激光金属汽化汽离混合区状态参量的稳定性及其影响因素分析

在汽离混合区激光强度时空修正的基础上,近似求解了流体力学模型下的状态参数,找出了稳定状态参数的共同自洽参量,分析了自洽参量的取值方法,研究了相关参数对自洽参量的影响机制,结果发现:(1)汽离混合区内,状态参量的稳定性可用自洽参量的稳定性来表征;(2)当入射激光强度小于108W.cm-2时,自洽参量随入射激光强度变化相对较快,稳定性差;当激光强度大于108W.cm-2时,自洽参量随入射激光强度变化相对较慢,稳定性高;(3)汽离混合区各处的约化自洽参量随辐照激光的波长成变周期增加的变化,波长越长,约化自洽参量越大;(4)要使自洽参量稳定,纹波较小,宜采取短波激光辐照;(5)当蒸汽压强小于2.7×106Pa时,自洽参量随蒸汽压强成指数递减规律变化;当蒸汽压大于2.7×106Pa时,自洽参量与蒸汽压强之间没有对应关系.     

中国无烟煤焦气化活性的研究——水蒸气与二氧化碳气化活性的比较

在常压和920℃~1050℃下，采用热重方法，进行了六种中国典型无烟煤焦水蒸气与二氧化碳气化活性比较的研究。结果表明，无烟煤焦与水蒸气气化反应的活性与无烟煤的煤化程度相对应，无烟煤煤化程度越高，水蒸气气化反应活性越小。无烟煤焦与二氧化碳气化反应的活性与煤中矿物质的催化作用有密切关系，煤中矿物质的催化作用越大，二氧化碳气化反应活性越大。无烟煤焦与二氧化碳气化反应活性明显小于与水蒸气气化反应活性，后者比前者大10倍左右。初步探讨了无烟煤焦与水蒸气和二氧化碳的气化机理。     

Properties and Characterization of Modified HZSM—5 Zeolites

Physicochemical and catalytic properties of phosphorus and boron modified HZSM-5 zeolites treated with 100% steam at 673K were investigated.The acidity and distribution of acidic sites were studied by infrared spectroscopy using pyridine as probe molecule and temperature programmed desortion (TPD) of ammonia.The structure of the samples was characterized by XRD,and the textural properties of the catalysts were determined by nitrogen isothermal adsorption-desorption measurements and scanning electron microscopy(SEM).The XRD results show that the modified samples have no novel crystalline phase,indicating a high dispersion of phosphorus and boron species.After treatment,the microporous volume and surface area of the samples markedly decrease,implying the bolockage of the channel.The nitrogen adsorption-desorption measurements suggest that the isothermal type of all samples is a combination of isothermal type Ⅰ and Ⅳ，and all hysteresis loops resemble the H4-type in the IUPAC classification.The total acidity of the modified samples,determined by pyrldine adsorption IR and TPD of ammonia,decreases in contrast to that of the parent HZSM-5.The conversion of n-heptane over P and B steammodified HZSM-5 is higher than that of P and B-modified HZSM-5 zeolites but lower than that of the parent HZSM-5.     

Enhancing the enzymatic hydrolysis of cellulosic materials using simultaneous ball milling

One of the limiting factors restricting the effective and efficient bioconversion of softwood-derived lignocellulosic residues is the recalcitrance of the substrate following pretreatment. Consequently, the ensuing enzymatic process requires relatively high enzyme loadings to produce monomeric carbohydrates that are readily fermentable by ethanologenic microorganisms. In an attempt to circumvent the need for larger enzyme loadings, a simultaneous physical and enzymatic hydrolysis treatment was evaluated. A ball-mill reactor was used as the digestion vessel, and the extent and rate of hydrolysis were monitored. Concurrently, enzyme adsorption profiles and the rate of conversion during the course of hydrolysis were monitored. α-Cellulose, employed as a model substrate, and SO₂-impregnated steam-exploded Douglas-fir wood chips were assessed as the cellulosic substrates. The softwood-derived substrate was further posttreated with water and hot alkaline hydrogen peroxide to remove >90% of the original lignin. Experiments at different reaction conditions were evaluated, including substrate concentration, enzyme loading, reaction volumes, and number of ball beads employed during mechanical milling. It was apparent that the best conditions for the enzymatic hydrolysis of α-cellulose were attained using a higher number of beads, while the presence of air-liquid interface did not seem to affect the rate of saccharification. Similarly, when employing the lignocellulosic substrate, up to 100% hydrolysis could be achieved with a minimum enzyme loading (10 filter paper units/g of cellulose), at lower substrate concentrations and with a greater number of reaction beads during milling. It was apparent that the combined strategy of simultaneous ball milling and enzymatic hydrolysis could improve the rate of saccharification and/or reduce the enzyme loading required to attain total hydrolysis of the carbohydrate moieties.     

含硫液体烃燃料水蒸气重整制氢I．Pt／Ce0．8Gd0．2O1．9催化剂的制备、表征和抗硫性能

以柠檬酸溶胶-凝胶法合成的具有萤石结构的Ce0.8Gd0.2O1.9（CGO）复合氧化物为载体，用初湿浸润法制备了负载型Pt催化剂．纯异辛烷的重整反应结果显示，600和800℃焙烧的催化剂达到了热力学平衡转化，1000℃焙烧会导致Pt的聚集和氧化物的严重烧结，因而催化剂活性较差．抗硫测试表明，800℃焙烧的催化剂抗硫性能最好，在300μg／g硫存在下，100h内异辛烷均接近完全转化；在500μg／g硫存在下催化剂仍表现出良好抗硫性能．程序升温还原和X射线分析结果显示．800℃焙烧时Pt与CGO载体间的相互作用最强，同时催化剂具有良好的热稳定性，这是催化剂具有抗硫性能并且抗硫作用持久的根本原因．反应条件下噻吩硫完全转化成H2S，硫的转化可能是通过氧化-还原机理进行的．     

CuZnAl水滑石衍生催化剂上甲醇水蒸气重整制氢Ⅰ. 催化剂焙烧温度的影响

 以类层柱CuZnAl水滑石为前体,经不同温度焙烧制备了一系列甲醇水蒸气重整制氢催化剂. 在250 ℃、 水/甲醇比1.3和重时空速2.5 h-1下的反应结果表明, 600 ℃焙烧的催化剂具有优异的活性和稳定性,而≤500 ℃和≥700 ℃焙烧后的催化剂活性较差. 热重、 X射线衍射、 傅里叶变换红外光谱和程序升温还原分析结果表明, 600 ℃焙烧时水滑石分解较为完全,析出纳米CuO粒子的同时伴生CuAl2O4尖晶石相,进而在反应过程中对金属Cu纳米粒子和ZnO起到良好的隔离和稳定作用. 焙烧温度≥700 ℃时CuO纳米粒子发生二次团聚,同时CuAl2O4尖晶石相大量生成,造成催化活性位减少,活性较低; 而焙烧温度≤500 ℃时水滑石分解不完全,生成 (Cu,Zn)AlxOy(CO3)z复合物且无尖晶石相伴生,造成反应中金属Cu纳米粒子和ZnO聚集,导致催化剂活性较低.     

甲醇重整反应中Pt/γ-Al2O3催化剂纳米Pt粒径与催化性能关系研究

利用硝基甲烷还原法在室温条件下得到了纳米Pt粒径可控的担载Pt/γ-Al₂O₃催化剂, 并利用甲醇重整反应为反应探针考察了Pt粒径与催化反应性能之间的关系, 发现催化反应的性能与担载贵金属颗粒粒径之间存在明显的相关性. 通过透射电镜(TEM)、X射线衍射(XRD)、程序升温还原(TPR)等测试手段对催化剂进行表征, 发现钠米Pt的粒径大小不但影响甲醇重整反应的活性, 同时也影响反应的选择性, 即催化剂的催化性能与担载贵金属粒径之间存在明显的尺度效应.     

Cu/ZrO2催化剂上乙醇水蒸气重整反应的研究: Ⅱ 反应条件的影响

采用沉淀法或醇凝胶法、浸渍法制备Cu/ZrO2催化剂，在常压微型固定床石英管反应器上进行乙醇水蒸气重整反应，采用程序升温还原（TPR）技术表征催化剂的还原特性。考察了催化剂还原温度、反应温度、水醇比、空速等对反应的影响以及催化剂的稳定性。结果表明，在300℃～500℃，随反应温度升高，乙醇转化率增大，H2选择性下降。不同还原温度对转化率的影响不是很大，对于H2选择性，300℃、400℃还原的催化剂优于500℃还原的催化剂。高水醇比有利于提高转化率和H2选择性。随空速增大，转化率和H2选择性呈现下降的趋势。8%Cu/ZrO2催化剂在400℃或450℃反应22h显示出良好的稳定性。     

液化石油气水蒸气重整镍催化剂新型载体研究

以共沉淀法合成了硅铝系载体（AS和SA），并采用改性天然高铝石为原料合成了矿物质载体（MC-1和MC-2）,采用浸渍法合成了镍负载型催化剂。用常压固定床管式反应器，考察了液化石油气水蒸气重整反应活性，通过XRD、物理吸附等手段对催化剂进行了表征。结果表明，以MC-1、MC-2和SA、AS为载体的催化剂的水蒸气重整活性明显高于目前普遍使用的Ni/α-Al2O3催化剂。以SA为载体，负载5%镍的催化剂具有最好的水蒸气重整活性。在750 ℃，水碳比为2.0的条件下转化率达100％，C1选择性达94.46％。XRD分析结果表明1 300 ℃焙烧后的SA载体中存在α-Al2O3晶型和莫来石结构。硅、铝添加次序对水蒸气重整活性影响较大，硅-铝添加次序的催化剂样品的活性高于铝-硅添加次序的样品，C1选择性提高12.7％。     

Flammability studies of 3-methyl pyridine/water system

In industrial processes, information on the safety property of chemicals is essentially crucial for safe handling during unit operations. Ensuring the safe use of combustible or flammable substances in processes is unlikely without detailed investigations of their flammability characteristics and related hazards. We studied 3-methyl pyridine (3-picoline), e.g., flammability limits (LFL/UFL), maximum explosion pressure (P _max), maximum explosion pressure rise (dP/dt)_max, minimum oxygen concentration (MOC), vapor deflagration index (K _g), and characterized the influence of inert steam (H₂O) on critical parameters for 3-picoline/water mixtures at 270°C, 1 atm, various oxygen concentrations, and vapor mixing ratios (100/0, 30/70, 10/90 and 5/95 vol.%) with a 20-L-Apparatus in simulated conditions, respectively. The results showed that the flammability characteristics of 3-picoline_(aq) all increased with the oxygen concentration. However, as the composition of inert steam increased, the flammability parameters and the degree of fire and explosion hazards were significantly reduced, instead. This study elucidated the flammability properties of 3-picoline mixed with inert steam. The conclusions could be applied to proactively prevent the relevant processes from incurring fire and explosion accidents.