ABSTRACT
In this study, two types of catalysts were prepared by the combination of gemini quaternary ammonium salt with two distinct species of phosphotungstic acid. Catalysts prepared by the Wells-Dawson type of phosphotungstic acid and Keggin-type phosphotungstic acid both exhibited dual-phase catalytic behavior, demonstrating both heterogeneous and homogeneous catalytic activities. In comparison to the catalyst prepared by the Keggin-type phosphotungstic acid, due to the higher size of Wells-Dawson type of phosphotungstic acid, hydrogen bonding could not effectively affect the catalyst prepared by H6P2W18O62. Subsequently, the influential factors on the catalytic reaction were investigated. Through the utilization of techniques such as XPS, FT-IR, Raman spectra and other characterization methods, two distinct structure and reaction mechanisms for these catalysts were elucidated under the influence of hydrogen bonding.
ABSTRACT
In this study, we have developed a novel catalyst synthesized by phosphotungstic acid and a gemini quaternary ammonium cation salt. This quaternary ammonium salt not only reduces the interfacial tension between olefins and hydrogen peroxide but also forms a notably stable structure with phosphotungstic acid. Dodecene was successfully epoxidized to epoxy dodecane with a selectivity of 82.9 %. The impact of initial conditions was systematically investigated such as molar ratio, temperature, reaction time, and catalyst dosage on the catalytic performance. Characterization of the catalyst morphology was performed by SEM, TEM and SAXS. Raman spectra, FT-IR and XPS spectra were employed to perform the catalyst transformation during the epoxidation reaction. This catalytic mechanism study could provide the industrial application in the epoxidation of long-chain olefins.
ABSTRACT
This study aims to report a relatively rare entity-intramedullary tuberculum of cervical spine-and describe its management and some key learning points. Intramedullary tuberculomas are rare entities. Intramedullary tuberculoma is most commonly found in the thoracic cord of a patient and is rarely seen in the cervical cord. We present an intramedullary cervical tuberculoma in a 21-year-old patient with finding of spinal cord compression. All 4 limbs were spastic, with grade 1 power on the right side and grade 3 power on the left side. Sensory deficit was found below the C6 level. Magnetic resonance imaging showed an intramedullary lesion at the C5 to C6 levels. Intramedullary tuberculoma was diagnosed based on clinical symptoms, physical examination, previous history, and magnetic resonance imaging. A C5 to C7 laminectomy was performed. Intramedullary tuberculoma was resected by microsurgery. One year after the surgery, strength returned to normal grade 5. Excellent clinical outcome was obtained with a combination of both medical and surgical treatments. Intramedullary cervical tuberculoma should be removed without delay to eliminate any mass effect on the neurons as soon as possible.
