HZSM-5 zeolites undergoing the high-temperature process for boosting the bimolecular reaction in n-heptane catalytic cracking

High-temperature treatment is key to the preparation of zeolite catalysts.Herein,the effects of hightemperature treatment on the property and performance of HZSM-5 zeolites were studied in this work.X-Ray diffraction,N2physisorption,27Al magic angle spinning nuclear magnetic resonance(MAS NMR),and temperature-programmed desorption of ammonia results indicated that the hightemperature treatment at 650℃ hardly affected the inherent crystal and texture of HZSM-5zeolites but facilitated the conversion of framework Al to extra-framework Al,reducing the acid site and enhancing the acid strength.Moreover,the high-temperature treatment improved the performance of HZSM-5 zeolites in n-heptane catalytic cracking,promoting the conversion and light olefins yield while inhibiting coke formation.Based on the kinetic and mechanism analysis,the improvement of HZSM-5 performance caused by high-temperature treatment has been attributed to the formation of extra-framework Al,which enhanced the acid strength,facilitated the bimolecular reaction,and promoted the entropy change to overcome a higher energy barrier in n-heptane catalytic cracking.

High-temperature treatment to engineer the single-atom Pt coordination environment towards highly efficient hydrogen evolution

Development of high-performance and cost-effective catalysts for electrocatalytic hydrogen evolution reaction(HER)play crucial role in the growing hydrogen economy.Recently,the atomically dispersed metal catalysts have attracted increasing attention due to their ultimate atom utilization and great potential for highly cost-effective and high-efficiency HER electrocatalyst.Herein,we propose a hightemperature treatment strategy to furtherly improve the HER performance of atomically dispersed Ptbased catalyst.Interestingly,after appropriate high-temperature treatment on the atomically dispersed Pt0.8@CN,the Pt species on the designed N-doped porous carbon substrate with rich defect sites can be re-dispersed to single atom state with new coordination environment.The obtained Pt0.8@CN-1000 shows superior HER performance with overpotential of 13 m V at 10 m A cm^(-2)and mass activity of 11,284 m A/mgPtat-0.1 V,much higher than that of the pristine Pt0.8@CN and commercial Pt/C catalyst.The experimental and theoretical investigations indicate that the high-temperature treatment induces the restructuring of coordination environment and then the optimized Pt electronic state leads to the enhanced HER performances.This work affords new strategy and insights to develop the atomically dispersed high-efficiency catalysts.

Effects of Steam Heat Treatment on the Surface Contact Angle of Chinese Fir

The aim of this study was investigate the effects of heat treatment on the contact angle of Chinese fir, and the indicators affecting the change of contact an-gle change. It was determined that the duration of treatment had significant effect on the change curves of contact angle of Chinese fir wood due to the change curves of contact angle became more centralized and orderly after the specimens heat treated at 180 ℃. Compared with the untreated wood, the contact angle in-creased from 51＆#176; to 124＆#176; after 4 h treatment, and hydroxyl absorbance of hy-drophilic functional groups decreased from 2.08 to 1.63, while carbonyl absorbance from 0.92 to 0.62. The surface roughness has not significant influence on the con-tact angle. Heat treatment of the Chinese fir caused surface morphological change, which produced hol owed-out phenomenon. The increased surface contact angle caused by heat treatment can be used for outdoor and sauna facilities.

Creation of surface defects on carbon nanofibers by steam treatment

A direct strategy for the creation of defects on carbon nanofibers (CNFs) has been developed by steam treatment.Nitrogen physisorption,XRD,Raman spectra,SEM and TEM analyses proved the existence of the new defects on CNFs.BET surface area of CNFs after steam treatment was enhanced from 20 to 378 m2/g.Pd catalysts supported on CNFs were also prepared by colloidal deposition method.The different activity of Pd/CNFs catalysts in the partial hydrogenation of phenylacetylene further demonstrated the diverse surfaces of CNFs could be formed by steam treatment.

High-temperature thermal stability of C/C−ZrC−SiC composites via region labeling method

To investigate the thermal stability of ceramic-matrix composites,three kinds of C/C−ZrC−SiC composites with different Zr/Si molar ratios were synthesized by reactive melt infiltration.Employing region labeling method,the high-temperature thermal stability of the composites was systematically studied by changing the temperature and holding time of thermal treatment.Results show that the mass loss rate of low Si composites has a growth trend with increasing temperature,and a crystal transformation from β-SiC toα-SiC occurs in the composites.In the calibrated area,SiC phase experiences Ostwald ripening and volume change with location migration,while ZrC phase experiences a re-sintering process with diffusion.Moreover,it is found that increasing temperature has a more obvious effect on the thermal stability than extending holding time,which is mainly attributed to the faster diffusion rate of atoms.

Poly(ionic liquid)-crosslinked graphene oxide/carbon nanotube membranes as efficient solar steam generators

Graphene oxide(GO)is regarded as a promising candidate to construct solar absorbers for addressing freshwater crisis,but the easy delamination of GO in water poses a critical challenge for practical solar desalination.Herein,we improve the stability of GO membranes by a self-crosslinking poly(ionic liquid)(PIL)in a mild condition,which crosslinks neighbouring GO nanosheets without blemishing the hydrophilic structure of GO.By further adding carbon nanotubes(CNTs),the sandwiched GO/CNT@PIL(GCP)membrane displays a good stability in pH=1 or 13 solution even for 270 days.The molecular dynamics simulation results indicate that the generation of water nanofluidics in nanochannels of GO nanosheets remarkably reduces the water evaporation enthalpy in GCP membrane,compared to bulk water.Consequently,the GCP membrane exhibits a high evaporation rate(1.87 kg m^(-2)h^(-1))and displays stable evaporation rates for 14 h under 1 kW m^(-2)irradiation.The GCP membrane additionally works very well when using different water sources(e.g.,dye-polluted water)or even strong acidic solution(pH=1)or basic solution(pH=13).More importantly,through bundling pluralities of GCP membrane,an efficient solar desalination device is developed to produce drinkable water from seawater.The average daily drinkable water amount in sunny day is 10.1 kg m^(-2),which meets with the daily drinkable water needs of five adults.The high evaporation rate,long-time durability and good scalability make the GCP membrane an outstanding candidate for practical solar seawater desalination.

Methane dehydro-aromatization over Mo/HZSM-5 catalysts in the absence of oxygen:Effect of steam-treatment on catalyst stability

The effect of steam-treatment to HZSM-5 zeolite and Mo/HZSM-5 with a steaming time range of 0.5-1 h on the catalytic performance of methane dehydro-aromatization （MDA） over Mo/HZSM-5 catalyst prepared with impregnation has been studied in detail in combination with the characterization of 1H MAS NMR technique. Both the deactivation rate constant （kd） and the Brtnsted acid sites per unit cell were calculated to quantitatively evaluate the stability of Mo/HZSM-5 catalysts treated with steam at 813 K before and after impregnation of molybdenum species, and the corresponding variation of their Brtnsted acid sites. The results reveal that a V-shape relationship between kd and the number of B 1 acid sites per unit cell is presented on Mo/HZSM-5 catalyst under the tested steam-treatment and reaction conditions.

湿热处理对杂豆馒头淀粉消化特性及风味品质的影响

目的研究湿热处理对杂豆馒头消化特性及风味品质的影响。方法选取湿热处理豌豆、红豆、白芸豆3种杂豆制作杂豆馒头,对湿热杂豆馒头的色度、比容、感官评分等进行评价,通过固相微萃取-气相色谱-质谱法(solid phase microextraction-gas chromatography-mass spectrometry,SPME-GC-MS)分析湿热粉杂豆馒头挥发性风味物质变化规律,并对馒头进行体外淀粉消化实验。结果湿热处理杂豆粉的添加降低了馒头的比容,改变了馒头的色度。对豌豆馒头和白芸豆馒头感官评分没有影响,但可显著提高红豆馒头的感官评分(P<0.05)。SPME-GC-MS从湿热杂豆馒头中共检出47种挥发性成分,主要为醛类、醇类、酯类、酮类、芳香族类、烷烃类及杂环类。淀粉体外消化特性表明3种杂豆馒头的抗性淀粉含量显著高于小麦馒头,淀粉水解率低于小麦馒头。结论湿热处理可使杂豆馒头风味品质改善,使红豆馒头和白芸豆馒头抗性淀粉含量提高和淀粉水解率降低,但对豌豆馒头没有影响。研究结果为淀粉基杂豆营养健康食品的加工提供数据支撑。

不同热处理方式对小麦粉特性及其蒸饼品质的影响

目前蒸饼的制作大多采用传统的半烫面工艺,工序较为复杂,为解决这一问题,该研究采用不同热处理方式(蒸汽处理、微波处理、干热处理)对小麦粉进行热处理,研究了不同处理方式对小麦粉的糊化特性、热机械学特性、微观结构等的影响,并将处理后的小麦粉添加到未处理的小麦粉中制成蒸饼,考察了所制得的蒸饼的水分分布、质构特性及感官品质。结果表明:3种热处理的适当处理时间都可以提高小麦粉的黏度和回生值;经干热处理和微波处理后的小麦粉的破损淀粉含量高于经蒸汽处理的小麦粉。3种热处理小麦粉的添加均可以提高面团的吸水率,蒸汽处理小麦粉的添加使面团耐揉性降低、蒸煮稳定性提高,微波和干热处理小麦粉的添加使面团的耐揉性和内部结构稳定性提高。适当处理时间的热处理小麦粉的添加可以提高蒸饼的结合水含量、硬度、弹性和咀嚼性等。其中,经蒸汽处理40 min、微波处理2 min和干热处理30 min后的小麦粉的添加制得的蒸饼有相对适中的强韧性、较高的结合水含量和感官评分。该研究结果表明添加热处理后的小麦粉代替传统的烫面工艺制作高品质蒸饼具有可行性,同时能够为蒸饼的工业化生产提供相应的基础数据和一定的理论指导。

基于蒸制处理的黄精麻味物质研究

目的:探索黄精产生麻味特征的物质基础。方法:采用“九蒸九制”的方法对8个产地的黄精进行炮制,并分析不同蒸制次数下黄精中皂苷、多酚、草酸钙针晶含量的变化;采用细胞溶血率试验以及感官评价方法评价黄精麻味程度的变化,并进行麻味相关性分析。结果:随着蒸制次数的增加,不同产地的黄精中多酚和皂苷含量均呈先升后降的趋势,而草酸钙针晶含量、细胞溶血率以及麻味评分均逐渐下降;相关性分析表明,草酸钙针晶含量与黄精麻感程度之间呈显著正相关(P<0.05)或者极显著正相关(P<0.01);扫描电镜结果显示,蒸制处理后草酸钙针晶结构逐步遭到破坏,与黄精麻味的变化规律相吻合。结论:草酸钙针晶是黄精具有麻味特征的关键物质。

超声协同蒸汽处理对壳鸡蛋表面大肠杆菌的杀菌机理及动力学分析

为了探究超声蒸汽协同处理对蛋壳表面大肠杆菌的预测杀菌效果以及细菌损伤和死亡的机制,本研究以大肠杆菌为研究对象,构建了超声蒸汽协同处理对蛋壳表面大肠杆菌的杀菌动力学模型。通过控制蛋壳表面细菌液的浓度,讨论超声、蒸汽和超声与蒸汽协同作用对大肠杆菌的灭活作用,并与商业化杀菌中常用的次氯酸钠浸泡法进行比较。采用线性模型、Weibull模型、Log-Logistic模型和Modified Gompertz模型拟合了超声辅助蒸汽处理大肠杆菌的灭活曲线,对灭菌前后细胞形态的破坏程度和细胞内容物的泄漏情况进行分析。结果表明,经过180 s的150 W超声预处理和3 s的蒸汽处理后,大肠杆菌总数的对数值从6.26下降到2.04,死亡率达到67%。超声辅助蒸汽处理的灭菌过程更符合非线性动力学模型,且随着超声强度的增加和蒸汽处理时间的延长,Weibull模型更适合描述灭菌的动态过程。此外,协同处理会破坏大肠杆菌的超微结构以及菌体细胞的外部结构,使菌体细胞质溢出,从而改变膜的通透性。因此,超声协同蒸汽处理会加剧细菌的变形和损伤,导致细菌死亡。实验结果可为蛋壳表面大肠杆菌的灭活提供理论依据,综合贮藏期鸡蛋品质分析结果,该方法在禽蛋洁蛋生产中具有一定的应用前景。

不同脱皮方式对榄钱品质的影响

以鲜榄钱为原料,采用沸水漂烫、蒸汽热烫和80℃超声辅助3种方式脱皮处理,探究不同脱皮方式对榄钱脱皮率、色泽、质地等物理性质,可溶性蛋白质、淀粉、可溶性糖等营养成分及总叶绿素、可溶性单宁、抗坏血酸、类黄酮、总酚等化学成分变化的影响,结果表明:沸水漂烫法脱皮率最高;沸水漂烫与蒸汽热烫均能起到护色效果;80℃超声辅助脱皮对硬度、脆度、黏性、咀嚼性影响最小;沸水漂烫脱皮的榄钱抗坏血酸含量和总酚含量最高,可溶性糖含量与蒸汽热烫脱皮无显著差异;蒸汽热烫脱皮的可溶性蛋白质含量和类黄酮含量最高;80℃超声辅助脱皮的榄钱总叶绿素含量最高,脱涩效果最好;3种脱皮方式处理的榄钱淀粉含量均无显著差异。经加权分析可知,采用沸水漂烫脱皮的榄钱品质优于蒸汽热烫和80℃超声辅助脱皮的榄钱品质。

High-temperature stability of retained austenite and plastic deformation mechanism of ultra-fine bainitic steel isothermally treated below Ms

The mechanical properties of the sample and the stability of retained austenite were studied by designing two kinds of ultra-fine bainitic steel with different heat treatment methods austempering above and below Ms(martensite start tem-perature),which were subjected to tensile tests at 20 and 450℃,respectively.The results show that compared to room temperature(20℃)tensile properties,the uniform elongation of the sample at high temperature(450℃)significantly decreased.Specifically,the uniform elongation of the sample austempered above Ms decreased from 8.0%to 3.5%,and the sample austempered below Ms decreased from 10.9%to 3.1%.Additionally,the tensile strength of the sample austempered above Ms significantly decreased(from 1281 to 912 MPa),and the sample austempered below Ms slightly decreased(from 1010 to 974 MPa).This was due to the high carbon content(1.60 wt.%),high mechanical stability,low thermal stability for the retained austenite of the sample austempered below Ms.Besides,the retained austenite decomposed at high temper-atures,the carbon content and transformation driving force were significantly reduced,the transformation rate increased,and the phase transformation content reduced.

Enhanced high-temperature mechanical properties of laser-arc hybrid additive manufacturing of Al-Zn-Mg-Cu alloy via microstructure control

Recently,rapid and cost-effective additive manufacturing solutions for lightweight aluminum alloys with excellent high-temperature mechanical properties have been increasingly in demand.In this study,we combined laser-arc hybrid additive manufacturing with solution and artificial aging treatments to achieve Al-Zn-Mg-Cu alloy with favorable high-temperature strength via microstructure control.Hydrogen pores became the major defect in the as-deposited and heat-treated specimens.The continuous distribution of eutectics with hard-brittle characteristics at the grain boundaries was destructed following heat treat-ment.High-densityηprecipitates were uniformly dispersed in the heat-treated Al-Zn-Mg-Cu alloy,whereas appeared coarsened and dissolved at 473 K,owing to the rapid diffusion of Zn and Mg.The average 0.2%yield strength(318±16 MPa)and ultimate tensile strength(362±20 MPa)at 473 K af-ter heat treatment were enhanced by approximately 58%and 51%,respectively,compared to those of the as-deposited specimen.In addition,theηprecipitates contributed to lattice distortions and strain fields,which prevented dislocation motion and increased slip deformation resistance at high temper-atures.The as-deposited specimen exhibited intergranular fracture at 473 K,with cracks preferring to propagate along the aggregated eutectics.However,crack propagation proceeded in the sections with more pores in the heat-treated specimen.Our approach may provide a valid option for achieving alu-minum alloys with excellent high-temperature mechanical properties.

蒸汽爆破对木质纤维素高值化利用的研究进展

木质纤维素生物质是一种量大面广且廉价易得的可再生资源,已逐步实现由生物质向生物燃料、饲料原料和其他附加值产品的开发及应用,这样的高值转化与综合利用成为“走绿色发展道路、构建绿色生产体系”的重要部分。然而,木质纤维素的天然抗降解屏障及其独特的理化性质,纤维素-半纤维素-木质素三大组分的刚性网络一直是高效转化的瓶颈所在,合理有效的预处理技术则是资源化进程的关键步骤。本文落脚于木质纤维素生物质的基本组成和结构特性分析,在总结物理法、化学法、生物法等传统预处理方法优劣势的基础上,着重阐述了蒸汽爆破的发展历程、加工类型、适用范围、工作原理、反应阶段、技术特点、影响因素、主要参数和可能的副产物效应等,以及在生物质的纤维改性、结构变化、溶解特性、低聚糖制备、活性成分提取与反刍饲料化利用层面的研究进展。此外,还指出蒸汽爆破辅以真菌、细菌为主的微生物发酵,以及糖酶外源添加的后处理流程的发展趋势。最后,归纳了蒸汽爆破在未来商业化、工业化和规模化生产推广中可能面临的困难和挑战,分析提出相应的突破点和解决策略。并就蒸汽爆破技术对常见副产物类型饲料原料的降解效果,及其在单胃动物日粮中的合理应用进行展望,以期为该技术对生物质资源的开发、增值、饲料化应用的诸多潜能提供新思路和技术指导。

球形氧化铝载体结构优化

将拟薄水铝石与适量硝酸混合,形成溶胶溶液,滴入油-盐柱中固化后形成球形氧化铝凝胶,通过调节老化温度、时间以及增加水蒸气处理过程,成功制备出大可几孔径、高机械强度、酸性适宜的球形氧化铝载体。利用N_(2)吸附-脱附、颗粒机械强度测试、NH3-TPD、XRD等表征方法研究了老化前后以及水蒸气处理过程中,球形氧化铝孔结构、机械强度、表面酸性、晶相结构的变化规律,并确定最佳老化时间在4 h左右,最佳二段水蒸气处理时间在6 h左右。

基于气化和热解的医疗垃圾−废旧轮胎联合资源化利用系统性能分析

【目的】随着固体废物产生量的逐年增加,传统的处理方法难以满足日益严格的环保要求和资源循环利用的需求。为实现固体废物资源的高效利用,提出一种基于气化和热解的医疗垃圾−废旧轮胎联合资源化利用系统。【方法】该系统充分结合等离子气化技术以及热解技术的优势,将医疗垃圾等离子气化发电技术与轮胎热解技术进行耦合,将气化和热解过程得到的合成气共同作为燃气轮机的燃料加以利用,同时,燃气透平产生的高温烟气为轮胎热解提供热源,之后再通过余热锅炉回收烟气热量。在无害化处理医疗垃圾−废旧轮胎的同时,实现了能量的梯级利用。在固定给料速率的条件下,对所提出系统进行了能量分析和经济性分析。【结果】该系统能实现23.59 MW总能量的输出,总能量利用效率达到52.56%,远高于传统的垃圾发电效率。该系统具有良好的经济收益,在20年的生命周期内,可以实现相对净现值72797.81万元,且动态投资回收周期仅为3.13年。【结论】研究成果为固体废物资源的高效协同处理提供了新的技术路径。

印染企业蒸汽锅炉节能减排技术的研究

蒸汽锅炉目前已经应用于各个行业中,但是存在资源浪费率高、排放物污染严重的问题。为了解决该问题,提出了基于无磷水处理技术的节能减排方案,并用于印染企业蒸汽锅炉的节能减排中。对无磷水处理技术进行仿真试验,结果显示,使用该技术处理后的废水排放时各项指标的达标率都为100%,并且将磷质量浓度降低到了0.0001 mg/L,汞的质量浓度和废水急性毒性降低为0 mg/L。再对使用该技术的节能减排方案在印染行业中的效果进行分析。结果显示,使用该方案后,蒸汽锅炉每季度的天然气用量、污水排放量、锅炉水制备费用和磷酸盐投放量都明显降低。基于无磷水处理技术的节能减排方案能降低蒸汽锅炉的能源消耗、减少污水排放量并且降低使用成本。

生活垃圾焚烧发电厂设计参数与焚烧负荷变化的统计分析

以我国2016—2022年部分运营的超300座焚烧厂为研究对象,对单炉处理规模、主蒸汽设计参数、焚烧负荷率等设计和运营参数的变化规律进行统计分析。结果表明:单炉处理规模600 t/d以下的炉排炉数量占比最高,为63.54%,750 t/d及以上处理规模的大型炉排炉数量近些年明显增加;余热锅炉蒸汽参数中温中压(4.0MPa、400℃)占比为59.37%,13.5 MPa、450℃及13.7 MPa、485℃等更高参数焚烧厂数量有增加趋势。2016-2022年,我国垃圾焚烧处理总规模由2.558×10^(5)t/d提高至8.047×10^(5)t/d,同时焚烧负荷率由86.60%下降至72.78%。生活垃圾焚烧发电设施协同处置工业有机固废有助于提升焚烧厂焚烧负荷率,提升技术经济效益。

渣处理散逸蒸汽消能回收系统设计与应用

高炉渣处理生产过程中,采用锥斗沉淀池、气力提升机、螺旋分级机进行细渣沉淀、提取、分离时,螺旋分级机处会散逸大量蒸汽,加剧了区域钢结构及设备的腐蚀,影响周边环境,危及岗位职工身体健康和作业安全。文章提出的蒸汽效能回收系统通过选用玻璃钢离心风机,配合可移动式密封吸附罩、波纹管、风管等设备负压捕集逸散蒸汽,均匀分散至回水沟内,通过冲渣水实现蒸汽的冷凝、回收。该系统成本投入低、简单易实现、后期检修维护方便,并实现了蒸汽的回收利用,降低补水消耗的同时,取得了很好的环保效益。