57 documents found, page 1 of 6
Acetoxylation of pinene over activated carbons
Castanheiro, JPinene is renewable resources that is used in the pharmaceutical, cosmetic and food industries. The acetoxylation of pinene is synthetic methods to produce compounds with high commercial value. Traditionally, this reaction is carried out using homogenous catalysts, like sulfuric acid. However, due to the environmental problems, the homogeneous catalysts have been replaced by heterogenous catalyst. The acetoxyla...
Acetalization of glycerol over silicotungstic acid supported in silica
Castanheiro, J; Pinto, A; Lopes, ME; Santos, FIThe acetalization of glycerol with butanal was carried out in the presence of silicotungstic acid (HSiW) immobilized in silica, by sol-gel technique, at 70ºC. The products of glycerol acetalization with butanal were (Z + E)-(2-propyl-1,3-dioxolan-4-yl) methanol and (Z + E)-2-propyl-1,3-dioxan-5-ol. Catalysts with different amount of HSiW were prepared. The catalysts were characterized by FTIR, XRD, ICP and N2 a...
Zeolites as heterogeneous catalysts to valorization of monoterpenes into flavor...
Castanheiro, J; Pinto, AP; Lopes, MEZeolites are aluminosilicate with high surface area and uniform microporosity. Monoterpenes are renewable resources. The catalytic transformation of terpenes are synthetic routes to valuable compounds. Strong homogeneous acid catalysts have been used in the acid reactions. Due to enviromental problems, homogeneous catalysts have been replaced by heterogeneous catalysts, which are reusable and easy to be separat...
Green processes to biofuel additives production from glycerol over heterogeneou...
Castanheiro, JThe glycerol is a by-product in the biodiesel production. For every 9 kg of biodiesel produced, about 1 kg of a crude glycerol is formed. Due to the increase of biodiesel production, an increase of glycerol production has been observed. The glycerol can be converted into solketal, by acetalization reaction with acetone, which can be used as fuel additive. Usually, homogeneous acid catalysts have been used in th...
METHOXYLATION OF LIMONENE OVER SULFONATED STARCH
Castanheiro, J; Cruz, JMethoxylation of limonene was carried out in the presence of sulfonated starch. The main product of methoxylation of limonene is alpha-terpinyl methyl ether. Catalysts with different amounts of sulfonic acid groups were prepared. The catalytic activity increased with the amount of sulfonic acid groups in starch. All catalysts show high selectivity to alpha-terpinyl methyl ether (about 80%). Catalytic stability ...
SBA-15 with sulfonic acid groups as acid solid catalyst for glycerol conversion...
Henriques, P; Castanheiro, JAcetalization of glycerol with pentanal was carried out in the presence of SBA-15 with sulfonic acid groups. Materials with different amounts of sulfonic acid groups were prepared. It was observed that the catalytic activity increases with the amount of sulfonic acid groups on SBA-15 until a maximum. With high amount of sulfonic groups, a decrease of activity is observed. All catalysts show high selectivity to ...
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...
Green esterification: the synthesis of aromas in the presence of an acid resin.
Castanheiro, J; Teixeira, A; Pereira, ASynthesis of aromas by esterification of a carboxylic acid (acetic and butanoic acid) with an alcohol (methanol, ethanol, pentanol) has been carried out in the presence of strong homogeneous acid catalysts (e.g. sulphuric acid, hydrochloric acid). However, these mineral acids are corrosive and they are usually neutralised after reaction (with consequent salt formation). In order to overcome the above-mentioned ...
Biofuel Additives: Conversion of Glycerol with Benzyl Alcohol over SBA‐15 with ...
Castanheiro, J; canhão, PThe etherification of glycerol with benzyl alcohol was carried out over mesostructured silica, SBA‐15, with sulfonic acid groups. The products of glycerol etherification are ethers (glycerol mono‐ether, glycerol di‐ether and tri‐glycerol ether). It was prepared with different catalysts, consisting of SBA‐15 with different amounts of sulfonic groups (SBA‐15, [SO3H]1‐SBA‐15, [SO3H]2‐SBA‐15, and [SO3H]3‐SBA‐15). I...
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 ...