Reaction conditions and reactor geometry for producing acrylates in high yield from lactic acid-derived 2-acetoxypropanoic acid (APA) esters are presented. An acrylate ester yield of 75% is achieved from methyl and benzyl APA esters at 550 °C in a fixed bed reactor filled with nonporous silica particles, carbon dioxide as a diluent gas, and acetic acid as a co-feed with the APA ester. The yield from methyl and benzyl APA esters is remarkably higher than from ethyl or butyl esters of APA, which have hydrogen atoms on the β-carbon of the ester functional group and thus can undergo alkene elimination, leading to reduced acrylate yield. Under optimum conditions, APA conversion to acrylates is stable over 30 h of continuous operation with little carbon deposition on the contact material.

The effect of water on higher alcohol and noncondensable gas formation in condensed-phase ethanol Guerbet chemistry over Ni/La2O3/γ-Al2O3 catalysts is investigated. Addition of 10 wt % water to anhydrous ethanol has a modest effect on conversion rate but significantly reduces both n-butanol and C6+ alcohol yields and increases noncondensable gas yields. Removal of water formed during Guerbet condensation reactions was accomplished by installing a recirculating loop that passed the reacting solution through a bed of 3 Å molecular sieves at low temperature. Removal of reaction water further reduces gas selectivity to less than 10% and increases alcohol selectivity to greater than 75% at 50% ethanol conversion. Water present in reaction is postulated to adsorb on the nickel surface as −OH, increasing C–C bond breakage of the adsorbed acetaldehyde intermediate, and also interact with basic sites responsible for the condensation reaction, weakening their activity.

Higher alcohols (C4+) can be formed from ethanol via condensation pathways collectively known as Guerbet reactions. Most prior Guerbet reaction studies involve vapor-phase reactions, with n-butanol yields typically no higher than 30% of theoretical. We report here condensed-phase Guerbet reactions of ethanol over Ni/γ-Al2O3 catalysts modified by La2O3. Higher alcohol selectivities in excess of 80% at 230 °C and autogenous pressures are obtained in batch autoclave reactions. At these conditions, which are near the critical temperature of ethanol, the liquid phase is significantly expanded, byproduct gases (CH4 and CO2) are significantly dissolved in the liquid phase, and the vapor phase contains significant quantities of alcohols. To accurately compute ethanol conversion and product yields, both composition and quantity of each phase present at reaction conditions must be determined. To do this, the SR-Polar equation of state is combined with chromatographic analysis of liquid-phase samples taken during reaction to model the phase equilibrium in the reactor at reaction conditions. Composition, density, and total number of moles of the vapor and liquid phases in the reactor are determined from the model and analysis, and they are used to calculate more accurate values of conversion and product yield than those calculated by liquid-phase samples alone.

Esterification of butyric acid with ethanol, n-butanol, and ethanol/n-butanol mixtures was studied using Amberlyst 70 cation-exchange resin and homogeneous p-toluene sulfonic acid as catalysts. The kinetics of individual alcohol esterification were first examined in batch reactions at different temperatures and catalyst loadings, and then esterification in ethanol/n-butanol mixtures of varying concentration ratios was characterized. Both nonideal solution and ideal solution kinetic models were developed. These models accurately predict the esterification of butyric acid by the individual alcohols; a simple additive combination of the individual alcohol esterification kinetics properly describes mixed alcohol esterification, indicating that the alcohols do not compete with each other or inhibit esterification when present together. When solution density is included in the kinetic rate expression to account for the actual concentration of −OH groups in ethanol and n-butanol, butyric acid esterification kinetics with the two alcohols are described by a common rate constant. This rate constant also predicts butyric acid esterification kinetics with other alcohol combinations, suggesting a generalized esterification rate constant for simple alcohol esterification of butyric acid over Amberlyst 70 catalyst. These results provide significant predictive capabilities for simulating processes such as reactive distillation processes for mixed alcohol esterification.

The reaction kinetics for the acetylation of 1,2-propylene glycol (PG) catalyzed by p-toluenesulfonic acid (p-TSA) were determined using an in situ1H NMR method. Both primary and secondary monoacetate esters of PG were observed as well as the diester. The reaction kinetics were characterized as a function of PG to acetic acid (AA) stoichiometry, p-TSA concentration, and temperature. The acetylation reactions and the transacetylation of the diester with PG were modeled as reversible second order reactions. Equilibrium constants were determined experimentally for each reaction. Activation energies for the consecutive acetylation of PG and PG monoacetate ester (PGMA) were 56 and 47 kJ/mol, respectively. The activation energy for intermolecular transacetylation of PG with its diacetate ester to form PG monoacetate was 63 kJ/mol.

The four cyclic glycerol acetal isomers can be readily produced via the acid-catalyzed reaction of glycerol with acetaldehyde or a related acetal species. In the presence of the acid catalyst used in acetal formation, the isomers interconvert to form an equilibrated mixture that contains similar quantities of the four products. Vacuum distillation can separate the four acetals into their purified forms, with the cis-5-hydroxy-2-methyl-1,3-dioxane (1) as the most volatile. When the distillation is carried out in the presence of an acid catalyst to promote interconversion, 1 is obtained as a nearly pure distillate stream. This is further adapted to a continuous reactive distillation which produced 90–96% 1. Thus a novel process is presented to convert glycerol to the desired acetal (1), which can be further converted to products such as 1,3-propanediol and dihydroxyacetone.

Diethyl succinate is continuously produced from succinic acid and ethanol in a 6-m tall, elevated pressure reactive distillation column. Esterification is carried out in excess ethanol such that water and ethanol are produced in the distillate and diethyl succinate is produced in the bottoms stream. The reaction is catalyzed by Amberlyst 70 cation exchange resin contained in KATAPAK SP-11® structured packing within the stainless steel column. Succinic acid conversions approaching 100%, and diethyl succinate yields of up to 98% have been experimentally achieved in the lab scale column. The esterification process has been simulated using the Radfrac module in Aspen Plus®. Simulations used reaction kinetic and phase equilibrium data collected in our laboratory to predict the steady state stream compositions from the column. Good agreement between experimental and simulation results was observed, thus facilitating the use of the model for design and scale up of the reactive distillation process.Highlights► Diethyl succinate is produced by esterification of succinic acid with ethanol via reactive distillation. ► Experiments are carried out in a pilot plant scale reactive distillation unit operated in continuous. ► Amberlyst 70 is used as catalyst in KATAPAK SP-11 as structured packing. ► Succinic acid complete conversion is achieved and >98.5% purity diethyl succinate is obtained as bottom product. ► Simulations in Aspen Plus agree reasonably well with experimental observations.

Representative reaction kinetics are difficult to obtain in multiphase laboratory trickle bed reactors, particularly when the gaseous reactant is rate-limiting, because of mass transport resistances and reactor hydrodynamics in the trickle bed regime. The ruthenium-catalyzed hydrogenolysis of lactic acid to propylene glycol has been examined in trickle bed and batch reactors to better understand the influence of mass transfer and partial wetting and to identify operating conditions where intrinsic kinetic rates can be obtained. At high liquid flow rates and low conversions in the trickle bed reactor, propylene glycol formation rates agree well with intrinsic rates obtained in a stirred batch reactor, with rate independent of feed flow rate or bed configuration in the trickle bed reactor. Application of a mass transport model to the trickle bed reactor at lower flow rates allows rates to be predicted outside the intrinsic kinetic regime. These results provide guidance for proper operation of laboratory trickle bed reactors and make it possible to predict performance in a trickle-bed reactor based on experiments conducted in bench-scale batch reactors.

A novel approach to recover succinic acid from fermentation broth via acidification and esterification in ethanol is presented. Acid salts from fermentation are placed in ethanol along with a slight stoichiometric excess of sulfuric acid. Simultaneous acidification and esterification take place, with the inorganic sulfate salt formed precipitating out of the ethanol solution. The succinate is recovered as a solution of free succinic acid, monoethyl succinate, and diethyl succinate in ethanol, a mixture suitable for further esterification via reactive distillation. Recoveries of succinate species in excess of 95% were obtained for both model succinate salt solutions and for actual fermentation broth mixtures.Graphical abstractHighlights► Succinic acid recovery from fermentation broth by reactive extraction with ethanol. ► Process successfully evaluated with different succinate salts (Na+, Ca2+, Mg2+). ► Succinic acid recovery as a mixture of esterification products >90% was achieved. ► Process validated with pure salts and real fermentation products. ► Other carboxylic acids present in the broth can also be recovered.

Esterification of mixtures of succinic acid and acetic acid, commonly produced via fermentation of biomass carbohydrates, with ethanol in a continuous reactive distillation unit has been studied. Experiments were carried out in a 6 m tall, 51 mm diameter pilot-scale stainless steel column with the reactive zone consisting of Katapak-SP11 structured packing containing Amberlyst 70 cation exchange resin as catalyst. Noncatalytic BX structured gauze packing was used in stripping and enrichment sections. Steady-state experiments were performed under different conditions by varying the composition and number of inlet streams, the column pressure, the reboiler power, and the reflux ratio. Conversions approaching 100% for both succinic acid and acetic acid were verified experimentally; succinate esters were obtained as bottom products with purities of diethyl succinate as high as 98%, and ethyl acetate was recovered in the distillate. Computer simulations based upon experimental phase equilibrium data and chemical kinetics were performed in Aspen Plus using RadFrac to reproduce steady-state results. Good agreement between experiment and simulation was observed under diverse operating conditions. The model developed here can be used to design commercial-scale systems for succinic acid production when acetic acid is also formed during the fermentation.

A detailed model of glycerol hydrogenolysis in a trickle-bed reactor is presented that includes a mechanistically based kinetic rate expression, energy transport, mass transport across the gas−liquid and liquid−solid interfaces, intraparticle catalyst mass transfer, and partial wetting of the bed. Optimal kinetic parameters for the glycerol hydrogenolysis rate expression were determined via nonlinear regression analysis on the basis of experiments conducted in a laboratory-scale trickle-bed reactor over a broad range of operating conditions. Model predictions agree well with experimental data and accurately predict trends in reactor performance with liquid flow rate, temperature, hydrogen pressure, and base promoter concentration. The model is thus a useful tool for predicting laboratory reactor performance and for design of commercial-scale trickle-bed systems.

The irreversible adsorption and decomposition of glycerol and other polyhydric alcohols over ruthenium metal at 298–353 K has been examined in a recirculating microreactor system. The quantity of glycerol (GO), propylene glycol (1,2-propanediol, herein PG), ethylene glycol (EG), or 1,3-propanediol (1,3-PDO) adsorbed on a reduced and evacuated bulk Ru metal powder at saturation is 0.8 ± 0.2 μmol/g, a value approximately one-tenth that of CO adsorbed (9.0 μmol/g) on the same material. The quantity of polyol adsorbed is independent of temperature, but is strongly affected by the condition of the Ru surface—saturating the metal surface with hydrogen prior to exposure to the polyol significantly reduces the quantity of polyol adsorbed. When they are present together in solution, GO adsorbs more readily than PG, to the point of excluding PG from adsorbing when excess GO is present. Removal of adsorbed species in their original form by heating or flushing with water is not possible, but all carbon is accounted for as desorbed methane when the Ru catalyst is heated under hydrogen.

The reaction kinetics of the reversible esterification reaction of succinic acid with ethanol to form monoethyl and diethyl succinate are presented. The reaction was studied in batch isothermal experiments catalyzed by macroporous Amberlyst-15 ion-exchange resin. Experimental data were obtained between 78 and 120 °C at different mole ratios of ethanol to succinic acid and at ion-exchange resin catalyst concentrations from 1 to 5 wt % of solution. Kinetic modeling was performed using a pseudohomogeneous mole fraction model which acceptably fits the experimental data. The kinetic model is useful for the design and simulation of processes such as reactive distillation for diethyl succinate formation.

Amino alcohols are important building blocks for a variety of pharmaceutical, insecticidal, and other specialty compounds. Hydrogenation of amino acids to amino alcohols is a route that allows for the incorporation of biorenewable-derived chemicals into traditional petroleum-based industrial processes. This study examines the effect of multiple substrates on aqueous-phase hydrogenation rates of the amino acids serine, alanine, and valine. Hydrogenation reactions were carried out in a high-pressure reactor at 7.0 MPa hydrogen pressure and 130 °C over carbon supported ruthenium catalyst. Samples taken at regular intervals and analyzed by high-performance liquid chromatography allowed calculation of conversion rates and product yields. In general, competition between the amino acid substrates results in reduced reaction rates relative to that for hydrogenation of a single amino acid substrate. Kinetics of mixed amino acid hydrogenation was modeled using a Langmuir−Hinshelwood-type mechanism with surface reaction as the rate-limiting step.

Adsorption of reactant and product species can have a major effect on local pore concentrations in activated carbon-supported metal catalysts. Individual and combined adsorption of glycerol (GO) and propylene glycol (PG) onto activated carbon in aqueous solution is reported here at concentration ranges of 0.05–2.0 M and temperatures from 25 °C to 160 °C. Langmuir and Freundlich isotherms are used to model the single component data, with the Langmuir model best describing results below 0.75 M. The extended Langmuir model has been used to model the competitive adsorption system – model parameters determined from single component experiments accurately predict two component adsorption data over the temperature and concentration ranges studied. Propylene glycol adsorbs more strongly than GO onto the activated carbon supports studied, and also adsorbs to a somewhat greater extent compared to GO. This is attributed to the greater organic character of PG, which favors its selective adsorption onto the support material.

New mesoporous base catalysts (CM-HMS and CM-MCM-41) were synthesized by generating uniform particles of cerium and manganese oxides (MnOx/CeO2) in situ within hexagonal mesoporous silica (HMS) and MCM-41 supports. These catalysts were characterized by N2 adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), FTIR, temperature-programmed desorption of CO2 (CO2-TPD), and diffuse reflectance UV–visible (UV–vis) spectroscopy. Spectroscopic studies reveal that some particles of MnOx/CeO2 are incorporated into the walls of the silica network of HMS and MCM-41, while others are highly dispersed onto the surface of the HMS or MCM-41. The catalytic activity of CM-HMS and CM-MCM-41 for the ketonization of carboxylic acids was confirmed; better utilization of Ce and Mn was observed than in unsupported MnOx/CeO2. The citrate-based preparation of MnOx/CeO2 catalyst supported on HMS and MCM-41 has not been previously reported in the literature.Graphical abstractNew mesoporous solid base catalysts, abbreviated as CM-HMS and CM-MCM-41, were synthesized by incorporating active base centers of MnOx/CeO2 into two different mesoporous silica supports (HMS and MCM-41). CM-HMS and CM-MCM-41 are more efficient catalysts than unsupported MnOx/CeO2 in ketonization of carboxylic acids.Download high-res image (104KB)Download full-size imageResearch highlights► Uniformly dispersed solid base catalysts prepared on mesoporous silicas (CM-HMS, CM-MCM-41). ► Characterization shows MnOx/CeO2 primarily present on walls and surface of silica supports. ► CM-HMS and CM-MCM-41 are highly selective catalysts for ketonization of carboxylic acids.