O2/CO2/H2O气氛下CO燃烧机理的分子动力学模拟研究

采用反应分子动力学(ReaxFF MD)模拟方法研究了O₂/CO₂/H₂O气氛下CO的燃烧。结果表明：根据化学平衡原理,高浓度CO₂抑制CO的氧化,同时CO₂在高温下参与反应CO₂+H—→CO+OH,进一步抑制CO氧化。在较低温度条件下,较高浓度H₂O的三体效应显著,抑制了CO氧化。另一方面,在较高温度条件下,H₂O参与的H₂O+H—→H₂+OH和H₂O+O—→OH+OH反应占据其化学作用的主导地位,进而促进CO氧化。随着O₂浓度的增加,CO的氧化速度加快。     

H2O2作添加剂对SNCR脱硝工艺的影响

为了改善选择性非催化还原(SNCR)脱硝工艺的反应特性,以H2O2为添加剂,对SNCR过程进行了实验研究。在小型SNCR实验台上进行实验,以N2作为载气,以纯NO模拟NOx气氛,初始NO浓度为360μL/L,O2=4%,H2O=8%,NSR=1.5。通过对实验结果进行分析,得到H2O2对低温下的脱硝率有促进作用,对最大脱硝率以及最佳脱硝温度没有影响,最大脱硝率依然为80%左右,最佳脱硝温度为925℃。另外还分析了H2O2对NH3浓度、HNCO浓度、NO2浓度、N2O浓度以及N2转化率的影响及其原因。     

竹木质素的NaOH-乙醇水溶液热降解及产物分析

本研究以NaOH-乙醇水溶液为溶剂体系对竹木质素进行热降解,主要考察了NaOH浓度、反应温度、反应时间、乙醇用量等条件对竹木质素降解转化为酚类化合物的影响。通过GC-MS及FT-IR对降解产物进行分析检测,得出最佳反应条件为：竹木质素5 g,NaOH浓度（基于乙醇水溶液）20 g/L,乙醇10 mL,反应时间2 h,反应温度240℃。在此条件下,降解产物中总的酚类化合物的相对峰面积为73.88%,残渣率为30.67%。竹木质素的降解主要产物是酚类化合物：苯酚（17.98%）、2-甲氧基苯酚（16.49%）及1,2-苯二酚（10.03%）。与现有文献相比,本文竹木质素在碱性乙醇溶剂体系中降解能够获得较高产量的酚类化合物,有望实现竹木质素的高值化利用。     

铝锂/镁合金与H_2O反应的热力学分析

根据吉布斯能最小原理,利用FactSage计算研究了Al-Li-H2O体系和Al-Mg-H2O反应体系的热力参数,研究了温度、合金组成和H2O量的影响。结果表明:Al-Li-H2O体系氧化反应可以自发进行,随着温度的升高反应放出的热量减少;合金组成中Al含量越高,生成的H2越少;随着Li含量增大,固态产物由Al2O3向LiAlO2、Li2O转变。Al-Mg-H2O体系氧化反应可以自发进行,随着温度的升高反应放出的热量减少;合金组成中Al含量越高生成的H2越多;随着Mg含量增大,最终固态产物由Al2O3向MgAl2O4、MgO转变。Al中添加Li或Mg因产物发生转变而对制氢反应有促进作用;H2O量增加有助于反应最终温度的降低,温差为1800~2000 K,对金属制氢的实施应用有指导意义。     

NaOH/H2O2预处理促进玉米秸秆酶解产糖工艺条件的研究

采用正交实验初步探讨了NaOH/HO2O2对经白腐菌Hyrophous sp.254处理15 d的玉米秸秆进行预处理的最佳条件.在NaOH/H2O2预处理过程中,NaOH浓度、H2O2体积分数、底物浓度及预处理时间均对秸秆的纤维素酶酶解效率存在一定影响.试验表明,NaOH/H2O2的最佳预处理条件:NaOH浓度为7g/L,H2O2体积分数为0.7%,底物浓度为50g/L,处理时间为24h.在优化的工艺条件下,玉米秸秆的还原糖产量达到了0.417 g/g,H2O2用量减少了30%,废水排放量减少了60%.     

O2/CO2气氛下生物质混煤燃烧SO2排放特性的实验研究

在水平管式炉上通过在线烟气分析仪研究了O2/CO2气氛下生物质混合比例、温度、燃烧气氛及氧浓度对生物质混煤SO2排放特性的影响规律。结果表明,O2/CO2气氛下,随着生物质混合比例的增大,生物质混煤SO2释放峰值减小,SO2排放完毕的时间减少,SO2的排放量降低;随着温度的升高,生物质混煤SO2的排放量增加。O2/CO2和O2/N2气氛下随着氧浓度的增大,生物质混煤SO2的排放量均增加。相同氧浓度时,O2/CO2气氛下生物质混煤SO2的排放量略小于O2/N2气氛下的情况,其降低幅度约为5%左右。     

Fe-Ag/La_2O_3-ZrO_2催化乙醇水蒸气重整制氢

用草酸盐沉淀法制备La2O3-ZrO2复合氧化物载体,用浸渍法制备Fe-Ag/La2O3-ZrO2催化剂;用X射线衍射技术表征催化剂;考察了催化剂在乙醇水蒸气重整反应中的催化活性。结果表明,La含量较低的La2O3-ZrO2复合载体具有明显的四方晶相结构;Fe-Ag/La2O3-ZrO2催化剂在乙醇水蒸气重整反应中表现出良好的催化性能,气相产物中H2物质的量分数很高,CO和CH4物质的量分数很低;La,Ag,Fe含量影响催化剂的活性及选择性。在以(1Ag20Fe)20(2La8Zr)为催化剂,反应温度为823 K、乙醇与水物质的量比为1∶6,乙醇水溶液流速为0.1 mL/min的反应条件下,乙醇转化率达到95.7%,气相产物中H2物质的量分数为78.7%、CO的物质的量分数小于1.2%。     

氧气和双氧水水热降解飞灰中二恶英的研究

通过水热法研究O2、H2O2降解医疗垃圾焚烧飞灰中二恶英的规律。研究结果表明,2MPa氧气和8.36mL双氧水,其他条件相同时,飞灰中二恶英降解效率基本相同;50℃和通氧条件下,飞灰中二恶英降解效率最高84.2%;在氧化剂存在时,PCDFs的降解效率高于PCDDs的降解效率;除T4CDD-2378的降解效率低于60%外,其余16种有毒二恶英降解效率均高于70%,其中T4CDF-2378在200℃和通氧条件下降解效率最高为94.1%;水热法降解二恶英过程中存在高代二恶英的脱氯反应。     

超临界水中2-萘酚氧化分解的研究

建立了超临界水中有机物连续氧化分解的实验装置,确定了本实验体系适宜的工艺条件,初步探索了超临界水中2-萘酚氧化分解产物。实验表明:萘酚在实验条件下氧化分解主要降解产物主要为邻苯二甲酸、1-2萘醌、苯、苯甲酸和苯酚,氧化分解路线为2-萘酚→1,2萘醌→邻苯二甲酸→苯甲酸和苯→苯酚→短链羧酸→H2O,CO2等小分子。     

蒽醌-2-羧酸作为光催化剂催化解聚木质素

木质素是自然界中丰富的可再生芳香碳资源,其解聚得到的单体可以作为重要的化工原料。以蒽醌-2-羧酸作为光催化剂,在硝基苯存在和LED光源照射下,5 h内木质素模型化合物中β-O-4键有80%的转化率。对于木质素β-O-4多聚体,该体系也表现出了光催化活性,将蒽醌-2-羧酸负载在非均相载体上,在光催化降解中也可以获得77%的底物转化率。该反应涉及了木质素β-O-4中C_α—C_β键和C_β—O键的断裂,在催化剂的作用下,首先发生C_α—OH的脱氢,随后经过分子内的断键和重新成键生成苯甲醛和愈创木酚。本研究加深了对光催化木质素氧化过程中C—C键断裂过程的认识,有助于理解木质素的解聚机制。     

纳米TiO2协同Fenton试剂光催化降解甲基橙

采用纳米TiO2协同Fenton试剂光催化降解甲基橙,研究了纳米TiO2与Fenton试剂的协同效应,考察了H2O2用量、甲基橙溶液的初始浓度及初始pH值对降解效率的影响,并对其降解动力学规律作了初步探讨。结果表明:纳米TiO2强化了Fenton试剂对甲基橙的降解效率,它们之间产生了较强烈的协同效应。在实验过程中,纳米TiO2协同Fenton试剂光催化降解初始浓度30mg/L、pH=3.0的甲基橙120min,其降解率达到99.4%,分别是同等实验条件下单独纳米TiO2降解率的2.63倍,单独Fenton试剂降解率的2.32倍,是两者算术和的1.2倍。在实验浓度范围内,甲基橙的降解反应符合准一级动力学过程;与Fenton反应相比,在0.2、0.4、0.6g/L纳米TiO2的协同作用下,甲基橙的降解表现反应常数分别提高了1.71、2.51和3.36倍,半衰期相应缩短。另外,H2O2用量、甲基橙溶液初始浓度及初始pH对降解率有一定影响。     

基于HCCI模型的过氧化氢对柴油机燃烧性能的影响分析

根据柴油机的燃烧性质建立均质压燃混合模型-HCCI仿真模型,使正庚烷、空气及过氧化氢均匀混合喷入气缸中燃烧,并通过改变过氧化氢的浓度和在混合气体中的体积分数,分析燃烧过程中不同时刻气体温度和压力的变化.研究表明:过氧化氢的添加确实在某种程度上改善了柴油机的燃烧特性,提高了柴油机的经济效益;但不同的添加比例对柴油机的燃烧...     

H_2O_2/Nafion-纳米TiO_2复合膜强化日光光解脱色甲基橙染料研究

用流延法在石墨板上成功制备出用于光催化的Nafion-纳米TiO_2复合膜。在H_2O_2存在的条件下,用Nafion-纳米TiO_2复合膜对甲基橙染料进行可见光照射处理。结果表明,H2_O_2/Nafion-纳米TiO_2复合氧化工艺中甲基橙降解脱色速率显著提高,两者之间存在明显的协同效应。在协同体系中,酸性媒介比碱性媒介更有利于甲基橙染料光解脱色。实验所用的NO_3~-、Cl~-和SO_4~(2-)等阴离子,均对降解脱色有抑制作用,其中NO_3~-对脱色作用抑制最显著。可见光辐射处理前后,UV-Vis谱图分析表明在H_2O_2/Nafion-纳米TiO_2复合膜处理中甲基橙溶液脱色是因为染料发生氧化光解作用。     

Fenton预处理突发苯胺类污染河水试验及现场工程应急处置

针对某化工园区爆炸事故中高苯胺类、高CODCr污染河段水体,提出Fenton氧化法进行预处理,在单因素试验的基础上进行正交试验,研究了初始pH值、(H2O2)/(Fe2+)摩尔比、H2O2与Fe2+投加量及反应时间对受污染水体处理效果的影响。试验结果表明,当反应时间为60 min、初始pH值为5、(H2O2)/(Fe2+)摩尔比为8∶1、投加量为(CODCr)/(H2O2)质量比1∶2时,处理效果最佳,出水苯胺类未检出,CODCr可降至119 mg/L,去除率达79.6%。根据试验结果指导现场工程应急处置的实施,运行后出水苯胺类浓度可降至0.31~0.77 mg/L,CODCr降至235~301 mg/L,达到园区原有污水处理系统进水水质要求。     

日光作用下草酸铁/过氧化氢体系中偶氮染料降解的试验研究

利用太阳能使有机污染物降解以改善水环境质量已引起环境保护工作的重视、扩展有机物降解中光谱响应范围,充分利用太阳能是需要研究解决的关键问题。以偶氮染料为目标物,对自然光源下,应用草酸铁／过氧化氢体系的降解过程进行了试验研究,以一级反应动力学方程为基础,对影响反应的主要因素进行了分析,并与应用ＴｉＯ２、Ｗｏ３为催化剂的试验进行了比较。结果表明,通过日／草酸铁／过氧化氢的作用,可有效地净化含染料废水。     

Constructing 1D/2D heterojunction photocatalyst from FeSe2 nanorods and MoSe2 nanoplates with high photocatalytic and photoelectrochemical performance

Although the traditional metal oxide catalyst has high activity and strong degradation ability, the forbidden bandgap is generally larger, and the utilization rate of sunlight is much low. Moreover, the high internal resistance inhibits carrier transfer, so the photoelectrochemical performance needs to be improved. Selenides with narrow bandgap and low internal resistance are promising candidates for photocatalysts. A new type of 1D/2D selenide heterojunction was constructed by compositing MoSe₂ and FeSe₂, two kinds of narrow bandgap metal selenides. In this 1D/2D heterojunction, MoSe₂ presents a three-dimensional network structure, which can effectively collect and transport optical carriers, and it is an ideal heterostructure as a substrate loaded with 1D FeSe₂ nanorods. Moreover, this heterojunction has good light absorption characteristics and can achieve full spectrum absorption of ultraviolet and visible light. This FeSe₂/MoSe₂ composite has photocatalytic performance more than 3.4 times that of MoSe₂, and its photoelectrochemical performance is more than 2 times. The experimental results show that FeSe₂/MoSe₂ is an ideal composite system with great potential in photocatalysis.     

Effects of H2O and CO2 on the homogeneous conversion and heterogeneous reforming of biomass tar over biochar

The effects of H₂O and CO₂ reforming agents on the homogeneous conversion and heterogeneous reforming of biomass tar were studied in the presence of a biochar catalyst to better understand the transformation pathway between tar and biochar. Catalysis was performed in a two-stage fluidized bed/fixed bed reactor while Raman analysis and Gas Chromatograph-Mass Spectrometry were used to investigate biochar and tar characteristics. The results show temperatures of 700–900 °C are required for the homogeneous transformation of tar in the presence of H₂O/CO₂, which especially affect polycyclic aromatic hydrocarbons. The tar homogeneous reforming effect of 15 vol.% H₂O is significantly higher than that of 29 vol.% CO₂. During heterogeneous reforming of tar over biochar at 800 °C, the tar yield decreases in varying degrees with the H₂O and CO₂ concentration increasing. H₂O and CO₂ not only directly affect the tar transformation on biochar, but also indirectly influence the reforming of tar through changing the structure of biochar catalyst. The formation of additional oxygen-containing functional groups and transformation of small aromatic rings to larger aromatic rings in the biochar structure are promoted with the concentration of H₂O and CO₂ increasing. Under a H₂O/CO₂ atmosphere, a higher degree of aromatic ring heterogeneous reforming occurs over biochar than for non-aromatic tar components. Heterogeneous reforming reactivity of tar is promoted by the biomass tar structure (e.g the substituents, large aromatic ring size and five-carbon ring structures) over biochar under H₂O/CO₂ atmospheres. Further increasing H₂O and CO₂ concentration enhances this effect.     

Supercritical water gasification of naphthalene over iron oxide catalyst: A ReaxFF molecular dynamics study

ReaxFF molecular dynamics simulation has been employed to investigate the iron oxide-catalyzed supercritical water gasification (SCWG) of naphthalene (NAP), a common component of refractory polycyclic aromatic hydrocarbons. Simulation results showed that synergistic effects between SCW and iron oxide catalyst enormously promoted the degradation of NAP and the production of H₂ and CO. During the gasification process, SCW served not only as H source for H₂ generation but also as O source for CO generation and lattice oxygen recompense, while the major roles of iron oxide catalyst were to provide lattice oxygen with high hydrogen-abstraction ability, catalyze SCW to produce more active species, and weaken the C–C bonds. The effects of different parameters were subsequently revealed: increasing the use of H₂O molecules raised H₂ and CO yields along with the lattice oxygen supplement but slowed the rate of CO generation, high hydrogen recovery was achieved at high NAP concentration accompanied by a low carbon gasification efficiency. Our simulated results further demonstrated that the deactivation of iron oxide catalyst was caused by carbon deposition, lattice oxygen exhaustion and iron loss. SCW media effectively inhibited the iron loss, while calcination in O₂ environment could successfully regenerate the iron oxide catalyst by cleaning up the carbon deposition and replenishing the lattice oxygen.     

Nickel volatilization phenomenon on the Ni-CGO anode in a cathode-supported SOFC operated at low concentrations of H2

Rapid degradation phenomenon is generally occurred when Ni-based anode on a cathode-supported SOFC is operated in low concentrations of hydrogen at high current density. In order to clarify this phenomenon, homogenous NiO-Ce_0.8Gd_0.2O_1.9 (CGO) composites powder with fixed weight ratio of Ni:Ce was synthesized using a nitric-citrate sol-gel method, and coated on LSM-CGO cathode-supported SOFC using slurry coating method. As-prepared fuel cells exhibited good performance when they were operated at pure H₂. However, rapid degradation phenomenon on Ni-CGO anode usually happened when low concentration of H₂ was used as fuel at high current density. Obvious microstructure damage and sintering of Ni were observed in SEM micrographs of Ni-CGO anode after repeated degradation process in 5.66% of H₂ at high current density. Furthermore, the decrease in Ni amount in Ni-CGO anode was also found via EDX analysis when this degradation process was repeated for several times. It is inferred that the volatilization of nickel hydroxide should happen at triple-phase boundaries of Ni-CGO anode when high partial pressure ratio of H₂O and H₂ appeared in this case.     

O_2/CO_2条件下生物质焦和煤焦燃烧动力学特性

为得到富氧条件下生物质焦和煤焦的燃烧动力学特性规律,利用热重研究了麦秆焦,木屑焦以及烟煤焦在富氧气条件下的燃烧特性。实验结果表明:无论是生物质焦还是煤焦,相同的O2浓度下,O2/CO2气氛下焦样的着火相对于O2/N2气氛均发生了延迟,燃烧特性指数也均低于O2/N2气氛下对应值;在O2/CO2气氛和O2/N2气氛下,随着O2浓度的增加,焦样的着火温度均降低,燃烧特性指数增大,且提高O2浓度对煤焦着火的改善程度显著优于木屑焦。