Note: Descriptions are shown in the official language in which they were submitted.
>~t
PROCESS FOR THE CATALYTIC CRACKING OF
HYDROC~RBON OILS AND CATALYST FOR THIS PROCESS
The present invention relates to a process for the
the caJalytic cracking of hydrocarbon oils in the
preser^e of a cracking catalyst containing at least
one c-ystalline zeolite. Such catalysts are used on
a lar_e scale in indu~strial cracking units for the
manuf_cture of motor fuels or components thereof.
The crystalline zeolite-containing catalysts differ
from the amorphous conventional cracking catalysts
consisting of alumina and silica by their higher
degree of activity and selectivity. A drawback is,
howev_r, that the crystalline zeolites are more or
less subject to contamination by heavy metals, such
as cobalt, molybdenum, tungsten, copper~ vanadium,
nickel and in particular iron. Especially the latter
three metals are present in certain crude oils and
in certain crude oil fractions to be catalytically
cracked.
'' ' ' `
Although methods are known for removing sueh heavy
metals from erude oils or fraetions thereof, it is
still desirable to search for means whieh obviate the
necessity of this removal before the required eon-
version of the hydroearbon oils. During the eatalytieeraeking o~ hydroearbon oils the contaminating effeet
of the heavy metals manifests itself in a gradual
reduction in the activity and seleetivity of the
eatalysts and in an inerease in the formation of eoke,
an undesirable by-produet. The deterioration of the
desired properties is attended by a gradual inerease
of the heavy metal eontent of the eracking catalysts.
According to the invention the unfavourable effect
of the heavy metals on the cracking catalysts can be
reduced or suppressed by incorporating a small quantity
of boron in the catalyst.
The invention therefore relates to a process for
the eatalytie eraeking of hydroearbon oils in the
presenee of a eatalyst whieh eontains at least one
erystalline zeolite and which is contaminated by
small quantities of at least one heavy metal, in
partieular iron, whieh catalyst contains also 0.01
to 2.5~ by weight of boron.
The eatalytie eracking process is suitably earried
25 out at a ternperature in the range from 400C to 650C
and at a pressure ranging from subatmospherie pressure
~32~Z~
to several hundred bar. A fixed bed, a moving bed, a
fluid catalyst, suspensoid or riser type operation may
be applied. Hydrogen is not added and specific con-
ditions depend upon the character of the feed and the
products desired. The feedstocks to the cracking oper-
ation are hydrocarbon oils derived from petroleum,
shale oil and/or tar sand and have an initial boiling
point above the final boiling point of gasoline.
Suitable feedstocks are, for example, gas oils, fuel
oils, deasphalted oils, waxes and residual oils.
The present process employs a catalyst which is
composited with a naturally occurring or synthetic
crystalline alumino silicate, i.e., a zeolite. The
zeolite component of the catalyst has suitably been
ion-exchanged with non-poisoning metallic ions, such
as rare earth metal ions, which improve the activity
of the catalyst.
The boron can be incorporated in the catalyst
before as well as during the cracking reaction by
methods which are known as such, for example ion-
exchange, dry-mixing, impregnation or precipitation.
This incorporation is very suitably carried out by
adding volatile boron compounds or solutions of
organic or inorganic boron compounds in water or
organic solvents to the gas used to regenerate the
catalyst, to the hydrocarbon feed or the recycling
z~
oils or to the steam used for stripping the ca~alyst
before regeneration. During the regeneration of the
catalyst, the boron or the boron compound is almost
invariably converted into boron oxide.
The treating agent used in the process according
to the invention is a compound of boron. It may be
organic or inorganic. A suitable treating agent is
either boron oxide or is convertible to boron oxide
upon calcination of the catalyst containing the treat-
ing agent. Examples of treating agents are ortho
boric acid, tetra boric acid, boron pentasulphide,
boron trichloride, ammonium bi-borate, calcium borate,
diborane, magnesium borate, methyl borate, butyl
borate, tricyclohexyl borate, 2,6-ditert.-butylphenyl
dibutyl borate, cyclohexyl boronic acid, monoethyl
dodecyl acid boronate and mixtures of these. Treating
agents containing significant proportions of sodium,
such as sodium tetraborate or treating agents con-
taining other known cracking catalyst poisons are
less desirable.
A suitable organic boron compound is an alcohol
ester of boric acid, e.g., tri-n-pentylborate. This
may be dissolved or dispersed in a suitable carrier,
e g., xylene, and added to the hydrocarbon oil charge
stock to the cracking process to be contacted with
the catalyst under cracking conditions. Alternately,
a boron-containing treating agent, such as boric acid
in aqueous solution, may be introduced into the regener-
ation zone along with the conventionally applied
stripping steam. If the impregnation method is used,
the boron-containing treating agent can be dissolved
in either an aqueous or a non-aqueous solution. For
example, an aqueous solution of ammonium biborate may
be used or if a non-aqueous solvent is desired, a
xylene solution of an aryl borate compound, such as
2,6-di-ter~.-butylphenyl borate may be used.
The normal operation of the cracking process is
not affected by the presence of boron in the catalyst,
so that it is possible to choose the usual values
for the cracking and regenerating temperatures, the
rate of feeding the hydrocarbons, the feed/recycle
oil ratio and other parameters. The catalyst prefer-
ably contains 0.1 to 1.5% by weight of boron, the
weight percentage being based on that of the fresh
catalyst. The quantities of contaminating heavy metals,
in particular iron, normally vary between 0.1 and
2.0% by weight, calculated as the total quantity of
metals based on the weight of the fresh catalyst.
EXQMPLE 1
A series of cracking experiments have been carried
out in the presence of a cracking catalyst containing
faujasite-Y, under the following conditions:
~3'~
pressure 1 bar
reaction temperature 485C
regeneration temperature 600C
feed Kuwait distillate
space velocity 6.4 kg/kgh
The relative selectivity (SR) of the conversion,
during the cracking operation,is determined according
to the formula:
PB
_
in which PB = total weight of the product fraction
C5 - 221C, expressed as a percentage based on the
feed and PC = total weight of coke, expressed as a
percentage based on feed.
A quantity of iron naphthenate (0.65% by weight
of Fe) is added to the catalyst by impregnation.
Further, the quantity of passivating boron stated
in the Table is added by impregnation, with inorganic
salt solutions.
The Table states the data found, which reveal that
the addition of boron to a catalyst containing iron
has a favourable effect on the production of gasoline,
a negative effect on the formation of coke and thus a
favourable effect on the relative selectivity.
~L3Z~
TABLE
Exp. Fe ¦Boron PB C ,c
% by wtl% by wt % gasoline ~ coke
1 o o 51.1 7.6 6.7
2 o.6s o 48.3 lo.o 4.85
3 o.6s 0.2 48.95 9.4 5.2
4 o.6s o.3 49.75 8.~ ~.65
0.65 o.4 49.65 8.6 5.75
.65 o.6 49.85 7 55 6.6
EXAMPLE 2
Catalysts 1 and 2 were equilibrium catalysts ob-
tained from commercial cracking operations using a
feed derived from a U.S.A. mid-continent crude oil.
5 Each of the catalysts was treated with a boron-treating
agent and the treated catalysts are numbered catalysts
lA and 2A, respectively. The concentration of metals
and boron on the catalysts at the beginning of each
run were as follows:
Catalyst 1 lA 2 2A
~etal content, %wt
Nickel 0. 27 o .270.13 0.13
Vanadium 0.63 0.63o.ll o.ll
Iron 0-59 0-59 o.66 o.66
B 0 0.43 o 0.052
Z2
Boron was added to the catalyst lA by impregnation
with a solution of 5.44 grams of tripentylborate in
15 ml toluene applied to 50 ~rams of catalyst. Follow-
ing the boron impregnation, the catalyst was dried to
5 a temperature of 482C under nitrogen (to avoid
hazardous oxidation of the toluene) and then was
calcined in air at about 482C. For the catalyst 2A
the boron was added by impregnation with an aqueous
solution of 0. 74 grams of boric acid in 7.5 ml of
water to 25 grams of catalyst, followed by drying
in N2 for I hour at 482C followed by calcination in
air for one hour at temperatures of about 482C.
The catalysts were tested in a fixed bed catalytic
cracking unit under conditions as shown in the follow-
15 ing Table:
Feed preheat temperature 480C
Catalyst temperature 480C
~talyst/oil ratio 2.5/1 - 7/1
The gas oil feed used had the following properties:
Density (kg/m3) 894
Sulphur~ %wt 0. 8
Saturates, %wt 56.88
~onoaromatics, %wt 18.9LI
Diaromatics, %wt 17.04
Triaromatics, %wt 6.o4
Tetra-aromatics, %wt 0.10
Basic nitrogen, %wt 0.20
- . . ..
~ : '
~3~
Feed rate was varied to give at least three con-
version levels to permit interpolation of the catalyst
performance data to 70 or 75% by weight conversion as
follows:
Catalyst 1 lA 2 2A
_
70% conv. 75% conv.
Space velocity (kg of
oil per kg of catalyst
per hour) 12 12 13.2 15
lO Yields at 70% conv. 75% conv.
CTasoline (C5 - 232C),%wt 51.2 55 57 59
Coke, %wt 8.6 5 6.2 4.6
~ rom the above it is apparent that gasoline yield
has been increased and coke yield has been significantly
reduced when operating the catalytic cracking process
according to the invention.
EXAMPLE 3
A sample of the contaminated catalyst 1 was
impregnated with an aqueous solution of boric acid so
as to give the same level of added boron as in catalyst
lA. The boron-containing catalyst was dried to a temper-
ature of 482C under nitrogen. One half of the dried
catalyst (catalyst 3) was tested to determine its
cracking performance. The other half of the dried
catalyst (catalyst 4) was calcined in air at 482C for
one hour to fix the boron on the catalyst. Results
~' '~ '' ' '
~.3~
of the testing of the catalysts are summarized below:
Catalyst 1 3 4
Space velocity for 70% con-
version (kg of oil per kg
of catalyst per hour) 12 12.5 12.5
Yields at 70% conversion
G~soline (C5 - 232C), %wt 51-2 55 55
Coke, %wt 8.6 5.0 4.8
From the results it appears that the calcination
environment has no significant effect on the perform-
ance of contaminated catalysts impregnated with boric
acid. Similar studies with an organo-boron (tri-
pentylborate) impregnated catalyst showed slightly
higher activity for the air calcined catalyst. It is
worthy of note that, within the experimental uncertainty
of the tests, the catalysts 3 and 4 showed the same
catalytic performance as catalyst lA indicating that
an organoboron compound and boric acid are essentially
equivalent in their efficacy for passivation of metal
contaminants.
