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.

The effect of doping and steam treatment on the catalytic activities of nano-scale H-ZSM-5 in the methanol to gasoline reaction

In the transformation of methanol to gasoline （MTG）, the selectivity to gasoline and the aromatic content in the produced gasoline are important factors. The catalytic activities of steam-treated and non-steam-treated nano-scale H-ZSM-5 （NHZ5） catalysts impregnated with Ag（I）, Zn（II） or P（V） have been investigated in a continuous flow fixed bed reactor. The NH3-TPD results showed that after impregnation, the Ag/NHZ5, Zn/NHZ5 and P/NHZ5 catalysts contained comparatively more strong, medium-strong and weak acid sites, respectively. Treatment with steam decreased the number of acid sites in all the catalysts, but the pore volumes in the catalysts were larger which improved carbon deposition resistance resulting in prolonged lifetimes. After 6 h of MTG reaction, the selectivity to gasoline for the steam-treated catalysts, Agrho/NHZ5, ZnH2o/NHZ5 and PH2o/NHZ5 were 70.5, 68.4 and 68.7 wt-%, respectively, whereas their respective aromatic contents in the produced gasoline were 61.9, 55.4 and 39.0 wt-%. Thus Pn2o/NHZ5 is the most promising catalyst for MTG applications which can meet the China IV gasoline standard that the amount of aromatics in gasoline should be less than 48 wt-%.

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.

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.

Catalytic activity of phosphorus and steam modified HZSM-5 and the theoretical selection of phosphorus grafting model

The modification of HZSM-5 zeolite with phosphorus and steam has been studied. Results show that 1% phosphorus and steam modified HZSM-5 has the highest catalytic activity for n-heptane. Physicochemical and catalytic properties of 1% phosphorus and steam modified HZSM-5 zeolites have been investigated. The X-ray diffraction （XRD） results exhibit that there is considerable variation in the relative intensity of the individual diffraction peaks. The acidity of the samples decreases with an increase in the steaming temperature, which is determined by the IR of adsorbed pyridine and temperature programmed desorption （TPD） of ammonia. The oxidation state of phosphorus shown by XPS is ＋5, and a model for surface structure modification is proposed. The nitrogen adsorption isotherm for all samples is a combination of type I and type IV, all hysteresis loops resemble the H4-type. The density functional and cluster model methods have been invoked to select the phosphorus grafting model, and it was found that the phosphorus grafting model were more probable in the form of the terminal oxygen coordinating with aluminum.

CHEMICAL AND PHYSICAL CHANGES OF STEAM TREATED WOOD CHIP

High dimensional stable particlcboards could be produced by usisng saturated steam treated wood chip at elevated pressures. Sample Particleboards were made from wood chip of Birch (Platyphylla). The component changes of steam treated wood chip were analysed by infrared. Infrared spectra demonstrated that the hemicelluloses in steam treated chip were less than those in untreated chip. This is one of the main reasons why steam treatment could improve particlcboard stability. The free radical concentration of steam treated chip surfaces was analysed by ESR spcctroscopy. The results showed that free radical concentration of treated chip surface was higher than that of untreated chip surface. The glueyncss of chip increased and particlcboard resin content decreased.

Pore Structure and Catalytic Performance of Steam-Dealuminated ZSM-5/Y Composite Zeolites

For investigating the effect of dealumination on the pore structure and catalytic performance, ZSM-5/Y composite zeolites synthesized in situ from NaY gel were dealuminated by steaming at different temperatures. XRD (X-ray diffraction) characterization indicates that the relative crystallinity of the composite zeolites decreases with the increase in Si/Al ratio after steaming. N2 adsorption-desorption suggests that more mesopores are formed while the BET (Brunauer, Emmett and Teller) specific surface area and the micropore specific surface area decrease as the temperature of steaming rises. Daqing heavy oil was used as feedstock to test the catalytic cracking activity of ZSM-5/Y composite zeolites. The experimental results of the catalytic cracking performance reveal that the distribution of products differs due to the different conditions of hydrothermal treatment. Further hydrothermal treatment leads to an increase in the yield of light oil, and a decrease in the yield of gas products and coke.

蒸汽处理对上部白肋烟重要香味物质的影响研究

【目的】考察蒸汽处理对上部白肋烟重要香味物质的影响。【方法】利用动态水分吸附脱附仪,在95%相对湿度下,研究蒸汽处理温度和处理时长对上部白肋烟非酶棕色化反应产物、苯丙氨酸类降解产物、类胡萝卜素降解产物和西柏烷类降解产物含量的影响,分析这4类重要香味物质在不同处理条件下的变化趋势。【结果】在实验范围内,提高处理温度或增加处理时长会使非酶棕色化反应、类胡萝卜素降解、西柏烷类降解三类产物的含量先增加后减少,而苯丙氨酸类降解产物的含量则呈下降趋势。在60℃处理3h时,上部白肋烟这4类重要香味物质的总含量增加了12.53%,且香气和杂气等感官品质指标明显提高。【结论】蒸汽处理可作为一种有效调控上部白肋烟香味物质和感官品质的方法。

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。

微波处理和压力汽蒸对河粉品质的影响

为推进微波处理和压力汽蒸技术在河粉加工中的应用,将籼稻砻谷碾白后,采用不同微波功率(280、420、560、700 W)处理,以未处理作对照,测定籼米理化及糊化特性,然后采用湿法加工成籼米粉,分别进行常压汽蒸和压力汽蒸制备河粉,以常压作对照,测定河粉外观品质、质构特性及感官评分,分析微波处理对籼米理化、糊化特性及压力汽蒸河粉品质的影响。结果表明:280 W微波功率处理对籼米垩白、直链淀粉含量影响不显著,而对新鲜度影响显著(P<0.05),呈增大趋势,此条件下籼米的黏度值升高;随微波功率的增加,河粉品质先升后降,在280 W时最好;与常压汽蒸相比,压力汽蒸河粉亮度增加,硬度增大,黏性降低,韧性、延展性增大,均呈显著变化(P<0.05),感官评价总分提升。因此,适宜的微波功率(280 W)处理能提升籼米新鲜程度、改善其吸水特性,压力汽蒸有利于提升河粉综合品质。

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。

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。

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。

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。

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。

铁基粉末冶金零件蒸汽处理膜层的影响因素及评价体系

蒸汽处理技术是一种应用广泛的铁基粉末冶金产品化学强化方法,能够在产品表层形成一层结合性强、硬度高且致密的保护膜,具有耐腐蚀、抗磨损、提升产品硬度的效果。本文系统阐述了蒸汽处理技术的反应原理,讨论了反应热力学和动力学过程对蒸汽处理保护膜质量的影响。由于目前对蒸汽处理层的检验检测手段不统一,为推动铁基粉末冶金零件蒸汽处理工艺的标准化,本文结合生产现状系统总结了蒸汽处理保护膜膜厚、结构、成分以及结合力的检测方法,并结合实际实验结果说明了各检测方法的优劣势。

毛竹纤维束活性炭的制备及其对苯酚的吸附

苯酚是一种高毒污染物,广泛存在于石油、涂料、造纸、聚合物和制药等行业的工业废水中,因此,开发一种具有高吸附性能的活性炭以提升水质十分重要。以经过高温饱和蒸汽处理后生态分离出的竹纤维束作为原料,对其进行炭化,再用氢氧化钠活化制备竹纤维束活性炭。分析了炭化时间(0.50~1.50 h)、炭化温度(300~400℃)、竹碱比(1∶1.0~1∶4.0)在800℃活化1 h的情况下,对竹纤维束活性炭性能的影响。采用比表面积及孔径分析仪、扫描电镜及能谱仪、傅里叶变换红外光谱等技术对活性炭结构进行表征。研究发现,对炭化时间和温度进行优化后,即可获得微孔占比87%以上的活性炭;比表面积随碱添加量的增加而增加。在350℃下炭化0.75 h后,以竹碱比1∶4.0在800℃活化1 h,能够获得最高比表面积的活性炭BFAC-TC-4,比表面积达2817.00 m^(2)/g,总孔体积为1.6157 mL/g,且微孔占比达94.89%,碘吸附值可达2769.88 mg/g。在室温下,活性炭对质量浓度为200 mg/L的苯酚废水吸附容量可达297 mg/g,吸附过程符合拟二级动力学模型,并且在10 min内就可以完成对苯酚的吸附。

渣处理散逸蒸汽消能回收系统设计与应用

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