Patent Application
20190031964
The present novel invention relates to a process for the extreme purification of renewable oils used to make renewable fuels such as animal fats/oils and various seed based oils, soy, rapeseed, palm, especially those seed oils that have been collected after use to prepare food, commonly known as Used Cooking Oil (UCO). These oils can contain deleterious material, gums, metals, sulfur, ash, water and other undesirable materials that interfere with the conversion process to renewable fuels or as feedstock for use in the chemical industry or other conversion processes where high purity is required. Having this level of purity prolongs catalyst life in processes, reduces corrosion in plant processes, and requires less conversion chemicals to reach the end goal of a process.
The present invention relates to processes for removing undesirable materials, sulfur, and ash, including one or more metals, water, unsaponifiable matter, free fatty acid, insoluble impurities from renewable oils. More particularly, the invention relates to such processes that are capable of extreme purification of these oils.
Renewable Oils are defined as seed based, animal based. The craft process for pulping wood to make paper for example produces crude tall oil which is a renewable oil.
Seed oils can be soy oil, rapeseed oil, palm oil, camelina or other. These oils are currently in demand for the production of Biofuel, fatty acid methyl ester (FAME).
Tallow oil is a rendered form of fat, from beef, poultry, lamb, or other animals.
Tallow manufacture consists of freeing fat from its associated tissues by heat rendering and then refining it to separate it from the solids and water which would lead to its deterioration. Tallow oil (also known as “tallow”) is used in animal feed, to make soap, shoe polish, for cooking and as a bird food. It can be used as a raw material for the production of biodiesel and other chemicals. Tallow also has a history of use as a lubricant for machinery as well as for ammunition. In addition to fat, tallow typically contains parts per million levels of a variety of minerals or metals. In one particular study, the level of such minerals was found to range from about 10-20 ppm sodium, 2-3 ppm potassium, 1-2 ppm calcium, 0.4-0.5 ppm iron, 1.1-1.2 ppm lead, 0.4 to 0.5 ppm magnesium, 0.070 ppm cadmium, 0.025 to 0.055 ppm zinc, 0.8 to 1.0 ppm chromium. Ali, Pakistan JOURNAL OF NUTRITION 7 (5) 717-720, 2008.
Conventionally, water acid degumming is used to remove phosphatides from vegetable oils and animal oils/fats. This process is being used as part of biodiesel manufacturing plant. In this process oil is heated up to about 70-90° C. followed by mixing of 0.05 to 0.1% phosphoric acid in a Continuous Stirrer Tank Reactor (CSTR). The residual acid is neutralized in subsequent CSTR by mixing with caustic followed by removal of gums by centrifugation and water washing. The process requires huge quantity of water for water washing and its disposal. Caustic used for neutralization of residual phosphoric acid also reacts with free fatty acids present in oils and fats and forms stable emulsion which is very difficult to break and requires longer time. The process is not suitable for removal of trace metals below 20 ppm.
U.S. Pat. No. 3,879,282 discloses a method for reducing ash and lead in motor oils. The method requires elevated temperature and pressure, does not address sulfur reduction and does not disclose the use of high gravity force centrification. Further, this invention and how it is applied will not work on triglyceride based oils as the method will convert the triglyceride oils to soap.
U.S. Pat. No. 5,239,096 disclosed a process for reducing non-hydratable gums and wax content in edible oils. The process involves mixing with 0.01 to 0.08% acid (in the form 10-15% aqueous solution), adding 1-5% base solution followed by slow mixing for 1-4 hrs, separating gums and water washing of oil. As discussed above the process will suffer due to drawbacks of water washing and neutralization steps.
U.S. Pat. No. 6,407,271 disclosed a method for eliminating metals from fatty acid substances and gum associated with said metals. Method comprises mixing of vegetable oil with aqueous solution of salt of polycarboxylic acid (Sodium salt of ethylenediaminetetraacetic acid, EDTA) in the droplets or micelles in the weight ratio above 3. The aqueous phase is separated from oil by centrifuging or ultra filtration. Process uses very expensive chemicals and huge quantity of water about 33% of vegetable oil.
U.S. Pat. No. 6,844,458 disclosed improved refining method for vegetable oils. In this method, aqueous organic acid and oil subjected to high and low shear followed by centrifuge to remove gums. As cited in examples process uses about 10% water of oil quantity to dilute the acid solution and treated oil still contain about 20 ppm of metals.
U.S. Pat. No. 7,494,676 disclosed a pretreatment process comprising of a) enzymatic degumming with or without citric acid and sodium hydroxide b) bleaching with 2-4%) bleaching earth and 0-1% activated carbon c) dewaxing at low temperature of 18-20° C. with gentle stirring for about 12-18 hrs to achieve <5 ppm phosphorous. The process uses up to 2.5% of water and centrifuge for separation of gums. As described above, caustic react with free fatty acids present in oil and fats and forms stable emulsion which is very difficult to break and require longer time. The complete process takes very long time of about 15-20 hrs. Hence the size of dewaxing vessel will be huge and also require high energy for stirring. Moreover, process did not discuss the removal of other metals such as Fe, Cu, Na, K, Ca, Mg etc. present in the oil.
U.S. Pat. Application No. 2013/0197251 discloses a treatment method involving the mixture of phosphoric acid and citric acid and clay to reduce metals. This disclosure does not discuss which type of clay (there are hundreds) is used. This disclosure is based around not requiring water washing and not requiring centrifuging, but the use of counter current washing to minimize the use of clay.
U.S. Pat. No. 8,912,351 discloses a method of metals reduction using Ionic liquids. The reduction of sulfur is not looked at nor is high gravity force centrification.
What is not disclosed in any of the prior art and what is needed in the industry is a method to reduce sulfur, nitrogen, metals, ash and other impurities to a very low level and do this in a very economical manner in a continuous plant environment and able to be scaled to high output levels to supply a petroleum refinery. This is the basis for our invention. All other methods including existing RBD (capital intensive) are not practical.
The present invention provides a simple and cost effective method to substantially reduce sulfur, metals and other impurities in renewable oils and used motor oil. Renewable oils are those defined as coming from the rendering of animals (tallow), from seed crops such as rapeseed, soy, corn, palm and others. These oils can also be treated after use such as from used cooking oil (UCO) which is a seed oil used for frying foods. The process may also be applied to petroleum oils such as used motor oil and the like. The process involves first mixing the oil with a mild citric water solution at 60 C and then centrifuging the material in a centrifugal device producing a minimum of 7000 Gs to remove gums, then contacting the oil with a mixture containing water, a straight chain hydro-treated ester compound, and a phosphate derivative at a minimum temperature of 100° C. for 10 minutes, then raising temperature to between 120° C. and 130° C. for approximately 30 to 90 minutes to complete reaction. The mixture is then allowed to cool and again centrifuged in a centrifugal device producing a minimum of 7000 Gs.
The process involves first centrifuging the renewable oil or petroleum based oil in a centrifugal device producing a minimum of 7000 Gs. The temperature of the oil is the temperature at which maximum insolubility of the oil and impurities is determined (about 130° F.), but is determined by prior laboratory work using steps as are known to persons of ordinary skill in the art. This first step pre-conditions the oil and removes larger impurities that will interfere with the reaction in step two. Step two, the oil (96.7%) is then contacted with a mixture containing water (1 to 3%), a straight chain hydro-treated ester compound (0.1 to 0.5%), and a phosphate derivative (0.01 to 0.06%) at a minimum temperature of 100° C. for a minimum of 10 minutes under reduced pressure, then raising temperature to between 120° C. and 130° C. for approximately 30 to 90 minutes under reduced pressure to complete reaction. At this point, a precipitate is formed which is a salt form of all or most of the impurities. To remove these impurities, step three, the mixture is then allowed to cool and again centrifuged in a centrifugal device which produces a minimum of 7000 Gs. This oil is then checked for compliance to the required specification.
Referring to
Prepare a solution as follows. Into each one liter of feedstock oil add a mixture of 100 ml water to which has been added 2 gm to 6 gm citric powder depending on the quantity of gums in the oil. Heat this total mixture to approximately 60 C and mix for approximately 15 min. Then centrifuge at 7,000 G to 12,000 G to remove gums and particulates. Place the centrifuged feedstock into a 2 liter glass beaker, with stir bar, onto a stirring hot plate equipped with a temperature control probe.
Heat the feedstock to 50 C. Separately, prepare a solution 0.5 to 5.0 gm of diammonium phosphate (DAP) in 20 cc of water in a 30 ml vial. The DAP will dissolve into the water. The amount of DAP (i.e. 0.5 to 5 gr) is a decision made based on level of treatment required. Add the DAP solution to the heated feedstock and increase the oil temperature to 100 C while stirring. Hold for 15 minutes while water evaporates, use vigorous mixing. Then raise the temperature to 130 to 150 C and hold for 90 minutes.
Then remove the beaker form the heat source and allow to cool to under 45 C. Then add 20 gm of a nitrogen absorption catalyst such as BASF F24X or 25X and continue stirring for 30 minutes. Then turn off stir bar and decant oil off into centrifuge tubes or run through a high speed centrifuge at 7,000 G to 12,000 G to remove particulates and the catalyst granules.
If needed, heat the treated oil to 60° C. and filter through a 1 micron micro-glass filter to remove particulates not already removed by the centrifuge operation.
The feedstock is then tested for residual nitrogen, metals, insolubles, ash, sulfur and other tests as required.
Reasonable variation and modification are possible within the scope of the foregoing disclosure, the drawing and the appended claims of the invention, the essence of which is that there has been provided a method for purifying renewable oils. Numerous variations and improvements are possible by those skilled in the art. Therefore, the claims define the inventions, which are not limited to the disclosure above.
This application claims priority from provisional Application No. 62/537,554, filed Jul. 27, 2017, incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62537554 | Jul 2017 | US |
