Table 3.

Boehm titration for the catalyst with different modification times (unit: mmol/g).

Sample	Acid Functional Groups	Basic Functional Groups	Phenolic Hydroxyl Groups	Carboxyl
10 min	3.6000	0.0000	0.0000	0.0172
20 min	0.4500	2.8000	0.0035	0.0033
30 min	3.6500	0.0500	0.0082	0.0075
40 min	3.8000	0.0000	0.0107	0.0078