Raman Spectroscopy Study on Chemical Transformations of Propane at High Temperatures and High Pressures

At a Glance

Metadata	Details
Publication Date	2020-01-30
Journal	Scientific Reports
Authors	D. A. Kudryavtsev, Timofey Fedotenko, Egor Koemets, Saiana Khandarkhaeva, Vladimir Kutcherov
Institutions	Gubkin Russian State University of Oil and Gas, University of Bayreuth
Citations	11
Analysis	Full AI Review Included

Technical Documentation & Analysis: HPHT Propane Transformation

Reference: Raman Spectroscopy Study on Chemical Transformations of Propane at High Temperatures and High Pressures (Scientific Reports, 2020)

Executive Summary

This research utilized laser-heated Diamond Anvil Cells (DACs) to investigate the chemical fate of propane (C₃H₈) under extreme pressure and temperature conditions relevant to the Earth’s upper mantle.

Core Achievement: Demonstrated that propane transforms into complex hydrocarbon systems (C₁-C₆ alkanes and alkenes) and solid carbon (soot/graphite) without the need for external catalysts.
Material Requirement: Experiments relied on high-quality, synthetic CVD-type IIa diamond anvils for pressure generation and optical access for in situ Raman spectroscopy.
Operational Range: The study covered an extensive thermobaric range: 3 to 22 GPa pressure and 900 to 3000 K temperature.
Methodology: Double-sided YAG laser heating (1064 nm) was employed, utilizing thin gold (Au) foil (~1-2 µm) as the heat-absorbing medium.
Geophysical Relevance: Results suggest that propane acts as a precursor for heavier hydrocarbons deep within the Earth’s interior (depths > 130 km), clarifying the role of carbon-bearing fluids in the global carbon cycle.
Key Products Identified: Methane (CH₄), ethane (C₂H₆), n-butane (C₄H₁₀), n-pentane (C₅H₁₂), n-hexane (C₆H₁₄), and elemental carbon (C).

Technical Specifications

The following hard data points were extracted from the experimental setup and results:

Parameter	Value	Unit	Context
Pressure Range Investigated	3 to 22	GPa	DAC Experiments
Temperature Range Investigated	900 to 3000	K	Laser Heating
Diamond Anvil Type Used	Synthetic CVD, Type IIa	N/A	High-purity optical window
Diamond Culet Size	250	µm	DAC geometry
Gasket Material / Thickness	Rhenium / 25	µm	Indented thickness
Heat Absorber Material / Thickness	Gold (Au) Foil / 1-2	µm	Laser heating medium
Primary Heating Wavelength	1064	nm	YAG Laser
Primary Raman Excitation	632.8	nm	He-Ne Laser
Raman Spectral Resolution	2	cm^-1	LabRam Spectrometer
Temperature Measurement Range	570-830	nm	Black body radiation fitting
Maximum Observed Pressure (Propane Stability)	14	GPa	Stable up to 930 K

Key Methodologies

The HPHT experiments were conducted using a specialized laser-heated DAC setup, focusing on precise control of thermobaric conditions and in situ Raman analysis.

Sample Loading: Propane (99.99% purity) was cryogenically loaded into symmetric BX-90-type DACs.
Anvil Configuration: Synthetic CVD Type IIa diamonds with 250 µm culets were used to generate pressure and provide optical access.
Gasket Preparation: Rhenium gaskets were pre-indented to 25 µm thickness, and pressure chambers were prepared using laser ablation and drilling.
Heat Absorption: Thin gold (Au) foil (~1-2 µm) was placed in the chamber to act as the laser radiation absorber, minimizing catalytic effects often associated with noble metals like Ir.
Laser Heating: Samples were heated using a transferable double-sided setup employing two YAG lasers (1064 nm central wavelength).
Temperature Determination: Temperature was measured in situ by fitting the thermal emission spectra of the heated area to the Plank radiation function (570-830 nm range).
Raman Analysis: Raman spectra were collected using a LabRam spectrometer (2 cm^-1 resolution), primarily excited by a He-Ne laser (632.8 nm).
Pressure Calibration: Pressure was determined either via the calibrated high-pressure behavior of propane or by monitoring the first-order diamond peak.

6CCVD Solutions & Capabilities

The success of this HPHT research hinges on the quality and precision of the diamond anvils and associated components. 6CCVD is uniquely positioned to supply the necessary materials and customization required to replicate or advance this high-pressure chemistry work.

Research Requirement	6CCVD Material Solution	Customization Potential & Value Proposition
High-Purity Diamond Anvils (CVD Type IIa)	Optical Grade Single Crystal Diamond (SCD)	We provide SCD plates (Type IIa equivalent) up to 500 µm thick, featuring ultra-low nitrogen content and low birefringence. This ensures maximum optical transmission for Raman spectroscopy (632.8 nm and 514.5 nm) and minimal thermal absorption during YAG laser heating (1064 nm).
Custom Culet Geometry (250 µm culets)	Precision Machining and Polishing Services	6CCVD specializes in custom SCD fabrication. We can supply anvils with precise culet sizes (e.g., 100 µm to 1000 µm) and specific bevel angles tailored to achieve target pressures (3-22 GPa range). Our SCD polishing achieves surface roughness Ra < 1 nm.
Integrated Heat Absorber (Thin Au Foil, 1-2 µm)	In-House Custom Metalization	We eliminate the need for separate foil handling by offering direct, high-precision metal deposition onto the SCD anvil surface. Available metals include Au, Pt, Ti, W, and Pd, allowing researchers to tune the thermal absorption profile and minimize catalytic interference.
Study of Carbon Products (Soot, Graphite)	Polycrystalline Diamond (PCD) Substrates	For follow-up studies requiring large-area, high-purity carbon sources or substrates for catalytic reactions, 6CCVD offers PCD plates up to 125mm in diameter and up to 500 µm thick, polished to Ra < 5 nm.
Global Logistics	Reliable Global Shipping	We ensure prompt, secure global delivery (DDU default, DDP available) of sensitive SCD components, supporting international research collaborations like those described in the paper (Sweden, Germany, Russia).

Engineering Support

6CCVD’s in-house PhD team can assist with material selection for similar HPHT Geophysics and Hydrocarbon Synthesis projects. Whether optimizing SCD thickness for specific optical windows or designing custom metalization stacks for precise thermal control, our expertise ensures the highest quality components for extreme environment research.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

Tech Support

Original Source

DOI: https://doi.org/10.1038/s41598-020-58520-7