Note: Descriptions are shown in the official language in which they were submitted.
115~475
1 H.31030
Production of hydrocarbons
THIS INVENTION relates to the production of
hydrocarbons, in particular by cracking higher hydrocarbons
or by reaction of small molecular compounds, in the
presence of zeolite MCH as catalyst.
Reactions leading to hydrocarbon products have been
described using as catalyst a zeolite of the large-pore
type such as X or Y or of the medium-pore type such as the
ZSM-5 family. The latter reactions, whether they start
from hydrocarbons having relatively long chains which are
to be cleaved or from hydrocarbons and their derivatives
having single carbon atoms or short chains up to (for
example C4) which are to be polymerised, usually lead to
the formation of aromatic hydrocarbons unless special
measures such as low pass conversion or modified catalysts
are adopted.
We have now found that our recently discovered
zeolite MCH can catalyse the conversion of such feedstocks
to hydrocarbons containing 6 or fewer carbon atoms.
The invention provides a process of making a
hydrocarbon containing 6 or fewer carbon atoms in the
molecule by reacting a feedstock comprising a hydrocarbon
different from the intended product and containing 2 or
more carbon atoms in the molecule and/or a hydrocarbon
derivative containing hydrogen-carbon links over a
catalyst comprising zeolite MCH as hereinafter defined.
Zeolite MCH has the typical chemical composition
2 2 3 . 4 to 7 SiO2 . O to 8H20
where R is a monovalent cation or n of a cation of valency
n. It has a characteristic X-ray diffraction pattern
similar to herschelite but with all lines broadened as
a result of the small crystal size. The characteristic
lines have a half peak height breadth greater than 1 degree
in degrees 2 theta units at the diffraction angles shown
in Table 1~
, ~ _
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Table 1
. _ , --
2~ ¦d (A)Intensity I/Io x 100
, I
9.3 9.5 33
16.3 5.4 12
20.9 4.25 66
27.5 *3.24 23
30.5 *2.9~ 100
34.0 *2.64 13
__ .
(*These lines were incompletely resolved).
The half peak height breadths are more typically in the
range 1,5 to 3.5 degrees 2 theta units. These correspond
to a crystallite size under 200, especially under 100
Angstrom units.
Zeolite MCH in preferred forms is characterised further
by the capacity to exchange at least 25% of its sodium
ions with magnesium ions and substantially all its sodium
ions with ammonium or rare earth ions.
It is characterisçd yet further by having a sorptive
capacity, when in the sodium form, of at least 1.5% of
n-hexane and 1% of para xylene, measured by weight at
25C at half the saturation vapour pressure.
For a fuller description of zeolite MCH and its
preparation reference is made to our UK patent Specification No.
2,061,900A, published ~1~y 20, 1981. The zeolite MCH to be used
in the process of the invention should be sufficiently
pure to exert the required level of catalytic activity.
Conveniently it is material synthesised ir conditions
leading to simultaneous formation of gmelinite, typically
up to 30, especially 5 to 20% by weight.
In order to be useful to a preferred extent in the
process of the invention, MCH is converted from the form
in which it is hydrothermally produced, in which form it
3 H.31030
contains alkali metal oxide, to an active form by ion
exchange. The alkali metal compounds content of MCH as
used in the process of the invention is preferably less
than 3, especially less than 2% W/w, calculated as equivalent
Na20. Useful activity is observed even when that alkali
content is 0.5% W/w or over. Preferably the MCH is activ-
ated by heating at 400 to 600C in air or oxygen-free gas
before beginning the reaction; such treatment is also
suitable for reactivating used catalyst. The water content
of freshly activated or reactivated catalyst is preferably
O to 2 mols in the above chemical composition formula.
In the active form the alkali metal ions have been
replaced at least partly by hydrogen or ions of polyvalent
metals. Replacement by hydrogen can be effected by exchange
with acid or with ions of ammonium or non-quaternary amine,
since such ions decompose on calcination to leave hydrogen
ions. me polyvalent metal is preferably selected from
those having little or no catalytic activity for hydrogenation,
except when synthesis is to accompany conversion, as
described below. Suitable metals are from Group II or the
rare earth group of the Periodic Table as set out in
"Abridgments of Specifications" published by the UK
Patent Office. Preferably hydrogen ions and polyvalent
ions are both present. Calcium-hydrogen MCH appears to be
especially selective for producing ethylene and propylene.
MCH may be used at full strength or in mixtures with
diluent material such as inert silica, alumina or clay ,
a suitable proportion of diluent being in the range 10 to
40% by weight. The diluent may facilitate forming MCH
into shapes (such as 1 to 10 mm cylinders or spheres for
use in a fixed bed or into fine particles for use in a
fluidised bed) and also enables the rates of the wanted
and unwanted reactions over it to be controlled. The
diluent can, if desired, be a zeolite; a convenient com-
bination is a mixture of MCH with a zeolite such as gmelinite,as synthesised together by suitable choice of conditions.
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4 H.31030
The feedstock can be for example a normally
gaseous (up to C4) hydrocarbon or mixture such as LPG or
a readily vaporisable hydrocarbon or mixture (C5 to C12)
such as natural gas liquids or naphtha or higher volatilis-
able hydrocarbons such as kerosene or gas oil. If it isa hydrocarbon derivative it is suitably one having at
least 2 hydrogen atoms linked to at least some of its
carbon atoms. Oxygenated hydrocarbons such as alcohols,
ethers, carboxylic acids, esters, aldehydes and ketones
and their acetals are very suitable feedstocks. An
especially useful application of the process is the production
of olefins from methanol and/or dimethyl ether, since MCH,
unlike for example the ZSM-5 family of zeolites, appears to
be selective for the production of normally gaseous
hydrocarbons and against the production of aromatic
hydrocarbons. Crude feed and/or waste streams containing
organic sulphur or nitrogen compounds can be upgraded to
useful products by the process of the invention.
The products of reaction over MCH may include
unwanted hydrocarbon derivatives and possibly also
unconverted feedstock. The crude product is separated by
condensation of the normally liquid compounds in it and
the gaseous fraction is resolved by distillative fraction-
ation or by adsorption. Unwanted and unreacted materials,
after recovery of the required products and separation of
other products such as methane, carbon oxides, water and
(when appropriate) hydrogen, can be subject to further
stages of conversion over MCH or recycled for further
conversion with the main feedstock.
The reaction temperature is suitably in the range
300 to 450, especially 350 to 400C when the product
olefin is to contain 4 to 6 carbon atoms, but 400 to 550
especially 425 to 525C when ethylene and/or propylene
are to be the main products.
The pressure at which the process is carried out
is suitably in the range 1 to 50 atm. abs., especially
1 to 15 atm. abs. but higher pressures for example to
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H.31030
300 atm. abs. can be used if convenient, for example
when methanol or a like synthesis is combined with the
process of the invention.
The space velocity should be controlled so as to
give the required product distribution. Thus, for example,
when the feedstock is methanol, reaction at a liquid hourly
space velocity of about 1.0 produces a higher proportion
of dimethyl ether than when the space velocity is 0.2.
The dimethyl ether can be recycled or reacted in a separate
bed of MCH or other catalyst. It appears that the
conversion of methanol is preferably incomplete, for
example in the range 75 to 98~.
The catalyst maintains its activity for substantial
period, but can be regenerated by heating in the conditions
preferably used for activating it. Very suitably it is
used in the form of a fluidised bed and catalyst is
continuously withdrawn, passed through a regeneration
zone and returned to the olefin-forming reaction.
The process of the invention can be used in
combination with a process of synthesis of hydrocarbons
and/or oxygenated hydrocarbons by catalytic reaction of
carbon oxides with hydrogen. Synthesis products can be
separated before the reaction over MCH but, if desired,
the MCH catalyst can be disposed so as to act on the
synthesis products in advance of any product separation
step, for example in a bed downstream of the synthesis
catalyst, or by using a mixture of discrete pieces of
synthesis catalyst and MCH catalyst, or by using discrete
pieces made by shaping a mixture of powdered MCH and synthe-
sis catalysts or by applying to MCH by impregnation orion-exchange one or more compounds of metals or oxides
having such synthesis activity. Suitable synthesis
catalysts contain for example one or more of copper, zinc
oxide, chromium oxide and the non-noble or noble metals
from Group VIII of the Periodic Table. The pressure of
the reaction over MCH can be chosen to suit the conditions
of the synthesis reaction.
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As Example 2 shows, MCH is relatively inactive for
cracking hydrocarbons having a large "CSA" ~ diameter,
that is, width of the molecule in the plane in which its
cross-sectional area is a minimum. Consequently the
invention provides processes in which molecules of small
CSA diameter are selectively cracked. One such process
is the de-waxing of a hydrocarbon feedstock, by cracking
alkanes and leaving a product enriched in aromatic
hydrocarbons, especially polynuclear hydrocarbons, such
as may be used as a lube oil base stock or a source of
intermediates for chemical processing.
EXAMPLE 1
Hexadecane crackin~
Samples (0.26 ml) of MCH as described below were
charged to a pulse microreactor and activated by heating
at 450C for 1 hour in a current of air at 3 litres per
hour, 4.4 atm. abs., pressure. Then the air was replaced
by an equal nitrogen stream and at 450C a 1 microlitre
sample of hexadecane was injected upstream of the
catalyst. ~he gas leauing the catalyst was analysed by
gas chromatography. For each sample the hydrocarbon product
distribution showed that hydrocarbons containing less than
6 carbon atoms were the only products. The catalyst
details and percentage conversions are shown in Table 2.
Table 2
__
Catalyst and composition % conversion
A RE-MCH 99.1
B H-MCH 99.9
C RE-MCH 99.9
EX~MPLE 2
(a) Example 1 was repeated with 1 microlitre samples
of decalin (52% cis, 48% trans). The product distribution,
percentage conversion and percentage yields are shown
11~9~7e~
7 H.31030
in Table 3. It is to be noted that as a consequence of
the analytical technique used, the C8-C10 fraction
includes some C7 aromatics and the C11-,C15 fraction
includes! some C10 aromatics. Residual coke on the
5 catalyst is not included.
(b) Example 1 was repeated with 1 microlitre samples of
1-methylnaphthalene. The results are shown in Table 4.
The C11+ fraction reported does not include unconverted
feed.
It is evident that the activity of MCH, especially
H-MCH, is much lower for cracking polynuclear hydrocarbons
than for hexadecane, and thus that it would be effective
in removing alkanes from a mixture with polynuclear
hydrocarbons.
Table 3
, Catalyst ~ A ~ C
Products (%)
under C6 10.6 4.0 11.0
C6 + C717.1 2.7 13.6
C8 ~ C1014.3 1.6 12.9
decalin37.5 45.2 39.4
cis-decalin 20.5 46.5 23.0
.
Conversion (%) 42.0 8.3 137.6
Yields (%) l l
under C6 25.2 ¦48.2 29.4
C6 + C7 40.7 32.5 36.1
C8 ~ C10 34 1 19 3 34.4
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8 H.~1030
Table 4
~ . _
Catalyst ¦ A ~ B ~ C
.
Products (~0)
~C6 . O O O
C6 + C7 0 0 0
C8 - C10 O O O
naphthalene 19.1 2.7 19.7
1-methylnaphthalene 64.8 97.3 66.9 .
C11+ 16.1 0 13.4
, _
Conversion (%) 35.2 2.7 33.1
_
Yields (%)
~6 0 0 0
` C6 + C7 0 0 0
C8 - C10 O O O
naphthalene 54.3 100 59.5
C11+ 45 7 0 40.5
EXAMPLE 3
Cracking of a mixturQ (gas oil)
Example 1 was repeated with 1 microlitre samples of
20 an Ekofisk light gas oil (initial b.p. 205C, final
b.p. 390C, mean average b.p. 300C). The results are
shown in Table 5.~ _
~59'1~
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Catalyst A B ¦ C
Products (%) ~
~6 44.6 43.9 42.3
C6 + C7 11.2 1.5 11.7
C8 ~ C10 17.4 5.5 20.3
C11+ 26.9 49.1 25.7
Conversion (%) 73.1 50.9 74.3
Yields (%)
<i~6 61.0 86.2 56.9
C6 + C7 15.2 3.o 15.8
- C8 ~ C10 23.B 10.8 27.3
EXAMPLE 4
Crackin~ of a mixture (li~ht cYcle oil)
Example 4 was repeated with 1 microlitre samples of
a light cycle oil from a catalytic cracking plant. The
results are shown in Table 6.
-
-
1159475
H.31030
Table_6
Catalyst A B ¦ C
Products (%)
~C611.1 19.5 5.6
C6 + C7 2.3 <0.1 0.7
C8 ~ C1010.6 3.2 9.1
C11+76.077.~ 84.6
Conversion (%)24.022.715,4.
Yields (%)
~C646.2 85.9 36.4
C6 + C7 9.6 0.2 4.6
C8 ~ C1044.2 14.1 59.1
EXAMPLE 5
Formation of gaseous hydrocarbons from n-hexane or methanol
A micro-reactor set up to analyse C1 - C4
hydrocarbons was operated first with a fresh sample of
catalyst A, then with a different preparation of rare earth
MCH (catalyst F). Each catalyst test consisted of a run
using n-hexane, a run using methanol, an injection of 100
20microlitres of methanol to simulate ageing and then a second
n-hexane run and methanol run. The runs each used 0.6
microlitre of starting material but otherwise experimental
conditions were essentially as in Example 1. The product
gas compositions are shown m Table 7
//
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1~15~47 Ir~
11 H.31030
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~ l ~ o
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cC a~ X a~ u~ ~ O O O O
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U~ ~1 ~ ~X X ~C X ~:: X ~ X
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~5~9~ 7 5
12 H.31030
EXAMPLE 6
Conversion of methanol over ion-exchanged MCH samPles
In the conditions of Example 5 the following
catalysts were tested:
B H-MCH
D Ba-MCH
E Ca-MCH
The results are shown in Table 8.
Table 8
Catalyst B B D D E E
condition fresh aged fresh aged fresh aged
TC 450 450 450 450 450 450
Gas % V/v
CH4 3.6 2.1 4.1 2.8 4.7 4.7
C2H6 0.2 0.9 0.2 1.0 0.2 o.3
C2H416.6 16.2 15.1 18.2 16.2 21.5
C3H822.4 33.2 24.7 29.7 26.5 30.2
C3H641.2 18.4 32.5 39.7 42.1 28.3
i C4H10 O O O O O O
n C4H104.9 23.4 10.5 4.0 6.2 13.7
1 C4H8 2.7 0.8 2.0 1.1 0.7 0
i C4H8 2.0 0.6 1.0 0.3 0.6 ~0.1
2-C4Ha 4.9 3.2 6.3 3.2 2.7 <0.1
DLM/JH
