme(S-scheme)photocatalytic mechanism operates in this composite,suppressed the recombination of useful electron and holes and provides higher reduction potential for efficient CO_(2) conversion to CO and CH_(4).More im-portantly,when light intensity was increased by 5 folds,CH_(4) production rate was increased by 3.59 folds under visible light.The performance of composite catalyst was further investigated in a fixed-bed and monolith photoreactor and found monolithic support increased CO production by 2.64 folds,whereas,53.99 times lower CH_(4) production was noticed.The lower photocatalytic activity in a monolith photore-actor was due to lower visible light penetration into the microchannels.Thus,2D MAX Ti_(3) AlC_(2) composite catalyst can be constructed for selective photocatalytic CO_(2) methanation under visible light in a fixed-bed photoreactor.

沸石堆积高度对反应器蓄放热性能的影响

吸附蓄热的储能密度高,热损失小,可实现太阳能等可再生能源的跨季节利用。然而,仍需要对吸附蓄热过程进行深入研究以提高反应器的蓄放热性能。本文搭建了吸附蓄热实验系统,并进行了多组蓄、放热实验。在不同堆积高度条件下,当反应器入口空气参数保持不变时,实测沸石13X的蓄放热性能显示:反应器输出温度是否存在稳定阶段与沸石快速吸附阶段时长相关,当反应器输出温度未出现稳定阶段时,快速吸附阶段时长小于反应器达到峰值输出温度的时长。随着沸石堆积高度的增加,沸石的储能密度保持不变,反应器的平均输出功率呈现出先逐渐增加而后趋于稳定的趋势。在吸附入口空气温度和湿度分别为22.0℃和14.9g/kg条件下,本实验中沸石的储能密度可达到220.9kWh/m^(3);相应地,当堆积高度大于1580mm时,吸附平衡过程中反应器的平均输出功率不再随堆积高度的增加而改变。

分子筛膜的应用研究进展

膜技术因具有连续分离、能耗低、易于放大、操作条件温和、效率高等优点,在石油化工行业受到广泛关注。无机分子筛膜材料具有分子尺寸水平的孔径、高比表面积、化学性质可调等特点,是一种具有高渗透性能的膜材料,在重要化工领域展现出广阔的应用前景。不同拓扑类型的分子筛膜因孔道结构、孔径大小和硅铝比等性能差异,可在不同领域发挥作用,包括分离(有机溶剂脱水、有机混合物分离)、净化(海水净化、天然气除杂)、催化反应器(酯化、醚化、脱氢和加氢反应)等,但目前仅在个别领域实现了工业化应用。本文介绍了近几年分子筛膜的应用研究进展,为分子筛膜在工业中的推广应用提供思路。

Palladium nanoparticles supported on amine-functionalized glass fiber mat for fixed-bed reactors on the effective removal of hexavalent chromium by catalytic reduction

Palladium nanoparticles were deposited on the amine-grafted glass fiber mat （GFM-NH2） catalyst support by a conventional impregnation process followed by the borohydride reduction in aqueous solution at room temperature to create the designed Pd/GFM-NH2 catalyst. By the use of large size glass fiber mat without nano/mesopores as the catalyst support, the internal mass transfer limitations due to the existence of nano/mesopores on the catalyst support were eliminated and the Pd/GFM-NH2 catalyst could be easily separated from treated water due to the large size of the catalyst support. Batch experiments demonstrate its good catalytic reduction performance of Cr（VI） with formic acid as the reducing agent. It also demonstrated an efficient Cr（VI） removal and stability in a lab-prepared, packed fixed-bed tube reactor for the continuous treatment of Cr（VI）-containing water. Thus, it has a good potential for the catalytic reduction of Cr（VI） in the water treatment practice.

生物沸石反应器在微污染水源水处理中的应用

首次利用生物沸石反应器去除微污染水源水中的 NH3- N、NO- 2 - N、Mn、有机物、色度、浊度等 .经长期运行测试 ,生物沸石反应器对 NH3- N平均去除率可达 93%,对 NO- 2 - N的平均去除率为 90 %,对有机物可去除 32 %,并提出了反应器的最佳过滤速度为 8～ 1 0 m/h,最佳填料填充高度为 60 0～ 80 0 mm.生物沸石反应器具有和生物活性炭、生物陶粒一样的性能 .该技术为微污染水源水质净化提供了一种新材料 ,新途径 .