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Synthesis of 2,2′-dibenzoylaminodiphenyl disulfide based on Aspen Plus simulation and the development of green synthesis processes

  • Yan Zhang , Deluo Ji , Song Ma , Wenbo Wang , Ruiguo Dong , Lilong Shi , Linlin Pan , Xiaolai Zhang EMAIL logo and Mengcheng Du EMAIL logo
Published/Copyright: April 29, 2020
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Green Processing and Synthesis
From the journal Green Processing and Synthesis Volume 9 Issue 1

Abstract

The rubber peptizer 2,2′-dibenzoylaminodiphenyl disulfide is typically synthesized from C7H5NS, NaOH, H2SO4, and H2O2, but these reactants were replaced with C6H4ClNO2, C2H6O, Na2S, S, and N2H4·H2O, and these raw materials effectively improved the synthesis yield, reduced the number of synthetic steps, and made the synthetic process greener. Although the catalyst is difficult to recover, it effectively avoids using ethanol as a volatile organic solvent. The Aspen Plus method was used to simulate the key processes in the synthesis in the experimental conditions as the boundary conditions. The simulation results show that the feed ratio of C7H5NS, H2O2, and C7H5ClO directly determines the yield of the reaction, and the equivalents of NaOH, H2SO4, and Na2CO3 indirectly affect the yield of the reaction by changing the reaction environment and controlling the formation of byproducts. The temperature of the ring-opening reaction and the acylation reaction should be maintained within 110–120°C to maximize the yield. The oxidation reaction temperature also directly affects the reaction yield and should be kept below 40°C. The simulation results are consistent with practical industrial production conditions. Based on the developed green synthesis process and the optimal process parameters obtained from the simulation, the industrial-scale production of 10,000 tons of 2,2′-di benzoyl amino diphenyl disulfide was carried out. Compared with that of o-nitrochlorobenzene, the yield of 2,2′-dibenzoylaminodiphenyl disulfide increased from approximately 72% to more than 90%. Using this method instead of the original synthesis method avoids the use of o-nitrochlorobenzene, which is neurotoxic; Raney nickel as the metal catalyst, which is difficult to recycle with existing environmental protection technologies; and ethanol as the organic solvent, which is associated with environmental problems. The amine tail gas that is easily generated in the original synthesis method is not generated in this system, and the drying step is eliminated.

Keyword: rubber peptizer; process synthesis; Aspen Plus simulation; process optimization; clean production

1 Introduction

The peptizers used as rubber additives play a very important role in improving rubber processing and the quality of rubber products. These additives improve the effects of chemical mastication, decrease the time required for mastication, and increase plasticity while having no effect on the aging of rubber products, making them especially suitable for the processing of dense materials [1]. The important raw materials of early rubber peptizers are benzene, aniline, carbon disulfide, phenol, aldehydes, and their derivatives. With the increasing processing requirements for rubber products and the increasing strict environmental protection regulations, research and development involving green plasticizers as rubber additives has attracted substantial interest but remains quite difficult.

Currently, research and development involving rubber peptizers and mainstream production techniques is mainly focused on 2,2′-dibenzoylaminodiphenyl disulfide (hereinafter referred to as DBD). Engels [2,3] combined benzenesulfonyl chloride and its derivatives to form disulfide bonds, which can then be converted to diphenyl disulfides by treatment with N2H4 and HI/HCl, and then, N2H4/NaOH can be added to the disulfide species to form sodium thiophenolate [4]. Chedekel et al. [5] and Adelaere et al. [6] used N2H4 to ring-open C7H5NS to obtain C6H7NS as an intermediate. Ankodia et al. [7] formed disulfide bonds with C6H7NS by using H2O2 to form a di-disulfide compound (DATA), and DBD was formed as the final product using C7H5ClO.

The synthesis methods are roughly divided into two categories: one is based on C6H7N and NaHS, and the target product is synthesized through addition, hydrolysis, oxidation, and acylation [2,3]; the other is the synthesis of o-nitrochlorobenzene, using C6H4ClNO2 as the raw material, and reacting it with NaHS, Na2S2, (NH4)2S, and Na2SO4 to prepare the target product [5,6]. However, both the synthesis methods have common technical problems. On the one hand, the synthesis processes are operationally complicated, have low product yields, and generate several byproducts. On the other hand, in the production process, substantial amounts of “three wastes” are discharged, and they are difficult to handle. The severity of these problems can vary depending on the raw materials. The waste products are highly toxic, explosive, and dangerous substances with a low safety factor. Therefore, the research on new synthetic routes and the development of green synthetic techniques are important for industrial applications.

In this article, C7H5NS, NaOH, H2SO4, and H2O2 replaced C6H4ClNO2, C2H6O, Na2S, S, and N2H4·H2O as the raw materials for the synthesis. The green synthesis process was optimized to improve the yield, reduce the number of synthetic steps, and effectively solve the problems associated with the poor recyclability of the catalyst while avoiding the use of ethanol as a volatile organic solvent [8]. The Aspen Plus method was used as the boundary conditions for the experimental conditions, and the synthesis was simulated based on its key steps to obtain the best process parameters, and the simulation results were compared with the actual industrial production process [9,10,11].

2 Experimental research on green synthesis process for accessing DBD

Currently, the main synthetic route to o-nitrochlorobenzene used throughout the world is shown in Figure 1.

Figure 1 Synthetic route to o-nitrochlorobenzene.
Figure 1

Synthetic route to o-nitrochlorobenzene.

The reaction pathway is based on C6H4ClNO2, C2H6O, Na2S, S, and N2H4·H2O, and C6H4ClNO2 is a dangerous drug substance. Two intermediate products are formed in this synthetic route, and the two intermediates must be dried and distilled to remove the reaction solvent and then ground to prepare them for the next step. In the pulverization process, some intermediate products are lost in the form of dust, and the generated dust containing the amino and nitro compounds is a sensitization hazard. The entire reaction process requires Raney nickel as the metal catalyst, but it is difficult to recycle with existing environmental protection technologies. The yield of the entire synthesis process is low, and the unique catalytic activity of Raney nickel makes it highly combustible and prone to explosion when exposed to the oxygen in air. The entire reaction process is complicated and difficult to control accurately.

On the basis of the aforementioned problems, a reaction path involving benzothiazole was developed to make the production process greener. Compared with the traditional o-nitrochlorobenzene synthesis route, C7H5NS, NaOH, H2SO4, and H2O2 replaced C10H4ClNO2, C2H6O, Na2S, S, and N2H4·H2O as the raw synthetic materials, and H2SO4 was used as the activating agent to greatly improve the oxidation performance of H2O2 [12,13] and avoid the use of Raney nickel as the metal catalyst. In the reaction pathway, instead of proceeding through two intermediates, only one intermediate was involved in the synthesis of the target product, and the number of reaction steps was reduced, effectively improving the synthesis yield and simplifying the reaction control process. Ethanol was not used at any stage of the reaction process, and the drying step was eliminated to avoid having to recover the ethanol in an environmentally friendly manner.

The developed benzothiazole method is obviously greener, and the reaction yield was increased from 72% to over 90%, while avoiding highly toxic C6H4ClNO2, catalytic Raney nickel that is extremely explosive, and the use of ethanol as a solvent. The number of intermediates in the reaction process was decreased from two to one, and the drying process was eliminated, simplifying the tedious control procedures for the entire reaction process. The entire synthesis process effectively solves the problems associated with the o-nitrochlorobenzene method, which readily resulted in a human sensitization hazard and posed environmental recycling problems. The developed benzothiazole method and the DBD synthesis process are shown in Figure 2.

Figure 2 Benzothiazole synthesis route.
Figure 2

Benzothiazole synthesis route.

The laboratory adopts the following preparation scheme, and the synthetic route is divided into two steps: in the first step, first, the accurately weighed C7H5NS and 32% NaOH are added, the temperature is gradually increased to 110°C and to reflux, and this temperature is maintained for 5 h and the mixture is cooled down before using. H2O, 98% H2SO4, and 30% H2O2 are configured as oxidants and added dropwise to the aforementioned reaction system to control the reaction endpoint pH to 6–7. After stirring for 30 min, the system is cooled to room temperature and the mixture is suction filtered. The mixture is dried to obtain intermediate dithiodiphenylamine (hereinafter referred to as DATA). In the second step, first, the accurately weighed intermediate DATA and the solvents C7H8 and Na2CO3 are added, the temperature is gradually increased to reflux, and C7H5ClO is added to the system dropwise. After the reaction reached the end point, water is added to wash the salt, and the brine is separated while hot. Then, the mother liquor system is cooled to room temperature, and the solid is filtered by suction to obtain the target product DBD. The experimental results are presented in Tables 1 and 2.

Table 1

Effect of reactant ratio on reaction yield

NaOH/C7H5NSYield of C6H7NS (%)H2SO4/H2O2Yield of DATA (%)C7H5ClO/Na2CO3Yield of DBD (%)
2.094.61.277.21.673.6
2.599.11.496.81.885.3
3.099.51.697.12.092.6
3.599.61.896.72.294.2
4.099.82.097.12.494.5
Table 2

Effect of reaction temperature on reaction yield

Alkaline hydrolysis temperature (°C)Yield of C6H7NS (%)Oxidation temperature (°C)Yield of DATA (%)Acylation temperature (°C)Yield of DBD (%)
8080.41597.29058.3
9087.92097.510088.2
10094.82597.111095.9
11098.64095.512095.1
12099.45086.413093.5

3 Process simulation and optimization of the benzothiazole synthesis

The traditional scale-up process, from the laboratory scale to the industrial production scale, in addition to requiring large investments of time and money, is quite complex. This is not surprising as the relationship between the various synthetic process parameters is complex. It is difficult to scale-up processes to the industrial scale, and it is especially difficult to optimize systems throughout the production process to achieve effective engineering amplification and the ultimate goal.

Since the late 1990s, various process simulation software programs have been widely used in industrial amplification and process optimization control in real-world industrial settings. Among them, Aspen Plus is one of the most common and widely used in the chemical, oil refining, oil and gas processing, petrochemical, and other industries, and it has been widely recognized by the engineering community [12,13]. However, Aspen Plus software has rarely been used to assess the rubber additive production. Therefore, it is necessary to carry out the relevant Aspen Plus simulation on the newly developed benzothiazole-based synthesis (DBD) to optimize the whole production system to achieve a high reaction yield, reduce energy consumption, and make the reaction greener.

With the help of Aspen Plus, the experimental data and a large amount of engineering data were used as boundary conditions to select accurate and reliable physical methods and models [14,15]. By using the sensitivity tool analysis in Aspen Plus, simulation results from different working conditions can be obtained while avoiding problems such as a large experimental workload and simplifying the analysis process. The results obtained from the simulations can be used as the initial values of the engineering operating conditions, reducing the adjustment interval.

The key to the entire simulation is having a database of known physical and chemical properties. However, currently, a complete database of physical and chemical properties is difficult to obtain. In this article, we use the physical properties of pure substances such as C7H5NS, NaOH, H2O2, H2SO4, Na2CO3, C7H5ClO, C7H8, and H2O built in Aspen Plus. For the substances C6H7NS, DATA, and DBD, which are not in the physical property database, we use physical property estimation to make a preliminary estimation of the missing data and then establish the related calculation methods to obtain the physical and chemical property data. Therefore, relevant calculation methods must be established to determine the physical and chemical properties relevant to the synthesis process [16,18].

The evaluation of the DBD synthesis path developed herein starts with the construction of a reaction force field model and the calculation of the bond order (BO) between any two atoms to determine the instantaneous atom connectivities, as shown in equation (1) [19].

(1)Esystem=Ebond+Elp+Eover+Eunder+Eval+Epen+Ecoa+EC2+Etriple+Etors+Econj+EHbond+EvdWaals+ECoulomb

The most basic assumption of the BO definition in the reaction force field is that there is a certain mathematical relationship between the BO and the distance between the atoms. Based on the distance between the atoms, the BO between any two atoms can be directly obtained. In the ReaxFF reaction force field, the bond level BOij is defined as a function of the interatomic distance rij, and the bond level is divided into three parts in the chemical sense using the definitions of single bond BOij, double bond BOij and triple bond BOij in the chemical bond contribution, as equation (2) [20].

(2)BOij′=BOijσ+BOijπ+BOijππ=exp[pbo1⋅(rijroσ)pbo2]+exp[pbo3⋅(rijroπ)pbo4]+exp[pbo5⋅(rijroππ)pbo6]

The energy of any two groups is represented by a key parameter, such as the bonding function (equation (3) [21]):

(3)Ebond=−Deσ⋅BOijσ⋅exp[pbo1⋅(1−(BOijσ)pbo2)]−Deπ⋅BOijπ−Deππ⋅BOijππ

Gauss View is used to obtain chemical kinetic information and thermodynamic information. According to the Schrodinger equation and the Hartree–Fock equation, combined with the density functional theory (DFT), E0 is calculated in equation (4)):

(4)E0=−∑aZa∫∑i|θiks|2ria−12∑iθiks|∇i2|θiks+12∬∑i|θiksl|2ρ(r2)ri2dr1dr2+EXC(ρ)

By using the KiSTheIP program, a transition state theory method was first constructed. The calculation of the reaction path degeneracy σ is as follows (equation (5)):

(5)σ=σ(R)×n(R)/[σ(TS)×n(TS)]

σ(R) and σ(TS) refer to the rotational symmetry numbers of the reactant and the transition state structure, respectively, and n(R) and n(TS) refer to the number of the chiral isomers of the reactant and the transition state structure, respectively. For bimolecular reactants (equation (6)):

(6)σ=σrotRσrotTS=σrotR1×σrotR2/σrotTS

The thermodynamic and kinetic parameters of the obtained DBD reaction are presented in Table 3.

Table 3

Reaction thermodynamics and kinetic parameters

Reaction heat (kcal/mol)Rate constant (cm3/molec/s)
Alkaline reaction19.45.80 × 10−9
Oxidation reaction−72.59.23 × 10−12
Acylation reaction−7.612.59 × 10−16

Finally, combining the available physical and chemical data [18], Aspen Plus was used to model the process flow. By using the experimental data for the initial design, sensitivity analysis was used to analyze and optimize the feed and kettle temperatures at each stage. The final simulation optimization maximized the yield of DBD and provided a platform and guidance for determining future operating conditions and optimizing the actual processes.

In the actual production operation, DBD will undergo a series of complex physical and chemical changes. The simulation needs to simplify the model while remaining consistent with the actual situation to simplify the calculation process and ensure the accuracy of the simulation. In this simulation, this article uses the NRTL and ELECNRTL physical properties methods and the built-in physical property library of Aspen Plus. In combination with the actual operating state, Aspen Plus simulations propose the following assumptions [14]:

  1. The DBD production process is in a stable operating state in which none of the parameters change with time.

  2. Because the heat transfer in the reactor is efficient, the temperature distribution in the reactor can be regarded as a uniform.

  3. Based on the previous experimental results, excess water in the feed does not affect the synthesis process; in addition, when the gasification rate is greater than 0.4, the synthesis can be carried out smoothly. Thus, neither the water content in the feed nor the benzene extraction temperature is considered. The benzene gasification rate should be >0.4.

The model of the actual DBD production process [14] is shown in Figure 3. For reactions with known equations for which the effects of equilibrium and kinetics must be considered [13], the RCSTR module was selected first. C7H5NS and NaOH are mixed in MIX1 and then introduced into R1 and heated to reflux. C6H7NS is then cooled, and a small amount of CO2 may be generated by SEP1 and SEP2 removal. The oxidant prepared by using H2SO4, H2O2, and H2O is reacted with alkali-releasing outlet stream 5 to obtain DATA in R2, and outlet stream 7 and C7H8 are mixed and heated prior to separation in Decanter1. The aqueous phase is discharged through stream WATER1. The oil phase is discharged from stream 10, mixed with C7H5ClO and Na2CO3 through FSPLIT, and introduced two identical acylation tanks, R3-1 and R3-2, to afford DBD products containing impurities. DBD was purified by washing in Decanter2, crystallization in CRY, and centrifugation in CFUGE. Both the crystals from CRY and the centrifuged C7H8 from CFUE were refluxed with MIX6, and fresh C7H8 was added [21]. The temperatures of the alkaline hydrolysis reactor, the acylation reactor, and the extraction kettle are high, causing some of the materials to be vaporized. To keep the pressure in the kettle constant, the experimental system was equipped with a reflux condenser, but this was not considered in the model; instead, the reactor pressure was set to 1 atm. The temperature of the reactor is controlled by a protective jacket and a coolant configured by H2O/C2H5OH. At the same time, in the actual production, the logistics of the pump used to transport the material must be considered. When the model is built, it is directly ignored, and the default steady flow is used instead; this results in a difference in energy loss between the actual process and the model, but the material loss is consistent. The neglected losses can be considered equal to actual process outputs.

Figure 3 The process flowchart for DBD production in Aspen Plus.
Figure 3

The process flowchart for DBD production in Aspen Plus.

4 DBD synthesis process aspen plus simulation

General process studies involve reaction concentrations, reaction temperatures, reaction times, and the like. However, in terms of making the process greener, due to the particularities of the synthesis of the DBD reaction, the reaction time must remain within a narrow range, so the feed ratio and the reaction temperature must be directly used to control the product yield and the production of byproducts. Therefore, this process relies most heavily on the reactor module, and the remaining modules are considered as supplements. Each module is built in turn, and each influencing factor is independently analyzed and optimized and applied to subsequent modules, thereby obtaining the optimal yield of the final product (Figure 4).

Figure 4 The main reaction equation in the DBD production process.
Figure 4

The main reaction equation in the DBD production process.

4.1 Alkaline hydrolysis

4.1.1 Effect of the NaOH/C7H5NS feed ratio on the yield of C6H7NS

Figure 5 shows that the C6H7NS yield increases linearly as the NaOH/C7H5NS feed ratio was increased from 2.4 to 2.7 at a constant initial temperature. At feed ratios of 2.7–2.9, the C6H7NS yield curve gradually levels off. This pattern is mainly due to the effects of stirring; the flow is initially fully incorporated in the reactor, and the reaction is promoted to the maximum extent, but the stirring capacity is limited and there is inhomogeneity in the reactor. As the reaction time increases, the parameters in the detention zone will begin to apply to the retention zone and eventually the homogeneous zone of the reaction, and the yield of C6H7NS will change only slightly. When the feed ratio is greater than 3.0, the yield of C6H7NS reaches a maximum of 98.7%. NaOH provides the alkaline environment for the C7H5NS ring opening, causing NaOH to indirectly affect the synthesis of C6H7NS, while the production of C7H5NS directly affects the synthesis of C6H7NS. As the specific gravity of the NaOH feed increases, almost all of the C7H5NS participates in the reaction. Excess NaOH has no effect on the yield of C6H7NS, but it does affect the oxidation reaction, resulting in wastage of raw materials. Therefore, the feed ratio of NaOH/C7H5NS was set at 2.9 to allow the collection of C6H7NS. This ratio offers almost the same reaction rate while avoiding the wastage of raw materials.

Figure 5 Relationship between NaOH/C7H5NS feed ratio and C6H7NS yield.
Figure 5

Relationship between NaOH/C7H5NS feed ratio and C6H7NS yield.

4.1.2 Effect of the temperature of the alkaline reactor on the yield of C6H7NS

The relationship between the temperature of the alkali decanter and the yield of C6H7NS is obtained. The effect of the temperature of the alkali dehydration on the yield of C6H7NS is significant. When the temperature in the kettle was <120°C, the yield of C6H7NS gradually changed with the increasing temperature. At 120–130°C, the reaction yield reached its maximum, and temperature is no longer the dominant factor influencing the reaction outcome. As the temperature was further increased, the yield of C6H7NS remained constant at the maximum. In this study, the optimal reactor temperature was 120°C, and the optimized conditions for the alkali hydrolysis reaction resulted in a C6H7NS yield of 99.5% (Figure 6).

Figure 6 Relationship between the temperature of the alkali hydrolysis reactor and the yield of C6H7NS.
Figure 6

Relationship between the temperature of the alkali hydrolysis reactor and the yield of C6H7NS.

4.2 Oxidation reaction

4.2.1 Effect of the oxidant feed ratio on data yield and pH in the kettle

As shown in Figure 7, C6H7NS has a significant effect on H2O2 under acidic conditions, and the –S–H bond breaks to form an S–S– bond. H2O2 participates in the oxidation reaction, and H2SO4 does not participate in the reaction but controls the pH in the reactor. When the H2SO4/H2O2 feed ratio was <1.25, the DATA yield increased slowly, and the reaction environment became alkaline. When the feed ratio was between 1.25 and 1.4, the pH in the kettle changed rapidly from alkaline to an acidic. The yield of DATA increased linearly, and the slope of the production curve increased as the reaction rate increased. When the feed ratio was further increased, the yield of DATA reached is maximum and stabilized. The H2SO4/H2O2 feed ratio of 1.4 was selected.

Figure 7 Relationship between the feed ratio of H2SO4/H2O2 and the DATA yield and pH in the kettle.
Figure 7

Relationship between the feed ratio of H2SO4/H2O2 and the DATA yield and pH in the kettle.

4.2.2 Effect of the oxidation reactor temperature on the DATA yield

As shown in Figure 8, the temperature has a large influence on the DATA yield. Temperature ≤35°C favored the formation of DATA and provided the maximum yield; as the temperature increases, the yield of DATA began to decrease. When the temperature was >45°C, the yield of DATA decreased rapidly and reached less than 10% at 60°C. The simulation results suggest that H2SO4 is generated by the oxidant, and the water encounters a large amount of heat from the exothermic reaction in the autoclave, and the oxidation reaction proceeds more smoothly at low temperatures. Therefore, the temperature inside the reactor should be strictly controlled, and the reactor should be precooled. In this article, the temperature of the autoclave was 25°C, and the optimized conditions of the oxidation reaction afforded a DATA yield of 98.2%.

Figure 8 Relationship between the oxidation reactor temperature and the DATA yield.
Figure 8

Relationship between the oxidation reactor temperature and the DATA yield.

4.3 Acylation reaction

4.3.1 Effect of C7H5ClO/Na2CO3 feed ratio on the DBD yield

As shown in Figure 9, because C7H5ClO directly participates in the acylation reaction, the specific gravity of the feed directly affects the DBD yield. When the feed ratio of C7H5ClO/Na2CO3 was <1.9, the yield of DBD increases linearly; when the feed ratio was 1.9–2.1, the yield of DBD gradually increased to its maximum value; when the feed ratio was further increased, the DBD yield remained almost constant. This trend was caused by the fact that NaOH is formed as a byproduct in the acylation reaction, the specific gravity of the feed of C7H5ClO is increased, and the amount of HCl is also increased, and the amount of Na2CO3 is insufficient to neutralize the generated HCl, which restricts the DBD yield. Therefore, the C7H5ClO/Na2CO3 feed ratio of 2.1 was chosen.

Figure 9 Relationship between the feed ratio of C7H5ClO/Na2CO3 and the DBD yield.
Figure 9

Relationship between the feed ratio of C7H5ClO/Na2CO3 and the DBD yield.

4.3.2 Effect of acylation reactor temperature on product DBD yield

As shown in Figure 10, when the temperature was lower than 100°C, the yield of DBD increased linearly; from 110°C to 112°C, the slope decreases and the yield reaches its maximum. However, when the temperature is further increased, the yield of DBD begins to decrease. On the one hand, the temperature may be above the optimum reaction temperature, which shifts the reaction equilibrium to the left, and the DBD is gradually consumed. On the other hand, it may be that the temperature being too high favors the side reaction, and the increase in the formation of byproducts affects the DBD yield. In this article, the temperature of the acylation reactor was 110°C, and the optimized acylation reaction conditions afforded a DBD yield of 96.4%.

Figure 10 Relationship between the acylation reactor temperature and the DBD yield.
Figure 10

Relationship between the acylation reactor temperature and the DBD yield.

4.4 Crystallization

Figure 11 shows that when the temperature of the crystallization kettle is low, a large amount of C7H8 is present in the DBD, and the crystallization effect is poor. When the temperature is >120°C, the purity of the DBD in stream 18 can reach 95%, and the content of C7H8 is less than 0.5%, and the crystallization effect is better. For the optimization of C7H8 feed flow in the crystallization stage, we first explored to determine the optimal feed equivalent of C7H8 without introducing a recycle stream and then used the optimization module in Aspen Plus to optimize the toluene loss as the optimization goal. The introduced recycling logistics is selected as the tear logistics, and the recycling logistics is optimized to ensure the maximum recovery rate of C7H8 and ensure low-emission green production.

Figure 11 Relationship between the crystallizer temperature and the purity of the DBD and the C7H8 in stream 18.
Figure 11

Relationship between the crystallizer temperature and the purity of the DBD and the C7H8 in stream 18.

The stream exiting the crystallization vessel contains a small portion of C7H8. Therefore, it is necessary to centrifuge this stream to remove the C7H8 impurities in the DBD, and the separated C7H8 can be recycled. Under normal centrifuge operation conditions, the conversion rate of the final product (DBD) is 92.5%, which meets the quality requirements for the final product.

5 Clean synthetic process

On the basis of the previous generation of production process experience, we have developed 10,000 ton 2,2′-dibenzoylamino diphenyl disulfide based on the laboratory synthesis stage of DBD, the pilot test stage, and the Aspen Plus process simulation stage. The industrial production process and the device are as shown in Figure 12. The process consists mainly of a purification system for the reaction system, the intermediate products and the final products, as well as a toluene circulation system, a heat exchanger, and other auxiliary systems. C7H5NS is mixed with NaOH and heated to reflux to form C6H7NS as an intermediate. At the end of the reaction, a preformulated oxidant is added at low temperature to control the formation of DATA. Then, this solution is mixed with toluene and heated to reflux. The aqueous phase is separated in the extraction vessel, and the residual oil phase is mixed with C7H5ClO and Na2CO3 and heated to reflux in the acylation reactor [7] to obtain DBD containing impurities; the DBD is purified by washing and crystallization. The final product (DBD) is obtained by centrifugation. Toluene separated during the crystallization and centrifugation steps can be recycled and is fed together with fresh toluene into the extraction vessel.

Figure 12 Diagram of the industrial process for producing DBD.
Figure 12

Diagram of the industrial process for producing DBD.

The simulation results in this article provide initial values for the actual operating parameters for the production of DBD as a rubber additive by Shandong Yanggu Huatai Co. Ltd, which reduces the debugging interval. Compared with the synthesis of o-nitrochlorobenzene (72%), the yield of 2,2′-dibenzoylaminodiphenyl disulfide is increased to over 90%. The use of this method instead of the original synthesis method avoids the use of o-nitrochlorobenzene, which is neurotoxic, and catalytic Raney nickel, which is difficult to recycle with existing environmental protection technologies, and the environmental problems associated with the volatile amine tail gas easily generated in the original synthesis method. The drying step is eliminated, and the use of ethanol as an organic solvent is avoided, making the overall reaction greener.

6 Conclusion

The model of the actual production process of DBD established using Aspen Plus is consistent with the actual operation data of the project. The model can reasonably predict different working conditions for the DBD production process.

While controlling other variables, the feed amount and the temperature of each process module were analyzed and optimized, and the feeds can be further optimized. The feed ratio between the best streams is 2.9 for NaOH/C7H5NS, 1.4 for H2SO4/H2O2, and 2.1 for C7H5ClO/Na2CO3. The temperature optimization results show that the temperatures of the alkali hydrolysis reactor, oxidation reactor, and acylation reactor should be controlled at ≥120°C, ≤35°C, and 110–115°C, respectively, and the temperature of the crystallization kettle should be controlled at >110°C.

The practical 10,000 ton DBD production process showed that the reaction yield can reach over 90% while still avoiding the use of neurotoxic o-nitrochlorobenzene and the use of catalytic Raney nickel, which is difficult to recycle using existing environmental protection technologies. The original synthetic method is prone to crucial environmental problems related to the amine tail gas. The drying step is eliminated, and the use of ethanol as an organic solvent is avoided, making this a greener reaction method. The comparison between the simulation results and the actual feed quantity, operation parameters, DBD output, and yield is presented in Table 4.

Table 4

The simulation results are compared with the enterprise parameters

Operating conditions and resultsMaterials and equipmentSimulation parametersActual parameterDeviation from actual
Feed rate (kg/h)Benzothiazole≥800875−75
32% sodium hydroxide2,250–2,4002,285−35
30% hydrogen peroxide≥350401−51
98% sulfuric acid≥650641+9
One water intake1,5002,000−500
Methylbenzene2579.11,885+694.1
Sodium carbonate≥8001,000−200
Benzoyl chloride≥400412−12
Secondary water intake≥2,5001,500+1,000
Operating parameters (°C)Alkaline hydrolysis kettle≥120125−5
The oxidizing kettle≤35≤40−5
The acylation kettle110–1151100
Crystallization axe1101100
Product production (kg/h)Stream 211289.71,200+89.7
Product yield92.5%90%+2.5%

Acknowledgments

The project was funded by the National Science and Technology Support Program (Plan No. 2009BAE76B00) and the Shandong Provincial Key Research and Development Program (Project No. 2017CXGC11012).

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Received: 2019-12-13
Revised: 2020-03-12
Accepted: 2020-03-17
Published Online: 2020-04-29

© 2020 Yan Zhang et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

Articles in the same Issue

  1. Obituary for Prof. Dr. Jun-ichi Yoshida
  2. Regular Articles
  3. Optimization of microwave-assisted manganese leaching from electrolyte manganese residue
  4. Crustacean shell bio-refining to chitin by natural deep eutectic solvents
  5. The kinetics of the extraction of caffeine from guarana seed under the action of ultrasonic field with simultaneous cooling
  6. Biocomposite scaffold preparation from hydroxyapatite extracted from waste bovine bone
  7. A simple room temperature-static bioreactor for effective synthesis of hexyl acetate
  8. Biofabrication of zinc oxide nanoparticles, characterization and cytotoxicity against pediatric leukemia cell lines
  9. Efficient synthesis of palladium nanoparticles using guar gum as stabilizer and their applications as catalyst in reduction reactions and degradation of azo dyes
  10. Isolation of biosurfactant producing bacteria from Potwar oil fields: Effect of non-fossil fuel based carbon sources
  11. Green synthesis, characterization and photocatalytic applications of silver nanoparticles using Diospyros lotus
  12. Dielectric properties and microwave heating behavior of neutral leaching residues from zinc metallurgy in the microwave field
  13. Green synthesis and stabilization of silver nanoparticles using Lysimachia foenum-graecum Hance extract and their antibacterial activity
  14. Microwave-induced heating behavior of Y-TZP ceramics under multiphysics system
  15. Synthesis and catalytic properties of nickel salts of Keggin-type heteropolyacids embedded metal-organic framework hybrid nanocatalyst
  16. Preparation and properties of hydrogel based on sawdust cellulose for environmentally friendly slow release fertilizers
  17. Structural characterization, antioxidant and cytotoxic effects of iron nanoparticles synthesized using Asphodelus aestivus Brot. aqueous extract
  18. Phase transformation involved in the reduction process of magnesium oxide in calcined dolomite by ferrosilicon with additive of aluminum
  19. Green synthesis of TiO2 nanoparticles from Syzygium cumini extract for photo-catalytic removal of lead (Pb) in explosive industrial wastewater
  20. The study on the influence of oxidation degree and temperature on the viscosity of biodiesel
  21. Prepare a catalyst consist of rare earth minerals to denitrate via NH3-SCR
  22. Bacterial nanobiotic potential
  23. Green synthesis and characterization of carboxymethyl guar gum: Application in textile printing technology
  24. Potential of adsorbents from agricultural wastes as alternative fillers in mixed matrix membrane for gas separation: A review
  25. Bactericidal and cytotoxic properties of green synthesized nanosilver using Rosmarinus officinalis leaves
  26. Synthesis of biomass-supported CuNi zero-valent nanoparticles through wetness co-impregnation method for the removal of carcinogenic dyes and nitroarene
  27. Synthesis of 2,2′-dibenzoylaminodiphenyl disulfide based on Aspen Plus simulation and the development of green synthesis processes
  28. Catalytic performance of the biosynthesized AgNps from Bistorta amplexicaule: antifungal, bactericidal, and reduction of carcinogenic 4-nitrophenol
  29. Optical and antimicrobial properties of silver nanoparticles synthesized via green route using honey
  30. Adsorption of l-α-glycerophosphocholine on ion-exchange resin: Equilibrium, kinetic, and thermodynamic studies
  31. Microwave-assisted green synthesis of silver nanoparticles using dried extracts of Chlorella vulgaris and antibacterial activity studies
  32. Preparation of graphene oxide/chitosan complex and its adsorption properties for heavy metal ions
  33. Green synthesis of metal and metal oxide nanoparticles from plant leaf extracts and their applications: A review
  34. Synthesis, characterization, and electrochemical properties of carbon nanotubes used as cathode materials for Al–air batteries from a renewable source of water hyacinth
  35. Optimization of medium–low-grade phosphorus rock carbothermal reduction process by response surface methodology
  36. The study of rod-shaped TiO2 composite material in the protection of stone cultural relics
  37. Eco-friendly synthesis of AuNPs for cutaneous wound-healing applications in nursing care after surgery
  38. Green approach in fabrication of photocatalytic, antimicrobial, and antioxidant zinc oxide nanoparticles – hydrothermal synthesis using clove hydroalcoholic extract and optimization of the process
  39. Green synthesis: Proposed mechanism and factors influencing the synthesis of platinum nanoparticles
  40. Green synthesis of 3-(1-naphthyl), 4-methyl-3-(1-naphthyl) coumarins and 3-phenylcoumarins using dual-frequency ultrasonication
  41. Optimization for removal efficiency of fluoride using La(iii)–Al(iii)-activated carbon modified by chemical route
  42. In vitro biological activity of Hydroclathrus clathratus and its use as an extracellular bioreductant for silver nanoparticle formation
  43. Evaluation of saponin-rich/poor leaf extract-mediated silver nanoparticles and their antifungal capacity
  44. Propylene carbonate synthesis from propylene oxide and CO2 over Ga-Silicate-1 catalyst
  45. Environmentally benevolent synthesis and characterization of silver nanoparticles using Olea ferruginea Royle for antibacterial and antioxidant activities
  46. Eco-synthesis and characterization of titanium nanoparticles: Testing its cytotoxicity and antibacterial effects
  47. A novel biofabrication of gold nanoparticles using Erythrina senegalensis leaf extract and their ameliorative effect on mycoplasmal pneumonia for treating lung infection in nursing care
  48. Phytosynthesis of selenium nanoparticles using the costus extract for bactericidal application against foodborne pathogens
  49. Temperature effects on electrospun chitosan nanofibers
  50. An electrochemical method to investigate the effects of compound composition on gold dissolution in thiosulfate solution
  51. Trillium govanianum Wall. Ex. Royle rhizomes extract-medicated silver nanoparticles and their antimicrobial activity
  52. In vitro bactericidal, antidiabetic, cytotoxic, anticoagulant, and hemolytic effect of green-synthesized silver nanoparticles using Allium sativum clove extract incubated at various temperatures
  53. The green synthesis of N-hydroxyethyl-substituted 1,2,3,4-tetrahydroquinolines with acidic ionic liquid as catalyst
  54. Effect of KMnO4 on catalytic combustion performance of semi-coke
  55. Removal of Congo red and malachite green from aqueous solution using heterogeneous Ag/ZnCo-ZIF catalyst in the presence of hydrogen peroxide
  56. Nucleotide-based green synthesis of lanthanide coordination polymers for tunable white-light emission
  57. Determination of life cycle GHG emission factor for paper products of Vietnam
  58. Parabolic trough solar collectors: A general overview of technology, industrial applications, energy market, modeling, and standards
  59. Structural characteristics of plant cell wall elucidated by solution-state 2D NMR spectroscopy with an optimized procedure
  60. Sustainable utilization of a converter slagging agent prepared by converter precipitator dust and oxide scale
  61. Efficacy of chitosan silver nanoparticles from shrimp-shell wastes against major mosquito vectors of public health importance
  62. Effectiveness of six different methods in green synthesis of selenium nanoparticles using propolis extract: Screening and characterization
  63. Characterizations and analysis of the antioxidant, antimicrobial, and dye reduction ability of green synthesized silver nanoparticles
  64. Foliar applications of bio-fabricated selenium nanoparticles to improve the growth of wheat plants under drought stress
  65. Green synthesis of silver nanoparticles from Valeriana jatamansi shoots extract and its antimicrobial activity
  66. Characterization and biological activities of synthesized zinc oxide nanoparticles using the extract of Acantholimon serotinum
  67. Effect of calcination temperature on rare earth tailing catalysts for catalytic methane combustion
  68. Enhanced diuretic action of furosemide by complexation with β-cyclodextrin in the presence of sodium lauryl sulfate
  69. Development of chitosan/agar-silver nanoparticles-coated paper for antibacterial application
  70. Preparation, characterization, and catalytic performance of Pd–Ni/AC bimetallic nano-catalysts
  71. Acid red G dye removal from aqueous solutions by porous ceramsite produced from solid wastes: Batch and fixed-bed studies
  72. Review Articles
  73. Recent advances in the catalytic applications of GO/rGO for green organic synthesis
https://doi.org/10.1515/gps-2020-0026
Keywords for this article
rubber peptizer; process synthesis; Aspen Plus simulation; process optimization; clean production
Creative Commons
BY 4.0

Articles in the same Issue

  1. Obituary for Prof. Dr. Jun-ichi Yoshida
  2. Regular Articles
  3. Optimization of microwave-assisted manganese leaching from electrolyte manganese residue
  4. Crustacean shell bio-refining to chitin by natural deep eutectic solvents
  5. The kinetics of the extraction of caffeine from guarana seed under the action of ultrasonic field with simultaneous cooling
  6. Biocomposite scaffold preparation from hydroxyapatite extracted from waste bovine bone
  7. A simple room temperature-static bioreactor for effective synthesis of hexyl acetate
  8. Biofabrication of zinc oxide nanoparticles, characterization and cytotoxicity against pediatric leukemia cell lines
  9. Efficient synthesis of palladium nanoparticles using guar gum as stabilizer and their applications as catalyst in reduction reactions and degradation of azo dyes
  10. Isolation of biosurfactant producing bacteria from Potwar oil fields: Effect of non-fossil fuel based carbon sources
  11. Green synthesis, characterization and photocatalytic applications of silver nanoparticles using Diospyros lotus
  12. Dielectric properties and microwave heating behavior of neutral leaching residues from zinc metallurgy in the microwave field
  13. Green synthesis and stabilization of silver nanoparticles using Lysimachia foenum-graecum Hance extract and their antibacterial activity
  14. Microwave-induced heating behavior of Y-TZP ceramics under multiphysics system
  15. Synthesis and catalytic properties of nickel salts of Keggin-type heteropolyacids embedded metal-organic framework hybrid nanocatalyst
  16. Preparation and properties of hydrogel based on sawdust cellulose for environmentally friendly slow release fertilizers
  17. Structural characterization, antioxidant and cytotoxic effects of iron nanoparticles synthesized using Asphodelus aestivus Brot. aqueous extract
  18. Phase transformation involved in the reduction process of magnesium oxide in calcined dolomite by ferrosilicon with additive of aluminum
  19. Green synthesis of TiO2 nanoparticles from Syzygium cumini extract for photo-catalytic removal of lead (Pb) in explosive industrial wastewater
  20. The study on the influence of oxidation degree and temperature on the viscosity of biodiesel
  21. Prepare a catalyst consist of rare earth minerals to denitrate via NH3-SCR
  22. Bacterial nanobiotic potential
  23. Green synthesis and characterization of carboxymethyl guar gum: Application in textile printing technology
  24. Potential of adsorbents from agricultural wastes as alternative fillers in mixed matrix membrane for gas separation: A review
  25. Bactericidal and cytotoxic properties of green synthesized nanosilver using Rosmarinus officinalis leaves
  26. Synthesis of biomass-supported CuNi zero-valent nanoparticles through wetness co-impregnation method for the removal of carcinogenic dyes and nitroarene
  27. Synthesis of 2,2′-dibenzoylaminodiphenyl disulfide based on Aspen Plus simulation and the development of green synthesis processes
  28. Catalytic performance of the biosynthesized AgNps from Bistorta amplexicaule: antifungal, bactericidal, and reduction of carcinogenic 4-nitrophenol
  29. Optical and antimicrobial properties of silver nanoparticles synthesized via green route using honey
  30. Adsorption of l-α-glycerophosphocholine on ion-exchange resin: Equilibrium, kinetic, and thermodynamic studies
  31. Microwave-assisted green synthesis of silver nanoparticles using dried extracts of Chlorella vulgaris and antibacterial activity studies
  32. Preparation of graphene oxide/chitosan complex and its adsorption properties for heavy metal ions
  33. Green synthesis of metal and metal oxide nanoparticles from plant leaf extracts and their applications: A review
  34. Synthesis, characterization, and electrochemical properties of carbon nanotubes used as cathode materials for Al–air batteries from a renewable source of water hyacinth
  35. Optimization of medium–low-grade phosphorus rock carbothermal reduction process by response surface methodology
  36. The study of rod-shaped TiO2 composite material in the protection of stone cultural relics
  37. Eco-friendly synthesis of AuNPs for cutaneous wound-healing applications in nursing care after surgery
  38. Green approach in fabrication of photocatalytic, antimicrobial, and antioxidant zinc oxide nanoparticles – hydrothermal synthesis using clove hydroalcoholic extract and optimization of the process
  39. Green synthesis: Proposed mechanism and factors influencing the synthesis of platinum nanoparticles
  40. Green synthesis of 3-(1-naphthyl), 4-methyl-3-(1-naphthyl) coumarins and 3-phenylcoumarins using dual-frequency ultrasonication
  41. Optimization for removal efficiency of fluoride using La(iii)–Al(iii)-activated carbon modified by chemical route
  42. In vitro biological activity of Hydroclathrus clathratus and its use as an extracellular bioreductant for silver nanoparticle formation
  43. Evaluation of saponin-rich/poor leaf extract-mediated silver nanoparticles and their antifungal capacity
  44. Propylene carbonate synthesis from propylene oxide and CO2 over Ga-Silicate-1 catalyst
  45. Environmentally benevolent synthesis and characterization of silver nanoparticles using Olea ferruginea Royle for antibacterial and antioxidant activities
  46. Eco-synthesis and characterization of titanium nanoparticles: Testing its cytotoxicity and antibacterial effects
  47. A novel biofabrication of gold nanoparticles using Erythrina senegalensis leaf extract and their ameliorative effect on mycoplasmal pneumonia for treating lung infection in nursing care
  48. Phytosynthesis of selenium nanoparticles using the costus extract for bactericidal application against foodborne pathogens
  49. Temperature effects on electrospun chitosan nanofibers
  50. An electrochemical method to investigate the effects of compound composition on gold dissolution in thiosulfate solution
  51. Trillium govanianum Wall. Ex. Royle rhizomes extract-medicated silver nanoparticles and their antimicrobial activity
  52. In vitro bactericidal, antidiabetic, cytotoxic, anticoagulant, and hemolytic effect of green-synthesized silver nanoparticles using Allium sativum clove extract incubated at various temperatures
  53. The green synthesis of N-hydroxyethyl-substituted 1,2,3,4-tetrahydroquinolines with acidic ionic liquid as catalyst
  54. Effect of KMnO4 on catalytic combustion performance of semi-coke
  55. Removal of Congo red and malachite green from aqueous solution using heterogeneous Ag/ZnCo-ZIF catalyst in the presence of hydrogen peroxide
  56. Nucleotide-based green synthesis of lanthanide coordination polymers for tunable white-light emission
  57. Determination of life cycle GHG emission factor for paper products of Vietnam
  58. Parabolic trough solar collectors: A general overview of technology, industrial applications, energy market, modeling, and standards
  59. Structural characteristics of plant cell wall elucidated by solution-state 2D NMR spectroscopy with an optimized procedure
  60. Sustainable utilization of a converter slagging agent prepared by converter precipitator dust and oxide scale
  61. Efficacy of chitosan silver nanoparticles from shrimp-shell wastes against major mosquito vectors of public health importance
  62. Effectiveness of six different methods in green synthesis of selenium nanoparticles using propolis extract: Screening and characterization
  63. Characterizations and analysis of the antioxidant, antimicrobial, and dye reduction ability of green synthesized silver nanoparticles
  64. Foliar applications of bio-fabricated selenium nanoparticles to improve the growth of wheat plants under drought stress
  65. Green synthesis of silver nanoparticles from Valeriana jatamansi shoots extract and its antimicrobial activity
  66. Characterization and biological activities of synthesized zinc oxide nanoparticles using the extract of Acantholimon serotinum
  67. Effect of calcination temperature on rare earth tailing catalysts for catalytic methane combustion
  68. Enhanced diuretic action of furosemide by complexation with β-cyclodextrin in the presence of sodium lauryl sulfate
  69. Development of chitosan/agar-silver nanoparticles-coated paper for antibacterial application
  70. Preparation, characterization, and catalytic performance of Pd–Ni/AC bimetallic nano-catalysts
  71. Acid red G dye removal from aqueous solutions by porous ceramsite produced from solid wastes: Batch and fixed-bed studies
  72. Review Articles
  73. Recent advances in the catalytic applications of GO/rGO for green organic synthesis
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