Plasma dissociation reaction kinetics. I. Methyl methacrylate

✍ Scribed by Y. Vickie Pan; Denice D. Denton

• Book ID: 101255244
• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 403 KB
• Volume: 73
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19990705)73:1<1::aid-app1>3.0.co;2-4

✦ Synopsis

Fourier transform infrared spectroscopy (FTIR) was utilized to study the plasma gas-phase reaction kinetics and reaction mechanisms in capacitively coupled glow discharges of methyl methacrylate (MMA) under zero monomer flow rate conditions. The gas-phase study shows two major electron-impact-induced dissociation pathways in MMA plasmas: the C-O bond cleavage reaction and decarboxylations. The C-O bond cleavage reaction accounts for approximately one-half of the MMA dissociation, and neutral formaldehyde and dimethyl ketene (DMK) are produced via intramolecular rearrangement. Decarboxylations produce CO, CO 2 , and a number of radicals that subsequently stabilize to form neutrals, including propylene, allene, and methanol. These intermediate species then further dissociate in the plasma to small hydrocarbons (methane, acetylene, and ethylene), CO, CO 2 , and H 2 . Plasma power and initial monomer pressure have only minor effects on the MMA fragmentation chemistry. However, the reaction rate increases at higher-power and lower initial monomer pressure conditions. The modeling also reveals the relative reactivities of the neutrals. A time-scale transformation technique based on the MMA decomposition half-life significantly reduces the effects of the reactor condition on the kinetics. In addition, mass balance ratios are utilized to calculate the portion of plasma species that have been accounted for by the in situ technique.