U.S. patent application number 11/644882 was filed with the patent office on 2007-07-26 for production of high-cetane diesel fuel from low-quality biomass-derived feedstocks.
Invention is credited to Michio Ikura, Jacques Monnier, Guy Tourigny.
Application Number | 20070170091 11/644882 |
Document ID | / |
Family ID | 37888484 |
Filed Date | 2007-07-26 |
United States Patent
Application |
20070170091 |
Kind Code |
A1 |
Monnier; Jacques ; et
al. |
July 26, 2007 |
Production of high-cetane diesel fuel from low-quality
biomass-derived feedstocks
Abstract
A method is taught for producing diesel fuels of high cetane
value from a triglyceride feedstock, comprising pretreating the
triglyceride feedstock by thermal cracking or rapid pyrolysis to
partially convert the triglycerides and produce a middle
distillates stream, and catalytically hydrotreating the middle
distillate fraction to produce high cetane value diesel fuels. A
biomass-derived diesel fuel is also taught having sulphur content
below 10 ppm, a cetane-value of at least 70, a cloud point below
0.degree. C. and a pour point of less than -4.degree. C. A blended
diesel fuel is also taught comprising 5 to 20 vol. % of the
biomass-derived diesel fuel of the present invention and 80 to 95
vol. % of a petroleum diesel, based on total volume of the blended
diesel fuel.
Inventors: |
Monnier; Jacques; (Ottawa,
CA) ; Ikura; Michio; (Ottawa, CA) ; Tourigny;
Guy; (Gatineau, CA) |
Correspondence
Address: |
KIRBY EADES GALE BAKER
BOX 3432, STATION D
OTTAWA
ON
K1P 6N9
CA
|
Family ID: |
37888484 |
Appl. No.: |
11/644882 |
Filed: |
December 26, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11234175 |
Sep 26, 2005 |
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11644882 |
Dec 26, 2006 |
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Current U.S.
Class: |
208/15 ;
208/60 |
Current CPC
Class: |
C10G 2300/202 20130101;
C10L 1/026 20130101; C10G 2300/1014 20130101; C10G 2400/04
20130101; Y02E 50/10 20130101; C10L 1/08 20130101; C10G 31/09
20130101; Y02E 50/13 20130101; C10G 2300/1018 20130101; C10G
2300/301 20130101; C10G 3/46 20130101; C10G 2300/1011 20130101;
C10G 45/08 20130101; Y02P 30/20 20151101; C10G 2300/1055 20130101;
C10G 2300/4081 20130101; C10G 3/50 20130101; C10G 2300/304
20130101; C10L 10/12 20130101; C10G 2300/307 20130101 |
Class at
Publication: |
208/015 ;
208/060 |
International
Class: |
C10L 1/04 20060101
C10L001/04; C10G 69/02 20060101 C10G069/02 |
Claims
1. A method of producing diesel fuels of high cetane value from a
triglyceride feedstock, comprising: a. pretreating the triglyceride
feedstock by thermal cracking to partially convert the
triglycerides and produce a middle distillates fraction; and b.
catalytically hydrotreating the middle distillate fraction to
produce high cetane value diesel fuels.
2. The method of claim 1 wherein the triglycerides feedstock is
selected from the group consisting of restaurant trap grease,
animal fats, waste greases, low-quality vegetable oils and
combinations thereof.
3. The method of claim 1 wherein the middle distillates have a
boiling point in the range of from 160.degree. C. to 345.degree.
C.
4. The method of claim 1 wherein thermal cracking is conducted at a
temperature of from 390.degree. C. to 460.degree. C.
5. The method of claim 1 wherein thermal cracking is conducted at a
temperature of from 410.degree. C. to 430.degree. C.
6. The method of claim 1 wherein catalytic hydrotreating consumes
less than 2.0 kg of hydrogen) per 100 kg of middle distillate fed
to the hydrotreating step.
7. The method of claim 1 wherein catalytic hydrotreating is
conducted at a temperature of from 330.degree. C. to 400.degree.
C.
8. The method of claim 6 wherein catalytic hydrotreating is
conducted at a temperature of from 350.degree. C. to 390.degree.
C.
9. The method of claim 1 wherein catalytic hydrotreating is
conducted using a commercial hydrotreating catalyst.
10. The method of claim 9 wherein the commercial hydrotreating
catalyst is nickel-molybdenum, cobalt-molybdenum or nickel-tungsten
on a catalyst support.
11. The method of claim 1, further comprising filtering the
triglyceride feedstock to remove macroscopic contaminant particles
before thermal cracking.
12. The method of claim 1, further comprising conducting separation
after catalytic hydrotreating to produce a gas stream, a water
stream and a liquid organic product stream.
13. The method of claim 12, further comprising distilling the
liquid organic product stream to further separate diesel fuels from
paraffinic residues.
14. The method of claim 12, further comprising the step of
recycling the gas stream as hydrogen recycle during catalytic
hydrotreating.
15. A biomass-derived diesel fuel having a cetane-value of at least
70, a cloud point below 0.degree. C. and a pour point of less than
-4.degree. C.
16. The diesel fuel of claim 15, having a sulphur content of below
10 ppm.
17. The diesel fuel of claim 15, produced by the process of claim
1.
18. A blended diesel fuel comprising 5 to 20 vol. % biomass-derived
diesel fuel as described in claim 15 and 80 to 95 vol. % petroleum
diesel, based on a total volume of the blended diesel fuel.
19. The blended diesel fuel of claim 18 comprising 10 vol. %
biomass-derived diesel fuel as described in claim 15 and 90 vol. %
petroleum diesel, based on a total volume of the blended diesel
fuel.
20. A method of producing diesel fuels of high cetane value from a
triglyceride feedstock, comprising: a. pretreating the triglyceride
feedstock by rapid pyrolysis to partially convert the triglycerides
and produce a middle distillates fraction; and b. catalytically
hydrotreating the middle distillate fraction to produce high cetane
value diesel fuels.
21. The method of claim 20 wherein the triglycerides feedstock is
selected from the group consisting of restaurant trap grease,
animal fats, waste greases, low-quality vegetable oils and
combinations thereof.
22. The method of claim 20 wherein the middle distillates have a
boiling point in the range of from 160.degree. C. to 345.degree.
C.
23. The method of claim 20 wherein rapid pyrolysis is conducted at
a temperature of from 480.degree. C. to 600.degree. C.
24. The method of claim 20 wherein rapid pyrolysis is conducted at
a temperature of from 550.degree. C. to 600.degree. C.
25. The method of claim 20 wherein rapid pyrolysis is conducted at
a temperature of from 565.degree. C. to 585.degree. C.
26. The method of claim 20 wherein the triglyceride feedstock is
fluidized with steam.
27. The method of claim 26 wherein the steam to triglyceride
feedstock ratio ranges from 0.5 to 1.5.
28. The method of claim 27 wherein the steam to triglyceride
feedstock ratio is 0.9.
29. The method of claim 20 wherein an inert gas is used to purge
any oxidizing agents during rapid pyrolysis.
30. The method of claim 29 wherein the inert gas is nitrogen.
31. The method of claim 20 wherein a catalyst is used during rapid
pyrolysis to enhance the cracking of triglycerides to largely free
fatty acids.
32. The method of claim 31 wherein the catalyst is selected from
the group consisting of acid washed activated carbon, calcined
sewage sludge solids and silica sand.
33. The method of claim 20 wherein catalytic hydrotreating consumes
less than 2.0 kg of hydrogen) per 100 kg of middle distillate fed
to the hydrotreating step.
34. The method of claim 20 wherein catalytic hydrotreating is
conducted at a temperature of from 330.degree. C. to 400.degree.
C.
35. The method of claim 34 wherein catalytic hydrotreating is
conducted at a temperature of from 350.degree. C. to 390.degree.
C.
36. The method of claim 20 wherein catalytic hydrotreating is
conducted using a commercial hydrotreating catalyst.
37. The method of claim 36 wherein the commercial hydrotreating
catalyst is nickel-molybdenum, cobalt-molybdenum or nickel-tungsten
on a catalyst support.
38. The method of claim 20, further comprising filtering the
triglyceride feedstock to remove macroscopic contaminant particles
before rapid pyrolysis.
39. The method of claim 20, further comprising conducting
separation after catalytic hydrotreating to produce a gas stream, a
water stream and a liquid organic product stream.
40. The method of claim 39, further comprising distilling the
liquid organic product stream to further separate diesel fuels from
paraffinic residues.
41. The method of claim 39, further comprising the step of
recycling the gas stream as hydrogen recycle during catalytic
hydrotreating.
42. The diesel fuel of claim 15, produced by the process of claim
20.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of U.S.
patent application Ser. No. 11/234,175 filed Sep. 26, 2005.
FIELD OF THE INVENTION
[0002] The present invention relates to a two-step method for
producing diesel fuel having a high cetane value from low quality
biomass-derived feedstocks.
BACKGROUND OF THE INVENTION
[0003] In recent years, the area of biomass-derived diesel fuels
has drawn a great deal of attention. These fuels are plant and
animal based and are produced from such sources as canola, corn,
soybean etc. Biomass-derived fuels are generally environmentally
less damaging to use than traditional fossil fuels.
[0004] Another potential source for biomass-derived diesel fuels is
from the waste greases of animal rendering facilities and waste
cooking oils, such as those found as restaurant trap greases.
However these waste greases and oils tend to contain contaminants
that must effectively be removed before processing.
[0005] In the past, catalytic hydrotreating has been performed on
triglyceride feedstocks in an attempt to produce high-cetane diesel
fuels. Examples of such processes can be seen in U.S. Pat. Nos.
5,705,722 and 4,992,605, herein incorporated by reference.
[0006] The cetane value of a diesel fuel is a measure of how easily
the fuel will auto-ignite at predetermined pressure and temperature
and is often used to determine fuel quality. However, large
quantities of hydrogen are required for this process, which is a
major operating cost in the production of biomass-derived diesel
fuel by catalytic hydrotreating. Reducing the volume of hydrogen
consumed in the process would make the process economics more
favourable. As well, hydrotreating was found to work best for very
high quality feedstocks, such as tallow, vegetable oils (canola
oil, soya oil, etc.) and yellow grease. Lower quality feedstocks,
such as restaurant trap grease were found to be difficult to
convert by catalytic hydrotreating, due to their heterogeneous
nature and the presence of contaminants. These contaminants were
found to rapidly deactivate the catalyst, thereby reducing
hydrotreating reactor time on stream, requiring large quantities of
catalyst to be used, and increasing operating costs. There is
therefore a great need to find efficient methods of producing a
high cetane value product from low quality waste triglyceride
feedstocks, such as restaurant trap greases and other waste
greases, which can be used as a diesel fuel or as diesel fuel
blending stock. There is also a need to find efficient methods to
reduce hydrogen consumption in the catalytic hydrotreating
stage.
SUMMARY OF THE INVENTION
[0007] The present invention thus provides a method of producing
diesel fuels of high cetane values from triglyceride feedstocks,
comprising pretreating the triglyceride feedstocks by thermal
cracking or rapid pyrolysis to partially convert the triglycerides
and produce a middle distillates stream, and catalytically
hydrotreating the middle distillate fraction to produce high cetane
value diesel fuels.
[0008] The present invention also provides a biomass-derived diesel
fuel having sulphur content below 10 ppm, a cetane-value of at
least 70, a cloud point below 0.degree. C. and a pour point below
-4.degree. C.
[0009] In yet another embodiment, the present invention provides a
blended diesel fuel comprising 5 to 20 vol. % of the
biomass-derived diesel fuel of the present invention and 80 to 95
vol. % of a petroleum diesel, based on total volume of the blended
diesel fuel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The present invention will now be described in further
detail with reference to the following drawings, in which: FIG. 1
is a flow diagram of a first preferred process for carrying out the
present invention; and
[0011] FIG. 2 is a flow diagram of a second preferred process for
carrying out the present invention.
DEFINITIONS
[0012] Biomass-derived diesel fuel--a diesel fuel produced by
catalytic hydrotreating of biomass feedstocks and containing
practically no oxygen. [0013] Biodiesel--a diesel fuel produced
from the transesterification of biomass-derived oils with alcohol
and containing oxygen. [0014] Cetane number--measure of the
ignition quality of diesel fuel obtained by comparing it to
reference fuels or blends of reference fuels of known cetane number
in a standardized engine test. The reference fuels are n-cetane,
having good ignition quality (CN=100), and heptamethylnonane,
having poor ignition quality (CN=15). [0015] High cetane value--for
the purposes of the present invention a high cetane value is
defined as a value of at least 70. [0016] Waste triglyceride
feedstock--a triglyceride from waste sources such as restaurant
trap grease, waste from animal rendering facilities and other waste
oil and grease sources, generally having at least some
contaminants. [0017] Catalytic hydrotreating--a refinery process
for catalytically converting and removing sulphur, nitrogen and
oxygen from fuels and fuel feedstocks at elevated hydrogen
pressures and appropriate temperatures. [0018] Middle
distillates--encompass a range of petroleum fractions from kerosene
to lubricating oil and include light fuel oils and diesel fuel,
generally having a boiling point in the range of 150 to 345.degree.
C. [0019] Thermal cracking--the process of breaking down large
hydrocarbon molecules into smaller molecules under high temperature
and pressure. [0020] Cloud point--a measure of the ability of a
diesel fuel to operate under cold weather conditions. Defined as
the temperature at which wax first becomes visible when diesel fuel
is cooled under standardized test conditions. [0021] Pour
point--the lowest temperature at which a fuel flows, when cooled
under standardized test conditions. Generally taken to be 3.degree.
C. (5.4.degree. F.) or 1.degree. C. (1.8.degree. F.) (depending on
selected temperature interval) above the temperature of the no-flow
point at which a test vessel of fuel shows no movement when
applying a controlled burst of nitrogen gas onto the specimen
surface (ASTM D 5949). [0022] Rapid pyrolysis--a process of
decomposing chemicals at very high temperatures and in the absence
of an oxidizing agent. Rapid pyrolysis has very short residence
times compared to other thermal decomposition methods.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The present process employs a novel combination of thermal
cracking followed by catalytic hydrotreating to convert low quality
triglycerides feedstock into usable biomass-derived diesel fuel. In
the present process, thermal cracking is used as a pre-treatment
step before catalytic hydrotreating, to partially break down the
triglycerides into lower molecular weight components and fatty
acids, which can then easily be hydrotreated to produce a diesel
fuel having a high cetane value and low sulphur content. As an
alternate to thermal cracking, rapid pyrolysis of waste
triglycerides can also be used in the present process and details
of rapid pyrolysis are given below.
[0024] A flow diagram of the process steps and streams of a one
embodiment of the present invention is shown in FIG. 1. A feedstock
of low quality triglycerides is fed to thermal cracking unit 10.
The feedstock can be any variety of waste biomass, including
restaurant trap greases, waste greases from animal rendering
facilities and other forms of waste oils and greases and
low-quality vegetable oils. Preferably, the feedstock 18 is
restaurant trap grease and other low-quality feedstocks. The
feedstock stream 18 can be heterogeneous in nature and can contain
water, carbon particles and have oxygen content as high as 14 wt. %
or more.
[0025] In the thermal cracking unit 10, the feedstock 18 is
partially converted into a mixture of fatty acids and lower
molecular weight hydrocarbons. Thermal cracking is preferably
carried out under mild cracking conditions which are defined as
preferably an operating temperature in the range of from 390 to
460.degree. C., more preferably from 410 to 430.degree. C., and
preferably an operating pressure of from 0 to 415 kPa, more
preferably from 205 to 275 kPa. Thermal cracking produces various
fractions including gases 24, naphtha plus water 26, middle
distillate 22, and residue 20.
[0026] In an optional embodiment (not shown), the triglyceride
feedstock may be filtered to remove any macroscopic contaminant
particles.
[0027] The middle distillate stream 22 makes up more than half of
the thermally cracked product and has been found to have suitable
characteristics for further hydrotreating. Middle distillates
typically encompass a range of petroleum equivalent fractions from
kerosene to lubricating oil and include light fuel oils and diesel
fuel. In one embodiment of the present invention the middle
distillates were found to have a boiling point range of from 150 to
345.degree. C., and more preferably from 165 to 345.degree. C. The
middle distillates fraction was found to contain as much as 40%
less oxygen than the starting triglycerides feedstock 18, resulting
in less hydrogen being required in the subsequent hydrotreating
step.
[0028] The middles distillate stream 22 is fed to a catalytic
hydrotreating unit 12 containing a catalyst to facilitate and
enhance the hydrotreating process. This catalyst is a commercial
hydrotreating catalyst such as, for example, nickel-molybdenum,
cobalt-molybdenum or nickel-tungsten on a catalyst support. It is
preferably a supported nickel-molybdenum catalyst. Known methods in
the art can be used to maintain activation of the catalyst, thereby
lengthening the useful life of the catalyst.
[0029] Hydrogen 28 is also fed to the hydrotreating unit 12. The
present inventors have found that, by partially removing oxygen
from the feed in the thermal cracking pre-treatment stage, hydrogen
consumption in the hydrotreating step decreases significantly.
Typical hydrogen consumption for hydrotreatment of clean, high
quality biomass feedstock, without thermal cracking, is in the
range of 2.3 to 3.0 kg H.sub.2 per 100 kg of feedstock. By
contrast, hydrogen consumption during hydrotreating of the
thermally cracked middle distillates stream 22 is only between 1.5
to 2.0 kg H.sub.2 per 100 kg of middle distillate feed 22 to the
hydrotreating unit 12.
[0030] It has also been observed that, when processing thermally
cracked waste triglycerides, hydrotreating can be conducted at
lower temperatures than those required for clean, high quality
biomass feedstock. Hydrotreating temperatures in the range of 330
to 400.degree. C., and more preferably 350 to 390.degree. C., are
used in the present invention, compared to at least 375.degree. C.
typically required for hydrotreating uncracked, clean
biomass-derived feedstocks.
[0031] Hydrotreated product 30 can optionally then be fed to a
separator 14 in which the product 30 is separated into a gas stream
35, a water stream 36 and a liquid organic product stream 38. The
gas stream 35 can be recycled back to the hydrotreating unit 12 as
a hydrogen recycle stream 32, or it can form a fuel gas by-product
stream 34.
[0032] In a preferred embodiment, the separated liquid organic
product stream 38 is fed to a distillation column 16 to further
separate diesel fuel 40 from any paraffinic residues 42.
[0033] Naphtha 26 and gases 24 from the thermal cracking unit 10
and fuel gas 34 from the hydrotreating step can optionally be sold
as valuable by-products. The residue streams 20 and 42 are small
and can be discarded by well known means in the art. Stream 42 is
much cleaner than stream 20 and can also possibly be used as
feedstock for petrochemical applications.
[0034] Catalytic hydrotreatment of the middle distillate stream 22
produces a biomass-derived diesel fuel having a cetane value of
from 75 to 80 and sulphur content below 10 ppm. Oxygen content of
the resultant diesel fuel, an indication of the extent of
conversion of the feedstock to diesel fuel, was found to be in the
range of 0.09 wt % or less, on the basis of the weight of product
diesel.
[0035] The biomass-derived diesel fuel of the present invention
also exhibits excellent cold-flow properties. The cloud point of
the fuel is as low as -1.4 to -2.5 .degree. C. and the pour point
is -4.degree. C. or less.
[0036] In a further embodiment, the biomass-derived diesel fuel of
the present invention can be used as diesel blending stock to
produce a high cetane value blended diesel fuel. Preferably the
blended diesel fuel comprises 5 to 20 vol. % of the biomass-derived
diesel fuel of the present invention and 80 to 95 vol. % petroleum
diesel, based on a total volume of the blended diesel fuel. More
preferably, the blended diesel fuel comprises 10 vol. % of the
biomass-derived diesel fuel of the present invention and 90 vol. %
petroleum diesel, based on a total volume of the blended diesel
fuel. The cetane value of the blended diesel fuel was found to be
proportional to the quantities of biomass-derived diesel and
petroleum diesel used in the blend and was generally higher than
typical values of 40 to 50 for standard petroleum diesel. Cold flow
properties of such a blended diesel fuel are improved by the
addition of petroleum diesel and are superior to those of the
biomass-derived diesel fuel alone.
[0037] As mentioned earlier, the step of thermal cracking can
optionally be replaced by a step of rapid pyrolysis. This process
is shown in FIG. 2. Rapid pyrolysis is a process of decomposing a
chemical at very high temperatures and in the absence of an
oxidizing agent. Rapid pyrolysis has very short residence times
when compared to thermal cracking.
[0038] In the present invention, rapid pyrolysis of triglycerides,
more specifically trap grease, was conducted at temperatures
ranging from 480.degree. C. to 600.degree. C. for approximately 2
seconds. The triglycerides 18 are fed to a fluidized bed reactor 44
which is preferably fluidized with steam 46, although other
suitable fluidizing media known in the art can also be used and are
encompassed by the present invention. Steam 46 may be fed to the
reactor at a ratio ranging from 0.5 to 1.5, relative to the
triglyceride feed stream 18. The preferred steam to triglyceride
feed ratio is 0.9.
[0039] Any known inert gas 48 can optionally be added to the
reactor to purge the reactor of free oxygen during pyrolysis. The
inert gas 48 is preferably nitrogen. A catalyst may also be added,
and suitable catalysts include, but are not limited to acid washed
activated carbon, calcined sewage sludge solids and silica sand,
such as silica alumina. The catalyst acts to enhance the selective
cracking of triglyceride molecules to largely free fatty acid
molecules.
[0040] Sample data from rapid pyrolysis trials on a trap grease
feedstock is listed in Table 1 below. The resultant pyrolysis
products are shown in Table 2. TABLE-US-00001 TABLE 1 Rapid
pyrolysis conditions Run ID 261 265 253 Temperature (.degree. C.)
511 575 580 Fluidizing media Steam Steam Steam Steam/Feed ratio
.about.0.9 .about.0.9 .about.0.9 by weight N.sub.2 purge/Feed
.about.7 .about.7 .about.7 ratio by weight Catalyst Acid washed
Sewage sludge Silica sand activated solids, carbon, calcined at 35
mesh minus 750.degree. C. Gas phase contact .about.2 .about.2
.about.2 time (s)
[0041] TABLE-US-00002 TABLE 2 Rapid Pyrolysis Products 261 265 253
Gas 28.2 11.3 7.6 Liquid 50.3 89.4 90.7 Solids (coke) 9.0 Trace 1.4
Total above 87.5 100.7 99.7
[0042] The liquid fraction identified in Table 2 above contains
middle distillates 22 as well as naphtha 26 and some residue 20.
The boiling point distribution of the liquid fraction was
determined by thermogravimetric analysis (TGA) and is given in
Table 3 below. The middle distillates yield is given in Table 4.
These tables indicate that rapid pyrolysis of triglycerides
produces an even larger proportion of desirable middle distillates
than thermal cracking. TABLE-US-00003 TABLE 3 Boiling point
distribution of the liquid fraction (from TGA) 261 265 253 Naphtha
(IBP .about.165.degree. C.) 86% 10% 8% Middle distillate 12% 75%
64% (165.about.345.degree. C.) Residue (345.degree. C. plus) 2% 15%
28%
[0043] TABLE-US-00004 TABLE 4 Middle distillate yield with respect
to feed 261 265 253 Middle distillate (wt % of feed) 6% 67% 58%
[0044] The middle distillate fraction 22 produced by rapid
pyrolysis was found to have varying free fatty acids (FFA) content,
depending on the pyrolysis conditions. These details are shown in
Table 5 below: TABLE-US-00005 TABLE 5 Fatty acids in the middle
distillate fraction Run ID 261 265A 265B 253 Pyrolysis
Temperature(.degree.C.) 511 575 575 580 Total FFA wt % 0.63 45.70
45.50 33.17
[0045] It was noted that the largest middle distillates fraction
was produced by rapid pyrolysis at a temperature of 575.degree. C.
As well, FFA content was highest for this temperature range. A
preferred temperature range for rapid pyrolysis of the present
process is therefore from 550.degree. C. to 600.degree. C. and a
most preferred range is from 565.degree. C. to 585.degree. C.
[0046] The difference in middle distillates yield between the run
at 575.degree. C. and the run at 580.degree. C. is thought to be
due to the difference in catalysts rather than the small difference
in temperature. Catalyst derived from sewage sludge is less acidic
than silica sand. Thus, although the run with silica sand produced
a slightly larger liquids fraction by deoxygenation, this was
accompanied by higher coke and residue formation, resulting in an
overall lower level of middle distillates. Thus the sewage sludge
appears to provide a preferred balance between higher middle
distillate yield and lower coke formation.
[0047] It has also been noted that middle distillates produced by
rapid pyrolysis comprise about 0.3 ppm nitrogen, compared with 5200
ppm nitrogen content in middle distillates obtained by mild thermal
cracking.
[0048] As well, total sulphur in the middle distillate obtained by
mild thermal cracking was in the order of 500 ppm whereas that in
the middle distillate obtained by rapid pyrolysis was 150 ppm.
[0049] The following examples better illustrate the process of the
present invention:
EXAMPLE 1
Conversion of Restaurant Trap Grease into Biomass-Derived
Diesel
[0050] Restaurant trap grease having an average density of 0.925
g/mL, and an oxygen content of 13.72 wt % was fed to a thermal
cracking unit where it was cracked at a temperature of
418.5.degree. C. and a pressure of 300 kPa for 40 minutes. Thermal
cracking produced a gas stream, a naphtha stream, a middle
distillate stream having a boiling point in the range of from 165
to 345.degree. C., water and residue. The middle distillates stream
made up 63.0 wt % of the total cracked product and its oxygen
content was only 7.99 wt %.
[0051] The middle distillate stream was then fed to a catalytic
hydrotreating unit. Hydrotreating produced a biomass-derived diesel
fuel having a cetane value of 75.4, a pour point of -6.0.degree. C.
and a cloud point of -2.5.degree. C. The diesel was found to have
less than 10 ppm sulphur content, which is well within tolerable
commercial limits.
EXAMPLE 2
Conversion of Yellow Grease into Biomass-Derived Diesel
[0052] Yellow grease is waste grease resulting for rendering of
animal fat. In this case, yellow grease, having a density of 0.918
g/mL and an oxygen content of 11.56 wt. % was fed to a thermal
cracking unit in which it was cracked at 411.degree. C. and 100 kPa
for 40 minutes. Thermal cracking produced a product containing 68.6
wt % middle distillates (165.degree. C.-345.degree. C.), 7.0 wt %
naphtha and the remainder gas, water and residues.
[0053] The middle distillate stream, which was found to have 8.29
wt % oxygen, was then fed to a catalytic hydrotreating unit. The
resultant biomass-derived diesel stream had a cetane value of 79.2,
a pour point of -4.0.degree. C. and a cloud point of -1.4.degree.
C. The sulphur content of the diesel was found to be less than 10
ppm.
[0054] This detailed description of the process and methods is used
to illustrate one embodiment of the present invention. It will be
apparent to those skilled in the art that various modifications can
be made in the present process and methods and that various
alternative embodiments can be utilized. Therefore, it will be
recognized that various modifications can also be made to the
applications to which the method and processes are applied without
departing from the scope of the invention, which is limited only by
the appended claims.
* * * * *