Semi-batch reactor systems can be used at different areas due to its advantages of the feed manipulation. Common practices are temperature control of the exothermic reactions or selectivity adjustment of the production process include serial and parallel reactions. Bisphenol A (BPA) is theoretically synthesized with 2 moles of phenol and 1 mol of acetone. During the reaction, a stoichiometric ratio or high acetone concentration causes the formation of by-products. This situation has been confirmed by density functional theory (DFT) calculations. In these calcula-tions, the B3LYP method and the 6-311++G(d, p) basis set were used. DFT calculations show that by-products can be formed in the synthesis of bisphenol a. The common method used to solve the by-product problem is to work with high molar phenol/acetone ratios. But this brings additional operating and investment costs. In this study, semi-batch reaction experiments were performed which stoichiometric acetone was fed in reactor with various pulsed modes in the presence of homogenous and heterogonous catalysts. Time versus conversion and selectivity data were collected at various catalyst concentrations. All runs were compared with the results of batch and semi-batch runs performed in over molar ratio of phenol/acetone. As a result, it has been shown that high conversion and selectivity can be achieved by providing energy efficiency with pulsed mode semi batch reactor.