Probing deactivation by coking in catalyst pellets for dry reforming of methane using a pore network model

Dry reforming of methane(DRM) is an attractive technology for utilizing the greenhouse gases(CO_(2) and CH_(4)) to produce syngas. However, the catalyst pellets for DRM are heavily plagued by deactivation by coking, which prevents this technology from commercialization. In this work, a pore network model is developed to probe the catalyst deactivation by coking in a Ni/Al_(2)O_(3) catalyst pellet for DRM. The reaction conditions can significantly change the coking rate and then affect the catalyst deactivation. The catalyst lifetime is higher under lower temperature, pressure, and CH_(4)/CO_(2) molar ratio, but the maximum coke content in a catalyst pellet is independent of these reaction conditions. The catalyst pellet with larger pore diameter, narrower pore size distribution and higher pore connectivity is more robust against catalyst deactivation by coking, as the pores in this pellet are more difficult to be plugged or inaccessible.The maximum coke content is also higher for narrower pore size distribution and higher pore connectivity, as the number of inaccessible pores is lower. Besides, the catalyst pellet radius only slightly affects the coke content, although the diffusion limitation increases with the pellet radius. These results should serve to guide the rational design of robust DRM catalyst pellets against deactivation by coking.

CF-BFT:A Dual-Mode Byzantine Fault-Tolerant Protocol Based on Node Authentication

The consensus protocol is one of the core technologies in blockchain,which plays a crucial role in ensuring the block generation rate,consistency,and safety of the blockchain system.Blockchain systems mainly adopt the Byzantine Fault Tolerance(BFT)protocol,which often suffers fromslow consensus speed and high communication consumption to prevent Byzantine nodes from disrupting the consensus.In this paper,this paper proposes a new dual-mode consensus protocol based on node identity authentication.It divides the consensus process into two subprotocols:Check_BFT and Fast_BFT.In Check_BFT,the replicas authenticate the primary’s identity by monitoring its behaviors.First,assume that the systemis in a pessimistic environment,Check_BFT protocol detects whether the current environment is safe and whether the primary is an honest node;Enter the fast consensus stage after confirming the environmental safety,and implement Fast_BFT protocol.It is assumed that there are 3f+1 nodes in total.If more than 2f+1 nodes identify that the primary is honest,it will enter the Fast_BFT process.In Fast_BFT,the primary is allowed to handle transactions alone,and the replicas can only receive the messages sent by the primary.The experimental results show that the CF-BFT protocol significantly reduces the communication overhead and improves the throughput and scalability of the consensus protocol.Compared with the SAZyzz protocol,the throughput is increased by 3 times in the best case and 60%in the worst case.

Acoustic radiation force on a rigid cylinder between two impedance boundaries in a viscous fluid

Acoustofluidic technology combines acoustic and microfluidic technologies to realize particle manipulation in microchannels driven by acoustic waves,and the acoustic radiation force(ARF)with boundaries is important for particle manipulation in an acoustofluidic device.In the work reported here,the ARF on a free cylinder immersed in a viscous fluid with an incident plane wave between two impedance boundaries is derived analytically and calculated numerically.The influence of multiple scattering between the particle and the impedance boundaries is described by means of image theory,the finite-series method,and the translational addition theorem,and multiple scattering is included partly in image theory.The ARF on a free rigid cylinder in a viscous fluid is analyzed by numerical calculation,with consideration given to the effects of the distances from cylinder edge to boundaries,fluid viscosity,cylinder size,and boundary reflectivity.The results show that the interaction between the two boundaries and the cylinder makes the ARF change more violently with different frequencies,while increasing the viscosity can reduce the amplitude of the ARF in boundary space.This study provides a theoretical basis for particle manipulation by the ARF in acoustofluidics.

Modeling of propane dehydrogenation combined with chemical looping combustion of hydrogen in a fixed bed reactor

A redox process combining propane dehydrogenation(PDH)with selective hydrogen combustion(SHC)is proposed,modeled,simulated,and optimized.In this process,PDH and SHC catalysts are physically mixed in a fixed-bed reactor,so that the two reactions proceed simultaneously.The redox process can be up to 177.0%higher in propylene yield than the conventional process where only PDH catalysts are packed in the reactor.The reason is twofold:firstly,SHC reaction consumes hydrogen and then shifts PDH reaction equilibrium towards propylene;secondly,SHC reaction provides much heat to drive the highly endothermic PDH reaction.Considering propylene yield,operating time,and other factors,the preferable operating conditions for the redox process are a feed temperature of 973 K,a feed pressure of 0.1 MPa,and a mole ratio of H_(2) to C_(3)H_(8) of 0.15,and the optimal mass fraction of PDH catalyst is 0.5.This work should provide some useful guidance for the development of redox processes for propane dehydrogenation.

miR-933 accelerates the growth of liver cancer cells by enhancing pyruvate kinase isoform M2

MicroRNAs(miRNAs)have been found to play an important role in human tumorigenesis.A study indicates that the plasma level of miR-933 was elevated in patients with dementia.1 Notably,miR-933(RS79402775)may contribute to the reduction of gastric cancer susceptibility.

3,7-二甲基-7-羟基-2-辛烯-6-内酯类似物的合成及杀菌活性

以环氧化-内酯化和Sharpless不对称双羟基化反应作为关键步骤,以55%~90%的总收率实现了消旋及光活性3,7-二甲基-7-羟基-2-辛烯-6-内酯类似物的合成.它们的结构经过^(1)H NMR,^(13)C NMR,HR-ESI-MS和X射线衍射的表征.对它们的杀菌活性进行了评价,结果表明活性最好的化合物3-苯基-7-甲基-7-羟基-2-辛烯-6-内酯(4)和3-(呋喃-2-基)-7-甲基-7-羟基-2-辛烯-6-内酯(5)对6种植物病原菌的EC_(50)值为0.5-20.0μg/mL,可以作为先导结构进行进一步结构优化.

金属有机骨架材料的复合成型

金属有机骨架材料(MOFs)是由有机配体与金属离子(簇)配位而成的有序杂化多孔框架晶体材料,具有比表面积高、密度低、孔结构可调、配体可设计及易修饰等特性,已广泛应用于分离、催化、传感和药物递送等研究领域。MOFs本身以粉体形式存在,在实际应用中不易于加工处理和回收再利用,甚至会导致粉体污染。因此对MOFs粉末进行复合成型,制备成复合颗粒或者膜材料,有利于推进其工业应用。本文按照MOFs制备和成型的先后顺序,对MOFs复合微珠、薄膜和混合基质膜成型体的制备方法进行综述,对推进MOFs成型体的大规模制备以及开发新的MOFs成型方法提供技术参考。

Multifunctional polymeric micelle-based chemo-immunotherapy with immune checkpoint blockade for efficient treatment of orthotopic and metastatic breast cancer

Immunotherapy has become a highly promising paradigm for cancer treatment. Herein, a chemo-immunotherapy was developed by encapsulating chemotherapeutic drug doxorubicin(DOX) and Toll-like receptor 7 agonist imiquimod(IMQ) in low molecular weight heparin(LMWH)-D-α-tocopheryl succinate(TOS) micelles(LT). In this process, LMWH and TOS were conjugated by ester bond and they were not only served as the hydrophilic and hydrophobic segments of the carrier, but also exhibited strong anti-metastasis effect. The direct killing of tumor cells mediated by DOX-loaded micelles(LT-DOX)generated tumor-associated antigens, initiating tumor-specific immune responses in combination with IMQ-loaded micelles(LT-IMQ). Furthermore, the blockade of immune checkpoint with programmed cell death ligand 1(PD-L1) antibody further elevated the immune responses by up-regulating the maturation of DCs as well as the ratios of CD8+ CTLs/Treg and CD4+ Teff/Treg. Therefore, such a multifunctional strategy exhibited great potential for inhibiting the growth of orthotopic and metastatic breast cancer.

Metal-organic framework UiO-66 membranes

Metal-organic frameworks(MOFs)have emerged as a class of promising membrane materials.UiO-66 is a prototypical and stable MOF material with a number of analogues.In this article,we review five approaches for fabricating UiO-66 polycrystalline membranes including synthesis,secondary synthesis,biphase synthesis,gas-phase deposition and electrochemical deposition,as well as their applications in gas separation,pervaporation,nanofiltration and ion separation.On this basis,we propose possible methods for scalable synthesis of UiO-66 membranes and their potential separation applications in the future.

Development of a simplified n-heptane/methane model for high-pressure direct-injection natural gas marine engines

High-pressure direct-injection (HPDI) of natu- ral gas is one of the most promising solutions for future ship engines, in which the combustion process is mainly controlled by the chemical kinetics. However, the employment of detailed chemical models for the multi-dimensional combustion simulation is significantly expensive due to the large scale of the marine engine. In the present paper, a reduced n-heptane/methane model consisting of 35-step reactions was constructed using multiple reduction approaches. Then this model was further reduced to include only 27 reactions by utilizing the HyChem (Hybrid Chemistry) method. An overall good agreement with the experimentally measured ignition delay data of both n-heptane and methane for these two reduced models was achieved and reasonable predictions for the measured laminar flame speeds were obtained for the 35-step model. But the 27-step model cannot predict the laminar flame speed very well. In addition, these two reduced models were both able to reproduce the experimentally measured in-cylinder pressure and heat release rate profiles for a HPDI natural gas marine engine, the highest error of predicted combustion phase being 6.5%. However, the engine-out CO emission was over-predicted and the highest error of predicted NOx emission was less than 12.9%. The predicted distributions of temperature and equivalence ratio by the 35-step and 27-step models are similar to those of the 334-step model. However, the predicted distributions of OH and CH2O are significantly different from those of the 334-step model. In short, the reduced chemical kinetic models developed provide a high-efficient and dependable method to simulate the characteristics of combustion and emissions in HPDI natural gas marine engines.

Divergent synthesis of four isomers of 6,7-dihydroxy-3,7-dimethyloct-2-enoic acid,esters and evaluation for the antifungal activity

The four isomers of 6,7-dihydroxy-3,7-dimethyloct-2-enoic acid 2 were synthesized via the selective direct Sharpless asymmetry dihydroxylation of geraniol as the key step in 35.0%-48.0% overall yields with91.9%-97.7% ee values for esters 4 and 31,3%-36.4% overall yields with 90.3-97.5% ee values for acids 2 using cis-and trans-geraniol as raw materials. Their structures were characterized by;H,;C NMR and HR-ESI-MS data. The in vivo bioassay results showed that the chiral acid（Z, S）-2 was a good lead compound with 80%-100% inhibitory rates against P. cubensis, E. graminis, P. sorghi and C. gloeosporioides at the concentration of 400 μg/mL.

Heterojunction architecture of Nb_(2)O_(5)/g-C_(3)N_(4)for enhancing photocatalytic activity to degrade organic pollutants and deactivate bacteria in water

Water pollution has become a serious problem owing to the development of society.Photocatalysis is a promising approach to remove various pollutants in water,such as organic pollutants and antibiotic resistance bacteria.Meanwhile,the design of heterojunction between two semiconductors is an effective path to improve photocatalytic properties due to its potential in improving separation and transfer of photoinduced carriers.In this study,Nb_(2)O_(5)/g-C_(3)N_(4)(NO/CN)composite materials were prepared through a one-step heating method.Characterizations confirmed successful preparation of NO/CN heterojunction structure and better optical properties than pure g-C_(3)N_(4) and Nb_(2)O_(5).NO/CN composite materials showed excellent photocatalytic efficiency for Escherichia coli(E.coli)inactivation(95%)compared with the pure Nb_(2)O_(5)(10%) and g-C_(3)N_(4)(77%).Meanwhile,NO/CN exhibited better organic pollutants removal(Rh B for94%,methyl orange(MO)for 15%and methylene blue(MB)for 87%)under visible light,which is likely owing to the heterojunction structure between g-C_(3)N_(4) and Nb_(2)O_(5) that leads to the good separation of photogenerated electron-hole pair.Free radical scavenging and electron spin resonance(ESR)experiments demonstrated that superoxide radicals(·O_(2)^(-)) and holes(h^(+)) were the dominant radicals.Therefore,the NO/CN was proposed to be a promising material for effective disinfection and removal of organic contaminants in water treatment.

Polybenzimidazole(PBI)and benzimidazole-linked polymer(BILP)membranes

Polybenzimidazoles(PBIs)and benzimidazole-linked polymers(BILPs)have exceptional thermal and chemical stability,and hence,their membranes were developed and used under harsh conditions.In this review,the formation,structures,and properties of these polymers are studied follow by the fabrication of membranes.Applications,such as gas separation,organic solvent nanofiltration,water treatment,pervaporation and proton exchange,are extensively reviewed.The relationship of membrane performance and structure is established,highlighting the importance of processing protocols and post treatments.Future directions are provided on the basis of the conclusions.

The risk management of perishable supply chain based on coloured Petri Net modeling

The supply chain of perishable products is a combination of information organization,sharing and integration.The information modeling of supply chain is constructed to abstract key quality information including environment information,processing procedures and product quality assessments based on principle of quality safety factors and property of decay rate.The coloured Petri Net is applied for integrated description of independent information classification,aiming at risk identification and risk management framework.Well,according to the quality deterioration tendency,risk grades management and decision-making system are established.Practically,the circulation system of aquatic products is studied in this paper for full processing description.The simulation experiments are manipulated on environmental information,processing information and product quality information by the coloured Petri Net.Eventually,the conclusion turns out precisely as such that the coloured Petri Net conclusive for information classification and information transmission while integrated information management is available of efficient risk identification and decision-making system in supply chain of perishable products.Meanwhile,the validity of evaluating management and shelf-life estimation of perishable products are technically feasible.