DEVELOPMENT OF GAS SENSORS AND DECOMPOSITION CATALYST SYSTEM FOR NITROUS OXIDE USED IN OPERATING ROOMS

手术室用一氧化二氮气体传感器和分解催化剂系统的开发

基本信息

批准号：
11559015
负责人：
YAMAZOE Noboru
金额：
$ 8.7万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

Nitrous oxide (N_2O), called "laughing gas", is an anesthetic gas used extensively for surgical operations where waste N_2O is released into the atmosphere without treatment. This release may be hazardous to the atmospheric environment, since N_2O is a green-house-effect gas, the global warming coefficient of which is about 300 times higher than that of CO_2, beside being one of the gases leading to ozone layer disruption. It is thus desirable to catalytically decompose N_2O into N_2 and O_2 before release. It has recently been reported that contamination of indoor atmospheres with N_2O may cause health hazards for staff routinely working under such conditions. This project aims to develop a catalytic N_2O decomposition system and N_2O sensor.1).N_2O sensorsIn order to develop a semiconductor type gas sensor applicable to the monitoring of N_2O in air, a search for the semiconducting oxides sensitive to N_2O was carried out. Among the 23 kinds of single oxides tested, SnO_2 turned out … More to give the highest sensitivity to N_2O, although the sensitivity was not high enough. The N_2O sensitivity was found to be promoted effectively when SnO_2 was loaded with a small amount of a basic oxide such as SrO, CaO, BaO, Bi_2O_3 and Sm_2O_3. The promotion was particularly conspicuous with SrO loading. For example, 0.5wt%SrO-loaded SnO_2, exhibited the N_2O sensitivity about 3 times as high as that of pure SnO_2, and could detect N_2O in air fairly well in the concentration range of 10-300 ppm.A stabilized-zirconia based electrochemical device attached with an oxide electrode was developed for monitoring N_2O in air at elevated temperatures. Among the 11 kinds of monoxides tested for tubular zirconia device, SnO_2 was found to exhibit the best sensing electrode properties, giving a relatively high sensitivity in air at 475 ℃. The addition of a foreign oxide (e.g., Bi_2O_3 and Sm_2O_3 to SnO_2 was effective to improve the N_20 sensitivity. Especially the element using Sm_2O_3 (0.5wt%)-SnO_2 sensing electrode exhibited the N_2O sensitivity about 1.5 times as high as that using the pure SnO_2 electrode, allowing to detect about 35 ppm N_2O in air. On the basis of the measurements of anodic and cathodic polarization curves, the sensing mechanism was confirmed to involve a mixed potential at the sensing electrode.2).N_2O decomposition catalystsMore than 40 catalysts were subjected to the screening test ; they were transition or precious metal catalysts loaded onto oxide supports such as zeolites, Al_2O_3, TiO_2, or SiO_2. The direct decomposition of N_2O proceeded with all the catalysts tested, but the activity was strongly dependent on both the active ingredient and the support. Among these catalysts, metal-loaded Al_2O_3 exhibited the most potent decomposition activity, the actual level depending on the active ingredient (Pd>Ru>Pt). With the most active catalyst (5wt% Pd/Al_2O_3), the direct decomposition of N_20 from the dry model gas started around 250℃ and reached completion at 300℃. Although the decomposition activity was inhibited by co-existing water, 5wt%Pd/Al_2O_3 retained its high activity even in the presence of 2.3% water, N_2O decomposition starting and being completed at 300℃ and 400℃, respectively.3).Field monitoring of N_2O at a operating roomIt was found that the ambient N_2O concentration in an operating room reached 100-150ppm when a scavenging system did not work well. Especially, the N_2O concentration near a patient and/or equipment for anesthetic gas supply was more than 500 ppm. Less

一氧化二氮（N_2O），被称为“笑气”，是一种用于外科手术的麻醉气体，其中废弃的N_2O未经处理就释放到大气中，这种释放可能对大气环境造成危害，因为N_2O通常是温室气体。其全球变暖系数比CO_2高约300倍，而且是导致臭氧层破坏的气体之一，因此需要催化分解。 N_2O在释放前转化为N_2和O_2 最近有报道称，N_2O污染室内空气可能会对在这种条件下日常工作的工作人员造成健康危害。本项目旨在开发一种催化N_2O分解系统和N_2O传感器。1).N_2O。传感器为了开发适用于空气中N_2O监测的半导体型气体传感器，寻找对N_2O敏感的半导体氧化物在所测试的 23 种单一氧化物中，SnO_2 对 N_2O 的灵敏度最高，但发现当少量 SnO_2 负载时，N_2O 灵敏度得到了有效提升。例如，SrO、CaO、BaO、Bi_2O_3 和 Sm_2O_3 等碱性氧化物的促进作用尤其明显。负载0.5wt%SrO的SnO_2,其N_2O灵敏度约为纯SnO_2的3倍,在10-300 ppm浓度范围内可以很好地检测空气中的N_2O。开发了一种氧化物电极，用于在高温下监测空气中的 N_2O 在管状氧化锆装置测试的 11 种一氧化物中，研究发现SnO_2表现出最好的传感电极性能，在475℃的空气中具有相对较高的灵敏度。在SnO_2中添加外来氧化物（例如Bi_2O_3和Sm_2O_3）可以有效提高N_20的灵敏度。特别是使用Sm_2O_3的元件（ 0.5wt%)-SnO_2传感电极的N_2O灵敏度是使用普通电极的1.5倍左右纯SnO_2电极，可检测空气中约35 ppm的N_2O。根据阳极和阴极极化曲线的测量，证实传感机制涉及传感电极处的混合电位。2）N_2O分解催化剂超过40种。催化剂经过筛选测试；它们是负载在氧化物载体上的过渡金属或贵金属催化剂，例如沸石、Al_2O_3、TiO_2或所有测试的催化剂均能进行SiO_2.N_2O的直接分解，但其活性强烈依赖于活性成分和载体，其中负载金属的Al_2O_3表现出最强的分解活性，实际水平取决于催化剂的活性。在活性最强的催化剂(5wt% Pd/Al_2O_3)下,干燥模型气体开始直接分解N_20。尽管共存水抑制了分解活性，但5wt%Pd/Al_2O_3在2.3%水存在下仍保持较高的活性，N_2O分解在300℃开始并完成。 400℃。 3).手术室N_2O现场监测发现手术室环境N_2O浓度达到100-150ppm，当清除系统无法正常工作时，尤其是患者和/或麻醉气体供应设备附近的 N_2O 浓度超过 500 ppm。