Exploring optimal operating and investment costs of bisphenol-a production process

Bisphenol-A (BPA) is an important industrial raw material which used in the production of polycarbonates and epoxy resins. Beside these materials, it uses to produce phenoxy resins, acrylic and polysulfone resins, antioxidants (PVC) and compact discs. Theoretically, BPA is synthezied with the condensation of the sitociometric 2 mole phenol and 1 mole acetone. Homogeneous, liquid (HCL, H2SO4) and heterogeneous, solid (amberlist, zeolite) catalysts are used at this reaction. Both catalyst types have advantages and disadvantages. High conversion at low operating temperature among the advantages of the homogenous catalyts. However, high corrosion and recycling difficulty is the major problems of these catalysts. Lesser corrosion and easy seperation from the reaction media are the advantages of the heterogeneous catalysts. Nevertheless, lesser selectivity and lower reaction rate (so conversion) are the main issues of this type of catalysts. Production of the BPA with sitoichiometric 2:1 phenol:acetone molar ratio is not preferred in the industrial scale because of the side reaction which occurs due to high amounts of acetone in the reaction media. At the acidic reaction media self-condensation of the acetone forms mecytyl oxides, hence the high concentraion of acetone reduces the conversion to BPA and BPA selectivity. To reduce the negative effect of the side products excess amount of phenol (which the mole ratios of the phenol to acetone are 10:1 , 5:1 etc) is generally used in industry. Decreasing of the usage of excess phenol hence reducing of the operation and plant cost is the main aim of this study. For that reason, studies of sitoichiometric 2:1 molar ratio of phenol to acetone, were carried out. HCl and amberlyst-15 used as catalysts at the experiments. Semi-batch reactor with different feeding modes were used to minimize the concentration of the acetone in the reaction media. Purity of the products and conversion of acetone were investigated. Production cost of the BPA is one of the contents of thesis. Beside, the experiments with different feeding modes, certain amounts of HCl (%5, %15 %25 of total reactants) were tested. The reason for these experiments are conversion of acetone and purity of BPA are varied with the using of different amounts of catalyst. Hence the separation cost is varied with the catalyst amount. Thus, the optimum energy necessity which is directly related with the operating cost can be calculated. Experiment resulted with highest conversion and purity was selected and then different experiments were conducted with these parameters. Additionally some experiments include 2-mercaptoethanol as co-catalyst, amberlist-15 as heterogeneous catalyst and excess amount of phenol (3,5:1-5:1-10:1 molar ratio of phenol to acetone) were also explored. Considering the design cost, determining of potential optimum conversion and purity are aimed according to the results of all these experiments, Samples were analyzed with melting point analyzer, NMR, GC-MS and GC-FID. Using results, which are obtained from the experiments, the graphics of time/conversion are drawed with MATLAB© and heat duty of distilation, heat exchanger and reactors are calculated with CHEMCAD©. As a conclusion, it is seen that increasing of catalyst amount the conversion of acetone is increased. Moreover, addition of co-catalyzer increased the conversion of acetone. Results of the batch and semi-batch condition of sitoiciometric 2:1 phenol to acetone show that more impurity formed in the batch condition experiments. Also, the samples which taken from batch reactors have darker colour in regard of the sample taken from the semi-batch reactors. Colour of pure BPA is white and dark colour indicates impurities. Calculation of heat duties of distillation units of reboiler, condenser and heat exchanger and reactor from the simulated with CHEMCAD show that, excess amount of phenol (10:1-5:1-3.5:1 phenol:acetone molar ratio) causes more energy requirement in comparison with sitociometric (2:1 phenol:acetone molar ratio) phenol. In addition, with the more phenol feeding, height and diameter of distillation column and reactor size increase along with plant cost.