Biomass-derived porous carbon with single-atomic cobalt toward high-performance aqueous zinc-sulfur batteries at room temperature

Aqueous zinc-sulfur batteries at room temperature hold great potential for next-generation energy storage technology due to their low cost,safety and high energy density.However,slow reaction kinetics and high activation energy at the sulfur cathode pose great challenges for the practical applications.Herein,biomass-derived carbon with single-atomic cobalt sites(MMPC-Co)is synthesized as the cathode in Zn-S batteries.The catalysis of single-atom Co sites greatly promotes the transform of cathode electrolyte interface(CEI)on the cathode surface,while offering accelerated charge transfer rate for high conversion reversibility and large electrochemical surface area(ECSA)for high electrocatalytic current.Furthermore,the rich pore structure not only physically limits sulfur loss,but also accelerates the transport of zinc ions.In addition,the large pore volume of MMPC-Co is able to relieve the stress effect caused by the volume expansion of Zn S during charge/discharge cycles,thereby maintaining the stability of electrode structure.Consequently,the sulfur cathode maintains a high specific capacity of 729.96 m A h g^(-1)after 500 cycles at4 A g^(-1),which is much better than most cathode materials reported in the literature.This work provides new insights into the design and development of room-temperature aqueous Zn-S batteries.

Efficient electrooxidation of biomass-derived aldehydes over ultrathin Ni V-layered double hydroxides films

Selective upgrading of C=O bonds to afford carboxylic acid is significant for the petrochemical industry and biomass utilization.Here we declared the efficient electrooxidation of biomass-derived aldehydes family over NiV-layered double hydroxides(LDHs) thin films.Mechanistic studies confirmed the hydroxyl active intermediate(-OH*) generated on the surface of NiV-LDHs films by employing electrochemical impedance spectroscopy and the electron paramagnetic resonance spectroscopy.By using advanced techniques,e.g.,extended X-ray absorption fine structure and high-angle annular dark-field scanning transmission electron microscopy,NiV-LDHs films with 2.6 nm could expose larger specific surface area.Taking benzaldehyde as a model,high current density of 200 mA cm^(-2)at 1.8 V vs.RHE,81.1% conversion,77.6% yield of benzoic acid and 90.8% Faradaic efficiency were reached,which was superior to most of previous studies.Theoretical DFT analysis was well matched with experimental findings and documented that NiV-LDHs had high adsorption capacity for the aldehydes to suppress the side reaction,and the aldehydes were oxidized by the electrophilic hydroxyl radicals formed on NiV-LDHs.Our findings offer a universal strategy for the robust upgrading of diverse biomass-derived platform chemicals.

Importance of oxygen-containing functionalities and pore structures of biochar in catalyzing pyrolysis of homologous poplar

Biochar and bio-oil are produced simultaneously in one pyrolysis process,and they inevitably contact and may interact,influencing the composition of bio-oil and modifying the structure of biochar.In this sense,biochar is an inherent catalyst for pyrolysis.In this study,in order to investigate the influence of functionalities and pore structures of biochar on its capability for catalyzing the conversion of homologous volatiles in bio-oil,three char catalysts(600C,800C,and 800AC)produced via pyrolysis of poplar wood at 600 or 800℃or activated at 800℃,were used for catalyzing pyrolysis of homologous poplar wood at 600℃,respectively.The results indicated that the 600C catalyst was more active than 800C and 800AC for catalyzing cracking of volatiles to form more gas(yield increase by 40.2%)and aromatization of volatiles to form more light or heavy phenolics,due to its abundant oxygen-containing functionalities acting as active sites.The developed pores of the 800AC showed no such catalytic effect but could trap some volatiles and allow their further conversion via sufficient aromatization.Nevertheless,the interaction with the volatiles consumed oxygen on 600C(decrease by 50%),enhancing the aromatic degree and increasing thermal stability.The dominance of deposition of carbonaceous material of a very aromatic nature over 800C and 800AC resulted in net weight gain and blocked micropores but formed additional macropores.The in situ diffuse reflectance infrared Fourier transform spectroscopy characterization of the catalytic pyrolysis indicated superior activity of 600C for removal of -OH,while conversion of the intermediates bearing C=O was enhanced over all the char catalysts.

Integration of pore structure modulation and B,N co-doping for enhanced capacitance deionization of biomass-derived carbon

Biomass-derived carbon has demonstrated great potentials as advanced electrode for capacitive deionization(CDI),owing to good electroconductivity,easy availability,intrinsic pores/channels.However,conventional simple pyrolysis of biomass always generates inadequate porosity with limited surface area.Moreover,biomass-derived carbon also suffers from poor wettability and single physical adsorption of ions,resulting in limited desalination performance.Herein,pore structure optimization and element co-doping are integrated on banana peels(BP)-derived carbon to construct hierarchically porous and B,N co-doped carbon with large ions-accessible surface area.A unique expansionactivation(EA)strategy is proposed to modulate the porosity and specific surface area of carbon.Furthermore,B,N co-doping could increase the ions-accessible sites with improved hydrophilicity,and promote ions adsorption.Benefitting from the synergistic effect of hierarchical porosity and B,N co-doping,the resultant electrode manifest enhanced CDI performance for NaCl with large desalination capacity(29.5 mg g^(-1)),high salt adsorption rate(6.2 mg g^(-1)min^(-1)),and versatile adsorption ability for other salts.Density functional theory reveals the enhanced deionization mechanism by pore and B,N co-doping.This work proposes a facile EA strategy for pore structure modulation of biomass-derived carbon,and demonstrates great potentials of integrating pore and heteroatoms-doping on constructing high-performance CDI electrode.

Ignition processes and characteristics of charring conductive polymers with a cavity geometry in precombustion chamber for applications in micro/nano satellite hybrid rocket motors

The arc ignition system based on charring polymers has advantages of simple structure,low ignition power consumption and multiple ignitions,which bringing it broadly application prospect in hybrid propulsion system of micro/nano satellite.However,charring polymers alone need a relatively high input voltage to achieve pyrolysis and ignition,which increases the burden and cost of the power system of micro/nano satellite in practical application.Adding conductive substance into charring polymers can effectively decrease the conducting voltage which can realize low voltage and low power consumption repeated ignition of arc ignition system.In this paper,a charring conductive polymer ignition grain with a cavity geometry in precombustion chamber,which is composed of PLA and multiwall carbon nanotubes(MWCNT)was proposed.The detailed ignition processes were analyzed and two different ignition mechanisms in the cavity of charring conductive polymers were revealed.The ignition characteristics of charring conductive polymers were also investigated at different input voltages,ignition grain structures,ignition locations and injection schemes in a visual ignition combustor.The results demonstrated that the ignition delay and external energy required for ignition were inversely correlated with the voltages applied to ignition grain.Moreover,the incremental depth of cavity shortened the ignition delay and external energy required for ignition while accelerated the propagation of flame.As the depth of cavity increased from 2 to 6 mm(at 50 V),the time of flame propagating out of ignition grain changed from 235.6 to 108 ms,and values of mean ignition delay time and mean external energy required for ignition decreased from 462.8 to 320 ms and 16.2 to 10.75 J,respectively.The rear side of the cavity was the ideal ignition position which had a shorter ignition delay and a faster flame propagation speed in comparison to other ignition positions.Compared to direct injection scheme,swirling injection provided a more favorable flow field environment in the cavity,which was beneficial to ignition and initial flame propagation,but the ignition position needed to be away from the outlet of swirling injector.At last,the repeated ignition characteristic of charring conductive polymers was also investigated.The ignition delay time and external energy required for ignition decreased with repeated ignition times but the variation was decreasing gradually.

基于代价敏感Char-CNN的Web威胁识别方案

随着互联网技术的迅速发展,网络安全面临的威胁越发严峻,Web攻击量连年翻倍增长.针对当前Web威胁识别方法手动提取特征识别准确率低、正常和恶意类别样本分布不均衡的问题,本文提出了基于代价敏感的字符级卷积神经网络(Character-level Convolutional Neural Networks,Char-CNN)的Web威胁识别方案.首先分析Web请求特征,将原始数据统一格式,读取数据并拼接成字符序列,根据预先指定的索引字典将字符序列进行编码;其次利用字符级别CNN提取请求信息,对字符编码进行特征提取和特征选择用于模型训练;最后嵌入代价敏感学习,修改神经网络模型交叉熵损失函数,增加恶意样本分类错误的代价,通过反向传播调整模型参数及权值,进而利用Softmax层进行威胁识别.实验表明,基于代价敏感的字符级卷积神经网络进行Web威胁识别方案的准确率达到98.99%,相比已有威胁识别方案,在精确率、召回率和F1分数均有提升,并验证了本方案在不平衡数据集上的有效性.

An embedded ReS_(2)@MAPbBr_(3) heterostructure with downhill interfacial charge transfer for photocatalytic upgrading of biomass-derived alcohols to aldehydes and H_(2)

Solar-driven selective upgrading of lignocellulosic biomass-derived alcohols to value-added chemicals and clean fuel hydrogen(H_(2))shows great potential for tackling the energy crisis and environmental pollu-tion issues.Here,we construct a MAPbBr_(3)/ReS_(2) heterostructure by embedding distorted tetragonal(1T)phase ReS_(2) nanoflowers into large-sized MAPbBr_(3) for green value-added utilization of biomass-derived alcohols.The embedded structure effectively enlarges the contact interface between the ReS_(2) and the MAPbBr_(3),and importantly,induces a strong built-in electric field aligned between the spatially well-defined MAPbBr_(3) and ReS_(2) nanoflowers.Moreover,the distorted 1T phase ReS_(2) with low work function well matches the energy band of MAPbBr_(3),forming a heterostructure with a downward band bending at the interface.These features empower the MAPbBr_(3)/ReS_(2) photocatalyst with high capability to promote charge separation and expedite the surface redox reaction.Consequently,optimal BAD and H_(2) production rates of about 1220 μmol h-1 g-1 are realized over a MAPbBr_(3)/ReS_(2) 2%sample,which are approximately 9 times greater than those of blank MAPbBr_(3).This work demonstrates the great potential of constructing an embedded transition metal dichalcogenide@metal halide perovskites heterostructure with downhill interfacial charge transfer for photocatalytic upgrading of biomass-derived alcohols.

Biomass-derived nitrogen-doped hierarchical porous carbon as efficient sulfur host for lithium–sulfur batteries

Lithium-sulfur(Li-S) battery is a potential energy storage technology with high energy density and low cost. However, the gap between theoretical expectation and practical performance limits its wide implementation. Herein, we report a nitrogen-doped porous carbon derived from biomass pomelo peel as sulfur host material for Li-S batteries. The hierarchical porous architecture and the polar surface introduced by N-doping render a favorable combination of physical and chemical sulfur confinements as well as an expedite electron/ion transfer, thus contributing to a facilitated and stabilized sulfur electrochemistry. As a result, the corresponding sulfur composite electrodes exhibit an ultrahigh initial capacity of 1534.6 mAh g^-1, high coulombic efficiency over 98% upon 300 cycles, and decent rate capability up to 2 C. This work provides an economical and effective strategy for the fabrication of advanced carbonaceous sulfur host material as well as the significant improvement of Li-S battery performance.

Biomass-derived porous carbon materials for advanced lithium sulfur batteries

Biomass, as the most widely used carbon sources, is the main ingredient in the formation of fossil fuels. Biomass-derived novel carbons(BDNCs) have attracted much attention because of its adjustable physical/chemical properties, environmentally friendliness, and considerable economic value. Nature contributes to the biomass with bizarre microstructures with micropores, mesopores or hierarchical pores.Currently, it has been confirmed that biomass has great potential applications in energy storage devices,especially in lithium-sulfur(Li–S) batteries. In this article, the synthesis and function of BDNCs for Li–S batteries are presented, and the electrochemical effects of structural diversity, porosity and surface heteroatom doping of the carbons in Li-S batteries are discussed. In addition, the economic benefits, new trends and challenges are also proposed for further design excellent BDNCs for Li–S batteries.

In situ construction of Co/N/C-based heterojunction on biomass-derived hierarchical porous carbon with stable active sites using a Co-N protective strategy for high-efficiency ORR,OER and HER trifunctional electrocatalysts

The facile designs and fabrication of noble metal-free electrocatalysts are highly required to achieve multifunctional catalytic activity with excellent stability in Zn-air batteries,fuel cells and water splitting systems.Herein,a heterostructure engineering is applied to construct the high performance Co,Ncontaining carbon-based multifunctional electrocatalysts with the feature of isotype(i.e.n-n type Co_(2)N_(0.67)-BHPC)and anisotype(i.e.p-n type Co_(2)O_(3)-BHPC)heterojunctions for ORR,OER and HER.The nn type Co_(2)N_(0.67)-BHPC,in which biomass(e.g.mushroom)-derived hierarchical porous carbon(BHPC)incorporated with nonstoichiometric active species Co_(2)N_(0.67),is fabricated by using an in situ protective strategy of macrocyclic central Co-N_(4) from CoTPP(5,10,15,20-tetrakis(phenyl)porphyrinato cobalt)precursor through the intermolecularπ-πinteractions between CoTPP and its metal-free analogue H_(2) TPP.Meanwhile,an unprotected strategy of macrocyclic central Co-N_(4) from CoTPP can afford the anisotype Co_(2)O_(3)-BHPC p-n heterojunction.The as-prepared n-n type Co_(2)N_(0.67)-BHPC heterojunction exhibited a higher density of Co-based active sites with outstanding stability and more efficient charge transfer at the isotype heterojunction interface in comparison with p-n type Co_(2)O_(3)-BHPC heterojunction.Consequently,for ORR,Co_(2)N_(0.67)-BHPC exhibits the more positive onset and half-wave potentials of 0.93 and 0.86 V vs.RHE,respectively,superior to those of the commercial 20 wt%Pt/C and most of Cobased catalysts reported so far.To drive a current density of 10 mA cm^(-2),Co_(2)N_(0.67)-BHPC also shows the lower overpotentials of 0.34 and 0.21 V vs.RHE for OER and HER,respectively.Furthermore,the Zn-air battery equipped with Co_(2)N_(0.67)-BHPC displays higher maximum power density(109 mW cm^(-2))and charge-discharge cycle stability.Interestingly,the anisotype heterojunction Co_(2)O_(3)-BHPC as trifunctional electrocatalyst reveals evidently photoelectrochemical enhancement compared with the photostable Co_(2)N_(0.67)-BHPC.That is to say,isotype heterojunction material(n-n type Co^(2)N_(0.67)-BHPC)is equipped with better electrocatalytic performance than anisotype one(p-n type Co_(2)O_(3)-BHPC),but the opposite is true in photoelectrochemical catalysis.Meanwhile,the possible mechanism is proposed based on the energy band structures of the Co_(2)N_(0.67)-BHPC and Co_(2)O_(3)-BHPC and the cocatalyst effects.The present work provides much more possibilities to tune the electrocatalytic and photoelectrochemical properties of catalysts through a facile combination of heterostructure engineering protocol and macrocyclic central metal protective strategy.

In-situ growth of ZnS/FeS heterojunctions on biomass-derived porous carbon for efficient oxygen reduction reaction

It is an urgent task to develop highly efficient non-noble metal electrocatalysts in the direction of ORR,but still a huge and long-term challenge.Herein,an efficient one-step pyrolysis of Sichuan pepper powder,2,2-bipyridine,FeCl3,Na SCN,and ZnCl2 at 900℃ provides the FeS/ZnS@N,S-C-900 hybrid catalyst.Transmission electron microscopy(TEM)images and Mott-Schottky curves clearly reveal the in-situ constructed abundant FeS/ZnS-based p-n junctions dispersed on the biomass-derived porous carbon surface of FeS/ZnS@N,S-C-900.The as-prepared FeS/ZnS@N,S-C-900 hybrid exhibits superior ORR performance in comparison with Pt/C in 0.1 M KOH with high onset(Eonset)and half-wave potentials(E1/2)of 1.00 and 0.880 V vs.RHE,large limiting current density(JL)of 5.60 mA cm-2,and robust durability and methanol tolerance.Impressively,upon the light irradiation,FeS/ZnS@N,S-C-900 produces a photocurrent as high as ca.0.3μA cm-2,resulting in further improvement over Eonset,E1/2,and JLof FeS/ZnS@N,S-C-900 to1.10 V vs.RHE,0.885 V vs.RHE,and 6.02 mA cm-2.Experiment in combination with theoretical calculations demonstrate the significant effect of FeS/ZnS heterojunction on the enhanced ORR catalytic activity of FeS/ZnS@N,S-C-900.This work is useful for the development of advanced heterojunction-based ORR catalysts for various energy conversion devices.

Biomass-derived Porous Carbon Materials for Supercapacitor Electrodes:A Review

The development of renewable,cost-efficient,and environmentally friendly electrode materials with excellent performance is urgently needed for improving supercapacitors(SCs).Recently,biomass-derived porous carbons(BPCs)have received increasing attention due to their excellent physical and chemical properties,widespread availability,and low production cost.In this review,the progress in preparing BPCs and the properties of prepared BPCs are presented and discussed.In addition,the applications of BPCs as electrode materials for supercapacitors are also summarized.More importantly,the pore structure and surface properties of BPCs are all determining factors to improve electrochemical performance.Moreover,a high energy density and power density can be pursued by using composites based on BPCs as electrode materials,of which combining transition metallic oxide with BPCs is one of the most attractive selections.Therefore,rational design of BPCs with respect to the supercapacitor's performance should be conducted in the future.

Catalytic Conversion of Biomass-Derived Polyols into Para-xylene over SiO2-Modified Zeolites

This work proved that biomass-based polyols (sorbitol, xylitol, erythritol, glycerol and ethanediol) were able to be converted into high-value chemical (p-xylene) by catalytic cracking of polyols, alkylation of aromatics, and the isomerization of xylenes over the SiO2-modified zeolites. Compared to the conventional HZSM-5 zeolite, the SiO2-containing zeolites considerably increased the selectivity and yield of p-xylene due to the reduction of external surface acidity and the narrowing of pore entrance. The influences of the methanol additive, reaction temperature, and types of polyols on the selectivity and yield of p-xylene were investigated in detail. Catalytic cracking of polyols with methanol significantly enhanced the production of p-xylene by the alkylation of toluene with methanol. The highest p-xylene yield of 10.9 C-mol% with a p-xylene/xylenes ratio of 91.1% was obtained over the 15wt%SiO2/HZSM-5 catalyst. The reaction pathway for the formation of p-xylene was addressed according to the study of the key reactions and the characterization of catalysts.

Advancement in the Utilization of Biomass-Derived Heterogeneous Catalysts in Biodiesel Production

Solid oxide catalysts derived from various renewable sources have produced significant yield of methyl esters of enhanced purity. These materials are sourced for due to their advantages ranging from low cost, recoverability and reusability, environmental benign-ness, thermal stability and high quality product generation. For a possible greener production process, many researchers in literature reported the use of biomass-derived heterogeneous catalyst in biodiesel synthesis producing high quality pure product. The catalysts were majorly modified through simple physical cost effective and energy saving operations. This paper explores some of these bio-based heterogeneous catalyst used in biodiesel production via transesterification and esterification approach and their performance in FAME yield and conversion. The feedstock consideration which warrant the route selection, various approaches that are adopted in biodiesel production, performance of renewable heterogeneous catalyst and the measures that were adopted to enhance efficiency of the catalyst were considerably highlighted. It is observed that the prospects of organic-based solid catalyst in biodiesel development is a promising enterprise compared to the conventional methods utilizing homogeneous chemical catalyst, which generates wastewater requiring treatment before disposal and generates product that may cause engine malfunction. This review work aimed at providing detailed and up-to-date record of the trend in renewable catalyst development in biodiesel synthesis. This is expected to inform a suitable selection and reaction conditions in the development of biodiesel from the very many feed stocks.

Regulating the Localization of Intumescent Flame Retardant for Improving the Flame Retardancy of Ethylene-vinyl Acetate Copolymer Using Polyamide 6 as a Charring Agent

Polyamide 6 (PA6) was employed as a charring agent of intumescent flame retardant (IFR) to improve the flame retardancy of ethylene-vinyl acetate copolymer (EVA). Different processing procedures were used to regulate the localization of IFR in the EVA matrix. Localizations in which IFR was dispersed in the PA6phase or in the EVA phase were prepared. The effect of the localization of IFR on the flame retardancy of EVA was investigated. The limited oxygen index (LOI), vertical burning (UL 94) and cone calorimeter test (CCT)showed that the localization of IFR in the EVA matrix exhibited a remarkable influence on the flame retardancy.Compared with EVA/IFR, a weak improvement in the flame retardancy was observed in the EVA/PA6/IFR blend withthe localization of IFR in the PA6 phase. When IFR was regulated from the PA6 phase to the EVA matrix,a remarkable increase in the flame retardancy was exhibited. The LOI was increased from 27.8%to 32.7%, and the UL 94 vertical rating was increased from V-2 to V-0. Moreover, an approximately 41.36%decrease in the peak heat release rate was exhibited. A continuous and compact intumescent charring layer that formed in the blends with the localization of IFR in the EVA matrix should be responsible for its excellent flame retardancy.

A Novel Siamese Network for Few/Zero-Shot Handwritten Character Recognition Tasks

Deep metric learning is one of the recommended methods for the challenge of supporting few/zero-shot learning by deep networks.It depends on building a Siamese architecture of two homogeneous Convolutional Neural Networks(CNNs)for learning a distance function that can map input data from the input space to the feature space.Instead of determining the class of each sample,the Siamese architecture deals with the existence of a few training samples by deciding if the samples share the same class identity or not.The traditional structure for the Siamese architecture was built by forming two CNNs from scratch with randomly initialized weights and trained by binary cross-entropy loss.Building two CNNs from scratch is a trial and error and time-consuming phase.In addition,training with binary crossentropy loss sometimes leads to poor margins.In this paper,a novel Siamese network is proposed and applied to few/zero-shot Handwritten Character Recognition(HCR)tasks.The novelties of the proposed network are in.1)Utilizing transfer learning and using the pre-trained AlexNet as a feature extractor in the Siamese architecture.Fine-tuning a pre-trained network is typically faster and easier than building from scratch.2)Training the Siamese architecture with contrastive loss instead of the binary cross-entropy.Contrastive loss helps the network to learn a nonlinear mapping function that enables it to map the extracted features in the vector space with an optimal way.The proposed network is evaluated on the challenging Chars74K datasets by conducting two experiments.One is for testing the proposed network in few-shot learning while the other is for testing it in zero-shot learning.The recognition accuracy of the proposed network reaches to 85.6%and 82%in few-and zero-shot learning respectively.In addition,a comparison between the performance of the proposed Siamese network and the traditional Siamese CNNs is conducted.The comparison results show that the proposed network achieves higher recognition results in less time.The proposed network reduces the training time from days to hours in both experiments.

继发性噬血细胞综合征病因、临床特点及预后分析

目的:了解继发性噬血细胞综合征(HLH)的病因、临床特征及预后,以提高对HLH的认识,减少临床HLH的误诊和漏诊率。方法:收集2015年1月至2021年12月经本院收治的75例成人继发性HLH患者的病历资料,对其病因、临床特点、实验室检查结果、治疗及预后等进行回顾性分析。随访至末次出院时间。结果:75例患者中,感染相关HLH最常见(45.33%),其次为淋巴瘤相关HLH(17.33%)。临床表现以发热最为常见(97.67%),实验室指标中NK细胞活性(98.31%降低)、sCD25浓度(93.22%升高)、血清铁蛋白(94.44%升高)在诊断中灵敏度更高。将不同病因HLH患者初诊时临床表现及实验室指标进行比较,性别、淋巴结肿大、骨髓形态是否可见噬血现象对原发病的诊断更有价值(均P<0.05)。将不同病因HLH患者的治疗方案与临床转归进行比较,自身免疫性疾病相关HLH采用激素+环孢素治疗临床缓解率最高(83.3%)(P<0.05)。患者总体12个月的生存率为26.7%,其中感染相关HLH患者12个月的生存率最低(14.7%),自身免疫性疾病相关HLH患者12个月的生存率最高(63.6%)。结论:成人继发性HLH病因和临床特点多样,预后凶险,病情严重程度具有异质性,早期明确病因对HLH预后具有重要意义,需要进一步提高对HLH的认识。

准东煤分步和直接化学链燃烧特性

化学链燃烧作为高效的低碳排放燃烧技术,在提高燃料利用率和减少CO_(2)排放方面显示出其独特优势。采用Fe_(2)O_(3)/Al_(2)O_(3)载氧体,利用两段式固定床反应器开展了准东煤直接和分步化学链燃烧试验,探究了载氧体反应前后理化特性。发现准东煤热解挥发分化学链燃烧碳转化率和CO_(2)选择性随温度和载氧体与煤质量比(OC/C)增加而升高。OC/C和温度升高提高半焦化学链燃烧碳转化率,但降低CO_(2)选择性。相比煤直接化学链燃烧,在相同条件,分步化学链燃烧CO_(2)选择性大幅提高、碳转化率有所降低。反应温度800℃,分步化学链燃烧CO_(2)选择性达89.51%,相比直接化学链燃烧提升了29.18%。反应温度950℃,分步化学链燃烧碳转化率在60.40%,比直接化学链燃烧降低6.78%。与半焦反应后载氧体还原程度高于与煤热解挥发分反应后载氧体,半焦与载氧体的反应是煤化学链燃烧的限制因素之一。本研究为实现准东煤低碳清洁燃烧提供重要理论依据和技术支撑。

C/CO_(2)摩尔比对CO_(2)气氛流态化预热活化半焦特性的影响

我国工业领域涉及的行业多,碳减排压力大。富氧燃烧是燃烧中碳捕集的核心工艺,将流态化富氧预热活化与工业窑炉富氧燃烧过程耦合是拓宽燃料适应性、实现工业领域燃烧中碳捕集的新途径。利用小型流化床连续给料实验系统,在1050℃、CO_(2)流化速度为0.17 m/s条件下,通过调整给料速度,考察C/CO_(2)摩尔比(CC比)对半焦原料(RC)流态化预热活化的影响,分析煤气组分及低位热值,计算CO_(2)还原率,表征粗颗粒活化半焦(LC)和细颗粒活化半焦(FC)的比表面积、孔隙结构和碳架结构,并利用高温管式炉热天平实验系统评价了RC和FC在1300℃条件下的反应活性。结果表明:采用流态化预热活化技术实现了CO_(2)的资源化利用,制备出富CO煤气,CC比由1增至4时,煤气中CO+H_(2)体积分数由69.24%增至79.08%,CO体积分数最高为68.96%,CO_(2)体积分数由29.48%降至20.13%,CO_(2)还原率由50.37%提升至57.56%,煤气低位热值由8.69 MJ/m^(3)增至9.83 MJ/m^(3),是参考文献所述工程产出煤气低位热值的1.55~1.88倍,有利于窑炉系统的着火及稳定燃烧。随CC比增加,FC和LC的比表面积先增加后减小,FC和LC的最高比表面积分别为291.21 m^(2)/g和477.15 m^(2)/g,分别为半焦原料的48倍和78倍;FC和LC具有丰富的微孔结构,且石墨化程度比RC降低、活性点位增加;FC和LC的微孔面积占比表面积的54.93%~68.42%;相比较而言,LC具有更高的比表面积和增量孔容积,主要是由于LC在反应器内的停留时间较长,促进了孔隙的发展,形成了大量微孔。不同CC比条件下所得FC的反应活性指数R0.5、质量平均反应速率均高于RC,表明FC具有较高的反应活性,可预测在高温气固活化态热燃料燃烧过程中,FC将实现高效转化。提出了碳基燃料流态化富氧预热活化-高温气固活化态热燃料富氧燃烧的新思路,获得了CC比对CO_(2)气氛流态化预热活化半焦特性的影响规律,揭示了CO_(2)作为碳和氧载体的积极作用,研究结果为流态化预热活化技术在工业窑炉富氧燃烧行业的应用提供了数据支持。

含磷POSS阻燃乙烯基酯树脂性能研究

将含磷POSS(DMPOSS)以5wt%、10wt%和15wt%的添加量添加到乙烯基酯树脂中,通过差示扫描量热仪(DSC)、热重分析(TG)、极限氧指数(LOI)、锥形量热仪和扫描电镜(SEM)测试研究了DMPOSS对乙烯基酯树脂玻璃化转变温度、热稳定性和燃烧性能的影响。DSC测试结果表明:DMPOSS的加入能够明显提升乙烯基酯树脂的玻璃化转变温度。LOI测试结果表明:添加DMPOSS改性的乙烯基酯树脂的氧指数随DMPOSS含量的增加而逐渐升高。当添加15wt%DMPOSS时,乙烯基酯树脂的氧指数达到23.8%。锥形量热仪测试结果表明:DMPOSS的加入能够有效降低乙烯基酯树脂的热释放。当添加15wt%DMPOSS时,乙烯基酯树脂的热释放速率峰值降低了44.9%,总的热释放降低了30.4%。