40 documents found, page 1 of 4
Acetalization of glycerol with hexanal in the presence of SBA-15 with sulfonic ...
Castanheiro, José; Vital, J; Fonseca, Isabel; Ramos, AnaAcetalization of glycerol with hexanal was studied over sulfonic acid-functionalized mesoporous silica (SBA-15), at 70 ºC. The product obtained were (2-pentyl-1,3-dioxolan-4-yl)methanol and 2-pentyl-1,3-dioxan-5-ol. Materials with different amounts of sulfonic acid groups were prepared. The support functionalization was achieved by the introduction of 3-(mercaptopropyl)trimethoxysilane onto the surface of these...
Tungstophosphoric acid immobilised in SBA-15 as an efficient heterogeneous acid...
Castanheiro, J; Fonseca, I; Ramos, A; Vital, JAlkoxylation of α−pinene, β−pinene and limonene was performed in the presence of SBA-15-occluded tungstophosphoric acid (HPW). The HPW was immobilised in SBA-15 using the sol-gel method. The catalysts were characterised by N2 adsorption, FT-IR, Raman spectroscopy, X-Ray diffraction, ICP-AES and TEM. A series of catalysts with different heteropolyacid loadings ranging from 1.8 to 19.3 wt. % were prepared. PW4-SB...
Mesoporous Carbon as effective and sustainable catalyst for fine chemistry
Castanheiro, J; Matos, I; Bernardo, M; Neves, P; Vital, J; Fonseca, IIt is well known that activated carbon with welldeveloped porosity is a promising material that have been used for several applications, from adsorption to catalysis. Research in this field has intensified in recent years, looking for new and improved characteristics and applications. Our research group, recently renamed Materials for Adsorption and Catalysis group (MAC) in LAQV-REQUIMTE, has also devoted many ...
New method for the immobilization of nitroxyl radical on mesoporous silica
Castanheiro, JE; Machado, A; Casimiro, M; Ferreira, L; Ramos, A; Vital, J; Fonseca, IThis work reports the covalent attachment of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4- hydroxy-TEMPO) on the mesoporous silicas MCM-41 and SBA-15, by using ,4-diisocyanatobutane as a binder. The catalysts were characterized by nitrogen adsorption/desorption, XRD, TEM, TGA, DSC and FTIR spectroscopy. Catalytic tests were performed on the liquid phase oxidation of benzyl alcohol and the secondary alcohol ...
Methoxylation of a-pinene over mesoporous carbons and microporous
Castanheiro, J; Matos, I; Silva, M; Ruiz-Rosas, R; Vital, J; Rodríguez-Mirasol, J; Cordero, T; Fonseca, IA biomass derived carbon, a commercial microporous carbon and a xerogel mesoporous carbon catalysts were used in the study of a-pinene methoxilation reaction and the influence of textural and physical–chemical properties of the carbons was evaluated. Biomass carbon presented the higher activity, whereas the commercial one is the less active in the conditions studied. The main product of the reaction was a-terpi...
Alkoxylation of camphene over silica-occluded tungstophosphoric acid
Castanheiro, J; Caiado, M; Machado, A; Santos, R; Matos, I; Fonseca, I; Ramos, A; Valente, A; Vital, JSilica-occluded tungstophosphoric acid (PW-Ssg) was used as an efficient, nvironmentally friendly heterogeneous catalyst for the liquid-phase alkoxylation of camphene into their more valuable alkyl isobornyl ether, which is used as perfume and cosmetic products, in the pharmaceutical industry, as well as in the food industry. The lkoxylation of camphene with C1–C4 alcohols (methanol, ethanol, 1- propanol, 2-pro...
Esterification of free fatty acids over chitosan with sulfonic acid groups
Caetano, CS; Caiado, M; Ramos, A; Fonseca, I; Vital, J; Castanheiro, JChitosan, which is an abundant biopolymer, with sulfonic acid groups was used as an efficient, environmentally friendly heterogeneous catalyst for the esterification of free fatty acids with methanol into their more fatty acid methyl ester. Sulfonic acid catalysts supported on chitosan have been studied in the esterification of palmitic acid with methanol at 60 C. The sulfonic acid groups were introduced onto c...
Mesoporous carbon as an efficient catalyst for alcoholysis and aminolysis of ep...
Matos, I; Neves, P; Castanheiro, J; Perez-Mayoral, E; Martin-Aranda, R; Duran-Valle, C; Vital, J; Botelho do Rego, A; Fonseca, IThe ring opening reaction of epoxides by alcohols and amines using mesoporous activated carbon as efficient and environmentally friendly heterogeneous catalyst is reported. Carbon xerogels were synthesized by polymerization of resorcinol and formaldehyde. The surface of the activated carbon was oxidized in liquid phase with HNO3 and then functionalized with H2SO4. Chemical and textural characterization by eleme...
Hydrolysis of sucrose over composite catalysts
Pito, D; Fonseca, I; Ramos, A; Vital, J; Castanheiro, JThe hydrolysis of sucrose into glucose and fructose was carried out over composite catalysts at 80 ◦C. These catalysts consisted of USY and Beta zeolites dispersed in polymeric matrices (PDMS and PVA). The swelling degree of polymers increased with the amount of zeolite immobilised in PDMS and PVA. This result can be explained by the increase in the polymeric matrix channelling. Additionally, the effective diff...
SBA-15 with sulfonic acid groups as a Green Catalyst for the acetoxylation of α...
Machado, J; Castanheiro, J; Matos, I; Ramos, A; Vital, J; Fonseca, IThe acetoxylation of a-pinene was carried out over SBA-15 with sulfonic acid groups. The products of acetoxylation of a-pinene are acetates (a-terpinyl acetate, bornyl acetate and b-fenchyl acetate) and hydrocarbons (camphene, tricyclene, limonene, g-terpinene, terpinolene and a-terpinene). Catalysts with different amount of sulfonic acid groups were prepared. It was observed that the activity increases with in...