Preparation of methylamines using shape selective chabazites

FIELD OF THE INVENTION
This invention relates to processes for the preparation of methylamines from methanol or dimethylether and ammonia using microporous compositions as catalyst.
BACKGROUND OF THE INVENTION
The reaction of methanol and ammonia to produce methylamines, comprising a mixture of mono-, di- and trimethylamine, is a well known reaction. The reaction product is an equilibrium mixture with about 35 wt % of the reaction product consisting of monomethylamine (MMA), 27 wt % dimethylamine (DMA), and 38 wt % trimethylamine (TMA) produced at a temperature of 350.degree. C., 1 atmosphere pressure and an ammonia to methanol ratio (N/R) of 3.5. Substantial process efforts have been made for the development of processes which would alter the product slate resulting from the reaction of methanol and ammonia. Process variables influencing product slate, although limited, include space time, ammonia to methanol molar ratio and temperature. Product slate modifications primarily have been made via shape selective catalysts such as zeolites.
Representative patents which illustrate various processes for the production of a methylamine reaction product having non equilibrium levels of MMA, DMA and TMA by the reaction of methanol and ammonia are as follows:
U.S. Pat. No. 4,485,261 discloses a process for the preparation of a methylamine reaction product rich in DMA and lean in TMA which comprises introducing a mixture of methylamines and ammonia to a porous; solid acid catalyst comprising silica, alumina, Y and X type zeolites, thereby forming a first reaction product and then subjecting at least a part of the reaction product to a catalytic reforming reaction in the presence of ammonia and a crystalline alumino-silicate having a pore size of 3 to 8 .ANG.. A variety of catalysts having a pore size of 3 to 8 .ANG. is set forth, and these catalysts include clinoptilolite, erionite, mordenite, chabazite and various synthetic zeolites. U.S. Pat. No. 4,205,012 discloses a process for producing amines by the reaction of an alkanol with ammonia, e.g., the manufacture of methylamines by the reaction of methanol and ammonia in the presence of an FU-1 zeolite, said FU-1 zeolite having essentially all of the sodium cations replaced by bivalent or trivalent cations.
U.S. Pat. No. 4,602,112 discloses a process for producing DMA in high selectivity by the reaction of methanol or dimethylether and ammonia in the presence of an acidic H-ZSM-5 zeolite catalyst.
U.S. Pat. No. 3,384,667 discloses the alkylation of ammonia in the presence of a dehydrated naturally occurring crystalline alumino-silicate catalyst having pores of a diameter permitting absorption of primary and secondary, but not tertiary, amine products. Examples of natural zeolites include ferrierites, chabazite, erionite and mordenite.
U.S. Pat. No. 4,737,592 discloses a process for producing a reaction product rich in DMA by reacting methanol and/or dimethylether and ammonia in the presence of an acidic zeolite catalyst selected from the group consisting of natural, H-exchanged and M-exchanged chabazites, each having a geometric selectivity index (GSI) greater than about 3. Alkali metal ions suited for exchange include sodium, potassium, rubidium and cesium.
U.S. Pat. Nos. 4,458,092; 4,398,041 and 4,434,300 disclose processes for producing methylamine by carrying out the reaction utilizing zeolite type catalysts. The '092 patent discloses the use of a highly acidic dehydrated alumino-silicate catalyst exchanged with a rare earth or hydrogen metal ion exchanged Y-zeolite. The '300 patent discloses the preparation of the amines using macroporous H-chabazite-erionite as the preferred amination catalyst. Anaconda chabazite-erionite was used as a specific catalyst and that catalyst system achieved high methanol conversion rates with minimal TMA production.
U.S. Pat. Nos. 4,254,061 and 4,313,003 disclose the production of a methylamine rich in MMA ('061) and DMA ('003). The '061 patent discloses the reaction of methanol and ammonia in the presence of mordenite, erionite, clinoptilolite, etc. to produce MMA, while the '003 discloses the reaction of MMA and ammonia in the presence of the '061 patent catalysts to produce a reaction product rich in DMA.
U.S. Pat. No. 4,082,805 discloses the production of amines by the reaction of C.sub.1 to C.sub.5 alcohols or ethers with ammonia in the presence of a crystalline alumino-silicate having the structure ZSM-5, ZSM-11 or ZSM-21.
SUMMARY OF THE INVENTION
This invention relates to an improved process for the production of a methylamine reaction product having nonequilibrium levels of TMA. One of the basic processes for producing a methylamine reaction product with excellent conversion of methanol/dimethylether and reduced trimethylamine content comprises reacting methanol/dimethylether with ammonia, monoethylamine, dimethylamine and trimethylamine in the presence of a zeolitic catalyst. Alternatively, another process for producing a methylamine-rich reaction product relies on reforming a monomethylamine containing feedstock over a catalyst. One part of the improvement in the basic process resides in producing a reaction product with reduced levels of trimethylamine and excellent conversion of methanol/dimethylether resides in the utilization of a zeolite catalyst consisting essentially of a zeolite, preferably a chabazite, having a shape selectivity index (SSI) of above about 5, a GSI of less than 3 and a 1-propanol sorption value of greater than 0.5 mmol/g. The shape selective zeolites or synthetic chabazites typically are exchanged with alkali metal ions such as sodium, potassium, rubidium and cesium. A second part of the improvement in the basic process resides in passing a feedstock comprising monomethylamine over such catalyst thereby reforming such monomethylamine to a product slate rich in dimethylamine.
There are several significant advantages which can be achieved through the utilization of the zeolites and synthetic chabazites having an SSI index and propanol sorption value as stated and these advantages include:
an ability to produce a reaction product rich in mono and dimethylamine with reduced levels of trimethylamine;
an ability to produce methylamines via the amination of methanol with excellent rates of reaction;
an ability to produce a reaction product comprising methylamines with excellent methanol conversions;
an ability to produce a reaction product having nonequilibrium levels of mono, di and TMA distribution;
an ability to operate a methanol amination process over a substantial length of time without catalyst deactivation;
an ability to operate over an extended period of time; and ability to recycle a monomethylamine containing feedstock over the catalyst to obtain a nonequilibrum product slate.

DRAWINGS
FIG. 1 is a plot showing the correlation between SSI and GSI for a large number of chabazite catalysts, including calcined and uncalcined catalysts.
FIG. 2 is a plot showing the relationship of shape selectivity index (SSI) on the TMA selectivity for both calcined and uncalcined chabazite catalysts.
FIG. 3 is a plot of geometric selectivity index (GSI) vis-a-vis the TMA selectivity for synthetic chabazite catalysts as compared to natural chabazite catalysts.

DETAILED DESCRIPTION OF THE INVENTION
One of the basic routes for producing alkylamines is through the amination of alkanols and alkylethers. The route for producing methylamines generally involves the reaction of methanol (MeOH) and/or dimethylether (DME) with ammonia, monomethylamine (MMA), dimethylamine (DMA) or trimethylamine (TMA), depending on available feeds and desired product slate, under conditions sufficient to effect amination. Typically, the nitrogen/carbon (N/R) molar ratio will range from about 0.2 to about 10, preferably 1 to 5, with reaction temperatures ranging from about 225.degree. C. to 450.degree. C. (preferably 250.degree. C. to 375.degree. C.). Reaction pressures may vary, but typically range from 50 to 1000 psig, preferably 150 to 500 psig, at total feed space velocities of from about 200 to 8000 hr.sup.-1, preferably 500 to 5000 hr.sup.-1. The term "space velocity" or GHSV, is defined as the ratio of the feed rate in cm.sup.3 gas at STP/hr to the catalyst bed volume in cm.sup.3.
The resulting conversion of methanol and/or DME to methylamines generally will range from about 50% to 100% (on a molar basis of methanol) with total selectivity to methyl amines greater than 95 wt % and low TMA being 20 wt % or less, and generally less than 15 wt %. Typically, the weight percentage of MMA in the reaction product will range from 36 to 50 wt %, and the percentage of DMA in the reaction product will range from 25 to 60 wt %.
Another feedstock suited for the practice of the process is one containing monomethylamine. The monomethylamine is reformed over the catalyst to a product slate rich in dimethylamine. Optionally, ammonia and other components, e.g., trimethylamine can be present in the feedstock. But no significant advantages are seen in the product slate when trimethylamine is incorporated into the feedstock.
The key to the amination process for producing high conversion and excellent reaction rates with low TMA production resides in the use of a catalyst system comprising a microporous catalyst having a geometric selectivity index (GSI) less than 3, a shape selectivity index (SSI) greater than about 5 and which sorbs at least about 0.5 mmol 1-PrOH per gram catalyst (3 wt % 1-PrOH). The preferred catalyst system is one consisting of a synthetic chabazite having an SSI of about 7 to 25. The term "shape selectivity index" (SSI) is defined by the formula:
SSI=Quantity of 1-PrOH sorbed divided by the quantity of 2-PrOH sorbed by the catalyst at 20.degree. C. over a 24 hour period and the relative pressure P/Po is 0.5. The sorption is expressed in wt %, i.e., grams sorbate per 100 grams of zeolite catalyst.
Many of the prior art processes that carried out methanol amination in the presence of chabazite catalyst systems are generated from naturally occurring chabazites. The key to the success of natural chabazites resided in a geometric selectivity index (GSI) as noted in U.S. Pat. No. 4,737,592, where the GSI must be greater than about 3. The geometric selectivity index was determined by the formula:
GSI=net sorption of methanol (MeOH) divided by the net sorption of 1-PrOH (n-PrOH) measured at 25.degree. C. and relative pressure P/Po of 0.1 to 0.5 for a period of 20 hours exposure to the sorbate vapor. The sorption is expressed in wt %, i.e., grams sorbate per 100 grams of zeolite.
It has been found that GSI is not altogether predictable for determining the effectiveness of the catalyst in terms of selectivity or activity. Synthetic chabazite catalysts, in particular, do not follow this parameter in terms of selectivity and activity. It has been found that the activity and shape selectivity of zeolites and particularly chabazites, as a catalyst can be predicted with greater accuracy through the use of a parameter referred to as shape selectivity index (SSI) and another relating to 1-propanol sorption. SSI can assess the size and shape of either pore mouth opening or cavity while GSI evaluates cavity size using molecular packing. As the SSI value increases, the size and/or shape of the microporous structure preferentially excludes 2-PrOH to a greater extent than 1-PrOH. SSI, since it uses a branched alcohol 2-PrOH, as opposed to a straight chain alcohol, places a greater emphasis on the size and shape of the catalyst pore mouth than on the cavity, although it accounts for both effects. GSI uses straight chain alcohols in its determination and, therefore, it is more useful for assessing how molecules pack within a microporous cavity and does not indicate an ability of the catalyst to permeate reactant or product from within the cage structure. A correlation between the two concepts is apparent if the catalysts differ only in cavity size via cation occupancy or the lattice constant changes.
The requirement of a minimum sorption value of 1-propanol for the catalyst provides a measure of the ability of the catalyst to achieve high methanol reaction rates, e.g., rates leading to greater than 50% and generally greater than 75% conversion at operating temperature and space velocity. A catalyst having low propanol sorption values, although having a high SSI or GSI may provide shape selectivity but generally will also exhibit poor methanol/dimethylether conversion.
Metal cations in the zeolitic structure have an influence on both the SSI and activity of the catalyst. Large metal cations limit the sorption capacity of the zeolite framework and reduce its ability to sorb 2-propanol. Cations, e.g., H may not be positioned or occupy sufficient space within the zeolitic framework thus leading to zeolites having low SSI values and to equilibrium distributions of methyl amines. Cations should be selected such that the zeolite or chabazite has an SSI within the preferred range and sufficient acidity to maintain activity. Representative cations which may be used include H, Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Ga, Fe, Sr, La, Cu, Zn, Ni, B, Ce, Sn and Ru. Of these, the alkali metals, K and Na, are preferred.
Methods of preparation of such chabazite materials are known and examples are found in U.S. Pat. No. 4,925,460 which is incorporated by reference. After preparation, the chabazite preferably is heated to a temperature of at least 375.degree. C. to effect the calcination of the catalyst system. Although both the uncalcined and calcined catalyst systems can be utilized in the practice of the methanol amination process, the calcined chabazite affords higher methanol conversion rates than does the uncalcined chabazite catalyst system, and the calcined synthetic chabazite system also affords reduced levels of TMA.
As with all shape selective catalysts, there is an ability to "override" the shape selectivity afforded by the catalyst. When that happens, the product slate approaches an equilibrium distribution. Shape selectivity is diminished when the catalytic effect is shifted from the cavity network of the zeolite to surface catalysis. There are many factors which can lead to an equilibrium distribution of methylamine product via a shape selective catalyst and these include excessive temperature, low space velocity, catalyst coking and the like. Reaction temperature, in particular, is the primary method of shifting the product slate from that of a shape selective distribution toward an equilibrium distribution. The following examples are provided to illustrate various embodiments of the invention and comparisons to the prior art. All percentages are expressed as weight percentages unless otherwise specified.
EXAMPLE 1
Preparation of a Synthetic Potassium Chabazite
A sample of potassium chabazite was prepared by the general procedure of Coe and Gaffney in U.S. Pat. No. 4,925,460. More specifically, 48 gms of ammonium- Y zeolites, LZY62 extrudates from UOP were calcined at 500.degree. C. for 2 hrs, then cooled and humidified. The humidified extrudates were then added to and digested in a premixed solution of 189 gms of colloidal silica (14% SiO.sub.2) and 672 ml of 1M KOH. Nine (9) such digestions were done simultaneously in separate Nalgene bottles. The mixture was held at 95.degree.-100.degree. C. for 96 hrs. The solids were recovered and washed with deionized water until a pH of 7 was reached. Elemental analysis gave the following composition as weight % of the oxides: 17.80% K.sub.2 O, 0.02% Na.sub.2 O, 24.30% Al.sub.2 O.sub.3 and 56.50% SiO.sub.2. The bulk Si/Al ratio was 1.97 and the framework Si/Al ratio by .sup.29 Si MASNMR was 2.4. X-ray diffraction spectroscopy showed that the product was spectroscopically pure chabazite with no trace of Y type zeolite contaminant. The ratio of (K+Na) to total Al content indicates that about 80% of the Al was in the zeolite framework.
EXAMPLE 2
Preparation of an Ammonium Exchanged Synthetic Chabazite
A sample of ammonium exchanged chabazite was prepared by ion exchange of a portion of the K-Chabazite sample prepared in Example 1. The hydrated K-Chabazite was added to a 30 wt % NH.sub.4 NO.sub.3 solution at a ratio of 2 ml solution to 1 gm chabazite, then heated to 95.degree.-100.degree. C. and held for 2 hrs, then the solid was recovered and thoroughly washed with deionized water. This exchange and wash procedure was repeated 5 additional times. After drying at 110.degree. C., 450 gms of NH.sub.4 chabazite product was recovered. The residual K comprised approximately 11% of the ion exchange capacity.
EXAMPLE 3
Preparation of a 95% Potassium Exchanged Synthetic Chabazite
A sample of potassium exchanged chabazite was prepared by ion exchange of a portion of the NH.sub.4 -Chabazite sample prepared in Example 2. 30 gms of the dried NH.sub.4 -Chabazite was humidified, added to 300 ml of 1M KNO.sub.3 solution at 95.degree.-100.degree. C. for 2 hrs, then the solid was recovered and washed with deionized water. This exchange and wash procedure was repeated one additional time. Elemental analysis of the product gave the following composition as weight % of the oxides: (17.17% K.sub.2 O, <0.02% Na.sub.2 O, 24.6% Al.sub.2 O.sub.3 and 56.60% SiO.sub.2. The K content of the sample comprised approximately 94.5%, of the ion exchange capacity.
EXAMPLE 4
Preparation of a 58% Sodium Exchanged Synthetic Chabazite
A sample of sodium exchanged chabazite was prepared by ion exchange of a portion of the NH.sub.4 -chabazite sample prepared in Example 2. 50 gms of the dried NH.sub.4 Chabazite was humidified, added to 300 ml of 1M NaNO.sub.3 solution at 95.degree.-100.degree. C. for 2 hrs, then the solid was recovered and washed with deionized water. This exchange and wash procedure was repeated 1 additional time. Elemental analysis of the product gave the following composition as weight % of the oxides: 1.32% K.sub.2 O, 7.63% Na.sub.2 O, 27.20% Al.sub.2 O.sub.3 and 64.20% SiO.sub.2. The Na and K contents of the sample comprised approximately 57.5% and 6.5%, respectively, of the ion exchange capacity.
EXAMPLE 5
Preparation of a 99+% Sodium Exchanged Synthetic Chabazite
A sample of sodium exchanged chabazite was prepared by ion exchange of a portion of the NH.sub.4 -chabazite sample prepared in Example 2. 30 gms of the dried NH.sub.4 -chabazite was humidified, added to 1000 ml of 1M NaNO.sub.3 solution at 95.degree.-100.degree. C. for 2 hrs, then the solid was recovered and washed with distilled, deionized water. This exchange and wash procedure was repeated 5 additional times. Elemental analysis of the product gave the following composition as weight percent of the oxides: 0.05% K.sub.2 O, 12.66% Na.sub.2 O, 25.80% Al.sub.2 O.sub.3 and 61.20% SiO.sub.2. The Na and K contents of the sample comprised approximately 99+% and 0.5%, respectively, of the ion exchange capacity.
EXAMPLE 6
Preparation of a 66% Sodium Exchanged Synthetic Chabazite
The preparation of the sodium exchanged chabazite involved a three step procedure. These steps are:
A. A sample of potassium chabazite was prepared by the general procedure of Example 1. 160 gms of LZY64 extrudates obtained was calcined at 500.degree. C. for 2 hrs, then cooled and humidified. The humidified extrudates were then added to and digested in a premixed solution of 630 gms of Nalco.TM. 2326 colloidal silica (14% SiO.sub.2) and 2240 ml of 1M KOH. Three such digestions were done simultaneously in separate Nalgene bottles. The mixtures were held at 95.degree.-100.degree. C. for 96 hrs. The solids were recovered, combined and washed with deionized water until a pH of 7 was reached then dried at 110.degree. C. The ratio of K+Na to total Al content indicated that 84% of the Al was in the zeolite framework.
B. A sample of ammonium exchanged chabazite was prepared by ion exchange of a portion of the K-chabazite sample synthesized in step A. 50 gms of the dried NH.sub.4 -chabazite was humidified, added to 125 ml of 30 wt % NH.sub.4 NO.sub.3 solution at 95.degree.-100.degree. C. for 2 hrs, then the solid was recovered and thoroughly washed with deionized water. This exchange and wash procedure was repeated five additional times.
C. A sodium exchanged chabazite was prepared by ion exchange of the NH.sub.4 -chabazite sample prepared in accordance with step B. All of the hydrated NH.sub.4 -chabazite was added to 300 ml of a 1M NaNO.sub.3 solution at 95.degree.-100.degree. C. for 2 hrs, then the solid was recovered and washed with deionized water. This exchange and wash procedure was repeated 1 additional time. Elemental analysis of the product gave the following composition as weight % of the oxides: 0.28% K.sub.2 O, 8.46% Na.sub.2 O, 25.20% Al.sub.2 O.sub.3 and 66.10% SiO.sub.2. The Na and K contents of the sample comprised approximately 66% and 1.4%, respectively, of the ion exchange capacity.
EXAMPLE 7
Preparation of an Potassium Exchanged Synthetic Chabazite
A sample of potassium chabazite was prepared by the digestion procedure of Example 6 except that a different lot of LZY64 was used.
EXAMPLE 8
Preparation of a 80% Sodium Exchanged Synthetic Chabazite
A sample of sodium exchanged chabazite was prepared by ion exchange of a portion of the K-chabazite sample prepared above in Example 7. 50 gms of the dried K-chabazite was humidified, added to 1665 ml of 1M NaNO.sub.3 solution at 95.degree.-100.degree. C. for 2 hrs, then the solid was recovered and washed with deionized water. This exchange and wash procedure was repeated one additional time. Elemental analysis of the product gave the following composition as weight % of the oxides: 3.76% K.sub.2 O, 10.02% Na.sub.2 O, 24.40% Al.sub.2 O.sub.3 and 62.00% SiO.sub.2. The Na and K contents of the sample comprised approximately 80% and 20%, respectively, of the ion exchange capacity.
EXAMPLE 9
Preparation of a 99% Sodium Exchanged Synthetic Chabazite
A sample of sodium exchanged chabazite was prepared by ion exchange of a portion of the K-chabazite sample prepared above in Example 7. 50 gms of the dried K-chabazite was humidified, added to 1665 ml of 1M NaNO.sub.3 solution at 95.degree.-100.degree. C. for 2 hrs, then the solid was recovered and washed with deionized water. This exchange and wash procedure was repeated five additional times. Elemental analysis of the product gave the following composition as weight percent of the oxides: 0.23% K.sub.2 O, 12.37% Na.sub.2 O, 24.50% Al.sub.2 O.sub.3 and 62.80% SiO.sub.2. The Na and K contents of the sample comprised approximately 99% and 1%, respectively, of the ion exchange capacity.
EXAMPLE 10
Calcination of an Ammonium Exchanged Synthetic Chabazite
A sample of the ammonium exchanged chabazite prepared in Example 2 was calcined in air at 350.degree. C. The dried product from Example 2 was placed in a muffle furnace at 110.degree. C., then raised at about 5.degree. C./min to 350.degree. C. and held there for 2 hrs. Elemental analysis of the calcined product gave the following composition as weight percent of the oxides: 2.46% K.sub.2 O, 0.02% Na.sub.2 O, 29.20% Al.sub.2 O.sub.3 and 68.30% SiO.sub.2.
EXAMPLES 11-15
Calcination of Cation Exchanged Synthetic Chabazites
Samples of the cation exchanged chabazites prepared in Examples 4,5,6, 8 and 9 were individually calcined at 450.degree. C. using the general procedure given in Example 10. The treatment process is shown in Table 1.
TABLE 1______________________________________ STARTING PRE- CALCINATIONEXAMPLES MATERIAL CURSOR ATMOSPHERE______________________________________EXAMPLE 11 Example 4 LZY62 AIREXAMPLE 12 Example 5 LZY62 AIREXAMPLE 13 Example 6 LZY64 AIREXAMPLE 14 Example 8 LZY64 AIREXAMPLE 15 Example 9 LZY64 100% Steam______________________________________
EXAMPLES 16-21
Geometric Selectivity and Shape Selectivity Indexes
Several catalysts were measured with respect to GSI and SSI in accordance with the sorption procedures described. More specifically, the GSI was determined by measuring the sorption of methanol and 1-PrOH on the catalyst system when exposed to sorbate vapors at 20.degree. C. for a period of 20-24 hours. In determining the geometric selectivity index (GSI) the general procedure of U.S. Pat. No. 4,737,592 was followed. In determining the Shape Selectivity Index (SSI) Each catalyst sample was outgassed, in situ, at a rate of 1.degree. C. per minute to a temperature of 400.degree. C. and held under vacuum of 0.1 millitorr for 10-12 hours. Each catalyst sample was then cooled to 20.degree. C. and exposed to the respective vapor for about 24 hours at a relative pressure (p/p.sub.o) of 0.5. The temperature for sorption of methanol, 1-PrOH and 2-PrOH was 20.degree. C. The order of sorption for each of the catalyst systems was 2-PrOH, 1-PrOH and methanol. After exposure to each of the sorbate vapors, the test catalysts were degassed overnight at 400.degree. C. under vacuum and the catalyst sample weighed to determine whether all of the sorbate vapor had been removed. If some sorbate vapor remained, and the original dry weight of the catalyst system was not reached, the test catalyst was again outgassed. The corresponding indexes were calculated.
Table 2 below sets forth the synthetic and natural catalyst systems and their corresponding GSI and SSI values. The natural chabazites are used for illustrative purposes only. By their very nature minerals differ not only between natural deposits, but within a deposit.
TABLE 2__________________________________________________________________________ MEOH N-PROH I-PROHEXAMPLES CATALYST (mmol/g) (mmol/g) (mmol/g) GSI SSI__________________________________________________________________________EX 1 100% KChab 5.19 2.29 0.10 1.21 22.90EX 3 95% KChab 5.10 1.53 0.10 1.78 15.30EX 4 58% NaChab 5.03 2.33 0.33 1.15 7.06EX 5 99% NaChab 6.24 3.03 0.14 1.10 21.64EX 10 11% KChab 4.49 1.48 0.16 1.62 9.25EX 11 58% NaChab 5.05 2.33 0.25 1.16 9.32EX 12 99% NaChab 5.21 1.81 0.12 1.53 15.08EX 13 66% NaChab 6.15 2.95 0.42 1.11 7.02EX 15 99% NaChab 1.66 0.15 0.10 5.90 1.50EX 16 DURKEE* 5.94 0.94 0.23 3.37 4.09EX 17 NOVA SCOTIA* 7.14 1.20 0.05 3.19 23.90EX 18 CHRISTMAS* 5.06 2.39 0.51 1.13 4.69EX 19 BOWIE* 6.36 2.97 0.76 1.14 3.91EX 20 BUCKHORN* 4.61 1.36 0.17 1.81 8.00EX 21 LZY62 5.90 3.11 2.87 1.01 1.08__________________________________________________________________________ *These are naturally occurring zeolites.
EXAMPLE 22
Methanol Amination: Chabazite Catalysts
Several methanol aminations were carried out by reacting methanol with ammonia utilizing various catalyst systems. Table 3 sets forth the catalyst description, its origin and the reaction conditions, and Table 4 sets forth the results of each reaction.
TABLE 3______________________________________Catalysts & Reaction Conditions CAT- ALYST TYPE Mole Pres- EX- CATA- Ratio GHSV Temp sureRUN AMPLES LYSTS N/R (1/hr) (.degree.C.) (PSIG)______________________________________1 EX 1 100% 3.5 1000 350 250 KChab uncal- 375 250 cined2 EX 3 95% 3.5 1000 350 250 KChab uncal- 3.5 500 350 250 cined 2.3 1000 350 250 2.3 500 350 2503 EX 4 58% 3.5 1000 350 250 NaChab uncal- 3.5 500 350 250 cined4 EX 5 99% 3.5 1000 350 250 NaChab uncal- 3.5 500 350 250 cined5 EX 11 58% 3.5 1000 350 250 NaChab calcined6 EX 12 99% 3.5 1000 350 250 NaChab calcined7 EX 13 66% 3.5 1000 350 250 NaChab calcined8 EX 15 99% 3.5 1000 350 250 NaChab calcined______________________________________
TABLE 4__________________________________________________________________________Reaction Conditions and ResultsRUN N/R GHSV (.degree.C.) (PSIG) GSI SSI MeOH CONV % % TMA SEL.__________________________________________________________________________1 3.5 1000 350 250 1.21 22.90 51 6 3.5 1000 375 250 62 52 3.5 1000 350 250 1.78 15.30 65 7 3.5 500 350 250 86 6 2.3 1000 350 250 62 5 2.3 500 350 250 81 63 3.5 1000 350 250 1.15 7.06 94 33 3.5 500 350 250 96 204 3.5 1000 350 250 1.10 21.64 76 4 3.5 500 350 250 90 45 3.5 1000 350 250 1.16 9.32 98 156 3.5 1000 350 250 1.53 15.08 73 47 3.5 1000 350 250 1.11 7.02 99 138 3.5 1000 350 250 5.90 1.50 34 1__________________________________________________________________________
By contrast, FIG. 3 shows the geometric selectivity index (GSI) vis-a-vis TMA selectivity for synthetic chabazite catalysts. From the plot, it is shown that the excellent selectivity and activity regarding methylamine production can be achieved with a low GSI. Therefore, SSI is a more valuable parameter on which to base catalyst performance.
SUMMARY
Runs 1 and 4 show the effect of cation type in uncalcined catalysts on methanol conversion and TMA selectivity. Runs 4 and 6 at 99+% cation exchange levels show the Na cation form at high SSI values afford higher conversions than the K cation form (Run 2). The Na and K exchanged catalysts have SSI values of about 22 and 23, respectively, and afford TMA selectivities that are much less than equilibrium values of 35 wt %. The catalysts gave GSI values less than 3. With such similar SSI values, the difference in conversion reflects the cation type, not pore diffusion resistance.
Runs 1 and 2 show that the methanol conversion of the K cation form can be increased by partially exchanging NH.sub.4.sup.+ for K.sup.+ even though the GSI is less than 3. By maintaining an SSI value greater than about 7 for these uncalcined catalysts. TMA selectivities are still very low. This effect is also seen for the Na cation form by comparing Runs 3 and 4 where conversion increases from 76% to 94% while TMA is still less than 35 wt %.
Runs 7 and 8 for the 99% Na chabazite show that SSI values of less than 3 are not desirable for methylamines synthesis. Run 8 utilized a catalyst with 1-PrOH sorption capacity of less than 0.5 mmol/g. In this case the low SSI value results from significant exclusion of both 1-PrOH and 2-PrOH, whereas its GSI of about 6 indicates that methanol is still highly accessible. According to the prior art this would be an acceptable catalyst since its TMA selectivity is only 1 wt % indicating that its activity is still dominated by the zeolite interior surface. However, its conversion (34%) is unacceptable, i.e., less than 50% at 350.degree. C.
Runs 3 and 5, and 4 and 6 show the effect of calcination. For Runs 3 and 5 the GSI values for the 58% uncalcined and calcined Na chabazites remain less than 3 but the SSI increased from 7 to 9 with calcination resulting in a decrease of TMA selectivity from 33 wt % to 15 wt %. Meanwhile, the conversion increased from 94% to 98%. Run 3 shows uncalcined catalyst to be extremely active but relatively non-selective with respect to TMA as compared to the calcined form. At very high SSI values, e.g., >25, it is expected that pore diffusion resistance might limit both conversion and TMA selectivity catalysis would be limited to surface catalysis and the product slate would approach that of an equilibrium distribution. In Runs 4 and 6 where the catalyst has greater than about 99% of its ion exchangeable cation as Na and the SSI values are 22 and 15, respectively, calcination at 450.degree. C. has little or no effect on conversion or TMA selectivity.
Runs 5, 6 and 7 show the effect of cation exchange in a series of calcined catalysts with GSI values less than 3 and SSI values which range from 7 to 15. Decreasing the Na cation exchange from 99% to 66% causes an increase in conversion from 73% to 99% and an increase in TMA selectivity from 4 wt % to 13 wt %. Further decreasing the Na exchange from 66% to 58% shows no conversion benefit under the stated process conditions and a small increase in TMA selectivity from 13 wt % to 15 wt %.
FIGS. 1-3 were generated from the data obtained from the above runs for the purpose of pictorially evaluating SSI as a tool for forecasting amination product slate. FIG. 1 is a drawing comprising a plot of the data from Tables 3 and 4. It shows an absence of correlation between SSI and GSI for a large number of chabazite catalysts. FIG. 2 is a plot of SSI and TMA selectivity and shows the inverse effect of SSI on the TMA selectivity for both calcined and uncalcined chabazite catalysts. From FIG. 2 as the SSI value increases, the size and/or shape of the microporous structure preferentially excludes 2-PrOH to a greater extent than 1-PrOH. Thus, an uncalcined catalyst with an SSI of about 7 or larger may afford TMA selectivities of 35 wt % or less. A calcined catalyst with SSI of about 3 or larger will afford similar results.
EXAMPLE 23
Methanol Amination: Comparative and Base Treatment Studies
A series of comparative methanol aminations were carried out by reacting methanol with ammonia utilizing various catalyst systems.
The base treated chabazite was prepared by placing a 20 g sample of K-Chabazite in 200 ml of a 0.5M KOH and heated to 100.degree. C. without stirring for a period of 2 hours. The solution was drained from the solid washed with deionized water for about 5 minutes. The treatment was repeated except that the mixture was held at 100.degree. C. for 16 hours. After washing with distilled water and drying, the sample was analyzed to contain 21.2% Al.sub.2 O.sub.3, 57.7% SiO.sub.2 and 17.37% K.sub.2 O.
The sample then was humidified by placing in a closed vessel with a petri dish filled with water for 16 hr. The sample was treated three times with 30% NH.sub.4 Cl (10 ml/g) at 100.degree. C. for 1 hour. After each treatment the sample was washed with H.sub.2 O for 10 minutes. The exchanged sample was dried at 110.degree. C. and calcined at 450.degree. C. for 2 hours.
Table 5 sets forth the catalyst description, its origin and the results of each reaction. All runs were performed at 350.degree. C., GHSV=1000 hr.sup.1, N/R=3.5 and Pressure=250 psig., except where specified.
TABLE 5__________________________________________________________________________RUN EXAMPLES CATALYST ORIGIN GSI SSI % CONV % MMA % DMA % TMA__________________________________________________________________________1 AMORPHOUS Al.sub.2 O.sub.3 /SiO.sub.2 AKZO N/A N/A 77 39 23 382 NATURAL HFORM AW500 1.03 1.81 97 36 25 39 CHABAZITE3 SYNTHETIC HFORM LZY64 N/A N/A 98 37 26 37 CHABAZITE4 SYNTHETIC Base LZY64 2.21 12.5 96.7 44.1 48.7 7.2 Treatment H.sup.+ CHABAZITE *300.degree. C.5. SYNTHETIC Base LZY62 2.21 12.5 94.2 23.1 51.5 25.4 Treatment H.sup.+ CHABAZITE *350.degree. C.__________________________________________________________________________
Runs 1 and 2 of Table 5 show comparative data for an amorphous silica-alumina catalyst and an H Form of AW500 natural chabazite. The 1-PrOH sorption for the H Form of natural chabazite is high at 2.39 mmol/g. Thus, this data shows that while the H Form of natural chabazite can afford improved conversions over the amorphous catalyst (it is more active) or certain synthetic chabazites, with a GSI less than 3 and SSI less than 5 it gives a TMA selectivity which is similar to that of the amorphous catalyst of Run 1.
Runs 2 and 3 of Table 5 are comparative Examples that show similar, high conversions and nonselective methylamines distribution are obtained for the H-forms of both natural and synthetic chabazites. No shape selectivity is introduced. Runs 4 and 5 use the shape selective H form base treated catalyst. It has the H.sup.+ ion positioned within the framework for enhanced reaction and shape selectivity.
The calcined synthetic chabazites having an SSI of from 5 to 25 afforded the highest methanol conversions and essentially the lowest percent TMA selectivity. In contrast, the chabazites having a GSI greater than 3, although effective, were not as catalytically active.
The importance of the SSI value, particularly as the number exceeds about 5, demonstrates the importance of SSI in terms of methanol/dimethylether conversion rate and percent TMA selectivity. For example, for a synthetic chabazite having an SSI toward the lower end of the range, as for example the uncalcined synthetic chabazites, the percent TMA selectivity increases substantially, and the catalyst remains highly active.
EXAMPLE 24
Monomethylamine Feedstock Reforming
The procedure of Example 23 was repeated except that monomethylamine containing feedstocks were substituted for methanol as the feedstock. One feedstock contained about 30% monomethylamine in ammonia, another contained pure monomethylamine. The catalyst employed in the reaction was a hydrogen/potassium exchanged chabazite similar to base treated chabazite of Example 23. Table 6 sets forth the reaction conditions and results.
TABLE 6______________________________________MMA REFORMING OVER CHABAZITE CATALYSTSReaction Conditions and ResultsNH.sub.3 /MeOH 30% MMA* Pure MMA Pure MMA______________________________________% Conv 94.9 91.5MMA 26.4 28.8 23.9 19.6DMA 69 66.2 72.4 72TMA 4.6 5 3.7 8.4Temp 300 300 300 300N/R 1 1 1 1GHSV 1000 1000 1000 500______________________________________ *Feedstock contained 30% MMA in NH.sub.3
The above results show excellent conversion and excellent selectivity of monomethylamine to dimethylamine over the chabazite catalyst. Little TMA is produced. The results show the addition of ammonia to the monomethylamine feed did not inhibit conversion significantly.

Number	Name	Date
3384667	Hamilton	May 1968
4082805	Kaeding	Apr 1978
4205012	Parker	May 1980
4254061	Weigert	Mar 1981
4313003	Weigert	Jan 1982
4398041	Cochran et al.	Aug 1983
4434300	Deeba et al.	Feb 1984
4458092	Deeba et al.	Jul 1984
4485261	Ashina et al.	Nov 1984
4602112	Gier et al.	Jul 1986
4737592	Abrams et al.	Apr 1988

Preparation of methylamines using shape selective chabazites

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