Effects of ultrasound on the desulfurization performance of hot coal gas over Zn-Mn-Cu supported on semi-coke sorbent prepared by high-pressure impregnation method

Zn-Mn-Cu/SC（U） sorbent was hydrothermally synthesized by ultrasound-assisted high-pressure impregnation method with semi-coke（SC）as support and the mixed solution of zinc nitrate,manganese nitrate and copper nitrate as active component precursors.The desulfurization performances of hot coal gas on the prepared sorbent at a mid-temperature of 500°C were tested in fixed-bed reactor.Morphology and pore structure of the prepared sorbent were also characterized by TEM,N2adsorption/desorption isotherms and XRD.For comparison,the sorbent of Zn-Mn-Cu/SC prepared by conventional high-pressure impregnation was also evaluated and characterized in order to study the effects of ultrasound treatment.Zn-Mn-Cu/SC（U） sorbent prepared by high-pressure impregnation under ultrasound-assisted condition showed a better desulfurization performance than Zn-Mn-Cu/SC.It could remove H2 S from 1000×10-6m3/m3 to 0.1×10-6m3/m3 at 500°C and maintained for 12.5 h with the sulfur capacity of 7.74%,in which both the breakthrough time and sulfur capacity were about 32% and 51% higher than those of Zn-Mn-Cu/SC sorbent.The introduction of ultrasound during high-pressure impregnation process greatly improved the morphology and pore structure of the sorbent.The ultrasonic treatment made particle size of active components smaller and made them more evenly disperse on semi-coke support,which provided more opportunities to contact with H2S in coal-based gases.However,there were no any difference in compositions and existing forms of active components on the Zn-Mn-Cu/SC and Zn-Mn-Cu/SC（U） sorbents.

Earth abundant spinel for hydrogen production in a chemical looping scheme at 550℃

Operating chemical looping process at mid-temperatures(550–750℃)presents exciting potential for the stable production of hydrogen.However,the reactivity of oxygen carriers is compromised by the detrimental effect of the relatively low temperatures on the redox kinetics.Although the reactivity at mid-temperature can be improved by the addition of noble metals,the high cost of these noble metal containing materials significantly hindered their scalable applications.In the current work,we propose to incorporate earth-abundant metals into the ironbased spinel for hydrogen production in a chemical looping scheme at mid-temperatures.Mn0.2Co0.4Fe2.4O4 shows a high hydrogen production performance at the average rate of~0.62 mmol g^(-1) min^(-1) and a hydrogen yield of~9.29 mmol g^(-1) with satisfactory stability over 20 cycles at 550℃.The mechanism studies manifest that the enhanced hydrogen production performance is a result of the improved oxygen-ion conductivity to enhance reduction reaction and high reactivity of reduced samples with steam.The performance of the oxygen carriers in this work is comparable to those noble-metal containing materials,enabling their potential for industrial applications.

Enhanced thermoelectric performance in p-type ZrCoSb based half-Heusler alloys employing nanostructuring and compositional modulation

ZrCoSb based half-Heusler(HH)alloys have been widely studied as a p-type thermoelectric(TE)material for power generation applications in the mid-temperature regime.However,their intrinsically high thermal conductivity has been found to be detrimental for the improvement in their thermoelectric figure-of-merit(ZT),which presently is far below unity.In the current work,a state-of-the-art ZT~1.1 at 873 K was realized in an optimized composition of nanostructured Zr1-xHfxCoSb_(0.9)Sn_(0.1) HH alloys by employing compositional modulation i.e.grain-by-grain compositional variations,which leads to a substantial increase in its power factor coupled with a concurrent decrease in its thermal conductivity.Significant reduction in the phonon mean-free-path is observed on Hf substitution,which is comparable to the average crystallite size(~25 nm),thus leading to a very low thermal conductivity of~2.2Wm^(-1)K^(-1) at 873 K,which is amongst the lowest reported in HH alloys.The TE device characteristics,estimated using cumulative temperature dependence model for quantitative evaluation of TE performance,yielded an output power density of~10 Wcm
2 with a leg efficiency of~10%in the optimized composition of nanostructured Zr_(1-x)Hf_(x)CoSb_(0.9)Sn_(0.1) HH alloys,which is comparable to the reported efficiencies of other state-of-the-art TE materials.

Influence of film stretching on crystalline phases and dielectric properties of a 70/30 mol%poly(vinylidenefluoride-tetrafluoroethylene)copolymer

Polyvinylidene fluoride(PVDF)-based copolymers with tetrafluoroethylene(P(VDF-TFE)),trifluoroethylene(P(VDF-TrFE))or hexafluoropropylene(P(VDF-HFP))are of strong interest due to the underlying fundamental mechanisms and the potential ferro-,pyro-and piezo-electrical applications.Their flexibility and their adaptability to various shapes are advantageous in comparison to inorganic ferroelectrics.Here,we study the influence of stretching temperature on the crystalline phases and the dielectric prop-erties in P(VDF-TFE)films by means of Dielectric Relaxation Spectroscopy(DRS),Fourier-Transform InfraRed spectroscopy(FTIR),Wide-Angle X-ray Diffraction(WAXD),Differential Scanning Calorimetry(DSC)and Dynamic Mechanical Analysis(DMA).Especially,the effect of stretching and the influence of the temperature of stretching on the mid-temperature(T_(mid))transi-tion are studied in detail.The results show that stretching has a similar effect as that on PVDF,and we observe an increase in the fraction of ferroelectric b-phase with a simultaneous increment in both melting point(T_(m))and crystallinity(X_(c))of the copolymer.While an increase in the stretching temperature does not have a profound impact on the amount of ferroelectric phase,the stability of the ferroelectric phase seems to improve-as seen in the reduction of the Full Width at Half Maximum(FWHM)of the WAXD peaks in both parallel and perpendicular directions to the molecular chain axis.The observation is also supported by the reduction of dissipation losses with an increase in stretching temperature-as seen in DRS measurements.Finally,both stretching itself and the temperature of stretching affect the various molecular processes taking place in the temperature range of the T_(mid) transition.

Ultrahigh figure-of-merit of Cu2Se incorporated with carbon coated boron nanoparticles

Cu2Se based thermoelectric materials are of great potential for high-temperature energy harvesting due to their high-temperature figure-of-merit(zT).For further development of Cu2Se,both engineering and mid-temperature figure-of-merit need to be improved.In this work,we report that carbon-coated boron(C/B)nanoparticles incorporation can significantly improve both mid-and high-temperature zT in Cu2Se.The nanoparticle inclusions can result in a homogeneous distribution of Cu:C:B interfaces responsible for both improvement of the Seebeck coefficient and significantly reduction in thermal conductivity.Ultrahigh mid-and high temperature thermoelectric performance with zT=1.7 at 700 K and 2.23 at 1000 K as well as significantly improved engineering zT are achieved in the C/B incorporated Cu2Se with desirable mechanical properties and cycling stability.Our findings will stimulate further study and exploration for the Cu2Se based thermoelectric materials for broad applications in converting waste heat to electricity with competitive energy conversion efficiency.