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An Acetaldehyde Supply Mechanism for the Improved Production of Pentaerythritol

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An Acetaldehyde Supply Mechanism for the Improved Production of Pentaerythritol COPYRIGHT AND CITATION CONSIDERATIONS FOR THIS THESIS/ DISSERTATION o Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. o NonCommercial — You may not use the material for commercial purposes. o ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original. How to cite this thesis Surname, Initial(s). (2012) Title of the thesis or dissertation. PhD. (Chemistry)/ M.Sc. (Physics)/ M.A. (Philosophy)/M.Com. (Finance) etc. [Unpublished]: University of Johannesburg. Retrieved from: https://ujdigispace.uj.ac.za (Accessed: Date). AN ACETALDEHYDE SUPPLY MECHANISM FOR THE IMPROVED PRODUCTION OF PENTAERYTHRITOL by Graham Robert Jennery Submitted to Technikon Witwatersrand in part fUlfilment of the requirements for the Masters Diploma in Chemical Engineering. october 1992 supervisor: Dr. K. Richter Co-supervisor Mr. L.A. Van Niel To Susan Thanks for so much. To Eileen May you reach your goals. i SUMMARY The work presented here constitutes an account of the optimization of a chemical reaction process with special reference to the methodology of reagent addition in the case of fast reactions. The chemical reaction process for manufacture of the Formaldehyde Acetaldehyde condensation product Pentaerythritol (Penta) as it is conducted at the plant of National Chemical Products, a division of Sentrachem, was studied in detail. The industrial scale reactor design was critically examined, 'with emphasis on the evaluation of mixing and reagent dispersion efficacy and its effect on chemical reactor performance. Batches of Pentaerythritol products were prepared in a laboratory bench scale reactor. Reagent concentrations and proportions were controlled· at various values and the reaction temperature profiles were controlled so as to be similar for all the tests. Moreover the mode and intensity of liquid agitation and reagent admixture was varied in a controlled manner between the various tests. The reaction liquors from the various batches were sampled and the samples sUbjected to chemical analysis. The results were then compared in order to show the effect of agitation and reagent dispersion intensity on the reaction process and products. The results indicate conclusively that liquid flow or agitation intensity and reagent admixture or sparging variation has an effect on the type and relative amounts of chemical species produced in the laboratory apparatus. ii This effect is especially significant with respect to the side products Di-pentaerythritol and Bis Penta Mono-formal (B.P.M.F.). The effect is also demonstrated for the gamut of various side products collectively and arbitrarily designated as the so-called "unknowns". Furthermore the formation of coloured products in the reaction· is distinctly influenced by the same variation. High intensity agitation and reagent sparging enhances Di­ penta formation and inhibits formation of the Formal B.P.M.F, "unknowns" and colour. At very low agitation and sparging intensity Di-penta production is diminished while B.P.M.F., "unknowns" and colour formation is favoured. The work includes a proposal for the manufacture and installation of improved reagent sparging systems in the NCP Transvaal commercial scale Penta Reactor.A tentative method for the design of a continuous reactor for penta production using optimised Tee mixers for high velocity in-line reagent sparging is also developed. iii ACKNOWLEDGEMENTS Various people have in many ways, knowingly and otherwise contributed towards the present work. This has given me the opportunity to study an interesting but often little understood chemical reaction engineering topic, which has led to new light being shed on a special aspect, which is rewarding in itself. The help of the following persons is gratefully acknowledged L.A. Van Niel of NCP Projects and Engineering Division for his suggestion of the topic in the first instance, support generally, and constructive criticism; D.P. Bowyer, General Manager of NCP Transvaal, and to NCP management for permission to present this work as a dissertation to Technikon Witwatersrand; Dr. K. Richter of Technikon Witwatersrand for his supervision, constructive criticism and encouragement; M.A. McEvoy of NCP Transvaal for support, suggestions, ideas and many hours of discussion ; Dr. H.A.H. Laue, Dr. C. D. simon, and members of the NCP Research & Development team for advice and suggestions, support and technical assistance ; C. Manushewitz, NCP Projects and Engineering Division, for helpful practical discussion of reactor details ; J.L. Steyn, P.F. Tack and the Pentaerithritol and Penta chemicals production and technical team members at NCP for support and assistance; iv Miss T. C. Mvelase of NCP R&D Process Chemistry, who painstakingly provided expert technical assistance with the laboratory testwork ; Miss H. Comninos of NCP R&D Analytical Chemistry, who diligently performed the numerous specialised chemical analyses ; E. W. James of NCP Projects and Engineering Division, who prepared the figures in Chapters 4 and 8 using a PC CAD package. v TABLE OF CONTENTS PAGE.NO. SUMMARY i ACKNOWLEDGEMENTS iii LIST OF FIGURES viii NOMENCLATURE x CHAPTER 1 : INTRODUCTION AND OBJECTIVES 1 1.1 INTRODUCTION: HISTORICAL AND GENERAL 1 1.2 THE NCP PROCESS AND DISADVANTAGES 3 1.3 AIMS AND OBJECTIVES 4 CHAPTER 2 : PENTAERYTHRITOL PROCESS CHEMISTRY 6 2.1 PREPARATION OF PENTAERYTHRITOL INTRODUCTION 6 2.2 PENTA PREPARATION CHEMISTRY: A DETAILED DESCRIPTION 8 2.2.1 ALDOL CONDENSATION 8 2.2.1.1 Mechanism 8 2.2.1.2 Kinetics 9 2.2.1.3 Conclusions 11 vi 2.2.2 CANNIZZARO REACTION 13 2.2.2.1 Mechanism 13 2.2.2.2 Kinetics 14 2.2.2.3 Conclusions 14 2.2.3 PENTAERYTHRITOL FORMATION 15 2.2.3.1 The specific reactions 15 2.2.3.2 Side reactions 15 2.3 SUMMARISED CONCLUSIONS 17 2.4 RECENT RESEARCH SOME SPECIAL ASPECTS 18 CHAPTER 3 CHEMICAL REACTORS FOR PENTA PRODUCTION 20 3.1 CHEMICAL REACTORS AN INTRODUCTION 20 3.1.1 THE IDEAL BATCH REACTOR 20 3.1.2 STEADY-STATE MIXED FLOW REACTOR 21 3.1.3 STEADY-STATE PLUG FLOW REACTOR 22 3.1.4 IDEAL AND NON-IDEAL FLOW IN REACTORS 24 3.2 REACTORS FOR THE PREPARATION OF PENTAERYTHRITOL 25 3.3 SOME INDUSTRIAL PROCESSES 26 3.3.1 HERCULES POWDER CO. PROCESS 26 3.3.2 JOSEF MEISSNER PROCESS 28 3.3.2.1 Meissner process with 28 Sodium Hydroxide catalyst vii 3.3.2.2 Meissner process with 28 Calcium Hydroxide catalyst 3.3.3 PERSTORP PROCESS 31 CHAPTER 4 : THE NATIONAL CHEMICAL PRODUCTS PROCESS 32 4 . 1 THE CHEMI CAL REACTOR 32 4.1.1 NCP PRIMARY REACTOR AND COOLING CIRCUIT 32 4.1.2 REAGENT ADDITION AND SPARGING SYSTEM 36 4.2 REACTION PROCESS CONDITIONS 40 4.2.1 MOLE RATIO 40 4 . 2 . 2 REAGENT STRENGTHS 40 4.2.3 REACTION TEMPERATURE 40 4.2.4 REAGENT ADDITION PROCEDURE 41 CHAPTER 5 PROBLEM, STRATEGY AND EXPERIMENTAL DESIGN 42 5.1 THE NCP REACTOR PROBLEM 42 5.2 OBJECTIVE STATEMENT AND PRACTICAL CONSTRAINTS 43 5.3 EXPERIMENTAL DESIGN 44 viii CHAPTER 6 THE EXPERIMENT 47 6.1 TEST MATERIALS 47 6.2 EXPERIMENTAL APPARATUS 48 6.3 EXPERIMENTAL PROCEDURE 52 6.3.1 ADJUSTMENT OF INDEPENDENT VARIABLES 53 6.3.1.1 Agitation and reagent dispersion 53 6.3.1.2 Mole ratio 53 6.3.2 REAGENT ADDITION RATE 54 6.4 CHEMICAL ANALYSES 54 6.5 CRITICAL EXAMINATION OF RESULTS 54 6.6 TESTWORK SETS 55 CHAPTER 7 RESULTS AND DISCUSSION 56 7.1 RESULTS 56 7.2 DISCUSSION 63 7.3 CONCLUSIONS 64 CHAPTER 8 : REAGENT SPARGING SYSTEMS 66 8.1 PENTA REACTOR SPARGING SYSTEMS: 66 PRACTICAL CONSIDERATIONS ix 8.2 THE DESIGN OF REAGENT SPARGING EQUIPMENT 68 FOR THE NCP REACTOR 8.2.1 ACETALDEHYDE SPARGER 68 8.2.1.1 Calculations: Acetaldehyde sparger 69 8.2.2 CAUSTIC SODA SOLUTION SPARGER 72 8.2.2.1 Calculations: Caustic sparger 73 8.3 ALTERNATIVE SPARGING METHODS 77 8.4 CONCLUSION: A RECOMMENDATION 78 FOOTNOTE TO CHAPTER 8 : SPARGERS : IMPLEMENTATION 79 CHAPTER 9 : TEE MIXERS 80 9.1 TEE MIXERS: GENERAL 80 9.2 A TEE MIXER FOR THE NCP REACTOR 81 CHAPTER 10 STEADY-STATE FLOW REACTORS 85 10.1 STEADY-STATE REACTORS GENERAL 85 10.2 REACTORS FOR PENTA: ESSENTIAL REQUIREMENTS 87 10.3 A CONTINUOUS PENTAERYTHRITOL REACTOR 87 10.3.1 CONCEPTUAL DESIGN 87 10.3.2 DISCUSSION 90 x 10.4 RECENT RESEARCH 91 AND INDICATIONS FOR THE FUTURE APPENDIX 1 : REACTOR PARAMETERS 92 A1.1 DISCHARGE FLOW NUMER, Nq 92 A1.2 AGITATION INTENSITY NUMBER, N, 94 . A1. 3 BLEND TIME, 8n 94 A1.4 POWER NUMBER" Np 95 A1.5 REYNOLDS NUMBER, . Re tllll 95 APPENDIX 2 : CALCULATION OF RESULTS FROM EXPERIMENTAL DATA 96 A2.1 PRODUCTS AS % mjm OF TOTAL PRODUCTS 96 A2.2 YIELDS BASED ON ACETALDEHYDE 97 A2.3 SELECTIVITIES 98 A2.4 EXPERIMENTAL RESULTS 98 REFERENCES 102 xi LIST OF FIGURES Figure page No. 2.1 Dependence of yields of pentaerythritol 18 on reaction starting conditions. 3.1 Classification of reactor types 23 3.2 Flowsheet of Hercules Powder Company Penta 27 process. 3.3 Flowsheet of Josef Meissner Company Penta 30 process 4.1 NCP Primary reactor system, cooling circuit and reagent charging. 35 4.2 NCP primary stirred tank reactor showing principal dimensions. 38 6.1 Laboratory bench scale reactor for pentaerythritol preparation. 50 6.2 Bench scale test rig for reactor parameter experiments with controlled stirring and reagent sparging. 51 6.3 Bench scale stirred tank reactor showing principal dimensions. 51 7.1 Monopenta as % mjm of total products. 58 7.2 Penta by-products as % mjm of total products.
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