U.S. patent application number 11/853504 was filed with the patent office on 2008-10-09 for charged polymers for ethanol dehydration.
Invention is credited to Michael C. Berg, William A. Mowers, David Soane, Kristoffer K. Stokes.
Application Number | 20080249339 11/853504 |
Document ID | / |
Family ID | 39184122 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080249339 |
Kind Code |
A1 |
Stokes; Kristoffer K. ; et
al. |
October 9, 2008 |
Charged Polymers for Ethanol Dehydration
Abstract
The systems and methods described herein provide for modified
lignins and other compositions that may be useful as entrainers. In
embodiments, they may be useful for dehydrating ethanol so that it
can be used as an energy source.
Inventors: |
Stokes; Kristoffer K.;
(Jamaica Plain, MA) ; Soane; David; (Chestnut
Hill, MA) ; Berg; Michael C.; (Somerville, MA)
; Mowers; William A.; (Lynn, MA) |
Correspondence
Address: |
ELMORE PATENT LAW GROUP, PC
515 Groton Road, Unit 1R
Westford
MA
01886
US
|
Family ID: |
39184122 |
Appl. No.: |
11/853504 |
Filed: |
September 11, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60843815 |
Sep 12, 2006 |
|
|
|
Current U.S.
Class: |
568/916 ;
428/304.4; 523/218 |
Current CPC
Class: |
C07C 29/84 20130101;
C07C 29/80 20130101; C07C 29/76 20130101; Y10T 428/249953 20150401;
C07C 29/84 20130101; C07C 31/08 20130101; C07C 31/08 20130101; C07C
31/08 20130101; C07C 29/76 20130101; C07C 29/80 20130101 |
Class at
Publication: |
568/916 ;
523/218; 428/304.4 |
International
Class: |
C07C 29/74 20060101
C07C029/74; C08K 7/22 20060101 C08K007/22; B32B 3/26 20060101
B32B003/26 |
Claims
1. A method for dehydrating an ethanol solution comprising
distilling the ethanol solution in the presence of a molecular
sieve characterized by a porous core and a water-permeable
polymeric coating impermeable to ethanol.
2. The method in accordance with claim 1 wherein the surface of the
molecular sieve is characterized by a high charge density.
3. The method in accordance with claim 2 wherein the coating has a
thickness of less than about 100 nm.
4. The method in accordance with claim 2 wherein the coating
comprises pores having a mean diameter less than 4 Angstroms.
5. The method in accordance with claim 1 wherein the porous core
comprises silica or a polyanionic polymer.
6. The method in accordance with claim 5 wherein the coating
comprises a polycationic polymer.
7. The method in accordance with claim 6 wherein the polycationic
polymer is crosslinked.
8. The method in accordance with claim 6 further comprising an
additional coating comprising a polyanionic polymer.
9. The method in accordance with claim 3 wherein the coating
comprises a nonionic polymer.
10. The method in accordance with claim 1 wherein the porous core
comprises a polycationic polymer.
11. The method in accordance with claim 10 wherein the coating
comprises a polyanionic polymer.
12. The method in accordance with claim 11 wherein the polyanionic
polymer is crosslinked.
13. The method in accordance with claim 11 further comprising an
additional coating comprising a polycationic polymer.
14. The method in accordance with claim 10 wherein the coating
comprises a nonionic polymer.
15. A molecular sieve characterized by a porous core and a
water-permeable polymeric coating impermeable to ethanol.
16. The molecular sieve in accordance with claim 15 comprising the
porous core comprises a polyanionic polymer.
17. The molecular sieve in accordance with claim 16 wherein the
coating comprises a polycationic polymer.
18. The molecular sieve in accordance with claim 17 wherein the
polycationic polymer the coating has a thickness of less than about
100 nm.
19. The molecular sieve in accordance with claim 15 comprising the
porous core comprises a polycationic polymer.
20. The molecular sieve in accordance with claim 19 wherein the
coating comprises a polyanionic polymer.
21. The molecular sieve in accordance with claim 20 wherein the
polyanionic polymer the coating has a thickness of less than about
100 nm.
22. A method for dehydrating an ethanol solution comprising
distilling the ethanol solution in the presence of an entrainer
comprising a lignin or lignin derivative.
23. The method in accordance with claim 22 wherein the entrainer is
a carboxylated lignin.
24. The method in accordance with claim 22 wherein the entrainer is
produced by reacting a lignin with an anhydride.
25. The method in accordance with claim 24 wherein the anhydride is
a succinic anhydride.
26. The method in accordance with claim 24 wherein the anhydride is
an alkylated succinic anhydride.
27. The method in accordance with claim 22 wherein the lignin is a
kraft lignin characterized by hydroxyl groups.
28. The method in accordance with claim 27 wherein between about 50
and 100% of the hydroxyl groups are functionalized.
29. The method in accordance with claim 22 wherein the entrainer is
a solid.
30. The method in accordance with claim 23 wherein the entrainer is
further characterized by a hydrophilic polymer substituent.
31. The method in accordance with claim 30 wherein the hydrophilic
polymer substituent is selected from the group consisting of a
polyethylene oxide and a polypropylene oxide.
32. The method in accordance with claim 31 wherein the hydrophilic
polymer substituent is selected from the group consisting of a
polyethylene oxide diglycidyl ether and a polypropylene oxide
diglycidyl ether.
33. The method in accordance with claim 32 wherein the hydrophilic
polymer substituent has a molecular weight between about 700 and
2500 g/mol.
Description
RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/843,815, filed on Sep. 12, 2006. The entire
teachings of the above application are incorporated herein by
reference.
FIELD OF APPLICATION
[0002] This application relates generally to surfactant
compositions useful for production of fuel-grade ethanol.
BACKGROUND
[0003] As world-wide energy needs continue to grow, there is
concern that demand for energy may outstrip its supply. Alternative
fuel technologies are desirable to reduce economic dependency on
petroleum-based fuels. As an example, anhydrous ethanol (99.5 vol.
% ethanol) may be combined with gasoline for use in internal
combustion engines, thereby decreasing the amount of
petroleum-based fuel that automobiles consume.
[0004] Currently, automobile engines can run efficiently with
gasoline mixtures containing up to 20% anhydrous ethanol, and many
states have mandated that automobile fuel contain a certain
percentage of anhydrous ethanol, typically 5-10%. With engine
modifications, anhydrous ethanol may be used alone to fuel
vehicles. Although production and blending of ethanol with gasoline
have been used throughout the world for several decades, use of
these technologies has been limited by the high costs of producing
anhydrous alcohol.
[0005] Ethanol is typically produced by fermentation of biomass
material and distillation to form a single liquid phase containing
approximately equal volumes of ethanol and water. The EtOH/water
mixture may then be separated using chemicals like cyclohexane to
yield an anhydrous alcohol phase, which may contain minor amounts
of other alcohols, such as propanol or butanol. Adsorption and
solvent extraction are alternative or supplemental methods of
separating alcohol and water.
[0006] Ethanol distillation techniques and their modifications
produce 95% by weight ethanol solutions efficiently. However,
concentrating an ethanol solution beyond 96.4% by weight has been
difficult. At approximately this concentration, equilibrium is
reached between the liquid and the vapor phases, where both phases
have the same concentration of ethanol and water. This solution in
equilibrium is called an azeotrope, or a constant-boiling mixture.
For ethanol, a binary, minimum-boiling azeotrope is formed.
[0007] To dehydrate an ethanol solution beyond the 96.5%
concentration, one of two main procedures may be employed. One
procedure involves azeotropic distillation. This method has been
used for decades as a means for purification of chemicals from
azeotropic mixtures. The distillation procedure involves adding a
third chemical called an entrainer to the system. This third
component interacts with both of the water and ethanol to create a
ternary azeotrope which is stronger than the original binary
azeotrope. A typical ternary phase separation is achieved through
the use of benzene as an entrainer. This system yields three
distinct regions on the column that represent different
compositions. The uppermost region yields anhydrous ethanol.
[0008] As an alternative procedure for dehydrating ethanol beyond
the 96.5% concentration, molecular sieves may be used for the
dehydration step. Molecular sieves include zeolites, which are
highly ordered aluminosilicates having very precise pore sizes.
They are produced as small beads or pellets. The pore structure is
capable of performing size exclusion on the molecular level.
Ethanol is on the order of4.4 Angstroms and water is approximately
2.8 Angstroms. Molecular sieves selected with a pore size of3.0
Angstroms can therefore be used to separate the water from the
ethanol via size differences. To use this dehydration method, the
azeotropic stream of vaporized alcohol and water is passed through
a vessel containing the molecular sieves. The water is then
adsorbed into the pores and the larger ethanol passes by and is
condensed into tanks. Since the water adsorption occurs via a
surface phenomenon, the particles can be regenerated for reuse by
drying with heat or by vacuum. While this system is efficient and
does not impart chemical contamination, it does require the use of
expensive zeolites.
[0009] While a variety of techniques exist for dehydrating the
water-ethanol azeotrope, none are cheap or efficient, and all have
significant drawbacks. There remains a need in the art for
efficient and cost-effective systems and methods to facilitate
ethanol dehydration, so that anhydrous ethanol may become more
readily available for energy production.
SUMMARY
[0010] The invention relates to novel materials and methods useful
in dehydrating ethanol. In embodiments, the invention relates to
methods for dehydrating an ethanol solution comprising distilling
the ethanol solution in the presence of a molecular sieve
characterized by a porous core and a water-permeable polymeric
coating impermeable to ethanol. In particular, the molecular sieve
can be characterized by a high charge density. This can be achieved
by using a porous core comprises a polyanionic polymer. In
embodiments, the coating comprises a polycationic polymer or
nonionic polymer, either of which can be optionally crosslinked.
Alternatively, the porous core comprises a polycationic polymer. In
embodiments, the coating comprises a polyanionic polymer or
nonionic polymer, either rof which can be optionally
crosslinked.
[0011] The invention also relates to molecular sieves characterized
by a porous core and a water-permeable polymeric coating
impermeable to ethanol, the molecular sieves being those described
above.
[0012] In embodiments, the invention relates to a method for
dehydrating an ethanol solution comprising distilling the ethanol
solution in the presence of an entrainer comprising a lignin or
lignin derivative. The lignin or lignin derivative can be solid in
ethanol. The entrainer can be a carboxylated lignin, such as can be
produced by reacting a lignin with an anhydride, including a
succinic anhydride or alkylated succinic anhydride. The lignin can
also be a kraft lignin characterized by hydroxyl groups. In
embodiments, between about 50 and 100% of the hydroxyl groups of
the lignin are functionalized. In addition, or alternatively, the
entrainer is further characterized by a hydrophilic polymer
substituent, such as a polyethylene oxide and a polypropylene
oxide.
DESCRIPTION
[0013] In other embodiments useful for ethanol dehydration,
particles may be formed from highly charged (hence hydrophilic)
polyelectrolyte cores and an alcohol-insoluble skin to create an
organic analog of a molecular sieve. While it is known in the art
that high charge density coatings are capable of dehydrating
ethanol via permvaporation methodologies (see Toutianoush, and
Tieke Materials Science and Engineering C 22 (2002) 459-463), a
similar method might be efficiently utilized without the use of
energy intensive distillative process. For example, a selectively
adsorbent particle may be used in a typical filtration manner to
remove residual water and produce dehydrated ethanol in accordance
with the systems and methods disclosed herein.
[0014] In embodiments, water may be absorbed onto such a particle,
and ethanol may be excluded. In one embodiment, the particle may
comprise a polyanion core material, and the exterior may be covered
with a polycation that creates a complex at the interface and an
insoluble skin with a high crosslink density (either electrostatic
or physical crosslinks) that excludes ethanol from the particle
interior. In other embodiments, the coating around a polyanion core
could consist of a nonionic material that is insoluble in ethanol.
Polyanions are not the only particles that can be used as the high
charge density material. In embodiments, a polycationic material
could be used as the core material treated with either a polyanion
or nonionic polymer coating. In another embodiment, a nonionic,
water soluble core material can be coated with another material,
either nonionic, cationic, or anionic.
[0015] Not to be bound by theory, the systems and methods disclosed
herein may have in common a water soluble core with some type of
passivating coating on the surface, whereby the coating maintains
water within the core.
[0016] In embodiments, the exterior coating may be oppositely
charged from that of the core. The coating polyelectrolyte may
condense upon the core creating three "zones", one anionic, one
cationic, and a middle phase. The resulting middle phase,
consisting of tight ion pairs due to the electrostatic charge
attraction, is a passivated, area between the two oppositely
charged regions (the core and the surface). Using this middle zone
as a semipermeable membrane, water may be preferably kept within
the core, with minimal flux back into the ethanol environment.
[0017] As an exemplary embodiment, a particle may be formed using a
substance such as encapsulated Carbopol, which is a crosslinked
polyacrylic acid. A protective skin may be formable on such a
particle using a polycation such as chitosan to complex the
cationic charges on the surface. In embodiments, the desired
particle may be formed with layering to control its porosity. In
another embodiment, a micron sized particles such as Carbopol may
be surrounded by polycationic polymers such as branched or linear
polyethyleneimine with molecular weights between 2000 and 100,000
gmol.sup.-1. Oligomeric entities may also be usable to create the
layered core-shell morphology. Mixing the particles into an
anhydrous solution of polycation may form a coating on the surface
of the particle upon introduction. The coating may be less than 100
nm in thickness for increased transport properties across the
coating. In embodiments, naturally occurring polysaccharide
multi-carboxylates could also be used to form the exterior complex,
for example materials such as pectin and carboxymethylcellulose. In
these illustrative embodiments, the charge on the core particle may
be varied to alter the thickness of the coating.
[0018] In other embodiments, particles may be formed comprising an
inorganic-organic hybrid. For example, the core may be formed with
an inexpensive porous silicate or other naturally occurring or
synthetic desiccant. In embodiments, the porous substrate may first
be loaded with salts that would be effective in absorbing water,
for example potassium carbonate, before encapsulating the assembly
with a skin formed in situ. In embodiments, the skin may be a
charge-charge complex (a tight molecular network) to exclude
alcohol from penetrating into the core. For example, chitosan can
be deposited spontaneously on silica, then complexed with a
polyanion. A composite such as this would allow water absorption
and ethanol exclusion to be separately performed by the core and
skin of such engineered particles. In embodiments, to concentrate
ethanol using such particles, they may be added to hydrated alcohol
in an appropriate amount so that water may be absorbed onto the
particles and dehydrated effluent alcohol may be collected for use
as a fuel additive. The water-containing particles may be dried out
and reused, thus enhancing the efficiency of the process.
[0019] Disclosed herein are systems and methods useful in energy
applications, with particular applicability to the dehydration of
azeotropic ethanol solutions. In embodiments, the systems and
methods described herein may involve the use of modified lignins
and formulations thereof. Lignin is a naturally-occurring
cross-linked, polymerized macromolecule comprised of aliphatic and
aromatic portions with alcohol functionality interspersed. Lignin
polymers incorporate three monolignol monomers, methoxylated to
various degrees: p-coumaryl alcohol, coniferyl alcohol, and sinapyl
alcohol. These are incorporated into lignin in the form of the
phenylpropanoids, p-hydroxyphenyl, guaiacyl, and syringal
respectively. The systems and methods disclosed herein describe how
naturally-occurring (i.e., native) and unnatural or modified lignin
may be modified through functionalization of the resident alcohol
moieties to alter the properties of the polymer. Such a
functionalized lignin may be termed a "modified lignin." The word
"lignin", as used herein is intended to include natural and
non-natural lignins which possess a plurality of lignin monomers
and is intended to embrace lignin, kraft lignin, lignin isolated
from bagasse and pulp, oxidized lignin, alkylated lignin,
demethoxylated lignin, lignin oligomers, and the like.
[0020] Lignin and oxidized lignin are waste products from the paper
industry. Oxidized lignin is characterized by a plurality of
hydroxyl groups which can be conveniently reacted. Oxidized lignin
is described, for example, in U.S. Pat. No. 4,790,382 and is
characterized by a plurality of hydroxyl groups which can be
conveniently reacted. Similarly, kraft lignins, such as indulins,
including Indulin AT, can be used. For example, the hydroxyl groups
can be reacted with succinic anhydride and similar compounds to
form a carboxylic acid-substituted lignin, by a ring opening
reaction. The systems and methods disclosed herein describe how
naturally-occurring (i.e., native) lignin may be modified through
functionalization of the resident alcohol moieties to alter the
properties of the polymer. Such a functionalized lignin may be
termed a modified lignin.
[0021] In embodiments, adding a reactive agent such as succinic
anhydride or alkylated succinic anhydride to a native lignin may
produce a modified lignin of the invention. Alkylated succinic
anhydride is commonly used in the paper industry as a sizing agent.
The alkyl additions are long chain hydrocarbons typically
containing 16-18 carbon atoms. However, alkylated succinic acids
having alkyl side chains having more than 1 carbon atom, such as 1
to 30 carbon atoms can be used as well. Such alkyl groups are
defined herein to include straight chain, branched cahain or
cyclized alkyls as well as saturated and unsaturated alkyls.
Examples of alkylated succinic anhydride include EKA ASA 200.RTM.
(a mixture of C16 and C18 ASA) and EKA ASA 210.RTM. (a C18 ASA).
Addition of an anhydride, such as a succinic anhydride or alkylated
succinic anhydride to the resident alcohol groups result in new
ester linkages and the formation of carboxylic acids via a ring
opening mechanism. Addition of anhydride to the resident alcohol
groups result in new ester linkages and/or the formation of
carboxylic acids via a ring opening mechanism. With the newly added
carboxylic acid functionality, the lignin becomes more water
soluble.
[0022] In other embodiments, the hydroxyl group can be reacted with
a dicarboxylic acid, such as maleic acid, or activated esters or
anhydrides thereof to form a carboxylic acid substituted lignin.
For example, the anhydride derived from many acids can be utilized,
such as adipic acid, or the functionality can be derived from
natural compounds such as a polysaccharide that contains carboxylic
acid groups. Non-limiting examples include pectin or alginate, and
the like, and synthesized polymers such as polyacrylic or
methacrylic acid homo or co-polymers. Further, activated esters can
be used in place of the anhydride. Other examples will be apparent
to those of ordinary skill in the art. The degree of
functionalization (i.e., the percentage of hydroxyl groups that are
reacted to present an ionic moiety) can be between 20% and 80%,
preferably between 50% and 80%.
[0023] In other embodiments, lignin (oxidized or native) may be
treated by chemically reacting it with reagents to tune the
hydrophilicity to present alcohol groups. Examples of such reagents
include hydrophilic molecules, or hydrophilic polymers, such as
poly(ethylene glycol) (PEG) or poly(propylene glycol) (PPO) and
combinations thereof. In a preferred embodiment, the hydrophilic
polymer can have a molecular weight between 700 and 2500 g/mol
Addition of PEG or PPO (with or without acidification) can be
useful in stabilization of the product in salt solutions,
particularly divalent cation salts. In this embodiment, the amount
of polymer to lignin is preferably added in an amount between 25%
and 75%.
[0024] As described above, ethanol is naturally hydrated when it is
fermented and must be dehydrated and purified prior to its use as a
fuel. In embodiments, a modified lignin base may be formed to
create a branched or networked polymer with functional groups that
form hydrogen bonds to disrupt the inherent water-ethanol azeotrope
during distillation. In embodiments, the dehydration of ethanol may
be accomplished by using particles designed to absorb water while
excluding ethanol by utilizing a molecularly designed architecture
on a porous substrate, for example, or by creating a layered
substrate with a water soluble/swellable core with a charge complex
exterior shell to exclude ethanol while preferentially absorbing
water.
[0025] For the dehydration of ethanol, oxidized lignin may be used
without further modification, or it may be oxidized further to
create a largely branched molecule with a high molecular weight and
a large number of alcohol groups of various types (primary,
secondary, tertiary and benzylic). Using lignin by itself to act as
a solid entrainer added to the distillation apparatus may be
possible due to the alcohol functionalities. These functionalities
are expected to change the thermodynamic equilibrium enough to
create a different azeotropic composition, preferably more than the
standard azeotrope at 96.4% by weight. By adding modified or
unmodified lignin to an ethanol-water mixture followed by
distillation, the resulting distillate may be more pure than the
feed.
[0026] The solid entrainers of the invention are not removed with
the ethanol during distillation and, accordingly, can be readily
removed and optionally recycled.
EXAMPLE 1
[0027] Indulin AT is used as the lignin source. Indulin AT is a
purified form of the lignin obtained from the black liquor in the
Kraft pulping process. Here, Indulin AT (5.0 g) is suspended in 150
ml of acetone. Alkyl succinic anhydride in the form of Eka SA 210
(25.0 g) is added to the suspension. The reaction is performed in a
bomb and heated to 70.degree. C. over the course of 48 hours.
EXAMPLE 2
[0028] Indulin AT (5.0 g) is mixed with 10.0 g Eka SA 210 in a bomb
filled with 150 ml of acetone. The mixture is heated to 70.degree.
C. over 48 hours, and the product is recovered.
EXAMPLE 3
[0029] Indulin AT (5.0 g) is mixed with 5.0 g Eka SA 210 in a bomb
filled with acetone. The mixture is heated to 70.degree. C. over 48
hours. The resulting mixture is filtered; the supernatant is
recovered and diluted with alkaline water and dried.
EXAMPLE 4
[0030] Indulin AT (5.0 g) is mixed with 4.0 g Eka SA 210 in a bomb
filled with 150 ml of acetone. The mixture is heated to 70.degree.
C. over 48 hours. The resulting mixture is filtered; the
supernatant is recovered, diluted with alkaline water and
dried.
EXAMPLE 5
[0031] Indulin AT (5.0 g) is mixed with3.0 g Eka SA 210 in a bomb
filled with 150 ml of acetone. The mixture is heated to 70.degree.
C. over 48 hours. The resulting mixture is filtered; the
supernatant is recovered, diluted with alkaline water and
dried.
EXAMPLE 6
[0032] Indulin AT (5.0 g) is mixed with 2.5 g Eka SA 210 in a bomb
filled with 150 ml of acetone. The mixture is heated to 70.degree.
C. over 48 hours. The resulting mixture is filtered; the
supernatant is recovered, diluted with alkaline water and
dried.
EXAMPLE 7
[0033] Indulin AT (5.0 g) is mixed with 1.0 g Eka SA 210 and3.0 g
succinic anhydride in a bomb filled with 150 ml of acetone. The
mixture is heated to 70.degree. C. over 48 hours. The resulting
mixture is filtered; the supernatant is recovered, diluted with
alkaline water and dried.
EXAMPLE 8
[0034] Indulin AT (5.0 g) is mixed with 2.0 g Eka SA 210 and 2.0 g
succinic anhydride in a bomb filled with 150 ml of acetone. The
mixture is heated to 70.degree. C. over 48 hours. The resulting
mixture is filtered; the supernatant is recovered, diluted with
alkaline water and dried.
EXAMPLE 9
[0035] Indulin AT (5.0 g) is mixed with3.0 g Eka SA 210 and 1.0 g
succinic anhydride in a bomb filled with 150 ml of acetone. The
mixture is heated to 70.degree. C. over 48 hours. The resulting
mixture is filtered; the supernatant is recovered, diluted with
alkaline water and dried.
EXAMPLE 10
[0036] Indulin AT (5.0 g) is mixed with 4.0 g Eka SA 210 and 1.0 g
polyethylene glycol diglycidyl ether in a bomb filled with 150 ml
of acetone. The mixture is heated to 70.degree. C. over 48 hours.
The resulting mixture is filtered; the supernatant is recovered,
diluted with alkaline water and dried.
EXAMPLE 11
[0037] Indulin AT (5.0 g) is mixed with3.0 g Eka SA 210 and 1.0 g
polypropylene oxide diglycidyl ether in a bomb filled with 150 ml
of acetone. The mixture is heated to 70.degree. C. over 48 hours.
The resulting mixture is filtered; the supernatant is recovered,
diluted with alkaline water and dried.
EQUIVALENTS
[0038] While specific embodiments of the subject invention have
been discussed, the above specification is illustrative and not
restrictive. Many variations of the invention will become apparent
to those skilled in the art upon review of this specification. The
full scope of the invention should be determined by reference to
the claims, along with their full scope of equivalents, and the
specification, along with such variations.
[0039] Unless otherwise indicated, all numbers expressing
quantities of ingredients, reaction conditions, and so forth used
in the specification and claims are to be understood as being
modified in all instances by the term "about." Accordingly, unless
indicated to the contrary, the numerical parameters set forth in
this specification and attached claims are approximations that may
vary depending upon the desired properties sought to be obtained by
the present invention.
* * * * *