Mesoporous silica molecular sieves MCM-41 containing zinc and aluminum ions (Zn-Al-MCM-41) with Si/(Zn + Al) ratios equal to 75, 151, 228, 304, and 380 and only aluminum ions with Si/Al ratios equal to 21, 42, 62, 83, and 104 were synthesized under hydrothermal conditions using cetyltrimethylammonium (CTMA(+)) surfactants as templates in the absence of auxiliary organics. The mesoporous materials, viz., Zn-Al-MCM-41 and Al-MCM-41, were characterized using several techniques, e.g., ICP-AES, XRD, FTIR, TG/DTA, nitrogen adsorption, Al-27 MAS NMR, SEM, TEM, XPS, and pyridine acidity (TPD and FTIR) measurements. The number of acid sites in Zn-Al-MCM-41 is higher than that in Al-MCM-41 due to the aluminum ion nonframework by the introduction of zinc ions. However, tetrahedral aluminum is replaced by zinc, producing two negative ions with a tetrahedral environment. The ions are associated with Bronsted acid sites, and the tetrahedral aluminum ions become octahedral aluminum ions and are associated with Lewis acid sites. Thus, the numbers of Bronsted and Lewis acid sites in Zn-Al-MCM-41 are the same, but the number of acid sites is higher than that in Al-MCM-41. The effect of reaction temperature, WHSV (weight hourly space velocity), and 2-propanol/toluene ratios on the selectivity of p-cymene were studied. The Zn-Al-MCM-41(75) catalyst containing a higher number of Bronsted acid sites was found to be more effective in the alkylation of alkyl aromatics, for example, in the production of p-cymene from toluene, using 2-propanol as the alkylating reagent. The selectivity of p-cymene under varying experimental conditions, viz., reaction temperature, WHSV, and ratio of 2-propanol to toluene, for the various catalysts follows the sequence Zn-Al-MCM-41(75) > Al-MCM-41(21) > Zn-Al-MCM-41(151) > Al-MCM41-(42) > Zn-Al-MCM-41(228) > Al-MCM-41(62) > Zn-Al-MCM-41(304) > Al-MCM-41(83) > Zn-Al-MCM-41(380) > Al-MCM-41(104).