Carbon resistance of xNi/HTASAO5 catalyst for the production of H2 via CO2 reforming of methane

xNi/HTASAO5 catalysts (x = 2.5, 3.3, 4.4, 5.8, 8.2) were prepared for CO₂ reforming of methane. No crystalline nickel species formed on the catalysts with lower nickel content (≤4.4%), and large Ni⁰ crystallite formed on 5.8% (10 nm) and 8.2 wt%Ni/HTASAO5 (17 nm), whereas the surface concentration of Ce³⁺ decreased with Ni loading. The initial conversion of CH₄ increased from 29.5% to 46.9% with Ni loading. The xNi/HTASAO5 (x ≤ 4.4%) performed stably in the reaction due to the presence of dispersed Ni species and high surface Ce³⁺ content without coke formation, however, 5.8% and 8.2 wt%Ni/HTASAO5 exhibited decreased activity with time on stream, because of the formation of large Ni particles with lower surface Ce³⁺, leading to carbon accumulation. Thus, CH₄ conversion stabilized at about 43% and no carbon formed on 4.4 wt%Ni/HTASAO5 with optimum Ni loading.     

Unique structure of fibrous ZSM-5 catalyst expedited prolonged hydrogen atom restoration for selective production of propylene from methanol

A unique mesostructured fibrous silica@ZSM-5 (HSi@ZSM-5) catalyst was synthesized via microemulsion ZSM-5 zeolite seed assisted synthesis method and successfully applied in enhanced propylene formation in methanol to olefin (MTO) process. Characterization of the catalysts were carried out by FESEM, TEM, XRD, TGA, N₂ adsorption-desorption, NH₃ and KBr probed FTIR. Catalytic performance of as-synthesized catalyst was examined using a micro-pulse reactor and compared with the commercial HZSM-5. The reaction mechanism was elucidated by in-situ methanol FTIR spectroscopy. It was found that HSi@ZSM-5 produced higher propylene selectivity (56%) and was stable for long time on stream (80 h), nearly three-fold higher than that of commercial HZSM-5. In addition, HSi@ZSM-5 displayed higher rate of methanol dehydration, surface methoxy species generation and olefin methylation, indicating that alkene catalytic cycle is the dominant reaction mechanism. The higher selectivity towards propylene was correlated to the existence of moderate acidity which impeded the formation of paraffins and polymethylbenzene intermediates. These observations are further supported by KBr probed FTIR findings which revealed negligible paraffinic carbon species on HSi@ZSM-5. Thus, the unique fibrous silica@ZSM-5 retarded coke deposition due to suppression of undesired side reactions thereby signifying intensified propylene formation, which is highly desirable in commercial MTO processes.     

Synthesis and Biological Activity of New Brassinosteroid Analogs of Type 24-Nor-5β-Cholane and 23-Benzoate Function in the Side Chain

Brassinosteroids are polyhydroxysteroids that are involved in different plants’ biological functions, such as growth, development and resistance to biotic and external stresses. Because of its low abundance in plants, much effort has been dedicated to the synthesis and characterization of brassinosteroids analogs. Herein, we report the synthesis of brassinosteroid 24-nor-5β-cholane type analogs with 23-benzoate function and 22,23-benzoate groups. The synthesis was accomplished with high reaction yields in a four-step synthesis route and using hyodeoxycholic acid as starting material. All synthesized analogs were tested using the rice lamina inclination test to assess their growth-promoting activity and compare it with those obtained for brassinolide, which was used as a positive control. The results indicate that the diasteroisomeric mixture of monobenzoylated derivatives exhibit the highest activity at the lowest tested concentrations (1 × 10⁻⁸ and 1 × 10⁻⁷ M), being even more active than brassinolide. Therefore, a simple synthetic procedure with high reaction yields that use a very accessible starting material provides brassinosteroid synthetic analogs with promising effects on plant growth. This exploratory study suggests that brassinosteroid analogs with similar chemical structures could be a good alternative to natural brassinosteroids.     

Development of Selective TGR5 Ligands Based on the 5,6,7,8-Tetrahydro-5,5,8,8-tetramethylnaphthalene Skeleton

TGR5, a G-protein-coupled receptor (GPCR), plays an important role in several physiological functions. TGR5 activation through bile acids induces an increase in energy expenditure. Therefore, synthetic TGR5 ligands could be useful for the treatment of obesity or dyslipidemia. In this study, we designed and synthesized a set of TGR5 ligands with a 5,6,7,8-tetrahydro-5,5,8,8-tetramethylnaphthalene (TMN) skeleton, and evaluated their TGR5 agonistic activity. We also investigated the selectivity of the synthesized compounds for TGR5 relative to the farnesoid X receptor (FXR) and retinoic acid receptor (RAR). Our results show that compound 4 b [N-(2-chlorophenyl)-5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenecarboxamide] exhibited potent TGR5 agonist activity with an IC₅₀ value of 8.4 nM without significant cytotoxicity. In addition, compound 4 b showed only slight agonistic activity toward FXR and RAR at 1 μM treatment. These data indicate that compound 4 b is a selective TGR5 agonist, and could be a promising therapeutic agent for dyslipidemia.     

基于Massive MIMO及频谱叠加的5G SA网络上行优化方法

大规模多输入多输出(Multiple-Input Multiple-Output, MIMO)可以有效提升5G SA网络的上行链路数据传输速率以及可靠性。针对5G SA网络上行链路速率和覆盖不均衡的情况,提出了基于大规模MIMO的分组算法,将发送信号矢量进行分组,组内采用最大似然检测,组外采用基于正交三角分解(QR分解)的干扰消除检测,并且结合5G频谱的叠加策略,在降低算法复杂度的同时,有效提升网络覆盖和速率。通过5G SA现网实测,通过MIMO降低分组数量能够提升分组检测性能,结合上行低频段频谱叠加策略能够有效提升5G SA网络上行覆盖30%,提升5G SA网络上行平均速率40%~80%,特别是弱覆盖边缘的网络速率,最高可达600%。     

Heterofullerene C48B12-impregnated MOF-5 and IRMOF-10 for hydrogen storage: A combined DFT and GCMC simulations study

The H₂ storage properties of isoreticular metal-organic framework materials (IRMOFs), MOF-5 and IRMOF-10, impregnated with different numbers and types of heterogeneous C₄₈B₁₂ molecules were investigated using density functional theory and grand canonical Monte Carlo (GCMC) calculations. The excess hydrogen adsorption isotherms of IRMOFs at 77 K within 20 bar indicate that suitable number and type of C₄₈B₁₂ molecules play a crucial role in improving the H₂ storage properties of IRMOFs. Among the studied pure and nC₄₈B₁₂ (n = 1, 2, 4, 8) in Ci symmetry impregnating into MOF-5, at 77 K under 6 bar, MOF-5-4C₄₈B₁₂ with a 3.5 wt% and 29.9 g/L hydrogen storage density, and at 77 K under 12 bar, the pure MOF-5 with a 4.9 wt% and 31.0 g/L hydrogen storage density has the best hydrogen storage properties. Whereas, among the studied pure and nC₄₈B₁₂ (n = 1, 2, 4, 8) in S6 symmetry impregnating into IRMOF-10, IRMOF-10-8C₄₈B₁₂ always shows the best hydrogen storage properties among the pure and C₄₈B₁₂-impregnated IRMOF-10 at 77 K within 20 bar. IRMOF-10-8C₄₈B₁₂ has a 6.0 wt% and 34.6 g/L hydrogen storage density at 77 K under 6 bar, and has a 7.1 wt% and 41.4 g/L hydrogen storage density at 77 K under 12 bar. The confinement effect of IRMOFs on C₄₈B₁₂ molecules, and steric hindrance effect of C₄₈B₁₂ molecules on IRMOFs mainly affects the H₂ uptake capacity by comparing the absolute H₂ molecules in individual IRMOFs units, C₄₈B₁₂ molecules, and IRMOFs-nC₄₈B₁₂ compounds. The absolute hydrogen adsorption profiles show that eight C₄₈B₁₂ molecules impregnating into MOF-5 can exert obvious steric effects for H₂ adsorption. The saturated gravimetric and volumetric H₂ densities of IRMOF-10-8C₄₈B₁₂ higher than those of MOF-5-8C₄₈B₁₂ due to with larger free volume.     

Pd2(dba)3-catalyzed amination of C5-bromo-imidazo[2,1-b][1,3,4] thiadiazole with substituted anilines at conventional heating in Schlenk tube

ABSTRACT

An efficient Pd₂(dba)₃-catalyzed amination of C5-bromo-imidazo[2,1-b][1,3,4]thiadiazole using conventional heating is reported. The C5-bromoimidazo[2,1-b][1,3,4]thiadiazole was synthesized using a multistep approach which started by cyclization of thiosemicarbazide with a carboxylic acid to give 2-amino[1,3,4]thiadiazoles which were further treated with 2-haloketones to give imidazo[2,1-b][1,3,4]thiadiazoles. Then, the bromination of imidazothiadiazole was done using N-bromosuccinimide to give the C5-bromo-imidazo[2,1-b][1,3,4]thiadiazole. Afterward, various C-N bond-forming approaches were attempted such as S_NAr, Cu(I), Cu(II), Pd(OAc)_2, Pd₂(dba)₃ catalyst with different ligand, additive, base, solvent and temperature conditions. Out of various approaches used, only Buchwald Hartwig amination, performed with conventional heating, gave N-arylamine-5-imidazothiadiazoles. Then, 10 different anilines with different electron-withdrawing and donating groups at different positions were employed to examine the scope and limitations of the method. Salient features of this method include conventional heating in a Schlenk tube as the reaction condition, the absence of the use of toxic isocyanides, the wide nature of substituent tolerance with anilines, and moderately good product yields.     

Growth mechanism of primary Ti5Si3 phases in special brasses and their effect on wear resistance

In the present work, in-situ Ti₅Si₃ reinforced special brasses were prepared by melt reaction method. The synthesized Ti₅Si₃ phase shows various morphologies in brasses with different Ti₅Si₃ content, and the3 D morphological evolution of primary Ti₅Si₃and its growth mechanism were investigated. The Ti₅Si₃ crystal, which bears D8₈ hexagonal crystal structure, grows along <0001> direction and is revealed by{1010} faces during growth. With the increase of Ti₅Si₃ content in the brasses, the morphology of primary Ti₅Si₃significantly changes from fibers to hexagonal prisms to short-rods with hollow. In addition,the influence of Ti₅Si₃ volume fraction and morphology on the wear behavior of special brass was also revealed. It was substantiated that the wear resistance increases with the increasing volume fraction of Ti₅Si₃, and the corresponding wear mechanism changes from delamination to slight adhesive wear and abrasive wear. However, the friction coefficient shows an abnormal increase when most of the Ti₅Si₃ containing hollows appears in the brass. That is mainly due to the fact that the Ti₅Si₃ is easier to break and fall off resulted by the hollow as a crack source, which makes it unable to resist the plastic deformation of the contact surface during the sliding.     

Investigation of a few oxazolone molecules as corrosion inhibitor for API5LX60 steel in 1N H2SO4 solution

Corrosion is recognized as a notable problem in oil sector where API5LX60 steel transmission pipelines are in frequent use. In this report, three oxazolone derivatives as potential corrosion inhibitors were investigated on API5LX60 graded carbon steel in 1N H₂SO₄ solution in stagnant conditions at concentrations 50–200 ppm. Gravimetric weight loss coupons and electrical resistance corrosion monitoring techniques performed on test samples showed inhibitory properties with best at 200 ppm inhibitor concentration. The results further revealed that the degree of inhibition was concentration dependent. Inhibitor I exhibited the highest inhibition efficiency of 90.70% at 200 ppm concentration. Statistical analysis using multiple linear regression model procreated high R² value of 0.998 and p-value < 0.0001 asserting a smooth linear dependence of inhibitor efficiency on oxazolone concentration and weight loss of the steel. Again, surface analysis affirmed the formation of protective coating of inhibitor on steel surface. Furthermore, the oxazolone inhibitor adsorbed physically on the steel surface and obeyed the Langmuir isotherm which is evident from the linear correlation coefficient value of 0.9992.