Intensified and safe ozonolysis of fatty acid methyl esters in liquid CO2 in a continuous reactor

We demonstrate a continuous reactor for performing the ozonolysis of fatty acid methyl esters (FAMEs) using liquid CO₂ as solvent. The fast reaction kinetics allows the use of small‐volume reactors to completely convert the FAMEs, forming secondary ozonides as the primary products. The short residence times also help maximize the yields of the secondary ozonides by minimizing over‐oxidation and the formation of oligomeric products. The liquid CO₂ medium promotes safe reactor operation by providing an essential fraction of overall reactor cooling and by diluting the vapor phase organics. We also demonstrate a continuous stirred reactor for the safe thermal decomposition of the secondary ozonides to their corresponding acids and aldehydes. Using a lumped kinetic model for the thermal decomposition of the ozonolysis products, we estimate activation energy values of 108.6 ± 0.6 kJ mol^?1 for the decomposition of secondary ozonides and 122 ± 3 kJ mol^?1 for the decomposition of the undesired oligomeric species. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2819–2826, 2017     

Influence of Reactor Configuration on the Selective Oxidation of Glycerol over Au/TiO2

The oxidation of glycerol by molecular oxygen in the aqueous phase over Au/TiO₂ was investigated in both a batch reactor and a continuous upflow fixed bed reactor. The effects of catalyst particle size, gas flow rate, liquid flow rate, reaction temperature, dioxygen pressure, and solution pH were examined in the fixed bed system. The unique hydrodynamics of the fixed bed system allowed for secondary oxidation products such as tartronic acid and oxalic acid to form in substantial amounts, which contrasts the product distribution observed in a batch system. These results suggest that reactor configuration can play an important role in the observed product selectivity from oxidation reactions over highly active gold catalysts.     

Vapor phase dehydrogenation of methanol to methyl formate in the catalytic membrane reactor with Cu/SiO2/ ceramic composite membrane

The Cu/SiO₂/ceramic composite membrane was prepared on the SiO₂/ceramic mesoporous membrane by an ion exchange method, and vapor phase dehydrogenation of methanol to methyl formate in the catalytic membrane reactor was investigated. It showed much better performance in the catalytic membrane reactor than that in the fixed-bed reactor under the same reaction conditions. At 240 °C, 57.3% conversion of methanol and 50.0% yield of methyl formate were achieved in the catalytic membrane reactor and only 43.1% conversion of methanol and 36.9% yield of methyl formate were achieved in the fixed-bed reactor.     

Experimental investigation of vinyl chloride polymerization at high conversion—reactor dynamics

A series of suspension polymerizations of vinyl chloride monomer (VCM) was carried out in a 5-L pilot plant reactor over the temperature range, 40–70°C. The reactor pressure and monomer conversion were monitored simultaneously every 7–8 min. The critical conversion X_f, at which the liquid monomer phase is consumed, was considered to occur when the reactor pressure fell to 98% of the vapor pressure of VCM for suspension at the polymerization temperature. The reactor model predictions of pressure are in excellent agreement with the experimental data over the entire conversion and temperature ranges studied. The mechanism of reactor pressure development for VCM suspension polymerization is discussed herein in some detail. For isothermal batch polymerization, the reactor pressure falls in two stages due to the effect of polymer particle morphology on pressure drop. The first stage is due to the volume increase of the vapor phase as a result of volume shrinkage due to conversion of monomer to polymer. The monomer phase is not yet consumed at this stage, but it is trapped in the interstices between primary particles creating a mass transfer resistance; therefore, the reactor pressure drops slowly. The second stage is due to both the volume increase of the vapor phase and to the monomer in the vapor phase diffusing into the polymer phase because of the subsaturation condition with respect to monomer in the polymer phase. The reactor pressure drops dramatically with an increase in monomer conversion at this stage. The present model can be used to predict reactor dynamics during suspension polymerization under varying temperature and pressure conditions.     

Kinetics of the Syntheses of Mesityl Oxide (MO) and Methyl Isobutyl Ketone (MIBK) in a Fixed-Bed Flow Reactor (FBR)

Nb₂O₅/SiO₂ and Pd/Nb₂O₅/SiO₂ catalysts were studied for the liquid phase syntheses of mesityl oxide (MO) and methyl isobutyl ketone (MIBK) in a fixed bed flow reactor (FBR). Catalyst activities as high as 1.7 g/h g_cat and selectivities ranging from 93.4 to 100% for MO synthesis were observed. The catalyst activity was found to be a strong function of space velocity likely due to product inhibition. A synergistic effect was observed whereby the catalyst activity for all organic products increased by 22% and the MIBK productivity increased by 20% at 160 °C and WHSV = 8.6 h^?1 from the introduction of hydrogen to the reactor. However, the MIBK selectivity was constrained to less than 83.5% due to competing reactions.     

Regioselective nitration of o-xylene to 4-nitro-o-xylene using nitric acid over solid acid catalysts

The regioselective nitration of o-xylene to 4-nitro-o-xylene (4-NOX) has been studied in the liquid and vapor phase over zeolites H-beta, H-ZSM-5 and silica supported molybdenum oxide (MoO₃/SiO₂) catalysts. Zeolite H-beta showed the maximum conversion of 28% and 63% selectivity for 4-NOX in liquid phase nitration at 70 °C with 70% HNO₃. The conversion increased to 65% when the reaction was carried out in vapor phase at 150 °C using dilute 30% HNO₃. The formation of α-methylphenyl nitromethane by alkyl nitration in liquid phase was decreased in vapor phase reaction. The formation of oxidation products was also decreased in vapor phase reaction with minor amounts of dinitro and ipso-products. The influence of experimental parameters such as temperature, nitric acid concentration and WHSV on conversion and selectivity has been investigated. The use of dilute nitric acid and the selective formation of 4-NOX using dilute HNO₃ makes this process environmental friendly with a potential for commercialization.     

Bridging the gap between liquid and vapor phase hydrocracking

Research aimed at fundamental understanding of industrial reactions often leads to important differences, or so-called gaps, between laboratory and industrial conditions. Vapor and liquid phase hydrocracking of parapur, a mixture of linear alkanes in the range from C₉ to C₁₄, has been performed on a Pt/H-USY zeolite at temperatures between 503 and 533 K, total pressures between 1 and 7.7 MPa and molar inlet hydrogen to hydrocarbon ratios from 3 to 300. At these conditions ideal hydrocracking occurs, except for the heaviest components at the highest temperatures, lowest pressures and highest molar inlet hydrogen to hydrocarbon ratios. The individual component product distributions obtained at vapor and liquid phase conditions were identical to those reported in the literature for pure n-alkane hydrocracking. A preferential conversion of the heavier hydrocarbons in the mixture was observed for vapor phase parapur hydrocracking. At liquid phase conditions this preferential conversion of heavier hydrocarbons is still observed, but much less pronounced.A single kinetic model accounting for all these features allows to adequately describe both vapor and liquid phase parapur hydrocracking. It suffices to account explicitly for (i) the non-ideality of the fluid phase, (ii) the destabilization of the physisorbed phase in the catalyst micropores and (iii) the increased strength of the acid sites at the liquid phase conditions. The last two effects are quantified by so-called physisorption and protonation excess.     

Pyrolysis of used sunflower oil in the presence of sodium carbonate by using fractionating pyrolysis reactor

Pyrolysis of used sunflower oil was carried out in a reactor equipped with a fractionating packed column (in three different lengths of 180, 360 and 540 mm) at 400 and 420°C in the presence of sodium carbonate (1, 5, 10 and 20% based on oil weight) as a catalyst. The use of packed column increased the residence times of the primer pyrolysis products in the reactor and packed column by the fractionating of the products which caused the additional catalytic and thermal reactions in the reaction system and increased the content of liquid hydrocarbons in gasoline boiling range. The conversion of oil was high (42–83 wt.%) and the product distribution was depended strongly on the reaction temperature, packed column length and catalyst content. The pyrolysis products consisted of gas and liquid hydrocarbons, carboxylic acids, CO, CO₂, H₂ and water. Increase in the column length increased the amount of gas and coke–residual oil and decreased the amount of liquid hydrocarbon and acid phase. Also, increase of sodium carbonate content and the temperature increased the formation of liquid hydrocarbon and gas products and decreased the formation of aqueous phase, acid phase and coke–residual oil. The major hydrocarbons of the liquid hydrocarbon phase were C₅–C₁₁ hydrocarbons. The highest C₅–C₁₁ yields (36.4%) was obtained by using 10% Na₂CO₃ and a packed column of 180 mm at 420°C. The gas products included mostly C₁–C₃ hydrocarbons.     

尿素醇解法合成氨基甲酸甲酯平衡常数的测定

文章测定了尿素醇解法合成氨基甲酸甲酯的平衡常数。在433.15K时,无催化剂条件下,甲醇和尿素在高压釜内反应生成氨基甲酸甲酯,待反应达到平衡后,通过气相色谱仪和液相色谱仪测定平衡混合物的组成来计算反应的平衡常数。气相可近似认为是氨气和甲醇组成的二元混合物,液相近似认为是尿素、甲醇和氨基甲酸甲酯组成的三元混合物。实验结果表明,实验重现性较好,平衡常数数值是可靠的。     

Free radical polymerizations of some vinyl monomers in carbon dioxide fluid

The effect of pressure ranging from ambient atmosphere to 28.5 MPa on the free radical polymerizations of methyl methacrylate (MMA) in carbon dioxide (CO₂) was investigated and discussed. The poly(methyl methacrylate) (PMMA) with high molecular weight was synthesized at quite high conversion of MMA in the polymerization at or below 9.2 MPa, as compared to those polymerized under 11.8–28.5 MPa. A phase transition behavior of MMA‐CO₂ binary mixture from homogeneous state to vapor‐liquid equilibrium (VLE) state was observed below 10.51 MPa. In such a VLE system, almost all MMA was found to exist in the liquid phase with higher concentration than that in homogenous system. Thus, the fast polymerization rate of MMA and high molecular weight of PMMA could be related to the VLE state of MMA/CO₂ under low pressure. Similar phenomena were also observed in the polymerization systems of styrene and vinyl acetate in CO₂, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Vapor phase esterification of levulinic acid over ZrO2/SBA-15 catalyst

ZrO₂/SBA-15 catalysts with different ZrO₂ loadings prepared by impregnation method were tested for the esterification of levulinic acid in a fixed-bed reactor in vapor phase conditions at atmospheric pressure for the first time and found that the catalyst with 7 weight percent ZrO₂ exhibited 100% conversion of levulinic acid and 96% selectivity to methyl levulinate due to the presence of more number of moderate acidic sites. It is interesting to observe the formation of γ-valerolactone as the alcohol chain length increases at the expense of alkyl levulinate, through MPV reduction mechanism.     

Production of hydrocarbons by pyrolysis of methyl esters from rapeseed oil

The pyrolysis of a mixture of methyl esters from rapeseed oil has been studied in a tubular reactor between 550 and 850°C and in dilution with nitrogen. A specific device for the condensation of cracking effluents was used for the fractionated recovery of liquid and gaseous effluents, which were analyzed on-line by an infrared analyzer and by gas chromatography. The cracking products in the liquid effluent were identified by gas chromatography/mass spectrometry coupling. The effects of temperature on the cracking reaction were studied for a constant residence time of 320 ms and a constant dilution rate of 13 moles of nitrogen/mole of feedstock. The principal products observed were linear 1-olefins,n-paraffins, and unsaturated methyl esters. The gas fraction also contained CO, CO₂, and H₂. The middle-chain olefins (C₁₀–C₁₄ cut) and short-chain unsaturated esters, produced with a high added value, had an optimum yield at a cracking temperature of 700°C.     

Simulation and Experimental Validation of Two‐Phase Flow in an Aerosol Counter‐Flow Reactor using Computational Fluid Dynamics

A simulation of the hydrodynamic behavior of an aerosol‐counter flow reactor was conducted using an Euler‐Lagrange method. The simulation results were then verified with experiments. The process simulated was a separation process required during the production of biodiesel (fatty acid methyl ester). In this process, the liquid ester/glycerol phases are continuously injected through a hollow cone nozzle with an overpressure of 10⁶ Pa into the reactor, operated at 15000 Pa. The liquid is atomized because of the pressure drop and a liquid particle spray is generated with an inlet velocity of 44.72 m/s. Water vapor of temperature 333 K is injected tangentially through two side, gas inlets with an inlet velocity of 1.2 m/s. Excess methanol is subjected to a mass transfer from the liquid phase into the gas phase, which is withdrawn through the head of the reactor and condensed in an external condenser unit. The stripping of the methanol off the liquid leads to a sharp interface between the glycerol and the ester phase, which can then be easily separated by gravity or pumping. The gas velocity field, pressure field and the liquid particle trajectories were calculated successfully. Simulated dwell time distribution curves were derived and analyzed with the open‐open vessel dispersion model. Experimental dwell time distribution curves were measured, analyzed with the open‐open vessel dispersion model, and compared with the simulated curves. A good consistency between simulated and measured Bodenstein numbers was achieved, but 25 % of the simulated particles exited at the reactor's head, contrary to experimental observations. The difference between simulated and measured dwell times was within one order of magnitude.     

EFFECT OF EQUATION OF STATE ON PREDICTION OF TRICKLE BED REACTOR MODEL PERFORMANCE

Trickle bed reactors are widely employed in hydrotreating pocesses that operate at conditions where a significant portion of the liquid phase will flash. This partial vaporization of the feed affects the reactor performance. In order to determine the extent of liquid flashing and its effect on reactor performance, an equation of state is needed. In this study we used seven cubic equations of state to determine their effect in predicting reactor performance as well as parameter estimation

Two important variables that are calculated from the equation of state are the vapor liquid equilibrium and the molar density of the liquid phase. It was observed that although the distribution coefficients calculated by each equation of state are significantly different from each other, they do not affect the reactor model appreciably. However, molar density determination has a large effect both on modelling of reactor performance and the parameter estimation.     

Degradation of solvolysis lignin using Lewis acid catalysts

Alcell‐derived lignin was depolymerized in a batch reactor using the Lewis acid catalysts NiCl₂ and FeCl₃. The objective was to investigate the use of Lewis acids in the production of useful liquid products directly from solvolysis lignin. The effects of reaction temperature, time and catalyst were studied on the conversion of this lignin to gas, solid and liquid products. Also, selected monomeric compounds in the ether solubles were monitored in terms of the variation in their yields with different reaction conditions. The highest conversions, 30% and 26% from Ni and Fe, respectively, were both attained at the reaction conditions of 305°C and 1 h reaction time. The Ni produced a somewhat higher yield of ether solubles, reflecting its slightly higher performance. Under the reaction conditions studied, both catalysts apparently favour condensation reactions leading to the formation of insoluble reactor residue from solvolysis lignin. Low quantities of monomeric compounds were produced, with phenols dominating over ketones and aldehydes for both catalysts.     

Opposite effect of gas phase H2O2 on photocatalytic oxidation of acetone and benzene vapors

The effect of additions of gas phase H₂O₂ was measured for gas phase photocatalytic oxidation of organic vapors. Photocatalytic oxidation of benzene vapor over TiO₂ in a flow reactor resulted in a quick catalyst deactivation. Additions of gas phase H₂O₂ into the reactor feed provided enhanced and sustained oxidation of benzene vapor. The increase of inlet H₂O₂ vapor concentration from 0 to about 1000 ppm led to the one order of magnitude growth of benzene vapor complete oxidation rate. The highest rate of 1.1 nmol/s was observed at C₆H₆ concentration 124 ppm and H₂O₂ concentration 1000 ppm. In the case of acetone vapor photocatalytic oxidation, the rate of complete oxidation in the flow reactor decreased with an increase of gas phase H₂O₂ inlet concentration. TiO₂ Degussa P25 provided higher oxidation rate in the presence of H₂O₂ than pure anatase TiO₂.     

Analysis of the dark-colored impurities in sulfonated fatty acid methyl ester

A fractionally distilled C₁₄−C₁₆ fatty acid methyl ester, derived from palm oil, was sulfonated with gaseous SO₃ in a falling film reactor to form an α-sulfo fatty acid methyl ester (α-SF; unbleached and unneutralized form). The included dark-colored impurities were then separated from α-SF as a diethyl ether-insoluble matter. After purification by thin-layer chromatography, the colored species were analyzed by ion-exchange chromatography, gel-permeation chromatography, and nuclear magnetic resonance spectrometry. These data suggested that the colored species were polysulfonated compounds with conjugated double bonds. Minor components in the raw fatty acid methyl ester, found by gas chromatography/mass spectrometry, were spiked into the purified methyl palmitate and then sulfonated. The unsaturated methyl ester and hydroxy ester showed the worst color results. The methyl oleate and methyl 12-hydroxystearate were then sulfonated and analyzed. Deep black products were obtained, which showed the same properties as the colored species in α-SF. It was concluded that low levels of unsaturated fatty acid methyl esters and hydroxy esters in the fatty acid methyl ester are the main causes of the coloring.     

A new process for the synthesis of diphenyl carbonate from dimethyl carbonate and phenol over heterogeneous catalysts

The two-step synthesis of diphenyl carbonate (DPC) from dimethyl carbonate (DMC) and phenol has been compared in liquid phase and gas phase, both over heterogeneous catalysts. In the first step, equilibrium yields of methyl phenyl carbonate (MPC) in the transesterification of DMC and phenol were very low at low temperatures in the liquid phase although reaction rates were fast. This endothermic reaction was more favorable at high temperatures in the gas-phase reaction. Titanium oxide catalysts supported on SiO₂ or activated carbon were found to be effective in a continuous gas flow reactor. In case of the second step, the disproportionation of MPC, selective formation of DPC was not feasible in the gas-phase reaction due to extensive side reactions. However, there was no by-product in the liquid-phase reaction over the TiO₂/SiO₂ catalyst. Therefore, our proposed two-step synthesis process consists of the gas-phase transesterification of DMC and phenol followed by the liquid-phase disproportionation of MPC to DPC, both over the TiO₂/SiO₂ catalyst. This revised version was published online in July 2006 with corrections to the Cover Date.     

Vapour phase oxidation of toluene in V/Al2O3–TiO2 catalytic reactors

The catalytic membrane reactor and the inert packed bed membrane reactor were studied in the vapour phase selective oxidation of toluene. Different feeding policies for the membrane were explored and their influence on the selectivity to the desired products (benzaldehyde and benzoic acid) was investigated. The active phase was prepared by depositing vanadium on a Al₂O₃–TiO₂ support prepared through the sol–gel technique. Higher selectivity to benzaldehyde was obtained using the catalytic membrane reactor. Differences were seen in the catalytic membrane reactor performance only when the active phase was heavily charged along the membrane cross-section.     

Influence of Temperature on SO2 Removal Enhanced by Water Vapor Using a Corona‐Discharge Reactor

A reactor using d.c. corona discharge of negative polarity was applied to remove sulfur dioxide from an oxygen‐nitrogen mixture in the presence or absence of water vapor for temperatures ranging from room temperature to 350 °C. It was observed that increasing the reactor temperature caused a decrease in the removal efficiency. Mixing water vapor with the process gas resulted in an increase of the removal efficiency. The effect of the presence of water vapor on improving the removal efficiency was significant under low temperature conditions, while it was relatively moderate under high temperature conditions. In addition, the solid deposit formed inside the reactor at two temperatures, room temperature and 200 °C, was analyzed with both a differential scattering calorimeter and an X ray diffractometer. The analysis indicated that SO₂ was ultimately converted to solid sulfur in both the presence and absence of water vapor in the gas flow.