Life cycle assessment of vitamin D3 synthesis: from batch to photo-high p,T

Abstract

Purpose Novel process windows allow the development of faster, flexible, and greener processes. Therefore, novel process windows were applied to develop a greener process for the synthesis of vitamin D 3. In this study the environmental impacts of several batch pathways to obtain vitamin D 3 are benchmarked against the continuous microflow process, where novel process windows such as high temperature and pressure were applied. To evaluate the environmental impact of these processes, life cycle assessments were conducted. Methods A new process concept was developed to optimize and simplify the synthesis of crystalline vitamin D 3. This process was conducted in microflow by combining UV photoirradiation and high-p,T (photo-high-p,T) processing. Microreactors allow a high photon flux and enable the harsh conditions, respectively. The process was coupled with an integrated continuous crystallization, and its feasibility has been proven and reported before. The potential environmental impacts were assessed from a cradleto-gate perspective. Both processes, continuous and batch, were modeled in Aspen Plus using foreground data from the experimental continuous setup, and background data from different patents. The assessment was performed in the software Umberto NXL LCA using the ReCiPe Midpoint 2008 method. Results and discussion The continuous process has a significantly lower environmental impact than the batch processes. This lower impact is largely due to the fact that fewer amounts of material, particularly solvents, are used. Moreover, the continuous process is faster and has fewer steps, i.e., process-simplified. Among the industrial processes, the synthesis conducted in isopropanol has the lowest environmental impact, although, even in this case, the impact is between 20 and 30 times higherdepending on the conditions-compared with the continuous process. When the batch process is conducted in benzene, the worst environmental impact is obtained. Finally, recycle of the solvent for the best batch case was assessed. This improved the batch process to make it comparable with the continuous process. Conclusions The continuous production of vitamin D 3 leads to an interesting alternative to the industrial process. Continuous manufacturing of vitamin D 3 is faster, requires fewer steps, and uses less solvents compared with the industrial synthesis. However, although the environmental impact of this continuous process is already lower than that of the batch processes, the continuous process can still benefit from further optimization, particularly the introduction of a recycle loops for the solvents methyl tert-butyl ether and acetonitrile.

Quantitative Sustainability Assessment of Flow Chemistry–From Simple Metrics to Holistic Assessment

“…As Figure indicates, the values of the human toxicity potential (HTPinf) and Global Warming Potential (GWP) for the batch process scenarios, considering benzene as a solvent in the synthesis step, are 92–124 and 23–31 times higher than that of the intensified process. Overall, the novel process exhibits a better environmental profile than the batch process scenarios for all studied impact categories, with the exception of the solvent recycle scenario in which the batch process demonstrates a lower value for three impact categories …”

“…The intensified flow-chemistry synthesis route of crystalline vitamin D 3 by means of UV photoirradiation combines with harsh operating conditionshigh- T and high- P , meaning it will merge two kinds of flow-specific activation modes . In the specific LCA analysis, a batch process has been investigated for different scenarios with respect to the synthesis and crystallization steps.…”

“…The letters denote the different scenarios with respect to the solvent used for dissolving the vitamin D3 resin: (A) benzene, (B) acetone, and (C) methyl formate. Reprinted with permission from ref . Copyright 2019, Springer.…”

“…The intensified flow-chemistry synthesis route of crystalline vitamin D 3 by means of UV photoirradiation combines with harsh operating conditionshigh-T and high-P, meaning it will merge two kinds of flow-specific activation modes. 103 In the specific LCA analysis, a batch process has been investigated for different scenarios with respect to the synthesis and crystallization steps. As Figure 16 indicates, the values of the human toxicity potential (HTPinf) and Global Warming Potential (GWP) for the batch process scenarios, considering benzene as a solvent in the synthesis step, are 92−124 and 23−31 times higher than that of the intensified process.…”

“…Overall, the novel process exhibits a better environmental profile than the batch process scenarios for all studied impact categories, with the exception of the solvent recycle scenario in which the batch process demonstrates a lower value for three impact categories. 103 Critical value of case studies 2 and 3: Extrapolation to hypothetical processing and its assessment are intrinsic qualities and limitations of LCA. Most of ten, this refers to making conclusions f rom lab-scale experiments to production scale.…”