Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Silicon containing or process of making
Reexamination Certificate
2000-02-11
2001-09-18
Oswecki, Jane C. (Department: 1626)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Silicon containing or process of making
C502S324000, C558S274000
Reexamination Certificate
active
06291392
ABSTRACT:
The present invention relates to platinum metal-containing mixed oxide catalysts which have been prepared in a sol-gel process and their use in a process for preparing diaryl carbonates by reacting aromatic hydroxy compounds with carbon monoxide and oxygen.
It is known that organic carbonates can be prepared by oxidative reaction of aromatic hydroxy compounds with carbon monoxide in the presence of a noble metal catalyst (DE-OS 28 15 512). Palladium is preferably used as the noble metal. In addition a co-catalyst (e.g. manganese or cobalt salts), a base, a quaternary salt, a variety of quinones or hydroquinones and a drying agent may also be used. The procedure may be performed in a solvent, preferably in methylene chloride.
In order to perform this process in an economic manner, effective recovery of the noble metal catalyst is a critical factor, in addition to the activity and selectivity of the catalyst. On the one hand the noble metal catalyst represents a large cost factor. Losses of noble metal catalyst have to be replaced at great cost. On the other hand no residues of the noble metal catalyst should remain in the product. The economic and efficient recovery of homogeneous catalysts for the process of oxidative carbonylation of aromatic hydroxy compounds to give diaryl carbonates has not hitherto been described. The separation of a noble metal catalyst from a liquid reaction mixture, e.g. by filtering or centrifuging, can be performed at low cost if heterogeneous supported catalysts are used.
In EP-A 572 980, EP-A 503 581 and EP-A 614 876 noble metal supported catalysts are used which contain 5% palladium on carbon supports. However, these types of supported catalysts produce only very unsatisfactory conversions or even none at all, so that these are also unsuitable for an economically viable process.
JP-A 01/165 551 (cited in accordance with C.A. 112:76618j (1990)) describes using palladium or palladium compounds such as palladium acetylacetonate, in combination with alkali metal or alkaline earth metal iodides or ‘onium’ iodides, such as tetrabutylammonium iodide, and at least one zeolite to prepare aromatic carbonates.
JP-A 04/257 546 and JP-A 04/261 142 each describe an example of a supported catalyst for preparing aromatic carbonates in which silicon carbide granules are used as the support material for a supported catalyst in a distillation column. Although drastic conditions (high pressure, high temperature) are used in the relevant examples, these catalysts produce only very low space-time yields. These low space-time yields make the economic production of aromatic carbonates with this type of supported catalyst impossible.
EP-A 736 324 describes the preparation of diaryl carbonates with heterogeneous catalysts which contain a platinum metal, preferably palladium, and a co-catalytic metal compound, preferably a metal from the group Mn, Cu, Co, Ce and Mo. When preparing the catalysts the co-catalytic metals are applied to a support.
EP-A 736 325 describes the preparation of diaryl carbonates with heterogeneous catalysts which contain a platinum metal, preferably palladium, on a support which consists of a metal oxide in which the metal may exist in several valency states.
Although these supported catalysts enable the preparation of aromatic carbonates for the first time, a further increase in activity is desirable from an economic point of view.
It has now been found that higher catalyst activities can be obtained if mixed oxides e.g. of V, Mn, Ti, Cu, La, the rare-earth metals and mixtures thereof which have been prepared in a sol-gel process and which contain platinum metals are used a catalysts.
The invention provides catalysts which contain
(i) an oxide of the elements silicon, aluminium, titanium, zirconium or a mixture of oxides of these elements,
(ii) one or more co-catalytic metal oxides from groups 4, 5, 6, 7, 11, 12, 13, 14, the iron group (atomic numbers 26 to 28) or the rare-earth metals (atomic numbers 58 to 71) in the periodic system of the elements in accordance with the new IUPAC nomenclature, and
(iii) one or more platinum metals or one or more compounds of platinum metals (atomic numbers 44 to 46 and 77 and 78) in an amount 0.01 to 15 wt. %, calculated as platinum metal and with respect to the total weight of catalyst,
which are obtained by preparing a gel from one or more suitable precursor(s) of the components mentioned under (i) and (ii) and the platinum metal component (iii), ageing, drying and optionally annealing the gel.
The gel according to the invention can be prepared by almost any known method. Methods which are known for preparing mixed oxides based on a gel are preferably used. This includes, for example, the hydrolysis of one or more metal alkoxides and/or hydrolysable metal compounds under acid, neutral or basic conditions in suitable solvents at temperatures of 0° C. to 200° C. In this case mixtures of different precursors of one or more elements may also be used.
Suitable precursors of silicon dioxide are alkoxides of silicon such as, for example, tetraethoxysilane, tetramethoxysilane.
Suitable precursors of aluminium oxide are lower alkoxides such as trimethoxyaluminium, triethoxyaluminium, tri-n-propoxyaluminium, tri-iso-propoxyaluminium, tri-sec-butoxyaluminium, tri-sec-butoxyaluminium, or tri-tert-butoxyaluminium or aluminium alkoxides with chelating ligands such as dibutoxyaluminium-ethylacetoacetate.
Suitable precursors of titanium oxide are tetramethoxytitanium, tetraethoxytitanium, tetraisopropoxytitanium; suitable precursors of zirconium oxide are tetraethoxyzirconium, tetra-tert-butoxyzirconium, tetra-n-butoxyzirconium, tetra-iso-propoxyzirconium. Suitable hydrolysable salts are for example titanium tetrachloride, organic salts such as aluminium acetylacetonate, zirconium acetylacetonate or the corresponding mixed metal compounds and salts.
Suitable solvents are, for example, monohydric alcohols such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, 2-butanol, t-butanol, polyhydric alcohols such as glycol, 1,2-propanediol, 1,3-propanediol, monofunctional or polyfunctional ketones such as acetone, 1,3-pentanedione(acetylacetone), cyclic or linear ethers with one to three oxygen atoms such as tetrahydrofuran, dioxan, diethyl ether, glycoldiethyl ether or diethyleneglycoldiethyl ether, ether-alcohols such as glycolmonomethyl ether, nitriles such as acetonitrile and benzonitrile and amides such as dimethylformamide. Alcohols, diketones and ether-alcohols are preferred. Obviously mixtures of solvents may also be used.
The solvents are used in amounts such that the molar ratio of alkoxide to solvent is 1:0.2 to 1:100.
Partially alkylated precursors R
1
x
M(OR
2
)
y
may also be used in the process according to the invention, wherein M represents one of the elements mentioned under (i), (x+y) is the valency of the element and R
1
and R
2
, independently of each other, represent alkyl, aralkyl or aryl groups with 1 to 20 carbon atoms. The following may be mentioned by way of example: methyltriethoxysilane, ethyltriethoxysilane.
Co-catalytic compounds which may be mentioned are one or more compounds of elements from the groups 4, 5, 6, 7, 11, 12, 13, 14, the iron group (atomic numbers 26 to 28) or the rare-earth metals (atomic numbers 58 to 71) in the periodic system of elements (IUPAC, new) with a total molar proportion of the components mentioned under (ii) of 0.1% to 99.9%, preferably 0.1% to 40%, in particular 0.5% to 20%, with respect to the total number of moles of the components mentioned under (i) and (ii), introduced into the catalyst, preferably Mn, Cu, Co, V, Nb, W, Zn, Ce, Mo, in particular Mn, Co, Cu, Mo, Ce, quite specifically Mn and/or Ce.
Suitable precursors of the co-catalytic metals are basically known, and the following may be used for example: inorganic salts such as halides, oxides, nitrates, sulphates, carboxylates, salts of monofunctional or polyfunctional organic C
2
to C
15
carboxylic acids such as acetates, cyclohexane butyrates, diketonates such as acetylacetonate, ethyl hexanoate, a
Hesse Carsten
Notheis Ulrich
Rechner Johann
Bayer Aktiengesellschaft
Franks James R.
Gil Joseph C.
Oswecki Jane C.
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