Urgent help: Method for determining the dimethyl ether content in liquefied petroleum gas
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This post was last edited by zjp on 2010-9-25 19:59. How to determine the dimethyl ether content in liquefied petroleum gas? What chromatography column to use, and what method for quantification?
My two questions haven’t been answered at all; moderator, please help!
It seems like you mentioned this question before; why are you asking it again? Could it be that the original post wasn’t posted by you? Go and search; it seems we’ve already provided the answer, so we won’t repeat it here
Go and check the standards; it seems there is an analysis for dimethyl ether in isobutylene. A non-polar capillary column (polydimethylsiloxane) with a FID detector should meet your requirements
It’s already available online at http://bbs.hcbbs.com/viewthread.php?tid=122985; please search first before posting
Use an OV-6201 FId detector; for analysis at a constant temperature if there are no recombinant components present
Reply to 5# zbx: Thank you, moderator. The information you provided is very useful, but it relates to the determination of pure dimethyl ether. What I’m referring to is a situation where dimethyl ether is intentionally mixed into liquefied gas, say at a volume fraction of 25%; in this case, the matrix is liquefied gas, so the column used should not be the same as one used for pure dimethyl ether!
Reply to 7# chenhaidong5758: You can refer to this method and create a few standard samples by yourself to give it a try; there are many analysis methods that require you to explore on your own
Reply to 8# zbx: Haha, if there are sufficient experimental conditions, I’ll do my best to work on areas within my capabilities! We are just a small private company, and we can’t afford to buy standard gases. I’ve tried using several columns; those that can separate dimethyl ether fail to fully separate the components of liquefied gas. Columns made of dibutyl phthalate seem to be able to detect the presence of dimethyl ether qualitatively, as under normal conditions this compound does not separate from n-isobutylene on such columns, forming a single peak. However, when dimethyl ether is present in liquefied gas, this peak splits into two peaks, resulting in poor separation – which allows for qualitative detection but not quantitative analysis! Anyway, I’m still very grateful to Haichuan; I’ve learned a lot here
Using a standard gas as the external standard, the chromatographic columns were an elastic quartz capillary column of polystyrene-divinylbenzene (PLOT-Q) with dimensions of 30m*0.53*40μm, and a stainless steel divinylbenzene-styrene copolymer column with dimensions of 3m*3mm and a particle size of 0.18mm–0.25mm. The capillary method was employed, with programmed temperature elevation: initial temperature of 50°C, initial retention time of 2 minutes, temperature increase rate of 10°C per minute, final temperature of 150°C, and final retention time of 15 minutes. ; Vaporization chamber temperature: 250°C; Detector temperature: 250°C; Column method: Initial temperature: 50°C, initial time: 6 minutes, heating rate: 10°C/minute, final temperature: 80°C, holding time: 15 minutes, heating rate: 10°C/minute, final temperature: 150°C, final time: 15 minutes. The temperature of the gasification chamber is 250°C; the temperature of the detector is 360°C. For the methane conversion furnace, the temperature is also 360°C. The carrier gas is high-purity nitrogen.