Telomerization of Isoprene with Short Alcohols Using Novel Solid Molecular Phosphine Polymers

"… Despite the introduction of high-throughput and combinatorial methods that certainly can be useful in the process of catalysts optimization, it is recognized that the generation of fundamental knowledge at the molecular level is key for the development of new concepts and for reaching the final objective of solid catalysts by design …" Read more in the Editorial by Avelino Corma.

<p>Recent increased environmental awareness and the stimulus of greener chemistry has driven the rapid development of heterogeneous catalysts, particularly solid acids, for a wide range of organic synthesis applications. Typical homogenous acids suffer drastic drawbacks in terms of their corrosivity, toxicity, and reusability, in addition to their separation that generates large amounts of industrial wastes which exceeds in many cases the amount of the formed products. Crystalline aluminosilicate inorganic polymers (zeolites) have successfully replaced the typical homogenous Lewis acids in many industrially important applications, the majority of which are in the petrochemical industries, e.g. production of olefins and aromatics. The fine chemical industries, however, are more challenging and still mainly use homogenous catalysts. Typical zeolite catalysts are hindered by their restricted micropores, and the low hydrothermal stability of other mesoporous M-silicates (such as MCM-41) results in structural deformation in aqueous solutions at elevated temperatures. Other highly promising solid catalysts suffer drawbacks of high cost, sophisticated synthesis procedures, and environmental risks from the use of toxic reagents. Thus, there is still a need for new cost-efficient reactive heterogeneous solid catalysts that are also environmentally benign. This thesis reports the development of amorphous aluminosilicate inorganic polymers (known as geopolymers) as a novel class of heterogeneous solid acid catalysts. These geopolymers can be synthesised with the desired acidity and porosity in a very energy-efficient and simple procedure which does not involve lengthy thermal treatments or the use of costly and sometimes toxic structural directing agents that are required for the synthesis of zeolite or other mesoporous aluminosilicates. Microporous, mesoporous and hierarchical geopolymer-based catalysts were synthesised from different precursors with high surface area and acidic sites (Bronsted and Lewis) generated within their structure by ion-exchange with ammonium ions followed by thermal treatment, allowing the nature of these acidic sites to be tailored to specific applications. Furthermore, some of the resulting geopolymer catalysts were subjected to post synthetic treatments (demetallation) which provided improved acidity and porosity. In the first instance, the geopolymer-based catalysts were synthesised from a naturally occurring clay mineral and their catalytic performance was evaluated in the industrially important Beckmann rearrangement of cyclohexanone oxime to 𝜀-caprolactam. High catalytic reactivity and selectivity was achieved over the geopolymer-based catalysts that possess high surface area and weak surface acidities consisting of H-bonded silanol nests and vicinal silanols. The catalytic reactivity of the clay-based geopolymer catalysts was further evaluated in the Friedel-Crafts alkylation of large substituted arenes with benzyl halide as alkylating agent, where typical microporous zeolites show poor reactivity due to diffusional limitations. In this reaction, the thermal treatment was adjusted to generate the required Bronsted and Lewis acidic sites. High reactivity was achieved over several mesoporous geopolymer-based catalysts, with the best performance being observed over a hierarchical geopolymer-based catalyst that exhibits the highest acidity of all these new catalysts. In another approach, highly reactive geopolymer-based catalysts were synthesised from industrial wastes precursors (fly ash). Several fly ashes were collected from different sources and the influence of their chemical and physical properties on the resulting geopolymers was investigated. These fly ash-based catalysts demonstrated excellent catalytic performance in the alkylation of benzene and substituted benzenes and their active sites were ascribed to a combination of Fe2O3 present in the raw fly ash, together with the Bronsted and Lewis acid sites that were generated within the geopolymers framework by the ion-exchange process followed by thermal treatment. The use of the fly ash-based catalysts was also demonstrated in another highly demanding catalytic process, the Friedel-Crafts acylation of aromatics. High reactivity and selectivity was achieved in the acylation reactions of anisole and mesitylene using benzoylchloride as the acylating agent. In addition to their excellent catalytic reactivities, the fly ash-based geopolymer catalysts provide a valuable approach of the utilisation of industrial wastes such as fly ash, the vast production of which is becoming a world-wide concern. The geopolymer-based catalysts developed in this work are reusable without significant loss of reactivity and their catalytic performance is superior to other commonly used solid acid catalysts. The results presented in this thesis demonstrate a great potential for geopolymers as active candidates in the field of heterogeneous catalysis, representing as they do a new class of solid acids with highly desirable features such as catalytic efficiency as well as ecological friendliness, cost effectiveness and ease of synthesis.</p>

<p>Recent increased environmental awareness and the stimulus of greener chemistry has driven the rapid development of heterogeneous catalysts, particularly solid acids, for a wide range of organic synthesis applications. Typical homogenous acids suffer drastic drawbacks in terms of their corrosivity, toxicity, and reusability, in addition to their separation that generates large amounts of industrial wastes which exceeds in many cases the amount of the formed products. Crystalline aluminosilicate inorganic polymers (zeolites) have successfully replaced the typical homogenous Lewis acids in many industrially important applications, the majority of which are in the petrochemical industries, e.g. production of olefins and aromatics. The fine chemical industries, however, are more challenging and still mainly use homogenous catalysts. Typical zeolite catalysts are hindered by their restricted micropores, and the low hydrothermal stability of other mesoporous M-silicates (such as MCM-41) results in structural deformation in aqueous solutions at elevated temperatures. Other highly promising solid catalysts suffer drawbacks of high cost, sophisticated synthesis procedures, and environmental risks from the use of toxic reagents. Thus, there is still a need for new cost-efficient reactive heterogeneous solid catalysts that are also environmentally benign. This thesis reports the development of amorphous aluminosilicate inorganic polymers (known as geopolymers) as a novel class of heterogeneous solid acid catalysts. These geopolymers can be synthesised with the desired acidity and porosity in a very energy-efficient and simple procedure which does not involve lengthy thermal treatments or the use of costly and sometimes toxic structural directing agents that are required for the synthesis of zeolite or other mesoporous aluminosilicates. Microporous, mesoporous and hierarchical geopolymer-based catalysts were synthesised from different precursors with high surface area and acidic sites (Bronsted and Lewis) generated within their structure by ion-exchange with ammonium ions followed by thermal treatment, allowing the nature of these acidic sites to be tailored to specific applications. Furthermore, some of the resulting geopolymer catalysts were subjected to post synthetic treatments (demetallation) which provided improved acidity and porosity. In the first instance, the geopolymer-based catalysts were synthesised from a naturally occurring clay mineral and their catalytic performance was evaluated in the industrially important Beckmann rearrangement of cyclohexanone oxime to 𝜀-caprolactam. High catalytic reactivity and selectivity was achieved over the geopolymer-based catalysts that possess high surface area and weak surface acidities consisting of H-bonded silanol nests and vicinal silanols. The catalytic reactivity of the clay-based geopolymer catalysts was further evaluated in the Friedel-Crafts alkylation of large substituted arenes with benzyl halide as alkylating agent, where typical microporous zeolites show poor reactivity due to diffusional limitations. In this reaction, the thermal treatment was adjusted to generate the required Bronsted and Lewis acidic sites. High reactivity was achieved over several mesoporous geopolymer-based catalysts, with the best performance being observed over a hierarchical geopolymer-based catalyst that exhibits the highest acidity of all these new catalysts. In another approach, highly reactive geopolymer-based catalysts were synthesised from industrial wastes precursors (fly ash). Several fly ashes were collected from different sources and the influence of their chemical and physical properties on the resulting geopolymers was investigated. These fly ash-based catalysts demonstrated excellent catalytic performance in the alkylation of benzene and substituted benzenes and their active sites were ascribed to a combination of Fe2O3 present in the raw fly ash, together with the Bronsted and Lewis acid sites that were generated within the geopolymers framework by the ion-exchange process followed by thermal treatment. The use of the fly ash-based catalysts was also demonstrated in another highly demanding catalytic process, the Friedel-Crafts acylation of aromatics. High reactivity and selectivity was achieved in the acylation reactions of anisole and mesitylene using benzoylchloride as the acylating agent. In addition to their excellent catalytic reactivities, the fly ash-based geopolymer catalysts provide a valuable approach of the utilisation of industrial wastes such as fly ash, the vast production of which is becoming a world-wide concern. The geopolymer-based catalysts developed in this work are reusable without significant loss of reactivity and their catalytic performance is superior to other commonly used solid acid catalysts. The results presented in this thesis demonstrate a great potential for geopolymers as active candidates in the field of heterogeneous catalysis, representing as they do a new class of solid acids with highly desirable features such as catalytic efficiency as well as ecological friendliness, cost effectiveness and ease of synthesis.</p>

Oil palm empty fruit bunch (EFB) is one of the palm biomass produced in abundance after oil extraction in Malaysia. This study was focused to utilize this waste biomass as a beneficial raw materials. EFB was used to prepare new solid acid catalyst for biodiesel production. EFB was converted into solid catalyst via direct impregnation method and it was used to catalyse esterification of oleic acid. Transition metal sulfide salt, Fe2(SO4)3 was impregnated on EFB fibres. Effect of different calcination temperature was studied on the properties of catalyst. The result shows that Fe2(SO4)3 based solid acid catalyst which calcined at 500°C exhibited the highest catalytic activity with 93.90% esterification rate was achieved. The morphology and surface chemistry and function group determination for the solid acid catalyst were characterized by SEM-EDX and FTIR.

Biodiesel production by transesterification using tetraalkylammonium hydroxides immobilized onto SBA-15 as a solid catalyst

preview not available - see full-text PDF article.

1,5-Benzothiazepines derivatives were obtained first by starting from 1,3-diphenylpropenone derivatives (chalcones) and 2-aminothiophenol by using aluminosilicate solid catalysts. However, diffusional limitations and the strong adsorption of products on the catalyst are deleterious for catalyst activity and life. Then a structured amorphous mesoporous catalyst with large pores and mild acidity that works at higher temperatures allowed us to obtain high conversions (99 %) and selectivities (98 %) of the desired product. A one-pot synthesis of 1,5-benzothiazepines that starts from benzaldehyde, acetophenone, and 2-aminothiophenol with 95 % yield was performed by combining optimized solid base and acid catalysts in batch mode as well as in a continuous-flow reactor system. Much better conversion and selectivity as well as process intensification has been achieved with the structured mesoporous materials by avoiding intermediate and final neutralization and purification steps required in the synthesis reported previously that uses homogeneous catalysts.

Isobutane alkylation with solid catalysts based on beta zeolite

An important phase of the MgO-SiO2-Al2O3 system, α-cordierite was studied for its catalytic transesterification activity in preparing palm biodiesel. The prime drawback of such solid catalyst is its low activity. To overcome this problem, the transesterification was combined with microwave irradiation. The effect of reaction time and catalyst loading on biodiesel yield was investigated in a batch reaction mode. The synthesis of biodiesel was confirmed by 1H NMR spectroscopy. It reveals that an enhanced yield of biodiesel was obtained, whereas the maximum yield was reached in less than 30 min regardless the catalyst loading. As a solid type catalyst, this result becomes a platform to develop the flow mode reaction unit using a cordierite based structured catalyst without modifying surface chemistry of cordierite.

We synthesized Ca-containing FSM-16 (Ca-FSM-16) for use as a solid base catalyst for the Knoevenagel condensation reaction. Extended X-ray absorption fine structure (EXAFS) results indicated that Ca species were introduced as a calcium silicate-like phase with distorted tetrahedral coordination into the pore walls of FSM-16. Compared with conventional aminopropyl-functionalized mesoporous silica, Ca-FSM-16 showed higher activity as a solid-base catalyst for the Knoevenagel condensation reaction. Ca-containing mesoporous silica (Ca-FSM-16) was synthesized for use as a solid base catalyst for the Knoevenagel condensation reaction.

Atomically dispersed 3d metal bimetallic dual-atom catalysts and classification of the structural descriptors

TBD-grafted activated carbon as an efficient solid base catalyst for continuous Knoevenagel reaction

ConspectusDiazocarbonyl compounds have become essential tools in organic synthesis, due to their ability to in situ generate reactive carbenes and be inserted in a variety of otherwise stable bonds, such as C-H, C-C, H-O, and so on. However, a soluble metal salt or complex catalyst is generally required to selectively activate and couple the carbene, and the metals employed so far are expensive (Rh, Au, Ag, Cu) and often unrecoverable. It is noteworthy that the price of ligands can make a cheaper metal catalyst (i.e., Cu) as expensive as other ligand-free noble metal catalysts. In the realm of modern sustainable chemistry, most of these methodologies are now unacceptable and must be adapted, and simple strategies for that include carbene photoactivation and the use of recoverable solid catalysts. Unfortunately, despite research in the field of carbene insertion reactions that has extended now for more than 50 years, examples with solid catalysts are still minor, and efficient solid catalysts have only been reported in the last two decades.This Account shows the journey faced by our group in the last eight years to find solid catalysts for challenging carbene insertion reactions, employing diazocarbonyl compounds as carbene precursors. We will contextualize our results with those of previous solid catalysts. The discovery in 2017 that a quasi-linear Pd4 cluster stabilized within a metal-organic framework (MOF) was able to catalyze the Büchner and other carbene insertion reactions, spurred the design of supported metal clusters as catalysts for a variety of carbene insertion reactions. The Pd4-MOF could be reused 20 times in batch and implemented in a flow process. Following this, other catalytic solids, including Au and Ag as metals, not only in the same MOF but also on solid oxides and zeolites as supports, showed good activity for carbene insertion reactions and were also recoverable and reusable.Our journey temporarily finishes in 2024 when "blank" experiments with a dealuminated zeolite surprisingly revealed that this simple solid acid, without any metal, easily activates the diazocarbonyl compound and catalyzes a variety of carbene insertion reactions, thus providing a cheap, commercially available, and reusable solid catalyst for these challenging reactions. Overall, rapid progress in solid-catalyzed diazocarbonyl compound activation, carbene formation, and insertion reactions has been achieved during these years, moving from expensive and difficult to prepare solid catalysts based on supported metal clusters to simple acid zeolites, pointing to confined Brønsted acids as the catalysts to study in the near future.

Mg-doped graphitic carbon nitride (g-C3N4) composites were prepared using a facile thermal polymerization process under air atmosphere. The obtained materials can be employed as the solid base catalysts in Knoevenagel condensation reactions. The Mg-doped g-C3N4 composites show excellent performance as a solid catalyst and superior catalytic activity compared to the pure CN-U. The introduction of Mg species improved the overall basic property of CN-U, favoring Knoevenagel condensations. The 5MgCN-U catalyst exhibited high benzaldehyde conversion of 97.4% at 70 °C and good cycling stability for four cycles, with 87.7% benzaldehyde conversion and nearly 100% benzylidene malononitrile selectivity. Additionally, the Mg-doped g-C3N4 composites from urea showed superior catalytic performance than those produced from dicyandiamide and melamine, indicating that the precursors contribute to the efficiency of Knoevenagel condensation reactions.

Preparation, characterization and catalytic activity of tin oxide-supported 12-tungstophosphoric acid as a solid catalyst