Laminaria digitata and Palmaria palmata Seaweeds as Natural Source of Catalysts for the Cycloaddition of CO2 to Epoxides

Seaweed powder has been found to act as an effective catalyst for the fixation of CO2 into epoxides to generate cyclic carbonates under solvent free conditions. Model background reactions were performed using metal halides and amino acids typically found in common seaweeds which showed potassium iodide (KI) to be the most active. The efficacy of the seaweed catalysts kelp (Laminaria digitata) and dulse (Palmaria palmata) was probed based on particle size, showing that kelp possessed greater catalytic ability, achieving a maximum conversion and selectivity of 63.7% to styrene carbonate using a kelp loading of 80% by weight with respect to epoxide, 40 bar of CO2, 120 °C for 3 h. Maximizing selectivity was difficult due to the generation of diol side product from residual H2O found in kelp, along with a chlorinated by-product thought to form due to a high quantity of chloride salts in the seaweeds. Data showed there was loss of organic matter upon use of the kelp catalyst, likely due to the breakdown of organic compounds and their subsequent removal during product extraction. This was highlighted as the likely cause of loss of catalytic activity upon reuse of the Kelp catalyst.


Laminaria digitata and Palmaria palmata Seaweeds as Natural Source of Catalysts for the Cycloaddition of CO2 to Epoxides
James W. Comerford*, Thomas Gray, Yann Lie, Duncan J. Macquarrie, Michael North and Alessandro Pellis Table /  Figure Description Page Table S1a Conversions to styrene carbonate and diol by-product using metal halides and histidine co-catalyst 2 Table S1b Conversion to styrene carbonate and diol by-product using metal halides lysine co-catalyst 2 Table S1c Conversion to styrene carbonate and diol by-product using metal halides glycine co-catalyst 2 Table S1d Conversion to styrene carbonate and diol by-product using metal halides alone 2 Table S1e Conversion to styrene carbonate and diol by-product using amino acids alone 2

Figure S1
Variation in Kelp catalyst loading in the synthesis of styrene carbonate 3 Table S2 Effect of CO2 pressure on conversion to styrene carbonate using Kelp D <125 nm as a catalyst 3

Figure S2
Conversion to styrene carbonate over time using Kelp D catalyst and larger reaction scale of 20 mmols in a single Parr reactor. 3 Table S3 Calculation of water content from TGIR analysis of unused Kelp seaweeds B-D <125 4 Table S4 % Organic vs inorganic content for Kelp seaweeds B, C and D 4 Figure S3 TGIR Analysis of Kelp B (Red), C (Blue) and D (Green). TG used to assess residual moisture content of the dried seaweeds 5 Figure S4 IR over time to measure water loss. TGIR of Kelp B (left), Kelp C (middle) and Kelp D (right) 6 Figure S5 1 H NMR of conversion to styrene carbonate using Kelp B 300-500 nm particle size as shown in table 3 along with an example carbonate conversion calculation 7 Figure S6 GC/MS Chromatogram of conversion to styrene carbonate using Kelp D <125 nm particle size as shown in table 3. 8 Figure S7 M/S of Peak 1 -Benzaldehyde 9 Figure S8 M/S of Peak 2 -Styrene Oxide 10 Figure S9 M/S of Peak 3 -1-Phenyl-2-chloroethanol 11 Figure S10 M/S of Peak 4 -1-Phenyl-1,2-ethanediol 12 Figure S11 M/S of Peak 5 -Styrene carbonate 13 Figure S12 High resolution M/S of reaction mixture showing phenylacetaldehyde, 1phenyl-1,2-ethanediol and styrene carbonate 14 Figure S13 ICP-MS raw data 15-22 Method S1 Detailed HPLC method for amino acid analysis 23-24      (19.9) = 100 × 1 (13.78) 1 (13.78) + 2 (7.17) + 3(16.16) + 5(30.11) + 6(0.38) + 7(1.55) Figure S6. GC/MS Chromatogram of conversion to styrene carbonate using Kelp D <125 nm particle size as shown in table 3.  Diluent was prepared by mixing 48.5 mL of eluent A with 1.5 mL concentrated phosphoric acid.
Internal standard solution consisted (ISTDsol) in a 1.5 mM Norleucine solution in water.
The pre-column derivatisation was done in the HPLC needle by an automated procedure as follows:

Auto-sampler program for pre-column derivatisation
Function Parameter Draw Draw 50.00 μL from location "P2-A1" with default speed using default offset Draw Draw 1.00 μL from air with default speed Draw Draw 2.00 μL from location "P2-A2" with default speed using default offset Draw Draw 2.00 μL from sample with default speed using default offset Draw Draw 12.00 μL from air with default speed Mix Mix 4.00 μL from air with default speed for 5 times Wait Wait 1 min Eject Eject 12.00 μL to seat with default speed Wash Wash needle in flushport for 5 s Draw Draw 2.00 μL from location "P2-A3" with default speed using default offset Draw Draw 12.00 μL from air with default speed Mix Mix 6.00 μL from air with default speed for 5 times Wait Wait 0.15 min Eject Eject 12.00 μL to seat with default speed Wash Wash needle in flushport for 5 s Draw Draw 4.00 μL from location "P2-A4" with default speed using default offset Draw Draw 12.00 μL from air with default speed Mix Mix 10.00 μL from air with default speed for 5 times Eject Eject 12.00 μL to seat with default speed Inject Inject Hydrolysis of the microalgae samples was done as follow: 20 mg of algal powder in 25 mL 6M HCl with 1% (w/v phenol) were heated at 150 •C for 30 min in a CEM discover microwave. The resulting mixture was filtered and evaporated under reduce pressure. The resulting solid was re-suspended in 30 mL of suspension solution consisting of Water:MeOH:ISTDsol (5:4:1). The suspension was sonicated for 10 s and filtrated through 0.22 um Whatman filters.