A New Process For The Synthesis Of O-Hydroxybenzaldehyde

O-hydroxybenzaldehyde has a wide range of market applications as a common pharmaceutical intermediates.Although the traditional method is cheap,the process is simple and mature,it leads to serious pollution and side reactions,also low yield,so the improvement of the synthesis process of o-hydroxybenzaldehyde has been receiving much attention.In this thesis,a new process for the synthesis of o-hydroxybenzaldehyde with simple process,few by-products,simple separation and high yield is discussed.The synthesis of o-hydroxybenzaldehyde is carried out by two steps:(1)using phenol and paraformaldehyde as raw materials to synthesize Salicyl alcohol;(2)Salicyl-alcohol is then oxidized to o-hydroxybenzaldehyde by oxidation.The main content of this paper includes:1.Synthesis of o-hydroxybenzyl alcohol.Synthesis of o-hydroxybenzyl alcohol by hydroxymethylation of phenol and paraformaldehyde,Optimized process parameters,determine zinc acetate as a catalyst and water as a solvent.The optimal conditions for the synthesis of o-hydroxybenzyl alcohol were determined by orthogonal experiments.The optimal process conditions for the methylolation reaction are as follows:reaction time 6 h,catalyst addition amount 0.9 g,reactant ratio phenol:paraformaldehyde 1.3,water addition amount 4 g,temperature 72?,under optimal reaction conditions The conversion of the reaction is 78.63%,and the yield is 65.86%.2.Synthesis of o-hydroxybenzaldehyde.It is determined that the direct oxidation method is used to synthesize o-hydroxybenzaldehyde,the normal temperature and pressure are selected.The optimal combination of catalysts is obtained as the main catalyst of cuprous chloride,and phenanthroline(5%)/Tetramethylethylenediamine(3%)/N-methylimidazole(2%)is a combined ligand,methanol as solvent.The optimum process conditions for the obtained oxidation reaction are reaction time 42 h,catalyst addition amount 2 g,temperature 25?,solvent addition amount 60 mL,and under the optimal reaction conditions,the oxidation reaction yield is 85.63%,two-step reaction the final yield is 56.39%.3.Purification of o-hydroxybenzaldehyde.Taking the product o-hydroxybenzaldehyde as the research object,the subsequent separation and purification process was explored,and the optimal separation process was obtained by single factor analysis:the rotary distillation temperature was 35?,the time was 25 min,the addition reaction temperature was 35?,and the acidification system pH was 4.The acidifying solvent is benzene,the acidification temperature is 30?,and the acidification time is 3 h.Under these conditions,the purity of the product can reach more than 95%,and the average yield is 36.39%.4.Aspen simulation of 100 ton/year industrial production of o-hydroxybenzaldehyde.In the simulation process,the physical method uses NRTL-Redlich Kwong,the reactor selects the reaction stoichiometric reactor RStoic module for simulation,the RadFrac module is selected in the rectification simulation,and the equilibrium model Equilibrium is used for calculation.Through the simulation of the synthesis process of o-hydroxybenzaldehyde by Aspen Plus,the required simulation separation requirements are completed,and the o-hydroxybenzaldehyde with a purity of more than 99%is obtained,which meets the purity requirement and has certain guiding significance for the process production.