Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2001-10-30
2003-01-28
Richter, Johann (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C502S305000, C502S311000, C502S312000, C502S321000
Reexamination Certificate
active
06512141
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for preparing a metal oxide catalyst for producing acrylic acid by gas phase catalytic oxidation of propane and a process for producing acrylic acid using the catalyst.
BACKGROUND OF THE INVENTION
Acrylic acid has been produced by a two-stage process comprising catalytic oxidation of propylene with oxygen to once prepare acrolein, which is then catalytically oxidized with oxygen. A one-stage process for acrylic acid synthesis comprising oxidation of propane has been studied as a promising process that would greatly reduce the production cost compared with the two-stage process.
For example, JP-A-9-316023 proposes a four-component metal oxide catalyst for the one-stage process, which is composed of Mo, V, Sb, and a metal selected from Nb, Ta, W, Ti, Cr, Fe, etc. A four-component metal oxide catalyst comprising similar metals is also described in JP-A-10-45664.
JP-A-10-120617 discloses a metal oxide catalyst superior to the above-described four-component systems in conversion and selectivity in the acrylic acid synthesis, which is composed basically of five components including the four components according to JP-A-10-316023 supra which are impregnated with a solution containing an additional component selected from As, P or an alkali metal. According to the disclosure, one-stage oxidation of propane in the presence of the five-component metal oxide catalyst achieves an acrylic acid yield of about 20 to 25%.
JP-A-10-28862 proposes a metal oxide catalyst, which is designed chiefly for catalytic oxidation reaction between alkane and ammonia to synthesize nitrile. This catalyst comprises the four-component metal oxide system of JP-A-10-45664 supra which further has supported thereon at least one element selected from Mo, W, Zr, Cr, Ti, Nb, Ta, Fe, P, Si, an alkali metal, an alkaline earth metal, etc.
SUMMARY OF THE INVENTION
The present invention provides a process for preparing a metal oxide catalyst for acrylic acid production which comprises calcining a metal compound mixture at 400° C. or higher to prepare a metal oxide powder comprising Mo, V, Sb and at least one element selected from the group consisting of Nb and Ta, and supporting a compound comprising at least one element selected from the group consisting of Sb, Tl, Se, As, Pb, Sn, Ag, Cu, Ru and Rh on the metal oxide powder; and a process for producing acrylic acid using the catalyst.
The present invention also provides a process for preparing a metal oxide catalyst for acrylic acid production which comprises calcining a metal compound mixture at 400° C. or higher to prepare a metal oxide powder comprising Mo, V, Sb, at least one element selected from the group consisting of Nb and Ta, and at least one element selected from the group consisting of Ag, Zn, Sn, Pb, As, Cu, Ti and Se, and supporting a compound comprising at least one element selected from the group consisting of Sb, Ti, Se, As, Pb, Sn, Ag, Cu, Ru and Rh, Na, and K on the metal oxide powder; and a process for producing acrylic acid using the catalyst.
According to the present invention, a catalyst for producing acrylic acid by gas phase oxidation of propane in a high yield is provided.
DETAILED DESCRIPTION OF THE INVENTION
The metal oxide on which a compound comprising at least one element selected from the group consisting of Sb, Ti, Se, As, Pb, Sn, Ag, Cu, Ru and Rh (hereinafter referred to as element X) is to be supported is a metal oxide composed of Mo, V, Sb, at least one of Nb and Ta (hereinafter referred to as element A), and oxygen (hereinafter referred to as “metal oxide (a)”). The metal oxide on which a compound comprising at least one element selected from the group consisting of the element X, Na, and K is to be supported is a metal oxide composed of Mo, V, Sb, A, at least one element selected from the group consisting of Ag, Zn, Sn, Pb, As, Cu, Tl, and Se (hereinafter referred to as element B), and oxygen (hereinafter referred to as metal oxide (ab)).
The metal oxide (a) is preferably prepared by a process comprising a first step in which a pentavalent vanadium compound (e.g., ammonium metavanadate or vanadium pentoxide) and a trivalent antimony compound (e.g., antimony trioxide or antimony acetate) are allowed to react at 70° C. or higher in an aqueous medium in the presence of a hexavalent molybdenum compound (e.g., ammonium molybdate, molybdenum oxide or molybdic acid), a second step in which the resulting reaction product is uniformly mixed with a compound comprising the element A (hereinafter “metal A compound”), and a third step in which the resulting mixture is calcined.
The calcining temperature should be higher than 400° C. For example, calcination usually completes at 450 to 700° C. for 1 to 3 hours.
The metal A compound includes niobium oxide, niobic acid, tantalum oxide, and tantalic acid.
The metal oxide (a), when represented by a compositional formula:
MoV
g
Sb
h
A
i
(1)
preferably has such an atomic ratio that g and h are each 0.01 to 1.5 at h/g=0.3 to 1; and i is 0.01 to 3.0. If h/g is smaller than 0.3, the selectivity to acrylic acid is low. If i is smaller than 0.001, the catalyst is prone to deterioration. If i exceeds 3.0, the catalyst has low activity, resulting in a low conversion of propane.
The metal oxide (ab) can be obtained in the same manner as for the metal oxide (a), except that a compound containing the element B (hereinafter “metal B compound”) is used in combination with the hexavalent molybdenum compound in the first step or that the metal B compound is added together with the metal A compound in the second step.
The metal B compound includes silver compounds, such as silver nitrate, silver acetate and silver carbonate; zinc compounds, such as zinc nitrate and zinc oxide; tin compounds, such as stannous chloride and stannic chloride; lead compounds, such as lead acetate and lead chloride; arsenic compounds, such as arsenic trioxide and arsenic oxide; copper compounds, such as copper nitrate, cupric oxide and cuprous oxide; thallium compounds, such as thallous nitrate and thallic nitrate; and selenium compounds, such as selenic acid, selenious acid, and selenic chloride.
The metal oxide (ab), when represented by a compositional formula:
MoV
g
Sb
h
A
i
B
j
(2)
preferably has such an atomic ratio that g and h are each 0.01 to 1.5 at h/g=0.3 to 1; i is 0.001 to 3.0; and j is 0.0001 to 0.05. If h/g is less than 0.3, the selectivity to acrylic acid is low. If i is smaller than 0.001, the catalyst is apt to deteriorate. If i exceeds 3.0, the catalyst has low activity, and the propane conversion is poor. If j is smaller than 0.0001, the effect of addition of the element B is insubstantial. If j is greater than 0.05, the yield of acrylic acid is reduced.
In the preparation of the metal oxide (a) or the metal oxide (ab), the reaction of the first step is preferably carried out at around the boiling point of the aqueous medium for 10 to 30 hours.
In order to accelerate the redox reaction among Sb
+3
, V
+5
and Mo
+6
in the first step, it is a preferred embodiment that oxygen gas is blown into the reaction system, or hydrogen peroxide is dropped in the reaction system after the redox reaction has proceeded to some extent.
Oxygen-containing gas, such as air, can be used in place of oxygen gas. A preferred oxygen concentration in the oxygen-containing gas is at least 0.5% by volume, particularly 1 to 20% by volume, especially 2 to 15% by volume. Introduction of oxygen-containing gas is preferably continued for 4 hours or longer.
In dropping hydrogen peroxide, aqueous hydrogen peroxide having a concentration of 0.01 to 35% by weight is preferred. Hydrogen peroxide is preferably added in an amount of 0.2 to 1.2 mol per mole of Sb. The reaction mixture to which hydrogen peroxide is added is preferably kept at 80 to 100° C. Dropwise addition of hydrogen peroxide may be completed in a short period of time or over a long period of time.
In the second step, the metal A compound (i.e., an Nb compound and/or a Ta compound
Niizuma Hiroshi
Takahashi Mamoru
Tu Xinlin
Forohar Farhad
Richter Johann
Sughrue & Mion, PLLC
Toagosei Co. Ltd.
LandOfFree
Process for preparing metal oxide catalyst for acrylic acid... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for preparing metal oxide catalyst for acrylic acid..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for preparing metal oxide catalyst for acrylic acid... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3026266