Topics in Current Chemistry (2019) 377:1
1 3
1 Introduction
One of the main challenges of the twenty‑first century concerns the progressive
transition from a petrobased chemical industry to a biobased alternative. Four‑
teen years ago, the US Department of Energy (DoE) issued a list of the most
promising biobased molecules (named “platforms”) for kickstarting a new era
in the chemical industry [1, 2]. Biobased platforms are defined as widely avail‑
able compounds of low molecular mass that are derived from biomass. Platform
molecules are typically oxygenated compounds of low molecular complexity that,
upon applying an appropriate combination of a few chemical steps, can be trans‑
formed into a wide variety of entities with small (defunctionalization processes)
or large (functionalization processes) molecular masses. Biobased platforms are
employed as building blocks for the synthesis of value‑added chemicals for indus‑
trial applications, and are intended for use as potential alternatives to petrore‑
sources [3, 4].
This context has stimulated intensive research aimed at developing new chem‑
istries and new technologies that can be applied to create novel processes that
increase the value of platform molecules. Continuous flow chemistry is now
widely adopted as an enabling technology in the chemist’s toolkit, and many
reports have emphasized its benefits in chemical processing [5, 6]. The contribu‑
tion of continuous flow chemistry to the design of safer and more reliable chemi‑
cal processes using facilities with a small environmental footprint is now well
established [7–11]. Despite the emergence of shale gas, the progressive depletion
of fossil resources has largely driven the development of biobased continuous
flow processes [5, 12–14].
The implementation of continuous flow technology in various fields, includ‑
ing the pharmaceutical industry, has triggered intense research efforts, and this
technology is currently used in various commercial processes [15]. In contrast,
the field of biobased platform molecules is still maturing, so these molecules are
yet to show their true worth. Some of the greatest challenges associated with the
use of biobased molecules relate to the availability of and the variability in the
quality of these biobased platforms, as the composition of the initial biomass may
vary depending on (for instance) field location and meteorology. Biobased pro‑
cesses are economically attractive as long as efficiency and robustness are guar‑
anteed, which means, for example, that sustained feedstocks must be available
and waste generation must be low.
This review considers a selection of representative continuous flow processes
which use currently popular platform molecules (Fig. 1) to chemicals that are
industrially relevant, including (a) commodity chemicals, (b) specialty and fine
chemicals, and (c) fuels and fuel additives. Note that this review only consid‑
ers liquid and solid platform molecules [16–18]. Studies relating to the upgrad‑
ing of ethanol, formic, and acetic acid, which have already been extensively
reviewed, are not included [19–22]. Most of the examples described herein deal
with alternative continuous flow processes starting from platforms toward tradi‑
tionally petrobased chemicals. Some examples illustrate the emergence of new,
112
Reprinted from the journal
1 3
1 Introduction
One of the main challenges of the twenty‑first century concerns the progressive
transition from a petrobased chemical industry to a biobased alternative. Four‑
teen years ago, the US Department of Energy (DoE) issued a list of the most
promising biobased molecules (named “platforms”) for kickstarting a new era
in the chemical industry [1, 2]. Biobased platforms are defined as widely avail‑
able compounds of low molecular mass that are derived from biomass. Platform
molecules are typically oxygenated compounds of low molecular complexity that,
upon applying an appropriate combination of a few chemical steps, can be trans‑
formed into a wide variety of entities with small (defunctionalization processes)
or large (functionalization processes) molecular masses. Biobased platforms are
employed as building blocks for the synthesis of value‑added chemicals for indus‑
trial applications, and are intended for use as potential alternatives to petrore‑
sources [3, 4].
This context has stimulated intensive research aimed at developing new chem‑
istries and new technologies that can be applied to create novel processes that
increase the value of platform molecules. Continuous flow chemistry is now
widely adopted as an enabling technology in the chemist’s toolkit, and many
reports have emphasized its benefits in chemical processing [5, 6]. The contribu‑
tion of continuous flow chemistry to the design of safer and more reliable chemi‑
cal processes using facilities with a small environmental footprint is now well
established [7–11]. Despite the emergence of shale gas, the progressive depletion
of fossil resources has largely driven the development of biobased continuous
flow processes [5, 12–14].
The implementation of continuous flow technology in various fields, includ‑
ing the pharmaceutical industry, has triggered intense research efforts, and this
technology is currently used in various commercial processes [15]. In contrast,
the field of biobased platform molecules is still maturing, so these molecules are
yet to show their true worth. Some of the greatest challenges associated with the
use of biobased molecules relate to the availability of and the variability in the
quality of these biobased platforms, as the composition of the initial biomass may
vary depending on (for instance) field location and meteorology. Biobased pro‑
cesses are economically attractive as long as efficiency and robustness are guar‑
anteed, which means, for example, that sustained feedstocks must be available
and waste generation must be low.
This review considers a selection of representative continuous flow processes
which use currently popular platform molecules (Fig. 1) to chemicals that are
industrially relevant, including (a) commodity chemicals, (b) specialty and fine
chemicals, and (c) fuels and fuel additives. Note that this review only consid‑
ers liquid and solid platform molecules [16–18]. Studies relating to the upgrad‑
ing of ethanol, formic, and acetic acid, which have already been extensively
reviewed, are not included [19–22]. Most of the examples described herein deal
with alternative continuous flow processes starting from platforms toward tradi‑
tionally petrobased chemicals. Some examples illustrate the emergence of new,
112
Reprinted from the journal