Laurea Magistrale in Scienza dei Materiali Materiali Inorganici Funzionali. CO 2 pollutant or resource?

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1 Laurea Magistrale in Scienza dei Materiali Materiali Inorganici Funzionali CO 2 pollutant or resource? Prof. Dr. Antonella Glisenti -- Dip. Scienze Chimiche -- Università degli Studi di di Padova

2 Geological storage options Geological Storage Subterraneous storage through high-pressure injection (> 0.8 km, which is much deeper than usable sources of groundwater). T and P > the critical values for CO 2 (31 C and 72.8 atm): the fluid diffuses through porous and permeable storage rock and occupies its intergranular spaces. It must be trapped underground by impermeable cap rock (CO 2 dense than water and oil less The injection pressure is chosen to be sufficiently high to force CO 2 into the porous space but low enough to not break through the cap rock. Distance of storage sites to earthquake regions Ocean storage, where CO 2 can form dense sinking plumes or bottom lakes when injected at depths of more than 3 km (CO 2 will be isolated for at least a few hundred years but the effects of increased CO 2 concentrations in ocean water on organisms are largely unknown)

3 CO 2 POSSIBLE USES ENERGY PRODUCTION AND FUELS CHEMICALS

4 Chemical Transformations of CO 2 Other uses: chemical industry Naturally abundant. CO 2 has been suggested as a sustainable replacement for organic solvents in a number of chemical processes (extractions, dry cleaning, and in parts degreasing) Non-toxic: food and pharmaceutical industry

5 Substitution of fossil fuels by synthetic renewable fuels electric grid energy storage energy carriers High energy density Storage and transportation in the existing infrastructure Low energy density Storage and transportation from the production regions Reduction in transportation: Electric (batteries), large scale? Biofuels = max supply 20-30% Fuel energy densities: net systems volumetric and gravimetric energy densities

6 Substitution of fossil fuels by synthetic renewable fuels If renewable sources could be used as the energy vector to transform CO 2 into fuels, one has a most attractive route to providing carbonaceous fuels that would not contribute to net CO 2 emissions. Synthetic fuels do not contain any sulphur. Methanol (the simplest synthetic carbonaceous fuel) is a candidate both as a hydrogen source for a fuel cell vehicle and indeed as a transport fuel, and dimethyl ether is a superclean diesel fuel

7 Carbon cycles Natural photosynthesis uses solar energy to recycle CO 2 (and H 2 O) into new plant life (biomass) and ultimately fuels (biofuels). Sustainable, tri-reforming uses CO 2, renewable energy and CH 4 (or biogas) to yield syngas and, ultimately, synthetic fuels and commodity chemicals.

8 Carbon cycles Chemical and/or Biological processes Biomasses A possible carbon cycle for synthetic fuel production from biomass

9 Thermodynamic Aspects Gibbs free energy of formation for selected chemicals To use CO 2 : High energy input Catalysts Reactor optimization The enthalpy of reactions Large number of industrialscale chemical manufacturing processes are currently operated on the basis of strongly endothermic chemical reactions + 20% energy Different H 2 /CO ratio

10 Methanol: an highly required chemicals Methanol industrial demand

11 Methanol consuming industries Solvent/feedstock for production of chemicals (formaldehyde, acetic acid, methyl methacrylate, dimethyl terephthalate, methylamines and chloromethanes) and fuel additives (fatty acid methyl esters) Light olefins (ethylene and propylene), which can be used for manufacturing polymers and hydrocarbon fuels, are produced using the methanol-to-olefins process Dimethyl carbonate (intermediate for polycarbonates and polyurethanes, is synthesized from methanol in supercritical CO 2 ) Liquid energy-carrier (transportation), alternative fuel, and blended with gasoline Fuel Cells

12 Methanol: commercial production From natural gas through a syngas route. Steam methane reforming produces a mixture of CO, CO 2 and H 2 Syngas is then converted to methanol ( C, pressure, 5 10 MPa, CuO/ZnO/Al 2 O 3 catalyst) To facilitate methanol synthesis, syngas CO is converted to CO 2 through the water-gas shift (WGS) reaction The addition of CO 2 in the CO/H 2 feed significantly improves methanol yield and the energy balance. CO 2 is directly converted to methanol without preliminary reduction

13 Renewable, synthetic methanol: a sustainable organic fuel A cycle for sustainable methanol production 3H 2 + CO 2 CH 3 OH + H 2 O Catalytic hydrogenation of CO 2 focused at small, delocalized production sites as an alternative to the current large-scale, localized sites producing methanol by steam reforming of CH 4.

14 CO 2 reduction to methanol 1. Separation of the reaction products Low temperature High pressure Minimize side-reactions Minimize crystallization of the catalyst (Cu, ZnO) 2. Poor catalytic activity at T lower than 250 C > T > CO 2 activation: formation of CO; revers WGS Formation of higher alcohols and by-products High selectivity is essential With H 2 /CO 2 = C & 5MPa: Conversion = 27%; Selectivity = 68% 125 C & 30MPa: Conversion = > 80%

15 CO 2 reduction to methanol: catalysts Traditional catalyst for methanol production from syngas: Cu/ZnO Cu/ZnO/Al 2 O 3 Synthesis/Deposition procedures Different supporting strategy Promoters (Ce, Mn) Perovskite based catalysts (manganites, cromites, ferrites ) Pd based catalysts (Pd/Ga 2 O 3 )

16 Fisher and Tropsch Dry-reforming CO 2 + CH 4 2CO + 2H 2 (1) H = 247 KJ/mol (298 C) High P and T CO 2 + H 2 H 2 O + CO H = 41 KJ/mol (2) 2CO CO 2 + C H = -172 KJ/mol (3) CH 4 2H 2 + C H = 75 KJ/mol (4) (1) a (2) b (3) b (4) a T ( C) Minumum (a) and maximum (b) temperature for the reactions Coke formation from 557 to 700 C Active species Pd, Rh Ni, Fe, Co Supports Perovskites - LaNi 1-x Rh x O 3, AE x La 1-x Ni 0.3 Al 0.7 O 3 (AE = Sr, Ca ) Zeolites Argille

17 Dry-reforming by Ni-based perovskites LaNiO 3 LaNiCuO 3 Conversion (%) Temperature ( C) 800 LaCaNiCuO 3 LaCaNiO 3 La can be substituted by Ca for 50%

18 Tri-reforming: using flue gas for CO 2 conversion it would be highly desirable if flue gas mixtures (typically 8 10% CO 2, 18 20% H 2 O, 2 3% O 2 and 60 70% N 2 ) could be used directly for CO 2 conversion without costly pre-separation of CO 2. Main reactions for syngas production by tri-reforming of natural gas. > durability and lifetime of metal nanoparticle catalysts 95 per cent methane conversion at K. Optimizaion of the waste heat in the power plant and heat generated in situ from partial oxidation of methane for the endothermic processes Nanosized Ni and Co (Co/Al 2 O 3 ) Optimized H 2 /CO for methanol, methyl ether, hydrocarbons

19 Tri-reforming: Plant improvement Magnetic Fluidized Bed CH 4 Magnetic Fluidized Bed Conventional Fluidized Bed Fixed Bed CO 2 Magnetic Fluidized Bed Conventional Fluidized Bed Fixed Bed C deposition after reaction in Fixed Bed C deposition after reaction in Magnetic Fluidized Bed Plant engineering to low C poison and increase conversion

20 Photochemical production of synthetic fuels CO 2 recycling Storing intermittent solar energy 1. Absorption of photons in a photocatalyst material, and formation of electron hole pairs (spatially separated) to drive red-ox reaction 2. Absorption coupled with Multielectron redox reactions: CO 2 reduction and reductant (water) oxidation

21 Photochemical production of synthetic fuels The overall conversion efficiency is lower than that of photovoltaic solar systems. CO 2 photoreduction catalysts are less effective than current solar water-splitting catalysts inefficient absorption of solar energy fast recombination processes and backward redox reactions

22 Photochemical production of synthetic fuels TiO 2 -based photocatalysts Cu Promoters Cu 2 O-SiC Cu-Ce CdS quantum dots FeTiO 3 CdS-Bi 2 S 3 InNbO 2 NiO/InNbO 2

23 Titania nanotubes and other CdS Bi 2 S 3 visible

24 TiO 2 FeTiO 3 /TiO 2 d = 50% FeTiO 3 20% FeTiO 3 c = 20% FeTiO 3 b = 10% FeTiO 3 a = TiO 2 e = P25

25 Fischer-Tropsh Process Generic process block diagram for FT synthesis of hydrocarbon fuels.

26 Chemical reactions The main reaction: (2n+1) H 2 + n CO -> C n H 2n+2 + n H 2 O (1) Exothermic reaction (it liberates heat: 39.4 kcal / mole of CO). Hence the reactor has to be cooled down. Other products: nco + 2n H 2 -> C n H 2n + n H 2 O (2) nco + 2 nh 2 -> C n H (2n+1) OH + (n-1) H 2 O (3) Parasite reactions: CO + H 2 O -> H 2 + CO 2 (4) 2 CO -> C + CO 2 (5) Destruction of the catalyst: x M + C -> M x C (6) (M is the catalyst, usually Iron Fe or Cobalt Co)

27 Types of products The importance of each reaction depends on the catalyst used, P, T. Iron based catalysts and a high operating temperature ( C) will produce mostly light hydrocarbons, the final product will be mostly Gasoline. Cobalt based catalysts and a lower operating temperature (200 C) will produce heavier hydrocarbons, the final product will be mostly Diesel. Quality of the products Very pure and high quality hydrocarbon: Less than 1ppm of sulfur (10 to 500 ppm for regular fuels) Less than 1% of aromatics