Immobilization of enzymes usually improves the recyclability and stability and can sometimes also improve the activity compared to enzymes free in solution. Mesoporous silica is a widely studied material as host for immobilized enzymes because of its large internal surface area and tunable pores. It has previously been shown that the pore size is critical both for the loading capacity and for the enzymatic activity; however, less focus has been given to 20 the influence of the particle size. In this work the effect of particle size and particle morphology on the immobilization of lipase from Mucor miehei and Rhizopus oryzae have been investigated. Three kinds of mesoporous silica, all with 9 nm pores but with varying particle size (1000 nm, 300 nm and 40 nm) have been synthesized and were used as host for the lipases. The two lipases, which have the same molecular size but widely different 25 isoelectric points, were immobilized into the silica particles at varied pH values within the interval 5 to 8. The 300 nm particles were proven to be the most suitable carrier with respect to specific activity for both enzymes. The lipase from Mucor miehei was more than four times as active when immobilized at pH 8 compared to free in solution whereas the difference was less pronounced for the Rhizopus oryzae lipase. 30

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Graphene oxide, nanographene oxide and partially reduced graphene oxide have been studied as possible foam stabilizing agents for CO2 based enhanced oil recovery. Graphene oxide was able to stabilize CO2/synthetic sea water foams, while nanographene oxide and partially reduced graphene oxide were not able to stabilize foams. The inability of nanographene oxide for stabilizing foams was explained by the increase of hydrophilicity due to size decrease, while for partially reduced graphene oxide, the high degree of reduction of the material was considered to be the reason. Graphene oxide brine dispersions showed immediate gel formation, which improved foam stability. Particle growth due to layer stacking was also observed. This mechanism was detrimental for foam stabilization. Gel formation and particle growth caused these particles to block pores and not being filterable. The work indicates that the particles studied are not suitable for CO2 enhanced oil recovery purposes.

The purpose of this study was to compare the efficiency of new chemistry yellow demulsifiers with already commercially available yellow demulsifiers in destabilizing two types of systems: petroleum crude oil emulsions and model densely packed layers (DPL). Oil-water separation was measured by low field NMR, which allows monitoring the water content in emulsion as function of the sample height and the time. Separation profiles measured by NMR depicted an increase of the free water release kinetic as the concentration of demulsifier increased, as well as the sedimentation velocity. There was no observation of DPL formation in the crude oil emulsions.4 different demulsifiers were tested on a model DPL and compared with normal crude oil emulsions. One chemical showed a higher efficiency in DPL than in crude oil emulsion. To gain more understanding on the destabilization mechanism, the interfacial rheology properties of the systems were determined. The interfacial experiments showed an increase on the elastic modulus (E'), therefore a stronger interface, as the concentration of demulsifier increased. The viscous modulus (E'') tend to reach a minimum value at low concentrations. There are differences on the experimental procedure for both techniques but the increment of the elastic modulus is not totally understood. The most important parameters were represented by Principal Component Analysis (PCA). PCA analysis did not contribute in a better characterization of the chemicals. The new generation of yellow demulsifiers has not reproduced the efficiency of commercially yellow available demulsifiers

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