(444a) Novel Catalysts and Reactor Concepts for Sustainable Processes: the Use of LCA Data in Process Design

Novel
catalysts and reactor concepts for sustainable processes: the use of LCA data
in process design

Polina Yaseneva and Alexei Lapkin

Department of Chemical Engineering and Biotechnology, University of
Cambridge, Cambridge, CB2 3RA, United Kingdom

Abstract

We
present a multi-step assessment framework, which was developed to guide
decision making process in a process development context. Reaction mass
intensity metric, gate-to-gate flowsheet analysis and LCA are used at
appropriate stage gates. Specifically results of LCA assessment will be
discussed for the case studies of a novel catalyst for water purification
process, an intensive process of a pharmaceutical API synthesis and a novel
organometallic catalytic process for intermediates synthesis.

Introduction

Assessment
of sustainability of novel processes for decision-making purposes is a complex
task, as frequently uncertainty of the data precludes the use of full LCA
methodology, whereas proxy methods such as mass or energy metrics provide
incomplete information. At the same time, information about sustainability of
novel technologies is now routinely requested even within research projects.
Thus, most EU projects in the area of chemical technologies are accompanied by
LCA studies.

Within
a large integrated project SYNFLOW (www.synflow.eu)
we have developed a three-step approach, using reaction mass efficiency metric
for selection of chemical routes, gate-to-gate mass and energy metrics for
assessment on flow sheet options and finally LCA for evaluation of the
demonstration case studies. These steps coincide with stage-gating within a
project: confidence in chemistry to be taken up for process development,
evaluation of process options with a focus on clean technologies (novel
solvents, process intensification) and finally the detailed analysis of
complete process at the stage of demonstration with LCA, targeting detailed
flowsheet optimisation.

Here
we present results of LCA studies for three specific examples. We show LCA of a
novel carbon nanotube-based catalyst for water purification, focusing on
comparison of the manufacture of the catalyst, a study of a novel flow-process
of stoichiometric reduction of artemisinin, leading to manufacture of an
important pharmaceutical API (focusing on comparison of batch vs continuous
process) and finally a study of a novel catalytic Buchwald-Hartwig amination
under overall flow conditions.

Results and Discussion

Carbon nanotube catalyst for water purification

A
highly active catalyst was developed for reduction of an emergent aqueous
pollutant, bromate, based on 0.3 %wt Pd deposited onto carbon nanotubes, grown
on sintered metal fibre. The TOF of the catalyst was found to be an order of
magnitude higher than that of a conventional catalyst based on alumina support
(Pd/Al₂O₃). However, there remained the question whether
high-temperature CVD process used in the manufacture of carbon nanotubes
resulted in a cleaner overall process. The LCA study focused on the manufacture
of the two catalysts. In this specific case all environmental impacts for the
new catalysts were lower. Detailed analysis of contributions of the individual
manufacturing steps to various impacts, e.g. analysis of contributions to
cumulative energy demand shown in Figure 1, allows to reveal further options
for optimisation of the novel catalyst manufacture [1].

Figure
1. Individual contributions to cumulative energy demand (CED) of the
manufacture of the two catalysts.

Artemisinin reduction under intensive flow conditions

We
have developed a flow process for reduction of artemisinin to overcome the
limitations of a conventional batch process [2]. In the current study we
extended the reaction to the final step in the manufacture of the antimalarial
API, but also performed an LCA study to compare the novel flow process with the
conventional batch reaction [3]. Analysis of LCA results revealed that the
solvent used in the manufacture and storage of the reducing agent required for
the flow process is having a massive negative impact, see Figure 2. It is
becoming critically important to replace the solvent used in a particular stage
of the overall process. In this case LCA is instrumental in identifying the
critical stage of the overall process that requires optimisation.

Figure
2. Individual contributions to environmental impacts in artemisinin reduction
under flow conditions.

Buchwald-Hartwig amination in flow

The
three-step decision making process is illustrated on the example of
Buchwald-Hartwig amination. Reaction mass efficiency, process efficiency and
LCA are evaluated for this reaction at the different stages in the process
design. This approach complements the parallel chemistry-process design
methodology being developed within Synflow project, ultimately aiming at a
significant reduction of time required for commercialisation of novel
technologies, which are also sustainable. Thus, for the initial reaction
options we have used RME metric to evaluate the importance of solvent and
catalyst recycle. The new process is currently being scaled-up to a
demonstrator at an Invite facility of Bayer. We will show the results of
stage-gating metrics and initial LCA data.

[1]
P. Yaseneva et al., Reduction of bromates on carbon nanofibre supported
structured Pd catalysts: experimental and life cycle assessment study,
Submitted.

[2] X. Fan, V. Sans, P.
Yaseneva, D. Plaza, J.M.J. Williams, A. Lapkin, Facile stoichiometric
reductions in flow:

example of artemisinin, Org Proc Res Dev 16
(2012) 1039-1042.

[3] P. Yaseneva et al., Optimisation of the flow
process of manufacture of artemether and its LCA study, Submitted.

Acknowledgement:
This work was supported by the European Community's Seventh Framework
Programme under project "SYNFLOW", NMP2-LA-2010-246461.