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11Chemical Journal of Kazakhstan
ISSN 1813-1107 https://doi.org/10.51580/2021-1/2710-1185.07
Volume 1, Number 73 (2021), 70 - 78
UDC 541.128
N. ZHANGABAY'*, A. UTELBAYEVA ', M. YERMAKHANOV A. KIRGIZBAYEVA 2, B. KHASSANKHODJAYEVA 3
1 M. Auezov South Kazakhstan University, Shymkent, Republic of Kazakhstan;
2 S. Asfendiyarov Kazakh national medical University, Almaty, Republic of Kazakhstan;
3 Silkway International university, Shymkent, Republic of Kazakhstan.
*E-mail: [email protected]
HYDROGENATION OF BENZENE IN BATCH REACTOR
Abstract. In this article is considered hydrogenation of benzene in liquid phase at presence rhodium support catalyst.where as carrieris usedpillar structural montmorillonite obtaining from bentonite clay..The degree of using an internal surface of porous system is depended.of the size particles.Increase the concentration of chromium above 20 mmole per gram of clay does not lead to the further growth of distance. It is probably connected by that in a solution there are not hydrolized forms of chromium chloride which do not influence formation pillar structures. Modifying montmorillonite minerals containing in bentonite clay gives to them heat resistance. The specific surface of samples(containing 15-30 mmole Cr3+) were defined after heat treatment at 180°C are 240-260 m2/g and increasing the temperature up to 500-560°C decreases this value insignificant to 220-240 M2/r, accordingly. Not modified bentonite clay lost their porosity at 140°C, and a specific surface made 20 m2/g.
Besides reaction of hydro-dehydrogenation of cyclic hydrocarbons a huge interest are represented in hydrogen technology. Everyone mole of benzene and its derivatives attaching of three and more quantities of hydrogen, and are unique objects at storages and transportation of hydrogen. Thereby, necessity to develop of catalysts of hydro-dehyro-genation also follows under rather soft conditions. developed rhodium support catalyst for hydrogenation of benzene and defined the factor of efficiency using the internal surface of porosity systems. Presence of water in hydrogenated system leads to phasic course of restoration of benzene on a surface of the catalyst with formation cyclohexane and cyclo-hexene. The received experimental results expand a circle of data in the field of hydro-dearomatization motor fuels, especially transformations of aromatic hydrocarbons cyclo-alkans.
Keywords: hydrogenation, benzene, liquid phase, rhodium, catalyst,cycloalkane.
Introduction. Decrease in the maintenance of aromatic hydrocarbons, especially benzene in motor fuel is an actual and urgent problem. Toxic action of benzene and a product of its incomplete oxidation benzpyrene - cancerogenic substance accumulated in an environment, renders negative influence on safety of ability to live of people and fauna [1]. Necessity to improve technology of oil refining and its separate stages for reduction of the maintenance of benzene and its
derivatives. One of such processes is catalytic hydrodearomatization-transfor-mations of aromatic hydrocarbons tocyclohexane and its derivatives. However, the maintenance in oil distillates heterocyclic compoundswhich deactivate catalysts, demand their perfection and more detailed studying of the mechanism catalytic transformation of hydrocarbons [2-8].
Besides reaction of hydro-dehydrogenation of cyclic hydrocarbons a huge interest are represented in hydrogen technology. Everyone mole of benzene and its derivatives attaching of three and more quantities of hydrogen,and are unique objects at storages and transportation of hydrogen. Thereby, necessity to develop of catalysts of hydro-dehyrogenation also follows under rather soft conditions.
The aim of the present work was studying the hydrodearomatization of benzene-the component of motor fuels at presence rhodium support catalysts where as carrier is used pillar structural montmorillonite obtaining from bentonite clay. Pillared clays have significant potential for application in industry and in petrochemistry but relatively few studies of these types of materials have been carried out [ 9].
EXPERIMENTAL PART
Catalysts and their preparations. For preparation rhodium support catalyst (0,5-1,0 mass. % Rh) was used chloride of rhodium-RhQ3-3H2O, as a carrier was used modifiedbentonite clay. For modifying natural clay topillar structural form were used polyhydroxocomlexes of chromium [5].
To aqueous solution of chloride chromium gradually flowed the solution of sodium hydroxide at gradual hashing up to pH~3-4. Concentration of chloride chromium was paid off proceeding from calculation 5-30mmole Cr3+ per gram clay. Suspension bentonite (~1,0 mass. %) received by intensive hashing it in water during 4 h, pH-water extract of clay makes -8-9. Acidity of environment supervised by means of digital pH meter OP-208/1. In order to prevent coagulation of a solutionpolyhydroxocomlexes of chromium, it was slowly added to suspension of clay. «Reserve of basicity » Cr3+:/OH-allowing to prevent coagulation chloride of rhodium made 1/3. After endurance processed suspensions of clay during 24 h, a deposit was washed by water and condensed.The sample, after separate from a liquid phase, dried at first at the room temperature, and then at 110°C (2h) with the subsequent rise the temperature up to 180°C (4h). After cooling the firm mass was pounded to a powder, it was sifted in fractions with the certain sizes of particles. Fractions of particles modifying clay in the further was impregnated with aqueous solution o rhodium-RhCh^^O (0,5-1,0 mass% Rh ). The received dense mass was dried on a water bath, then subjected heat treatment during 6 h at 180°C.
Definition of catalytic activity. Before experience sample ofthe catalyst 0,1g was reduced by hydrogen at 250 °C during 4 h. After reduction the catalyst was cooled in the environment of hydrogen up to a room temperature and under a layer of cyclohexane was transferred to a steel autoclave with working capacity 100 cm3 the supplied by mixer and a sampler. For the hydrodearomatization is taken 50 cm3
71
mixture of benzene and cyclohexane/V (benzene:V(cyclohexane) = 1:1/ Dilution by cyclohexanewas made for dispersion of heat allocated athydrogenation of benzene and aspiration process to spend in conditions of ideal mixture. Initial rate of hydrogenation was defined bydifferential graphic method fromthe change concentration of benzene independence of time.Pressure of hydrogen was measured by a manometer and varied in an interval 0.5-6.0 МПа, and temperature of reactions changed from 120 up to 200 °C.
X-raying analyse of samples was obtained on diffractometer using CuK -radiation. A specific surface of catalysts it wasdefined by adsorption method.
The analysis of reaction products were spent by Chrom-4. Length of a column is 3 m,diameter - 3 mm filled by firm carrier « Chromaton-N» processed with liquid phase « Polyethylenglycol adipate» (15 % mass. of the carrier).
Temperature of a column 100°C, temperature of the evaporator 150 °C. Gas carrier-argon, velocity of the gas ocarrier - 50 cm3/minute. 0,50-0,54 cm3/g, interlaminar distances d001 from 0,90 up to 2,04 nanometers.
RESULTS AND DISCUSSION
Usingadsorbents of pillar structural form in catalyseand sorbtion processes was an incitement for development of methods of their synthesis and their reception from natural clay. Table 1 shows some physical characteristics ofrhodium support-catalyst were as carrier is served pillar structural montmorillonite containing inbentonite clay received from the South-Kazakhstan area of Republic Kazakhstan. Modifying bentonite clay by polyhydroxocomlexes Cr(III) leads to growth of a specific surface from 64 up to 260 m2/g, total volume of porous from 0,18 cm3/g up to 54 cm3/g, interlaminar distances from 0.90 up to 2.04 nm.
Table 1 - Some parameters of pillar structural montmorillonite modified by chromium
The maintenance of ions chromium, mmole/g.clay S, m2/g d00inano meter Total volume of porous, cm3/g Loss of thermostability
T,°C SSP,m2/g
- 64 0,90 0,18 140 20
5 130 1,30 0,40 360 80
10 160 1,60 0,46 440 110
15 240 2,02 0,50 500 220
20 260 2,04 0,54 560 240
30 240 1,90 0,51 500 230
The maximal distance 2,00-2,04 nanometers corresponds to concentration of chromium about 15-20 mmole per gram of clay where between the layers settle down polyhydroxocomplexions of chromium [6].
Increase the concentration of chromium above 20 mmoleper gram of clay does not lead to the further growth of distance. It is probably connected by that in a
solution there are not hydrolized forms of chromium chloride which do not influence formation pillar structures. The similar phenomenon with polyhydro-xocomplex ions of iron (III) also was revealed in [7]. Modifying montmorillonite minerals containing in bentonite clay gives to them heat resistance. The specific surface of samples(containing 15-30 mmole Cr3+) were defined after heat treatment at 180°C are 240-260 m2/g and increasing the temperature up to 500-560°C decreases this value insignificant to 220-240 M2/r, accordingly. Not modified bentonite clay lost their porosityat 140°C, and a specific surface made 20 m2/g.
Received modified montmorillonitewas used for preparation rhodium support catalysts (0,5-1,0 mass. % Rh) which was used for hydrogenation of benzene.
The specific surface of support catalysts are enoughand firstly were defined influence of an internal surface of catalysts to the hydrogenation rate of benzene.In order to was defined a criterion Tyle -Zeldovich which directly proportional to the resulted radius of the catalyst
where R 0 - the resulted radius of particles of the catalyst (for spherical particle Rc=R/3); k - a constant of rate of reaction; D - effective factor of diffusion of reacting molecules on a surface inside of porous
For gases the factor of diffusion has the order of 0,1 cm2/sec, and for liquid molecular diffusion -10-5 cm2/sec. [8]. On their data, the factor of diffusion for gas dissolved in a liquid has the same order, as for the liquid of 10-5 cm2/sec. At 120°C saturated vapor pressure of benzene, is equal 2 bar. Fugacity of benzene vapor in this condition is equal f ~ 0,80 bar. Activity coefficient of liquid benzene at 120°C and 40 bar is equal 0.95. At the general of pressure of system 40 bar fugacity of benzene is equal to 38 bar. Constant of phase balance: k=47.5 which allows to judge that benzene is basically in a liquid phase Constant reaction rate of hydrogenation of benzene was defined at presence of a powder of the catalyst with the average size of particles about 0,1 mm which has value 2,3 10-2 sec-1. The factor of efficiency - a degree of use of an internal surface is defined from the relation th^/^, and the value of th^ calculated by equality:
The calculated values of parameters for hydrogenation of benzene at presence of porous catalysts are shown in table 2.
Data of table 2 shows, that using the catalysts with average diameter of articles about 1 mm the factor of efficiency is 0.86 and at 2 mm - 0,63. On the basis of these data, it is possible to conclude thatthe internal surface of system is used effectively, at the size of particles of catalysts less than 0.8 mm.
For the subsequent experiences at the hydrogenation of benzene were used catalysts with the average size of particles less than 0,4 mm. As experiences were spent at intensive hashing (2000 rev/min) the influence of external diffusion can be neglected.
th^ =[exp9)-exp(-9)]/ [exp(^) + exp(-^)] .
Table 2 - Change the factor of efficiency from the size of particles on the 0,5 % Rh/carrier Condition: m (kt) = 0,1 g, t = 120°C, P (H2) = 40 bar., C(benzene) = 2.8 mol/L
The average size of diameter of particles of the catalyst, mm Ф th ф 5
0,2 0,13 0,14 0,99
0,4 0,31 0,30 0,98
0,6 0,47 0,44 0,94
0,8 0,62 0,55 0,90
1,0 0,75 0,64 0,86
2,0 1,56 0,97 0,63
d, mm
Condition: t = 120 0C; P(H2) = 40 bar. C(benzene) = 2.8 mol/L Figure 1 - Change of rate hydrodearomatization as a functionof of the size catalyst particles
At the hydrogenation of benzene, in the studied conditions, the unique product of reduction was cyclohexane.
The change acidity of support catalysts often leads to change its selectivity.
Well-known, preadsorbed water promotes formation variety acid and basicity centers of surface [3].
Next experimentation carry on to figure out the influence of water to hydrogenation of benzene at presencesupport catalysts where as carrier is used pillar structural montmorillonite modifyingby polyhydroxocomplex chromium. Results of hydrogenation of an aromatic ring are presented in table 3.
From table 3 follows, presence of water in system at hydrogenation of benzene on 20 minute of process leads to formation of 6 % mass cyclohexeneand 28 % mass.of cyclohexane . The further increase in volume of water leads to reduction of an output of products of hydrogenation.
In our opinion, the aromatic ring, after connection of four atoms of hydrogen is hydrogenated up to cyclohexane not leaving a surface of the catalyst. Alongside with it, it is possible to believe, formed cyclohexeneis superseded by molecules of water [10-12].
Table 3 - Hydrogenation of benzene at presence of water on 0,5 % the Rh/carrier. Condition: m (kt) = 0,1 r, t = 120°C, P (H2) = 40 atm.
Initial mix, ml Output of products of hydrogenation (% mass.) on time, minute
C6H10 C6H12 C6H10 C6H12 C6H10 C6H12
C6H6 C6H14 H2O 10 20 30
25 25 - - 30 - 58 - 74
25 20 5 2,5 20 4,0 36 3,0 48
25 15 10 3,0 18 6,0 28 5,0 41
25 10 15 2,0 14 3,0 24 3,0 30
25 5 20 1,0 10,0 2,0 14 2,0 18
The given circumstance testifies in favour of consecutive connection of hydrogen to aromatic ring.
However, in reactionary system the formation of cyclohexadiene which should be superseded also by molecules of water from the surface of catalyst is not observed. Probably, velocity of hydrogenation of cyclohexadiene prevails its desorption. Alongside with it it is possible to believe, that formation intermediate cycloolefines promotes character of adsorption of benzene which can be carried out in the form of plane and costal orientation. Combinations of the support rhodium catalyst at presence of molecules of water creates favorable conditions to destruction - electronic system of an aromatic ring, focusing costal adsorption of benzene. Probably, in structure of the activated complex benzene participates with 4р-electrons of rings which subsequently attaches four atoms of hydrogen. The given assumption does not contradict 18-electronic rule [13].
Conclusion. Thus, it is developed rhodium supportcatalyst forhydrogenation of benzene and defined the factor of efficiency using the internal surface of porosity systems. Presence of water in hydrogenated system leads to phasic course of restoration of benzene on a surface of the catalyst with formation cyclohexane and cyclohexene. The received experimental results expand a circle of data in the field of hydrodearomatization motor fuels, especially transformations of aromatic hydrocarbons cycloalkans.
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Резюме
Н. Жанабай, А. Утелбаева, М. Ермаханов, А. Киргизбаева, Б. Хассанкходжаева
ПЕРИОДТЫ РЕАКТОРДА БЕНЗОЛДЫ ГИДРОГЕНИЗАЦИЯЛАУ
Келпршген статьяда тасымалдагышка отыргызылган родий катализаторы ка-тысында с^йык фазада бензолды гидрогенизациялау какарастырылган. Тасымалда-гыш ретшде бентонит сазын к¥райтын монтмориллонит минералы пайдалынады, Бентонит сазына кеуекп к¥рылым беру Yшiн полигодроксокомплекс тYзетiн хром ионары пайдаланылган. Кеуектi к¥рылым алу барысында эрбiр грамм топырак сазына 20 ммоль хром ионыныц мeлшерi жеткiлiктi. Концентрацияны арттыру барысында хромныц гидролизге ^шырайтындыгы ескерiлген. Монтмориллонитке берш-ген кеуектi к¥рылым тасымалдагыш бойына термиялык т^рактылык жэне оныц меншiктi аудан бетiнiн артуына себепшi болады. Кдоамында 15-30 ммоль Cr3+ мeлшерi бар кеуектi к¥рылымды бентонитп 180 оС температурасында кыздыруга ^шыратып ендегеннен сон онын меншiктi аудан беп 240-260 м2/г, шамасын, ал температураны 500-560 °C дейiн жогарылащанда, шамала гана 220-240 м2/г, шама-сына eзгеретiндiгi аныкталган. внделмеген бентонит саз топырактары кеуектшк-терiн 140оС температурасында кыздырганда жогалтады жэне б^л 20 м2/г шамасында болады. Кеуекп к¥рылымнын iшкi куыс беттерiн пайдалану, алынган белшектер-дiн елшем тYрiне байланысты болады. Аталынган гидрлеу - дегидрлеу реакциялары газ кYЙiндегi сутекп тасымалдау жэне сактау мэселелерiмен айналысатын сутектiк технология саласын да катты кызыктыруда. Ароматты сакинанын эрбiр молi eзiнен Yш есе кеп мелшердеп сутегiнi к¥рамына косып алады. Демек, тиiмдi технология-лык жагдайларда гидрлеу Yдерiсiн жузеге асыру Yшiн химиялык eзгерiстердi онтайлы жYргiзетiн катализаторлар жуйелерш алу жэне оларды синтездеу мэселелерi туын-
дайды. Аталган мэселелердi шешу жолында тасымалдагыш бетiне отыргызылган родий косылыстары карастырылды. Алынган катализаторлардын iшкi куыс беттерш пайдалануды сипаттайтын коэффициент шамасы аныкталынды. Yдерiстi жYргiзу барысында эрекеттесу жYЙесiнде аздаган су болуы химиялык реакцияньщ циклогек-сен аркылы сатылап етепндтн кврсетедi.АлынFан мэлiметтер ароматикалык саки-налы косылыстарды сутекпен катализатор катысында циклоалкандарга айналдыру т^ргысындагы мэлiметтердi кенейтедi.
Тушн свздер: гидрлеу, бензол, с^йык фаза, реактор, родий, катализатор, цикло-алкан.
Резюме
Н. Жанабай, А. Утелбаева, М. Ермаханов, А. Киргизбаева, Б. Хассанкходжаева
ГИДРОГЕНАЦИЯ БЕНЗОЛА В РЕАКТОРЕ ПЕРИОДИЧЕСКОГО ДЕЙСТВИЯ
В статье рассматривается гидрирование бензола в жидкой фазе в присутствии нанесенного родиевого катализатора. В качестве носителя используется столбчатый структурный монтмориллонит, получаемый из бентонитовой глины. Повышение концентрации хрома выше 20 ммоль на грамм глины не приводит к дальнейшему росту расстояния. Вероятно, это связано с тем, что в растворе отсутствуют гидроли-зованные формы хлорида хрома, которые не влияют на формирование столбчатых структур. Модификация минералов монтмориллонита, содержащихся в бентонитовой глине, придает им термостойкость. Удельная поверхность образцов (содержащих 15-30 ммоль Сг3+), определенная после термообработки при 180 °С, составляет 240-260 м2/г, а повышение температуры до 500-560 °С снижает это значение незначительно до 220-240 м2/г, соответственно. Немодифицированная бентонитовая глина потеряла пористость при 140 ° С, а удельная поверхность составила 20 м2/г. Степень использования внутренней поверхности пористой системы зависит от размера частиц. Реакции гидрирования - дегидрирования циклических углеводородов огромный интерес представляют в водородной технологии для сохранения газообразного водорода. Каждый моль бензола и его производные присоединяют три и более количества водорода, и является уникальным объектом при хранении и транспортировке газообразного водорода. Таким образом, необходимость разработки катализаторов гидродегидрирования также возникает в достаточно мягких условиях. Разработан родиевый носитель катализатора для гидрирования бензола и определен коэффициент полезного действия с использованием внутренней поверхности пористых систем. Присутствие воды в гидрогенизированной системе приводит к поэтапному процессу восстановления бензола на поверхности катализатора с образованием цикло-гексана и циклогексена. Полученные экспериментальные результаты расширяют круг данных в области гидродеароматизации моторных топлив, особенно превращений ароматических углеводородов в циклоалканы.
Ключевые слова: гидрирование, бензол, жидкая фаза, реактор, родий, катализатор, циклоалкан.
Information about authors:
Zhangabay Nurlan Zhangabayuly Director of the Department testing laboratory, candidate of technical Sciences, associate Professor of the Department "Industrial, civil and road construction", M. Auezov South Kazakhstan University, Shymkent, Kazakhstan; [email protected]; http://orchid.org/0000-0002-8153-1449
Utelbayeva Akmaral Bolysbekovna Doctor of chemical Sciences, associate Professor of "Chemistry", M. Auezov South Kazakhstan University, Shymkent, Kazakhstan; mako [email protected]; http://orchid.org/0000-0002-4771-9835
Yermakhanov Myrzabek Nysanbekovich Head of the Department of Chemistry, M. Auezov South Kazakhstan University, Shymkent, Kazakhstan; [email protected]; https://orcid.org/0000-0003-0939-1792
Kirgizbayeva А ray Askanbayevna Associate Professor of the Department of "Biochemistry" of the Kazakh National Medical University named after S. Asfen-diyarov, Almaty, Kazakhstan; aray [email protected]; http://orchid.org/0000-0002-3130-1469
Khassankhodjayeva Bibi-Mariyam Sheralikyzy Master of pedagogical Sciences, lecturer of the Department «Chemistry and biology», Silkway International university, Shymkent, Kazakhstan; perhaps [email protected]; https://orcid.org/0000-0002-3568-2043
