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The first published method of Starbon sulphonation was described by Budarin et al. [17]. In this synthesis, sulphonation was carried out on Starbon having been pre‐carbonised at 400 °C (Starbon‐400) as this was considered to have the best ratio of hydrophilic and hydrophobic functional groups. The Starbon‐400 was heated for four hours at 80 °C in a suspension of H₂SO₄ (99.999% purity) at a ratio of 10 ml acid to 1 g Starbon, and the sulphonated material was subsequently washed with distilled water until no further acid was leached. This was followed by conditioning in toluene for four hours at 150 °C and then in water for three hours at 100 °C. The resultant solid acid was dried overnight in an oven at 100 °C. Subsequent publications from the same authors noted a reduction in the aqueous conditioning temperature to 80 °C [18, 19].

Figure 3.3 Comparison of porosity of the three major Starbon types.

Source: Original data adapted from Budarin et al. [9], White et al. [10], White et al. [11].

A more recent publication expanded on this synthesis by variation of the sulphonating agent and suspension times [20]. In this report, Starbon‐300 was chosen as the base material. The first synthesis was similar to that previously reported, except that a ratio of 0.2 g Starbon to 10 ml H₂SO₄ (96%) was used, and a suspension time of 15 hours. Further syntheses were reported using a mixture of ClSO₃H/H₂SO₄ as the sulphonating agent, in ratios of 2 : 10 and 3 : 10 by volume, respectively. In these cases, sulphonation was carried out at reflux for five hours.