Fatty oil hydrogenation in supercritical solvents: Process design and safety issues

A simulation study of a SCF process is carried out using Aspen™ with previously available catalytic kinetics for the simulation of the reactor. Two supported catalysts were considered: a standard Pd/carbon, and an egg-shell Pd/alumina, in a vapour-phase process that uses propane as solvent. Best reactor-catalyst combination was selected using optimization. Optimal reactor-catalyst conditions were: Pd (0.5 wt%) on alumina catalyst in tubes, shell cooling, inlet temperature 170 °C, space-time 100 s, 4 mol% of H₂ in the feed, oil feed 1 mol%, propane 95 mol%, with pressure up to 20 MPa. Three SC solvents, were considered in the simulation. These were (i) SC propane, (ii) a cosolvent case with hexane-modified CO₂, and (iii) a case with pure liquid hexane. In plant simulation, three recycle streams (H₂, CO₂ and cosolvent) complicate the separations. In order to assess the safety differences between these options, a study was done using the Dow Fire and Explosion Index to roughly figure out process safety. It is shown that plant complexity increases with cosolvent use, but the hazard index is sensibly reduced, from F&EI = 150 (pure propane) to a low value (F&EI = 60) for a plant with CO₂ with 40 mol% of hexane as cosolvent.     

Modeling of reaction rate constants and selectivities in soybean oil hydrogenation

A simple approach to model the rate constants and selectivities for soybean oil hydrogenation with nickel catalyst is presented. The rate constant models were constructed on the basis of Arrhenius Law and Power series. The parameters were temperature, hydrogen pressure, concentration of catalyst and agitation expressed in terms of power per unit volume of oil. The models agree with the general knowledge in hydrogenation and the data were fitted fairly well by the models. Presented at AOCS Annual Conference, New York, NY, April 1980.     

Kinetics of catalytic transfer hydrogenation of soybean oil

The catalytic transfer hydrogenation of soybean oil was studied by using various concentrations of sodium formate solutions, an emulsifier and paladium on a carbon catalyst. Sodium formate concentration and addition of the emuldifier significantly affect the reaction rate because of their influence on the liquid/liquid interface. Under conditions in which diffusion effects are eliminated, all reactions carried out in diluted sodium formate solution obey first-order kinetics with respect to fatty acids. This allows control over the hydrogenation process of soybean oil, needed to obtain partially hydrogenated oil containing about 1% linolenic acid and a relatively high level of linoleic acid with no increase in the stearic acid concentration.     

Glycerol in subcritical and supercritical solvents

Glycerol conversion to added value chemicals is a research avenue that has attracted significant interest in recent years. The utilization of critical solvents such as water and organic solvents in critical conditions as well as subcritical conditions (or hot compressed solvent) and supercritical conditions can offer several advantages to batch processes and in continuous flow systems in view of their potential implementation in industry. This review has been aimed to highlight most recent key processes for glycerol valorization to valuable products using different types of catalysts and processes. © 2016 Society of Chemical Industry     

Kinetics of bitumen extraction from oil sands using organic solvents

The kinetic study of bitumen extraction from oil sands is significant for efficiency improvement and reactor design in industrial applications. Here, an improved pseudo-first-order kinetic model was established with the assumption of a constant Sherwood number, which took into account the mass transfer area. Five organic solvents were used for the extraction kinetics of the prepared bitumen microbeads. The improved pseudo-first-order kinetic model exhibited excellent fitting effects. Petroleum ether/dichloromethane was proved to be the best solvent. The results also showed an exponential decrease in the diameter of the bitumen microbeads and a linear increase in mass transfer coefficients with time for all the solvents. The kinetics of bitumen extraction from oil sands using different solvents were predicted according to the corresponding average mass transfer coefficients. The experimental results confirmed that the improved kinetic model was capable of describing the mass transfer process of bitumen extraction from oil sands.     

Coal hydrogenation: Quality of start-up solvents and partially process-derived recycle solvents

The performance of three sets of start-up solvents and one set of partially process-derived recycle solvents was studied in small autoclave coal hydrogenation tests. The start-up solvents were obtained by catalytically hydrotreating anthracene oils or creosote oils. It is shown that this preparation procedure converts polynuclear aromatics and two-ring aromatics to hydroaromatics and, ultimately, to alicyclics. Coal conversions using start-up solvents are found to reach a maximum at intermediate degrees of solvent hydrogenation which is believed to correspond to a maximal abundance of hydroaromatic solvent hydrogen donors. A solvent hydrogen donor index (SHDI), simply derived from ¹H n.m.r. spectral data, was devised and is found to successfully correlate coal conversions obtained using different start-up solvents, especially where N₂ gas rather than H₂ gas is employed in the autoclave tests. A set of partially process-derived recycle solvents were produced in multiple cycle continuous coal hydrogenation experiments. These were tested under relatively severe hydrogenation conditions in the presence of hydrogen gas, using the small autoclave unit. Substantial donation of solvent hydrogen was found to occur and coal conversions to hexane — and toluene-soluble products are found to be a smooth function of the solvent hydrogen donor index. It is concluded that the hydrogen donor capacity of a solvent is a major factor governing coal conversion, especially when the demand for solvent hydrogen is high. The SHDI parameter is useful in rationalizing the behaviour of start-up solvents. Also, at least in the first few cycles of a continuous two stage coal hydrogenation process, the SHDI parameter allows solvent quality to be monitored, and consequently optimized.     

Kinetics of liquid phase hydrogenation of cottonseed oil with nickel catalysts

The hydrogenation of cottonseed oil has been carried out in a batch reactor using both unmodified and chromia modified nickel catalysts. The process variables include chromium to nickel atomic ratio (0.00–0.35), catalyst particle size (200–400 micron), temperature (120–140°C) and pressure (5–10 bar). Chromia was found to suppress the stearate formation completely, although it retarded the overall hydrogenation activity of nickel. Its optimum content in the catalyst was found to be 0.17 Cr/Ni atomic ratio; the data corresponded to 5 hr reaction time. The kinetics of the process was tested and found to follow a first order reaction with respect to linoleate and half order with respect to hydrogen. The activation energy was found to be 11.8 kcal/mole.     

Physically and chemically mixed TiO2-supported Pd and Au catalysts: unexpected synergistic effects on selective hydrogenation of citral in supercritical CO2

The selective hydrogenation of citral was studied with various TiO₂-supported monometallic and bimetallic Pd and Au catalysts and their physical mixtures in supercritical CO₂ (scCO₂). Significant synergistic effects appeared when active Pd species was chemically or physically mixed with less active Au species. The total rate of conversion was greatly enhanced and the selectivity to citronellal (CAL) was improved. The physical properties of those catalysts were characterized by TEM, HRTEM-EDS, XPS, and UV/Vis and their features of H₂ desorption were examined by TPD. The physical and chemical characterization results were used to discuss the reasons for the unexpected synergistic effects observed. The same selective hydrogenation was also conducted in a conventional non-polar organic solvent of n-hexane to examine the roles of scCO₂. The use of scCO₂ was effective for accelerating the hydrogenation of citral and improving the selectivity to CAL.     

Kinetics and specificity of Lipozyme-catalysed oil hydrolysis in supercritical CO2

Blackcurrant seed oil is rich in linoleic and linolenic acids. Selective enzyme-catalysed oil hydrolysis was studied with aim to obtain different levels of α- and/or γ-linolenic acid in the mixture of liberated fatty acids and in the fraction of di- and monoacylglycerols, making them suitable for special dietary needs. The oil was dissolved in supercritical carbon dioxide flowing through a packed bed reactor (temperature 40 °C, pressure 15–28 MPa, and superficial velocity 0.1–0.7 mm s⁻¹) with Lipozyme^®, a 1,3-specific lipase from Mucor miehei immobilised on a macroporous ion-exchange resin. The enzyme activity was stable as long as water precipitation in the reactor was prevented. The reaction was found to be controlled by both Michaelis–Menten kinetics and mass transfer. The maximum rate of fatty acids liberation per unit amount of enzyme, 2.6 × 10⁻³ mol s⁻¹ kg⁻¹, was achieved at the maximum flow velocity and pressure. Compared to oil, the liberated fatty acids contained more α-linolenic, palmitic and stearic acids, while di- and monoacylglycerols contained increased levels of γ-linolenic and stearidonic acids.     

Sunflower oil and its applications

Sunflower is one of the oldest oilseeds in the Americas. It is the state flower of Kansas State and constitutes a significant segment of oilseeds produced in the former Soviet Union Block. Sunflower is admired worldwide for its vibrant beauty and is an important source of food. Its oil is viewed as a healthy vegetable oil and its seeds contain a wide range of nutrients that are enjoyed as a tasty snack as well as nutritious ingredient in many foods, such as health bars, salad garnish and spreads similar to peanut butter. Sunflower is an important crop choice for US growers from the northern plains of Dakotas to Texas panhandle. The oil has very good taste and appearance. Today, there is the traditional sunflower oil, which is high in linoleic acid content that makes it excellent for both domestic and industrial use. The high linoleic acid content makes the oil unstable in industrial or institutional frying. Mid‐oleic sunflower, which contains higher oleic acid and lower level of linoleic acid than the garden variety sunflower oil is more suitable for industrial and institutional frying along with the applications such as salad oil and cooking oil. High oleic sunflower oil, that contains 80% or higher oleic acid and very low linoleic acid, is one of the most stable oils for all applications, including industrial and institutional frying, and also for industrial non‐food applications such as lubricant, as transformer oil and various other applications.     

Kinetics of hydrogenation of rapeseed oil: I. Influence of transport steps in kinetic study

The influence of mass transfer steps in the kinetic study of rapeseed oil hydrogenation in a laboratory reactor was estimated. Hydrogenations were carried out at 140–200 C and at 0.3–10 atm hydrogen pressure in the presence of 0.087% of commercial nickel-on-kieselguhr catalyst, corresponding to 0.05% of nickel. Despite intense mixing conditions on the macroscale of the bulk oil, corresponding to a reaction rate independent of further increase of the stirrer rate, the concentration differences across the liquid film surrounding the bubbles and the catalyst particles could not be neglected. The pore transport of triglycerides and hydrogen molecules was found not to be a slow step in most hydrogenations.     

Kinetics of supercritical carbon dioxide extraction of borage and evening primrose seed oil

In the present work, high‐pressure extraction of borage (Borago officinalis L.) and evening primrose (Oenothera biennis L.) seed oil, containing the valuable γ‐linolenic acid (GLA), has been investigated. Extraction was performed with supercritical carbon dioxide on a semi‐continuous flow apparatus at pressures of 200 and 300 bar, and at temperatures of 40 and 60 °C. A constant flow rate of carbon dioxide in the range from 0.17 to 0.20 kg/h was maintained during extraction. The extraction yields obtained using dense CO₂ were similar to those obtained with conventional extraction using hexane as solvent. The composition of extracted crude oil was determined by GC analysis. The best results were obtained at 300 bar and 40 °C for both seed types extracted, where the quality of oil was highest with regard to GLA content. The evening primrose seed oil extracted with supercritical fluid extraction was particularly rich in unsaturated fatty acids: up to 89.7 wt‐% of total free fatty acids in the oil. The dynamic behavior of the extraction runs was analyzed using two mathematical models for describing the constant rate period and the subsequent falling rate period. Based on the experimental data, external mass transfer coefficients, diffusion coefficients and diffusivity in solid phase were estimated. Results showed good agreement between calculated and experimental data.     

Kinetics of the hydrogenation of rapeseed oil: II. Rate equations of chemical reactions

The kinetics of rapeseed oil hydrogenation was studied at 140–220 C and at 0.3–10 atm hydrogen pressure in a laboratory reactor in the presence of 0.05% nickel catalyst. A mathematical model was fitted to the experimental data, and temperature and pressure dependence of the different reaction steps was discussed on the basis of the model. The adequacy of the model was tested by means of a residual analysis.     

Kinetics of the liquid-phase hydrogenation and isomerisation of sunflower seed oil with nickel catalysts

The kinetics of the hydrogenation of sunflower seed oil were investigated over the temperature range 138–238° C and the pressure range 2.2–3.4 bar in a batch reactor, using a nickel catalyst supported by silica. A theoretical reaction scheme using the Langmuir-Hinshelwood model described satisfactorily the experimental data.