Synthesis, Characterization And Catalytic Activity Of Mcm-41 Imidazolium Halide Catalysts For The Reaction Between Epoxides And Carbon Dioxide

Penetapan kimia karbon dioksida (CO2) telah mendapat perhatian yang semakin meningkat sebagai sumber karbon yang berpotensi dalam proses kimia perindustrian berikutan kebimbangan yang semakin meningkat daripada kesan rumah hijau. Salah satu cara yang paling menjanjikan untuk penggunaan berharga CO2 adalah melalui sintesis karbonat siklik. The chemical fixation of carbon dioxide (CO2) has received increasing attention as a potential carbon source in industrial chemical processes due to the growing concern of the greenhouse effect. One of the most promising ways for valuable utilization of CO2 is the synthesis of cyclic carbonates

Graphene oxide exhibits differential mechanistic action towards Gram-positive and Gram-negative bacteria

The antibacterial nature of graphene oxide (GO) has stimulated wide interest in the medical field. Although the antibacterial activity of GO towards bacteria has been well studied, a deeper understanding of the mechanism of action of GO is still lacking. The objective of the study was to elucidate the difference in the interactions of GO towards Gram-positive and Gram-negative bacteria. The synthesized GO was characterized by Ultraviolet–visible spectroscopy (UV–vis), Raman and Attenuated Total Reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR). Viability, time-kill and Lactose Dehydrogenase (LDH) release assays were carried out along with FESEM, TEM and ATR-FTIR analysis of GO treated bacterial cells. Characterizations of synthesized GO confirmed the transition of graphene to GO and the antibacterial activity of GO was concentration and time-dependent. Loss of membrane integrity in bacteria was enhanced with increasing GO concentrations and this corresponded to the elevated release of LDH in the reaction medium. Surface morphology of GO treated bacterial culture showed apparent differences in the mechanism of action of GO towards Gram-positive and Gram-negative bacteria where cell entrapment was mainly observed for Gram-positive Staphylococcus aureus and Enterococcus faecalis whereas membrane disruption due to physical contact was noted for Gram-negative Escherichia coli and Pseudomonas aeruginosa. ATR-FTIR characterizations of the GO treated bacterial cells showed changes in the fatty acids, amide I and amide II of proteins, peptides and amino acid regions compared to untreated bacterial cells. Therefore, the data generated further enhance our understanding of the antibacterial activity of GO towards bacteria

Review on Carbon Dioxide Utilization for Cycloaddition of Epoxides by Ionic Liquid-Modified Hybrid Catalysts: Effect of Influential Parameters and Mechanisms Insight

The storage, utilization, and control of the greenhouse (CO2) gas is a topic of interest for researchers in academia and society. The present review article is dedicating to cover the overall role of ionic liquid-modified hybrid materials in cycloaddition reactions. Special emphasis is on the synthesis of various cyclic carbonate using ionic liquid-based modified catalysts. Catalytic activity studies have discussed with respect to process conditions and their effects on conversion and product selectivity for the reaction of cycloaddition of CO2 with styrene oxide. The reaction temperature and the partial pressure of CO2 have found to play a key role in cyclic carbonate formation. The role of other influential parameter (solvent effect) is also discussed for the conversion of cyclic/aromatic oxides to polycarbonate production. Our own research work that deals with ionic liquid-based halide-modified mesoporous catalyst (MCM-41 type) derived from rice husk waste has also been discussed. Finally, the role of carbon dioxide activation and ring-opening mechanisms involved in the cyclic carbonate product formation from CO2 have been discussed

ZnAlMCM-41: a very ecofriendly and reusable solid acid catalyst for the highly selective synthesis of 1,3-dioxanes by the Prins cyclization of olefins

The Prins cyclization of styrene (SE) with paraformaldehyde (PFCHO) was conducted with mesoporous ZnAlMCM-41 catalysts for the synthesis of 4-phenyl-1,3-dioxane (4-PDO) using a liquid phase heterogeneous catalytic method. For a comparison study, the Prins cyclization reaction was also conducted over different nanoporous catalysts,e.g.mesoporous solid acid catalysts, AlMCM-41(21) and ZnMCM-41(21), and microporous catalysts, USY, Hβ, HZSM-5, and H-mordenite. The recyclable mesoporous ZnAlMCM-41 catalysts were reused in this reaction to evaluate their catalytic stabilities. Since ZnAlMCM-41(75) has higher catalytic activity than other solid acid catalysts, washed ZnAlMCM-41(75)/W-ZnAlMCM-41(75) was prepared using an efficient chemical treatment method and used with various reaction parameters to find an optimal parameter for the highly selective synthesis of 4-PDO. W-ZnAlMCM-41(75) was also used in the Prins cyclization of olefins with PFCHO and formalin (FN, 37% aqueous solution of formaldehyde (FCHO)) under different reaction conditions to obtain 1,3-dioxanes, which are widely used as solvents or intermediates in organic synthesis. Based on the nature of catalysts used under different reaction conditions, a reasonable plausible reaction mechanism for the Prins cyclization of SE with PFCHO is proposed. Notably, it can be seen from the catalytic results of all catalysts that the W-ZnAlMCM-41(75) catalyst has higher 4-PDO selectivity with exceptional catalytic activity than other microporous and mesoporous catalysts

The utilization of rice husk silica as a catalyst: review and recent progress

In this review article, we report the recent development and utilization of silica from rice husk (RH)for the immobilization of transition metals and organic moieties. Silicon precursor was obtained in the form of sodium silicate and as rice husk ash (RHA). Sodium silicate was obtained by direct silica extraction from rice husk via a solvent extraction method while rice husk ash was obtained by pyrolyzing the RH in the range of 500–800 ◦C for 5–6 h. Transition metals were immobilized into the silica matrix via the sol–gel technique while the organic moieties were incorporated using a grafting method. 3- (Chloropropyl)triethoxy-silane (CPTES) was used as a bridge to link the organic moieties to the silica matrix. All the catalysts exhibited good physical and catalytic potential in various reactions

Biomedical Applications of Polyhydroxyalkanoate in Tissue Engineering

Tissue engineering technology aids in the regeneration of new tissue to replace damaged or wounded tissue. Three-dimensional biodegradable and porous scaffolds are often utilized in this area to mimic the structure and function of the extracellular matrix. Scaffold material and design are significant areas of biomaterial research and the most favorable material for seeding of in vitro and in vivo cells. Polyhydroxyalkanoates (PHAs) are biopolyesters (thermoplastic) that are appropriate for this application due to their biodegradability, thermo-processability, enhanced biocompatibility, mechanical properties, non-toxicity, and environmental origin. Additionally, they offer enormous potential for modification through biological, chemical and physical alteration, including blending with various other materials. PHAs are produced by bacterial fermentation under nutrient-limiting circumstances and have been reported to offer new perspectives for devices in biological applications. The present review discusses PHAs in the applications of conventional medical devices, especially for soft tissue (sutures, wound dressings, cardiac patches and blood vessels) and hard tissue (bone and cartilage scaffolds) regeneration applications. The paper also addresses a recent advance highlighting the usage of PHAs in implantable devices, such as heart valves, stents, nerve guidance conduits and nanoparticles, including drug delivery. This review summarizes the in vivo and in vitro biodegradability of PHAs and conducts an overview of current scientific research and achievements in the development of PHAs in the biomedical sector. In the future, PHAs may replace synthetic plastics as the material of choice for medical researchers and practitioners

Simple method for functionalization of silica with alkyl silane and organic ligands

3–(chloropropyl)triethoxysilane (CPTES) with imidazole and sodium silicate from rice husk ash (RHA) successfully reacted within a short time in one–pot synthesis in purely homogenous method. A similar procedure was used for the immobilization of melamine and saccharine to demonstrate a generally applicable method. No reflux was needed, and a green solvent was used as the reaction medium. The surface areas of the prepared materials were very high compared with the materials which have similar structure prepared by the traditional method. The TGA/DTA confirmed that all the materials were highly stable. The FT-IR shows that all expected the functional groups were present. The HRTEM showed that the materials had ordered mesoporous straight-channels which were like the MCM-41. The synthesis procedure is simple, repeatable with different organic ligands and does not require toxic solvents or multiple steps with high products yield

Synthesis, characterization and catalytic activity of melamine immobilized MCM-41 for condensation reactions

In the present study, melamine immobilized MCM-41 is synthesized by grafting on modified MCM-41. The surface area, pore size and pore volume of MCM-41-Mela were found to be decreased after immobilization of melamine. FTIR and Raman spectroscopy results revealed the successful grafting of melamine on the surface of MCM-41. The 29Si CP/MAS NMR of MCM-41-Mela showed the existence of T2, T3, Q3 and Q4 silicon centres. The catalytic activities were investigated through a liquid phase Knoevenagel condensation reaction between furfural and acetylacetone. A conversion of 93.1% was achieved with 100% selectivity towards 3-(2-furylmethylene)-2,4-pentanedione (FMP) under solvent-free condition. The catalytic activity of MCM-41-Mela was then successfully carried out for Knoevenagel condensation with different substrates, giving excellent yields of the corresponding products. The catalyst was easily regenerated and could be reused for three times without loss of catalytic activity. Simple preparation methods, high efficiency and reusability of the heterogeneous MCM-41-Mela catalyst demonstrate a great potential for future catalysis application

Highly efficient green mesostructured urea functionalized on SBA-15 catalysts for selective synthesis of benzlidenemalononitrile

A series of urea-immobilized SBA-15 catalysts were synthesized via post grafting method using 3-chloropropyltriethoxysilane (CPTES) as the anchoring agent. The solid catalyst was characterized by PXRD, N2 adsorption-desorption, FT-IR, elemental analyzer, TEM, CO2-TPD and 29Si CP/MAS NMR. Detailed analysis of the pore size illustrated the mesoporous nature of the immobilized catalyst. The as-prepared catalyst was further evaluated in the Knoevenagel condensation reaction under different reaction conditions. Benzaldehyde was employed in the Knoevenagel condensation reaction with malononitrile. Catalytic results showed that the Urea(4.8)/SBA-15 exhibits high efficacy (98% of yield) for promoting this reaction at 40 °C and in the absence of a solvent. Under the same reaction conditions, acetylacetone led to a lower benzaldehyde conversion of 10%, whereas ethyl cyanoacetate provides up to 88% conversion. The catalyst could be recycled and reused for at least five reaction cycles with slight loss of catalytic activity