Production Process Simulation And Economic Analysis Of Biological-based P-xylene

In recent years,with the emphasis on the environment and the promotion of policies to reduce greenhouse gas CO₂emissions,the production of fuel and chemical products from green,environmentally friendly and renewable biomass as raw materials has gradually become a research focus.As a bulk organic chemical,p-xylene is widely used in the plastic industry.Several companies have developed production routes of bio-based PX,but due to the poor economy of bio-based PX,it is not enough to compete with petroleum-based PX,and the industrial production process of bio-based PX has been slow in recent years.Therefore,in this paper,the feasibility of several existing bio-based PX production routes was studied,and the economy of the process was improved through both process optimization and experimental optimization.The main research contents are as follows:1.Firstly,the information of different production routes of bio-based PX was collected,and the exploration routes were determined as isobutanol pathway,5-hydroxymethylfurfural pathway and the newly proposed two-step pathway via HDO.Secondly,according to the collected physical property data and experimental data,the process flow of reaction and separation was designed preliminarily,and the basic information of process simulation was determined.The whole process simulation was carried out on the steady-state simulation software Aspen plus for 3 processes（6 routes）.2.In order to explore the feasibility of the process and propose a plan to improve the process economy,preliminary technical and economic calculations were made for different routes according to the basic results of the process simulation.To determine the optimal solvent separation recovery scheme for the HMF pathway based on literature data and based on laboratory data.All the distillation processes involved in the process were optimized with the index of cost minimization.After optimization,the total cost of isobutanol pathway,HMF pathway designed based on laboratory data,HMF pathway designed based on literature data and HDO pathway were reduced by 3.26%,28.09%,11.94%and 50.84%,respectively.The economic calculation results of three processes（four ways）were compared,the cost composition of each route was analyzed,and the scheme to reduce PX production cost was determined.3.According to the analysis results,the HDO route was optimized from the aspect of process,and the solvent recovery part of single rectifying column was replaced by three-effect distillation,and the total production cost of PX was reduced by 24.44%after optimization.The sensitivity analysis of catalyst packing density and reactor equipment cost was carried out to determine whether the assumed factors were valid.The influence of raw material price fluctuation and reaction condition change on PX production cost was also explored.After the optimization suggestions proposed in this paper were adopted,the total cost of PX was reduced by58.03%after the experimental oil-water ratio of HDO route was reduced and the raw material concentration was increased.Combined with experiments and process optimization,the total cost of PX production by HDO route decreased by 64.6%.4.In order to further reduce the production cost of PX,cheaper bagasse was used as raw material,and the pretreatment process of it was explored in an attempt to utilize cellulose,hemicellulose and lignin.Firstly,the conditions of organic acid oxalic acid pretreatment of bagasse were optimized.The optimal conditions were determined to treat bagasse at 120℃for 35 min with 3 wt%oxalic acid.More than 78%of xylan could be removed after single step acid treatment.The effect of organic alkali on lignin removal was investigated.It was found that the effect of organic alkali on lignin removal was not ideal,and the lignin content in bagasse was still more than 20%after treatment.The conditions of inorganic acid and alkali pretreatment of bagasse were investigated,and the concentration of H₂SO₄and Na OH was optimized.Combined with the economy and treatment effect,the optimal concentration of H₂SO₄and Na OH was determined at the concentration of 1.5 wt%and 1 wt%.The cost calculation of the total process of PX production by pretreating cellulose with bagasse as raw material showed that the production cost of PX with cheap bagasse as raw material was 15 971 yuan/ton,and the cost of PX could be reduced to 11081yuan/ton if the yield of cellulose was further increased and lignin and lactic acid were combined to produce.