Estimation and Improvement of the 1,3-Butadiene Production Process from Lignin through Pinch Analysis

摘要

In this paper, a process for 1,3-butadiene (1,3-BD) production from lignin via phenolic compounds, cydohexane, and n-butene is proposed. The process comprised four unit operations: depolymerization, hydrodeoxygenation, catalytic cracking/dehydrogenation, and dehydrogenation/isomerization. The process was simulated with regard to two cases: (1) one where it was simply combined with previously reported operations (SC case) and (2) one where it was combined with theoretical unit operations in which the ideal chemical reaction occurred and the equilibrium composition was obtained (TH case). For the SC and TH cases, the 1,3-BD yields on a dry and ash-free basis were 0.1 and 11.4 wt %, respectively. When the moisture content of lignin as a feedstock was 80 wt % and the capacity of the process was 500 t/day on a wet basis, the effective energy utilization was determined through pinch analysis to evaluate the economics of the proposed process. For the SC and TH cases, the minimum external required heats were 230 and 248 MW, respectively, indicating that the required input energy hardly decreased even if the chemical reaction in each step proceeded ideally under the reported reaction conditions. In the depolymerization step, the condenser temperature in the distillation column and amount of MeOH used as a solvent were dominant factors for determining the external required heat. Economic evaluation through pinch analysis suggested that increasing the condenser temperature from 65 to 120 degrees C using a heat pump and drastically decreasing (by >97%) the amount of MeOH used led to an effective decrease in the required input energy to 22 MW.