Effects Of Reaction Variables Research Articles

Effect of Reaction Variables on TPA-EG Continuous Esterification with Recycling in PET Production Process

ABSTRACTSimulations of a continuous recycle process were carried out for the direct esterification between terephthalic acid and ethylene glycol in the production of poly(ethylene terephthalate). The influence of reaction pressure, recycle ratio and residence time on the oligomer characteristics was examined and the following results were obtained: (1) The main reactions go on further under higher reaction pressure but the side reactions on diethylene glycol (DEG) proceed to a greater extent than the main reactions. (2) The higher residence time ratio of the first reactor to the total promotes esterification remarkably as the pressure becomes high. (3) As the recycle ratio becomes high, the polymerization degree becomes high, but, at higher degrees of polymerization, the tendency is reversed. (4) The oligomer characteristics are almost the same at the same esterification degree independently of the reaction conditions.

Supported PdCl 2CuCl 2 catalysts for carbon monoxide oxidation 1. Effects of catalyst composition and reaction conditions

Effects of reaction variables and catalyst components were studied on the activity of supported Wacker-type catalysts for low-temperature CO oxidation. The PdCl 2CuCl 2 catalysts supported on alumina or carbon were active in the conversion of CO at ambient conditions and were also stable for at least 100 h as long as water was supplied with the reactant gas mixture. Unlike homogeneous Wacker systems, the active phase of the copper was solid Cu 2Cl(OH) 3 as seen by X-ray diffraction. Silica was an inactive support because it was not able to stabilize the active copper phase. Carbon was a more active support than alumina. The activity of alumina-supported PdCl 2CuCl 2 showed a marked dependence on the partial pressure of water whereas the carbon-supported catalyst showed no dependence. This difference in catalytic behavior appeared to stem from the catalysts' different interaction with water.

Heterogeneous catalysis in organic chemistry Part 8.: The use of supported palladium catalysts for the Heck arylation

It has been found that the Heck arylation proceeds smoothly over supported Pd catalysts to give the same reaction products as are obtained with the more commonly used homogeneous catalysts. The effect of reaction variables on the regioselectivity of the process is about the same for both the homogeneous and heterogeneously catalyzed reactions, so the use of the supported metal catalyst in such reactions appears to be straightforward. Such materials should be considered as viable alternatives for the commonly used homogeneous catalytic species.

Role of ceric ion in the heterogeneous graft polymerization of olefins on cellulose

The heterogeneous graft copolymerization of vinyl monomers on cellulose initiated by aqueous ceric ion is studied theoretically. Mechanistic aspects are considered. Some suggestions are made about: polymerization schemes; concerted disproportionation of cellulose-ceric ion complexes; oxidation sites in cellulose or cellulose sites of grafting (block and graft copolymer formation); reactivity of olefins towards cellulose radicals; reactivity of olefins in homopolymerization initiated by ceric ion; reactivity of radical chains in termination by ceric ion; estimation of reaction parameters (rate of graft copolymerization, rate of homopolymerization, rate of ceric ion consumption, grafting efficiency, molecular weight, number of polymer chains, grafting frequency and initiation efficiency) in terms of the reaction variables; and a polymerization scheme for electron-rich monomers. The effect of reaction variables on reaction parameters can be accounted for by equations developed in this paper. Consequently, some characteristics of the copolymers and copolymerization reactions can be understood. A way of demonstrating transitions between competitive reactions is developed.

Formation of Acrylaldehyde by Vapor-Phase Aldol Condensation I. Basic Oxide Catalysts

Abstract Vapor-phase aldol condensation of formaldehyde with acetaldehyde to form acrylaldehyde was studied with various oxides supported on silica gel using 35% formalin as the source of formaldehyde. The silica gel unsupported catalyst prepared from colloidal silica showed a relatively high activity and selectivity to form acrylaldehyde. The catalytic activity was markedly enhanced by the incorporation of a basic or amphoteric oxide into the silica gel, while it fell with the incorporation of an acidic oxide such as P2O5 or B2O3. The highest yields of acrylaldehyde were obtained with the Si–Mg, Si–Li, Si–Na, and Si–Zn oxide systems. Effects of reaction variables were also studied using a catalyst with an Si : Mg atomic ratio of 100 : 10.

Oxidation of Cycloalkanes in a Radiofrequency Plasma

Abstract Cyclopentane, cyclohexane, cycloheptane, and cyclooctane were reacted in a radiofrequency plasma containing oxygen to give mixtures of the corresponding cycloalkanones and cycloalkanols. Tetralin was also oxidized to 1-tetralone and 1-tetralol. Based on the effects of reaction variables on the oxidation rate, the reaction scheme involving the autoxidation of cycloalkyl radicals was proposed.

Carbonylation of n-alkylallylamines with CO/H 2 mixtures

The homogeneously catalyzed carbonylation of N-alkylallylamines to N-alkyl-2-pyrrolidones has been studied and the effects of reaction variables have been evaluated. Contrary to expectations, the reaction proceeded at milder conditions with a CO/H 2 1:1 mixture than with pure carbon monoxide, and with phosphine-free rhodium complexes than in the presence of phosphines, which enhanced simultaneous double-bond hydroformylation. Studies of the reaction of Rh(I) complexes with amines indicate that the carbonylation proceeds via Rh(0) clusters.

Effect of reaction variables on the catalytic hydrocracking of Athabasca bitumen

The effects of catalyst particle size on the hydrocracking reactions of Athabasca bitumen were studied in the presence of CoOMoO 3/Al 2O 3 catalyst. Six different catalyst particle sizes, namely 3.2, 1.7, 1.18, 0.6, 0.3 and < 0.15 mm were employed in the hydrocracking reactions. Reducing the catalyst size resulted in a significant increase in the conversion of asphaltenes. Mass transfer of reactants to the active surface of the catalysts was found to have a negligible effect when catalyst particles of < 0.3 mm were used. The effects of sulphiding the CoOMoO 3/Al 2O 3 catalyst on the hydrocracking reactions were determined and used to conclude that sulphiding of the catalyst, by the sulphur-rich bitumen, occurred during the initial heat-up period of the reaction. The pore size distributions of CoOMoO 3/Al 2O 3 and CoOMoO 3/TiO 2SiO 2 catalysts were determined and the median pore sizes calculated to be 9 and 10 nm, respectively.

Effects of reaction variables on nephelometric and turbidimetric responses for the immunochemical reaction of immunoglobulin G.

Here we report a kinetic study of the immunoprecipitin reaction involving immunoglobulins G, A, and M. We used stopped-flow mixing adapted for simultaneous monitoring of nephelometric and turbidimetric signals for some studies and centrifugal mixing for others. The variables having the most significant effects on the kinetic responses in the regions of excess antibody and excess antigen are polyethylene glycol concentration, ionic strength, and the ratio of antigen to antibody. We document effects of these variables on maximum velocities and signal changes over a fixed-time interval for both monitoring modes and on the maximum signal change for nephelometry. We use response-surface methodology to help identify interactive effects among these variables (polyethylene glycol, NaCl, and antibody concentrations) and to select the best combination to use to quantify antigen in all regions of the immunoprecipitin curve. We also observe that turbidimetric responses are more reproducible and much simpler than are nephelometric responses. Implications of these results for quantification of the immunoglobulins are discussed.

Selective Fischer-Tropsch synthesis on metal powder catalysts prepared by the potassium reduction of halides in THF

Metal powders such as Fe, Co, Ni, FeCo, and FeNi prepared by reducing metal iodides or bromides with potassium metal in refluxing THF were used as catalysts for Fischer-Tropsch syntheses. These metal powders contained very small particles and have large BET surface areas (28–36 m 2/g). The metal powder catalysts, such as Fe and FeCo (80:20), gave l-butene with more than 35 wt% selectivity at a rather high CO conversion of over 10 wt% at 533–553 K, while products on the Co catalyst obeyed conventional Schulz-Flory type distribution. The Ni catalyst showed little activity. Effects of reaction variables (temperature, H 2 CO feed gas ratio, and composition of FeCo) were investigated.

Preparation of poly(N‐methylmethacrylamide) microspheres containing peroxy ester groups and their use in graft copolymerization

AbstractPoly(N‐methylmethacrylamide) [poly(1)] microspheres, carrying peroxy ester groups, were prepared by radical copolymerization of 1 with a small amount of di‐tert‐butyl perfumarate (2) in benzene. Thermal and photo‐induced polymerizations of vinyl monomers with the microspheres were carried out, to produce graft copolymers. Ethanol as additive was found to accelerate the polymerization of benzyl methacrylate (3) at 80°C although the accelerating effect levels off at higher concentrations of ethanol. The grafting efficiency was not high (up to 16,5%) and exhibited a maximum on varying the ethanol concentration. On the other hand, in the photo‐induced polymerization the conversion of 3 increased with increasing ethanol concentration. The grafting efficiency similarly showed a maximum on varying the ethanol concentration. The effects of reaction variables on the thermal and photo‐induced graft copolymerizations of 3 onto the microspheres in the presence of a definite amount of ethanol were examined in the light of the conversion of 3, the grafting efficiency and the percentage of grafting. Long‐lived propagating poly(1) radicals (6) were observed by ESR during heating at 70°C or UV‐irradiation at 30°C of the microspheres in a toluene/ethanol mixture. Thermolysis or photolysis of the microspheres in the presence of 3 yielded a stable propagating poly(3) radical (7). Similarly, this microsphere method was applied to the preparation of long‐lived propagating polymer radicals of some other vinyl monomers.

ChemInform Abstract: Selective Oxidation of Acrolein to Acrylic Acid by V2O5‐P2O5 Catalysts.

Abstract V 2 O 5 P 2 O 5 catalysts were found to be effective for the partial oxidation of acrolein to acrylic acid. The addition of phosphorus to V 2 O 5 induces a large increase in the selectivity to acrylic acid, though it also induces a marked decrease in the oxidation activity. The best results for the formation of acrylic acid are obtained with the P/V atomic ratio = 1.2 catalyst. The selectivity to acid remains unchanged at 90 to 95 mol% up to the acrolein conversion of about 95%. More than 95 mol% of the produced acid was found to be acrylic acid. The selectivity of the P/V = 1.2 catalyst was higher than that of the MoO 3 V 2 O 5 (Mo/V atomic ratio = 4.7) catalyst. B 2 O 3 , TeO 2 , Co 3 O 4 , and ZrO 2 were added to the P/V = 1.2 system, but the selectivity was not improved. It is proposed that the phosphorus plays a role in suppressing the basic property of catalyst which contribute to the consecutive oxidation of acrylic acid. The effects of reaction variables, such as oxygen concentration, acrolein concentration, water vapor, on the activity and selectivity were also studied.

Enhanced oil production from coal by a new reductive alkylation reaction in a glass flask

A new method is proposed to obtain oil from coal under mild reaction conditions. This method consists of coal anionization by molten potassium metal under refluxing THF with the aid of ultrasonic energy and alkylation of the coal anion by alkyl iodide. Butylated and ethylated Yubari coals, prepared by 6 h of anionization time with 1.33 potassium to coal (weight) ratio, gave oil (n-hexane soluble portion) with 53 and 51 wt.% yields, respectively. The effects of reaction variables on the extent of the reaction were investigated, such as amount of potassium metal, anionization time, kinds of reaction solvent, alkyl groups, and raw coals. The structural parameters of a series of oils indicate that highly effective depolymerization and alkylation of the present reaction result in the conversion of much of the condensed aromatic portion of the coal to oil.

Selective oxidation of acrolein to acrylic acid by V2O5-P2O5 catalysts

V2O5P2O5 catalysts were found to be effective for the partial oxidation of acrolein to acrylic acid. The addition of phosphorus to V2O5 induces a large increase in the selectivity to acrylic acid, though it also induces a marked decrease in the oxidation activity. The best results for the formation of acrylic acid are obtained with the P/V atomic ratio = 1.2 catalyst. The selectivity to acid remains unchanged at 90 to 95 mol% up to the acrolein conversion of about 95%. More than 95 mol% of the produced acid was found to be acrylic acid. The selectivity of the P/V = 1.2 catalyst was higher than that of the MoO3V2O5 (Mo/V atomic ratio = 4.7) catalyst. B2O3, TeO2, Co3O4, and ZrO2 were added to the P/V = 1.2 system, but the selectivity was not improved. It is proposed that the phosphorus plays a role in suppressing the basic property of catalyst which contribute to the consecutive oxidation of acrylic acid. The effects of reaction variables, such as oxygen concentration, acrolein concentration, water vapor, on the activity and selectivity were also studied.

Partial oxidation of propylene on V 2O 5P 2O 5-based catalysts

The vapor-phase oxidation of propylene was studied over V 2O 5, V 2O 5P 2O 5, and V 2O 5P 2O 5TeO 2 catalysts in the presence of water vapor. On pure V 2O 5, the oxidation products were acetic acid and carbon oxides, plus a small amount of acetone. As the content of phosphorus added to V 2O 5 increases, the oxidation activity markedly decreases; on the other hand, the selectivity to acrylic acid increases and passes through a maximum at P V atomic ratio = 1.15 to 1.6, while that to acetic acid gradually decreases. With the V 2O 5P 2O 5 ( P V = 1.15 ) catalyst, the yield of acrylic acid attains 25 mol%, that of acetic acid is less than 10 mol%, and that of acrolein is less than 0.7 mol%. The effects of the third components added to V 2O 5P 2O 5 ( P V = 1.15 ) were also studied. It was found that TeO 2 is the sole additive which can improve the catalyst performance. As the amount of TeO 2 increases, the specific oxidation activity increases, as do the formation of acrolein and the sum of the yields of acrylic acid and acrolein, while the formation of acetic acid passes through a maximum at Te V = 0.02 to 0.04 . With the V 2O 5P 2O 5TeO 2 (Te/P/V = 0.15/1.15/1) catalyst, the yield of acrylic acid attains 38 mol% when air is used as the oxidant and 42 mol% when oxygen is so used. The effects of reaction variables, such as the oxygen concentration, the propylene concentration, the water vapor, and the temperature, on the activity and selectivity were also studied.

Oxidative dehydrogenation of isobutyric acid on V 2O 5P 2O 5 catalysts

V 2O 5P 2O 5 binary oxides were found to be effective for the synthesis of methacrylic acid (MAA) in the vapor-phase air oxidation of isobutyric acid (IBA), much like vanadium-containing heteropoly compounds. The products are MAA, acetone, propylene, and carbon oxides. With an increase in the content of phosphorus, the selectivity to acetone steadily decreases, while that to propylene increases. The selectivity to MAA passes through a maximum (50 to 60 mol%) at a P V atomic ratio between 1.0 and 1.6, and it is little affected by the method of catalyst preparation. It was found that the selectivity is clearly related to the acid-base property of the catalyst. The oxidation activity attains a maximum at P V = 1.0 to 1.6 , and the activities of the V-P (1–1.6) catalysts are of the same order of magnitude as that of H 5PMo 10V 2O 40. The effects of reaction variables, such as oxygen concentration, IBA concentration, water vapor, and temperature, on activity and selectivity were studied for both the V 2O 5P 2O 5 and H 5PMo 10V 2O 40 catalysts, and an attempt was made to clarify the difference in catalytic performance between V 2O 5P 2O 5 and H 5PMo 10V 2O 40.

Oxidation of methyl ethyl ketone to diacetyl on V 2O 5-P 2O 5 catalysts

A V 2O 5-P 2O 5 catalyst with a P V atomic ratio of 1.6 prepared by using oxalic acid as a reducing agent was found to be effective for the synthesis of diacetyl in the vapor-phase air-oxidation of methyl ethyl ketone (MEK). The selectivity to diacetyl was about 40 mol% at MEK conversions of up to 70%, and it decreased slightly with a further increase in the conversion. The selectivity for the oxidative CC fission to form acetic acid and acetaldehyde varied from 58 to 56 mol% with an increase in the conversion. The rate was nearly proportional both to the oxygen concentration up to 20 vol% and to the MEK concentration up to 10 vol%, even at the low temperature of 140 °C. The apparent activation energy was 7.6 kcal/mol. The addition of water vapor favors the oxidative fission against the diacetyl formation. The effects of reaction variables on the selectivity was also studied. A peroxide-like reaction mechanism was proposed.

Relation of the chemical structure of coal to its hydropyrolysis

The hydropyrolysis of Illinois No. 6 coal has been studied in a batch reactor, in which the reactions were initiated by explosion of H2O2 mixtures. The ratio of H2 to O2 was kept at 8, while the total pressure of the gas mixture was changed to vary the reaction temperature. The heating rate was ≈ 50 000 °C s−1, and the reaction time was < 50 ms. The conversion of the feed coal increased from 19% at 620 °C to 81%at ⪢ 1500 °C. At conversions < 50%, the gaseous product consisted of mainly CH4 and CO in almost equal proportions, and at conversions ⪢ 60% the concentration of CO increased. Comparison with results from a large flow reactor revealed that comparable conversions were obtained in the present batch reactor, although product distributions were markedly different from each other. The dissimilar product distribution is attributed to different reacting media: preburning of H2 and O2 in the flow reactor versus in situ burning of the mixture in the batch reactor. The H/C ratios of solid residues after the hydropyrolysis decreased linearly as the conversion increased, revealing that the portions of coal having high H/C ratios were preferentially gasified. This observation was substantiated by a high H/C ratio, 1.74 of the first portion of coal gasified, and by a sharp decrease in H/C ratio in subsequent gasified portions. These data indicated that aliphatic side chains (or linkages) and single-ring aromatic clusters in the feed coal were gasified first, followed by larger aromatic clusters. Semi-quantitative determination of the distribution of different aromatic clusters showed good agreement with current structural information on coal. Thus, the effects of reaction variables were explained in terms of the structural features of coal, and the ratelimiting steps in the hydropyrolysis process were identified.

HPLC assay for guanidine salts based on pre-column derivatization with acetylacetone.

A specific, isocratic HPLC assay procedure for guanidine hydrochloride is developed. A key step in the procedure, pre-column derivatization with acetylacetone, is performed under conditions that permit direct injection of the reaction mixture onto an HPLC column. Specific directions for carrying out the derivatization are given and the effects of reaction variables are discussed. In addition, chromatographic conditions are given for the separation of the derivative formed from other components of the reaction mixture. The derivatization also is demonstrated to be applicable to guanidine carbonate, nitrate, and sulfate.

Effects of reaction variables on the hydrolysis of lean beef tissue by alcalase

The effects of the reaction variables, pH, time, temperature, enzyme: meat ratio and meat concentration, on the hydrolysis and solubilisation of lean meat protein by Alcalase have been determined. Experiments were performed with both dilute meat suspensions and undiluted ground meat. Reaction progress curves were similar to those for the enzymic hydrolysis of other proteins, with rapid initial reaction rates followed by a gradual decline in rate. The optimum reaction pH was 8·5. Optimum temperatures were found to be 55°C for the hydrolysis reaction and 60°C for meat solubilisation. Both solubilisation and degree of hydrolysis increased with increasing enzyme concentration. At an enzyme: meat ratio of 80 mg Alcalase 0·6L per gram of dry meat, a solubilisation of 94% and a degree of hydrolysis of 18% were achieved after a 3-h reaction period. As meat concentration was increased, degree of hydrolysis decreased slightly and solubilisation decreased markedly.