Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a process for
- producing hydrocarbon fuels from renewable biomass, and more
particularly, to those processes in which biomass material
can be converted directly)> into an oil by heating small
biomass particles with water, catalysts and reducing agents
to temperatures up to 350C.
It is known that biomass can be thermochemically
converted to liquid fuels by two main routes. The route No.
1 is called Indirect liquefaction, i.e., thermal gasification
inducing conversion of biomass to a mixture of gas, liquids
and tars by pyrolysis followed by catalytic liquefaction
of the products. The route No. 2 is called Direct lique-
faction, i.e. conversion in one step biomass to an oil by
heating biomass particles in water in presence of reducing
agents and catalysts to temperature up to 350.
The advantage of indirect liquefaction (vs direct)
is minimization of oxygenated compounds in the liquid hydro-
carbon fuel product as teached by US patent Nos. 4,320,241
and 4,308,411 to Frankiewicz by use of catalysts and the
disadvantages are the low conversion yield, the low energy
conversion efficiency, the need of two-step processes
(gasification and liquefaction) requiring more complex process
design and higher costs. Direct liquefaction provides a very
high overall energy conversion efficiency and a conversion
yield of about 35~ the weight of the feed. The heavy oil
obtained with up to 20~ oxygen content and with a heating
value of 1450-1500 Btu/lb may be upgraded by distillation
or by hydrogenation which would convert phenol to aromatic
hydrocarbons.
It is desirable to develop procedures by which the
yields and the quality of the liquid fuels can be upgraded
in one step during the conversion to permit their immediate
use as it without costly refining or upgrading.
The present invention therefore provides a
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procedure for obtaining a higher yield and quality liquid
fuel from the direct liquefaction process.
The invention relates to a process for converting
directly biomass into hydrocarbons in one step which consists
of liquefying and deoxygenating solid particles of biomass
dispersed in water in presence of a catalyst system comprising
- a crystalline aluminosilicate zeolite containing finely
divided and dispersed metal particles at conditions sufficient
to obtain hydrocarbons~
The present invention relates to a process for
producing hydrocarbon fuels from renewable biomass. Examples
of biomass are spruce pine and poplar residues. The invented
process is not limited to these examples and can be applied
to any biomass materials such as agricultural residues and
urban refuse, and land- and water-based plant material such
as trees, grasses and alguae. Such a biomass is preferably
of a particle size above 0.350 mm and is dispersed in water
in percentage ratio of 10 to 30.
The subject invention is directed to a process for
the thermal conversion of biomass at about 280C to about
350C in presence of water and a catalyst system, wherein
increased yields of liquid and gaseous hydrocarbons produced
can be used as fuels and as feedstocks for chemical manufacture.
The excess char is removed to serve as fuel.
The process according to the subject invention is
conducted in an inert or reducing atmosphere.
It has been observed that the residence time
has an effect upon the yields and quality of hydrocarbon
liquids. Shorter residence times would increase liquid
production. Suitable residence times are about 2 to about
5 minutes in the conversion zone operated at the mean
temperature of 320C. Higher residence time leads to lower
yields due to secondary reactions such as polymerisation
and tar formation. The Applicant has found that hydrocarbon
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liquid fuel yield and quality be further increased, while
maintaining high overall process efficiency by using specific
catalysts.
These catalysts are generally described as crystal-
line aluminosilicate zeolite minerals having SiO2/A1203 ratiohigher than 4 and a pore size of about 4.0 to about 8.OA.
Such zeolites may be for example H-Y zeolite, ZSM-5 and H-
mordenite. These zeolites are described in detail in US
Patent No. 3,702,886 and from S.A. Rabo (Zeolite chemistry
and catalyst, ACS 1975) and do not constitute part of this
invention.
The Applicant has also found that mono and poly-
metallic particles finely dispersed and deposited in the
zeolites enhance considerably the deoxygenation rate and
the water shift reaction. Metals are dispersed in the pores
and cavities as cations by well known techniques in the art
such as ion exchange technique and are reduced under hydrogen
at about 400C. Metals used are selected among iron, nickel,
palladium, piatinum, cobalt, molybdenum, chromium, titanium,
copper, ruthenium and zinc. The content of metals in
zeolites is from 1 to 10%.
It is well known in the art that the first step
in a direct liquefaction process is a thermal depolymerisation
of carbohydrate polymer (cellulose, hemicellulose) and
phenolic polymer (lignin) followed by deoxygenation reaction,
to give liquid fuels; and that the depolymerisation products
are potent precursor for coke formation, the shape selective>~
zeolites are not themselves capable of efficient deoxygenation
even in water medium in presence of steam. The Applicant has
found that an inert and thermall~ stable support has a
marked eEfect on the rate of coke formation besides the
residence time process parameter. The dilution of active
zeolite catalysts with a support having a surface area higher
than 0.5 m2g-1 such as alumina, abestos and synthetic silica-
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alumina yields a composite having ~low coking tendencies andenhances activity for converting oxygenated depolymerized
products of biomass to hydrocarbons. Methods for preparing
admixture of zeolite catalysts dispersed in a solid support
with a binder are well known in the art. The ratio of
zeolite to support may vary from 0.01 to 0.30. Supports
are selected based on their thermal stability. Silica must
be avoided because of its volatility in steam at high tempe-
rature.
In a preferred embodiment, the catalytic liquefaction
process of this invention may be carried out in the presence
of hydrogen, carbon monoxide or a suitable inert gas e.g.
nitrogen or argon at temperature of 280 to 350C and
pressure of 1300 to 3000 psi with residence time of 2 to 5
minutes. Water is used as solvent.
In order to better understand the invention without
limiting the same, reference is made to the accompanying
drawing which is a schematic illustration of the invention
according to which the biomass is thermally converted to
liquids composed of aliphatic, aromatic, olefine and function-
alized compounds containing oxygen and nitrogen, and gases
such as methane and ethane acetylene. The thermal conversion
zone consists of a high pressure vessel equipped with a
rotating stirred basket holding the catalysts. Low residence
time of the product in the thermal conversion zone is obtained
by ejecting the reaction mixture to a let-down water cooling
vessel. Residence time in the thermal conversion zone is
from 0.2 minute to any time. The quenching time from 350C
to 90C is 1.5 minutes.
Referring to the appended diagram, the plant biomass
is ground to flour of 0.350 mm size and mixed with water to
obtain a slurry of 10 to 30 percent by weight. The slurry is
heated to 70C and fed to a reactor feeder system. The
reactor zone is flushed with nitrogen and heated to about
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400C to 450C. The catalyst basket is rotated to 500 rpm
and the slurry is injected rapidly~(about 10 sec) in the
conversion zone by a water piston at 200 psi. The reactional
mixture reaches 300 to 350C and developes 1000 to 3000 psi
in less than 1 minute. The product can then be ejected out
of the conversion zone by a water cooled valve to a let-down
water-cooled vessel. Steam is then injected to the reactor
zone to remove solid tar formed in the catalyst basket. The
product oil is extracted with dichloromethane, the water
layer containing less than 5% of organic products is mixed
- with fresh waste and recycled.
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