Name: ammonia synthesis at low pressure
Uploaded: 2017-08-23T13:00:00.000+00:00
Duration: 8 min 14 s
Description: Watch this Scientific Journal Video about Ammonia Synthesis at Low Pressure at JoVE.com

这项工作主要由 ARPA-E，美国能源部明尼苏达州环境和天然资源信托基金，部分建议立法公民委员会对明尼苏达州资源和 MNDRIVE 的一项倡议明尼苏达大学。额外支持来自德雷福斯基金会。

1.飞行员厂启动 <ol><li>氮生产系统 <ol><li>转上空气干燥机、 空气压缩机、 氮发生器。验证至少 800 kPa 的空气压缩机储气罐。这不断发送氮到缓冲罐，直至不超过 0.004%(40 ppm) 氧氮。</li>
		<li>开启氮气气体增压器。气体增压器开始填充氮气供应坦克，在压力下高达 17 MPa。</li>
	</ol></li> <li>制氢系统 <ol><li>打开冷水机组、 水去离子装置和电解槽。电解槽将无法运行没有排气系统，因为那里是措施负压通风为了让电解槽启动流量传感器。率为 0.54 公斤/h，产生氢气和排气压力将约 1.5 MPa。</li>
		<li>氢开启气体增压器。冷水机组是业务和冷却液流动通过验证。氢供应坦克将填补达 17 MPa。</li>
	</ol></li> <li>氨防滑启动 <ol><li>使用在控制室的计算机执行以下操作: <ol><li>验证为大厦的紧急出口。</li>
			<li>确保建筑中的氧、 氢和氨的浓度分别是小于 20%，19 ppm 和 35 ppm。</li>
			<li>验证，氢气和氮气供应坦克收取到 17 MPa。</li>
			<li>确保绕过氨采样器和重量罐阀。</li>
			<li>通过设置防滑加压与氮防滑 &#39; s 氮入口调节器到 2.5 MPa。设置为 300 磅/平方英寸的氮压力调节器，然后打开氮旁路阀填补打滑与氮到 300 磅/平方英寸。然后关闭氮气阀，当达到这种压力。设置氢定期为 1,200 psi 和打开氢气阀允许滑到 1,200 psi 填充。然后关闭氢旁路阀。</li>
			<li>氢进水阀打开并设置防滑 &#39; s 氢入口调节器到 10 MPa。</li>
			<li>设置为 1 MPa 的 NH 3 压力调节器。</li>
			<li>使用 GUI 控制软件来关闭/打开多个旁路阀上打滑、 空压机和空气阀。</li>
			<li>使用 GUI 控制软件来打开几个 PID 控制器以确保打滑厌倦 N 2 1:3 比例: H 2.</li>
			<li>从控制室，和使用主 GUI 控制软件，开始打滑。压缩机启动分发的气体在打滑，并注入新鲜饲料。</li>
			<li>在 GUI 控制软件，设置的反应和冷凝温度。电抗器和冷凝器温度 440 ° C 和-25 ° C，分别定。 
			注意: 使用它时反应器到达设定点温度，达到稳态状态达 4 天。</li>
		</ol></li></ol></li></ol> 2。实验装置启动 <ol><li>反应器制备及减少 <ol><li>重量 3 g 的预还原催化剂。催化剂颗粒的粒径减少到小于 1 毫米，用研钵和杵。</li>
		<li>催化剂装入在油管，0.25 和两侧放置石英羊毛。</li>
		<li>使用 PID 控制器，并增加反应器温度对反应温度 (400 ° C) 与适当的坡道，同时通过与 500 标准立方厘米每分钟 (SCCM) 流量反应器流动氢。使用 （表 1 总结） 坡道。 
		注: 温度升高应非常顺利，以获得适当的催化剂活性。</li>
		<li>继续为 24 h.确保没有空气和杂质都要用到的催化剂的还原过程。始终保持在氮毯子下的反应堆。</li>
	</ol></li> <li>吸收剂制备 <ol><li>CaCl 2 吸水 80g 装入减振器列 (ID: 2.3 厘米，长度: 30 厘米)。根据不同的吸水尺寸，不同减振器包装支持将使用减振器，两边都为了固定填料的床。</li>
		<li>要删除任何湿度，增加至 350 ° C 的吸收塔温度而流动氮随流速的 200 SCCM 为 24 h.</li>
	</ol></li> <li>起始反应分离测试 <ol><li>将反应器和吸收塔温度增加到 400 ° C 及 180 ° C，分别. 
		注意: 使用适当的温度坡道来提高反应器的温度。使用变压器使温度控制更顺畅。保存在系统的空闲模式下的氮毯子。在开始之前任何测试、 系统装到 5 MPa 氮几次，然后释放压力。</li>
		<li>使用 GUI 来控制氢和氮的质量流量控制器。</li>
		<li>与氮气和氢气，与 1:3 的比例收取的目标压力装置。</li>
		<li>一旦达到目标压力，关闭进水阀，打开反应器出口阀，并打开，循环泵。由于放热反应和吸收，反应器和吸收塔温度可能需要更精细的控制，在过程的开始。</li>
		<li>继续测试 5 个小时，直到点当吸收塔开始突破。</li>
	</ol></li> <li>的氨解吸 <ol><li>打开入口和出口阀门。</li>
		<li>降低系统 &#39; s 到大气压力的压力和增加吸收器的温度而随流速的 100 SCCM 5 个小时来解吸氨吸收材料的流动氮。</li>
	</ol>
	</li>
</ol>

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作者没有透露。

反应吸收实验装置的关键步骤:
确保氮气和氢气系统中没有杂质。吸水材料在每次循环后都会发生变化。在大多数情况下, 在高温和氨的存在下, 吸水材料的保险丝和形成一个大的固体混凝土。根据每个金属卤化物和氨络合物的热力学性质, 应采用适当的吸收和解吸温度。在每次测试之前, 应检查系统的压降 (吸收器、反应器、油管、阀门、管件、等), 以确保回流回路、减震...

氨是一种重要的工业化学品。它是通过哈伯-博世工艺生产的, 它被称为 20th世纪12中最重要的创新之一。氨合成是在一个非均相催化剂的存在下进行的, 在高温 (#62; 375 ° c) 和压力 (和 #62; 100 bar)3。如此高的温度和压力要求使氨合成非常能量-和 capital-intensive。大约1.5亿吨氨每年生产4, 占世界能源消耗的 1-3%, 5% 的天然气消耗量, 以及多达3% 的气候变化气体排放量5,6, 7。
氨有两个主要的潜在用途。首先, 氨是一种合成氮肥1。如果没有这种肥料, 目前人口的一半将无法获得足够的粮食。其次, 氨水可以作为一种能量载体, 或者作为一种碳中性液体燃料或间接氢载体8,9,10,11。典型地, 可再生资源 (例如风) 在稀少农村地区是可利用的, 在那里可以被夺取;这种类型的孤立风和太阳能被称为 "搁浅"。在这种情况下, 可再生能源的电能和热能被转换成能量密集的碳中性液氨。所生产的液氨可以运往城市中心, 在那里可以直接用于氨基燃料电池12和内燃机的13, 也可以分解成氢气, 然后用于氢燃料电池或氢气站因此, 我们可以把美国大草原的风移到美国拥挤的城市地区。
主要是由于化肥的使用, 合成氨生产是一个重要的行业。在室温下, 氨合成反应是放热的, 因此-至少, 在原则上自发的14, 但是, 在环境条件下实现反应非常困难, 因为强氮氮键15. 为了克服这一点, 弗里茨哈伯著名地使用高温来达到快速的动力学, 但这些高温意味着反向反应抑制生产。为了减少这种反向反应的抑制作用, 哈伯使用高压来改善转换。他执行了 large-scale 反应在枪管, 仍然装饰 BASF 植物在路德维希港。
当反应可能在更温和的条件下运行时, 必须同时使用高温和压力, 这使化学家们沮丧了一个世纪2。即使在这个过程被商业化之后, 卡尔. 博世和巴斯夫的一个庞大的队伍在整个周期表中搅动着寻找更好的催化剂。尽管博世没有取得什么成功, 但搜索仍在继续。甚至在去年, 一个新的研究计划, 旨在寻求一个新的催化剂启动16,17。详细的氨合成化学现在已经很好的理解14, 如果寻找新的催化剂是成功的, 它肯定是值得的努力。然而, 我们认为, 过去的失败减少了未来成功的机会。
本文介绍了 small-scale 氨合成工艺, 并对其进行了研究。
小规模的过程:
风力发电氨 我们正在改进哈伯-博世合成氨的工艺, 寻求一个更小, 更简单的过程, 可以在当地运行, 但产生微不足道的二氧化碳量。在一个位于莫里斯, 锰的试验工厂已经证明了当地氨制造的可行性, 并显示在图 118。莫里斯坐在水牛脊, 在明尼苏达州西南角的六十英里的连绵起伏的山丘的形成。山脊有异常稳定, 强风, 横跨草原滚动。因此, 它是风力发电的圣地。
用这种电, 我们已经从风中生产氨, 使用的是比现有的化石燃料商业操作小4万倍的植物。一些风力发电是用来使空气中的氮气通过变压吸附, 一种既定的方法, 空气分离使用, 例如, 对于肺气肿患者需要富氧空气。然而, 更多的电力是用来制造氢气的电解水。在图 2中示意的过程中, 这些气体与常规催化剂结合在一起。反应后, 气体通过冷却分离, 浓缩液氨。未气体, 以及 uncondensed 氨, 被回收。
试验工厂详情 在我们的试验工厂, 明尼苏达大学的可再生氢和氨试验厂, 电力是由一个合用的1.65 兆瓦风力涡轮机提供。该试验工厂使用约10% 的功率产生, 剩余的电力使用的明尼苏达大学, 莫里斯校区。
氢气生产系统使用一个电解槽, 增压压缩机, 和一个热冷水机组。该系统每小时生产0.54 公斤氢气, 储存在 2400 psi, 使用24千瓦时电能。利用反渗透和离子系统纯化 on-site 井的水。然后, 水以高达15升/小时的速度供应给电解槽. 氮气是用氮气发生器、pre-air 压缩机、空气干燥器和增压压缩机产生的。氮气储存在 2400 psi, 使用约6千瓦小时的电力。
合成氨的合成使用定制的刹车。它包括一个压缩机, 一个反应堆, 一个制冷冷却回路, 和一个20千瓦的电加热器。该橇使用约28千瓦小时的电力生产2.7 公斤的氨水, 然后储存在 150 psi。采用集成 PLC 和 HMI 系统控制合成氨生产过程。生产的氢气和氮气储存在现场18氮斯道拉恩索ge 坦克和54储氢罐。氨水也在3100加仑的容器内存放在现场。
风力发电是昂贵的 这一过程的电是由风制成的, 因此制造氨水的燃料是免费的, 不需要使用任何化石燃料。然而, 这一试点工厂的资本成本主要是以氢气生产和合成氨的投资为主导。迄今为止的操作表明, 制造 small-scale 氨的成本大约是传统的基于化石燃料的氨水的两倍。虽然我们继续优化我们的过程, 我们相信, small-scale 风产生的氨将不会在目前的天然气价格竞争力。每块质量氨的资本成本可以通过一个更大的常规过程来减少, 或者通过一个类似于本文接下来所描述的替代过程来降低。
吸收过程:
吸收增强生产 用于合成氨的催化剂在上个世纪19几乎保持不变。因此, 我们在这项研究中采取了不同的方法。我们应用了当前的催化剂和操作温度, 但一旦形成, 就会在适度的压力下吸收氨水。我们回收任何未的氢和氮。该过程类似于图 3中的示意图, 与常规过程相似, 但用填充床吸收器代替了凝汽器。
初始反应动力学不改变 该系统的低转换实验表明, 初始反应速率与本系统早期的许多研究是一致的3,14,15,20,21,22,23, 如图 4所示。左面板显示初始速率, 随温度的变化强烈。虽然这些速率也随压力而变化, 但变化较小, 如右面板所示。在我们的新的过程中, 我们使用相同的催化剂和类似的操作条件, 但寻求方法, 以改善氨生产使用在较低的压力吸收。因此, 我们希望降低氨合成的资本成本。
吸收增强转换 在我们的工作中, 我们用填料床代替了小型的冷凝器, 这是一个充满了吸收剂的小颗粒的圆柱形容器。我们强调了主要由氯化镁和氯化钙制成的吸附剂11,24。这种氨吸收剂有两种作用。首先, 它们将回收气体中的氨浓度降低到接近零。第二, 他们有效地减少了分离的时间到接近零。此策略具有生产性25、26、27。例如, 在图 5中, 我们显示了使氨的速率与系统中总压强的下降成正比, 比没有吸收要大得多。特别是, 红色圆圈显示的 90 bar 上的反应, 比与吸收剂的反应更不完整, 由蓝色三角形27显示。这是真的, 即使没有吸收剂的反应发生的压力几乎是吸收反应的两倍。在早期的实验中 (这里没有显示), 我们还表明, 该过程的最终转换是约20% 没有吸收剂, 但超过95% 的吸收剂。
反应速率随吸收温度的变化而降低。这在图 6中显示, 它再次报告合成氨为总压力vs时间27。改变反应温度60° c 对反应速率影响不大。这与图 4中的初始速率形成了对比, 它显示了几乎是一个数量级的反应速率的变化。图 4和图 6的结果是不同的, 因为反向反应的效果已经降低, 因此化学动力学不再是对总体速率负责的唯一步骤。

<table><tbody><tr><td>&lt;strong&gt;Experimental Apparatus&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Magnesium Chloride</td><td>Sigma Aldrich</td><td>7786-30-3</td><td>St. Louis, MO</td></tr><tr><td>Calcium Chloride</td><td>Sigma Aldrich</td><td>10043-52-4</td><td>St. Louis, MO</td></tr><tr><td>Ultra Pure Hydrogen</td><td>Matheson</td><td>SG PHYF30050</td><td>New Brighton, MN</td></tr><tr><td>Ultra Pure Nitrogen</td><td>Matheson</td><td>SG G1881112</td><td>New Brighton, MN</td></tr><tr><td>Iron Based Catalyst</td><td>Clariant/Sud Chemie</td><td>-</td><td>Charlotte, NC</td></tr><tr><td>Variable Piston Pump</td><td>PumpWorks Inc.</td><td>PW2070N</td><td>Minneapolis, MN</td></tr><tr><td>Omega Ceramic Heater</td><td>Omega</td><td>CRFC-36/115-A</td><td>Stamford, CT</td></tr><tr><td>PID Controller</td><td>Omega</td><td>CN96211TR</td><td>Stamford, CT</td></tr><tr><td>Signal Conditioner</td><td>Omega</td><td>DRG-SC-TC</td><td>Stamford, CT</td></tr><tr><td>Pressure Transducer</td><td>WIKA</td><td>50426877</td><td>Lawrenceville, Georgia</td></tr><tr><td>Mass Flow Controller</td><td>Brooks Instruments</td><td>SLA5850</td><td>Hatefield, PA</td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Pilot Plant&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Electrolyzer</td><td>Proton OnSite</td><td>H6 Series</td><td>Wallingford, CT</td></tr><tr><td>Gas Booster</td><td>PDC Machine</td><td>3 2500&amp;nbsp;</td><td>Warminster, PA</td></tr><tr><td>Wind Turbine</td><td>Vestas</td><td>V82</td><td>Portland, OR</td></tr><tr><td>Chiller</td><td>Thermal Care</td><td>SQ Series</td><td>Niles, IL</td></tr><tr><td>Water Purifier</td><td>Elga Pure Lab</td><td>S-15</td><td></td></tr><tr><td>Nitrogen Generator</td><td>Innovative Gas System</td><td>NS-10</td><td>Huoston, TX</td></tr><tr><td>Air Compressor</td><td>Hydrovane</td><td>HV05</td><td></td></tr></tbody></table>

ammonia synthesis at low pressure

氨可通过使用氨选择性吸收剂在低气压下合成。这一过程可以用风能驱动, 在需要合成氨的地区, 可在当地获得合成肥料。这样的风能通常被称为 "搁浅", 因为它只能从可以直接使用的人口中心获得。
在所提出的低压过程中, 氮气是由空气中的变压吸附制得的, 而氢是由电解产生的水。当这些气体可能起反应在大约400° c 在被促进的常规催化剂的存在时, 转换由反向反应经常限制, 使这个反应仅可行在高压。这种限制可以通过吸收氨的钙或氯化镁来消除。这种碱性金属卤化物能有效去除氨, 从而抑制反应的平衡约束。在所建议的吸收增强氨合成过程中, 反应速率可以不受化学动力学和吸收率的控制, 而是由未气体的循环速率来调节。这一结果与传统的小型哈伯-博世工艺的氨水相比是有利的。

中的试装置上莫里斯，锰证明为当地氨制造18，风之可行性，如图 1所示。风力发电，用以使氮气和氢气通过的空气压力回转吸收法和电解水，分别。反应器使用常规催化剂组合的氮气和氢气的气体，使氨。氨是用凝汽器然后分离的。
这里介绍的方法包括进程回收任何未反应的氢和氮。?...

Watch this Scientific Journal Video about Ammonia Synthesis at Low Pressure at JoVE.com

Ammonia Synthesis at Low Pressure

通过使用常规的催化剂和氨选择性吸附剂可以在低压力为原料合成氨气。

低压氨合成

Ammonia can be synthesized at low pressure by the use of an ammonia selective absorbent. The process can be driven with wind energy, available locally in ...

Research

JoVE Journal

Bioengineering

26.4K 次观看.  University of Minnesota – Twin Cities. 通过使用常规的催化剂和氨选择性吸附剂可以在低压力为原料合成氨气。

视频: Ammonia Synthesis at Low Pressure

Calibrated Passive Sampling - Multi-plot Field Measurements of NH3 Emissions with a Combination of Dynamic Tube Method and Passive Samplers

Agricultural ammonia (NH3) emissions (90% of total EU emissions) are responsible for about 45% airborne eutrophication, 31% soil acidification and 12% fine dust formation within the EU15. But NH3 emissions also mean a considerable loss of nutrients. Many studies on NH3 emission from organic and mineral fertilizer application have been performed in recent decades. Nevertheless, research related to NH3 emissions after application fertilizers is still limited in particular with respect to relationships to emissions, fertilizer type, site conditions and crop growth. Due to the variable response of crops to treatments, effects can only be validated in experimental designs including field replication for statistical testing. The dominating ammonia loss methods yielding quantitative emissions require large field areas, expensive equipment or current supply, which restricts their application in replicated field trials. This protocol describes a new methodology for the measurement of NH3 emissions on many plots linking a simple semi-quantitative measuring method used in all plots, with a quantitative method by simultaneous measurements using both methods on selected plots. As a semi-quantitative measurement method passive samplers are used. The second method is a dynamic chamber method (Dynamic Tube Method) to obtain a transfer quotient, which converts the semi-quantitative losses of the passive sampler to quantitative losses (kg nitrogen ha-1). The principle underlying this approach is that passive samplers placed in a homogeneous experimental field have the same NH3 absorption behavior under identical environmental conditions. Therefore, a transfer co-efficient obtained from single passive samplers can be used to scale the values of all passive samplers used in the same field trial. The method proved valid under a wide range of experimental conditions and is recommended to be used under conditions with bare soil or small canopies (&#60;0.3 m). Results obtained from experiments with taller plants should be treated more carefully.

Calibrated Passive Sampling - Multi-plot Field Measurements of NH3 Emissions with a Combination of Dynamic Tube Method and Passive Samplers

Ammonia emissions are a major threat to the environment by eutrophication, soil acidification and fine particle formation and stem mainly from agricultural sources. This method allows ammonia loss measurements in replicated field trials enabling statistical analysis of emissions and of relationships between crop development and emissions.

校准被动采样 - NH多情节场测量<sub&gt; 3</sub&gt;与动态管法和被动采样的组合排放

Agricultural ammonia (NH3) emissions (90% of total EU emissions) are responsible for about 45% airborne eutrophication, 31% soil acidification and 12% ...

科研

环境科学

Ammonia Fiber Expansion (AFEX) Pretreatment of Lignocellulosic Biomass

Lignocellulosic materials are plant-derived feedstocks, such as crop residues (e.g., corn stover, rice straw, and sugar cane bagasse) and purpose-grown energy crops (e.g., miscanthus, and switchgrass) that are available in large quantities to produce biofuels, biochemicals, and animal feed. Plant polysaccharides (i.e., cellulose, hemicellulose, and pectin) embedded within cell walls are highly recalcitrant towards conversion into useful products. Ammonia fiber expansion (AFEX) is a thermochemical pretreatment that increases accessibility of polysaccharides to enzymes for hydrolysis into fermentable sugars. These released sugars can be converted into fuels and chemicals in a biorefinery. Here, we describe a laboratory-scale batch AFEX process to produce pretreated biomass on the gram-scale without any ammonia recycling. The laboratory-scale process can be used to identify optimal pretreatment conditions (e.g., ammonia loading, water loading, biomass loading, temperature, pressure, residence time, etc.) and generates sufficient quantities of pretreated samples for detailed physicochemical characterization and enzymatic/microbial analysis. The yield of fermentable sugars from enzymatic hydrolysis of corn stover pretreated using the laboratory-scale AFEX process is comparable to pilot-scale AFEX process under similar pretreatment conditions. This paper is intended to provide a detailed standard operating procedure for the safe and consistent operation of laboratory-scale reactors for performing AFEX pretreatment of lignocellulosic biomass.

Ammonia Fiber Expansion AFEX Pretreatment of Lignocellulosic Biomass

Ammonia fiber expansion (AFEX) is a thermochemical pretreatment technology that can convert lignocellulosic biomass (e.g., corn stover, rice straw, and sugarcane bagasse) into a highly digestible feedstock for both biofuels and animal feed applications. Here, we describe a laboratory-scale method for conducting AFEX pretreatment on lignocellulosic biomass.

氨纤维膨胀（AFEX）预处理利诺纤维素生物量

Lignocellulosic materials are plant-derived feedstocks, such as crop residues (e.g., corn stover, rice straw, and sugar cane bagasse) and purpose-grown ...

Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films

Organo-lead halide perovskites have recently attracted great interest for potential applications in thin-film photovoltaics and optoelectronics. Herein, we present a protocol for the fabrication of this material via the low-pressure vapor assisted solution process (LP-VASP) method, which yields ~19% power conversion efficiency in planar heterojunction perovskite solar cells. First, we report the synthesis of methylammonium iodide (CH3NH3I) and methylammonium bromide (CH3NH3Br) from methylamine and the corresponding halide acid (HI or HBr). Then, we describe the fabrication of pinhole-free, continuous methylammonium-lead halide perovskite (CH3NH3PbX3 with X = I, Br, Cl and their mixture) films with the LP-VASP. This process is based on two steps: i) spin-coating of a homogenous layer of lead halide precursor onto a substrate, and ii) conversion of this layer to CH3NH3PbI3-xBrx by exposing the substrate to vapors of a mixture of CH3NH3I and CH3NH3Br at reduced pressure and 120 &#176;C. Through slow diffusion of the methylammonium halide vapor into the lead halide precursor, we achieve slow and controlled growth of a continuous, pinhole-free perovskite film. The LP-VASP allows synthetic access to the full halide composition space in CH3NH3PbI3-xBrx with 0&#160;&#8804; x&#160;&#8804; 3. Depending on the composition of the vapor phase, the bandgap can be tuned between 1.6 eV&#160;&#8804; Eg&#160;&#8804; 2.3 eV. In addition, by varying the composition of the halide precursor and of the vapor phase, we can also obtain CH3NH3PbI3-xClx. Films obtained from the LP-VASP are reproducible, phase pure as confirmed by X-ray diffraction measurements, and show high photoluminescence quantum yield. The process does not require the use of a glovebox.

Here, we present a protocol for the synthesis of CH3NH3I and CH3NH3Br precursors and the subsequent formation of pinhole-free, continuous CH3NH3PbI3-xBrx thin films for the application in high efficiency solar cells and other optoelectronic devices.

可调谐带隙无针孔 Methylammonium 铅卤化物钙钛矿薄膜的低压蒸气辅助解决工艺

Organo-lead halide perovskites have recently attracted great interest for potential applications in thin-film photovoltaics and optoelectronics. Herein, ...

化学

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

The importance of understanding the fate of nitrate (NO3&#8722;), which is the dominant N species transferred from terrestrial to aquatic ecosystems, has been increasing because global nitrogen loads have dramatically increased following industrialization. Dissimilatory nitrate reduction to ammonium (DNRA) and denitrification are both microbial processes that use NO3&#8722; for respiration. Compared to denitrification, quantitative determinations of the DNRA activity have been carried out only to a limited extent. This has led to an insufficient understanding of the importance of DNRA in NO3&#8722; transformations and the regulating factors of this process. The objective of this paper is to provide a detailed procedure for the measurement of the potential DNRA rate in environmental samples. In brief, the potential DNRA rate can be calculated from the 15N-labeled ammonium (15NH4+) accumulation rate in 15NO3&#8722; added incubation. The determination of the 14NH4+ and 15NH4+ concentrations described in this paper is comprised of the following steps. First, the NH4+ in the sample is extracted and trapped on an acidified glass filter as ammonium salt. Second, the trapped ammonium is eluted and oxidized to NO3&#8722; via persulfate oxidation. Third, the NO3&#8722; is converted to N2O via an N2O reductase deficient denitrifier. Finally, the converted N2O is analyzed using a previously developed quadrupole gas chromatography&#8211;mass spectrometry system. We applied this method to salt marsh sediments and calculated their potential DNRA rates, demonstrating that the proposed procedures allow a simple and more rapid determination compared to previously described methods.

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

A series of methods to determine the potential DNRA rate based on 14NH4+/15NH4+ analyses is provided in detail. NH4+ is converted into N2O via several steps and analyzed using quadrupole gas chromatography&#8211;mass spectrometry.

基于14NH 4 + /4+ 15NH 4= 通过顺序转换为 N2O 的分析，测量异化硝酸盐降低至铵的潜在率

The importance of understanding the fate of nitrate (NO3&#8722;), which is the dominant N species transferred from terrestrial to aquatic ecosystems, has ...

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for specialized equipment to achieve modest pressures, and can even be used to achieve higher pressures in more specialized equipment and sturdier reaction vessels. At the end of the reaction, the vials can be easily depressurized by opening at room temperature. In the present example CO2 serves as both a putative directing group as well as a way to passivate amine substrates, thereby preventing oxidation during the organometallic reaction. In addition to being easily added, the directing group is also removed under vacuum, obviating the need for extensive purification to remove the directing group. This strategy allows the facile &#947;-C(sp3)-H arylation of aliphatic amines and has the potential to be applied to a variety of other amine-based reactions.

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Here we present a protocol for performing reactions in simple reaction vessels under low-to-moderate pressures of CO2. The reactions can be performed in a variety of vessels simply by administering the carbon dioxide in the form of dry ice, without the need for costly or elaborate equipment or set-ups.

用干冰作为固体 CO2源实现密封容器中的适度压力

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for ...

Fast and Accurate Exhaled Breath Ammonia Measurement

This exhaled breath ammonia method uses a fast and highly sensitive spectroscopic method known as quartz enhanced photoacoustic spectroscopy (QEPAS) that uses a quantum cascade based laser. The monitor is coupled to a sampler that measures mouth pressure and carbon dioxide. The system is temperature controlled and specifically designed to address the reactivity of this compound. The sampler provides immediate feedback to the subject and the technician on the quality of the breath effort. Together with the quick response time of the monitor, this system is capable of accurately measuring exhaled breath ammonia representative of deep lung systemic levels. 
Because the system is easy to use and produces real time results, it has enabled experiments to identify factors that influence measurements. For example, mouth rinse and oral pH reproducibly and significantly affect results and therefore must be controlled. Temperature and mode of breathing are other examples. As our understanding of these factors evolves, error is reduced, and clinical studies become more meaningful. This system is very reliable and individual measurements are inexpensive. 
The sampler is relatively inexpensive and quite portable, but the monitor is neither. This limits options for some clinical studies and provides rational for future innovations.

Ammonia is an important physiologic metabolite relevant to various disease and wellness states. It is also a difficult molecule to measure in breath, which demands particular precautions be taken to obtain accurate results. Not all factors influencing ammonia are known, but progress can be difficult without accounting for these factors.

快速，准确的呼出气测量氨

This exhaled breath ammonia method uses a fast and highly sensitive spectroscopic method known as quartz enhanced photoacoustic spectroscopy (QEPAS) that ...

医学

High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

Nuclear magnetic resonance (NMR) spectroscopy represents an important technique to understand the structure and bonding environments of molecules. There exists a drive to characterize materials under conditions relevant to the chemical process of interest. To address this, in situ high-temperature, high-pressure MAS NMR methods have been developed to enable the observation of chemical interactions over a range of pressures (vacuum to several hundred bar) and temperatures (well below 0 &#176;C to 250 &#176;C). Further, the chemical identity of the samples can be comprised of solids, liquids, and gases or mixtures of the three. The method incorporates all-zirconia NMR rotors (sample holder for MAS NMR) which can be sealed using a threaded cap to compress an O-ring. This rotor exhibits great chemical resistance, temperature compatibility, low NMR background, and can withstand high pressures. These combined factors enable it to be utilized in a wide range of system combinations, which in turn permit its use in diverse fields as carbon sequestration, catalysis, material science, geochemistry, and biology. The flexibility of this technique makes it an attractive option for scientists from numerous disciplines.

The molecular structures and dynamics of solids, liquids, gases, and mixtures are of critical interest to diverse scientific fields. High-temperature, high-pressure in situ MAS NMR enables detection of the chemical environment of constituents in mixed phase systems under tightly controlled chemical environments.

高温高压原位魔角旋转核磁共振光谱

Nuclear magnetic resonance (NMR) spectroscopy represents an important technique to understand the structure and bonding environments of molecules. There ...

Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented herein. The novel strategy is based on a facile one-pot pyrolysis treatment of cobalt (II) acetylacetonate and nitrogen-rich organic precursors under Ar atmosphere at 800 &#176;C, resulting in the formation of Co- and N- co-doped carbon nanotube with earthworm-like morphology. The obtained catalyst was found to have a high density of defect sites, as confirmed by Raman spectroscopy. Here, cobalt (II) nanoparticles were stabilized on the atomically dispersed cobalt- and nitrogen-doped carbon nanotubes. The catalyst was confirmed to be effective in the catalytic hydrolysis of ammonia borane, in which the turnover frequency was 5.87 mol H2&#183;molCo-1&#183;min-1, and the specific hydrogen generation rate was determined to be 2447 mL H2&#183;gCo-1&#183;min-1. A synergistic function between the Co nanoparticle and the doped carbon nanotubes was proposed for the first time in the catalytic hydrolysis of ammonia borane reaction under a mild condition. The resulting hydrogen production with its high energy density and minimal refueling time could be suitable for future development as energy sources for mobile and stationary applications such as road trucks and forklifts in transport and logistics.

Here, we present a protocol to synthesize Co nanoparticles supported on carbon nanotubes with Co- and N- dopants for hydrogen productions.

碳纳米管负载掺杂Co和N原子金属纳米粒子的合成及其在制氢中的催化应用

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented ...

Le Ch&#226;telier's Principle

Source: Laboratory of Dr. Lynne O&#39;Connell &#8212; Boston College
When the conditions of a system at equilibrium are altered, the system responds in such a way as to maintain the equilibrium. In 1888, Henri-Lewis Le Ch&#226;telier described this phenomenon in a principle that states, &#34;When a change in temperature, pressure, or concentration disturbs a system in chemical equilibrium, the change will be counteracted by an alteration in the equilibrium composition.&#34;
This experiment demonstrates Le Ch&#226;telier&#39;s principle at work in a reversible reaction between iron(III) ion and thiocyanate ion, which produces iron(III) thiocyante ion:
Fe3+(aq) + SCN- (aq) <img alt="Reversibly Equals" src="/files/ftp_upload/10138/reversible.jpg" /> FeSCN2+ (aq)
The concentration of one of the ions is altered either by directly adding a quantity of one ion to the solution or by selectively removing an ion from the solution through formation of an insoluble salt. Observations of color changes indicate whether the equilibrium has shifted to favor formation of the products or the reactants. In addition, the effect of a temperature change on the solution at equilibrium can be observed, which leads to the ability to conclude whether the reaction is exothermic or endothermic.

Le Chatelier&#039;s Principle: Effect of Concentration and Temperature on Chemical Equilibrium

Le Châtelier 原则

Source: Laboratory of Dr. Lynne O&#39;Connell &#8212; Boston College
When the conditions of a system at equilibrium are altered, the system responds in ...

教育

JoVE Science Education

普通化学

Preparation of Amines: Alkylation of Ammonia and Amines

Alkylation is one of the methods used to prepare amines. Direct alkylation of ammonia or a primary amine with an alkyl halide gives polyalkylated amines along with a quaternary ammonium salt through successive SN2 reactions. This process of making the quaternary salt through the direct alkylation method is called exhaustive alkylation.
Each alkylation step makes the nitrogen center more nucleophilic, which triggers successive alkylations until a quaternary ammonium salt is formed. Considering this, specific reaction conditions, such as excess ammonia, must be used to exclusively make primary amines.
Since tertiary halides are more hindered, they are not the substrates of choice for alkylation reactions. Although secondary alkyl halides are far less hindered and can be alkylated, they are also not preferred as substrates due to their tendency to undergo elimination reactions.
Since ammonia is cheaply available, alkylations using ammonia as the substrate are the most common.

胺的制备:氨和胺的烷基化

Alkylation is one of the methods used to prepare amines. Direct alkylation of ammonia or a primary amine with an alkyl halide gives polyalkylated amines ...

低压氨合成

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校准被动采样 - NH多情节场测量