Removal of cobalt (II) ions from aqueous solution by Peganum Harmala seeds

The batch extraction of cobalt [Co(II)] ions from an aqueous solution, utilizing the seeds of Peganum harmala has been evaluated in this study. After gathering Peganum harmala, the plants are beaten to separate the seeds, after which the seed undergo a fine filtration process to remove any debris. The prepared adsorption material is defined by Fourier transform infrared spectroscopy (FTIR). The adsorption process is conducted an incubator in 50 mL flasks. The studied process variables included pH, contact time, Co(II) concentration, adsorbent dose and reaction temperature. Co(II) is assessed with the use of a UV-vis spectrophotometer at a wavelength of 512 nm. Optimal Co(II) removal is noted at a pH of 6; increased alkalinity resulted in the generation of cobalt hydroxide. When contact time is increased from 5 to 40 min, the removal of Co(II) ions increased from 8 to 88%. This represented the maximum adsorption of Co(II) into Peganum harmala. After this time, equilibrium was achieved, with no further Co(II) extraction occurring. The higher the dose of adsorbent, the higher the degree of Co(II) ion removal; increasing the adsorbent from 0.1 to 0.4g/L result in an increase in extraction from 60 to 84%. A larger dose of adsorbent, up to 0.5 g/L, diminished further Co(II) ion subtraction. The Langmuir adsorption isotherm show a superior model fit compared with the Freundlich isotherm

Ruthenium Catalyst for Epoxidation Reaction

The role of ruthenium as a heterogeneous catalyst for epoxidation reaction has not been investigated extensively. Therefore, the purpose of this chapter is to provide overview of the epoxidation of alkene using ruthenium catalysts. The chapter is divided into two main sections. The first section is about epoxidation of alkene using supported ruthenium catalysts, while the second using ruthenium complexes (homogenous catalysts)

Effects of reaction conditions on the conversion of epoxides to cyclic carbonates through CO2 inclusion

This thesis targets to the synthesis of cyclic carbonates as they are compounds of high importance in a number of different applications. The one-pot synthesis of cyclic carbonates consists of two sequential reactions of epoxidation of the olefin and the subsequent cycloaddition reaction of CO2 with the epoxide. To obtain more information on the roles of catalyst components, the epoxidation of 1-decene (first step) and the cycloaddition of CO2 with epoxide (second step) were conducted individually. The supported cobalt catalysts, prepared by a wet-impregnation method, were active in the epoxidation of 1-decene in the presence of oxygen from air as the primary oxidant and a very small amount of the radical initiator at 80°C. Using TiO2 as a support for cobalt resulted in a significant reduction in the quantity of the leached cobalt catalyst compared with the use of MgO as a support. 1-Decene epoxidation was also performed over supported gold catalysts in the presence of a very small amount of the radical initiator using oxygen as the oxidant. Supported gold catalysts prepared by the sol-immobilisation method displayed the highest activity. Gold nanoparticles supported on TiO2 and SiO2 showed the highest activity. The cycloaddition of CO2 with different epoxides were studied using different catalysts. Tetrabutylammonium bromide (Bu4NBr) was the most active quaternary ammonium salts. Other heterogeneous catalysts such as polydiallyldimethylammonium bromide and imidazole supported onto silica were found to be effective catalysts for this reaction. The compatibility between these two catalysts for the two different steps before coupling them in a one-pot reaction for the direct synthesis of cyclic carbonate was also investigated. The epoxide selectivity was significantly reduced in the presence of Bu4NBr or polydiallyldimethylammonium bromide (40% PDDABr/SiO2) or imidazole supported on silica (Imid/SiO2). No effect of supported gold catalysts was observed on the cycloaddition of CO2 with 1,2-epoxydecane. A simple and highly efficient preparation of cyclic carbonates from 1-decene was achieved by the use of 1%Au/support-Bu4NBr/ZnBr2 catalysts. The oxidative carboxylation process for a range of different cycloalkenes is challenging. For the epoxidation step, it was shown previously in our group that smaller ring size, such as cyclopentene, became less selective to the epoxidation. However, regarding the cycloaddition step, the opposite trend was found. Cyclopentene oxide and cyclohexene oxide gave high selectivity for cyclic carbonate,whereas the insertion of CO2 in carbonylation of cyclooctene oxide and cyclododecane oxide to form cyclic carbonate was a challenging step and the main product was ketone

Peganum Harmala plant as an adsorbent for the removal of Copper(II) ions from water

Batch removal of Cu(II) from water by powdered seeds of Peganum Harmala has been investigated in this research. The Peganum Harmala seeds were collected after which they have been beaten slowly, separated and then cleaned using a sieve. The prepared sorption is characterized by FT-IR. Batch adsorption studies have been undertaken in 100 ml Erlenmeyer flasks, inside an incubator container. The main process parameters that are considered are pH, contact time, Cu(II) concentration, the Adsorbent dose effect and reaction temperature effect. Cu(II) is measured at a wavelength of 620 nm, using a UV-vis spectrophotometer. The result evidence that the maximum removal of Cu(II) is observed at pH 6.2, with the pH over 6.2 result to participate the copper hydroxide. Clearly, the uptake process of the Cu(II) ion occurres very swiftly from the outset of the experiments during the first 15 min, after which there is a low decrease until 40 min, when maximum adsorption of Cu(II) ion onto Peganum Harmala is observed. An increased Cu(II) ions removal percentage occurres with increasing dose of adsorbents, increasing from 0.2 to 0.6 g followed by an increased percentage removal from 63.50% to 66.02%. Subsequently, the removal of Cu(II) ions decline, with an increased dose to 1g. Langmuir adsorption isotherm is more appropriate than the Freundlich adsorption isotherm, while the pseudo second-order reaction model is suitable for adsorption of the Copper ion onto the active centers of the Peganum Harmala surface compared with the pseudo first-order model

Peganum Harmala plant as an adsorbent for the removal of Copper(II) ions from water

163-171Batch removal of Cu(II) from water by powdered seeds of Peganum Harmala has been investigated in this research. The Peganum Harmala seeds were collected after which they have been beaten slowly, separated and then cleaned using a sieve. The prepared sorption is characterized by FT-IR. Batch adsorption studies have been undertaken in 100 ml Erlenmeyer flasks, inside an incubator container. The main process parameters that are considered are pH, contact time, Cu(II) concentration, the Adsorbent dose effect and reaction temperature effect. Cu(II) is measured at a wavelength of 620 nm, using a UV-vis spectrophotometer. The result evidence that the maximum removal of Cu(II) is observed at pH 6.2, with the pH over 6.2 result to participate the copper hydroxide. Clearly, the uptake process of the Cu(II) ion occurres very swiftly from the outset of the experiments during the first 15 min, after which there is a low decrease until 40 min, when maximum adsorption of Cu(II) ion onto Peganum Harmala is observed. An increased Cu(II) ions removal percentage occurres with increasing dose of adsorbents, increasing from 0.2 to 0.6 g followed by an increased percentage removal from 63.50% to 66.02%. Subsequently, the removal of Cu(II) ions decline, with an increased dose to 1g. Langmuir adsorption isotherm is more appropriate than the Freundlich adsorption isotherm, while the pseudo second-order reaction model is suitable for adsorption of the Copper ion onto the active centers of the Peganum Harmala surface compared with the pseudo first-order model

Oxidative carboxylation of 1-decene to 1,2-decylene carbonate

Cyclic carbonates are valuable chemicals for the chemical industry and thus, their efficient synthesis is essential. Commonly, cyclic carbonates are synthesised in a two-step process involving the epoxidation of an alkene and a subsequent carboxylation to the cyclic carbonate. To couple both steps into a direct oxidative carboxylation reaction would be desired from an economical view point since additional work-up procedures can be avoided. Furthermore, the efficient sequestration of CO2, a major greenhouse gas, would also be highly desirable. In this work, the oxidative carboxylation of 1-decene is investigated using supported gold catalysts for the epoxidation step and tetrabutylammonium bromide in combination with zinc bromide for the cycloaddition of carbon dioxide in the second step. The compatibility of the catalysts for both steps is explored and a detailed study of catalyst deactivation using X-ray photoelectron spectroscopy and scanning electron microscopy is reported. Promising selectivity of the 1,2-decylene carbonate is observed using a one-pot two-step approach

The effect of ring size on the selective carboxylation of cycloalkene oxides

Carbon dioxide utilisation technology can contribute to the reduction of atmospheric CO2 levels both through its sequestration from flue gases and indirectly by relieving pressure on conventional feedstocks in chemical manufacturing. A promising approach is to employ CO2 to produce valuable cyclic carbonates (CCs) in reaction with suitable epoxides. This also has the advantage that carbon dioxide replaces toxic and hazardous reactants such as phosgene. In earlier work we have investigated the synthesis of epoxides from cycloalkenes using supported gold and gold–palladium nanoparticles as catalysts and oxygen from air as the oxidant under solvent free conditions. A strong dependence of epoxide selectivity on ring size was observed with C5 < C6 < C7 ≪ C8. In this study we extend this work to the investigation of cycloaddition of CO2 to different cycloalkene oxides with the ultimate aim of designing a process in which both epoxidation of an alkene and incorporation of CO2 could be achieved in a single process. However, we have found the opposite trend for the selectivity to carbonates: smaller ring cycloalkene oxides giving the highest carbonate selectivities while large rings do not yield CCs at all. The product distributions suggest that an alternative ring opening of the epoxides to yield alcohols and ketones is preferred under all the experimental conditions explored for larger ring systems. Additionally, the mechanism of the CC synthesis using a quaternary ammonium salt and ZnBr2 as the catalyst system was investigated using DFT methods. The results of the calculations support the experimental findings

Oxidative carboxylation of 1-Decene to 1,2-Decylene carbonate

© 2018 The Author(s) Cyclic carbonates are valuable chemicals for the chemical industry and thus, their efficient synthesis is essential. Commonly, cyclic carbonates are synthesised in a two-step process involving the epoxidation of an alkene and a subsequent carboxylation to the cyclic carbonate. To couple both steps into a direct oxidative carboxylation reaction would be desired from an economical view point since additional work-up procedures can be avoided. Furthermore, the efficient sequestration of CO 2 , a major greenhouse gas, would also be highly desirable. In this work, the oxidative carboxylation of 1-decene is investigated using supported gold catalysts for the epoxidation step and tetrabutylammonium bromide in combination with zinc bromide for the cycloaddition of carbon dioxide in the second step. The compatibility of the catalysts for both steps is explored and a detailed study of catalyst deactivation using X-ray photoelectron spectroscopy and scanning electron microscopy is reported. Promising selectivity of the 1,2-decylene carbonate is observed using a one-pot two-step approach

Solvent-free aerobic epoxidation of 1-decene using supported cobalt catalysts

In this study, active cobalt-based catalysts are reported for the solvent-free aerobic epoxidation of 1-decene as a non-noble metal, alternative to the conventionally used gold catalyst. No sacrificial reductant is applied and air is used as primary oxidant at ambient pressure. The influence of different radical initiators and the product distribution over time is investigated. Evidence for a reaction mechanism similar to the previously reported gold-catalysed aerobic epoxidation of 1-decene, is given. Furthermore, it is shown that the catalyst stability is influenced by the choice of the support