Preparation Of Cumene By Catalytic Transformation Of Lignin

Concerns about the steady decline in fossil fuel reserves and the increase in carbon dioxide emissions have accelerated advances in alternative fuels or chemicals using biomass feedstocks.Lignin is an important renewable aromatics resource.So far,the directional transformation of lignin into the desired chemicals is still a challenging task.As far as we know,there is no report regarding directional production of cumene from lignin.Here,we demonstrated that lignin was directionally converted into cumene by a three-step process.This process included the catalytic pyrolysis of lignin into the mixture aromatics,followed by the dealkylation of aromatics to benzene and the alkylation of benzene-rich aromatics to cumene by room-temperature liquid phase reactions using the ionic liquid catalysts.The main results are as follows:1.The catalytic pyrolysis of lignin into the mixture aromaticsLignin is a three dimensional amorphous polymer.To achieve the directional transformation of lignin,the first step is deoxygenation and depolymerization.Considering the effects of different catalysts,the addition of methanol and temperature on the catalytic process,the catalytic pyrolysis was carried out at 450 ℃with a methanol addition of 50 wt%over the selected 1%Zn/HZSM-5 catalyst by optimizing experimental conditions.The mixture aromatics obtained had a yield of 25.1 wt%with the monocyclic aromatics selectivity of 85.7 wt%.The reactions involved include pyrolysis,decarbonylation,decarboxylation,dehydroxylation,aromatization and so on.It was also found that adding methanol into the lignin was beneficial for the yield of aromatics and suppressed the coke deposition on the catalyst surface caused by the polymerization of aromatics.2.Reforming of mixture aromatics into benzeneAchieving the directional cinversion of lignin,it’s necessary to further catalytic dealkylation to obtain the key product of benzene.The dealkylation process were studied using the mixture aromatics derived from catalytic pyrolysis.The resulting benzene-rich aromatics contained benzene with the selectivity of 93.6 wt%under the optimal condition(Hβ catalyst,30 wt%methanol,WHSV=0.4 h-1,T=600 ℃),To explore the relationship between the structure and the performance of catalyst,found that acidity of catalysts is the key controlling factor in dealkylation.The content of benzene in organic liquid should be affected by the dealkylation of aromatics,the oligomerizations of aromatics and the aromatization of methanol.3.The alkylation of benzene-rich aromatics to cumeneDesired production of cumene was able to be produced by the catalytic alkylation of benzene-rich aromatics with propylene.Influence of catalysts and different parameters(time,temperature and flow velocity of propylene,etc.)on the yield and selectivity of cumene were discussed.And cumene presented a selectivity of 91.6 C-mol%when benzene-rich aromatics reacted with propylene(the flow rate of 30 cm3min-1)using the selected[bmim]Cl-2AlCl3 ionic liquid catalyst at room temperature(20 ℃)for 15 min.The results showed that lignin can be converted into cumene with a high selectivity.The alkylation of aromatics is a consecutive reaction process,and the primary products can generally undergo a second alkylation reactions.