The volume fraction of CO at temperatures 200–250 °C shows a dramatically sharp decrease and decreases to a minimum value at 450 °C; then, both in the ranges of 250–400 and 450–500 °C, the CO volume fraction has a slight increase with increasing temperature but represents a decreasing trend in the overall temperature range.
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The sentences
With increasing temperature, the BET specific surface area showed an increasing trend in the overall temperature range.