Study of Phase Transition in Hard Microcrystalline Waxes and Wax Blends by Differential Scanning Calorimetry

Abstract

Phase transition temperature and associated energies in hard high melting microcrystalline waxes and its various blend with paraffin wax (melting range from 60 to 97°C) have been determined by DSC in both heating and cooling mode. The dependence of these on the composition and properties of waxes have been analyzed. The solid liquid transition temperature obtained by DSC has been compared with ASTM drop melting point of these wax samples. The present study has demonstrated that DSC can be of great use in identifying whether the wax sample is blend of different waxes or not.     

Fractionation and Characterization of Waxes

By using short path molecular distillation (SPD) and supercritical fluid extraction (SFE) techniques, petroleum waxes have been fractionated into different fractions. These wax fractions were analyzed for their composition and phase transitions by gas chromatography (GC) and differential scanning calorimetry (DSC). GC data and the DSC thermograms indicated that the waxes vary significantly in their properties and composition.     

费-托合成蜡溶剂精制及其结构性质的研究

采用甲乙酮-甲苯溶剂对含油量较高的费-托合成蜡进行脱油精制,研究蜡脱油前后在不同溶剂中的溶解性能。结果表明：甲乙酮-甲苯溶剂可以作为费-托合成蜡脱油精制的溶剂。使用X射线衍射仪对蜡样品的晶体结构进行分析研究,用差示扫描量热法（DSC）测定脱油精制蜡样品的熔点为90.68 ℃。对蜡样品的DSC曲线分析表明：费-脱合成蜡仅有一个熔融峰,没有明显的固-固晶体转变,这与石油蜡区别明显。     

PHASE TRANSITIONS IN PETROLEUM WAXES DETERMINED BY INFRARED SPECTROSCOPY

In the present paper attempts have been made to study the phase transition temperatures in petroleum waxes by infrared spectroscopy and the resulting data were correlated with phase transition temperatures obtained by differential scanning calorimetry (DSC).     

Composition and Properties of Some Petroleum Waxes

Structural composition of paraffin waxes and soft wax fraction derived from microcrystalline wax were determined. Waxes were fractionated by multistage solvent crystallization at different temperatures. The n-alkane components of the waxes were separated by urea adduction. The average structural parameters of parent waxes, their fractions, and urea adductables were estimated by ¹h and ¹³C NMR spectroscopy. The thermal parameters viz. phase transition temperature and the associated energy during phase transitions were determined by using DSC and correlated with the penetration temperature behavior of waxes. The carbon number distribution determined by GC for these waxes and their n-alkane components were also correlated with physical properties and thermal parameters.     

Characterization and Classification of Some Egyptian Petroleum Crude Waxes Using Different Techniques

Abstract

In order to characterize and identify some crude waxes, derived from various Egyptian petroleum distillates and residues, suitable for production of different types of petroleum waxes, many standard test procedures have been used for measurement the physical characteristics of crude waxes and wax products. Moreover, some analytical techniques such as gas chromatography (GC), Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (H-NMR), urea adducting analysis, and solid-liquid chromatography have been used to characterize the crude waxes. Finally, one stage fractional crystallization has been done to separate the hard waxes from El-Ameria and Suez heavy slack waxes and Alexandria and Suez crude petrolatums using ethyl acetate solvent at an ambient temperature of 20^○C and at fixed dilution and washing solvent ratios of 7:1 and 6:1 by weight, respectively. The resulting wax products are evaluated according to TAPPI-ASTM equation and petroleum wax specifications.     

Composition and Properties of Some Petroleum Waxes

Abstract

Structural composition of paraffin waxes and soft wax fraction derived from microcrystalline wax were determined. Waxes were fractionated by multistage solvent crystallization at different temperatures. The n-alkane components of the waxes were separated by urea adduction. The average structural parameters of parent waxes, their fractions, and urea adductables were estimated by ¹h and ¹³C NMR spectroscopy. The thermal parameters viz. phase transition temperature and the associated energy during phase transitions were determined by using DSC and correlated with the penetration temperature behavior of waxes. The carbon number distribution determined by GC for these waxes and their n-alkane components were also correlated with physical properties and thermal parameters.     

Determination of wax content in crude oil

Wax deposition is one of the chronic problems in the petroleum industry. The various crude oils present in the world contain wax contents of up to 32.5%. Paraffin waxes consist of straight chain saturated hydrocarbons with carbons atoms ranging from C18 to C36. Paraffin wax consists mostly with normal paraffin content (80–90%), while, the rest consists of branched paraffins (iso-paraffins) and cycloparaffins. The sources of higher molecular weight waxes in oils have not yet been proven and are under exploration. Waxes may precipitate as the temperature decreases and a solid phase may arise due to their low solubility. For instance, paraffinic waxes can precipitate out when temperature decreases during oil production, transportation through pipelines, and oil storage. The process of solvent dewaxing is used to remove wax from either distillate or residual feedstocks at any stage in the refining process. The solvents used, methyl-ethyl ketone and toluene, can then be separated from dewaxed oil filtrate stream by membrane process and recycled back to be used again in solvent dewaxing process.     

STUDY OF THE TEMPERATURE AND ENTHALPY OF WAX CRYSTALLIZATION FROM MIDDLE DISTILLATE BY DSC

The temperature and enthalpy of the wax crystallization as well as of melting have been studied in the middle distillate (boiling range: 250-375°C) obtained from the indigenous Bombay-High (Off-Shore) crude oil by using a differential scanning calorimeter (DSC). In order to have better understanding of the gel formation processes the broad distillate fraction was fractionated into five narrow fractions of 25°C interval each. From these narrow subfractions the saturates were separated from aromatics by column chromatography, and from saturates the n-paraffins were separated from iso-and cyclo-paraffins by urea adduction, to obtain the n-paraffins concentrates (urea adductables)--the wax- and the saturated solvent portion--the UNA. The thermal behaviour of narrow subfractions alongwith their urea adductables and the solvent portions have been studied and the wax appearance temperature (WAT) thus measured has been compared with those obtained by optical microscopy and with the ASTM cloud point, wherever possible. To obtain a clearer picture of the solidification process, further study has been done by preparing synthetic blends of urea adductables in different concentrations in the respective aromatic and iso- and cyclo-paraffinic solvents (UNA) and studying the thermal behaviour of each blend. It is found that the variation in WAT with wax concentration as measured by DSC is identical with that measured by optical microscopy and the ASTM cloud point. However, DSC values are lower than microscopic values and higher than ASTM cloud point. The enthalpy of the blends with the same amount of wax in the aromatic and iso- and cyclo-parffinic solvents indicated that it is higher in the saturated solvent in comparison to aromatic solvent. This confirms the fact that in an aromatic solvent the solubility of the wax is greater, and hence a comparatively lower WAT. The results are further discussed.     

STUDY OF THE TEMPERATURE AND ENTHALPY OF WAX CRYSTALLIZATION FROM MIDDLE DISTILLATE BY DSC

ABSTRACT

The temperature and enthalpy of the wax crystallization as well as of melting have been studied in the middle distillate (boiling range: 250–375°C) obtained from the indigenous Bombay-High (Off-Shore) crude oil by using a differential scanning calorimeter (DSC). In order to have better understanding of the gel formation processes the broad distillate fraction was fractionated into five narrow fractions of 25°C interval each. From these narrow subfractions the saturates were separated from aromatics by column chromatography, and from saturates the n-paraffins were separated from iso-and cyclo-paraffins by urea adduction, to obtain the n-paraffins concentrates (urea adductables)–-the wax- and the saturated solvent portion–-the UNA. The thermal behaviour of narrow subfractions alongwith their urea adductables and the solvent portions have been studied and the wax appearance temperature (WAT) thus measured has been compared with those obtained by optical microscopy and with the ASTM cloud point, wherever possible. To obtain a clearer picture of the solidification process, further study has been done by preparing synthetic blends of urea adductables in different concentrations in the respective aromatic and iso- and cyclo-paraffinic solvents (UNA) and studying the thermal behaviour of each blend. It is found that the variation in WAT with wax concentration as measured by DSC is identical with that measured by optical microscopy and the ASTM cloud point. However, DSC values are lower than microscopic values and higher than ASTM cloud point. The enthalpy of the blends with the same amount of wax in the aromatic and iso- and cyclo-parffinic solvents indicated that it is higher in the saturated solvent in comparison to aromatic solvent. This confirms the fact that in an aromatic solvent the solubility of the wax is greater, and hence a comparatively lower WAT. The results are further discussed.     

煤焦油制蜡技术的研究

以中低温煤焦油轻油为原料,采用直接加氢-溶剂脱蜡耦合工艺制备煤基蜡;在三管式固定床加氢反应器,考察反应温度、反应压力及空速对煤焦油直接加氢产物性质及正构烷烃含量的影响;采用溶剂脱蜡技术得到煤基蜡产品,并对其熔点、正构烷烃组分含量进行测定。结果表明：煤焦油直接加氢-溶剂脱蜡耦合工艺的最优条件为反应温度380 ℃,反应压力13 MPa,液体体积空速0.3 h-1,酮苯质量比8:1,剂油质量比5:1;在最优条件下制备的煤基蜡熔点为50.7 ℃,正构烷烃质量分数为93.7%。     

CHARACTERIZATION OF TOTAL WAXES DERIVED FROM SOME INDIAN CRUDE OILS BY FRACTIONATION

Characterization of total refined waxes separated from Indian origin Ratna & BorhoHa crude oils have been made by fractionation. Solvent crystallization and vaccum distillation technique have been used for the fractionation of the waxes. The study indicated that each wax had different melting point distribution characteristics.     

低熔点高硬度特种蜡的研究与开发

采用聚乙烯蜡和月桂酸作为石蜡改性剂,考察了改性工艺条件和改性剂加入量对石蜡性能的影响。结果表明：最佳工艺条件为改性时间3 h、改性温度130 ℃、搅拌速率600 r/min,聚乙烯蜡添加量为5%,月桂酸的添加量为8%;通过对两种添加剂的调合,制备出滴熔点低和硬度适宜的改性石蜡产品;在此基础上,以聚乙烯蜡量为5%、月桂酸量为8%、硬脂酸为0~25%作为复合添加剂,可以得到滴熔点更低且硬度也有所提高的改性蜡;并采用SPSS软件进行线性回归,得出聚乙烯蜡、月桂酸和硬脂酸的添加量与石蜡滴熔点、针入度（25 ℃）的关系。     

CHARACTERISATION OF PARAFFIN WAXES BY DSC AND HIGH TEMPERATURE GC

Paraffin waxes of different crude oil sources were characterised using Differential Scanning Calorimetry, and High Temperature Capillary GC techniques. The carbon number distribution of the waxes were determined by calibrating the GC with standard n-paraffins blend. The δH_s-s transition obtained in DSC. thermogram of the waxes were correlated with its normal paraffin content. This correlation was further validated by obtaining n-paraffins content through High Temperature GC technique.     

CHARACTERISATION OF PARAFFIN WAXES BY DSC AND HIGH TEMPERATURE GC

ABSTRACT

Paraffin waxes of different crude oil sources were characterised using Differential Scanning Calorimetry, and High Temperature Capillary GC techniques. The carbon number distribution of the waxes were determined by calibrating the GC with standard n-paraffins blend. The δH_s?s transition obtained in DSC. thermogram of the waxes were correlated with its normal paraffin content. This correlation was further validated by obtaining n-paraffins content through High Temperature GC technique.     

Separation of Paraffin Wax Using Solvent Fractionation

In order to separate and characterize some grades of paraffin waxes from El-Ameria crude waxes (slack waxes), a one-stage fractional crystallization technique has been done to separate the paraffin waxes with different characteristics by using different solvents and solvent mixtures at ambient temperature of 20°C and fixed dilution and washing solvent ratios (S/F) of 4:1 and 2:1 by weight, respectively. The fractionating solvents used are n-hexane, methyl isobutyl ketone (MIBK), dioxane, ethyl acetate, and butyl acetate as a single solvent and a mixture of methyl ethyl ketone (MEK) containing benzene (B) and toluene (T) as a mixed solvent. The resulting data revealed that dioxane and n-hexane solvents are not suitable for fractional crystallization of slack waxes, and the most suitable solvents for separating paraffin waxes with the standard specifications are ethyl and butyl acetates, MIBK, and the mixture of MEK, B, and T (60:20:20 by weight, respectively).     

CHARACTERIZATION OF TOTAL WAXES DERIVED FROM SOME INDIAN CRUDE OILS BY FRACTIONATION

ABSTRACT

Characterization of total refined waxes separated from Indian origin Ratna & BorhoHa crude oils have been made by fractionation. Solvent crystallization and vaccum distillation technique have been used for the fractionation of the waxes. The study indicated that each wax had different melting point distribution characteristics.     

CHARACTERIZATION OF PETROLEUM WAXES BY HIGH TEMPERATURE GAS CHROMATOGRAPHY - CORRELATION WITH PHYSICAL PROPERTIES

Hydrocarbon waxes of different composition were characterized by high temperature gas chromatography. The resulting GC data were correlated with various physical properties of the waxes, such as needle-penetration, refractive index, melting point, and kinematic viscosity. In addition to HTGC, SFC was also performed Comparison of chromatographic techniques for the separation of n-alkanes from waxes by HTGC and SFC were also done.     

高熔点相变蜡的研究

以09号蜡和己二胺为原料,在无催化剂、无交换气、常压的条件下合成高熔点相变蜡。通过正交试验设计优化实验方案,然后采用控制单一变量的方法确定的最优工艺条件为n(己二胺)：n(09号蜡)=0.65,低温反应温度165～175 ℃,低温反应时间2.0～2.5 h,高温反应温度190～195 ℃,高温反应时间1.5～2.0 h。经过DSC差式扫描量热仪表征,高熔点相变蜡的焓变量大于170 J/g,熔点为140～145 ℃,其焓变量和熔点高于目前国内同类产品。     

Separation of Paraffin Wax Using Solvent Fractionation

Abstract

In order to separate and characterize some grades of paraffin waxes from El-Ameria crude waxes (slack waxes), a one-stage fractional crystallization technique has been done to separate the paraffin waxes with different characteristics by using different solvents and solvent mixtures at ambient temperature of 20°C and fixed dilution and washing solvent ratios (S/F) of 4:1 and 2:1 by weight, respectively. The fractionating solvents used are n-hexane, methyl isobutyl ketone (MIBK), dioxane, ethyl acetate, and butyl acetate as a single solvent and a mixture of methyl ethyl ketone (MEK) containing benzene (B) and toluene (T) as a mixed solvent. The resulting data revealed that dioxane and n-hexane solvents are not suitable for fractional crystallization of slack waxes, and the most suitable solvents for separating paraffin waxes with the standard specifications are ethyl and butyl acetates, MIBK, and the mixture of MEK, B, and T (60:20:20 by weight, respectively).