scholarly journals A Direct Method to Measure14CO2Lost by Evasion from Surface Waters

Radiocarbon ◽  
2006 ◽  
Vol 48 (1) ◽  
pp. 61-68 ◽  
Author(s):  
M F Billett ◽  
M H Garnett ◽  
S M L Hardie
Keyword(s):  
Surface Waters ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Direct Method ◽  
Initial Period ◽  
Drainage System ◽  
Isotopic Signature ◽  
Direct Measurements ◽  
Floating Chamber ◽  
A Direct Method

Recent methodological advances in the use of zeolite molecular sieves for measuring the isotopic signature of CO2have provided the opportunity to make direct measurements of14CO2 in various field situations. We linked a portable molecular sieve/pump/IRGA system to a floating chamber to demonstrate the potential of the method to quantify the isotopic signature (δ13C and14C) of CO2lost by evasion (outgassing) from surface waters. The system, which was tested on a peatland stream in Scotland, involved 1) an initial period of scrubbing ambient CO2from the chamber, 2) a period of CO2build-up caused by surface water evasion, and 3) a final period of CO2collection by the molecular sieve cartridge. The field test at 2 different sites on the same drainage system suggested that the results were reproducible in terms of δ13C and14C values. These represent the first direct measurements of the isotopic signature of CO2lost by evasion from water surfaces.

scholarly journals Plastic waste to fuels by hydrocracking at mild conditions

2021 ◽  
Vol 7 (17) ◽  
pp. eabf8283
Author(s):  
Sibao Liu ◽  
Pavel A. Kots ◽  
Brandon C. Vance ◽  
Andrew Danielson ◽  
Dionisios G. Vlachos
Keyword(s):  
Direct Method ◽  
Acid Sites ◽  
Liquid Fuels ◽  
High Yield ◽  
Tandem Catalysis ◽  
Hy Zeolite ◽  
Environmental Threat ◽  
Single Use ◽  
Initial Activation ◽  
A Direct Method

Single-use plastics impose an enormous environmental threat, but their recycling, especially of polyolefins, has been proven challenging. We report a direct method to selectively convert polyolefins to branched, liquid fuels including diesel, jet, and gasoline-range hydrocarbons, with high yield up to 85% over Pt/WO3/ZrO2 and HY zeolite in hydrogen at temperatures as low as 225°C. The process proceeds via tandem catalysis with initial activation of the polymer primarily over Pt, with subsequent cracking over the acid sites of WO3/ZrO2 and HY zeolite, isomerization over WO3/ZrO2 sites, and hydrogenation of olefin intermediates over Pt. The process can be tuned to convert different common plastic wastes, including low- and high-density polyethylene, polypropylene, polystyrene, everyday polyethylene bottles and bags, and composite plastics to desirable fuels and light lubricants.

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