Figure 5 ‘45-15’ feeding mode a) conversion against time /mol ratio without co-catalyst b) conversion against time /mol ratio without co-catalyst c) conversion against time/HCl (%) without co-catalyst, d) conversion against time/HCl (%) with co-catalyst.
The first thing that stands out in the graphs is that when the co-catalyst is used, the structure of the graphs shifts from concave to convex. Figure 5-b shows that if trial was performed for ‘45-15’ feeding mode with co-catalyst at a 5/1 molar ratio, 83% conversion would be achieved in 6th hours. In ‘45-15’ feeding mode, when 2/1 mole ratio is used with 25% HCl, the conversion increases from 50% to 60% by using co-catalyst. It is also seen from the graphs that the molar ratio makes a steeper output in the form of the graph and the change over time is smoother.
4 | Conclusions
In the bisphenol a synthesis reaction, different by-products are obtained with many serial and parallel reactions. This result has also been demonstrated as a result of DFT studies, in this paper. Therefore, the solution proposal was investigated in the laboratory environment. Originated high concentration of acetone, high molar phenol/acetone ratios are being used in the industry to prevent serial and parallel reactions in the reaction medium. This imposes energy costs on the plant. Studies in this paper were carried out based on above challenge. In a semi-batch reactor working at stoichiometric ratios, acetone feed profile which will achieve high conversion and selectivity also the effect of catalyst type and concentration of HCl were investigated. It has been found that ‘45-15’ feeding modes are the best among the various feed profiles. Also, the amount of HCl increased from 5% to 15% conversions increased by 60% and increasing HCl percent from 15% to 25% conversion increased around 20%. With the increase of the amount of HCl from 5% to 15%, the selectivity has increased from 87% to 91.5%. The highest conversion with the Amberlyst catalyst was obtained as 5.1 with 5/1 phenol-acetone ratio with a selectivity of 60%. Using Amberlyst in the presence of co-catalyst in the stoichiometric ratio, the selectivity increased from 64% to 94% and conversion from 1.4% to 3%. The use of co-catalyst has been shown to contribute positively to conversion and selectivity in all cases. The energy required for reboiler in the distillation column is 95476 in the case of 100% acetone conversion at molar ratio of 10/1 mol. In the case of 60% conversion at molar ratio of 2/1 and co-catalyst usage, the energy requirement is 16671. It is understood that the energy requirement is 6 times greater. While 60% conversion and %85 selectivity were obtained at molar ratio of 2/1. In the ’45-15’ feeding mode 60% conversion and 97% selectivity were achieved. At this manner effective result was obtained both energy and selectivity aspects. After these, an ANN model was obtained with the obtained experimental data. Feeding time, waiting time, HCl percent and reaction time were selected as input parameters of the model. Only conversion, only selectivity and both of them were examined respectively as output. Although high correlations could not be obtained in the cases where selectivity was involved, high regression coefficients were obtained for conversion and the model predictions were plotted. As a result, pulsed feed semi-batch reactors are seen as usable in many similar processes in the energy, selectivity and efficiency axis.