Heterogeneous Superacidic Catalyst for Friedel-Crafts Alkylation
Location
Culp Ballroom
Start Date
4-7-2022 9:00 AM
End Date
4-7-2022 12:00 PM
Poster Number
100
Faculty Sponsor’s Department
Chemistry
Name of Project's Faculty Sponsor
Aleksey Vasiliev
Competition Type
Competitive
Type
Poster Presentation
Project's Category
Chemical Sciences
Abstract or Artist's Statement
Long-chain alkylbenzenes are industrially synthesized precursors to commercial surfactants such as laundry detergent. The process of benzene alkylation currently utilizes homogeneous acidic catalysts (HF, AlCl3, etc.), which cause a multitude of problems such as production of toxic waste, hazards to workers, and corrosion of expensive industrial equipment. These problems can be avoided by the use of heterogeneous highly acidic catalysts. Solid catalysts do not corrode equipment and are relatively simple to remove from the post-reaction mixture. Phosphotungstic acid (PTA) supported on silica gel could be a possible catalyst due to its high acidity with an estimated pKa ≈ -13. However, it is soluble in many solvents and can be leached from silica gel during the process. The objective of this research is to obtain a superacidic stable heterogeneous catalyst containing covalently immobilized PTA, and evaluate its activity and stability in the alkylation of benzene by long-chain alkenes. The catalyst PTA/SiO2 was prepared via the sol-gel method by co-condensation of PTA with tetraethoxysilane in acidic media. Surfactant Pluronic P123 was used as a template to form porous structure. Then the catalyst was granulated to prevent caking of the powder during reaction. For granulation, the powder PTA/SiO2 was mixed with aluminum oxide (an inert adhesive agent) and pressured at 7 t to make tablets. The tablets were converted to granules of 1-2 mm diameter and calcined at 400 °C to remove moisture. FT-IR spectra confirmed the presence of PTA in the obtained material. Analysis by atomic absorption spectroscopy showed PTA contents of 0.027 mmol/g. The catalyst was mesoporous with BET surface area of 168 m2/g and mean particle size of 856 nm. The reaction of alkylation of benzene by octene-1 and decene-1 was carried out in a fixed bed flow reactor at 200-250 °C where mixtures of benzene and an alkene flowed through the catalyst with constant rate. Products were collected and analyzed on a GC chromatograph. The catalyst demonstrated good catalytic activity at temperatures above 200 °C. In all experiments mixtures of isomeric alkylbenzenes were obtained with 2-phenylalkanes as main products. Decreasing of flow rate and ratio alkene:benzene favored conversion of alkenes. Characterization of the catalyst after the reaction showed little changes in porosity and particle size. No leaching of PTA was observed. However, carbon deposits were found on the catalyst that requires regeneration before next use in catalysis.
Heterogeneous Superacidic Catalyst for Friedel-Crafts Alkylation
Culp Ballroom
Long-chain alkylbenzenes are industrially synthesized precursors to commercial surfactants such as laundry detergent. The process of benzene alkylation currently utilizes homogeneous acidic catalysts (HF, AlCl3, etc.), which cause a multitude of problems such as production of toxic waste, hazards to workers, and corrosion of expensive industrial equipment. These problems can be avoided by the use of heterogeneous highly acidic catalysts. Solid catalysts do not corrode equipment and are relatively simple to remove from the post-reaction mixture. Phosphotungstic acid (PTA) supported on silica gel could be a possible catalyst due to its high acidity with an estimated pKa ≈ -13. However, it is soluble in many solvents and can be leached from silica gel during the process. The objective of this research is to obtain a superacidic stable heterogeneous catalyst containing covalently immobilized PTA, and evaluate its activity and stability in the alkylation of benzene by long-chain alkenes. The catalyst PTA/SiO2 was prepared via the sol-gel method by co-condensation of PTA with tetraethoxysilane in acidic media. Surfactant Pluronic P123 was used as a template to form porous structure. Then the catalyst was granulated to prevent caking of the powder during reaction. For granulation, the powder PTA/SiO2 was mixed with aluminum oxide (an inert adhesive agent) and pressured at 7 t to make tablets. The tablets were converted to granules of 1-2 mm diameter and calcined at 400 °C to remove moisture. FT-IR spectra confirmed the presence of PTA in the obtained material. Analysis by atomic absorption spectroscopy showed PTA contents of 0.027 mmol/g. The catalyst was mesoporous with BET surface area of 168 m2/g and mean particle size of 856 nm. The reaction of alkylation of benzene by octene-1 and decene-1 was carried out in a fixed bed flow reactor at 200-250 °C where mixtures of benzene and an alkene flowed through the catalyst with constant rate. Products were collected and analyzed on a GC chromatograph. The catalyst demonstrated good catalytic activity at temperatures above 200 °C. In all experiments mixtures of isomeric alkylbenzenes were obtained with 2-phenylalkanes as main products. Decreasing of flow rate and ratio alkene:benzene favored conversion of alkenes. Characterization of the catalyst after the reaction showed little changes in porosity and particle size. No leaching of PTA was observed. However, carbon deposits were found on the catalyst that requires regeneration before next use in catalysis.