BIOBASED CHEMICALS
Figure 3 – Drift IR of A series Starbon as a function of temperature
Source : A Borisova , Advances in characterisation , preparation & application of polysaccharide-derived mesoporous carbons for environmental remediation , PhD thesis , University of York , 2015
with adsorption in one solvent , where the compound of interest selectively sticks to the Starbon ; and desorption in another , where it is removed . As the Starbon acts through physisorption , the process is entirely repeatable , and it can be reused up to 100 times with little drop in efficiency . Such systems have been demonstrated in a wide range of applications , for instance the separation of caffeine from tea , chemotherapy drugs from fermentation broths , UV actives from seaweed and cannabinoids from hemp extracts . This technology allows for either isolation of the target compound in very high purity or in producing a significantly less complex mixture in which the target compound concentration has been greatly enhanced . Outcomes depend on the system of interest . As an example , Figure 2 shows adsorption ( everything that does not stick ) and desorption ( everything that is selectively isolated ) of compounds from seaweed . The major compound in the seaweed extract is a non- UV-active sugar that does not bind to Starbon . As such the desorption fraction contains the target compound at high concentration . No conventional purification technique was able to separate the target from the sugar at larger than analytical scale .
How Starbons are made
Starbons are produced in three steps :
• Gelling of the polysaccharide in water to produce a porous network
• Sympathetic drying to produce an aerogel via removal of water without collapsing the pore structure
• Pyrolysis to fix the pore structure and surface chemistry
The change in chemical functionality as a function of temperature is best indicated by looking at drift infrared ( IR ) of the surface of A Series Starbon materials .
Sample
SBET surface m 2 / g
Vp BJH cm 3 / g
VpDFT cm 3 / g
Figure 3 illustrates the transition from polysaccharide OH and acidic groups to ketone and aldehyde carbonyls , coupled with increasing carbon-carbon unsaturation that eventually leads to fully-aromatic rings as the pyrolysis temperature increases . Note that IR data for 800 ° C material does not give meaningful data due to the conductivity of its poly-aromatic structure . The effect on temperature on porosity is also well documented ( Table 1 ).
Conclusion
Starbons are a tuneable platform technology with numerous commercial applications . In the field of separations , Starbon materials ’ unique physical characteristics allow quick , mild and simple isolation of target compounds , even from complex systems . If an isolation is proving difficult using standard techniques , Starbons may well be the solution . • * - Starbon is a registered trade mark of Starbons Ltd .
Rob McElroy
Table 1 – Surface area & pore volume as a function of starting material & temperature Source : R . A . Milescu et al ., Sustain . Chem . Pharm ., 2020 , 15 , 10023
CTO
STARBONS LTD k + 44 1904 561551 J rob . mcelroy @ starbons . com j www . starbons . com
Micropore volBJH cm 3 / g
Micropore volDFT cm 3 / g
Mesopore volBJH cm 3 / g
DBJH nm
S000 85.62 0.488 0.472 0.009 0.010 0.479 12.68 S300 291.98 0.609 0.557 0.045 0.058 0.564 11.44 S550 629.61 0.713 0.838 0.196 0.189 0.517 11.73 S800 773.84 0.678 1.025 0.261 0.244 0.417 10.5 A000 83.09 0.448 0.392 0.000 0.000 0.448 8.51 A300 137.29 0.198 0.348 0.010 0.016 0.188 12.04 A550 508.06 0.673 0.670 0.141 0.158 0.531 6.81 A800 689.20 0.962 1.139 0.147 0.176 0.815 11.7 P000 83.62 1.398 1.348 0.006 0.000 1.392 3.53 P300 100.33 0.525 0.438 0.000 0.007 0.525 13.86 P550 264.17 0.737 0.693 0.054 0.053 0.682 12.16 P800 631.18 0.986 0.997 0.158 0.158 0.828 9.93