TECHNO-ECONOMIC AND LIFE CYCLE ASSESSMENT OF INNOVATIVE ROUTES TO CHEMICAL PRODUCTS

Abstract

The goal of the chemical industry is to design large-scale industrial chemical processes that are both environmentally benign and economically viable. Building upon the latest advances in green chemistry and sustainability in chemical processes, this dissertation applies a proposed assessment methodology that encourages earlier consideration of emerging and newly developed technologies in the design process. The goal of the assessment methodology is to evaluate the potential of using innovative technologies to achieve profitable alternative chemical processes, while also incorporating sustainability goals in the design thinking. Two case studies were examined using the proposed general assessment methodology. In the first case study, an alternative phosgene-free process to produce polycarbonate using CO2 as raw material was developed and evaluated. The developed polycarbonate process uses alternative intermediates to produce polycarbonate by the transesterification of diphenyl carbonate with bisphenol A and without using phosgene. The second case study addressed the large economic constraint in the conventional methanol synthesis process caused by the equilibrium-limited single-pass conversion, which requires an expensive and energy-intensive synthesis gas recycle loop. To eliminate the recycle loop, an alternative single-pass process using a condensing reactor was proposed and evaluated. The selected reactor technology is capable of condensing methanol as it forms on the catalyst bed, so more gas can be reacted to equilibrium and very high conversion of syngas to methanol is achieved in a single-pass. After-tax discounted cash flow analysis and life cycle assessment (LCA) were used in this study to assess the economic feasibility and the environmental impact of the developed alternative processes. The results showed that, for an annual capacity of 65,000 metric tons polycarbonate, the alternative phosgene-free polycarbonate process is profitable with an NPV of 100.76 million USD, yet it causes 37.2% lower global warming potential and significantly lower human health impact, compared to the conventional phosgene polycarbonate process. The results also showed that the alternative single-pass methanol synthesis process has an incremental DNPV of 78.06 million USD and a 32% reduction in global warming potential compared to the conventional methanol synthesis process. The proposed assessment methodology was applied to develop a complete process using new chemical routes and new process technologies in the first case study. In the second case study, it was applied to improve an established process, by making simple changes that can have large effects on profitability and sustainability. This showed that this assessment methodology applies to disparate types of process designs. Overall,