Note: Descriptions are shown in the official language in which they were submitted.
~0~04'74
The invention relates to improvements in the cata-
l~tic hydration o~ nitriles with water to produce amides by
a continuous process us~ng certain solid heterogeneouQ cata-
lysts ~or the reaction, More particularly, the invention
provides an improvement in solid catalyst used ~or such re-
action, havlng improved physical strength which improves the
length o~ use~ul catalyst life with consequent increase Or
the amount Or product that can be produced with a given
amount Or the catalyst.
The particular type Or catalyst to which the inven-
tion relates was in use be~ore it was improved by the present
invention,
This particular type o~ catalyst, called copper-
magnesium silicate catalyst, was prepared by precipitation
copper and magnesium ~rom aqueous solution by introducing
alkall metal silicate and alkali metal carbonate into a solu-
tlon o~ copper and magnesium salts. The copper-magnesium
carbonate silicate precipitate wa~ separated by ~iltration
~rom the mother liquor, washed, dried and pressed or e~truded
to ~orm pellets, beads, or the like which were ~urther dried
and then shipped, stored and charged to the reactor in dry
pellet ~orm. Treatment with a reducing gas was de~erred
until ~ust be~ore the catalyst use. Catalysts o~ this type
may pre~erably also contain in minor proportions, e.g. .01
2~ to about 5 percent by weight, o~ one or several promoters
; ~uch as compounds o~ barium, zinc, cadmium, chromium, molyb-
i
dsnum, tungsten, vanadium, uranium, titanium, thorium or the
like. Catalyst~ with such promoters are prepared in some
; ~nstances by precipitating the promoter together with the
insoluble copper and magne~ium compounds ~rom a similar
copper magnesium solution which ~urther contains a corre-
~ spondingly small amount o~ a dissolved salt o~ the ~elected
- promoter metal in addltion to the copper and magnesium salts.
4'74
Rererence i9 made to the German Patent No. 869,o52 ror more
detailed de~cription Or the preparation Or catalysts o~ the
type de~cribed. Belgium Patentq No. 813,973 and No~ 813,974
described typical hydration Or acrylonitrile using such cat-
alysts, A typical catalyst o~ this type is available com-
mercially from Badische Anilin ~ Soda Fabrik AG, Ludwigsha~en,
West Germany under the tradename BASF Cataly~t R3-11, also
called BTS Catalyst~ It contains approximately 30 percent
by weight Or copper combined in compounds Or copper disper-
sed throughout the magnesium silicate matr~. This catalystis supplied in cylindrical pellets about 1/8 inch long
3/16 inch diameter,
For its partlcular use in the hydration Or nitrile
the catalyst i8 activated by redu¢tion with hydrogen or other
errective reducing agents, ~rererably the reduction la car-
ried out with hydrogen at 180 to 230C, and prererably with
the catalyst already placed ln the rixed-bed reactor and also
prererably ~ust prlor to use Or the catalyst ror the contin-
UOU8 hydration process, Arter the catalyst has been reduced
the reduced catalyst is kept away rrom o~ygen to avoid o~i-
dation o~ catalytic copper surrace areas and consequent 1088
Or catalytic activity.
Combined copper in the catalyst is conveniently
reduced to elemental copper by ~irst charging the cataly~t
pellets to the bed Or a ri~ed bed catalytic reactor which is
to be used ror the hydration proce~s, Then a stream Or re-
ducing gas is red through the catalyst bed at temperature
in the range from 180-230C, until there i~ no ~urther re-
duction to elem~ntal copper at the selected reducing con-
- 30 dition~, The reducing gas is prererably hydrogen, but other
reducing gas such as carbon mono~ide or the l~e could be
used. It ia prererred to rirst heat the catalyst with not
nitrogen to about 120 to 160C, and then gradually add
~ ~ k - 2 -
- . ; - . , - ~ . - .
. .
~Of~0~74
hydrogen to the nitrogen stream until the bed temperature
is raised to about 180-230C. m e reaction ~or reduction
o~ copper with hydrogen is e~othermic and the bed temper-
ature is maintained at the selected temperature by regulating
the gas ~eed rate and ad~u3ting the concentration o~ reduc-
ing gas in the gas reed. Depending upon the particular re-
ducing conditions selected, the reduction step as described
usually is completed in about 8 to 24 hours. A~ter cooling
the catalyst bed, the reactor is ready ~or introduction Or
a nitrile-in-water reactant solution a~ the ~eed stream to
commence the continuous hydration reaction. ~uring the
treatment with reducing gas to reduce the copper, the cata-
lyst is sensitive to exces~ive temperature and it is nec-
essary to ¢are~ully regulate the bed temperature durlng re-
1~ ductlon to avold deactlvatlon by overheatlng the catalyst,We pre~er to avoid heating the catalyst bed beyond an upper
limlt o~ about 230-250C. to pre3erve the catalyst dur-
ing the reducing reaction. Deactivation, or at least a con-
siderable 1088 o~ activity can be expected as temperatures
about 250C. are approached or exceeded during portions o~,
or all o~ the reduction step.
For the hydration o~ acrylonitrile with water the
catalyst obtained commercially and reduced as described, was
round to produce very hiBh yield Or acrylamide at conversion
rate~ comparable with thoss obtained with a good reduced
copper chromium oxide oatalyst, notwithstanding the consider-
ably lower proportion o~ copper in this catalyst. Thi8 cata-
lyst was clearly superior to a good copper chromium o~ide
catalyst on the basis o~ higher conversion per hour per pound
3~ Or copper in the catalyst and on the basis o~ longer catalyst
li~e, that is, a slower rate o~ decay o~ the catalytic ac-
tivity as the hydration process was carried out continuously.
A principal disadvantage with this catalyst was that the
-- 3 ~
()4'74
catalyst particles did not have as much physical strength as would have
been desired. This was particularly so after the catalyst had been reduced
and washed with the liquid reactants The pellets were apt to fracture and
cr~ble causing blockage and channeling in the fixed catalyst bed with --
consequent loss of circulation of reactants to much of the effective
catalytic surface area in the catalyst bed, This was found to be especially
severe in large industrial size catalyst beds containing several tons of
the catalyst Furthermore, solid polymer was apt to form at regions of
lost circulation in the catalyst bed causing those regions to solidify
Such events would drastically reduce the effective activity of the catalyst
bed Thus, because of the inadequate physical strength of the catalyst
particles, much of the advantage of the long catalyst life would be lost by
irreversible physical deterioration of the catalyst bed structure during use.
The present invention provides in a process for catalytic hydration
of acrylonitrile to produce acrylamide by flowing a reactant solution com-
prising acrylonitrile in water through a fixed bet of copper magnesium
silicate type catalyst after reduction of the catalyst, the improvement
wherein said catalyst has been treated prior to the hydration reaction by
calcining the catalyst in a non-reactive atmosphere at calcining temperature
in the range from 300 to 500C. for time from about 1 to 24 hours sufficient
to substantially decrease the rate of decay of catalytic activity during use
of the reduced catalyst in the defined hydration process.
According to the invention, catalyst particles of the copper
magnesium silicate type described herein are treated by calcining the
catalyst particles at high temperature in an essentially, non-reactive
atmosphere, The calcining can be carried out either b0fore or after the
catalyst has been reduced. It was expected that the high temperature needed
for effective calcining to improve particle strength ~300-500C.) would
cause physical deterioration of the particles, either by fracture and
crumbling of the particles or by sintering of the active copper, or would
4 _
! ~ , . , ' . ' . , , , ' ' . . . '
10~;0474
otherwise cause deactivation of the catalytic copper, thus spoiling the
catalyst for subsequent use, Deactivation of the same catalyst had in
fact been reported during reductions carried out at excessively high
temperature, Also, destructive physical deterioration of the catalyst
had been observed during attempts at high temperature oxidation for
' _ 4a -
.. ..
,... .. .. : . . . .
regeneration of the spent catalyst. It is found however, that
calcining the catalyst before it is used in the hydration reaction,
either before or after the reduction of the catalyst, at calcining
temperatures in the range from about 300C. to about 500C. for
periods in the range from about one hour up to about 48 hours,
does not cause as much physical deterioration or deactivation of
the catalyst during such calcining step as might have been expected.
The calcining does in fact physically stengthen the catalyst.
; More important, such calcining is found to increase the effective
catalyst life as the catalyst is used in a fixed bed reactor for
the hydration of acrylonitrile with water.
It had been anticipated that high temperature calcining
before the reduction step would cause chemical changes of the
copper compounds during calcining, and it was expected that such
chemical change probably would detract substantially from the
excellent activity and catalyst life when the calcined catalyst
was reduced and used for the catalytic hydration reaction. As
, was expected, the calcining does in most instances reduce the
initial activity of the catalyst, but this can be kept to a
tolerable extent. However, the rate of decay of catalyst activity
; ..
~3 of the catalyst in a fixed bed-reactor during the continuous
,~ hydration reaction is so much improved by the calcining treatment,
that the increase of effective catalyst life by slower decay of
activity will more than compensate for the reduced initial activi- -
ty. More acrylamide will be produced during the extended useful
life of the calcined catalyst than would be produced with the
higher initial activity but faster decay of the uncalcined
catalyst.
The process o~ precalcining the catalyst before the
initial reduction step is distinguished from the step of
preheat~ng t~e catalyst to reduction temperature that
- 5
, ; ~ , - - ~ , - . -
0474
was u~ed to begin the prior nrt reduction ~t~n ~ cribe(~
above. In both methods the cataly~t i~ heated prior to the
initial reduction, and both may be carried out with the cat-
alyst already placed in the reactor, but in the prior art
process the catalyst was preheated only to about 140-180C.
to help initiate the reduction reaction. In the prior art
pro~ess the temperature was carerully regulated during re-
duction, including the preheating step, to avoid overheating
the cataly~t. In the calcining proces~ the catalyst is
heated in a non-reactive atmo~phere, either be~ore or arter
the reducing step, to a calcining temperature that is higher
as contrasted with tho~e temperatures which had been previ-
ously ~ound ~uitable ~or the reducing ~tep.
When the calcining proces~ i3 carried out be~ore
rcduction o~ the catal~t, we re~er to that process as pre-
¢alcining, as distinguished ~rom post-reduction calcining.
Precalcinlng is carried out in a non-reactive, e.g. non-
reducing, atmo~phere and the high temperature ~or the pre-
calcining treatment is applied to the catalyQt ~or a period
lone enough to e~ect ~ubstantial strengthening o~ the cata-
~; lyst during ~uch period o~ high temperature calcining. An
atmosphere o~ heated air or other non-reducing atmosphere
can be used to surround and heat the cataly~t during the
precalcining step. If air or any other atmosphere contain-
ing an oxidizing agent is u~ed during precalcining, one
~hould care~ully purge the cataly~t bed with inert gas, e.g.
~ ~ .
~ ; nitrogen, be~ore introducing the reducing gas, e.g. hydro-
:: `
~; gen, to avoid any danger Or explo~ion, It is pre~erred,
a~ter precalcining,~to cool the catalyst at least to a lower
temperature that i9 suitable ~or the reduction step be~ore
beginning the reduction ~tep,
It i~ u~ually mo~t convenient, but not necessary
; in all in~tances, to calcine the catalyst after it has been
-- 6 --
. - ~ - . . . . ~ . . .
: ,: . . ~ - . ,
10~0474
placed in the catalytic reactor. Alternatively, the cata-
lyst can be precalcined el~ewhere under the temperature and
other conditions prescribed herein ~or calcining; ~or ex-
ample, the catalyst particles might be precalcined as a final
step in the manuracture Or the catalyst. me precalcined
catalyst prior to reduction is stable, not sub~ect to de-
activatlon by exposure to air, and can be handled, stored
and shipped, the same as had been done in the past berore
reduction o~ the uncalcined catalyst.
Arter the catalyst has been precalcined, the ac-
tivation by reduction and the use Or the reduced catalyst
ror hydration are carr-ed out es~entially the same as de-
. .
scribed ~bove ror the activation o~ an untreated catalyst,
Examxle 1
A sample taken rrOm a bat¢h Or BASF Catalyst R3-11,
as received, i9 tested ~or crush strength, A sinele cylin-
dri¢al pellet o~ the catalyst is crushed by application Or
mechanical ~orce in a recording prsssure press, The crush-
ing rorce is applied at opposed sides along the length Or
the cylindrioal pellet. Crushing rorce applied is divided by
length Or the pellet to obtain a comparative crush strength
value in units Or pounds rorce per inch length. Nominal di-
ameter Or all Or the pellets tested is 3/16 inch. The same
test ror crush stren8th is used for all the examples herein.
Crush strength o~ the dry pellets rrom one batch (Batch II)
as received was 126 + 27 lb./in. Wetting the pellet~ with
water i9 found to reduce the crush strength and not all Or
the original strength is restored when the wet pellet is
~; ~ dried, Notioeable variation in crush strength was round
~rom one batch to another. -Los~ Or crush strength also re-
~ults from several kind9 of treatment o~ the catalyst, par-
tioularly aqueous wash or soak treatments at elevated tem-
perature,
~t`~4 h?ark 7
. . . . . . . . . . ..
~ 4t~
From another batch (Batch IV) Or the 8ASF R3-11
A catalyst ~he dry crush ~trength Or sample pellets, tested as
received, was 95 + 21 lb./in. Pellet~ ~rom this batch cru~h-
ed in the wet state at 56 + 9 lb./in. arter being wet ror one
hour and 40 + 7 lb./in. arter 14 days wetting. Pellets rrom
this batch whlch were wet and then dried in air at 110C.,
crushed dry at 61 + 9 lb,/in. Pellets wet and then dried and
then wet again ror one hour, crushed wet at 28 + 6 lb./in.
Other pellets ~rom this same batch were calcined, as re-
ceived, at 40ooc. ror 16 hours. Another sample rrom thesame batch was calcined at 450C. ror 16 hours. Arter cal-
cining, the pellets which were calcined at 400C. crushed
dry at 168 + 41 lb~/in. and crushed wet, arter being wet ror
one hour, at 88 + 25 lb./in. The pellets calcined at 450C.
crushed dry at 155 + 44 lb./in. and crushed wet, a~ter being
wet ror ono hour, at 91 + 12 lb./in.
Sin¢e the eatalyst ln use is wet and in reduced
state, ~urther measurements Or the catalyst strength were
carried out arter reduction and washing with water ror two
days. It was round that catalyst Or the same lot (Batch II)
which was reduced wlthout prior treatment (see E~ample 2
ror reduction procedures) and then washed with deaerated
and deionized water at 75C. ror two days cru~hed wet at
18 * 2 lb./in. Furtherm~re, arter about 4 months operation
~ .
25 the catalyst was round to have a wet crush strength o~ only
about 10 lbs./in. with many pellets 90 badly ~ragmented or
80 ~o~t to the touch that the strength o~ those pellets
could not be measured. The same ¢atalyst calcined at 400C.
or 16 hours, reduced and washed ror two days crushed wet
30 at 30 + 6 lb./in. Likewise, ¢atalyst ¢al¢ined at 450C.
reduced and washed ~or two days ¢rushed wet at 36 + 6 lb./in.
Cal¢ination a~ter redu¢tion was also investigated.
Batch IV catalyst was reduced, then calcined at 350C. ~or 17
~ ~ ~ac/~ mc~ ~k - 8
474
hours and washed for two days. The wet crush strength was ;
39 + 10 lb.tin. Continued washing fOT one month reduced the wet
strength to 30 + 7 lb./in. In exactly the same manner, if calcina-
tion after reduction is carried out at 400 &., the wet strength
is 54 + 17 lb./in. after two days washing and 37 + 8 lb./in. after
one months washing.
The results show that there is a severe loss of strength
when the catalyst is reduced. Furthermore, the catalyst continues
to lose strength with time in use. It is therefore of considerable -~
im~ortance in industrial sized deep beds intended for continuous
operating for a period of about a year or more to increase the
initial strength of the catalyst so that the catalyst will retain
strength sufficient for use in the reactors over a longer period.
These tests established that increase of both dry and
wet crus-h strengths would be obtained by calcining the catalyst
~ut the e~ects of calcining on the catalytic activity in the
hydration reaction were still uncertain. Further tests under `
conditions simulating actual operating conditions were conducted
to examine catalytic activity in use of the calcined catalyst
in a fixed bed catalytic reactor for the hydration o acrylonitrile.
EX~lé 2
A. In an oven, 90.7 gms. of BASF Catalyst R3-11 from ~ -
Batch II as received is heated to 450C. and calcined at that
temperature for 45 hours and then gradually cooled. The
calcined catalyst is charged to a laboratory fixed bed con-
tinuous reactor. The reactor is purged with nitrogen to re-
~sve all of the air. The next step is to reduce the catalyst
and this is done by f.irst bringing the bed temperature to
180 C. and then beginning gradual addition of hydrogen into
a stream of nitrogen flowing through the bed. At first, the
Trademark
.~ 9 ,.~ .
)474
concentration of hydrogen in the nitrogen stream is about 1.5 per-
cent and this is gradually increased ~sneeded to maintain the bed
temperature in the range from 180 to 220C. as the exothermic re-
duction of copper proceeds. The total reduction time is about 6 - 7
hours. When there is no further reduction the bed is gradually
cooled to room temperature after which the flow of deaerated and
deionized (DA-DI~ water at 75C. is begun and continued for a
period of about 40 hours to remove soluble inorganics. Then the
reaction is begun by introducing a 7 percent solution of deaerated
acrylonitrile in DA-DI water as the reactant stream to the reactor.
: -
During most of the continuous hydration the flow rate of the re-
actant stream is regulated to maintain about 85 to 90 percent con-
version but at periodic intervals the flow rate is varied to ob- -
tain several diferent conversion rates for short times for test
purposes, The reaction temperature is maintained at about 70C.
~.i
As the activity o~ the catalyst declines the feed rate is de-
creased to maintain the conversion rate in the selected operating
range, The selectivity of conversion to acrylonitrile is near
100 percent throughout the continuous process. The reactor, tem-
2a perature is maintained at about 70 C, throughout the operation
by a constant temperature oil bath in ~hich the reactor is sub-
mesged, The reactor is run continuously for several months.
The catalyst activity at the beginning of the reaction is indicat-
ed by an initial productivity rate of 112 lbs. AMD produced per
1~ . . .
I000 lbs. catalyst per hour, At the observed activity decay rate,
; productivity declines to 92 at the end of three months, to 78at the end o~ six month~, and to 68 at the end of nine months.
All o the productivity rates expressed herein are
the values o~tained by measurements made at a selected conver-
3~ s~on o~ 60 percent conversion per pass during the short test
per~ds, T~us, the reported productivity rates for all
.
10 .`
,.. , . .. , - .. ~ .... . ...... .. .~ . .
l()~U474
o~ the hydration reaction~ that were run at the 3ame reac-
tion temperature are directly comparable ~or indication o~
the relative catalytic activitie~.
B. A control run i9 operated in another identical
reactor u~ing other catalyst rrom the same batch which i~
prepared without calcining. The cataly~t a~ received i9
charged to the reactor and washed with water at 75C. for
2 - 3 days and then dried with air at 100C. berore reduction
and the catalyst i9 reduced by the same proce~ described
ror reduction Or the previouQ catalyst. The control cata-
lyst i9 then u~ed in the continuous hydration reaction the
same as in the previously de~cribed reaction. At the be-
ginning Or the hydration at 70C. the freshly reduced cat-
alyst has an initial productlvity rate o~ 132. At the ob-
served dec~y rate, the prodùctivit~ rate at the end Or three
, months continuous running will have declined to 98 and thento 77 àt six months and to 64 at nine months.
C, Another reactor is prepared by loading the re-
actor with 63 gm. catalyst ~rom the same Lot II, reducing
the catalyst with hydrogen in a nitrogen stream a~ described
above and then calcining the catalyst by gradually increas-
ing the catalyst temperature to the calcining temperature Or
350c. by rlowing hot nitrogen (with trace a~ount Or hydro-
gen) through the bed. The catalyst bed temperature is held
at,350C. ror three hours and then gradually cooled by
reducing the temperature Or the flowing nitrogen. The
catalyst bed i~ then washed ror 2 - 3 dayY with water rlow-
ing through the bed at 75C. and then the reactor i8 charged
with a reed ~tream o~ 7 percent acrylamide aqueous solution
at 70C. to begin the continuou9 catalytic hydration process.
The ~eed rate i~ adjusted to obtain B5-90 percent conversion
per pass. Initial actiYity Or the catalyst is indicated by
an initial productivit~ rate Or 111, At the end Or three
1()~(~474
months on stream the productivity declines to 93, decreas-
itlg to 80 at ~ix months to 70 at nine month~.
In the three continuous hydration reaction~ de-
scribed above, the control cataly~t has higher initial ac-
tivity but su~rers a more precipitou~ decline o~ activity.
At the end o~ 9i~ months all three cataly3ts have roughly
equivalent activities and at the end o~ nine months the
a¢tivity Or the control catalyst has rallen below the ac-
tiv1tieq o~ the calcined catalysts. The avera~e productiv-
ity o~ each o~ the three catalysts over three, si~ and ninemonth periods was calculated and is tabulated below. Over
the nine month period the control ¢atalyst has produced only
slightly more acrylamide than the calcined catalyst. As the
production continues beyond nine months, the average produc-
tivity o~ the calcined catalyst will exceed that o~ the un-
cal¢ined catalyst.
__ . . .
Average Productivity at 70C. over
period o~
3 months 6 months 9 months ¦
Example 2a. 101 93 86
_ _
Zb, 113 100 90
2c. 102 94 ~7
By operating the continuous reaction at 85C. in-
tead Or 70C. the reaction is accelerated and the cata-
lyst decay is also accelerated. mus, the contrast o~ be-
havior of a calcined catalyst and a control catalyst i8 more
marked within a given period.
D. A conbrol catalyst i8 prepared and used the
same a~ described in 2(b) above e~cept the contlnuous hy-
dration reaction temperature is maintained at ~5C. insteado~ 70C. Initial produ¢tivity is 248, declining to 160 at
the end Or throe month9, 118 at si~ months and 94 at nine
months.
- 12 -
4'74
E A post-reduction calcined catalyst iQ prspared
qnd used ~he same as in 2(c) above except the continuou~ hy-
dration reaction temperature is maintained at 85C. instead
o~ 70C. The initial productivity i~ 215, declining to 174
at the end Or three monthsJ to 146 at the end o~ si~ months
and 126 at the end o~ nine months,
The avera~e productivity Or the two catalyst~ over --
three, siz and nine month periods is tabulated below. At the
end Or si~ months the calcined catalyst has produced more
acrylamide than the control, and 3till more at the end of
nine months.
. . _ . . ~
Average Productivity at 85C over
period Or
3 months 6 months 9 months
._ .
15Example 2d. 198 167 147
2e. 193 176 162
Example 3
For commercial production Or acrylamide by cata-
lyt~c hydration o~ acrylonitrile, it has been round advan-
20 tageou~ to treat the BASF Catalyst R3-11 with an aqueou~
solution o~ a soluble sul~ate, such as an alkali metal sul-
rate, in order to rix barium in the catalyst. Thi8 pre-
vents leaching Or barium rrom the ~olid catalyst into the --
liquid product stream as the catalytic reaction is carried
out
A. A laboratory size, rl ed-bed reactor is charged
with 100 gm. o~ BASF Catalyst R3-11 rrom another batch des-
ignated Batch IV, as recelved. Berore any heat treatment,
the catalyst bed i9 soaked ~or about 20 - 24 hours in a 5
percent ~a2S04 aqueous solution at 75C. The sul~ate solu-
tion is drained o~, and the catalyst bed i9 then washed with
water circulated throug~ the bed at 75C. ror 2 - 3 days to
remove sul~ate. After waQhing, the bed i~ dried by ~lowing
h~k - 13 -
,
.
4'74
air heated to 110C. through the bed until dry. The tem-
perature o~ the bed i~ then raised to 400C. b~ rlowin~
heated air through the bed, and the catalyst bed temper-
ature i8 held at 400C. ror 21 hours to calcine the catalyst.
The cataly~t bed i9 then cooled and purged with nitrogen and
reduced with hydrogen, cooled and then ~tarted on stream with
an aqueous 7 percent acrylonitrile reactant solution, all by
procedures essentially the same as those descr1bed in E~-
ample 2 e~cept the wash is omitted arter the reduction step.
The continuous hydration reaction is carried out at 70C.,
85-90 percent conversion.
B. A control reactor is prepared by preparing
and reducing the catalyst bed the same, using catalyst from
the same batch, e~cept the calcining step is omitted and the
¢ataly~t bed is charged with 65 gms. instead Or 100 gms.
cataly~t because the rea¢tor size is not the s~me. The hy-
dration reaation i9 carried out the same in the ¢ontrol
reactor as in the test reactor.
C. Still another test rea¢tor i8 prepared by rirst
calcining 115 gm8. Or catalyst rrom the same bat¢h at 400C.
ror 17 hours, cooling the bed and then redu¢ing, cooling to
about 75C. and then soaking the reduced catalyst with de-
aerated ~ percent Na2S04 solution overnight at 75C. and
then wQshing with deaerated, deionised water ror 2 - 3 days.
2~ me reactor i9 then operated in the h~dration reaction as
described above, at 70C., 85-90 percent converslon.
Productivity initially and at the end Or three,
.
~' 8i~ and nine month periods at the observed decay rate are
tabulated below. The calculated average productivity ror
each rea¢tion over three month, 8i~ month and nine month
periods are also tabulated for each reaction. At the end
of 8i~ month~, both Or the calcined catalysts have pro-
duced more acrylamide, at the average productivity ror that
- 14 -
- - -
: , .. . .
1()60474
period, than the control catalyst has produced. At the end
Or three ~onths, the activity o~ the control catalyst,
though initially higher, ha~ declined to activity below
that o~ either o~ the calcined catalysts.
1~ '
.:
` ~'
~ 30
- 15 -
- - . -: .. ~; " , .
1()6Q474
, C.7
~a 0~ O) O
~ ~ ~0
1~~
;~ '~ ~ .,
. .~ ~ ~ ~ :'
00 _ .,
~ 00 ~ ~
,
.~ ~ U~ ~
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~: ~:
.
- 16 ~
04'74
Example 4
E~periment~ were carried out to investigate the
interaction Or po~t-reduction calcination time and temper-
ature and the resulting er~ect on catalyst strength, ac-
tivity and lire,
Batch IV cataly~t was used in all cases. me
catalyst was reduced in the reactor as described in the
previous e~amples and then calcined in the reactor by M ow-
ing hot nitrogen (with a trace Or hydrogen) through the bed
Or reduced catalyst. The calcining temperature and time
held at that temperature is shown in the Table below ror
each run. Arter calclning and cooling, the catalyst was
washed by rlowing Or DA-DI water ror two days through the
bed, In the case o~ the control, calcination was not car-
1~ ried out. Wet crush strength o~ catalyst samples was mea-
sured, The reactors were operated as described in the
previous e~amp1es ~or the h~dration reactions, e~cept the
reaction temperature was maintained at 800C. in all re-
actors. The results are shown in the attached ~able. This
e~ample demonstrates that post-reduction calclnation at
lower temperatures but ~or longer times is errective ~or
giving increased crush strength and catalyst li~e while
minimizing the 1088 Or initial activity.
Optimum conditions ror post-reduction calcination
appear to be calcining in the temperature range Or 300-350C.
or one to two day~.
'
:, . . .
106(~4~74
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j ~ I ~ N 'I ~
~ r
~ h b~ ¦ p~ v ~ 2 o~ ~ , IY; ~
h ~ ~: :~ ~ O ~ r-
0 :~ h ~ +1 +1 +1 +1 +1 +1
0 . . _ . .. . ,
U ~ '~0~
~: .. o ~ ~ r- ~ ~ . .
~o ~ ~ a~
: C~ o ~ ~o~
:: ~ ~0 ~ ~,
h ~ ~ o ~ o o o O O
O~d ~ ~ t
~t
- 18 -
-
10~04'~4
Calcining o~ the catalyst e~ther be~ore or a~ter
t~.e rcduction ~tep i~ round to cause Qome le99 Or initial
catalyst activity but it also improve~ the rate Or decay o~
~; cataly~t activity. Thererore, the calcined catalysts remain
actlve oYer Q longsr period Or use in the reactor than the
use~ul period ror the uncalcined catalyst. When the cal-
cining i9 carried out arter the cataly~t has been reduced
lt is neces~ary to protect the catalyst ~rom oxidizing
agents during calcining and 90 an atmosphere Or heated ni-
trogen or other inert gas surrounds the catalyst during thecalcining operation, A sma}l amount of hydrogen (e.g. 1%,)
may be added to purge any transient o~idizing agents.
It is observed that milder calcining condition~,
i~e. lower temperatures, cause less 1088 Or initial catalyst
activity while more severe calcining conditions oause more
improv0ment Or the physlcal strength, hen¢e longer catalyst
lire, While it has not yet been determined ~ust which com-
bination8 o~ the several variable calcining conditions will
produce the optimum calcined catalyst, there iB enough e~-
perimental data to demonstrate the improvements obtainedand to derine certain general ranges Or calcining conditions
ror improving the catalyst. It i8 al~o noticed that the
~; copper magnesium silicate catalysts Or the type treated by
~;~ the invention may tend to vary in small degree rrom one lot
to another with respect to the values Or several properties
arrected by a similar treatment, such as initial activity,
crush strength, et , 80 that precise productivity values
and rate Or decay Or the catalytic activlty may be round
to vary in some instances to small degree depending on the
particular properties of any catalyst lot. While precise
quantitative values are not always reproducible, a general
improvement Or the total quantity Or product obtained with
a catalyst lot treated by the invention is obtained by
.
10~()474 :
improvement Or the rate Or decay Or the catalytlc activity
qs the treated catalyst is used ror the hydration Or nitriles :~
in a rixed bed reactor and by the e~pected longer catalyst
li~e due to increase o~ catalyst strength by calcining.
, .
::
,,
:
,
,:
; .
~ - 20 -
.
