Papers by Keyword: Solid Acid Catalyst

Abstract: The effect of sulfonic agents on the performance of solid acid catalysts in esterification reactions of long-chain fatty acids has been studied. Herein, sulfonated activated carbon with sulfanilic acid (SAC-SA) and sulfuric acid (SAC-SO4) as a sulfonic agent were prepared and used for esterification reaction to convert long-chain fatty acids into methyl esters within 5 h at 65°C. The obtained SAC-SA has a higher surface area than SAC-SO4 of 1301.981 and 1182.096 m²/g, respectively. When SAC-SO4 and SAC-SA catalysts were applied to the esterification reaction, the FAME product conversion results were 74.47 and 46.98 %, respectively. The physical property of SAC-SO4 has more macropores size distribution than mesopores size based on the BJH method. Large pore size on the catalyst will support the diffusion of large organic molecules to improve catalytic ability. The pore size determines the performance of solid acid catalysts, especially in long-chain fatty acid reactants for biodiesel production.

Abstract: The increasing human population drives up energy consumption, particularly in the transportation and industrial sectors. Due to the limited and non-renewable availability of fossil fuels encourages various technological developments in the field of renewable energy, including biodiesel. Biodiesel is a biodegradable, non-toxic, and environmentally favorable renewable fuel. One of typical technique of biodiesel production is involving esterification reaction between fatty acids and alcohols by addition acid catalyst to enhance reaction rate. Solid acid catalysts are widely utilized for esterification reaction due to their ability to overcome the drawback of homogeneous catalysts that are difficult to separate. Solid acid catalysts can be produced from cellulose aerogel derived from coir fiber, which is then pyrolyzed into carbon aerogel and sulfonated through grafting process. Although sulfuric acid is a common sulfonic agent used in the catalyst sulfonation process, it has a lengthy grafting time. The addition of 4-aminobenzenesulfonic acid (sulfanilic acid) as a sulfonic agent alternative for sulfuric acid was investigated in this work. This paper reports the methods for preparing cellulose aerogel derived from coir fiber, pyrolysis of cellulose aerogel into carbon aerogel, sulfonation of carbon aerogel into solid acid catalyst, and application of solid acid catalyst for ethyl acetate production. The solid acid catalyst characterization tests include acid density, adsorption-desorption nitrogen analysis, SEM, and FTIR analysis. According to the adsorption-desorption nitrogen analysis results, the sulfonated carbon aerogel catalyst has a specific surface area of 220.29 g/m². Sulfonated carbon aerogel catalyst with acid density value of 2.81 mmol/g can be obtained at the mass ratio of sulfanilic acid to carbon substrates of 1:1 and pyrolysis temperature of 700°C. The esterification reaction was carried out at 80°C and reached a conversion of 31.37% after 4 h.

Abstract: Oil palm empty fruit bunch (EFB) is one of the palm biomass produced in abundance after oil extraction in Malaysia. This study was focused to utilize this waste biomass as a beneficial raw materials. EFB was used to prepare new solid acid catalyst for biodiesel production. EFB was converted into solid catalyst via direct impregnation method and it was used to catalyse esterification of oleic acid. Transition metal sulfide salt, Fe₂(SO₄)₃ was impregnated on EFB fibres. Effect of different calcination temperature was studied on the properties of catalyst. The result shows that Fe₂(SO₄)₃ based solid acid catalyst which calcined at 500°C exhibited the highest catalytic activity with 93.90% esterification rate was achieved. The morphology and surface chemistry and function group determination for the solid acid catalyst were characterized by SEM-EDX and FTIR.

Abstract: The studies based on morphological characterization to assess the effects of ultrasound irradiation on synthesis of solid acid catalysts. Three sets of catalyst formulation were synthesized by both wet impregnation method and ultrasound assisted methods with different wt. % of Ni loading on γ-Al₂O₃. The XRD, BET, TEM and FESEM techniques were used to characterize the nano-particles. Physicochemical characterization revealed that the synthesized catalysts particles using ultrasound irradiation were in nano size range (1-24.5 nm) with equal dispersion of metal oxide, high surface area with increase of metal loading and high phase purity than the catalysts synthesized conventional method. These catalysts were also found in various crystal structures like cubic, monoclinic and tetrahedral. The use of ultrasound irradiation has great significance over the wet impregnation method in relation to the rate of synthesis of nanocatalysts. The high surface area, high thermal stability and small particle size (up to 1 nm) are the basic elements for high activity of solid acid catalysts in hydrocracking and hydrodeoxygenation of various feedstock in petroleum industries.

Abstract: From literature it is depicted that the conversion of biomass to renewable chemicals and fuels is becoming a pivotal research topic for the last few decades. Cellulose is a rich biomass, which is formed by carbon dioxide and water by sunlight. However the efficient chemical conversion of cellulose is considered to be a challenge for the researchers because of its persistent property. A lot of research is carried out on heterogeneous catalyst, among the others, solid acid catalyst are recognized as the most attractive choice for the conversion of cellulose because they are tunable and durable in nature. In this article, an overview of the conversion of cellulose into platform chemicals using the solid acid catalyst is carried out.

Abstract: Sulfated Zirconia (SZ) has opened up a very interesting area for application predominantly as catalyst for various acid catalyzed organic syntheses and transformation reactions. Catalytic properties of SZ vary with methods of preparation. Lot of efforts is made to modify SZ to increase reactivity and stability of the catalyst. This review focuses on the individual synthesis routes to prepare nano-sized and –crystalline SZ, short discussion on its characterization and exhaustive survey on its utility in organic chemistry for the development of new synthetic methodologies, which provide simple direction having enormous practical significance. As can be realized, the nano-sized and –crystalline SZ as solid acid catalyst exhibits exceptionally better catalytic activity and selectivity for the synthesis of trisubstituted and tetrasubstituted imidazoles, acetyl salicylic acid, dypnone, esterification of acetic acid, caprylic acid and so on.

Abstract: In this work, we were study the selective synthesis of GME from oleic acid and glycerol using two types of solid heteropoly acid catalysts, namely silicotungstic acid bulk (STAB) and STA-silica sol gel (STA-SG). The performance and selectivity of STAB and STA-SG in the esterification reaction have been investigated and compared to the sulphuric acid (H₂SO₄) as conventional homogeneous catalyst. The catalysts were then characterized their physical and chemical properties using BET, XRD, TEM and XPS. XPS analyses were shown a significant formation of W-O-Si, W-O-W and Si-O-Si bonding in STA-SG compared to that in STAB. The main spectra of O1s (90.74 %, 531.5 eV) followed by other O1s peak (9.26 %, 532.8 eV) were due to the presence of W-O-W and W-O-Si bonds, respectively. The STA-SG catalyst was found to be the more environmentally benign solid acid catalyst for the esterification reaction between oleic acid and glycerol due to its lower toxicity in terms of the relatively lower pH value (pH 3.7) than the STAB (pH 2.8). In addition, the ease of separation for STA-SG catalyst was attributed to its insoluble state in the product phase. The esterification products were then analysed by FTIR and HPLC. Both the H₂SO₄ and the STAB gave high conversion of 100 % and 98 %, but at a lower selectivity of GME with 81.6% and 89.9%, respectively. On the contrary, the STA-SG enabled a conversion of 94 %, but with a significantly higher GME selectivity of 95 % rendering it the more efficient solid acid catalyst.

Abstract: A low-cost solid acid catalyst derived from kaolin and sulphuric acid, was utilized for the removal of thiophene from coking benzene. The effect of various factors, such as sintering temperature, sintering time, acid treatment temperature, acid treatment time and the acid content, were investigated to improve the catalytic activity in the removal of thiophene, estimated by UV-vis spectrum. The results showed that kaolin calcined at 973 K for 6 h and refluxed for 3 h in 3 mol/L H₂SO₄ at 363 K displayed higher thiophene removal efficiency. The highest one was up to 93.05%. In that process, acetic anhydride was appended in order to improve the efficiency of desulfurization.

Abstract: Solid acid catalyst has high catalytic esterification activity but with a free acid excess problem. In this paper, washing pretreatments were adopted in the catalyst preparation processes and their influences on catalytic activity and residual free acid amount were investigated. Residual free acid amount can be reduced by 33% with both washing before calcinations and washing after calcinations pretreatments. But their influences on catalyst activities were different. Washing before calcinations pretreatment reduced the catalytic activity from 80.29% to 57.72% while the other washing pretreatment had little influence on the catalyst activity. In order to describe the influence mechanism of washing pretreatments, catalysts were characterized by FT-IR and XRD. Finally, typical compounds in bio-oil were selected to form a bio-oil model compounds system. The catalyst pretreated by washing after calcinations was used on the esterification research of this bio-oil model system. The volume ratio of propanol to bio-oil model compound was 3:1. The reaction temperature was 90 °C and the amount of catalyst was 2wt% of total liquid mass. Combined with the GC-MS qualitative and quantitative results, carboxylic acids, such as formic acid, acetic acid, propionic acid were converted to esters effectively.

Abstract: Glycerol monooleate (GMO) as an esterification product of oleic acid and glycerol is highly potential as an anti-friction substance in the engine lubricant. The purpose of this work is to study the synthesis, characterization and catalytic performance of solid heteropoly acid catalysts, namely silicotungstic acid bulk (STAB) and STA-silica sol gel (STA-SG). The activity and selectivity of STAB and STA-SG in the esterification reaction have been investigated and compared to the homogeneous catalyst i.e. sulphuric acid (H₂SO₄). The synthesized catalysts were characterized by BET, XRD, TEM, XPS and TPD-NH₃. BET analyses shown that the STA-SG catalyst is very high in surface area compared to STAB of 460.11 m²/g and 0.98 m²/g, respectively. From the XPS analyses, there was a significant formation of W-O-Si, W-O-W and Si-O-Si bonding in STA-SG compared to that in STAB. The main species of O1s (90.74 %, 531.5 eV) followed by other O1s peak (9.26 %, 532.8 eV) were due to the presence of W-O-W and W-O-Si bonds, respectively. In addition, the ease of separation for STA-SG catalyst was attributed to its insoluble state in the product phase. The esterification products were then analysed by FTIR and HPLC. Both the H₂SO₄ and the STAB gave high conversion of 100% and 98%, while lower selectivity of GME with 81.6% and 89.9%, respectively. On the contrary, the STA-SG enabled a conversion of 94%, while significantly higher GME selectivity of 95% rendering it the more efficient solid acid catalyst.