The kinetics of the reverse deacon reaction

Nanda, Arun

doi:10.1016/0360-3199(88)90042-0

Cited by 13 publications

(6 citation statements)

References 25 publications

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“…Additionally, a higher gas line temperature in these laboratory experiments may affect the relative abundance of the oxychlorine decomposition products that are introduced onto the Tenax trap after pyrolysis. Perhaps the most significant example of this, as it pertains to our study, is that the reaction of Cl 2 with H 2 O shifts more toward the production of HCl and O 2 at higher temperatures [ Nanda and Ulrichson , ]. This would affect the potential degradation of the Tenax trap materials, as HCl is less reactive than Cl 2 .…”

Section: Methodsmentioning

confidence: 83%

“…The slower He flow rate on SAM means that volatiles released during pyrolysis would take longer to reach the Tenax trap, thereby allowing more time for reactions to occur in the pyrolysis oven and GPS. Nanda and Ulrichson [] also found that increasing the flow rate of H 2 O results in a corresponding increase in the rate of reaction between Cl 2 and H 2 O to form HCl. Therefore, Cl 2 may remain in the pyrolysis oven and GPS for a longer period of time, before being converted to HCl, than in our experiments.…”

Section: Methodsmentioning

confidence: 99%

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Evaluation of the Tenax trap in the Sample Analysis at Mars instrument suite on the Curiosity rover as a potential hydrocarbon source for chlorinated organics detected in Gale Crater

et al. 2015

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The Sample Analysis at Mars (SAM) instrument suite aboard Curiosity has detected chlorinated organic compounds in Martian sediment samples. The chlorine in these molecules is thought to derive from oxychlorine salts in Martian sediments, but the carbon source remains under investigation. To constrain possible carbon sources, we investigated how the composition and concentration of oxychlorine phases in solid samples affect organic molecules released from the Tenax traps on board SAM. We created Mars analogue soils by spiking olivine sand with calcium perchlorate, magnesium perchlorate, or ferric iron chloride and analyzed the volatiles generated during pyrolysis-gas chromatography-mass spectrometry using commercial instruments operated under SAM-like conditions, with and without a Tenax trap. Benzoic acid, phthalic anhydride, high molecular weight aromatics, and chlorobenzenes are produced from the trap in response to volatiles released during Cl salt pyrolysis. Changes in composition or concentration of oxychlorine phases between samples could thus potentially produce an increase in chlorobenzene, as observed between samples from Rocknest and Cumberland. However, in our experiments benzoic acid, phthalic anhydride, and chlorobenzenes increase in proportion with the amount of HCl sent to the trap, while in Cumberland samples the chlorobenzene increase showed no corresponding increase in HCl. Based on our experiments, the Tenax trap is a possible source of the traces of chlorobenzene observed at Rocknest, John Klein, and Confidence Hills. The order-of-magnitude higher chlorobenzene abundances observed at Cumberland cannot be attributed to the Tenax trap. Furthermore, we found no evidence of significant trap degradation after hundreds of experiments with Cl salt-containing analogue soils.

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Section: Methodsmentioning

confidence: 83%

Section: Methodsmentioning

confidence: 99%

Evaluation of the Tenax trap in the Sample Analysis at Mars instrument suite on the Curiosity rover as a potential hydrocarbon source for chlorinated organics detected in Gale Crater

et al. 2015

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“…Once the reaction takes place, the outlet stream is cooled down and mixed with methanol before the hydrochlorination reactor (R-2). normalC normall 2 + normalH 2 → 2 normalH normalC normall 1 2 O 2 + H 2 → H 2 O The reverse Deacon process is another alternative that can be relevant in this case since the H 2 of the electrolyzer is used to produce methanol. It occurs in a furnace (Deacon furnace) because it requires elevated temperatures, between 627 and 927 °C, and natural gas is utilized to provide energy. , The reaction is presented in eq , and it has been modeled following chemical equilibria; see the SI. As the conversion of this reactor is high, the reactor output stream only consists of hydrogen chloride, water, and oxygen. normalC normall 2 + normalH 2 normalO → 2 normalH normalC normall + 1 2 normalO 2 …”

Section: Methodsmentioning

confidence: 99%

Economic and Environmental Comparison of Integrated Processes to Produce Chloromethanes from Brine Waste and CO₂

Santamaría

Hernández

Martín

2023

ACS Sustainable Chem. Eng.

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This work provides an economic and environmental comparison of two processes (direct chlorination of methane and hydrochlorination of methanol) to produce chloromethanes from waste brine and CO2. Both processes are modeled using an equation-based approach. This allows for determining the optimal operating conditions of all of the units involved in the process. In particular, those related to the reactors. The optimization determines that hydrochlorination of methanol is a more profitable process (a minimum selling price of $1.8/kgmethyl chloride) than direct chlorination (∼$5/kgmethyl chloride) since the conversion achieved in hydrochlorination is approximately 5 times greater, although the desired product among all of the chloromethanes in direct chlorination is also methyl chloride. Furthermore, direct hydrochlorination also has higher emissions, 16.2 kgCO2 /kgmethyl chloride vs 4.6 kgCO2 /kgmethyl chloride, for hydrochlorination of methanol. These emissions are mainly due to the electricity required in the electrolyzer and could be reduced to −0.5 kgCO2 /kgmethyl chloride (CO2 is absorbed) if the electricity source is fully renewable.

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“…The deacon reaction is mildly exothermic (∆H 0 = −113.6 kJ mol −1 ) and equilibrium-limited. Lower reaction temperatures favor the formation of Cl 2 [42]. For Pt sin redispersed at 520 • C, equilibrium chlorine concentration in the reaction system is lower than that which is redispersed at 460 • C, whereas more PtOCl species were formed (Figure 3a, Table 1) and a higher redispersion efficacy were observed ( Table 1).…”

Section: Effects Of Operation Conditions On Redispersion Efficacymentioning

confidence: 97%

Oxychlorination Redispersion of Pt Catalysts: Surface Species and Pt-Support Interactions Characterized by X-ray Absorption and FT-IR Spectroscopy

Hung

Yeh

Shih³

et al. 2019

Catalysts

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To help elucidate the oxychlorination redispersion reaction mechanism, the surface species formed on the surface of -Al2O3 was characterized by X-ray absorption spectroscopy (XAS). The efficacy of redispersion was assessed by the Pt–Pt coordination number (CNPt–Pt) of redispersed, and then reduced samples. A nearly fully redispersed complex (Ptrd52) was prepared by treating a sintered model Pt/-Al2O3 catalyst at 520 °C, Air/EDC (ethylene dichloride) of 30, and WHSV (Weight Hourly Space Velocity) of 0.07 h−1 for 16 h. For investigating temperature effects, samples treated at 460 (Ptrd46) and 560 C (Ptrd56) were also prepared for comparison. It was found that, while an octahedral resembling Pt(Os)3–4(O–Cl)2–3 (Os represents support oxygen or hydroxyl oxygen) complex was formed on -Al2O3 of Ptrd52, less O–Cl ligands were formed on the redispersed complexes, Ptrd46 and Ptrd56. A negative correlation of CNPt–Pt with CNPt–Cl* (Cl* represents the Cl atom in O–Cl ligand) for these three samples further suggested that the formation of Pt–O–Cl played a key role in the redispersion process. Pt–O–Cl could be formed in the reaction of reactive Cl and PtO2. At an operation temperature of lower-than-optimal temperatures of 520 C, less Cl2 dissociation and less O–Cl ligands were formed. On the other hand, higher temperatures may facilitate Cl2 dissociation, but reduce the equilibrium conversion of HCl to Cl2, leading to increased HCl reaction with Pt (PtO2) clusters to form Pt–Cl (Cl is the atom bonded directly to Pt), and decreased formation of Pt–O–Cl.

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The kinetics of the reverse deacon reaction

Cited by 13 publications

References 25 publications

Evaluation of the Tenax trap in the Sample Analysis at Mars instrument suite on the Curiosity rover as a potential hydrocarbon source for chlorinated organics detected in Gale Crater

Evaluation of the Tenax trap in the Sample Analysis at Mars instrument suite on the Curiosity rover as a potential hydrocarbon source for chlorinated organics detected in Gale Crater

Economic and Environmental Comparison of Integrated Processes to Produce Chloromethanes from Brine Waste and CO₂

Oxychlorination Redispersion of Pt Catalysts: Surface Species and Pt-Support Interactions Characterized by X-ray Absorption and FT-IR Spectroscopy

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The kinetics of the reverse deacon reaction

Cited by 13 publications

References 25 publications

Evaluation of the Tenax trap in the Sample Analysis at Mars instrument suite on the Curiosity rover as a potential hydrocarbon source for chlorinated organics detected in Gale Crater

Evaluation of the Tenax trap in the Sample Analysis at Mars instrument suite on the Curiosity rover as a potential hydrocarbon source for chlorinated organics detected in Gale Crater

Economic and Environmental Comparison of Integrated Processes to Produce Chloromethanes from Brine Waste and CO2

Oxychlorination Redispersion of Pt Catalysts: Surface Species and Pt-Support Interactions Characterized by X-ray Absorption and FT-IR Spectroscopy

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Economic and Environmental Comparison of Integrated Processes to Produce Chloromethanes from Brine Waste and CO₂