Producing Acetonitrile From Biomass Catalyzed By Co/HZSM-5

In recent years,the rapid development of the global economy and society has led to an increasing demand for fossil resources.The gradual consumption of fossil resources and the pollution problems have made it urgent to develop sustainable resources that can replace fossil resources.At present,abundant biomass resources are the only sustainable organic carbon source.Through different transformation pathways,biomass resources can be efficiently converted into alternative fuels and bulk chemicals.Acetonitrile is a bulk chemical widely used in pharmaceuticals,perfume preparation,dyeing,and industrial applications.At present,acetonitrile is mainly obtained by the side reaction of acrylonitrile,which is easily limited by the market demand of acrylonitrile.This preparation method could no longer meet the increasing demand of acetonitrile.Moreover,the raw materials for acetonitrile production are mainly obtained from fossil resources,which are non-renewable and pollute the environment.Previous studies on the preparation of acetonitrile from biomass resources have not been conducted.To solve the above problems,we have developed a new reaction pathway,catalytic fast pyrolysis and ammonization(CFP-A),which can directly convert biomass or biomass derivatives to acetonitrile by catalysis in an ammonia atmosphere.This provides a new idea for the conversion and utilization of biomass resources and the sustainable production of acetonitrile.Chapter 1.It mainly introduced the composition,distribution,characteristics of biomass resources and the main current utilization method of biomass resources.Then,the main thermochemical conversion pathway of biomass and the preparation methods of acetonitrile were introduced in detail.Chapter 2.In this chapter,CoOx/HZSM-5 was used as the catalyst to convert the real biomass(including cellulose,xylose,lignin,bagasse,rice husk and birch)into acetonitrile by catalytic fast pyrolysis and ammonization(CFP-A).At the same time,factors that may affect the product distribution(temperature,residence time,ammonia flow rate,etc.)were investigated.Under the optimal reaction conditions,the carbon yield of acetonitrile was 32.5%and the selectivity was 84.6%.Then,we also explored the acetonitrile formation pathway.Combining with the calculation of density functional theory(DFT),the results showed that the-Co-O-Si-site of CoOx/HZSM-5 promoted the selective pyrolysis of cellulose into C2 oxygenates such as acetaldehyde,acetic acid and so on,and then these small molecular oxygenates futher reacted with ammonia to form imines and amides which are then dehydrogenated or dehydrated to form acetonitrile.Chapter 3.In this chapter,a series of catalysts including different metal oxides loading on HZSM-5(Si/Al=25)and cobalt oxides loading on different supports were tested to catalytic fast pyrolysis and ammonization(CFP-A)of biomass derived polylactic acid(PLA)to produce acetonitrile under ammonia atmosphere.Both the metal and the acid of the catalyst had a crucial influence on the yield of acetonitrile and Cof/HZSM-5(25)produced most acetonitrile.Other factors that might affect the product distribution including cobalt loading,reaction temperature,resident time and NH3 flow rate have been investigated systematically.Under the optimized CFP condition(650 ℃;resident time 2.4 s;NH3 flow rate 80 ml/min),the carbon yield and selectivity of acetonitrile in liquid product reached 50.2%and 83.6%,respectively.The possible reaction pathway from PLA to acetonitrile was also studied and proposed.PLA firstly cracked into lactic acid through thermal decomposition and formed lactide at the same time.Then lactic acid and lactide cracked into low-molecular aldehydes,ketones and acids.These aldehydes and ketones reacted with ammonia to form imines,acids to amides,and finally to acetonitrile and small amount of proponitrile under the catalysis of Co/HZSM-5 catalyst.Chapter 4.This chapter is summary and outlook.This paper mainly focused on selectively producing acetonitrile from real biomass and biomass derivatives via catalytic fast pyrolysis and ammonization(CFP-A).The optimal reaction conditions were obtained by investigating the factors affecting the reaction results,such as catalyst,reaction mode,temperature,residence time and so on.The reaction mechanism from biomass and biomass derivatives to acetonitrile has been investigated and elucidated in depth.These not only expanded the pathway of biomass conversion and utilization,but also provided a new choice for the preparation of acetonitrile.And then,we analyzed the advantages and disadvantages of catalytic fast pyrolysis and ammonization(CFP-A)to point out the direction for subsequent exploration and improvement.