Conversion Of Propionic Acid Research Articles

Surface acidity and catalytic activity of aged /SnO2 catalyst supported with WO3

Abstract New solid acid was prepared by loading of aged 15 wt.% SO 4 2 - /SnO2 catalyst with 15 and 35 wt.% WO3. The catalysts were calcined at 400 and 650 °C. The surface areas of the catalysts were determined by the data of N2 adsorption at −196 °C. The surface acidity was measured potentiometricaly using n-butylamine solution in acetonitrile. The types of acidic sites were determined by FT-IR spectra of adsorbed pyridine. The catalytic activities of the catalysts were tested toward esterification of propionic acid (PA) with n-butanol (B). The SBET values of the ISS were decreased with an increase in the calcination temperature, whereas, the SBET of the loaded catalysts was maximum at 400 °C. The results reveal that the used catalysts possess very strong acid sites and contain both Bronsted and Lewis acidic sites. The acid strength, total surface acidity and the conversion of PA were maxima for 400 °C products. The effect of the reaction parameters was also studied, and shows that the PA conversion was increased with an increase in the reaction temperature and the catalyst weight. The reactant molar ratio shows a maximum conversion at PA:B = 1:2. The kinetics study indicates that the catalytic esterification of PA with B obey first order kinetics equation. The results were compared with previously prepared non-aged catalysts. The comparison reveals that the aging of the support would causes a decrease in SBET, acid strength and catalytic activity, but increases the acid amount of the catalyst.

Some physico-chemical properties and catalytic activity of sulfate ion supported on WO3/SnO2 catalyst

Solid acid catalyst 15wt%WO3/SnO2 was synthesized and loaded with 15wt%SO4. The obtained catalyst was calcined at 400, 500, 650 and 800°C. The prepared catalysts were characterized by TG-DTA, XRD, FTIR and N2 adsorption at −196°C. The surface acidity was measured by non aqueous potentiometric titration and FT-IR spectra of chemisorbed pyridine. The catalytic performance was evaluated on the esterification of propionic acid with n-butanol in liquid phase. The TG-DTA analysis shows that the decomposition of sulfate species occurred at >500°C. XRD measurements showed that WO3 dispersed completely on the surface of SnO2 and that the sulfating of WO3/SnO2 tends to hinder the crystallization of SnO2. The specific surface area, total pore volume and micropore volume are increased with increasing thermal treatment up to 500°C, and then decreased gradually with a further increase in calcination temperature. The prepared catalysts possess very strong acid sites and contain both Brønsted and Lewis acid sites. The total surface acidity decreased with raising of the calcination temperature. The highest conversion of propionic acid was for 400°C product, and decreased with an increase in calcination temperature. The effect of the reaction parameters, i.e., time of reaction, reaction temperature, and reactant molar ratio and the weight of the catalyst were also studied. The reaction obeys the second order kinetic equation with respect to propionic acid concentration. Brønsted and Lewis acid sites appeared to be needed for catalytic activity in n-butyl propionate formation.

Deoxygenation of propionic acid on heteropoly acid and bifunctional metal-loaded heteropoly acid catalysts: Reaction pathways and turnover rates

Reaction pathways of the gas-phase deoxygenation of propionic acid in the presence of heteropoly acid and bifunctional metal-loaded heteropoly acid catalysts were investigated in a fixed-bed reactor at 250–400°C in flowing H2 or N2. Silica-supported H3PW12O40 (HPW) and bulk acidic salt Cs2.5H0.5PW12O40 (CsPW), both in H2 and in N2, exhibited ketonisation activity between 250 and 300°C to yield 3-pentanone, CsPW being more selective than HPW. At 400°C, HPW and CsPW were active for decarbonylation and decarboxylation of propionic acid to yield ethene and ethane, respectively. Loading Pd or Pt onto CsPW greatly enhanced decarbonylation in flowing H2 but had little effect in N2. Similar performance exhibited Pd/SiO2 and Pt/SiO2, giving almost 100% selectivity to ethene in H2. These results are consistent with hydrodeoxygenation of propionic acid on Pd and Pt, suggesting that hydrogenolysis of CC bond plays essential role. In contrast to the Pd and Pt catalysts, Cu catalysts, Cu/CsPW and Cu/SiO2, were both active in hydrogenation of CO bond to yield propanal and 1-propanol. Turnover rates of propionic acid conversion on metal catalysts followed the order Pd>Pt>Cu for both CsPW-supported and silica-supported metal catalysts.

Synthesis, characterization and catalytic properties of sulfonic acid functionalized magnetic-poly(divinylbenzene-4-vinylpyridine) for esterification of propionic acid with methanol

The magnetic-poly(divinylbenzene-4-vinylpyridine) [m-poly(DVB-4VP)] microbeads (average diameter: 180–212 μm) were synthesized by copolymerizing of divinylbenzene (DVB) with 4-vinylpyridine (4VP) and by mixing this copolymer with Fe 3O 4 nanoparticles. The resultant material was characterized by N 2 adsorption/desorption, ESR, elemental analysis, scanning electron microscope (SEM) and swelling studies. After functionalized with sulfonic acid, m-poly(DVB-4VP-SO 3H) was characterized by FT-IR and TGA analysis. The results showed that both of Fe 3O 4 and –SO 3H are bonded to the polymer successfully. N 2 adsorption/desorption isotherms of synthesized samples had the hysteresis behaviour associated with mesoporous materials (pore diameter: 3.73 nm). Sulfonic acid functionalized mesoporous m-poly(DVB-4VP-SO 3H) has been demonstrated to have higher reactivity than commercially available solid acid catalysts for the conversion of propionic acid to methyl ester. The apparent activation energy was found to be 38.5 kJ mol −1 for m-poly(DVB-4VP-20%SO 3H). The catalyst showed negligible loss of activity after four repetitive cycles.

Heterogeneous Catalysed Esterification of Propionic Acid with n-Amyl Alcohol over a Microporous Cation-exchange Resin Dowex 50Wx4

Abstract Kinetics of heterogeneous catalysed esterification of propionic acid with n-amyl alcohol was studied with a microporous cation-exchange resin catalyst, Dowex 50Wx4, in a stirred batch reactor to synthesise amyl propionate. Effects of various parameters such as speed of agitation, catalyst loading, and reaction temperature on reaction rate were investigated. The equilibrium conversion of propionic acid increased with in catalyst loading and reaction temperature. Stirrer speed had virtually no effect on the reaction rate under the experimental conditions. The apparent activation energy was found to be 43.167 kJmol−1 for the formation of amyl propionate and the equilibrium constant, which is independent of temperature ranging from 318 to 348 K, was found to be 4.05. It was also observed that the initial reaction rate decreased with water concentrations and increased with that of acid and increased with that of alcohol linearly. The reaction was found to occur between an adsorbed acid molecule and a molecule of alcohol in the bulk and it was concluded that the reaction mechanism can be represented by Eley-Rideal model.

Kinetics of Catalytic Esterification of Propionic Acid with Methanol over Amberlyst 36

The kinetic behavior of heterogeneous esterification of propionic acid with methanol over an acidic cation-exchange resin, Amberlyst 36, was investigated by using a fixed-bed reactor. The kinetic experiments were conducted at temperatures from 313.15 to 333.15 K, and molar ratios of methanol to propionic acid in the feed stream from 1 to 5. The reaction rate was found to increase with increasing temperature, but the equilibrium conversions of propionic acid changed only slightly over the entire range of reaction temperatures indicating that the heat effect of this reaction is minor. It was also found that the equilibrium conversion of propionic acid increases with the molar ratios of feed increasing from 1 to 5. The relative adsorption strength between any two reacting species was determined from the results of binary adsorption experiments. The magnitude of adsorption strengths follows the order of water > methyl propionate > propionic acid > methanol. The kinetic data were correlated with the ideal-quas...

Steady state and dynamic simulation of a hybrid reactive separation process

AbstractModelling and simulation of hybrid reactive separation system in steady state and in dynamic regime was carried out. The investigated hybrid process consisted of a reactive distillation column and a pervaporation membrane located in the distillate stream to remove water from the process. Heterogeneously catalysed esterification of propionic acid with propan-1-ol to propyl propionate and water was chosen as the model chemical reaction. Esterification reactions are a typical example of equilibrium-limited reactions producing water as a by-product. Using just a pervaporation membrane brings the biggest benefit in increasing the yield of one of the reactants due to the removal of water. To study reactive separation processes, a model of the hybrid system in steady state and in dynamic regime was developed. Steady state behaviour of the model was studied for different hybrid system configurations. The effect of catalyst amount doubling was also investigated. Dynamic behaviour of the system during the step changes of propionic acid feed flow rate and during the membrane module failure was investigated. For this reason, the conversion of propionic acid, purity of the product stream, mole fraction of water, and the temperature in three different parts of the reactive distillation column were monitored.

Kinetics of catalytic esterification of propionic acid with different alcohols over Amberlyst 15

AbstractThe kinetics of the esterification reaction between propionic acid and methanol, ethanol, and 1‐butanol over the ion exchange resin, Amberlyst 15, was investigated. Experiments were conducted using a fixed‐bed plug flow reactor over the temperature range of 298–328 K. Acid to alcohol molar ratios of 3:1, 1:1, and 1:3 were employed. For each esterification system, the equilibrium conversion of propionic acid was found to increase with increasing reaction temperature. Several kinetic models were tested to correlate the collected data under kinetically controlled conditions; the pseudo‐homogeneous (P‐H), Eley–Rideal (E–R), Langmuir–Hinshelwood (L–H), and Pöpken (P‐P) models. In all cases, the activity coefficients were estimated using the UNIFAC model to account for the nonideal thermodynamic behavior of the reactants and products. The P‐P model was found to best represent the kinetic data of the investigated esterification systems with a total average error of less than 3%. The increase of alcohol chain length had a negative impact on the conversion of propionic acid due to steric hindrance. The activation energy of the esterification reaction is influenced by the chain length of the alcohol used. The adsorption equilibrium constants estimated by the P‐P model and the solubility parameters reported by AICHE DIPPER® followed the same trend; ester < acid < alcohol < water. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 432–448, 2009

Synthesis of esters: Development of the rate expression for the Dowex 50 Wx8-400 catalyzed esterification of propionic acid with 1-propanol

The kinetics of the esterification reaction of propionic acid with 1-propanol over the ion-exchange resin Dowex 50Wx8-400 has been studied in this investigation. Kinetic experiments were conducted using a 1 L Lab-Max system at a stirrer speed of 900 rpm over a temperature range of 303.15 –333.15 K. The catalyst loading was varied from 10 to 60 g dry cat/L and acid to alcohol molar ratios of 1:1, 1:2, 1:4, 2:1 and 4:1 were employed. The equilibrium constants for this reaction were determined in separate experiments at 303.15, 313.15 and 323.15 K. The values were equal to 33.18, 30.62 and 28.37, respectively, with a standard enthalpy change of reaction of 6.4 kJ/mol. These values show the reaction to be mildly exothermic. It was found that both external and internal diffusion limitations did not affect the overall reaction rate. The conversion of propionic acid increased with increasing temperature and catalyst loading and decreased with increasing initial mole fraction of acid. The increase in chain length of acid or alcohol or branching had a retarding effect on the conversion. Several kinetic models were tested to correlate the kinetic data, the pseudo-homogeneous (P-H) model, the Eley–Rideal (E–R) model, the Langmuir–Hinshelwood (L–H) model, the modified Eley–Rideal (M-E–R) model and the modified Langmuir–Hinshelwood (M-L–H) model. In all models, the activity coefficients were estimated using UNIFAC to account for the non-ideal thermodynamic behavior of reactants and products. A correction factor for the resin affinity for water ( α ) was used in both M-E–R and M-L–H models. The above models predicted the kinetic behavior of the studied system with an overall error ranging from 1.65% to 13.32%. Water was found to be more strongly adsorbed than other species present in the system. The M-E–R model between adsorbed 1-propanol and non-adsorbed propionic acid which assumes surface reaction as the rate controlling step, with α equal to 2, was found to be the best model with the least overall error (1.65%). The activation energy for the esterification was estimated to be 67.3 kJ/mol by this model.

Kinetics of esterification of propionic acid with n-amyl alcohol in the presence of cation exchange resins

Esterifications of n-amyl alcohol with propionic acid catalyzed by macroporous (Amberlyst-15) and microporous (Dowex 50 W and Amberlite IR-120) polymeric ion-exchange resins were carried out between 333–348 K. When these catalysts were used as commercially available, Amberlyst-15 was observed to be the most effective catalyst with respect to rate constants, but after drying it became the less effective one. The reaction rate increased with increase in catalyst concentration and reaction temperature. Stirrer speed and different mesh sizes had virtually no effect on the rate under the experimental conditions. The effect of divinylbenzene content was examined for the microporous resin Dowex 50W, and the results showed that the propionic acid conversion decreased as the divinylbenzene content was increased. The rate data were correlated with a second-order homogeneous reaction model. The apparent activation energies, reaction enthalpies and entropy values were calculated for each catalyst. Reaction monitoring is simple and fast by volumetric method and the reproducibility of this method was the order of ± %2.54.

No lactic acid absorbed from the caecum and rumen of sheep

A comparative study of the absorption of lactic acid, volatile fatty acids (VFA), glucose, and ammonia from caecal and rumen pouches was undertaken in anaesthetised sheep. Test solutions varying in pH, osmolarity, lactic acid concentration, and with fixed concentrations of VFA, ammonia, and glucose (100, 7, and 4 mmol/L, respectively) were introduced into the clean, surgically sealed pouches. Studies were undertaken in 9 sheep, each with 2 pouches in the caecum and 1 in the rumen. Samples were taken at 10-min intervals for 50 min to determine rate of absorption. Neither L-lactic acid nor D-lactic acid was absorbed from the caecal or rumen pouch and there was a slight increase in both isomers of lactic acid (0·39%/min of L-lactic acid and 0·24%/min of D-lactic acid averaged for the caecum and rumen values) which was presumably due to conversion of propionic acid and tissue metabolism during the experiment. The rate of increase per unit area in the caecum (0·06 µmol/cm2·min) was much greater than that in the rumen (0·015 µmol/cm2·min) based on the average of L- and D-lactic acid. The absorption rates of acetic, propionic, and butyric acids from the caecum (0·49, 0·17, and 0·08 µmol/cm2 ·min, respectively) and the rumen (0·48, 0·16, and 0·08 µmol/cm2· min, respectively), based on absorptive surface area of the pouches, were very similar. Glucose was apparently absorbed from rumen pouches (0·18 µmol/cm2 ·min), but not from caecal pouches (-0·01 µmol/cm2·min). The mean absorption rate of ammonia from caecal pouches (0·60 µg N/cm2·min) was 2·5 times greater than that from rumen pouches (0·24 µg N/cm2·min) (P < 0·0001). The mean absorption rate of ammonia for the caecal and rumen pouches was about 2·6 times higher at pH 6·5 (0·99%/min) than that at pH 4·5 (0·38%/min) (P < 0·0001) at the same osmolarity and lactic acid concentration. A decrease in pH, osmotic pressure, or the concentration of lactic acid resulted in corresponding increases in the absorption of VFA.

Propionic acid fermentation from glycerol: comparison with conventional substrates

Instead of the conventional carbon sources used for propionic acid biosynthesis, the utilization of glycerol is considered here, since the metabolic pathway involved in the conversion of glycerol to propionic acid is redox-neutral and energetic. Three strains, Propionibacterium acidipropionici, Propionibacterium acnes and Clostridium propionicum were tested for their ability to convert glycerol to propionic acid during batch fermentation with initially 20 g/l glycerol. P. acidipropionici showed higher efficiency in terms of fermentation time and conversion yield than did the other strains. The fermentation profile of this bacterium consisted in propionic acid as the major product (0.844 mol/mol), and in minimal by-products: succinic (0.055 mol/mol), acetic (0.023 mol/mol) and formic (0.020 mol/mol) acids and n-propanol (0.036 mol/mol). The overall propionic acid productivity was 0.18 g l−1h−1. A comparative study with glucose and lactic acid as carbon sources showed both less diversity in end-product composition and a 17% and 13% lower propionic acid conversion yield respectively than with glycerol. Increasing the initial glycerol concentration resulted in an enhanced productivity up to 0.36 g l−1h−1 and in a maximal propionic acid concentration of 42 g/l, while a slight decrease of the conversion yield was noticed. Such a propionic acid production rate was similar or higher than the values obtained with lactic acid (0.35 g l−1h−1) or glucose (0.28 g l−1h−1). These results demonstrated that glycerol is a carbon source of interest for propionic acid production.

Stimulation of Ethylene Production in Tomato Tissue by Propionic Acid

Propionic acid (10(-3)m) increases ethylene production by about 30 to 60% in tissue from green and half-ripe tomatoes (Lycopersicon esculentum Mill. var. Homestead) but does not increase ethylene production in tissue from ripe fruit. Stimulation is not due to the conversion of propionic acid to ethylene but appears to be secondary in nature and to operate on the endogenous ethylene-forming system. Thus conversion of methionine to ethylene in green and half-ripe tomato tissue is increased in the presence of propionic acid. Inhibitors which affect the normal endogenous ethylene-forming system similarly affect the propionic acid-stimulated system. Endogenous propionic acid may play a role in the regulation of ethylene production in tomato tissues.

Propionicacidemia, a new inborn error of metabolism.

Extract: A male sibling who was born of healthy parents and who died at the age of five days with the clinical picture of severe hypotonia, areflexia, hyperventilation, and grunting is described. An older female sibling with identical symptoms had died some years previously. The parents were unrelated and had three other healthy children. The patient exhibited severe metabolic acidosis which was resistant to therapy. This acidosis was caused by the presence in blood of propionic acid in a very high concentration (5.4 mM/l). The high levels of urea and potassium also present were probably the result of a markedly reduced urine production caused by dehydration. The levels of amino acid in plasma revealed low values for one amino acid, normal values for other amino acids, and high values for lysine, histidine, valine, isoleucine, and leucine. At autopsy, except for a right descending aortic arch, no gross anomalies were found, although the liver was enlarged, probably because of increased fat content. Microscopic examination showed a fatty degeneration of liver cells, degeneration of the Purkinje cells and the granular layer in the cerebellum, and macrophages containing debris of blood cells in the bone marrow and in the spleen. Gas chromatography was used to determine the nature of the accumulated fat in the liver. Among the normal constituents of liver triglycerides, three abnormal fractions were observed, two of which contained C15 and C17 straight chain fatty acids. These were not observed in normal liver fat. The combination of propionicacidemia and the storage of fatty acids with an uneven chain number in the liver pointed to a block in the conversion of propionic acid into methylmalonic acid. Speculation: It is suggested that the propionicacidemia found in this patient is due to a metabolic block in the conversion of propionic acid into methylmalonic acid. The increased concentration of odd-numbered fatty acids (C15 and C17) in the liver may arise from either a decreased breakdown of these fatty acids or an increased synthesis initiated by the high concentration of propionyl-CoA. It is proposed that the missing enzyme is propionyl coenzyme A carboxylase. The fact that a sibling with identical symptoms had died forms a strong argument to postulate that a hereditary abnormality of recessive inheritance is the cause of this as yet undescribed syndrome.

Oxidation of propionic acid by Nocardia corallina.

Two pathways have been postulated for the conversion of propionic acid to pyruvic acid by liver mitochondria. Mahler and Huennekens (1953) suggested that propionic acid was oxidized to acrylic acid which was converted to pyruvic acid through Land D-lactic acids. The alternative pathway involves a direct carboxylation of propionic acid to succinic acid (Lardy and Adler, 1956; Flavin et al., 1955). An enzyme system which catalyzes the carboxylation of propionic acid has been demonstrated in Propionibacterium pentosaceum (Barban and Ajl, 1951), Chlorobium thiosulfatophilum (Larsen, 1951), Micrococcus lactilyticus (Whiteley, 1953) and Veillonella gazogenes (Delwiche et al., 1954). Cells of a thiamin deficient Nocardia corallina oxidized propionic acid to pyruvic acid which accumulated in the system. This communication includes results which suggest that two pathways operate in N. corallina for the oxidation of propionic acid.