Chemistry: molecular biology and microbiology – Apparatus – Including condition or time responsive control means
Reexamination Certificate
1999-12-22
2003-01-28
Beisner, William H. (Department: 1744)
Chemistry: molecular biology and microbiology
Apparatus
Including condition or time responsive control means
C435S289100, C435S299100, C435S286600, C435S287500
Reexamination Certificate
active
06511842
ABSTRACT:
The present invention relates to the continuous operation of reactors in non-conventional medium, i.e. non-aqueous, in particular for catalytic reactions utilizing essentially a solid phase and a gas phase.
Solid/gas catalytic reactions in which the solid phase of the reactor is constituted by an enzyme and the substrates or products of the reaction are in the form of a gas have been described by Pulvin S., Legoy M. D., Lortie R., Pensa M. and Thomas D. (1986) Enzyme technology and gas phase catalysis: alcohol dehydrogenase example. Biotechnol. Lett., 8, 11, pp 783-784. Catalytic systems which make use of whole cells as constituent elements of the solid phase of the reactor are also known.
Solid/gas catalysis offers in fact certain advantages compared to the conventional systems of the solid/liquid type:
it makes it possible to dispense with the use of solvents and to operate solely with the substrates and the products of the reaction in the immediate environment of the enzyme;
since the solid phase is composed of the biocatalytic element itself, the binding and immobilization steps prove not to be necessary.
the productivity is improved since the mass transfers are large owing to the high diffusivity and the low viscosity of the gas phases.
the gas phase is composed of pure substrates and products and of a vector gas, no solvent is used which facilitates the treatment downstream of the reaction medium.
Solid/gas catalysis requires a higher working temperature than conventional systems. As a result the risks of microbial contamination of the elements of the reactors are less.
The principle of it is the following:
The conversion of a gas substrate optionally transported by a vector gas undergoes conversion at the interface of a solid biocatalyst (enzyme or whole cells), the reaction products being recovered in the form of a gas.
The principles of solid/gas catalysis, the parameters of the reactions concerned are described in Biotechnology and Bioengineering, vol. 45, pages 387-397 (1995).
At present, it has been possible to obtain only a few chemical compounds such as epoxides, aldehydes and esters by solid/gas catalysis systems (ref.). But the principal limit of the existing system is the maintenance of an active biocatalyst and, consequently, its compatibility with industrial use.
A promising application for the reactors of this type relates to the treatment of polluted gas effluents since the range of molecules which need to be eliminated from industrial wastes before their release into the atmosphere is increasing incessantly. They include aldehydes, alcohols, ketones, carboxylic acids, cresols, phenols, sulfur-containing derivatives, cyclic amines, alkanes or esters. An improvement in the depollution procedures of soils may also be achieved by such systems.
However, the solid/gas catalysis systems are related in the first instance by the multiplicity of the constitutive elements which leads to a lack of control of the different parameters, in particular those depending on the complex role of water. In fact, the state of hydration of the enzyme preparation exerts an antagonist effect on the catalytic activity and on the stability of the catalyst with time.
The solid/gas phase reactors developed up to now (Lamare et al., Trends iin Biotechnology (1993) 10 (117): 413-418) are designed to operate at atmospheric pressure, although they are capable of working at temperatures ranging up to 220° C. with a controlled thermodynamic activity for each constituent. The definition and importance of the term activity in carrying out the solid/gas enzymatic reaction is described below.
They are inoperative for all the applications in which the components are poorly volatile, i.e. for all the components whose boiling point is situated in the range of 150-250° C. Now to-day many reactions capable of being developed because they represent an industrial interest involve compounds whose saturation pressures are low and even close to 0 at the working temperatures used located between 50 and 150° C., temperatures compatible with maintenance of the biocatalyst in an active form.
The principal obstacle of the existing systems lies in effecting the transfer to the gas phase of all the components of the system, the reaction substrates and products obtained. No bioreactor permits this conversion. Furthermore, the expense caused by the massive use of a neutral vector gas for a large scale supply to a solid/gas reactor makes the use of this reaction procedure prohibitive for industrial purposes.
Many examples attest to the important role of water in enzymatic catalysis in non-conventional medium. A simple manner of defining the thermodynamic activity of water consists of using the water vapour pressure of the gas phase in equilibrium with the system considered. One may then write:
a
w
=Pp/Ppref
where Pp is the partial pressure of the water above the system and Ppref the so-called reference partial pressure measured at the same temperature above pure water. The a
w
of a system is hence a function of physical parameters characterizing a system such as the absolute pressure and the temperature: it is the equilibrium parameter permitting the state of the water to be defined; it allows the influence of water to be unequivocally quantified in a system where the polarity, the dielectric constant of the present chemical entities, the number of phases, the temperature have a considerable influence on the distribution of water in the different phases of the system.
Halling (Halling P. (1984) in Effect of water on equilibria catalysed by hydrolytic enzymes in biphasic reaction systems, Enzyme Microb. Technol., 6, pp 513-515) has illustrated the equilibrium which may exist between the different states of water and the different phases of a complex medium (state of hydration of the biocatalyst and of the other components, quantity of water dissolved in the solvent, partial pressure of water vapour above the system), this equilibrium being a function of the activity of the water.
The value of the thermodynamic activity of the water of a system depends on the physical parameters characterizing this system, such as the absolute pressure and the temperature. The value of the thermodynamic activity of the water is therefore regulated in order to establish the equilibrium operating conditions between the different phases of the reactor; it is thus a decisive parameter for optimizing the reactor and its operating conditions.
The present invention proposes a solution to the problems evoked above by implementing reactions catalysed in the solid/gas phase at reduced pressure in order to optimize the productivity and reduce the expense by minimizing, and even eliminating, the use of a neutral gas vector, by referring to the thermodynamic activities of the water and of the compounds used.
More precisely, the object of the invention is a continuous reaction process by essentially solid/gas catalysis in non-conventional medium, implementing different gas substrates in order to obtain defined products. This process consists of controlling the temperature, which determines the reference saturation pressure of each pure compound, the total pressure of the system and the molar fluxes of the compounds in order to regulate the molar composition of the gas mixture as a function of the values of thermodynamic activity determined for the compounds.
The invention also relates to a reactor featuring suitable means for implementing this process. Such a reactor comprises pumps for controlling the flux of each of the liquid substrates, mass flow meters for the addition of a vector gas and probes for controlling the temperature of an expansion mixer of the substrates in the gas phase, of a reaction chamber comprising a bioreactor containing a biological catalyst and in which the substrates are introduced via a heat exchanger, of the bioreactor and of an analytical sampler at the reaction chamber outlet. A vacuum pump coupled to a vacuum regulation valve is also mounted at the reaction chamber outlet. The pumps, the probes and the valv
Lamare Sylvain
Legoy Marie-Dominique
Beisner William H.
L'Universite de la Rochelle
Merchant & Gould P.C.
LandOfFree
Continuous reaction method by solid/gas catalysis in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Continuous reaction method by solid/gas catalysis in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Continuous reaction method by solid/gas catalysis in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3000725