Solid acid catalysts are of great interest in several industrial reactions, being among them the zeolites the most widespread ones. Their main advantages are their crystalline structures with small, regular pore size and high stability, and their strong and uniform acidity. However, their small pore size is a major disadvantage for reactions involving bulky molecules as reagents or products, leading to diffusion limitations or even impeding the reaction. Thus, ordered mesoporous materials gain attention as a solution to these drawbacks. They are amorphous solids which are synthesized with large, uniform pores in their structure due to the addition of a template together with the precursors, which is later removed.
SBA-15 is one of the best candidates for catalytic applications . It was reported for the first time by Zhao in 1998 . It is an amorphous silica with thick walls, uniform cylindrical pores arranged in a 2-D hexagonal structure and some random pore interconnections. The synthesis procedure requires high acidic media and the presence of the non-ionic surfactant P123 © as a template. The removal of the latter (detemplation) could be performed via calcination , extraction , irradiation [4, 5] or oxidation .
SBA-15 synthesis comprises two primary steps. The first one is carried out at atmospheric pressure, under stirring and at relatively low temperatures, and is usually called ripening. This is usually followed by a second stage consisting of the treatment of the gel in an autoclave, at higher temperature and self-generated pressure, without agitation, which is usually called ageing.
The first stage (ripening) results in the appearance of the mesostructure, through the formation of surfactant micelles and the condensation of silica around them in a cooperative self-assembly process . The second stage (ageing) improves the crosslinking of the silica and is crucial for the consolidation of the structure, and entails minor transformations (enlarged pores, development of interconnections).
Since the silica has no intrinsic acidity, acidic functional groups must be added in order to obtain a catalytic active material. The attachment of organic functional groups could tune the hydrophilic-hydrophobic character of the silica surface to give sorbent chemical selectivity for specific molecules or ions . In the case of propyl-sulfonic functional groups, their incorporation can be done via post-synthesis grafting techniques or co-condensation in the first synthesis step (direct synthesis) .
Grafting techniques have several drawbacks, such as that they involve extra steps, require high amounts of solvent per gram of catalyst, and in addition there are concerns about the uniform anchoring of the groups along the pores. The main disadvantages of this method includes: (i) the reductions of pore size and pore volume caused by the attachment of functional group on pore surface ; (ii) density limitation of reactive silanol group that would limit the loading of functional group on the pore surface, being possible that cross-linking between functional groups and silanol groups on surface occurs ; (iii) difficulty in achieving uniformity of the functional group and tedious process which involves more than one step of preparation .
The co-condensation of the functional precursor seems to be more convenient to obtain standard catalysts for industrial applications. There is evidence that the direct synthesis leads to a uniform dispersion of the functional groups on the surface of the material while its structure is preserved . A disadvantage of this procedure is that the functional groups are already present in the material when the surfactant is going to be removed, thus limiting the detemplation to extraction methods which are not harmful to them. Standard procedures involve large amounts of solvent per gram of catalyst, long contact time and limited yield of the template removal.
It has been shown that co-condensation procedure yields better results when, instead of mixing all the precursors at the beginning of the ripening step, a pre-hydrolysis of the silica precursor is allowed (0.5 to 3 h) and the functional precursor, along with the oxidant agent is added later, and then 24 h ripening is completed .
However, several authors have reported that the formation of the mesostructure is relatively fast in SBA-15  and within an interval from 30 minutes to a few hours a material with similar properties to that obtained after 24 h of ripening can be obtained [14, 15].
Therefore, a reduction in the synthesis time is studied in this work, keeping the pre-hydrolysis step, after which the functional precursor is added and ripening takes place for only 4 h. The ageing and extraction steps are not altered. The materials obtained in this way exhibits very similar properties to those prepared complying with a standard ripening of 24 h.
Regarding the extraction, typical procedures involve stirring and reflux for 24 h in ethanol (approximately 250 ml solvent per gram of as-synthesized material) . The use of Soxhlet apparatus can reduce significatively the time and the amount of solvent needed, since the material is always contacted by fresh solvent being refluxed and the extracted polymer concentrates in the bottom flask (Scheme 1, Supplementary data) . Zhang et al. studied the template removal by extraction with absolute ethanol in a Soxhlet apparatus , considering different extraction times and ageing temperatures. They found that the template content decreased rapidly during the first three hours of extraction and then remained almost constant. Complete removal of the surfactant was not achieved and the remaining content was lower as the pore size was larger. The amount of ethanol employed was still high (approximately 250–1000 ml per gram of sample). Ávila et al.  studied the extraction with a Soxhlet apparatus using different solvents. Water, acetonitrile, dichloromethane, acetone, methanol and ethanol were assessed as solvents (approximately 42 ml per gram of sample). Water was not effective and methanol, acetonitrile and ethanol proved to be the best solvents amongst the studied. Remaining surfactant was almost constant for 6, 24 and 48 h extractions, in agreement with the findings already mentioned.
Hydrochloric acid solutions in ethanol and diethyl ether were also employed for the removal of organic templates in mesoporous materials . Extracted materials showed a higher degree of cross-linkage in comparison with the as-synthesized samples. A small contraction of the lattice was also observed.
Since extraction is an energy-intensive operation and an important source of waste, it is the objective of this work to develop a standard procedure which allows achieving a high yield of detemplation and optimizes the amount of solvent needed and the time required, as well as use a cheap, commercially available solvent. Therefore, the protocol, together with a synthesis time reduction, would be feasible to be industrially applied for large-scale catalyst synthesis.
Obtained materials exhibited high surface area and a good degree of mesoscopic order, comparable with materials obtained by the above-mentioned procedures. A high degree of template removal was achieved and the sulfonic groups were preserved in functionalized materials.