Scale-up and thermal stability analysis of fluidized bed reactors for ethylene polymerization

A set of hydrodynamic similarity laws is applied to the scale-up of ethylene polymerization fluidized bed reactors(FBRs)under the condensed mode operation.The thermal stability of open-loop controlled FBRs is investigated by the homotopy continuation method.And the Hopf bifurcation point is selected as an index of the thermal stability similarity.The simulation results show the similarity in state variables,operation parameters,the space-time yield(STY),and the thermal stability of FBRs with different scales.Furthermore,the thermal stability behaviors and similarity of the closed-loop controlled FBRs with different scales are analyzed.The observed similar trend of Hopf bifurcation curves reveals the similarity in the thermal stability of closed-loop controlled FBRs with different scaling ratios.In general,the results of the thermal stability similarity confirm that the hydrodynamics scaling laws proposed in the work are applicable to the scale-up of FBRs under the condensed mode operation.

Well-Dispersed Graphene Enhanced Lithium Complex Grease Toward High-Efcient Lubrication

Graphene as a lubricating additive holds great potential for industrial lubrication. However, its poor dispersity and compatibility with base oils and grease hinder maximizing performance. Here, the infuence of graphene dispersion on the thickening efect and lubrication function is considered. A well-dispersed lubricant additive was obtained via trihexyl tetradecyl phosphonium bis(2-ethylhexyl) phosphate modifed graphene ([P_(66614)][DEHP]-G). Then lithium complex grease was prepared by saponifcation with 12-OH stearic acid, sebacic acid, and lithium hydroxide, using polyalphaolefn (PAO20) as base oil and the modifed-graphene as lubricating additive, with the original graphene as a comparison. The physicochemical properties and lubrication performance of the as-prepared greases were evaluated in detail. The results show that the as-prepared greases have high dropping point and colloidal stability. Furthermore, modifed-graphene lithium complex grease ofered the best friction reduction and anti-wear abilities, manifesting the reduction of friction coefcient and wear volume up to 18.84% and 67.34%, respectively. With base oil overfow and afux, well-dispersed [P_(66614)][DEHP]-G was readily adsorbed to the worn surfaces, resulting in the formation of a continuous and dense graphene deposition flm. The synergy of deposited graphene-flm, spilled oil, and adhesive grease greatly improves the lubrication function of grease. This research paves the way for modulating high-performance lithium complex grease to reduce the friction and wear of movable machinery.

Synthesis of a new ordered mesoporous NiMoO_4 complex oxide and its efficient catalytic performance for oxidative dehydrogenation of propane

Highly ordered mesoporous NiMoO4material was successfully synthesized using mesoporous silica KIT-6 as hard template via vacuum nanocasting method. The structure was characterized by means of XRD, TEM, N2adsorption-desorption, Raman and FT-IR. The mesoporous NiMoO4with the coexistence of α-NiMoO4and β-NiMoO4showed well-ordered mesoporous structure, a bimodal pore size distribution and crystalline framework. The catalytic performance of NiMoO4was investigated for oxidative dehydrogenation of propane. It is demonstrated that the mesoporous NiMoO4catalyst with more surface active oxygen species showed better catalytic performance in oxidative dehydrogenation of propane in comparison with bulk NiMoO4.

Clinical Analysis of Bevacizumab Plus FOLFIRI Regimen as Front-Line Therapy for Chinese Patients with Advanced Colorectal Cancer

The study was designed to evaluate the therapeutic and side effects of Bevacizumab plus FOLFIRI regimen as front-line therapy for Chinese patients with advanced colorectal cancer. A total of 15 previously untreated patients with advanced colorectal cancer received Bevacizumab plus FOLFIRI regimen as font-line therapy, in detail, irinotecan 180 mg/m2 was given intravenously on day1, then calcium folinate (CF) 200 mg/m2, F-fluorouracil (5-Fu) 400 mg/m2 given in bolus immediately after CF, day 1 - 2;5-Fu 600 mg/2 given continuously after bolus for 22 hours on day1, day2;Bevacizumab was given intravenously at dosage of 5 mg/kg, on day-1. Therapeutic and side effects were evaluated at least after four cycles of treatment. The results showed that all the cases among the group were valid for response evaluation, with CR 0, PR 10, SD 3, and PD 2. The response rate is 66.7% and median time to progression (mTTP) was 10.6 months. The main toxicities were bone marrow suppression, nausea and vomiting, stomach pain and diarrhea;there was no chemotherapy-related death. The data suggested that the combination regimen with Bevacizumab plus FOLFIRI regimen was effective as front-line therapy for Chinese patients with advanced colorectal cancer, and the side effects were tolerable and manageable.

Solvent-free carbon sphere nanofluids towards intelligent lubrication regulation

By simply switching the electrical circuit installed on steel/steel contact,the tribological behaviors of nanofluids(NFs)can be regulated in real time,thereby achieving the desired performance of friction reduction and wear resistance.Herein,solvent-free carbon spherical nanofluids(C-NFs)were successfully prepared for intelligent lubrication regulation.C-NFs with excellent lubrication performance can immediately reduce the coefficient of friction(COF)despite applying a weak electric potential(1.5 V).Moreover,polyethylene glycol 400(PEG400)containing 5.0 wt%C-NFs remained responsive to electrical stimulation under the intermittent voltage application with an average coefficient of friction(ACOF)reduction of 20.8%over PEG400.Such intelligent lubrication regulation of C-NFs under an external electric field(EEF)mainly depends on the orderly arranged double-electric adsorption film of ion canopy-adsorbed carbon spheres(CSs).The intermittent electrical application can continuously reinforce the adsorption film and its durability for real-time controlling the sliding interfaces.Electrical-stimulation-responsive intelligent lubricants provide a new technical support for realizing intelligent stepless control of devices.

Alkali/alkaline-earth metal-modified MnO_(x) supported on three-dimensionally ordered macroporous–mesoporous Ti_(x)Si+(1-x)O_(2) catalysts:Preparation and catalytic performance for soot combustion

The performance of catalysts used in after-treatment systems is the key factor for the removal of diesel soot,which is an important component of atmosphericfine particle emissions.Herein,three-dimensionally ordered macroporous–mesoporous Ti_(x)Si+(1-x)O_(2)(3DOM-m Ti_(x)Si+(1-x)O_(2)) and its supported MnO_(x)catalysts doped with different alkali/alkaline-earth metals (AMnO_(x)/3 DOM-m Ti_(0.7)Si_(0.3)O_(2)(A:Li,Na,K,Ru,Cs,Mg,Ca,Sr,Ba)) were prepared by mesoporous template (P123)-assisted colloidal crystal template (CCT) and incipient wetness impregnation methods,respectively.Physicochemical characterizations of the catalysts were performed using scanning electron microscopy,X-ray diffraction,N_(2)adsorption–desorption,H_(2)temperature-programmed reduction,O_(2)temperature-programmed desorption,NO temperature-programmed oxidation,and Raman spectroscopy techniques;then,we evaluated their catalytic performances for the removal of diesel soot particles.The results show that the 3DOM-m Ti_(0.7)Si_(0.3)O_(2)supports exhibited a well-defined 3DOM-m nanostructure,and AMnO_(x)nanoparticles with 10–50 nm were evenly dispersed on the inner walls of the uniform macropores.In addition,the as-prepared catalysts exhibited good catalytic performance for soot combustion.Among the prepared catalysts,CsMnO_(x)/3DOM-m Ti_(0.7)Si_(0.3)O_(2)had the highest catalytic activity for soot combustion,with T10,T50,and T90(the temperatures corresponding to soot conversion rates of 10%,50%,and 90%) values of 285,355,and 393℃,respectively.The high catalytic activity of the CsMnO_(x)/3 DOM-m Ti_(0.7)Si_(0.3)O_(2)catalysts was attributed to their excellent low-temperature reducibility and homogeneous macroporous–mesoporous structure,as well as to the synergistic effects between Cs and Mn species and between CsMnO_(x)and the Ti_(0.7)Si_(0.3)O_(2)support.

K-modified MnO_(δ)catalysts with tunnel structure and layered structure:Facile preparation and catalytic performance for soot combustion

Air pollution from particulate matter produced by incomplete combustion of diesel fuel has become a serious environmental pollution problem,which can be addressed by catalytic combustion.In this work,a series of K-modified MnO_(δ)catalysts with different microstructures were synthesized by the hydrothermal method,the relationship between structure of the catalysts and their catalytic performance for soot combustion was studied by characterization techniques and density functional theory(DFT)calculations.Results showed that the prepared catalysts had good catalytic performance for soot combustion and could completely oxidize soot at temperatures below 400℃.The cryptomelane-type K_(2−x)Mn_(8)O_(16)(K-OMS-2)with tunnel structure had excellent NO oxidation capacity and abundance of Mn^(4+)ions(Mn^(4+)/Mn^(3+)=1.24)with good redox ability,it demonstrated better soot combustion performance than layered birnessite-type K_(2)Mn_(4)O_(8)(K-OL-1).The T_(10),T_(50),T_(90)temperatures of KOMS-2 were 269,314,346℃,respectively.The K-OMS-2 catalyst also showed excellent stability after five catalytic cycles,with T_(10),T_(50),T_(90)values holding in the ranges of 270±2,316±2,348±3℃,respectively.

Flour-derived borocarbonitride enriched with boron-oxygen species for the oxidative dehydrogenation of propane to olefins

The preparation of porous materials by the simple and low-cost methods is one of the hot topics in materials science.Here,the porous carbon-incorporated BN(P-CBN)was synthesized from the low-cost flour by a fermentation combined with freezedrying technology and ammonolysis.P-CBN-x samples not only maintain the pores of the fermented dough,but also produce abundant oxygen-containing boron species(B-OH,O-O and B-O).Due to the unique structural advantages,P-CBN-x catalysts exhibit remarkably better catalytic performance than bulk BN for the oxidative dehydrogenation of propane(ODHP)to produce olefins.Attractively,P-CBN-23 obtains high C_(3)H_(8 )conversion of 62.1%and olefin yield of 42.7%.In-situ DRIFTS experiments and DFT calculations demonstrate the B-OO-B species in P-CBN-x framework is the most active species for the C3H8activation and the B-O…O-B species can be readily regenerated by O_(2),thus promoting the conversion of propane to olefin.

Insights into the tribological behavior of choline chloride-urea and choline chloride-thiourea deep eutectic solvents

Deep eutectic solvents(DESs)have been considered as novel and economic alternatives to traditional lubricants because of their similar physicochemical performance.In this study,choline chloride(ChCl)DESs were successfully synthesized via hydrogen-bonding networks of urea and thiourea as the hydrogen bond donors(HBDs).The as-synthesized ChCl-urea and ChCl-thiourea DESs had excellent thermal stability and displayed good lubrication between steel/steel tribo-pairs.The friction coefficient and wear rate of ChCl-thiourea DES were 50.1%and 80.6%,respectively,lower than those of ChCl-urea DES for GCr15/45 steel tribo-pairs.However,for GCr15/Q45 steel,ChCl-urea DES decreased the wear rate by 85.0%in comparison to ChCl-thiourea DES.Under ChCl-thiourea DES lubrication,the tribo-chemical reaction film composed of FeS formed at the interfaces and contributed to low friction and wear.However,under high von Mises stress,the film could not be stably retained and serious wear was obtained through direct contact of friction pairs.This illustrated that the evolution of the tribo-chemical reaction film was responsible for the anti-friction and anti-wearproperties of the DESs.

Design and analysis of a hypersonic inlet with an integrated bump/forebody

Numerical simulations and experiments showed that bump inlet had a remarkable effect on boundary layer diversion of supersonic flow.However,the design and analysis of bump in hypersonic flow was still few.In this paper,the mechanism of a supersonic bump inlet is introduced to the design of hypersonic forebody.A hypersonic inlet with an integrated bump/forebody is obtained by the Method Of Characteristics(MOC)based on a chin inlet.Numerical simulations show that the modified inlet achieves diversion of low-speed flow.Besides,the integrated bump/-forebody is also beneficial to inlet start.During the starting process,the shape of the separation zone is rebuilt by the modified forebody surface which makes spillage much easier.This new design leads to a reduction of the self-start Mach number by 0.95.

Carbon-based solid-liquid lubricating coatings for space applications-A review

Despite continuous improvements in machine elements over the past few decades,lubrication issues have impeded human exploration of the universe because single solid or liquid lubrication systems have been unable to satisfy the ever-increasing performance requirements of space tribology.In this study,we present an overview of the development of carbon-based films as protective coatings,with reference to their high hardness,low friction,and chemical inertness,and with a particular focus on diamond-like carbon(DLC)films.We also discuss the design of carbon-based solid-liquid synergy lubricating coatings with regards to their physicochemical properties and tribological performance.Solid-liquid composite coatings are fabricated via spinning liquid lubricants on solid lubricating films.Such duplex lubricating coatings are considered the most ideal lubrication choice for moving mechanical systems in space as they can overcome the drawback of adhesion and cold-welding associated with solid films under harsh space conditions and can minimize the crosslinking or chain scission of liquid lubricants under space irradiation.State of the art carbon-based solid-liquid synergy lubricating systems therefore holds great promise for space applications due to solid/liquid synergies resulting in superior qualities including excellent friction reduction and anti-wear properties as well as strong anti-irradiation capacities,thereby meeting the requirements of high reliability,high precision,high efficiency,and long lifetime for space drive mechanisms.

Amino-functionalized Ti_(3)C_(2)T_(x) with anti-corrosive/wear function for waterborne epoxy coating

Two-dimensional Ti_(3)C_(2)T_(x) flakes have great application potential in various areas due to their optical,electronic,electrochemical and mechanical properties,but their anti-corrosion and wear-resistance performance were not well understood.The difficulties in achieving good dispersity and interface interaction of inorganic additives in organic coatings hinder the incorporation of Ti_(3)C_(2)T_(x) into the epoxy coating.Here,few-layered Ti_(3)C_(2)T_(x) sheets with amino-functionalization were prepared,and as reinforced-additives were added into the waterborne epoxy coating.Anti-corrosion and tribological properties of as-prepared composite coatings were investigated in detail.The results reveal that the composite coating with 0.5 wt.%amino-functionalized Ti_(3)C_(2)T_(x) sheets shows excellent corrosion protection(the lowest frequency impedance was 3.12×10^(9) cm^(2))and wear resistance(wear rate was reduced by 72.74%).The greatly improving performance of composite coatings mainly depends on:(a)good dispersity and compatibility of amino-functionalized Ti_(3)C_(2)T_(x) in organic matrix,(b)high adhesion strength between coating and metal substrate and(c)the intrinsic properties of Ti3C2Tx sheets.The work provides a good path for applications of MXene as multifunctional additives.

Tribological properties of conductive lubricating greases

Three kinds of new conductive lubricating greases were prepared using lithium ionic liquids as the base oil and the polytetrafluoroethylene(PTFE)as the thickener.These lithium ionic liquids([Li(PEG)X])were obtained by blending lithium salts(LiBF4,LiPF6 and LiNTf2)with poly(ethylene glycol)(PEG)because lithium salts have an extremely high solubility in PEG.The conductivities and contact resistances of the prepared lubricating greases were investigated using the DDSJ‐308A conductivity meter and the reciprocating ball‐on‐disk UMT‐2MT sliding tester.In addition,their tribological properties were investigated in detail.Scanning electron microscopy and X‐ray photoelectron spectroscopy were employed to explore the friction mechanisms.The results suggest that the prepared lubricating greases have high conductivities and excellent tribological properties.The high conductivities are attributed to ion diffusion or migration of the lithium ionic liquids with an external electric field,and the excellent tribological properties depend on the formation of boundary protective films.

Improving the lubrication and anti-corrosion performance of polyurea grease via ingredient optimization

Thickener formulation plays a significant role in the performance characteristics of grease.The polyurea greases(PUGs)were synthesized using mineral oil(500SN)as the base oil,and by regulating the reaction of diphenylmethane diisocyanate(MDI)and different organic amines.The as‐prepared PUGs from the reaction of MDI and cyclohexylamine/p‐toluidine exhibit the optimum physicochemical and friction‐wear properties,confirming that the regulation of thickener formulation can improve the performance characteristics of grease,including friction reduction,wear,corrosion resistance,and load‐carrying capacity.The anticorrosion and lubrication properties of as‐prepared PUGs depend on good sealing functions and a boundary lubrication film(synergy of grease‐film and tribo‐chemical reaction film),as well as their chemical components and structure.

Comparative study on corrosion resistance and lubrication function of lithium complex grease and polyurea grease

In this study,lithium complex grease(LCG)and polyurea grease(PUG)were synthesized using mineral oil(500 SN)and polyalphaolefin(PAO40)as base oil,adsorbed onto lithium complex soap and polyurea as thickeners,respectively.The effects of grease formulation(thickener and base oil with different amounts(80,85,and 90 wt%)on the corrosion resistance and lubrication function were investigated in detail.The results have verified that the as-prepared greases have good anti-corrosion ability,ascribed to good salt-spray resistance and sealing function.Furthermore,the increase in the amount of base oil reduces the friction of the contact interface to some extent,whereas the wear resistance of these greases is not consistent with the friction reduction,because the thickener has a significant influence on the tribological property of greases,especially load-carrying capacity.PUG displays better physicochemical performance and lubrication function than LCG under the same conditions,mainly depending on the component/structure of polyurea thickener.The polyurea grease with 90 wt%PAO displays the best wear resistance owing to the synergistic lubrication of grease-film and tribochemical film,composed of Fe_(2)O_(3),FeO(OH),and nitrogen oxide.

Important mesoscale phenomena in gas phase fluidized bed ethylene polymerization

Gas phase fluidized bed processes have been widely applied to polyethylene production.In these processes,the flow,mass transfer,and reaction rate on the microscale and macroscale are strongly coupled because of the multiphase and multiscale nature of the fluidization system.Understanding mesoscale phenomena is therefore essential to the quantitative translation of the knowledge obtained from the microscale to the macroscale.This paper reviews the development of ethylene polymerization gas phase processes while focussing on studies regarding mesoscale phenomena.These include experimental characterizations,mathematical modelling and control strategies.Trends and future developments in this field are also discussed.

Hierarchical Ti_(3)C_(2)T_(x)@MoS_(2) heterostructures:A first principles calculation and application in corrosion/wear protection

Surface and interface engineering plays a crucial role in modulating the properties of materials,especially two-dimensional(2D)materials.Hence,a strategy,forming heterostructures with MoS_(2),is proposed to overcome the natural agglomeration of Ti_(3)C_(2)T_(x) MXene nanosheets.Most importantly,the interactions between Ti_(3)C_(2)Tx and MoS_(2) were elaborately investigated by first-principles calculations based on density functional theory(DFT)for the first time.The calculations demonstrate that van der Waals forces dominate the interface interactions of Ti_(3)C_(2)T_(x) and MoS_(2),rendering Ti_(3)C_(2)T_(x)@MoS_(2) heterostructures favorable stability.The Ti_(3)C_(2)T_(x)@MoS_(2) heterostructure composites were synthesized through a facile one-step hydrothermal method and exhibit a 2D hierarchical structure.Furthermore,the corrosion and tribological properties of epoxy composite coatings with varying proportions of Ti_(3)C_(2)T_(x)@MoS_(2) composites were studied in detail.As a result,the epoxy composite coating with 0.1 wt.%Ti_(3)C_(2)T_(x)@MoS_(2) composites(Ti_(3)C_(2)T_(x)@MoS_(2)-0.1)exhibits excellent corrosion protection and antiwear performances.The Ti_(3)C_(2)T_(x)@MoS_(2)-0.1 keeps the largest low-frequency impedance modulus(|Z|_(0.)01 Hz)and coating resistance(R_(c))during the whole immersion period.Its wear rate is 0.09μm^(3)/(Nμm)under the load of 10 N,one half of that of pure epoxy coating(EP).This work further broadens the application of MXene-based heterostructure composites.

Synergistic lubrication of few-layer Ti_(3)C_(2)T_(x)/MoS_(2) heterojunction as a lubricant additive

The few-layer Ti_(3)C_(2)T_(x)/MoS_(2) heterostructure was successfully prepared via vertically growing of MoS_(2) nanosheets on the few-layer Ti3C2Tx matrix using hydrothermal method.The tribological properties as additive in mineral oil(150N)were evaluated in detail.The 0.3 wt% of few-layer Ti_(3)C_(2)T_(x)/MoS_(2) heterostructure addition amount can reduce the friction and wear of 150N by 39% and 85%,respectively.Moreover,the enhancement effect of few-layer Ti_(3)C_(2)T_(x)/MoS_(2) on tribological properties of 150N is superior to that of few-layer Ti_(3)C_(2)T_(x),MoS_(2) nanosheets,and their mechanical mixture.Based on the characterization and analysis of wear debris and wear track,such excellent tribological properties of the few-layer Ti_(3)C_(2)T_(x)/MoS_(2) heterostructure derive from its structural advantage toward good dispersion,the synergistic lubrication of Ti_(3)C_(2)T_(x) and MoS_(2) nanosheets during the rubbing process,and the formation of tribo-film.

Tribological properties of spherical and mesoporous NiAl particles as ionic liquid additives

In this study,spherical and mesoporous NiAl particles(abbreviated as sNiAl and mNiAl)were introduced as lubricant additives into two alkyl-imidazolium ionic liquids(ILs)(l-butyl-3-methylimidazolium tetrafluoroborate(LB104)and l-butyl-3-methyl imidazolium hexafluorophosphate(LP104))to explore their tribological properties.The sNiAl and mNiAl particles were modified in-situ by anion and cation moieties of ILs through chemical interaction,thereby enhancing their dispersibility and stability in ILs.The mNiAl particles have better dispersibility than the sNiAl ones in ILs because of high specific surface area.LP104-modified sNiAl particles show better friction reduction and wear resistance,mainly relying on the synergy of the hybrid lubricant.These particles form a protective layer that prevents friction pairs from straight asperity contact and improves the tribological behaviors.

Construction of ternary PEG200-based DESs lubrication systems via tailoring tribo-chemistry

Designing novel lubricants with easily customized structures,devisable compositions,and simple and economic synthesis over traditional lubricants is critical to fulfilling complex applications,prolonging machine lifetime,and saving energy.Deep eutectic solvents(DESs),which show tunable composition,adjustable structure,easy fabrication,and environmental friendliness,are promising candidates for variable and complicated lubricants applications.To promote the use of DESs as lubricants,a series of PEG200-based DESs with active heteroatoms were fabricated to tailor the tribological performance via tribo-chemistry.Thereinto,PEG200/boric acid(BA)DES shows optimal lubrication performance by forming tribo-chemical reaction film composited of B2O3,iron oxides,and FeOOH,and PEG200/thiourea(TU)DES displays abrasive wear-reducing property by producing FeS tribo-chemical film.Given the excellent abrasive wear-resistance of PEG200/TU DES and friction reduction of PEG200/BA DES,ternary PEG200/BA/TU DESs,composited of PEG200/TU DES and PEG200/BA DES,are first exploited.The ternary DESs possess superior wettability and thermal stability,which render them potential lubricants.Tribological tests of the ternary DESs demonstrate that synergistic lubrication is achieved by forming a transfer film consisting of FexBy,BN,B2O3,and FeS.Wherein FexBy,BN,and B2O3 increase load bearing of the film,and FeS mitigates severe abrasive wear.The proposed design philosophy of novel DESs as lubricants opens up a unique realm that is unattainable by traditional DESs lubrication mechanisms and provides a platform to design next-generation DESs lubrication systems.