The Synthesis Of ?-naphthol From Naphthalene With The Steps Of Hydrogenation,Oxidation And Dehydrogenation

Alpha-naphthol is a very important fine chemical intermediate.As a synthetic raw material,it is widely used in the pesticide,pharmaceutical and dye industries.The existing industrial production process of a-naphthol has the disadvantages of complicated production process,long process flow,severe equipment corrosion,multiple wastes,and large environmental pollution.In this paper,industrial naphthalene is used as raw material,and?-naphthol is synthesized through hydrogenation,oxidation,and dehydrogenation.The synthesis route adopts different synthesis methods,improves and optimizes each step,and is cleaner than the existing naphthol process,at the same time,the atom utilization rate is improved,and the industrialization prospect is better.Before hydrogenation of naphthalene,the industrial naphthalene is treated and the benzothiophene combined in industrial naphthalene is desulfurized by a chemical method.Using the acid oxidation method and condensation removal method,we Compare the desulfurization efficiency of naphthalene with different acids and hydrogen peroxide and aqueous formaldehyde solution.In the method of n(HCOOH):n(HCHO):n(naphthalene)=1:0.66:0.16,we found that the removal rate of benzothiophene in naphthalene can reach more than 99%,and the recovery rate can reach 89%.The refined naphthalene was obtained.Refined Naphthalene Hydrogenation Selects Raney Nickel Catalyst by Comparing the Hydrogenation Effects of Pd/C and Raney Nickel.At the same time,by comparing the effects of different solvents and different reaction conditions on hydrogenation,we find the conversion of naphthalene can reach more than 99%,while tetrahydronaphthalene selectivity can reach 98%when hydrogenation reaction process run as follows:n-butanol was used as the hydr-ogenation solvent,the mass ratio of the catalyst was 10%,the hydrogen pressure was 0.5 MPa,and the temperature was 70?.At the same time,the conversion of naphthalene can still remain over 99%when the catalyst is recycled to use for three times.The oxidation of tetrahydronaphthalene uses NHPI as a non-metal catalyst,and NHPI/Mg-Al-LDH and KMn04/LDH catalysts are synthesized to investigate the effect of different catalysts on the oxidation of tetrahydronaphthalene.In the high pressure reaction,by adjusting the amount of catalyst and the type and amount of additives,we find the best reaction process is carried as follows:the mass ratio is m(tetralin):m(cat):m(anthraquinone)= 1:0.01:0.01,at the temperature of 80?,with the oxygen pressure of 1 MPa and the reaction is held for 5h.The conversion of tetralin can reach 65%and the yield of tetralone can reach 42%.The oxidation conversion of tetralin with supported catalysts NHPI/LDH and KMn04/LDH under high pressure can reach up to 68%.However,there are too many byproducts in the high pressure reaction process.The oxidation process under normal pressure conditions shows that the KMnO4/LDH catalyst activity is better.At 60?,the conversion rate of tetrahydronaphthalene can reach 40%and it is con-venient for recycling.The cycle life is longer.Tetralol is oxidized with MnO2 and HCl in air,allowing tetralone yields of up to 40%.In the process of separation of tetralone,coking problems happens and the coking mass ratio can reach 40%.The oxidation product,tetralone,is then subjected to a dehydrogenation process to prepare a-naphthol.The Raney nickel catalyst is also selected as the dehydrogenation catalyst,and the conversion rate and yield were the highest under the condition of anisole as solvent,m(reactant):m(cat)=1:7.5%,and 90??The oxidation product,tetralone,is then subjected to a dehydrogenation process to prepare a-naphthol.Dehydrogenation catalysts also use Raney nickel catalysts to compare dehydrogenation effects of different solvents and different reaction conditions.We find the highest yield can reach 80%,while the conversion of tetralone can reach 98%when the process is carried as follows:using anisole as solvent,the mass ratio of the catalyst is 7.5%,and operated at 90?..The catalyst was recycled within 3 times to maintain a high dehydrogenation activity.