Patent Application
20090131711
This invention relates to the esterification of oils and fats to form products useful, for example, as fuels or fuel additives or lubricants. More particularly, the invention relates to such processes that can be used for the production of so-called biodiesel fuels as well as other products.
Diesel fuels derived from refining crude oil and other forms of petroleum raw feed stocks are relatively inexpensive to produce and therefore are widely used to power internal combustion engines for numerous light- and heavy-duty transportation and stationary industrial applications. However, combustion of such diesel fuels typically produces significant amounts of gaseous pollutants in the attendant exhaust gases including nitric oxide, nitrogen dioxide, sulphur dioxide, carbon monoxide, and hydrocarbons. Furthermore, temperatures achieved in most diesel-fired engines are not sufficiently high enough to provide complete combustion of diesel fuels thereby generating significant amounts of particulate emissions in the form of black soot or smoke from the engine exhaust stacks. Consequently, numerous regulatory agencies have established and promulgated long-term escalating emission standards for reducing gaseous and particulate matter in diesel engine exhaust gases.
Various strategies have been implemented to achieve current and pending regulatory standards for emissions from diesel engines, including: (a) modification of engine designs to provide more efficient and complete fuel combustion, (b) extending and modifying refining processes to provide more highly-purified and cleaner burning petroleum-derived diesel fuels, (c) development of chemically synthesized additives for mixing into refined diesel fuels to improve their combustion and emissions properties, and (d) assessment of alternative raw feed stocks such as animal and plant-derived fats and oils for the production of fuels commonly called “biofuels” or “biodiesel”, that have similar thermal combustion and power-generating properties to petroleum-based diesel fuels.
There is considerable interest in the use of plant-derived oils and animal fats as feedstocks for production of biodiesel fuels for use in diesel engines because these alternative fuels are significantly cleaner burning, i.e., their exhaust gases contain significantly reduced levels of gaseous and particulate emissions, compared to petroleum-based diesel fuels. Biodiesel fuels are typically produced by processes which involve esterification of triglycerides and free fatty acids present in the feedstocks with short-chain alcohols to form alkyl esters of the fatty acids as the primary products as well as commercially useful by-products such as glycerol. The esterification reaction is generally described as:
There are three basic processes known for conversion of oil and fat feedstocks into biodiesel fuels:
It is known that hydrogenated and unhydrogenated animal fats, rendered fats, vegetable oils, fish oils, spent restaurant grease, and waste industrial frying oils are suitable feedstocks for production of biodiesel fuels by such esterification processes. The simplest and therefore most common process is the base-catalyzed reaction because it does not require exotic catalysts such as those disclosed in U.S. Pat. Nos. 5,508,457, 5,525,126 and 6,878,837, or system configurations such as those disclosed in U.S. Pat. Nos. 6,174,501, 6,187,939 and 6,887,283, and can be performed with relatively lower temperatures, pressures and reaction/synthesis times. However, in order to produce a sufficiently purified biodiesel fuel or fuel additive suitable for use with current diesel engine designs, Dmytryshyn et. al.(2004, Bioresource Technology 92: 55-64) teach that the base-catalyzed process must be conducted in two stages as exemplified in
The exemplary embodiments of the present invention, at least in preferred forms, are directed to processes for producing alkyl esters useful as biodiesel fuels and lubricants from a feedstock containing glyceride-containing substances, said alkyl esters produced in a single-stage alkylation reaction of the glycerides in said feedstock with an alcohol containing therein a reaction catalyst.
According to a preferred embodiment of the present invention, there is provided a process for producing alkyl esters from a feedstock containing glyceride-containing substances in a single-stage esterification reaction wherein the first step is dewatering of the feedstock after which, the dewatered feedstock is combined with an alcohol (preferably anhydrous or dewatered from a previous stage of the process) containing therein a reaction catalyst for esterification of the glycerides thereby producing alkyl esters in a single-stage alkylation reaction. The single-stage alkylation reaction provides a reaction product comprising alkyl esters suitable for use as biodiesel fuels and lubricants, and a reaction by-product comprising reaction catalyst-containing alcohol, glycerols and glycerol-containing substances. The reaction product is preferably de-watered and purified after separation from the reaction mixture.
According to one aspect, the glyceride-containing feedstock is an oil-based feedstock prepared from plant materials. In a preferred form, the plant-based oil-containing feedstock is a material prepared from the seeds of a plant selected from the group comprising brassicas, legumes, maize, cotton, flax and palms. Non-limiting examples of useful plant seeds include mustard, canola, soybean, corn, cotton, flax and oil-seed palms.
According to another aspect, the glyceride-containing feedstock is an oil-based feedstock prepared from animal materials. In a preferred form, the animal-based oil-containing feedstock is a material prepared from rendered animal fats.
According to yet another aspect, the glyceride-containing feedstock is an oil-based feedstock selected from the group comprising waste restaurant frying oils, waste vehicular and/or locomotive and/or marine engine oils, and waste industrial lubricants and oils, said waste oils and lubricants characterized by a low free fatty acid content.
According to another preferred embodiment of the present invention, there is provided a process comprising a single-stage esterification reaction for producing an alkyl ester reaction product from a glyceride-containing feedstock. The single stage reaction comprises contacting a dewatered glyceride-containing feedstock with an alcohol containing therein a suitable reaction catalyst. The reaction is preferably conducted in a pressure-resistant vessel wherein temperature and negative pressure are controllably maintainable for a period of time sufficient to convert said glycerides into an alkyl ester reaction product and a reaction by-product mixture comprising glycerols and/or glycerol-containing substances and said alcohol, after which, the reaction product is separated from the reaction by-product.
According to one aspect, the alcohol is preferably a short-chain alcohol. It is preferred that the alcohol is selected from the group comprising methanol, ethanol, propanol and butanol.
According to another aspect, the reaction temperature is preferably selected from the range of 50° C. to 100° C. It is preferable that the negative pressure is selected from the range of 99 mmHg(A) to 760 mmHg(A).
According to yet another aspect, the alky ester reaction product separated from the reaction by-product, is de-watered. The de-watered alky ester reaction product is purified by contacting the reaction product with an adsorbent material. In a preferred form, the adsorbent material is selected from the group comprising silicas and clays. It is preferable that the adsorbent material is a silica.
According to a further aspect, the catalyst-containing alcohol is separated from the reaction by-product mixture. It is preferred that the separated catalyst-containing alcohol is de-watered and recycled for use in another single-stage esterification reaction.
According to a yet further aspect, the glycerols and glycerol-containing substances comprising the reaction by-product mixture are separated from said mixture. Said separated glycerols and glycerol-containing substances may optionally be further separated and purified.
According to yet another preferred embodiment, there is provided an alkyl ester product produced from a glyceride-containing feedstock by a single-step esterification reaction of the present invention. The glyceride-containing feedstock is preferably an oil-based feedstock prepared from materials selected from the group comprising plant materials, animal materials and fish materials. In a preferred form, the plant materials are selected from the group comprising brassica seeds, legumes seeds, maize seeds, mallow seeds, flax seeds and palm nuts.
According to a further preferred embodiment, there is provided a glycerol-containing product produced from a glyceride-containing feedstock by a single-step esterification reaction of the present invention.
Other exemplary embodiments provide a process for producing alkyl esters in a single-stage esterification reaction of a dewatered feedstock containing therein glyceride-containing substances, thereby providing a reaction product comprising alkyl esters and a reaction by-product comprising glycerol-containing substances.
The present invention will be described in conjunction with reference to the following drawing, in which:
The present invention provides a process for producing alkyl esters from a feedstock containing oils or fats, in a single-stage esterification reaction performed under controlled temperature and pressure conditions that are significantly lower than those disclosed and taught in the prior art. The first step in the process of the present invention is to dewater the feedstock by raising the temperature of the feedstock to within the range of 50° C. to 100° C. after which, the heated feedstock is sprayed into a vessel whereto a negative pressure in the range of 99 mmHg(A) to 760 mmHg(A) has been applied and wherein the temperature of the heated feedstock is maintained while the feedstock is agitated to maintain a turbulent flow until the feedstock is substantially free of water, i.e., it contains less than 1% water (v/v). Alternatively, the feedstock may be added into a temperature- and pressure-controllable vessel, wherein it is agitated to maintain a turbulent flow under a negative pressure in the range of 99 mmHg(A) to 760 mmHg(A) while its temperature is raised to within the range of 50° C. to 100° C. and then maintained in a turbulent flow at said temperature until the feedstock is substantially free of water. The dewatered feedstock is cooled prior to mixing with a short-chain alcohol containing a basic esterification catalyst thereby initiating an exothermic reaction whereby the triglycerides present in the feedstock are alkylated in a single stage to produce alkyl esters suitable for use as biodiesel fuels and lubricants. It is preferable that the single-stage esterification reaction is conducted within temperature- and pressure-controllable vessels provided with mixing equipment capable of producing and maintaining a turbulent flow so that the temperature and agitation of the feedstock can be precisely controlled during the esterification reaction. Temperatures may be precisely controlled during the exothermic reaction by providing said vessels with external water jackets or alternatively, with cooling coils within the vessels. There are also provided methods for purifying the alkyl esters produced by the process of the present invention for single-stage esterification of a dewatered feedstock. The process of the present invention additionally produces as reaction by-products such as crude glycerol and soaps which if so desired, may be further purified for other types of use.
The process of the present invention is suitable for use with any feedstock containing plant-derived oils such as oils obtained for example from crushing seeds from mustard, canola, soybean, corn, cotton, flax, or palm and other plants producing seeds with high oil-content. Alternatively, the process of the present invention is also suitable for use with feedstocks containing fish oils or animal fats including rendered fats or tallow. Furthermore, the process of the present invention can also be used with feedstocks comprising waste restaurant or industrial grease and/or frying oils containing very low levels of free fatty acids.
The alcohol used in the process of the present invention is preferably a dewatered short chain alcohol within the range of C1-4 containing less than 1% water (v/v). It is preferable to use absolute methanol; however, absolute ethanol, absolute propanol and absolute butanol can be used satisfactorily in the process of the present invention. It is important to thoroughly mix a basic esterification catalyst into the alcohol prior to adding the alcohol-basic catalyst mixture into a dewatered feedstock. While the process of the present invention can be employed with any basic esterification catalyst mixed into the alcohol, it is preferred to use potassium hydroxide or alternatively, sodium hydroxide.
In one preferred embodiment of the present invention, the process illustrated in
The examples presented below are included as embodiments of the present invention, but are not intended to limit the scope of the present invention.
A 1,700 kg quantity of mustard oil was sprayed with a nozzle pressure of 10.0±5.0 psi into a temperature- and pressure-controlled water-jacketed reactor. After the mustard oil was added to the reactor, a negative pressure of 110 mmHg(A) was applied by vacuum, and the oil was dewatered by heating to and maintenance at 100° C.±5° C. under negative pressure while being maintained in a turbulent flow by agitation until there was no trace of bubbling at the oil surface after which, the oil was cooled to 50° C.±2° C.
While the oil was being dewatered, 340.0 kg of absolute methanol (20% w/w of the oil) was added to a stirred vessel and then 17.0 kg of KOH (1% w/w of the oil) was added while the methanol was vigorously agitated until the KOH was completely dissolved. The KOH-methanol mixture was added under vacuum to the 1,700 kg of dewatered oil maintained in a turbulent flow by agitation after which, the negative pressure within the reactor was broken with nitrogen gas which was used to flush and then maintain the headspace within the reactor. Addition of the KOH-methanol mixture to the dewatered oil initiated an exothermic esterification reaction and therefore, the temperature within the water-jacketed reactor was carefully maintained at 50° C.±2° C. during the reaction period. The esterification reaction proceeded for 4.5 hrs while the oil was maintained in a turbulent flow by agitation. At the end of this time period, agitation was ceased and the methylated mustard oil was maintained in the reactor for 2 hrs to allow the reaction mixture to separate into two phases comprising a top layer containing the methyl ester reaction product above a bottom layer containing the reaction by products, i.e., spent methanol and crude glycerol.
After the phase separation was complete, the bottom layer containing the reaction by-products was removed from the reaction vessel after which the temperature of the retained methyl ester product was adjusted to 50° C. Then, 500 L of water heated to 95° C. was added to the methyl ester phase under vacuum after which, the negative pressure was released and the mixture was agitated for 30 min at atmospheric pressure to wash water-soluble impurities out of the methyl ester reaction product after which, agitation was stopped. The mixture was allowed to separate over an 8-hr period into 2 phases comprising a top layer containing washed methyl ester reaction product above a bottom layer containing water-soluble by-products removed from the methyl ester reaction product.
After the second phase separation was complete, the bottom layer was removed. A negative pressure of 110 mmHg(A) was then applied by vacuum to the washed methyl ester reaction product remaining in the reactor while the temperature of the reaction product was raised to 95° C.±5° C. under agitation to dewater the washed methyl ester water product. After dewatering was completed, the temperature of the methyl ester reaction product was adjusted to 60° C.±3° C. after which, 2% (w/w) TriSyl® 615 adsorbent (TriSyl is a registered trademark of W.R. Grace & Co.) was added to the reaction product and mixed for 30 min to remove any remaining impurities. The adsorbent was removed from the methyl ester reaction product by recycling the methyl esters through a pressure filter apparatus until clarity was achieved. The methyl ester reaction product was then packaged and analyzed.
The data in Table 1 show that the process of the present invention provided a 99% conversion of the triglyceride compounds present in mustard oil into methyl esters, the purity of the final methyl ester product was 98.95%, and the recovery was 91.8%, i.e., 1,700 kg of mustard oil yielded 1,560 kg of methyl ester product containing 1,531 kg methyl esters. The data in Table 2 show that the 91.8% of the starting raw material (i.e., crude mustard oil) was recovered and purified methyl ester reaction product.
A 500 g quantity of canola oil was added into temperature- and pressure-controlled water-jacketed reactor 2 L all Stainless Steel Pressure Reactor (Parr Instrument Company, Moline, Ill., USA). The canola oil was dried by a negative pressure of 110 mmHg(A) applied by vacuum, and the oil was dewatered by heating to and maintenance at 100° C.±5° C. under negative pressure while being maintained in a turbulent flow by agitation until there was no trace of bubbling at the oil surface after which, the oil was cooled to 50° C.±2° C.
While the oil was being dewatered, 100 g of absolute methanol (20% w/w of the oil) was added to a stirred vessel and then 5 g of KOH (1% w/w of the oil) was added while the methanol was vigorously agitated until the KOH was completely dissolved. The KOH-methanol mixture was added under vacuum to the 500 g dewatered oil maintained in a turbulent flow by agitation after which, the negative pressure within the reactor was broken with nitrogen gas which was used to flush and then maintain the headspace within the reactor. Addition of the KOH-methanol mixture to the dewatered oil initiated an exothermic esterification reaction and therefore, the temperature within the water-jacketed reactor was carefully maintained at 50° C.±2° C. during the reaction period. The esterification reaction proceeded for 4 hrs while the oil was maintained in a turbulent flow by agitation. At the end of this time period, agitation was ceased and the methylated canola oil was transferred to a separation funnel where it was maintained for 18 hrs to allow the reaction mixture to separate into two phases comprising a top layer containing the methyl ester reaction product above a bottom layer containing the reaction by products, i.e., spent methanol and crude glycerol.
After the phase separation was complete, the bottom layer containing the reaction by-products was removed from the separation funnel after which, the top methyl ester layer was removed into a separate container. The temperature of the methyl ester product was adjusted to about 75 after which water heated to 95° C. was added to the methyl ester phase until a ratio of 85:10 methyl ester:water was reached. The mixture was then vigorously agitated for 10 min and then centrifuged at 4,200 rpm for 10 min to separate the mixture into 2 phases comprising a top layer containing washed methyl ester reaction product above a bottom layer containing water-soluble by-products removed from the methyl ester reaction product. The top layer containing the washed methyl ester product was decanted and transferred to rotary evaporator flasks wherein any remaining water was removed.
After dewatering was completed, the temperature of the methyl ester reaction product was adjusted to 60° C.±3° C. after which, 0.5 2% (w/w) TriSyl® 615 adsorbent was added to the reaction product and mixed for 15 min to remove any remaining impurities. The adsorbent was removed from the methyl ester reaction product by recycling the methyl esters through a pressure filter apparatus until clarity was achieved. The methyl ester reaction product was then packaged and analyzed.
The data in Tables 3 and 4 show that the process of the present invention provided a 99% conversion of the triglyceride compounds present in canola oil into methyl esters, the purity of the final methyl ester product was 100%, and the recovery was 85% i.e., 500 g of canola oil yielded 425 g of methyl ester product containing 421 g methyl esters.
A 500 g quantity of soybean oil was added into temperature- and pressure-controlled water-jacketed reactor 2 L all stainless steel pressure Reactor (Parr Instrument Company, Moline, Ill., USA). The soybean oil was dried by a negative pressure of 110 mmHg(A) applied by vacuum, and then heating and maintaining the oil at 100° C.±5° C. under negative pressure while being maintained in a turbulent flow by agitation until there was no trace of bubbling at the oil surface after which, the oil was cooled to 50° C.±2° C.
While the soybean oil was being dewatered, 100 g of absolute methanol (20% w/w of the oil) was added to a stirred vessel and then 5 g of KOH (1% w/w of the oil) was added while the methanol was vigorously agitated until the KOH was completely dissolved. The KOH-methanol mixture was added under vacuum to the 500 g dewatered soybean oil maintained in a turbulent flow by agitation after which, the negative pressure within the reactor was broken with nitrogen gas which was used to flush and then maintain the headspace within the reactor. Addition of the KOH-methanol mixture to the dewatered oil initiated an exothermic esterification reaction and therefore, the temperature within the water-jacketed reactor was carefully maintained at 50° C.±2° C. during the reaction period. The esterification reaction proceeded for 4 hrs while the oil was maintained in a turbulent flow by agitation. At the end of this time period, agitation was ceased and the methylated soybean oil was transferred to a separation funnel where it was maintained for 18 hrs to allow the reaction mixture to separate into two phases comprising a top layer containing the methyl ester reaction product above a bottom layer containing the reaction by products, i.e., spent methanol and crude glycerol.
After the phase separation was complete, the bottom layer containing the reaction by-products was removed from the separation funnel after which, the top methyl ester layer was removed into a separate container. The temperature of the methyl ester product was adjusted to about 75 after which water heated to 95° C. was added to the methyl ester phase until a ratio of 85:10 methyl ester:water was reached. The mixture was then vigorously agitated for 10 min and then centrifuged at 4,200 rpm for 10 min to separate the mixture into 2 phases comprising a top layer containing washed methyl ester reaction product above a bottom layer containing water-soluble by-products removed from the methyl ester reaction product. The top layer containing the washed methyl ester product was decanted and transferred to rotary evaporator flasks wherein any remaining water was removed.
After dewatering was completed, the temperature of the methyl ester reaction product was adjusted to 60° C.±3° C. after which, 2% (w/w) TriSyl® 615 adsorbent was added to the reaction product and mixed for 15 min to remove any remaining impurities. The adsorbent was removed from the methyl ester reaction product by recycling the methyl esters through a pressure filter apparatus until clarity was achieved. The methyl ester reaction product was then packaged and analyzed.
The data in Tables 5 and 6 show that the process of the present invention provided a 100% conversion of the triglyceride compounds present in soybean oil into methyl esters, the purity of the final methyl ester product was 100%, and the recovery was 88.6%, i.e., 500 g of soybean oil yielded 443 g of methyl ester product containing 443 g methyl esters.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA06/01238 | 7/27/2006 | WO | 00 | 12/3/2008 |
| Number | Date | Country | |
|---|---|---|---|
| 60703447 | Jul 2005 | US |
