CA1038597A - Process for reacting nitric oxide with hydrogen - Google Patents

Process for reacting nitric oxide with hydrogen

Info

Publication number
CA1038597A
CA1038597A CA204,866A CA204866A CA1038597A CA 1038597 A CA1038597 A CA 1038597A CA 204866 A CA204866 A CA 204866A CA 1038597 A CA1038597 A CA 1038597A
Authority
CA
Canada
Prior art keywords
gas
liquid
column
process according
bubbles
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA204,866A
Other languages
French (fr)
Other versions
CA204866S (en
Inventor
Werner Graf
Johann K. Forrer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Inventa AG fuer Forschung und Patentverwertung
Original Assignee
Inventa AG fuer Forschung und Patentverwertung
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Inventa AG fuer Forschung und Patentverwertung filed Critical Inventa AG fuer Forschung und Patentverwertung
Application granted granted Critical
Publication of CA1038597A publication Critical patent/CA1038597A/en
Expired legal-status Critical Current

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00Nitrogen; Compounds thereof
    • C01B21/082Compounds containing nitrogen and non-metals and optionally metals
    • C01B21/14Hydroxylamine; Salts thereof
    • C01B21/1409Preparation
    • C01B21/1418Preparation by catalytic reduction of nitrogen oxides or nitrates with hydrogen

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
  • Catalysts (AREA)
  • Gas Separation By Absorption (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

ABSTRACT OF THE DISCLOSURE
Method and apparatus for reacting nitric oxide with H2 in the presence of noble metal catalysts in which waste gas is obtained by separating the gas contained in a liquid medium flowing countercurrently to the bubbles in a counter-current bubble column. Preferably, only a portion of the separated gas is removed as waste gas, the remainder being recycled. The apparatus comprises a counter-current bubble column having a gas recycling circuit to permit the recycling of excess NO contained in the separated gas.

Description

i ~
~ ;

* * * * *
,f lo The present invention relates to a process or reacting nitric oxide with hydrogen.
The reaction of N0 with H2 in acid solution in the presence of noble-metal catalysts is carried out for preparing hydroxylamine salts. The choice of a suitable catalyst is a pre-.., requisite, selective hydrogenation o~ the ~0 to yield hydroxylamine '~, bein~ also necessary in addit~n to high reaction activity.
Economically carrying out the reaction to produceh~droxylamine salts which serve, for example, as a starting product for the commercially important synthesis of caprolactam may be ;
;~ 20 achieved, inter alia, in bubble columns. In this case, if a ~ suitable apparatus is used for distributing the gases in the liquid, i the production of a flow of liquid in the opposite direction to the ascending bubbles yields the following advantages: -It makes it possible to carry the heat of reaction off vutside the reaction chamber by means of cooling r~ devices of simple design;
It allows an increase in the dwell time of the gas bubbles in the, reaction chamber, along with the higher mass .

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~3859 t~ansfer associated therewith.
When continuously carrying out the reaction in a counter~
current bubble column, adequate conversion values of the NO
gas will not generally occur, so far as it is desired to achieve economically reasonable volume-time yields. However, the amount of reacted NO can be increased by uslng a gas circuit.

. . , ' ~
i Complete conversion cannot be obtained even by using a gas circuit, however, since the recirculation ratio of -10 the amount of recycle gas to amount of top gas cannot be increased to any degree that may be desired. The reason for this is that the gaseous by-pyoducts formed during the ~1 reaction and, in particular, the inert constituents present in the charging gases in industrial operations must be removed as waste gas. No gas is in addition lost in the . ~:
process of removing the waste gas. ~:
; It has been found that when a counter-current bubble column is employed, gas is discharged from the reaction 3 chamber with the liquid if certain liquid charges are 20 exceeded. Analysis shows that this gas contains little if ;~
any NO, which is surprising.
Accordingly, the present invention relates to a process `
-i for reacting nitric oxide with H2 in the presence of noble-~ metal catalysts which are suspended in an acid liquid. The . ~ , novel feature comprises introducing said liquid adjacent `
the upper end of a bubble column and fIowing said liquid ~;
~, downwardly at a liquid flow rate, introducing said NO and ` H2 adjacent the lower end of said column whereby large ;
and small bubbles are formed in said liquid~ adjusting ~ 30 said flow rate so as to permit said larger gas bubbles `¦ to rise and collect adjacent the top of said column to ~ 3859~
form top gas and to aarry said smaller bubbles entrained ~:~
~` in said liquid to the lower end of said column, ~ , , , removing said liquid and said smaller bubbles from the ~;
~`~ bottom of said column, separating said smaller bubbles ;:
i from said liquid to form bottom gas, `1 returning at least a part of said bottom gas and said ~
top gas to said lower end of said column, returning part .
of said liquid to the upper end of said column and with~
~. . , . ; ~ . .
;. drawing the rest of said liquid, which liquid contains ``. 10 said hydroxylamine. ` :~;

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According to a preferred embodiment, the was~e.gas ~o be .- : :
separated is produced by means of liquid char~es of 80 - 350 ;:~
m3/m2 per hour.
Advantageously, only a proportion o:E the separated gas ".
is removed as waste gas and the remainder is passed back into the . gas circuit.
Taking advantage of these circumstances and further .. in accordance with this invention, in the catalytic hydrogenation of NO, an apparatus according to Figure 1 was set up comprising a `~ counter-current bubble column with a gas circuit, a liquid charge ; ;.
'1 which entrained at least an amount of gas corresponding to the inert ;.~: ~
~ ~constituents to be discharged which, after the separation of the . :
.~ gas from the liquid, was discharged as waste gas. The waste gas yield was free from NO and allowed complete-NO conversion to be achieved, which is a sLgnificant technical advance. ..
In an apparatus operated on the principle described, the . :.
lowest specific consumption of NO per quantity of hydroxlamine produced is achieved.
In addition to this economically favorable aspect, `;
another prime advantage of the described process is that in a ;
~ process in which NO is reacted with H2, a waste gas is obtained~ ~.?;` '. ~' ~ which is free from NO and does not have to undergo any costly .~ treatments before being given off:into the atmosphere ~ ~3 ~S~7 In a preferred embodLment of the inven~ion, the gas ~ : .
mixture in the counter-current bubble column is split up by :~
adjusting the flow of liquid such that a mixture of H2 and inert gas with a comparatively high NO content is i-ormed as top gas at ;
the upper end of the column. As a result, a gas mixture practically .
free of NO is formed in conjunction with the liquid at the lower ~:
end of the counter-current bubble column. The gas mixture is then withdrawn at the bottom and separated from the suspension. This i last mentioned gas mixture is divided into~
.
a) a portion which is returned to the gas circuit, and :
b) waste gas which is so adjusted in quantity that the inert gases introduced with the fresh gases or formed in secondary reactions are discharged .
The process ac~ording to the invention will be explained with reference to Fig. l. In the counter-current bubble column ~ 4 there is produced a flow of liquid which is conveyed in the X direction of the arrow from top to bottom,then through the ¦ line 7, the gas separator 6, the line 14 and the pump 5 and :3 back to the upper end of the counter~current bubble column 4.
i 20 A portion of the liquid which, in addition to the suspended 3 catalyst, contains the ~esired end product ~say hydroxylamine salt) and, if occasion arises, by-product (such as ammonium salt), is drawn off through the line 12 and replaced by a corresponding quantity of fresh liquid via the line ll.
On the other side, a gas mixture consisting of NO, H2 `
and inert gases flows via the line 3 into the lower end of the ., .
';i ~ , ~ -4-:, , ;

L~3~597 ~ counter-current bubble column. The last-mentioned gases, such as .
nitrogen, are partly introduced from the start and are partly formed during the reaction3 such as nitrous oxide The rate of flow of the liquid is so adjusted that larger bubbles ascend slowly and `
i their content accumulates at the top of the column 4, while smailer bubbles are retained in the lower part of the column by the flow or brought back again into the lower part of the column by the said flow Surprisingly, there accumulates in this way in the lower part of the ; column a gas mixture which is practically completely free of nitric lo oxide. The nitric oxide its-elf ascends, together with part of the ;~
- hydrogen and inert gas. As far as the nitric oxide has not reacted -through the catalyst suspended in the liquid to form the end product, -~
it accumulates as top gas at the top of the column together with parts of the remainlng constituents of the gas mixture, that is with part of the hydrogen and of the inert gases.
The gas which has accumulated in the lower part of the column is'carried by the said flow of liquid via the line 7 into the gas separator 6.

The design of the gas separator is also adapted to take 1 20 care of the problems which normally occur in practice, such as for ~`

instance high foam formation, which is done in conventional manner.
The gas is separated from the liquid in the separator 6 and conveyed through the line 8 into the line 9. Part of this gas .
, ;
(about 10-80% by mass) escapes, generally via a pressure relief valve, through the line 10. The remainder flows to the bubble ~ -.. ....
~1 column 4 via the line 9, then through the line 13, the gas circuit ! ~

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lQ38S97 ,~ ~
compressor 2 and the line 3. The liquid charge is so adjusted that the amount of gas separated in the gas separator 6 is greater than the amount discharged at 10 The top gas, which has a NO content of about 5 - 15%
by volume, escapes upwardly via the line 15 and is supplied to the circuit via the lines 13 and 3 ~ogether with the gas flowing from the line 9.
The introduction of the recycle branch 6-8-9 is novel.
In this way, the top gas is prevented from being able to pass unused lo into the open air via the line 15-9-10, because in fact gas free from NO flows downwardly in the line 9, which prevents the ascent of the N0. As a result, with ~ull assurance of pressure equaliza- ; `.
tion in the system, firstly the yield of reacted N0 is improved and ~ . .
secondly pollution of the environment by N0 is avoided, which ~signiies a considerably technical advance -Fresh N0/H2 mixture of the conventional commercial purity i~ received in the part 13-2-3 of the gas circuit via the line 1 and introduced into the bubble column. In quantity, it corresponds approximately to those parts which are converted in the reaction `~
20 chamber, plus those which!are carried off via the line 10 for the purpose of dLscha~ging the inert gas constituents.
~ . The advantages of the described principle in comparison 3s with the conventional operation of a counter-current bubble column~
having a gas circuit, in which the waste gas is removed at the top ~:
of the column, will be illustrated with the aid of the following :~
~¦: Examplqs.

: ~:

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103B597 `~
; In these Examples, "N" - "normal", i,e. condi~ions at '';
760 mm'Hg and 0C. '' Exam~le 1 , ~ :
In an apparatus according to Fig. 1, 7.018 Nm3 of H2, `
3.793 Nm3 of N0 and 0.789 Nm3 of inert gases were fed per hour , via the line 1 together with the recycle gas flowing in from the line 13, on the suction side of the gas circuit compress,or 2, I via the 'line 3 to the counter-current bubble column 4. The ;? ~ ~ :column was filled for the ~ajor part (4/5 of its height~ with ', ii lo one of the known acid catalyst suspensions. This suspension, for its part, flowed downwardly in the direction of the arrow through the bubble column 4, then through the line 7 and the gas separator (or one of the conventional gas separator systems) 6 and back into the bubble column 4 via the line 14 and the pumy 5, ,' A ~mall part of the end-product containing liquid corresponding to the reacted NG plus H2 was drawn off by means of the line 12, a ` ~ ~' corresponding amount of fresh catalyst suspension belng supplie~ to ',',~
~ the liquid circuit via the line Ll. The amount of this catalyst ~ , 'I suspension was so adjuted by means of the pump 5 that a liquid , 20 charge of 250 m3/m2 per hour was obtained in the bubble column.
'; The quan~ity of gas separated from the flow of liquid by means of , the gas separator 6 (Nm3/hour) was conveyed via the line 8, "1 for the larger part via the lines 9 and 13 to the suction side ',''~ of the gas circuit compressor 2, and for the smaller part (1.916 Nm3/hour~ was discharged through the line ~0 as waste ~-t . gas. The waste gas was free from N0, corresponding to a N0 ,;
`' conversion of 100%. ' ~,i , , ~

385 97 ` A ~
~f -;, Example 2 ~Comparison Example) . ... ~
.,. , ~ ~, . .
~ Under similar conditions for the amounts of gas supplied ,~ :
:~ and the liquid circuit as those indicated in Example 1, in an ; .
l , ~ ,:, --' a~paratus according to Fig. 1, which, however, was operated ~,j without a gas separator .6 and a line 8 for separating ~he entrained gas, the waste gas was discharged direc~ly as a ., proportion of the top gas (in line 15) through the line 10 in an amount of 2.691 Nm3/hour. . -;~
,l, The NO content of the waste gas was 11~3~/o by volume, .
.i .~ :: . :-o corresponding to 0.303 Nm3/hour. The degree of NO conversion .
was 92%. ~, ;l Modiications in and to the above described embodiments .: ;
:i :l . '.
"! may be,made by those skilled in the art. It is .intended to '''`if cover all such modiications which do not depar~ rom the spirit , ~1 and scope of the invention as defined in the claims appended hereto.

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Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows-
1. In a process for the production of hydroxyl amine by reaction of No and H2 in the presence of at least one noble metal catalyst suspended in an acid liquid, the improvement which comprises introducing said liquid adjacent the upper end of a bubble column and flowing said liquid downwardly at a liquid flow rate, introducing said NO and H2 adjacent the lower end of said column whereby large and small bubbles are formed in said liquid, adjusting said flow rate so as to permit said larger gas bubbles to rise and collect adjacent the top of said column to form top gas and to carry said smaller bubbles entrained in said liquid to the lower end of said column, removing said liquid and said smaller bubbles from the bottom of said column, separating said smaller bubbles from said liquid to form bottom gas, returning at least a part of said bottom gas and said top gas to said lower end of said column, returning part of said liquid to the upper end of said column and with-drawing the rest of said liquid, which liquid contains said hydroxylamine.
2. A process according to claim 1 wherein fresh NO and H2 are introduced into said top and bottom gases before said gases enter said column.
3. A process according to claim 1 wherein fresh acid liquid and noble metal catalyst are introduced into said liquid before its entry into said column.
4. A process according to claim 1 wherein part of said bottom gas is withdrawn after leaving the lower end of said column.
5. A process according to claim 1 wherein the withdrawn liquid is replaced by fresh acid.
6. A process according to claim 1 wherein said acid is sulfuric acid.
7. A process according to claim 1 wherein said top gas comprises H2 and inert gas having a high NO content and said bottom gas is substantially free of NO, including the step of separating said bottom gas into a first gas stream and a second gas stream, said first gas stream being returned to said column, said second gas stream being discharged as waste, the quantity of said discharged gas being approximately equal to the amount of introduced gas plus the amount of gaseous byproducts generated, less the amount used in the reaction.
8. A process according to claim 1 characterized in that the waste gas to be separated is discharged at liquid flow rates of 80-350 m3/m2 per hour in said column.
CA204,866A 1973-07-17 1974-07-16 Process for reacting nitric oxide with hydrogen Expired CA1038597A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1036273A CH584163A5 (en) 1973-07-17 1973-07-17

Publications (1)

Publication Number Publication Date
CA1038597A true CA1038597A (en) 1978-09-19

Family

ID=4362397

Family Applications (1)

Application Number Title Priority Date Filing Date
CA204,866A Expired CA1038597A (en) 1973-07-17 1974-07-16 Process for reacting nitric oxide with hydrogen

Country Status (16)

Country Link
JP (1) JPS5529925B2 (en)
AR (1) AR199539A1 (en)
BE (1) BE817700A (en)
CA (1) CA1038597A (en)
CH (1) CH584163A5 (en)
DE (1) DE2433967B2 (en)
EG (1) EG11522A (en)
ES (1) ES428311A1 (en)
FR (1) FR2237835B1 (en)
GB (1) GB1463857A (en)
IN (1) IN141812B (en)
IT (1) IT1029605B (en)
MY (1) MY7800016A (en)
NL (1) NL7409661A (en)
PH (1) PH10936A (en)
TR (1) TR18418A (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2736872B2 (en) * 1977-08-16 1979-07-19 Basf Ag, 6700 Ludwigshafen Process for the preparation of hydroxylammonium salts
DE3130305A1 (en) * 1981-07-31 1983-02-17 Basf Ag, 6700 Ludwigshafen METHOD FOR PRODUCING HYDROXYLAMMONIUM SALTS
JPH03124752U (en) * 1990-03-28 1991-12-17

Also Published As

Publication number Publication date
FR2237835B1 (en) 1978-12-29
BE817700A (en) 1974-11-18
FR2237835A1 (en) 1975-02-14
TR18418A (en) 1977-01-28
PH10936A (en) 1977-10-05
GB1463857A (en) 1977-02-09
DE2433967B2 (en) 1977-02-17
CH584163A5 (en) 1977-01-31
IN141812B (en) 1977-04-23
IT1029605B (en) 1979-03-20
NL7409661A (en) 1975-01-21
JPS5043099A (en) 1975-04-18
JPS5529925B2 (en) 1980-08-07
EG11522A (en) 1978-03-29
DE2433967A1 (en) 1975-02-13
MY7800016A (en) 1978-12-31
ES428311A1 (en) 1976-07-16
AR199539A1 (en) 1974-09-09

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