Effect of mesopore spatial distribution of HZSM-5 catalyst on zinc state and product distribution in 1-hexene aromatization

1-hexene aromatization is a promising technology to convert excess olefin in fluid catalytic cracking(FCC)gasoline to high-value benzene(B),toluene(T),and xylene.Besides,the increasing market demand of xylene has put forward higher requirements for new generation of catalyst.For increasing xylene yield in 1-hexene aromatization,the effect of mesopore structure and spatial distribution on product distribution and Zn loading was studied.Catalysts with different mesopore spatial distribution were prepared by post-treatment of parent HZSM-5 zeolite,including NaOH treatment,tetra-propylammonium hydroxide(TPAOH)treatment,and recrystallization.It was found the evenly distributed mesopore mainly prolongs the catalyst lifetime by enhancing diffusion properties but reduces the aromatics selectivity,as a result of damage of micropores close to the catalyst surface.While the selectivity of high-value xylene can be highly promoted when the mesopore is mainly distributed interior the catalyst.Besides,the state of loaded Zn was also affected by mesopores spatial distribution.On the optimized catalyst,the xylene selectivity was enhanced by 12.4%compared with conventional Zn-loaded parent HZSM-5 catalyst at conversion over 99%.It was attributed to the synergy effect of mesopores spatial distribution and optimized acid properties.This work reveals the role of mesopores in different spatial positions of 1-hexene aromatization catalysts in the reaction process and the influence on metal distribution,as well as their synergistic effect two on the improvement of xylene selectivity,which can improve our understanding of catalyst pore structure and be helpful for the rational design of high-efficient catalyst.

A Technical Roadmap for China’s Petrochemical Industry Upgrading to Achieve Carbon Neutrality

1.Introduction Human’s consumption of fossil fuel energy,accompanied by enormous quantities of carbon dioxide(CO_(2))emissions,is closely related to glacier melting,sea level rise,and the frequent occurrence of extreme weather in the 20th century.The Intergovernmental Panel on Climate Change(IPCC)put forward the goal of carbon neutrality in October 2018.So far,more than 130 countries and regions around the world have proposed their corresponding goal of carbon neutrality.China has also proposed to achieve a carbon peak and carbon neutrality[1].

A DFT and TD-DFT study on electronic structures and UV-spectra properties of octaethyl-porphyrin with different central metals(Ni, V, Cu, Co)

In this work,the octaethyl-porphyrins with different central metals(M-OEP,M=Ni,VO,Cu,Co)were used to investigate the ground-state molecular structure,electron distribution and UV-spectra properties on molecular level by density functional theory(DFT).The results showed that the calculation structure parameters of metalloporphyrins agreed well with the experimental value.According to the Natural Bond Orbital(NBO)analysis,the charge distribution of different metalloporphyrins was found that the charge values of the central metal M decreased with the order of VO<Ni<Co<Cu,while the bonding strength between M and the coordinating atom N was VO>Ni>Co>Cu.At the same time,the frontier molecular orbital calculations showed that the SOMO energy of VO(OEP)molecules in the open-shell system was higher than that of Co(OEP)and Cu(OEP),which means that its UV absorption characteristic peak would be red-shifted.In addition,the IEFPCM model of Time-dependent Density functional theory(TD-DFT)was further utilized to simulate the four substance in toluene solution:Co(OEP),Ni(OEP),Cu(OEP)and VO(OEP),and the Soret band peaks were calculated respectively as:382 nm,383 nm,391 nm and 401 nm.Furthermore,the quantitative simulation analysis of metalloporphyrins was combined with experimental data.It could be found that the location rules of the four kinds of metalloporphyrins calculated absorption characteristic peaks were consistent with the experimental ones,and the relative errors of each peak were within 3%.These methods used above provide a theoretical path for analyzing and identifying unknown porphyrin compounds in petroleum.

Influence of zinc state on the catalyst properties of Zn/HZSM-5 zeolite in 1-hexene aromatization and cyclohexane dehydrogenation

Rational design of Zn-containing HZSM-5 zeolite(Zn/HZSM-5)with high reactivity and excellent aromatization performance for olefin aromatization is crucially desired.We develop a new and uncomplicated method to synthesize Zn/HZSM-5(IMX/Z5)with superior aromatization performance in the paper.Compared to incipient wetness impregnation(IMP/Z5)and mechanical mixing(MIX/Z5),the asprepared IMX/Z5 presents a higher amount of surface ZnOH^(+)species(2.87%)while keeping identical bulk zinc content.As a result,more surface ZnOH^(+)favor both the aromatization of 1-hexene and cyclohexane dehydrogenation.For the two olefin aromatization pathways(hydrogen transfer and dehydrogenation),it is the first time found both the hydrogen transfer ability and the dehydrogenation ability increase linearly with the amount of surface ZnOH^(+)species while keeping identical bulk zinc content.We believe that the linear relationships are essential to design next generation olefin aromatization catalysts.

Boosting of reversible capacity delivered at a low voltage below 0.5 V in mildly expanded graphitized needle coke anode for a high-energy lithium ion battery

The rate performance and cycle stability of graphitized needle coke(GNC)as anode are still limited by the sluggish kinetics and volume expansion during the Li ions intercalation and de-intercalation process.Especially,the output of energy density for lithium ion batteries(LIBs)is directly affected by the delithiation capacity below 0.5 V.Here,the mildly expanded graphitized needle coke(MEGNC)with the enlarged interlayer spacing from 0.346 to 0.352 nm is obtained by the two-step mild oxidation intercalation modification.The voltage plateau of MEGNC anode below 0.5 V is obviously broadened as compared to the initial GNC anode,contributing to the enhancement of Li storage below the low voltage plateau.Moreover,the coin full cell and pouch full cell configured with MEGNC anode exhibit much enhanced Li storage ability,energy density and better cycling stability than those full cells configured with GNC and commercial graphite anodes,demonstrating the practical application value of MEGNC.The superior anode behaviors of MEGNC including the increased effective capacity at low voltage and superior cyclic stability are mainly benefited from the enlarged interlayer spacing,which not only accelerates the Li ions diffusion rate,but also effectively alleviates the volume expansion and fragmentation during the Li ions intercalation process.In addition,the above result is further confirmed by the density functional theory simulation.This work provides an effective modification strategy for the NC-based graphite to enhance the delithiation capacity at a low voltage plateau,dedicated to improving the energy density and durability of LIBs.

Extraordinary Compatibility to Mass Loading and Rate Capability of Hierarchically Porous Carbon Nanorods Electrode Derived from the Waste Tire Pyrolysis Oil

The conversion of waste tire pyrolysis oil(WTPO)into S-doped porous carbon nanorods(labeled as WPCNs)with hierarchical pore structure is realized by a simple template-directed approach.The specific surface area of as-obtained porous carbon nanorods can reach up to 1448 m^(2) g^(−1) without the addition of any activating agent.As the capacitive electrode,WPCNs possess the extraordinary compatibility to capacitance,different electrolyte systems as well as long-term cycle life even at a commercial-level areal mass loading(10 mg cm^(−2)).Besides,only an extremely small capacitance fluctuation is observed under the extreme circumstance(−40 to 80℃),reflecting the excellent high-and low-temperature performance.The relationship between the pore structure and capacitive behavior is analyzed by comparing WPCNs with mesopores-dominated asphalt-derived porous carbon nanorods(APCNs)and micropores-dominated activated carbon.The molecular dynamics simulation further reveals the ion diffusion and transfer ability of the as-prepared carbon materials under different pore size distribution.The total ion flow(NT)of WPCNs calculated by the simulation is obviously larger than APCNs and the N_(T) ratio between them is similar with the experimental average capacitance ratio.Furthermore,this work also provides a valuable strategy to prepare the electrode material with high capacitive energy storage ability through the high value-added utilization of WTPO.

Mechanism transformation of cyclohexene-thiophene competitive adsorption in FAU zeolite

Competition of hydrocarbon compounds with sulfides in gasoline has caused a not very high selectivity of sulfides in adsorption desulfurization so far,resulting in a reduction of catalyst lifetime as well as more sulfur oxide emissions.Tostudy the whole competitive process changing with the increase of the loading,the dynamic competition adsorption mechanism of cyclohexene and thiophene in siliceous faujasite(FAU)zeolite was analyzed by the Monte Carlo simulation.The results showed that with the increase of the loading,thiophene and cyclohexene had different performances before and after the inflection point of 40 molecule/UC.The adsorbates were distributed ideally at optimal sites during the stage that occurred before the inflection point,which is called the“optimal-displacement adsorption”stage.When approaching the inflection point,the competition became apparent and the displacement appeared accordingly,some thiophene molecules at S sites(refers to the sites inside the supercages)were displaced by cyclohexene.After the inflection point,the concentration of adsorbates at W sites(refers to the 12-membered ring connecting the supercages)was significantly reduced,whereas the adsorbates at S sites got more concentrated.The stage some cyclohexene molecules displaced by thiophene and inserted into the center of the supercage can be named as the“insertion-displacement adsorption”stage,and both the adsorption behavior and the competitive relationship became localized when the adsorption amount became saturated.This shift in the competitive adsorption mechanism was due to the sharp increase of interaction energy between the adsorbates.Besides,the increase in temperature and ratio of Si/Al will allow the adsorbates,especially thiophene molecules to occupy more adsorption sites,and it is beneficial to improve the desulfurization selectivity.

Exfoliated multi-layered graphene anode with the broadened delithiation voltage plateau below 0.5 V

The commercial graphite(CG)is the conventional anode material for lithium ion batteries(LIBs)due to its low delithiation voltage plateau(below 0.5 V)and extraordinary durability.Nevertheless,the further promotion of energy density of LIBs is restricted by the limited capacity below 0.5 V of CG.Here,based on the supercritical CO2 exfoliation technique,the production of multi-layered graphene(MLG)is achieved from the pilot scale production line.The great merit of the exfoliated MLG anode is that the voltage plateau below 0.5 V is broadened obviously as compared to those of natural graphite and CG.Additionally,no obvious lithium dendrites are observed for MLG during the lithiation process.The large delithiation capacity under the low voltage plateau of MLG is mainly benefited from the combination of Li intercalation and boundary storage mechanism,which is further confirmed by the density functional theory calculations.The LiFePO4/MLG full cell can afford the satisfactory electrochemical property with respect to the capacity,energy density and ultralong cycling stability(90%capacity retention after 500 cycles at 2 C),significantly better than that of LiFePO4/CG.Besides,this developed technique not only dedicates to producing the high-performance anode for LIBs but also opens a door for the mass production of MLG in the industrial scale.

Optimizing support acidity of NiMo catalysts for increasing the yield of benzene, toluene and xylene in tetralin hydrocracking

To enhance the yields of benzene,toluene,and xylene in tetralin hydrocracking,the effect of the support acid properties of NiMo catalysts on hydrocracking performance of tetralin were investigated in this study.NaY zeolites were modified by hydrothermal treatment to form USY zeolites at different temperatures and adjust the type and amount of acid.In addition,H-Beta was loaded into the USY to further adjust the acidic properties of the catalysts.The result shows that when the total B acid content of the catalyst is maintained between 150 and 200μmol·g^(-1),the total acid amount is maintained between 1.7 and 1.9 mmol·g^(-1),and the L/B(L and B acids)ratio is maintained between 1.5 and 2,the catalysts have favorable performances on tetralin hydrocracking.Under this condition,the catalysts have a yield of benzene,toluene,and xylene higher than 30 wt%and a selectivity for benzene,toluene,and xylene higher than 35%.The tetralin conversion is greater than 85 wt%.The AB6 catalyst obtains the best hydrocracking effect with the conversion of tetralin reaching 90.24 wt%,the yields of benzene,toluene,and xylene reaching 33.58 wt%,and the selectivity of benzene,toluene,and xylene reaching 37.21%,respectively.

Synergistic effects and kinetics analysis for co-pyrolysis of vacuum residue and plastics

This study utilizedathermogravimetric analyzer to assess the thermal decomposition behaviors and kinetics properties of vacuum residue(VR)and low-density polyethylene(LDPE)polymers.The kinetic parameters were calculated using the Friedman technique.To demonstrate the interactive effects between LDPE and VR during the co-pyrolysis process,the disparity in mass loss and mass loss rate between the experimental and calculated values was computed.The co-pyrolysis curves obtained through estimation and experimentation exhibited significantdeviations,whichwerei influencedby temperature and mixing ratio.A negative synergistic interaction was observed between LDPE and VR,although this inhibitory effect could be mitigated or eliminated by reducing the LDPE ratio in the mixture and increasing the co-pyrolysistemperature.Theco-pyrolysisprocess resulted in a reduction in carbon residue,which could be attributed to the interaction between LDPE and the heavy fractions,particularly resin and asphaltene,present in VR.These findings align with the pyrolysis behaviors exhibited by the four VR fractions.Furthermore,it was observed that the co-pyrolysis process exhibited lower activation energy as the VR ratio increased,indicating a continuous enhancement in the reactivity of the mixed samples during co-pyrolysis.

溶剂结构对萃取分离直馏柴油中不同环数芳烃的影响

“双碳”目标为我国炼化行业带来巨大挑战,产品结构调整势在必行.直馏柴油作为重要的石油一次加工产品,包含约80 wt%烷烃,是优质的低碳烯烃裂解原料.然而20 wt%的芳烃易在裂解过程中结焦,导致生产周期短,乙烯收率仅20 wt%左右.因此,需对直馏柴油进行高效的芳烃脱除.为此,本研究通过量子化学计算耦合液液相平衡实验的方法,对直馏柴油溶剂萃取脱芳烃过程中溶剂结构与不同环数芳烃的萃取性能关系进行探究.结果发现,强极性、环状且空间位阻较小的溶剂利于直馏柴油芳烃的脱除,随着芳烃环数的增加,其与溶剂的相互作用位点增多,脱除率和选择性越强.这不仅为芳烃萃取溶剂的优化提供理论支撑,也为不同环数芳烃的更精细的分离提供了思路.

表面活性物质影响下单个自由上升微气泡传质过程的直接数值模拟

2017年,国际标准化组织将直径介于1~100μm之间的气泡定义为微气泡,本研究参照上述定义,针对微气泡容易受到表面活性物质影响的特点,通过直接数值模拟对不同尺寸单个自由上升微气泡在表面活性物质影响下的传质速率进行研究。通过与模拟结果对比发现,微气泡的运动速度及传质速率均可用Clift等总结的爬流范围内的理论进行较为准确的预测。表面活性物质在微气泡表面的吸附会降低气泡的液相传质系数,但对于受表面活性物质影响程度较大的微气泡,其液相传质系数随气泡尺寸减小呈持续增加趋势,而与洁净微气泡先减小后增加的趋势有所不同。因此在无法排除表面活性物质影响的应用场合,进一步缩小微气泡的初始尺寸,不仅可以增加气相的比表面积,微气泡的液相传质系数也会进一步增加,其传质能力将得到进一步加强。

清洁油品生产中溶剂萃取分离技术的研究进展

溶剂萃取分离技术广泛应用于石油化工领域,为石油石化产品的分离和提纯生产提供了有力的技术支撑.本文介绍了溶剂萃取分离技术在清洁油品生产过程中的研究进展,如芳烃抽提、溶剂萃取脱硫和关键组分定向分离技术等;分析讨论了溶剂萃取分离技术的优劣势,并就国VI汽油生产中烯烃的转化、汽油产品结构调整等社会急需解决的难题,对溶剂萃取分离技术的发展进行了展望.

Particle clustering(mesoscale structure)of high-flux gas-solid circulating fluidized bed

Particle clustering is an important dynamic phenomenon in circulating-fluidized-bed(CFBs)systems,and has been suggested as a key contributing factor to the non-uniform hydrodynamics of CFBs.Studies show that particle clusters can be affected by solids flux,in terms of frequency,duration,and solids holdup.To understand the characteristics of particle clusters under high-solids-flux conditions,experimental and modeling studies in high-solids-flux gas-solids CFBs were reviewed and summarized.Optical and electrical measurements and imaging methods were used to monitor the particle-clustering phenomenon in CFBs.Particles were found to cluster in high-flux CFBs,and were characterized by a denser cluster-solids holdup and a shorter time fraction,which was different from the behavior in low-flux CFBs.Particle properties affected particle clustering in high-flux CFBs significantly.In modeling work,Eulerian-Eulerian and Eulerian-Lagrangian methods were used to study the particle-cluster characteristics.Good results can be obtained by using the Eulerian-Eulerian method to simulate the CFB system,especially the high-flux CFBs,and by considering the effects of particle clusters.The Eulerian-Lagrangian method is used to obtain detailed cluster characteristics.Because of limits in computing power,no obvious results exist to model particle clusters under high-solids-flux conditions.Because high-solids-flux conditions are used extensively in industrial applications,further experimental and numerical investigations on the clustering behavior in HF/DCFBs are required.

Self-assembly with varying hydrophobic centers:Synthesis of red blood cell-like basic magnesium carbonate microspheres

Basic magnesium carbonate microspheres with a red blood cell （RBC）-like appearance and diameters of ~3μm were synthesized by amphiphilic molecule-participated self-assembly under hydrothermal conditions, In the self-assembly, sodium dodecyl benzene sulfonate served as a template for the formation of Mg（OH）2 spherical micelles and also as a reactant precursor that releases CO2 to react with Mg（OH）2. The growth of the microspheres is driven by the continuous generation of new hydrophobic centers because of the consumption of hydrophilic poles （--SO3-）. The surfactant-directed self-assembly can be applied to the synthesis of other carbonate or metallic oxide self-assemblies, indicating that it is a universal self-assembly method for amphiphilic molecules.

Numerical simulation of gas-solid flow with two fluid model in a spouted-fluid bed

The flow characteristics in a spouted-fluid bed differ from those in spouted or fluidized beds because of the injection of the spouting gas and the introduction of a fluidizing gas. The flow behavior of gas-solid phases was predicted using the Eulerian-Eulerian two-fluid model （TFM） approach with kinetic theory for granular flow to obtain the flow patterns in spouted-fluid beds. The gas flux and gas incident angle have a significant influence on the porosity and particle concentration in gas-solid spouted-fluid beds. The fluidizing gas flux affects the flow behavior of particles in the fountain. In the spouted-fluid bed, the solids volume fraction is low in the spout and high in the annulus. However, the solids volume fraction is reduced near the wall.

One-step synthesis of basic magnesium sulfate whiskers by atmospheric pressure reflux

We have developed a one-step process for the synthesis of basic magnesium sulfate （5Mg（OH）2-MgSO4-3H20, abbreviated as 513MOS） whiskers from MgSO4,7H20 and MgO by refluxing at atmospheric pressure. The process shows potential for the low-cost mass production of controlled- structure whiskers. Their 0.3-1.0 μm diameter and 40-80 μm length correspond to an aspect ratio of 40-260. The 513MOS whisker morphology is related closely to MgSO4 concentration and reflux time. The optimized MgSO4 concentration is 1.2-1.5 mol/L with a 25-30 h reflux time. X-ray diffractometry revealed that the b-axis is the predominant growth direction of the whiskers. Their growth mechanism is by the relatively slow liquid-phase deposition of Mg2＋, OH-, and SO42-. The long reaction time and high MgSO4 concentration are conducive to the formation of 513MOS whiskers under gentle reaction conditions. Porous MgO whiskers with a fibrous structure were obtained after calcination of the 513MOS whiskers at 1020 ℃.

Effect of wall boundary condition on CFD simulation of CFB risers

The effect of solid-phase wall boundary condition on the numerical simulation of gas-solid flow in CFB risers containing FCC particles was investigated using the two-fluid model incorporating the kinetic the- ory of granular flow. Both the Gidaspow drag model and the EMMS-based drag model were used. The Johnson and Jackson （1987） wall boundary condition was applied to describe the interaction between particles and wall. Based on the experimental system of Li and Kwauk （1994）, parametric studies of spec- ularity coefficient （cp = 1.0, 0.6, 0.0005, 0.00005, 0） and particle-wall restitution coefficient （ew = 0.6, 0.9, 0.95, 0.99, 0.999） were performed to evaluate their effects on axial voidage profile, solids flux, meso-scale and heterogeneous structures. Simulation results showed that solid-phase wall boundary condition had little effect on axial voidage profile when the Gidaspow drag model was used. However, the specular- ity coefficient ~a had a pronounced influence on flow behavior when the EMMS-based drag model was used, and a small specularity coefficient （cp = 0.00005, 0） could result in better agreement with exper- imental data. The particle-wall restitution coefficient ew plays but a minor role in the holistic flow characteristics.

Desulfurization mechanism of FCC gasoline:A review

This paper reviews the most important developments on the desulfurization mechanism of Fluid Catalytic Cracking(FCC)gasoline.First,the origin of sulfur compounds in FCC gasoline and the current developed desulfurization approaches and technologies are briefly introduced,and then the researches on desulfurization mechanism are summarized from experimental and theoretical perspectives.Further researches on the desulfurization mechanism will lay a foundation for optimizing desulfurization sorbents and technologies.

Porous carbon spheres anode with the stable output of low delithiation plateau and constant delithiation ratio for lithium ion hybrid capacitor

Porous carbon spheres derived from the facile hydrothermal treatment associated with the calcination process exhibit the good spherical morphology and unique porous structure.For the Li-based half-cell test,porous carbon spheres electrode not only exhibits larger reversible capacities and better compatibility as compared to the widely-used graphite,but also provides stable delithiation plateaus under different current density.Additionally,the delithiation ratio below 1 V almost accounts for a constant value(around 70%)with the increase of current density,evidencing that Li intercalation storage is the dominant model and Li insertion/extraction processes are propitious.The lithium ion hybrid capacitor configured with S-doped mesoporous graphene and porous carbon spheres as cathode and anode,delivers satisfied energy and power densities(up to 177 Wh kg^(−1) and 12,303 W kg^(−1),respectively)as well as long-term cyclability,which is superior to the corresponding S-doped mesoporous graphene//graphite and activated carbon//porous carbon spheres.In addition,the developed synthesis strategy is in favor of the realization of the scalable production of porous carbon spheres.