The Catalyst Review December 2019 - 18

MOVERS & SHAKERS

Leonardo Palmisano, PhD

Professor of Chemistry, University of Palermo (Italy)
Professor Leonardo Palmisano received both his undergraduate and graduate degrees from the University of
Palermo in Italy. He then joined the Institute of Inorganic Chemistry at the same university before moving on
to the Department of Chemical Engineering of Processes and Materials as associate professor. He became a
full professor in 2000. His scientific interests have mainly focused on the field of heterogeneous photocatalysis,
and his scientific publications and book chapters deal with various topics concerning the preparation,
characterization, and testing of various types of bare and doped polycrystalline photocatalysts. He has
collaborated with many scientists around the world producing more than 300 joint papers in international
journals and books, five patents, and roughly 400 papers found in proceedings of national and international
conferences. He can be reached at leonardo.palmisano@unipa.it

The Catalyst Review asked Professor Palmisano to share his insights into novel heterogeneous
photocatalytic selective processes used in the production of high value-added compounds.
The classical field of heterogeneous photocatalysis and its applications has focused mainly on environmental remediation
due to the capability of irradiated semiconductors to efficiently degrade a great variety of organic pollutants. This unique
oxidation process is currently experiencing renewed importance due to the highly selective organic and inorganic syntheses
which can be carried out according to "green chemistry" requirements. A growing number of reports in this field deal with
the production of valuable compounds such as drugs, vitamins, fragrances, polymers, and various industrial intermediates
obtained through several transformative processes (e.g., oxidations, reductions, isomerizations, additions, cyclizations,
and polymerizations). Fundamental research carried out in the past highlights the complex interplay between the factors
influencing the selectivity of photocatalytic reactions. It is, therefore, possible to selectively address the generally unselective
radical chain photocatalytic reactions towards the production of a target compound. The results, remarkable in terms of
conversion and selectivity along with the mild operative conditions, allow for the option of exploiting solar light irradiation,
using water as the solvent, to make heterogeneous photocatalysis a promising alternative to traditional organic chemistry
syntheses. Some of the above-mentioned processes have been scrutinized in the relevant literature yielding interesting
results in terms of output and efficiency. Notably, in most of the photocatalytic syntheses reported in literature, the product
has not been isolated and purified, but only spectroscopically detected. Even if these reactions possess great scientific value,
they must be optimized and implemented from the applicative point of view before assessing their industrial potential.
In our opinion, times are now appropriate to deal with engineering and applicative issues enabling technological transfer
from the laboratory to industry as illustrated by the following example: Among inorganic syntheses, elemental bromine
production can be a green alternative to the industrially applied process, which occurs at a temperature of ca. 100 °C,
stoichiometrically, and by using chlorine as the oxidant. Instead, photocatalytic bromine production proceeds in the
presence of oxygen at room temperature with remarkable selectivity.
Oxidation of aromatic alcohols to the corresponding aldehydes is one of the most relevant processes among the organic
syntheses. The highly specific nature of the light-matter interaction requires tailored solutions for each considered substrate.
These photocatalytic reactions generally occur with high yields even under sunlight irradiation in the presence of suitable
photocatalysts and, for this reason, have been extensively studied. A relevant example is the photocatalytic synthesis of
vanillin, which has worldwide importance as a flavour compound. Vanillin synthesis has been performed in photocatalytic
membrane reactors by coupling photocatalysis with a pervaporation separation unit, and highly pure vanillin crystals (99.9
%) have been isolated. Due to the industrial importance of vanillin, this reaction is one of the few photocatalytic syntheses
for which some engineering issues such as reactor design and process intensification and optimization have been discussed
in the relevant literature. It is also worth mentioning the photocatalytic sulfoxidation of alkanes, which occurs under visible
light for the production of degradable long-chain surfactants. This reaction is industrially relevant because it occurs in
solvent-free conditions and with high regioselectivity.

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The Catalyst Review

December 2019

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The Catalyst Review December 2019

Table of Contents for the Digital Edition of The Catalyst Review December 2019