charact-carbons-Kasetsart_Bhatia_UQ

Slide 1 : Suresh K. Bhatia Division of Chemical Engineering The University of Queensland Brisbane, Australia CHARACTERIZATION OF NANOPOROUS CARBONS

The University of Queensland : The University of Queensland Among the top four Universities in Australia (UQ, UNSW, Sydney, Melbourne). Three campuses (St. Lucia, Gatton, Ipswich – suburbs of Brisbane). Seven faculties (Chem. Eng. in School of Eng., part of Faculty of Engineering, Physical Sciences and Architecture). Approximately 23,000 students (4,500 postgraduate), and 5,000 academics.

Slide 3 : The University of Queensland

Division of Chemical Engineering : Division of Chemical Engineering Leading higher institution and PhD degree provider in chemical engineering in Australia (over 360 PhDs graduated since 1990) - among the top in the world Internationally recognised research and graduates (graduates at NASA, Los Alamos Nat. Lab., DuPont, Shell, BP, GM, and many universities) 18 academic staff 25 postdocs/professional research staff 100 postgraduates 300 undergraduates (2nd, 3rd, 4th years) Research budget of about $6M

Research Areas : Research Areas

Slide 6 : Dr Kate O’Brien, Environmental engineering Research areas: Water quality modelling in creeks, weirs rivers, lakes, reservoirs and estuaries, to predict: toxic algal blooms impacts of management and other system changes (e.g. recycling, land-use and climate change) Minimising environmental impact of water and energy usage

Slide 7 : Organic Waste CAMBI Thermal Hydrolysis Fermentation Feedstock: Organic Acids Waste to Plastic Biopolymer Production Biomass full of polymer PHA Bioplastic PHA bioplastics can replace conventional plastics: Similar properties to conventional plastics, Produced from renewable resources, Truly biodegradable. Dr. Paul Lant: paul.lant@uq.edu.au

Slide 8 : Key core skills Characterisation, rheology, processing, simulation and product development Key project streams [application areas] BIOPOLYMERS AND NANOSTRUCTURED POLYMERS Renewable polymer processing and product design Biofluids rheology - Swallowing fluids, CF sputum Nanostructured polymers [DM] Biomedical polymer processing [JCW] ENGINEERING POLYMERS High value industrial polymers Food processing and added nutrition foods Rheology and processing and simultation [TN] Polymer Properties [RT] Centre for High Performance Polymers – Engineering Dr. Peter Halley: p.halley@uq.edu.au

Slide 9 : Functional Nanomaterials for Solar Energy Conversion Dr. Lianzhou Wang, l.wang@uq.edu.au New Nanomaterials Water splitting for H2 fuel production Low cost solar cells for electricity Pollutant degradation for water/air purification Surface coating for anti-bacterial/self-cleaning

Slide 10 : Projects Prof. Anh Nguyen (anh.nguyen.eng.uq.edu.au) Molecular phenomena at saline water interfaces. This project investigates many complex molecular phenomena and interactions at the saline water interfaces which underpin increasing use of saline water in industries. It will combine experiment and molecular modelling to characterise the interfaces. Tailoring nano-crystal suspensions for foliar fertilisers. This project develops an innovative suspension release system for delivering ionic nutrients to plants through the leaves. It will involve collaboration with AgriChem – Liquid Fertilisr Pty Ltd. Ultra clean coal. This project develops advanced interface-based separation processes for producing ultra clean coal energy. This experimentally based project will involve collaboration with BHP Billition Mitsubishi Alliance. Separation of fine nickel sulfide minerals in hyper-saline water. This project develops improved technologies for recovering fine minerals for Ni production for the steel industry. It will use advanced colloid and surface diagnostic tools such as atomic force microscopy, and will involve collaboration with BHP Billition. AFM images showing nanobubbles (left) of dissolved gases and self assembled hemimicelles (right) of a surfactant on a hydrophobic surface in water. These nanostructures underlie many interfacial phenomena used in a wide range of industrial applications. Interface Science and Engineering for Clean Water, Chemical, Coal and Mineral Separation Technologies

Slide 11 : Projects Prof. Suresh Bhatia (s.bhatia@uq.edu.au) Mixture adsorption in nanoporous solids. This project develops novel theories of mixture transport in new nanomaterials such as carbon nanotubes and silicas such as MCM-41, with the help of simulation. 2. Novel nanoporous carbons. This project involves the synthesis of novel nanocarbons of well tailored pore size using using negative templating, and their characterisation and application to molecular sieving. This project will combine experiment, modelling and simulation. 3. Molecular modelling of carbon nanostructure and confined fluids. This project aims to develop molecular models for novel carbons synthesized in our laboratory, and to investigate adsorption and diffusion of simple gases such as CH4 and CO2 in these model structures via simulation methods. 4. Novel separation method for hydrogen isotopes by quantum confinement. This project seeks to study the low temperature transport of H2/D2 mixtures using carbon molecular sieves and other nanoporous materials, experimentally as well as with computer simulation. Collaboration with a French group. Conversion of waste plastics to liquid fuels using mesoporous catalysts. Molecular modelling of carbon nanostructure and its adsorption properties Activated carbons, carbon fibres and carbon nanotubes for gas separation and storage Nanoscale Science and Engineering

Slide 12 : Professor Suresh Bhatia Head, Division of Chemical Engineering The University of Queensland Brisbane, Australia Email: s.bhatia@uq.edu.au

Slide 13 : Role of Characterisation

Carbon Structure : Carbon Structure

Carbon Structure : Carbon Structure Norit R1E activated carbon, largely single and two layer walls Sharma, Kyotani and Tomita (1999) Pocahontas 3 coal char, walls essentially infinitely thick

Characterization by Adsorption : Characterization by Adsorption Steele 10-4-3 potential most commonly used with molecular models. - Smooth pore walls - Infinitely thick pore walls

Pore Wall Thickness Distribution : Typically S ~ 1,000-2,500 m2/g for most carbons  g ~ 1.0-2.0 (mean number of layers per wall). Since carbons are disordered, for such small values of g fluctuations from the mean will be important and will affect adsorption. Pore Wall Thickness Distribution

PSD of Activated Carbon Fiber : PSD of Activated Carbon Fiber False shoulder at 3.7 A (center-to center 7.1 A) pore width eliminated by our approach. Novoloid fibers from American Kynol Corpn. BPL

Slide 19 : Pore Wall Thickness Distribution of Activated Carbon Fibers

PWTD: Heat Treated Norit R1 Extra : PWTD: Heat Treated Norit R1 Extra Correlation with XRD Pore wall thickness distribution Pore size distribution

Isotherm Prediction for other Gases : Isotherm Prediction for other Gases BPL carbon Data of Levan and Pigorini (1997), Vidal et al. (1990). Data of Russel and Levan (1997).

Accessibility Problem in AC : Accessibility Problem in AC Data of Gusev et al., 1986 BPL carbon CH4 Variability between batches leads to differences in data between groups.

Accessibility Problem: PCB Carbon : Accessibility Problem: PCB Carbon Data of Ritter and Yang (1986), Choi et al. (2003). CH4

Effect of Temperature : Effect of Temperature Percolation model suggests that accessibility is independent of temperature. Literature evidence suggests otherwise. The capacity for argon is higher at 313 K, as compared to 87 K, suggesting differences in accessibility. Maggs (Nature, 1952). Bae and Bhatia (Energy & Fuels, 2006).

Hybrid Reverse Monte Carlo Method(Opletal G et al., Mol. Sim. 2002; 28:927-38) : Hybrid Reverse Monte Carlo Method(Opletal G et al., Mol. Sim. 2002; 28:927-38) Old configuration New configuration Eo, go(r) En, gn(r) E is determined from EDIP: Marks NA. Phys Rev B 2002, 65: 075411; J Phys: Condens. Matter 2002, 14: 2901

Reconstructed Saccharose Based Carbon : Reconstructed Saccharose Based Carbon E

Adsorption Equilibrium of Argon at 87K : Adsorption Equilibrium of Argon at 87K A snapshot of argon adsorption Nguyen, Bhatia, Jain and Gubbins, Molecular Simulation (2006).

Methodology : Methodology 1. Main principle: pore connectivity is determined based on continuity of closely packed adsorbed phase 2. Implement: three main steps Step 1: construction of closely packed adsorbed phase in porous material (GCMC) Step 2: clustering the closely packed adsorbed phase (Breadth-first search algorithm) Step 3: determination of connected and disconnected clusters (supercell)

Saccharose Char : Saccharose Char Unit cell Supercell

Pore Connectivity of Saccharose Char : Pore Connectivity of Saccharose Char Disconnected at 77 K Connected at 300 K Diffusion of Nitrogen through detected close pore

Temperature Dependent Accessibility : Temperature Dependent Accessibility Disconnected at 77 K Connected at 300 K

Crossing Time Using Transition State Theory : Crossing Time Using Transition State Theory For a single particle, the crossing time, tA->B, from cage A to cage B at low loading limit is given as where k is a transmission coefficient. Cage B Cage A

Crossing Time of Argon and Nitrogen : Crossing Time of Argon and Nitrogen 1. Significant variation of the crossing time with temperature, ranging from experimental time scale at low temperature to MD scale at high temperature indicates inaccessibility at low temperatures. 2. tA->B significantly larger than tB->A at low temperature, indicates hysteresis phenomena in microporous materials 3. Extremely large crossing time of nitrogen at 77 K compared to argon at 87 K indicates use of the argon adsorption at 87 K preferable for characterization of microporous materials

Hysteresis in Takeda 3 Å Carbon Molecular Sieve : Hysteresis in Takeda 3 Å Carbon Molecular Sieve CO2 shows no hysteresis at 273 K N2 shows hysteresis at 77 K, indicative of some inaccessibility in this case. Nguyen and Bhatia, Langmuir (2008).

Pore size distributions of BPL and PCB carbons : Pore size distributions of BPL and PCB carbons

Accessibility Problem in AC: CH4 : Accessibility Problem in AC: CH4

Inaccessibility in Char Gasification : Inaccessibility in Char Gasification Variation of surface area (per unit initial mass) with conversion, for air oxidation of Yarrabee coal char heat treated at various temperatures. Variation of reactivity (i.e. reaction rate per unit surface area) with conversion, for air oxidation of Yarrabee coal char. Feng, Barry and Bhatia, Carbon (2003).

Gasification of Petroleum Coke in Air at 773 K : Gasification of Petroleum Coke in Air at 773 K Variation of helium density with conversion, for coke calcined at 1225 ºC. Variation of BET area with conversion (area per unit current mass) Tran et al., Ind. Eng. Chem. Res. (2007).

Conclusions : Conclusions Isotherms can be analyzed to determine pore size and pore wall thickness distribution in carbons. Most carbons have relatively thin walls, with a large proportion being single layer walls. HRMC method, combining RMC with an energy constraint, provides an improved technique for reconstructing the carbon Molecular models of carbons can be analyzed for pore accessibility using our new algorithm. Argon at 87 K is a better adsorptive for carbon characterisation than nitrogen at 77 K, and has fewer accessibility issues. At low conversion accessibility of mesopores is an important issue in gasification. Most mesopores are opened up by about 5% conversion, and this occurs by progressive opening up of pore mouths and entrances to mesopores.

ACKNOWLEDGEMENT : ACKNOWLEDGEMENT National Supercomputing Facility, Canberra High Performance Computing Unit, The University of Queensland Collaborators Thanh Nguyen Dr. Owen Jepps Dr. Debra Searles Dr. David Nicholson Prof. Keith Gubbins

Configuration from Reverse Monte Carlo (Opletal G et al., Mol. Sim. 2002; 28:927-38) : Configuration from Reverse Monte Carlo (Opletal G et al., Mol. Sim. 2002; 28:927-38) Highly-strained structure with predominantly 3-member rings

Configuration from Metropolis Monte Carlo with EDIP : Configuration from Metropolis Monte Carlo with EDIP Highly strained rings are minimized. However, match between simulated and experimental PDF is poor.

The Principle of Analysis of Pore Connectivity : The Principle of Analysis of Pore Connectivity RC[i][j] RC[i][i] For particles in in different clusters [i] and [j]: and, for particles in the same cluster [i]:

Unphysical Adsorption in Closed Pores by GCMC Simulation : Unphysical Adsorption in Closed Pores by GCMC Simulation GCMC simulation does not distinguish inaccessible pores.

Models for Nanoporous Carbons : Models for Nanoporous Carbons Early models of carbons emphasized disordered crystallites (Biscoe and Warren, 1942; Franklin, 1951) Slit pore models, provide a pore size distribution - triangular, rectangular cross section pores - junction pore model (Maddox et al., 1997) - randomly etched graphite pore (Seaton et al.,1997) Random platelet model (Segarra and Glandt, 1994). Chemically constrained models (Acharya et al., 1999) Reverse Monte Carlo simulation based models (Snook et al.; Gubbins et al., Bhatia et al.)