Sulphur-free Odorants in Natural Gas: Determination by GC

摘要

Natural gas is a precious energy source for the whole world. For safety reasons it is odorised with strongly smelling organic substances. A new class of these odorants has been developed and introduced into the European market. For the first time sulphur-free compounds - mainly methyl acrylate [CAS 96-33-3] and ethyl acrylate [CAS 140-88-5] - are used. Three methods have been developed for determining methyl and ethyl acrylate in the matrix natural gas by GC-TCD and GC-FID equipped either with capillary and packed column. With these methods an external calibration has been carried out considering the aspects of quality assurance. The statistical data have proven that both methods with GC-FID are well suitable for determining the concentration of methyl and ethyl acrylate in the low concentration range (c velence 5-20 mg(centre dot)m~(-3)) used in gas treatment. Natural gas which plays an important rule in many fields of the industry and our daily life is a hazardous material. Preferred properties are its energy transfer during combustion and the easy transport under normal conditions because of its gaseous state of aggregation. It becomes dangerous to the environment because of its explosiveness in a certain concentration range, the risk of suffocation to humans and animals in saturated atmospheres and the lack of an own odour which could be smelled. Hence the gas producing industry adds strongly smelling substances - so-called odorants - to the natural gas. Their purpose is leak warning. In former times mainly sulphur-containing compounds like mercapthanes and thiophenes were used as odorants. Nowadays a new class of odorants without sulphur has been developed and introduced into the market. The aim of this work is the development and evaluation of three different determination methods for methyl acrylate and ethyl acrylate using GC-FID and GC-TCD with either capillary and packed column.