Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Aging of reaction-crystallized benzoic acid
KTH, Superseded Departments, Chemical Engineering and Technology.
KTH, Superseded Departments, Chemical Engineering and Technology.
KTH, Superseded Departments, Chemical Engineering and Technology.
2004 (English)In: Industrial and engineering chemistry research, ISSN 0888-5885, Vol. 43, 6694-6702 p.Article in journal (Refereed) Published
Abstract [en]

Benzoic acid has been crystallized by mixing sodium benzoate and hydrochloric acid in a T-mixer. The suspension is collected in an agitated crystallizer, and aging of the solid product is evaluated by microscopy. In addition, the kinetics of aging is examined by population balance modeling and nonlinear parameter estimation. Microscopic observations reveal that the crystal shape is quite irregular immediately after the T-mixer crystallizer, but during the aging the crystals turn into nice well-shaped platelets. A model on Ostwald-type ripening gives a fairly good description of the evolution of the crystal size distribution during the aging, provided that the observed changes in crystal shape are accounted for in the model.

Place, publisher, year, edition, pages
2004. Vol. 43, 6694-6702 p.
Keyword [en]
precipitation, kinetics, simulation, sulfate
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-8875DOI: 10.1021/ie049828aISI: 000224393400007Scopus ID: 2-s2.0-4944256089OAI: oai:DiVA.org:kth-8875DiVA: diva2:14347
Note
QC 20100930 QC 20110914Available from: 2005-12-05 Created: 2005-12-05 Last updated: 2011-09-14Bibliographically approved
In thesis
1. Process modeling of semibatch reaction crystallization
Open this publication in new window or tab >>Process modeling of semibatch reaction crystallization
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis aims at increasing the fundamental understanding of reaction crystallization by modeling, simulations and parameter estimation. Benzoic acid is used as the model compound.

A population balance model of single-feed semi-batch reaction crystallization is developed, accounting for chemical reaction, mixing, nucleation, growth, and growth rate dispersion. The model is evaluated by comparing the results with data from previously published semi-batch experiments. Two different mechanistic mixing models are used to describe mixing: the engulfment model with mesomixing and the segregated feed model. When the engulfment mixing model is used, the semi-batch model correctly captures the variation in weight mean size with varying agitation rate, feed point location, reactant concentration, feed pipe diameter, and total feed time. However, at scaling-up, a decrease in weight mean size with increasing crystallizer volume is predicted, which is not found experimentally. When the segregated feed model is used to describe mixing, the results are unsatisfactory.

The crystallization kinetics have a great impact on the performance of the model, influencing both the final mean size, and the predicted influence of changes in the processing conditions. The kinetics of nucleation and growth are determined from T-mixer experiments. Three population balance models of increasing complexity are developed and used in parameter estimations by non-linear optimization. The T-mixer model accounts for nucleation, growth and growth rate dispersion. Five or six kinetic parameters are estimated using data from 14 experiments at 8 different initial supersaturation levels. Depending on the assumptions in the model, different kinetics are estimated. The main differences are found in the nucleation and growth rate constants. The T-mixer kinetics yields unsatisfactory results in the semi-batch simulations, with a predicted mean size that is significantly smaller than the experimental and a less pronounced influence of processing conditions that are related to mesomixing.

An attempt is made to model aging of benzoic acid precipitates formed at high supersaturation. A model of Ostwald ripening gives a reasonably good description of the changes in the size distribution, provided that the observed shape change during aging is accounted for. However, significant deviations remain, in particular, the broadening of the aged size distribution is more pronounced in the experiments than in the simulations. There are indications that the observed aging might be caused by kinetic ripening, driven by a transformation to a more regular shape or a less strained crystal, rather than by Ostwald ripening.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. x, 67 p.
Series
Trita-KET, ISSN 1104-3466 ; 223
Keyword
Reaction crystallization, benzoic acid, nucleation, growth, kinetics, growth rate dispersion
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-538 (URN)91-7178-212-5 (ISBN)
Public defence
2005-12-12, F3, Lindstedtsvägen 26, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20100930Available from: 2005-12-05 Created: 2005-12-05 Last updated: 2010-09-30Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopushttp://pubs.acs.org/cgi-bin/abstract.cgi/iecred/2004/43/i21/abs/ie049828a.html

Search in DiVA

By author/editor
Ståhl, MarieÅslund, BengtRasmuson, Åke C.
By organisation
Chemical Engineering and Technology
Physical Chemistry

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 99 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf