Hydrothermal reaction kinetics and pathways of phenylalanine alone and in binary mixtures

Shujauddin Changi, Minghan Zhu, Phillip E. Savage

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

We examined the behavior of phenylalanine in high-temperature water (HTW) at 220, 250, 280, and 350°C. Under these conditions, the major product is phenylethylamine. The minor products include styrene and phenylethanol (1-phenylethanol and 2-phenylethanol), which appear at higher temperatures and longer batch holding times. Phenylethylamine forms via decarboxylation of phenylalanine, styrene forms via deamination of phenylethylamine, and phenylethanol forms via hydration of styrene. We quantified the molar yields of each product at the four temperatures, and the carbon recovery was between 80-100 % for most cases. Phenylalanine disappearance follows first-order kinetics with an activation energy of 144±14 kJ mol-1 and a pre-exponential factor of 1012.4±1.4 min-1. A kinetics model based on the proposed pathways was consistent with the experimental data. Effects of five different salts (NaCl, NaNO3, Na2SO4, KCl, K2HPO4) and boric acid (H3BO3) on phenylalanine behavior at 250°C have also been elucidated. These additives increase phenylalanine conversion, but decrease the yield of phenylethylamine presumably by promoting formation of high molecular weight compounds. Lastly, binary mixtures of phenylalanine and ethyl oleate have been studied at 350°C and three different molar concentration ratios. The presence of phenylalanine enhances the conversion of ethyl oleate and molar yields of fatty acid. Higher concentration of ethyl oleate leads to increased deamination of phenylethylamine and hydration of styrene. Amides are also formed due to the interaction of oleic acid/ethyl oleate and phenylethylamine/ammonia and lead to a decrease in the fatty acid yields. Taken collectively, these results provide new insights into the reactions of algae during its hydrothermal liquefaction to produce crude bio-oil.

Original languageEnglish (US)
Pages (from-to)1743-1757
Number of pages15
JournalChemSusChem
Volume5
Issue number9
DOIs
StatePublished - Jan 1 2012

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Phenethylamines
reaction kinetics
Binary mixtures
Phenylalanine
Reaction kinetics
Styrene
hydration
Fatty acids
Hydration
Phenylethyl Alcohol
fatty acid
decarboxylation
kinetics
Boric acid
Kinetics
Oleic acid
acid
Liquefaction
Algae
Amides

All Science Journal Classification (ASJC) codes

  • Environmental Chemistry
  • Chemical Engineering(all)
  • Materials Science(all)
  • Energy(all)

Cite this

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title = "Hydrothermal reaction kinetics and pathways of phenylalanine alone and in binary mixtures",
abstract = "We examined the behavior of phenylalanine in high-temperature water (HTW) at 220, 250, 280, and 350°C. Under these conditions, the major product is phenylethylamine. The minor products include styrene and phenylethanol (1-phenylethanol and 2-phenylethanol), which appear at higher temperatures and longer batch holding times. Phenylethylamine forms via decarboxylation of phenylalanine, styrene forms via deamination of phenylethylamine, and phenylethanol forms via hydration of styrene. We quantified the molar yields of each product at the four temperatures, and the carbon recovery was between 80-100 {\%} for most cases. Phenylalanine disappearance follows first-order kinetics with an activation energy of 144±14 kJ mol-1 and a pre-exponential factor of 1012.4±1.4 min-1. A kinetics model based on the proposed pathways was consistent with the experimental data. Effects of five different salts (NaCl, NaNO3, Na2SO4, KCl, K2HPO4) and boric acid (H3BO3) on phenylalanine behavior at 250°C have also been elucidated. These additives increase phenylalanine conversion, but decrease the yield of phenylethylamine presumably by promoting formation of high molecular weight compounds. Lastly, binary mixtures of phenylalanine and ethyl oleate have been studied at 350°C and three different molar concentration ratios. The presence of phenylalanine enhances the conversion of ethyl oleate and molar yields of fatty acid. Higher concentration of ethyl oleate leads to increased deamination of phenylethylamine and hydration of styrene. Amides are also formed due to the interaction of oleic acid/ethyl oleate and phenylethylamine/ammonia and lead to a decrease in the fatty acid yields. Taken collectively, these results provide new insights into the reactions of algae during its hydrothermal liquefaction to produce crude bio-oil.",
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Hydrothermal reaction kinetics and pathways of phenylalanine alone and in binary mixtures. / Changi, Shujauddin; Zhu, Minghan; Savage, Phillip E.

In: ChemSusChem, Vol. 5, No. 9, 01.01.2012, p. 1743-1757.

Research output: Contribution to journalArticle

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