Hydrodehalogenation process using a catalyst containing nickel

Details Hydrodehalogenation process using a catalyst containing nickel Hydrodehalogenation process using a catalyst containing nickel

2000-10-12

2003-04-22

Silverman, Stanley S. (Department: 1754)

Chemistry of inorganic compounds

Modifying or removing component of normally gaseous mixture

Halogenous component

Reexamination Certificate

active

06551566

ABSTRACT:

TECHNICAL FIELD
This invention relates to hydrotreating processes and, in particular, to hydrodehalogenation processes and, more particularly, to hydrodehalogenation and deoxo processes.
BACKGROUND OF THE INVENTION
Catalytic processes are used to promote, as well as enhance, the efficiency of various industrial processes, such as synthesis, conversion and/or fluid treatment processes. But one common weakness that many of these catalytic processes suffer from is a near-zero tolerance of halogenated hydrocarbons (halohydrocarbons) or carbon oxides that may be present in a gaseous feedstock to some processes. Consequently, the presence of small amounts of halohydrocarbons or oxides can lead to substantially increased process operating costs by premature reduction in catalyst activity (i.e., catalyst poisoning). Catalyst poisoning reduces process efficacy and efficiency, as well as increases the catalyst systems' replacement frequency, which in turn, increase downtime and operating costs.
Some processes that have little to no tolerance to halohydrocarbons or oxides in the process feedstream include, without limitation, ammonia synthesis, hydrogenation (e.g., methyl acetylene and propadiene hydrogenation to propylene and propane), butadion (BDO) production, toluene diamine (TDA) production, hexamethyldiamine (HMDA) production, and hydrogen peroxide (H
2
O
2
) production. For example, halohydrocarbons often corrode equipment and/or poison catalysts, thereby reducing its catalytic activity. As another example, at low concentrations, sulfur, chlorine and halohydrocarbons can be poisons to catalysts used in the above-mentioned hydrogenation reaction and BDO, TDA, HMDA and H
2
O
2
production. Also, sulfur, chlorine, halohydrocarbons and oxygen can be poisons at low concentrations to ammonia synthesis catalysts.
Accordingly, there has been a continuing effort to reduce or eliminate halohydrocarbons, present in various chemical process feedstocks, by converting halohydrocarbons to compounds that can be removed by conventional means or that do not have a deleterious effect on the catalysts.
Also, certain halogenated hydrocarbons, often called halohydrocarbons, have wide-ranging applications including use in adhesives, aerosols, various solvents, pharmaceuticals, dry cleaning textile processing and as reaction media. However, many halohydrocarbons, particularly fluorohydrocarbons and chlorohydrocarbons, can be toxic to human health and the environment at relatively low concentrations. In view of this potential toxicity, the use and environmentally acceptable emissions of many halohydrocarbons is becoming more stringently regulated in Europe, the United States, Canada and many other industrially developed communities. Accordingly, there have also been efforts to reduce or eliminate the halohydrocarbons by catalytically converting halohydrocarbons to less toxic or nontoxic compounds that have a reduced risk to health and the environment.
For example, in U.S. Pat. No. 4,039,623, Lavanish et al. disclose a hydrated nickel (Ni) oxide catalyst for lowering the C
2
to C
4
halohydrocarbon content in an oxygen-containing gaseous stream, such as an air stream. Lavanish et al. require that their hydrodehalogenation process be conducted at a temperature in the range from 20° to 500° C. and with a stoichiometric amount of oxygen (O
2
) sufficient for converting the carbon content to carbon dioxide. As well, hydrated nickel oxides having Ni in a +2, +3 or +4 oxidation state must be used for catalyzing the Lavanish hydrodehalogenation reaction.
Also, U.S. Pat. No. 5,021,383 and U.S. Pat. No. 5,114,692, both by Berty, disclose catalytically converting halohydrocarbons to nontoxic products using a catalyst composition having both a metal based catalyst and an alkali or alkali-earth carbonate, preferably with the catalyst dispersed in the carbonate. Berty discloses metal catalysts comprising a metal such as manganese, copper, silver, iron or aluminum or a metal oxide, such as nickel oxides, cobalt oxide, aluminum oxide, vanadium oxide, tungsten oxide, molybdenum oxide or mixtures thereof. The carbonate is required in Berty's catalyst composition to react with hydrochloric acid (HCl) formed during the catalytic conversion process to prevent reformation of new halohydrocarbons. According to Berty, a carbonate, such as CaCO
3
, will react with HCl immediately, thereby preventing gaseous HCl from vaporizing and reoxidizing back to chlorine gas (Cl
2
), which can subsequently chlorinate another organic compound in the reaction feedstock. Thus, Berty believes a metal catalyst/carbonate composition is important to effectively hydrodehalogenating a feedstock.
As reported in the
Journal of Catalysis
, 74, 136-134 (1982), Weiss et al. studied hydrodechlorination and oligomerization of carbon tetrachloride (CCl
4
) using a nickel-based sodium Y zeolite (NiNaY) catalyst composition prereduced in a hydrogen (H
2
) atmosphere at 370° or 530° C. The reduced NiNaY catalyst was subsequently used to catalyze the reaction between H
2
and CCl
4
at 370° C. Weiss et al. observed that NiNaY catalyzed reaction of H
2
and CCl
4
produced small amounts of methane (CH
4
), ethane (C
2
H
6
), propane (C
3
H
8
) and butane (C
4
H
10
). To their surprise, however, they found that the NiNaY catalyst, most particularly a mixed nickel/cobalt (NiCo) Na Y zeolite, was most active and selective for producing predominantly 1,1,1,2-tetrachloroethane (Cl
3
CCH
2
Cl) per mole of CCl
4
(i.e., 0.4 mole of Cl
3
CCH
2
Cl per mole of CCl
4
at 80-100% conversion). And at lower CCl
4
conversions chloroform (CHCl
3
) and hexachloroethane (C
2
Cl
6
) were also primary reaction products as well as Cl
3
CCH
2
Cl.
Weiss et al. concluded further, from X-ray photoelectron diffraction measurements, that “in the case of the nickel-exchanged NaY catalyst, it is the nickel metal that is clearly the catalytic agent, the amount of Ni
0
being a function of reduction temperature.” Also, they hypothesized that “the zeolite environment is central to the tailoring of the reaction system [and] [n]ickel that has migrated out of the supercage behaves differently than Ni
0
inside the supercage.”Accordingly, Weiss et al. provided evidence that a Ni
0
supported on a NaY zeolite can contribute to a hydrodehalogenation reaction, but with Cl
3
CCH
2
Cl, CHCl
3
and C
2
Cl
6
being the primary reaction products, among other halohydrocarbons. Moreover, Weiss et al. showed that NiNaY catalyst could produce only minor amounts of fully hydrogenated products, such as CH
4
, C
2
H
6
, C
3
H
8
and C
4
H
10
, while predominantly producing halohydrocarbon products.
In U.S. Pat. No. 4,436,532, Yamaguchi et al. disclosed using a nickel-based, nickel/molybdenum-based (Ni/Mo) or cobalt/molybdenum-based (Co/Mo) catalyst in sulfided form to hydrodehalogenate gaseous feedstock, called pyrolysis gas, produced from pyrolyzing solid wastes at 550° C. or greater. The pyrolysis gas is composed primarily of H
2
, carbon monoxide (CO), carbon dioxide (CO
2
), CH
4
, C
2
and higher hydrocarbons, as well as smaller amounts of HCl, methyl chloride (CH
3
Cl) (i.e., about 1,000-1,500 ppm), ammonia (NH
3
), hydrogen sulfide (H
2
S), 100-1000 ppm of organosulfuric compounds, hydrogen cyanide (HCN) and trace amounts of other chlorohydrocarbons. Yamaguchi et al. observed that a non-sulfided hydrogenating catalyst would drive the methanation reaction (i.e., converting CO and CO
2
into CH
4
). They also observed that this methanation reaction was undesired because it would produce “troubles,” such as excessive temperature excursions due to high concentrations of CO and CO
2
, for the hydrodesulfurization (HDS) and hydrodehalogenation (HDH) reactions important to reducing the overall toxicity of the product stream. Accordingly, Yamaguchi et al. stressed the importance of using a Ni-, Ni/Mo- or Co/Mo-based catalyst in sulfided form to-concurrently promote both the HDS and HDH reactions, while at the same time suppressing the undesired methanation reaction

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