Study Of Palladium-based Catalysts In The Hydrogenation Of Biotin Intermediate

Biotin is a kind of high value-added pharmaceutical fine chemicals widely used in feed,medicine,food and other industries.In recent years,the demand worldwide has been on the rise.Since our country broke the foreign monopoly and realized independent industrial production of biotin in 2004,its production capacity has been continuously increasing.In the past ten years,our country has never stopped exploring and improving the relevant processes for the production of biotin by the lactone-thiolactone synthesis method.This article takes the hydrogenation of biotin intermediate catalyzed by palladium-based catalysts as the research object,and is mainly dedicated to solving the problem of easy deactivation of catalysts faced by enterprises in the actual production process.The specific content of the article is as follows:Chapter 1 gives a brief introduction to biotin and summarizes the relevant strategies for the total synthesis of biotin.In the actual production process of using palladium-carbon catalyst to hydrogenate biotin intermediate,the problem that the catalyst is easily poisoned and deactivated and cannot be reused is discussed.Based on the current situation of the industry and previous studies,the basis for the topic selection and the research plans are put forward.Chapter 2 explores the basic technology of hydrogenation of biotin intermediate.Experiments compared the effects of different preparation methods of palladium-carbon,additives,temperature and pressure on catalytic hydrogenation.Finally,it is determined that 5 wt%Pd/C prepared by immersion-deposition precipitation method plus a small amount of alkaline additives and the conditions of 80℃ and 2 MPa are the best catalytic conditions.Chapter 3 mainly focuses on the modified design of the catalyst.From the perspective of metal active components,N-ligand@5 wt%Pd/C is obtained by using nitrogen-containing compounds to coordinate the palladium precursor.The electron-rich N in the ligand tends to accumulate electric charge locally,which can stabilize the active metal,greatly enhance the hydrogenation activity,and enable the hydrogenation selectivity to be greater than 97.4%when the conversion rate of a single tank reaches 100%,which meets the actual production requirements.Later,it is found that the metal was lost and the catalyst was deactivated.From the perspective of the support,nitrogen-containing species were further used to dope and modify the activated carbon support,and N-ligand@5 wt%Pd/CN was prepared to enhance the binding capacity between the support and the metal,and the catalyst can be reused up to 4 times.Chapter 4 explores other new catalysts.Pd4S is prepared by the aqueous phase method,hoping to enhance the sulfur poisoning resistance through its special structure.In addition,the palladium-carbon catalyst prepared using co-metal modification can be reused twice in the hydrogenation reaction of the biotin intermediate.Finally,the research results of this article are summarized and prospected.