CO_(2)-assisted oxidation dehydrogenation of light alkanes over metal-based heterogeneous catalysts

Light olefins are important platform feedstocks in the petrochemical industry,and the ongoing global economic development has driven sustained growth in demand for these compounds.The dehydrogenation of alkanes,derived from shale gas,serves as an alternative olefins production route.Concurrently,the target of realizing carbon neutrality promotes the comprehensive utilization of greenhouse gas.The integrated process of light alkanes dehydrogenation and carbon dioxide reduction(CO_(2)-ODH)can produce light olefins and realize resource utilization of CO_(2),which has gained wide popularity.With the introduction of CO_(2),coke deposition and metal reduction encountered in alkanes dehydrogenation reactions can be effectively suppressed.CO_(2)-assisted alkanes dehydrogenation can also reduce the risk of potential explosion hazard associated with O_(2)-oxidative dehydrogenation reactions.Recent investigations into various metal-based catalysts including mono-and bi-metallic alloys and oxides have displayed promising performances due to their unique properties.This paper provides the comprehensive review and critical analysis of advancements in the CO_(2)-assisted oxidative dehydrogenation of light alkanes(C2-C4)on metal-based catalysts developed in recent years.Moreover,it offers a comparative summary of the structural properties,catalytic activities,and reaction mechanisms over various active sites,providing valuable insights for the future design of dehydrogenation catalysts.

Co-feeding with DME:An effective way to enhance gasoline production via low temperature aromatization of LPG

The aromatization of light alkenes in liquefied petroleum gas (LPG) with and without dimethyl ether (DME) addition in the feed was investigated on a modified ZSM-5 catalyst.The results showed that under the given reaction conditions the selectivity of alkenes to high-octane gasoline blending components was markedly enhanced and the formation of propane and butanes was greatly suppressed with the addition of DME.It was also found that the distribution of C5+ components was changed a lot with DME addition into the LPG feed.The formation of branched hydrocarbons (mainly C6 C8 i-paraffin) and multi-methyl substituted aromatics,which are high octane number gasoline blending components,was promoted significantly,while the content of n-paraffins and olefins in C5+ components was decreased obviously,indicating that in addition to the oligomerization,cracking,hydrogen-transfer and dehydrogenation-cyclization of alkenes,the methylation of the formed aromatics and olefins intermediates also plays an important role in determining the product distribution due to the high reactivity of surface methoxy groups formed by DME.And this process,in combination with the syngas-to-methanol/DME technology,provides an alternative way to the production of high-octane gasoline from coal,natural gas or renewable raw materials.

Study of Seals on Long Stroke and Reciprocating Motion Condition

The equipment has a high and strict requirement of dynamic seals, especially working with Long stroke reciprocating motion under a sandy condition and with a great deal of gas. The seal form of power cylinder on the underground part of hydraulic power rodless type oil extraction equipment is studied. We design three seal structures, do the performance testing and the life testing with related equipment. It turned out that the seal form that combines gap seal with sand prevention techniques has high performance, longer life. The power cylinder works stably and reliably.

Einstein Probe discovery of EP240408a:A peculiar X-ray transient with an intermediate timescale

We report the discovery of a peculiar X-ray transient,EP240408a,by Einstein Probe(EP)and follow-up studies made with EP,Swift,NICER,GROND,ATCA and other ground-based multiwavelength telescopes.The new transient was first detected with Wide-field X-ray Telescope(WXT)on board EP on April 8th,2024,manifested in an intense yet brief X-ray flare lasting for 12 s.The flare reached a peak flux of 3:9×10^(−9) erg cm^(−2) s^(−1) in 0.5-4 keV,∼300 times brighter than the underlying X-ray emission detected throughout the observation.Rapid and more precise follow-up observations by EP/FXT,Swift and NICER confirmed the finding of this new transient.Its X-ray spectrum is non-thermal in 0.5-10 keV,with a power-law photon index varying within 1.8-2.5.The X-ray light curve shows a plateau lasting for∼4 d,followed by a steep decay till becoming undetectable∼10 d after the initial detection.Based on its temporal property and constraints from previous EP observations,an unusual timescale in the range of 7-23 d is found for EP240408a,which is intermediate between the commonly found fast and long-term transients.No counterparts have been found in optical and near-infrared,with the earliest observation at 17 h after the initial X-ray detection,suggestive of intrinsically weak emission in these bands.We demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far,by comparison with,in particular,jetted tidal disruption events,gamma-ray bursts,X-ray binaries and fast blue optical transients.The nature of EP240408a thus remains an enigma.We suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of∼10 d.The detection and follow-ups of more of such objects are essential for revealing their origin.

Thermodynamic study of direct amination of isobutylene to tert-butylamine

On basis of thermodynamic empirical equations, the thermodynamic parameters for the direct amination of isobutylene to tert‐butylamine, an atomically economic and green chemical reaction,were calculated. In particular, the equilibrium conversion of isobutylene under various reactionconditions close to those used in industry was calculated and discussed. Isobutylene amination is atemperature sensitive reaction due to its exothermic nature and isobutylene equilibrium conversiondecreases with temperature. However, kinetically, the amination reaction will be faster at ahigher temperature. Thus, there must be an optimum temperature for the reaction. A high pressureand n(NH3)/n(i‐C4H8) molar ratio promote the transformation of isobutylene to tert‐butylamine.Developing a highly efficient catalyst under mild reaction conditions is preferred for the aminationprocess. The reaction was investigated over a series of acidic zeolites. ZSM‐11 zeolite exhibited thebest performance with 14.2% isobutylene conversion (52.2% of the equilibrium conversion) and >99.0% tert‐butylamine selectivity. The effect of reaction conditions on the performance of the ZSM‐11 catalyst agreed with the thermodynamic results, which provides guidance for further catalyst development and reaction condition optimization.

Knitted self-powered sensing textiles for machine learning-assisted sitting posture monitoring and correction

With increasing work pressure in modern society,prolonged sedentary positions with poor sitting postures can cause physical and psychological problems,including obesity,muscular disorders,and myopia.In this paper,we present a self-powered sitting position monitoring vest(SPMV)based on triboelectric nanogenerators(TENGs)to achieve accurate real-time posture recognition through an integrated machine learning algorithm.The SPMV achieves high sensitivity(0.16 mV/Pa),favorable stretchability(10%),good stability(12,000 cycles),and machine washability(10 h)by employing knitted double threads interlaced with conductive fiber and nylon yarn.Utilizing a knitted structure and sensor arrays that are stitched into different parts of the clothing,the SPMV offers a non-invasive method of recognizing different sitting postures,providing feedback,and warning users while enhancing long-term wearing comfortability.It achieves a posture recognition accuracy of 96.6%using the random forest classifier,which is higher than the logistic regression(95.5%)and decision tree(94.3%)classifiers.The TENG-based SPMV offers a reliable solution in the healthcare system for non-invasive and long-term monitoring,promoting the development of triboelectric-based wearable electronics.

Active-Sensing Epidermal Stretchable Bioelectronic Patch for Noninvasive,Conformal,and Wireless Tendon Monitoring

Sensors capable of monitoring dynamic mechanics of tendons throughout a body in real time could bring systematic information about a human body’s physical condition,which is beneficial for avoiding muscle injury,checking hereditary muscle atrophy,and so on.However,the development of such sensors has been hindered by the requirement of superior portability,high resolution,and superb conformability.Here,we present a wearable and stretchable bioelectronic patch for detecting tendon activities.It is made up of a piezoelectric material,systematically optimized from architectures and mechanics,and exhibits a high resolution of 5:8×10^(−5)N with a linearity parameter of R^(2)=0:999.Additionally,a tendon real-time monitoring and healthcare system is established by integrating the patch with a micro controller unit(MCU),which is able to process collected data and deliver feedback for exercise evaluation.Specifically,through the patch on the ankle,we measured the maximum force on the Achilles tendon during jumping which is about 16312 N,which is much higher than that during normal walking(3208 N)and running(5909 N).This work not only provides a strategy for facile monitoring of the variation of the tendon throughout the body but also throws light on the profound comprehension of human activities.