Space-filling models of the methane molecule

Solid methane exists in several modifications. Presently nine are known. The familiar smell of natural gas as used in homes is achieved by the addition of an odorant, usually blends containing tert-butylthiol, as a safety measure. Methane has a boiling point of -161.5 degrees Celsius at a pressure of one atmosphere. As a gas, it is flammable over a range of concentrations in air at standard pressure. The primary chemical reactions of methane are combustion, steam reforming to syngas, and halogenation. In general, methane reactions are difficult to control. Partial oxidation of methane to methanol, a more convenient, liquid fuel, is challenging because the reaction typically progresses all the way to carbon dioxide and water even with an insufficient supply of oxygen. The enzyme methane monooxygenase produces methanol from methane, but cannot be used for industrial-scale reactions. Combustion of methane is a multiple step reaction. Peters four-step chemistry is a systematically reduced four-step chemistry that explains the burning of methane. Methane is used in industrial chemical processes and may be transported as a refrigerated liquid. While leaks from a refrigerated liquid container are initially heavier than air due to the increased density of the cold gas, the gas at ambient temperature is lighter than air. Gas pipelines distribute large amounts of natural gas, of which methane is the principal component. Contributor: Junjie Chen, ORCID: 0000-0001-5055-4309, E-mail address: [e-mail], Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China

固态甲烷存在多种晶型，目前已发现9种。民用天然气的标志性气味是通过添加加臭剂实现的，这类加臭剂通常为含有叔丁基硫醇(tert-butylthiol)的复配体系，作为安全预警措施。甲烷在1标准大气压下的沸点为-161.5摄氏度。在标准压力下，气态甲烷在空气中的一定浓度范围内具有可燃性。甲烷的主要化学反应包括燃烧、水蒸气重整制合成气(syngas)以及卤化反应。总体而言，甲烷的反应较难控制。将甲烷部分氧化制备甲醇（一种更便于储运的液态燃料）颇具挑战，因为即便氧气供给不足，反应通常仍会完全进行至生成二氧化碳与水。甲烷单加氧酶(methane monooxygenase)可将甲烷转化为甲醇，但无法应用于工业规模的反应。甲烷的燃烧是多步骤反应。彼得斯四步反应机理是经过系统简化的四步反应模型，可用于阐释甲烷的燃烧过程。甲烷可应用于工业化工流程，也可作为冷冻液态形式进行储运。尽管低温液态甲烷容器泄漏时，初期因低温气体密度较高而比空气重，但当气体升至环境温度后，其密度会小于空气。输气管道用于输送大量天然气，而甲烷是天然气的主要组分。贡献者：陈俊杰，ORCID: 0000-0001-5055-4309，电子邮箱：[e-mail]，河南理工大学机械与动力工程学院能源与动力工程系，中国河南省焦作市世纪大道2000号，邮编454000，中华人民共和国。