Most solid acids do not function effectively for cellulose hydrolysis because the surfaces of these solids do not have strong acid sites or the acid sites are hard to contact P-1,4-glucans. The type and amount of catalysts have a great impact on the conversion of cellulose. High catalytic acidity leads to higher reaction rate, so the most convenient method to improve hydrolysis efficiency is to load more catalyst to provide more acid sites access to |5-1,4-glucans in cellulose. The adequate catalyst loading is necessary to obtain the maximum conversion rate of cellulose to glucose. Table 15.1 summarizes hydrolysis results over some typical solid acid catalysts in water (except for FeCl3/silica). It can be seen that, catalyst weight is higher than that of cellulose in most of cases. Fe3O4-SBA-SO3H is the most active one, and that is related to its high amount of B acid sites. Catalyst amount is closely related to reac­tion time and hydrolysis yield. It was found that less catalyst requires longer reaction time to achieve high conversion rate [4]. The more catalyst, the higher concentra­tion of acidic sites, resulting in [H+] attacking on |5-1,4-glucans to produce more glucose.