Siloxane Detection via Thermal Desorption and FTIR

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Solution Overview

Problem

Existing methods for detecting siloxanes in gaseous streams using Fourier Transform Infrared (FTIR) spectroscopy face significant errors due to background absorption and inability to effectively analyze individual siloxane species, resulting in low detection limits and inaccurate measurements.

Innovation Solution

A method and system utilizing thermal desorption tubes and FTIR spectrometers, optionally with gas chromatography, to pre-concentrate and separate siloxane samples, allowing for precise identification and quantification of individual siloxane components by increasing path lengths and using higher reflective coatings in the FTIR sample cell.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If FTIR spectroscopy is used to measure siloxanes in gaseous streams, then all gaseous constituents can be measured simultaneously, but significant errors occur due to background absorption of unwanted species

Engineering Contradiction:

Improvesimultaneous measurement capabilityVSAvoidmeasurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent applies segmentation by separating the gaseous stream into individual components using gas chromatography before analysis. Each siloxane species is isolated and measured separately, eliminating the background absorption interference that occurs when all gases are measured simultaneously by FTIR alone.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces gas chromatography as an intermediary system between the gaseous stream and FTIR analysis. This intermediary separates and purifies the siloxane species before they enter the FTIR detector, removing the harmful background absorption effects while preserving the simultaneous measurement capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If classical least squares is used to analyze siloxane species, then spectral fitting can be performed, but accurate quantification is impossible due to similar infrared absorption features of various siloxane species

Engineering Contradiction:

Improvesimplicity of analysis methodVSAvoidquantification accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent segments the complex spectral analysis problem by separating each siloxane species into individual chromatographic peaks before FTIR detection. This allows each species to be analyzed independently with classical least squares, avoiding the spectral overlap problem while maintaining method simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary separation of siloxane species via gas chromatography before they reach the FTIR detector. This preliminary action resolves the spectral overlap issue by ensuring that only one siloxane species is present in the detection path at any given time, enabling accurate quantification.

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If surrogate analysis technique is used to characterize siloxane classes, then analysis can be simplified, but detection limit remains poor at about 200 ppb due to signal-to-background limitations

Engineering Contradiction:

Improvesimplicity of analysisVSAvoiddetection limit

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent extracts the siloxane species from the complex gaseous background using gas chromatography separation. By isolating each siloxane component individually before FTIR detection, the harmful background absorption is removed, improving the signal-to-background ratio and achieving detection limits 100 times better than surrogate analysis.

Inventive Principle:

Principle #2Taking out (Extraction)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach significantly improves detection limits by 100 times compared to conventional techniques, enabling accurate characterization and quantification of siloxanes without the need for surrogate analysis, allowing for near-real-time monitoring in biogas streams and preventing damage to equipment.

Implementation Method 1

collecting a sample in a thermal desorption tube

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

desorbing siloxanes from the thermal desorption tube

Methodology Applied

Scientific EffectThermal desorption: Desorption

Implementation Method 3

separating the siloxanes by gas chromatography

Methodology Applied

Scientific EffectGas chromatography: Chromatography

Implementation Method 4

analyzing the desorbed siloxanes or the siloxanes separated by gas chromatography with a Fourier Transform Infrared Spectrometry system

Methodology Applied

Scientific EffectInfrared absorption: Absorption (EM radiation)

Data Source

PatentUS11029292B2Method for identification and quantification of siloxanes in gaseous stream

Publication Date: 2021.06.08 MLS ACQ INC D B A MAX ANALYTICAL TECH

AI summary

A method and system for detecting siloxanes using thermal desorption tubes and FTIR spectrometers with intervening gas chromatography systems.