Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Inorganic carbon containing
Reissue Patent
1997-04-04
2001-08-14
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Inorganic carbon containing
C502S183000, C502S184000, C568S861000, C568S863000
Reissue Patent
active
RE037329
ABSTRACT:
The present invention relates to a method for production in a fixed bed reactor of lower polyhydric alcohols and their mixtures, comprising hydrogenolysis under pressure of higher polyhydric alcohols in the presence of a supported metal catalyst.
In the present description, the term higher polyhydric alcohols means products such as sorbitol, mannitol and xylitol derived from catalytic hydrogenation of carbohydrates (and in particular of glucose, fructose and their mixtures). The term lower polyhydric alcohols means polyalcohols having a maximum of 6 carbon atoms and a maximum of 3 hydroxyl groups, in particular ethanediol, propylene glycol, butanediol and glycerol.
The invention also relates to a new supported ruthenium-based catalyst and its use in the production of chemicals from renewable raw materials (carbohydrates and their derivatives); in particular for selective transformation of low molecular weight polyhydric alcohol hexoses.
U.S. Pat. Nos. 2,868,847 and 4,476,331 describe the use of a ruthenium-based catalyst on a powdered active carbon support. The methods of hydrogenation and catalytic hydrogenolysis described in these documents comprise batch reactions in which the powdered catalyst is supplied to the reactor together with the reagents.
A first object of the present invention is to provide a method of the type specified initially in the description, which enables hydrogenolysis of higher polyhydric alcohols to take place in a continuous fixed bed reactor.
For this purpose, a second aspect of the invention consists of use of a ruthenium-based catalyst supported on granulated activated carbon, having:
a specific surface area of 600 to 1000 m
2
/g (B.E.T. method);
a total pore volume of 0.5 to 1.2 cm
3
/g (combined nitrogen-mercury method);
an apparent specific weight (bulk density) of 0.45 to 0.55 g/cm
3
;
an actual specific weight of 1.9 to 2.3 g/cm
3
;
a total volume of micropores having a radius smaller than 75 A of 0.4 to 0.55 cm
3
/g; and
an ash content of 2 to 5 weight %.
The specific type of activated carbon used having the aforementioned features also has high mechanical resistance and a particle size which make it suitable for use in a fixed reactor of the trickle-bed type.
The possibility of being able to carry out fixed bed hydrogenation/hydrogenolysis enables increased productivity of the plant to be obtained. It has also been found unexpectedly that fixed bed hydrogenolysis enables increased selectivity of lower polyhydric alcohols to be obtained in comparison with a reaction in batch form.
The specific surface area of the granulated activated carbon support is preferably between 800 and 1000 m
2
/g, and the total volume of the pores is between 0.6 and 0.7 cm
3
/g.
By granulated activated carbon is meant a carbon which has a particle size of between 5.7 and 0.5 mm (3 and 32 mesh) and preferably a particle size of between 4.7 and 2.4 mm (4 and 8 mesh, Tiller series). The optimum particle size is selected on the basis of the process parameters, according to known criteria.
Use of activated carbon which has the above-described characteristics is critical for the purposes of the activity of the catalyst and the possibility of using it on a fixed bed.
Activated carbon of the aforementioned type is available commercially in the form of the activated carbons made by ACQUE NYMCO having the references GH12132 and CA12132.
In the hydrogenolysis method according to the invention, the reaction temperature is generally between 200° and 300° C., and preferably 220° -270° C., the spatial hourly velocity of the fluid is between 0.3 and 4, and preferably between 0.67 and 2.50 h
−1
, and the reaction pressure is between 5 and 20 MPa and preferably between 7.5 and 15 MPa. The continuous reactor is preferably supplied with a reaction promoter selected from amongst alkaline and alkaline earth hydroxides, and preferably sodium hydroxide, or basic reaction salts; the molar ratio between the higher polyhydric alcohols and the promoter supplied is between 3 and 30. The reactor is preferably also supplied with sulphides as reaction moderators (in order to avoid the formation of undesirable final products such as methane), with a concentration in the solution supplied lower than 150 ppm calculated relative to the sulphide ion.
The concentration of the ruthenium on the activated carbon is between 0.5 and 5 weight %, and preferably between 1 and 3 weight %.
The higher polyhydric alcohol or mixture of higher polyhydric alcohols is supplied to the hydrogenation reactor, preferably in an aqueous solution in a concentration of 20 to 40 weight %.
The higher polyhydric alcohol or mixture of higher polyhydric alcohols is preferably obtained in a first stage of hydrogenation of carbohydrates, carried out at a low basic pH and preferably between 7.5 and 8 with a reaction temperature of between 120° and 150° C. This first stage is also preferably carried out in an aqueous solution in the presence of a basic promoter, such as those previously described, in a quantity sufficient to maintain the pH in the above-described field. In this first stage the carbohydrate may consist of monosaccharides or disaccharides. However the supply preferably consists of an aqueous solution of glucose which is converted with virtually maximum theoretical yield into sorbitol. In this hydrogenation stage also, which is carried out continuously on a fixed bed, the ruthenium catalyst supported on granulated activated carbon, as previously described, is advantageously used.
The method of preparing the catalyst according to the invention comprises the main stages of suspending the granulated activated carbon in water, adding a ruthenium chloride solution to the suspension, adjusting the pH of the suspension to a value of between 4.5 and 8 by adding an alkaline agent, heating the suspension to a temperature of between 70° and 100° C. and maintaining the suspension at this temperature for a time of between 30 minutes and 2 hours, separating the solid from the suspension by filtration, re-suspending the solid in a solution of alkaline agent, heating the suspension to a temperature of between 60° and 100° C., bubbling a hydrogen flow into the suspension for a time of between 1 and 3 hours, and separating the solid from the suspension.
The catalyst thus obtained has the features of porosity, specific surface area and specific weight of the original activated carbon.
Further advantages and features of the method of producing the catalyst and of the method according to the invention which uses this catalyst will become apparent from the attached examples, which should not be understood as limitations of the scope of the present invention.
REFERENCES:
patent: 2868847 (1959-01-01), Boyers
patent: 3978000 (1976-08-01), Schmitt, Jr. et al.
patent: 4052336 (1977-10-01), Monfoort et al.
patent: 4430253 (1984-02-01), Dubeck et al.
patent: 4476331 (1984-10-01), Dubeck et al.
patent: 4496780 (1985-01-01), Arena
patent: 4560672 (1985-12-01), Attg et al.
patent: 075952 (1983-04-01), None
patent: 191373 (1986-08-01), None
patent: 2034292 (1980-06-01), None
patent: 2103649 (1983-02-01), None
Casale Bruno
Gubitosa Giuseppe
Cave LLP Bryan
Wood Elizabeth D.
LandOfFree
Ruthenium-based catalyst for producing lower polyhydric... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ruthenium-based catalyst for producing lower polyhydric..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ruthenium-based catalyst for producing lower polyhydric... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2537479