Pyridine base synthesis process and catalyst for same

An improved base synthesis process and catalyst for the preparation of pyridine or its alkylpyridine derivatives involving the catalytic reaction of one or more aldehydes and/or ketones containing from one to about five carbon atoms, with at least one reactant having more than one carbon atom, with ammonia in the gas phase. The improved catalyst comprises an effective amount of a shape-selective zeolite which has been modified by treatment with one or more metal ions or compounds of tungsten. zinc or tin. The preferred zeolite has a constraint index of about 1 to 12 and a high silica content and correspondingly low concentration of ion-exchange sites with minimal to no acidic sites present.

BACKGROUND OF THE INVENTION 
This invention relates to an improved process for pyridine base synthesis, 
and to a particular class of shape-selective zeolite catalysts for use in 
the same which have been advantageously modified by treatment with one or 
more compounds containing tungsten, zinc or tin. 
The term "base synthesis" is known and used in the pyridine field and in 
this application to identify a process by which bases of pyridine or 
alkylpyridine derivatives are prepared by reacting aldehydes and/or 
ketones with ammonia in the gas phase using a heterogeneous catalyst. Some 
examples of base synthesis reactions (and their common names where 
appropriate) include: the synthesis of pyridine and beta-picoline from 
acetaldehyde and formaldehyde (the "pyridine-beta reaction"); the 
synthesis of alpha- and gamma-picoline from acetaldehyde (the "alpha-gamma 
reaction"); the synthesis of 2,6-dimethylpyridine ("2,6-lutidine") from 
acetone and formaldehyde; the synthesis of 2,4,6-trimethylpyridine 
("sym-collidine") from acetone alone or with acetaldehyde; the synthesis 
of pyridine and beta-picoline from acrolein alone or with acetaldehyde; 
the synthesis of 3,5-dimethylpyridine from propionaldehyde and 
formaldehyde; and the synthesis of beta-picoline from acetaldehyde, 
formaldehyde and propionaldehyde. Many others are known and reported or 
practiced in the art, and are equally considered within the scope of the 
description and invention herein. 
The catalysts used in these pyridine base synthesis reactions have varied 
from alumina which was used early-on either alone or as a support for zinc 
fluoride or other metal salts to an amorphous structure incorporating both 
silica and alumina which became an important commercial catalyst. See U.S. 
Pat. Nos. 2,807,618 and 2,744,904; and German Patent No. 1,255,661. 
Similarly, the reactor designs for these heterogeneous gas-phase reactions 
have varied within the basic categories of fixed-bed and fluid-bed forms. 
The advantages of fluidized beds were recognized early-on (see U.S. Pat. 
No. 2,807,618) as evidenced by the fact that the handful of 
commercial-scale base synthesis units operating today worldwide all 
incorporate fluidized catalyst beds. One reason for this is that base 
synthesis reactions always produce deposits of dark, mostly carbonaceous 
materials referred to as "coke" which tend to foul the catalyst thereby 
gradually reducing its activity. Although variations are observed, all 
catalysts accumulate these coke deposits at a appreciable rate such that 
periodic action is required. As discarding catalyst is not desirable for 
economic reasons, regeneration by heating in air or other 
oxygen-containing gases is commonly employed. This regeneration/combustion 
process is very exothermic and also best carried out in a fluid bed 
Process. C. L. Thomas, "Catalytic Processes and Proven Catalysts", 
Academic Press. N.Y., pp. 11-14 (1970). 
Accordingly, a common technique has long been to run two fluid beds 
concurrently, one for reaction and one for regeneration,. with catalyst 
continuously or intermittently cycled between the beds. Operating 
parameters such as circulation rates, contact times, temperatures and the 
like are readily determined by skilled operators in view of the specific 
reactions and/or ingredients used. See, e.g., German Patent No. 2,203,384. 
An ancillary benefit of this technique is that product yields from base 
synthesis reactions carried out in fluidized beds are recognized to be 
generally higher than in corresponding fixed-bed reactions. This was 
emphasized in two families of patents issued to BP Chemicals U.K. Ltd. of 
London, England, one for alpha-gamma synthesis (British Patent No. 
1,188,891; German Patent 1,903,879; and Canadian Patent No. 852 745) and 
the other for pyridine-beta synthesis (British Patent No. 1,235,390; 
Canadian Patent No. 851,727; and German Patent No. 1,903,878). These BP 
patents, and German Patent No. 1,903,878 in particular, compare fixed- and 
fluid-bed reactions using catalysts of amorphous silica-alumina or of 
metal compounds such as the oxides or fluorides of lead, zinc and cadmium 
on amorphous silica-alumina supports. 
This same advantage of fluid-bed usage was reported by Feitler et al. in 
U.S. Pat. No. 4,675,410 for base synthesis catalysts composed of 
shape-selective aluminosilicates (commonly referred to as "zeolites") used 
in their acidic form. These crystalline zeolites had earlier been reported 
for base synthesis reactions by Chang et al. in U.S. Pat. No. 4,220,783 
both in their acid- or H-form and as ion-exchanged with cadmium, copper or 
nickel. Several examples in the Chang patent demonstrated deactivation of 
the catalyst over time thereby also suggesting the desirability of a 
fluid-bed to reactivate the catalyst by heating in air in any commercial 
application. 
In general, these base synthesis reactions have received universal 
acceptance as evidenced by their continuous commercial use for many years. 
The products of base synthesis, including pyridine, alpha-, beta- and 
gamma-picoline, nearly all the lutidines, and primarily the symmetrical 
isomer of collidine, have all shown commercial importance in the world 
chemical market albeit of varying values and volume requirements. See Goe, 
"Pyridine and Pyridine Derivatives," Encyclopedia of Chemical Technology, 
Vol. 19, 3rd. Ed. (1982). It is also the case that improvement in the 
yields of these reactions and variation in their product ratios may be 
desirable according to market trends for such pyridine-derivative products 
as the herbicide paraquat, vitamins such as niacin and niacinamide, tire 
cord adhesive derived from 2-vinylpyridine, the tuberculosis drug 
Isoniazid, and so forth. One approach to this end has examined variations 
in reaction conditions such as temperature, velocity or contact time, mole 
ratios of feed stocks, and the like. Here, optimization of yield or 
product ratio is generally accomplished by known techniques employed by 
those skilled in this area. A second approach has involved catalyst 
variation in which far less predictability exists. 
For example, while work early-on was with amorphous silica-alumina or other 
catalysts, the concentration in recent years has shifted to these 
so-called shape-selective zeolites which are aluminosilicates of definite 
crystal structure having activities and pores of size similar to that of 
other commercially-interesting molecules. See, e.g., E. G. Derouane. "New 
Aspects of Molecular Shape-Selectivity: Catalysis by Zeolite ZSM-5", 
Catalysis by Zeolites, ed. B. Imelik et al., Elsevier, Amsterdam, pp. 5-18 
(1980). These materials are often defined by a constraint index which is 
an experimentally-derived number based on the observed relative rates of 
reaction of straight and branched-chain molecules. Frillette et al., J. 
Catal., 67, 218 (1981). The term "zeolite" has even acquired a broader 
meaning in the art, and is accordingly used in this application to mean 
more than the original crystalline aluminosilicate materials. For example, 
"zeolite" is understood and meant to also include compositions such as 
gallosilicates, ferrosilicates, chromosilicates and borosilicates. 
Crystalline aluminum phosphates ("ALPO's") and silicon-aluminum phosphates 
("SALPO's") are also included in its coverage because of their catalytic 
ability, as is even theoretically-pure crystalline silicalite such as a 
S-115 material marketed by Union Carbide Corporation of N.Y. 
In these zeolite materials, some ion-exchange properties are generally 
thought to exist due to positive ions associated with the trivalent 
molecular centers (e.g., aluminum, boron. gallium, etc.) that are present 
in the network of tetravalent silicon centers. Although ALPO is an 
exception to this, and silicalite may be an exception but for residual 
aluminum in its crystal structure, it has also been thought that catalytic 
activity is associated somehow with these ion-exchange sites. As 
synthesized, zeolites typically have sodium or quaternary ammonium ions in 
their crystal structures. If these ions are exchanged for ammonium 
(NH.sub.4 +) ions and the resulting ammonium zeolite heated, an acidic or 
"H-form" zeolite results with these acid centers believed to be associated 
with some catalytic activity. For instance, an H-form of ZSM-5 zeolite is 
marketed by The Mobil Corporation of N.Y. and is used in the synthesis of 
gasoline from methanol. 
One approach at optimizing yield and/or product ratios from base synthesis 
reactions has been to stress maximizing these acidic sites. For example, 
the Feitler patent claims the specific benefit of a higher ratio of 
pyridine in the pyridine-beta synthesis by use of a zeolite catalyst of 
preferably 80-100% this H-form although no direct comparison with other 
ion-exchanged zeolites is reported. 
Other positive ions have also been exchanged for the sodium, ammonium or 
H-sites in the zeolite structure. For example, cracking catalysts have 
used a rare earth ion-exchanged form of the large-pore zeolite Y (called 
"REY"). C. L. Thomas, "Catalytic Processes and Proven Catalysts", supra, 
pp. 30-31. Precious metals have been exchanged in both large-pore and 
shape-selective zeolites to produce reforming catalysts. E.G. Derouane, 
"New Aspects of Molecular Shape-Selectivity: Catalysis by Zeolite ZSM-5", 
supra, p. 17. The Chang patent also reported use of zeolites ion-exchanged 
with cadmium, copper or nickel ions in addition to the H-form of Mobil's 
ZSM-5 material in base synthesis reactions. The Chang patent did test the 
catalytic activity of these metal ion-forms, but did not speculate on 
whether they existed solely or survived in their ionic state or were 
reduced to base metals. 
More recently, Shimizu et al. described base synthesis reactions using 
shape-selective zeolites treated with thallium, lead or cobalt ions or 
compounds in an European application, Serial No. 232,182 published Aug. 
12, 1987. These metals were ion-exchanged into a zeolite of alkali, 
ammonium or acid form in an aqueous medium or were mixed in the solid 
state with no apparent effect from the mode of mixing used. As the Feitler 
patent, Shimizu also reported the desire for a low yield of beta-picoline 
from pyridine-beta base synthesis. However, this work does not permit 
direct comparison with Feitler as Shimizu used a reaction mixture with so 
little formaldehyde (0.5 moles per mole of acetaldehyde) that it 
necessarily produced about equal amounts of beta- and gamma-picoline which 
are of questionable commercial utility. See, e.g., Beschke, Ullmann 
Encyclopedia, p. 593 (1980). 
It is in the light of this background, and of the large body of general 
chemical literature concerned with base synthesis processes (see F. Brody 
and P. R. Ruby. Pyridine and Its Derivatives, E. Klingsberg ed., Vol. 1 
(1960); N. S. Boodman et al., Ibid, Supplement Abramovitch ed., Vol. 1 
(1975); T. D. Bailey, G. L. Goe and E. F. V. Scriven, Ibid. Supplement G. 
R. Newkome ed., Vol. 5 (1984)), that the applicants approached this study 
with the objectives of providing at least equivalent overall yields and, 
where appropriate, the selectivity to vary product ratios within reason to 
meet varying economic conditions. 
SUMMARY OF THE INVENTION 
The present invention meets these goals through the discovery that 
shape-selective zeolite materials can be advantageously modified with 
compounds of tungsten, zinc or tin to produce catalysts that give improved 
and selective product yields. This is done without the drastic reduction 
of beta-picoline observed and desired by the Feitler and Shimizu 
references in the pyridine-beta reaction. Equivalent or improved yields 
are also achieved in other base synthesis reactions such as the 
alpha-gamma synthesis in which a high ratio of alpha picoline is obtained 
without simply decreasing the yield of gamma-picoline from the reaction. 
Other aspects of the discovery are that these modified zeolite catalysts 
differ substantially from those previously taught or suggested in the art 
as being preferred. For example, contrary to the Feitler Patent, minimal 
to no acid sites are preferred in the zeolite structure as modified. 
Although the Feitler, Chang and Shimizu references disclose a wide range 
of silica-to-alumina ratios, a high-end ratio and therefore lower fraction 
of ion-exchangeable alumina or other sites are preferred here in the 
original zeolite structure to be modified. This reduces the sites 
available for acidic species which may also reduce the concentration of 
tungsten, zinc or tin needed to be taken up through ion-exchange or 
otherwise in the treated catalyst to achieve the beneficial effects 
characteristic of this invention. 
The invention further avoids the practical problems encountered with the 
metal ions taught by the Chang and Shimizu references for use in 
ion-exchange. Of the six ions mentioned, for example, thallium compounds 
are extremely toxic and pose severe health hazards as the fluid-bed 
reactors often used for base synthesis require finely powdered catalysts, 
some of which inevitably escapes from the system regardless of the care 
taken. Lead and cadmium compounds are not quite so acutely toxic, but 
chronic exposure particularly to lead is known to cause severe problems in 
children. The problem is aggravated in a plant operation where some escape 
is expected. Nickel and its compounds, on the other hand, are suspected 
carcinogens and cobalt is a heavy metal known to be environmentally 
undesirable. Copper compounds, although comparatively innocuous, are known 
to be toxic and to present waste disposal problems. See, e.g., C. A. Owen, 
Copper Deficiency and Toxicity, pp. 116-120 (1981) and D. C. H. McBrien, 
"Anaerobic Potentiation of Copper Toxicity and Some Environmental 
Considerations", Biological Roles of Copper. pp. 301-313 (1980). 
Such concerns for environmental and human safety are paramount objectives 
and benefits of the invention along with the surprising catalytic 
effectiveness and selectivity that has been observed. In this regard, very 
desirable and unexpected results have been achieved for these base 
synthesis reactions as described above by the use of the applicants' 
modified zeolite catalysts. 
Related objects and variations as to the detailed aspects of the invention 
will become apparent from the following description of the preferred 
embodiment. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
For the purposes of promoting an understanding of the principles of the 
invention, reference will now be made to certain embodiments and specific 
language will be used to describe the same. It will nevertheless be 
understood that no limitation of the scope of the invention is thereby 
intended, such alterations and further modifications of these embodiments, 
and such further applications of the principles of the invention as 
described herein being contemplated as would normally occur to one skilled 
in the art to which the invention relates. 
As already stated, one embodiment of the invention is the discovery of an 
improved catalyst and base synthesis process for the preparation of 
pyridine or its alkylpyridine derivatives involving the catalytic reaction 
of one or more aldehydes and/or ketones containing from one to about five 
carbon atoms, with at least one reactant having more than one carbon atom, 
with ammonia in the gas phase. The improved catalyst comprises an 
effective amount of a shape-selective zeolite, as broadly defined above, 
which has been modified by treatment with one or more metal ions or 
compounds from the group of consisting of tungsten, zinc or tin. The 
preferred zeolite has a constraint index of about 1 to 12 and a high 
silica content and correspondingly low concentration of ion-exchange sites 
with minimal to no acidic sites present. 
The reactants and their ratios used in the invention will vary 
significantly according to many factors, not the least of which is the 
base synthesis process under study and the particular pyridine or 
alkylpyridine base product yield or ratio sought to be achieved. Suitable 
combinations of reactants include those set forth above and in the 
Examples below as well as many others known to those skilled in this art. 
For example, listings and tables of such common reactants and product 
yields having known commercial importance appear in the Feitler patent 
(U.S. Pat. No. 4,675,410) and the published Shimizu application (Serial 
No. EP 232,182). both of which are incorporated herein by reference as to 
all relevant and material subject matter contained therein. It is 
understood that all such base synthesis processes and reactant and product 
combinations are suitable and within the scope of the invention. 
Similarly, the reaction conditions such as the molar amounts, temperatures 
and times used and the appropriate equipment and procedures such as the 
desirability of pre-mixing or of operating in an inert environment will 
likewise vary and are well within the skill and knowledge of those 
practiced in this area. Accordingly, the same require no further 
elaboration in this specification except as contained in the Examples 
below, it being understood that such variations are also within the scope 
of the invention. 
Preparation of the modified catalysts in accordance with the invention 
first involves selection of a shape-selective zeolite material. Many 
suitable zeolites are known and are commercially available for this 
purpose. As already stated, one preference is that the zeolite which 
comprises a crystalline aluminosilicate or other substituted-silicate 
material have a constraint index of about 1 to 12. Such values are known 
for many commercial zeolites (see, e.g., the Feitler and Shimizu 
disclosures incorporated herein by reference) and are otherwise easily 
calculated by known methods. Frillette et al., J. Catalysis, vol. 67, 
218-222 (1981). 
Other preferences are that the selected zeolite have a relatively low 
concentration of ion-exchange sites in its structure and that 
minimal-to-no acidic sites be present after treatment. The first of these 
is characteristic of a zeolite having a high atomic amount or ratio of 
silica to the alumina or other substituted-metal ion in its structure. 
Whereas a silica ratio of 12 to 1,000 is taught by the Feitler and Shimizu 
disclosures, the preference in this invention is for a ratio in excess of 
about 100, with the Union Carbide S-115 silicalite material being 
preferred from work to date. This ratio for S-115 is reported in the 
Feitler patent to be 350, although available literature from Union Carbide 
states only that the material is over 99% pure SiO.sub.2. Silica ratios 
approaching about 1,000 or more are acceptable, with the desired result 
being a high concentration of silica in the zeolite structure with 
minimal-to-no alumina or other sites susceptible of ion-exchange. 
This second preference directly contradicts the Feitler teaching of 
maximizing the acidic form of the finished zeolite catalyst. The improved 
catalyst and process of this invention have surprisingly resulted in 
effective catalytic activity and unexpected product yields and selectivity 
of various bases by minimizing this same acidic form. In this regard, such 
use of the term "minimal" or its likeness in this application is meant to 
define a modified zeolite catalyst having less than 10% of the sites which 
are available for ion-exchange in fact occupied by hydrogen ions or other 
acidic species as described in the Feitler patent. A very low 
alumina-content zeolite is thus preferred, such as the S-115 silicalite 
material from Union Carbide with only trace amounts of alumina or other 
such metal ions present in its crystal structure. 
Once a zeolite is selected, an improved catalyst is made in accordance with 
the invention by effectively modifying the zeolite material through 
treatment with one or more of the preferred metal ions of tungsten, zinc 
or tin or compounds containing the same. This treatment may be carried out 
in any number of ways known in the art and may be carried out several 
times if desired to ensure substantial metal uptake on the zeolite. 
For example, a preferred method of treatment is to add the zeolite to an 
aqueous solution of the desired tungsten, zinc or tin compound in 
stoichiometric excess and then to heat the mixture for some time at a 
predetermined temperature accompanied by stirring. The metal compounds 
used are soluble salts such as ammonium tungstate in the case of tungsten 
and nitrates, halides or acetates in the case of zinc or tin. This is 
followed by filtering, rinsing and drying, and then calcining at elevated 
temperature to obtain the finished catalyst. An alternate or possible 
further procedure is to prepare a physical mixture of the zeolite and the 
desired metal salt either dry or in the presence of enough water to 
constitute a paste or similar consistency, and then to complete the 
modification by blending or other suitable physical means. These and other 
similar procedures known in the art are all within the scope of the 
invention. 
As a result of this treatment procedure, an effective amount of the 
tungsten, zinc or tin metal is taken up in the zeolite structure thereby 
modifying it to produce the improved catalyst in accordance with the 
invention. The amount and method of this uptake will vary depending on 
many factors such as the identity and concentration of reactants, the 
specific treatment procedures and the like, all of which are within the 
skill of those experienced in this area to select and to control. For 
example, no minimum or threshhold level of metal uptake is required with 
all amounts expected to produce some improved catalytic activity or 
effectiveness in later use. The same are therefore within the scope of the 
invention so long as the characteristics described herein are met. 
Nevertheless, concentrations up to about 1.0 mg equivalent/g of the 
selected metal in the modified catalyst are obtainable and may be desired 
in a given circumstance. 
Similarly, no particular method of uptake is required with physical 
absorption, adsorption and other forces coming into play and with chemical 
means such as ion-exchange and the like also occurring with given 
reactants exposed to certain treatment procedures. With zinc and tin, for 
example, an added benefit is that any available or existing acidic sites 
in the zeolite are believed to be substantially ion-exchanged with the 
preferred metal during the treatment procedure thereby minimizing these 
acidic sites as preferred in accordance with the invention. The same may 
also be an aspect of or involved in the uptake of tungsten as well, but 
its mechanism of modifying and affecting the zeolite whether physical or 
chemical or both is less clear from testing performed thus far. 
In any case, the treatment procedure may occur before or after the zeolite 
is formulated into a catalyst matrix or binder. In this regard, pure 
zeolites are commonly in the form of very fine powders suitable neither 
for fixed- or fluid-bed usage. To be useful, the zeolite powders are 
typically incorporated into a binder or matrix and then pelletized or 
extruded (With a fixed-bed catalyst) or ground or spray-dried (with a 
fluid-bed catalyst) to produce a form having commercial application. The 
applicants' improved base synthesis process may be operated in a fixed- or 
a fluid-bed reactor to achieve the overall effective yields and selective 
product ratios characteristic of the invention. Nevertheless, a fluid-bed 
reactor and catalyst are preferred in order to also achieve the expected 
higher yields and ease of regeneration and use characteristic of such 
systems. The equipment set up and operation of fluid-bed reactors vary 
according to many factors tied to the particular reaction under 
consideration. The same are readily constructed by those of ordinary skill 
in the art, and are all within the scope of the invention herein. Reaction 
parameters such as temperature, feed mole ratios, feed velocity and 
contact time and the like vary over a wide range of operable conditions 
also well known and within the scope of the invention. 
As previously discussed, many base synthesis processes are known and are 
also within the scope of the invention herein. In addition to the specific 
Examples below and to the disclosures incorporated by reference above, for 
the pyridine-beta synthesis it is generally preferred that a feed of 
formaldehyde to acetaldehyde in a mole ratio of at least about 1:1 is 
used. The addition of methanol to the extent of about 5 to 70% of the 
formaldehyde component is also preferred, as originally described in U.S. 
Pat. No. 2,807,618. At least a portion of the formaldehyde can further be 
replaced by paraformaldehyde or sym-trioxane, and water can be present as 
desired to provide a stable, storable solution. Ammonia is supplied in a 
ratio of at least about 0.6:1 to the total organic components in the feed, 
with a range of about 0.7 to 1.5 being more preferred and about 0.8 to 1.2 
being most preferred from testing to date. The feed rate is in turn chosen 
to give good fluidization of the bed, usually in the range of a 
superficial velocity between about 0.3 to 4.0 ft./sec. Temperature of the 
reaction is preferably between about 350.degree. C. and 550.degree. C. 
more preferably between about 400.degree. C. and 500.degree. C. and most 
preferably at about 450.degree. C. The products of the reaction, being 
pyridine and beta-picoline, are condensed and separated into pure 
compounds by drying and distillation as is well known in the art. By way 
of a second example, the alpha-gamma reaction is preferably carried out in 
much the same way except that formaldehyde and methanol are left out of 
the feed mixture. 
While the invention has been described in detail in the foregoing 
description, the same is to be considered as illustrative and not 
restrictive in character, it being understood that only the preferred 
embodiments have been described and that all changes and modifications 
that come within the spirit of the invention are desired to be protected. 
In the same regard, the following specific Examples are given in further 
explanation and description of these embodiments and are meant to be 
exemplary and not limitations thereof.

EXAMPLE 1 
Modified Catalyst Preparation and Use 
Several modified zeolite catalysts in accordance with the invention were 
prepared using representative procedures well known in the art, there 
being other known techniques equally suitable and within the scope of the 
invention. In the Examples below, this involved use of a S-115 silicalite 
powder obtained from Union Carbide which had been already formulated into 
a silica-alumina matrix at a 25% weight concentration and spray-dried to 
an appropriate particulate size and configuration for use in a 
fluidized-bed reactor. An alternative was to directly treat this S-115 
powder with one or more of the preferred tungsten, zinc or tin compounds, 
followed by mixing this modified zeolite with wet kaolin powder which was 
later dried and calcined to form an appropriate catalyst for fluid-bed 
usage. 
In either case, one method of treatment involved heating the formulated 
silicalite catalyst or unformulated powder at temperatures in the range of 
about 70.degree.-100.degree. C. with stirring in an aqueous solution 
containing a stoichiometric excess of the selected metal compound. 
Stirring was continued for at least 2 hours to assure substantial 
modification of the catalyst in accordance with the invention, and was 
followed by filtering, rinsing thoroughly with water, drying and calcining 
the catalyst at about 500.degree. C. or above before subsequent use. A 
second alternate or additional procedure involved mixing the formulated or 
unformulated silicalite with the selected metal compound in a paste-like 
consistency to permit modification, followed by drying and calcining as 
before. 
One base synthesis process used to test these modified zeolite catalysts 
was the pyridine-beta synthesis. The reaction was conducted in an 
externally gas-heated fluid-bed reactor of standard design having a 1.6 
inch internal diameter and containing 750 mL of catalyst. The temperature 
of the catalyst bed was maintained at 450.degree. C. The organic feed into 
the reactor comprised acetaldehyde and formaldehyde in a 1:1 mole ratio, 
with the formaldehyde being a mixture containing 45% formaldehyde, 10% 
methanol and the remainder water. Ammonia was also fed into the reactor at 
a mole ratio of 1.2 compared to the total organic feed. This organic feed 
was injected directly above the distributor plate, while ammonia was 
introduced below the distributor plate according to common and known 
procedures. The products exiting the top of the reactor were captured and 
condensed. Methanol was added to homogenize the product mixture which was 
then analyzed using standard gas chromatography techniques. 
A second base synthesis reaction also tested was the alpha-gamma synthesis. 
This reaction was conducted similar to the procedure for pyridine-beta 
synthesis except that the organic feed contained only acetaldehyde. The 
overall yield and product mix was again determined by gas chromatographic 
analysis as reported in the specific Examples below. 
EXAMPLE 2 
Tungsten-modified zeolite catalyst was prepared according to the procedures 
of Example 1 by first wetting 62.5 g (0.25 mol) of H.sub.2 WO.sub.4 with 
40 mL of water. This wet mixture was then heated with 400 mL of 
concentrated ammonium hydroxide for a few minutes at about 50.degree. C., 
and the solution was diluted to 2.5 L with water. 1 Kg of 25% S-115 
catalyst in a silica-alumina matrix was then added and the mixture stirred 
for 2 hours at about 80.degree. C. The mixture was filtered, rinsed with 
four 2.5 L amounts of water, and was dried overnight in a wide pan. The 
modified catalyst was then calcined for 4 hours at 500.degree. C., during 
which significant tungsten uptake was confirmed by the characteristic pale 
yellow appearance of the catalyst. An appropriate amount of this tungsten 
modified zeolite catalyst was then used in the pyridine-beta synthesis 
reaction as described in Example 1, with the product mixture containing 32 
weight percent pyridine and 16 weight percent beta-picoline compared to 
the total organic feed stream passed through the reactor. The amount of 
alpha-picoline also detected was 1 weight percent. 
EXAMPLE 3 
Zinc-modified zeolite catalyst was prepared in accordance with the 
procedure of Example 1 by dissolving 74.4 g (0.25 mol) of 
Zn(NO.sub.3).sub.2 .multidot.6H.sub.2 O in water and diluting this 
solution to 2.5 L with additional water. 1 Kg of 25% S-115 catalyst 
formulated in a silica-alumina matrix was then added and the mixture 
heated and stirred for 2 hours at about 80.degree. C. The mixture was 
filtered and rinsed with four 2.5 L equivalents of water. The modified 
catalyst was dried overnight in a wide pan and calcined for four hours at 
500.degree. C. Significant zinc uptake on the catalyst, and a 
corresponding and desired decrease in acidic sites to minimal levels, was 
confirmed by acid leaching of the catalyst making the leachate basic and 
subsequent precipitation with hydrogen sulfide. Use of this zinc-modified 
zeolite catalyst in the pyridine-beta synthesis reaction described in 
Example 1 yielded product containing 34 weight percent pyridine, 14 weight 
percent beta-picoline and 1 weight percent of alpha-picoline compared to 
the total organic feed stream passed through the reactor. Use of this same 
catalyst in the alpha-gamma synthesis reaction also of Example 1 gave a 
product containing 16 weight percent alpha-picoline and 14 weight percent 
gamma-picoline with 3 weight percent pyridine. 
EXAMPLE 4 
Tin-modified zeolite catalyst was prepared in accordance with the procedure 
of Example 1 by dissolving 74.4 g (0.25 mol) of stannous chlor in a 
solution of 1.5 L water and 0.5 L concentrated nitric acid, and diluting 
this solution to 2.5 L with additional water. 1 Kg of 25% S-115 catalyst 
formulated in a silica-alumina matrix was then added and the mixture 
heated and stirred for two hours at about 80.degree. C. The mixture was 
filtered, rinsed with four 2.5 L equivalents of water. The modified 
catalyst was dried overnight in a wide pan and calcined for 4 hours at 
500.degree. C. Significant tin uptake on the catalyst, and a corresponding 
and desired decrease in acidic sites to minimal levels, was confirmed by 
fusing an amount of catalyst with KOH and then dissolving this in water 
and precipitating with sodium sulfide. Use of this tin-modified zeolite 
catalyst in the pyridine-beta synthesis reaction described in Example 1 
yielded product containing 34 weight percent pyridine, 14 weight percent 
beta-picoline and 1 weight percent of alpha-picoline compared to the total 
organic feed stream passed through the reactor. Use of this same catalyst 
in the alpha-gamma synthesis reaction also of Example 1 gave a product 
containing 23 weight percent alpha-picoline and 15 weight percent 
gamma-picoline with 2 weight percent pyridine. 
EXAMPLE 5 
Zinc-tungsten modified catalyst was prepared in accordance with the 
procedure of Example 1 by adding 1 Kg of 25% S-115 formulated in a 
silica-aluminum matrix to a 2.5 L aqueous solution which already contained 
74.4 g (0.25 mol.) Zn(NO.sub.3).sub.2 .multidot.6H.sub.2 O. The mixture 
was stirred for 2 hours at about 80.degree. C., and the catalyst filtered 
and rinsed with four 2.5 L amounts of water followed by drying for about 
18 hours at 120.degree. C. A second solution was then prepared by wetting 
62.5 g (0.25 mol ) of H.sub.2 WO.sub.4 with 40 mL of water. 400 mL of 
concentrated ammonium hydroxide was then added and the mixture stirred at 
about 50.degree. C. until the H.sub.2 WO.sub.4 dissolved. The solution was 
then diluted to 2.5 L with additional water. The dried zinc-modified 
zeolite catalyst was then added to this second solution and the mixture 
stirred for 2 hours at about 80.degree. C. The mixture was filtered and 
the catalyst was once again rinsed with four 2.5 L portions of water, 
dried overnight in a wide pan, and calcined for 4 hours at 500.degree. C. 
Confirmation of the significant tungsten uptake was once again made by the 
characteristic pale yellow appearance of the catalyst, and confirmation of 
zinc uptake was by acid leaching of the catalyst making the leachate basic 
and subsequent precipitation with hydrogen sulfide as in Example 3. 
Subsequent use of this zinc-tungsten modified catalyst in the 
pyridine-beta synthesis reaction of Example 1 gave a product containing 34 
weight percent pyridine and 16 weight percent beta-picoline with 1 weight 
percent alpha-picoline being present compared to the total organic feed 
stream passed through the reactor. These results, as with all the Examples 
above, were significant yields both of the overall reaction and of 
individual components which have established and valuable commercial uses 
around the world.