CH_4/O_2等离子体反应直接合成甲醇的研究

高效甲烷转化技术一直是学术界及工业界的研究热点,其中,甲烷转化制甲醇颇受业界关注。然而,甲烷分子结构稳定且C—H键能大(413 k J/mol)导致转化困难。采用新型介质阻挡放电反应器,以循环水为接地极,在低温常压条件下通过分子氧实现甲烷直接氧化制甲醇。结果表明,在短停留时间和低功率条件下可以达到较高的甲醇选择性,在温度为85℃、n(CH4)∶n(O2)为2∶1、停留时间为0. 393 s和功率为30 W条件下,甲烷转化率达到4. 1%,甲醇选择性达到42. 2%,液体产物选择性达到76. 2%。     

生物质粗燃气自热重整调变的热力学分析

运用吉布斯自由能最小化方法对生物质粗燃气自热重整过程进行了热力学分析,研究了重整反应过程中的温度,O2/CH4摩尔比及焦油摩尔分数等因素对平衡产物组成的影响规律。研究结果表明:低温有利于CO歧化与加氢反应,而高温促进了CH4和CO2的转化,提高合成气H2+CO摩尔分数,降低H2/CO摩尔比。O2/CH4摩尔比的增加有利于生物质燃气从部分氧化反应向完全氧化反应转变,促进了CH4的重整反应而抑制了CO2的转化;O2/CH4摩尔比的增加降低了合成气H2+CO摩尔分数,降低了H2/CO摩尔比,在重整后的生物质粗燃气中,n(H2)/n(CO)≈1。积碳量随温度升高和O2/CH4摩尔比的增加逐渐减少,随着焦油(C10H8)物质的量的增加而增加。焦油物质的量增加提高了合成气中H2与CO摩尔分数,是重整反应的重要原料。优化的生物质燃气自热重整反应条件为温度1 023 K,O2/CH4摩尔比0.7,焦油摩尔分数<1%。     

不同结构微反应器下甲烷水蒸气重整制氢性能对比

微通道反应器是便携式制氢领域目前最有发展前景的技术之一。为了提高甲烷水蒸气重整在微反应器内制氢的效果,设计了三种不同结构的微反应器几何模型,分别为直管(Pipe)模型、平板圆弧弯道(FCC)模型和三纹内螺旋枪管(Tri-g ISB)模型,利用Ansys Fluent流体仿真软件结合甲烷水蒸气重整制氢的CHEMKIN反应机理文件对三种不同结构的微反应器进行了数值模拟分析。通过研究不同条件下微反应器出口气体组分变化可知,入口速度越小,CH4转化率和H2体积分数越高;S/C>3时,CH4转化率增大至80%以上、H2含量增加至73vol%以上;壁面温度越大,CH4转化率可稳定在99.9%,几乎完全转化,H2含量增大到77vol%以上,但温度过高会降低H2产量,增加CO含量。通过计算不同条件下微反应器达到稳定所需时间可知,随入口速度和S/C增加稳定时间均逐渐减小并趋于稳定,随壁面温度增加,稳定时间先减小后增加。通过对比三种微反应器可知,复杂结构可以强化微反应器的性能,但会增加微反应器达到稳定所需的时间。在微反应器性能方面：FCC模型最优,Pipe模型最差;而在稳定时间方面：随着结构复杂性增加稳定时间反而增长,Pipe模型最短,Tri-g ISB模型最长;微反应器结构的复杂程度不同,对性能的提升也不同,过于复杂的结构反而会抑制微反应器的性能。     

气体组分对绝热甲烷化反应温度和总转化率的影响研究

近年来,受天然气需求增加和环保压力影响,煤制天然气和焦炉煤气制天然气成为能源领域研究热点,而甲烷化技术是煤制天然气和焦炉煤气制天然气相关技术的核心之一。采用Aspen Plus模拟软件,模拟选取7组典型甲烷化反应原料气,研究了原料气组分变化对甲烷化反应温度和总碳转化率的影响。研究结果表明:绝热甲烷化反应器出口温度随着H2、CO的浓度增加而增加,随着CH4、CO2、N2和H2O浓度增加而降低,其中CH4和H2O的变化影响较为显著,所以在工艺流程设计和现场装置操作时,选取CH4和H2O作为甲烷化反应的主要控制手段。∑CO+CO2的总碳转化率随着原料气中CO、CO2浓度的增加而降低,随H2浓度增加而快速增加,而与N2、CH4和H2O的浓度影响较小。研究结果既可作为甲烷工艺设计的技术基础,也可对甲烷化现场装置的安全操作提供技术指导,促进煤制气产业的健康、快速发展。     

甲烷常压非催化部分氧化热模实验研究

氧气/甲烷摩尔比、操作负荷以及二氧化碳添加的研究对天然气非催化部分氧化转化炉运行优化和调节合成气氢气/一氧化碳摩尔比非常重要。文中搭建了天然气非催化部分氧化热模实验平台,考察了上述因素对出口合成气组成的影响。在研究范围内得出以下结论:氧气/甲烷摩尔比从0.85增加到1.10,出口甲烷摩尔分数随之降低,有效合成气(一氧化碳+氢气)摩尔分数先增大后减小,在氧气/甲烷摩尔比为0.95时达到最大值87.75%;由于壁面热损失和停留时间的影响,提升操作负荷有利于提高有效合成气摩尔分数,但会导致甲烷转化率下降;添加的二氧化碳参加了逆水蒸气变换反应及甲烷二氧化碳重整反应,使合成气中一氧化碳摩尔分数随二氧化碳/甲烷摩尔比的增加而增加,氢气的变化趋势则与之相反。     

气体组分对绝热甲烷化反应温度和总转化率的影响研究

近年来,受天然气需求增加和环保压力影响,煤制天然气和焦炉煤气制天然气成为能源领域研究热点,而甲烷化技术是煤制天然气和焦炉煤气制天然气相关技术的核心之一。文章采用Aspen Plus模拟软件,模拟选取7组典型甲烷化反应原料气,研究了原料气组分变化对甲烷化反应温度和总碳转化率的影响。研究结果表明:绝热甲烷化反应器出口温度随着H2、CO的浓度增加而增加,随着CH4、CO2、N2和H2O浓度增加而降低,其中CH4和H2O的变化影响较为显著,所以在工艺流程设计和现场装置操作时,选取CH4和H2O作为甲烷化反应的主要控制手段。∑CO+CO2的总碳转化率随着原料气中CO、CO2浓度的增加而降低,随H2浓度增加而快速增加,而与N2、CH4和H2O的浓度影响较小。文章研究结果既可作为甲烷工艺设计的技术基础,也可对甲烷化现场装置的安全操作提供技术指导,促进煤制气产业的健康、快速发展。     

流化床反应器中CO2甲烷化过程实验研究

设计制造一套千瓦级容量甲烷化流化床反应装置,进行甲烷化流化床反应器运行特性实验研究.综合考察温度、空速、压力对甲烷化反应转化特性的影响,并在此基础上对电转气工艺设计思路进行探讨和分析.结果表明:随着温度的升高,CO2转化率先逐渐上升再下降,因此在单级流化床反应器内难以兼顾反应转化效率和副产蒸汽品质;甲烷化反应速率快,空速增大时CO2转化率只有小幅降低,因此采用大空速可节省催化剂用量,但可能会带来颗粒破碎隐患;压力增大可有效提高CO2转化率,但会提高电转气工艺投资成本,应采用分离设备或水汽冷凝脱除设备,低压下实现高转化率.     

压力对CH4/CO2重整制取合成气反应性能的影响

以Ni／CeO2-Al2O3为催化剂,考察了压力对CH4／CO2重整反应的影响。实验结果表明,提高反应压力不仅使甲烷和二氧化碳的转化率降低,并由于积炭的加剧致使催化剂的失活速度加快。提高原料气中CO2与CH4摩尔比,气体空速,反应温度可以提高催化剂稳定性,减缓催化剂的失活速度。向反应体系中加入消碳能力强的O2同样可以提高催化剂稳定性。     

焦炉煤气三重整制合成气的工艺比较及催化剂改性

在固定床反应器中,对焦炉煤气H2O/O2/CO2三重整制合成气的3种工艺———非催化工艺、催化工艺和二段工艺进行了比较;同时考察了以共浸法加入助剂CaO、Co、Cu、Fe对二段工艺中催化反应性能的影响。结果表明,焦炉煤气中氢气的存在不利于甲烷的转化,但有利于二氧化碳的转化。反应温度高于800℃时,二段工艺的甲烷和二氧化碳转化率明显高于其他2种工艺,与催化工艺相比,二段工艺中焦炉煤气的空速可达6 945 h-1;碱金属氧化物CaO的加入促进了CH4和CO2的转化;助剂Cu提高了催化剂的高温活性,900℃时CH4转化率可达99.1%,CO收率可达95.5%;Fe提高了催化剂的低温活性。XRD结果表明,CaO能削弱Ni2Al4O4的特征峰,催化剂的还原性和分散性较好。     

循环流化床合成气甲烷化过程模拟及影响因素分析

以甲烷化循环流化床反应器为研究对象,采用计算颗粒流体力学(CPFD)方法,耦合了甲烷化反应动力学模型,实现了甲烷化在循环流化床中的反应过程。将模拟结果同文献中的实验数据进行了对比验证,获得了反应器的内部流场、温度场以及组分浓度分布。数值模拟研究了不同操作条件对甲烷化特性的影响规律。结果表明:催化剂颗粒在反应器内的流化行为对反应影响显著,反应器提升管固体密相区是反应进行的主要区域;通过提高反应压力和H2/CO(物质的量之比),降低空速,可以提高CO转化率和CH4收率。     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究

建立了测定地球化学样品中包括As、Cr、Ge、V等18种微量、痕量元素的ICP-MS方法。地化试样用HF-HNO3混酸分解后,以1 1 HNO3溶解干渣。由于制样不使用盐酸,避免了Cl对As、Cr、Ge、V的质谱干扰。用国家一级地球化学标准物质GBW 07309制备溶液优化仪器工作参数,并用于校准。方法测定限(6s)为:0.007~6.4μg/g,精密度(RSD%,n=12)为:29%~9.4%,经过国家一级地球化学标准物质的分析验证,结果与标准值吻合。方法已应用于国土资源调查的试样分析。