Optimisation of Heterogeneous Catalysed Esterification Reaction for n-Hexyl Acetate Synthesis part 8

Optimisation of Heterogeneous Catalysed Esterification Reaction for n-Hexyl Acetate Synthesis part 8

Concentration Profile of Components

Figure 11 below shows one of the concentration profiles of acetic acid (A),
n-hexanol (B), n-hexyl acetate (C) and water (D). The concentration of acetic acid comes down rapidly from 1.5 Kmol/m³ to 0.1 Kmol/m³ in only 1 hour.

Water and n-hexyl acetate have similar concentration profiles and their maximum concentration is reached after 1 hour. The profile displayed served to confirm that at equilibrium state, correct stoichiometric ratios of
1:1:1:1 (A:B:C:D) were established.

CONCLUSIONS

This study has succeeded in obtaining control parameters conducive to high conversion and fast initial reaction rate, thereby optimising ester yield. The results also gave us an insight into reaction conditions and factors on an
industrial setting.

It is clearly evident that the F.M.R is one of the foremost factors affecting rate of reaction and achieving a higher overall conversion at equilibrium. The choice between 3:1 and 4:1 is made by taking into account the costing
and required yield, as detailed in the discussion.

At higher temperatures, there is little distinction between the trendlines, which indicate weaker temperature dependence of reaction rate and overall conversion at higher temperature intervals. However, at 368 K, equilibrium is
reached noticeably quicker than at 353 K. 

Catalyst loading also factors heavily in the extent of conversion and furthermore there is no economic deterrent for using higher loadings (on the contrary, there is greater productivity when using a high proportion of resin) due
to its recycle property.

No side-products were detected over the course of the experiment, which reinforced our decision to limit the catalyst weight loading. What is interesting is that ever higher catalyst loadings will not drive the equilibrium conversion
to a higher level, this factor will only serve to drive the reaction more efficiently at lower weight percentages i.e. in the 1 – 2% (w/w) interval. 

The choice of an optimal catalyst would be the CT-124 gelular resin, mainly due to its versatility in dealing with masses of water in the batch system, where aqueous mediums are commonly encountered in industry, in comparison with
the macroporous catalysts used. The earlier findings with regard to the effect of agitation speed and activity of re-used catalyst were also confirmed by this study.

Proposals for further study of this ester synthesis may involve extensive observations over wider temperature ranges so as to elicit a value for Arrhenius-related constants to ascertain whether the esterification is solely controlled
by the kinetic step of the reaction.

To optimise the system, one could feasibly enhance the removal of water from the system, so as to shift the equilibrium to achieve higher acetic acid conversion.

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Posted by Ahmed Tariq on Jan 5 2012. Filed under Sci-Tech. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry