3.2 Effect of temperature and residence time
The CB conversion is an important parameter that can be used to
characterize the reaction process and measure the reaction rate; it also
affects the selectivity. The CB conversion was investigated as a
function of temperature and residence time, as shown in Figure
2 . The mass fraction of sulfuric acid was 95%. The results showed that
under the condition of incomplete CB conversion, the conversion
increased with increasing residence time, and at the same residence
time, the conversion increased with increasing temperature, indicating
that higher temperatures significantly increased the reaction rate. It
is worth noting that the reaction was carried out at a low temperature
and with a short residence time. When the conversion was very low, the
concentration of nitric acid did not obviously decrease and was
approximated to be constant. Therefore, the conversion of CB increased
linearly and in accordance with pseudo-first-order reaction kinetics.