CA2036385A1

CA2036385A1 - Permeable, porous body for the treatment of gases and/or vapors and/or liquids and method of producing it

Info

Publication number: CA2036385A1
Application number: CA002036385A
Authority: CA
Inventors: Rainer Rohlig; Hans-Jurgen Gestwa; Reinhold Sicken; Axel Fischer
Original assignee: Individual
Current assignee: Sintermetallwerk Krebsoege GmbH
Priority date: 1989-07-12
Filing date: 1990-07-10
Publication date: 1991-01-13
Also published as: JPH04500777A; KR920700741A; EP0410200A1; WO1991000770A1

Abstract

Abstract 1. Permeable, porous body for the treatment of gases and/or vapors and/or liquids and method of producing it.
2.1 For catalysts and filters for the treatment of gases, vapors of liquids, for example the exhaust gases of internal combustion engines, porous ceramic bodies have been used in the past. These bodies are sensitive to shocks and, because of the poor thermal conductivity of the ceramic material, are in danger of overheating up to thermal destruc-tion when the soot deposits burn away.
2.2 By employing a body made of a permeable, porous sintered metal which may at least in part include the catalytically active components, there not only results increased strength which offers structural advantages but also improved operating characteristics. If, for example, the bodies are employed as soot filters, the ignition process begins earlier due to their better thermal conductivity compared to the ceramic material. Thus the soot deposits burn off more uniformly.
3. Figure 1

Description

2~35~

PC~ P9o/olll~

Translation:

Title~ PERM~ABLE, POROUS BODY FO~ T~E TREATMENT OF GASES
AND/OR VAPORS AN~/OR LIQUIDS AND METHOD OF
P~O~C~NG IT

5 ~peci ficati,o,n:
The invention rel~tes to a body made o~ a porous materia~ f~r the ~reatment of gases ana/or v~pors and~or 1 iquids that flow through the body.
In the treatmen~ of gases by the utilization o the catalytic effect of Cer~ain substa~ces~ porous, cerami~
bodies ~ an appropriate comp~si~ion can also be employe~ in addit~on to loose bulk material~. Loo~e ~ulk materials a~e e~ployed prim~r~ly in industry ~OX high vol~me throughpu~s, while cerami~ bodies can ~e emp~oyed ~or manufacturing te~hnology rea~ons for smaller volume throughputs~ Since, depending ~A ~he chemical reac~i~n in a ca~alytic process, heat is either released or required, bulk materials, and particularly porous ceramic bodies, exhibit considerable drawbac~s due ~o ~he poor thermal conduc~ivity of the 20 mat;er~

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PC~ EP90J01118 F~r a ~pecial application, namely the ~reatment of Diese~ exhau~t gase~, European.Patent ~o. ~,05~,58~ discloses a soo~ filter ~or ~he trea~ment of ~iesel exhaust gases where the fil~er i5 composed of a porous, mono~ithic ceramia b~dy.
5 This ceramic body has a plurality o~ mutually parallel thin-walled channels which are ea~h either closed or open in a chec~erboard pattern at their end $aaes serving as gas inlets and gas ou~lets, ~e~pectively. Each channel has one open and one closed end. When the soot colleoted in such a filter body bu~n~, it i~ possible, under certain opera~ing con-ditions, that such high temper~ures develop th~t the melting temperature of the cerami~ ma~erial is reached or even exceeded and the cer~mi~ body ~elt~ together, thus ma~ing the entire ~ilter deviae unusable.
A device ac~ording to European ~aten~ ~o. o,0~6,367 attempts to alle~iate this drawback in that channels of a larger ¢ross section are disposed in a porous ceramic body, with molded me~al ~ ments ~oa~ed with catalytically a~tive mdterials being inserted into t~ese channels. This is intended to cause the filtered-out soo~ pa~ticles to burn uni~ormly so that the above~descri~ed excess temperatures are dvvided..

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2~136~3 PCTJ~P~0~01118 However, in ~o~ cases, porous ceramio ~odies are required fo~ the p~rely me~hanioal filtering process, ~his has disadvantages, however, when suc~ filter deviae~ are ins~alled in motor ~ehicles sin~e it re~uires a considera~le amount of construction expendi~ures to install the shock sensitive ceramic filter body in the exhaust cond~it in such a manner that it will not be damaged or even destroyed by impaats and shock~ tha~ are unavoidable during operation.
It is now an objec~ of the invention to provide a body o~ the above-mentioned type with i~proved mechanical and/or ~truct~ral chara~eristics and/or possible appliaations.
This is A~omplished according to the in~ention in that the pi~rt o~ the body ~hr~ugh which ~low i~ possible i~
composed o~ a permeabl~, porous sintered metal. Such a body, particularly a ~onolithic body, produaed of a porous ~intered metal ha6 a mu~h greater mechanical strength than compara~le ceramic ~odies. Thus, a very much simpler structure xesults ~or ~uch a body Which aan be emplo~ed as a gas filter or a gas càtalys~, since this body is sel~-supporting i~nd ca~ be proce~sed like a shaped me~al member, for example fastened by mei~n~ o~ ~ w~lding pr~cess or welded together of a plu~i~lity o~ in~ividual bodies to form a larger aomponent. This is of , " , , ;, ",; . :, . .
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significance, ~or example, ~or industrial ~pplications.
Another advantage is ~ha~ su~h sintere~ metal ~odles canno~
only be produced in aacurate ~hapes ~ut can also ~e worked on so th~, due to the minimal diferences in dimenSions, inst~llation is simplified. Another ope~ational adva~tage of bodies made of A permea~le, porous sin~ered metal r~sults ~rom the better ~hermal conductivi~y of a metal compaxed to a bul~ material or a porous c:examic body so ~ha~, for example~
i~ it is employed as a catalyst in catalysis processes, any heat ~hat is xeleased can be dissipated or heat req~ired for the pro~e;~; can be introduced . The ~avorable ther~[ al con~uc:tion charac~eris~ s thtls permit the maintaining o~ a given te~peratu~e level which, with an appropriate design, ~an be maintained uniformly over the entire ~ody.
According to the invention, ~he porosity of ~he body may be set to lie between 20 and 80g~, ~hat is within wide limitq.
In this w~y it is posQible to dire~tly influence ~he per-meability. If used as cat~,ly~;ts, the highes~ possible porosity will be selected and if used as filters, a lower 20 ~oro~i~y Will be seleated wnich is ~dap~e~ ~o ~he particle si~e 'Co he ~eparated. A prefe~red porosity lies between 40 and 60%.

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2~363~3 PCT~EPgO/01118 ~ his porosity is realized by an appr~priate selaction of the grain size spectr~ of the metal powder mixture employed to produ¢e the body. The grain size may lie betwee~ 50 and 500 ~. By employing so~calied sputtery powders, the porosity in this range can also be in~luenced. In a preferred metal powder mixture, the grain sizes lie between lOo and 200 ~, which results in a poxosity of about 50~ or a metal powder mixture having a gx~in size spec~rum ~etween 200 and 300 ~, which corresponds to a porosit~ of a~out 60 to 65~. With a porosity o~ 40 to 50%, ~he required degree of separation for soot particles i5 S~ maintained in Diesel ~oot filters.
For use as exhaust gas catalyst, the higher porosity is advisable since then the ~low resistance i5 lower.
Regar~ing the aomposition o~ su~stances, powder ~ixtures based on chromium, nio~el and iron have ~een ~ound to be advantageous. For ex~mple, essentially ~he ~ollowing composltlon:
(a) Cr 15%, Ni 75%, remainder Fe;
(b) ~r 21%, Ni 61%, Mo 9%, remainder Fe;
(c) ~ lG%, Ni 35~, Cu 3%, remainder Fe~
~n ad~ition to ~hese basic s~bstances ~orming the body, ~ich have catalytic characte~istics also for the intended ' '; ' , ,', ;~'' - , " ' ' .

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p~r/Ep9 o/ 01118 purpose with res~e¢~ to thQir chromium and nic~el components, other ca~al~ti~lly acting ~u~tances, a~ they are known as ca~aly~ts rOr t~e oxidation of combustible components in the exhaust gases o~ interna~ com~us~ion en~ines ~n be added to the powder ~ixtures or additionally applied to the bodies, for example, by vapor deposition of these substanae~. The a~ove-stated powder mixtures are preferably employed as alloyed powders. Thi~ ensures, an the one h~nd, a good ~intering ch~racteristic. On the other hand, it provides 1~ the ca~alytic aharacteristic and the corrosion re~istance against aggressivç components in ~he exhauSt gasesl In addition, powdered aomponents of other substanaes, which ha~e a speaial catalytic effeo~ for the intended purpose, par-ticularly metal~ and/or metal mixtures, c~n be added to the alloyed powder. However, these components must a}so be selected wi~h respeot to their suitability for a sintering p~oGe~; that is, they mus~ ha~e a melting point in the range o~ or a~ove the melting point of the basic powder mixture.
Th~ advan~ages o~ s~ch a body become evident also in its co~bined ~e as catalyst and ~ilter, for example when employe~ as a Die~el soot ~ilter ~ince here the reduced $gnition tempera~ure given ~y the cataly~ic components is :, ', ,' , ' ' ' ' ' ' '~ , " ,: , 3 '~ ~

PCT~EP9o/01:118 reached much fas~er so that, even if t;here are only thin layers of soot, ~he ~iltered ou~ ~oot components will burn o~. Moreover, this brings abou~ the direct ~onsequence that the den~ity o~ the depo~it i5 less an~ ~hus there exists a high gas permeability ~nd correspondin~l~ a reduced flow resi~tance. A~ the same time, the ~flow ch~nnels" in the 8~ ntered metal extend over a relati~ely long leng~h, ensurin~
relia~le separation of even the ~mallest par~icles when used as a Die~el soot ~ilter, and a large contact area ~or the exhaust ga~ to ~e treated when used as a catalyst. Another advantage o the body made of porous sintered metal is that, with the appropria~e gr~in ~ize spectrum of ~he sta~ting powder, the outer Pa¢es o~ the body are rough so that better ~hermal ~onduc~ion pr~pertie~ and thu~ improved opera~ion re~ult.
Another advan~age is that the aacumu~ation of heat, dr~aaed in oonnection wi~h the ceramic bodies when employed 4~al~tically or as ~ filter, for examplè upon burning o~ the ~oot layex, is avoided due to the bette~ ~hermal conduction o~ a ~etal ~ilter body. Because of the good ~ermal conduc-t~ity of ~he ~intered metal bodies, the he~ rele~sed generally over a limi~ed area due to the combustion of the , ~3~

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Diesel 500t deposits is released fas~er to ~he exhau~t gas stre~m and primarily to the adjacent re~ions of the body so ~hat the combustion pro¢es~ expands more rapidly o~er the surface and thus is made more uni~orm as a ~hole. Another advan~age is that the metal powder mixt~re ~or the produotiQn of such ~ sintered metal body ~an alread~ be given such ~
composition that the metal powder mixture alr~ady ~ontains ~uch metals and metal oxides ~hich, as catalySts, enhance the reduction of the ignition ~empera~ure of the ~iltered-out Diesel soot par~icles and/or ~he comhustion o~ gaseous conl;aminants .
An advanta~eous ~eature of the i~vention provides that the porosi~y, with referen~e to the directi~n o~ flow o~ the ga~ to ~e ~x~ted, is dif~erent at the inlet end than ~t the 15 outlet en~. In thi~ way, i~ is possible ~o in~luence the ~low ~urv~, particularly for ~ataly~ic pro~esses. If there i~ an increase in volume, the g~eater porosi~y ~u~t exist at ~ ~he outlet end. I~ there ~s a reduction in volume, the arrangemen~ mus~ be reversed. I~ employed as a ~ie~el soot ~ilter, the greater poro~ity must be present at the inlet end ~ n ord er t~ permit the particles to pene~ate as deeply as po~sible, thus ~aking combustion more uniform.

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PCT/~P~ O~ g To si~plify the manufaature of ~his permeab}e, porous sintered metal body, i~ i~ advisable for the bod~ to be ~omposed of ~ ast two firmly sin~ered together lay~rs of different porosity so that the porosity changes in stages~
In a &uitable embodiment o~ the inven~ion for use as a catalyst~ the sin~ered metal is ~ompo~ed at least in part o~
a catalytically acting material. However, i~ is o f par-t~cular advan~age i~ the catalytically acting material is applled as a layer onto the basic ma~e~ial defininy the pore 10 ¢hannel~, at least in the suxface region of the porous body.
This can be e~fe~ed by vapor-deposition or by sin~ering i~
on. I~ ~intering is employed, the pore channels of the porou~ body a5 a whole or b~ l~yers may be provided with a~
appro~riate coating so ~hat the per~orma~ce of the catalytic treatment o~ gases and/or vapors that are ~ree o~ solids can be improved.
In another embodiment of the invention it is provided that in th~ part o~ the body composed o~ permeable, porous ~intered metal, there is disposed at least one channel having an impe~mea~le wall. In this way, lt becomes pos-sible, by the direc~ additio~ or removal of heat, ~o in-~luence the ca~alytic process within the sintered body even ,,, ~ , , .

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pcr/~p~O/01118 if the bodies are lar~e. The ~h~nnel may be shaped ~s a tube in the molded metal powder blank so that ~he bo~y is "shrunken~ onto the tube during the sintering process and a good thermally conducti~e aonne~ion exists.
S As a ~urther ~eature of the inven~ion, it i5 provided that the body is configured as a monolithic ~ody and is provided with a plurali~y of channels whi~h pre~erably pass through the body parallel to one another~ It i~ particularly advisable for ~he width of the channels, which preferably have a sg~are cross ~ection, to be app~oximately equal to the wall thickness o~ the partitions ~eparating two ~djacent channels. ln this way, there results, on the one hand, a ~avorable i~luence on the exhaust gases, particularl~ in ca~e~ in which the exhaust g~se~ to be treated must either be iltered or in which the exhaus~ gas flows through the partition~ in order to increase the period o~ d~ell on the catalytically a~tive surface and, on the other hand, a high strerlgth ~nolithic body.
Since the body m~de o~ porous sintered metal h~s a high mechanical strength, it is pos~i~le to install it in a hou~ing in a sel~-~upporting ~ann~r, or exar,lple so ~hat one end o~ the body is rigidly seated in a housing wall and the -- 10 ~-2 ~

pcrJEp~o/olll8 o~her end is displa~eably held in the other housing wall.
Thus the body is able to freely expand in leng~h under ch~nging temperature influences so that no thermal stresses can deve-op~
In a suitable emhodiment invalving a monolithio ~ody in which the chann~ls are each al~ernatingly open at one chann~l end and closed at the other ~hannel end, the inven~ion provides that ~he ~lo~ure o~ the one p~rt of the channels is e~ected by a shap~d-on end ~ace forming the ohannel ends and a~ ~he other end by a perf~ra~ed plate whiah is set in froht o~ the channels. Thi~ has the advan~age ~hat the closing of the channel ends at one side can ~lready be e~ected ~uring manu~aature, that is, in one process phase, while the closing o~ the other e~d is ef~ected by an additional comp~nent which adYisably may simultaneously also be used to fix the body in the housing.
~ feature of the inven~ion there~ore provides that the perforated plate is composed of a punahed sheet ~etal plate ~n which the regions ~onning the alosure are e~ah ~ormed by an embosæment engaging into ~he associated channel openings.
While it i~ pos~ible in principle, to ~ix the body at one end ~o a housing wall by means of a welding process, a ~ 3 3 ~

P~T/EP90~01118 particularly advantageous ~eature o~ the inven~ion which is ~avorable ~rom a manufacturing technology poin~ o~ view provides th~t the end of t~e body to be ~ixed to the housing includes a shaped-on, continuous holdin~ collar. Such a holding collar no~ ~nly simpli~ies installa~ion, sinoe the body is initiall~ ~eld in a form-locking and centered manner already when it is inserted into ~he housing, welding is also easier i~ ~he conn~ction is made by welding. ~he arrangement of a holding collar also makes i~ possible to create, instead o~ an expe~sive wel~ed connection, a simple form-lo~king ~onn~ction~ since the body can be clamped i~ by way of the holding collar. As a ~itable reature it i5 her~ provided tha~ a~ leas~ one end face of the holding oollar is given a conically tapered shape. ~hi~ si~plifies ins~allation sin~e with a correspondingly conically shaped con~act sur~ace at the housing, the inser~ed body is able to center itself and arrange itsel~ parallel to the housing axis.
A ~xm-lcc~ing connection according tO the invention can be realized in that the body is placed against the as-~ociated housing wall by way o~ its holding collar and ac~rrs~ponding press-on ring~

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In another ~mbodimen~ it i~ provid~d a~aording to the invention that the po~ous body in~ludes at least one tu~ular bod~ which i~ closed at one end and i~ oriented in the flow direction in a flow guid~nce housing. Such candle-shaped tubular bodies made of s~ntered metal haVe a much higher mechanical strength than ~eramic elements and therefore are better suited, ~or example, ~or use in ~iesel engines, particularly mo~or vehicle Diesel engine~. They may be arranged in the ~low housing in multiple number~ parallel to one another so that the porous sintered body permits the reali~ation o~ a large flow cros~ ~ection even in a small space. This resul~s ln a very much simpler structure for ~uch an ~X~aust ga~ filter since the ~ubular bodies are self-~upporting and can be pro~essed in the manner of a metal 1~ ~olded aomponen~, for example, can be fas~ened by welding~
Another adva~t~ge is that such sintered metal ~odies canno~
only be produced in accurate shapes ~u~ can also be wor~ed so that, due to the small differences in dimensions, ins~alla-tion i5 simplified. Another o~erational advantage of ~ilter boAie~ made o~ a porous sintered metal results fro~ the better thermal con~U~iVity of a metal compared to ~ ceramic mat~rial so that here the reduced ignition te~per~t,ure .
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P~ 3P90/01118 prede~ermined by the ca~alytic componen~s is reached ~uch faster and the fil~ered out soot particles hurn of~ already when thexe a~e only thin layers of soot. ~oreover, this leads to the direct aonsequence that the densi~y of the deposit is less and thus high ~as permeability ~nd a co~-respondingly lower ~low re~istance exists. ~he parti¢ular ~dvantage o~ a sintered metal body is that in its case a high por~ity o~ almost 50~ is realized together with a fa~orable ~low re~i~tance. At the same time, the ~flow channels" in 1~ the sintered metal have a relatively long length so that reliable separa~ion o~ even the smallest particles is ensured. Another advantage of the tubular bodies ~ade o~ a porous ~intered metal i8 that, with an appropriate manu~ac-turing process, na~ely pressing the powder mixture around a steel core with ~he aid o~ an elastic cu~, the ex~erior ~ac~s o~ th~ tubul~r bodies are rough, resulting in better thermal oonductivity properties and thus improved operation.
Since the i~dividual tubular bodies made of porous ~i~terQd ~tal. have a high mechanical strength, it i5 possi~le to inst~ll the tubular bodies in the housing in a self-supporting manner. As one feature of the invention it is there~ore provided that the tubular bodies are fastened to : ; ~

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'che housirlg walls at at ~east one end, preferably at bo~h ends. In this connec:tion, it is par~icularly advisable ~or the ~ubular bodies ~o be fixed rigidly to the one hou~ing wall at their one end and tc) be displac~eably held in the other housing wall at their other end. ~hus, eaçh tubular body i~ able to freely expand in length under chan~in~
temperature influences æo that no therm~l s~e~es can d~velop. ~he rigid fixing prefera~ly ~akes plaae at the open end of the tubular body.
Aacording to the invention, the open ends o~ the tubular boaies are held in a housin~ partitio~ in whi~h only the ~ube openings form passages for the exhaust ~as. I~ at lqast two housing walls are utilized to ~asten the tubular ~odies, then a rurther ~eature o~ the invention provides that the tubular bodies are held in the region of their closed ends in at least one ~urther partition which is provided with push-through openings ~or ~he tubular bodies and additionally with exhau~t ~ pa~age ~penings~
While it i~ po~ le in principle to fix one end of the ~0 tubular bod~ 85 to the respective housing partition by means o~ a ~elding process, ~ parti~ularl~ advantageous feature of the invention which is favorable ~rom a manu~ac~uring Pc~/Ep9o~ollls ~echnology aspe~t provides that the end of the ~uhular body ~o be fi~ed to ~he housing is provided with a ~haped-on con~inuous hol~ing collar. Such a holding ~ollar not only simp~ifies ins~allation, sinae the tubular bodies are initially held in a form-locking mannex as soon as they are inserted into corresponding ~ores in the respective housing wall. The ~nnection by means of a welding process simpli-fies the welding so ~ha~, for example, meahani~ed welding proce~es o~ the type of a burn-off butt-welding proaess or the like can be e~ployed. However, the arrangement of a holding colla~ also makes i~ po~sible to create a ~imple 2~rm-loaking con~catio~ instead of the expensive welded ¢onnection, since the tubular bodies aan be cla~ped in by way of the holding collar. A suitable ~eature here provides that ~5 at lea~t one end face of the holding collar is given a coniaally tapered ~h~pe. This simpli~ies ins~all~tion since, with corre~pondingly conically shaped passage bores, the ins0r~ed tubular boaies center themselves and arrange th~ lves parallel ~o one another.
24 A ~or~-loak~ng aonnection can be made according to the invention in that the tubular ~odies are ~ixed by way of their holding collar in the associated housing partition by '~ ~ 3 ~

PcT~P~0~01118 means of a press-on p~ate pro~i~ed with ~orrespo~ding openings.
As a further advanta~eous feature of the invention, it is pro~ided that the respective exterior ~ace of the tubular bodies is smoo~hed at least a~ one end by a prefera~ly mechanical proces~. Pre~erably, that end o~ the tubular ~ody is smoothed which is displaceably he~d in a housing partition so that here it is possible for the ~u~ular body to properly expand undex the in~luence o~ temperature.
As a further feature o~ the inven~ion it is provided that at least ~he end o~ the tubular bo~y provided with a holding collar has a dif~eren~ ¢ompo~ition o~ ma~erials which is directed toward increased strength. In this eature as well, the advan~age o~ using a metal ~lntered ma~exial for such porous bo~ies is evident. The possibilities of the manu~acturing proaess permit the use of, ~or example for the ~tening end o~ the tu~ular body~ a tigh~ly sintering and thus mechanically highly s~ressable powder mi~ture which is ~hen ~ollowed by a powder m~xture that meets the de~ired zo poro~ity reguirements~
As a method ~or producing porous bodies from sintered metal, par~iau~arly monolithiq bo~ies having a plurality of PCT/~P~0/01118 preferably para~lel extending channels/ the invention provides th~t a flowable metal pow.der mixture havin~ a grain size spectrum between 50 and ~0 ~, mixed with a maximum o~
~% (by weigh~) phenol containing liquid ~ynthetic resin i5 blown by means of compressed air, pre~erably injected, through an opening into a mold which corresponds to the outer contour o~ the body and whose inner wall is provided with ~olding elements corresponding to the channels to be fo~med. ~hen the filled mold is supp~ied wi~h a catalyti~al-ly acting medium ~or hardenin~ the synthetic resin andtherea~ter the molded blank is remo~ed ~rom the mold and slntered. With su~h a process it is possible to produce a porous blanX having a complicated ex~erior ~ontour and/or relatively thin walls, wi~h suah blank, after unmo~ding, being manageable wi~hout di:e~iculty and sinterable. Xf the mold is appropriatel~ longitudinally separable, the process AlSO permits the ~haping o~ a continuous holding oollar to ~he ou~er circum~erence. The ~ompact~on of the metal powder e~eoted durlng the blowing-in proc~, particularly during the inje~tion o~ the metal powder into the mold with simul taneous removal o~ the air contained in the mold ahamber, ensures a uni~orm grain distri~ution so that an essentially PCT/EPgO/01118 uniform porosity is realized over the length as well a~ the aross se~tion~ Surprisingly, it h~s been ~ound that the thus produced ~ank can be s~jecte~ to ~he sintering proces~
without auxiliary or supporting mol~ he molding process 5 ~urther permits the provision of any desired a~oss-~ea~ional configuration fo~ the ahanne~s as well as for the outer contour o such a monolithic body. Thus, in addition to circular cross seoti~ns, oval or elliptiaal or al~o poly~on-al, ~or example rectangular, cross sections can also be pr~du~ed. By blowing in charges of metal powder~ having di~erent grain size ~pectra, it i~ possible to produce a layered ~tru¢~u~e in the blan~ with di~ferenceS in porosity.
I~ the sintered metal ~ody is to include channels having i~p~rmeable wal~s, the molding elements are ap-lS ~ropriately &haped tu~es which are releasably connected withthe mold, are remo~ed togethe~ with the b~ank, and take part in the slntering proces~ so that they are ~irmly bonded into the porou~ ~intered metal body~ The blowing or injeation proces~ ~or the introdu~t~on of the metal powder ~i~ed w~th ~0 the ~ynthetic resin liguid here makes it pos~ible to also produce compliaa~ed tubular ~hapes, ~or example a tube coil.

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~CT~EP9OJo~

The metal powder mixture, for whose composition examples were ~iven abo~e, is now introduced under pressure in~o a pot~ e mold. The introduction may ~e e~ected, for example, in tha~ the metal powder ~ixture is fluidized in a reservoir container and is then ~lown into the mold with ~e aid of a compressed air jet. Sinae, however, the danger o~
demixing exists du~ing the ~luidizing process, it is ad-vi~able ~o~ the metal powder mixture to be in~ected into the pot-~ike mold. ~his is done in th~t the me~al powder quantity to be molded i~ introduced into a preliminary ~essel that i~ aonnected with the mold to ~e filled and i~ then charge~ with compre~sed air so that, due to the sudden expan~ion, the guan~ of metal powder ~ontained in the ~reliminary container i~ injected into the mold at high ~peed~ ~he mold itsel~ is here not charged by the compressed ~ir pres~ure. The atmospheric air aontained in the mold is removed through a~ropriate ventilation opening~ or ventila-tion channels.
81n¢e a maximum ~ 2% ~by we1ght) phenol containlng syn~hetiç resin in l~uid ~orm is incorporated in the metal powder mixture, the ~illed mold is ~apor-treated with a catalytically acting medium, ~or example tertia~y amine, so l~CT/EP90/01118 that the ~yntheti~ resin hardens. The hardened synthetic resin now holds the individual metal par~iales firml~
together so that the mold can be opened and the ~lank removed. The strength is here so high that the blanX aah be worked without difficulty in the subse~uent processing phases. I~ so-called ~puttery powders are employed/ the individual metal pOwaer particles are not only held together by the hardened synthetic resin par~ia~es, the~ ~re also mechan~cally ~Iclamped t~getherll in the ~bove-described injection process. ~he result o~ this is that the molded bO~ can ~e sln~ere~ ln ~he convention~l m~ er~ f~r example, in an em~edment, prefer~bly under a va~uum. I~ is p~ssible to produce such molded bodies very true t~ di~ensions.
As a further feature, the method acaording to the invention permits the particularly advantageous introduction o~ ~he ca~alytically active components. In thi~ case, the component~ are mixed With the liquid synthetiC resin so that the ~etal powder mixture itself doe~ not contai~ these com~onents. ~rter the molding process, the ~ata~y~ically ~ctive components are thus disposed wi~hin the synthetic r~sin layer, in each case on the surfa~e o~ ~he metal p~rticles. ~ring sintering, the synthetic resin i~ driven _ z~, _ 3 3 ~3 PC~/EP90/01}18 out while the catalytically active componen~s are sintered onto the ~ac~s de~ining the p~re channel~.
~ he term ga~ in the ~ense o~ ~he present invention is understood to mean gases ~nd gas mixtures in the a~tual sense as well as vapors and ~as~s çharged with ~olids. ~n conneo~
tion with liquidg, it may ~e important to evaporate them in or by way ~f such a porous body so that there is no cataly~ic e~fe~t, but addi~ional heat i~ supplied throug~ shaped-in channel~ having impermeable wall~.
The inVention will now ~e described in greater detail with re~erence to e~odiments thereo~ ~hat are illustrated in ~hematic drawing igures. I~ i~ shown in~
Fig. 1, a longitudinal sectional ~iew thro~gh a gas channel with inserted monolithic body;
Fig. 2, a partia~ top view, to a larger ~cale, of the ~rQ~ end o~ the ~o~olithic body in which all channel~ extend ln the longitudinal direct~on;
Fig. 3, a longitudinal ~ectional view of a monolithic body ha~ing channels that are closed at alternating end~;
Fig. 4, a ~op ~iew, to the same scale, of the ~ront ~ " ~,7 ~ 2'~

PCT/~:PgO/01118 end of a monolithic ~ody havin~ ~hannels that are closed at al~ernating ends;
Fiq. 5, a lon~itudinal se~tional view of an em~odiment in ~he form of an assembled filtex cartridge for a Diesel soot fil~er including perme~ble, porous bodies confi~ured as ~ubular bodies;
Fig. 6, a front view seen in the direc~ion of arrow A
of ~i~ure 5;
Fig. 7, a fron~ ~iew seen in the direc~ion o~ arrow B
o~ Figure 5:
~ig. 8, a detail X of Figur~ 5 to an enlar~ed scale;
Fig. 9, a sectional ~iew o~ an embodiment ha~ing ayers o~ di~erent poro~ity;
~ig. 10, an e~bodiment including shaped-in channels h~ving impermeable w~116.

Figure l show~ an embodim~nt as i~ aan be emplo~ed as a catal~t ~or the treatment o~ ga~es, ~or exa~ple for the exh~u~t ga~es o~ inte~nal combu~ti~n engines. Here, a monolithic, porous ~intered mstal body 2 equipped with a plu~ality o~ parallel extending continuous channels 3 is disposed in an exhaust gas conduit 1. At its one end, the '~3~3~

PC:'r/EP~ Ot 01118 body 2 has a continuous, external hulding collar 4 ~y mean$
o~ which it is form-lockingly ~astened to a holding ~ube 5.
The holding tube 5 is provided with a cor~espondin~ conical receptacle 6 in which ~he holding collar 4 is fastened by way of a corre~ponding, oppositely conioal holding ring 7.
Holding tube 5 i5 ~ixed to exhaus~ gas pipe ~, for example by welding, The conneetion between hol~ing ring 7 and holding tu~e 5 may here also be made by welding, ~or example by dot welding. This purely ~orm-locking a~tachment has the advantage that thermal stre~es due to ~ea~ly f}uctuating temperature di~srences in the ~a tening region are avoided.
~ owever, the ~ody may also be welded directly ~o holding tu~e g in the region o~ its holdin~ collar.
~he othe~ end 8 of holding tube 5 is supported 1009ely in exhaust gas pipe 1. Body 2, in ~urn, is s~ported in ~he holdi~g tube, ~or example by way of punched-ou~ t~b~ 9, so th~t holding tube 5 as well as ~ody 2 are able to ~reely expand in length.
The exhaus~ gase~ to be treated flo~ through ~ody 2, for exa~ple in the direa~ion o~ arrow 10, undergoing the desired xeactlon proae~es initiated by the a~lytic components o~
She ~int~red metal and possibly b~ ~n additionally applied - 24 ~

~3~

PCT~EP90/01118 aoating o~ ~a~alytically aative materials whiah are not contained in the s~arting powder mixture. ~he coating is here applied i~ such a manner that the pe~meable pores are not clogged.
Figure 2 shows i~ a frontal ~iew seen in ~irec~ion of arrow A the ~rrangement of ahannels 3 in body 2 in a sche-matic illustration.
Pigure 3 snow~ a somewhat modified embodiment of body ~
a~ it is employed, for example, for ~iesel soo~ filters. In thi~ embodiment, ~h~ channels in body 2 are not arranged to be continuous ~ut are clo~ed alternatingly at one end and the othex Bnd o~ the body so that channel ~a is open only towa~d one end and the adjacent channel 3b is open toward khe other end.
Figure 4 is an enlarged and again s~hema~ic ~ront view which indiaates that channels 3a and 3~ are alternatinqly ~losed and open in a mutually offset chec~erboard arxange-ment. In ~he illustr~ed e~bodiment, ~he closure o~ the channel~ at the end indicated by arrow 11 is produced already 29 during manufacture o~ body Z, namely in such a manner that the m~lding n~e~les employed in ~he produ~tion mold to form the channel~ 3b are shorter than the moldin~ needles employed - ~5 -.
.

6~

PCT~EPgO/01118 for the produc~ion of channels 3a so that ~he free ends of the molding needles are covered by sintering material~
However, it is ~lso possible, s~rting wit~ a body as shown in Figure ~, to p~od~ce the re~ ed closure by th~ insertion 5 of plug~; in a further proc:ess step.
~ orresponding1y, at the end of body ~ identified by arrow 12, channels 3a are closed and ~hannels 3b are open.
In ~he illuatrated embodimen~, the ~losure is here ef~e~ted ~y a per~orated plate 13 into which the aorresponding passage 10 openings 14 have been punched so ~ha~, when see~ ~rom the ~ron~, the same con~iguration re~ults as in the fron~ ~iew along arrow 11, ~3xcept that: the openings are c:orrespondingly exchanged here. Per~orated plate 13 may ~e provided with embossments lS in ~he re~ion of the ~hannels ~a to be closed, so that here the form lock be~ween body 2 and perforated plate 13 which simultaneousl~ serves as fas~ening means is improved.
The exh~ust gas ~lowing in exhaust gas conduit 1, for exam~le, in the direction o~ arr~w 10 now en~ers channels 3b a~ ~he end ~a~e, flows through the partitions between the in~i~idual adj aaent channels and le~ves the bod~ through the opsn rs~r enAs of channels 3a ~s indicated by the curved -- 2~ --'3~

~CT/EP~0/01118 arrows. In use as a Diesel soot ~ilter, ~he soot par~icles oontained in the ~xhaust ga~es are re~ained on the interior wa~ls of channels 3b. Since the ho~ exhaust gases heat sintered metal body 2 which contains ~a~aly~icallY a~tive material to a tempera~ure which lies in ~he range o~ the ignition temper~tU~e, reduced ~y ~he catalys~s~ for Diesel soot, the soo~ Will burn of~ even if the ~oot layexs are relatively ~hln~ with the te~perature incr~aae as a result of the burning continuing the ~urning of ~he soot deposits over the entire channel surface wi~hin the shortest possible time.
Due to the high porosity of such a porous sintered metal body~ the embodimen~ ~hown in Figure 3 C~n a~so be ~sed as an exh~u~t gas catalyst ~or the treatment of the exhaust g~ses o~ Otto engines~ Due to the fact that the exhaus~
gases, in contra~ to in the embodiment of Figure ~, do not flow only along the channel ~urface bu~, due to the alternat-ing closure o~ the individual channels, must also flow th~ough the par~ition~, the time period during which ~he exhaust gases come in contact with the ca~lyticallY ac~i~e sur~a~Q5 is extended, thus ~ur~her improving the ~nversion o~ harmful su~stances.

, 2 ~ Q3 PC~P90/01118 ~ i~ure S ~hows in a lo~gitudinal seotional view an embodimen~ for use as a filter ~artridg~ for~a Diesel soot fi~ter which is in~erted into a eorrespondin~ly widened por~ion of the exhaust gas conduit o~ a Viesel engine. The filte~ cartridge is essen~ially composed of a ~low ~uidance housing 16 which has a cylindri~al cross section - a shown hexe - or al50 so~e other cross~sectional configuration, for example, oval. The one end face is terminated by a housing p~rti~ion 17 a~d the other end face by a housing pa~tition 18, which aarry in aorresponding openings a plurality o~
parallel extending tubular bodies 19 made of a porous sintered me~al. The ~ubular bodies 1~ are open at one end ~0 and closed at the other end 21. Partition 17 is here prov~ded with ~as pas~age openings 22 which are identical to the opening~ in tubular bodies 1~, as evident in t~e front Yiew~ o~ ~igures ~ and 7. Housing partition 18 is provided With pas~a~e openings 23 through which the end 21 o~ tu~ular bo~s 19 is pushed and the remaining spaces axe provided with ga~ passage openings 2~.
ThB ~hau~t ga~es are now able to ~low ~hrough ~he ~ er cartridge ~hown in Figure ~ from ~he directioll of arrow A as well as ~rom the direction of arrow B~ If they .

t~@3~3~

PCT~EP~o/01118 ~low in the direction of arrow A, the exhaus~ ~ses enter the interior o~ tubulax body 1~ and ~low, as indicated by arrows 25, through t~e porous walls of the ~u~ular bodies and en~er through ~aa passage openings 24 into ~he connected exhaus~
gas conduit which is not shown in detail. Howe~er~ the gas may also flow ~hro~gh the filter body from the other side so that ~he ~low would then ~e correspondingly reversed.
Tubular bodies 1~ aXe now fixed in the parti~ions in such a ma~ner that one tube end is fixedly connected wi~h a ~ousing partition and the other tube end i~ held in a corresponding opening so as to b~ freel~ displaceable. I'he ~as~ening may o~cur, for example, by welding the respective tube end. In the il~ustrated embodiment, howe~er, a par-~icularly advantageous ~orm-locking connection has been sele~ted. As ~hown in Figu~e ~, a continuous holding ~ollar 26 is shaped to eac~ tubular body 1~ in the region o~ its open end, wi~h the two end faces 27, 28 of the holding colldr having a conica~ly tapered shape. The housing partition 17 is here ~ade of two parts. ~ach wall portion is produced, ~or example, by a punching process in whi¢h the hol~ an~ their conical contact faces for the end faces 27, ~8 o~ holding collar 2~ and a connecting flange 29 are ,.f~ fz ~

PCT/EP90~01118 produced in one process step. Both wall portions ar~
identical 50 that initially wall portion 17a can ~e conne~ted with hous~ng 16, for example ~y welding, ~nd then housing partition 18 i~ also connected wi~ the housi~ Therea~ter, tubular ~odie~ 19 are inserted in the direction o~ arrow A, w~ll portion 17b i~ put on ~hus aentering ~he conical end face ~7 and then the bodies are we~ded to housing l~.
In ord~ to increase the resistance o~ the arrangement again~t damage and ~hocks, an additional p~rtition, not shown in detail here, can be pro~ided as a supplemental measure in the ~orm o~ a housing partition 18 whi~h is disposed in ~he hou~ing between parti~ions 17 and 1~.
Since the ~ur~ace of tu~ular body l~ is relatively rough, roughness peaXs projeat through the developing ~oot 15 layer so that, in spite o~ the heat insul~ing e~fect of the 500t layer, heat from the exhaust gas s~xeam is introduced into the tubular ~ody and thus the ignition tempe~ture is realized e~rly. Burning ~hus occurs already if there is only ~ thin deposit and thus ~ore frequently and as a whole more uniformly.
The sahem~tic illus~r~tion in Figure 9 ~hows a permeable porou~ monolithic sintered metal body 30 disposed in a flow ~J~3 ~

PCT/El?gO/ 01118 channel 31. In ~he i~lustrated embodiment, body 30 has such ~ compo~ition ~ha~ it aontains components which have a catalytic effect with respect to the gas ~o ~e treated and are in~erted into the bOdy in a manufacturing mannex des-cribed in gre~ter de~ail abo~e. The geometric shape of thesintered me~al body 30 depends on the process technology condi~ions which need not be considered here in detail. ~n the illustrated embodiment, the body is composed o~ three layers, with ~he ~irst layer 30a, wi~h respec~ ~o ~he lo dire~tion o~ flow (arrow 32), having a high porosity, the s4cond layer 3Ob a ~omparatively lower porosity and a third layer 30a having a further reduae~ porosity. Since these three layers are ~uc~essively brought ~ogether in the above-de~cribed in~ection process with appropriately matched metal ~owder ~ixturés a~d the thus resulting three-layer blank is then sub~ected to the sin~ering process, it is ensured that ~he three layers ~in~er firmly together and thus a solid ~orloli~hic body is available which has a correspondingly ~raduated pore structure. Such a layer stru~ure may al~o be employed, ~or example, ~or bodies as shown in, and described in connectton with, Fi~ures 1 and 5.

P~/EPgo/o~

The schematic illustration o~ the embodiment o~ Figure 10 shows a permea~le, porous ~ntered me~al block 33 in which channels 34 are ~ormed which ha~e imperme~ble walls.
If, for example, a bloak of such con~iguration i~ again inserted into a flow ch~nnel 31, i~ is possible here to condu~t a ~owable thermal conductor through the channels ~4 having the impe~meable walls so a~ to supply neat to or remove heat ~rom the channels dependinq on the prooess ~o be per~ormed, By utilizing the good thermal ~on~uc~i~ity of a sintered metal body wi~h the appropria~e distribution o~ Su~n ahannels, a uniform ~emperature distribution c~n be realiæed over ~he en~ire cross-sectional area. With respect to the treatment process ~o be performed, channel 3~ may ~e mold~d direa~ly into those regions o~ sintered me~al body 33 which ~5 require a positive supply or ~emoval of hea~.
In the manu~acturing proce~s descri~ed in detail above, in whiah a metal powder mixture mixed wi~h a synthetic resin liyuid ~s a bindex i~ injected into a mold, one is not forced to provide linear and/or s~ooth-sur~aced channels 34.
~a~her, the procefi~ also permits the use of other ~pes of channel ~hape~, ~or example in the ~orm o~ tube coils or the li~e, ribbed tubes or the li~e~ The shaping ~nd positioning j éP

PCr/EP90/0111~

within the ma~ufaaturing mold m~st mere~y be effec~ed so that it is ensured that ~he man~facturing ~old is ~illed uniformly dur~ng ~he injection process. Metal tub~ are e~ployed with preference, wi~h me~als ha~ing ~o be u~ed hsre which are able to with~tan~ ~he ~in~ering ~e~perature. Instead of tubes, other bodies can also ba shaped in ~hi~ way into the porous ~intexed body. For example, rod-shape~ eleatrical heat conductors or also only pin-~haped fastening mean~ whi~h ~roject beyond the ex~erior face o~ the ~intered body.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows:

1. A body of a porous material for the treatment of gases and/or vapors and/or liquids flowing through the body, characterized in that the part of the body (2:19:30) through which the medium is able to flow is composes of a permeable, porous sintered metal.

2. A body according to claim 1, characterized in that the porosity lies between 20 and 80%.

3. A body according to claim 2, characterized in that the porosity lies between 40 and 60%.

4. A body according to claims 1 and 2, particularly for the treatment of solids containing gases, characterized in that the porosity, with respect to the direction of flow of the gas to be treated, is different at the inlet end than at the outlet end.

5. A body according to claim 4, characterized in that the body (2; 19; 30) is composed of at least two firmly sintered together layers (30a, b, c) of different porosity so that the porosity changes in stages.

6. A body according to claims 1 to 5, characterized in that the permeable, porous sintered metal is composed at least in part of catalytically active materials.

7. A body according to claim 6, characterized in that the catalytically active materials are each vapor-deposited onto the basic material defining the pore channels.

8. A body according to claim 6, characterized in that the catalytically active materials are each sintered onto the basic material defining the pore channels.

9. A body according to claims 1 to 8, characterized in that the body is configured as a monolithic body (2;33) and includes a plurality parallel to one another.

10. A body according to claim 9, characterized in that at least the walls of the channels (3) are additionally provided with a coating of catalytically active materials.

11. A body according to claim 1 or 10, characterized in that the width of the channels which preferably have a square cross section is at least approximately equal to the wall thickness of the partitions separating two respectively adjacent channels (3).

12. A body according to claims 1 to 11, characterized in that at least one channel (34) having impermeable walls is disposed in the part of the body (33) composed of permeable, porous sintered metal.

13. A body according to one of claims 1 to 12, wherein the channels (3a,3b) are each alternatingly open at one channel end and closed at the other channel end, charac-terized in that the closure of the one part of the channels (3b) is effected by a shaped-on end face which forms the channel ends and that the closure of the other part of the channels (3a) is effected by a perforated plate (13) put upstream of them.

14. A body according to one of claims 1 to 13, charac-terized in that the perforated plate (13) is composed of a punched sheet metal plate in which the regions forming the closure are each formed by an embossment (15) engaging in the associated channel opening.

15. A body according to one of claims 1 to 14, charac-terized in that the end of the body (2) to be fixed to the housing is provided with a shaped-on continuous holding collar (4),

16. A body according to one of claims 1 to 15, charac-terized in that the body is fixed to the associated housing wall by way of its holding collar (43 and a corresponding press-on ring (7).

17. A body according to claims 1 to 16, characterized in that at least one tubular body (19) whose one end (21) is closed and which is oriented in the direction of flow is disposed in a flow guidance housing (16).

18. A body according to claim 17, characterized in that the individual tubular body (19) is fastened in housing walls (17, 18) at at least one end, preferably at both ends 920, 21).

19. A body according to claim 17 or 18, characterized in that the tubular body (19) at one end, preferably at the open end (20), is rigidly held at one housing wall (17) and at the other end (21) is displaceably held at the other housing wall (18).

20. A body according to one of claims 17 to 19, characterized in that the open end (20) of the tubular body (19) is held in a housing partition (17) in which the only exhaust gas passage (22) possible is through the tube opening.

21. A body according to one of claims 17 to 20, characterized in that, in the region of its closed end (21), the tubular body (19) is held i at least one further partition (180 which is provided with push-through openings (23) for the tubular body and with additional exhaust gas passage openings (24).

22. A body according to one of claims 1 to 21, charac-terized in that the end of the tubular body (2; 19) which is to be fixed to the housing (16) is provided with a shaped-on continuous holding collar (26).

23. A body according to claims 1 to 22, characterized in that at least one end face (27, 28) of the holding collar (26) has a conically tapered shape.

24. a body according to claims 1 to 23, characterized in that the tubular body (19) is form-lockingly fixed by way of its holding collar (260 in receptacles (22) in the housings (1;16).

25. A body according to one of claims 1 to 24, charac-terized in that the tubular body (2, 19) is fixed to the housing by way of its holding collar (26) by means of a press-on plate (13;17b) that is provided with appropriate openings.

26. A body according to one of claims 1 to 25, charac-terized in that the exterior face of the tubular body (2;19) is smoothed by rolling at least at one end.

27. A body according to one of claims 1 to 26, charac-terized in that at least one end, preferable the end of the tubular body (2;19) provided with the holding collar (26), has a different material composition which is directed toward increased strength.

28. A body according to one of claims 1 to 27, charac-terized in that the body (30) is composed of at least two sintered-together partial bodies (30a, 30b, 30c) of different porosity.

29. A method of manufacturing a body of a permeable, porous material and having at least one channel extending within the body according to one of claims 1 to 28, charac-terized in that a flowable metal powder mixture having a grain size spectrum between 50 and 500µ, mixed with at most 2% of phenol containing synthetic resin, is blown by means of compressed air, preferably injected, through an opening into a mold corresponding to the exterior contour of the body, with its inner wall being provided with molding elements cor-responding to the channels to be formed, thereafter the filled mold is provided with a catalytically active medium so as to harden the synthetic resin and then the blank is removed from the mold and sintered.

30. A method particularly according to claim 29, for producing a body of a permeable, porous material having catalytic properties, characterized in that the catalytically active components are mixed with the phenol containing synthetic resin added as binder to the metal powder mixture before said synthetic resin is introduced into the metal powder mixture.

31. a method according to claim 29, or 30, charac-terized in that the mold body forming the channels is preferably configured as a tube and is releasably connected with the mold, is removed from the mold, after the synthetic resin has hardened, together with the molded blank is bonded thereinto by the sintering.