Acids used in Friedel-Crafts alkylation
Brønsted Acid has been used in Friedel-Crafts alkylation before (for example, Ref.1). According to this reference, when toluene use as the solvent, the F-C alkylation reaction of toluene is fruitful for tertiary and secondary alkyl bromides, tosylates, and alkenes (which give both carbocations upon protonation). However, the only primary bromide, which worked in this alkylation are benzyl and cinnamyl bromides. Other active primary bromides such as allyl and crotonyl bromides gave ditolyl products (e.g., crotyl group substituted first, then underwent double bond protonation followed by hydride shift to give secondary benzyl carbocation, which then reacted with the second toluene nucleus to give 1,1-ditolylbutane). Keep in mind that these reactions worked only with activated phenyl nucleus. For example, chlorobenzene gave only trace of products even with higher temperatures.
Later, this reaction is successfully used in Tandem-Friedel-Crafts alkylation reactions to synthesize hitherto unknown perylene derivatives (Ref.2):

References:

Mathew P. D. Mahindaratne, Kandatege Wimalasena, &quot;Detailed Characterization of p-Toluenesulfonic Acid Monohydrate as a Convenient, Recoverable, Safe, and Selective Catalyst for Alkylation of the Aromatic Nucleus,&quot; J. Org. Chem. 1998, 63(9), 2858–2866 (https://doi.org/10.1021/jo971832r).
Mark A. Penick, Mathew P. D. Mahindaratne, Robert D. Gutierrez, Terrill D. Smith, Edward R. T. Tiekink, George R. Negrete, &quot;Tandem Friedel–Crafts Annulation to Novel Perylene Analogues,&quot; J. Org. Chem. 2008, 73(16), 6378–6381 (https://doi.org/10.1021/jo800558c)(PDF).