Christian Doblin

Magnetic Metal–Organic Frameworks for Efficient Carbon Dioxide Capture and Remote Trigger Release

Magnetic metal-organic framework (MOF) composites show highly efficient CO2 desorption capacities upon their exposure to an alternating magnetic field, demonstrating a magnetic induction swing strategy for potentially low-energy regeneration of MOF adsorbents.

Titanium Powder from the TiRO™ Process

A new continuous process for the direct production of CP titanium powder is being developed at CSIRO. The TiRO™ process has two major steps. The first step is conducted in a fluidised bed where titanium tetrachloride and magnesium powder react to form small (1.5 µm) titanium metal particles uniformly dispersed inside larger spheroidal magnesium chloride particles with an average particle size of 350 µm. The second step involves vacuum distillation in which the magnesium chloride is removed from the titanium. During vacuum distillation the magnesium chloride is volatilised and the micron sized titanium particles come together to form partially sintered predominantly spheroidal porous particles with a similar shape to the starting particle, some which appeared to be hollow. A mechanism for their formation is proposed. The spheroidal particles are all lightly sintered together. The vacuum distilled product was very lightly ground to liberate the spheroidal particles which had an average particle size of about 200 µm. With further grinding an angular Ti powder was produced. The ground titanium was free flowing and had a tap density of 2.4 g/cm3.

A Robust Metal-Organic Framework for Dynamic Light-Induced Swing Adsorption of Carbon Dioxide.

Adsorbents for CO2 capture need to demonstrate efficient release. Light-induced swing adsorption (LISA) is an attractive new method to release captured CO2 that utilizes solar energy rather than electricity. MOFs, which can be tailored for use in LISA owing to their chemical functionality, are often unstable in moist atmospheres, precluding their use. A MOF is used that can release large quantities of CO2 via LISA and is resistant to moisture across a large pH range. PCN-250 undergoes LISA, with UV flux regulating the CO2 desorption capacity. Furthermore, under UV light, the azo residues within PCN-250 have constrained, local, structural flexibility. This is dynamic, rapidly switching back to the native state. Reusability tests demonstrate a 7.3 % and 4.9 % loss in both adsorption and LISA capacity after exposure to water for five cycles. These minimal changes confirm the structural robustness of PCN-250 and its great potential for triggered release applications.

Shape selective cracking ofn-octane and 2,2,4-trimethylpentane over an alumina-pillared clay

A mixture ofn-octane (nC8) and 2, 2, 4-trimethylpentane (224-TMP) was cracked over an alumina-pillared montmorillonite (Al-PILC) acid catalyst as a means of characterising its pore structure and shape selectivity. The shape selectivity of the catalyst was quantified by a time dependent parameter analogous to the constraint index, called the selectivity ratio (SR), and defined as log (fraction of nC8 remaining)/log (fraction of 224-TMP remaining). The SR was measured over Al-PILC, a 0.16 wt% Pt loaded Al-PILC, a Y zeolite, and an amorphous silicaalumina. The SR was greater over Al-PILC compared with Y-zeolite even though the pore openings of the Al-PILC were of similar or larger size than those in the Y-zeolite. Doping AlPILC with Pt caused a large increase in the SR. As found with constraint index measurements, internal pore dimensions and reaction mechanisms appear to be the determinants of SR. However, SR is better capable of discriminating larger pore microporous materials.

MaLISA – a cooperative method to release adsorbed gases from metal–organic frameworks

Metal organic frameworks (MOFs) have emerged as ideal adsorbents for carbon capture owing to their exceptionally high surface areas and chemical versatility. However, the significant energy penalty for the regeneration of MOF adsorbents is one of the biggest barriers to their widespread deployment. To overcome this challenge, there has been a recent surge of high quality research to adapt MOFs to be responsive to external stimuli including light and magnetic fields such that they might expel adsorbed molecules at low energy cost and high efficiency. To further minimize the energy cost required for the regeneration of MOF adsorbents, we present a robust dual stimuli-responsive MOF, magnetic PCN-250 (mPCN), which shows strong responses to both magnetic induction and UV light following two distinct working mechanisms, magnetic induced localised heat and light induced localised bending of the MOF organic linkers. Both responses are able to collaboratively trigger a record high gas desorption (up to 96.8% of CO2 desorption at 1 bar) from mPCN through a MaLISA process, confirming a potentially low-energy yet highly efficient strategy to regenerate MOF adsorbents on a large scale. This is the 1st exploration in the use of multiple stimuli to improve gas liberation from MOF adsorbents.

The TiRO™ Process for the Continuous Direct Production of Titanium Powder

The CSIRO is developing the TIRO™ process for the continuous direct production of titanium powder. The process comprises two stages. The first stage is a fluidised bed reactor (FBR) in which TiCl4 is reacted with magnesium powder to form solid magnesium chloride particles about 350 µm in diameter in which micron sized titanium particles are dispersed. The second stage is a continuous vacuum distillation operation where the titanium is separated from the magnesium chloride and sintered to form a friable “biscuit”. The biscuit comprises porous titanium spheres about 250 µm in diameter which can be liberated by very light grinding. The overall process has a throughput of 0.2 kg/h Ti, limited by the vacuum distillation unit and is being scaled up. The process has generated Ti powder with ≤0.25 wt% O and < 200 ppm Cl and meets CP2 specifications. Ring grinding the vacuum distilled product for short periods reduced the particle size, however longer grinding times caused agglomeration of the particles. Ring grinding in air resulted in a large increase in oxygen concentration

Processing TiROTM Powder for Strip Production and other Powder Consolidation Applications

The TiROTM process has been developed at CSIRO for the continuous direct production of Ti powder. The process has two main steps; a reaction step where the Ti is produced as very fine particles dispersed in larger particles of magnesium chloride. The MgCl2 is separated from the Ti powder in a continuous vacuum distillation unit. The Ti product from this unit comprises a lightly sintered “biscuit” of Ti particles that can be broken up into individual particles powder with a d50 around 200 μm. These particles have a unique morphology which is a function of the process.For many powder metallurgical applications TiROTM powder will require further processing to tailor its morphology for the specific application. A small sample of Ti strip has been produced from ring milled TiROTM powder by a CSIRO patented combination of direct powder rolling (DPR) followed by hot roll densification (HRD). The Ti strip was annealed and characterised in terms of microstructure and chemistry.A powder manipulation technology (PMT) has been developed to modify TIROTM particulates without the need of more expensive hydride-dehydride (HDH) or gas atomization routes to improve density, flowability, size, distribution and shape for cold spray and additive manufacturing applications.