WO2015079117A1

WO2015079117A1 - Method for enzyme recovery in biofuel production process

Info

Publication number: WO2015079117A1
Application number: PCT/FI2014/050926
Authority: WO
Inventors: Krister Eskilsson; Michael Recktenwald; Ilkka VIRKAJÄRVI; Jesper BERNER
Original assignee: Kemira Oyj
Current assignee: Kemira Oyj
Priority date: 2013-11-29
Filing date: 2014-11-28
Publication date: 2015-06-04
Anticipated expiration: 2016-05-29
Also published as: FI125311B; FI20136199A7

Abstract

The invention relates to a method for enzyme recovery in biofuel production process. The method comprises steps of producing, by using liquid enzymes, an intermediate product mixture comprising a top phase comprising fatty acid esters and a bottom phase comprising glycerol; adding cationic polymer and an anionic surfactant or non-ionic surfactant to the intermediate product mixture; allowing an emulsion phase to form, the emulsion phase comprising liquid enzymes; and separating the emulsion phase from the intermediate product mixture.

Description

METHOD FOR ENZYME RECOVERY IN BIOFUEL PRODUCTION PROCESS

The invention relates to a method for enzyme recovery in biofuel production process employing enzyme catalysts according to the preamble of enclosed independent claim.

There is an increasing interest in biofuel production, especially biodiesel production, as biofuels are becoming an alternative for traditional petroleum products.

Biodiesel is produced from various feedstocks, either from virgin oil feedstocks, such as soybean oil, or from waste feedstocks, such as waste vegetable oils, grease, animal fats. In commercial scale biodiesel is normally produced from the different feedstocks by using acidic and/or alkali catalysts. Triglycerides as well as di- and monoglycerides react with an alcohol in the presence of a catalyst to produce an intermediate product mixture comprising fatty acid esters and glycerol. This reaction is called transesterification.

It is possible to use enzyme catalysts in the production of biofuel, such as biodiesel. In fact, use of enzymes in biofuel, e.g. biodiesel, production provides a number of advantages, such as smaller energy consumption and high quality glycerol by-product. The drawback of the processes, which employ enzyme catalysts, is the price of the enzymes. Therefore it would be economically advantageous to be able to recycle the enzymes in the biofuel production process. At the present immobilized enzymes are used in biofuel production. Immobilized enzymes are bound to a solid surface of a carrier, such as ceramic beads or ion- exchange resins. Immobilization of enzymes may reduce the mass-transfer rate of the biofuel reaction and even further increase the enzyme costs. Liquid enzymes, which are immersed in the liquid reaction medium and not bound to any carrier particle, would be an interesting alternative for biofuel production. Their mass transfer resistance is negligible and no addition of solid carrier system, which may impede the transesterification reaction, is needed. However, the difficulty of separating and recovering the liquid enzymes from the intermediate product mixture has seriously limited the interest to use liquid enzymes, at least for commercial scale production. An object of the present invention is to minimise or even completely eliminate the problems existing in the prior art.

One object of the present invention is thus to provide a method, with which the enzyme can be easily separated from the intermediate product mixture and optionally recycled back in the process.

These objects are attained with a method and an arrangement having the characteristics presented below in the characterising parts of the independent claims.

Some preferable embodiments of the present invention are described in the dependent claims.

Typical method according to the present invention for enzyme recovery in biofuel production process, comprises

- producing, by using liquid enzymes, an intermediate product mixture comprising a top phase comprising fatty acid esters and a bottom phase comprising glycerol,

- adding cationic polymer and an anionic surfactant or non-ionic surfactant to the intermediate product mixture,

- allowing an emulsion phase to form, the emulsion phase comprising liquid enzymes and

-separating the emulsion phase from the intermediate product mixture.

Now it has been surprisingly found that liquid enzymes are effectively concentrated to an emulsion phase, which is formed when an anionic or non-ionic surfactant and a cationic polyacrylamide are added to an intermediate product mixture in biofuel production process. The emulsion phase with liquid enzymes may be formed between the lighter top phase comprising fatty acid esters (FAE) and heavier bottom phase comprising glycerol. The top phase is separated and transferred to biofuel processing and the bottom phase is separate and transferred to a further processing step. The emulsion phase, which comprises liquid enzymes, is easily separated from the top and bottom phase and the enzymes can be recycled back to process if desired.

The method of interaction is not yet fully understood, but it has been found out that a separable emulsion phase is formed when anionic or non-ionic surfactant and cationic polymer is added to the intermediate product mixture according to the present invention. The formed emulsion phase is quite distinct from the other phases of the intermediate mixture, i.e. FAE and glycerol phases. It has been observed that the liquid enzymes are concentrated to the emulsion phase and can be separated with it. In context of the present application the term "intermediate product mixture" is understood as a liquid mixture which comprise at least transesterification products, i.e. fatty acid esters (FAE); glycerol; liquid enzymes. The intermediate product mixture may further comprise water and/or residual alcohol. The invention is suitable for biofuel production by transesterification with liquid enzymes, such as lipases. In this context the term "liquid enzymes" is understood as enzymes that are free from attachment to surfaces of carrier elements, such as particles, and which are fully immersed into the reaction mixture. Liquid enzymes are fully dispersed in the reaction mixture, whereby they have good contact between the phases.

According to one preferred embodiment the separation of the emulsion phase comprising liquid enzymes from the bottom phase is performed by gravity sedimentation. Optionally, centrifugation may be used, but it is not necessary. The sedimentation time may vary between a few minutes up to a few hours, depending on the batch size. The anionic or non-ionic surfactant and the cationic polymer may be added to the intermediate product mixture in any order. In other words, it is possible to first add the anionic or non-ionic surfactant and then the cationic polymer, or alternatively to add first the cationic polymer and then the anionic or non-ionic surfactant. According to an advantageous embodiment the anionic surfactant or non-ionic surfactant and the cationic polymer are added simultaneously to the intermediate product mixture.

The anionic or non-ionic surfactant may be added in any suitable amount. For example, the anionic surfactant may be added in amount up to 2800 ppm, normally in amount of 0.7 - 1400 ppm, preferably 140 - 420 ppm, more preferably 280 - 350 ppm, given as active agent. Anionic or non-ionic surfactant is usually used in form of a solution. Preferably an anionic surfactant and a cationic polymer are added to the intermediate product mixture.

The anionic surfactant may be selected from linear alkyl sulphates, branched alkyl sulphates, sulphosuccinates, linear alkyl benzene sulphonates, branched alkyl benzene sulphonates, alkylnaphthalenesulphonat.es and alkyldiphenyloxide disulphonates. According to one embodiment of the invention the anionic surfactant is sodium dioctyl sulphosuccinate.

The non-ionic surfactant may be selected from suitable ethoxylates.

The cationic polymer may be selected from a group comprising cationic polyacrylamide, polydiallyldimethylammonium chloride (poly-DADMAC), polyamine, cationic starch and chitosan. Preferably the cationic polymer is cationic polyacrylamide. Cationic polyacrylamide may be obtained by copolymerizing acrylamide with a cationic monomer or methacrylamide with a cationic monomer. The cationic monomer may be selected from the group consisting methacryloyloxyethyltrimethyl ammonium chloride, acryloyloxyethyltrimethyl ammonium chloride, 3-(methacrylamido) propyltrimethyl ammonium chloride, 3- (acryloylamido) propyltrimethyl ammonium chloride, diallyldimethyl ammonium chloride, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, and similar monomers. According to one preferred embodiment of the invention cationic polyacrylamide is copolymer of acrylamide or methacrylamide with (meth)acryloyloxyethyltrimethyl ammonium chloride. Cationic polyacrylamide may also contain other monomers, as long as its net charge is cationic and it has an acrylamide/methacrylamide backbone. An acrylamide or methacrylamide based polymer may also be treated after the polymerisation to render it cationic, for example, by using Hofmann or Mannich reactions

Cationic polyacrylamide may have charge density of 0.15 - 4.0 meq/g, preferably 0.5 - 3.5 meq/g, more preferably 1 .5 - 3.0 meq/g. The cationic polymer, such as cationic polyacrylamide, may be added in any suitable amount, for example in amount up to 4000 ppm, normally in amount of 1 - 2000 ppm, preferably 200 - 600 ppm, more preferably 200 - 400 ppm, given as active agent. According to one embodiment of the invention the cationic polymer is used in form of dry powder.

The present invention is especially suitable for processes where biodiesel is produced by reacting glycerides (tri-, di-, mono-) with methanol in the presence of a liquid enzyme catalyst to produce an intermediate product mixture comprising fatty acid methyl esters (FAME) and glycerol.

The present invention is also suitable for biofuel production process, which comprises transesterification with liquid enzymes, such as lipases, from virgin vegetable oil feedstocks, such as soybean oil, or from waste feedstocks, such as waste vegetable oils, grease, animal fats. EXPERIMENTAL

One embodiment of the invention is more closely described in the following non- limiting example.

Example 1

A batch of biodiesel was prepared in lab scale. The batch was a two-phase mixture composed of the clear top phase of fatty acid methyl ester (FAME), and of the emulsion phase at the bottom of the reaction vessel. After the separation of the top phase, about 1 litre of intermediate product mixture was left for lab trials.

Anionic surfactant comprising sodium dioctyl sulphosuccinate (KemFoamX 2970, Kemira Oyj) and cationic polyacrylamide flocculant (Superfloc C494, Kemira Oyj) were used in the experiments. Anionic surfactant was diluted to 10 weight-% aqueous solution and cationic polymer was diluted to 0.5 weight-% aqueous solution

The anionic surfactant and cationic polymer were added successively to 500 ml of intermediate product mixture upon fast mixing at room temperature. Fast mixing was continued for 5 minutes. After the mixing period, the mixture was allowed to settle for 30 minutes.

The results were evaluated visually, and the results are given in Table 1 . The dosages are given as amount of active substance.

Table 1 . Results of Example 1

It could be observed that for Sample 3 an effective separation of emulsion phase appeared already in 30 minutes. The emulsion phase was situated between a top phase comprising fatty acid methyl ester (FAME) and a bottom phase comprising glycerol. The bottom phase comprising glycerol could be easily separated from emulsion phase by using gravity settling. Correspondingly, the top phase comprising FAME can be separated for further processing for biodiesel. The emulsion phase comprising liquid enzymes can be recycled back to the process.

Even if the invention was described with reference to what at present seems to be the most practical and preferred embodiments, it is appreciated that the invention shall not be limited to the embodiments described above, but the invention is intended to cover also different modifications and equivalent technical solutions within the scope of the enclosed claims.

Claims

1 . Method for enzyme recovery in biofuel production process, the method comprising

- producing, by using liquid enzymes, an intermediate product mixture comprising a top phase comprising fatty acid esters and a bottom phase comprising glycerol, characterised in

- adding a cationic polymer and an anionic surfactant or non-ionic surfactant to the intermediate product mixture, allowing an emulsion phase to form, the emulsion phase comprising liquid enzymes and separating the emulsion phase from the intermediate product mixture.

2. Method according to claim 1 , characterised in forming the emulsion phase, which comprises liquid enzymes, between the top phase and the bottom phase.

3. Method according to claim 1 or 2, characterised in recycling the separated emulsion phase, which comprises liquid enzymes, back to the product step where the intermediate product mixture is produced.

4. Method according to any of preceding claims 1 - 3, characterised in performing the separation of the emulsion phase from the bottom phase by gravity sedimentation and/or by centrifugation.

5. Method according to any of preceding claims 1 - 4, characterised in adding an anionic surfactant and a cationic polymer to the intermediate product mixture.

6. Method according to claim 5, characterised in that the anionic surfactant is selected from linear alkyl sulphates, branched alkyl sulphates, sulphosuccinates, linear alkyl benzene sulphonates, branched alkyl benzene sulphonates, alkylnaphthalenesulphonat.es and alkyldiphenyloxide disulphonates..

7. Method according to claim 6, characterised in that the anionic surfactant is sodium dioctyl sulphosuccinate.

8. Method according to any of preceding claims 1 - 4, characterised in selecting non-ionic surfactant from ethoxylates.

9. Method according to any of preceding claims 1 - 8, characterised in adding anionic surfactant or non-ionic surfactant in amount of 0.7 - 1400 ppm, preferably 140 - 420 ppm, more preferably 280 - 350 ppm, given as active agent.

10. Method according to any of preceding claims 1 - 9, characterised in adding cationic polymer in amount up to 4000 ppm, preferably 1 - 2000 ppm, more preferably 200 - 600 ppm, even more preferably 200 - 400 ppm, given as active agent.

1 1 . Method according to any of preceding claims 1 - 10, characterised in that the cationic polymer is selected from group comprising cationic polyacrylamide, polydiailyldimethylammonium chloride (poly-DADMAC), polyamine, cationic starch and chitosan.

12. Method according to claim 1 1 , characterised in that the cationic polymer is cationic polyacrylamide.

13. Method according to claim 12, characterised in that cationic polyacrylamide has charge density of 0.15 - 4.0 meq/g, preferably 0.5 - 3.5 meq/g, more preferably 1 .5 - 3.0 meq/g.

14. Method according to any of preceding claims 1 - 13, characterised in that the cationic polymer is added simultaneously with the anionic surfactant to the intermediate product mixture.

15. Method according to any of preceding claims 1 - 14, characterised in

- separating the top phase and transferring it to biofuel processing, and

- separating the bottom phase and transferring it to a further processing step.

16. Method according to any of preceding claims 1 - 15, characterised in the biofuel production process comprises transesterification with liquid enzymes, such as lipases, from virgin vegetable oil feedstocks, such as soybean oil, or from waste feedstocks, such as waste vegetable oils, grease, animal fats.

17. Method according to any of preceding claims 1 - 16, characterised in the biofuel production process where biodiesel is produced by reacting glycerides, such as tri- , di-, monoglycerides, with methanol in the presence of a liquid enzyme catalyst to produce an intermediate product mixture comprising fatty acid methyl esters and glycerol.