Academic literature on the topic 'Supported catalyst'

The rapid separation and efficient recycling of catalysts after a catalytic reaction are considered important requirements along with the high catalytic performances. In this view, although heterogeneous catalysis is generally less efficient if compared to the homogeneous type, it is generally preferred since it benefits from the easy recovery of the catalyst. Recycling of heterogeneous catalysts using traditional methods of separation such as extraction, filtration, vacuum distillation, or centrifugation is tedious and time-consuming. They are uneconomic processes and, hence, they cannot be carried out in the industrial scale. For these limitations, today, the research is devoted to the development of new methods that allow a good separation and recycling of catalysts. The separation process should follow a procedure economically and technically feasible with a minimal loss of the solid catalyst. The aim of this work is to provide an overview about the current trends in the methods of separation/recycling used in the heterogeneous catalysis.

The supported catalyst featuring highly dispersed active phase on support is the most important kind of industrial catalyst. Extensive research has demonstrated the critical role (in catalysis) of the interfacial interaction/perimeter sites between the active phase and support. However, the supported catalyst prepared by traditional methods generally presents low interface density because of limit contact area. Here, an ion-exchange inverse loading (IEIL) method has been developed, in which the precursor of support is controllably deposited onto the precursor of active phase by ion-exchange reaction, leading to an active core surrounded (by support) catalyst with various structures. The unique surrounded structure presents not only high interface density and mutually changed interface but also high stability due to the physical isolation of active phase, revealing superior catalytic performances to the traditional supported catalysts, suggesting the great potential of this new surrounded catalyst as the upgrade of supported catalyst in heterogeneous catalysis.

Abstract The oxidation reaction of 2-ethyl-1-hexanol with potassium permanganate in the presence and absence of silica-gel-supported phase-transfer catalyst (PTC) in triphasic conditions was studied. In a batch reactor, the performance of the solid-supported catalysts was compared with unsupported catalyst and without the catalyst. The effect of speed of agitation, catalyst concentration, potassium permanganate concentration and temperature on reaction rate was studied. The reaction is found to be in the kinetic regime. The rate of reaction with the catalyst immobilised on the silica gel was less compared to the catalyst without immobilisation. Triphase catalysis with supported PTCs has potential applications in the continuous quest for greener industrial practices.


 Biodiesel production is carried out through homogeneous catalysis that forms complex reaction mixtures and has high operating costs. The aim of this work is to synthesize basic, active and selective heterogeneous catalysts for the transesterification reaction with vegetable oils employing g-alumina as support and potassium as active species. The catalysts were characterized by X-ray diffraction and infrared spectroscopy. The amount of catalyst used in the reaction was scanned in a range of 1-10% w, obtaining a maximum conversion of 85% at 55 °C with 6.5% w/w of catalyst with respect to the reagent load and with a methanol-oil molar ratio of 6: 1, reaching equilibrium conversion at six hours. The catalysts were tested at 40, 45, 50 and 55 °C in the transesterification reaction using refined sunflower oil and anhydrous methanol as reagents in a 6: 1 ratio. The 40% K catalyst obtained the best conversion at 55 °C with 85% and showed a selectivity of 45%.

Heterogeneous catalysis, although known for over a century, is constantly improved and plays a key role in solving the present problems in chemical technology. Thanks to the development of modern materials engineering, solid supports for catalytic phases having a highly developed surface are available. Recently, continuous-flow synthesis started to be a key technology in the synthesis of high added value chemicals. These processes are more efficient, sustainable, safer and cheaper to operate. The most promising is the use of heterogeneous catalyst with column-type fixed-bed reactors. The advantages of the use of heterogeneous catalyst in continuous flow reactors are the physical separation of product and catalyst, as well as the reduction in inactivation and loss of the catalyst. However, the state-of-the-art use of heterogeneous catalysts in flow systems compared to homogenous ones remains still open. The lifetime of heterogeneous catalysts remains a significant hurdle to realise sustainable flow synthesis. The goal of this review article was to present a state of knowledge concerning the application of Supported Ionic Liquid Phase (SILP) catalysts dedicated for continuous flow synthesis.

In this review, we present an assessment of recent advances in alkyne functionalization reactions, classified according to different classes of recyclable catalysts. In this work, we have incorporated and reviewed the activity and selectivity of recyclable catalytic systems such as polysiloxane-encapsulated novel metal nanoparticle-based catalysts, silica–copper-supported nanocatalysts, graphitic carbon-supported nanocatalysts, metal organic framework (MOF) catalysts, porous organic framework (POP) catalysts, bio-material-supported catalysts, and metal/solvent free recyclable catalysts. In addition, several alkyne functionalization reactions have been elucidated to demonstrate the success and efficiency of recyclable catalysts. In addition, this review also provides the fundamental knowledge required for utilization of green catalysts, which can combine the advantageous features of both homogeneous (catalyst modulation) and heterogeneous (catalyst recycling) catalysis.

As catalysis plays a significant role in the development of economical and sustainable chemical processes, increased attention is paid to the recovery and reuse of high-value catalysts. Although homogeneous catalysts are usually more active and selective than the heterogeneous ones, both catalyst recycling and product separation pose a challenge for developing industrially feasible methods. In this respect, membrane-supported recovery of organocatalysts represents a particularly useful tool and a valid option for organocatalytic asymmetric synthesis. However, catalyst leaching/degradation and a subsequent decrease in selectivity/conversion are significant drawbacks. As the effectivity of the membrane separation depends mainly on the size of the catalyst in contrast to the other solutes, molecular weight enlargement of small organocatalysts is usually necessary. In the last few years, several synthetic methodologies have been developed to facilitate their recovery by nanofiltration. With the aim of extending the possibilities for the membrane-supported recovery of organocatalysts further, this contribution presents a review of the existing synthetic approaches for the molecular weight enlargement of organocatalysts.

It is essential to reduce iridium in water electrolysers without compromising performance to lower the cost of green hydrogen. One strategy often used in catalysis to reduce precious metal catalyst usage is to deposit catalysts on high surface area supports. However, the catalyst supports need to be stable under the reaction conditions and also economically viable. Additionally, the catalyst-support moieties need to be sufficiently conductive. In this project, we explore platinum coated titanium dioxide as supports for iridium catalysts. Platinum is necessary to improve conductivity of the support motifs. Without this conductive platinum layer, extremely high (75 wt%) iridium loadings are needed to prepare commercially viable supported iridium catalysts.1, 2 In this work we synthesise and characterise a systematic series of catalysts whereby the Pt loading is varied in order to understand the loading effect on conductivity, and thus, electrocatalytic activities and durabilities. Previously, we have demonstrated the efficacy of a Pt conductive layer as an effective strategy for boosting the mass activity of Iridium in a half-cell configuration.4 However, translating the performance, more critically durability, in a device remained to be demonstrated. Here, we also begin by rapidly assessing the electrochemical performance of the library of prepared catalysts in a half-cell configuration (rotating disk electrodes, RDEs). Subsequently, catalysts that show promising activity and durability in half-cell are integrated into a PEM electrolyser. This approach is economic and efficient since integrating catalysts into membrane electrode assemblies and running electrolyser tests are resource and time intensive. However, there are challenges associated with replicating activity and durability from half-cell to device performance.3 Thus, we also explore methodologies and strategies to optimise our half-cell investigations to mimic full device conditions more closely. We have demonstrated that our strategy to engineer iridium catalysts has led to greater than 50% reduction in iridium content necessary in water electrolysers. And yet, our devices show performance and durability comparable to state-of-the-art technology. In this presentation we will discuss remaining challenges for hydrogen production using proton exchange membrane water electrolysers. We will also present materials characterisations and electrochemical performance of our catalysts in half-cell and full device configuration. Reference: K. Ayers, N. Danilovic, R. Ouimet, M. Carmo, B. Pivovar and M. Bornstein, Annu Rev Chem Biomol Eng, 2019, 10, 219-239. M. Bernt, A. Hartig‐Weiß, M. F. Tovini, H. A. El‐Sayed, C. Schramm, J. Schröter, C. Gebauer and H. A. Gasteiger, Chemie Ingenieur Technik, 2020, 92, 31-39. T. Lazaridis, B. M. Stühmeier, H. A. Gasteiger and H. A. El-Sayed, Nature Catalysis, 2022, 5, 363-373. Y. N. Regmi, E. Tzanetopoulos, G. Zeng, X. Peng, D. I. Kushner, T. A. Kistler, L. A. King and N. Danilovic, ACS Catalysis, 2020, 10, 13125-13135.

A vapour deposition (VD) method was established for preparation of the UiO-66-supported Fe (Fe/UiO-66) catalyst, which provided the first case of the metal-organic framework (MOF)-supported Fe catalyst prepared by using the vapour-based method. The Fe loading was around 7.0–8.5 wt% under the present preparation conditions. The crystal structure of UiO-66 was not obviously influenced by the Fe loading, while the surface area significantly decreased, implicating most of the Fe components resided in the pores on UiO-66. The results for the methyl orange (MO) removal tests showed that MO in aqueous solution can be removed by UiO-66 by adsorption, and in contrast, it can be oxidized by H 2 O 2 with the catalysis of Fe/UiO-66. Further catalytic tests showed that Fe/UiO-66 was rather effective to catalyse the oxidation of benzene derivatives like aniline in water in terms of chemical oxygen demand (COD) removal efficiency. The catalytic test results for Fe/UiO-66 were compared to those of Fe/Al 2 O 3 with the same Fe loading and to the catalysts reported in the literature. This paper provides a general strategy for VD preparation of MOF-supported Fe catalyst on the one hand, and new catalysts for removing organic pollutants from water, on the other hand.