CA1050044A - Production of unsaturated acids, esters and nitriles, and catalyst therefor - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Alkanoic acids, esters of such acids, and alkyl nitriles are reacted with formaldehyde in the presence of a basic catalyst comprising pyrogenic silica to form .alpha.,.beta.-unsaturated acids, the esters of such unsaturated acids or .alpha.,.beta.-unsaturated nitriles. The pyrogenic silica is especially effective when treated with activating agents which provide basic sites on the pyrogenic silica catalyst support, such as organic bases, inorganic bases of Group IIA and IIIA metals, and precursors of such bases.

Description

105~044 This invelltioll Ielates to a process ior the pr~duc-tion of ~ nsaturated aeids, tlle esters o~ ~uc~. acids, unsaturated nitrllec-" and to a no~el catalvst used in S~lCh process. ~lore particulally~ tllis invention relates to a method for the reaction of alkanoic acids, esters of such acids, and alkyl nitriles with iormaldehyde and a novel catalyst system -for use in such reactions.
Unsaturated acids, such a~ methacrylic and acrylic acids, acrylonitrile, and the esters of such acids, such as methyl methacrylate, are widely employed for the production of corresponding polymers, resins and the like. Various processes and catalysts have been proposed for the conversion of alkanoic acids, such as propionic acid, and formaldehyde to the corresponding unsaturated monocar~oxylic acid, e.g.
methacrylic acid. Generally, the reaction of the acid and formaldehyde takes place in the vapor or gas phase while in the presence of a basic catalyst.
Various catalysts have been proposed for such reaction.
For example, U.S. Patent No. 3,247,248 describes a process for the reaction of formaldehyde and acetic acid or p.opionic acid in the presence of a natural or synthetic aluminosilicate catalyst that may include alkali or alkaline earth metalsg such as the aluminosilicates of sodium, potassium rubudi~m, magnesium, calcium, strontium or barium. In addition, the use of silica gel in combination with an alkali metal or alkaline earth metal hydroxide as a catalyst for this reaction is describ~d. Similarly, U.S. Patent ~o. 3,051,74, describes the preparation of acrylic acids by reacting an alkanoic acid and formaldehyde in the presence of a catalyst comprising an

-2- ~

105004~
alkali metal salt of the alkanoic acid supported on alumina.
Similar teachings are found in an article by Vitcha et al entitled "Yapor Phase Aldol Reaction"; "I & EC Product Research and Development", ~ol. 5, No. 1, (March 1966) at pages 50-53, wherein the vapor phase reaction of acetic acid and formal-dehyde is described employing catalysts comprising alkali and alkaline earth metal aluminosilicates, silica gel, alumina and the like.
It has now been found that alkanoic acids, their esters, and alkyl nitriles may be reacted with formaldehyde in the presence of a novel catalyst that is capable of providing greater conversions, yields and accountabilities than are provided with the catalysts of the prior art. In accordance with the present invention, alkanoic acids, esters thereof, and alkyl nitriles are reacted with formaldehyde in the presence of a basic catalyst comprising pyrogenic silica. Thus, for example, alkanoic acids containing between 2 and 9 carboD
atoms, e.g., propionic acid, are reacted with formaldehyde in the presence of a basic catalyst comprising pyrogenic ~ silica to proYide unsaturated monocarboxylic acids, e.g., methacrylic acid. Likewise, the esters of such alkanoic acids, e.g., methyl propionate, may be reacted in the presence of a pyrogenic silica catalyst to provide esters of such unsaturated acids, e.g., methyl methacrylate. ~oreover, alkyl nitriles, such as acrylonitrile~ may be reacted with formal-dehyde in the presence of such basic catalyst to provide the corresp~nding unsaturated nitrile, i.e., acrylonitrile.

~ -3-' .~L

~50~4 The present invention, therefore, resides in a process for the production of~ ethylenically unsaturated acids, esters of such acids, and nitriles, of the general formula CH2=C~-X , wherein X is -C02R or -CN and R is hydrogen or lower alkyl, which comprises reacting formaldehyde with an alkanoic acid, ester or alkyl nitrile of the formula R-CH2-X, wherein R and X are as defined above, in the presence of a catalyst consisting of pyrogenic silica, with a total surface area of from about 150 to about 300 square meters per gram, a total porosity volume of 3 to 15 cubic centimeters per gram and a pore size distribution such that pores having a diameter in excess of 100,000 A, and pores having a diameter between 100,000 A
and 10,000 A, total at least ~0~ of the total pore content, and less than 30% of the total pore content is constituted by pores having a diameter of less than 1,000 A, with the remainder of the pore content being constituted by pores having a diameter in the range of between about 1,000 A and about 10,000 A, and having been calcined with a base activating agent which increases the basicity of the silica, said reaction being carried out at a temperature in the range of from about 330C. to about 390-C., with the molar ratio of said alkanoic acid, ester or alkyl nitrile to said formaldehyde being in the range of about 0.3:1 to about

3:1.

-3a-E~

~0500~
The fumed or pyrogenic silicas display radically different properties from silica gel. For example, pyrogenic silica is characterized by its lack of internal porosity, small diameter and the agglomeration of its composi~e p~rticles. The surface area of pyrogenic silica is almost totally external, and thereby provides a readily available catalytic surface, whereas the surface area of silica gel is substantially internal and therefore less readily available.
In addition to providing increased conversion, yield and accountability, less carbonaceous material is deposited on the pyrogenic silica catalyst of the present invention as compared with prior art catalysts. Accordingly, less frequent catalyst regeneration is necessitated. In addition, by virtue of the open and readily available structure of the pyrogenic silica, a more controlled and even burn-off is experienced during the oxidative regenerative of the catalys~. Thus, catalyst deactivation may be minimized.
Any suitable pyrogenic silica may be employed in the process of the present invention. Commercially available pyrogenic silica generally contains over 99.8 percent silica (as SiO2 on a moisture-free basis). Accordingly, only a minimum of impurities such as aluminum, titanium and iron are present in such commercially available pyrogenic silica.
The presence of such impurities in large quantities is undesirable and, generally, it is desirable to employ pyrogenic silica containing no more than about 10 percent of such impurities.
The total surface area of the pyrogenic silica of the present invention is suitably, for example, in the range between about 40 and about 500 square meters per gram, pre-ferably, between about 100 and about 400 square meters per gram.

~S0(~44 An especially preferred total surface area for the pyrogenic silica is between about 150 and about 300 square meters per gram.
A significant characterisic of the pyrogenic silica is its total porosity, which as will be hereinafter demonstrated, is much greater than that of the prior art supports, such as silica gel and the aluminosilicates. Thus, the pyrogenic silica of the present invention suitably has a total porosity volume in the range of between about 3 and about 15 cubic centimeters (cc.) per gram, preferably between about 5 and about 11 cc. per gram. An especially preferred range is between about 6 and about 10 cc. per gram.
The pore size distribution of the total porosity of the pyrogenic silica of the present invention may vary over a broad range. For example, the macropores, (i.e., pores having a diameter in excess of 100,000 Angstrom units) and the submacropores (i.e., those between 100,000 and 10,000 Angstroms) content should total at least 50 percent. Like-~ise, less than 30 percent of the pyrogenic silica and preferably less than 25 percent thereof comprises micropores, i.e , pores having an average diameter of less than 1,000 Angstrom units. An especially preferred range for such micropores is less than about 20 percent. The balance of the pyrogenic silica comprises medium sized pores in the range of between about 10,000 and about 1,000 Angstrom units in diameter.
The preparation of pyrogenic silica is described, for example, in U.S. Patents 2,871,140, 2,876,119; 2,882,254;
2,892,730; 2,898,391; 2,951,044; 2,990,~49; 3,006,738;
3,033,801; 3,083,115; 3,086,851; and 3,103,495.

l~S~
As previously indicated, the process of the present invention comprises the reaction of formaldehyde with an alkanoic acid, an ester of such alkanoic acid, or an alkyl nitrile. Suitable alXanoic acids include those ha~ing an ~-hydrogen, i.e., a hydrogen atom that is alpha to the carboxyl group of the acid. Suitable alkanoic acids include, for example, alkanoic acids containing from about 2 to about 9 carbon atoms, preferably between about 2 and about 5 carbon atoms. Thus, suitable alkanoic acids include acetic acid, propionic acid, butyric acid, isovaleric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid and the like.
An especially preferred alkanoic acid for the purposes of the present invention is propionic acid, which reacts with formalde-hyde to produce methacrylic acid. Similarly, esters of the foregoing acids may be reacted with formaldehyde in order to provide the corresponding unsaturated ester. Thus, the methyl, ethyl, propyl, butyl, etc. esters of the foregoing acids will react with formaldehyde in the same manner as does the alkanoic acid to provide the corresponding ester of the unsaturated acid. Thus, suitable esters may contain, for example, 3 to 14 carbon atoms per molecule. Thus, methyl propionate will react with formaldehyde to form methyl methacrylate. Moreover, alkyl nitriles having, for example, from about 2 to about 9 carbon atoms per molecule, preferably, from about 2 to about 5 carbon atoms per molecule, such as acetonitrile, propionitrile, butyronitrile, etc., may be ~05~
reacted with formaldehyde to provide the corresponding unsaturated nitrile, e.g., acrylonitrile. A preferred alkyl nitrile is propionitrile~
The reaction of the acids, esters and nitriles with formaldehyde is a base-catalyzed reaction. Accordingly, if desired, the pyrogenic silica may be employed as the sole catalytic material as it does possess basic sites. Likewise, the pyrogenic silica may be treated with any suitable material that will provide basic sites on the catalyst. Preferably, pyrogenic silica is treated prior to use with an activating material which, upon calcination, will yield basic sites on the pyrogenic silica. Suitable activating agents include, for example, compounds having a pH of between 3 and 14 when the pH measurement is performed on a 0.3 molar solution.
Since the treatment of a pyrogenic silica with the activating agent must yield basic sites upon the silica, the activating agent must be a basic material or a material capable of being converted, upon calcination, into a basic material, viz., a base precursor. Thus, while activating agents, such as potassium oxalate and sodium acetate have a pH of about 3 or 4 in a 0.3 molar solution, and thus do not provide a basic pH, pyrogenic silica may be treated with such materials thereafter calcined whereupon basic sites are provided on the pyrogenic silica. Therefore, such activating agents are apparently "base precursorsi' and are converted upon calcin-ation to a basic form. Suitable activating agents include, for example, an organic or an inorganic basic compound. Thus, for example, the pyrogenic silica may be ~reated in any lOSOi:~4 suitable manner with a nitrogen-containing organic base, such as a~monia~ pyridine, the substituted pyridines3 the various alkyl amines, e.g., methylamine, or the like in - o~der to increase the basicity o~ the pyrogenic silica catalyst.
Likewise, the pyrogenic silica may be treated with high molecular weight amine hydrochloride activating agents, such as the benzyl trialkyl ammonium hydrochlorides, wherein the benzyl ring may be unsubstituted or may be substituted by one or two alkyl groups, each substituted alkyl group containing L0 from one to 12 carbon atoms per molecule. The N-substituted alkyl groups may contai~, for example, from one to 16 carbon atoms per molecule, and may include substituted alkyl groups.
Examples of such compounds include Diisobutyl phenoxy ethoxy ethyl dimethyl benzyl ammonium chloride monohydrate Diisobutyl cresoxy ethoxy ethyl dimethyl benzyl ammonium chloride~monohydrate;
Methyl dodecyl benzyl trimethyl ammonium chloride;
Methyl dodecyl xylylene bis(trimethyl ammonium chloride);
N-dodecyl dimethyl benzyl ammo~ium chloride;
N-tetradecyl dimethyl benzyl ammonium chloride;
N-hexadecyl dimethyl benzyl ammonium chloride; or the like.
Upon calcination of the pyrogenic silica that has - been treated with such high molecular weight amine, hydrogen chloride is driven off and the amine remains, thereby providing basic sites to the pyrogenic silica.

'"' ~, 105~(~44 Moreover, the pyro~enic silica may be treated ~ith an acti~atin~ aoent comprising a sulfur-containing organic base, such as trime-thyl sulfoniu~ hydroxide.
The preferred group of basic materials are the inorganic bases, such as metals of Groups IA, II~ and IIIB, including the alkali and alkaline earth metals including sodium, potassium, rubidium, magnesium, calcium, strontium, barium, cesium and the like which may be employed. Likewise,~
the hydroxides, oxides, superoxides, amides and sa~ts of such ) metals which decompose below 450C. may be employed. Thus?
basic materials such as scandium hydroxide, scandium oxide, rubidium hydroxide, lanthanum oxide, barium hydroxide, lanthanum f.' hydroxide, cerium oxide, lithium hydroxide, and the like may ~e employed. Like vise, other bases and base precursors may be employed as activating a~ents, to treat the pyrogenic silica. Thus, Sba~, Bi20~, Na~B407 10H20, Na~PO4, NaaCO~, H3BO~-Na~B407 lOH20B, NaaHPO~, Fe(OH)a, KOCH3, K~C4H~Of~-l/2H20, Na~SiO3, Na4SiO4-, CaH3COaNa, NaaWO4 2H20, La20D, Cs2MoO4, SnOa, MgAlSiO4, and the like , may be suitably utilized.
O The preferred inorganic bases include the Group IA and IIA bases, such as sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium carbonate, calcium hydroxide, sodium oxalate, sodium amide, cesium silicate and the like.
The alkaline metal hydroxides, such as potassium and cesium hydroxide are especially preferred.
The activating agent may be provided to the pyrogenic silica in any suitable manner. Thus, for example, a base, ~uch as aqueous potassium hydroxide, may be slurried ~vith the pyxogenic silica, heated and ag~itated to form a paste ~vhich 105~44 may be driecl and ca'cined to form the res~ll;ani catalys-t.
In thi~ manner the a~ded base is mulled wiih the finely di~ided silica. Any suitable calcin~ng condltions may be utilized. Thus, for exanple, calcining temperatures in the range of between about 330 and abo~t 460-C. rnay be employed.
Preferably, lower temperatures are utilized, e.g., between about 340 and 3~5C. 7 as higher temp~ratures may reduce the surface area of the catalyst and hence result in lower conversions. Calcination may be conducted in any suita~le atmosphere, e.g.~ nitrogen, air, or the like.
Alternatively, the silica may be preformed into the desired shape, e.g. pellets, spheres or the like, and the added base may be impregnated into the silica. Thus, any desired mear.s of forming the catalyst may be e~ployed. ..
A basic pyrogenic silica catalyst is req~lired for ~he process of the present invention, since the base reacts with the acidic ~-hydrogen atom on the methylene group in order to provide a carbanion for conversion to the unsaturated acid. Accordingly, any material, whether organic or inorganic I which when dissolved in deionized water provides a pH of 3.0 or higher may be employed with the pyrogenic silic~ in order to pro~ide the basic catalyst of the present invention. A
pH of 3.0 is sufficiently basic for the purposes of the present in~ention because of the high acidity of the ~-hydrogen atom on the alkanoic acid or its ester.
Ihus, according to the prcferred form of the catalyst of the present invention, the catalys~ comprises between about 0.25 and about 5 }nole percent by weight of an organic

4~
or inorganic base, preferably between about one and a~out 2 mole percent based upon the pyrogenic silica. Although pyrogenic silica provides an excellent catalyst for the process of the present invention, pyrogenic zirconia and pyrogenic titania are unsuitable, since their use results in an uncontrollable rise in temperature in the reaction zone and there~y causes excess gas to be produced. However, it has been found that the addition of between about one and about 10 percent by weight of pyrogenic zirconia in admixture with the pyrogenic silica of the present invention, provides an excellent catalyst. Likewise, pyrogenic zirconia and titania may be produced by a synthesis route which is similar to that described above for pyrogenic silica, e.g., pyrogenic zirconia may be produced from zirconium tetrachloride.
Suitable reaction conditions for the reaction of the alkanoic acid or its ester with formaldehyde include the use of elevated temperatures. For example, suitable temper-atures include, for example, between about 330 and about 390C., preferably between about 340 and about 370C. Atmospheric pressure is preferred, however, elevated pressures may be employed if desired. The concentration of reactants employed may be varied over a wide range. For example, between about 0.1 and about 15 moles of the alkanoic acid, its ester or the alkyl nitrile may be employed per mole of formaldehyde used, preferably between about 0.3 and about 3 moles of acid, ester or nitrile per mole of formaIdehyde. An especially preferred range is between about 0.8 and about 2 moles of acid, ester or nitrile per mole of formaldehyde. Likewise, the amounts cf water and methyl alcohol present along with 1~ ``" , 105~044 acid or ester and ~ormaldehyde may be varied over a wide range. Fol~ example, the mole ratio o.f acid to formaldehyde to water to methanol is in the range ~f 1/1/0.01/0 to 1/1/6/0,03.
Likewise, the ratio of catalyst to feedstoc~ may be varied over a broad range. A suitable flow rate which may be employed is, for example, a W/~ (grams of catalyst/
liter of feed/minute) of between a.bout 100/0.2 and about ~00/10. A gaseous hourly space velocity in the range of -between about 50 or 100 and about 2000 or 3000 1, preferably in the range of between about 300 and about 600 GHSV may be utilized.
The present invention may be more fully un~erstood from the following illustrative examples wherein the ratios and percentages are by weight and the temperatures are in degrees Centigrade unless otherwise specified.

1!

1~5~044 EXA~IPI,I~ 1 ~
i A four-liter resin flash is charged wit~I 2500 milliliters of deionizcd water and 200 grams of a pyrogenic silica having a surace area of 136 square meters per gram, a total porosity of.10 cubic centimeters per gram and a macropore content (pores having a diameter greater than lOO,OOOA) of 56 percent. Additional physical properties of the pyrogenic silica emp].oyed herein are given in Table I below, in connection with Catalyst A along with the 0 properties of other pyrogenic silicas that are employed in examples hereafter presented:

Table I

Sur~acePore Size Distribution Total Area(Ac x 1000~ Porosity Catalyst(m2/g)~100 100-10 10-1 C l__(cc/
A 1~6 56 21 13 . 11 10 B 400 31 40 20 9.2 7.8 C 117 38 45 12 5.2 8.8 Dl 150 48 27 14 11 12 .
Silica structure modified with 16 percent alumina ~0 The mixture is slurried at room temperature, and 2.45 grams of 85.5 percent potassium hydroxide in 90 milli-liters of deionized water are added. The slurry is agitated and heated until a thick paste is formed. The paste is dried at a temperature of 120C. ~vernight and calcined for 8 hours in air at a temperature of 3~0 to 385C. in a sealed muff,e furnace. The re~ulting maLcrial is then sieved ~o provide a catalyst having a 6 to 20 mesh particle size.

~5~044 EXA~ilP~~. 2 The catalyst of ~xample 1 in a~ amount of 123 grams is charged to a one inch by thirty--t~o inch tubular reactor that is equippcd with a preheater. The reactor is heated to a temperature of 370'C., v~hile a feedstream having propionic acid to formaldehyde to ~ater to methyl alcohol mole ratio of 20j2~5~/1 is fed to the reactor. The ratio of the catalyst (in grams) to the total gas flow (liters per mi.nute) or W/F factor is 100/1.
o The conversion to monomer ~methacrylic acid and methyl methacrylate) based on formaldehyde and propionic acid fed, is 34 percent, while the yield of monomer is about 62 percent, based upon the formaldehyde consumed and abo~lt 71 percent based upon the propionic acid that is consumed.
The formaldehyde accountability, i.e. the percentage either reco~Jered as such (and hence recyclable) or convertcd to monomer is about 79 percent. The corresponding value for propionic acid is about 87 percent.
The following equations lllustrate the manner in g which percent conversion, yield and accountability are calcu~
lated for the purpose of -this and other Examples:

Conversion of Formaldehvde to Monomer:

Percent conYersion = moles of ~A and M~ recovered moles F fed to reactor where ~ = methacrylic acid MM = methyl methacrylate F = formaldehyde ii l;
~ i lOS~
Conversiorl vf i'rop-.onic _ ici to ~lonomer:

Percent c~nversion = = x 100 where PA = propionic acid Yield of Monomer Based on Formaldehyde:

Percent yield = moles Ff ~ and dI~I recovered x 100 Yield Of ~lonomer Based on Propionic Acid:

- . moles of ~ and ~IM recovered Percent yleld = ~ x 10 moles rA converteu ~, Accountability of Formaldehyde:

. moles of F ~ and ~UI recovered 100 `~
Percent accountabillty moles F fed x Accountability_of Propionic Acid:

moles of PA, ~, MA
P t o tability = and ~1 reco~ered x 100 where MP = methyl propionate EXA~lPLE 3 F~r comparati~e purposes, a silica gel catalyst is proYided with potassium hydroxide in the manner described in Example 1. Thus, 2.45 grams of 85.S percent potassium hydroxide are dissolved in 90 milliliters of deionized water and are added to 200 grams of silica gel, having the properties shown in T~ble Il, below, in connectiorl w:ith Catalyst E:

0~
TABLE II

Surface Pore Siæe Distribution Total Area~A~ x 10001 Porosity Support ~M2/g) 100 100-10 1~-1 1 (cc/g) El 447 7.7 77 13 2.5 0.68 Fl 675 0 0 100 0 0.02 G~ 542 25 75 0 0 0.08 H~ 95.7 15 66 11 2.17 I3 113 0 17 67 0.09 .. .. ... . . . _ 1 Commercial silica gels 2 Laboratory synthesized catalyst that is prepared as a pre-cipitate by adding HCl to a sodium silicate solution.
3 Sodium aluminosilicate.

After the potassium hydroxide is added to the silica gel, the resu'ting solid is dried and calcined for 8 hours at a temperature of 363-383C.
The resulting catalyst having a particle size of 6-20 mesh is employed in the reactor of Example 2 with the feed and conditions of Example 2. Employing the silica gel catalyst, only 28 percent of the reactants are converted to monomer. The yield based upon formaldehyde is about 58 percent and the yield based upon propionic acid is about 58 percent as well. The formaldehyde and propionic acid accountabili-ties are 80 and about 82 percent, respectively.

EX~MPLE 4 For further comparative purposes, a sodium alumino-silicate catalyst is provided with one percent potassium hydroxide in the manner described for the pyrogenic silica of i~l y 10SOa)~4 Example 1. Thus, 2.5 ~rams. of ~6.5 percent potassium hydroxide, dissolved in 1~0 milliliters o~ deionizcd water are added to 200 grams of sodium alum nosilicate, which has the properties specified for Catalyst I in Ta~l.e II, i.~e., a surface area of 113 square meters per gram and a total porosity of 0.09 cc.
per gram. The mixture is dried and calcined for 8 hours at a temperature o~ 383C.
Formaldehyde, propionic aci.d, water and methanol are fed to the tubular reactor in the amounts and under the conditions described in Example 2. The resulting conversion is 8.7 percent, while the yield based upon ormaldehyde and propionic acid are 23 and 27 percent 9 respectively. The formal-dehyde and propionic acid accountabilities are 71 and 79 percent,respectively.
As showll in Table III, below, the pyrogenic silica not only produce~ higher conversions of feed to monomer (methacrylic acid and methyl methacrylate), but also provides higher yields and accountabilities.

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,~ o Q. 11~ i-n o o o ~. -x .
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;c ~LI)5~044 ~XA~'J.~,S 5-~

The procedure of Example 2 is repeated employing the other pyrogenic silica Catalysts B, C and D ~ho5Q propQ~ hs are indicated in Table I. Thus, propionic acid and formalde-hyde are reacted at a temperature of 370C. employing each o~
the Catalysts B, C and D of Table I wherein each catalyst contains one percent potassium hydroxide, which has been provided to the catalyst in the manner described in Example 1. The results are shown in Table IV, below.

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o ~.~
a ,~ ~1 ~ 1 a~ td CO t-n a~

O ~, O
~- ~
u~
a: . ' `, a ~
o ~ ::
P a~
,~
ss ~' ~ c~
6~ ~
p~ o, . ,;
~ ~ c~ ~ In 'p,, ~ ~ W CD C~ ~
G) CC ~-~n ~ ~ . o . ~
a h^
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~ ,q a ~
h C O c~ oo j O O--~ .

h E ~ o o o . a '9 Z; ~
C) ~
~ C~ m ~ ~
X o ~?~ ~

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As can b~ seell upon viewing ~`able I~, a hi~h con-version, yield and accountability are provided employing the p~rogenic silica Cataiyst B and CO However, pyrogenic silica Catalyst D, wt~ich contains l& percent alumina, results in lo~Yer conversion, yield and accountability. r EXAhlPLES 8-10 -The procedure of Example 2 is repeated employing the silicà Catalysts F, G and H having the properties indicated in Table II. Thus, the silica gel Catalysts F and ~ and the lV precipitated silica Catalyst H, each of whose physical properties are set forth in Table II, ar~ provided with one percent potassium hydroxide in the manner described for the pyrogenic silica of Example 1 and are employed for the reaction~
of propionic acid and formaldehyde in the manner described in Example 2. The results are set forth in Table V, below:

I

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~(~50~9~4 a C ~
o ~, .
, ~
~ C~ t-,, ~
C ~
~5 ~3 ,, a h ~ ~-c~ . . ',:
~q '~' s. a~ o .r j ~ `

Pl ~~ a ~

t~

C h ~ . h POaO~

~1 ~ Vi~ a ~,1 .~

.N

~ ~ O C
~ . ~

1050~4~, As seen upon vie~ing Table V, the conversions and yields are well below that achieved with the pyrogenic silica of the previous :E;xamples.

A number of diverse catalysts employing a wide variety of supports and carrying one percent potassium hydroxide are synthesi~ed and evaluated in the process of Example 2.
The results are shown in Table VI, below:

~,i tf'' ~` i ` !

44 ;.
a~

.
~ 0 e h C ~ . _ o ~ O 0~ ~5) 0 0 N N Cd ~ O It~

. , o o l Q~ S ~ ' ~ , ' ~,, ~ ~ N C~
^ r!', h Oh a ,~ a: ~ o oo r~ O a, ~: t- ~ o ~
. ~ m 0 oh~ .-E-~ ~ a .' C ~ ~ ~ C"

U E~ . ~ , ~

' l ~ ~ ~ ~ ., ~
- 3 o 5~ ~

u ~ o .~ C) Ln ~ v u o~ 2 h ~ ; n ~-- ~

f~ f ~ ~ ' ff ~ J `, ,:

lQ5004~
As can be seen upon viewing Table VI, all of the catalysts tested are inferior to the pyrogenic sllica catalyst of Example 11.

EXAMPLE 21 ~S~

A buffered cesium hydroxide catalyst composition is prepared by adding a solution containing 4.5 grams of cesium hydroxide, 0.05 gram of disodium hydrogen phosphate, 0.09 gram of borax and 100 milliliters of water, to a stirxed SU5-pension of 156 grams of pyrogenic silica in 1850 milliliters of deionized water.
The resulting composition is stripped while stirring to remove solvent, dried and calcined for 8 hours at a temper-ature of 383~C.
The resultin~ catalyst is employed for the conversion of propionic acid and formaldehyde in the manner described in Example 2. A con~ersion of 34 percent is achieved at a temperature of 370C., while yields based upon formaldehyde and propionic acid are 69 and 80 percent, respectively. The formaldehyde accountability is 85 percent, while the propionic acid accountability is 93 percent.

EXAMFfLE 22 ~ he pyrogenic silica cat~lyst described in Example 1 is heated to a temperature of 355C. Meanwhile, a feed-stream comprising 20 mole percen f~ formaldehyde, 20 mole per-cent acetic acid, 59 mole percent Nater and 1 mole percent methanol is passed over the pyrogeDic silica cataly~t bed at a W/F factor of 100 to 1 grams per liter per minute.

p y ~I~S0C~44 Conversion to monomer ~acrylic acid and methyl acrylate~ is 12 percent, while yielcis based upon ormaldehyde and acetic acid are 46 and 72 percent, respecti~ely. The formaldchyde and acetic acid accountabilities are 8~ and 95 percent, respective~y. ~1 ~XAMPLE 23 A pyrogenic silica catalyst containing about 6 percent by weight zirconia is employed in the reactor described in ~xample 2 with the feedstock and conditions utilized therein, with the exception that a lower conversion temperature of 340~C. is used.
A conversion of 25 percent is achieved.

~XA~LE 24 The procedure of Example 2 is repeated with the exception that methyl propionate is substituted for propionic acid.
The conversion is 25 percent, while the combined yields of monomer (MAA~ based on formaldehyde and methyi propionate are 63 percent and 44 percent, respectively, while another 40 percent of the methyl propionate goes to propionic acid. The formaldehyde accountability is 85 per-cent, while that for methyl propionate is 91 percent.

10501D~ ~
_ IPI.E 25 The procedure of Example 2 is repeated with the exception that acetonitrile is substituted for propionic acid. The conversion is 6.5 percent while the yield of acrylo-nitrile based on formaldehyde and on acetonitrile, respectively is 15 percent. The formaldehyde and acetonitrile accounta-bilities are 65 and 64 percent, respectively.

In the following examples, pyrogenic silisas that D have been treated with a variety of materials and then calcined in the manner described in Example 1, are evaluated employing the feedstreamJ reac-tor and conditions set forth in ~xample 2. The results of this e~aluation are given in Table VII, below. All of the cesium-containing catalysts have been buffered with disodium phosphate and sodium tetraborate in the manner described in Example 21.
.

t~ f'' ;. ~ o~

~ o ~, 0 ~1 ~ ~r ~t N~) rl 1$~
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C~
0~ ~
~v ~r o os~ ~O O
P O
, E~
O ~ C~
S~ ~ O G) ~ ~CS~

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Although the invention has been described in con-siderable detail wi~h particular rcference to certain preferred embodiments thereof, variations and modifications can be e~iected within the spirit and scope of the invention as described hereinbefore, and as defined in the appended claims.

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Claims (13)

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

1. A process for the production of .alpha.,.beta.-ethylenically unsaturated acids, esters of such acids, and nitriles, of the general formula , wherein X is -CO2R or -CN and R is hydrogen or lower alkyl, which comprises reacting formaldehyde with an alkanoic acid, ester or alkyl nitrile of the formula R-CH2-X, wherein R and X are as defined above, in the presence of a catalyst consisting of pyrogenic silica, with a total surface area of from about 150 to about 300 square meters per gram, a total porosity volume of 3 to 15 cubic centimeters per gram and a pore size distribution such that pores having a diameter in excess of 100,000 .ANG., and pores having a diameter between 100,000 .ANG.
and 10,000 .ANG., total at least 50% of the total pore content, and less than 30% of the total pore content is constituted by pores having a diameter of less than 1,000 .ANG., with the remainder of the pore content being constituted by pores having a diameter in the range of between about 1,000 .ANG. and about 10,000 .ANG., and having been calcined with a base activating agent which increases the basicity of the silica, said reaction being carried out at a temperature in the range of from about 330°C. to about 390°C., with the molar ratio of said alkanoic acid, ester or alkyl nitrile to said formaldehyde being in the range of about 0.3:1 to about 3:1.

2. The process of claim 1, wherein the compound of formula R-CH2-X which is reacted with formaldehyde is a lower alkanoic acid.

3. The process of claim 2, wherein said lower alkanoic acid is propionic acid.

4. The process of claim 1, wherein said catalyst contains as a base activating agent a compound selected from the group consisting of hydroxides, oxides, superoxides, or amides and salts of a metal of Group IA, IIA or IIIB.

5. The process of claim 4, wherein said base activating agent is an alkali metal hydroxide.

6. The process of claim 5, wherein said alkali metal hydroxide is potassium hydroxide or cesium hydroxide.

7. The process of claim 1, wherein said pyrogenic silica has a total porosity of between about 6 and about 10 cubic centimeters per gram.

8. The process of claim 1 wherein the compound of formula R-CH2-X which is reacted with formaldehyde is an ester.

9. The process of claim 8, wherein said ester is methyl propionate.

10. The process of claim 1, wherein the compound of formula R-CH2-X which is reacted with formaldehyde is a lower alkyl nitrile.

11. The process of claim 10, wherein said lower alkyl nitrile is propionitrile.

12. The process of claim 1, wherein said process is conducted at a temperature in the range of between about 340°
and about 370°C.

13. The process of claim 1, wherein between about 1 and about 10 percent by weight of zirconia is admixed with said pyrogenic silica.