Study Of New Methods,device And Standard Reference Materials For Speciation And Total Analysis Of Sulfur In Gas

With the development of science,the harm caused by various volatile sulfide compounds（VSCs）in many fields,such as human health,environment,energy and chemical industry,has become more and more serious.The requirement for the analysis of the total and speciation analysis of sulfur in various gases have been demanding in recent years.However,it is very difficult to accurately determine the total and speciation analysis of sulfur directly by commercial instruments because of the features of sulfur gas,such asmulti components,wide content range and strong reactivity.Therefore,it is very important to develop new analytical methods with higher sensitivity,accuracy and precision,simplicity,low price and fast analysis,which can also provide technical support for the preparing and revising the standard operation procedures（SOP）of volatile sulfide analytical methods for various gas samples.The main work of this dissertation focuses on the use of functional materials for the detection of volatile sulfides to improve the efficiency of analysis.On the other hand,the work also focuses on modifying gas chromatography with sulfur chemiluminescence detector（GC-SCD）and developing a pre-rich device of sulfur gas to detect the total and sulfur species in various gases online.Furthermore,a standard reference material,Trace Hydrogen Sulfide in Nitogen Gas,was also prepared,and the related technique was also repoeted here.In detail,this dissertation includes the following studies:（1）The g-C₃N₄@Fe composite developed by doping Fe atoms into a new n-type nonmetallic semiconductor material,was used as the cataluminescence（CTL）catalyst for the detection of H₂S at a low-temperature.An automatic gas sampling device with a reaction and detection system was built for the cataluminescence to realize automatic injection and measurement.The method has the advantages of fast response,high sensitivity and good selectivity.（2）A simple method was developed in this work for facile and visual detection of H₂S by using a paper-based fluorescent（FL）sensor coated with CdTe quantum dots（QDs）in headspace,and quenched the FL of CdTe QDs in a linear manner through a gas-solid reaction,with any possible liquid-phase interference avoided.This method can also be used for the indirect measurement of S^2-with the addition of hydrochloric acid（HCl）,the target S^2-in liquid phase would transform to H₂S which immediately released to headspace.Moreover,the preparation of this paper sensor was facile and did not require any complicated or time-consuming procedures for additional modification or functionalization as other probes previously reported,which endowed this method with more practical utility.（3）A new detection system consisted of a flame ionization detector（FID）and a sulfur chemiluminescence detector（SCD）was developed for sensitive and interference free determination of total sulfur in natural gas by non-separation gas chromatography.In this system,sulfur containing compounds and hydrocarbons were firstly burned in the FID using oxygen rich flame and converted to SO₂,CO₂and H₂O,respectively.The products from FID were transported into the SCD with hydrogen rich atmosphere wherein only SO₂ could be reduced to SO and reacted with O₃ to produce characteristic chemiluminescence.Therefore,the chemiluminescence of CO found in conventional SCD were eliminated because CO₂could not be reduced to CO under these conditions.The proposed method not only retains the advantages of the conventional SCD but also provides several unique advantages including hydrocarbon interference-free and better stability.The highly selective determination of total sulfur in natural gas was realized using this method.（4）For the first time,we developed a new system combining on-line dilution preparation primary reference gas mixtures（PRGMs）,online cryogenic preconcentration device（-30℃）and gas chromatography-sulfur luminescence detector.A novel low temperature adsorbent material was used for high-efficiency pre-enriched nine volatile sulfide compounds.The analytical performance was much better than the previously reported ones,with higher detection sensitivity and more diversified selective detection.This system can detect volatile sulfides with 10^-9levels in hydrogen products online,and can monitor many trace volatile sulfides produced in hydrogen production in real time without liquid nitrogen used in the traditional analysis.Based on the above new detection system,another new concentration system with lower temperature has been further developed（-90℃,also without liquid nitrogen）.Combined with GC-SCD,it can be used for on-line analysis of volatile sulfides at the 10^-9 levels in ambient air.In addition,the preparation technology of a series of trace sulfide gas standard reference materials with different balance gases such as nitrogen,helium,hydrogen,methane and air has been studied.All of them are prepared by primary method-gravimetric method,which has good homogeneity and stability.The period of validity can be more than 12 months.The series of gas standard reference materials prepared by this method are used to verify the accuracy of the analytical methods developed in this work,to ensure the reliability of the results and they have a good practicability and commercial prospect.