1. Field of the Invention
The invention relates to the oxidation and ammoxidation of methanol or formaldehyde to hydrogen cyanide or methanol to formaldehyde.
2. Description of the Prior Art
Hydrogen cyanide is a basic chemical building block for many chemical processes. Hydrogen cyanide has been mainly produced by the ammoxidation of methane (Andrussow process) and is also obtained as a by-product in the preparation of acrylonitrile by the ammoxidation of propylene. Because hydrogen cyanide is poisonous, shipment of large amounts of hydrogen cyanide has been avoided. Usually hydrogen cyanide is produced and consumed at the same location.
Frequently, hydrogen cyanide-consuming facilities were developed next to facilities that produced hydrogen cyanide, e.g., acrylonitrile units. Recnt improvements in the catalyst for acrylonitrile production have resulted in increased yields of acrylonitrile at the expense of reduced yields of hydrogen cyanide. Accordingly, there has been quite a demand for better methods of making hydrogen cyanide from inexpensive, easily transportable, starting materials such as methanol or formaldehyde.
In Japanese Kokai No. 51 1976-10200, a metal oxide catalyst, for the ammoxidation of methanol to HCN, consisting of antimony and at least one of iron, cobalt, nickel, manganese, zinc, and uranium, with an atomic ratio of antimony to additional elements varying from 1:10 to 10:1 is disclosed. This catalyst can be used with or without a support, but a silica support is preferred.
Japanese Kokai No. 54 1979-126698 discloses a catalyst for ammoxidation of methanol of HCN, which catalyst is supported on 30 to 70 weight percent silica and has the following empirical formula: EQU A.sub.a MoBi.sub.b Fe.sub.f Na.sub.n P.sub.p O.sub.q
where A is potassium, rubidium, cesium, molybdenum, bismuth, iron, sodium, phosphorus, and oxygen and the subscripts represent the number of atoms of each component.
U.S. Pat. No. 3,911,089, the teachings of which are incorporated by reference, discloses a process for preparing hydrogen cyanide from methanol or formaldehyde using a catalyst primarily containing molybdenum and bismuth oxide. In its broadest teaching, there is disclosed catalyst whose active components correspond to the formula Mo.sub.a Bi.sub.b Fe.sub.c X.sub.d Y.sub.e Z.sub.f O.sub.g wherein X is Cr, Mn, Co, Ni, Zn, Cd, Sn, W or Pb. Y is one or more of Pi and elements of Group 1A or 2A in the Periodic Table. Z is one or more of P, As, and Sb. The catalyst can be used alone, or is preferably incorporated on a suitable carrier such as silica, alumina, diatomaceous earth, silicon carbide or titanium oxide.
The catalysts disclosed in the examples of this patent usually contain three to six active elements, not counting the support and oxygen. One of the catalysts disclosed contained small amounts of manganese and phosphorus, in addition to the molybdenum and bismuth which are the primary catalytic components. This catalyst is shown in Example 16, Table 3 and has the following composition: EQU Mo.sub.12 Bi.sub.1 P.sub.0.008 Fe.sub.2 Ni.sub.7 Mn.sub.2 Tl.sub.0.530.5 15Si.sub.2
When this catalyst was tested by the patentee for conversion of methanol into hydrogen cyanide, it was not especially active. It gave a 65% yield of hydrogen cyanide. Practically every other catalyst in Table 3 (a total of 21 catalysts) gave better yields, only three gave worse yields.
I wanted to develop an active catalyst system for use in the ammoxidation of methanol to hydrogen cyanide which would not require complicated catalyst manufacturing procedures and which would also give yields as good as or better than the more complicated prior art catalysts.
I discovered that a very simple catalyst system was effective for the ammoxidation of methanol to hydrogen cyanide, as long as the ratio of active catalytic elements was carefully maintained.