Application of Nonthermal Plasma to Chemical Conversion of CO2 Shigeru FUTAMURA National Institute of Advanced Industrial Science and Technology AIST Tsukuba West, 16-1 Onogawa, Tsukuba, Ibaraki, 35-8569 Japan Voice: +81 (29) 861-8497; FAX: +81 (29) 861-8866 E-mail: s-futamura@aist.go.jp Application of Nonthermal Plasma to Chemical Synthesis N2 +32+ 3 2N32 N2 +22+ 2 N2-N2. Uyama et al., Plasma Chem. Plasma Process., 13(1), 117 (1993); ibid., 14(4), 491 (1994) 2C C4 + O2 2CO C3O A. Mizuno et al., IEEE Trans. Ind. Applicat., 34(5),, pp, ( ), 94 (1998); ibid., 35(5), 125 (1999)
Outline Introduction - Reforming reactions with NTP -CO2 as an oxidant in NTP Experimental Results and Discussion - Structure-dependent behavior - Temperature effect - Reaction mechanism Summary Time Profile for the Numbers of Papers Relevant to Plasma Processing of Chemical Substances Nu mber of papers 16 14 12 1 8 6 4 2 2 production Fuel reforming Pyrolysis/gasification Plasma-aided combustion 1994 1995 1996 1997 1998 1999 2 21 Year 22 23 24 25 26
Endothermicities of NTP Reactions Investigated Reaction Δ o (kj mol -1 ) CO 2 + 2 O CO + 2 + O 2 524.8 Endothermicity CO 2 CO +.5 O 2 C 4 + CO 2 2 CO + 2 2 2 O 2 +.5 O 2 C 4 + 2O CO + 3 2 283. 247.1 241.8 25.9 C 3 O CO + 2 2 9.5 Typical Reaction Modes of Catalytic Reforming Processes for Natural Gas Steam reforming Temperature > 1K, pressure > 2. MPa, Ni catalyst, Steam / C 2.5~3 3. [2] / [CO] > 3. Reformer Natural gas CO2 reforming Temperature > 9K, pressure > 2MP 2. MPa, steam or catalyst (Ir, Ru, Rh, sulfided Ni), [2]/[CO]<1 [CO] 1. CO2 2 CO Partial Oxidation Temperature > 15K, pressure 3. ~ 7. MPa, pure oxygen, no catalyst, [2] / [CO] < 2.
L. Bromberg et al., Low Power Compact Plasma Fuel Converter, WO 1/3356 A1 Fuel converter A Reaction chamber Discharge Gap Conduit 2 (1 %), CO (16 %), CO 2 (6 %), and C 4 (.7 %) from Gasoline (.12 g/s) and air (1.1 g/s) Flame propagates along the gas flow in the AC power-driven plasmatron. Electrode Insulator A: Conductive structure Useful at higher pressures Increases in voltages for breakdown and glow discharge sustenance. M. Czernichowski, Electrically Assisted Partial loxidation of flight htydrocarbons By Oxygen, WO 99/11572 2: Electrodes 4: Gliding electric discharge 12: igh voltage connections 14: Ceramic plate separating 15a and 15b 15a: Plasma zone 15b: Post-plasma zone 19: Metal Ni sticks keeping temp. low 2: temp. resistance furnace Syngas ( 2 /CO = 1.55 ~ 2.19) from natural gas Temperature: 1238 ~ 1388K Pressure: ~ 6. MPa O 2 /C:.25 ~.65
Ferroelectric Packed-bed Reactor (FPR) Effective reaction length 127 mm; gap distance 15.4 mm; BaTiO 3 pellets: 1 mm in diameter; ε = 5 at r. t. Application of NTP to 2 Production and Fuel Reforming 2 from (C3)3N 1) Syngas from C4 +2O 4) 2O C3O C4 2), 3) 3) 3) C4 + CO2 C3O + 2O CO2 + 2O 5) 6) 7) 1) Jpn. Patent No. 2,934,861 (1999) 2) Chem. Lett., 1314 (21) 3) US Patent No. 6,884,326 B2 (25); Ger. Patent DE 121112.4; IEEE Trans. Ind. Applicat., 39(2), 34 (23) 4) Jpn. Patent No. 3,834,614 (26); Chem. Lett., 118 (22); IEEE Trans. Ind. Applicat., 4(6), 1476-1481 1481 (25) 5) IEEE Trans. Ind. Applicat., 4(6), 1515-1521 (25); Catal. Today, 115, 1-4, 211-216 (26) 6) IEEE Trans. Ind. Applicat., 4(6), 1459-1466 (24) 7) Stud. Surf. Sci. Catal., 153, 119-124 (24)
Typical Landfill Gas Evolution Gas temp. 38 to 54 o C C4 CO2 N2 Landfill Off-gas Collection and Treatment Systems, Department of the Army, U.S. Army Corps of Engineers, Washington DC, 2314-1, 4/17/1995. Application of NTP to Methane Reforming C4 NTP 2, CO, CO2 Cat 15 o C 2, CO2 Technical merits of NTP 1) Non-catalytic process 2) igh energies at short residence times 3) Quick response 4) System compactness 5) Easy operations Technical challenges for NTP 1) Improvement of energy efficiency 2) Power-up of the reactor system
Schematic Diagram of Experimental Set-up Oscilloscope MFC Reactor Gas in igh voltage amplifier Gas out FTIR MFC MFC MFC GC (FID + TCD) GC-MS umidifier NOx C/ CO 2 / analyzer N N 2 N 2 2 Ozone analyzer GC (FID) Definitions for the Conversions of C n 2(n+1) andco 2, and the Yields of 2, CO, and Byproduct ydrocarbons (C m l ) C n 2(n+1) conv. (mol%) = 1 X {1 (C n 2(n+1) concentration / Initial C n 2(n+1) concentration)} CO 2 conv. (mol%) = 1 X {1 (CO 2 concentration / Initial CO 2 concentration)} 2 yield (mol%) = 1 X 2 concentration / [(n+1) X Initial C n 2(n+1) concentration] CO yield (mol%) = 1 X CO concentration / Initial CO 2 concentration C m l yield (mol%) = 1 X C m l concentration / {(n/m) X Initial C n 2(n+1) concentration} (m,l) = (1,4), (2,6), (2,4), (2,2)
Product Distributions for the CO2-Reforming of C4, C38, and C512 C RED (kj/l) Conv. (mol%) 2 Product yield (mol%) CO C4 C26 C24 C22 C4.81 17 9.1 17.7 - - - - C38.83 29 12.4 16.1 5.2.9.8 1. C512 76.76 76.76 63 11.2 26.3 5.8 58 5.5 1.1 11 16 1.6 [C] =.5 %, [CO2] = 1. %, in N2, 298K, Q =.2 L/min. version (mol% %) C con Temperature Effect on C Conversion in the CO2 Reforming 8 7 6 5 4 3 2 1. 5.5 1 1. Reactor energy density (kj/l) C4 298K C4 373K C4 433K C38 298K C38 373K C38 433K C512 298K C512 373K C512 433K FPR, [C] =.5 %, [CO2 ] = 1. %, in N2, Q =.2 L/min.
Bond Dissociation Energies of C-O, -C, and C-C C in the Substrates and CO Bond BDE (kj mol - 1 ) C-O 1,83.9 O=CO 532.2 -C3 438.9 -C2C2C3 423.3 -C(C3)2 399.6 -C2C(C C(C3)3) 418.8 8 C3-C2C 363.4 C3-C(C3)3 338.2 Relationship between CO2 Conversion and CO Yield mol%) yield ( 25 2 15 CO2 298K CO 298K CO2 433K CO 433K Convers sion or 1 5 FPR, [CO2] = 1. %, in N2, Q =.2 L/min.. 5.5 1 1. Reactor energy density (kj/l)
CO2 Conversion in the Presence of ydrocarbons at 298K ol%) nversi ion (m O 2 co 2 15 1 5 FPR, [C] =.5 %, [CO2] = 1. %, in N2, Q =.2 2L/ L/min. None C4 C38 C512 C. 5.5 1 1. Reactor energy density (kj/l) CO2 Conversion in the Presence of ydrocarbons at 433K ol%) nversi ion (m O 2 co 1 8 6 4 2 FPR, [C] =.5 %, [CO2] = 1. %, in N2, Q =.2 2L/ L/min. None C4 C38 C512 C. 2.2 4.4 6.6 Reactor energy density (kj/l)
Plasma-assisted Cleavage of Covalent Bonds C C C C C C C C C Methane Propane Neopenatne Secondary Decomposition Induced by Radicals C C C C C C C C C Processes of ydrocarbon Decomposition C 4 + e* C 3 + + e (1) C 3 C 2 C 3 + e* C 3 + C 2C 3 + e + C 3 CC 3 + e (2) (3) C 3 C(C 3 ) 3 + e* C 3 + C(C 3 ) 3 + e (4) + C 2 C(C 3 ) 3 + e (5) CO 2 + e* CO + O + e (6) S + O S + O [S = C 4, C 3 C 2 C 3, C 3 C(C 3 ) 3 ] C 4 + R C 3 + R (R :, O, O) C 3 C 2 C 3 + R C 3 CC 3 + R (7) (8) (9) C 3 C(C 3 ) 3 + R C 2 C(C 3 ) 3 + R (1)
Effects of ydrocarbon Structure and Temperature on 2 Yield l%) ield (mo 2 y 18 16 14 12 1 8 6 FPR, [C] =.5 %, [CO2] = 1. %, in N2, Q = 2 ml/min. C4 298K C4 373K C4 433K C38 298K C38 373K C38 433K C512 298K C512 373K C512 433K 4 2..2.4.6.8 1. 1.2 Reactor energy density (kj/l) Processes of 2 Formation C 4 + e* C 3 C 2 C 3 + e* C 3 C(C 3 ) 3 + e* C 3 + + e C 3 + C 2 C 3 + e + C 3 CC 3 + e C 3 + C(C 3 ) 3 + e + C 2 C(C 3 ) 3 + e C 4 + C 3 + 2 C 3 C 2 C 3 + C 3 CC 3 + 2 C 3 C(C 3 ) 3 + C 2 C(C 3 ) 3 + 2 (1) (2) (3) (4) (5) (6) (7) (8) C 2 C 3 + 2 + C 2 =C 2 C 3 CC 3 + 2 + C 2 =CC 3 ydrogen donors better than propane and neopentane (9) (1) C(C 3 ) 3 + 2 + C 2 =C(C 3 ) 2 (11)
Stoichiometric Syngas Composition Reaction [ 2 ] / [CO] C 4 + CO 2 2 2 + 2 CO 1. C 3 8 + 3 CO 2 4 2 + 6 CO.67 C 5 12 + 5 CO 2 6 2 + 1 CO.6 C Structure-dependent Composition of Synthesis Gas at 433K (I) [ 2] / [C CO] (-) 3. 2.5 2. =1% inn2 1.5 FPR, [C] =.5 %, [CO2] 1. %, N2, 433K, Q = 2 ml/min. 1. C4 Sine C4 Square C4 Triangle C38 Sine C38 Square C38 Triangle C512 Sine C512 Square C512 Triangle.5.. 2. 4. 6. 8. Reactor energy density (kj/l)
C Structure-dependent Composition of Synthesis Gas at 433K (II) 1..8 FPR, [CO2] / [C in C] = 2., in N2, 433K, Sine, Vp-p 14. kv, Q = 2 ml/min. [ 2] / [CO O] (-).6.4.2 C4 C38 C512.. 5. 1. 15. 2. 25. Reactor energy density (kj/l) Effect of C Structure on Carbon Balance in the CO2 Reforming at 298K (ppm) 5 FPR, [C] =.5 %, [CO2 ] = 1. %, 4 298K, in N2, Q =.2 L/min. 3 Δ[CO] 2 1 C4 C38 C512 5 1 15 2 - {n XΔ[C Δ[Cn2(n+1)] +Δ[CO2]} (ppm)
Effect of C38 Concentration on Carbon Balance in the CO2 -Reforming 8.8.6 (%) Δ[CO].4.2 C38.125 % C38.25 % C38.5 % C38 1. % FPR, CO2 2. %, in N2, 298K, Q =.2 L/min....4.8 1.2 1.6 2. 2.4 - {3 X Δ[C38] + Δ[CO2]} (%) Effect of Temperature on Carbon Balance in the CO2 Reforming of Aliphatic ydrocarbons at 433K 12 pm) Δ[Tota al C in the prod ducts] (p 1 8 6 4 2 FPR, [C] =.5 %, [CO2 ] = 1. %, 433K, in N2, Q =.2 L/min. C4 C38 C512 5 1 15 2 - {n X Δ[Cn2(n+1)] + Δ[CO2]} (ppm)
Effect of [C512] / [CO2] on Carbon Balance in the CO2 Reforming of C512 at 433K the prod ducts] (p ppm) Δ[Tot tal C in 12 1 8 6 4 2 FPR, 433K, in N2, Q =.2 L/min. [C512] / [CO2] =.5 [C512] / [CO2] =.1 5 1 15 2 - {5 X Δ[C512] + Δ[CO2]} (ppm) Processes of CO Formation S + e* S + + e [S = C 4, C 3 C 2 C 3, C 3 C(C 3 ) 3 ] (1) CO 2 + e* CO + O + e (2) S + O S + O (3) S - O - S' CO - O Olefins Aldehydes, Ketones (5) (4) Aldehydes, Ketones - O CO (6)
Potential of Nonthermal Plasma in Various Types of fch Chemical Reactions Substrate Concn. Temp. Catalyst Conv. Cl 2 C=CCl a) 2 Cl 2 C=CCl Ph b), PhC 3 1, ppm 33K 2 ppm 33K No 98 % MnO 2 9 % C 3 O c) 1. % 33K No 99 % C 3 C 2 C 3 with CO d) 2 1. % 433K No 6 % a) IEEE Trans. Ind. Applicat., 33(2), 447-453 (1997); b) ibid., 37(5), 447-453 (21); c) ibid., 4(6), 1459-1466 (24); d) ibid., 41(6), 1515-1521 (25). Summary 2 and CO are obtained as the major products in the CO 2 -reforming of methane, propane, and neopentane in nonthermal plasma (NTP). Their reactivities are greatly affected by their chemical structures and reaction temperature. CO 2 reactivity is not affected by reaction temperature. CO is quantitatively obtained from CO 2 in the absence of the counterpart hydrocarbon. Temperature effect on the 2 yield ildis greatly affected by the chemical structures of the aliphatic hydrocarbons (Cs). The molar ratio of 2 to CO, and the carbon balance are affected by the chemical structures of Cs, [C] / [CO 2 ], and reaction temperature.