Preparation of furan

Catalytic vapor phase process wherein the feed stream comprising, on a molar basis, the sum of which is 100%, 10-32% of at least one linear unsaturated C.sub.4 -hydrocarbon selected from 1-butene, 2-butene and 1,3-butadiene, 10-25% oxygen, 3-30% water and 13-77% inert diluent, is contacted with a modified bismuth molybdenum oxide catalyst at 350.degree.-600.degree. C. at a pressure of at least 1 atmosphere (about 100 kPa) for 0.1-10 seconds, said catalyst being selected from: PA1 (a) BiMo.sub.a M.sub.b Q.sub.c R.sub.d O.sub.x wherein M is at least one element selected from In, Ce, Cr, Fe and Cu, Q is at least one element selected from V, P, Sb and Te, R is Na or Ag, a is 0.7-60.0, b is 0.1-33.0, c is 0-7.0, d is 0-1.5 and x is such a number as is necessary to satisfy the valences of the elements, with the proviso that a/1+b.gtoreq.0.5 and a/1+b+c.gtoreq.0.19 and the proviso that c>0 when d>0; and PA1 (b) BiMo.sub.a As.sub.b Z.sub.c O.sub.x wherein Z is at least one element selected from Na and Ca, a is 1.3-2.0, b is 0.1-0.3, c is 0.3-0.7 and x is such a number as is necessary to satisfy the valences of the elements, to produce an off-gas containing at least 1% furan.

DESCRIPTION 
TECHNICAL FIELD 
This invention relates to a vapor phase catalytic process for producing 
furan from a linear monoolefin or diolefin having four carbon atoms. 
BACKGROUND ART 
Processes for the vapor phase oxidation of diolefins to furan utilizing 
selected catalysts such as heterogeneous bismuth molybdates, manganese 
molybdates and tungstates and processes for the oxidative dehydrogenation 
of alkenes or alkadienes to furan with selected transition metal phosphate 
catalysts are well known in the art. Although such processes use low to 
high concentrations of hydrocarbon in the gaseous feed mixtures, 
generally, the hydrocarbon feed level is no greater than 5%, in which case 
the concentration of furan in the resultant off-gases is less than 1%. 
Because of the low concentrations of furan realized by such processes, 
isolation of the furan may be excessively costly and/or difficult due to 
process inefficiencies, such as inordinately high compressor demands, 
vapor entrainment and the like. 
Since the furan concentration index, a measure of the effectiveness of the 
process in producing furan, is the product of the concentration of C.sub.4 
-hydrocarbon in the feed mixture.times.C.sub.4 -hydrocarbon 
conversion.times.furan selectivity, it is imperative that these three 
variables be maximized for high furan production. The term "C.sub.4 
-hydrocarbon conversion" is defined, in %, as 100 times the number of 
moles of C.sub.4 -hydrocarbon converted to oxidation products other than 
butadiene divided by the number of moles of C.sub.4 -hydrocarbon in the 
initial feed mixture. The term "selectivity" is defined, in %, as 100 
times the number of moles of a specific oxidation product produced in the 
reaction and normalized to a C.sub.4 -base divided by the total number of 
moles of C.sub.4 -hydrocarbon converted to oxidation products other than 
butadiene. 
One method of obtaining a higher ultimate furan concentration is to 
increase the hydrocarbon feed concentration without incurring simultaneous 
decreases in hydrocarbon conversion and/or furan selectivity. In general, 
such an approach, using known bismuth molybdate catalysts and high 
concentrations of the unsaturated hydrocarbon, at conversion levels of 12% 
or greater, even in the presence of excess oxygen in the gas exit stream, 
results in marked decreases in furan selectivity and sharp increases in 
the production of carbon oxides and, ultimately, cracking products due to 
severe coking of the catalysts. 
The primary object of this invention, therefore, is to provide a catalytic 
process for the vapor phase oxidation of a diolefin to furan, which 
process uses high concentrations (at least 10%) of the hydrocarbon in the 
feed stream, without significant losses in hydrocarbon conversion or furan 
selectivity, and yields a furan concentration in the off-gases of at least 
1%. 
All percentages disclosed herein, unless otherwise specified, are mole 
percentages. 
DISCLOSURE OF INVENTION 
For further comprehension of the invention, and of the objects and 
advantages thereof, reference may be made to the following description and 
to the appended claims in which the various novel features of the 
invention are more particularly set forth. 
The invention resides in a process wherein a linear unsaturated C.sub.4 
-hydrocarbon (1-butene, 2-butene, 1,3-butadiene, or a mixture thereof) is 
reacted with oxygen, under carefully controlled concentrations and 
reaction conditions, over a selective, supported or unsupported, modified 
bismuth molybdate catalyst. The active and selective catalysts of the 
process of the invention are capable of producing furan at an off-gas 
concentration of greater than 1%, preferably at least 1.8%, without 
inducing cracking or coking, using a feed mixture containing 10-32% 
C.sub.4 -hydrocarbon and 10-25% oxygen. Since 1,3-butadiene is the C.sub.4 
-hydrocarbon which is directly oxidized to furan in the reaction, when the 
cheaper 1- and/or 2-butenes are employed as the feedstock, they undergo 
oxidative dehydrogenation to 1,3-butadiene in the initial step of the 
reaction. The bismuth molybdate species present in the catalyst of the 
process of this invention are capable of rapidly converting these linear 
C.sub.4 -alkenes into 1,3-butadiene prior to its oxidation to furan. 
More specifically, the invention resides in the catalytic vapor phase 
process wherein the feed stream comprising, on a molar basis, the sum of 
which is 100%, 10-32% of at least one linear unsaturated C.sub.4 
-hydrocarbon selected from 1-butene, 2-butene and 1,3-butadiene, 10-25% 
oxygen, 3-30% water and 13-77% inert diluent, is contacted with a modified 
bismuth molybdenum oxide catalyst at 350.degree.-600.degree. C. at a 
pressure of at least 1 atmosphere (about 100 kPa) for 0.1-10 seconds, said 
catalyst being selected from: 
(a) BiMo.sub.a M.sub.b Q.sub.c R.sub.d O.sub.x wherein M is at least one 
element selected from In, Ce, Cr, Fe and Cu, Q is at least one element 
selected from V, P, Sb and Te, R is Na or Ag, a is 0.7-60.0, b is 
0.1-39.8, c is 0-7.0, d is 0-1.5 and x is such a number as is necessary to 
satisfy the valences of the elements, with the proviso that 
a/1+b.gtoreq.0.5 and a/1+b+c.gtoreq.0.19 and the proviso that c&gt;0 when 
d&gt;0; and 
(b) BiMo.sub.a As.sub.b Z.sub.c O.sub.x wherein Z is at least one element 
selected from Na and Ca, a is 1.3-2.0, b is 0.1-0.3, c is 0.3-0.7 and x is 
such a number as is necessary to satisfy the valences of the elements, to 
produce an off-gas containing at least 1% furan. In preferred embodiments 
of the process, the feed stream comprises 25-29% C.sub.4 -hydrocarbon, 
14-20% oxygen, 13-20% water and 31-48% inert diluent, the temperature is 
450.degree.-550.degree. C., the pressure is 1-3 atmospheres (about 100-300 
kPa) and the catalyst is selected from BiMo.sub.3 InO.sub.x, BiMo.sub.1.5 
In.sub.0.5 P.sub.0.5 O.sub.x, BiMo.sub.1.56 In.sub.0.11 P.sub.0.11 
Ag.sub.0.11 O.sub.x, BiMo.sub.6.67 Ce.sub.0.67 O.sub.x, BiMo.sub.2.67 
In.sub.0.44 Cr.sub.0.44 P.sub.0.11 O.sub.x and BiMo.sub.1.7 As.sub.0.3 
Ca.sub.0.65 O.sub.x. It is to be understood that the formulas for these 
catalysts are written empirically so that one gram atom of bismuth is 
shown in each formula. Equivalent formulas can be written, wherein more or 
less than one gram atom of bismuth is shown, and wherein the order of 
recitation of the elements is varied. For example, BiMo.sub.1.7 As.sub.0.3 
Ca.sub.0.65 O.sub.x can be written, as in Example 26, as Ca.sub.3.25 
Bi.sub.5 As.sub.1.5 Mo.sub.8.5 O.sub.x. 
The catalysts for this oxidation process comprise mixed modified bismuth 
molybdenum oxides of Mo/Bi atom ratio of 0.67-60/1 plus modifying oxides 
of In, Ce, Cr, Fe, Cu, V, P, As, Sb, Te, Na, Ag and/or Ca in varying 
amounts depending upon the selection of modifiers introduced into the 
mixed bismuth molybdenum oxides. 
The catalyst used in the process of the invention can be prepared in either 
unsupported or supported form and, if supported, they can be prepared in a 
range of particle sizes for use either in fixed- or fluid bed type 
operations. Unsupported catalysts can be prepared by combining the 
appropriate metal salts and/or oxides in water, followed by evaporating to 
dryness with stirring and subsequently firing at the desired temperature, 
or they can be prepared from the appropriate oxides, carbonates and the 
like by use of standard solid state reaction techniques. 
If supported catalysts are desired, preformed supports such as silica, 
alumina, mixed silica-aluminas and silicon carbide can be impregnated with 
aqueous solutions and/or slurries of the desired compositions, followed by 
evaporation to dryness and subsequent calcination at the desired 
temperature. Silica at a concentration of about 50 weight % is a preferred 
support for the catalysts described herein, and the preferred method of 
incorporating this support into the catalysts is to mix a colloidal silica 
solution with aqueous solutions and/or slurries of the desired 
compositions, followed by either gelling these mixtures or concentrating 
them to low volume with stirring, using gentle heat (.about.100.degree. 
C.), removing the residual water at a temperature of about 100.degree. C., 
and then calcining for the desired time and temperature. If a fluid bed 
type catalyst is desired, the colloidal silica solution containing the 
requisite catalyst components and at the appropriate viscosity can be 
spray dried prior to the calcining step. 
If the catalyst compositions described herein lose activity during use 
through partial reduction or through carbonization, they can be 
regenerated by refiring in air at substantially the same temperature as 
that used in the initial calcination step. Calcination temperatures for 
these catalysts can vary from about 350.degree. to 800.degree. C. with the 
preferred temperature range being 500.degree.-600.degree. C. Calcination 
times can vary from 3 to 36 hours with the preferred time being about 6-18 
hours. 
To be an economically viable process, the concentration of furan in the 
off-gases must be at least 1%. Assuming optimum catalyst performance, 25% 
C.sub.4 -conversion and 40% furan selectivity, a minimum C.sub.4 
-hydrocarbon concentration of about 10% in the feed stream is necessary in 
order to obtain the 1% concentration of furan in the off-gases, that is, 
100(0.1.times.0.25.times.0.4)=1.0%. Depending upon the specific catalyst 
and feed mixture, an upper limit of 28-30% C.sub.4 -hydrocarbon feed 
concentration can be employed without inducing cracking. A hydrocarbon 
concentration higher than 32% should not be used. The optimum hydrocarbon 
concentration is 25-29%. 
The oxygen used in the reaction of the process of the invention can be 
introduced in the form of pure oxygen or as a mixture with gaseous inert 
diluents such as nitrogen, carbon dioxide, argon, helium and/or water. 
Generally, the gaseous inert diluent is nitrogen. The amount of oxygen in 
the feed stream is 10-25%, with about 14-20% being preferred. When air is 
used to provide the oxygen, some bottled (tonnage) oxygen can be employed 
in conjunction with air to obtain the requisite concentrations. As already 
indicated hereinabove, the inert diluent comprises 13-77%, preferably 
31-48%, of the feed stream. 
The presence of some water in the feed has been found to have a beneficial 
effect on the furan selectivity. It is postulated that this species tends 
to suppress carbonaceous build-up on the catalyst through removal by way 
of the water-gas reaction. The amount of water in the feed stream is 
3-30%, with 13-20% being preferred. 
The vapor phase oxidation of 1-butene, 2-butene, and/or 1,3-butadiene 
admixed with oxygen, water and inert gases to furan is carried out in a 
heated reactor containing the appropriate catalyst having a particle size 
sufficient to avoid the build-up of excessive back pressure. For a fixed 
bed process, catalyst particle size can vary from about 4 to 60 mesh (U.S. 
Sieve Series), with 10-20 mesh being preferred. 
Reaction temperatures can vary from about 350.degree. to 600.degree. C., 
with the preferred temperature range being about 450.degree.-550.degree. 
C., depending upon the catalyst activity. Reactor pressure can vary from 
atmospheric to superatmospheric, with 1-3 atmospheres (about 100-300 kPa) 
being preferred. Nominal contact times, that is, the time that the feed 
stream is in contact with the catalyst, as expressed by the ratio of bulk 
catalyst volume to gaseous feed volume passed over the catalyst per second 
(gas flows calculated at room temperature) can vary from about 0.1 to 10 
seconds, with about 0.25-1 second being preferred. 
Oxidation products normally produced in this reaction in addition to the 
desired furan comprise carbon dioxide, carbon monoxide, acrolein and 
lesser amounts of other species which can include, depending upon the 
specific catalyst employed, such compounds as ethylene, propylene, 
formaldehyde, maleic anhydride and/or monobasic acids such as acrylic 
acid. The amounts of feed gases employed and gaseous oxidation products 
produced in the reactions described herein were determined by means of 
standard gas chromatographic analysis. Acids produced were determined by 
titration of aqueous aliquots through which the reactor off-gases were 
bubbled. 
The following examples serve to illustrate specific embodiments of the 
invention. In these examples are described detailed typical procedures 
which are used to prepare some of the preferred catalysts and the 
performance of these catalysts under operating conditions, at atmospheric 
pressure (about 100 kPa), wherein furan is produced by way of the vapor 
phase oxidation of linear unsaturated C.sub.4 -hydrocarbons. In the 
disclosure of each example, only the concentration of C.sub.4 -hydrocarbon 
is given; the concentrations of the other components of the feed stream 
are within the ranges disclosed hereinabove.

EXAMPLE 1 
Silica Supported Catalyst--Gel Preparative Technique--1,3-Butadiene Feed 
A. Preparation of Catalyst BiIn Mo.sub.3 O.sub.x /SiO.sub.2 
To a stirred silica sol of 180 g of Ludox.RTM. LS (30% concentration of 
SiO.sub.2) was added in two simultaneous streams: (a) 35.59 g of 
(NH.sub.4).sub.6 Mo.sub.7 O.sub.24.4H.sub.2 O dissolved in 40 ml of 
H.sub.2 O and (b) 7.72 g of In metal and 14.04 g of Bi metal dissolved in 
HNO.sub.3 so as to have a final volume of about 70 ml. The resultant 
slurry was gelled by the addition of sufficient conc. NH.sub.4 OH so as to 
bring the final pH of the system to a value of about 5.8. The gel was 
dried for about 16 hrs at 120.degree. C. and then gently air fired to 
about 400.degree. C. so as to drive off the residual NH.sub.4 NO.sub.3 
present from the neutralization reaction. The resultant solids were 
screened to 10-20 mesh and after air firing for about 16 hours at 
550.degree. C. were ready for catalyst use. The surface area was about 53 
m.sup.2 /g. 
B. Oxidation of 1,3-Butadiene over BiInMo.sub.3 O.sub.x /SiO.sub.2 
A feed containing 29.9% 1,3-butadiene was passed over 3 cc of 10-18 mesh 
BiInMo.sub.3 O.sub.x /SiO.sub.2 catalyst in a fixed-bed reactor at a flow 
rate of about 500 cc/min at reaction temperatures of 470.degree., 
498.degree., and 506.degree. C. Conversion and selectivity data plus 
percent furan in the off-gases obtained in the resultant oxidations are 
listed in Table I. 
TABLE I 
______________________________________ 
% 
C.sub.4 Furan 
Temp. Conv. Selectivity (%) in Off- 
(.degree.C.) 
(%) Furan Acrolein 
CO.sub.2 
CO Other gases 
______________________________________ 
470 11 34 12 35 16 3 1.1 
498 19 28 12 33 22 5 1.6 
506 19 32 11 36 17 4 1.8 
______________________________________ 
C. Stability of BiInMo.sub.3 O.sub.x /SiO.sub.2 Catalyst with Use 
The BiInMo.sub.3 O.sub.x /SiO.sub.2 catalyst was tested over a six-day 
period for the generation of furan from feeds containing some 26.3-28.4% 
1,3-butadiene. After an initial decrease in activity, the production of 
furan was observed to level out during this test interval. Data are as 
follows in Table II. 
TABLE II 
______________________________________ 
Reaction Temperature (.degree.C.) 
.about.530.degree. 
.about.500.degree. % Furan 
Day of 
C.sub.4 Furan % Furan in 
C.sub.4 
Furan in Off- 
Test Conv. Select. Off-gases 
Conv. Select. 
gases 
______________________________________ 
1 21 31 1.7 23 30 1.8 
2 14 37 1.5 18 36 1.8 
3 -- -- -- 19 39 2.1 
4 12 39 1.2 17 37 1.7 
5 13 41 1.5 17 36 1.7 
6 -- -- -- 18 36 1.7 
______________________________________ 
EXAMPLE 2 
Silica Supported Catalyst--Gel Preparative Technique--1,3-Butadiene Feed 
A. Preparation of Catalyst AgInBi.sub.9 Mo.sub.14 PO.sub.x /SiO.sub.2 
To a stirred silica sol of 170 g of Ludox.RTM. LS was added a solution of 
1.52 g of (NH.sub.4).sub.2 HPO.sub.4 in 5 ml of H.sub.2 O. Two 
simultaneous streams of liquid were subsequently added that comprised: (a) 
28.41 g of (NH.sub.4).sub.6 Mo.sub.7 O.sub.24.4H.sub.2 O dissolved in 28 
ml of H.sub.2 O and (b) 1.32 g of In metal dissolved in HNO.sub.3 and then 
added to a solution of 1.95 g of AgNO.sub.3 and 50.17 g of 
Bi(NO.sub.3).sub.3.5H.sub.2 O in a mixture of 20 ml of H.sub.2 O and 8 ml 
of HNO.sub.3. The resultant slurry was gelled by the addition of 
sufficient conc. NH.sub.4 OH so as to bring the final pH of the system to 
a value of about 6.8. The gel was dried for about 16 hrs at 120.degree. C. 
and then gently air fired to decompose the residual NH.sub.4 NO.sub.3 
present from the neutralization reaction. The resultant solids were air 
fired for about 6 hrs at 600.degree. C. and, following sieving to 10-20 
mesh, were ready for catalyst use. 
B. Oxidation of 1,3-Butadiene over AgInBi.sub.9 Mo.sub.14 PO.sub.x 
/SiO.sub.2 
A feed containing 26.1% 1,3-butadiene was passed over 3 cc of 10-18 mesh 
AgInBi.sub.9 Mo.sub.14 PO.sub.x /SiO.sub.2 catalyst in a fixed-bed reactor 
at a flow rate of about 475 cc/min at reaction temperatures of about 
500.degree. and 530.degree. C. Conversion and selectivity data plus 
percent furan in the off-gases obtained in the resultant oxidations are 
listed in Table III. 
TABLE III 
______________________________________ 
% 
C.sub.4 Selectivity (%) Furan in 
Temp. Conv. Acro- Oth- Off- 
(.degree.C.) 
(%) Furan lein CO.sub.2 
CO er gases 
______________________________________ 
501 15 37 16 27 16 4 1.4 
530 21 36 14 28 18 4 2.0 
499 13 38 15 28 15 4 1.3 
______________________________________ 
EXAMPLE 3 
Unsupported Catalyst--Aqueous Slurry/Dry Preparative 
Technique--1,3-Butadiene Feed 
A. Preparation of Catalyst BiCe.sub.1.4 Mo.sub.16 O.sub.x 
A solution of 14.55 g of Bi(NO.sub.3).sub.3.5H.sub.2 O and 18.50 g of 
Ce(NO.sub.3).sub.3.6H.sub.2 O in 36 ml of H.sub.2 O and 3.6 ml of 
HNO.sub.3 was added with stirring to a solution of 85.75 g of 
(NH.sub.4).sub.6 Mo.sub.7 O.sub.24.4H.sub.2 O in 400 ml of H.sub.2 O that 
was heated on a steam bath. The resultant slurry was dried down on the 
steam bath; the residue was dried for about 16 hrs at 120.degree. C. and, 
after a gentle heating at about 300.degree. C. to decompose the nitrates 
present, was air fired for 6 hrs at 575.degree. C. Following coarse 
crushing and screening to 10-20 mesh, the catalyst was ready for use. Its 
surface area was about 3.6 m.sup.2 /g. 
B. Oxidation of 1,3-Butadiene over BiCe.sub.1.4 Mo.sub.16 O.sub.x 
A feed containing about 29%, 1,3-butadiene was passed over 3 cc of 10-18 
mesh BiCe.sub.1.4 Mo.sub.16 O.sub.x catalyst in a fixed bed reactor at a 
flow rate of about 500 cc/min at reaction temperatures of 475.degree., 
510.degree., and 530.degree. C. Conversion and selectivity data plus 
percent furan in the off-gases obtained in the resultant oxidations are 
listed in Table IV. 
TABLE IV 
______________________________________ 
% 
C.sub.4 Selectivity (%) Furan in 
Temp. Conv. Acro- Oth- Off- 
(.degree.C.) 
(%) Furan lein CO.sub.2 
CO er gases 
______________________________________ 
475 14 43 13 25 15 4 1.7 
510 18 38 13 25 19 5 2.0 
530 19 34 14 24 21 7 1.9 
______________________________________ 
EXAMPLE 4 
Unsupported Catalyst--Solid State Preparation 1,3-Butadiene Feed 
A. Preparation of Catalyst Ce.sub.8.53 Bi.sub.0.3 Fe.sub.0.1 TeMo.sub.12 
O.sub.x 
A mixture of 22.02 g of CeO.sub.2, 25.91 g of MoO.sub.3, 2.39 g of 
TeO.sub.2, 1.45 g of Bi.sub.2 O.sub.3, and 0.12 g of Fe.sub.2 O.sub.3 was 
wet-ground to a fine paste under acetone and then air dried. The resultant 
powder was prefired in air for one hour at 500.degree. C. and then 
reground and air dried as before. It was then air fired for 6 hrs at 
550.degree. C. The final product was reground again and then pelleted to 
10-20 mesh size for catalyst use. 
B. Oxidation of 1,3-Butadiene over Ce.sub.8.53 Bi.sub.0.3 Fe.sub.0.1 
TeMo.sub.12 O.sub.x 
A feed containing about 28.7% 1,3-butadiene was passed over 3 cc of 10-18 
mesh Ce.sub.8.53 Bi.sub.0.3 Fe.sub.0.1 TeMo.sub.12 O.sub.x catalyst in a 
fixed-bed reactor at a flow rate of about 500 cc/min. At a reaction 
temperature of 528.degree. C., a butadiene conversion of about 14% 
resulted in the generation of furan at a selectivity of about 30%, giving 
a concentration of about 1.2% furan in the resultant off-gases. 
EXAMPLE 5 
Gel Preparation--1,3-Butadiene/1-butene Feed 
A. Preparation of Catalyst Na.sub.2.1 Bi.sub.6.3 AsMo.sub.9.25 O.sub.x 
/SiO.sub.2 
To a stirred silica sol of 90 g of Ludox.RTM. LS was added a solution of 
1.6 g of (NH.sub.4)H.sub.2 AsO.sub.4 in 5 ml of H.sub.2 O followed by a 
solution of 2.5 g of Na.sub.2 MoO.sub.4.2H.sub.2 O in 10 ml of H.sub.2 O. 
Two simultaneous streams of liquid were then added that comprised: (a) 
30.6 g of Bi(NO.sub.3).sub.3.5H.sub.2 O dissolved in 16 ml of H.sub.2 O 
and 1.6 ml of HNO.sub.3 and (b) 14.03 g of (NH.sub.4).sub.6 Mo.sub.7 
O.sub.24.4H.sub.2 O dissolved in 18 ml of H.sub.2 O. The resultant slurry 
was gelled by the addition of 20 ml of conc. NH.sub.4 OH; the gel was then 
dried at about 120.degree. C. The resultant dried solids were calcined in 
air at 450.degree. C. for about 18 hrs and then for about 5 hrs at 
630.degree. C. Following sieving, the catalyst was ready for use. 
B. Oxidation of 1-Butene/1,3-Butadiene over Na.sub.2.1 Bi.sub.6.3 
AsMo.sub.9.25 O.sub.x /SiO.sub.2 
A feed containing about 3.8% 1-butene and 24.4% 1,3-butadiene was passed 
over 3 cc of 10-20 mesh Na.sub.2.1 Bi.sub.6.3 AsMo.sub.9.25 O.sub.x 
/SiO.sub.2 catalyst in a fixed-bed reactor at a flow rate of about 420 
cc/min at temperatures of 555.degree., 563.degree., and 570.degree. C. 
Conversion and selectivity data plus percent furan in the resultant 
off-gases are listed in Table V. 
TABLE V 
______________________________________ 
% 
C.sub.4 Selectivity (%) Furan in 
Temp. Conv. Acro- Oth- Off- 
(.degree.C.) 
(%) Furan lein CO.sub.2 
CO er gases 
______________________________________ 
555 11 42 12 27 18 1 1.3 
563 13 41 13 25 19 2 1.5 
570 14 41 13 25 20 1 1.6 
______________________________________ 
EXAMPLES 6-26 
Oxidation of Linear Unsaturated C.sub.4 -Hydrocarbons Employing Selective 
Catalysts 
In Table VI are listed additional catalysts which are within the scope of 
the process of the invention and which can be employed to bring about the 
preparation of furan via oxidation of linear unsaturated C.sub.4 
-hydrocarbons at high hydrocarbon feed mixture concentrations employing 
gas flow rates and catalyst volumes so as to give nominal contact times 
within the limits heretofore defined. These catalysts, either supported or 
unsupported, were prepared by the techniques described herein. As may be 
seen from the table the amounts of furan produced in the off-gases by the 
process of the invention are &gt;1%. In the table "BD" is 1,3-butadiene and 
"Bt" is 1-butene. 
TABLE VI 
__________________________________________________________________________ 
% C.sub.4 -- 
% 
% C.sub.4 -- 
Hydro- Furan 
Hydro- carbon 
Furan 
in 
Ex. carbon 
Temp 
Con- Selec. 
Off- 
No. 
Catalyst in Feed 
(.degree.C.) 
version 
(%) gases 
__________________________________________________________________________ 
6 Bi.sub.2.97 Fe.sub.0.91 Te.sub.0.09 Mo.sub.2 O.sub.x 
24.8 BD 
5.0 Bt 
493 17 27 1.4 
7 Bi.sub.3 FeMo.sub.2 O.sub.12 /SiO.sub.2 
30.1 BD 
502 19 23 1.3 
8 Bi.sub.2 FeSb.sub.3 Mo.sub.2 O.sub.x /SiO.sub.2 
26.9 BD 
531 13 38 1.3 
9 BiFe.sub.19.7 Mo.sub.29.5 O.sub.x /SiO.sub.2 
27.0 BD 
471 19 28 1.4 
501 20 27 1.4 
10 BiCr.sub.0.2 Mo.sub.1.2 O.sub.x /SiO.sub.2 
23.8 BD 
2.7 Bt 
529 15 37 1.5 
11 BiCr.sub.39.8 Mo.sub.59.3 O.sub.x /SiO.sub.2 
26.5 BD 
531 15 35 1.4 
12 Bi.sub.6 CrSbMo.sub.9 O.sub.x /SiO.sub.2 
26.9 BD 
501 15 36 1.5 
531 17 34 1.5 
13 Bi.sub.9 Cr.sub.8 PMo.sub.24 O.sub.x /SiO.sub.2 
26.2 BD 
501 21 26 1.4 
14 Bi.sub.9 Cr.sub.4 In.sub.4 PMo.sub.24 O.sub.x /SiO.sub.2 
26.2 BD 
470 17 35 1.6 
501 21 33 1.8 
531 22 32 1.8 
15 Bi.sub.9 Fe.sub.4 In.sub.4 VMo.sub.24 O.sub.x /SiO.sub.2 
26.2 BD 
501 24 20 1.3 
16 Bi.sub.9 Fe.sub.4 In.sub.4 PMo.sub.24 O.sub.x /SiO.sub.2 
26.2 BD 
501 21 25 1.4 
17 BiIn.sub.10 PMo.sub.15 O.sub.x /SiO.sub.2 
26.1 BD 
531 19 33 1.6 
18 BiInPMoO.sub.x /SiO.sub.2 
26.1 BD 
474 15 29 1.1 
507 21 31 1.7 
532 22 32 1.8 
19 BiCe.sub.1.5 CuVPMo.sub.16 O.sub.x 
28.2 BD 
470 22 26 1.6 
20 BiCe.sub.11 VTeMo.sub.18 O.sub.x /SiO.sub.2 
26.5 BD 
503 21 25 1.4 
21 BiCe.sub.0.67 Mo.sub.6.67 O.sub.x /SiO.sub.2 
26.7 BD 
472 20 27 1.4 
501 22 31 1.8 
22 BiCe.sub.1.5 Na.sub.0.3 P.sub.0.1 Mo.sub.5.25 O.sub.x /SiO.sub.2 
27.7 BD 
470 20 27 1.5 
499 21 28 1.6 
23 BiCe.sub.1.5 Na.sub.1.5 P.sub.0.5 Mo.sub.11.25 O.sub.x /- 
27.7 BD 
501 21 28 1.6 
SiO.sub.2 528 22 30 1.8 
24 BiCeNa.sub.0.3 P.sub.0.1 Te.sub.0.1 Mo.sub.4.1 O.sub.x /- 
26.9 BD 
502 21 30 1.7 
SiO.sub.2 
25 BiCe.sub.1.5 In.sub.1.25 P.sub.1.25 Mo.sub.3.75 O.sub.x /- 
26.9 BD 
499 20 25 1.3 
SiO.sub.2 
26 Ca.sub.3.25 Bi.sub.5 As.sub.1.5 Mo.sub.8.5 O.sub.x /SiO.sub.2 
23.1 BD 
3.0 Bt 
560 17 42 1.9 
__________________________________________________________________________ 
EXAMPLES 27-32 (CONTROL) 
Oxidation of Linear Unsaturated C.sub.4 -Hydrocarbons Employing Catalysts 
Known in the Art 
These examples, which lie outside the scope of the invention, demonstrate 
the optimum furan concentration in the off-gases produced with a series of 
catalysts prepared according to the art and tested under conditions 
comparable to those described in Examples 1-26. Data are listed in Table 
VII. Note that as the conversion of unsaturated C.sub.4 -hydrocarbons is 
increased while using unmodified bismuth molybdate catalysts, the furan 
selectivity decreases markedly. Other catalysts of the art (not containing 
bismuth) fail to produce furan at a level greater than 1% in the 
off-gases. In the table "BD" is 1,3-butadiene and "Bt" is 1-butene. 
TABLE VII 
______________________________________ 
% 
% C.sub.4 -- 
C.sub.4 -- Hydro- % 
Hydro- carbon Furan 
carbon Con- Furan in 
Ex. in Temp. ver- Select. 
Off- 
No. Catalyst Feed (.degree.C.) 
sion (%) gases 
______________________________________ 
27 Bi.sub.2 Mo.sub.2 O.sub.9 
27.4 BD 533 5 38 0.5 
28 Bi.sub.2 Mo.sub.2 O.sub.9 /SiO.sub.2 
24.0 BD 
4.9 Bt 465 10 30 0.9 
480 13 32 1.2 
500 21 16 1.0 
29 Bi.sub.2 Mo.sub.2 O.sub.9 /SiO.sub.2 
24.9 BD 
4.5 Bt 517 23 15 1.0 
30 MnMoO.sub.4 27.0 BD 471 15 10 0.4 
500 15 9 0.4 
31 Fe.sub.5.4 PO.sub.x 
27.0 BD 473 19 10 0.5 
503 17 9 0.4 
32 Co.sub.1.9 MoP.sub.1.4 O.sub.x 
27.0 BD 473 18 19 0.9 
503 24 9 0.6 
______________________________________